Data on the synthesis processes optimization of novel β-NiS film modified CdS nanoflowers heterostructure nanocomposite for photocatalytic hydrogen evolution

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Yu Zhang

2018-02-01

Full Text Available The data presented in this article are related to a research article entitled ‘Novel β-NiS film modified CdS nanoflowers heterostructure nanocomposite: extraordinarily highly efficient photocatalysts for hydrogen evolution’ (Zhang et al., 2018 [1]. In this article, we report original data on the synthesis processes optimization of the proposed nanocomposite on the basis of their optimum photocatalytic performance together with the comparison on the results of literatures and comparative experiments. The composition, microstructure, morphology, photocatalytic hydrogen evolution and photocatalytic stability of the corresponding samples are included in this report. The data are presented in this format in order to facilitate comparison with data from other researchers in the field and understanding the mechanism of similar catalysts. Keywords: NiS/CdS nanoflowers heterostructure, Photocatalysts, Water splitting, Hydrothermal synthesis, Optimization

In situ growing Bi_2MoO_6 on g-C_3N_4 nanosheets with enhanced photocatalytic hydrogen evolution and disinfection of bacteria under visible light irradiation

International Nuclear Information System (INIS)

Li, Juan; Yin, Yunchao; Liu, Enzhou; Ma, Yongning; Wan, Jun; Fan, Jun; Hu, Xiaoyun

2017-01-01

Graphical abstract: TEM image and schematic diagram of photocatalytic mechanism of Bi_2MoO_6/g-C_3N_4 composite. - Highlights: • BM/CNNs heterojunctions were obtained by an in situ solvothermal method. • 2D CNNs are superior to CN as photocatalysts and supporting materials. • The photocatalytic hydrogen evolution of BM/CNNs has been first studied. • The photocatalytic disinfection of bacteria by BM/CNNs has been first studied. • The photocatalytic mechanism of BM/CNNs heterojunction was described. - Abstract: Bi_2MoO_6/g-C_3N_4 heterojunctions were fabricated by an in situ solvothermal method using g-C_3N_4 nanosheets. The photocatalytic activities of as-prepared samples were evaluated by hydrogen evolution from water splitting and disinfection of bacteria under visible light irradiation. The results indicate that exfoliating bulk g-C_3N_4 to g-C_3N_4 nanosheets greatly enlarges the specific surface area and shortens the diffusion distance for photogenerated charges, which could not only promote the photocatalytic performance but also benefit the sufficient interaction with Bi_2MoO_6. Furthermore, intimate contact of Bi_2MoO_6 (BM) and g-C_3N_4 nanosheets (CNNs) in the BM/CNNs composites facilitates the transfer and separation of photogenetrated electron-hole pairs. 20%-BM/CNNs heterojunction exhibits the optimal photocatalytic hydrogen evolution as well as photocatalytic disinfection of bacteria. Furthermore, h"+ was demonstrated as the dominant reactive species which could make the bacteria cells inactivated in the photocatalytic disinfection process. This study extends new chance of g-C_3N_4-based photocatalysts to the growing demand of clean new energy and drinking water.

Effect of sacrificial agents on the dispersion of metal cocatalysts for photocatalytic hydrogen evolution

Science.gov (United States)

Cao, Shaowen; Shen, Baojia; Huang, Qian; Chen, Zhe

2018-06-01

Surface photodeposition of noble metal cocatalyst has been regarded as an effective approach to facilitate the separation of charge carriers and reduce the over-potential of water reduction, thus to enhance the photocatalytic H2-production activities of semiconductor photocatalyst. Herein, the influences of sacrificial agents used in the photodeposition process on the dispersion of noble metal nanoparticles are investigated, via a series of technique of photocatalytic hydrogen evolution test, microstructure analysis and photoelectrochemical measurement. As a result, the sacrificial agents are found to show large impact on the loading amount, particle size and distribution of different metals on the surface of g-C3N4. The real loading amount of Pt and Au is higher in methanol solution than that in triethanolamine solution. Better distribution and smaller size of Pt nanoparticles are achieved in the presence of methanol; while better distribution and smaller size of Au nanoparticles are achieved in the presence of triethanolamine. As a result, quite different charge transfer ability is achieved for the synthesized Pt and Au decorated g-C3N4, which subsequently leads to disparate photocatalytic activities of the same g-C3N4 photocatalyst under various conditions. The finding in this work indicates that the valid deposition content, particle size and distribution of metal cocatalysts should be carefully taken into account when comparing the photocatalytic activities among various samples.

Non-noble metal vanadium phosphites with broad absorption for photocatalytic hydrogen evolution

International Nuclear Information System (INIS)

Song, Jun-Ling; Zhang, Jian-Han; Mao, Jiang-Gao

2016-01-01

We reported the synthesis and crystal structures of alkali metal and alkali-earth metal phosphite, namely, CsV 2 (H 3 O)(HPO 3 ) 4 (1), and Ba 3 V 2 (HPO 3 ) 6 (2). Both compounds were prepared by hydrothermal reactions and feature unique new structures. They both exhibit 3D complicated frameworks based on VO 6 octahedra which are connected by HPO 3 tetrahedra via corner-sharing. Alkali or alkali earth metal cations are filled in the different channels of the frameworks. Topological analysis shows that the framework of CsV 2 (H 3 O) (HPO 3 ) 4 (1) is a new 3,3,3,4,5-connected network with the Schläfli symbol of {4.6 2 } 2 {4 2 .6 6 .8 2 }{6 3 }{6 5 .8}. The investigations of X-ray photoelectron spectroscopy (XPS) and magnetic measurement on CsV 2 (H 3 O)(HPO 3 ) 4 suggest a +3 oxidation state of the vanadium ions in compound 1. Photocatalytic performance was evaluated by photocatalytic H 2 evolution and degradation of methylene blue, which shows that both compounds exhibit activity under visible-light irradiation. IR spectrum, UV–vis-NIR spectrum and thermogravimetric analysis (TGA) of compounds were also investigated. - Graphical abstract: Metal vanadium phosphites with broad absorption for photocatalytic hydrogen evolution and the degradation of methylene blue aqueous solution. - Highlights: • Two new vanadium phosphites, CsV 2 (H 3 O)(HPO 3 ) 4 and Ba 3 V 2 (HPO 3 ) 6 , are reported. • CsV 2 (H 3 O)(HPO 3 ) 4 and Ba 3 V 2 (HPO 3 ) 6 feature complicated 3D framework structures with different channels. • CsV 2 (H 3 O)(HPO 3 ) 4 and Ba 3 V 2 (HPO 3 ) 6 exhibit strong and broad absorptions in the visible and Near IR region. • Photocatalytic properties of CsV 2 (H 3 O)(HPO 3 ) 4 and Ba 3 V 2 (HPO 3 ) 6 are investigated. • The magnetic measurement of CsV 2 (H 3 O)(HPO 3 ) 4 was performed in the temperature range of 2–300 K.

In situ photodeposition of cobalt on CdS nanorod for promoting photocatalytic hydrogen production under visible light irradiation

Science.gov (United States)

Chen, Wei; Wang, Yanhong; Liu, Mei; Gao, Li; Mao, Liqun; Fan, Zeyun; Shangguan, Wenfeng

2018-06-01

Non-noble metal Co were loaded on CdS for enhancing photocatalytic activity of water splitting by a simple and efficient in situ photodeposition method. The Co particles with diameter ca. 5 nm were photoreduced and then loaded on the surface of CdS. The loading of Co can not only effectively promote the separation of electrons and holes photoexcited by CdS, but reduce the overpotential of hydrogen evolution as well, thus enhancing photocatalytic activity of water splitting. The highest photocatalytic H2 evolution rate of Co/CdS reaches up to 1299 μmol h-1 under visible light irradiation(λ > 420 nm) when the amount of loading is 1.0 wt%, which is 17 times of that of pure CdS and achieves 80% of that of 0.5 wt%Pt/CdS. This work not only exhibits a pathway to obtain photocatalysts with high photocatalytic activity for hydrogen production, but provides a possibility for the utilization of low cost Co as a substitute for noble metals in photocatalytic hydrogen production.

In situ growing Bi{sub 2}MoO{sub 6} on g-C{sub 3}N{sub 4} nanosheets with enhanced photocatalytic hydrogen evolution and disinfection of bacteria under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Li, Juan [School of Chemical Engineering, Northwest University, Xi’an, 710069 (China); School of Environmental Engineering and Chemistry, Luoyang Institute of Science and Technology, Luoyang, 471023 (China); Yin, Yunchao; Liu, Enzhou; Ma, Yongning; Wan, Jun [School of Chemical Engineering, Northwest University, Xi’an, 710069 (China); Fan, Jun, E-mail: fanjun@nwu.edu.cn [School of Chemical Engineering, Northwest University, Xi’an, 710069 (China); Hu, Xiaoyun, E-mail: hxy3275@nwu.edu.cn [School of Physics, Northwest University, Xi’an, 710069 (China)

2017-01-05

Graphical abstract: TEM image and schematic diagram of photocatalytic mechanism of Bi{sub 2}MoO{sub 6}/g-C{sub 3}N{sub 4} composite. - Highlights: • BM/CNNs heterojunctions were obtained by an in situ solvothermal method. • 2D CNNs are superior to CN as photocatalysts and supporting materials. • The photocatalytic hydrogen evolution of BM/CNNs has been first studied. • The photocatalytic disinfection of bacteria by BM/CNNs has been first studied. • The photocatalytic mechanism of BM/CNNs heterojunction was described. - Abstract: Bi{sub 2}MoO{sub 6}/g-C{sub 3}N{sub 4} heterojunctions were fabricated by an in situ solvothermal method using g-C{sub 3}N{sub 4} nanosheets. The photocatalytic activities of as-prepared samples were evaluated by hydrogen evolution from water splitting and disinfection of bacteria under visible light irradiation. The results indicate that exfoliating bulk g-C{sub 3}N{sub 4} to g-C{sub 3}N{sub 4} nanosheets greatly enlarges the specific surface area and shortens the diffusion distance for photogenerated charges, which could not only promote the photocatalytic performance but also benefit the sufficient interaction with Bi{sub 2}MoO{sub 6}. Furthermore, intimate contact of Bi{sub 2}MoO{sub 6} (BM) and g-C{sub 3}N{sub 4} nanosheets (CNNs) in the BM/CNNs composites facilitates the transfer and separation of photogenetrated electron-hole pairs. 20%-BM/CNNs heterojunction exhibits the optimal photocatalytic hydrogen evolution as well as photocatalytic disinfection of bacteria. Furthermore, h{sup +} was demonstrated as the dominant reactive species which could make the bacteria cells inactivated in the photocatalytic disinfection process. This study extends new chance of g-C{sub 3}N{sub 4}-based photocatalysts to the growing demand of clean new energy and drinking water.

Photocatalytic Hydrogen or Oxygen Evolution from Water over S- or N-Doped TiO2 under Visible Light

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Kazumoto Nishijima

2008-01-01

Full Text Available S- or N-doping of TiO2 powder having an anatase or rutile phase extended the photocatalytic activity for water oxidation and reduction under UV light and visible light irradiation. For the reduction of water, anatase-doped TiO2 showed higher level of activity than that of doped TiO2 having a rutile phase using ethanol as an electron donor. Furthermore, the activity level of S-doped TiO2 for hydrogen evolution was higher than that of N-doped TiO2 photocatalysts under visible light. Photocatalytic oxidation of water on doped TiO2 having a rutile phase proceeded with fairly high efficiency when Fe3+ ions were used as electron acceptors compared to that on doped TiO2 having an anatase phase. In addition, water splitting under visible light irradiation was achieved by construction of a Z-scheme photocatalysis system employing the doped TiO2 having anatase and rutile phases for H2 and O2 evolution and the I−/IO3− redox couple as an electron relay.

Self-optimization of the active site of molybdenum disulfide by an irreversible phase transition during photocatalytic hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Wang, Longlu; Duan, Xidong; Liu, Chengbin; Zhang, Shuqu; Zeng, Yunxiong [State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha (China); Liu, Xia; Pei, Yong [Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University (China); Luo, Jinming; Crittenden, John [Brook Byers Institute for Sustainable Systems and School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA (United States); Duan, Xiangfeng [Department of Chemistry and Biochemistry, University of California, Los Angeles, CA (United States)

2017-06-19

The metallic 1T-MoS{sub 2} has attracted considerable attention as an effective catalyst for hydrogen evolution reactions (HERs). However, the fundamental mechanism about the catalytic activity of 1T-MoS{sub 2} and the associated phase evolution remain elusive and controversial. Herein, we prepared the most stable 1T-MoS{sub 2} by hydrothermal exfoliation of MoS{sub 2} nanosheets vertically rooted into rigid one-dimensional TiO{sub 2} nanofibers. The 1T-MoS{sub 2} can keep highly stable over one year, presenting an ideal model system for investigating the HER catalytic activities as a function of the phase evolution. Both experimental studies and theoretical calculations suggest that 1T phase can be irreversibly transformed into a more active 1T' phase as true active sites in photocatalytic HERs, resulting in a ''catalytic site self-optimization''. Hydrogen atom adsorption is the major driving force for this phase transition. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Hydrothermal synthesis of core–shell TiO_2 to enhance the photocatalytic hydrogen evolution

International Nuclear Information System (INIS)

Jiang, Jinghui; Zhou, Han; Zhang, Fan; Fan, Tongxiang; Zhang, Di

2016-01-01

Graphical abstract: Core–shell TiO_2 with interior cavity was synthesized by a hydrothermal approach to enhance the photocatalytic performance. - Highlights: • Core–shell TiO_2 with interior cavity can be synthesized by hydrothermal approach. • Multiple reflection of incident light in cavity can increase the absorption. • Rutile can optimize the bandgap and delay the charge recombination. - Abstract: A hydrothermal approach was designed to synthesize core–shell TiO_2 with interior cavity by making sodium dodecyl sulfonate (SDS) as the surfactant and the mixture of water and ethanol as the solvent. The control experiment of solvent reveals ethanol and water are responsible for the formation of sphere and interior cavity, respectively. Besides, SDS can assist the growth of core–shell structure, and the sizes of sphere and interior cavity can be tuned by regulating the reaction time or temperature. UV–vis absorption proves core–shell structure with interior cavity can increase the absorption of incident light to enhance the optical activity of final product. The calculated bandgap and photoluminescence (PL) analyses reveal the coexistence of rutile in final product can optimize the bandgap to 3.03 eV and delay the charge recombination. As a result, an effective photocatalytic hydrogen evolution under full spectrum irradiation can be harvested by the as-synthesized core–shell spheres to reach a quantum yield, approximately 9.57% at 340 nm wavelength.

Hydrogen evolution from water splitting on nanocomposite photocatalysts

Directory of Open Access Journals (Sweden)

Wenfeng Shangguan

2007-01-01

Full Text Available The photocatalytic production of H2 in one step is potentially one of the most promising ways for the conversion and storage of solar energy. The paper overviews our recent studies on the photocatalysts splitting water into hydrogen under irradiation. The attention was mainly focused on the promotion effects of nanosized modifications in the interlayer and surface of photocatalysts for hydrogen evolution with visible light. The photocatalytic activity depended significantly on modification techniques, such as loading, proton exchange, and intercalation. The formation of a "nest" on the particle surface promoted a uniform distribution and strong combination of the nanosized particles on the surface of catalysts. By the methods of intercalation and pillaring as well as by selecting both host and guest, a large variety of molecular designed host–guest systems were obtained. Cadmium sulfide (CdS-intercalated composites showed higher activity and stability. This activity of K4Ce2M10O30 (M=Ta, Nb evolving H2 under visible light irradiation was enhanced by the incorporation of Pt, RuO2 and NiO as co-catalysts. Especially, the nanosized NiOx (Ni–NiO double-layer structure greatly prompted the photocatalytic H2 evolution significantly.

TiO{sub 2} nanocomposite with reduced graphene oxide through facile blending and its photocatalytic behavior for hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Pei, Fuyun; Liu, Yingliang; Zhang, Li; Wang, Shengping; Xu, Shengang, E-mail: xusg@zzu.edu.cn; Cao, Shaokui, E-mail: caoshaokui@zzu.edu.cn

2013-08-01

Graphical abstract: - Highlights: • TRG-COOH nanocomposite as a photocatalyst for hydrogen evolution is prepared. • The reduction of graphene oxide reconstructs a part of conjugated structure. • The band gap is red-shifted due to the reconstruction of conjugated structure. • RG-COOH covered and anchored by P25 blocks the aggregation and the stacking. • The photocatalytic efficiency of TRG-COOH was increased under 500 W Xenon lamp. - Abstract: TRG-COOH nanocomposite is prepared as a photocatalyst for hydrogen evolution by blending TiO{sub 2} with reduced graphene oxide (RG-COOH). TRG-COOH is characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and photoluminescent spectra. XPS result shows the reduction of monolayer graphene oxide (GO). The band gap is red-shifted from 3.25 eV for P25, which consists of 20% rutile and 80% anatase, to 2.95 eV for TGO and then to 2.80 eV for TRG-COOH due to the introduction of GO and the reconstruction of conjugated structure. TEM image illustrates that RG-COOH in TRG-COOH is covered and anchored by P25, which blocks the aggregation of TiO{sub 2} nanoparticles and the stacking of monolayer graphene. This allows RG-COOH to take a good role of electron-sink and electron-transporting bridge. The photocatalytic efficiency of TRG-COOH is respectively increased under Xenon lamp about 8.9 and 2.7 times compared to P25 and TGO.

Yttrium bismuth titanate pyrochlore mixed oxides for photocatalytic hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Merka, Oliver

2012-10-18

In this work, the sol-gel synthesis of new non-stoichiometric pyrochlore titanates and their application in photocatalytic hydrogen production is reported. Visible light response is achieved by introducing bismuth on the A site or by doping the B site by transition metal cations featuring partially filled d orbitals. This work clearly focusses on atomic scale structural changes induced by the systematical introduction of non-stoichiometry in pyrochlore mixed oxides and the resulting influence on the activity in photocatalytic hydrogen production. The materials were characterized in detail regarding their optical properties and their atomic structure. The pyrochlore structure tolerates tremendous stoichiometry variations. The non-stoichiometry in A{sub 2}O{sub 3} rich compositions is compensated by distortions in the cationic sub-lattice for the smaller Y{sup 3+} cation and by evolution of a secondary phase for the larger Bi{sup 3+} cation on the A site. For TiO{sub 2} rich compositions, the non-stoichiometry leads to a special vacancy formation in the A and optionally O' sites. It is shown that pyrochlore mixed oxides in the yttrium bismuth titanate system represent very active and promising materials for photocatalytic hydrogen production, if precisely and carefully tuned. Whereas Y{sub 2}Ti{sub 2}O{sub 7} yields stable hydrogen production rates over time, the bismuth richer compounds of YBiTi{sub 2}O{sub 7} and Bi{sub 2}Ti{sub 2}O{sub 7} are found to be not stable under irradiation. This drawback is overcome by applying a special co-catalyst system consisting of a precious metal core and a Cr{sub 2}O{sub 3} shell on the photocatalysts.

Ultrafast carrier dynamics unravel role of surface ligands and metal domain size on the photocatalytic hydrogen evolution efficiency of Au-tipped CdS nanorods: an ultrafast transient absorption spectroscopy study

Science.gov (United States)

Ben-Shahar, Yuval; Kriegel, Ilka; Scotognella, Francesco; Waiskopf, Nir; Dal Conte, Stefano; Moretti, Luca; Cerullo, Giulio; Rabani, Eran; Banin, Uri

2017-02-01

Semiconductor-metal hybrid nanostructures are interesting materials for photocatalysis. Their tunable properties offer a highly controllable platform to design light-induced charge separation, a key to their function in photocatalytic water splitting. Hydrogen evolution quantum yields are influenced by factors as size, shape, material and morphology of the system, additionally the surface coating or the metal domain size play a dominant role. In this paper we present a study on a well-defined model system of Au-tipped CdS nanorods. We use transient absorption spectroscopy to get insights into the charge carrier dynamics after photoexcitation of the bandgap of CdS nanorods. The study of charge transfer processes combined with the hydrogen evolution efficiency unravels the effects of surface coating and the gold tip size on the photocatalytic efficiency. Differences in efficiency with various surface ligands are primarily ascribed to the effects of surface passivation. Surface trapping of charge carriers is competing with effective charge separation, a prerequisite for photocatalysis, leading to the observed lower hydrogen production quantum yields. Interestingly, non-monotonic hydrogen evolution efficiency with size of the gold tip is observed, resulting in an optimal metal domain size for the most efficient photocatalysis. These results are explained by the sizedependent interplay of the metal domain charging and the relative band-alignments. Taken together our findings are of major importance for the potential application of hybrid nanoparticles as photocatalysts.

Preparation of NiS/ZnIn2S4 as a superior photocatalyst for hydrogen evolution under visible light irradiation

Directory of Open Access Journals (Sweden)

Liang Wei

2013-12-01

Full Text Available In this study, NiS/ZnIn2S4 nanocomposites were successfully prepared via a facile two-step hydrothermal process. The as-prepared samples were characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, transmission electron microscopy (TEM and high-resolution transmission electron microscopy (HRTEM. Their photocatalytic performance for hydrogen evolution under visible light irradiation was also investigated. It was found that the photocatalytic hydrogen evolution activity over hexagonal ZnIn2S4 can be significantly increased by loading NiS as a co-catalyst. The formation of a good junction between ZnIn2S4 and NiS via the two step hydrothermal processes is beneficial for the directional migration of the photo-excited electrons from ZnIn2S4 to NiS. The highest photocatalytic hydrogen evolution rate (104.7 μmol/h, which is even higher than that over Pt/ZnIn2S4 nanocomposite (77.8 μmol/h, was observed over an optimum NiS loading amount of 0.5 wt %. This work demonstrates a high potential of the developing of environmental friendly, cheap noble-metal-free co-catalyst for semiconductor-based photocatalytic hydrogen evolution.

Hydrogen evolution from aqueous-phase photocatalytic reforming of ethylene glycol over Pt/TiO{sub 2} catalysts: Role of Pt and product distribution

Energy Technology Data Exchange (ETDEWEB)

Li, Fuying [State Key Laboratory of Photocatalysis on Energy and Environment, Research Institute of Photocatalysis, Fuzhou University, Fuzhou 350002 (China); College of Resources and Chemical Engineering, Sanming University, Sanming 365004 (China); Gu, Quan [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shanxi Normal University, Xi’an 710062 (China); Niu, Yu [College of Resources and Chemical Engineering, Sanming University, Sanming 365004 (China); School of Chemical Engineering, Fuzhou University, Fuzhou 350116 (China); Wang, Renzhang [College of Resources and Chemical Engineering, Sanming University, Sanming 365004 (China); Tong, Yuecong; Zhu, Shuying; Zhang, Hualei [State Key Laboratory of Photocatalysis on Energy and Environment, Research Institute of Photocatalysis, Fuzhou University, Fuzhou 350002 (China); Zhang, Zizhong, E-mail: z.zhang@fzu.edu.cn [State Key Laboratory of Photocatalysis on Energy and Environment, Research Institute of Photocatalysis, Fuzhou University, Fuzhou 350002 (China); Wang, Xuxu [State Key Laboratory of Photocatalysis on Energy and Environment, Research Institute of Photocatalysis, Fuzhou University, Fuzhou 350002 (China)

2017-01-01

Highlights: • Photocatalytic EG reforming generates many hydrocarbons besides H{sub 2}, CO{sub 2} and CO. • Pt loading greatly improves the photocatalytic activity of TiO{sub 2} for EG reforming. • Half amount of the produced H{sub 2} over Pt/TiO{sub 2} originates from EG reforming. - Abstract: Pt nanoparticles were loaded on anatase TiO{sub 2} by the photodeposition method to investigate their photocatalytic activity for H{sub 2} evolution in an aqueous solution containing a certain amount of ethylene glycol (EG) as the sacrificial agent. The surface properties and chemical states of the Pt/TiO{sub 2} sample were characterized by X-ray powder diffraction analysis, Brunauer–Emmett–Teller surface area analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and electrochemical resistance. The aqueous-phase photocatalytic EG reforming using Pt/TiO{sub 2} and anatase TiO{sub 2} generated not only H{sub 2} and CO{sub 2}, but also CO, CH{sub 4}, C{sub 2}H{sub 6}, and C{sub 2}H{sub 4}. Moreover, the amount of formate and acetate complexes in the solution increased gradually. The EG adsorption and gas-phase intermediates during photocatalytic reaction processes were investigated by the in situ FTIR spectrum. Finally, the photocatalytic EG reforming reaction mechanism was elucidated. This helped to better understand the role of a sacrificial agent in a photocatalytic hydrogen production.

Effects of indium contents on photocatalytic performance of ZnIn_2S_4 for hydrogen evolution under visible light

International Nuclear Information System (INIS)

Song, Kelin; Zhu, Rongshu; Tian, Fei; Cao, Gang; Ouyang, Feng

2015-01-01

A series of ZnIn_xS_4_+_y (x=1.6, 2.0, 2.3, 2.6, 2.9, 3.1) photocatalysts were synthesized via a facile hydrothermal method and characterized by various analytical techniques, such as XRD, EDS, UV–vis DRS, SEM, TEM, BET and PL. The ZnIn_xS_4_+_y photocatalysts had a similar crystal structure. With the increase of indium content, the absorption edges of ZnIn_xS_4_+_y photocatalysts shifted to longer wavelength, their crystal sizes decreased firstly and then increased and the variation of the specific surface area and total pore volume was exactly opposite. Especially, when x=2.3, ZnIn_2_._3S_4_+_y catalyst had smallest crystal size, largest specific surface area and total pore volume. Additionally, the morphology of ZnIn_xS_4_+_y greatly depended on the contents of indium. The photocatalytic activity of ZnIn_xS_4_+_y was evaluated by photocatalytic hydrogen production from water under visible light. The ZnIn_2_._3S_4_+_y sample had the highest photocatalytic activity among these ZnIn_xS_4_+_y photocatalysts and its hydrogen production rate was 363 μmol/g h. - Graphical abstract: First, a series of catalysts were synthesized. And then those were characterized by various analytical techniques (such as SEM). finally, The photocatalytic activity of catalyst was evaluated by photocatalytic hydrogen production from water under visible light. - Highlights: • The photocatalytic property was studied upon visible-light irradiation. • ZnIn_xS_4_+_y photocatalysts show superior photocatalytic activity. • The catalyst of grain size, morphology and BET are related to indium content. • ZnIn_xS_4_+_y photocatalysts were synthesized via a facile hydrothermal method.

Formation of multilayer-Eosin Y-sensitized TiO{sub 2} via Fe{sup 3+} coupling for efficient visible-light photocatalytic hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Li, Yuexiang; Guo, Miaomiao; Peng, Shaoqin [Department of Chemistry, Nanchang University, Nanchang 330031 (China); Lu, Gongxuan; Li, Shuben [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2009-07-15

An efficient visible-light active photocatalyst of multilayer-Eosin Y-sensitized TiO{sub 2} is prepared through linkage of Fe{sup 3+} between not only TiO{sub 2} and Eosin Y but also different Eosin Y molecules to form three-dimensional polymeric dye structure. The multilayer-dye-sensitized photocatalyst is found to have high light harvesting efficiency and photocatalytic activity for hydrogen evolution under visible light irradiation ({lambda} > 420 nm). On the optimum conditions (1:1 initial molar ratio of Eosin Y to Fe(NO{sub 3}){sub 3}, initial 10 x 10{sup -3} M Eosin Y, and 1.0 wt% Pt deposited by in situ photoreduction), its maximal apparent quantum yield for hydrogen evolution is 19.1% from aqueous triethanolamine solution (TEOA aq). The present study highlights linking between dye molecules via metal ions as a general way to develop efficient visible-light photocatalyst. (author)

Nano cobalt oxides for photocatalytic hydrogen production

KAUST Repository

Mangrulkar, Priti A.

2012-07-01

Nano structured metal oxides including TiO 2, Co 3O 4 and Fe 3O 4 have been synthesized and evaluated for their photocatalytic activity for hydrogen generation. The photocatalytic activity of nano cobalt oxide was then compared with two other nano structured metal oxides namely TiO 2 and Fe 3O 4. The synthesized nano cobalt oxide was characterized thoroughly with respect to EDX and TEM. The yield of hydrogen was observed to be 900, 2000 and 8275 mmol h -1 g -1 of photocatalyst for TiO 2, Co 3O 4 and Fe 3O 4 respectively under visible light. It was observed that the hydrogen yield in case of nano cobalt oxide was more than twice to that of TiO 2 and the hydrogen yield of nano Fe 3O 4 was nearly four times as compared to nano Co 3O 4. The influence of various operating parameters in hydrogen generation by nano cobalt oxide was then studied in detail. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Photocatalytic hydrogen evolution of palladium nanoparticles decorated black TiO2 calcined in argon atmosphere

Science.gov (United States)

Wu, Ming-Chung; Hsiao, Kai-Chi; Chang, Yin-Hsuan; Chan, Shun-Hsiang

2018-02-01

Black TiO2 nanoparticles (BTN) was prepared by sol-gel derived precursor calcined in an argon atmosphere. The synthesized BTN with trivalent titanium ion, structural defect, and oxygen vacancy shows a remarkably high absorbance in the visible light spectrum. BTN thus behaves a higher visible-active nanoreactor than white TiO2 nanoparticles (WTN) in the aqueous solution for organic pollutant degradation. Moreover, palladium decoration on the BTN surface (Pd-BTN) demonstrates a fascinating clean energy application. The obtained Pd-BTN fulfills a satisfied green material demand in the photocatalytic hydrogen production application. Pd-BTN calcined at 400 °C (Pd-BTN-400) shows the high photocatalytic hydrogen generation rate of 5200 μmol/g h under UV-A irradiation and 9300 μmol/g h under UV-B irradiation, respectively. The well-developed material, Pd-BTN-400, could be one of the best solutions in the concern of clean energy and water-purification with regard to the continuous environmental issue.

Highly Efficient Photocatalytic Hydrogen Production of Flower-like Cadmium Sulfide Decorated by Histidine

Science.gov (United States)

Wang, Qizhao; Lian, Juhong; Li, Jiajia; Wang, Rongfang; Huang, Haohao; Su, Bitao; Lei, Ziqiang

2015-09-01

Morphology-controlled synthesis of CdS can significantly enhance the efficiency of its photocatalytic hydrogen production. In this study, a novel three-dimensional (3D) flower-like CdS is synthesized via a facile template-free hydrothermal process using Cd(NO3)2•4H2O and thiourea as precursors and L-Histidine as a chelating agent. The morphology, crystal phase, and photoelectrochemical performance of the flower-like CdS and pure CdS nanocrystals are carefully investigated via various characterizations. Superior photocatalytic activity relative to that of pure CdS is observed on the flower-like CdS photocatalyst under visible light irradiation, which is nearly 13 times of pure CdS. On the basis of the results from SEM studies and our analysis, a growth mechanism of flower-like CdS is proposed by capturing the shape evolution. The imidazole ring of L-Histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles. Furthermore, the photocatalytic contrast experiments illustrate that the as-synthesized flower-like CdS with L-Histidine is more stable than CdS without L-Histidine in the hydrogen generation.

TiO2 promoted by two different non-noble metal cocatalysts for enhanced photocatalytic H2 evolution

International Nuclear Information System (INIS)

Lin, Jing-Dong; Yan, Shi; Huang, Qin-Dong; Fan, Mei-Ting; Yuan, You-Zhu; Tan, Timothy Thatt-Yang; Liao, Dai-Wei

2014-01-01

TiO 2 photocatalysts modified by cobalt and nickel cocatalysts were prepared via polymerized complex method (PCM) and evaluated by photocatalytic hydrogen evolution. Hydrogen generation in 6 h for the TiO 2 promoted by cobalt and nickel (0.1%Co + 0.2%Ni/TiO 2 ) is about two times (2456 μmol H 2 ) compared to that of TiO 2 promoted only by cobalt (1180 μmol H 2 for 0.1%Co/TiO 2 ) or nickel (1127 μmol H 2 for 0.2%Ni/TiO 2 ), and mechanically mixed TiO 2 promoted by cobalt and TiO 2 promoted by nickel (0.1%Co/TiO 2 :0.2%Ni/TiO 2 = 1:1 (m/m), 1282 μmol H 2 ). The high photocatalytic H 2 evolution activity over TiO 2 promoted by cobalt and nickel is ascribed to enhanced photo response due to the presence of cobalt and nickel impurity level, and effective separation of photogenerated electrons and holes due to the synergistic effect of cobalt and nickel, which serve as active sites for H 2 evolution reaction (HER) and oxidation reaction (OR) respectively. This study demonstrates a viable strategy to design more active photocatalysts for photocatalytic H 2 evolution by substituting noble metals with more abundant elements using as HER and OR cocatalysts, respectively.

Physicochemical impact of zeolites as the support for photocatalytic hydrogen production using solar-activated TiO2-based nanoparticles

International Nuclear Information System (INIS)

Taheri Najafabadi, Amin; Taghipour, Fariborz

2014-01-01

Highlights: • Zeolite chemical properties are crucial to photocatalytic hydrogen production. • Basic zeolite, TiO 2 , heteropolyacid and cobalt together are active under visible light. • TiO 2 impregnation on zeolite causes band gap widening and band edges’ anodic shift. • Heteropolyacid enhances the visible light activity of the photocatalyst. • Zeolite’s basicity can overshadow the anodic shift, advancing hydrogen evolution. - Abstract: Silico-aluminates (zeolites) have been recently utilized promisingly as the support for photocatalytic hydrogen production using solar-activated TiO 2 -based nanoparticles. Aside from conventional advantages offered by the supports in photocatalysis, we demonstrate the unique physicochemical impact of zeolites on photocatalytic hydrogen production. Beside zeolites, our synthesized materials comprise titanium dioxide (TiO 2 ) as the semiconductor, cobalt ions as the hydrogen evolution sites, and heteropolyacids (HPAs) as the multifunctional solid acids with significant excitability under visible light. Four classes of zeolites (Na-Y, Na-mordenite, H-Y, and H-beta) with different Si/Al ratios and sodium contents were evaluated. Among the studied photocatalysts, Na-Y and Na-mordenite containing 10 wt% titania emerged as the potential candidates for the hydrogen evolution reaction, with corresponding rates of 250.8 and 187.2 μmol/g h, in comparison to 84.2 μmol/g h for Degussa P25; while these values for H-Y and H-beta were 96.8 and 100.1 μmol/g h, respectively. The higher photocatalytic activity of the first two classes is attributed to the basicity of the zeolite matrix, which is possibly due to the pH dependency of the TiO 2 band edges. The results indicate the importance of controlling the chemical properties of the zeolite as a photocatalyst support through the selection of suitable types. Furthermore, our analyses show that the precise pore size distribution of the zeolite framework rules over accommodating the

Enhanced photocatalytic activity for H2 evolution under irradiation of UV-vis light by Au-modified nitrogen-doped TiO2.

Science.gov (United States)

Zhao, Weirong; Ai, Zhuyu; Dai, Jiusong; Zhang, Meng

2014-01-01

Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV-vis light, respectively. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and photoelectrochemical characterizations. DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV-vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2). This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR) effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of TiO2 and increased the utilization of solar energy, greatly

Enhanced photocatalytic activity for H2 evolution under irradiation of UV-vis light by Au-modified nitrogen-doped TiO2.

Directory of Open Access Journals (Sweden)

Weirong Zhao

Full Text Available BACKGROUND PURPOSE: Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. METHODS: Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV-vis light, respectively. The samples were characterized using X-ray diffraction (XRD, transmission electron microscopy (TEM, X-ray photoelectron spectroscopy (XPS, UV-vis diffuse reflectance spectroscopy (DRS, photoluminescence spectroscopy (PL, and photoelectrochemical characterizations. RESULTS: DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV-vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2. This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. CONCLUSION: Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of

WS2 as an Effective Noble-Metal Free Cocatalyst Modified TiSi2 for Enhanced Photocatalytic Hydrogen Evolution under Visible Light Irradiation

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Dongmei Chu

2016-09-01

Full Text Available A noble-metal free photocatalyst consisting of WS2 and TiSi2 being used for hydrogen evolution under visible light irradiation, has been successfully prepared by in-situ formation of WS2 on the surface of TiSi2 in a thermal reaction. The obtained samples were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDX, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. The results demonstrate that WS2 moiety has been successfully deposited on the surface of TiSi2 and some kind of chemical bonds, such as Ti-S-W and Si-S-W, might have formed on the interface of the TiSi2 and WS2 components. Optical and photoelectrochemical investigations reveal that WS2/TiSi2 composite possesses lower hydrogen evolution potential and enhanced photogenerated charge separation and transfer efficiency. Under 6 h of visible light (λ > 420 nm irradiation, the total amount of hydrogen evolved from the optimal WS2/TiSi2 catalyst is 596.4 μmol·g−1, which is around 1.5 times higher than that of pure TiSi2 under the same reaction conditions. This study shows a paradigm of developing the effective, scalable and inexpensive system for photocatalytic hydrogen generation.

TiO2/ZnS/CdS Nanocomposite for Hydrogen Evolution and Orange II Dye Degradation

Directory of Open Access Journals (Sweden)

Václav Štengl

2011-01-01

Full Text Available TiO2/ZnS/CdS composites for photocatalytic hydrogen production from water were prepared by homogeneous hydrolysis of aqueous solutions mixture of TiOSO4, ZnSO4, and CdSO4 with thioacetamide. Hydrogen evolution was observed in the presence of palladium and platinum nanoparticles deposited on TiO2/ZnS/CdS composites. The morphology was obtained by scanning electron microscopy, the nitrogen adsorption-desorption was used for determination of surface area (BET and porosity. The method of UV-VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies of prepared TiO2/ZnS/CdS nano-composites. The photocatalytic activity of the prepared samples were assessed by photocatalytic decomposition of Orange II dye in an aqueous slurry under UV irradiation at 365 nm wavelength and visible light up to 400 nm wavelength. Doped titanium dioxide by the CdS increased band-gap energy and doping with ZnS increased photocatalytic activity. The best photocatalytic activity for H2 evolution shows sample named TiZnCd7 on surface deposited with palladium, which contains 20.21% TiO2, 78.5% ZnS, and 1.29% CdS.

Effects of indium contents on photocatalytic performance of ZnIn{sub 2}S{sub 4} for hydrogen evolution under visible light

Energy Technology Data Exchange (ETDEWEB)

Song, Kelin [Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055 (China); Zhu, Rongshu, E-mail: rszhu@hitsz.edu.cn [Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055 (China); Public Platform for Technological Service in Urban Waste Reuse and Energy Regeneration, Shenzhen 518055 (China); Tian, Fei [Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055 (China); Cao, Gang, E-mail: caog@hotmail.com [Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055 (China); Public Platform for Technological Service in Urban Waste Reuse and Energy Regeneration, Shenzhen 518055 (China); Ouyang, Feng [Harbin Institute of Technology Shenzhen Graduate School, Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen 518055 (China); Public Platform for Technological Service in Urban Waste Reuse and Energy Regeneration, Shenzhen 518055 (China)

2015-12-15

A series of ZnIn{sub x}S{sub 4+y} (x=1.6, 2.0, 2.3, 2.6, 2.9, 3.1) photocatalysts were synthesized via a facile hydrothermal method and characterized by various analytical techniques, such as XRD, EDS, UV–vis DRS, SEM, TEM, BET and PL. The ZnIn{sub x}S{sub 4+y} photocatalysts had a similar crystal structure. With the increase of indium content, the absorption edges of ZnIn{sub x}S{sub 4+y} photocatalysts shifted to longer wavelength, their crystal sizes decreased firstly and then increased and the variation of the specific surface area and total pore volume was exactly opposite. Especially, when x=2.3, ZnIn{sub 2.3}S{sub 4+y} catalyst had smallest crystal size, largest specific surface area and total pore volume. Additionally, the morphology of ZnIn{sub x}S{sub 4+y} greatly depended on the contents of indium. The photocatalytic activity of ZnIn{sub x}S{sub 4+y} was evaluated by photocatalytic hydrogen production from water under visible light. The ZnIn{sub 2.3}S{sub 4+y} sample had the highest photocatalytic activity among these ZnIn{sub x}S{sub 4+y} photocatalysts and its hydrogen production rate was 363 μmol/g h. - Graphical abstract: First, a series of catalysts were synthesized. And then those were characterized by various analytical techniques (such as SEM). finally, The photocatalytic activity of catalyst was evaluated by photocatalytic hydrogen production from water under visible light. - Highlights: • The photocatalytic property was studied upon visible-light irradiation. • ZnIn{sub x}S{sub 4+y} photocatalysts show superior photocatalytic activity. • The catalyst of grain size, morphology and BET are related to indium content. • ZnIn{sub x}S{sub 4+y} photocatalysts were synthesized via a facile hydrothermal method.

In situ growth of CdS nanoparticles on UiO-66 metal-organic framework octahedrons for enhanced photocatalytic hydrogen production under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Zhou, Jian-Jian; Wang, Rong; Liu, Xin-Ling; Peng, Fu-Min [School of Chemistry and Chemical Engineering and Innovation Lab for Clean Energy & Green Catalysis, Anhui University, Hefei 230601 (China); Li, Chuan-Hao, E-mail: chuanhao.li@yale.edu [School of Chemistry and Chemical Engineering and Innovation Lab for Clean Energy & Green Catalysis, Anhui University, Hefei 230601 (China); Department of Chemical & Environmental Engineering, Yale University, New Haven 06511 (United States); Teng, Fei [Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Sciences and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Yuan, Yu-Peng, E-mail: yupengyuan@ahu.edu.cn [School of Chemistry and Chemical Engineering and Innovation Lab for Clean Energy & Green Catalysis, Anhui University, Hefei 230601 (China); Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, School of Environmental Sciences and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China)

2015-08-15

Graphical abstract: Enhanced photocatalytic hydrogen generation was achieved though constructing the CdS/UiO-66 MOF hybrids. In addition, the resultant hybrids show excellent photostability for hydrogen generation. - Highlights: • CdS nanoparticles were hydrothermally grown on UiO-66 octahedrons. • The resultant CdS/UiO-66 hybrids show enhanced photocatalytic H{sub 2} generation under visible light irradiation. • CdS/UiO-66 hybrids possess excellent photostability for long-term hydrogen generation. - Abstract: CdS nanoparticles acting as photosensitizer was grown in situ upon UiO-66 metal-organic framework octahedrons through a hydrothermal process. The resultant CdS/UiO-66 hybrid photocatalysts show remarkably active hydrogen evolution under visible light irradiation as compared to CdS and UiO-66 alone. The optimum hybrid with 16 wt% CdS loading shows a hydrogen production rate of 235 μmol h{sup −1}, corresponding to 1.2% quantum efficiency at 420 nm. The improved photocatalytic hydrogen production over hybrid CdS/UiO-66 is ascribed to the efficient interfacial charge transfer from CdS to UiO-66, which effectively suppresses the recombination of photogenerated electron-hole pairs and thereby enhancing the photocatalytic efficiency.

A Facile Method for the Preparation of Colored Bi4Ti3O12−x Nanosheets with Enhanced Visible-Light Photocatalytic Hydrogen Evolution Activity

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Yizeng Zhang

2018-04-01

Full Text Available Bi4Ti3O12−x nanosheet photocatalysts with abundant oxygen vacancies are fabricated by a facile solid-state chemical reduction method for the first time. This method is simple in operation, has short reaction time, and can be conducted at mild temperatures (300~400 °C. The electron paramagnetic resonance, thermogravimetric analysis, X-ray photoelectron spectrometer, and positron annihilation lifetime spectra results indicate that oxygen vacancies are produced in Bi4Ti3O12−x, and they can be adjusted by tuning the reduction reaction conditions. Control experiments show that the reduction time and temperature have great influences on the photocatalytic activities of Bi4Ti3O12−x. The optimal Bi4Ti3O12−x is the sample undergoing the reduction treatment at 350 °C for 60 min and it affords a hydrogen evolution rate of 129 μmol·g−1·h−1 under visible-light irradiation, which is about 3.4 times that of the pristine Bi4Ti3O12. The Bi4Ti3O12−x photocatalysts have good reusability and storage stability and can be used to decompose formaldehyde and formic acid for hydrogen production. The surface oxygen vacancies states result in the broadening of the valence band and the narrowing of the band gap. Such energy level structure variation helps promote the separation of photo-generated electron-hole pairs thus leading to enhancement in the visible-light photocatalytic hydrogen evolution. Meanwhile, the narrowing of the band gap leads to a broader visible light absorption of Bi4Ti3O12−x.

Effect of annealing ambience on the formation of surface/bulk oxygen vacancies in TiO2 for photocatalytic hydrogen evolution

Science.gov (United States)

Hou, Lili; Zhang, Min; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

2018-01-01

The surface and bulk oxygen vacancy have a prominent effect on the photocatalytic performance of TiO2. In this study, TiO2 possessing different types and concentration of oxygen vacancies were prepared by annealing nanotube titanic acid (NTA) at various temperatures in air or vacuum atmosphere. TiO2 with the unitary bulk single-electron-trapped oxygen vacancies (SETOVs) formed when NTA were calcined in air. Whereas, TiO2 with both bulk and surface oxygen vacancies were obtained when NTA were annealed in vacuum. The series of TiO2 with different oxygen vacancies were systematically characterized by TEM, XRD, PL, XPS, ESR, and TGA. The PL and ESR analysis verified that surface oxygen vacancies and more bulk oxygen vacancies could form in vacuum atmosphere. Surface oxygen vacancies can trap electron and hinder the recombination of photo-generated charges, while bulk SETOVs act as the recombination center. The surface or bulk oxygen vacancies attributed different roles on the photo-absorbance and activity, leading that the sample of NTA-A400 displayed higher hydrogen evolution rate under UV light, whereas NTA-V400 displayed higher hydrogen evolution rate under visible light because bulk SETOVs can improve visible light absorption because sub-band formed by bulk SETOVs prompted the secondary transition of electron excited.

Photocatalytic hydrogen generation with Ag-loaded LiNbO3

Indian Academy of Sciences (India)

Administrator

rhodamine B decomposition under solar illumination was also reported (Stock ... photocatalytic hydrogen production. ... lytic hydrogen production from a methanol aqueous solu- .... estimated bandgap energy of Nb2O5 and LiNbO3 samples.

Gold nanoparticles embedded in Ta 2 O 5 /Ta 3 N 5 as active visible-light plasmonic photocatalysts for solar hydrogen evolution

KAUST Repository

Luo, Yujing

2014-07-10

Here, we demonstrate a new recreating photocatalytic activity of a Nano Au/Ta2O5 composite for hydrogen evolution from water as a visible-light-responsive plasmonic photocatalyst by embedding Au nanoparticles in a Ta2O5 host lattice. The Nano Au/Ta2O 5 composite samples were prepared through a simple Pechini-type sol-gel process. Further nitridating Nano Au/Ta2O5 composite samples in ammonia flow at 1123 K yielded Nano Au/Ta3N 5 composite samples. The obtained Nano Au/Ta3N5 composite exhibited a significantly enhanced photocatalytic activity in the visible region for hydrogen evolution from water compared with blank Ta 3N5 nanoparticles. UV-visible diffuse reflectance spectra and photocatalytic activity measurements indicated that the excitation of surface plasmon resonance of Au nanoparticles is responsible for the new recreating photocatalytic activity of the Nano Au/Ta2O5 composite and significantly enhanced photocatalytic activity of the Nano Au/Ta3N5 composite for hydrogen evolution in the visible region, which might be ascribed to the charge transfer effect in Nano Au/Ta 2O5 composite and the synergetic effect of charge transfer and near-field electromagnetic effect in Nano Au/Ta3N5 composite induced by surface plasmon resonance of embedded Au nanoparticles. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems for photocatalytic, photovoltaic and other optoelectronic devices. © the Partner Organisations 2014.

Photocatalytic and Photoelectrochemical Water Splitting by Inorganic Materials

KAUST Repository

Deng, Xiaohui

2012-12-01

Hydrogen has been identified as a potential energy carrier due to its high energy capacity and environmental harmlessness. Compared with hydrogen production from hydrocarbons such as methane and naphtha in a conventional hydrogen energy system, photocatalytic hydrogen evolution from water splitting offers a more economic approach since it utilizes the abundant solar irradiation as energy source and water as initial reactant. Powder photocatalyst, which generates electrons and holes under illumination, is the origin where the overall reaction happens. High solar energy conversion efficiency especially from visible range is commonly the target. Besides, cocatalyst for hydrogen and oxygen evolution is also playing an essential role in facilitating the charge separation and enhancing the kinetics. In this thesis, the objective is to achieve high energy conversion efficiency towards water splitting from diverse aspects. The third chapter focuses on a controllable method to fabricate metal pattern, which is candidate for hydrogen evolution cocatalyst while chapter 4 is on the combination of strontium titanium oxide (SrTiO3) with graphene oxide (GO) for a better photocatalytic performance. In the last chapter, photoelectrochemical water splitting by Ta3N5 photoanode and FeOOH as a novel oxygen evolution cocatalyst has been investigated.

Surface modification of mixed-phase hydrogenated TiO{sub 2} and corresponding photocatalytic response

Energy Technology Data Exchange (ETDEWEB)

Samsudin, Emy Marlina [Nanotechnology and Catalysis Research Center, University of Malaya, 50603 Kuala Lumpur (Malaysia); Hamid, Sharifah Bee Abd, E-mail: sharifahbee@um.edu.my [Nanotechnology and Catalysis Research Center, University of Malaya, 50603 Kuala Lumpur (Malaysia); Juan, Joon Ching; Basirun, Wan Jefrey [Nanotechnology and Catalysis Research Center, University of Malaya, 50603 Kuala Lumpur (Malaysia); Kandjani, Ahmad Esmaeiljadeh [Centre of Advanced Materials and Industrial Chemistry, RMIT University, Melbourne 3001 (Australia)

2015-12-30

Graphical abstract: - Highlights: • Grayish-blue hydrogenated TiO{sub 2} powder with surface disorders. • Extension of photons absorption covering infrared region. • Presence of surface Ti{sup 3+} and oxygen vacancies facilitates photocatalytic activity. • Fewer formation of charge traps for hydrogenated TiO{sub 2}. • Superior photo-kinetics performance of hydrogenated TiO{sub 2}. - Abstract: Preparation of highly photo-activated TiO{sub 2} is achievable by hydrogenation at constant temperature and pressure, with controlled hydrogenation duration. The formation of surface disorders and Ti{sup 3+} is responsible for the color change from white unhydrogenated TiO{sub 2} to bluish-gray hydrogenated TiO{sub 2}. This color change, together with increased oxygen vacancies and Ti{sup 3+} enhanced the solar light absorption from UV to infra-red region. Interestingly, no band gap narrowing is observed. The photocatalytic activity in the UV and visible region is controlled by Ti{sup 3+} and oxygen vacancies respectively. Both Ti{sup 3+} and oxygen vacancies increases the electron density on the catalyst surface thus facilitates ·OH radicals formation. The lifespan of surface photo-excited electrons and holes are also sustained thus prevents charge carrier recombination. However, excessive amount of oxygen vacancies deteriorates the photocatalytic activity as it serves as charge traps. Hydrogenation of TiO{sub 2} also promotes the growth of active {0 0 1} facets and facilitates the photocatalytic activity by higher concentration of surface OH radicals. However, the growth of {0 0 1} facets is small and insignificant toward the overall photo-kinetics. This work also shows that larger role is played by Ti{sup 3+} and oxygen vacancies rather than the surface disorders created during the hydrogenation process. It also demonstrates the ability of hydrogenated TiO{sub 2} to absorb wider range of photons even though at a similar band gap as unhydrogenated TiO{sub 2}. In

In situ photodeposition of amorphous CoSx on the TiO2 towards hydrogen evolution

Science.gov (United States)

Chen, Feng; Luo, Wei; Mo, Yanping; Yu, Huogen; Cheng, Bei

2018-02-01

Cocatalyst modification of photocatalysts is an important strategy to enhance the photocatalytic performance by promoting effective separation of photoinduced electron-hole pairs and providing abundant active sites. In this study, a facile in situ photodeposition method was developed to prepare amorphous CoSx-modified TiO2 photocatalysts. It was found that amorphous CoSx nanoparticles were solidly loaded on the TiO2 surface, resulting in a greatly improved photocatalytic H2-evolution performance. When the amount of amorphous CoSx was 10 wt%, the hydrogen evolution rate of the CoSx/TiO2 reached 119.7 μmol h-1, which was almost 16.7 times that of the pure TiO2. According to the above experimental results, a reasonable mechanism of improved photocatalytic performance is proposed for the CoSx/TiO2 photocatalysts, namely, the photogenerated electrons of TiO2 can rapidly transfer to amorphous CoSx nanoparticles due to the solid contact between them, and then amorphous CoSx can provide plenty of sulfur active sites to rapidly adsorb protons from solution to produce hydrogen by the photogenerated electrons. Considering the facile synthesis method, the present cheap and highly efficient amorphous CoSx-modified TiO2 photocatalysts would have great potential for practical use in photocatalytic H2 production.

Wrinkle-free atomically thin CdS nanosheets for photocatalytic hydrogen evolution

Science.gov (United States)

Pan, Ziwei; Li, Junnan; Zhou, Kebin

2018-05-01

Two-dimensional (2D) nanosheets of atomic thickness have attracted extensive research interest recently. In this work, atomically thin (0.7 nm) flat CdS (F-CdS) nanosheets of several tens of micrometers in lateral size were synthesized by a solvent-thermal method. The as-synthesized F-CdS could maintain flat morphology well in solution, while irreversible wrinkles could be generated after drying, forming wrinkled CdS (W-CdS) samples. It was revealed that the formation of wrinkles could reduce light absorbance, narrow the band gap, move down the conduction band position and accelerate electron–hole recombination. As photocatalysts, the F-CdS achieved a photocatalytic H2 evolution rate of 138.7 mmol g‑1 h‑1 without any co-catalyst under visible light, which was much higher than that of the W-CdS sample (with an H2 evolution rate of only 52.8 mmol g‑1 h‑1). This work demonstrates that great attention should be paid to the wrinkles in 2D materials as photocatalysts.

Enhancement of photocatalytic H2 evolution of eosin Y-sensitized reduced graphene oxide through a simple photoreaction

Directory of Open Access Journals (Sweden)

Weiying Zhang

2014-06-01

Full Text Available A graphene oxide (GO solution was irradiated by a Xenon lamp to form reduced graphene oxide (RGO. After irradiation, the epoxy, the carbonyl and the hydroxy groups are gradually removed from GO, resulting in an increase of sp2 π-conjugated domains and defect carbons with holes for the formed RGO. The RGO conductivity increases due to the restoration of sp2 π-conjugated domains. The photocatalytic activity of EY-RGO/Pt for hydrogen evolution was investigated with eosin Y (EY as a sensitizer of the RGO and Pt as a co-catalyst. When the irradiation time is increased from 0 to 24 h the activity rises, and then reaches a plateau. Under optimum conditions (pH 10.0, 5.0 × 10−4 mol L−1 EY, 10 μg mL−1 RGO, the maximal apparent quantum yield (AQY of EY-RGO24/Pt for hydrogen evolution rises up to 12.9% under visible light irradiation (λ ≥ 420 nm, and 23.4% under monochromatic light irradiation at 520 nm. Fluorescence spectra and transient absorption decay spectra of the EY-sensitized RGO confirm that the electron transfer ability of RGO increases with increasing irradiation time. The adsorption quantity of EY on the surface of RGO enhances, too. The two factors ultimately result in an enhancement of the photocatalytic hydrogen evolution over EY-RGO/Pt with increasing irradiation time. A possible mechanism is discussed.

Comparative Study on The Photocatalytic Hydrogen Production from Methanol over Cu-, Pd-, Co- and Au-Loaded TiO2

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Udani P.P.C.

2015-09-01

Full Text Available Photocatalytic hydrogen production from a methanol-water solution was investigated in a semi-continuous reactor over different metal-loaded TiO2 catalysts under UltraViolet (UV light irradiation. The catalysts were mainly prepared by the incipient wetness impregnation method by varying the metal weight ratio in the range of 1-10 wt%. The effects of metal loading and H2 pre-treatment on the photocatalytic activity were investigated. In addition, the activity of the catalysts was also compared with a reference Au-TiO2 catalyst from the World Gold Council (WGC. The photocatalysts were characterized by using X-Ray Diffraction (XRD and N2 physisorption before and after the activity measurements. The photocatalytic activity decreased in the order of Pd > Au > Cu > Co in the comparative study of Cu-TiO2, Co-TiO2, Au-TiO2 and Pd-TiO2. Optimum hydrogen evolution was achieved with 5 wt% Pd-TiO2 and 5 wt% Cu-TiO2.

Rational construction of multiple interfaces in ternary heterostructure for efficient spatial separation and transfer of photogenerated carriers in the application of photocatalytic hydrogen evolution

Science.gov (United States)

Shi, Jian-Wen; Ma, Dandan; Zou, Yajun; Fan, Zhaoyang; Shi, Jinwen; Cheng, Linhao; Ji, Xin; Niu, Chunming

2018-03-01

The design of efficient and stable photocatalyst plays a critical role in the photocatalytic hydrogen evolution from water splitting. Herein, we develop a novel ZnS/CdS/ZnO ternary heterostructure by the in-situ sulfuration of CdS/ZnO, which includes four contact interfaces: CdS-ZnS interface, ZnS-ZnO interface, CdS-ZnO interface and ZnS-CdS-ZnO ternary interface, forming three charge carrier-transfer modes (type-I, type-II and direct Z-scheme) through five carrier-transfer pathways. As a result, the separation and transfer of photoexcited electron-hole pairs are promoted significantly, resulting in a high hydrogen evolution rate of 44.70 mmol h-1 g-1, which is 2, 3.7 and 8 times higher than those of binary heterostructures, CdS/ZnO, CdS/ZnS and ZnS/ZnO, respectively, and 26.5, 280 and 298 times higher than those of single CdS, ZnO and ZnS, respectively. As a counterpart ternary heterostructure, CdS/ZnS/ZnO contains only two interfaces: CdS-ZnS interface and ZnS-ZnO interface, which form two charge carrier-transfer modes (type-I and type-II) through two carrier-transfer pathways, leading to its much lower hydrogen evolution rate (27.25 mmol h-1 g-1) than ZnS/CdS/ZnO ternary heterostructure. This work is relevant for understanding the charge-transfer pathways between multi-interfaces in multicomponent heterojunctions.

One-pot synthesis of K-doped g-C3N4 nanosheets with enhanced photocatalytic hydrogen production under visible-light irradiation

Science.gov (United States)

Wang, Yanyun; Zhao, Shuo; Zhang, Yiwei; Fang, Jiasheng; Zhou, Yuming; Yuan, Shenhao; Zhang, Chao; Chen, Wenxia

2018-05-01

Graphite carbon nitride (g-C3N4), as a promising low cost, visible light driven conjugated polymer semiconductor photocatalyst, has attracted wide attentions from researchers. However, low light absorption efficiency and inadequate charge separation limit the potential applications of g-C3N4. This paper exhibits K-doped g-C3N4 prepared by a facile thermal polymerization with KBr as the K source. The experiments of photocatalytic hydrogen evolution demonstrate that KBr content strongly affects the activity of the catalyst. XRD, FT-IR, XPS, SEM, TEM, UV-vis diffuse reflectance spectra, photoluminescence (PL) characterization methods are used to study the effects of potassium on the catalyst performance. The results find that K-modified g-C3N4 has a narrower band gap and enhanced light harvesting properties. Moreover, the photocatalytic hydrogen evolution rate (HER) of the optimized K-doped g-C3N4 nanosheets (10 wt % KBr) reaches 1337.2 μmol g-1h-1, which is about 5.6 times in comparison with that of pure g-C3N4 (239.8 μmol g-1h-1). The doping of the potassium may increase the π-conjugated systems and accelerate the electron transport rate, then improve the photocatalytic properties. Based on the results of the analysis, a possible mechanism is proposed.

Photocatalytic hydrogen production under direct solar light in a CPC based solar reactor: Reactor design and preliminary results

International Nuclear Information System (INIS)

Jing Dengwei; Liu Huan; Zhang Xianghui; Zhao Liang; Guo Liejin

2009-01-01

In despite of so many types of solar reactors designed for solar detoxification purposes, few attempts have been made for photocatalytic hydrogen production, which in our option, is one of the most promising approaches for solar to chemical energy conversion. Addressing both the similarity and dissimilarity for these two processes and by fully considering the special requirements for the latter reaction, a Compound Parabolic Concentrator (CPC) based photocatalytic hydrogen production solar reactor has been designed for the first time. The design and optimization of this CPC based solar reactor has been discussed in detail. Preliminary results demonstrated that efficient photocatalytic hydrogen production under direct solar light can be accomplished by coupling tubular reactors with CPC concentrators. It is anticipated that this first demonstration of concentrator-based solar photocatalytic hydrogen production would draw attention for further studies in this promising direction.

Room-temperature synthesis of Zn(0.80)Cd(0.20)S solid solution with a high visible-light photocatalytic activity for hydrogen evolution.

Science.gov (United States)

Wang, Dong-Hong; Wang, Lei; Xu, An-Wu

2012-03-21

Visible light photocatalytic H(2) production from water splitting is of great significance for its potential applications in converting solar energy into chemical energy. In this study, a series of Zn(1-x)Cd(x)S solid solutions with a nanoporous structure were successfully synthesized via a facile template-free method at room temperature. The obtained solid solutions were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS) and N(2) adsorption-desorption analysis. The solid solutions show efficient photocatalytic activity for H(2) evolution from aqueous solutions containing sacrificial reagents S(2-) and SO(3)(2-) under visible-light irradiation without a Pt cocatalyst, and loading of the Pt cocatalyst further improves the visible-light photocatalytic activity. The optimal photocatalyst with x = 0.20 prepared at pH = 7.3 displays the highest activity for H(2) evolution. The bare and 0.25 wt% Pt loaded Zn(0.80)Cd(0.20)S nanoparticles exhibit a high H(2) evolution rate of 193 μmol h(-1) and 458 μmol h(-1) under visible-light irradiation (λ ≥ 420 nm), respectively. In addition, the bare and 0.25 wt% Pt loaded Zn(0.80)Cd(0.20)S catalysts show a high H(2) evolution rate of 252 and 640 μmol h(-1) under simulated solar light irradiation, respectively. Moreover, the Zn(0.80)Cd(0.20)S catalyst displays a high photocatalytic stability for H(2) evolution under long-term light irradiation. The incorporation of Cd in the solid solution leads to the visible light absorption, and the high content of Zn in the solid solution results in a relatively negative conduction band, a modulated band gap and a rather wide valence bandwidth, which are responsible for the excellent photocatalytic performance of H(2) production and for the high photostability

Dye-Sensitized Photocatalytic Water Splitting and Sacrificial Hydrogen Generation: Current Status and Future Prospects

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Pankaj Chowdhury

2017-05-01

Full Text Available Today, global warming and green energy are important topics of discussion for every intellectual gathering all over the world. The only sustainable solution to these problems is the use of solar energy and storing it as hydrogen fuel. Photocatalytic and photo-electrochemical water splitting and sacrificial hydrogen generation show a promise for future energy generation from renewable water and sunlight. This article mainly reviews the current research progress on photocatalytic and photo-electrochemical systems focusing on dye-sensitized overall water splitting and sacrificial hydrogen generation. An overview of significant parameters including dyes, sacrificial agents, modified photocatalysts and co-catalysts are provided. Also, the significance of statistical analysis as an effective tool for a systematic investigation of the effects of different factors and their interactions are explained. Finally, different photocatalytic reactor configurations that are currently in use for water splitting application in laboratory and large scale are discussed.

Photocatalytic transformation of dyes and by-products in the presence of hydrogen peroxide.

Science.gov (United States)

Subba Rao, K V; Subrahmanyam, M; Boule, P

2003-08-01

The efficiency of the photocatalytic degradation of dyes and dyeing industry pollutants on immobilized photocatalysts can be improved by addition of hydrogen peroxide, due to its photocatalytic decomposition on TiO2. Experiments were carried out with two azodyes, Acid Orange-7 (AO-7) and Tartrazine (Tart), with 3-nitrobenzenesulfonic add (3-NBSA) which is a chemical intermediate in the dye industry and with real industrial wastewaters, using a thin-film fixed bed reactor. The effect of hydrogen peroxide is only significant for concentrations higher than 5 x 10(-3) M (170 mg l(-1)).

Modification of g-C{sub 3}N{sub 4} nanosheets by carbon quantum dots for highly efficient photocatalytic generation of hydrogen

Energy Technology Data Exchange (ETDEWEB)

Li, Kui; Su, Feng-Yun; Zhang, Wei-De, E-mail: zhangwd@scut.edu.cn

2016-07-01

Graphical abstract: Carbon quantum dots-modified graphitic carbon nitride nanosheets (CNNS/CQDs) catalysts with high and stable activity for photocatalytic generation of hydrogen through water splitting were successfully constructed. - Highlights: • Composite photocatalysts based on g-C{sub 3}N{sub 4} nanosheets and CQDs were prepared. • High visible light photocatalytic activity for H{sub 2} evolution. • Effective separation and transfer of charge carriers. - Abstract: Carbon quantum dots (CQDs) were deposited onto graphite-like carbon nitride nanosheets (CNNS) to form CNNS/CQDs composites. The prepared CNNS/CQDs composites exhibit much higher photocatalytic activity under visible light irradiation than pure CNNS do. The CNNS/CQDs-7 sample displays the highest photocatalytic performance, with H{sub 2} production rate of 116.1 μmol h{sup −1}, which is three times of that over pure CNNS (37.8 μmol h{sup −1}). Photoluminescence spectroscopy and photoelectrochemical (PEC) analysis reveal that the CQDs are favorable for trapping electrons and promoting the separation of photogenerated electron-hole pairs in CNNS. A possible photocatalytic mechanism of the enhanced photocatalytic performance for H{sub 2} generation over CNNS/CQDs will be proposed in this paper.

Efficient solar hydrogen production by photocatalytic water splitting: From fundamental study to pilot demonstration

Energy Technology Data Exchange (ETDEWEB)

Jing, Dengwei; Guo, Liejin; Zhao, Liang; Zhang, Ximin; Liu, Huan; Li, Mingtao; Shen, Shaohua; Liu, Guanjie; Hu, Xiaowei; Zhang, Xianghui; Zhang, Kai; Ma, Lijin; Guo, Penghui [State Key Lab of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, 28 Xianning West Road, Xi' an 710049 (China)

2010-07-15

Photocatalytic water splitting with solar light is one of the most promising technologies for solar hydrogen production. From a systematic point of view, whether it is photocatalyst and reaction system development or the reactor-related design, the essentials could be summarized as: photon transfer limitations and mass transfer limitations (in the case of liquid phase reactions). Optimization of these two issues are therefore given special attention throughout our study. In this review, the state of the art for the research of photocatalytic hydrogen production, both outcomes and challenges in this field, were briefly reviewed. Research progress of our lab, from fundamental study of photocatalyst preparation to reactor configuration and pilot level demonstration, were introduced, showing the complete process of our effort for this technology to be economic viable in the near future. Our systematic and continuous study in this field lead to the development of a Compound Parabolic Concentrator (CPC) based photocatalytic hydrogen production solar rector for the first time. We have demonstrated the feasibility for efficient photocatalytic hydrogen production under direct solar light. The exiting challenges and difficulties for this technology to proceed from successful laboratory photocatalysis set-up up to an industrially relevant scale are also proposed. These issues have been the object of our research and would also be the direction of our study in future. (author)

Nitrogen-Doped Graphene for Photocatalytic Hydrogen Generation.

Science.gov (United States)

Chang, Dong Wook; Baek, Jong-Beom

2016-04-20

Photocatalytic hydrogen (H2 ) generation in a water splitting process has recently attracted tremendous interest because it allows the direct conversion of clean and unlimited solar energy into the ideal energy resource of H2 . For efficient photocatalytic H2 generation, the role of the photocatalyst is critical. With increasing demand for more efficient, sustainable, and cost-effective photocatalysts, various types of semiconductor photocatalysts have been intensively developed. In particular, on the basis of its superior catalytic and tunable electronic properties, nitrogen-doped graphene is a potential candidate for a high-performance photocatalyst. Nitrogen-doped graphene also offers additional advantages originating from its unique two-dimensional sp(2) -hybridized carbon network including a large specific surface area and exceptional charge transport properties. It has been reported that nitrogen-doped graphene can play diverse but positive functions including photo-induced charge acceptor/meditator, light absorber from UV to visible light, n-type semiconductor, and giant molecular photocatalyst. Herein, we summarize the recent progress and general aspects of nitrogen-doped graphene as a photocatalyst for photocatalytic H2 generation. In addition, challenges and future perspectives in this field are also discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photocatalytic Hydrogen-Evolution Cross-Couplings: Benzene C-H Amination and Hydroxylation.

Science.gov (United States)

Zheng, Yi-Wen; Chen, Bin; Ye, Pan; Feng, Ke; Wang, Wenguang; Meng, Qing-Yuan; Wu, Li-Zhu; Tung, Chen-Ho

2016-08-17

We present a blueprint for aromatic C-H functionalization via a combination of photocatalysis and cobalt catalysis and describe the utility of this strategy for benzene amination and hydroxylation. Without any sacrificial oxidant, we could use the dual catalyst system to produce aniline directly from benzene and ammonia, and phenol from benzene and water, both with evolution of hydrogen gas under unusually mild conditions in excellent yields and selectivities.

Highly Efficient Photocatalytic Water Splitting over Edge-Modified Phosphorene Nanoribbons.

Science.gov (United States)

Hu, Wei; Lin, Lin; Zhang, Ruiqi; Yang, Chao; Yang, Jinlong

2017-11-01

Two-dimensional phosphorene with desirable optoelectronic properties (ideal band gap, high carrier mobility, and strong visible light absorption) is a promising metal-free photocatalyst for water splitting. However, the band edge positions of the valence band maximum (VBM) and conduction band maximum (CBM) of phosphorene are higher than the redox potentials in photocatalytic water splitting reactions. Thus, phosphorene can only be used as the photocathode for hydrogen evolution reaction as a low-efficiency visible-light-driven photocatalyst for hydrogen production in solar water splitting cells. Here, we propose a new mechanism to improve the photocatalytic efficiency of phosphorene nanoribbons (PNRs) by modifying their edges for full reactions in photocatalytic water splitting. By employing first-principles density functional theory calculations, we find that pseudohalogen (CN and OCN) passivated PNRs not only show desired VBM and CBM band edge positions induced by edge electric dipole layer, but also possess intrinsic optoelectronic properties of phosphorene, for both water oxidation and hydrogen reduction in photocatalytic water splitting without using extra energy. Furthermore, our calculations also predict that the maximum energy conversion efficiency of heterojunction solar cells consisting of different edge-modified PNRs can be as high as 20% for photocatalytic water splitting.

Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts

Science.gov (United States)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu

2017-02-01

Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H2) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu2MoS4) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H2 evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu2MoS4 nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu2MoS4nanosheets. These layered Cu2MoS4 nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H2 production by water splitting. We have obtained superior H2 production rates by using Cu2MoS4 loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Photocatalytic Water Splitting—The Untamed Dream: A Review of Recent Advances

Directory of Open Access Journals (Sweden)

Tahereh Jafari

2016-07-01

Full Text Available Photocatalytic water splitting using sunlight is a promising technology capable of providing high energy yield without pollutant byproducts. Herein, we review various aspects of this technology including chemical reactions, physiochemical conditions and photocatalyst types such as metal oxides, sulfides, nitrides, nanocomposites, and doped materials followed by recent advances in computational modeling of photoactive materials. As the best-known catalyst for photocatalytic hydrogen and oxygen evolution, TiO2 is discussed in a separate section, along with its challenges such as the wide band gap, large overpotential for hydrogen evolution, and rapid recombination of produced electron-hole pairs. Various approaches are addressed to overcome these shortcomings, such as doping with different elements, heterojunction catalysts, noble metal deposition, and surface modification. Development of a photocatalytic corrosion resistant, visible light absorbing, defect-tuned material with small particle size is the key to complete the sunlight to hydrogen cycle efficiently. Computational studies have opened new avenues to understand and predict the electronic density of states and band structure of advanced materials and could pave the way for the rational design of efficient photocatalysts for water splitting. Future directions are focused on developing innovative junction architectures, novel synthesis methods and optimizing the existing active materials to enhance charge transfer, visible light absorption, reducing the gas evolution overpotential and maintaining chemical and physical stability.

Graphitic carbon nitride nanosheet for photocatalytic hydrogen production: The impact of morphology and element composition

International Nuclear Information System (INIS)

Zhang, Zhao; Zhang, Yijie; Lu, Luhua; Si, Yanjie; Zhang, Si; Chen, Ying; Dai, Kai; Duan, Ping; Duan, Limei; Liu, Jinghai

2017-01-01

Highlights: • g-C_3N_4 with tunable morphology was prepared by varying pyrolysis time. • g-C_3N_4 showed reduced recombination of photogenerated electrons and holes. • g-C_3N_4 showed enhanced photocatalytic hydrogen evolution activity. - Abstract: The intrinsic morphology and basal plane defects on g-C_3N_4 nanosheet have important influences on its electronic structures and photocatalytic activity. In this work, we report extending thermal treatment time of g-C_3N_4 at 550 °C not only change the morphology of g-C_3N_4 but also element composition of g-C_3N_4. The morphology variation results in largely increased SSA from 40.22 to 117.27 m"2 g"−"1, obviously reduced pore size from 3.99 to 2.77 nm for g-C_3N_4 and formation of in-plane holes. Moreover, composition variation of g-C_3N_4 has also been found to have changed as the pyrolysis time extended. These changes have significant impact on the optical properties and photoelectrical characters of g-C_3N_4, which were investigated by UV-DSR, PL and Photocurrent measurement. The photocatalytic activity of g-C_3N_4 obtained via 9 h thermal treatment at 550 °C has shown highest photocatalytic activity, which is 1.77 times than that of g-C_3N_4 obtained via 3 h thermal treatment under visible irradiation and 1.99 times under UV irradiation respectively.

Visible-Light-Driven Hydrogen Evolution Using Planarized Conjugated Polymer Photocatalysts.

Science.gov (United States)

Sprick, Reiner Sebastian; Bonillo, Baltasar; Clowes, Rob; Guiglion, Pierre; Brownbill, Nick J; Slater, Benjamin J; Blanc, Frédéric; Zwijnenburg, Martijn A; Adams, Dave J; Cooper, Andrew I

2016-01-26

Linear poly(p-phenylene)s are modestly active UV photocatalysts for hydrogen production in the presence of a sacrificial electron donor. Introduction of planarized fluorene, carbazole, dibenzo[b,d]thiophene or dibenzo[b,d]thiophene sulfone units greatly enhances the H 2 evolution rate. The most active dibenzo[b,d]thiophene sulfone co-polymer has a UV photocatalytic activity that rivals TiO 2 , but is much more active under visible light. The dibenzo[b,d]thiophene sulfone co-polymer has an apparent quantum yield of 2.3 % at 420 nm, as compared to 0.1 % for platinized commercial pristine carbon nitride.

Gold nanoparticles embedded in Ta 2 O 5 /Ta 3 N 5 as active visible-light plasmonic photocatalysts for solar hydrogen evolution

KAUST Repository

Luo, Yujing; Liu, Xiaoming; Tang, Xinghua; Luo, Yan; Zeng, Qianyao; Deng, Xiaolei; Ding, Shaolei; Sun, Yiqun

2014-01-01

Here, we demonstrate a new recreating photocatalytic activity of a Nano Au/Ta2O5 composite for hydrogen evolution from water as a visible-light-responsive plasmonic photocatalyst by embedding Au nanoparticles in a Ta2O5 host lattice. The Nano Au/Ta2

Ag3PO4-TiO2-Graphene Oxide Ternary Composites with Efficient Photodegradation, Hydrogen Evolution, and Antibacterial Properties

Directory of Open Access Journals (Sweden)

Fu-Jye Sheu

2018-02-01

Full Text Available Ag3PO4-TiO2-graphene oxide ternary composite photocatalysts were fabricated by the photocatalytic reduction and ion exchange methods. The properties and photocatalytic activity of the composites were examined, and the photodegradation mechanism was investigated. More TiO2 nanoparticles in the composites were found to improve light absorption, but caused a larger impedance and inferior charge transport. Excess TiO2 nanoparticles distributed over the surfaces of Ag3PO4 and graphene oxide decreased the specific surface area and thus lowered light absorbance. An appropriate TiO2 content enhanced photocatalytic performance. When the molar ratio of Ag3PO4 to TiO2 was 0.6, the highest efficiency in photodegradation, hydrogen production (with a quantum efficiency of 8.1% and a hydrogen evolution rate of 218.7 μmole·g−1·h−1 and bacterial inactivation was achieved. Trapping experiments demonstrated that superoxide radicals and holes are the major active species involved in the photodegradation process.

Relationship between the electrochemical behavior of multiwalled carbon nanotubes (MWNTs) loaded with CuO and the photocatalytic activity of Eosin Y-MWNTs-CuO system

Science.gov (United States)

Bui, Duc-Nguyen; Kang, Shi-Zhao; Qin, Lixia; Li, Xiang-Qing; Mu, Jin

2013-02-01

The photocatalytic system containing Eosin Y, multiwalled carbon nanotubes (MWNTs) and CuO (Eosin Y-MWNTs-CuO) was fabricated; meanwhile its photocatalytic activity for hydrogen evolution from triethanolamine (TEOA) aqueous solution was evaluated. Under visible light irradiation, the amount of hydrogen (H2) evolution increased greatly due to introduction of CuO in the photocatalytic system. Moreover, the electrochemical behavior of MWNTs loaded with CuO was explored using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results clearly indicate that there is a strong relationship between the electrochemical behavior of MWNTs-CuO and the photocatalytic activity of Eosin Y-MWNTs-CuO, and the high photocatalytic activity of Eosin Y-MWNTs-CuO may mainly originate from the efficient electron-transfer in the system.

Insight into the Role of Surface Wettability in Electrocatalytic Hydrogen Evolution Reactions Using Light-Sensitive Nanotubular TiO2 Supported Pt Electrodes

Science.gov (United States)

Meng, Chenhui; Wang, Bing; Gao, Ziyue; Liu, Zhaoyue; Zhang, Qianqian; Zhai, Jin

2017-02-01

Surface wettability is of importance for electrochemical reactions. Herein, its role in electrochemical hydrogen evolution reactions is investigated using light-sensitive nanotubular TiO2 supported Pt as hydrogen evolution electrodes (HEEs). The HEEs are fabricated by photocatalytic deposition of Pt particles on TiO2 nanotubes followed by hydrophobization with vaporized octadecyltrimethoxysilane (OTS) molecules. The surface wettability of HEEs is subsequently regulated in situ from hydrophobicity to hydrophilicity by photocatalytic decomposition of OTS molecules using ultraviolet light. It is found that hydrophilic HEEs demonstrate a larger electrochemical active area of Pt and a lower adhesion force to a gas bubble when compared with hydrophobic ones. The former allows more protons to react on the electrode surface at small overpotential so that a larger current is produced. The latter leads to a quick release of hydrogen gas bubbles from the electrode surface at large overpotential, which ensures the contact between catalysts and electrolyte. These two characteristics make hydrophilic HEEs generate a much high current density for HERs. Our results imply that the optimization of surface wettability is of significance for improving the electrocatalytic activity of HEEs.

Graphitic carbon nitride nanosheet for photocatalytic hydrogen production: The impact of morphology and element composition

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhao; Zhang, Yijie [Engineering Research Center of Nano-Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo Road, Wuhan 430074 (China); Lu, Luhua, E-mail: lhlu@cug.edu.cn [Engineering Research Center of Nano-Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo Road, Wuhan 430074 (China); Zhejiang institute, China University of Geosciences Wuhan, Hangzhou 311305 (China); Si, Yanjie; Zhang, Si [Engineering Research Center of Nano-Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo Road, Wuhan 430074 (China); Chen, Ying [Engineering Research Center of Nano-Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo Road, Wuhan 430074 (China); Zhejiang institute, China University of Geosciences Wuhan, Hangzhou 311305 (China); Dai, Kai, E-mail: daikai94@ustc.edu.cn [College of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Duan, Ping [Engineering Research Center of Nano-Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo Road, Wuhan 430074 (China); Zhejiang institute, China University of Geosciences Wuhan, Hangzhou 311305 (China); Duan, Limei [Inner Mongolia Key Lab of Chemistry of Natural Products and Synthesis of Functional Molecules, College of Chemistry and Chemical Engineering, Inner Mongolia University for the Nationalities, Tongliao 028000 (China); Liu, Jinghai, E-mail: jhliu2008@sinano.ac.cn [Inner Mongolia Key Lab of Chemistry of Natural Products and Synthesis of Functional Molecules, College of Chemistry and Chemical Engineering, Inner Mongolia University for the Nationalities, Tongliao 028000 (China)

2017-01-01

Highlights: • g-C{sub 3}N{sub 4} with tunable morphology was prepared by varying pyrolysis time. • g-C{sub 3}N{sub 4} showed reduced recombination of photogenerated electrons and holes. • g-C{sub 3}N{sub 4} showed enhanced photocatalytic hydrogen evolution activity. - Abstract: The intrinsic morphology and basal plane defects on g-C{sub 3}N{sub 4} nanosheet have important influences on its electronic structures and photocatalytic activity. In this work, we report extending thermal treatment time of g-C{sub 3}N{sub 4} at 550 °C not only change the morphology of g-C{sub 3}N{sub 4} but also element composition of g-C{sub 3}N{sub 4}. The morphology variation results in largely increased SSA from 40.22 to 117.27 m{sup 2} g{sup −1}, obviously reduced pore size from 3.99 to 2.77 nm for g-C{sub 3}N{sub 4} and formation of in-plane holes. Moreover, composition variation of g-C{sub 3}N{sub 4} has also been found to have changed as the pyrolysis time extended. These changes have significant impact on the optical properties and photoelectrical characters of g-C{sub 3}N{sub 4}, which were investigated by UV-DSR, PL and Photocurrent measurement. The photocatalytic activity of g-C{sub 3}N{sub 4} obtained via 9 h thermal treatment at 550 °C has shown highest photocatalytic activity, which is 1.77 times than that of g-C{sub 3}N{sub 4} obtained via 3 h thermal treatment under visible irradiation and 1.99 times under UV irradiation respectively.

Neighboring Hetero-Atom Assistance of Sacrificial Amines to Hydrogen Evolution Using Pt-Loaded TiO2-Photocatalyst

Directory of Open Access Journals (Sweden)

Masahide Yasuda

2014-05-01

Full Text Available Photocatalytic H2 evolution was examined using Pt-loaded TiO2-photocatalyst in the presence of amines as sacrificial agents. In the case of amines with all of the carbon attached to the hetero-atom such as 2-aminoethanol, 1,2-diamonoethane, 2-amino-1,3-propanediol, and 3-amino-1,2-propanediol, they were completely decomposed into CO2 and water to quantitatively evolve H2. On the other hand, the amines with both hetero-atoms and one methyl group at the β-positions (neighboring carbons of amino group such as 2-amino-1-propanol and 1,2-diaminopropane were partially decomposed. Also, the photocatalytic H2 evolution using amines without the hetero-atoms at the β-positions such as ethylamine, propylamine, 1-butylamine, 1,3-diaminopropane, 2-propylamine, and 2-butylamine was inefficient. Thus, it was found that the neighboring hetero-atom strongly assisted the degradation of sacrificial amines. Moreover, rate constants for H2 evolution were compared among amines. In conclusion, the neighboring hetero-atom did not affect the rate constants but enhanced the yield of hydrogen evolution.

Loading Cd0.5Zn0.5S Quantum Dots onto Onion-Like Carbon Nanoparticles to Boost Photocatalytic Hydrogen Generation.

Science.gov (United States)

Zhou, Xiaolong; Wang, Xina; Feng, Xi; Zhang, Kun; Peng, Xiaoniu; Wang, Hanbin; Liu, Chunlei; Han, Yibo; Wang, Hao; Li, Quan

2017-07-12

Carbon dots (C dots, size < 10 nm) have been conventionally decorated onto semiconductor matrixes for photocatalytic H 2 evolution, but the efficiency is largely limited by the low loading ratio of the C dots on the photocatalyst. Here, we propose an inverse structure of Cd 0.5 Zn 0.5 S quantum dots (QDs) loaded onto the onionlike carbon (OLC) matrix for noble metal-free photocatalytic H 2 evolution. Cd 0.5 Zn 0.5 S QDs (6.9 nm) were uniformly distributed on an OLC (30 nm) matrix with both upconverted and downconverted photoluminescence property. Such an inverse structure allows the full optimization of the QD/OLC interfaces for effective energy transfer and charge separation, both of which contribute to efficient H 2 generation. An optimized H 2 generation rate of 2018 μmol/h/g (under the irradiation of visible light) and 58.6 μmol/h/g (under the irradiation of 550-900 nm light) was achieved in the Cd 0.5 Zn 0.5 S/OLC composite samples. The present work shows that using the OLC matrix in such a reverse construction is a promising strategy for noble metal-free solar hydrogen production.

Excellent photocatalytic hydrogen production over CdS nanorods via using noble metal-free copper molybdenum sulfide (Cu{sub 2}MoS{sub 4}) nanosheets as co-catalysts

Energy Technology Data Exchange (ETDEWEB)

Hong, Sangyeob; Kumar, D. Praveen; Reddy, D. Amaranatha; Choi, Jiha; Kim, Tae Kyu, E-mail: tkkim@pusan.ac.kr

2017-02-28

Highlights: • Developed Cu{sub 2}MoS{sub 4} nanosheets as co-catalysts. • Cu{sub 2}MoS{sub 4} as active replacements for precious noble metal. • Controlled charge recombination for use in photocatalytic H{sub 2} evolution. • Obtained superior rate of H{sub 2} production by using Cu{sub 2}MoS{sub 4} loaded CdS nanorods. - Abstract: Charge carrier recombination and durability issues are major problems in photocatalytic hydrogen (H{sub 2}) evolution processes. Thus, there is a very important necessitate to extend an efficient photocatalyst to control charge-carrier dynamics in the photocatalytic system. We have developed copper molybdenum sulfide (Cu{sub 2}MoS{sub 4}) nanosheets as co-catalysts with CdS nanorods for controlling charge carriers without recombination for use in photocatalytic H{sub 2} evolution under simulated solar light irradiation. Effective control and utilization of charge carriers are possible by loading Cu{sub 2}MoS{sub 4} nanosheets onto the CdS nanorods. The loading compensates for the restrictions of CdS, and stimulated synergistic effects, such as efficient photoexcited charge separation, lead to an improvement in photostability because of the layered structure of the Cu{sub 2}MoS{sub 4}nanosheets. These layered Cu{sub 2}MoS{sub 4} nanosheets have emerged as novel and active replacements for precious noble metal co-catalysts in photocatalytic H{sub 2} production by water splitting. We have obtained superior H{sub 2} production rates by using Cu{sub 2}MoS{sub 4} loaded CdS nanorods. The physicochemical properties of the composites are analyzed by diverse characterization techniques.

Improved Solar-Driven Photocatalytic Performance of Highly Crystalline Hydrogenated TiO2 Nanofibers with Core-Shell Structure

Science.gov (United States)

Wu, Ming-Chung; Chen, Ching-Hsiang; Huang, Wei-Kang; Hsiao, Kai-Chi; Lin, Ting-Han; Chan, Shun-Hsiang; Wu, Po-Yeh; Lu, Chun-Fu; Chang, Yin-Hsuan; Lin, Tz-Feng; Hsu, Kai-Hsiang; Hsu, Jen-Fu; Lee, Kun-Mu; Shyue, Jing-Jong; Kordás, Krisztián; Su, Wei-Fang

2017-01-01

Hydrogenated titanium dioxide has attracted intensive research interests in pollutant removal applications due to its high photocatalytic activity. Herein, we demonstrate hydrogenated TiO2 nanofibers (H:TiO2 NFs) with a core-shell structure prepared by the hydrothermal synthesis and subsequent heat treatment in hydrogen flow. H:TiO2 NFs has excellent solar light absorption and photogenerated charge formation behavior as confirmed by optical absorbance, photo-Kelvin force probe microscopy and photoinduced charge carrier dynamics analyses. Photodegradation of various organic dyes such as methyl orange, rhodamine 6G and brilliant green is shown to take place with significantly higher rates on our novel catalyst than on pristine TiO2 nanofibers and commercial nanoparticle based photocatalytic materials, which is attributed to surface defects (oxygen vacancy and Ti3+ interstitial defect) on the hydrogen treated surface. We propose three properties/mechanisms responsible for the enhanced photocatalytic activity, which are: (1) improved absorbance allowing for increased exciton generation, (2) highly crystalline anatase TiO2 that promotes fast charge transport rate, and (3) decreased charge recombination caused by the nanoscopic Schottky junctions at the interface of pristine core and hydrogenated shell thus promoting long-life surface charges. The developed H:TiO2 NFs can be helpful for future high performance photocatalysts in environmental applications.

Enhanced Photocatalytic Hydrogen Evolution by Loading Cd0.5Zn0.5S QDs onto Ni2P Porous Nanosheets.

Science.gov (United States)

Xiao, Lingfeng; Su, Tong; Wang, Zhuo; Zhang, Kun; Peng, Xiaoniu; Han, Yibo; Li, Quan; Wang, Xina

2018-02-02

Ni 2 P has been decorated on CdS nanowires or nanorods for efficient photocatalytic H 2 production, whereas the specific surface area remains limited because of the large size. Here, the composites of Cd 0.5 Zn 0.5 S quantum dots (QDs) on thin Ni 2 P porous nanosheets with high specific surface area were constructed for noble metal-free photocatalytic H 2 generation. The porous Ni 2 P nanosheets, which were formed by the interconnection of 15-30 nm-sized Ni 2 P nanoparticles, allowed the uniform loading of 7 nm-sized Cd 0.5 Zn 0.5 S QDs and the loading density being controllable. By tuning the content of Ni 2 P, H 2 generation rates of 43.3 μM h - 1 (1 mg photocatalyst) and 700 μM h - 1 (100 mg photocatalyst) and a solar to hydrogen efficiency of 1.5% were achieved for the Ni 2 P-Cd 0.5 Zn 0.5 S composites. The effect of Ni 2 P content on the light absorption, photoluminescence, and electrochemical property of the composite was systematically studied. Together with the band structure calculation based on density functional theory, the promotion of Ni 2 P in charge transfer and HER activity together with the shading effect on light absorption were revealed. Such a strategy can be applied to other photocatalysts toward efficient solar hydrogen generation.

Enhanced Photocatalytic Hydrogen Evolution by Loading Cd0.5Zn0.5S QDs onto Ni2P Porous Nanosheets

Science.gov (United States)

Xiao, Lingfeng; Su, Tong; Wang, Zhuo; Zhang, Kun; Peng, Xiaoniu; Han, Yibo; Li, Quan; Wang, Xina

2018-02-01

Ni2P has been decorated on CdS nanowires or nanorods for efficient photocatalytic H2 production, whereas the specific surface area remains limited because of the large size. Here, the composites of Cd0.5Zn0.5S quantum dots (QDs) on thin Ni2P porous nanosheets with high specific surface area were constructed for noble metal-free photocatalytic H2 generation. The porous Ni2P nanosheets, which were formed by the interconnection of 15-30 nm-sized Ni2P nanoparticles, allowed the uniform loading of 7 nm-sized Cd0.5Zn0.5S QDs and the loading density being controllable. By tuning the content of Ni2P, H2 generation rates of 43.3 μM h- 1 (1 mg photocatalyst) and 700 μM h- 1 (100 mg photocatalyst) and a solar to hydrogen efficiency of 1.5% were achieved for the Ni2P-Cd0.5Zn0.5S composites. The effect of Ni2P content on the light absorption, photoluminescence, and electrochemical property of the composite was systematically studied. Together with the band structure calculation based on density functional theory, the promotion of Ni2P in charge transfer and HER activity together with the shading effect on light absorption were revealed. Such a strategy can be applied to other photocatalysts toward efficient solar hydrogen generation.

Kinetic analysis on photocatalytic degradation of gaseous acetaldehyde, ammonia and hydrogen sulfide on nanosized porous TiO2 films

Directory of Open Access Journals (Sweden)

Iis Sopyan

2007-01-01

Full Text Available The characteristics of the UV illumination-assisted degradation of gaseous acetaldehyde, hydrogen sulfide, and ammonia on highly active nanostructured-anatase and rutile films were investigated. It was found that the anatase film showed a higher photocatalytic activity than the counterpart did, however, the magnitude of difference in the photocatalytic activity of both films decreased in the order ammonia>acetaldehyde>hydrogen sulfide. To elucidate the reasons for the observation, the adsorption characteristics and the kinetics of photocatalytic degradation of the three reactants on both films were analyzed. The adsorption analysis examined using a simple Langmuir isotherm, showed that adsorbability on both films decreased in the order ammonia>acetaldehyde>hydrogen sulfide, which can be explained in terms of the decreasing electron-donor capacity. Acetaldehyde and ammonia adsorbed more strongly and with higher coverage on anatase film (1.2 and 5.6 molecules/nm2, respectively than on rutile (0.6 and 4.7 molecules/nm2, respectively. Conversely, hydrogen sulfide molecules adsorbed more strongly on rutile film (0.7 molecules/nm2 than on anatase (0.4 molecules/nm2. Exposure to UV light illumination brought about the photocatalytic oxidation of the three gases in contact with both TiO2 films, and the decrease in concentration were measured, and their kinetics are analyzed in terms of the Langmuir–Hinshelwood kinetic model. From the kinetic analysis, it was found that the anatase film showed the photocatalytic activities that were factors of ~8 and ~5 higher than the rutile film for the degradation of gaseous ammonia and acetaldehyde, respectively. However, the activity was only a factor of ~1.5 higher for the photodegradation of hydrogen sulfide. These observations are systematically explained by the charge separation efficiency and the adsorption characteristics of each catalyst as well as by the physical and electrochemical properties of each

Enhanced photocatalytic hydrogen evolution from in situ formation of few-layered MoS2/CdS nanosheet-based van der Waals heterostructures.

Science.gov (United States)

Iqbal, Shahid; Pan, Ziwei; Zhou, Kebin

2017-05-25

Here we report for the first time that the H 2 bubbles generated by photocatalytic water splitting are effective in the layer-by-layer exfoliation of MoS 2 nanocrystals (NCs) into few layers. The as-obtained few layers can be in situ assembled with CdS nanosheets (NSs) into van der Waals heterostructures (vdWHs) of few-layered MoS 2 /CdS NSs which, in turn, are effective in charge separation and transfer, leading to enhanced photocatalytic H 2 production activity. The few-layered MoS 2 /CdS vdWHs exhibited a H 2 evolution rate of 140 mmol g (CdS) -1 h -1 and achieved an apparent quantum yield of 66% at 420 nm.

Hydrogen evolution reaction catalyst

Science.gov (United States)

Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan

2016-02-09

Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

Noble-metal-free NiO@Ni-ZnO/reduced graphene oxide/CdS heterostructure for efficient photocatalytic hydrogen generation

Science.gov (United States)

Chen, Fayun; Zhang, Laijun; Wang, Xuewen; Zhang, Rongbin

2017-11-01

Noble-metal-free semiconductor materials are widely used for photocatalytic hydrogen generation because of their low cost. ZnO-based heterostructures with synergistic effects exhibit an effective photocatalytic activity. In this work, NiO@Ni-ZnO/reduced graphene oxide (rGO)/CdS heterostructures are synthesized by a multi-step method. rGO nanosheets and CdS nanoparticles were introduced into the heterostructures via a redox reaction and light-assisted growth, respectively. A novel Ni-induced electrochemical growth method was developed to prepare ZnO rods from Zn powder. NiO@Ni-ZnO/rGO/CdS heterostructures with a wide visible-light absorption range exhibited highly photocatalytic hydrogen generation rates under UV-vis and visible light irradiation. The enhanced photocatalytic activity is attributed to the Ni nanoparticles that act as cocatalysts for capturing photoexcited electrons and the improved synergistic effect between ZnO and CdS due to the rGO nanosheets acting as photoexcited carrier transport channels.

Revealing the relationship between the photocatalytic property and structure characteristic of reduced TiO2 by hydrogen and carbon monoxide treatment.

Science.gov (United States)

Liu, Yunpeng; Li, Yuhang; Yang, Siyuan; Lin, Yuan; Zuo, Jianliang; Liang, Hong; Peng, Feng

2018-06-04

The hydrogenation (reduction) has been considered as an effective method to improve the photocatalytic activity of TiO2, however, the underlying relationship between structure and photocatalytic performance has still not been adequately unveiled so far. Herein, to obtain insight into the effect of structure on photocatalytic activity, two types of reduced TiO2 were prepared by CO (CO-TiO2) and H2 (H-TiO2), respectively. For H-TiO2, Ti-H bonds and oxygen vacancies are formed on the surface of H-TiO2, resulting in a more disorder surface lattice. However, for CO-TiO2, the more Ti-OH bonds are formed on the surface and the more bulk oxygen vacancies are introduced, the disorder layer of CO-TiO2 is relatively thin owing to the most of surface vacancies repaired by Ti-OH bonds. Under the simulated solar irradiation, the photocatalytic H2 evolution rate of CO-TiO2 reaches 7.17 mmol g-1 h-1, which is 4.14 and 1.50 times those of TiO2 and H-TiO2, respectively. The photocatalytic degradation rate constant of methyl orange on CO-TiO2 is 2.45 and 6.39 times those on H-TiO2 and TiO2. The superior photocatalytic activity of CO-TiO2 is attributed to the effective separation and transfer of the photo-generated electron-hole pairs, due to the synergistic effects of oxygen vacancies and surface Ti-OH bonds. This study reveals the relation between the photocatalytic property and structure, and provides a new method to prepare highly active TiO2 for H2 production and environmental treatment. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of high efficient Cu/TiO2 photocatalysts by grinding and their size-dependent photocatalytic hydrogen production

International Nuclear Information System (INIS)

Ni, Dawei; Shen, Haiyan; Li, Huiqiao; Ma, Ying; Zhai, Tianyou

2017-01-01

Highlights: • Cu nanodots were decorated on TiO 2 surface through ball milling method. • Its size distribution was investigated in water and ethanolic medium. • Photocurrent response and hydrogen evolution was improved. • Performance was found to be dependent on size of Cu nanodots. - Abstract: Recently, copper species have been extensively investigated to replace Pt as efficient co-catalysts for the evolution of H 2 due to their low cost and relatively high activity. Cu nanoparticles less than 5 nm are successfully decorated on TiO 2 surface in this work by an easy and mild milling process. These Cu nanoparticles are highly dispersed on TiO 2 when the loading amount of Cu is no more than 10 wt%. The sizes of Cu nanoparticles can be controlled by changing the milling environment and decrease in the order of Cu-ethanol > Cu-water > Cu nanoparticles obtained through drying milling. The highest and stable hydrogen generation can be realized on Cu/TiO 2 with 2.0 wt% Cu and sizes of Cu nanoparticles ranging from 2 to 4 nm, in which high and stable photocurrent confirms promoted photogenerated charge separation. Smaller Cu clusters are demonstrated to be detrimental to hydrogen evolution at same Cu content. High loading of Cu nanoparticles of 2–4 nm will benefit photogenerated electron-hole recombination and thus decrease the activity of Cu/TiO 2 . The results here demonstrate the key roles of Cu cluster size in addition to Cu coverage on photocatalytic activity of Cu/TiO 2 composite photocatalysts.

Hydrogen evolution catalyzed by cobalt diimine-dioxime complexes.

Science.gov (United States)

Kaeffer, Nicolas; Chavarot-Kerlidou, Murielle; Artero, Vincent

2015-05-19

Mimicking photosynthesis and producing solar fuels is an appealing way to store the huge amount of renewable energy from the sun in a durable and sustainable way. Hydrogen production through water splitting has been set as a first-ranking target for artificial photosynthesis. Pursuing that goal requires the development of efficient and stable catalytic systems, only based on earth abundant elements, for the reduction of protons from water to molecular hydrogen. Cobalt complexes based on glyoxime ligands, called cobaloximes, emerged 10 years ago as a first generation of such catalysts. They are now widely utilized for the construction of photocatalytic systems for hydrogen evolution. In this Account, we describe our contribution to the development of a second generation of catalysts, cobalt diimine-dioxime complexes. While displaying similar catalytic activities as cobaloximes, these catalysts prove more stable against hydrolysis under strongly acidic conditions thanks to the tetradentate nature of the diimine-dioxime ligand. Importantly, H2 evolution proceeds via proton-coupled electron transfer steps involving the oxime bridge as a protonation site, reproducing the mechanism at play in the active sites of hydrogenase enzymes. This feature allows H2 to be evolved at modest overpotentials, that is, close to the thermodynamic equilibrium over a wide range of acid-base conditions in nonaqueous solutions. Derivatization of the diimine-dioxime ligand at the hydrocarbon chain linking the two imine functions enables the covalent grafting of the complex onto electrode surfaces in a more convenient manner than for the parent bis-bidentate cobaloximes. Accordingly, we attached diimine-dioxime cobalt catalysts onto carbon nanotubes and demonstrated the catalytic activity of the resulting molecular-based electrode for hydrogen evolution from aqueous acetate buffer. The stability of immobilized catalysts was found to be orders of magnitude higher than that of catalysts in the

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production.

Science.gov (United States)

Reynal, Anna; Pastor, Ernest; Gross, Manuela A; Selim, Shababa; Reisner, Erwin; Durrant, James R

2015-08-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye ( RuP ) and a nickel bis(diphosphine) electrocatalyst ( NiP ) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H 2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP - NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP , which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP - NiP photocatalytic system, which can be widely applied to other photocatalytic systems.

Development of efficient photoreactors for solar hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Huang, Cunping; Yao, Weifeng; T-Raissi, Ali; Muradov, Nazim [University of Central Florida, Florida Solar Energy Center, 1679 Clearlake Road, Cocoa, Fl 32922-5703 (United States)

2011-01-15

The rate of hydrogen evolution from a photocatalytic process depends not only on the activity of a photocatalyst, but also on photoreactor design. Ideally, a photoreactor should be able to absorb the incident light, promoting photocatalytic reactions in an effective manner with minimal photonic losses. There are numerous technical challenges and cost related issues when designing a large-scale photoreactor for hydrogen production. Active stirring of the photocatalyst slurry within a photoreactor is not practical in large-scale applications due to cost related issues. Rather, the design should allow facile self-mixing of the flow field within the photoreactor. In this paper two types of photocatalytic reactor configurations are studied: a batch type design and another involving passive self-mixing of the photolyte. Results show that energy loss from a properly designed photoreactor is mainly due to reflection losses from the photoreactor window. We describe the interplay between the reaction and the photoreactor design parameters as well as effects on the rate of hydrogen evolution. We found that a passive self-mixing of the photolyte is possible. Furthermore, the use of certain engineering polymer films as photoreactor window materials has the potential for substantial cost savings in large-scale applications, with minimal reduction of photon energy utilization efficiency. Eight window materials were tested and the results indicate that Aclar trademark polymer film used as the photoreactor window provides a substantial cost saving over other engineering polymers, especially with respect to fused silica glass at modest hydrogen evolution rates. (author)

Effects of Composition and Calcination Temperature on Photocatalytic Evolution over from Glycerol and Water Mixture

Directory of Open Access Journals (Sweden)

Cancan Fan

2012-01-01

Full Text Available A series of sulfide coupled semiconductors supported on SiO2, (, was prepared by incipient wet impregnation method. The photocatalysts were characterized by XRD, XPS, TPR, and UV/Vis DRS. Characterization results show that the chemical actions between ZnS and CdS resulted in the formation of solid solutions on the surface of the support and the formation of them is affected by the molar ratio of ZnS/CdS and calcination temperature. Performance of photocatalysts was tested in the home made reactor under both UV light and solar-simulated light irradiation by detecting the rate of the photocatalytic H2 evolution from glycerol solution. The hydrogen production rates are related to the catalyst composition, surface structure, photoabsorption property, as well as the amount of solid solution. The maximum rate of hydrogen production, 550 μmol·h−1 under UV light irradiation and 210 μmol·h−1 under solar-simulated light irradiation, was obtained over Cd0.8Zn0.2S/SiO2 solid solution calcined at 723 K.

Correlation of Photocatalytic Activity with Band Structure of Low-dimensional Semiconductor Nanostructures

Science.gov (United States)

Meng, Fanke

band edge, unlike the mid-gap states introduced by oxygen vacancies, leading to an improvement in visible and UV photocatalysis. The Pt nanoparticles both enhanced separation of charge carriers and acted as reaction sites for hydrogen evolution. The photocatalytic hydrogen generation rate of the La 2Ti2O7 nanosheets was increased to ˜21 muM g-1 hr-1 from zero in visible light by nitrogen doping and Pt loading, showing the importance of the positioning of dopant energy levels within the band gap. Third, a hematite/reduced graphene oxide (alpha-Fe2 2O3/rGO) nanocomposite was synthesized by a hydrolysis method. The photocatalytic oxygen evolution rate of the hematite was increased from 387 to 752 muM g-1 hr-1 by incorporating rGO. Photoelectrochemical measurements showed that coupling the hematite nanoparticles with the rGO can greatly increase the photocurrent and reduce the charge recombination rate, overcoming the poor charge recombination characteristics of hematite and allowing its small band gap to be taken advantage of. Fourth, a Au/La 2Ti2O7/rGO heterostructure was synthesized to further enhance the photocatalytic hydrogen generation rate of the La 2Ti2O7 nanosheets. The enhanced performance of photocatalytic water splitting was due to plasmonic energy transfer, which resulted from the plasmonic Au nanoparticles on the La2Ti 2O7 nanosheets. This heterostructure showed doping, charge extraction, and plasmonics work synergistically. Fifth, nanoscale p-n junctions on the rGO were formed by depositing the p-type MoS 2 nanoplatelets onto the n-type nitrogen-doped rGO. The p-MoS2/n-rGO heterostructure had significant photocatalytic hydrogen generation activity under solar light irradiation. The enhanced charge generation and suppressed charge recombination due to the p-n junctions led to enhance solar hydrogen generation reaction while allowing replacement of the expensive Pt nanoparticles with an eco-friendly alternative. The research results in this dissertation are

Research Update: Photoelectrochemical water splitting and photocatalytic hydrogen production using ferrites (MFe2O4) under visible light irradiation

Science.gov (United States)

Dillert, Ralf; Taffa, Dereje H.; Wark, Michael; Bredow, Thomas; Bahnemann, Detlef W.

2015-10-01

The utilization of solar light for the photoelectrochemical and photocatalytic production of molecular hydrogen from water is a scientific and technical challenge. Semiconductors with suitable properties to promote solar-driven water splitting are a desideratum. A hitherto rarely investigated group of semiconductors are ferrites with the empirical formula MFe2O4 and related compounds. This contribution summarizes the published results of the experimental investigations on the photoelectrochemical and photocatalytic properties of these compounds. It will be shown that the potential of this group of compounds in regard to the production of solar hydrogen has not been fully explored yet.

Three-dimensional assembly structure of anatase TiO2 hollow microspheres with enhanced photocatalytic performance

Science.gov (United States)

Tang, Yihao; Zhan, Shuai; Wang, Li; Zhang, Bin; Ding, Minghui

The pure anatase TiO2 hollow microspheres are synthesized by a one-step template-free hydrothermal route. By defining temperature and time limits, we produce TiO2 hollow microspheres with a fluoride-mediated self-transformation. The surface morphology of TiO2 hollow microspheres was studied by SEM. The hollow microspheres have diameters of about 800 nm and are remarkably uniform. The UV-light photocatalytic activity and the stability/multifunction of TiO2 hollow microspheres structure were evaluated by photocatalytic degradation of methylene blue and photocatalytic hydrogen evolution. The excellent photocatalytic activity is attributed to large specific surface area, more active sites, unique hollow structures, and improved light scattering.

Nano-design of quantum dot-based photocatalysts for hydrogen generation using advanced surface molecular chemistry

KAUST Repository

Yu, Weili; Noureldine, Dalal; Isimjan, Tayirjan T.; Lin, Bin; Del Gobbo, Silvano; Abulikemu, Mutalifu; Hedhili, Mohamed N.; Anjum, Dalaver H.; Takanabe, Kazuhiro

2015-01-01

Efficient photocatalytic hydrogen generation in a suspension system requires a sophisticated nano-device that combines a photon absorber with effective redox catalysts. This study demonstrates an innovative molecular linking strategy for fabricating photocatalytic materials that allow effective charge separation of excited carriers, followed by efficient hydrogen evolution. The method for the sequential replacement of ligands with appropriate molecules developed in this study tethers both quantum dots (QDs), as photosensitizers, and metal nanoparticles, as hydrogen evolution catalysts, to TiO2 surfaces in a controlled manner at the nano-level. Combining hydrophobic and hydrophilic interactions on the surface, CdSe-ZnS core-shell QDs and an Au-Pt alloy were attached to TiO2 without overlapping during the synthesis. The resultant nano-photocatalysts achieved substantially high-performance visible-light-driven photocatalysis for hydrogen evolution. All syntheses were conducted at room temperature and in ambient air, providing a promising route for fabricating visible-light-responsive photocatalysts.

Synthesis of high efficient Cu/TiO2 photocatalysts by grinding and their size-dependent photocatalytic hydrogen production

Science.gov (United States)

Ni, Dawei; Shen, Haiyan; Li, Huiqiao; Ma, Ying; Zhai, Tianyou

2017-07-01

Recently, copper species have been extensively investigated to replace Pt as efficient co-catalysts for the evolution of H2 due to their low cost and relatively high activity. Cu nanoparticles less than 5 nm are successfully decorated on TiO2 surface in this work by an easy and mild milling process. These Cu nanoparticles are highly dispersed on TiO2 when the loading amount of Cu is no more than 10 wt%. The sizes of Cu nanoparticles can be controlled by changing the milling environment and decrease in the order of Cu-ethanol > Cu-water > Cu nanoparticles obtained through drying milling. The highest and stable hydrogen generation can be realized on Cu/TiO2 with 2.0 wt% Cu and sizes of Cu nanoparticles ranging from 2 to 4 nm, in which high and stable photocurrent confirms promoted photogenerated charge separation. Smaller Cu clusters are demonstrated to be detrimental to hydrogen evolution at same Cu content. High loading of Cu nanoparticles of 2-4 nm will benefit photogenerated electron-hole recombination and thus decrease the activity of Cu/TiO2. The results here demonstrate the key roles of Cu cluster size in addition to Cu coverage on photocatalytic activity of Cu/TiO2 composite photocatalysts.

Relation between Hydrogen Evolution and Hydrodesulfurization Catalysis

DEFF Research Database (Denmark)

Šaric, Manuel; Moses, Poul Georg; Rossmeisl, Jan

2016-01-01

A relation between hydrogen evolution and hydrodesulfurization catalysis was found by density functional theory calculations. The hydrogen evolution reaction and the hydrogenation reaction in hydrodesulfurization share hydrogen as a surface intermediate and, thus, have a common elementary step...

Potassium ions intercalated into g-C3N4-modified TiO2 nanobelts for the enhancement of photocatalytic hydrogen evolution activity under visible-light irradiation

Science.gov (United States)

Ma, Jian; Zhou, Wei; Tan, Xin; Yu, Tao

2018-05-01

Solar-to-chemical energy conversion is a challenging photochemical reaction for renewable energy storage. In recent decades, photocatalytic H2 evolution has been studied extensively. TiO2 is a well-established semiconductor in the field of photocatalytic H2 production; however, its low efficiency for solar energy utilization, and high photocarrier recombination rate, restrict its photocatalytic efficiency. Here, a series of K-intercalated g-C3N4-modified TiO2 nanobelts (TCN–Kx) with different dosages of K atoms were fabricated using a hydrothermal method followed by a calcination process. XRD, TEM and XPS tests indicate that a tight interfacial connection is formed between K–g-C3N4 and the TiO2 nanobelts. DFT calculations indicated that K dopants prefer to be at the interlayer sites of g-C3N4, suggesting increased charge transfer efficiency. The H2 production efficiency of the TCN–Kx composite materials from water splitting under visible-light irradiation was clearly improved. Steady fluorescence spectroscopy and photocurrent measurements confirmed that the improvement in photocatalytic H2 production activity was due to the superior charge separation and electron transfer efficiency of TCN–Kx composite materials.

Synthesis of high efficient Cu/TiO{sub 2} photocatalysts by grinding and their size-dependent photocatalytic hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Ni, Dawei; Shen, Haiyan; Li, Huiqiao; Ma, Ying; Zhai, Tianyou, E-mail: yingma@hust.edu.cn

2017-07-01

Highlights: • Cu nanodots were decorated on TiO{sub 2} surface through ball milling method. • Its size distribution was investigated in water and ethanolic medium. • Photocurrent response and hydrogen evolution was improved. • Performance was found to be dependent on size of Cu nanodots. - Abstract: Recently, copper species have been extensively investigated to replace Pt as efficient co-catalysts for the evolution of H{sub 2} due to their low cost and relatively high activity. Cu nanoparticles less than 5 nm are successfully decorated on TiO{sub 2} surface in this work by an easy and mild milling process. These Cu nanoparticles are highly dispersed on TiO{sub 2} when the loading amount of Cu is no more than 10 wt%. The sizes of Cu nanoparticles can be controlled by changing the milling environment and decrease in the order of Cu-ethanol > Cu-water > Cu nanoparticles obtained through drying milling. The highest and stable hydrogen generation can be realized on Cu/TiO{sub 2} with 2.0 wt% Cu and sizes of Cu nanoparticles ranging from 2 to 4 nm, in which high and stable photocurrent confirms promoted photogenerated charge separation. Smaller Cu clusters are demonstrated to be detrimental to hydrogen evolution at same Cu content. High loading of Cu nanoparticles of 2–4 nm will benefit photogenerated electron-hole recombination and thus decrease the activity of Cu/TiO{sub 2}. The results here demonstrate the key roles of Cu cluster size in addition to Cu coverage on photocatalytic activity of Cu/TiO{sub 2} composite photocatalysts.

Synergistically enhanced photocatalytic hydrogen evolution performance of ZnCdS by co-loading graphene quantum dots and PdS dual cocatalysts under visible light

Science.gov (United States)

Wang, Fang; Su, Yanhong; Min, Shixiong; Li, Yanan; Lei, Yonggang; Hou, Jianhua

2018-04-01

Here, we report that the co-loading of graphene quantum dots (GQDs) and PdS dual cocatalysts on ZnCdS surface achieves a high efficiency photocatalytic H2 evolution under visible light (≥420 nm). The GQDs/ZnCdS/PdS photocatalyst was prepared by a facile two steps: hydrothermal coupling of GQDs on ZnCdS surface followed by an in-situ chemical deposition of PdS. The resulted GQDs/ZnCdS/PdS exhibits a H2 evolution rate of 517 μmol h-1, which is 15, 7, and 1.7 times higher than that of pure ZnCdS, GQDs/ZnCdS, and ZnCdS/PdS, respectively, demonstrating the synergistic effects of GQDs and PdS dual cocatalysts. A high apparent quantum efficiency (AQE) up to 22.4% can be achieved over GQDs/ZnCdS/PdS at 420 nm. GQDs/ZnCdS/PdS also has a relatively good stability. Such a considerable enhancement of photocatalytic activity was attributable to the co-loading of the GQDs and PdS as respective reduction and oxidation cocatalysts, leading to an efficient charge separation and surface reactions.

High-temperature hydrogenation of pure and silver-decorated titanate nanotubes to increase their solar absorbance for photocatalytic applications

Energy Technology Data Exchange (ETDEWEB)

Plodinec, Milivoj [Ruđer Bošković Institute, Bijenička 54, HR-1002 Zagreb (Croatia); Gajović, Andreja, E-mail: gajovic@irb.hr [Ruđer Bošković Institute, Bijenička 54, HR-1002 Zagreb (Croatia); Jakša, Gregor; Žagar, Kristina; Čeh, Miran [Institute Jožef Stefan, Jamova 39, 1000 Ljubljana (Slovenia)

2014-04-05

Graphical abstract: The aim of the work is to study how annealing in a reducing atmosphere of titanate nanotubes (TiNT) and Ag decorated titanate nanotubes (TiNT@Ag) influenced on their structure, morphology, phase transitions, UV–ViS-NIR absorbance and photocatalytic activity. An increase of photocatalytic activity after a heat treatment in a reducing atmosphere was observed in the TiNT and TiNT@Ag. We found that the hydrogenated TiNT@Ag samples (TiNT@Ag-HA) had a two-times higher photodegradation impact on the caffeine than the TiNT samples, which is a consequence of the increased absorption of visible light and the synergetic effects between the silver and the TiO{sub 2} nanoparticles that increase the efficiency of the formation of electron–hole pairs and the charge transfer to the surface of the nanoparticles. -- Highlights: • Titanate nanotubes with and without Ag nanoparticles were hydrogenated at 550 °C. • TiO{sub 2} nanostructures obtained by hydrogenation have core–shell structure. • Hydrogenated samples show absorption in the visible spectral region. • Hydrogenated Ag decorated sample show stronger absorption in visible than in UV. • Photocatalytic efficiency is improved by hydrogenation and by Ag nanoparticles. -- Abstract: Titanate nanotubes (TiNTs) and silver-decorated titanate nanotubes (TiNTs@Ag) were synthesized using the hydrothermal method. In the decorated nanotubes the silver particles were obtained by the photoreduction of AgNO{sub 3} under UV light. Pure and Ag-decorated nanotubes were high-temperature heat treated at 550 °C in a hydrogen atmosphere and the “core–shell”-structured TiO{sub 2} nanoparticles were formed. For the structural characterization of all the titanate nanostructures we used conventional and analytical transmission electron microscopy (TEM) techniques, X-ray diffraction (XRD) and Raman spectroscopy. The Ag-decorated titanate nanostructures were additionally studied by X-ray photo

Research Update: Photoelectrochemical water splitting and photocatalytic hydrogen production using ferrites (MFe{sub 2}O{sub 4}) under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Dillert, Ralf [Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstr. 3, 30167 Hannover (Germany); Laboratorium für Nano- und Quantenengineering, Gottfried Wilhelm Leibniz Universität Hannover, Schneiderberg 39, 30167 Hannover (Germany); Taffa, Dereje H.; Wark, Michael [Institut für Chemie, Technische Chemie, Carl-von-Ossietzky Universität Oldenburg, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg (Germany); Bredow, Thomas [Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115 Bonn (Germany); Bahnemann, Detlef W. [Institut für Technische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstr. 3, 30167 Hannover (Germany); Laboratory for Nanocomposite Materials, Department of Photonics, Faculty of Physics, Saint-Petersburg State University, Ulianovskaia Str. 3, Peterhof, Saint-Petersburg 198504 (Russian Federation)

2015-10-01

The utilization of solar light for the photoelectrochemical and photocatalytic production of molecular hydrogen from water is a scientific and technical challenge. Semiconductors with suitable properties to promote solar-driven water splitting are a desideratum. A hitherto rarely investigated group of semiconductors are ferrites with the empirical formula MFe{sub 2}O{sub 4} and related compounds. This contribution summarizes the published results of the experimental investigations on the photoelectrochemical and photocatalytic properties of these compounds. It will be shown that the potential of this group of compounds in regard to the production of solar hydrogen has not been fully explored yet.

Photocatalytic hydrogen production over solid solutions between BiFeO{sub 3} and SrTiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Lu, Lingwei; Lv, Meilin [Shanghai Key Lab of Chemical Assessment and Sustainability, Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai, 200092 (China); Liu, Gang [Shenyang National laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, Shenyang 110016 (China); Xu, Xiaoxiang, E-mail: xxxu@tongji.edu.cn [Shanghai Key Lab of Chemical Assessment and Sustainability, Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai, 200092 (China)

2017-01-01

Graphical abstract: We have successfully prepared a series of SrTiO{sub 3}-BiFeO{sub 3} solid solutions. These materials own strong visible light absorption and demonstrate appealing photocatalytic activity under both full range and visible light irradiation. - Highlights: • Band gap values can be tuned by adjusting molar ratios between SrTiO{sub 3} and BiFeO{sub 3}. • Photocatalytic activity is greatly improved after constituting solid solutions. • Photocatalytic activity is influenced by surface area and light absorption. • Fe plays an important role for band gap reduction and catalytic activity. - Abstract: Constituting solid solutions has been an appealing means to gain control over various physicochemical properties. In this work, we synthesized a series of SrTiO{sub 3}-BiFeO{sub 3} solid solutions and systematically explored their structural, optical and photocatalytic properties. Our results show that all solid solutions crystallize in a primitive cubic structure and their band gap values can be easily tuned by adjusting molar ratios between SrTiO{sub 3} and BiFeO{sub 3}. Photocatalytic hydrogen production under both full range and visible light irradiation is greatly improved after forming solid solutions. The highest hydrogen production rate obtained is ∼180 μmol/h under full range irradiation (λ ≥ 250 nm) and ∼4.2 μmol/h under visible light irradiation (λ ≥ 400 nm), corresponding to apparent quantum efficiency ∼2.28% and ∼0.10%, respectively. The activity is found to be strongly influenced by surface area and light absorption. Theoretical calculation suggests that Fe contributes to the formation of spin-polarized bands in the middle of original band gap and is responsible for the band gap reduction and visible light photocatalytic activity.

Control of Redox Events by Dye Encapsulation Applied to Light-Driven Splitting of Hydrogen Sulfide

NARCIS (Netherlands)

Jing, X.; Yang, Y.; He, C.; Chang, Z.; Reek, J.N.H.; Duan, C.

2017-01-01

Solar production of hydrogen by consuming low-value waste products is an attractive pathway that has both economic and environmental benefits. Inspired by the reactive pocket of enzymes, a synthetic platform to combine photocatalytic hydrogen evolution with sulfide oxidation in a one-pot process via

Nano-ferrites for water splitting: Unprecedented high photocatalytic hydrogen production under visible light

KAUST Repository

Mangrulkar, Priti A.; Polshettiwar, Vivek; Labhsetwar, Nitin K.; Varma, Rajender S.; Rayalu, Sadhana Suresh

2012-01-01

In the present investigation, hydrogen production via water splitting by nano-ferrites was studied using ethanol as the sacrificial donor and Pt as co-catalyst. Nano-ferrite is emerging as a promising photocatalyst with a hydrogen evolution rate of 8.275 μmol h -1 and a hydrogen yield of 8275 μmol h -1 g -1 under visible light compared to 0.0046 μmol h -1 for commercial iron oxide (tested under similar experimental conditions). Nano-ferrites were tested in three different photoreactor configurations. The rate of hydrogen evolution by nano-ferrite was significantly influenced by the photoreactor configuration. Altering the reactor configuration led to sevenfold (59.55 μmol h -1) increase in the hydrogen evolution rate. Nano-ferrites have shown remarkable stability in hydrogen production up to 30 h and the cumulative hydrogen evolution rate was observed to be 98.79 μmol h -1. The hydrogen yield was seen to be influenced by several factors like photocatalyst dose, illumination intensity, irradiation time, sacrificial donor and presence of co-catalyst. These were then investigated in detail. It was evident from the experimental data that nano-ferrites under optimized reaction conditions and photoreactor configuration could lead to remarkable hydrogen evolution activity under visible light. Temperature had a significant role in enhancing the hydrogen yield. © 2012 The Royal Society of Chemistry.

Transferring Knowledge of Electrocatalysis to Photocatalysis: Photocatalytic Water Splitting

KAUST Repository

Takanabe, Kazuhiro

2017-06-24

One of the most attractive features of photocatalytic reactions is the ability to achieve energetically uphill (photosynthetic) reactions. In many photocatalytic reactions, the reactions involve multielectron transfers with the adsorbed intermediates. In this case, photocatalysis is nothing but electrocatalysis initiated and driven by the electron potential shift caused by the photocatalyst (photon absorber). This condition is indeed true for photocatalysts for water splitting, which are also electrocatalysts because both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) require multiple electron transfers at the active surfaces. This chapter deals with the product-side in the six-gear concept. It shows the electrocatalytic performance when using an electrocatalyst on the surface. The chapter further shows the current-potential curve for an electrocatalytic process isolated from the photocatalyst process. For an electrocatalyst to achieve electrochemical reactions, the potential of the catalyst must be shifted at the interface of the semiconductor, providing electromotive force or overpotential for redox reactions.

Transferring Knowledge of Electrocatalysis to Photocatalysis: Photocatalytic Water Splitting

KAUST Repository

Takanabe, Kazuhiro

2017-01-01

One of the most attractive features of photocatalytic reactions is the ability to achieve energetically uphill (photosynthetic) reactions. In many photocatalytic reactions, the reactions involve multielectron transfers with the adsorbed intermediates. In this case, photocatalysis is nothing but electrocatalysis initiated and driven by the electron potential shift caused by the photocatalyst (photon absorber). This condition is indeed true for photocatalysts for water splitting, which are also electrocatalysts because both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) require multiple electron transfers at the active surfaces. This chapter deals with the product-side in the six-gear concept. It shows the electrocatalytic performance when using an electrocatalyst on the surface. The chapter further shows the current-potential curve for an electrocatalytic process isolated from the photocatalyst process. For an electrocatalyst to achieve electrochemical reactions, the potential of the catalyst must be shifted at the interface of the semiconductor, providing electromotive force or overpotential for redox reactions.

MoS{sub 2}-coated microspheres of self-sensitized carbon nitride for efficient photocatalytic hydrogen generation under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Gu, Quan [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Sun, Huaming; Xie, Zunyuan; Gao, Ziwei [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, 710062 (China); Xue, Can, E-mail: cxue@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

2017-02-28

Highlights: • Successful coating of MoS{sub 2} onto self-sensitized carbon nitride microspheres. • The carbon nitride@MoS{sub 2} core-shell structure show enhanced H{sub 2} generation in visible light. • Synergistic effect of surface dyes and MoS{sub 2} coating enhances photocatalytic activities. - Abstract: We have successfully coated the self-sensitized carbon nitride (SSCN) microspheres with a layer of MoS{sub 2} through a facile one-pot hydrothermal method by using (NH{sub 4}){sub 2}MoS{sub 4} as the precursor. The resulted MoS{sub 2}-coated SSCN photocatalyst appears as a core-shell structure and exhibits enhanced visible-light activities for photocatalytic H{sub 2} generation as compared to the un-coated SSCN and the standard g-C{sub 3}N{sub 4} reference with MoS{sub 2} coating. The photocatalytic test results suggest that the oligomeric s-triazine dyes on the SSCN surface can provide additional light-harvesting capability and photogenerated charge carriers, and the coated MoS{sub 2} layer can serve as active sites for proton reduction towards H{sub 2} evolution. This synergistic effect of surface triazine dyes and MoS{sub 2} coating greatly promotes the activity of carbon nitride microspheres for vishible-light-driven H{sub 2} generation. This work provides a new way of future development of low-cost noble-metal-free photocatalysts for efficient solar-driven hydrogen production.

In Situ Measurement of Local Hydrogen Production Rate by Bubble-Evolved Recording

Directory of Open Access Journals (Sweden)

Xiaowei Hu

2013-01-01

Full Text Available Hydrogen visibly bubbles during photocatalytic water splitting under illumination with above-bandgap radiation, which provides a direct measurement of local gas-evolving reaction rate. In this paper, optical microscopy of superfield depth was used for recording the hydrogen bubble growth on Cd0.5Zn0.5S photocatalyst in reaction liquid and illuminated with purple light. By analyzing change of hydrogen bubble size as a function of time, we understood that hydrogen bubble growth experienced two periods, which were inertia effect dominated period and diffusion effect dominated period, respectively. The tendency of hydrogen bubble growth was similar to that of the gas bubble in boiling, while the difference in bubble diameter and growth time magnitude was great. Meanwhile, we obtained the local hydrogen production rate on photocatalyst active site by measuring hydrogen bubble growth variation characteristics. This method makes it possible to confirm local actual hydrogen evolution rate quantitatively during photocatalytic water splitting.

Photocatalytic performance of Cu-doped TiO2 nanofibers treated by the hydrothermal synthesis and air-thermal treatment

Science.gov (United States)

Wu, Ming-Chung; Wu, Po-Yeh; Lin, Ting-Han; Lin, Tz-Feng

2018-02-01

Series of transition metal-doped TiO2 (metal/TiO2) is prepared by combining the hydrothermal synthesis and air-thermal treatment without any reduction process. The selected transition metal precursors, including Ag, Au, Co, Cr, Cu, Fe, Ni, Pd, Pt, Y, and Zn, were individually doped into TiO2 nanofibers to evaluate the photocatalytic degradation activity and photocatalytic hydrogen generation. Consider the photocatalytic performance of these synthesized metal/TiO2 under UV-A irradiation, copper doped TiO2 nanofibers (Cu/TiO2 NFs) was chosen for further study due to its extraordinary reactivity. Systematical studies were spread to optimize the doping concentration and the calcination condition for much higher photocatalytic activity Cu/TiO2 NFs. In the photocatalytic degradation test, 0.5 mol%-Cu/TiO2 NFs calcined at 650 °C exhibits the highest activity, which is even higher than commercial TiO2-AEROXIDE® TiO2 P25 under UV-A irradiation. The synthesized 0.5 mol%-Cu/TiO2-650 NFs also have the capability in the photocatalytic hydrogen production. The hydrogen evolution rates are 200 μmol/g·h under UV-A irradiation and 280 μmol/g·h under UV-B irradiation. The density of state calculated by CASTEP for Cu/TiO2 indicates that Cu doping contributes to the states near valence band edge and narrows the band gap. The disclosed process in this study is industrial safe, convenient and cost-effective. We further produce a significant amount of TiO2-based catalysts without any hydrogen reduction treatment.

Strongly coupled CdS/graphene quantum dots nanohybrids for highly efficient photocatalytic hydrogen evolution: unraveling the essential roles of graphene quantum dots

KAUST Repository

Lei, Yonggang

2017-05-23

It have been recognized that the coupling of graphene quantum dots (GQDs) with semiconductor photocatalysts endow the resulting nanocomposites with enhanced photocatalytic performances, however, the essential roles of GQDs have not been clearly revealed yet. Herein, we report that a high efficiency of the photocatalytic H2 evolution was achieved using strongly coupled nanohybrids of CdS with GQDs (CdS/GQDs) as visible-light-driven photocatalysts. CdS/GQDs nanohybrids were synthesized by a facile hydrothermal method in which the crystallization of CdS precursor and coupling of GQDs could be accomplished in one-step. GQDs are firmly decorated on the surface of CdS nanoparticles, forming “dot-on-particle” heterodimer structures. GQDs have no significant influence on the crystallite structure of CdS but render the nanohybrids with strong light absorption at the wavelength beyond the band edge of CdS. Under visible light irradiation (≥420nm), CdS/GQDs nanohybrids reach the highest H2 production rate of 95.4μmol·h−1, about 2.7 times higher than that of pure CdS nanoparticles, at GQDs content of 1.0wt %, and the apparent quantum efficiency (AQE) was determined to be 4.2% at 420nm. Incident light-wavelength dependent experiments reveal that the light absorption of CdS dominated the performance of nanohybrids, and the excess light absorption coming from GQDs hardly contributes to the observed higher activity. Photocurrent response, steady-state and time-resolved PL, and EIS measurements suggest that the high activity of CdS/GQDs is attributed predominantly to the graphene-like nature of GQDs, which can act as an efficient electron acceptor to induce an efficient charge separation. This work clearly reveals that GQDs mainly played a role of electron acceptor instead of a photosensitizer in enhancing the photocatalytic H2 evolution performances of CdS/GQDs nanohybrids, which offers a new insight to understand the essential roles of GQDs in semiconductor

Temperature dependence of electrocatalytic and photocatalytic oxygen evolution reaction rates using NiFe oxide

KAUST Repository

Nurlaela, Ela; Shinagawa, Tatsuya; Qureshi, Muhammad; Dhawale, Dattatray Sadashiv; Takanabe, Kazuhiro

2016-01-01

The present work compares oxygen evolution reaction (OER) in electrocatalysis and photocatalysis in aqueous solutions using nanostructured NiFeOx as catalysts. The impacts of pH and reaction temperature on the electrocatalytic and photocatalytic OER

Optimised photocatalytic hydrogen production using core–shell AuPd promoters with controlled shell thickness

DEFF Research Database (Denmark)

Jones, Wilm; Su, Ren; Wells, Peter

2014-01-01

of these materials towards the reforming of alcohols for hydrogen production. The core–shell structured Au–Pd bimetallic nanoparticle supported on TiO2 has being of interest as it exhibited extremely high quantum efficiencies for hydrogen production. However, the effect of shell composition and thickness...... of the nanoparticles by a combination of X-ray absorption fine structure and X-ray photoelectron spectroscopy. Photocatalytic ethanol reforming showed that the core–shell structured Au–Pd promoters supported on TiO2 exhibit enhanced activity compared to that of monometallic Au and Pd as promoters, whilst the core......–shell Au–Pd promoters containing one ML equivalent Pd provide the optimum reactivity....

Controlled Synthesis of CuS/TiO2 Heterostructured Nanocomposites for Enhanced Photocatalytic Hydrogen Generation through Water Splitting.

Science.gov (United States)

Chandra, Moumita; Bhunia, Kousik; Pradhan, Debabrata

2018-04-16

Photocatalytic hydrogen (H 2 ) generation through water splitting has attracted substantial attention as a clean and renewable energy generation process that has enormous potential in converting solar-to-chemical energy using suitable photocatalysts. The major bottleneck in the development of semiconductor-based photocatalysts lies in poor light absorption and fast recombination of photogenerated electron-hole pairs. Herein we report the synthesis of CuS/TiO 2 heterostructured nanocomposites with varied TiO 2 contents via simple hydrothermal and solution-based process. The morphology, crystal structure, composition, and optical properties of the as-synthesized CuS/TiO 2 hybrids are evaluated in detail. Controlling the CuS/TiO 2 ratio to an optimum value leads to the highest photocatalytic H 2 production rate of 1262 μmol h -1 g -1 , which is 9.7 and 9.3 times higher than that of pristine TiO 2 nanospindles and CuS nanoflakes under irradiation, respectively. The enhancement in the H 2 evolution rate is attributed to increased light absorption and efficient charge separation with an optimum CuS coverage on TiO 2 . The photoluminescence and photoelectrochemical measurements further confirm the efficient separation of charge carriers in the CuS/TiO 2 hybrid. The mechanism and synergistic role of CuS and TiO 2 semiconductors for enhanced photoactivity is further delineated.

Enhanced photocatalytic hydrogen production on three-dimensional gold butterfly wing scales/CdS nanoparticles

Science.gov (United States)

Fang, Jing; Song, Guofen; Liu, Qinglei; Zhang, Wang; Gu, Jiajun; Su, Yishi; Su, Huilan; Guo, Cuiping; Zhang, Di

2018-01-01

Photocatalytic water splitting via utilizing various semiconductors is recognized as a promising way for hydrogen production. Plasmonic metals with sub-micrometer textures can improve the photocatalytic performance of semiconductors via a localized surface plasmon resonance (LSPR) process. Moreover, arrays of multilayer metallic structures can help generate strong LSPR. However, artificial synthesis has difficulties in constructing novel multilayer metallic arrays down to nanoscales. Here, we use three dimensional (3D) scales from Morpho didius forewings (M) to prepare 3D Au-wings with intact hierarchical bio-structures. For comparison, we use Troides helena forewings (T) which are known for their antireflection quasi-honeycomb structures resulting in strong light absorbing ability. Results show that multilayer rib structures of Au-M can significantly amplify the LSPR of 3D Au and thus can efficiently help the photocatalytic process (9-fold increase). This amplification effect is obviously more superior to the straightforward enhancement of the absorption of incident light (Au-T, 5-fold increase). Thus, our study provides the possibility to prepare highly efficient plasmonic photocatalysts (possessing 3D multilayer rib structures) via an easy method. This work will also be revealing for plasmonic applications in other fields.

Composite photocatalyst containing Eosin Y and multiwalled carbon nanotubes loaded with CuO/NiO: Mixed metal oxide as an active center of H2 evolution from water

International Nuclear Information System (INIS)

Kang Shizhao; Chen Lili; Li Xiangqing; Mu Jin

2012-01-01

A composite photocatalyst containing Eosin Y as a sensitizer, multiwalled carbon nanotubes as a supporter material or electron transfer channel, and CuO/NiO as an active center of H 2 evolution from water was fabricated and characterized with X-ray photoelectron spectroscopy and transmission electron microscope. Meanwhile, photocatalytic hydrogen evolution from water over this catalyst was explored using triethanolamine as a sacrificial reagent under visible irradiation. A rate of H 2 evolution of approximately 1.0 mmol g -1 h -1 was achieved under optimal conditions. Furthermore, for practical purposes, the photocatalytic hydrogen evolution was studied as a function of content of CuO/NiO, mass ratio of CuO to NiO, pH of solution, concentration of triethanolamine and dosage of Eosin Y, respectively. The results show that mixed metal oxides are a kind of promising active centers of H 2 evolution from water in the photocatalytic system studied.

Composite photocatalyst containing Eosin Y and multiwalled carbon nanotubes loaded with CuO/NiO: Mixed metal oxide as an active center of H2 evolution from water

Science.gov (United States)

Kang, Shi-Zhao; Chen, Lili; Li, Xiangqing; Mu, Jin

2012-06-01

A composite photocatalyst containing Eosin Y as a sensitizer, multiwalled carbon nanotubes as a supporter material or electron transfer channel, and CuO/NiO as an active center of H2 evolution from water was fabricated and characterized with X-ray photoelectron spectroscopy and transmission electron microscope. Meanwhile, photocatalytic hydrogen evolution from water over this catalyst was explored using triethanolamine as a sacrificial reagent under visible irradiation. A rate of H2 evolution of approximately 1.0 mmol g-1 h-1 was achieved under optimal conditions. Furthermore, for practical purposes, the photocatalytic hydrogen evolution was studied as a function of content of CuO/NiO, mass ratio of CuO to NiO, pH of solution, concentration of triethanolamine and dosage of Eosin Y, respectively. The results show that mixed metal oxides are a kind of promising active centers of H2 evolution from water in the photocatalytic system studied.

Highly Efficient Photocatalytic Hydrogen Production of Flower-like Cadmium Sulfide Decorated by Histidine

OpenAIRE

Wang, Qizhao; Lian, Juhong; Li, Jiajia; Wang, Rongfang; Huang, Haohao; Su, Bitao; Lei, Ziqiang

2015-01-01

Morphology-controlled synthesis of CdS can significantly enhance the efficiency of its photocatalytic hydrogen production. In this study, a novel three-dimensional (3D) flower-like CdS is synthesized via a facile template-free hydrothermal process using Cd(NO3)2•4H2O and thiourea as precursors and L-Histidine as a chelating agent. The morphology, crystal phase, and photoelectrochemical performance of the flower-like CdS and pure CdS nanocrystals are carefully investigated via various characte...

Hydrogen Production from Semiconductor-based Photocatalysis via Water Splitting

Directory of Open Access Journals (Sweden)

Jeffrey C. S. Wu

2012-10-01

Full Text Available Hydrogen is the ideal fuel for the future because it is clean, energy efficient, and abundant in nature. While various technologies can be used to generate hydrogen, only some of them can be considered environmentally friendly. Recently, solar hydrogen generated via photocatalytic water splitting has attracted tremendous attention and has been extensively studied because of its great potential for low-cost and clean hydrogen production. This paper gives a comprehensive review of the development of photocatalytic water splitting for generating hydrogen, particularly under visible-light irradiation. The topics covered include an introduction of hydrogen production technologies, a review of photocatalytic water splitting over titania and non-titania based photocatalysts, a discussion of the types of photocatalytic water-splitting approaches, and a conclusion for the current challenges and future prospects of photocatalytic water splitting. Based on the literatures reported here, the development of highly stable visible–light-active photocatalytic materials, and the design of efficient, low-cost photoreactor systems are the key for the advancement of solar-hydrogen production via photocatalytic water splitting in the future.

Composite photocatalyst containing Eosin Y and multiwalled carbon nanotubes loaded with CuO/NiO: Mixed metal oxide as an active center of H{sub 2} evolution from water

Energy Technology Data Exchange (ETDEWEB)

Kang Shizhao [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Chen Lili [Key Laboratory for Ultrafine Materials of the Ministry of Education, School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Li Xiangqing [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Mu Jin, E-mail: mujin@sit.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China)

2012-06-01

A composite photocatalyst containing Eosin Y as a sensitizer, multiwalled carbon nanotubes as a supporter material or electron transfer channel, and CuO/NiO as an active center of H{sub 2} evolution from water was fabricated and characterized with X-ray photoelectron spectroscopy and transmission electron microscope. Meanwhile, photocatalytic hydrogen evolution from water over this catalyst was explored using triethanolamine as a sacrificial reagent under visible irradiation. A rate of H{sub 2} evolution of approximately 1.0 mmol g{sup -1} h{sup -1} was achieved under optimal conditions. Furthermore, for practical purposes, the photocatalytic hydrogen evolution was studied as a function of content of CuO/NiO, mass ratio of CuO to NiO, pH of solution, concentration of triethanolamine and dosage of Eosin Y, respectively. The results show that mixed metal oxides are a kind of promising active centers of H{sub 2} evolution from water in the photocatalytic system studied.

Constructing a MoS2 QDs/CdS Core/Shell Flowerlike Nanosphere Hierarchical Heterostructure for the Enhanced Stability and Photocatalytic Activity

Directory of Open Access Journals (Sweden)

Shijing Liang

2016-02-01

Full Text Available MoS2 quantum dots (QDs/CdS core/shell nanospheres with a hierarchical heterostructure have been prepared by a simple microwave hydrothermal method. The as-prepared samples are characterized by XRD, TEM, SEM, UV-VIS diffuse reflectance spectra (DRS and N2-sorption in detail. The photocatalytic activities of the samples are evaluated by water splitting into hydrogen. Results show that the as-prepared MoS2 QDs/CdS core/shell nanospheres with a diameter of about 300 nm are composed of the shell of CdS nanorods and the core of MoS2 QDs. For the photocatalytic reaction, the samples exhibit a high stability of the photocatalytic activity and a much higher hydrogen evolution rate than the pure CdS, the composite prepared by a physical mixture, and the Pt-loaded CdS sample. In addition, the stability of CdS has also been greatly enhanced. The effect of the reaction time on the formations of nanospheres, the photoelectric properties and the photocatalytic activities of the samples has been investigated. Finally, a possible photocatalytic reaction process has also been proposed.

Hydrogen evolution by a metal-free electrocatalyst

KAUST Repository

Zheng, Yao

2014-04-28

Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics. © 2014 Macmillan Publishers Limited. All rights reserved.

Fast and simple microwave synthesis of TiO2/Au nanoparticles for gas-phase photocatalytic hydrogen generation

Science.gov (United States)

May-Masnou, Anna; Soler, Lluís; Torras, Miquel; Salles, Pol; Llorca, Jordi; Roig, Anna

2018-04-01

The fabrication of small anatase titanium dioxide (TiO2) nanoparticles (NPs) attached to larger anisotropic gold (Au) morphologies by a very fast and simple two-step microwave-assisted synthesis is presented. The TiO2/Au NPs are synthesized using polyvinylpyrrolidone (PVP) as reducing, capping and stabilizing agent through a polyol approach. To optimize the contact between the titania and the gold and facilitate electron transfer, the PVP is removed by calcination at mild temperatures. The nanocatalysts activity is then evaluated in the photocatalytic production of hydrogen from water/ethanol mixtures in gas-phase at ambient temperature. A maximum value of 5.3 mmol·gcat-1·h-1 (7.4 mmol·gTiO2-1·h-1) of hydrogen is recorded for the system with larger gold particles at an optimum calcination temperature of 450 °C. Herein we demonstrate that TiO2-based photocatalysts with high Au loading and large Au particle size (≈ 50 nm) NPs have photocatalytic activity.

Black TiO2 synthesized via magnesiothermic reduction for enhanced photocatalytic activity

Science.gov (United States)

Wang, Xiangdong; Fu, Rong; Yin, Qianqian; Wu, Han; Guo, Xiaoling; Xu, Ruohan; Zhong, Qianyun

2018-04-01

Utilizing solar energy for hydrogen evolution is a great challenge for its insufficient visible-light power conversion. In this paper, we report a facile magnesiothermic reduction of commercial TiO2 nanoparticles under Ar atmosphere and at 550 °C followed by acid treatment to synthesize reduced black TiO2 powders, which possesses a unique crystalline core-amorphous shell structure composed of disordered surface and oxygen vacancies and shows significantly improved optical absorption in the visible region. The unique core-shell structure and high absorption enable the reduced black TiO2 powders to exhibit enhanced photocatalytic activity, including splitting of water in the presence of Pt as a cocatalyst and degradation of methyl blue (MB) under visible light irradiation. Photocatalytic evaluations indicate that the oxygen vacancies play key roles in the catalytic process. The maximum hydrogen production rates are 16.1 and 163 μmol h-1 g-1 under the full solar wavelength range of light and visible light, respectively. This facile and versatile method could be potentially used for large scale production of colored TiO2 with remarkable enhancement in the visible light absorption and solar-driven hydrogen production.

Hydrogen evolution by a thermophilic blue-green alga. Mastigocladus laminosus

Energy Technology Data Exchange (ETDEWEB)

Mirua, Y; Yokoyama, H; Kanaoka, K; Saito, S; Iwasa, K; Okazaki, M; Komemushi, S

1980-01-01

The thermophillic blue-green alga (cyanobacterium), Mastigocladus laminosus isolated from a hot spring, evolved hydrogen gas under nitrogen-starved conditions in light when algal cells were grown in a nitrate-free medium. Cells grown in a nitrate-medium evolved no detectable hydrogen gas in light. The optimal temperature and pH for hydrogen evolution were 44-49 degrees C and 7.0-7.5. High activity of hydrogen evolution, 1.6 ml H/sub 2//mg chl.hr, was induced when algal cells grown in the nitrate medium were actively forming heterocysts in the nitrate-free medium in air. Hydrogen evolution in light was depressed by nitrogen gas and inhibited by salicylaldoxime or DNP. This hydrogen evolution by M. laminosus is attributed to the action of nitrogenase.

Nd-doped Bi2O3 nanocomposites: simple synthesis and improved photocatalytic activity for hydrogen production under visible light

Science.gov (United States)

Al-Namshah, Khadijah S.; Mohamed, Reda M.

2018-04-01

Bi2O3 has 2.4 eV band gap energy, which means it absorb in visible region. Though the photocatalytic activity of Bi2O3 is extremely little due to rapid rate of photogenerated electron-hole recombination. To face the economical and practical needs, the photocatalytic efficiency of Bi2O3 should be upgraded. In this paper, this was achieved by addition of neodymium to Bi2O3 nanosheets and Nd/Bi2O3 nanocomposites were prepared by a easy process at room temperature using a surfactant of Pluronic F127. The Bi2O3 nanosheets and Nd/Bi2O3 nanocomposites were investigated by many tools. The photocatalytic activity of Nd/Bi2O3 samples is better than Bi2O3 due to reduced band gap and reduced electron-hole recombination of Bi2O3 with addition of neodymium. In addition, Nd/Bi2O3 nanocomposites exhibit photocatalytic stability for hydrogen production which enables it to be reused on other occasions also.

Molten salt-mediated formation of g-C3N4-MoS2 for visible-light-driven photocatalytic hydrogen evolution

Science.gov (United States)

Li, Ni; Zhou, Jing; Sheng, Ziqiong; Xiao, Wei

2018-02-01

Construction of two-dimensional/two-dimensional (2D/2D) hybrid with well-defined composition and microstructure is a general protocol to achieve high-performance catalysts. We herein report preparation of g-C3N4-MoS2 hybrid by pyrolysis of affordable melamine and (NH4)2MoS4 in molten LiCl-NaCl-KCl at 550 °C. Molten salts are confirmed as ideal reaction media for formation of homogeneous hybrid. Characterizations suggest a strong interaction between g-C3N4 and MoS2 in the hybrid, which results in an enhanced visible-light-driven photocatalytic hydrogen generation of the hybrid with an optimal g-C3N4/MoS2 ratio. The present study highlights the merits of molten salt methods on preparation of 2D photocatalysts and provides a rational design of 2D/2D hybrid catalysts for advanced environmental and energy applications.

Trends in the exchange current for hydrogen evolution

DEFF Research Database (Denmark)

Nørskov, Jens Kehlet; Bligaard, Thomas; Logadottir, Ashildur

2005-01-01

A density functional theory database of hydrogen chemisorption energies on close packed surfaces of a number of transition and noble metals is presented. The bond energies are used to understand the trends in the exchange current for hydrogen evolution. A volcano curve is obtained when measured...... exchange currents are plotted as a function of the calculated hydrogen adsorption energies and a simple kinetic model is developed to understand the origin of the volcano. The volcano curve is also consistent with Pt being the most efficient electrocatalyst for hydrogen evolution. (c) 2005...

The effects of hydrothermal temperature on the photocatalytic performance of ZnIn2S4 for hydrogen generation under visible light irradiation

International Nuclear Information System (INIS)

Tian, Fei; Zhu, Rongshu; Song, Kelin; Niu, Minli; Ouyang, Feng; Cao, Gang

2015-01-01

Highlights: • The ZnIn 2 S 4 (120, 140, 160, 180, and 200 °C) was prepared. • The activities splitting water to hydrogen under visible light were evaluated. • The activity achieved the best when hydrothermal temperature was 160 °C. • The activity order is related to the surface morphology and surface defects. - Abstract: A series of ZnIn 2 S 4 photocatalysts were successfully synthesized using the hydrothermal method with different hydrothermal temperatures (120, 140, 160, 180, and 200 °C) and characterized by various analysis techniques, such as UV–vis, XRD, SEM, BET and PL. The results indicated that these photocatalysts had a similar band gap. The hydrothermal temperature had a huge influence on the properties of the photocatalysts such as the BET surface area, the total pore volume, the average pore diameter, the defects and the morphology. The photocatalytic activities of ZnIn 2 S 4 were evaluated based on photocatalytic hydrogen production from water under visible-light irradiation. The activity order is attributed to the coefficient of the surface morphology and the surface defects. The hydrogen production efficiency achieved the best when the hydrothermal temperature was 160 °C. On the basis of the characterization of the catalysts, the effects of the hydrothermal temperature on the photocatalytic activity of ZnIn 2 S 4 were discussed

Effects of donor doping and acceptor doping on rutile TiO2 particles for photocatalytic O2 evolution by water oxidation

Science.gov (United States)

Amano, Fumiaki; Tosaki, Ryosuke; Sato, Kyosuke; Higuchi, Yamato

2018-02-01

Crystalline defects of photocatalyst particles may be considered to be the recombination center of photoexcited electrons and holes. In this study, we investigated the photocatalytic activity of cation-doped rutile TiO2 photocatalysts for O2 evolution from an aqueous silver nitrate solution under ultraviolet light irradiation. The photocatalytic activity of rutile TiO2 was enhanced by donor doping of Ta5+ and Nb5+ with a valence higher than that of Ti4+, regardless of increased density of electrons and Ti3+ species (an electron trapped in Ti4+ sites). Conversely, acceptor doping of lower valence cations such as In3+ and Ga3+ decreased photocatalytic activity for O2 evolution by water oxidation. The doping of equal valence cations such as Sn4+ and Ge4+ hardly changed the activity of non-doped TiO2. This study demonstrates that Ti3+ species, which is a crystalline defect, enhanced the photocatalytic activity of semiconductor oxides, for example rutile TiO2 with large crystalline size.

Hydrogen storage and evolution catalysed by metal hydride complexes.

Science.gov (United States)

Fukuzumi, Shunichi; Suenobu, Tomoyoshi

2013-01-07

The storage and evolution of hydrogen are catalysed by appropriate metal hydride complexes. Hydrogenation of carbon dioxide by hydrogen is catalysed by a [C,N] cyclometalated organoiridium complex, [Ir(III)(Cp*)(4-(1H-pyrazol-1-yl-κN(2))benzoic acid-κC(3))(OH(2))](2)SO(4) [Ir-OH(2)](2)SO(4), under atmospheric pressure of H(2) and CO(2) in weakly basic water (pH 7.5) at room temperature. The reverse reaction, i.e., hydrogen evolution from formate, is also catalysed by [Ir-OH(2)](+) in acidic water (pH 2.8) at room temperature. Thus, interconversion between hydrogen and formic acid in water at ambient temperature and pressure has been achieved by using [Ir-OH(2)](+) as an efficient catalyst in both directions depending on pH. The Ir complex [Ir-OH(2)](+) also catalyses regioselective hydrogenation of the oxidised form of β-nicotinamide adenine dinucleotide (NAD(+)) to produce the 1,4-reduced form (NADH) under atmospheric pressure of H(2) at room temperature in weakly basic water. In weakly acidic water, the complex [Ir-OH(2)](+) also catalyses the reverse reaction, i.e., hydrogen evolution from NADH to produce NAD(+) at room temperature. Thus, interconversion between NADH (and H(+)) and NAD(+) (and H(2)) has also been achieved by using [Ir-OH(2)](+) as an efficient catalyst and by changing pH. The iridium hydride complex formed by the reduction of [Ir-OH(2)](+) by H(2) and NADH is responsible for the hydrogen evolution. Photoirradiation (λ > 330 nm) of an aqueous solution of the Ir-hydride complex produced by the reduction of [Ir-OH(2)](+) with alcohols resulted in the quantitative conversion to a unique [C,C] cyclometalated Ir-hydride complex, which can catalyse hydrogen evolution from alcohols in a basic aqueous solution (pH 11.9). The catalytic mechanisms of the hydrogen storage and evolution are discussed by focusing on the reactivity of Ir-hydride complexes.

PtNi Alloy Cocatalyst Modification of Eosin Y-Sensitized g-C3N4/GO Hybrid for Efficient Visible-Light Photocatalytic Hydrogen Evolution

Science.gov (United States)

Wang, Peng; Zong, Lanlan; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

2018-02-01

An economic and effective Pt-based alloy cocatalyst has attracted considerable attention due to their excellent catalytic activity and reducing Pt usage. In this study, PtNi alloy cocatalyst was successfully decorated on the g-C3N4/GO hybrid photocatalyst via a facile chemical reduction method. The Eosin Y-sensitized g-C3N4/PtNi/GO-0.5% composite photocatalyst yields about 1.54 and 1178 times higher hydrogen evolution rate than the Eosin Y-sensitized g-C3N4/Pt/GO-0.5% and g-C3N4/Ni/GO-0.5% samples, respectively. Mechanism of enhanced performance for the g-C3N4/PtNi/GO composite was also investigated by different characterization, such as photoluminescence, transient photocurrent response, and TEM. These results indicated that enhanced charge separation efficiency and more reactive sites are responsible for the improved hydrogen evolution performance due to the positive synergetic effect between Pt and Ni. This study suggests that PtNi alloy can be used as an economic and effective cocatalyst for hydrogen evolution reaction. [Figure not available: see fulltext.

Hydrogen peroxide-assisted synthesis of novel three-dimensional octagonal-like CuO nanostructures with enhanced visible-light-driven photocatalytic activity

Science.gov (United States)

Chen, Xiangyu; Chu, Deqing; Wang, Limin; Hu, Wenhui; Yang, Huifang; Sun, Jingjing; Zhu, Shaopeng; Wang, Guowei; Tao, Jian; Zhang, Songsong

2018-04-01

Novel three-dimensional octagonal-like CuO micro-/nanostructures with diameters ranging from 10 to 15 μm have been successfully prepared by hydrogen peroxide-assisted hydrothermal method and subsequent calcination. The product morphology can be changed by simply ordering the amount of hydrogen peroxide (H2O2). When the amounts of H2O2 is increased, the length of the corner portion is increased and the width is narrower. The obtained octagonal CuO nanostructures were evaluated for their ability for the degradation of hazardous organic contaminants in water under visible-light irradiation. Comparing with commercial CuO and other CuO products, the CuO octagonal nanostructures exhibit excellent performance for photocatalytic decomposition of RhB (Rhodamine B). It is well established that effective photocatalytic performance results from its unique 3D octagonal nanostructures. We believe that the present work will provide some ideas for further fabrication of other novel nanostructures and exploration of their applications.

Preparation of NaTaO3 by Spray Pyrolysis and Evaluation of Apparent Photocatalytic Activity for Hydrogen Production from Water

Directory of Open Access Journals (Sweden)

Hyun Woo Kang

2008-01-01

Full Text Available NaTaO3 photocatalyst was prepared by spray pyrolysis process and tested as photocatalyst for water splitting under UV light. Precursor solution was prepared from NaNO3 and Ta(OC2H55 in nitric acid solution and spray-pyrolyzed in air at between 973 and 1273 K. Considerable enhancement of photocatalytic activity was achieved by loading 0.05∼0.2 wt% of NiO on the surface of NaTaO3. The NiO loading was more effective on the NaTaO3 synthesized by spray pyrolysis in comparison with that synthesized by solid-state reaction. The quantum yield (QY of NiO/NaTaO3 photocatalyst was measured by chemical actinometry using potassium ferrioxalate and compared with the apparent photocatalytic activities (APA which would be more useful for the purpose of photocatalytic reactor design than the quantum yield. The apparent photocatalytic activity (APA was defined by the rate of hydrogen production divided by weight of catalyst, volume of reactant mixture, duration of irradiation, and power of UV lamp. The validity of the apparent photocatalytic activity (APA was discussed based on our results and reported activities of NaTaO3 photocatalyst loaded with or without NiO.

Hydrogen evolution by a metal-free electrocatalyst

KAUST Repository

Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Luhua; Han, Yu; Chen, Ying; Du, Aijun; Jaronieć, Mietek; Qiao, Shizhang

2014-01-01

Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All

Facile synthesis of flake-like TiO{sub 2}/C nano-composites for photocatalytic H{sub 2} evolution under visible-light irradiation

Energy Technology Data Exchange (ETDEWEB)

Yan, Baolin; Zhou, Juan; Liang, Xiaoyu; Song, Kainan; Su, Xintai, E-mail: suxintai827@163.com

2017-01-15

Highlights: • TiO{sub 2}/C nano-flakes were prepared by a facile phase-transfer strategy combined with salt-template calcination method. • The sub–10 nm of TiO{sub 2} NPs were uniformly dispersed on the carbon flakes. • The TiO{sub 2}/C nano-flakes showed a superior visible-light photocatalytic activity for H{sub 2} production. - Abstract: The production of H{sub 2} by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H{sub 2} by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO{sub 2}/C nano-flakes, which was used as an efficient visible-light photocatalyst for H{sub 2} evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO{sub 2} nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m{sup 2} g{sup −1} and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H{sub 2} production rate of 57.2 μmol h{sup −1} under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO{sub 2} and carbon in this hybrid catalyst. This work highlights the potential of TiO{sub 2}/C nano-flakes in the field of photocatalytic H{sub 2} evolution under visible-light irradiation.

Critical role of the semiconductor-electrolyte interface in photocatalytic performance for water-splitting reactions using Ta3N5 particles

KAUST Repository

Nurlaela, Ela

2014-08-26

Distinct photocatalytic performance was observed when Ta3N 5 was synthesized from commercially available Ta2O 5 or from Ta2O5 prepared from TaCl5 via the sol-gel route. With respect to photocatalytic O2 evolution with Ag+ as a sacrificial reagent, the Ta3N5 produced from commercial Ta2O5 exhibited higher activity than the Ta3N5 produced via the sol-gel route. When the Ta3N5 photocatalysts were decorated with Pt nanoparticles in a similar manner, the Ta3N5 from the sol-gel route exhibited higher photocatalytic hydrogen evolution activity from a 10% aqueous methanol solution than Ta3N5 prepared from commercial Ta2O5 where no hydrogen can be detected. Detailed surface and bulk characterizations were conducted to obtain fundamental insight into the resulting photocatalytic activities. The characterization techniques, including XRD, elemental analysis, Raman spectroscopy, UV-vis spectroscopy, and surface-area measurements, revealed only negligible differences between these two photocatalysts. Our thorough characterization of the surface properties demonstrated that the very thin outermost layer of Ta3N5, with a thickness of a few nanometers, consists of either the reduced state of tantalum (TaN) or an amorphous phase. The extent of this surface layer was likely dependent on the nature of precursor oxide surfaces. DFT calculations based on partially oxidized Ta3N4.83O0.17 and N deficient Ta3N4.83 consisting of reduced Ta species well described the optoelectrochemical properties obtained from the experiments. Electrochemical and Mott-Schottky analyses demonstrated that the surface layer drastically affects the energetic picture at the semiconductor-electrolyte interface, which can consequently affect the photocatalytic performance. Chemical etching of the surface of Ta3N5 particles to remove this surface layer unites the photocatalytic properties with the photocatalytic performance of these two materials. Mott-Schottky plots of these chemically etched Ta3N5 materials

Noble metal nanoparticle-functionalized ZnO nanoflowers for photocatalytic degradation of RhB dye and electrochemical sensing of hydrogen peroxide

International Nuclear Information System (INIS)

Hussain, Muhammad; Sun, Hongyu; Karim, Shafqat; Nisar, Amjad; Khan, Maaz; Ul Haq, Anwar; Iqbal, Munawar; Ahmad, Mashkoor

2016-01-01

Flower-like hierarchical Zinc oxide nanostructures synthesized by co-precipitation method have been hydrothermally functionalized with 8 nm Au NPs and 15 nm Ag nanoparticles. The photocatalytic and electrochemical performance of these structures are investigated. XPS studies show that the composite exhibits a strong interaction between noble metal nanoparticles (NPs) and Zinc oxide nanoflowers. The PL spectra exhibit UV emission arising due to near band edge transition and show that the reduced PL intensities of Au–ZnO and Ag–ZnO composites are responsible for improved photocatalytic activity arising due to increase in defects. Moreover, the presence of Au NPs on ZnO surface remarkably enhances photocatalytic activity as compared to Ag–ZnO and pure ZnO due to the higher catalytic activity and stability of Au NPs. On the other hand, Ag–ZnO-modified glassy carbon electrode shows good amperometric response to hydrogen peroxide (H_2O_2), with linear range from 1 to 20 µM, and detection limit of 2.5 µM (S/N = 3). The sensor shows high and reproducible sensitivity of 50.8 μA cm"−"2 μM"−"1 with a fast response less than 3 s and good stability as compared to pure ZnO and Au–ZnO-based sensors. All these results show that noble metal NPs-functionalized ZnO base nanocomposites exhibit great prospects for developing efficient non-enzymatic biosensor and environmental remediators.Graphical abstractZnO nanoflowers functionalized with noble metal nanoparticles enhance photocatalytic degradation of RhB dye and electrochemical sensing of hydrogen peroxide.

Noble metal nanoparticle-functionalized ZnO nanoflowers for photocatalytic degradation of RhB dye and electrochemical sensing of hydrogen peroxide

Energy Technology Data Exchange (ETDEWEB)

Hussain, Muhammad [PINSTECH, Nanomaterials Research Group, Physics Division (Pakistan); Sun, Hongyu [Tsinghua University, Laboratory of Advanced Materials and The State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering Beijing, National Center for Electron Microscopy (China); Karim, Shafqat; Nisar, Amjad; Khan, Maaz [PINSTECH, Nanomaterials Research Group, Physics Division (Pakistan); Ul Haq, Anwar [PINSTECH, Non-destructive testing Group (Pakistan); Iqbal, Munawar [University of the Punjab, Centre for High Energy Physics (Pakistan); Ahmad, Mashkoor, E-mail: mashkoorahmad2003@yahoo.com [PINSTECH, Nanomaterials Research Group, Physics Division (Pakistan)

2016-04-15

Flower-like hierarchical Zinc oxide nanostructures synthesized by co-precipitation method have been hydrothermally functionalized with 8 nm Au NPs and 15 nm Ag nanoparticles. The photocatalytic and electrochemical performance of these structures are investigated. XPS studies show that the composite exhibits a strong interaction between noble metal nanoparticles (NPs) and Zinc oxide nanoflowers. The PL spectra exhibit UV emission arising due to near band edge transition and show that the reduced PL intensities of Au–ZnO and Ag–ZnO composites are responsible for improved photocatalytic activity arising due to increase in defects. Moreover, the presence of Au NPs on ZnO surface remarkably enhances photocatalytic activity as compared to Ag–ZnO and pure ZnO due to the higher catalytic activity and stability of Au NPs. On the other hand, Ag–ZnO-modified glassy carbon electrode shows good amperometric response to hydrogen peroxide (H{sub 2}O{sub 2}), with linear range from 1 to 20 µM, and detection limit of 2.5 µM (S/N = 3). The sensor shows high and reproducible sensitivity of 50.8 μA cm{sup −2} μM{sup −1} with a fast response less than 3 s and good stability as compared to pure ZnO and Au–ZnO-based sensors. All these results show that noble metal NPs-functionalized ZnO base nanocomposites exhibit great prospects for developing efficient non-enzymatic biosensor and environmental remediators.Graphical abstractZnO nanoflowers functionalized with noble metal nanoparticles enhance photocatalytic degradation of RhB dye and electrochemical sensing of hydrogen peroxide.

Facile synthesis of polypyrrole functionalized nickel foam with catalytic activity comparable to Pt for the poly-generation of hydrogen and electricity

Science.gov (United States)

Tang, Tiantian; Li, Kan; Shen, Zhemin; Sun, Tonghua; Wang, Yalin; Jia, Jinping

2016-01-01

Polypyrrole functionalized nickel foam is facilely prepared through the potentiostatic electrodeposition. The PPy-functionalized Ni foam functions as a hydrogen-evolution cathode in a rotating disk photocatalytic fuel cell, in which hydrogen energy and electric power are generated by consuming organic wastes. The PPy-functionalized Ni foam cathode exhibits stable catalytic activities after thirteen continuous runs. Compared with net or plate structure, the Ni foam with a unique three-dimensional reticulate structure is conducive to the electrodeposition of PPy. Compared with Pt-group electrode, PPy-coated Ni foam shows a satisfactory catalytic performance for the H2 evolution. The combination of PPy and Ni forms a synergistic effect for the rapid trapping and removal of proton from solution and the catalytic reduction of proton to hydrogen. The PPy-functionalized Ni foam could be applied in photocatalytic and photoelectrochemical generation of H2. In all, we report a low cost, high efficient and earth abundant PPy-functionalized Ni foam with a satisfactory catalytic activities comparable to Pt for the practical application of poly-generation of hydrogen and electricity.

Exploring Hydrogen Evolution and the Overpotential

Science.gov (United States)

Lyon, Yana A.; Roberts, Adrienne A.; McMillin, David R.

2015-01-01

The laboratory experiment described provides insight into the energetics of hydrogen evolution at an electrode as well as the intrinsic barrier that typically impedes reaction. In the course of the exercise, students find that Sn(s) is thermodynamically capable of combining with protons to form hydrogen, but that the direct reaction occurs at a…

Highly efficient direct Z-scheme WO3/CdS-diethylenetriamine photocatalyst and its enhanced photocatalytic H2 evolution under visible light irradiation

Science.gov (United States)

Hu, Taiping; Li, Pengfei; Zhang, Jinfeng; Liang, Changhao; Dai, Kai

2018-06-01

Cadmium sulfide (CdS) has demonstrated great promise in artificial photocataytic hydrogen (H2) production. However, the serious photocorrosion hinders its effective interaction and real-life application. In this work, a typical direct Z-scheme WO3/CdS-diethylenetriamine (CdS-DETA) composite has been designed via facile in-situ solvothermal method, which exhibits excellent H2 production properties in visible light region. In this system, the inorganic-organic CdS-DETA nanobelts (NBs) possess enough active sites and large surface area for the encouraging nanojunction structure information. Furthermore, we also systematically calculated energy band structure and investigated charge transfer of the WO3/CdS-DETA by PL and photocurrent test, the results demonstrated that the suitable band gap matching between CdS-DETA and WO3 and high redox potential improve the separation of photogenerated holes and electrons, restraining intrinsic photocorrosion of CdS as well as improving the photocatalytic activity. 5%WO3/CdS-DETA presented the most outstanding H2 evolution rate (15522 μmol g-1 h-1), which is twice higher than that of pure CdS-DETA. WO3/CdS-DETA composites also presented high stability after three recycle H2 production experiment. Finally, direct Z-scheme photocatalytic mechanism is calculated.

Unbiased Photocatalytic Hydrogen Generation from Pure Water on Stable Ir-treated In 0.33 Ga 0.67 N Nanorods

KAUST Repository

Ebaid, Mohamed; Priante, Davide; Liu, Guangyu; Zhao, Chao; Sharizal Alias, Mohd; Buttner, Ulrich; Khee Ng, Tien; Taylor Isimjan, Tayirjan; Idriss, Hicham; Ooi, Boon S.

2017-01-01

InGaN-based nanostructures have recently been recognized as promising materials for efficient solar hydrogen generation. This is due to their chemical stability, adjustable optoelectronic properties, suitable band edge alignment, and large surface-to-volume ratio. The inherent high density of surface trapping states and the lack of compatible conductive substrates, however, hindered their use as stable photo-catalysts. We have designed, synthesized and tested an efficient photocatalytic system using stable In0.33Ga0.67N-based nanorods (NRs) grown on an all-metal stack substrate (Ti-Mo) for a better electron transfer process. In addition, we have applied a bifunctional ultrathin thiol-based organic surface treatment using 1,2-ethanedithiol (EDT), in which sulfur atoms protected the surface from oxidation. This treatment has dual functions, it passivates the surface (by the removal of dangling bonds) and creates ligands for linking Ir-metal ions as oxygen evolution centers on top of the semiconductor. This treatment when applied to In0.33Ga0.67N NRs resulted in a photo-catalyst that achieved 3.5% solar-to-hydrogen (STH) efficiency, in pure water (pH~7, buffer solution) under simulated one-sun (AM1.5G) illumination and without electrical bias. Over the tested period, a steady increase of the gas evolution rate was observed from which a turnover frequency of 0.23s-1 was calculated. The novel growth of InGaN-based NRs on a metal as well as the versatile surface functionalization techniques (EDT-Ir) have a high potential for making stable photo-catalysts with adjustable band gaps and band edges to harvest sun light.

Unbiased Photocatalytic Hydrogen Generation from Pure Water on Stable Ir-treated In 0.33 Ga 0.67 N Nanorods

KAUST Repository

Ebaid, Mohamed

2017-05-11

InGaN-based nanostructures have recently been recognized as promising materials for efficient solar hydrogen generation. This is due to their chemical stability, adjustable optoelectronic properties, suitable band edge alignment, and large surface-to-volume ratio. The inherent high density of surface trapping states and the lack of compatible conductive substrates, however, hindered their use as stable photo-catalysts. We have designed, synthesized and tested an efficient photocatalytic system using stable In0.33Ga0.67N-based nanorods (NRs) grown on an all-metal stack substrate (Ti-Mo) for a better electron transfer process. In addition, we have applied a bifunctional ultrathin thiol-based organic surface treatment using 1,2-ethanedithiol (EDT), in which sulfur atoms protected the surface from oxidation. This treatment has dual functions, it passivates the surface (by the removal of dangling bonds) and creates ligands for linking Ir-metal ions as oxygen evolution centers on top of the semiconductor. This treatment when applied to In0.33Ga0.67N NRs resulted in a photo-catalyst that achieved 3.5% solar-to-hydrogen (STH) efficiency, in pure water (pH~7, buffer solution) under simulated one-sun (AM1.5G) illumination and without electrical bias. Over the tested period, a steady increase of the gas evolution rate was observed from which a turnover frequency of 0.23s-1 was calculated. The novel growth of InGaN-based NRs on a metal as well as the versatile surface functionalization techniques (EDT-Ir) have a high potential for making stable photo-catalysts with adjustable band gaps and band edges to harvest sun light.

Photocatalytic hydrogen generation from water under visible light using core/shell nano-catalysts.

Science.gov (United States)

Wang, X; Shih, K; Li, X Y

2010-01-01

A microemulsion technique was employed to synthesize nano-sized photocatalysts with a core (CdS)/shell (ZnS) structure. The primary particles of the photocatalysts were around 10 nm, and the mean size of the catalyst clusters in water was about 100 nm. The band gaps of the catalysts ranged from 2.25 to 2.46 eV. The experiments of photocatalytic H(2) generation showed that the catalysts (CdS)(x)/(ZnS)(1-x) with x ranging from 0.1 to 1 were able to produce hydrogen from water photolysis under visible light. The catalyst with x=0.9 had the highest rate of hydrogen production. The catalyst loading density also influenced the photo-hydrogen production rate, and the best catalyst concentration in water was 1 g L(-1). The stability of the nano-catalysts in terms of size, morphology and activity was satisfactory during an extended test period for a specific hydrogen production rate of 2.38 mmol g(-1) L(-1) h(-1) and a quantum yield of 16.1% under visible light (165 W Xe lamp, lambda>420 nm). The results demonstrate that the (CdS)/(ZnS) core/shell nano-particles are a novel photo-catalyst for renewable hydrogen generation from water under visible light. This is attributable to the large band-gap ZnS shell that separates the electron/hole pairs generated by the CdS core and hence reduces their recombinations.

Metallic 1T-LixMoS2 Cocatalyst Significantly Enhanced the Photocatalytic H2 Evolution over Cd0.5Zn0.5S Nanocrystals under Visible Light Irradiation.

Science.gov (United States)

Du, Hong; Guo, Hong-Li; Liu, Ya-Nan; Xie, Xiao; Liang, Kuang; Zhou, Xiao; Wang, Xin; Xu, An-Wu

2016-02-17

In the present work, metallic 1T-LixMoS2 is utilized as a novel cocatalyst for Cd0.5Zn0.5S photocatalyst. The obtained LixMoS2/Cd0.5Zn0.5S hybrids show excellent photocatalytic performance for H2 generation from aqueous solution containing Na2S and Na2SO3 under splitting visible light illumination (λ ≥ 420 nm) without precious metal cocatalysts. It turns out that a certain amount of intercalating Li(+) ions ultimately drives the transition of MoS2 crystal from semiconductor triagonal phase (2H phase) to metallic phase (1T phase). The distinct properties of 1T-LixMoS2 promote the efficient separation of photoexcited electrons and holes when used as cocatalyst for Cd0.5Zn0.5S photocatalyst. As compared to 2H-MoS2 nanosheets only having edge active sites, photoinduced electrons not only transfer to the edge sites of 1T-LixMoS2, but also to the plane active sites of 1T-LixMoS2 nanosheets. The content of LixMoS2 in hybrid photocatalysts influences the photocatalytic activity. The optimal 1T-LixMoS2 (1.0 wt %)/Cd0.5Zn0.5S nanojunctions display the best activity for hydrogen production, achieving a hydrogen evolution rate of 769.9 μmol h(-1), with no use of noble metal loading, which is about 3.5 times higher than that of sole Cd0.5Zn0.5S, and 2 times higher than that of 2H-MoS2 (1.0 wt %)/Cd0.5Zn0.5S samples. Our results demonstrate that Li(+)-intercalated MoS2 nanosheets with high conductivity, high densities of active sites, low cost, and environmental friendliness are a prominent H2 evolution cocatalyst that might substitute for noble metal for potential hydrogen energy applications.

Hydrothermal growth of two dimensional hierarchical MoS2 nanospheres on one dimensional CdS nanorods for high performance and stable visible photocatalytic H2 evolution

Science.gov (United States)

Chava, Rama Krishna; Do, Jeong Yeon; Kang, Misook

2018-03-01

The visible photocatalytic H2 production from water splitting considered as a clean and renewable energy source could solve the problem of greenhouse gas emission from fossil fuels. Despite tremendous efforts, the development of cost effective, highly efficient and more stable visible photocatalysts for splitting of water remains a great challenge. Here, we report the heteronanostructures consisting of hierarchical MoS2 nanospheres grown on 1D CdS nanorods referred to as CdS-MoS2 HNSs as a high performance visible photocatalyst for H2 evolution. The as-synthesized CdS-MoS2 HNSs exhibited ∼11 fold increment of H2 evolution rate when compared to pure CdS nanorods. This remarkable enhanced hydrogen evolution performance can be assigned to the positive synergetic effect from heteronanostructures formed between the CdS and MoS2 components which assist as an electron sink and source for abundant active edge sites and in turn increases the charge separation. This study presents a low-cost visible photocatalyst for solar energy conversion to achieve efficient H2.

Time-Dependent Density Functional Theory Analysis of Triphenylamine-Functionalized Graphene Doped with Transition Metals for Photocatalytic Hydrogen Production.

Science.gov (United States)

Mota, Elder A V; Neto, Abel F G; Marques, Francisco C; Mota, Gunar V S; Martins, Marcelo G; Costa, Fabio L P; Borges, Rosivaldo S; Neto, Antonio M J C

2018-07-01

The electronic structures and optical properties of triphenylamine-functionalized graphene (G-TPA) doped with transition metals, using water as a solvent, were theoretically investigated to verify the efficiency of photocatalytic hydrogen production with the use of transition metals. This study was performed by Density Functional Theory and Time-dependent Density Functional Theory through Gaussian 09W software, adopting the B3LYP functional for all structures. The 6-31g(d) basis set was used for H, C and N atoms, and the LANL2DZ basis set for transition metals using the Effective Core Potentials method. Two approaches were adopted: (1) using single metallic dopants (Ni, Pd, Fe, Os and Pt) and (2) using combinations of Ni with the other dopants (NiPd, NiPt, NiFe and NiOs). The DOS spectra reveal an increase of accessible states in the valence shell, in addition to a gap decrease for all dopants. This doping also increases the absorption in the visible region of solar radiation where sunlight is most intense (400 nm to 700 nm), with additional absorption peaks. The results lead us to propose the G-TPA structures doped with Ni, Pd, Pt, NiPt or NiPd to be novel catalysts for the conversion of solar energy for photocatalytic hydrogen production, since they improve the absorption of solar energy in the range of interest for solar radiation; and act as reaction centers, reducing the required overpotential for hydrogen production from water.

Fabrication mechanism and photocatalytic activity for a novel graphene oxide hybrid functionalized with tetrakis-(4-hydroxylphenyl)porphyrin and 1-pyrenesulfonic acid

Science.gov (United States)

Luo, Qiang; Ge, Riyue; Kang, Shi-Zhao; Qin, Lixia; Li, Guodong; Li, Xiangqing

2018-01-01

A new type of nanohybrid (GO/THPP/PSA) was noncovalently constructed by anchoring 5, 10, 15, 20-tetrakis-(4-hydroxylphenyl)porphyrin (THPP) and 1-pyrenesulfonic acid hydrate (PSA) in graphene oxide (GO). The assembly mechanism of the nanohybrid was explored in detail. The results showed that THPP and PSA were attached in the GO by π-π stacking interaction and hydrogen bond. Compared with pure GO, GO/THPP or GO/PSA, the GO/THPP/PSA nanohybrid showed better photocatalytic activity for hydrogen evolution. The mechanism of electron transfer in the GO/THPP/PSA nanohybrid was investigated. It was shown that light absorption and separation of electron/hole pairs were improved dramatically due to wider light response and multi-channel electrons transfer in the hybrid. The results could initiate new ideas for constructing other graphene-based functionalized materials with high photocatalytic activity.

Temperature dependence of electrocatalytic and photocatalytic oxygen evolution reaction rates using NiFe oxide

KAUST Repository

Nurlaela, Ela

2016-01-25

The present work compares oxygen evolution reaction (OER) in electrocatalysis and photocatalysis in aqueous solutions using nanostructured NiFeOx as catalysts. The impacts of pH and reaction temperature on the electrocatalytic and photocatalytic OER kinetics were investigated. For electrocatalysis, a NiFeOx catalyst was hydrothermally decorated on Ni foam. In 1 M KOH solution, the NiFeOx electrocatalyst achieved 10 mA cm-2 at an overpotential of 260 mV. The same catalyst was decorated on the surface of Ta3N5 photocatalyst powder. The reaction was conducted in the presence of 0.1 M Na2S2O8 as a strong electron scavenger, thus likely leading to the OER being kinetically relevant. When compared with the bare Ta3N5, NiFeOx/Ta3N5 demonstrated a 5-fold improvement in photocatalytic activity in the OER under visible light irradiation, achieving a quantum efficiency of 24 % at 480 nm. Under the conditions investigated, a strong correlation between the electrocatalytic and photocatalytic performances was identified: an improvement in electrocatalysis corresponded with an improvement in photocatalysis without altering the identity of the materials. The rate change at different pH was likely associated with electrocatalytic kinetics that accordingly influenced the photocatalytic rates. The sensitivity of the reaction rates with respective to the reaction temperature resulted in an apparent activation energy of 25 kJ mol-1 in electrocatalysis, whereas that in photocatalysis was 16 kJ mol-1. The origin of the difference in these activation energy values is likely attributed to the possible effects of temperature on the individual thermodynamic and kinetic parameters of the reaction process. The work described herein demonstrates a method of “transferring the knowledge of electrocatalysis to photocatalysis” as a strong tool to rationally and quantitatively understand the complex reaction schemes involved in photocatalytic reactions.

Single-Atom Pt as Co-Catalyst for Enhanced Photocatalytic H2 Evolution.

Science.gov (United States)

Li, Xiaogang; Bi, Wentuan; Zhang, Lei; Tao, Shi; Chu, Wangsheng; Zhang, Qun; Luo, Yi; Wu, Changzheng; Xie, Yi

2016-03-23

Isolated single-atom platinum (Pt) embedded in the sub-nanoporosity of 2D g-C3 N4 as a new form of co-catalyst is reported. The highly stable single-atom co-catalyst maximizes the atom efficiency and alters the surface trap states of g-C3 N4 , leading to significantly enhanced photocatalytic H2 evolution activity, 8.6 times higher than that of Pt nanoparticles and up to 50 times that for bare g-C3 N4 . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tethering metal ions to photocatalyst particulate surfaces by bifunctional molecular linkers for efficient hydrogen evolution

KAUST Repository

Yu, Weili

2014-08-19

A simple and versatile method for the preparation of photocatalyst particulates modified with effective cocatalysts is presented; the method involves the sequential soaking of photocatalyst particulates in solutions containing bifunctional organic linkers and metal ions. The modification of the particulate surfaces is a universal and reproducible method because the molecular linkers utilize strong covalent bonds, which in turn result in modified monolayer with a small but controlled quantity of metals. The photocatalysis results indicated that the CdS with likely photochemically reduced Pd and Ni, which were initially immobilized via ethanedithiol (EDT) as a linker, were highly efficient for photocatalytic hydrogen evolution from Na2S-Na2SO3-containing aqueous solutions. The method developed in this study opens a new synthesis route for the preparation of effective photocatalysts with various combinations of bifunctional linkers, metals, and photocatalyst particulate materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tethering metal ions to photocatalyst particulate surfaces by bifunctional molecular linkers for efficient hydrogen evolution

KAUST Repository

Yu, Weili; Isimjan, Tayirjan T.; Del Gobbo, Silvano; Anjum, Dalaver Hussain; Abdel-Azeim, Safwat; Cavallo, Luigi; Garcia Esparza, Angel T.; Domen, Kazunari; Xu, Wei; Takanabe, Kazuhiro

2014-01-01

A simple and versatile method for the preparation of photocatalyst particulates modified with effective cocatalysts is presented; the method involves the sequential soaking of photocatalyst particulates in solutions containing bifunctional organic linkers and metal ions. The modification of the particulate surfaces is a universal and reproducible method because the molecular linkers utilize strong covalent bonds, which in turn result in modified monolayer with a small but controlled quantity of metals. The photocatalysis results indicated that the CdS with likely photochemically reduced Pd and Ni, which were initially immobilized via ethanedithiol (EDT) as a linker, were highly efficient for photocatalytic hydrogen evolution from Na2S-Na2SO3-containing aqueous solutions. The method developed in this study opens a new synthesis route for the preparation of effective photocatalysts with various combinations of bifunctional linkers, metals, and photocatalyst particulate materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photophysics and electrochemistry relevant to photocatalytic water splitting involved at solid–electrolyte interfaces

KAUST Repository

Shinagawa, Tatsuya

2016-08-04

Direct photon to chemical energy conversion using semiconductor-electrocatalyst-electrolyte interfaces has been extensively investigated for more than a half century. Many studies have focused on screening materials for efficient photocatalysis. Photocatalytic efficiency has been improved during this period but is not sufficient for industrial commercialization. Detailed elucidation on the photocatalytic water splitting process leads to consecutive six reaction steps with the fundamental parameters involved: The photocatalysis is initiated involving photophysics derived from various semiconductor properties (1: photon absorption, 2: exciton separation). The generated charge carriers need to be transferred to surfaces effectively utilizing the interfaces (3: carrier diffusion, 4: carrier transport). Consequently, electrocatalysis finishes the process by producing products on the surface (5: catalytic efficiency, 6: mass transfer of reactants and products). Successful photocatalytic water splitting requires the enhancement of efficiency at each stage. Most critically, a fundamental understanding of the interfacial phenomena is highly desired for establishing "photocatalysis by design" concepts, where the kinetic bottleneck within a process is identified by further improving the specific properties of photocatalytic materials as opposed to blind material screening. Theoretical modeling using the identified quantitative parameters can effectively predict the theoretically attainable photon-conversion yields. This article provides an overview of the state-of-the-art theoretical understanding of interfacial problems mainly developed in our laboratory. Photocatalytic water splitting (especially hydrogen evolution on metal surfaces) was selected as a topic, and the photophysical and electrochemical processes that occur at semiconductor-metal, semiconductor-electrolyte and metal-electrolyte interfaces are discussed.

Electrochemical Hydrogen Evolution

DEFF Research Database (Denmark)

Laursen, A.B.; Varela Gasque, Ana Sofia; Dionigi, F.

2012-01-01

The electrochemical hydrogen evolution reaction (HER) is growing in significance as society begins to rely more on renewable energy sources such as wind and solar power. Thus, research on designing new, inexpensive, and abundant HER catalysts is important. Here, we describe how a simple experiment...... catalysts based on this. Suited for upper-level high school and first-year university students, this exercise involves using a basic two-cell electrochemical setup to test multiple electrode materials as catalysts at one applied potential, and then constructing a volcano curve with the resulting currents...

A Facile Synthesis of Graphene-WO3 Nanowire Clusters with High Photocatalytic Activity for O2 Evolution

Directory of Open Access Journals (Sweden)

M.-J. Zhou

2014-01-01

Full Text Available In the present work, graphene-WO3 nanowire clusters were synthesized via a facile hydrothermal method. The obtained graphene-WO3 nanowire clusters were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, X-ray photoelectron spectroscopy (XPS, Fourier transform infrared spectroscopy (FT-IR, Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (DRS techniques. The photocatalytic oxygen (O2 evolution properties of the as-synthesized samples were investigated by measuring the amount of evolved O2 from water splitting. The graphene-WO3 nanowire clusters exhibited enhanced performance compared to pure WO3 nanowire clusters for O2 evolution. The amount of evolved O2 from water splitting after 8 h for the graphene-WO3 nanowire clusters is ca. 0.345 mmol/L, which is more than 1.9 times as much as that of the pure WO3 nanowire clusters (ca. 0.175 mmol/L. The high photocatalytic activity of the graphene-WO3 nanowire clusters was attributed to a high charge transfer rate in the presence of graphene.

Photocatalytic reforming of biomass for hydrogen production

NARCIS (Netherlands)

Ripken, R.M.; de Boer, V.J.H.W.; Gardeniers, J.G.E.; le Gac, S.

2017-01-01

Here, we describe a novel microfluidic device to determine the required bandgap for the photocatalytic reforming of biomass model substrates (ethylene glycol, glycerol, xylose and xylitol) in water. Furthermore, this device is applied to eventually elucidate the reaction mechanism of aqueous

Two-dimensional metal dichalcogenides and oxides for hydrogen evolution

DEFF Research Database (Denmark)

Pandey, Mohnish; Vojvodic, Aleksandra; Thygesen, Kristian Sommer

2015-01-01

We explore the possibilities of hydrogen evolution by basal planes of 2D metal dichalcogenides and oxides in the 2H and 1T class of structures using the hydrogen binding energy as a computational activity descriptor. For some groups of systems like the Ti, Zr, and Hf dichalcogenides the hydrogen...

Quantification of photocatalytic oxygenation of human blood.

Science.gov (United States)

Subrahmanyam, Aryasomayajula; Thangaraj, Paul R; Kanuru, Chandrasekhar; Jayakumar, Albert; Gopal, Jayashree

2014-04-01

Photocatalytic oxygenation of human blood is an emerging concept based on the principle of photocatalytic splitting of water into oxygen and hydrogen. This communication reports: (i) a design of a photocatalytic cell (PC) that separates the blood from UV (incident) radiation source, (ii) a pH, temperature and flow controlled circuit designed for quantifying the oxygenation of human blood by photocatalysis and (iii) measuring the current efficacy of ITO/TiO2 nano thin films in oxygenating human blood in a dynamic circuit in real time. The average increase in oxygen saturation was around 5% above baseline compared to control (p<0.0005). We believe this is one of the first attempts to quantify photocatalytic oxygenation of human blood under controlled conditions. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

The Synthesis and Electrocatalytic Activities of Molybdenum Sulfide for Hydrogen Evolution Reaction

KAUST Repository

Li, Zhengxing

2014-07-01

In the context of the future hydrogen economy, effective production of hydrogen (H2) from readily available and sustainable resources is of crucial importance. Hydrogen generation via water splitting by solar energy or electricity has attracted great attention in recent years. In comparison with photocatalytic water-splitting directly using solar light, which is ideal but the relevant technologies are not yet mature, electrolysis of water with catalyst is more practical at the current stage. The Pt-group noble metals are the most effective electrocatalysts for hydrogen evolution reaction (HER) from water, but their high costs limit their applications. Due to the earth-abundance and low price, MoS2 is expected to be a good alternative of the Pt-group metals for HER. Plenty of researches have been conducted for improving the HER activities of MoS2 by optimizing its synthesis method. However, it remains challenging to prepare MoS2 catalysts with high and controllable activity, and more investigations are still needed to better understand the structure-performance correlation in this system. In this thesis, we report a new strategy for fabricating MoS2 eletrocatalysts which gives rise to much improved HER performance and allows us to tune the electrocatalytic activity by varying the preparation conditions. Specifically, we sulfurized molybdenum oxide on the surface of a Ti foil electrode via a facile chemical vapor deposition (CVD) method, and directly used the electrode for HER testing. Depending on the CVD temperature, the MoO2-MoS2 nanocomposites show different HER activities. Under the optimal synthesis condition (400ºC), the resulting catalyst exhibited excellent HER activity: an onset potential (overpotential) of 0.095 V versus RHE and the Tafel slope of 40 mv/dec. Such a performance exceeds those of most reported MoS2 based HER electrocatalysts. We demonstrated that the CVD temperature has significant influence on the catalysts in crystallinity degree, particle

Two-dimensional porous architecture of protonated GCN and reduced graphene oxide via electrostatic self-assembly strategy for high photocatalytic hydrogen evolution under visible light

Energy Technology Data Exchange (ETDEWEB)

Pu, Chenchen; Wan, Jun; Liu, Enzhou; Yin, Yunchao; Li, Juan; Ma, Yongning [School of Chemical Engineering, Northwest University, Xi’an 710069 (China); Fan, Jun, E-mail: fanjun@nwu.edu.cn [School of Chemical Engineering, Northwest University, Xi’an 710069 (China); Hu, Xiaoyun, E-mail: hxy3275@nwu.edu.cn [School of Physics, Northwest University, Xi’an 710069 (China)

2017-03-31

Highlights: • The protonated GCN (pGCN) is prepared by acidic cutting and hydrothermal process. • The pGCN coupled with rGO are synthesized via electrostatic self-assembly strategy. • The pGCN-5 wt% rGO is obtained with a high specific surface area of 115.64 m{sup 2}g{sup −1}. • The pGCN-5 wt% rGO photocatalysts exhibit superb photocatalytic reduction capacity. - Abstract: Herein, porous protonated graphitic carbon nitride (pGCN) is prepared from bulk g-C{sub 3}N{sub 4} (GCN) directly by acidic cutting and hydrothermal process. The holey structure not only provides a lot of bounds on the accelerated and photo induced charge transfer and thus reduce the aggregation, but also endows the GCN with more exposure to the active site. The pGCN is obtained with an increased band gap of 2.91 eV together with a higher specific surface area of 82.76 m{sup 2}g{sup −1}. Meanwhile, the positively charged GCN resulted from the protonation pretreatment is beneficial for improving the interaction with negatively charged GO sheets. Compared with GCN, pGCN-rGO displays a significant decrease of PL intensities and an apparently enhancement of visible-light absorption, resulting a lower charge recombination rate and a better light absorption. Besides, the enhanced charge separation is demonstrated by photoluminescence emission spectroscopy and the transient photocurrent measurement. The photocatalytic performance studies for the degradation of MB indicate that pGCN-rGO exhibits the highest adsorption ability towards dye molecules. In addition, the pGCN-5 wt% rGO composite shows the optimal photocatalytic activity, the photodegradation rate of MB is 99.4% after 80 min of irradiation and the H{sub 2} evolution performance up to 557 μmol g{sup −1}h{sup −1} under visible light, which is much higher than the other control samples.

Advanced nanoporous TiO2 photocatalysts by hydrogen plasma for efficient solar-light photocatalytic application

Science.gov (United States)

An, Ha-Rim; Park, So Young; Kim, Hyeran; Lee, Che Yoon; Choi, Saehae; Lee, Soon Chang; Seo, Soonjoo; Park, Edmond Changkyun; Oh, You-Kwan; Song, Chan-Geun; Won, Jonghan; Kim, Youn Jung; Lee, Jouhahn; Lee, Hyun Uk; Lee, Young-Chul

2016-01-01

We report an effect involving hydrogen (H2)-plasma-treated nanoporous TiO2(H-TiO2) photocatalysts that improve photocatalytic performance under solar-light illumination. H-TiO2 photocatalysts were prepared by application of hydrogen plasma of assynthesized TiO2(a-TiO2) without annealing process. Compared with the a-TiO2, the H-TiO2 exhibited high anatase/brookite bicrystallinity and a porous structure. Our study demonstrated that H2 plasma is a simple strategy to fabricate H-TiO2 covering a large surface area that offers many active sites for the extension of the adsorption spectra from ultraviolet (UV) to visible range. Notably, the H-TiO2 showed strong ·OH free-radical generation on the TiO2 surface under both UV- and visible-light irradiation with a large responsive surface area, which enhanced photocatalytic efficiency. Under solar-light irradiation, the optimized H-TiO2 120(H2-plasma treatment time: 120 min) photocatalysts showed unprecedentedly excellent removal capability for phenol (Ph), reactive black 5(RB 5), rhodamine B (Rho B) and methylene blue (MB) — approximately four-times higher than those of the other photocatalysts (a-TiO2 and P25) — resulting in complete purification of the water. Such well-purified water (>90%) can utilize culturing of cervical cancer cells (HeLa), breast cancer cells (MCF-7), and keratinocyte cells (HaCaT) while showing minimal cytotoxicity. Significantly, H-TiO2 photocatalysts can be mass-produced and easily processed at room temperature. We believe this novel method can find important environmental and biomedical applications. PMID:27406992

Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

Science.gov (United States)

Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

2013-07-01

Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly.

Phosphate-bonded composite electrodes for hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Potvin, E.; Menard, H.; Lalancette, J.M. (Sherbrooke Univ., PQ (Canada). Dept. de Chimie); Brossard, L. (Institut de Recherche d' Hydro-Quebec, Varennes, PQ (Canada))

1990-03-01

A new process of cementing metallic powders to produce high surface area cathodes for alkaline water electrolysis is described. The binding compound is a tridimensional polymer of aluminium phosphate (AlPO{sub 4}). Phosphate-bonded composite electrodes give a low-polarization performance for hydrogen evolution in 1 M KOH aqueous solution in the case of 95wt% Pt and 98wt%Ni. When electrode materials are prepared with nickel powder, the electrocatalytic activity for the hydrogen evolution reaction, the chemical stability and the electrical conductivity depend on the Ni content and morphology of the electrode. The best performance and chemical stability with Ni as the starting material are obtained for spiky filamentary particles produced by the decomposition of nickel carbonyl. (author).

DFT investigation on two-dimensional GeS/WS2 van der Waals heterostructure for direct Z-scheme photocatalytic overall water splitting

Science.gov (United States)

Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Huang, Baibiao

2018-03-01

Recently, extensive attention has been paid to the direct Z-scheme systems for photocatalytic water splitting where carriers migrate directly between the two semiconductors without a redox mediator. In the present work, the electronic structure and related properties of two-dimensional (2D) van de Waals (vdW) GeS/WX2 (X = O, S, Se, Te) heterojunction are systematically investigated by first-principles calculations. Our results demonstrate that, the GeS/WS2 heterojunction could form a direct Z-scheme system for photocatalytic water splitting, whereas the GeS/WX2 (X = O, Se, Te) can't, because of their respective unsuitable electronic structures. For the GeS/WS2 heterojunction, the GeS and WS2 monolayers serve as photocatalysts for the hydrogen evolution reactionand oxygen evolution reaction, respectively. The internal electric field induced by the electron transfer at the interface can promote the separation of photo-generated charge carriers and formation of the interface Z-scheme electron transfer. Remarkably, the designed GeS/WS2 heterojunction not only enhances the hydrogen production activity of GeS and the oxygen production ability of WS2 but also improves the light absorption of the two monolayers by reducing the band gaps. Moreover, it is found that narrowing the interlayer distance could enhance the internal electric field, improving the photocatalytic ability of the vdW heterojunction. This work provides fundamental insights for further design and preparation of emergent metal dichalcogenide catalysts, beneficial for the development in clean energy.

Fullerene (C{sub 60})/CdS nanocomposite with enhanced photocatalytic activity and stability

Energy Technology Data Exchange (ETDEWEB)

Cai, Qiang [Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Hu, Zhuofeng, E-mail: st04hzhf@gmail.com [Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong (China); Zhang, Qian; Li, Boyuan [Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Shen, Zhurui, E-mail: shenzhurui@tju.edu.cn [Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)

2017-05-01

Highlights: • C{sub 60}/CdS nanocomposite has been fabricated as a novel visible-light-driven photocatalyst. • It exhibits enhanced photocatalytic activity and photostability than that of pure CdS reference. • The C{sub 60} improved the charge separation and transfer of nanocomposite due to its high electron affinity. - Abstract: Herein, the fullerene (C{sub 60})/CdS nanocomposite has been fabricated by a facile one-pot hydrothermal method. Its photocatatlytic hydrogen (H{sub 2}) evolution rate and degradation efficiency of Rhodamine B (Rh B) are evaluated under visible light irradiation (λ ≥ 420 nm). The content of C{sub 60} has been changed from 0.4 wt% to 8 wt%, and the optimal value for photocatalytic activity is determined to be 0.4 wt%. The H{sub 2} evolution rate over this optimal sample reaches 1.73 mmol h{sup −1} g{sup −1} and its apparent degradation rate of Rh B is 0.089 min{sup −1} (degradation efficiency of 97% within 40 min), which is 2.3 times and 1.5 times compared to that of pure CdS reference. Moreover, the photocorrosion of CdS in composite is effectively suppressed, and its photocatalytic activity can be well maintained after three recycles (97.8% retaining for composite vs. 84.4% retaining for CdS). Then, the enhanced photocatalytic activity and stability of C{sub 60}/CdS nanocomposite are further studied by spectroscopic and electrochemical methods. Results show that the C{sub 60} species covering on the surface of CdS can efficiently accelerate the separation and transfer of photoexcited charge carriers, which can improve its activity, and reduce the photocorrosion of CdS.

Fabrication of a Cu{sub 2}O/Au/TiO{sub 2} composite film for efficient photocatalytic hydrogen production from aqueous solution of methanol and glucose

Energy Technology Data Exchange (ETDEWEB)

Wang, Xi; Dong, Haitai; Hu, Zhe; Qi, Zhong; Li, Laisheng, E-mail: llsh@scnu.edu.cn

2017-05-15

Highlights: • A Cu{sub 2}O/Au/TiO{sub 2} film was synthesized successfully. • Hydrogen production of Cu{sub 2}O/Au/TiO{sub 2} film improved significantly. • The highest hydrogen production rate of the film was 125.3 mmol/h/m{sup 2}. • A Z-scheme charge transfer pathway was proposed. - Abstract: A novel Cu{sub 2}O/Au/TiO{sub 2} photocatalyst composite film was fabricated on a copper substrate for photocatalytic hydrogen production. The composite films, Cu{sub 2}O/Au/TiO{sub 2}, were stepwise synthesized by using electrochemical deposition, photodeposition, and coating methods. First, a Cu{sub 2}O film was synthesized using the electrochemical deposition method, after which Au was deposited onto the Cu{sub 2}O film through in-site photodeposition. Finally, TiO{sub 2} was coated on the surface of the Cu{sub 2}O/Au film. Its morphology and surface chemical composition was characterized by SEM, TEM, XRD and XPS. The optical characteristics (UV–Vis DRS, PL spectrum) of the films were also examined. The photocatalytic hydrogen production rate of the Cu{sub 2}O/Au/TiO{sub 2} composite film from a 20% vol. methanol solution increased to125.3 mmol/h/m{sup 2} under 300 W xenon lamp light irradiation. Compared to the TiO{sub 2} (13.5 mmol/h/m{sup 2}) film and Cu{sub 2}O/TiO{sub 2} film (83.2 mmol/h/m{sup 2}), the Cu{sub 2}O/Au/TiO{sub 2} film showed excellent photocatalytic performance for hydrogen generation. The Cu{sub 2}O/Au/TiO{sub 2} film has highly effective photocatalytic properties, which are attributed to the Z-scheme system and can not only enhance the absorption of solar light but also suppress the recombination of photogenerated electron-hole pairs. It is worth noting that by introducing Au into the interface of Cu{sub 2}O/TiO{sub 2}, the surface plasmon resonance (SPR)-induced local electric field formed at the Au site induces a Z-scheme charge transfer pathway inside the composite film (Cu{sub 2}O/Au/TiO{sub 2}), which promotes both the charge of the

Synthesis of hydrogen-carbon clathrate material and hydrogen evolution therefrom at moderate temperatures and pressures

Science.gov (United States)

Lueking, Angela [State College, PA; Narayanan, Deepa [Redmond, WA

2011-03-08

A process for making a hydrogenated carbon material is provided which includes forming a mixture of a carbon source, particularly a carbonaceous material, and a hydrogen source. The mixture is reacted under reaction conditions such that hydrogen is generated and/or released from the hydrogen source, an amorphous diamond-like carbon is formed, and at least a portion of the generated and/or released hydrogen associates with the amorphous diamond-like carbon, thereby forming a hydrogenated carbon material. A hydrogenated carbon material including a hydrogen carbon clathrate is characterized by evolution of molecular hydrogen at room temperature at atmospheric pressure in particular embodiments of methods and compositions according to the present invention.

Quantitative Analysis of the Morphology of {101} and {001} Faceted Anatase TiO ₂ Nanocrystals and Its Implication on Photocatalytic Activity

Energy Technology Data Exchange (ETDEWEB)

Liu, Jue [Chemical; Olds, Daniel [Chemical; Peng, Rui [Center; Yu, Lei [Department; Foo, Guo Shiou [Center; Qian, Shuo [Biology and; Keum, Jong [Center; Guiton, Beth S. [Department; Wu, Zili [Center; Page, Katharine [Chemical

2017-06-29

The atomistic structure and morphology (shape and size) of nanomaterials have strong influences on their physical and chemical properties. However, many characterization techniques focus exclusively on one length-scale regime or another when developing quantitative morphology/structural models. In this article, we demonstrate that powder X-ray diffraction and neutron pair distribution function (PDF) can be used to obtain accurate average morphology and atomistic structure of {001} and {101} faceted anatase TiO₂ nanocrystals based on differential evolution refinements using Debye scattering equation calculations. It is also demonstrated that the morphology polydispersity of TiO₂ nanocrystals can be effectively obtained from the diffraction data via a numerical refinement routine. The morphology refinement results are in good agreement with those from transmission electron microscopy and the modeling of small angle neutron scattering data. This method is successfully used to quantify the facet-specified photocatalytic hydrogen evolution activity of anatase TiO₂ nanocrystals with different {001} to {101} ratios. It is found that the sample with an intermediate amount of both {001} and {101} facets shows the best photocatalytic hydrogen evolution reaction (HER) activity. It is expected that the simultaneous structure and morphology refinement technique can be generally used to study the relationship between morphology and functionality of nanomaterials.

Controlled synthesis and photocatalytic investigation of different-shaped one-dimensional titanic acid nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Li, Qiuye [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); The Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 10080 (China); Key Laboratory of Special Functional Materials, Henan University, KaiFeng 475001 (China); Lu, Gongxuan [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2008-10-15

Different-shaped one-dimensional (1D) titanic acid nanomaterials (TANs) were prepared by hydrothermal synthesis. By changing the reaction temperature (120, 170 and 200 C), three kinds of 1D TAN, short-nanotubes (SNT), long-nanotubes (LNT), and nanorods (NR), were obtained. The obtained TANs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and solid-stated diffuse reflectance UV-vis spectra (UV-vis DRS) techniques. Based on these 1D TAN, Eosin Y-sensitized Pt-loaded TAN were prepared by the in situ impregnation and photo-reduction method. Their photocatalytic activity for hydrogen generation was evaluated in triethanolamine (TEOA) aqueous solution under visible light irradiation ({lambda} {>=} 420 nm). The results indicated that the morphology difference led to a significant variation of photocatalytic performance for hydrogen generation, with the activity order as follows: Eosin Y-sensitized Pt-loaded LNT > Eosin Y-sensitized Pt-loaded NR > Eosin Y-sensitized Pt-loaded SNT. The experimental conditions for photocatalytic hydrogen generation such as Pt loading content, the mass ratio of Eosin Y to TAN, and so on, were optimized. As a result, the highest apparent quantum yields of hydrogen generation for Eosin Y-sensitized Pt-loaded SNT, LNT, and NR were 6.65, 17.36, and 15.04%, respectively. The stability of these photocatalysts and the reaction mechanism of the photocatalytic hydrogen generation are also discussed in detail. (author)

Controlled synthesis and photocatalytic investigation of different-shaped one-dimensional titanic acid nanomaterials

Science.gov (United States)

Li, Qiuye; Lu, Gongxuan

Different-shaped one-dimensional (1D) titanic acid nanomaterials (TANs) were prepared by hydrothermal synthesis. By changing the reaction temperature (120, 170 and 200 °C), three kinds of 1D TAN, short-nanotubes (SNT), long-nanotubes (LNT), and nanorods (NR), were obtained. The obtained TANs were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and solid-stated diffuse reflectance UV-vis spectra (UV-vis DRS) techniques. Based on these 1D TAN, Eosin Y-sensitized Pt-loaded TAN were prepared by the in situ impregnation and photo-reduction method. Their photocatalytic activity for hydrogen generation was evaluated in triethanolamine (TEOA) aqueous solution under visible light irradiation (λ ≥ 420 nm). The results indicated that the morphology difference led to a significant variation of photocatalytic performance for hydrogen generation, with the activity order as follows: Eosin Y-sensitized Pt-loaded LNT > Eosin Y-sensitized Pt-loaded NR > Eosin Y-sensitized Pt-loaded SNT. The experimental conditions for photocatalytic hydrogen generation such as Pt loading content, the mass ratio of Eosin Y to TAN, and so on, were optimized. As a result, the highest apparent quantum yields of hydrogen generation for Eosin Y-sensitized Pt-loaded SNT, LNT, and NR were 6.65, 17.36, and 15.04%, respectively. The stability of these photocatalysts and the reaction mechanism of the photocatalytic hydrogen generation are also discussed in detail.

Tethered Transition Metals Promoted Photocatalytic System for Efficient Hydrogen Evolutions

KAUST Repository

Takanabe, Kazuhiro

2015-03-05

The present invention is directed, at least in part, to a process for improving the efficiency of a photocatalyst (a semiconductor photocatalyst) by tethering (depositing) a metal (e.g., metal ions of a late transition metal, such as nickel) to the semiconductor (photocatalyst) surface through the use of an organic ligand. More specifically, 1,2-ethanedithiol (EDT) functions as an excellent molecular linker (organic ligand) to attach a transition metal complex (e.g., nickel (Ni.sup.2+ ions)) to the semiconductor surface, which can be in the form of a cadmium sulfide surface. The photocatalyst has particular utility in generating hydrogen from H.sub.2S.

Tethered Transition Metals Promoted Photocatalytic System for Efficient Hydrogen Evolutions

KAUST Repository

Takanabe, Kazuhiro; Isimjan, Tayirjan; Yu, Weili; Del Gobbo, Silvano; Xu, Wei

2015-01-01

The present invention is directed, at least in part, to a process for improving the efficiency of a photocatalyst (a semiconductor photocatalyst) by tethering (depositing) a metal (e.g., metal ions of a late transition metal, such as nickel) to the semiconductor (photocatalyst) surface through the use of an organic ligand. More specifically, 1,2-ethanedithiol (EDT) functions as an excellent molecular linker (organic ligand) to attach a transition metal complex (e.g., nickel (Ni.sup.2+ ions)) to the semiconductor surface, which can be in the form of a cadmium sulfide surface. The photocatalyst has particular utility in generating hydrogen from H.sub.2S.

Pouous TiO2 nanofibers decorated CdS nanoparticles by SILAR method for enhanced visible-light-driven photocatalytic activity

Science.gov (United States)

Tian, Fengyu; Hou, Dongfang; Hu, Fuchao; Xie, Kui; Qiao, Xiuqing; Li, Dongsheng

2017-01-01

1D porous CdS nanoparticles/TiO2 nanofibers heterostructure has been fabricated via simple electrospinning and a successive ionic layer adsorption and reaction (SILAR) process. The morphology, composition, and optical properties of the resulting CdS/TiO2 heterostructures can be rationally tailored through changing the SILAR cycles. The photocatalytic hydrogen evolution and decomposition of rhodamine B (RhB) of the as-synthesized heterostructured photocatalysts were investigated under visible light irradiation. Compared to TiO2 nanofibers，the as-obtained CdS/TiO2 heterostructures exhibit enhanced photocatalytic activity for hydrogen production and decomposition of RhB under visible-light irradiation. The heterojunction system performs best with H2 generation rates of 678.61 μmol h-1 g-1 under visible light irradiation which benefits from the two effects: (a) the 1D porous nanofibrous morphology contributes to not only more active sites but also more efficient transfer of the photogenerated charges (b) the synergetic effect of heterojunction and photosensitization reducing the recombination of photogenerated electrons and holes.

Oxidation driven ZnS Core-ZnO shell photocatalysts under controlled oxygen atmosphere for improved photocatalytic solar water splitting

Science.gov (United States)

Bak, Daegil; Kim, Jung Hyeun

2018-06-01

Zinc type photocatalysts attract great attentions in solar hydrogen production due to their easy availability and benign environmental characteristics. Spherical ZnS particles are synthesized with a facile hydrothermal method, and they are further used as core materials to introduce ZnO shell layer surrounding the core part by partial oxidation under controlled oxygen contents. The resulting ZnS core-ZnO shell photocatalysts represent the heterostructural type II band alignment. The existence of oxide layer also influences on proton adsorption power with an aid of strong base cites derived from highly electronegative oxygen atoms in ZnO shell layer. Photocatalytic water splitting reaction is performed to evaluate catalyst efficiency under standard one sun condition, and the highest hydrogen evolution rate (1665 μmolg-1h-1) is achieved from the sample oxidized at 16.2 kPa oxygen pressure. This highest hydrogen production rate is achieved in cooperation with increased light absorption and promoted charge separations. Photoluminescence analysis reveals that the improved visible light response is obtained after thermal oxidation process due to the oxygen vacancy states in the ZnO shell layer. Therefore, overall photocatalytic efficiency in solar hydrogen production is enhanced by improved charge separations, crystallinity, and visible light responses from the ZnS core-ZnO shell structures induced by thermal oxidation.

Tuning Cu dopant of Zn 0.5 Cd 0.5 S nanocrystals enables high-performance photocatalytic H 2 evolution from water splitting under visible-light irradiation

Energy Technology Data Exchange (ETDEWEB)

Mei, Zongwei; Zhang, Bingkai; Zheng, Jiaxin; Yuan, Sheng; Zhuo, Zengqing; Meng, Xianguang; Chen, Zonghai; Amine, Khalil; Yang, Wanli; Wang, Lin. -Wang; Wang, Wei; Wang, Shufeng; Gong, Qihuang; Li, Jun; Liu, Fu. -Sheng; Pan, Feng

2016-08-01

Cu-doping into Zn1-xCdxS can greatly enhance the photocatalytic H2 evolution from water splitting under visible-light irradiation. However, it is still controversial for how the Cu-dopant improves this performance. Here, we report that appropriate Cu-doped Zn0.5Cd0.5S nanocrystals reach 21.4 mmol/h/g of H2 evolution rate without cocatalyst in the visible-light region, which is also 2.8 times as high as that of the undoped counterpart, and the corresponding apparent quantum efficiency is 18.8% at 428 nm. It is firstly confirmed that the Cu2+ changes into Cu+ after being doped by soft X-ray absorption spectroscopy (sXAS). We theoretically propose that the transformation of 2Cu2+ to 2Cu+ results in one adjacent S2- vacancy (VS) in host during the doping process, while the Cu+-dopant and VS attract the photoexcited holes and electrons, respectively. Accordingly, the photocatalytic activity is improved due to the enhanced separation of photoexcited carriers accompanied with the enhanced light absorption resulting from the Cu+-dopant and 2Cu+/VS complex as possible active site for photocatalytic H2 evolution.

Hydrogen bubble formation and evolution in tungsten under different hydrogen irradiation conditions

Energy Technology Data Exchange (ETDEWEB)

Hu, Wenhui; Luo, Fengfeng; Shen, Zhenyu [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Zheng, Zhongcheng; Wen, Yongming [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Ren, Yaoyao [Center for Electron Microscopy, Wuhan University, Wuhan 430072 (China)

2015-01-15

Highlights: • Direct and clear observation of hydrogen bubbles evolution by TEM is provided. • The role of temperature playing in bubble formation and evolution is fully explored. • Vacancy trapping mechanism is verified in this experiment. - Abstract: In order to see how hydrogen is behaving in tungsten and to understand the way bubbles form and grow up, specimens were irradiated by hydrogen ions from room temperature to 800 °C to fluence of 2.25 × 10{sup 21} m{sup −2}. Experimental results show that higher temperature helped bubble acquire higher internal pressure, causing interstitial loop punching to happen. In this process bubbles’ size grew and dislocation loops were formed but dislocation loops migrated away at and above 350 °C. And bubble number density reached peak value at 600 °C but then dropped dramatically at 800 °C. Because continuously increasing temperature would cause small bubbles dissolution or leaking out. Besides, high temperature also prevented tiny bubbles growing to be visible under TEM observation by their reaching equilibrium pressure before reaching threshold pressure for loop punching. In the other set of experiments, specimens were irradiated by low hydrogen fluence of 1 × 10{sup 20} m{sup −2} at 600 °C, in which case few hydrogen bubbles appeared. With further increasing irradiation fluence, bubble number density quickly increased. Small bubbles tended to coalesce to become larger visible bubbles. And they continued to grow through loop punching until their internal pressure cannot support their size expansion any more.

Formation of combustible hydrocarbons and H2 during photocatalytic decomposition of various organic compounds under aerated and deaerated conditions.

Science.gov (United States)

Mozia, Sylwia; Kułagowska, Aleksandra; Morawski, Antoni W

2014-11-26

A possibility of photocatalytic production of useful aliphatic hydrocarbons and H2 from various organic compounds, including acetic acid, methanol, ethanol and glucose, over Fe-modified TiO2 is discussed. In particular, the influence of the reaction atmosphere (N2, air) was investigated. Different gases were identified in the headspace volume of the reactor depending on the substrate. In general, the evolution of the gases was more effective in air compared to a N2 atmosphere. In the presence of air, the gaseous phase contained CO2, CH4 and H2, regardless of the substrate used. Moreover, formation of C2H6 and C3H8 in the case of acetic acid and C2H6 in the case of ethanol was observed. In case of acetic acid and methanol an increase in H2 evolution under aerated conditions was observed. It was concluded that the photocatalytic decomposition of organic compounds with simultaneous generation of combustible hydrocarbons and hydrogen could be a promising method of "green energy" production.

Carbon dots decorated vertical SnS_2 nanosheets for efficient photocatalytic oxygen evolution

International Nuclear Information System (INIS)

Cheng, Zhongzhou; Wang, Fengmei; Shifa, Tofik Ahmed; Liu, Kaili; Huang, Yun; Jiang, Chao; He, Jun; Liu, Quanlin

2016-01-01

Metal sulfides are highly desirable materials for photocatalytic water splitting because of their appropriate energy bands. However, the poor stability under light illumination in water hinders their wide applications. Here, two-dimensional SnS_2 nanosheets, along with carbon dots of the size around 10 nm, are uniformly grown on fluorine doped tin oxide glasses with a layer of nickel nanoparticles. Significantly, strong light absorption and enhanced photocurrent density are achieved after integration of SnS_2 nanosheets with carbon dots. Notably, the rate of oxygen evolution reached up to 1.1 mmol g"−"1 h"−"1 under simulated sunlight irradiation featuring a good stability.

In-situ investigation of hydrogen evolution behavior in vanadium redox flow batteries

International Nuclear Information System (INIS)

Wei, L.; Zhao, T.S.; Xu, Q.; Zhou, X.L.; Zhang, Z.H.

2017-01-01

Highlights: • An in-situ method to investigate hydrogen evolution in VRFBs is developed. • The rate of hydrogen evolution during battery operation is quantified. • The gas evolution behaviors in the charge process of VRFBs are observed. - Abstract: In this work, we conceived and fabricated a three-electrode electrochemical cell and transparent vanadium redox flow battery to in-situ investigate the hydrogen evolution reaction during battery operation. Experimental results show that operating temperature has a strong influence on the HER rate. In particular, compared with V"3"+ reduction reaction, HER is more sensitive to temperature variation. It is also found that, contrary to the conventional wisdom that side reactions occur at the late stage of the charge process, H_2 evolves at a relatively low SOC. About 0.26 and 1.94 mL H_2 were collected at an early (SOC lower than 20%) and end of the charge process, respectively, suggesting that attention to the hydrogen formation at the negative electrode in the early charge process should also be paid to during long-term battery operations. Moreover, the produced hydrogen gas at the negative side prefers to form macroscopically observable bubbles onto the electrode surface, covering the active sites for vanadium redox reactions, while oxygen evolution (including CO_2 production) at the positive side corrodes electrode surface and introduces certain oxygen-containing functional groups.

Transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons and the influence of the transformation strategies on the photocatalytic performance

Directory of Open Access Journals (Sweden)

Melita Rutar

2015-03-01

Full Text Available The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400–650 °C, (ii through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g/Ar(g flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti4+ to Ti3+. The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the

Solvent-Induced Deposition of Cu-Ga-In-S Nanocrystals onto a Titanium Dioxide Surface for Visible-Light-Driven Photocatalytic Hydrogen Production

KAUST Repository

Kandiel, Tarek

2015-11-25

In this paper, copper-gallium-indium-sulfide (CGIS) nanocrystals with different Ga/In ratios, i.e., CuGaxIn5-xS8, where x = 0, 1, 2, 3, 4 and 5, were synthesized and investigated for visible-light-driven hydrogen (H2) evolution from aqueous solutions that contain sulfide/sulfite ions. The synthesized CGIS nanocrystals were characterized by diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). With 1.0 wt.% Ru as a co-catalyst, the H2 evolution rate on CuGa2In3S8 (CGIS hereafter) showed the highest activity. The CGIS nanocrystals were deposited onto a TiO2 surface via a unique solvent-induced deposition method. The CGIS/TiO2 photocatalyst showed comparable activity to that obtained using bare CGIS nanocrystals when the photocatalyst amount was sufficient in the photoreactor system, suggesting that TiO2 remains intact in terms of photocatalytic activity. The quantity of CGIS nanocrystals, however, required to achieve the rate-plateau condition at saturation was much lower in the presence of TiO2. The enhanced activities at low CGIS loadings observed in the presence of TiO2 were explained by the improved dispersion of the powder suspension and optical path in the photoreactor. This TiO2 supported photocatalyst lowers the required amount of photocatalyst, which is beneficial from an economic point of view.

Dye-sensitized Pt@TiO2 core–shell nanostructures for the efficient photocatalytic generation of hydrogen

Directory of Open Access Journals (Sweden)

Jun Fang

2014-03-01

Full Text Available Pt@TiO2 core–shell nanostructures were prepared through a hydrothermal method. The dye-sensitization of these Pt@TiO2 core–shell structures allows for a high photocatalytic activity for the generation of hydrogen from proton reduction under visible-light irradiation. When the dyes and TiO2 were co-excited through the combination of two irradiation beams with different wavelengths, a synergic effect was observed, which led to a greatly enhanced H2 generation yield. This is attributed to the rational spatial distribution of the three components (dye, TiO2, Pt, and the vectored transport of photogenerated electrons from the dye to the Pt particles via the TiO2 particle bridge.

Chitosan catalyzes hydrogen evolution at mercury electrodes

Czech Academy of Sciences Publication Activity Database

Paleček, Emil; Římánková, Ludmila

2014-01-01

Roč. 44, JUL2014 (2014), s. 59-62 ISSN 1388-2481 R&D Projects: GA ČR(CZ) GAP301/11/2055 Institutional support: RVO:68081707 Keywords : Chitosan * Glucosamine-containing polymers * Catalytic hydrogen evolution Subject RIV: BO - Biophysics Impact factor: 4.847, year: 2014

Insights into highly improved solar-driven photocatalytic oxygen evolution over integrated Ag3PO4/MoS2 heterostructures

Science.gov (United States)

Cui, Xingkai; Yang, Xiaofei; Xian, Xiaozhai; Tian, Lin; Tang, Hua; Liu, Qinqin

2018-04-01

Oxygen evolution has been considered as the rate-determining step in photocatalytic water splitting due to its sluggish four-electron half-reaction rate, the development of oxygen-evolving photocatalysts with well-defined morphologies and superior interfacial contact is highly important for achieving high-performance solar water splitting. Herein, we report the fabrication of Ag3PO4/MoS2 nanocomposites and, for the first time, their use in photocatalytic water splitting into oxygen under LED light illumination. Ag3PO4 nanoparticles were found to be anchored evenly on the surface of MoS2 nanosheets, confirming an efficient hybridization of two semiconductor materials. A maximum oxygen-generating rate of 201.6 mol L-1 g-1 h-1 was determined when 200 mg MoS2 nanosheets were incorporated into Ag3PO4 nanoparticles, which is around 5 times higher than that of bulk Ag3PO4. Obvious enhancements in light-harvesting property, as well as electron-hole separation and charge transportation are revealed by the combination of different characterizations. ESR analysis verified that more active oxygen-containing radicals generate over illuminated Ag3PO4/MoS2 composite photocatalysts rather than irradiated Ag3PO4. The improvement in oxygen evolution performance of Ag3PO4/MoS2 composite photocatalysts is ascribed to wide spectra response in the visible-light region, more efficient charge separation and enhanced oxidation capacity in the valence band (VB). This study provides new insights into the design and development of novel composite photocatalytic materials for solar-to-fuel conversion.

Nanoplasmonically Engineered Interfaces on Amorphous TiO2 for Highly Efficient Photocatalysis in Hydrogen Evolution.

Science.gov (United States)

Liang, Huijun; Meng, Qiuxia; Wang, Xiaobing; Zhang, Hucheng; Wang, Jianji

2018-04-25

The nanoplasmonic metal-driven photocatalytic activity depends heavily on the spacing between metal nanoparticles (NPs) and semiconductors, and this work shows that ethylene glycol (EG) is an ideal candidate for interface spacer. Controlling the synthetic systems at pH 3, the composite of Ag NPs with EG-stabilized amorphous TiO 2 (Ag/TiO 2 -3) was synthesized by the facile light-induced reduction. It is verified that EG spacers can set up suitable geometric arrangement in the composite: the twin hydroxyls act as stabilizers to bind Ag NPs and TiO 2 together and the nonconductive alkyl chains consisting only of two CH 2 are able to separate the two building blocks completely and also provide the shortest channels for an efficient transfer of radiation energies to reach TiO 2 . Employed as photocatalysts in hydrogen evolution under visible light, amorphous TiO 2 hardly exhibits the catalytic activity due to high defect density, whereas Ag/TiO 2 -3 represents a remarkably high catalytic efficiency. The enhancement mechanism of the reaction rate is proposed by the analysis of the compositional, structural, and optical properties from a series of Ag/TiO 2 composites.

Promotion of atomic hydrogen recombination as an alternative to electron trapping for the role of metals in the photocatalytic production of H2.

Science.gov (United States)

Joo, Ji Bong; Dillon, Robert; Lee, Ilkeun; Yin, Yadong; Bardeen, Christopher J; Zaera, Francisco

2014-06-03

The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead.

Porous TiO_2 nanofibers decorated CdS nanoparticles by SILAR method for enhanced visible-light-driven photocatalytic activity

International Nuclear Information System (INIS)

Tian, Fengyu; Hou, Dongfang; Hu, Fuchao; Xie, Kui; Qiao, Xiuqing; Li, Dongsheng

2017-01-01

Graphical abstract: A heterojunction photocatalyst with CdS Nanoparticles self-assembled via SILAR Method at surfaces of electrospun TiO2 nanofibers shows enhanced visible-light photocatalytic activities. - Highlights: • Combined electrospinning and successive ionic layer adsorption and reaction process. • Pouous TiO_2 nanofibers decorated CdS nanoparticles. • Synergetic effect of photosensitization and heterojunction. - Abstract: 1D porous CdS nanoparticles/TiO_2 nanofibers heterostructure has been fabricated via simple electrospinning and a successive ionic layer adsorption and reaction (SILAR) process. The morphology, composition, and optical properties of the resulting CdS/TiO_2 heterostructures can be rationally tailored through changing the SILAR cycles. The photocatalytic hydrogen evolution and decomposition of rhodamine B (RhB) of the as-synthesized heterostructured photocatalysts were investigated under visible light irradiation. Compared to TiO_2 nanofibers，the as-obtained CdS/TiO_2 heterostructures exhibit enhanced photocatalytic activity for hydrogen production and decomposition of RhB under visible-light irradiation. The heterojunction system performs best with H_2 generation rates of 678.61 μmol h"−"1 g"−"1 under visible light irradiation which benefits from the two effects: (a) the 1D porous nanofibrous morphology contributes to not only more active sites but also more efficient transfer of the photogenerated charges (b) the synergetic effect of heterojunction and photosensitization reducing the recombination of photogenerated electrons and holes.

Alkaline hydrogen peroxide treatment for TiO_2 nanoparticles with superior water-dispersibility and visible-light photocatalytic activity

International Nuclear Information System (INIS)

Wu, Chung-Yi; Tu, Kuan-Ju; Lo, Yu-Shiu; Pang, Yean Ling; Wu, Chien-Hou

2016-01-01

Alkaline hydrogen peroxide treatment was proposed as a simple and green way to improve the performance of commercial TiO_2 powder for water-dispersibility and visible-light photocatalytic activity on the degradation of dye pollutants. The performance of treated TiO_2 was evaluated as a function of NaOH concentration, H_2O_2 concentration, and treatment time. The optimal conditions were determined to be 24 h in 100 mM H_2O_2 and 8 M NaOH. The treated samples were characterized by Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible spectrophotometry. The analysis revealed that the crystal structure, morphology, and absorption band gap were retained, but the surface of the treated TiO_2 was dramatically changed. The treated TiO_2 was highly dispersible with a uniform hydrodynamic size of 41 ± 12 nm and stable over months in water at pH 3 without any stabilizing ligand and could significantly enhance the visible-light photodegradation of dye pollutants. The superior performance might be attributed to the formation of abundant surface hydroxyl groups. This treatment paves the way for developing water-dispersible TiO_2 with superior visible-light induced photocatalytic degradation of dye pollutants without any complicated and expensive surface modification. - Highlights: • Alkaline hydrogen peroxide is proposed to treat commercial TiO_2 powder. • The treated TiO_2 powder exhibits superior water-dispersibility with a uniform size distribution. • The treated TiO_2 powder can significantly enhance the visible-light photodegradation of dyes.

Porous TiO{sub 2} nanofibers decorated CdS nanoparticles by SILAR method for enhanced visible-light-driven photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Tian, Fengyu; Hou, Dongfang, E-mail: dfhouok@126.com; Hu, Fuchao; Xie, Kui; Qiao, Xiuqing; Li, Dongsheng, E-mail: lidongsheng1@126.com

2017-01-01

Graphical abstract: A heterojunction photocatalyst with CdS Nanoparticles self-assembled via SILAR Method at surfaces of electrospun TiO2 nanofibers shows enhanced visible-light photocatalytic activities. - Highlights: • Combined electrospinning and successive ionic layer adsorption and reaction process. • Pouous TiO{sub 2} nanofibers decorated CdS nanoparticles. • Synergetic effect of photosensitization and heterojunction. - Abstract: 1D porous CdS nanoparticles/TiO{sub 2} nanofibers heterostructure has been fabricated via simple electrospinning and a successive ionic layer adsorption and reaction (SILAR) process. The morphology, composition, and optical properties of the resulting CdS/TiO{sub 2} heterostructures can be rationally tailored through changing the SILAR cycles. The photocatalytic hydrogen evolution and decomposition of rhodamine B (RhB) of the as-synthesized heterostructured photocatalysts were investigated under visible light irradiation. Compared to TiO{sub 2} nanofibers，the as-obtained CdS/TiO{sub 2} heterostructures exhibit enhanced photocatalytic activity for hydrogen production and decomposition of RhB under visible-light irradiation. The heterojunction system performs best with H{sub 2} generation rates of 678.61 μmol h{sup −1} g{sup −1} under visible light irradiation which benefits from the two effects: (a) the 1D porous nanofibrous morphology contributes to not only more active sites but also more efficient transfer of the photogenerated charges (b) the synergetic effect of heterojunction and photosensitization reducing the recombination of photogenerated electrons and holes.

Hydrogen evolution on Au(111) covered with submonolayers of Pd

DEFF Research Database (Denmark)

Björketun, Mårten; Karlberg, Gustav; Rossmeisl, Jan

2011-01-01

A theoretical investigation of electrochemical hydrogen evolution on Au(111) covered with submonolayers of Pd is presented. The size and shape of monoatomically high Pd islands formed on the Au(111) surface are determined using Monte Carlo simulations, for Pd coverages varying from 0.02 to 0.95 ML....... The energetics of adsorption and desorption of hydrogen on/from different types of sites on the Pd-Au(111) surface are assessed by means of density functional theory calculations combined with thermodynamic modeling. Based on the density functional and Monte Carlo data, the hydrogen evolution activity...... is evaluated with a micro-kinetic model. The analysis reproduces measured Pd-coverage-dependent activities for Pd submonolayers exceeding similar to 0.15 ML and enables the relative contributions from different types of electrocatalytically active sites to be determined. Finally, the implications of surface...

Fabrication of TiO{sub 2} hierarchical architecture assembled by nanowires with anatase/TiO{sub 2}(B) phase-junctions for efficient photocatalytic hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Qiu, Yong; Ouyang, Feng, E-mail: ouyangfh@hit.edu.cn

2017-05-01

Highlights: • H-titanate nanowires hierarchical architectures (TNH) were prepared by a hydrothermal method. • Calcinations of TNH leads to the formation of anatase/TiO{sub 2}(B) phase-junctions. • The hierarchical architecture offered enhanced light harvesting and large specific surface area. • The 1D nanowires and anatase/TiO{sub 2}(B) phase-junctions both can enhance the separation of photoinduced electron-hole. • The products calcined at the optimum conditions (450 °C) exhibited a maximum hydrogenproduction rate of 7808 μmol g{sup −1} h{sup −1}. - Abstract: TiO{sub 2} hierarchical architecture assembled by nanowires with anatase/TiO{sub 2}(B) phase-junctions was prepared by a hydrothermal process followed by calcinations. The optimum calcination treatment (450 °C) not only led to the formation of anatase/TiO{sub 2}(B) phase-junctions, but also kept the morphology of 1D nanowire and hierarchical architecture well. The T-450 load 0.5 wt% Pt cocatalysts showed the best photocatalytic hydrogen production activity, with a maximum hydrogen production rate of 7808 μmol g{sup −1} h{sup −1}. The high photocatalytic activity is ascribed to the combined effects of the following three factors: (1) the hierarchical architecture exhibits better light harvesting; (2) the larger specific surface area provides more surface active sites for the photocatalytic reaction; (3) the 1D nanowires and anatase/TiO{sub 2}(B) phase-junctions both can enhance the separation of photoinduced electron-hole pairs and inhibit their recombination.

Photocatalytic hydrogen generation enhanced by band gap narrowing and improved charge carrier mobility in AgTaO3 by compensated co-doping.

Science.gov (United States)

Li, Min; Zhang, Junying; Dang, Wenqiang; Cushing, Scott K; Guo, Dong; Wu, Nianqiang; Yin, Penggang

2013-10-14

The correlation of the electronic band structure with the photocatalytic activity of AgTaO3 has been studied by simulation and experiments. Doping wide band gap oxide semiconductors usually introduces discrete mid-gap states, which extends the light absorption but has limited benefit for photocatalytic activity. Density functional theory (DFT) calculations show that compensated co-doping in AgTaO3 can overcome this problem by increasing the light absorption and simultaneously improving the charge carrier mobility. N/H and N/F co-doping can delocalize the discrete mid-gap states created by sole N doping in AgTaO3, which increases the band curvature and the electron-to-hole effective mass ratio. In particular, N/F co-doping creates a continuum of states that extend the valence band of AgTaO3. N/F co-doping thus improves the light absorption without creating the mid-gap states, maintaining the necessary redox potentials for water splitting and preventing from charge carrier trapping. The experimental results have confirmed that the N/F-codoped AgTaO3 exhibits a red-shift of the absorption edge in comparison with the undoped AgTaO3, leading to remarkable enhancement of photocatalytic activity toward hydrogen generation from water.

Visualization of hydrogen gas evolution during deformation and fracture in SCM 440 steel with different tempering conditions

International Nuclear Information System (INIS)

Horikawa, Keitaro; Ando, Nobuaki; Kobayashi, Hidetoshi; Urushihara, Wataru

2012-01-01

Highlights: ► We visualize emission sites of hydrogen atoms on the microstructures during deformation. ► Hydrogen atoms are emitted from slip lines and inclusions when deformed. ► We show the sequence of hydrogen gas evolution during deformation. ► Hydrogen evolution amount will increase if the steels with high strength are tested. - Abstract: In the present study, the hydrogen gas evolution behavior was investigated in SCM 440 steel by using a hydrogen microprint technique (HMT) and a testing machine equipped with a quadrupole mass spectrometer (QMS) in a ultrahigh vacuum (UHV) atmosphere. SCM 440 steels prepared by varying the tempering temperature over the range 200–700 °C were evaluated in order to elucidate the relationship between the hydrogen gas evolution and the tempered microstructures in the deformation. Cathodic hydrogen charging was carried out with a current density of 100 A/m 2 for 1 h at room temperature. For comparison, a tensile specimen was prepared without hydrogen charging. The HMT showed that silver particles, which are indicative of the hydrogen emission sites, were present mainly in the matrix as well as on the slip lines after the deformation. It is believed that the silver particles on the slip lines represent the effect of hydrogen transportation due to mobile dislocations. In addition, accumulation of silver particles around non-metallic inclusions such as Al 2 O 3 was also identified. This tendency was observed for different tempering conditions. From the relationship between the stress–strain curves and the hydrogen evolution, determined by using QMS under a UHV atmosphere, it was found that the hydrogen gas evolution behavior varied with the deformation stage.

AB/sub 5/-catalyzed hydrogen evolution cathodes

Energy Technology Data Exchange (ETDEWEB)

Hall, D E; Sawada, T; Shepard, V R; Tsujikawa, Y

1984-01-01

The AB/sub 5/ metal compounds are highly efficient hydrogen evolution electrocatalysts in alkaline electrolyte. Three types of AB/sub 5/-catalyzed cathode structures were made, using the hydride-forming AB/sub 5/ compounds in particulate form. Plastic-bonded cathodes containing >90 w/o AB/sub 5/ (finished-weight basis) were the most efficient, giving hydrogen evolution overpotentials (/eta/ /SUB H2/ ) of about 0.05 V at 200 mA cm/sup -2/. However, they tended to swell and shed material during electrolysis. Pressed, sintered cathodes containing 40-70 w/o catalyst in a nickel binder gave /eta/ /SUB H2/ about0.08 V; catalyst retention was excellent. Porous, sintered cathode coatings were made with 30-70 w/o AB/sub 5/ catalyst loadings. Their overpotentials were similar to those of the pressed, sintered cathodes. However, at catalyst loadings below about 40 w/o, high overpotentials characteristic of the nickel binder were observed. The structural and electrochemical properties of the three AB/sub 5/-catalyzed cathodes are discussed.

Bioinspired molecular co-catalysts bonded to a silicon photocathode for solar hydrogen evolution

DEFF Research Database (Denmark)

Hou, Yidong; Abrams, Billie L.; Vesborg, Peter Christian Kjærgaard

2011-01-01

The production of fuels from sunlight represents one of the main challenges in the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and although platinum and other noble metals are efficient catalysts for photoelectrochemical hydrogen evolution, earth...... that harvests red photons in the solar spectrum. The current densities at the reversible potential match the requirement of a photoelectrochemical hydrogen production system with a solar-to-hydrogen efficiency in excess of 10% (ref. 16). The experimental observations are supported by density functional theory......-abundant alternatives are needed for large-scale use. We show that bioinspired molecular clusters based on molybdenum and sulphur evolve hydrogen at rates comparable to that of platinum. The incomplete cubane-like clusters (Mo3S 4) efficiently catalyse the evolution of hydrogen when coupled to a p-type Si semiconductor...

Ag-Decorated ATaO3 (A = K, Na) Nanocube Plasmonic Photocatalysts with Enhanced Photocatalytic Water-Splitting Properties.

Science.gov (United States)

Xu, Dongbo; Yang, Songbo; Jin, Yu; Chen, Min; Fan, Weiqiang; Luo, Bifu; Shi, Weidong

2015-09-08

Tantalate semiconductor nanocrystals have been at the forefront of the photocatalytic conversion of solar energy to supply hydrogen owing to their favorable and tunable optical and electronic properties as well as advances in their synthesis. However, a narrow band gap is required for response to improve the efficiency of the photocatalysts. Here we propose an efficient enhancement of the H2 generation under simulated sunlight and visible light irradiation by a dispersion of Ag-decorated KTaO3 and NaTaO3 nanocubes. X-ray diffraction and UV-vis diffuse reflectance spectra are used to characterize the products. Transmission electron microscope (TEM) and high-resolution high-angle annular dark-field scanning TEM (HAADF-STEM) images show that the Ag nanoparticles (NPs) are uniformly loaded on the surfaces of KTaO3 and NaTaO3. The photocatalytic water-splitting results over Ag-decorated KTaO3 and NaTaO3 show that the rate for H2 evolution from aqueous CH3OH solutions is up to 185.60 and 3.54 μmol/h·g under simulated sunlight and the rate for H2 evolution is more than 2 times than that of pure NaTaO3 and KTaO3 materials. However, under purely visible light illumination the highest H2 evolution of 25.94 and 0.83 μmol/h·g is observed in the case of Ag-decorated KTaO3 and NaTaO3 nanocubes. To the best of our knowledge, this is the first time that the photocatalytic water-splitting activity of the prepared Ag-decorated KTaO3 and NaTaO3 nanocubes has been reported.

Sustainable hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Block, D.L.; Linkous, C.; Muradov, N.

1996-01-01

This report describes the Sustainable Hydrogen Production research conducted at the Florida Solar Energy Center (FSEC) for the past year. The report presents the work done on the following four tasks: Task 1--production of hydrogen by photovoltaic-powered electrolysis; Task 2--solar photocatalytic hydrogen production from water using a dual-bed photosystem; Task 3--development of solid electrolytes for water electrolysis at intermediate temperatures; and Task 4--production of hydrogen by thermocatalytic cracking of natural gas. For each task, this report presents a summary, introduction/description of project, and results.

Dynamic modelling of hydrogen evolution effects in the all-vanadium redox flow battery

International Nuclear Information System (INIS)

Shah, A.A.; Al-Fetlawi, H.; Walsh, F.C.

2010-01-01

A model for hydrogen evolution in an all-vanadium redox flow battery is developed, coupling the dynamic conservation equations for charge, mass and momentum with a detailed description of the electrochemical reactions. Bubble formation at the negative electrode is included in the model, taking into account the attendant reduction in the liquid volume and the transfer of momentum between the gas and liquid phases, using a modified multiphase-mixture approach. Numerical simulations are compared to experimental data for different vanadium concentrations and mean linear electrolyte flow rates, demonstrating good agreement. Comparisons to simulations with negligible hydrogen evolution demonstrate the effect of gas evolution on the efficiency of the battery. The effects of reactant concentration, flow rate, applied current density and gas bubble diameter on hydrogen evolution are investigated. Significant variations in the gas volume fraction and the bubble velocity are predicted, depending on the operating conditions.

Functionalized nanostructures for enhanced photocatalytic performance under solar light

Directory of Open Access Journals (Sweden)

Liejin Guo

2014-07-01

Full Text Available Photocatalytic hydrogen production from water has been considered to be one of the most promising solar-to-hydrogen conversion technologies. In the last decade, various functionalized nanostructures were designed to address the primary requirements for an efficient photocatalytic generation of hydrogen by using solar energy: visible-light activity, chemical stability, appropriate band-edge characteristics, and potential for low-cost fabrication. Our aim is to present a short review of our recent attempts that center on the above requirements. We begin with a brief introduction of photocatalysts coupling two or more semiconductors, followed by a further discussion of the heterostructures with improved matching of both band structures and crystal lattices. We then elaborate on the heterostructure design of the targeted materials from macroscopic regulation of compositions and phases, to the more precise control at the nanoscale, i.e., materials with the same compositions but different phases with certain band alignment. We conclude this review with perspectives on nanostructure design that might direct future research of this technology.

Visualization of hydrogen gas evolution during deformation and fracture in SCM 440 steel with different tempering conditions

Energy Technology Data Exchange (ETDEWEB)

Horikawa, Keitaro, E-mail: horikawa@me.es.osaka-u.ac.jp [Department of Mechanical Science and Bioengineering, School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); Ando, Nobuaki; Kobayashi, Hidetoshi [Department of Mechanical Science and Bioengineering, School of Engineering Science, Osaka University, Toyonaka 560-8531 (Japan); Urushihara, Wataru [Surface Design and Corrosion Research Section, Materials Research Laboratory, Kobe Steel, Ltd., Kobe 651-2271 (Japan)

2012-02-01

Highlights: Black-Right-Pointing-Pointer We visualize emission sites of hydrogen atoms on the microstructures during deformation. Black-Right-Pointing-Pointer Hydrogen atoms are emitted from slip lines and inclusions when deformed. Black-Right-Pointing-Pointer We show the sequence of hydrogen gas evolution during deformation. Black-Right-Pointing-Pointer Hydrogen evolution amount will increase if the steels with high strength are tested. - Abstract: In the present study, the hydrogen gas evolution behavior was investigated in SCM 440 steel by using a hydrogen microprint technique (HMT) and a testing machine equipped with a quadrupole mass spectrometer (QMS) in a ultrahigh vacuum (UHV) atmosphere. SCM 440 steels prepared by varying the tempering temperature over the range 200-700 Degree-Sign C were evaluated in order to elucidate the relationship between the hydrogen gas evolution and the tempered microstructures in the deformation. Cathodic hydrogen charging was carried out with a current density of 100 A/m{sup 2} for 1 h at room temperature. For comparison, a tensile specimen was prepared without hydrogen charging. The HMT showed that silver particles, which are indicative of the hydrogen emission sites, were present mainly in the matrix as well as on the slip lines after the deformation. It is believed that the silver particles on the slip lines represent the effect of hydrogen transportation due to mobile dislocations. In addition, accumulation of silver particles around non-metallic inclusions such as Al{sub 2}O{sub 3} was also identified. This tendency was observed for different tempering conditions. From the relationship between the stress-strain curves and the hydrogen evolution, determined by using QMS under a UHV atmosphere, it was found that the hydrogen gas evolution behavior varied with the deformation stage.

Carbon dots decorated vertical SnS{sub 2} nanosheets for efficient photocatalytic oxygen evolution

Energy Technology Data Exchange (ETDEWEB)

Cheng, Zhongzhou [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190 (China); Wang, Fengmei; Shifa, Tofik Ahmed; Liu, Kaili; Huang, Yun; Jiang, Chao; He, Jun, E-mail: hej@nanoctr.cn [CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190 (China); CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190 (China); Liu, Quanlin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

2016-08-01

Metal sulfides are highly desirable materials for photocatalytic water splitting because of their appropriate energy bands. However, the poor stability under light illumination in water hinders their wide applications. Here, two-dimensional SnS{sub 2} nanosheets, along with carbon dots of the size around 10 nm, are uniformly grown on fluorine doped tin oxide glasses with a layer of nickel nanoparticles. Significantly, strong light absorption and enhanced photocurrent density are achieved after integration of SnS{sub 2} nanosheets with carbon dots. Notably, the rate of oxygen evolution reached up to 1.1 mmol g{sup −1} h{sup −1} under simulated sunlight irradiation featuring a good stability.

Exfoliated MoS2 nanosheets as efficient catalysts for electrochemical hydrogen evolution

International Nuclear Information System (INIS)

Ji, Shanshan; Yang, Zhe; Zhang, Chao; Liu, Zhenyan; Tjiu, Weng Weei; Phang, In Yee; Zhang, Zheng; Pan, Jisheng; Liu, Tianxi

2013-01-01

Graphical abstract: An efficient electrocatalyst for hydrogen evolution has been developed based on exfoliation of bulk MoS 2 crystals via a direct dispersion and ultrasonication method. Drop-casting method is used to fabricate the exfoliated MoS 2 nanosheets modified glass carbon electrode (E-MoS 2 /GCE) with various loadings. The E-MoS 2 /GCE with electrode loading of 48 μg cm −1 exhibits high catalytic activity for hydrogen evolution with a low overpotential (−0.12 V) and a high current density (1.26 mA cm −2 , at η = 150 mV). -- Highlights: • Two-dimensional MoS 2 nanosheets have been obtained by exfoliation of bulk MoS 2 crystals. • Exfoliated MoS 2 nanosheets show high electrocatalytic activity for H 2 production. • This study provides a new approach for renewable and economic H 2 production. -- Abstract: An efficient electrocatalyst for hydrogen evolution has been developed based on liquid exfoliation of bulk MoS 2 via a direct dispersion and ultrasonication method. Transmission electron microscopy and atomic force microscopy measurements show that the exfoliated MoS 2 consists of two-dimensional nanosheets. The exfoliated MoS 2 nanosheets modified glass carbon electrode (E-MoS 2 /GCE) with various loadings is fabricated via a drop-casting method. The electrocatalytic activity of E-MoS 2 /GCE toward hydrogen evolution reaction is examined using linear sweep voltammetry. It is shown that the E-MoS 2 /GCE with an electrode loading of 48 μg cm −2 exhibits a high catalytic activity for hydrogen evolution with a low overpotential (−0.12 V) and a high current density (1.26 mA cm −2 , at η = 150 mV)

Biomass transition metal hydrogen-evolution electrocatalysts and electrodes

Energy Technology Data Exchange (ETDEWEB)

Chen, Wei-Fu; Iyer, Shweta; Iyer, Shilpa; Sasaki, Kotaro; Muckerman, James T.; Fujita, Etsuko

2017-02-28

A catalytic composition from earth-abundant transition metal salts and biomass is disclosed. A calcined catalytic composition formed from soybean powder and ammonium molybdate is specifically exemplified herein. Methods for making the catalytic composition are disclosed as are electrodes for hydrogen evolution reactions comprising the catalytic composition.

Kinetic Monte Carlo study on the evolution of silicon surface roughness under hydrogen thermal treatment

Energy Technology Data Exchange (ETDEWEB)

Wang, Gang; Wang, Yu; Wang, Junzhuan; Pan, Lijia; Yu, Linwei; Zheng, Youdou; Shi, Yi, E-mail: yshi@nju.edu.cn

2017-08-31

Highlights: • The KMC method is adopted to investigate the relationships between surface evolution and hydrogen thermal treatment conditions. • The reduction in surface roughness is divided into two stages at relatively low temperatures, both exhibiting exponential dependence on the time. • The optimized surface structure can be obtained by precisely adjusting thermal treatment temperatures and hydrogen pressures. - Abstract: The evolution of a two-dimensional silicon surface under hydrogen thermal treatment is studied by kinetic Monte Carlo simulations, focusing on the dependence of the migration behaviors of surface atoms on both the temperature and hydrogen pressure. We adopt different activation energies to analyze the influence of hydrogen pressure on the evolution of surface morphology at high temperatures. The reduction in surface roughness is divided into two stages, both exhibiting exponential dependence on the equilibrium time. Our results indicate that a high hydrogen pressure is conducive to obtaining optimized surfaces, as a strategy in the applications of three-dimensional devices.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability.

Science.gov (United States)

Pawar, Rajendra C; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S

2016-08-08

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g(-1)) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g(-1)). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

Effects of calcining temperature on photocatalysis of g-C{sub 3}N{sub 4}/TiO{sub 2} composites for hydrogen evolution from water

Energy Technology Data Exchange (ETDEWEB)

Qu, Ailan, E-mail: elainqal@163.com; Xu, Xinmei; Xie, Haolong; Zhang, Yangyu; Li, Yuyu; Wang, Junxian

2016-08-15

Highlights: • TiO{sub 2} promotes melon to form at 400 °C, whereas it forms at 500 °C for only melamine. • The highest photocatalytic activity was achieved when calcination was performed at 400 °C. • Coordinated N−Ti−N bonds were formed in MA/TiO{sub 2} (400) and disappeared at high temperature. • The surface area decreased and the pore size increased with increasing of temperature. • Only MA/TiO{sub 2} (400) has a narrower band gap than pure g-C{sub 3}N{sub 4}. - Abstract: A composite of graphitic carbon nitride and TiO{sub 2} (g-C{sub 3}N{sub 4}/TiO{sub 2}) with enhanced photocatalytic hydrogen evolution capacity was achieved by calcining melamine and TiO{sub 2} sol-gel precursor. Characterization results reveal that heating temperature had a great influence on the structure, surface area and properties of the composites. Compared with the polycondensation of pure melamine, the presence of TiO{sub 2} precursor can promote the formation of melon at a low temperature. The highest photocatalytic activity of g-C{sub 3}N{sub 4}/TiO{sub 2}(400) was achieved when the calcination was performed at 400 °C, exhibiting H{sub 2} production rate of 76.25 μmol/h under UV–vis light irradiation (λ > 320 nm) and 35.44 μmol/h under visible light irradiation (λ > 420 nm). The highest photocatalytic performance of g-C{sub 3}N{sub 4}/TiO{sub 2}(400) can be attributed to: (1) the strong UV–vis light absorption due to the narrow bandgap caused by synergic effect of TiO{sub 2} and g-C{sub 3}N{sub 4}, (2) high surface area and porosity, (3) the effective separation of photo-generated electron-holes owing to the favorable heterojunction between TiO{sub 2} and g-C{sub 3}N{sub 4}.

Kinetics of hydrogen evolution in the thermal dissociation of the hydride ZrNiH /SUB 2.8/

International Nuclear Information System (INIS)

Chernavskii, P.A.; Lunin, V.V.

1985-01-01

The kinetics of hydrogen evolution in the thermal decomposition of ZrNiH /SUB 2.8/ has been studied. The kinetic curve has two rate maxima. It is presumed that the second maximum is related to the phenomenon of critical inhibition that accompanies the phase transition. Apparent activation energies were determined for hydrogen evolution in argon and argon-ethylene atmospheres. The apparent energy increases in the argon-ethylene mixture. On the basis of the activation energy measurements it is presumed that the rate-determining step in hydrogen evolution is either the formation of hydrogen molecules from atoms on the surface of the lateral diffusion of atomic hydrogen. In the region of hydrogen concentration in the hydride corresponding to the phase transition, the rate-determining step is hydrogen diffusion in the hydride

Dendritic Tip-on Polytriazine-Based Carbon Nitride Photocatalyst with High Hydrogen Evolution Activity

KAUST Repository

Bhunia, Manas Kumar

2015-11-23

Developing stable, ubiquitous and efficient water-splitting photocatalyst material that has extensive absorption in the visible-light range is desired for a sustainable solar energy-conversion device. We herein report a triazine-based carbon nitride (CN) material with different C/N ratios achieved by varying the monomer composition ratio between melamine (Mel) and 2,4,6-triaminopyrimidine (TAP). The CN material with a different C/N ratio was obtained through a two-step synthesis protocol: starting with the solution state dispersion of the monomers via hydrogen-bonding supramolecular aggregate, followed by a salt-melt high temperature polycondensation. This protocol ensures the production of a highly crystalline polytriazine imide (PTI) structure con-sisting of a copolymerized Mel-TAP network. The observed bandgap narrowing with an increasing TAP/Mel ratio is well simulated by density functional theory (DFT) calculations, revealing a positive shift in the valence band upon substitution of N with CH in the aromatic rings. Increasing the TAP amount could not maintain the crystalline PTI structure, consistent with DFT calculation showing the repulsion associated with additional C-H introduced in the aromatic rings. Due to the high exciton binding energy calculated by DFT for the obtained CN, the cocatalyst must be close to any portion of the material to assist the separation of excit-ed charge carriers for an improved photocatalytic performance. The photocatalytic activity was improved by providing a dendritic tip-on-like shape grown on a porous fibrous silica KCC-1 spheres, and highly dispersed Pt nanoparticles (<5 nm) were photodepos-ited to introduce heterojunction. As a result, the Pt/CN/KCC-1 photocatalyst exhibited an apparent quantum efficiency (AQE) as high as 22.1 ± 3% at 400 nm and the silica was also beneficial for improving photocatalytic stability. The results obtained by time-resolved transient absorption spectroscopy measurements were consistent with

Characteristics of hydrogen evolution and oxidation catalyzed by Desulfovibrio caledoniensis biofilm on pyrolytic graphite electrode

International Nuclear Information System (INIS)

Yu Lin; Duan Jizhou; Zhao Wei; Huang Yanliang; Hou Baorong

2011-01-01

Highlights: → The sulphate-reducing bacteria (SRB) have the ability to catalyze the hydrogen evolution and oxidation on pyrolytic graphite electrode. → The SRB biofilm decreases the overpotential and electron transfer resistance by the CV and EIS detection. → The SRB biofilm can transfer electrons to the 0.24 V polarized pyrolytic graphite electrode and the maximum current is 0.035 mA, which is attributed to SRB catalyzed hydrogen oxidation. → The SRB biofilm also can obtain electron from the -0.61 V polarized PGE to catalyze the hydrogen evolution. - Abstract: Hydrogenase, an important electroactive enzyme of sulphate-reducing bacteria (SRB), has been discovered having the capacity to connect its activity to solid electrodes by catalyzing hydrogen evolution and oxidation. However, little attention has been paid to similar electroactive characteristics of SRB. In this study, the electroactivities of pyrolytic graphite electrode (PGE) coated with SRB biofilm were investigated. Two corresponding redox peaks were observed by cyclic voltammetry detection, which were related to the hydrogen evolution and oxidation. Moreover, the overpotential for the reactions decreased by about 0.2 V in the presence of the SRB biofilm. When the PGE coated with the SRB biofilm was polarized at 0.24 V (vs. SHE), an oxidation current related to the hydrogen oxidation was found. The SRB biofilm was able to obtain electrons from the -0.61 V (vs. SHE) polarized PGE to form hydrogen, and the electron transfer resistance also decreased with the formation of SRB biofilm, as measured by the non-destructive electrochemical impendence spectroscopy detection. It was concluded that the hydrogen evolution and oxidation was an important way for the electron transfer between SRB biofilm and solid electrode in anaerobic environment.

Quinary wurtzite Zn-Ga-Ge-N-O solid solutions and their photocatalytic properties under visible light irradiation

Science.gov (United States)

Xie, Yinghao; Wu, Fangfang; Sun, Xiaoqin; Chen, Hongmei; Lv, Meilin; Ni, Shuang; Liu, Gang; Xu, Xiaoxiang

2016-01-01

Wurtzite solid solutions between GaN and ZnO highlight an intriguing paradigm for water splitting into hydrogen and oxygen using solar energy. However, large composition discrepancy often occurs inside the compound owing to the volatile nature of Zn, thereby prescribing rigorous terms on synthetic conditions. Here we demonstrate the merits of constituting quinary Zn-Ga-Ge-N-O solid solutions by introducing Ge into the wurtzite framework. The presence of Ge not only mitigates the vaporization of Zn but also strongly promotes particle crystallization. Synthetic details for these quinary compounds were systematically explored and their photocatalytic properties were thoroughly investigated. Proper starting molar ratios of Zn/Ga/Ge are of primary importance for single phase formation, high particle crystallinity and good photocatalytic performance. Efficient photocatalytic hydrogen and oxygen production from water were achieved for these quinary solid solutions which is strongly correlated with Ge content in the structure. Apparent quantum efficiency for optimized sample approaches 1.01% for hydrogen production and 1.14% for oxygen production. Theoretical calculation reveals the critical role of Zn for the band gap reduction in these solid solutions and their superior photocatalytic acitivity can be understood by the preservation of Zn in the structure as well as a good crystallinity after introducing Ge.

Hydrogen evolution on nano-particulate transition metal sulfides

DEFF Research Database (Denmark)

Bonde, Jacob Lindner; Moses, Poul Georg; Jaramillo, Thomas F.

2008-01-01

The hydrogen evolution reaction (HER) on carbon supported MoS2 nanoparticles is investigated and compared to findings with previously published work on Au(111) supported MoS2. An investigation into MoS2 oxidation is presented and used to quantify the surface concentration of MoS2. Other metal sul...

Tantalum nitride for photocatalytic water splitting: concept and applications

KAUST Repository

Nurlaela, Ela

2016-10-12

Along with many other solar energy conversion processes, research on photocatalytic water splitting to generate hydrogen and oxygen has experienced rapid major development over the past years. Developing an efficient visible-light-responsive photocatalyst has been one of the targets of such research efforts. In this regard, nitride materials, particularly Ta3N5, have been the subject of investigation due to their promising properties. This review focuses on the fundamental parameters involved in the photocatalytic processes targeting overall water splitting using Ta3N5 as a model photocatalyst. The discussion primarily focuses on relevant parameters that are involved in photon absorption, exciton separation, carrier diffusion, carrier transport, catalytic efficiency, and mass transfer of the reactants. An overview of collaborative experimental and theoretical approaches to achieve efficient photocatalytic water splitting using Ta3N5 is discussed.

Tantalum nitride for photocatalytic water splitting: concept and applications

KAUST Repository

Nurlaela, Ela; Ziani, Ahmed; Takanabe, Kazuhiro

2016-01-01

Along with many other solar energy conversion processes, research on photocatalytic water splitting to generate hydrogen and oxygen has experienced rapid major development over the past years. Developing an efficient visible-light-responsive photocatalyst has been one of the targets of such research efforts. In this regard, nitride materials, particularly Ta3N5, have been the subject of investigation due to their promising properties. This review focuses on the fundamental parameters involved in the photocatalytic processes targeting overall water splitting using Ta3N5 as a model photocatalyst. The discussion primarily focuses on relevant parameters that are involved in photon absorption, exciton separation, carrier diffusion, carrier transport, catalytic efficiency, and mass transfer of the reactants. An overview of collaborative experimental and theoretical approaches to achieve efficient photocatalytic water splitting using Ta3N5 is discussed.

Confinement dependence of electro-catalysts for hydrogen evolution from water splitting

Directory of Open Access Journals (Sweden)

Mikaela Lindgren

2014-02-01

Full Text Available Density functional theory is utilized to articulate a particular generic deconstruction of the electrode/electro-catalyst assembly for the cathode process during water splitting. A computational model was designed to determine how alloying elements control the fraction of H2 released during zirconium oxidation by water relative to the amount of hydrogen picked up by the corroding alloy. This model is utilized to determine the efficiencies of transition metals decorated with hydroxide interfaces in facilitating the electro-catalytic hydrogen evolution reaction. A computational strategy is developed to select an electro-catalyst for hydrogen evolution (HE, where the choice of a transition metal catalyst is guided by the confining environment. The latter may be recast into a nominal pressure experienced by the evolving H2 molecule. We arrived at a novel perspective on the uniqueness of oxide supported atomic Pt as a HE catalyst under ambient conditions.

Zinc electrodeposition from flowing alkaline zincate solutions: Role of hydrogen evolution reaction

Science.gov (United States)

Dundálek, Jan; Šnajdr, Ivo; Libánský, Ondřej; Vrána, Jiří; Pocedič, Jaromír; Mazúr, Petr; Kosek, Juraj

2017-12-01

The hydrogen evolution reaction is known as a parasitic reaction during the zinc electrodeposition from alkaline zincate solutions and is thus responsible for current efficiency losses during the electrolysis. Besides that, the rising hydrogen bubbles may cause an extra convection within a diffusion layer, which leads to an enhanced mass transport of zincate ions to an electrode surface. In this work, the mentioned phenomena were studied experimentally in a flow through electrolyzer and the obtained data were subsequently evaluated by mathematical models. The results prove the indisputable influence of the rising hydrogen bubbles on the additional mixing of the diffusion layer, which partially compensates the drop of the current efficiency of the zinc deposition at higher current flows. Moreover, the results show that the current density ratio (i.e., the ratio of an overall current density to a zinc limiting current density) is not suitable for the description of the zinc deposition, because the hydrogen evolution current density is always involved in the overall current density.

Alkaline hydrogen peroxide treatment for TiO{sub 2} nanoparticles with superior water-dispersibility and visible-light photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Wu, Chung-Yi; Tu, Kuan-Ju; Lo, Yu-Shiu [Department of Biomedical Engineering and Environmental Sciences, College of Nuclear Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Pang, Yean Ling [Department of Chemical Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 43000 Kajang, Selangor (Malaysia); Wu, Chien-Hou, E-mail: chwu@mx.nthu.edu.tw [Department of Biomedical Engineering and Environmental Sciences, College of Nuclear Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2016-09-15

Alkaline hydrogen peroxide treatment was proposed as a simple and green way to improve the performance of commercial TiO{sub 2} powder for water-dispersibility and visible-light photocatalytic activity on the degradation of dye pollutants. The performance of treated TiO{sub 2} was evaluated as a function of NaOH concentration, H{sub 2}O{sub 2} concentration, and treatment time. The optimal conditions were determined to be 24 h in 100 mM H{sub 2}O{sub 2} and 8 M NaOH. The treated samples were characterized by Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible spectrophotometry. The analysis revealed that the crystal structure, morphology, and absorption band gap were retained, but the surface of the treated TiO{sub 2} was dramatically changed. The treated TiO{sub 2} was highly dispersible with a uniform hydrodynamic size of 41 ± 12 nm and stable over months in water at pH 3 without any stabilizing ligand and could significantly enhance the visible-light photodegradation of dye pollutants. The superior performance might be attributed to the formation of abundant surface hydroxyl groups. This treatment paves the way for developing water-dispersible TiO{sub 2} with superior visible-light induced photocatalytic degradation of dye pollutants without any complicated and expensive surface modification. - Highlights: • Alkaline hydrogen peroxide is proposed to treat commercial TiO{sub 2} powder. • The treated TiO{sub 2} powder exhibits superior water-dispersibility with a uniform size distribution. • The treated TiO{sub 2} powder can significantly enhance the visible-light photodegradation of dyes.

An Influence Study of Hydrogen Evolution Characteristics on the Negative Strap Corrosion of Lead Acid Battery

Directory of Open Access Journals (Sweden)

Zhong Guobin

2015-01-01

Full Text Available Negative strap corrosion is an important reason for the failure of valve regulated lead acid battery. This paper selected the Pb-Sb alloy material and Pb-Sn alloy material, made an investigation on the negative corrosion resistance and hydrogen evolution of these two alloy materials by scanning electron microscope analysis, metallographic analysis, chemical study and linear sweep voltammetry, and discussed the influence of lead alloy hydrogen evolution on the negative strap corrosion. The results showed that the hydrogen evolution reaction rates of the alloys had an impact on the corrosion areas with the maximum thickness of the alloys and the depth of corrosion layers. Greater hydrogen evolution reaction rate can lead to shorter distance between the corrosion area with the maximum thickness and the liquid level; whereas the greater corrosion layer thickness can bring aggravated risk of negative strap corrosion failure.

Two-Dimensional Material Molybdenum Disulfides as Electrocatalysts for Hydrogen Evolution

Directory of Open Access Journals (Sweden)

Lei Yang

2017-09-01

Full Text Available Recently, transition metal dichalcogenides (TMDs, represented by MoS2, have been proven to be a fascinating new class of electrocatalysts in hydrogen evolution reaction (HER. The rich chemical activities, combined with several strategies to regulate its morphologies and electronic properties, make MoS2 very attractive for understanding the fundamentals of electrocatalysis. In this review, recent developments in using MoS2 as electrocatalysts for the HER with high activity are presented. The effects of edges on HER activities of MoS2 are briefly discussed. Then we demonstrate strategies to further enhance the catalytic performance of MoS2 by improving its conductivity or engineering its structure. Finally, the key challenges to the industrial application of MoS2 in electrocatalytic hydrogen evolution are also pointed out.

TiO{sub 2}-based nanotubes modified with nickel: synthesis, properties, and improved photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Qamar, M; Ganguli, A K [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016 (India); Kim, S J, E-mail: sjkim1@sejong.ac.k, E-mail: ashok@chemistry.iitd.ac.i [Department of Nano Science and Technology, Sejong Advanced Institute of Nano Technologies, Sejong University, 98, Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

2009-11-11

Titanate nanotubes containing 2.5 wt% Ni were synthesized from TiO{sub 2} sol using alkali hydrothermal treatment followed by a simple ion-exchange process. The changes in phase, shape and morphology, surface area, and photocatalytic activity of these nanotubes have been explored as a function of calcination temperature. The samples were characterized using standard techniques, including x-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductively coupled plasma spectrometry, energy dispersive x-ray spectroscopy, and Brauner-Emmett-Teller surface area analysis. The study revealed that the titanate phase containing Ni ions can be converted to the anatase phase after certain heat treatments but, at the same time, the tubular morphology was partially lost. Investigation of photocatalytic properties demonstrated that the as-prepared Ni-titanate nanotubes were photocatalytically inactive, but when heated at temperatures below 500 {sup 0}C their activity was significantly enhanced with the change in phase. The calcined nanotube samples carrying nickel ion showed better photocatalytic activity than calcined nanotube samples containing protons. The hydrogen adsorption capacity of these titanates has also been measured, and it was found that Ni-titanate nanotubes can adsorb more hydrogen than its counterpart Na-titanate.

Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

KAUST Repository

Garcia Esparza, Angel T.

2012-12-17

Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

KAUST Repository

Garcia Esparza, Angel T.; Cha, Dong Kyu; Ou, Yiwei; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

2012-01-01

Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The evolution of hydrogen and iodine by the decomposition of ammonium iodide and hydrogen iodide

International Nuclear Information System (INIS)

Ishikawa, Hiroshi; Nakane, Masanori; Ishii, Eiichi; Uehara, Itsuki; Miyake, Yoshizo

1977-01-01

As a fundamental study on thermochemical production of hydrogen from water, the evolution of hydrogen and iodine from ammonium iodide and hydrogen iodide was investigated. Hydrogen was evolved by the reaction of nickel with ammonium iodide or with hydrogen iodide, and the resulting nickel(II) iodide was decomposed thermally at 600 -- 700 0 C to form nickel. First, the iodination of powdered nickel with ammonium iodide was studied by heating their powder mixture. The maximum yield of hydrogen was obtained at a temperature near 430 0 C. The iodination of powdered nickel with gaseous ammonium iodide or with dry hydrogen iodide gas was also investigated. In this case, coating of nickel particles with a layer of resulting nickel(II) iodide prevented further conversion of nickel and lowered the reaction rate. Such a retardation effect was appreciably lessened by use of carrier. When nickel was supported on such a carrier as ''isolite'', the nickel was converted into nickel(II) iodide easily. In a reaction temperature from 400 to 500 0 C, the rate of reaction between nickel and hydrogen iodide increased slightly with the elevation of the reaction temperature. In the case of ammonium iodide, the reaction rate was higher than that for hydrogen iodide and decreased apparently with the elevation of the reaction temperature, because ammonium iodide decomposed to ammonia and hydrogen iodide. Tests using a fixed bed reactor charged with 8 -- 10 mesh ''isolite''-nickel (30 wt%) were also carried out. The maximum yield of hydrogen was about 80% for ammonium iodide at 430 0 C of reaction temperature and 60% for hydrogen iodide at 500 0 C. (auth.)

Enhanced hydrogen evolution rates at high pH with a colloidal cadmium sulphide–platinum hybrid system

International Nuclear Information System (INIS)

Schneider, Julian; Vaneski, Aleksandar; Susha, Andrei S.; Rogach, Andrey L.; Pesch, Georg R.; Yang Teoh, Wey

2014-01-01

We demonstrate enhanced hydrogen generation rates at high pH using colloidal cadmium sulphide nanorods decorated with Pt nanoparticles. We introduce a simplified procedure for the decoration and subsequent hydrogen generation, reducing both the number of working steps and the materials costs. Different Pt precursor concentrations were tested to reveal the optimal conditions for the efficient hydrogen evolution. A sharp increase in hydrogen evolution rates was measured at pH 13 and above, a condition at which the surface charge transfer was efficiently mediated by the formation of hydroxyl radicals and further consumption by the sacrificial triethanolamine hole scavenger

Enhanced hydrogen evolution rates at high pH with a colloidal cadmium sulphide–platinum hybrid system

Energy Technology Data Exchange (ETDEWEB)

Schneider, Julian; Vaneski, Aleksandar; Susha, Andrei S.; Rogach, Andrey L., E-mail: andrey.rogach@cityu.edu.hk [Department of Physics and Materials Science and Centre for Functional Photonics (CFP), City University of Hong Kong, 83 Tat Chee Avenue, Kowloon (Hong Kong); Pesch, Georg R.; Yang Teoh, Wey [Clean Energy and Nanotechnology (CLEAN) Laboratory, School of Energy and Environment, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon (Hong Kong)

2014-12-01

We demonstrate enhanced hydrogen generation rates at high pH using colloidal cadmium sulphide nanorods decorated with Pt nanoparticles. We introduce a simplified procedure for the decoration and subsequent hydrogen generation, reducing both the number of working steps and the materials costs. Different Pt precursor concentrations were tested to reveal the optimal conditions for the efficient hydrogen evolution. A sharp increase in hydrogen evolution rates was measured at pH 13 and above, a condition at which the surface charge transfer was efficiently mediated by the formation of hydroxyl radicals and further consumption by the sacrificial triethanolamine hole scavenger.

Photocatalytically active colloidal platinum-decorated cadmium sulphide nanorods for hydrogen production; Photokatalytisch Aktive Kolloidale Platindekorierte Cadmiumsulfidnanostaebchen zur Wasserstoffproduktion

Energy Technology Data Exchange (ETDEWEB)

Berr, Maximilian Josef

2012-12-07

This is the first study to have been successful in producing hydrogen by means of photocatalytically active colloidal semiconductor particles. Specifically, colloidal platinum-decorated cadmium sulphide nanorods were used to reduce water to hydrogen. Oxidation of water to oxygen was substituted by addition of a reducing agent (hole collector), e.g. sulphite, which itself is oxidised to sulphate by the photohole. During photochemical platinum decoration it was discovered that in addition to the expected platinum nanoparticles there had also formed platinum clusters in the subnanometer range. In spite of the small quantity of platinum deposited on the nanorods these clusters showed the same quantum efficiency as the intended product. [German] In dieser Arbeit wurde erstmals mit kolloidalen Halbleiternanopartikeln photokatalytische Wasserstoffproduktion erzielt. Im Detail wurde Wasser mit kolloidalen, platindekorierten Cadmiumsulfidnanostaebchen zu Wasserstoff reduziert. Die Oxidation des Wasser zu Sauerstoff wurde durch Zugabe eines Reduktionsmittels (Lochfaenger) substituiert, z.B. Sulfit, das durch das Photoloch zu Sulfat reduziert wird. Bei der photochemischen Platindekoration wurden neben den erwarteten Platinnanopartikeln mit 4 - 5 nm Durchmesser auch Subnanometer grosse Platincluster entdeckt, die trotz der geringeren Menge an deponierten Platin auf den Nanostaebchen die gleiche Quanteneffizienz demonstrieren.

Electrochemical Hydrogen Evolution: Sabatier's Principle and the Volcano Plot

Science.gov (United States)

Laursen, Anders B.; Varela, Ana Sofia; Dionigi, Fabio; Fanchiu, Hank; Miller, Chandler; Trinhammer, Ole L.; Rossmeisl, Jan; Dahl, Soren

2012-01-01

The electrochemical hydrogen evolution reaction (HER) is growing in significance as society begins to rely more on renewable energy sources such as wind and solar power. Thus, research on designing new, inexpensive, and abundant HER catalysts is important. Here, we describe how a simple experiment combined with results from density functional…

Thermal evolution of structure and photocatalytic activity in polymer microsphere templated TiO{sub 2} microbowls

Energy Technology Data Exchange (ETDEWEB)

Erdogan, Deniz Altunoz; Polat, Meryem [Department of Chemistry, Bilkent University, 06800 Ankara (Turkey); Garifullin, Ruslan; Guler, Mustafa O. [Institute of Materials Science and Nanotechnology, National Nanotechnology Research Center (UNAM), Bilkent University, 06800 Ankara (Turkey); Ozensoy, Emrah, E-mail: ozensoy@fen.bilkent.edu.tr [Department of Chemistry, Bilkent University, 06800 Ankara (Turkey)

2014-07-01

Polystyrene cross-linked divinyl benzene (PS-co-DVB) microspheres were used as an organic template in order to synthesize photocatalytic TiO{sub 2} microspheres and microbowls. Photocatalytic activity of the microbowl surfaces were demonstrated both in the gas phase via photocatalytic NO(g) oxidation by O{sub 2}(g) as well as in the liquid phase via Rhodamine B degradation. Thermal degradation mechanism of the polymer template and its direct influence on the TiO{sub 2} crystal structure, surface morphology, composition, specific surface area and the gas/liquid phase photocatalytic activity data were discussed in detail. With increasing calcination temperatures, spherical polymer template first undergoes a glass transition, covering the TiO{sub 2} film, followed by the complete decomposition of the organic template to yield TiO{sub 2} exposed microbowl structures. TiO{sub 2} microbowl systems calcined at 600 °C yielded the highest per-site basis photocatalytic activity. Crystallographic and electronic properties of the TiO{sub 2} microsphere surfaces as well as their surface area play a crucial role in their ultimate photocatalytic activity. It was demonstrated that the polymer microsphere templated TiO{sub 2} photocatalysts presented in the current work offer a promising and a versatile synthetic platform for photocatalytic DeNO{sub x} applications for air purification technologies.

Efficient hydrogen evolution catalysis using ternary pyrite-type cobalt phosphosulphide

KAUST Repository

Cabán-Acevedo, Miguel

2015-09-14

The scalable and sustainable production of hydrogen fuel through water splitting demands efficient and robust Earth-abundant catalysts for the hydrogen evolution reaction (HER). Building on promising metal compounds with high HER catalytic activity, such as pyrite structure cobalt disulphide (CoS 2), and substituting non-metal elements to tune the hydrogen adsorption free energy could lead to further improvements in catalytic activity. Here we present a combined theoretical and experimental study to establish ternary pyrite-type cobalt phosphosulphide (CoPS) as a high-performance Earth-abundant catalyst for electrochemical and photoelectrochemical hydrogen production. Nanostructured CoPS electrodes achieved a geometrical catalytic current density of 10 mA cm at overpotentials as low as 48mV, with outstanding long-term operational stability. Integrated photocathodes of CoPS on n -p-p silicon micropyramids achieved photocurrents up to 35 mA cm at 0 V versus the reversible hydrogen electrode (RHE), onset photovoltages as high as 450 mV versus RHE, and the most efficient solar-driven hydrogen generation from Earth-abundant systems.

Modification of Ga2O3 by an Ag-Cr core-shell cocatalyst enhances photocatalytic CO evolution for the conversion of CO2 by H2O.

Science.gov (United States)

Pang, Rui; Teramura, Kentaro; Tatsumi, Hiroyuki; Asakura, Hiroyuki; Hosokawa, Saburo; Tanaka, Tsunehiro

2018-01-25

A core-shell structure of Ag-Cr dual cocatalyst loaded-Ga 2 O 3 was found to significantly enhance the formation rate of CO and selectivity toward CO evolution for the photocatalytic conversion of CO 2 where H 2 O is used as an electron donor.

MoS2 @HKUST-1 Flower-Like Nanohybrids for Efficient Hydrogen Evolution Reactions.

Science.gov (United States)

Wang, Chengli; Su, Yingchun; Zhao, Xiaole; Tong, Shanshan; Han, Xiaojun

2018-01-24

A novel MoS 2 -based flower-like nanohybrid for hydrogen evolution was fabricated through coating the Cu-containing metal-organic framework (HKUST-1) onto MoS 2 nanosheets. It is the first time that MoS 2 @HKUST-1 nanohybrids have been reported for the enhanced electrochemical performance of HER. The morphologies and components of the MoS 2 @HKUST-1 flower-like nanohybrids were characterized by scanning electron microscopy, X-ray diffraction analysis and Fourier transform infrared spectroscopy. Compared with pure MoS 2 , the MoS 2 @HKUST-1 hybrids exhibit enhanced performance on hydrogen evolution reaction with an onset potential of -99 mV, a smaller Tafel slope of 69 mV dec -1 , and a Faradaic efficiency of nearly 100 %. The MoS 2 @HKUST-1 flower-like nanohybrids exhibit excellent stability in acidic media. This design opens new possibilities to effectively synthesize non-noble metal catalysts with high performance for the hydrogen evolution reaction (HER). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano cobalt oxides for photocatalytic hydrogen production

KAUST Repository

Mangrulkar, Priti A.; Joshi, Meenal M.; Tijare, Saumitra N.; Polshettiwar, Vivek; Labhsetwar, Nitin K.; Rayalu, Sadhana Suresh

2012-01-01

of various operating parameters in hydrogen generation by nano cobalt oxide was then studied in detail. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Efficient Photocatalytic Degradation of Rhodamine B Dye by Aligned Arrays of Self-Assembled Hydrogen Titanate Nanotubes

Directory of Open Access Journals (Sweden)

Sriparna Chatterjee

2014-01-01

Full Text Available We show that an aligned array of hydrothermally grown, multiwalled hydrogen titanate (H2Ti3O7 nanotubes—anchored to both faces of a metallic Ti foil—acts as an efficient photocatalyst. We studied the degradation of rhodamine B dye in the presence of the nanostructured photocatalyst under UV irradiation, by monitoring the optical absorption of the dye. Rhodamine B was chosen as a representative—and particularly harmful—industrial pollutant dye. The inner and outer diameters of the H2Ti3O7 nanotubes were 5 nm and 10 nm, respectively. The nanotube array catalyst is recyclable and structurally stable. Most importantly, it shows comparable or higher photodecomposition rate constant than those of both H2Ti3O7 nanotube powder and P-25 (Degussa. The enhanced photocatalytic performance may be ascribed to the nanotube array having a superhydrophilic surface with a high accessible surface area.

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc01349f Click here for additional data file.

Science.gov (United States)

Pastor, Ernest; Gross, Manuela A.; Selim, Shababa

2015-01-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye (RuP) and a nickel bis(diphosphine) electrocatalyst (NiP) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP–NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP, which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP–NiP photocatalytic system, which can be widely applied to other photocatalytic systems. PMID:28717491

Two-dimensional boron: Lightest catalyst for hydrogen and oxygen evolution reaction

Energy Technology Data Exchange (ETDEWEB)

Mir, Showkat H. [Centre for Nano Science, Central University of Gujarat, Gandhinagar 382030 (India); Chakraborty, Sudip, E-mail: sudiphys@gmail.com, E-mail: prakash.jha@cug.ac.in; Wärnå, John [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Uppsala 75120 (Sweden); Jha, Prakash C., E-mail: sudiphys@gmail.com, E-mail: prakash.jha@cug.ac.in [School of Applied Material Sciences, Central University of Gujarat, Gandhinagar 382030 (India); Soni, Himadri [Lehrstuhl für Theoretische Chemie, Friedrich-Alexander Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen (Germany); Jha, Prafulla K. [Department of Physics, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390 002 (India); Ahuja, Rajeev [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Uppsala 75120 (Sweden); Department of Materials and Engineering, Royal Institute of Technology (KTH), 10044 Stockholm (Sweden)

2016-08-01

The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) have been envisaged on a two-dimensional (2D) boron sheet through electronic structure calculations based on a density functional theory framework. To date, boron sheets are the lightest 2D material and, therefore, exploring the catalytic activity of such a monolayer system would be quite intuitive both from fundamental and application perspectives. We have functionalized the boron sheet (BS) with different elemental dopants like carbon, nitrogen, phosphorous, sulphur, and lithium and determined the adsorption energy for each case while hydrogen and oxygen are on top of the doping site of the boron sheet. The free energy calculated from the individual adsorption energy for each functionalized BS subsequently guides us to predict which case of functionalization serves better for the HER or the OER.

Single step fabrication method of fullerene/TiO2 composite photocatalyst for hydrogen production

International Nuclear Information System (INIS)

Kum, Jong Min; Cho, Sung Oh

2011-01-01

Hydrogen is one of the most promising alternative energy sources. Fossil fuel, which is the most widely used energy source, has two defects. One is CO 2 emission causing global warming. The other is exhaustion. On the other hand, hydrogen emits no CO 2 and can be produced by splitting water which is renewable and easily obtainable source. However, about 95% of hydrogen is derived from fossil fuel. It limits the merits of hydrogen. Hydrogen from fossil fuel is not a renewable energy anymore. To maximize the merits of hydrogen, renewability and no CO 2 emission, unconventional hydrogen production methods without using fossil fuel are required. Photocatalytic water-splitting is one of the unconventional hydrogen production methods. Photocatalytic water-splitting that uses hole/electron pairs of semiconductor is expectable way to produce clean and renewable hydrogen from solar energy. TiO 2 is the semiconductor material which has been most widely used as photocatalyst. TiO 2 shows high photocatalytic reactivity and stability in water. However, its wide band gap only absorbs UV light which is only 5% of sun light. To enhance the visible light responsibility, composition with fullerene based materials has been investigated. 1-2 Methano-fullerene carboxylic acid (FCA) is one of the fullerene based materials. We tried to fabricate FCA/TiO 2 composite using UV assisted single step method. The method not only simplified the fabrication procedures, but enhanced hydrogen production rate

Active Edge Sites Engineering in Nickel Cobalt Selenide Solid Solutions for Highly Efficient Hydrogen Evolution

KAUST Repository

Xia, Chuan; Liang, Hanfeng; Zhu, Jiajie; Schwingenschlö gl, Udo; Alshareef, Husam N.

2017-01-01

free energy for atomic hydrogen adsorption in NiCoSe, identified by temperature-dependent conductivities and density functional theory calculations, the authors have achieved unprecedented fast hydrogen evolution kinetics, approaching that of Pt

The suitability of silicon carbide for photocatalytic water oxidation

Science.gov (United States)

Aslam, M.; Qamar, M. T.; Ahmed, Ikram; Rehman, Ateeq Ur; Ali, Shahid; Ismail, I. M. I.; Hameed, Abdul

2018-04-01

Silicon carbide (SiC), owing to its extraordinary chemical stability and refractory properties, is widely used in the manufacturing industry. Despite the semiconducting nature and morphology-tuned band gap, its efficacy as photocatalysts has not been thoroughly investigated. The current study reports the synthesis, characterization and the evaluation of the capability of silicon carbide for hydrogen generation from water splitting. The optical characterization of the as-synthesized powder exposed the formation of multi-wavelength absorbing entities in synthetic process. The structural analysis by XRD and the fine microstructure analysis by HRTEM revealed the cubic 3C-SiC (β-SiC) and hexagonal α-polymorphs (2H-SiC and 6H-SiC) as major and minor phases, respectively. The Mott-Schottky analysis verified the n-type nature of the material with the flat band potential of - 0.7 V. In the electrochemical evaluation, the sharp increase in the peak currents in various potential ranges, under illumination, revealed the plausible potential of the material for the oxidation of water and generation of hydrogen. The generation of hydrogen and oxygen, as a consequence of water splitting in the actual photocatalytic experiments, was observed and measured. A significant increase in the yield of hydrogen was noticed in the presence of methanol as h + scavenger, whereas a retarding effect was offered by the Fe3+ entities that served as e - scavengers. The combined effect of both methanol and Fe3+ ions in the photocatalytic process was also investigated. Besides hydrogen gas, the other evolved gasses such as methane and carbon monoxide were also measured to estimate the mechanism of the process.

Enhanced photocatalytic activity towards degradation and H{sub 2} evolution over one dimensional TiO{sub 2}@MWCNTs heterojunction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiao [CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190 (China); Key Laboratory of Luminescence and Optical Information of the Ministry of Education Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044 (China); Cao, Shuang; Wu, Zhijiao [CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190 (China); Zhao, Suling, E-mail: slzhao@bjtu.edu.cn [Key Laboratory of Luminescence and Optical Information of the Ministry of Education Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044 (China); Piao, Lingyu, E-mail: piaoly@nanoctr.cn [CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190 (China)

2017-04-30

Highlights: • One dimensional TiO{sub 2}@MWCNTs core-shell photocatalyst constructed. • The TiO{sub 2} nanoparticles are highly dispersed on the MWCNTs. • The layer thickness adjusted for different nanocomposites. • The 1D heterojunction enhancing electron transfers. - Abstract: With the distinct electronic and optical properties, multiwall carbon nanotubes (MWCNTs) are identified as an outstanding catalyst support, which can effectively improve the performance of the TiO{sub 2} photocatalysts. Herein, the unique one dimensional TiO{sub 2}@MWCNTs nanocomposites have been prepared by a facile hydrothermal method. The TiO{sub 2} coating layers are extremely uniform and the thickness is adjustable for different nanocomposites. XPS measurements confirm that intimate electronic interactions are existed between MWCNTs and TiO{sub 2} via interfacial Ti−O−C bond and the photoluminescence intensity of the TiO{sub 2}@MWCNTs nanocomposites are effectively quenched compared with pure TiO{sub 2}, suggesting the fast electron transfer rates. The thickness of TiO{sub 2} coating layers of the TiO{sub 2}@MWCNTs nanocomposites plays a significant role in the photocatalytic degradation of organic pollutants, such as methylene blue (MB) and Rhodamine B (RhB), and photocatalytic H{sub 2} evolution from water. Due to the formation of one dimensional heterojunction of TiO{sub 2}@MWCNTs nanocomposites and the positive synergistic effect between TiO{sub 2} and carbon nanotubes, it is found that the photocatalytic activity of the system is significantly improved.

Constructing MnO{sub 2}/single crystalline ZnO nanorod hybrids with enhanced photocatalytic and antibacterial activity

Energy Technology Data Exchange (ETDEWEB)

Yu, Weiwei [College of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Liu, Tiangui, E-mail: tianguiliu@gmail.com [College of Physics and Microelectronics Science, Hunan University, Changsha 410082 (China); Cao, Shiyi; Wang, Chen [College of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Chen, Chuansheng, E-mail: 1666423158@qq.com [College of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China)

2016-07-15

In order to improve the photocatalytic and antibacterial activity of ZnO nanorods, ZnO nanorods decorated with MnO{sub 2} nanoparticles (MnO{sub 2}/ZnO nanorod hybrids) were prepared by using microwave assisted coprecipitation method under the influence of hydrogen peroxide, and the structure, photocatalytic activity and antibacterial property of the products were studied. Experimental results indicated that MnO{sub 2} nanoparticles are decorated on the surface of single crystalline ZnO nanorods. Moreover, the resultant MnO{sub 2}/ZnO nanorod hybrids have been proven to possess good photocatalytic and antibacterial activity, which their degradated efficiency for Rhodamin B (RhB) is twice as the pure ZnO nanorods. Enhancement for photocatalytic and antibacterial activity is mainly attributed to the low band gap energy and excellent electrochemical properties of MnO{sub 2} nanoparticles. - Graphical abstract: The MnO{sub 2}/single crystalline ZnO nanorods hybrids, which MnO{sub 2} nanoparticles are loaded on the surface of ZnO nanorods, were prepared by the step-by-step precipitation method under the assistance of ammonia and hydrogen peroxide. Display Omitted - Highlights: • MnO{sub 2}/ZnO nanorod hybrids were prepared by the step-by-step assembly method. • Single crystalline ZnO nanorods can be decorated by MnO{sub 2} nanoparticles. • MnO{sub 2}/ZnO nanorod hybrids possess good photocatalytic and antibacterial activity. • MnO{sub 2} can improve the photocatalytic activity of ZnO nanorods under visible light.

Nanocrystals and Nanoclusters as Cocatalysts for Photocatalytic Water Splitting

KAUST Repository

Sinatra, Lutfan

2016-12-04

The energy consumptions worldwide have increased simultaneously with the growth of the population and of the economy. Nowadays, finding an alternative way to satisfy the energy demand is one of the great challenges for the future of humanity, especially due to the limitation of fossil fuels and their effect on global warming. Hydrogen, as an alternative fuel for the future, is very attractive. Compared to traditional methods, such as the steam reforming of natural gas or coal gasification, photocatalytic water splitting (PWS) is considered to be the most sustainable alternative for producing hydrogen as a future fuel. PWS usually relies on semiconductor material that can transform the absorbed solar photon into photogenerated electrons and holes, creating a photopotential which can drive the electrochemical production of molecular hydrogen from the reduction of water. Despite its promising application, semiconductor-based PWS usually suffers from low carrier mobility and short diffusion length. Furthermore, the recombination of photogenerated electrons and holes might occur, especially if there are no suitable reaction sites available on the surface of the semiconductor. In order to facilitate the catalytic reactions on the surface of the semiconductor, the presence of a cocatalyst is necessary in order to obtain more efficient PWS processes. To this day, noble metals such as Pt, Pd, RuO2 and IrO2 are still the benchmark cocatalysts for PWS. Nevertheless, due to their high cost and limited supply, it is mandatory to develop a suitable strategy and to identify more efficient materials. Therefore, within the framework of this dissertation, novel cocatalysts and strategies that can improve the efficiency of the photocatalytic water splitting processes have been developed. Firstly, we developed a cocatalyst combining noble metals and semiconductors by means of partial galvanic replacement of the Cu2O nanocrystal with Au. The deposition of this cocatalyst on TiO2 was

Photocatalytic Nanofiltration Membranes with Self-Cleaning Property for Wastewater Treatment

Energy Technology Data Exchange (ETDEWEB)

Lv, Yan [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 China; Zhang, Chao [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 China; He, Ai [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 China; Yang, Shang-Jin [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 China; Wu, Guang-Peng [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 China; Darling, Seth B. [Nanoscience & Technology Division, Argonne National Laboratory, 9700 South Cass Avenue Lemont IL 60439 USA; Institute for Molecular Engineering, University of Chicago, Chicago IL 60637 USA; Xu, Zhi-Kang [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, and Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 China

2017-05-16

Membrane fouling is one of the most severe problems restricting membrane separation technology for wastewater treatment. This work reports a photocatalytic nanofiltration membrane (NFM) with self-cleaning property fabricated using a facile biomimetic mineralization process. In this strategy, a polydopamine (PDA)/polyethyleneimine (PEI) intermediate layer is fabricated on an ultrafiltration membrane via a co-deposition method followed by mineralization of a photocatalytic layer consisting of beta-FeOOH nanorods. The PDA-PEI layer acts both as a nanofiltration selective layer and an intermediate layer for anchoring the beta-FeOOH nanorods via strong coordination complexes between Fe3+ and catechol groups. In visible light, the beta-(F)eOOH layer exhibits efficient photocatalytic activity for degrading dyes through the photo-Fenton reaction in the presence of hydrogen peroxide, endowing the NFM concurrently with effective nanofiltration performance and self-cleaning capability. Moreover, the mineralized NFMs exhibit satisfactory stability under simultaneous filtration and photocatalysis processing, showing great potential in advanced wastewater treatment.

Supported black phosphorus nanosheets as hydrogen-evolving photocatalyst achieving 5.4% energy conversion efficiency at 353 K.

Science.gov (United States)

Tian, Bin; Tian, Bining; Smith, Bethany; Scott, M C; Hua, Ruinian; Lei, Qin; Tian, Yue

2018-04-11

Solar-driven water splitting using powdered catalysts is considered as the most economical means for hydrogen generation. However, four-electron-driven oxidation half-reaction showing slow kinetics, accompanying with insufficient light absorption and rapid carrier combination in photocatalysts leads to low solar-to-hydrogen energy conversion efficiency. Here, we report amorphous cobalt phosphide (Co-P)-supported black phosphorus nanosheets employed as photocatalysts can simultaneously address these issues. The nanosheets exhibit robust hydrogen evolution from pure water (pH = 6.8) without bias and hole scavengers, achieving an apparent quantum efficiency of 42.55% at 430 nm and energy conversion efficiency of over 5.4% at 353 K. This photocatalytic activity is attributed to extremely efficient utilization of solar energy (~75% of solar energy) by black phosphorus nanosheets and high-carrier separation efficiency by amorphous Co-P. The hybrid material design realizes efficient solar-to-chemical energy conversion in suspension, demonstrating the potential of black phosphorus-based materials as catalysts for solar hydrogen production.

Fabrication of the heterostructured CsTaWO{sub 6}/Au/g-C{sub 3}N{sub 4} hybrid photocatalyst with enhanced performance of photocatalytic hydrogen production from water

Energy Technology Data Exchange (ETDEWEB)

Lang, Junyu; Liu, Mengqing; Su, Yiguo; Yan, Lijuan; Wang, Xiaojing, E-mail: wang_xiao_jing@hotmail.com

2015-12-15

Graphical abstract: - Highlights: • A novel ternary CsTaWO{sub 6}/Au/g-C{sub 3}N{sub 4} hybrid photocatalyst was successfully fabricated. • Au particles act as an electron-conduction bridge between the heterostructure. • The photoctalytic hydrogen generation was promoted by the SPR of the Au. • CsTaWO{sub 6}/Au/g-C{sub 3}N{sub 4} shows significant photocatalytic activity in H{sub 2} generation. - Abstract: In this work, a novel CsTaWO{sub 6}/Au/g-C{sub 3}N{sub 4} hybrid photocatalyst is successfully fabricated. The photocatalytic performance of the heterostructured CsTaWO{sub 6}/Au/g-C{sub 3}N{sub 4} composite was investigated. Au nanoparticles were photo-deposited as the interlayer between g-C{sub 3}N{sub 4} and the surface of CsTaWO{sub 6}, which can facilitate the photoinduced electrons migration as an electron-conduction bridge as well as increase visible-light absorption via the surface plasmon resonance. This heterostructured interface bridging by Au particles may significantly retard the recombination of electron–holes, which is beneficial to promote the photocatalytic activity under visible-light irradiation. It is found the CsTaWO{sub 6}/Au/g-C{sub 3}N{sub 4} sample showed excellent photocatalytic activity of water splitting, even higher than the sum of g-C{sub 3}N{sub 4} and Au/CsTaWO{sub 6} samples, or the sum of CsTaWO{sub 6} and Au/g-C{sub 3}N{sub 4} samples. It indicates that the heterostructured combination of g-C{sub 3}N{sub 4} and CsTaWO{sub 6} bridging by Au particles provided the synergistic photocatalytic activity driving by solar light through an efficient electron transfer process.

Photocatalytic hydrogen production using visible-light-responsive Ta 3N5 photocatalyst supported on monodisperse spherical SiO2 particulates

KAUST Repository

Liu, Xiaoming

2014-01-01

Fine nanoparticles of Ta3N5 (10-20 nm) were synthesized on the surfaces of SiO2 spheres with a diameter of ∼550 nm. A sol-gel method was used to modify the surface of SiO2 with Ta2O5 from TaCl5 dissolved in ethanol in the presence of citric acid and polyethylene glycol. The resulting oxide composites were treated in an NH3 flow at 1123 K to form core-shell structured Ta3N5/SiO2 sub-microspheres. The obtained samples were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDX), transmission electron microscopy (TEM), and photocatalytic activity measurements for H 2 evolution from an aqueous methanol solution. The XRD results demonstrate the expected sequential formation of Ta2O5 layers, followed by Ta3N5 after nitridation on the Ta 2O5/SiO2 composite. SEM and TEM observations indicate that the obtained Ta3N5/SiO2 sub-microspheres have a uniform size distribution with high crystallinity and an obvious core-shell structure. The presence of support maintained the intrinsic photocatalytic activity of Ta3N5 nanoparticles, but it did drastically improve the dispersion of the photocatalysts in the solution. This study proposes the use of an inert support in photocatalytic reactors to improve ease of handling the powder photocatalyst for gas-phase photocatalysis and the suspension of the solution, controlling nature of light harvesting and degree of scattering of the photoreactor. © 2013 Elsevier Ltd. All rights reserved.

Carrier-selective p- and n-contacts for efficient and stable photocatalytic water reduction

DEFF Research Database (Denmark)

Bae, Dowon; Pedersen, Thomas; Seger, Brian

2017-01-01

The successful realization of carrier-selective contacts for crystalline silicon (c-Si) based device for pho-tocatalytic hydrogen production has been demonstrated. The proposed TiO2protected carrier-selectivecontacts resemble a metal-oxide-semiconductor configuration, including a highly-doped nan...

Preparation and elementary research on electrocatalytic hydrogen evolution of highly ordered titanium dioxide nanotube arrays

International Nuclear Information System (INIS)

Wu Qinglong; Liao Junsheng; Bai Yun

2010-01-01

Well ordered and uniform titanium dioxide nanotube arrays were fabricated by anodiaing process from a bath containing 1% NaF, 1mol/L Na 2 SO 4 , 0.5 mol/L H 2 SO 4 at room temperature. Surface morphology of titanium dioxide nanotube arrays were observed with SEM. The formation process of titanium dioxide nanotube arrays was suggested by current-time transient. Its catalytic hydrogen evolution behavior was studied by electrochemical measurements in a 5%(mass fraction) H 2 SO 4 solution. The results showed that the titanium dioxide nanotube arrays on titanium had better hydrogen evolution activity and trace palladium lead to the maximum electrocatalytic activity of hydrogen production. (authors)

Development of new generation of perovskite based noble metal/semiconductor photocatalysts for visible-light-driven hydrogen production

Science.gov (United States)

Shen, Peichuan

In recent decades, semiconductor photocatalysis has attracted a growing attention as a possible alternative to existing methods of hydrogen production, hydrocarbon conversion and organic compound oxidation. Many types of photocatalysts have been developed and tested for photocatalytic applications. However, most of them do not have notable activity in visible light region, which limits their practical applications. Development of photocatalysts, which can be activated by visible light provides a promising way forward to utilize both UV and visible portions of solar spectrum. In this thesis, two main methods to advance visible light driven photocatalysis, such as bandgap modification through doping and co-catalyst development, are investigated. The photocatalysts studied in this thesis included CdS and SrTiO3, which were extensively investigated and characterized. Rhodium doped strontium titanate was synthesized through different preparation methods. The synthesized samples have been investigated by various characterization techniques including XRD, TEM, STEM, XPS and UV-Vis spectroscopy. The effect of preparation conditions, such as doping concentration, calcination temperature and pH have been investigated and optimized. In addition, the photocatalytic activities for hydrogen production of the samples synthesized by different preparation methods were also studied. Among the preparation methods, polymerizable complex (PC) method was found to be the most effective synthesis method for SrTiO3: Rh. The samples prepared by PC method had higher photocatalytic activity as compared to that of samples synthesized by solid state reaction method and hydrothermal method. The reasons might be attributed to more effective doping and higher surface area. The results of this work suggest that PC method can also be applied to develop other perovskite materials for photocatalytic applications. Co-catalyst development for enhancement of photocatalytic hydrogen production is also

Preparation and Photocatalytic Properties of Sr2−xBaxTa3O10−yNz Nanosheets

Directory of Open Access Journals (Sweden)

Tatsumi Ishihara

2013-01-01

Full Text Available Sr2−xBaxTa3O10−yNz (x = 0.0, 0.5, 1.0 nanosheets were prepared by exfoliating layered perovskite compounds (CsSr2−xBaxTa3O10−yNz. The Sr1.5Ba0.5Ta3O9.7N0.2 nanosheet showed the highest photocatalytic activity for H2 production from the water/methanol system among the Sr2−xBaxTa3O9.7N0.2 nanosheets prepared. In addition, Rh-loaded Sr1.5Ba0.5Ta3O9.6N0.3 nanosheet showed the photocatalytic activity for oxygen and hydrogen production from water. The ratio of hydrogen to oxygen evolved was around two. These results indicate that the Rh-loaded Sr1.5Ba0.5Ta3O9.6N0.3 nanosheet is a potential catalyst for photocatalytic water splitting.

Light energy conversion by photocatalytic reaction

Energy Technology Data Exchange (ETDEWEB)

Fujishima, Akira; Yamagata, Sadamu [Univ. of Tokyo (Japan)

1989-01-01

The photocatalytic reaction, to be made to a suspended semiconductor powder system, was explained in summary. By using semiconductor as an electrode for the electrolyzation, etc. and projecting light on it to generate photoelectromotive force, a photocell can be composed. eg., by composing titanium oxide electrode, n-type semiconductor and platinum electrode, and irradiating light on the former electrode to generate electric current, oxygen and hydrogen are produced from the titanium oxide electrode and platinum electrode, respectively, which means the possibility of obtainment of clean energy from water as raw material. Such a wet type photocell, easy to produce, is active also in research. With white titanium oxide powder being suspended in water solution, hydrogen is produced by projecting light into it. Such a semiconductor is called photocatalyst, in which the research has been widely developed, mainly by taking notice of the hydrogen production on reduction side, since 1972. The photocatalysis using colloid and, differently, that doing heteropolyacid are also taken notice of. 24 refs., 6 figs.

Theoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applications

KAUST Repository

Laradhi, Shaikhah

2017-11-01

Converting solar energy to clean fuel has gained remarkable attention as an emerged renewable energy resource but optimum efficiency in photocatalytic applications has not yet been reached. One of the dominant factors is designing efficient photocatalytic semiconductors. The research reveals a theoretical investigation of optoelectronic properties of bismuth-based metal oxide and oxysulfide semiconductors using highly accurate first-principles quantum method based on density functional theory along with the range-separated hybrid HSE06 exchange-correlation functional. First, bismuth titanate compounds including Bi12TiO20, Bi4Ti3O12, and Bi2Ti2O7 were studied in a combined experimental and theoretical approach to prove its photocatalytic activity under UV light. They have unique bismuth layered structure, tunable electronic properties, high dielectric constant and low electron and effective masses in one crystallographic direction allowing for good charge separation and carrier diffusion properties. The accuracy of the investigation was determined by the good agreement between experimental and theoretical values. Next, BiVO4 with the highest efficiency for oxygen evolution was investigated. A discrepancy between the experimental and theoretical bandgap was reported and inspired a systematic study of all intrinsic defects of the material and the corresponding effect on the optical and transport properties. A candidate defective structure was proposed for an efficient photocatalytic performance. To overcome the carrier transport limitation, a mild hydrogen treatment was also introduced. Carrier lifetime was enhanced due to a significant reduction of trap-assisted recombination, either via passivation of deep trap states or reduction of trap state density. Finally, an accurate theoretical approach to design a new family of semiconductors with enhanced optoelectronic properties for water splitting was proposed. We simulated the solid solutions Bi1−xRExCuOS (RE = Y, La

Evolution of helium rich stars with hydrogen burning

International Nuclear Information System (INIS)

Roeser, M.

1975-08-01

Evolutionary tracks of stars with an initial chemical composition X = 0.100, Y = 0.8790, Z = 0.021 are calculated for masses of 0.35 M(sun), 0.66 M(sun), 1.00 M(sun), 2.00 M(sun), and 5.00 M(sun) and with X = 0.302, Y = 0.677, Z = 0.021 for masses of 1.00 M(sun), 3.00 M(sun), and 5.00 M(sun). The evolution is followed from hydrogen burning to helium burning and to carbon burning when the occasion arises. The data of evolution are presented and compared with normal Population I-stars. The helium rich stars show higher effective temperatures, much higher luminosities and therefore shorter time scales. They are situated in regions of the HR-diagram where observed helium stars are found. (orig.) [de

Seawater splitting for high-efficiency hydrogen evolution by alloyed PtNix electrocatalysts

Science.gov (United States)

Zheng, Jingjing

2017-08-01

Robust electrocatalyst is a prerequisite to realize high-efficiency hydrogen evolution by water splitting. Expensive platinum (Pt) is a preferred electrode catalyst for state-of-the-art hydrogen evolution reaction (HER). We present here a category of alloyed PtNix electrocatalysts by a facile green chemical reduction method, which are used to catalyze HER during seawater splitting. The catalytic performances are optimized by tuning stoichiometric Pt/Ni ratio, yielding a maximized catalytic behavior for PtNi5 electrode. The minimized onset potential is as low as -0.38 V and the corresponding Tafel slope is 119 mV dec-1. Moreover, the launched alloy electrodes have remarkable stability at -1.2 V over 12 h. The high efficiency as well as good durability demonstrates the PtNix electrocatalysts to be promising in practical applications.

Enhanced photocatalytic H{sub 2} production on CdS nanorod using cobalt-phosphate as oxidation cocatalyst

Energy Technology Data Exchange (ETDEWEB)

Di, Tingmin; Zhu, Bicheng; Zhang, Jun; Cheng, Bei [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Yu, Jiaguo, E-mail: jiaguoyu@yahoo.com [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

2016-12-15

Highlights: • Co-Pi/CdS composites were synthesized by a simple photodeposition method. • The composites showed superior photocatalytic H{sub 2} production activity. • The optimal H{sub 2} production rate of Co-Pi/CdS was even higher than that of Pt-CdS. • Co-Pi is a good oxidation cocatalyst used for capture of photogenerated hole. - Abstract: Employing visible light responsive semiconductor for photocatalytic hydrogen production by water splitting is an efficient way for utilizing renewable solar energy to solve the depletion of fossil fuel and environmental contamination. Herein, we report enhanced photocatalytic H{sub 2}-production performance over CdS nanorod using cobalt-phosphate (Co-Pi) as a water oxdation cocatalyst. The optimal Co-Pi modified CdS nanocomposite photocatalyst with the Co-Pi content of 8.4 mol% has a superior visible light H{sub 2}-production rate of 13.3 mmol h{sup −1} g{sup −1} with an apparent quantum efficiency of 24.3% at 420 nm, which is even higher than that of 1 wt% Pt-CdS (11.3 mmol h{sup −1} g{sup −1}) under the same conditions. The enhanced visible-light photocatalytic H{sub 2} production activity was attributed to the hole trapping and collecting ability of Co-Pi cocatalyst, which could effectively suppress the recombination of photogenerated electron-hole pairs and increase the electron density for hydrogen production. This work shows a possibility of using earth-abundant Co-Pi as cocatalyst for enhancing photocatalytic H{sub 2} production.

High-performance a -Si/c-Si heterojunction photoelectrodes for photoelectrochemical oxygen and hydrogen evolution

KAUST Repository

Wang, Hsin Ping

2015-05-13

Amorphous Si (a-Si)/crystalline Si (c-Si) heterojunction (SiHJ) can serve as highly efficient and robust photoelectrodes for solar fuel generation. Low carrier recombination in the photoelectrodes leads to high photocurrents and photovoltages. The SiHJ was designed and fabricated into both photoanode and photocathode with high oxygen and hydrogen evolution efficiency, respectively, by simply coating of a thin layer of catalytic materials. The SiHJ photoanode with sol-gel NiOx as the catalyst shows a current density of 21.48 mA/cm2 at the equilibrium water oxidation potential. The SiHJ photocathode with 2 nm sputter-coated Pt catalyst displays excellent hydrogen evolution performance with an onset potential of 0.640 V and a solar to hydrogen conversion efficiency of 13.26%, which is the highest ever reported for Si-based photocathodes. © 2015 American Chemical Society.

Investigation of hydrogen evolution activity for the nickel, nickel-molybdenum nickel-graphite composite and nickel-reduced graphene oxide composite coatings

International Nuclear Information System (INIS)

Jinlong, Lv; Tongxiang, Liang; Chen, Wang

2016-01-01

Graphical abstract: - Highlights: • Improved HER efficiency of Ni-Mo coatings was attributed to ‘cauliflower’ like microstructure. • RGO in nickel-RGO composite coating promoted refined grain and facilitated HER. • Synergistic effect between nickel and RGO facilitated HER due to large specific surface of RGO. - Abstract: The nickel, nickel-molybdenum alloy, nickel-graphite and nickel-reduced graphene oxide composite coatings were obtained by the electrodeposition technique from a nickel sulfate bath. Nanocrystalline molybdenum, graphite and reduced graphene oxide in nickel coatings promoted hydrogen evolution reaction in 0.5 M H_2SO_4 solution at room temperature. However, the nickel-reduced graphene oxide composite coating exhibited the highest electrocatalytic activity for the hydrogen evolution reaction in 0.5 M H_2SO_4 solution at room temperature. A large number of gaps between ‘cauliflower’ like grains could decrease effective area for hydrogen evolution reaction in slight amorphous nickel-molybdenum alloy. The synergistic effect between nickel and reduced graphene oxide promoted hydrogen evolution, moreover, refined grain in nickel-reduced graphene oxide composite coating and large specific surface of reduced graphene oxide also facilitated hydrogen evolution reaction.

Investigation of hydrogen evolution activity for the nickel, nickel-molybdenum nickel-graphite composite and nickel-reduced graphene oxide composite coatings

Energy Technology Data Exchange (ETDEWEB)

Jinlong, Lv, E-mail: ljlbuaa@126.com [Beijing Key Laboratory of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Zhongguancun Street, Haidian District, Beijing 100084 (China); State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Tongxiang, Liang; Chen, Wang [Beijing Key Laboratory of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Zhongguancun Street, Haidian District, Beijing 100084 (China); State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China)

2016-03-15

Graphical abstract: - Highlights: • Improved HER efficiency of Ni-Mo coatings was attributed to ‘cauliflower’ like microstructure. • RGO in nickel-RGO composite coating promoted refined grain and facilitated HER. • Synergistic effect between nickel and RGO facilitated HER due to large specific surface of RGO. - Abstract: The nickel, nickel-molybdenum alloy, nickel-graphite and nickel-reduced graphene oxide composite coatings were obtained by the electrodeposition technique from a nickel sulfate bath. Nanocrystalline molybdenum, graphite and reduced graphene oxide in nickel coatings promoted hydrogen evolution reaction in 0.5 M H{sub 2}SO{sub 4} solution at room temperature. However, the nickel-reduced graphene oxide composite coating exhibited the highest electrocatalytic activity for the hydrogen evolution reaction in 0.5 M H{sub 2}SO{sub 4} solution at room temperature. A large number of gaps between ‘cauliflower’ like grains could decrease effective area for hydrogen evolution reaction in slight amorphous nickel-molybdenum alloy. The synergistic effect between nickel and reduced graphene oxide promoted hydrogen evolution, moreover, refined grain in nickel-reduced graphene oxide composite coating and large specific surface of reduced graphene oxide also facilitated hydrogen evolution reaction.

Bio-inspired co-catalysts bonded to a silicon photocathode for solar hydrogen evolution

DEFF Research Database (Denmark)

Hou, Yidong; Abrams, Billie; Vesborg, Peter Christian Kjærgaard

2011-01-01

The production of fuels directly or indirectly from sunlight represents one of the major challenges to the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and while platinum and other noble metals are efficient catalysts for photoelectrochemical hydrogen...... at the reversible potential match the requirement of a photoelectrochemical hydrogen production system with a solar-to-hydrogen efficiency in excess of 10%. The experimental observations are supported by DFT calculations of the Mo3S4 cluster adsorbed on the hydrogen-terminated silicon surface providing insights...... deposited on various supports. It will be demonstrated how this overpotential can be eliminated by depositing the same type of hydrogen evolution catalyst on p-type Si which can harvest the red part of the solar spectrum. Such a system could constitute the cathode part of a tandem dream device where the red...

Photocatalysis in Generation of Hydrogen from Water

KAUST Repository

Takanabe, Kazuhiro

2015-04-18

Solar energy can be converted by utilizing the thermal or photoelectric effects of photons. Concentrated solar power systems utilize thermal energy from the sun by either making steam and then generating power or shifting the chemical equilibrium of a reaction (e.g., water splitting or CO2 reduction) that occurs at extremely high temperatures. The photocatalytic system contains powder photocatalysts. Each photocatalyst particle should collect sufficient photons from the solar flux to cause the required multielectron reactions to occur. The band gap and band edge positions of semiconductors are the most critical parameters for assessing the suitability of photocatalysts for overall water splitting. The most important requirement when selecting photocatalyst materials is the band positions relative to hydrogen and oxygen evolution potentials. For most photocatalysts, surface modification by cocatalysts was found to be essential to achieve overall water splitting.

Enhanced photocatalytic activity over Cd{sub 0.5}Zn{sub 0.5}S with stacking fault structure combined with Cu{sup 2+} modified carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Gong, Beini; Lu, Yonghong [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006 (China); Wu, Pingxiao, E-mail: pppxwu@scut.edu.cn [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006 (China); Guangdong Provincial Engineering and Technology Research Centre for Environment Risk Prevention and Emergency Disposal, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); Huang, Zhujian; Zhu, Yajie; Dang, Zhi [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006 (China); Zhu, Nengwu [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006 (China); Guangdong Provincial Engineering and Technology Research Centre for Environment Risk Prevention and Emergency Disposal, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); Lu, Guining; Huang, Junyi [School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006 (China); The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006 (China)

2016-03-01

Graphical abstract: - Highlights: • CdZnS with stacking faults was combined with Cu{sup 2+} modified carbon nanotubes. • Stacking faults and carbon nanotubes (Cu) synergized to promote charge separation. • The composite exhibited enhanced photocatalytic performance. - Abstract: For enhanced photocatalytic performance of visible light responsive CdZnS, a series of Cd{sub 0.5}Zn{sub 0.5}S solid solutions were fabricated by different methods. It was found that the semiconductor obtained through the precipitation-hydrothermal method (CZS-PH) exhibited the highest photocatalytic hydrogen production rate of 2154 μmol h{sup −1} g{sup −1}. The enhanced photocatalytic hydrogen production of CZS-PH was probably due to stacking fault formation as well as narrow bandgap, a large surface area and a small crystallite size. Based on this, carbon nanotubes modified with Cu{sup 2+} (CNTs (Cu)) were used as a cocatalyst for CZS-PH. The addition of CNTs (Cu) enhanced notably the absorption of the composites for visible light. The highest photocatalytic hydrogen production rate of the Cd{sub 0.5}Zn{sub 0.5}S-CNTs (Cu) composite was 2995 μmol h{sup −1} g{sup −1} with 1.0 wt.% of CNTs (Cu). The improvement of the photocatalytic activity by loading of CNTs (Cu) was not due to alteration of bandgap energy or surface area, and was probably attributed to suppression of the electron-hole recombination by the CNTs, with Cu{sup 2+} anchored in the interface optimizing the photogenerated electron transfer pathway between the semiconductor and CNTs. We report here the successful combination of homojunction and heterojunction in CdZnS semiconductor, which resulted in promotion of charge separation and enhanced photocatalytic activity.

Straightforward high-pressure synthesis and characterization of indium-based thiospinels: photocatalytic potential for hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Falcon, Horacio [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco (Spain); NANOTEC (Centro de Investigacion en Nanociencia y Nanotecnologia), Universidad Tecnologica Nacional-Facultad Regional Cordoba, Cordoba (Argentina); Tartaj, Pedro; Alonso, Jose Antonio [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco (Spain); Vaquero, Fernando; Navarro, Rufino M.; Fierro, Jose Luis G. [Instituto de Catalisis y Petroleoquimica, CSIC, Cantoblanco, Madrid (Spain); Bolletta, Juan P.; Paoli, Juan M. de; Carbonio, Raul E. [INFIQC - CONICET, Departamento de Fisicoquimica, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba (Argentina); Fernandez-Diaz, Maria Teresa [Institut Laue Langevin, Grenoble (France)

2016-04-15

Ternary chalcogenides (AB{sub 2}X{sub 4}) based on the spinel structure are gaining a great deal of attention because of the possibility of tuning their magnetic and optoelectronic properties not only by changing chemical composition but also by altering their degree of inversion. Here we report a rapid high-pressure synthetic method for the synthesis of MIn{sub 2}S{sub 4} powders starting from commercially available solid sulfides. We prove the versatility of our method by reporting the synthesis of six members of the MIn{sub 2}S{sub 4} family (M = Mn, Fe, Co, Ni, Zn, and Cd) under high-pressure conditions (3.5 GPa); these compounds show complete to moderate degrees of inversion. Furthermore, this family covers a spectral region that includes visible band gaps. Interestingly, the structural refinement carried out by X-ray and neutron diffraction allows one to establish positive correlations between the gap and different parameters, including the degree of inversion. Finally, as a proof-of-concept, these ternary chalcogenides show moderate photocatalytic hydrogen production from aqueous solutions. (Copyright copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Direct Z-scheme TiO2/CdS hierarchical photocatalyst for enhanced photocatalytic H2-production activity

Science.gov (United States)

Meng, Aiyun; Zhu, Bicheng; Zhong, Bo; Zhang, Liuyang; Cheng, Bei

2017-11-01

Photocatalytic H2 evolution, which utilizes solar energy via water splitting, is a promising route to deal with concerns about energy and environment. Herein, a direct Z-scheme TiO2/CdS binary hierarchical photocatalyst was fabricated via a successive ionic layer adsorption and reaction (SILAR) technique, and photocatalytic H2 production was measured afterwards. The as-prepared TiO2/CdS hybrid photocatalyst exhibited noticeably promoted photocatalytic H2-production activity of 51.4 μmol h-1. The enhancement of photocatalytic activity was ascribed to the hierarchical structure, as well as the efficient charge separation and migration from TiO2 nanosheets to CdS nanoparticles (NPs) at their tight contact interfaces. Moreover, the direct Z-scheme photocatalytic reaction mechanism was demonstrated to elucidate the improved photocatalytic performance of TiO2/CdS composite photocatalyst. The photoluminescence (PL) analysis of hydroxyl radicals were conducted to provide clues for the direct Z-scheme mechanism. This work provides a facile route for the construction of redox mediator-free Z-scheme photocatalytic system for photocatalytic water splitting.

The effect of urea on microstructures of Ni{sub 3}S{sub 2} on nickel foam and its hydrogen evolution reaction

Energy Technology Data Exchange (ETDEWEB)

Jinlong, Lv, E-mail: ljltsinghua@126.com [Beijing Key Laboratory of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Zhongguancun Street, Haidian District, Beijing 100084 (China); State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Tongxiang, Liang, E-mail: txliang@mail.tsinghua.edu.cn [Beijing Key Laboratory of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Zhongguancun Street, Haidian District, Beijing 100084 (China); State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China)

2016-11-15

The effects of urea concentration on microstructures of Ni{sub 3}S{sub 2}formed on nickel foam and its hydrogen evolution reaction were investigated. The Ni{sub 3}S{sub 2} nanosheets with porous structure were formed on nickel foam during hydrothermal process due to low urea concentration. While high urea concentration facilitated the forming of Ni{sub 3}S{sub 2} nanotube arrays. The resulting Ni{sub 3}S{sub 2} nanotube arrays exhibited higher catalytic activity than Ni3S2nanosheets for hydrogen evolution reaction. This was mainly attributed to a fact that Ni{sub 3}S{sub 2} nanotube arrays facilitated diffusion of electrolyte for hydrogen evolution reaction. - Graphical abstract: The resulting Ni{sub 3}S{sub 2} nanotube arrays exhibited higher catalytic activity than Ni{sub 3}S{sub 2} nanosheets for hydrogen evolution reaction. This was mainly attributed to a fact that Ni{sub 3}S{sub 2} nanotube arrays facilitated diffusion of electrolyte for hydrogen evolution reaction and hydrogen evolution. - Highlights: • Urea promoted to forming more Ni{sub 3}S{sub 2} nanotube arrays on nickel foam. • Ni{sub 3}S{sub 2} nanotube arrays showed higher catalytic activity in alkaline solution. • Ni{sub 3}S{sub 2} nanotube arrays promoted electron transport and reaction during the HER.

On the role of metal particle size and surface coverage for photo-catalytic hydrogen production; a case study of the Au/CdS system

KAUST Repository

Majeed, I.

2015-09-25

Photo-catalytic hydrogen production has been studied on Au supported CdS catalysts under visible light irradiation in order to understand the effect of Au particle size as well as the reaction medium properties. Au nanoparticles of size about 2-5 nm were deposited over hexagonal CdS particles using a new simple method involving reduction of Au3+ ions with iodide ions. Within the investigated range of Au (between 1 and 5 wt. %) fresh particles with mean size of 4 nm and XPS Au4f/Cd3d surface ratio of 0.07 showed the highest performance (ca. 1 molecule of H2 / Auatom s−1) under visible light irradiation (>420 nm and a flux of 35 mW/cm2). The highest hydrogen production rate was obtained from water (92%)-ethanol (8%) in an electrolyte medium (Na2S-Na2SO3). TEM studies of fresh and used catalysts showed that Au particle size increases (almost 5 fold) with increasing photo-irradiation time due to photo-agglomeration effect yet no sign of deactivation was observed. A mechanism for hydrogen production from ethanol-water electrolyte mixture is presented and discussed.

Enhanced kinetics of hole transfer and electrocatalysis during photocatalytic oxygen evolution by cocatalyst tuning

KAUST Repository

Nurlaela, Ela; Wang, Hai; Shinagawa, Tatsuya; Flanagan, Sean; Ould-Chikh, Samy; Qureshi, Muhammad; Mics, Zoltan; Sautet, Philippe; Le Bahers, Tangui; Canovas, Enrique; Bonn, Mischa; Takanabe, Kazuhiro

2016-01-01

Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic effi-ciency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the ef-fects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm2 V-1 s-1), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

Enhanced kinetics of hole transfer and electrocatalysis during photocatalytic oxygen evolution by cocatalyst tuning

KAUST Repository

Nurlaela, Ela

2016-05-23

Understanding photophysical and electrocatalytic processes during photocatalysis in a powder suspension system is crucial for developing efficient solar energy conversion systems. We report a substantial enhancement by a factor of 3 in photocatalytic effi-ciency for the oxygen evolution reaction (OER) by adding trace amounts (~0.05 wt%) of noble metals (Rh or Ru) to a 2 wt% cobalt oxide-modified Ta3N5 photocatalyst particulate. The optimized system exhibited high quantum efficiencies (QEs) of up to 28 and 8.4% at 500 and 600 nm in 0.1 M Na2S2O8 at pH 14. By isolating the electrochemical components to generate doped cobalt oxide electrodes, the electrocatalytic activity of cobalt oxide when doped with Ru or Rh was improved compared with cobalt oxide, as evidenced by the onset shift for electrochemical OER. Density functional theory (DFT) calculation shows that the ef-fects of a second metal addition perturbs the electronic structure and redox properties in such a way that both hole transfer kinetics and electrocatalytic rates improve. Time resolved terahertz spectroscopy (TRTS) measurement provides evidence of long-lived electron populations (>1 ns; with mobilities μe ~0.1-3 cm2 V-1 s-1), which are not perturbed by the addition of CoOx-related phases. Furthermore, we find that Ta3N5 phases alone suffer ultrafast hole trapping (within 10 ps); the CoOx and M-CoOx decorations most likely induce a kinetic competition between hole transfer toward the CoOx-related phases and trapping in the Ta3N5 phase, which is consistent with the improved OER rates. The present work not only provides a novel way to improve electrocatalytic and photocatalytic performance but also gives additional tools and insight to understand the characteristics of photocatalysts that can be used in a suspension system.

High-Sulfur-Vacancy Amorphous Molybdenum Sulfide as a High Current Electrocatalyst in Hydrogen Evolution

KAUST Repository

Lu, Ang-Yu

2016-08-31

The remote hydrogen plasma is able to create abundant S-vacancies on amorphous molybdenum sulfide (a-MoSx) as active sites for hydrogen evolution. The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.

Facile Hydrogen Evolution Reaction on WO3Nanorods

Directory of Open Access Journals (Sweden)

Rajeswari Janarthanan

2007-01-01

Full Text Available AbstractTungsten trioxide nanorods have been generated by the thermal decomposition (450 °C of tetrabutylammonium decatungstate. The synthesized tungsten trioxide (WO3 nanorods have been characterized by XRD, Raman, SEM, TEM, HRTEM and cyclic voltammetry. High resolution transmission electron microscopy and X-ray diffraction analysis showed that the synthesized WO3nanorods are crystalline in nature with monoclinic structure. The electrochemical experiments showed that they constitute a better electrocatalytic system for hydrogen evolution reaction in acid medium compared to their bulk counterpart.

Molybdenum sulphides on carbon supports as electrocatalysts for hydrogen evolution in acidic industrial wastewater

International Nuclear Information System (INIS)

Kokko, M.; Bayerköhler, F.; Erben, J.; Zengerle, R.; Kurz, Ph.; Kerzenmacher, S.

2017-01-01

Highlights: • MoS_x is an efficient and durable catalyst for H_2 evolution in acidic wastewater. • MoS_x outperformed Pt as H_2-catalyst in long term in acidic wastewater. • Improved activity over time was likely due to changes in MoS_x structure. - Abstract: Microbial electrolysis cells (MECs) are an attractive future alternative technology to generate renewable hydrogen and simultaneously treat wastewaters. The thermodynamics of hydrogen evolution in MECs can be greatly improved by operating the cathode at acidic pH in combination with a neutral pH microbial anode. This can easily be achieved with acidic industrial wastewaters that have to be neutralised before discharge. For the hydrogen evolution reaction (HER) in acidic wastewater, efficient and inexpensive catalysts are required that are compatible with the often complex chemical composition of wastewaters. In this study, molybdenum sulphides (MoS_x) on different carbon supports were successfully used for hydrogen evolution in different acidic media. At first, the cathodes were screened by linear sweep voltammetry in sulphuric acid (pH 0) or phosphate buffer (pH 2.2). After this, the overpotentials for H_2 production of the best cathodes and their long term performances (⩾1 week) were determined in acidic industrial wastewater (pH 2.4) obtained from a plant mainly producing cellulose acetate. For the most promising MoS_x cathodes, the overpotentials for HER (at 3 mA cm"−"2) were only ∼40 mV higher than for a platinum electrode. Most importantly, the catalytic efficiency of the MoS_x electrodes improved in the wastewater over time (7–17 days), while Pt electrodes were found to be slowly deactivated. Thus, MoS_x emerges as an affordable, efficient and especially durable electrocatalyst for HER in real acidic wastewaters and this could be an important contribution to take energy production from wastewaters in the form of hydrogen towards practical applications.

Silicon Nano wires with MoS_x and Pt as Electrocatalysts for Hydrogen Evolution Reaction

International Nuclear Information System (INIS)

Hsieh, S.H.; Ho, S.T.; Chen, W.J.

2016-01-01

A convenient method was used for synthesizing Pt-nanoparticle//silicon nano wires nano composites. Obtained Pt-/silicon nano wires electrocatalysts were characterized by transmission electron microscopy (TEM). The hydrogen evolution reaction efficiency of the Pt-/silicon nano wire nano composite catalysts was assessed by examining polarization and electrolysis measurements under solar light irradiations. The electrochemical characterizations demonstrate that Pt-/silicon nano wire electrodes exhibited an excellent catalytic activity for hydrogen evolution reaction in an acidic electrolyte. The hydrogen production capability of Pt-/silicon nano wires is also comparable to /silicon nano wires and Pt/silicon nano wires. Electrochemical impedance spectroscopy experiments suggest that the enhanced performance of Pt-/silicon nano wires can be attributed to the fast electron transfer between Pt-/silicon nano wire electrodes and electrolyte interfaces.

Artificial photosynthesis for production of hydrogen peroxide and its fuel cells.

Science.gov (United States)

Fukuzumi, Shunichi

2016-05-01

The reducing power released from photosystem I (PSI) via ferredoxin enables the reduction of NADP(+) to NADPH, which is essential in the Calvin-Benson cycle to make sugars in photosynthesis. Alternatively, PSI can reduce O2 to produce hydrogen peroxide as a fuel. This article describes the artificial version of the photocatalytic production of hydrogen peroxide from water and O2 using solar energy. Hydrogen peroxide is used as a fuel in hydrogen peroxide fuel cells to make electricity. The combination of the photocatalytic H2O2 production from water and O2 using solar energy with one-compartment H2O2 fuel cells provides on-site production and usage of H2O2 as a more useful and promising solar fuel than hydrogen. This article is part of a Special Issue entitled Biodesign for Bioenergetics--The design and engineering of electronc transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson. Copyright © 2016 Elsevier B.V. All rights reserved.

Efficient solar light harvesting CdS/Co{sub 9}S{sub 8} hollow cubes for Z-scheme photocatalytic water splitting

Energy Technology Data Exchange (ETDEWEB)

Qiu, Bocheng; Zhu, Qiaohong; Du, Mengmeng; Fan, Linggang; Xing, Mingyang; Zhang, Jinlong [Key Lab. for Advanced Materials and Inst. of Fine Chemicals, School of Chemistry and Molecular Engineering, East China Univ. of Science and Technology, Shanghai (China)

2017-03-01

Hollow structures with an efficient light harvesting and tunable interior component offer great advantages for constructing a Z-scheme system. Controlled design of hollow cobalt sulfide (Co{sub 9}S{sub 8}) cubes embedded with cadmium sulfide quantum dots (QDs) is described, using hollow Co(OH){sub 2} as the template and a one-pot hydrothermal strategy. The hollow CdS/Co{sub 9}S{sub 8} cubes utilize multiple reflections of light in the cubic structure to achieve enhanced photocatalytic activity. Importantly, the photoexcited charge carriers can be effectively separated by the construction of a redox-mediator-free Z-scheme system. The hydrogen evolution rate over hollow CdS/Co{sub 9}S{sub 8} is 134 and 9.1 times higher than that of pure hollow Co{sub 9}S{sub 8} and CdS QDs under simulated solar light irradiation, respectively. Moreover, this is the first report describing construction of a hollow Co{sub 9}S{sub 8} based Z-scheme system for photocatalytic water splitting, which gives full play to the advantages of light-harvesting and charges separation. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Design of Copper and Titanium Dioxide Nanoparticles Doped with Reduced Graphene Oxide for Hydrogen Evolution by Water Splitting

Science.gov (United States)

Yang, Yuhao; Huang, Wenhuan

2018-05-01

TiO2-graphene (P25-GR, PG) nanocomposite was fabricated from P25 titania and graphite oxide by hydrothermal method, and then Cu nanoparticles (Cu NPs) were assembled in P25-GR composite (Cu- P25-GR, CPG) under microwave-assisted chemical reduction. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-Vis absorption (UV-Vis) and Raman spectroscopies. Cu NPs were well dispersed on the surface of PG and are in metallic state. The ternary Cu-P25-GR (CPG) nanocomposites show an extended light absorption range and more efficient charge separation properties compared to binary P25-GR (PG) composite. Methylene blue photodegradation experiment proved that surface plasmon resonance (SPR) phenomenon had an effect on photoreaction efficiency. The corresponding hydrogen evolution rate for CPG prepared using 0.002 M Cu(NO3)2 solution was 10 times higher than with pure P25, and 2.3 times higher than with PG in the same test conditions. The improved photocatalytic performance can be attributed to the presence of GR in the prepared composite and to the SPR effect, leading to the longer lifetime of photogenerated electronhole pairs and faster interfacial charge transfer rate. We expect that our work would be useful for the further exploration of GR-based nanocomposites.

Cathodic over-potential and hydrogen partial pressure coupling in hydrogen evolution reaction of marine steel under hydrostatic pressure

International Nuclear Information System (INIS)

Xiong, X.L.; Zhou, Q.J.; Li, J.X.; Volinsky, Alex A.; Su, Y.J.

2017-01-01

Highlights: •Hydrostatic pressure increases the Volmer and the Heyrovsky reactions rates. •Hydrostatic pressure decreases the Tafel reaction rate. •Hydrogen adsorption conditions change with pressure under −1.2 and −1.3 V SSE . •Under −1.2 and −1.3 V SSE , the Heyrovsky reaction dominates the hydrogen recombination. •Under −1.0 and −1.1 V SSE , the Tafel reaction dominates the hydrogen recombination. -- Abstract: A new electrochemical impedance spectroscopy (EIS) model, which considers both the Tafel recombination and the Heyrovsky reaction under permeable boundary conditions, was developed to characterize the kinetic parameters of the hydrogen evolution reaction (HER) under hydrostatic pressure. The effect of the hydrostatic pressure on the kinetic parameters of the HER and the permeation of A514 steel in alkaline solution were measured using potentiodynamic polarization, the Devanathan cell hydrogen permeation, and EIS. The hydrostatic pressure accelerates the Volmer reaction and inhibits the Tafel recombination, which increases the number of adsorbed hydrogen atoms. On the other hand, the pressure accelerates the Heyrovsky reaction, which decreases the amount of adsorbed hydrogen atoms. At 10 to 40 MPa hydrostatic pressure within the −1.0 to −1.1 V SSE cathodic potential region, the HER is controlled by hydrogen partial pressure, and hydrogen adsorption is the Langmuir type. Within the −1.2 to −1.3 V SSE cathodic potential region, the HER is controlled by the potential, and hydrogen adsorption gradually transfers from the Langmuir type to the Temkin type with increasing hydrostatic pressure.

Photocatalytic H 2 production from water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled Pt/TiO 2 nanocrystal photocatalyst

Science.gov (United States)

Sreethawong, Thammanoon; Junbua, Chompoonuch; Chavadej, Sumaeth

Sensitized photocatalytic production of hydrogen from water splitting is investigated under visible light irradiation over mesoporous-assembled titanium dioxide (TiO 2) nanocrystal photocatalysts, without and with Pt loading. The photocatalysts are synthesized by a sol-gel process with the aid of a structure-directing surfactant and are characterized by N 2 adsorption-desorption analysis, X-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. The dependence of hydrogen production on the type of TiO 2 photocatalyst (synthesized mesoporous-assembled and commercial non-mesoporous-assembled TiO 2 without and with Pt loading), the calcination temperature of the synthesized photocatalyst, the sensitizer (Eosin Y) concentration, the electron donor (diethanolamine) concentration, the photocatalyst dosage and the initial solution pH is systematically studied. The results show that in the presence of the Eosin Y sensitizer, the Pt-loaded mesoporous-assembled TiO 2 synthesized by a single-step sol-gel process and calcined at 500 °C exhibits the highest photocatalytic activity for hydrogen production from a 30 vol.% diethanolamine aqueous solution with dissolved 2 mM Eosin Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic activity for hydrogen production are 3.33 g dm -3 and 11.5, respectively.

Photocatalytic degradation of bisphenol A in the presence of Ce–ZnO: Evolution of kinetics, toxicity and photodegradation mechanism

Energy Technology Data Exchange (ETDEWEB)

Bechambi, Olfa [Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Chimie des Matériaux et Catalyse, 2092, Tunis (Tunisia); Jlaiel, Lobna [Laboratoire de Bioprocédés Environnementaux, Centre de Biotechnologie de Sfax, B.P. 1177, 3018 Sfax (Tunisia); Najjar, Wahiba, E-mail: najjarwahiba2014@gmail.com [Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Chimie des Matériaux et Catalyse, 2092, Tunis (Tunisia); Sayadi, Sami [Laboratoire de Bioprocédés Environnementaux, Centre de Biotechnologie de Sfax, B.P. 1177, 3018 Sfax (Tunisia)

2016-04-15

Ce–ZnO (2 mol %) and undoped ZnO catalysts have been synthesized through hydrothermal method and characterized by X-ray diffraction (XRD), Nitrogen physisorption at 77 K; Fourier transformed infrared spectroscopy (FTIR), UV–Visible spectroscopy, Photoluminescence spectra (PL), and Raman spectroscopy. Ce-doping reduces the average crystallite size, increases the BET surface area, shifts the absorption edge, reduces the electron–hole recombination and consequently improves photodegradation efficiency of Bisphenol A (BPA) in the presence of UV irradiation and hydrogen peroxide. The photocatalytic optimum conditions were established by studying the influence of various operational parameters including catalyst concentration, initial BPA concentration, H{sub 2}O{sub 2} concentration and initial pH. Under optimum conditions, Ce–ZnO (2%) achieved 100% BPA degradation and 61% BPA mineralization after 24 h of UV irradiation. BPA degradation reaction followed pseudo first-order kinetics according to the Langmuir–Hinshelwood model. Based on the identified intermediate products, the possible mechanism for BPA photodegradation is proposed. Toxicity under the optimum condition was also evaluated. - Graphical abstract: Proposed photocatalytic degradation pathway of BPA in the presence of Ce– ZnO (2%)/UV/H{sub 2}O{sub 2} system. - Highlights: • Influence of different parameters on the degradation and mineralization of BPA. • Identification of possible degradation products. • Toxicity tests conducted with Vibrio fischeri. • Simple and direct photodegradation mechanism of BPA is proposed.

Photocatalytic hydrogen production on SOLECTRO {sup registered} titanium dioxide layers. Investigation of reaction processes and of the influence of various reaction parameters; Photokatalytische Wasserstoffgewinnung an SOLECTRO {sup registered} -Titandioxidschichten. Untersuchung der ablaufenden Reaktionsprozesse und des Einflusses verschiedener Reaktionsparameter

Energy Technology Data Exchange (ETDEWEB)

Keil, Doreen

2010-04-14

The dissertation investigated the reaction processes of photocatalytic hydrogen production on palladium and copper-doped SOLECTRO {sup registered} titanium dioxide layers. Methanol was used as electron donor. [German] In dieser Doktorarbeit werden die ablaufenden Reaktionsprozesse der photokatalytischen Wasserstoffentwicklung an palladium- und kupferbeladenen SOLECTRO {sup registered} -Titandioxidschichten untersucht. Als Elektronendonator wurde Methanol verwendet.

Remarkable photo-catalytic degradation of malachite green by nickel doped bismuth selenide under visible light irradiation

Science.gov (United States)

Kulsi, Chiranjit; Ghosh, Amrita; Mondal, Anup; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

2017-01-01

Bismuth selenide (Bi2Se3) and nickel (Ni) doped Bi2Se3 were prepared by a solvothermal approach to explore the photo-catalytic performance of the materials in degradation of malachite green (MG). The presence of nickel was confirmed by X-ray photoelectron spectroscopy (XPS) measurement in doped Bi2Se3. The results showed that the nickel doping played an important role in microstructure and photo-catalytic activity of the samples. Nickel doped Bi2Se3 sample exhibited higher photo-catalytic activity than that of the pure Bi2Se3 sample under visible-light irradiation. The photo-catalytic degradation followed first-order reaction kinetics. Fast degradation kinetics and complete (100% in 5 min of visible light irradiation) removal of MG was achieved by nickel doped Bi2Se3 in presence of hydrogen peroxide (H2O2) due to modification of band gap energies leading to suppression of photo-generated electron-hole recombination.

Copper-organic/octamolybdates: structures, bandgap sizes, and photocatalytic activities.

Science.gov (United States)

Luo, Lan; Lin, Haisheng; Li, Le; Smirnova, Tatyana I; Maggard, Paul A

2014-04-07

The structures, optical bandgap sizes, and photocatalytic activities are described for three copper-octamolybdate hybrid solids prepared using hydrothermal methods, [Cu(pda)]4[β-Mo8O26] (I; pda = pyridazine), [Cu(en)2]2[γ-Mo8O26] (II; en = ethylenediamine), and [Cu(o-phen)2]2[α-Mo8O26] (III; o-phen = o-phenanthroline). The structure of I consists of a [Cu(pda)]4(4+) tetramer that bridges to neighboring [β-Mo8O26](4-) octamolybdate clusters to form two-dimensional layers that stack along the a axis. The previously reported structures of II and III are constructed from [Cu2(en)4Mo8O26] and [Cu2(o-phen)4Mo8O26] clusters. The optical bandgap sizes were measured by UV-vis diffuse reflectance techniques to be ∼1.8 eV for I, ∼3.1 eV for II, and ∼3.0 eV for III. Electronic structure calculations show that the smaller bandgap size of I originates primarily from an electronic transition between the valence and conduction band edges comprised of filled 3d(10) orbitals on Cu(I) and empty 4d(0) orbitals on Mo(VI). Both II and III contain Cu(II) and exhibit larger bandgap sizes. Accordingly, aqueous suspensions of I exhibit visible-light photocatalytic activity for the production of oxygen at a rate of ∼90 μmol O2 g(-1) h(-1) (10 mg samples; radiant power density of ∼1 W/cm(2)) and a turnover frequency per calculated surface [Mo8O26](4-) cluster of ∼36 h(-1). Under combined ultraviolet and visible-light irradiation, I also exhibits photocatalytic activity for hydrogen production in 20% aqueous methanol of ∼316 μmol H2 g(-1) h(-1). By contrast, II decomposed during the photocatalysis measurements. The molecular [Cu2(o-phen)4(α-Mo8O26)] clusters of III dissolve into the aqueous methanol solution under ultraviolet irradiation and exhibit homogeneous photocatalytic rates for hydrogen production of up to ∼8670 μmol H2·g(-1) h(-1) and a turnover frequency of 17 h(-1). The clusters of III can be precipitated out by evaporation and redispersed into solution with

Effect of Rh oxide as a cocatalyst over Bi{sub 0.5}Y{sub 0.5}VO{sub 4} on photocatalytic overall water splitting

Energy Technology Data Exchange (ETDEWEB)

Chen, Wei, E-mail: chanwee@henu.edu.cn [College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, Henan (China); Yang, Bingbing; Yu, Qingtao; Mao, Liqun [College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, Henan (China); Fan, Zeyun [Research Center for Combustion and Environmental Technology, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Qizhao [College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Shangguan, Wenfeng, E-mail: shangguan@sjtu.edu.cn [Research Center for Combustion and Environmental Technology, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-11-15

Graphical abstract: - Highlights: • The effect of cocatalysts as active sites for water splitting was investigated. • Rh{sub 2}O{sub 3} was found to give the highest photocatalytic activity. • Compared to Pt, NiO, Rh{sub 2}O{sub 3} can reduce more overpotential of O{sub 2} evolution. • Rh{sub 2}O{sub 3} also promote the separation of electrons and holes apparently. - Abstract: Pt, Rh{sub 2}O{sub 3}, NiO nanoparticles as cocatalysts were loaded on BYV solid solution photocatalysts by an impregnation method to promote photocatalytic activity for overall water splitting. The cocatalysts loading could enhance the photocatalytic activity significantly. The (photo)electrochemical measurements and HR-TEM, PL analyses revealed that the effect of cocatalysts acted as active sites depended on the efficient separation of photoinduced charge carriers as well as the reduction of the overpotential of O{sub 2} evolution. Among the cocatalysts in this study, Rh{sub 2}O{sub 3} was found to give the highest photocatalytic activity. This is because, compared to Pt and NiO, Rh{sub 2}O{sub 3} nanoparticles are able to not only reduce more overpotential of O{sub 2} evolution, but also extremely promote the separation of electrons and holes. 0.5 wt% Rh{sub 2}O{sub 3}/BYV exhibited the highest photocatalytic activity for H{sub 2} and O{sub 2} evolution, reaching 104.4 μmol/h and 50.9 μmol/h, respectively. The present work will be useful to instruct cocatalyst loading for obtaining the photocatalysts with high photocatalytic activity for overall water splitting.

Fabrication of efficient visible light activated Cu–P25–graphene ternary composite for photocatalytic degradation of methyl blue

Energy Technology Data Exchange (ETDEWEB)

Jin, Zheng [Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044 (China); Duan, Wubiao, E-mail: wbduan@bjtu.edu.cn [Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044 (China); Liu, Bo; Chen, Xidong [Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044 (China); Yang, Feihua; Guo, Jianping [State Key Laboratory of Solid Wastes Resource Utilization and Energy Saving Building Materials, Beijing Building Materials Academy of Sciences Research, Beijing 100041 (China)

2015-11-30

Graphical abstract: This enhanced photocatalytic activity of multi-doped P25 arises due to the synergistic effect of dopants contribution to improve visible light absorption and increase of the lifetime of photo-generated charge carriers. Plausible mechanism for the photocatalytic degradation of MB on CPG nanocomposite is illustrated in the figure above. Graphene incooperated with TiO{sub 2} promotes the formation of Ti−C or Ti−O−C bonds that introduced an additional energy level above the valence band of TiO{sub 2}. Furthermore, copper and graphene serve as an inhibitor of recombination by trapping electrons to promote charge separation. Simultaneously, doping Cu{sup 2+} ions into TiO{sub 2} could also induce more oxygen vacancies, which can produce more hydroxyl groups. Finally, the enhanced adsorptivity of π–π interaction between MB and the composite catalyst was as well significant for photocatalytic activity. - Highlights: • Hydrothermal method was proposed to fabricate Cu–P25–graphene ternary composite at relative low temperature. • Degradation efficiency and hydrogen evolution rate of CPG-4 was up to 98% and 1.90 mmol g{sup −1} respectively. • The efficiency of MB removal by CPG-4 was sustainable and consistent. • The particles-on-a-sheet structure and synergistic effects of Cu{sup 2+} ions and GO lead to the improved photocatalytic activity. • The effects of pH values of methyl blue solution for photocatalysts was investigated. - Abstract: Cu–P25–graphene nanocomposite was fabricated through hydrothermal method at relatively low temperature. The technique used is P25–graphene (PG) binary composite was firstly prepared by P25 and graphite oxide (GO), and then Cu{sup 2+} ions were impregnated into PG composite. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance

Highly efficient photocatalytic conversion of solar energy to hydrogen by WO3/BiVO4 core-shell heterojunction nanorods

Science.gov (United States)

Kosar, Sonya; Pihosh, Yuriy; Bekarevich, Raman; Mitsuishi, Kazutaka; Mawatari, Kazuma; Kazoe, Yutaka; Kitamori, Takehiko; Tosa, Masahiro; Tarasov, Alexey B.; Goodilin, Eugene A.; Struk, Yaroslav M.; Kondo, Michio; Turkevych, Ivan

2018-04-01

Photocatalytic splitting of water under solar light has proved itself to be a promising approach toward the utilization of solar energy and the generation of environmentally friendly fuel in a form of hydrogen. In this work, we demonstrate highly efficient solar-to-hydrogen conversion efficiency of 7.7% by photovoltaic-photoelectrochemical (PV-PEC) device based on hybrid MAPbI3 perovskite PV cell and WO3/BiVO4 core-shell nanorods PEC cell tandem that utilizes spectral splitting approach. Although BiVO4 is characterized by intrinsically high recombination rate of photogenerated carriers, this is not an issue for WO3/BiVO4 core-shell nanorods, where highly conductive WO3 cores are combined with extremely thin absorber BiVO4 shell layer. Since the BiVO4 layer is thinner than the characteristic carrier diffusion length, the photogenerated charge carriers are separated at the WO3/BiVO4 heterojunction before their recombination. Also, such architecture provides sufficient optical thickness even for extremely thin BiVO4 layer due to efficient light trapping in the core-shell WO3/BiVO4 nanorods with high aspect ratio. We also demonstrate that the concept of fill factor can be used to compare I-V characteristics of different photoanodes regarding their optimization for PV/PEC tandem devices.

Photocatalytic applications with CdS • block copolymer/exfoliated graphene nanoensembles: hydrogen generation and degradation of Rhodamine B

International Nuclear Information System (INIS)

Skaltsas, T; Karousis, N; Pispas, S; Tagmatarchis, N

2014-01-01

Amphiphilic block copolymer poly(isoprene-b-acrylic acid) (PI-b-PAA) was used to stabilize exfoliated graphene in water, allowing the immobilization of semiconductor CdS nanoparticles forming CdS • PI-b-PAA/graphene. Characterization using high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy proved the success of the preparation method and revealed the presence of spherical CdS. Moreover, UV–Vis and photoluminescence assays suggested that electronic interactions within CdS • PI-b-PAA/graphene exist as evidenced by the significant quenching of the characteristic emission of CdS by exfoliated graphene. Photoillumination of CdS • PI-b-PAA/graphene, in the presence of ammonium formate as a quencher for the photogenerated holes, resulted in the generation of hydrogen by water splitting, monitored by the reduction of 4-nitroaniline to benzene-1,4-diamine (>80 ± 4% at 20 min; 100% at 24 min), much faster and more efficient compared to when reference CdS • PI-b-PAA was used as the photocatalyst (<30 ± 3% at 20 min; 100% at 240 min). Moreover, Rhodamine B was photocatalytically degraded by CdS • PI-b-PAA/graphene, with fast kinetics under visible light illumination in the presence of air. The enhancement of both photocatalytic processes by CdS • PI-b-PAA/graphene was rationalized in terms of effective separation of holes and electrons, contrary to reference CdS • PI-b-PAA, in which rapid recombination of the hole–electron pair is inevitable due to the absence of exfoliated graphene as a suitable electron acceptor. (paper)

Synthesis and photocatalytic activity of CuY{sub y}Fe{sub 2-y}O{sub 4}-CuCo{sub 2}O{sub 4} nanocomposites for H{sub 2} evolution under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Yan, Jianhui; Yang, Haihua; Yao, Maohai; Han, Yong [Department of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Shuyuan Load, Yueyang, Hunan 414000 (China); College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083 (China); Tang, Yougen; Lu, Zhouguang [College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083 (China); Zheng, Shuqin [Department of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Shuyuan Load, Yueyang, Hunan 414000 (China)

2009-11-15

Spinel-type CuY{sub y}Fe{sub 2-y}O{sub 4}-CuCo{sub 2}O{sub 4} nanocomposites have been successfully synthesized via a facile citric acid (CA)-assisted sol-gel method. And the as-synthesized nanocomposites have been characterized by techniques of X-ray diffraction (XRD), nitrogen adsorption BET method, and transmission electron microscopy (TEM). The samples are composed of primary ultrafine nanoparticles with nearly spherical morphology and mean particle size of about 80 nm. Moreover, the photocatalytic H{sub 2} evolution activity of the as-obtained samples has been evaluated from aqueous oxalic acid solution under visible light irradiation. The influence of photocatalyst type, calcination temperature, Y{sup 3+} doping content, and the durability of the as-obtained photocatalyst have been investigated in detail. The best photocatalytic H{sub 2} evolution activity was obtained over the as-synthesized CuY{sub 0.08}Fe{sub 1.92}O{sub 4}-CuCo{sub 2}O{sub 4} nanocomposite. (author)

Shape-Enhanced Photocatalytic Activities of Thoroughly Mesoporous ZnO Nanofibers

KAUST Repository

Ren, Xiaolong

2016-06-24

1D mesoporous materials have attracted extensive interest recently, owning to their fascinating properties and versatile applications. However, it remains as a grand challenge to develop a simple and efficient technique to produce oxide nanofibers with mesoporous architectures, controlled morphologies, large surface areas, and optimal performances. In this work, a facile foaming-assisted electrospinning strategy with foaming agent of tea saponin is used to produce thoroughly mesoporous ZnO nanofibers with high purity and controlled morphology. Interestingly, mesoporous fibers with elliptical cross-section exhibit the significantly enhanced photocatalytic activity for hydrogen production, as compared to the counterparts with circular and rectangular cross-sections, and they also perform better than the commercial ZnO nanopowders. The unexpected shape dependence of photocatalytic activities is attributed to the different stacking modes of the mesoporous fibers, and a geometrical model is developed to account for the shape dependence. This work represents an important step toward producing thoroughly mesoporous ZnO nanofibers with tailored morphologies, and the discovery that fibers with elliptical cross-section render the best performance provides a valuable guideline for improving the photocatalytic performance of such mesoporous nanomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sequential reduction–oxidation for photocatalytic degradation of tetrabromobisphenol A: Kinetics and intermediates

International Nuclear Information System (INIS)

Guo, Yaoguang; Lou, Xiaoyi; Xiao, Dongxue; Xu, Lei; Wang, Zhaohui; Liu, Jianshe

2012-01-01

Highlights: ► Sequential photocatalytic reduction–oxidation degradation of TBBPA was firstly examined. ► Different atmospheres were found to have significant effect on debromination reaction. ► A possible sequential photocatalytic reduction–oxidation pathway was proposed. - Abstract: C-Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC–MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N 2 -saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a two-stage reductive debromination/subsequent oxidative decomposition process in the UV-TiO 2 system by changing the reaction atmospheres.

Hydrogen evolution at the negative electrode of the all-vanadium redox flow batteries

Science.gov (United States)

Sun, Che-Nan; Delnick, Frank M.; Baggetto, Loïc; Veith, Gabriel M.; Zawodzinski, Thomas A.

2014-02-01

This work demonstrates a quantitative method to determine the hydrogen evolution rate occurring at the negative carbon electrode of the all vanadium redox flow battery (VRFB). Two carbon papers examined by buoyancy measurements yield distinct hydrogen formation rates (0.170 and 0.005 μmol min-1 g-1). The carbon papers have been characterized using electron microscopy, nitrogen gas adsorption, capacitance measurement by electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). We find that the specific electrochemical surface area (ECSA) of the carbon material has a strong influence on the hydrogen generation rate. This is discussed in light of the use of high surface area material to obtain high reaction rates in the VRFB.

Hydrogen production over Au-loaded mesoporous-assembled SrTiO3 nanocrystal photocatalyst: Effects of molecular structure and chemical properties of hole scavengers

International Nuclear Information System (INIS)

Puangpetch, Tarawipa; Chavadej, Sumaeth; Sreethawong, Thammanoon

2011-01-01

Graphical abstract: Formic acid, which is the smallest and completely-dissociated water-soluble carboxylic acid, exhibited the highest hydrogen production enhancement ability over the 1 wt.% Au-loaded mesoporous-assembled SrTiO 3 nanocrystal photocatalyst. Display Omitted Research highlights: → The 1 wt.% Au-loaded mesoporous-assembled SrTiO 3 nanocrystal photocatalyst was synthesized. → The molecular structure and chemical properties of hole scavengers affected H 2 production rate. → Formic acid exhibited the highest photocatalytic H 2 production enhancement ability. -- Abstract: The hydrogen production via the photocatalytic water splitting under UV irradiation using different compounds as hole scavengers (including methanol, formic acid, acetic acid, propanoic acid, hydrochloric acid, and sulfuric acid) under a low concentration range ( 3 nanocrystal photocatalyst. The results indicated that the hydrogen production efficiency greatly depended on the molecular structure, chemical properties, and concentration of the hole scavengers. Formic acid, which is the smallest and completely-dissociated water-soluble carboxylic acid, exhibited the highest hydrogen production enhancement ability. The 2.5 vol.% aqueous formic acid solution system provided the highest photocatalytic hydrogen production rate.

Hazards analyses of hydrogen evolution and ammonium nitrate accumulation in DWPF -- Revision 1

International Nuclear Information System (INIS)

Holtzscheiter, E.W.

1994-01-01

This revision consists of two reports, the first of which is an analysis of potential ammonium nitrate explosion hazards in the DWPF (Defense Waste Processing Facility). Sections describe the effect of impurities (organic and inorganic (chlorides, chromates, metals and oxides)); the consequences of a hydrogen deflagration or detonation; the role of confinement; the action of heat on ammonium nitrate; the thermal decomposition of ammonium nitrate; the hazard of spontaneous heating; and the explosive decomposition of ammonium nitrate. The second report, Hazard analysis of hydrogen evolution in DWPF: Process vessels and vent system for the late wash/nitric acid flowsheet, contains a description of a revised model for hydrogen generation based on the late wash/nitric acid process. The second part of the report is a sensitivity analysis of the base case conditions and the hydrogen generation model

Phase transformations during HLnTiO{sub 4} (Ln=La, Nd) thermolysis and photocatalytic activity of obtained compounds

Energy Technology Data Exchange (ETDEWEB)

Silyukov, Oleg I., E-mail: olegsilyukov@yandex.ru; Abdulaeva, Liliia D.; Burovikhina, Alena A.; Rodionov, Ivan A.; Zvereva, Irina A.

2015-03-15

Layered HLnTiO{sub 4} (Ln=La, Nd) compounds belonging to Ruddlesden–Popper phases were found to form partially hydrated compounds Ln{sub 2}Ti{sub 2}O{sub 7}·xH{sub 2}O during thermal dehydration as well as defect oxides Ln{sub 2}□Ti{sub 2}O{sub 7} as final products. Further heating of metastable defect Ln{sub 2}□Ti{sub 2}O{sub 7} substances leads to the formation of pyrochlore-type oxides Ln{sub 2}Ti{sub 2}O{sub 7} {sub (p)}, with subsequent transformation under higher temperatures to stable layered 110-type perovskites Ln{sub 2}Ti{sub 2}O{sub 7}. The occurring structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO{sub 4}hydrogen evolution from aqueous isopropanol solution. - Graphical abstract: Layered HLnTiO{sub 4} (Ln=La, Nd) compounds form partially hydrated Ln{sub 2}Ti{sub 2}O{sub 7}·xH{sub 2}O compounds during thermal dehydration, further heating results to the formation to defect oxides Ln{sub 2}□Ti{sub 2}O{sub 7}, pyrochlor-type oxides Ln{sub 2}Ti{sub 2}O{sub 7} {sub (p)}, with subsequent transformation to layered 110-type perovskites Ln{sub 2}Ti{sub 2}O{sub 7}. Structure transformations lead to an increase of photocatalytic activity in the order of HLnTiO{sub 4}photocatalytic activity of all obtained compounds. The hydrogen evolution rate increased in the course of the structure changes during thermolysis.

Design of Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} nanocomponent photocatalysts for hydrogen evolution under visible light irradiation using water-soluble Erythrosin B dye sensitization

Energy Technology Data Exchange (ETDEWEB)

Zhang, Piyong; Wang, Tingting; Zeng, Heping, E-mail: hpzeng@scut.edu.cn

2017-01-01

Highlights: • A novel photocatalyst Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} was designed, synthesized and characterized. • Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} was sensitized by Erythrosin B and a significant enhancement of H{sub 2} evolution rate was achieved. • Electrochemical properties were measured and a possible mechanism of H{sub 2} evolution was proposed. - Abstract: Cu-Cu{sub 2}O nanoparticles (NPs) decorated porous graphitic carbon nitride (g-C{sub 3}N{sub 4}) (Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4}) photocatalysts were prepared. When investment of copper source materials in the experiment increased to 7 wt%, the highest H{sub 2} evolution rate (400 μmol g{sup −1} h{sup −1}) was obtained under visible light irradiation in triethanolamine solution. This is about triple of pure g-C{sub 3}N{sub 4} (140 μmol g{sup −1} h{sup −1}). Moreover, various amount of Erythrosin B dye was added into Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} photoreaction solution and a significant enhancement of H{sub 2} production rate was achieved. The highest H{sub 2} production rate was 5000 μmol g{sup −1} h{sup −1} with 5 mg Erythrosin B in photoreaction system. Erythrosin B dye sensitized Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} presented stable photocatalytic H{sub 2} evolution ability and no noticeable degradation or change of photocatalyst were detected after six recycles. A possible photocatalytic mechanism of Erythrosin B dye sensitized Cu-Cu{sub 2}O/g-C{sub 3}N{sub 4} for the enhancement of photocatalytic H{sub 2} evolution is proposed.

Vectorial electron transfer for improved hydrogen evolution by mercaptopropionic-acid-regulated CdSe quantum-dots-TiO2 -Ni(OH)2 assembly.

Science.gov (United States)

Yu, Shan; Li, Zhi-Jun; Fan, Xiang-Bing; Li, Jia-Xin; Zhan, Fei; Li, Xu-Bing; Tao, Ye; Tung, Chen-Ho; Wu, Li-Zhu

2015-02-01

A visible-light-induced hydrogen evolution system based on a CdSe quantum dots (QDs)-TiO2 -Ni(OH)2 ternary assembly has been constructed under an ambient environment, and a bifunctional molecular linker, mercaptopropionic acid, is used to facilitate the interaction between CdSe QDs and TiO2 . This hydrogen evolution system works effectively in a basic aqueous solution (pH 11.0) to achieve a hydrogen evolution rate of 10.1 mmol g(-1)  h(-1) for the assembly and a turnover frequency of 5140 h(-1) with respect to CdSe QDs (10 h); the latter is comparable with the highest value reported for QD systems in an acidic environment. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and control experiments demonstrate that Ni(OH)2 is an efficient hydrogen evolution catalyst. In addition, inductively coupled plasma optical emission spectroscopy and the emission decay of the assembly combined with the hydrogen evolution experiments show that TiO2 functions mainly as the electron mediator; the vectorial electron transfer from CdSe QDs to TiO2 and then from TiO2 to Ni(OH)2 enhances the efficiency for hydrogen evolution. The assembly comprises light antenna CdSe QDs, electron mediator TiO2 , and catalytic Ni(OH)2 , which mimics the strategy of photosynthesis exploited in nature and takes us a step further towards artificial photosynthesis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Constructing 2D layered MoS2 nanosheets-modified Z-scheme TiO2/WO3 nanofibers ternary nanojunction with enhanced photocatalytic activity

Science.gov (United States)

Zhao, Jiangtao; Zhang, Peng; Fan, Jiajie; Hu, Junhua; Shao, Guosheng

2018-02-01

Advanced materials for photoelectrochemical H2 production are important to the field of renewable energy. Despite great efforts have been made, the present challenge in materials science is to explore highly active photocatalysts for splitting of water at low cost. In this work, we report a new composite material consisting of 2D layered MoS2 nanosheets grown on the presence of TiO2/WO3 nanofibers (TW) as a high-performance photocatalyst for H2 evolution. This composite material was prepared by a two-step simple process of electrospinning and hydrothermal. We found that the as-prepared TiO2/WO3@MoS2 (TWM) hybrid exhibited superior photocatalytic activity in the hydrogen evolution reaction (HER) even without the noble metal-cocatalyst. Importantly, the TiO2/WO3@MoS2 heterostructure with 60 wt% of MoS2 exhibits the highest hydrogen production rate. This great improvement is attributed to the positive synergetic effect between the WO3 and MoS2 components in this hybrid cocatalyst, which serve as hole collector and electron collector, respectively. Moreover, the effective charge separation was directly proved by ultraviolet photoelectron spectroscopy, electrochemical impedance spectroscopy, and photocurrent analysis.

High-performance for hydrogen evolution and pollutant degradation of reduced graphene oxide/two-phase g-C3N4 heterojunction photocatalysts.

Science.gov (United States)

Song, Chengjie; Fan, Mingshan; Shi, Weidong; Wang, Wei

2018-05-01

We have successfully synthesized the composites of two-phase g-C 3 N 4 heterojunction photocatalysts by one-step method. And the reduced graphene oxide/two-phase g-C 3 N 4 heterojunction photocatalyst was fabricated via a facile hydrothermal reduction method. The characterization results indicated that the two-phase g-C 3 N 4 was integrated closely, and the common phenomenon of agglomeration for g-C 3 N 4 was significantly reduced. Moreover, the oxidized graphene was reduced successfully in the composites and the graphene was overlaid on the surface or the interlayers of g-C 3 N 4 heterojunction composite uniformly. In addition, we have carried out the photocatalytic activity experiments by H 2 evolution and rhodamine B removal, tetracycline removal under the visible light irradiation. The results revealed that the composite has improved the separation efficiency a lot than the pure photocatalyst. The photocurrent test demonstrated that the recombination of electrons and holes were efficiently inhibited as well as enhanced the photocatalytic activity. The 0.4% rGO loaded samples, 0.4% rGOCN2, own the best performance. Its rate of H 2 evolution was 15 times as high as that of the pure g-C 3 N 4 .

Surface Functionalization of g-C 3 N 4 : Molecular-Level Design of Noble-Metal-Free Hydrogen Evolution Photocatalysts

KAUST Repository

Chen, Yin

2015-06-12

A stable noble-metal-free hydrogen evolution photocatalyst based on graphite carbon nitride (g-C3N4) was developed by a molecular-level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site onto the surface of the semiconducting g-C3N4. This catalyst family (with less than 0.1 wt% of Ni) has been found to produce hydrogen with a rate near to the value obtained by using 3 wt% platinum as co-catalyst. This new catalyst also exhibits very good stability under hydrogen evolution conditions, without any evidence of deactivation after 24h. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photosynthesis of hydrogen and methane as key components for clean energy system

Directory of Open Access Journals (Sweden)

Seng Sing Tan et al

2007-01-01

Full Text Available While researchers are trying to solve the world's energy woes, hydrogen is becoming the key component in sustainable energy systems. Hydrogen could be produced through photocatalytic water-splitting technology. It has also been found that hydrogen and methane could be produced through photocatalytic reduction of carbon dioxide with water. In this exploratory study, instead of coating catalysts on a substrate, pellet form of catalyst, which has better adsorption capacity, was used in the photo-reduction of carbon dioxide with water. In the experiment, some water was first absorbed into titanium dioxide pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing these wet pellets, which were then illuminated continuously using UVC lamps. Gaseous samples accumulated in the reactor were extracted at different intervals to analyze the product yields. The results confirmed that methane and hydrogen were photosynthesized using pellet form of TiO2 catalysts. Hydrogen was formed at a rate as high as 0.16 micromoles per hour (μmol h−1. The maximum formation rate of CH4 was achieved at 0.25 μmol h−1 after 24 h of irradiation. CO was also detected.

Fabrication of modified g-C3N4 nanorod/Ag3PO4 nanocomposites for solar-driven photocatalytic oxygen evolution from water splitting

Science.gov (United States)

Tian, Lin; Xian, Xiaozhai; Cui, Xingkai; Tang, Hua; Yang, Xiaofei

2018-02-01

Semiconductor-based photocatalysis has been considered as one of the most effective techniques to achieve the conversion of clean and sustainable sunlight to solar fuel, in which the construction of novel solar-driven photocatalytic systems is the key point. Here, we report initially the synthesis of modified graphitic carbon nitride (g-C3N4) nanorods via the calcination of intermediates obtained from the co-polymerization of precursors, and the in-situ hybridization of Ag3PO4 with as-prepared modified g-C3N4 to produce g-C3N4 nanorod/Ag3PO4 composite materials. The diameter of modified rod-like g-C3N4 materials is determined to be around 1 μm. Subsequently the morphological features, crystal and chemical structures of the assembled g-C3N4 nanorod/Ag3PO4 composites were systematically investigated by SEM, XRD, XPS, UV-vis diffuse reflectance spectra (DRS). Furthermore, the use of as-prepared composite materials as the catalyst for photocatalytic oxygen evolution from water splitting was studied. The oxygen-generating results showed that the composite photocatalyst modified with 600 mg rod-like g-C3N4 demonstrates 2.5 times higher efficiency than that of bulk Ag3PO4. The mechanism behind the enhancement in the oxygen-evolving activity is proposed on the basis of in-situ electron spin resonance (ESR) measurement as well as theoretical analysis. The study provides new insights into the design and development of new photocatalytic composite materials for energy and environmental applications.

Hydrogen Evolution on Supported Incomplete Cubane-type [Mo3S4](4+) Electrocatalysts

DEFF Research Database (Denmark)

Jaramillo, Thomas; Bonde, Jacob Lindner; Zhang, Jingdong

2008-01-01

Electrocatalytic properties of biomimetic supported incomplete cubane-type [Mo3S4](4+) clusters are investigated. The activity toward the hydrogen evolution reaction (HER) is evaluated on both a high surface area gas diffusion electrode in a membrane electrode assembly and on highly orientated...

Room temperature synthesis of heptazine-based microporous polymer networks as photocatalysts for hydrogen evolution.

Science.gov (United States)

Kailasam, Kamalakannan; Schmidt, Johannes; Bildirir, Hakan; Zhang, Guigang; Blechert, Siegfried; Wang, Xinchen; Thomas, Arne

2013-06-25

Two emerging material classes are combined in this work, namely polymeric carbon nitrides and microporous polymer networks. The former, polymeric carbon nitrides, are composed of amine-bridged heptazine moieties and showed interesting performance as a metal-free photocatalyst. These materials have, however, to be prepared at high temperatures, making control of their chemical structure difficult. The latter, microporous polymer networks have received increasing interest due to their high surface area, giving rise to interesting applications in gas storage or catalysis. Here, the central building block of carbon nitrides, a functionalized heptazine as monomer, and tecton are used to create microporous polymer networks. The resulting heptazine-based microporous polymers show high porosity, while their chemical structure resembles the ones of carbon nitrides. The polymers show activity for the photocatalytic production of hydrogen from water, even under visible light illumination. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Produksi Hidrogen Secara Fotokalitik dari Air Murni Pada Katalis NaTaO3

Directory of Open Access Journals (Sweden)

Husni Husin

2012-12-01

Full Text Available Study of hydrogen production as a green energy on NaTaO3 photocatalyst has been done. The aim of this work is to study the photocatalytic properties of NaTaO3 and NiO incorporated NaTaO3 used in water splitting reaction. The NaTaO3 powder with high crystallinity has been synthesized by a H2O2-asissted sol-gel route calcined at a temperature of 900 oC. NiO as a cocatalyst is deposited by impregnation of Ni(NO32.6H2O solution. The catalysts are characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, high resolution transmission electron microscopy (HRTEM, and diffuse reflectance UV-Vis (DR-UV-Vis. The photocatalysts have a band gap energy ca. 4.01 and 4.00 eV (corresponding to absorption edge of 310 and 311 nm. Photocatalytic activity towards hydrogen generation from water is investigated using a glass reactor under ultra violet (UV light illumination. Photocatalytic of H2 and O2 production on the pristine NaTaO3 are 0.61 and 0.30 mmol g-1 cat.h-1, respectively. The activities are greatly enhanced 8.5 times higher by the incorporation of NiO as cocatalysts on the prepared oxides. NiO is found to give rise to more efficient photocatalytic activity for hydrogen evolution. The NaTaO3 nanoparticles produces using this facile have: better crystallinity, smaller size, and higher photocatalytic activity. Keywords: Sodium tantalum oxide; Nickel oxide; Sol-gel; impregnation; Hydrogen evolution

Photocatalytic/Magnetic Composite Particles

Science.gov (United States)

Wu, Chang-Yu; Goswami, Yogi; Garretson, Charles; Andino, Jean; Mazyck, David

2007-01-01

Photocatalytic/magnetic composite particles have been invented as improved means of exploiting established methods of photocatalysis for removal of chemical and biological pollutants from air and water. The photocatalytic components of the composite particles are formulated for high levels of photocatalytic activity, while the magnetic components make it possible to control the movements of the particles through the application of magnetic fields. The combination of photocatalytic and magnetic properties can be exploited in designing improved air- and water treatment reactors.

Status and perspectives of CO2 conversion into fuels and chemicals by catalytic, photocatalytic and electrocatalytic processes

NARCIS (Netherlands)

Kondratenko, E.V.; Mul, Guido; Baltrusaitis, Jonas; Larrazábal, G.O.; Pérez-Ramírez, J.

2013-01-01

This review highlights recent developments and future perspectives in carbon dioxide usage for the sustainable production of energy and chemicals and to reduce global warming. We discuss the heterogeneously catalysed hydrogenation, as well as the photocatalytic and electrocatalytic conversion of CO2

Improved activity of SnO for the photocatalytic oxygen evolution

Directory of Open Access Journals (Sweden)

S. Kaizra

2018-01-01

Full Text Available SnO prepared by soft chemistry exhibits a black color and semiconducting properties. The X-ray diffraction indicates a tetragonal symmetry (SG: P4/nmm with nano crystallites of an average size of 85 nm. The forbidden band, determined from the diffuse reflectance is found to be 1.46 eV. The electrical conductivity occurs by polaron hopping and follows an Arrhenius type law with activation energy of 0.21 eV, the change in the slope at 526 K is attributed to the oxidation to SnO2. The photo-electrochemical study shows n type conduction with a flat band potential of −0.45 V, close to the photocurrent onset potential (−0.40 V. The electrochemical impedance spectroscopy shows the bulk contribution of SnO (Rb = 1.7 kΩ cm2 and decreases down to 1.89 kΩ cm2 under illumination. The photocatalytic properties have been evaluated for the first time for to the oxygen evolution. The valence band, deriving from Sn2+: 5p orbital with a potential (−0.80 VSCE/5.55 eV, is suitably positioned with respect to O2/H2O level (∼0.6 VSCE, leading to water oxidation under visible light. The best performance occurs at pH ∼ 7 with an oxygen liberation rate of 23 µmol mL h−1 (mg catalyst−1 and a quantum efficiency of 1.2%. An improvement of ∼13% is observed on the system SnO/clay.

In situ one-pot fabrication of g-C3N4 nanosheets/NiS cocatalyst heterojunction with intimate interfaces for efficient visible light photocatalytic H2 generation

Science.gov (United States)

He, Kelin; Xie, Jun; Li, Mingli; Li, Xin

2018-02-01

Constructing high-quality earth-abundant semionconductor/cocatalyst heterojunction remains a grand challenge in the promising fields of photocatalytic solar fuel H2 production. Herein, an intimate g-C3N4 nanosheet/NiS cocatalyst heterojunction is fabricated by in situ one-step calcination of urea, thiourea and nickel acetate. Interestingly, thiourea could act as both the precursor of g-C3N4 and the sulfur source of NiS. The H2-evolution activity of as-obtained photocatalysts was tested in a triethanolamine (TEOA) scavenger solution under visible light irradiation. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) mapping analysis clearly demonstrated that the NiS catalyst nanoparticles could be in situ fabricated and homogeneously distributed on the surface of g-C3N4 nanosheets without an obvious aggregation. The maximum H2-production rate of 29.68 μmol h-1 could be achieved, which is nearly comparable to that of 0.5 wt% Pt loaded sample. It is believed that the intimate heterojunction interfaces between NiS nanoparticles and g-C3N4 nanosheets could be in situ constructed by high temperature calcination, which achieved the improved charge separation, the enhanced oxidation ability of TEOA and the accelerated the sluggish H2-evolution kinetics, thus resulting in the remarkably enhanced hydrogen evolution. Therefore, our study provides insights into constructing high-quality robust g-C3N4-based heterojunction material for photocatalytic applications by using a simple one-step in-situ calcination technique.

Cuboid Ni2 P as a Bifunctional Catalyst for Efficient Hydrogen Generation from Hydrolysis of Ammonia Borane and Electrocatalytic Hydrogen Evolution.

Science.gov (United States)

Du, Yeshuang; Liu, Chao; Cheng, Gongzhen; Luo, Wei

2017-11-16

The design of high-performance catalysts for hydrogen generation is highly desirable for the upcoming hydrogen economy. Herein, we report the colloidal synthesis of nanocuboid Ni 2 P by the thermal decomposition of nickel chloride hexahydrate (NiCl 2 ⋅6 H 2 O) and trioctylphosphine. The obtained nanocuboid Ni 2 P was characterized by using powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. For the first time, the as-synthesized nanocuboid Ni 2 P is used as a bifunctional catalyst for hydrogen generation from the hydrolysis of ammonia borane and electrocatalytic hydrogen evolution. Owing to the strong synergistic electronic effect between Ni and P, the as-synthesized Ni 2 P exhibits catalytic performance that is superior to its counterpart without P doping. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst

KAUST Repository

Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Jaroniec, Mietek; Qiao, Shi Zhang

2016-01-01

Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst.

Science.gov (United States)

Zheng, Yao; Jiao, Yan; Zhu, Yihan; Li, Lu Hua; Han, Yu; Chen, Ying; Jaroniec, Mietek; Qiao, Shi-Zhang

2016-12-14

Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst

KAUST Repository

Zheng, Yao

2016-11-28

Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

Controlled Defects of Zinc Oxide Nanorods for Efficient Visible Light Photocatalytic Degradation of Phenol

Directory of Open Access Journals (Sweden)

Jamal Al-Sabahi

2016-03-01

Full Text Available Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region.

Formation of a p-n heterojunction on GaP photocathodes for H-2 production providing an open-circuit voltage of 710 mV

DEFF Research Database (Denmark)

Malizia, Mauro; Seger, Brian; Chorkendorff, Ib

2014-01-01

Photocatalytic water splitting for the sustainable production of hydrogen using a two-photon tandem device requires careful optimization of the semiconductors used as photon absorbers. In this work we show how the open-circuit voltage of photocathodes for the hydrogen evolution reaction based on ...

Photocatalytic H{sub 2} production from water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled Pt/TiO{sub 2} nanocrystal photocatalyst

Energy Technology Data Exchange (ETDEWEB)

Sreethawong, Thammanoon; Chavadej, Sumaeth [The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemicals, and Advanced Materials, Chulalongkorn University, Bangkok 10330 (Thailand); Junbua, Chompoonuch [The Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10330 (Thailand)

2009-05-15

Sensitized photocatalytic production of hydrogen from water splitting is investigated under visible light irradiation over mesoporous-assembled titanium dioxide (TiO{sub 2}) nanocrystal photocatalysts, without and with Pt loading. The photocatalysts are synthesized by a sol-gel process with the aid of a structure-directing surfactant and are characterized by N{sub 2} adsorption-desorption analysis, X-ray diffraction, UV-vis spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray analysis. The dependence of hydrogen production on the type of TiO{sub 2} photocatalyst (synthesized mesoporous-assembled and commercial non-mesoporous-assembled TiO{sub 2} without and with Pt loading), the calcination temperature of the synthesized photocatalyst, the sensitizer (Eosin Y) concentration, the electron donor (diethanolamine) concentration, the photocatalyst dosage and the initial solution pH is systematically studied. The results show that in the presence of the Eosin Y sensitizer, the Pt-loaded mesoporous-assembled TiO{sub 2} synthesized by a single-step sol-gel process and calcined at 500 C exhibits the highest photocatalytic activity for hydrogen production from a 30 vol.% diethanolamine aqueous solution with dissolved 2 mM Eosin Y. Moreover, the optimum photocatalyst dosage and initial solution pH for the maximum photocatalytic activity for hydrogen production are 3.33 g dm{sup -3} and 11.5, respectively. (author)

Facet Engineered Interface Design of Plasmonic Metal and Cocatalyst on BiOCl Nanoplates for Enhanced Visible Photocatalytic Oxygen Evolution.

Science.gov (United States)

Bai, Lijie; Ye, Fan; Li, Luna; Lu, Jingjing; Zhong, Shuxian; Bai, Song

2017-10-01

Integration of plasmonic metal and cocatalyst with semiconductor is a promising approach to simultaneously optimize the generation, transfer, and consumption of photoinduced charge carriers for high-performance photocatalysis. The photocatalytic activities of the designed hybrid structures are greatly determined by the efficiencies of charge transfer across the interfaces between different components. In this paper, interface design of Ag-BiOCl-PdO x hybrid photocatalysts is demonstrated based on the choice of suitable BiOCl facets in depositing plasmonic Ag and PdO x cocatalyst, respectively. It is found that the selective deposition of Ag and PdO x on BiOCl(110) planes realizes the superior photocatalytic activity in O 2 evolution compared with the samples with other Ag and PdO x deposition locations. The reason was the superior hole transfer abilities of Ag-(110)BiOCl and BiOCl(110)-PdO x interfaces in comparison with those of Ag-(001)BiOCl and BiOCl(001)-PdO x interfaces. Two effects are proposed to contribute to this enhancement: (1) stronger electronic coupling at the BiOCl(110)-based interfaces resulted from the thinner contact barrier layer and (2) the shortest average hole diffuse distance realized by Ag and PdO x on BiOCl(110) planes. This work represents a step toward the interface design of high-performance photocatalyst through facet engineering. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In Situ Fluorine Doping of TiO2 Superstructures for Efficient Visible-Light Driven Hydrogen Generation.

Science.gov (United States)

Zhang, Peng; Tachikawa, Takashi; Fujitsuka, Mamoru; Majima, Tetsuro

2016-03-21

With the aid of breakthroughs in nanoscience and nanotechnology, it is imperative to develop metal oxide semiconductors through visible light-driven hydrogen generation. In this study, TiOF2 was incorporated as an n-type F-dopant source to TiO2 mesocrystals (TMCs) with visible-light absorption during the topotactic transformation. The crystal growth, structural change, and dynamic morphological evolution, from the initial intermediate NH4 TiOF3 to HTiOF3, TiOF2, and F-doped TMCs, were verified through in situ temperature-dependent techniques to elucidate the doping mechanism from intermediate TiOF2. The visible-light efficiencies of photocatalytic hydrogen were dependent on the contents of the dopant as compared with the pure TMC and a controled reference. Using femtosecond time-resolved diffuse reflectance spectroscopy, the charge-transfer dynamics were monitored to confirm the improvement of charge separation after doping. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A high-porosity carbon molybdenum sulphide composite with enhanced electrochemical hydrogen evolution and stability

DEFF Research Database (Denmark)

Laursen, Anders B.; Vesborg, Peter C. K.; Chorkendorff, Ib

2013-01-01

This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show...

Photocatalytic properties and selective antimicrobial activity of TiO2(Eu)/CuO nanocomposite

International Nuclear Information System (INIS)

Michal, Robert; Dworniczek, Ewa; Caplovicova, Maria; Monfort, Olivier; Lianos, Panagiotis; Caplovic, Lubomir; Plesch, Gustav

2016-01-01

Highlights: • Nanocomposites composed of Eu-doped anatase grafted with CuO. • Increase in photocatalytic hydrogen production due to CuO acting as electrons sink. • CuO in composites decreasing the photoinduced total mineralization of phenol. • Selective photoinduced antimicrobial activity against Enterococcus species. - Abstract: TiO 2 (Eu)/CuO nanocomposites were prepared by precipitation method. The anatase nanocrystallites with a size of 26 nm exhibited well crystallized and characteristical dipyramidal morphology and {1 0 1} and {0 0 1} faceting. Transmission electron microscopy photographs with atomic resolution showed that the Eu(III) dopants were bounded on surface of titania. In the composites, the CuO nanocrystals exhibiting a monoclinic tenorite structure with a size in the range from 2 to 5 nm were grafted to the surface of titania. The influence of copper(II) oxide led to distinct selectivity in the photocatalytic and antimicrobial properties of the investigated TiO 2 (Eu)/CuO nanocomposites. While the presence of CuO nanocrystals strongly increased the photocatalytic production of hydrogen by ethanol reforming, it decreased the activity in photoinduced total mineralization of phenol comparing with non-modified TiO 2 (Eu). In investigated TiO 2 (Eu)/CuO powders, the photoinduced antimicrobial activity against membranes of Enterococcus species was influenced by the selective binding of CuO to the surface of the microorganism leading to distinct selectivity in their action. The activity against Enterococcus faecalis was higher than against Enterococcus faecium.

A Au/Cu2O-TiO2 system for photo-catalytic hydrogen production. A pn-junction effect or a simple case of in situ reduction?

KAUST Repository

Sinatra, Lutfan

2015-02-01

Photo-catalytic H2 production from water has been studied over Au-Cu2O nanoparticle deposited on TiO2 (anatase) in order to probe into both the plasmon resonance effect (Au nanoparticles) and the pn-junction at the Cu2O-TiO2 interface. The Au-Cu2O composite is in the form of ∼10 nm Au nanoparticles grown on ∼475 nm Cu2O octahedral nanocrystals with (111) facets by partial galvanic replacement. X-ray Photoelectron Spectroscopy (XPS) Cu2p and Auger L3M4,5M4,5 lines indicate that the surface of Cu2O is mainly composed of Cu+. The rate for H2 production (from 95 water/5 ethylene glycol; vol.%) over 2 wt.% (Au/Cu2O)-TiO2 is found to be ∼10 times faster than that on 2 wt.% Au-TiO2 alone. Raman spectroscopy before and after reaction showed the disappearance of Cu+ lines (2Eu) at 220 cm-1. These observations coupled with the induction time observed for the reaction rate suggest that in situ reduction from Cu+ to Cu0 occurs upon photo-excitation. The reduction requires the presence of TiO2 (electron transfer). The prolonged activity of the reaction (with no signs of deactivation) despite the reduction to Cu0 indicates that the latter takes part in the reaction by providing additional sites for the reaction, most likely as recombination centers for hydrogen atoms to form molecular hydrogen. This phenomenon provides an additional route for enhancing the efficiency and lifetime of Cu2O-TiO2 photocatalytic systems, beyond the usually ascribed pn-junction effect.

Active Edge Sites Engineering in Nickel Cobalt Selenide Solid Solutions for Highly Efficient Hydrogen Evolution

KAUST Repository

Xia, Chuan

2017-01-06

An effective multifaceted strategy is demonstrated to increase active edge site concentration in NiCoSe solid solutions prepared by in situ selenization process of nickel cobalt precursor. The simultaneous control of surface, phase, and morphology result in as-prepared ternary solid solution with extremely high electrochemically active surface area (C = 197 mF cm), suggesting significant exposure of active sites in this ternary compound. Coupled with metallic-like electrical conductivity and lower free energy for atomic hydrogen adsorption in NiCoSe, identified by temperature-dependent conductivities and density functional theory calculations, the authors have achieved unprecedented fast hydrogen evolution kinetics, approaching that of Pt. Specifically, the NiCoSe solid solutions show a low overpotential of 65 mV at -10 mV cm, with onset potential of mere 18 mV, an impressive small Tafel slope of 35 mV dec, and a large exchange current density of 184 μA cm in acidic electrolyte. Further, it is shown that the as-prepared NiCoSe solid solution not only works very well in acidic electrolyte but also delivers exceptional hydrogen evolution reaction (HER) performance in alkaline media. The outstanding HER performance makes this solid solution a promising candidate for mass hydrogen production.

Non-thermal plasma-induced photocatalytic degradation of 4-chlorophenol in water.

Science.gov (United States)

Hao, Xiao Long; Zhou, Ming Hua; Lei, Le Cheng

2007-03-22

TiO(2) photocatalyst (P-25) (50mgL(-1)) was tentatively introduced into pulsed high-voltage discharge process for non-thermal plasma-induced photocatalytic degradation of the representative mode organic pollutant parachlorophenol (4-CP), including other compounds phenol and methyl red in water. The experimental results showed that rate constant of 4-CP degradation, energy efficiency for 4-CP removal and TOC removal with TiO(2) were obviously increased. Pulsed high-voltage discharge process with TiO(2) had a promoted effect for the degradation of these pollutants under a broad range of liquid conductivity. Furthermore, the apparent formation rates of chemically active species (e.g., ozone and hydrogen peroxide) were increased, the hydrogen peroxide formation rate from 1.10x10(-6) to 1.50x10(-6)Ms(-1), the ozone formation rate from 1.99x10(-8) to 2.35x10(-8)Ms(-1), respectively. In addition, this process had no influence on the photocatalytic properties of TiO(2). The introduction of TiO(2) photocatalyst into pulsed discharge plasma process in the utilizing of ultraviolet radiation and electric field in pulsed discharge plasma process enhanced the yields of chemically active species, which were available for highly efficient removal and mineralization of organic pollutants.

Non-thermal plasma-induced photocatalytic degradation of 4-chlorophenol in water

International Nuclear Information System (INIS)

Hao Xiaolong; Zhou Ming Hua; Lei Lecheng

2007-01-01

TiO 2 photocatalyst (P-25) (50 mg L -1 ) was tentatively introduced into pulsed high-voltage discharge process for non-thermal plasma-induced photocatalytic degradation of the representative mode organic pollutant parachlorophenol (4-CP), including other compounds phenol and methyl red in water. The experimental results showed that rate constant of 4-CP degradation, energy efficiency for 4-CP removal and TOC removal with TiO 2 were obviously increased. Pulsed high-voltage discharge process with TiO 2 had a promoted effect for the degradation of these pollutants under a broad range of liquid conductivity. Furthermore, the apparent formation rates of chemically active species (e.g., ozone and hydrogen peroxide) were increased, the hydrogen peroxide formation rate from 1.10 x 10 -6 to 1.50 x 10 -6 M s -1 , the ozone formation rate from 1.99 x 10 -8 to 2.35 x 10 -8 M s -1 , respectively. In addition, this process had no influence on the photocatalytic properties of TiO 2 . The introduction of TiO 2 photocatalyst into pulsed discharge plasma process in the utilizing of ultraviolet radiation and electric field in pulsed discharge plasma process enhanced the yields of chemically active species, which were available for highly efficient removal and mineralization of organic pollutants

Synthesis and visible-light-driven photocatalytic activity of p-n heterojunction Ag2O/NaTaO3 nanocubes

Science.gov (United States)

Yang, Songbo; Xu, Dongbo; Chen, Biyi; Luo, Bifu; Yan, Xu; Xiao, Lisong; Shi, Weidong

2016-10-01

The constructing of p-n heterojunction photocatalytic system has received much attention in environmental purification and hydrogen generation from water. In this study, an efficient visible-light-driven p-n heterojunction Ag2O/NaTaO3 was successfully prepared by chemical precipitation method at room temperature. It showed an enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation, much higher than those of either individual Ag2O or NaTaO3. The reactive species scavenger results indicated the superoxide anion radicals (rad O2-) played key roles in RhB decoloration. From the experimental results and the relative band gap position of these semiconductors, a detailed possible photocatalytic mechanism of the Ag2O/NaTaO3 heterojunction under visible light was proposed. The enhancement of the photocatalytic activity was attributed to the interfacial electronic interaction between NaTaO3 and Ag2O and the high migration efficiency of photogenerated carriers.

Facile one-step hydrothermal synthesis toward strongly coupled TiO2/graphene quantum dots photocatalysts for efficient hydrogen evolution

International Nuclear Information System (INIS)

Min, Shixiong; Hou, Jianhua; Lei, Yonggang; Ma, Xiaohua; Lu, Gongxuan

2017-01-01

Highlights: • TiO 2 /GQDs composites were prepared by a facile one-step hydrothermal method. • GQDs were strongly coupled onto the surface of TiO 2 nanoparticles by this method. • The TiO 2 /GQDs showed enhanced light absorption and charge separation efficiency. • The TiO 2 /GQDs exhibited higher photocatalytic H 2 evolution activity than pure TiO 2 . • GQDs play synergistic roles by acting as both photosensitizer and electron acceptor. - Abstract: The coupling of semiconductor photocatalysts with graphene quantum dots (GQDs) has been proven to be an effective strategy to enhance the photocatalytic and photoelectrical conversion performances of the resulted composites; however, the preparation of semiconductor/GQDs composites usually involves several time-inefficient and tedious post-treatment steps. Herein, we present a facile one-step hydrothermal route for the preparation of GQDs coupled TiO 2 (TiO 2 /GQDs) photocatalysts using 1,3,6-trinitropyrene (TNP) as the sole precursor of GQDs. During the hydrothermal process, TNP molecules undergo an intramolecular fusion to form GQDs, which simultaneously decorate on the surface of TiO 2 nanoparticles, leading to a strong surface interaction between the two components. The effective coupling of GQDs on TiO 2 can effectively extend the light absorption of the TiO 2 to visible region and enhance the charge separation efficiency of TiO 2 /GQDs composites as a result of GQDs acting as a photosensitizer and an excellent electron acceptor. These key advances make the TiO 2 /GQDs photocatalyst highly active towards the H 2 evolution reaction, resulting in 7 and 3 times higher H 2 evolution rate and photocurrent response at optimal GQDs content than TiO 2 alone, respectively. This study provides a new methodology for the development of high-performance GQDs modified semiconductor photocatalysts for energy conversion applications.

High Electrocatalytic Response of a Mechanically Enhanced NbC Nanocomposite Electrode Towards Hydrogen Evolution Reaction

KAUST Repository

Coy, Emerson; Yate, Luis; Valencia, Drochss P; Aperador, Willian; Siuzdak, Katarzyna; Torruella, Pau; Azanza, Eduardo; Estrade, Sonia; Iatsunskyi, Igor; Peiró , Francesca; Zhang, Xixiang; Tejada, Javier; Ziolo, Ronald F.

2017-01-01

Resistant and efficient electrocatalysts for hydrogen evolution reaction (HER) are desired to replace scarce and commercially expensive platinum electrodes. Thin film electrodes of metal-carbides are a promising alternative due to their reduced

Hydrogen evolution reaction at Ru-modified nickel-coated carbon fibre in 0.1 M NaOH

Directory of Open Access Journals (Sweden)

Pierożyński Bogusław

2015-03-01

Full Text Available The electrochemical activity towards hydrogen evolution reaction (HER was studied on commercially available (Toho-Tenax and Ru-modified nickel-coated carbon fibre (NiCCF materials. Quality and extent of Ru electrodeposition on NiCCF tows were examined by means of scanning electron microscopy (SEM. Kinetics of the hydrogen evolution reaction were investigated at room temperature, as well as over the temperature range: 20-50°C in 0.1 M NaOH solution for the cathodic overpotential range: -100 to -300 mV vs. RHE. Corresponding values of charge-transfer resistance, exchange current-density for the HER and other electrochemical parameters for the examined fibre tow composites were recorded.

Electrochemical preparation and characteristics of Ni-Co-LaNi5 composite coatings as electrode materials for hydrogen evolution

International Nuclear Information System (INIS)

Wu Gang; Li Ning; Dai Changsong; Zhou Derui

2004-01-01

Electrocatalytic activity for the hydrogen evolution reaction on Ni-Co-LaNi 5 composite electrodes prepared by electrochemical codeposition technique was evaluated. The relationship between the current density for hydrogen evolution reaction and the amount of LaNi 5 particles in Ni-Co baths is like the well-known 'volcano plot'. The Surface morphology and microstructure of Ni-Co-LaNi 5 coatings were determined by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The kinetic parameters were determined from electrochemical steady-state Tafel polarization and electrochemical impedance spectroscopy technology in 1 M NaOH solution. The values obtained for the apparent energies of activation are 32.48, 46.29 and 57.03 kJ mol -1 for the Ni-Co-LaNi 5 , Ni-Co and Ni electrodes, respectively. The hydrogen evolution reaction on Ni-Co-LaNi 5 proceeds via Volmer-Tafel reaction route with the mixed rate determining characteristics. The composite coating Ni-Co-LaNi 5 is catalytically more active than Ni and Ni-Co electrodes due to the increase in its real surface areas and the decrease in the apparent free energy of activation caused by the electrocatalytic synergistic effect of the Ni-Co alloys and the hydrogen storage intermetallic particles on the electrode surface

Temperature dependent optical characterization of Ni-TiO2 thin films as potential photocatalytic material

Science.gov (United States)

De, Rajnarayan; Haque, S. Maidul; Tripathi, S.; Rao, K. Divakar; Singh, Ranveer; Som, T.; Sahoo, N. K.

2017-09-01

Along with other transition metal doped titanium dioxide materials, Ni-TiO2 is considered to be one of the most efficient materials for catalytic applications due to its suitable energy band positions in the electronic structure. The present manuscript explores the possibility of improving the photocatalytic activity of RF magnetron sputtered Ni-TiO2 films upon heat treatment. Optical, structural and morphological and photocatalytic properties of the films have been investigated in detail for as deposited and heat treated samples. Evolution of refractive index (RI) and total film thickness as estimated from spectroscopic ellipsometry characterization are found to be in agreement with the trend in density and total film thickness estimated from grazing incidence X-ray reflectivity measurement. Interestingly, the evolution of these macroscopic properties were found to be correlated with the corresponding microstructural modifications realized in terms of anatase to rutile phase transformation and appearance of a secondary phase namely NiTiO3 at high temperature. Corresponding morphological properties of the films were also found to be temperature dependent which leads to modifications in the grain structure. An appreciable reduction of optical band gap from 2.9 to 2.5 eV of Ni-TiO2 thin films was also observed as a result of post deposition heat treatment. Testing of photocatalytic activity of the films performed under UV illumination demonstrates heat treatment under atmospheric ambience to be an effective means to enhance the photocatalytic efficiency of transition metal doped titania samples.

Optical and Electrical Properties of Thin Films of CuS Nanodisks Ensembles Annealed in a Vacuum and Their Photocatalytic Activity

Directory of Open Access Journals (Sweden)

J. Santos Cruz

2013-01-01

Full Text Available Effects on the optical, electrical, and photocatalytic properties of undoped CuS thin films nanodisks vacuum annealed at different temperatures were investigated. The chemical bath prepared CuS thin films were obtained at 40°C on glass substrates. The grain size of 13.5±3.5 nm was computed directly from high-resolution transmission electron microscopy (HRTEM images. The electrical properties were measured by means of both Hall effect at room temperature and dark resistivity as a function of the absolute temperature 100–330 K. The activation energy values were calculated as 0.007, 0.013, and 0.013 eV for 100, 150, and 200°C, respectively. The energy band gap of the films varied in the range of 1.98 up to 2.34 eV. The photocatalytic activity of the CuS thin film was evaluated by employing the degradation of aqueous methylene blue solution in the presence of hydrogen peroxide. The CuS sample thin film annealed in vacuum at 150°C exhibited the highest photocatalytic activity in presence of hydrogen peroxide.

General Observation of Photocatalytic Oxygen Reduction to Hydrogen Peroxide by Organic Semiconductor Thin Films and Colloidal Crystals.

Science.gov (United States)

Gryszel, Maciej; Sytnyk, Mykhailo; Jakešová, Marie; Romanazzi, Giuseppe; Gabrielsson, Roger; Heiss, Wolfgang; Głowacki, Eric Daniel

2018-04-25

Low-cost semiconductor photocatalysts offer unique possibilities for industrial chemical transformations and energy conversion applications. We report that a range of organic semiconductors are capable of efficient photocatalytic oxygen reduction to H 2 O 2 in aqueous conditions. These semiconductors, in the form of thin films, support a 2-electron/2-proton redox cycle involving photoreduction of dissolved O 2 to H 2 O 2 , with the concurrent photooxidation of organic substrates: formate, oxalate, and phenol. Photochemical oxygen reduction is observed in a pH range from 2 to 12. In cases where valence band energy of the semiconductor is energetically high, autoxidation competes with oxidation of the donors, and thus turnover numbers are low. Materials with deeper valence band energies afford higher stability and also oxidation of H 2 O to O 2 . We found increased H 2 O 2 evolution rate for surfactant-stabilized nanoparticles versus planar thin films. These results evidence that photochemical O 2 reduction may be a widespread feature of organic semiconductors, and open potential avenues for organic semiconductors for catalytic applications.

Two-phase model of hydrogen transport to optimize nanoparticle catalyst loading for hydrogen evolution reaction

DEFF Research Database (Denmark)

Kemppainen, Erno; Halme, Janne; Hansen, Ole

2016-01-01

is the evolution and transport of gaseous H2, since HER leads to the continuous formation of H2 bubbles near the electrode. We present a numerical model that includes the transport of both gaseous and dissolved H2, as well as mass exchange between them, and combine it with a kinetic model of HER at platinum (Pt......) nanoparticle electrodes. We study the effect of the diffusion layer thickness and H2 dissolution rate constant on the importance of gaseous transport, and the effect of equilibrium hydrogen coverage and Pt loading on the kinetic and mass transport overpotentials. Gaseous transport becomes significant when...

Photocatalytic water splitting: Quantitative approaches toward photocatalysis by design

KAUST Repository

Takanabe, Kazuhiro

2017-10-11

A widely used term, “photocatalysis”, generally addresses photocatalytic (energetically down-hill) and photosynthetic (energetically up-hill) reactions and refers to the use of photonic energy as a driving force for chemical transformations, i.e., electron reorganization to form/break chemical bonds. Although there are many such important reactions, this contribution focuses on the fundamental aspects of photocatalytic water splitting into hydrogen and oxygen by using light from the solar spectrum, which is one of the most investigated photosynthetic reactions. Photocatalytic water splitting using solar energy is considered to be artificial photosynthesis that produces a solar fuel because the reaction mimics nature’s photosynthesis not only in its redox reaction type but also in its thermodynamics (water splitting: 1.23 eV vs. glucose formation: 1.24 eV). To achieve efficient photocatalytic water splitting, all of the parameters, though involved at different timescales and spatial resolutions, should be optimized because the overall efficiency is obtained as the multiplication of all these fundamental efficiencies. The purpose of this review article is to provide the guidelines of a concept, “photocatalysis by design”, which is the opposite of “black box screening”; this concept refers to making quantitative descriptions of the associated physical and chemical properties to determine which events/parameters have the most impact on improving the overall photocatalytic performance, in contrast to arbitrarily ranking different photocatalyst materials. First, the properties that can be quantitatively measured or calculated are identified. Second, the quantities of these identified properties are determined by performing adequate measurements and/or calculations. Third, the obtained values of these properties are integrated into equations so that the kinetic/energetic bottlenecks of specific properties/processes can be determined, and the properties can

Photocatalytic water splitting: Quantitative approaches toward photocatalysis by design

KAUST Repository

Takanabe, Kazuhiro

2017-01-01

A widely used term, “photocatalysis”, generally addresses photocatalytic (energetically down-hill) and photosynthetic (energetically up-hill) reactions and refers to the use of photonic energy as a driving force for chemical transformations, i.e., electron reorganization to form/break chemical bonds. Although there are many such important reactions, this contribution focuses on the fundamental aspects of photocatalytic water splitting into hydrogen and oxygen by using light from the solar spectrum, which is one of the most investigated photosynthetic reactions. Photocatalytic water splitting using solar energy is considered to be artificial photosynthesis that produces a solar fuel because the reaction mimics nature’s photosynthesis not only in its redox reaction type but also in its thermodynamics (water splitting: 1.23 eV vs. glucose formation: 1.24 eV). To achieve efficient photocatalytic water splitting, all of the parameters, though involved at different timescales and spatial resolutions, should be optimized because the overall efficiency is obtained as the multiplication of all these fundamental efficiencies. The purpose of this review article is to provide the guidelines of a concept, “photocatalysis by design”, which is the opposite of “black box screening”; this concept refers to making quantitative descriptions of the associated physical and chemical properties to determine which events/parameters have the most impact on improving the overall photocatalytic performance, in contrast to arbitrarily ranking different photocatalyst materials. First, the properties that can be quantitatively measured or calculated are identified. Second, the quantities of these identified properties are determined by performing adequate measurements and/or calculations. Third, the obtained values of these properties are integrated into equations so that the kinetic/energetic bottlenecks of specific properties/processes can be determined, and the properties can

Polyallylamine-Rh nanosheet nanoassemblies-carbon nanotubes organic-inorganic nanohybrids: A electrocatalyst superior to Pt for the hydrogen evolution reaction

Science.gov (United States)

Bai, Juan; Xing, Shi-Hui; Zhu, Ying-Ying; Jiang, Jia-Xing; Zeng, Jing-Hui; Chen, Yu

2018-05-01

Rationally tailoring the surface/interface structures of noble metal nanostructures emerges as a highly efficient method for improving their electrocatalytic activity, selectivity, and long-term stability. Recently, hydrogen evolution reaction is attracting more and more attention due to the energy crisis and environment pollution. Herein, we successfully synthesize polyallylamine-functionalized rhodium nanosheet nanoassemblies-carbon nanotube nanohybrids via a facile one-pot hydrothermal method. Three-dimensionally branched rhodium nanosheet nanoassemblies are consisted of two dimensionally atomically thick ultrathin rhodium nanosheets. The as-prepared polyallylamine-functionalized rhodium nanosheet nanoassemblies-carbon nanotube nanohybrids show the excellent electrocatalytic activity for the hydrogen evolution reaction in acidic media, with a low onset reduction potential of -1 mV, a small overpotential of 5 mV at 10 mA cm-2, which is much superior to commercial platinum nanocrystals. Two dimensionally ultrathin morphology of rhodium nanosheet, particular rhodium-polyallylamine interface, and three-dimensionally networks induced by carbon nanotube are the key factors for the excellent hydrogen evolution reaction activity in acidic media.

Non-noble metal Cu-loaded TiO2 for enhanced photocatalytic H2 production.

Science.gov (United States)

Foo, Wei Jian; Zhang, Chun; Ho, Ghim Wei

2013-01-21

Here we have demonstrated the preparation of high-quality, monodispersed and tunable phases of Cu nanoparticles. Structural and chemical composition studies depict the evolution of Cu-Cu(2)O-CuO nanoparticles at various process stages. The loading of Cu and Cu oxide nanoparticles on TiO(2) catalyst has enhanced the photocatalytic H(2) production. Comparatively, H(2) treatment produces well-dispersed Cu nanoparticles with thin oxide shells that show the highest H(2) production amongst the samples. The relatively higher photocatalytic performance is deemed to result from reduced structural defects, higher surface area and dispersivity as well as favorable charge transfer, which inhibits recombination. The Cu nanoparticles are shown to be a promising alternative to noble metal-loaded TiO(2) catalyst systems due to their low cost and high performance in photocatalytic applications.

Visible-light-induced hydrogen evolution reaction with WS x Se 2

Indian Academy of Sciences (India)

... of ternary sulphoselenides of tungsten (WS x Se 2 − x ) by the dye-sensitized hydrogen evolution.WSxSe2−x solidsolutions are found to exhibit high activity reaching 2339 μ mol h − 1 g − 1 for WSSe, which is three times higher than that of WS2 alone (866 μ mol h − 1 g − 1 ). The turnover frequency is also high (0.7 h − 1 ).

Multiwalled Carbon Nanotube-TiO2 Nanocomposite for Visible-Light-Induced Photocatalytic Hydrogen Evolution

Directory of Open Access Journals (Sweden)

Ke Dai

2014-01-01

Full Text Available Multiwalled carbon nanotube- (MWCNT- TiO2 nanocomposite was synthesized via hydrothermal process and characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, field emission scanning electron microscope, thermogravimetry analysis, and N2 adsorption-desorption isotherms. Appropriate pretreatment on MWCNTs could generate oxygen-containing groups, which is beneficial for forming intimate contact between MWCNTs and TiO2 and leads to a higher thermal stability of MWCNT-TiO2 nanocomposite. Modification with MWCNTs can extend the visible-light absorption of TiO2. 5 wt% MWCNT-TiO2 derived from hydrothermal treatment at 140°C exhibiting the highest hydrogen generation rate of 15.1 μmol·h−1 under visible-light irradiation and a wide photoresponse range from 350 to 475 nm with moderate quantum efficiency (4.4% at 420 nm and 3.7% at 475 nm. The above experimental results indicate that the MWCNT-TiO2 nanocomposite is a promising photocatalyst with good stability and visible-light-induced photoactivity.

Modifications for the improvement of catalyst materials for hydrogen evolution

Directory of Open Access Journals (Sweden)

DRAGAN SLAVKOV

2006-02-01

Full Text Available The structural and electrocatalytic characteristics of composite materials based on non-precious metals were studied. Precursors of metallic phase (Ni, Co or CoNi and oxide phase (TiO2 were grafted on a carbon substrate (Vulcan XC-72 by the sol-gel procedure and thermally treated at 250 ºC. Ni and CoNi crystals of 10–20 nm were produced, in contrast the Co and TiO2 were amorphous. The dissimilar electronic character of the components gives rise to a significant electrocatalytic activity for the hydrogen evolution reaction (HER, even in the basic series of prepared materials. Further improvement of the catalysts was achieved by modification of all three components. Hence, Mo was added into the metallic phase, TiO2 was converted into the crystalline form and multiwall carbon nanotubes (MWCNTs were used instead of carbon particles. The improvement, expressed in terms of the lowering the hydrogen evolution overpotential at 60 mA cm–2, was the most pronounced in the Ni-based systems grafted on MWCNTs (120 mV lower HER overpotential compared to 60 mV in case of Ni-based systems grafted on crystalline TiO2 (TiO2 prepared at 450 ºC and of Ni-based systems containing 25 at.% Mo. Nevertheless, even with the realized enhancement, of all the fested materials, the Co-based systems remained superior HER catalysts.

Improved photocatalytic activity of highly ordered TiO{sub 2} nanowire arrays for methylene blue degradation

Energy Technology Data Exchange (ETDEWEB)

Lv, Xiaojun, E-mail: xjlv@mail.ipc.ac.cn [Technical Institute of Physics and Chemistry, Key Laboratory of Photochemical Conversion and Optoelectronic Materials and HKU-CAS Joint Laboratory on New Materials, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Hao; Chang, Haixin [WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8578 (Japan)

2012-10-15

Although many efforts have been done on the photocatalytic properties of anodic TiO{sub 2} nanotubes, much less work is done on the photocatalytic performance of TiO{sub 2} nanowires. Self-organized anodic TiO{sub 2} nanowire arrays have been fabricated using a simple electrochemical approach and used as photocatalysts in photodegradation of methylene blue (MB) dyes. Here we found for the first time TiO{sub 2} nanowires have better photocatalytic properties and incident photon-to-current efficiency (IPCE) than TiO{sub 2} nanotubes. N doped TiO{sub 2} nanowires showed further enhancement in photodegradation activity and photocurrent response in the visible region. Such TiO{sub 2} nanowires are expected to have great potential in photodegradation of pollutants, photovoltaic solar energy conversion and water splitting for hydrogen generation as well. -- Highlights: Black-Right-Pointing-Pointer TiO{sub 2} nanowire arrays electrode fabricated via anodizing Ti foil. Black-Right-Pointing-Pointer TiO{sub 2} nanowire arrays have higher photodegradation activity. Black-Right-Pointing-Pointer N doped TiO{sub 2} nanowires enhanced visible-light photocatalytic activity.

Efficient photocatalytic hydrogen production from water over Pt-Eosin Y catalyst: A systemic study of reaction parameters

Science.gov (United States)

Wang, Li; Zhao, Hui; Chen, Yong; Sun, Ruimin; Han, Bing

2016-07-01

A high efficient homogeneous system for hydrogen production from water consisting of Eosin Y as a photosensitizer, methyl viologen (MV2+) as an electron transfer mediator, triethanolamine (TEOA) as a sacrificial electron donor and colloid Pt as a catalyst, has been systemicly studied. The initial system pH and the concentration of Eosin Y have remarkable effects on the rate of hydrogen evolution. The optimal pH and concentration of Eosin Y are 9 and 7.2×10-5 M. Triethanolamine (TEOA) as an electron donor, can reductively quench the oxidized Eosin Y and the quenching is well modeled by the Stern-Volmer equation. The optimal concentration of TEOA and the concentration of MV2+ are 0.3 M and 3.1×10-4 M, respectively. In addition, the role of colloid Pt has been investigated.

Widely available active sites on Ni2P for electrochemical hydrogen evolution - insights from first principles calculations

DEFF Research Database (Denmark)

Hansen, Martin Hangaard; Stern, Lucas-Alexandre; Feng, Ligang

2015-01-01

We present insights into the mechanism and the active site for hydrogen evolution on nickel phosphide (Ni2P). Ni2P was recently discovered to be a very active non-precious hydrogen evolution catalyst. Current literature attributes the activity of Ni2P to a particular site on the (0001) facet....... In the present study, using Density Functional Theory (DFT) calculations, we show that several widely available low index crystal facets on Ni2P have better properties for a high catalytic activity. DFT calculations were used to identify moderately bonding nickel bridge sites and nickel hollow sites for hydrogen...... adsorption and to calculate barriers for the Tafel pathway. The investigated surfaces in this study were the (10 (1) over bar0), ((1) over bar(1) over bar 20), (11 (2) over bar0), (11 (2) over bar1) and (0001) facets of the hexagonal Ni2P crystal. In addition to the DFT results, we present experiments on Ni2...

Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy.

Science.gov (United States)

Zheng, Jie; Sheng, Wenchao; Zhuang, Zhongbin; Xu, Bingjun; Yan, Yushan

2016-03-01

Understanding how pH affects the activity of hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is key to developing active, stable, and affordable HOR/HER catalysts for hydroxide exchange membrane fuel cells and electrolyzers. A common linear correlation between hydrogen binding energy (HBE) and pH is observed for four supported platinum-group metal catalysts (Pt/C, Ir/C, Pd/C, and Rh/C) over a broad pH range (0 to 13), suggesting that the pH dependence of HBE is metal-independent. A universal correlation between exchange current density and HBE is also observed on the four metals, indicating that they may share the same elementary steps and rate-determining steps and that the HBE is the dominant descriptor for HOR/HER activities. The onset potential of CO stripping on the four metals decreases with pH, indicating a stronger OH adsorption, which provides evidence against the promoting effect of adsorbed OH on HOR/HER.

Solvent-Induced Deposition of Cu-Ga-In-S Nanocrystals onto a Titanium Dioxide Surface for Visible-Light-Driven Photocatalytic Hydrogen Production

KAUST Repository

Kandiel, Tarek; Takanabe, Kazuhiro

2015-01-01

In this paper, copper-gallium-indium-sulfide (CGIS) nanocrystals with different Ga/In ratios, i.e., CuGaxIn5-xS8, where x = 0, 1, 2, 3, 4 and 5, were synthesized and investigated for visible-light-driven hydrogen (H2) evolution from aqueous

Synthesis, characterization of a new photosensitive compound [Ru(bpy)2 (TPAD)](PF6)2 and its application for photocatalytic hydrogen production

Science.gov (United States)

Zheng, Hui-Qin; Guo, Yi-Ping; Yin, Ming-Cai; Fan, Yao-Ting

2016-06-01

A new photosensitive compound based on triphenylamine donor and ruthenium(II), namely [Ru(bpy)2(TPAD)](PF6)2 (PS1, bpy = 2,2‧-bipyridine, TPAD = N-(4-(1H-imidazo[4,5-f][1,10] phenanthroline-2-yl)phenyl)-N-phenylbenzenamine), had been synthesized and characterized by elemental analysis, 1H NMR, MS spectra, UV, PL and CV measurements. The target photocatalyst, PS1/0.5 wt% Pt/TiO2, was prepared by sensitizing PS1 to 0.5 wt% Pt/TiO2 and characterized by SEM and XRD. The highest hydrogen evolution reached to 9500 μmol·(g·catalyst)-1 (475 μmol, 31.7 TON and TOF 5.8 vs. PS1) under the optimal conditions with 0.05 g·L-1 of PS1, and 5% of TEOA at pH 11 with the irradiation of 5.5 h. The mechanism of hydrogen evolution was also briefly discussed in the present work.

Correlation of electrical and physical properties of photoanode with hydrogen evolution in enzymatic photo-electrochemical cell

Energy Technology Data Exchange (ETDEWEB)

Bae, Sanghyun; Kang, Junwon [Department of Environmental Engineering, Yonsei University, 234 Maeji-ri, Hungub-myun, Wonju, Gangwon-do 220-710 (Korea); Shim, Eunjung [Department of Chemistry, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon 305-764 (Korea); Yoon, Jaekyung; Joo, Hyunku [Fossil Energy and Environment Research Department, Korea Institute of Energy Research, 71-2 Jang-dong, Yuseong-gu, Daejeon 305-343 (Korea)

2008-05-01

In this study, the electrical and physical properties, including the current density, open-circuit voltage, morphology and crystalline structure, of an anodized TiO{sub 2} electrode on a titanium foil are correlated with the hydrogen production rate in an enzymatic photo-electrochemical system. The effect of light intensity at ca. 74 and ca. 146 mW cm{sup -2} on the properties is also examined. Anodizing (20 V; bath temperature 5 C; anodizing time 45 min) and subsequent annealing (350-850 C for 5 h) of the Ti foils in an O{sub 2} atmosphere led to the formation of a tube-shaped, or a compact layered, TiO{sub 2} film on the Ti substrate depending on the annealing temperature. The annealing temperature has a similar effect on the properties of the sample and the hydrogen evolution rate. The generated electrical value, the chronoamperometry (CA), is +13 to -229 and +13 to -247 {mu}A for light intensities of ca. 74 and ca. 146 mW cm{sup -2}, while the corresponding open-circuit voltage (OCV) is in the range of -41 to -687 and -144 to 738 mV, respectively. In the absence of light (dark), the CA is 13-29 {mu}A and the OCV is +258 to -126 mW cm{sup -2}. The trend in the electrical properties for the different samples is well matched with the rate of hydrogen evolution. The samples with higher activities (450, 550, and 650 C) have similar X-ray diffraction (XRD) patterns, which clearly indicates that the samples showing the highest evolution rate are composed of both anatase and rutile, while those showing a lower evolution rate are made of either anatase or rutile. Increasing the intensity of the irradiated light causes a remarkable enhancement in the rate of hydrogen production from 71 to 153 {mu}mol h{sup -1} cm{sup -2}. (author)

Non-thermal plasma-induced photocatalytic degradation of 4-chlorophenol in water

Energy Technology Data Exchange (ETDEWEB)

Hao Xiaolong [Institute of Environmental Pollution Control Technologies, Xixi Campus, Zhejiang University, Hangzhou 310028, Zhejiang (China); Zhou Ming Hua [Institute of Environmental Pollution Control Technologies, Xixi Campus, Zhejiang University, Hangzhou 310028, Zhejiang (China); Lei Lecheng [Institute of Environmental Pollution Control Technologies, Xixi Campus, Zhejiang University, Hangzhou 310028, Zhejiang (China)]. E-mail: lclei@zju.edu.cn

2007-03-22

TiO{sub 2} photocatalyst (P-25) (50 mg L{sup -1}) was tentatively introduced into pulsed high-voltage discharge process for non-thermal plasma-induced photocatalytic degradation of the representative mode organic pollutant parachlorophenol (4-CP), including other compounds phenol and methyl red in water. The experimental results showed that rate constant of 4-CP degradation, energy efficiency for 4-CP removal and TOC removal with TiO{sub 2} were obviously increased. Pulsed high-voltage discharge process with TiO{sub 2} had a promoted effect for the degradation of these pollutants under a broad range of liquid conductivity. Furthermore, the apparent formation rates of chemically active species (e.g., ozone and hydrogen peroxide) were increased, the hydrogen peroxide formation rate from 1.10 x 10{sup -6} to 1.50 x 10{sup -6} M s{sup -1}, the ozone formation rate from 1.99 x 10{sup -8} to 2.35 x 10{sup -8} M s{sup -1}, respectively. In addition, this process had no influence on the photocatalytic properties of TiO{sub 2}. The introduction of TiO{sub 2} photocatalyst into pulsed discharge plasma process in the utilizing of ultraviolet radiation and electric field in pulsed discharge plasma process enhanced the yields of chemically active species, which were available for highly efficient removal and mineralization of organic pollutants.

Core-shell rhodium sulfide catalyst for hydrogen evolution reaction / hydrogen oxidation reaction in hydrogen-bromine reversible fuel cell

Science.gov (United States)

Li, Yuanchao; Nguyen, Trung Van

2018-04-01

Synthesis and characterization of high electrochemical active surface area (ECSA) core-shell RhxSy catalysts for hydrogen evolution oxidation (HER)/hydrogen oxidation reaction (HOR) in H2-Br2 fuel cell are discussed. Catalysts with RhxSy as shell and different percentages (5%, 10%, and 20%) of platinum on carbon as core materials are synthesized. Cyclic voltammetry is used to evaluate the Pt-equivalent mass specific ECSA and durability of these catalysts. Transmission electron microscopy (TEM), X-ray Photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX) techniques are utilized to characterize the bulk and surface compositions and to confirm the core-shell structure of the catalysts, respectively. Cycling test and polarization curve measurements in the H2-Br2 fuel cell are used to assess the catalyst stability and performance in a fuel cell. The results show that the catalysts with core-shell structure have higher mass specific ECSA (50 m2 gm-Rh-1) compared to a commercial catalyst (RhxSy/C catalyst from BASF, 6.9 m2 gm-Rh-1). It also shows better HOR/HER performance in the fuel cell. Compared to the platinum catalyst, the core-shell catalysts show more stable performance in the fuel cell cycling test.

Ruddlesden-Popper compounds (SrO)(LaFeO3)n (n = 1 and 2) as p-type semiconductors for photocatalytic hydrogen production

International Nuclear Information System (INIS)

Chen, Hongmei; Sun, Xiaoqin; Xu, Xiaoxiang

2017-01-01

Graphical abstract: Two layered ferrites LaSrFeO 4 and La 2 SrFe 2 O 7 have been investigated which demonstrate interesting p-type semconductivity and efficient hydrogen production from water. Display Omitted -- Abstract: Here we report two Ruddlesden-Popper type ferrite perovskites (SrO)(LaFeO 3 ) n (n = 1 and 2) which demonstrate p-type semiconductivity. Their crystal structure, optical absorption and other physicochemical properties have been systematically explored. Our results show that both ferrites crystallize in tetragonal symmetry with structural lamination along c axis. Efficient photocatalytic hydrogen production has been achieved for both samples under full range and visible light illumination. Better performance is noticed for LaSrFeO 4 with apparent quantum efficiency approaches 0.31% and 0.19% under full range and visible light illumination, respectively. The p-type semiconductivity is verified by their cathodic photocurrent as well as negative Mott-Schottky slop during Photoelectrochemical measurement. The relative lower activity for La 2 SrFe 2 O 7 compared to LaSrFeO 4 is likely due to its higher defect concentration which facilitates charge recombination. Both compounds exhibit anisotropic phenomenon for charge migrations according to theoretical calculations. Their p-type semiconductivity, strong visible light absorption, chemical inertness and high abundance of constituent elements signify promising applications in the field of solar energy conversion and optoelectronics.

Non-noble metal graphene oxide-copper (II) ions hybrid electrodes for electrocatalytic hydrogen evolution reaction

KAUST Repository

Muralikrishna, S.; Ravishankar, T.N.; Ramakrishnappa, T.; Nagaraju, Doddahalli H.; Krishna Pai, Ranjith

2015-01-01

Non-noble metal and inexpensive graphene oxide-copper (II) ions (GO-Cu2+) hybrid catalysts have been explored for the hydrogen evolution reaction (HER). We were able to tune the binding abilities of GO toward the Cu2+ ions and hence their catalytic

Hydrogen evolution in enzymatic photoelectrochemical cell using modified seawater electrolytes produced by membrane desalination process

Energy Technology Data Exchange (ETDEWEB)

Joo, Hyunku; Yoon, Jaekyung [Hydrogen Energy Research Center, New and Renewable Energy Research Division, Korea Institute of Energy Research, 71-2 Jang-dong, Yuseong-gu, Daejeon 305-343 (Korea); Bae, Sanghyun [Department of Environmental Engineering, Yonsei University, 234 Maeji-ri, Hungub-myun, Wonju, Gangwon-do 220-710 (Korea); Kim, Chunghwan; Kim, Suhan [Korea Institute of Water and Environment, K-Water, 462-1 Jeonmin-dong, Yuseong-gu, Daejeon 305-730 (Korea)

2009-09-15

In the near future, potential water shortages are expected to occur all over the world and this problem will have a significant influence on the availability of water for water-splitting processes, such as photocatalysis and electrolysis, as well as for drinking water. For this reason, it has been suggested that seawater could be used as an alternative for the various water industries including hydrogen production. Seawater contains a large amount of dissolved ion components, thus allowing it to be used as an electrolyte in photoelectrochemical (PEC) systems for producing hydrogen. Especially, the concentrate (retentate) stream shows higher salinity than the seawater fed to the membrane desalination process, because purified water (fresh water) is produced as the permeate stream and the waste brine is more concentrated than the original seawater. In this study, we investigated the hydrogen evolution rate in a photoelectrochemical system, including the preparation and characterization of an anodized tubular TiO{sub 2} electrode (ATTE) as both the photoanode and the cathode with the assistance of an immobilized hydrogenase enzyme and an external bias (solar cell), and the use of various qualities of seawater produced by membrane desalination processes as the electrolyte. The results showed that the rate of hydrogen evolution obtained using the nanofiltration (NF) retentate in the PEC system is ca. 105 {mu}mol/cm{sup 2} h, showing that this is an effective seawater electrolyte for hydrogen production, the optimum amount of enzyme immobilized on the cathode is ca. 3.66 units per geometrical unit area (1 cm x 1 cm), and the optimum external external bias supplied by the solar cell is 2.0 V. (author)

Enhanced Solar-to-Hydrogen Generation with Broadband Epsilon-Near-Zero Nanostructured Photocatalysts

KAUST Repository

Tian, Yi

2017-05-08

The direct conversion of solar energy into fuels or feedstock is an attractive approach to address increasing demand of renewable energy sources. Photocatalytic systems relying on the direct photoexcitation of metals have been explored to this end, a strategy that exploits the decay of plasmonic resonances into hot carriers. An efficient hot carrier generation and collection requires, ideally, their generation to be enclosed within few tens of nanometers at the metal interface, but it is challenging to achieve this across the broadband solar spectrum. Here the authors demonstrate a new photocatalyst for hydrogen evolution based on metal epsilon-near-zero metamaterials. The authors have designed these to achieve broadband strong light confinement at the metal interface across the entire solar spectrum. Using electron energy loss spectroscopy, the authors prove that hot carriers are generated in a broadband fashion within 10 nm in this system. The resulting photocatalyst achieves a hydrogen production rate of 9.5 µmol h-1  cm-2 that exceeds, by a factor of 3.2, that of the best previously reported plasmonic-based photocatalysts for the dissociation of H2 with 50 h stable operation.

Biomolecule-assisted synthesis of defect-mediated Cd1-xZnxS/MoS2/graphene hollow spheres for highly efficient hydrogen evolution.

Science.gov (United States)

Du, Ruifeng; Zhang, Yihe; Li, Baoying; Yu, Xuelian; Liu, Huijuan; An, Xiaoqiang; Qu, Jiuhui

2016-06-28

Moderate efficiency and the utilization of noble metal cocatalysts are the key factors that restrict the large-scale application of photocatalytic hydrogen production. To develop more efficient photocatalysts based on earth abundant elements, either a new material strategy or a fundamental understanding of the semiconductor/cocatalyst interfaces is highly desirable. In this paper, we studied the feasibility of in situ formation of defect-rich cocatalysts on graphene-based photocatalysts. A facile biomolecule-assisted strategy was used to self-assmble Cd1-xZnxS/MoS2/graphene hollow spheres. The defect-mediated cocatalyst and synergetic charge transfer around heterostructured interfaces exhibit a significant impact on the visible-light-driven photocatalytic activity of multicomponent solid solutions. With engineered interfacial defects, Cd0.8Zn0.2S/MoS2/graphene hollow spheres exhibited a 63-fold improved H2 production rate, which was even 2 and 3.8 times higher than those of CdS/MoS2/graphene hollow spheres and Cd0.8Zn0.2S/Pt. Therefore, our research provides a promising approach for the rational design of high-efficiency and low-cost photocatalysts for solar fuel production.

The hydrogen evolution and oxidation kinetics during overdischarging of sealed nickel-metal hydride batteries

NARCIS (Netherlands)

Ayeb, A.; Otten, W.M.; Mank, A.J.G.; Notten, P.H.L.

2006-01-01

The hydrogen evolution and oxidation kinetics in NiMH batteries have been investigated under temperature-controlled, steady-state, overdischarging conditions within a temperature range of 10 and 50°C and at discharging currents of 1–330 mA (0.0009 to 0.3 C rate). In situ Raman spectroscopic analyses

Symmetrical synergy of hybrid Co9S8-MoSx electrocatalysts for hydrogen evolution reaction

KAUST Repository

Zhou, Xiaofeng; Yang, Xiulin; Hedhili, Mohamed N.; Li, Henan; Min, Shixiong; Ming, Jun; Huang, Kuo-Wei; Zhang, Wenjing; Li, Lain-Jong

2017-01-01

There exists a strong demand to replace expensive noble metal catalysts with efficient and earth-abundant catalysts for hydrogen evolution reaction (HER). Recently the Co- and Mo-based sulfides such as CoS2, Co9S8, and MoSx have been considered

Photocatalytic properties and selective antimicrobial activity of TiO{sub 2}(Eu)/CuO nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Michal, Robert [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, 84215 Bratislava (Slovakia); Dworniczek, Ewa [Department of Microbiology, Wroclaw Medical University, 50368 Wroclaw (Poland); Caplovicova, Maria [STU Centre for Nanodiagnostics, Slovak University of Technology, 81243 Bratislava (Slovakia); Monfort, Olivier [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, 84215 Bratislava (Slovakia); Lianos, Panagiotis [Department of Chemical Engineering, University of Patras, 26500 Patras (Greece); Caplovic, Lubomir [Institute of Materials Science, Faculty of Materials Science and Technology, Slovak University of Technology, 91724 Trnava (Slovakia); Plesch, Gustav, E-mail: plesch@fns.uniba.sk [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, 84215 Bratislava (Slovakia)

2016-05-15

Highlights: • Nanocomposites composed of Eu-doped anatase grafted with CuO. • Increase in photocatalytic hydrogen production due to CuO acting as electrons sink. • CuO in composites decreasing the photoinduced total mineralization of phenol. • Selective photoinduced antimicrobial activity against Enterococcus species. - Abstract: TiO{sub 2}(Eu)/CuO nanocomposites were prepared by precipitation method. The anatase nanocrystallites with a size of 26 nm exhibited well crystallized and characteristical dipyramidal morphology and {1 0 1} and {0 0 1} faceting. Transmission electron microscopy photographs with atomic resolution showed that the Eu(III) dopants were bounded on surface of titania. In the composites, the CuO nanocrystals exhibiting a monoclinic tenorite structure with a size in the range from 2 to 5 nm were grafted to the surface of titania. The influence of copper(II) oxide led to distinct selectivity in the photocatalytic and antimicrobial properties of the investigated TiO{sub 2}(Eu)/CuO nanocomposites. While the presence of CuO nanocrystals strongly increased the photocatalytic production of hydrogen by ethanol reforming, it decreased the activity in photoinduced total mineralization of phenol comparing with non-modified TiO{sub 2}(Eu). In investigated TiO{sub 2}(Eu)/CuO powders, the photoinduced antimicrobial activity against membranes of Enterococcus species was influenced by the selective binding of CuO to the surface of the microorganism leading to distinct selectivity in their action. The activity against Enterococcus faecalis was higher than against Enterococcus faecium.

Remarkable photo-catalytic degradation of malachite green by nickel doped bismuth selenide under visible light irradiation

International Nuclear Information System (INIS)

Kulsi, Chiranjit; Ghosh, Amrita; Mondal, Anup; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

2017-01-01

Highlights: • Bi_2Se_3 and Ni doped Bi_2Se_3 were synthesized by solvothermal approach. • Presence of nickel was confirmed by X-ray photoelectron spectroscopy (XPS) measurement. • Complete degradation of malachite green (MG) dye was achieved by Ni doped Bi_2Se_3 with H_2O_2. • Remarkable photo-catalytic degradation by doped bismuth selenide has been explained. • Scavenger tests show degradation of MG is mainly dominated by ·OH oxidation process. - Abstract: Bismuth selenide (Bi_2Se_3) and nickel (Ni) doped Bi_2Se_3 were prepared by a solvothermal approach to explore the photo-catalytic performance of the materials in degradation of malachite green (MG). The presence of nickel was confirmed by X-ray photoelectron spectroscopy (XPS) measurement in doped Bi_2Se_3. The results showed that the nickel doping played an important role in microstructure and photo-catalytic activity of the samples. Nickel doped Bi_2Se_3 sample exhibited higher photo-catalytic activity than that of the pure Bi_2Se_3 sample under visible-light irradiation. The photo-catalytic degradation followed first-order reaction kinetics. Fast degradation kinetics and complete (100% in 5 min of visible light irradiation) removal of MG was achieved by nickel doped Bi_2Se_3 in presence of hydrogen peroxide (H_2O_2) due to modification of band gap energies leading to suppression of photo-generated electron-hole recombination.

Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

KAUST Repository

Wahab, A. K.; Odedairo, T.; Labis, J.; Hedhili, Mohamed N.; Delavar, A.; Idriss, H.

2013-01-01

Photocatalytic hydrogen production from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen production, rH2, over Pt/SrTiO3 is found to be far higher than that observed over Rh/SrTiO3 (4 × 10−6 mol of H2 g catal. −1 min−1 (1.1 × 10−6 mol of H2 m catal. −2 min−1) compared to 0.7 × 10−6 mol of H2 g catal. −1 min−1 (5.5 × 10−8 mol of H2 m catal. −2 min−1), respectively, under UV excitation with a flux equivalent to that from the sun light (ca. 1 mW cm−2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amount of methane are formed on the Rh containing catalyst compared to that observed on the Pt containing catalyst due to the capacity of Rh to break the carbon–carbon bond of the organic compound.

Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

KAUST Repository

Wahab, A. K.

2013-08-13

Photocatalytic hydrogen production from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen production, rH2, over Pt/SrTiO3 is found to be far higher than that observed over Rh/SrTiO3 (4 × 10−6 mol of H2 g catal. −1 min−1 (1.1 × 10−6 mol of H2 m catal. −2 min−1) compared to 0.7 × 10−6 mol of H2 g catal. −1 min−1 (5.5 × 10−8 mol of H2 m catal. −2 min−1), respectively, under UV excitation with a flux equivalent to that from the sun light (ca. 1 mW cm−2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amount of methane are formed on the Rh containing catalyst compared to that observed on the Pt containing catalyst due to the capacity of Rh to break the carbon–carbon bond of the organic compound.

Electrochemical preparation and characteristics of Ni-Co-LaNi{sub 5} composite coatings as electrode materials for hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Wu Gang; Li Ning; Dai Changsong; Zhou Derui

2004-02-15

Electrocatalytic activity for the hydrogen evolution reaction on Ni-Co-LaNi{sub 5} composite electrodes prepared by electrochemical codeposition technique was evaluated. The relationship between the current density for hydrogen evolution reaction and the amount of LaNi{sub 5} particles in Ni-Co baths is like the well-known 'volcano plot'. The Surface morphology and microstructure of Ni-Co-LaNi{sub 5} coatings were determined by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The kinetic parameters were determined from electrochemical steady-state Tafel polarization and electrochemical impedance spectroscopy technology in 1 M NaOH solution. The values obtained for the apparent energies of activation are 32.48, 46.29 and 57.03 kJ mol{sup -1} for the Ni-Co-LaNi{sub 5}, Ni-Co and Ni electrodes, respectively. The hydrogen evolution reaction on Ni-Co-LaNi{sub 5} proceeds via Volmer-Tafel reaction route with the mixed rate determining characteristics. The composite coating Ni-Co-LaNi{sub 5} is catalytically more active than Ni and Ni-Co electrodes due to the increase in its real surface areas and the decrease in the apparent free energy of activation caused by the electrocatalytic synergistic effect of the Ni-Co alloys and the hydrogen storage intermetallic particles on the electrode surface.

CdS nanoparticles/CeO_2 nanorods composite with high-efficiency visible-light-driven photocatalytic activity

International Nuclear Information System (INIS)

You, Daotong; Pan, Bao; Jiang, Fan; Zhou, Yangen; Su, Wenyue

2016-01-01

Graphical abstract: Coupling CdS with CeO_2 can effectively improve the light-harvesting ability of wide-band gap CeO_2 NRs as the photoinduced electrons on the conduction band of CdS are transfered to the conduction band of CeO_2. - Highlights: • Coupling CdS can effectively improve the light-harvesting ability of wide-band gap CeO_2. • CdS/CeO_2 composites show high photocatalytic activity under visible light irradiation. • The mechanism of photocatalytic H_2 evolution over CdS/CeO_2 was proposed. - Abstract: Different mole ratios of CdS nanoparticles (NPs)/CeO_2 nanorods (NRs) composites with effective contacts were synthesized through a two-step hydrothermal method. The crystal phase, microstructure, optical absorption properties, electrochemical properties and photocatalytic H_2 production activity of these composites were investigated. It was concluded that the photogenerated charge carriers in the CdS NPs/CeO_2 NRs composite with a proper mole ratio (1:1) exhibited the longest lifetime and highest separation efficiency, which was responsible for the highest H_2-production rate of 8.4 mmol h"−"1 g"−"1 under visible-light irradiation (λ > 420 nm). The superior photocatalytic H_2 evolution properties are attributed to the transfer of visible-excited electrons of CdS NPs to CeO_2 NRs, which can effectively extend the light absorption range of wide-band gap CeO_2 NRs. This work provides feasible routes to develop visible-light responsive CeO_2-based nanomaterial for efficient solar utilization.

Characterization of electrochemically deposited films from aqueous and ionic liquid cobalt precursors toward hydrogen evolution reactions

Energy Technology Data Exchange (ETDEWEB)

Dushatinski, Thomas; Huff, Clay; Abdel-Fattah, Tarek M., E-mail: fattah@cnu.edu

2016-11-01

Highlights: • Co films deposition via aqueous and ionic liquid Precursors. • Hydrogen evolution produced from reactive surfaces. • Co deposited films characterized by SEM, AFM, EDX and XRD techniques. - Abstract: Electrodepositions of cobalt films were achieved using an aqueous or an ethylene glycol based non-aqueous solution containing choline chloride (vitamin B4) with cobalt chloride hexahydrate precursor toward hydrogen evolution reactions from sodium borohydride (NaBH{sub 4}) as solid hydrogen feedstock (SHF). The resulting cobalt films had reflectivity at 550 nm of 2.2% for aqueously deposited films (ACoF) and 1.3% for non-aqueously deposited films (NCoF). Surface morphology studied by scanning electron microscopy showed a positive correlation between particle size and thickness. The film thicknesses were tunable between >100 μm and <300 μm for each film. The roughness (Ra) value measurements by Dektak surface profiling showed that the NCoF (Ra = 165 nm) was smoother than the ACoF (Ra = 418 nm). The NCoFs and ACoFs contained only α phase (FCC) crystallites. The NCoFs were crystalline while the ACoFs were largely amorphous from X-ray diffraction analysis. The NCoF had an average Vickers hardness value of 84 MPa as compared to 176 MPa for ACoF. The aqueous precursor has a single absorption maximum at 510 nm and the non-aqueous precursor had three absorption maxima at 630, 670, and 695 nm. The hydrogen evolution reactions over a 1 cm{sup 2} catalytic surface with aqueous NaBH{sub 4} solutions generated rate constants (K) = equal to 4.9 × 10{sup −3} min{sup −1}, 4.6 × 10{sup −3} min{sup −1}, and 3.3 × 10{sup −3} min{sup −1} for ACoF, NCoF, and copper substrate respectively.

MOF-derived Cu/nanoporous carbon composite and its application for electro-catalysis of hydrogen evolution reaction

International Nuclear Information System (INIS)

Raoof, Jahan-Bakhsh; Hosseini, Sayed Reza; Ojani, Reza; Mandegarzad, Sakineh

2015-01-01

In this work, metal-organic framework Cu_3(BTC)_2 [BTC = 1,3,5-benzenetricarboxylate] (commonly known as MOF-199 or HKUST-1), is used as porous template for preparation of a Cu/nanoporous carbon composite. The MOF-derived Cu/nanoporous carbon composite (Cu/NPC composite) is synthesized by direct carbonization of the MOF-199 without any carbon precursor additive. The physical characterization of the solid catalyst is achieved by using a variety of different techniques, including XRD (X-ray powder diffraction), scanning electron microscopy, thermo-gravimetric analysis, and nitrogen physisorption measurements. The electrochemical results have shown that the Cu/NPC composite modified glassy carbon electrode (Cu/NPC/GCE) as a non-platinum electrocatalyst exhibited favorable catalytic activity for hydrogen evolution reaction, in spite of high resistance to faradic process. This behavior can be attributed to existence of Cu metal confirmed by XRD and/or high effective pore surface area (1025 m"2 g"−"1) in the Cu/NPC composite. The electron transfer coefficient and exchange current density for the Cu/NPC/GCE is calculated by Tafel plot at about 0.34 and 1.2 × 0"−"3 mAcm"−"2, respectively. - Graphical abstract: Metal organic framework-derived Cu/nanoporous carbon composite (Cu/NPC composite) was prepared by direct carbonization of MOF-199 without addition of any carbon source at 900 °C. The Cu/NPC/GCE demonstrated an excellent electrocatalytic activity towards hydrogen evolution reaction compared with bare GCE. - Highlights: • MDNPC (MOF-199 derived nanoporous carbon) is prepared by direct carbonization. • MOF-199 is utilized as a template without addition of carbon resource. • The MDNPC has a good electrocatalytic activity in hydrogen evolution reaction. • High BET surface area and hydrogen adsorption property improved catalyst activity.

Anodic luminescence, structural, photoluminescent, and photocatalytic properties of anodic oxide films grown on niobium in phosphoric acid

Energy Technology Data Exchange (ETDEWEB)

Stojadinović, Stevan, E-mail: sstevan@ff.bg.ac.rs [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Tadić, Nenad [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia); Radić, Nenad [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoševa 12, 11000 Belgrade (Serbia); Stefanov, Plamen [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, 1113 Sofia (Bulgaria); Grbić, Boško [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoševa 12, 11000 Belgrade (Serbia); Vasilić, Rastko [University of Belgrade, Faculty of Physics, Studentski trg 12-16, 11000 Belgrade (Serbia)

2015-11-15

Graphical abstract: - Highlights: • Anodic luminescence is correlated to the existence of morphological defects in the oxide. • Spectrum under spark discharging reveals only oxygen and hydrogen lines. • Oxide films formed under spark discharging are crystallized and composed of Nb{sub 2}O{sub 5}. • Photocatalytic activity and photoluminescence of Nb{sub 2}O{sub 5} films increase with time. - Abstract: This article reports on properties of oxide films obtained by anodization of niobium in phosphoric acid before and after the dielectric breakdown. Weak anodic luminescence of barrier oxide films formed during the anodization of niobium is correlated to the existence of morphological defects in the oxide layer. Small sized sparks generated by dielectric breakdown of formed oxide film cause rapid increase of luminescence intensity. The luminescence spectrum of obtained films on niobium under spark discharging is composed of continuum radiation and spectral lines caused by electronic spark discharging transitions in oxygen and hydrogen atoms. Oxide films formed before the breakdown are amorphous, while after the breakdown oxide films are partly crystalline and mainly composed of Nb{sub 2}O{sub 5} hexagonal phase. The photocatalytic activity of obtained oxide films after the breakdown was investigated by monitoring the degradation of methyl orange. Increase of the photocatalytic activity with time is related to an increase of oxygen vacancy defects in oxide films formed during the process. Also, higher concentration of oxygen vacancy defects in oxide films results in higher photoluminescence intensity.

Fabrication of efficient TiO2-RGO heterojunction composites for hydrogen generation via water-splitting: Comparison between RGO, Au and Pt reduction sites

Science.gov (United States)

El-Bery, Haitham M.; Matsushita, Yoshihisa; Abdel-moneim, Ahmed

2017-11-01

A facile one-step synthesis approach of M/TiO2/RGO (M = Au or Pt) ternary composite by hydrothermal treatment for hydrogen generation via water-splitting was investigated. Photocurrent response measurements revealed that TiO2 (P25) nanoparticles anchored on the reduced graphene oxide (RGO) surface exhibited a p-n heterojunction interface by changing the photocurrent direction with the applied bias from reverse to forward potential. H2 evolution rate of TiO2/RGO (5 wt.%) composite was substantially enhanced by 12-fold in comparison to bare TiO2 under simulated solar light irradiation. Cyclic volatmmetry measurements manifested, that the optimized 0.3 wt.% of platinum metal loaded on TiO2/RGO composite was the most active catalytic reduction sites for hydrogen generation reaction with an initial hydrogen rate of 670 μmol h-1. This study sheds the light on the tunable semiconductor type of TiO2/RGO composite fabricated by solution mixing pathway and its merits to improve the photocatalytic activity.

Superaerophobic Ultrathin Ni-Mo Alloy Nanosheet Array from In Situ Topotactic Reduction for Hydrogen Evolution Reaction.

Science.gov (United States)

Zhang, Qian; Li, Pengsong; Zhou, Daojin; Chang, Zheng; Kuang, Yun; Sun, Xiaoming

2017-11-01

Hydrogen evolution reaction (HER) has prospect to becoming clean and renewable technology for hydrogen production and Ni-Mo alloy is among the best HER catalysts in alkaline electrolytes. Here, an in situ topotactic reduction method to synthesize ultrathin 2D Ni-Mo alloy nanosheets for electrocatalytic hydrogen evolution is reported. Due to its ultrathin structure and tailored composition, the as-synthesized Ni-Mo alloy shows an overpotential of 35 mV to reach a current density of 10 mA cm -2 , along with a Tafel slope of 45 mV decade -1 , demonstrating a comparable intrinsic activity to state-of-art commercial Pt/C catalyst. Besides, the vertically aligned assemble structure of the 2D NiMo nanosheets on conductive substrate makes the electrode "superaerophobic," thus leading to much faster bubble releasing during HER process and therefore shows faster mass transfer behavior at high current density as compared with drop drying Pt/C catalyst on the same substrate. Such in situ topotactic conversion finds a way to design and fabricate low-cost, earth-abundant non-noble metal based ultrathin 2D nanostructures for electrocatalytic issues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile preparation and improved photocatalytic H{sub 2}-production of Pt-decorated CdS/TiO{sub 2} nanorods

Energy Technology Data Exchange (ETDEWEB)

Yu, Qi [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Xu, Jie [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Ian Wark Research Institute, University of South Australia, Mawson Lakes Campus, SA 5095 (Australia); Wang, Wenzhong, E-mail: wzwang@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Lu, Chunli [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

2014-03-01

Graphical abstract: - Highlights: • Pt-CdS/TiO{sub 2} nanorods were firstly realized by electrospinning. • They exhibited high photocatalytic H{sub 2} production activity. • The mechanism of the high performance was discussed. - Abstract: Pt-CdS/TiO{sub 2} nanorods with different molar ratios of Cd:Ti were prepared through an electrospinning method followed by sulfidation treatment and photodeposition. The nanorod-like samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence spectra (PL), and UV–vis diffuse reflectance spectroscopy (DRS). The results indicated that the as-prepared samples exhibited wider light absorption range and lower recombination rate of photogenerated electron–hole pairs after the introduction of Pt and CdS. The photocatalysis experiments showed that Pt-modified CdS/TiO{sub 2} nanorods exhibited much higher activities than pure TiO{sub 2} in the evolution of hydrogen under simulated solar light irradiation.

Effective photocatalytic decolorization of methylene blue utilizing ZnO/rectorite nanocomposite under simulated solar irradiation

Energy Technology Data Exchange (ETDEWEB)

Li, Shi-qian, E-mail: shiqianli04@tom.com [College of Resource and Environmental Science, Wuhan University, Hubei Key Laboratory of Biomass-resource Chemical and Environment Bio-technology, Wuhan 430079 (China); Department of Biology and Chemical Engineering, FuQing Branch of Fujian Normal University, Fuqing 350300 (China); Zhou, Pei-jiang; Zhang, Wan-shun [College of Resource and Environmental Science, Wuhan University, Hubei Key Laboratory of Biomass-resource Chemical and Environment Bio-technology, Wuhan 430079 (China); Chen, Sheng [Department of Biology and Chemical Engineering, FuQing Branch of Fujian Normal University, Fuqing 350300 (China); Peng, Hong [State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Hubei, Wuhan 430072 (China)

2014-12-15

Highlights: • Preparation of ZnO inserted in rectorite as photocatalyst in methylene blue photodegradation. • The ZnO/rectorite can be used as adsorbents and photocatalysts. • The ZnO/rectorite system was easy to be gathered and recycled. • Inferred ZnO/rectorite the photocatalytic degradation methylene blue of aqueous micro mechanism. - Abstract: Preparation of a nanometer zinc oxide/rectorite (ZnO/REC) composites photocatalyst based on natural rectorite was conducted using a hydrothermal intercalation method. The structure, thermal property, and surface morphology of ZnO/REC were characterized by X-ray diffractor (XRD), thermogravimetric analysis (TGA), high-resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM) techniques. The photocatalytic activity of ZnO/REC was evaluated by photocatalytic decolorization of methylene blue (MB) in aqueous solution as a model pollutant under simulated sunlight irradiation. The HRTEM results revealed that well-dispersed and uniform ZnO/REC nanocomposites with diameters of 10 nm were embedded in rectorite. The ZnO/REC nanocomposite exhibited high photocatalytic activity under simulated solar irradiation. After 2 h of irradiation by simulated solar light, over 99% of methylene blue solution (15 mg/L) was decolorized with 0.9 g/L of the photocatalyst. The ZnO/REC was reusable, which meant that the adsorption photocatalytic decolorization process could be operated at a relatively low cost. Since this process does not require the addition of hydrogen peroxide but uses sunlight, it can be developed as an economically feasible and environmentally friendly method to decolorize or treat dye wastewater using solar.

Nanocrystalline electrodeposited Ni-Mo-C cathodes for hydrogen production

International Nuclear Information System (INIS)

Hashimoto, K.; Sasaki, T.; Meguro, S.; Asami, K.

2004-01-01

Tailoring active nickel alloy cathodes for hydrogen evolution in a hot concentrated hydroxide solution was attempted by electrodeposition. The carbon addition to Ni-Mo alloys decreased the nanocrystalline grain size and remarkably enhanced the activity for hydrogen evolution, changing the mechanism of hydrogen evolution. The Tafel slope of hydrogen evolution was about 35 mV per decade. This suggested that the rate-determining step is desorption of adsorbed hydrogen atoms by recombination. As was distinct from the binary Ni-Mo alloys, after open circuit immersion, the overpotential, that is, the activity of nanocrystalline Ni-Mo-C alloys for hydrogen evolution was not changed, indicating the sufficient durability in the practical electrolysis

A theoretical study on the mechanism of hydrogen evolution on non-precious partially oxidized nickel-based heterostructures for fuel cells.

Science.gov (United States)

Pan, Xinju; Zhou, Gang

2018-03-28

It is desirable, yet challenging, to utilize non-precious metals instead of noble-metals as efficient catalysts in the renewable energy manufacturing industry. Using first principles calculations, we study the structural characteristics of partially oxidized nickel-based nanoheterostructures (NiO/Ni NHSs), and the interfacial effects on hydrogen evolution. The origin of the enhanced hydrogen evolution performance is discussed at the microscopic level. This study identifies two types of active sites of the exposed Ni surface available for the hydrogen evolution reaction (HER). One is the hcp-hollow sites near the perimeter boundary that exhibit a more excellent HER performance than platinum (Pt), and the other the second nearest neighbor fcc-hollow sites away from the boundary that exhibit a similar performance to Pt. The interfacial effects result from the competitive charge transfer between NiO and Ni surfaces in NHSs, and enhance the reactivity of NiO/Ni NHSs by shifting the d-states of surface atoms down in energy. The illumination of the mechanism would be helpful for the design of more efficient and cheap transition metal-based catalysts.

Synthesis and visible-light-driven photocatalytic activity of p–n heterojunction Ag_2O/NaTaO_3 nanocubes

International Nuclear Information System (INIS)

Yang, Songbo; Xu, Dongbo; Chen, Biyi; Luo, Bifu; Yan, Xu; Xiao, Lisong; Shi, Weidong

2016-01-01

Highlights: • We firstly report a facile way to prepare the visible-light-driven Ag_2O/NaTaO_3p–n heterojunction by chemical precipitation method. • The Ag_2O/NaTaO_3 heterojunction shows the highest photocatalytic activity than the pure NaTaO_3 and Ag_2O nanoparticles under visible light. • The enhancement of the heterojunction photocatalytic activity was discussed and the photocatalytic mechanism was tested in our paper. • In summary, we think that the Ag_2O/NaTaO_3 heterojunction with the strong visible light absorption and efficient photocatalytic activity have been extended application in photocatalysis for organic dyes pollutants degradation and purification of water. - Abstract: The constructing of p–n heterojunction photocatalytic system has received much attention in environmental purification and hydrogen generation from water. In this study, an efficient visible-light-driven p–n heterojunction Ag_2O/NaTaO_3 was successfully prepared by chemical precipitation method at room temperature. It showed an enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation, much higher than those of either individual Ag_2O or NaTaO_3. The reactive species scavenger results indicated the superoxide anion radicals (·O"2"−) played key roles in RhB decoloration. From the experimental results and the relative band gap position of these semiconductors, a detailed possible photocatalytic mechanism of the Ag_2O/NaTaO_3 heterojunction under visible light was proposed. The enhancement of the photocatalytic activity was attributed to the interfacial electronic interaction between NaTaO_3 and Ag_2O and the high migration efficiency of photogenerated carriers.

TiO{sub 2} Processed by pressurized hot solvents as a novel photocatalyst for photocatalytic reduction of carbon dioxide

Energy Technology Data Exchange (ETDEWEB)

Reli, Martin, E-mail: martin.reli@vsb.cz [Institute of Environmental Technology, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava (Czech Republic); Kobielusz, Marcin [Faculty of Chemistry, Jagiellonian University in Kraków, ul. Ingardena 3, 30-060 Kraków (Poland); Matějová, Lenka [Institute of Environmental Technology, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava (Czech Republic); Daniš, Stanislav [Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic); Macyk, Wojciech [Centre ENET, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava (Czech Republic); Obalová, Lucie [Institute of Environmental Technology, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava (Czech Republic); Kuśtrowski, Piotr; Rokicińska, Anna [Faculty of Chemistry, Jagiellonian University in Kraków, ul. Ingardena 3, 30-060 Kraków (Poland); Kočí, Kamila [Institute of Environmental Technology, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava (Czech Republic); Centre ENET, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava (Czech Republic)

2017-01-01

Highlights: • Synthesis of anatase-brookite TiO{sub 2} photocatalysts has been described. • The materials photocatalyze carbon dioxide reduction to methane. • The photoactivity of the synthesized composites has been compared with the activity of anatase-rutile material (P25). • The influence of electronic structure on photocatalytic activity has been discussed. - Abstract: Anatase-brookite TiO{sub 2} photocatalysts were prepared by the sol-gel process controlled within reverse micelles and processing by pressurized hot solvents–water/methanol/water (TiO{sub 2}(M)) and water/ethanol/water (TiO{sub 2}(E)), as an unconventional alternative to common calcination. The main goal of this work was to prepare anatase-brookite mixtures by processing by two different alcohols (methanol and ethanol) and evaluate the influence of the alcohol on the photocatalytic activity. Prepared photocatalysts were characterized by organic elemental analysis, nitrogen physisorption, XRD, UV–vis, photoelectrochemical and spectroelectrochemical measurements and XPS. The prepared photocatalysts efficiency was tested on the photocatalytic reduction of carbon dioxide and compared with commercial TiO{sub 2} Evonik P25. Both prepared nanocomposites were more efficient towards methane production but Evonik P25 was the most efficient towards hydrogen generated through water splitting. The higher performance of anatase-brookite mixture towards methane production can be explained by (i) a higher photocatalytic activity of brookite than rutile; (ii) a large surface area of anatase-brookite composites enabling better carbon dioxide adsorption; (iii) the photoinduced electron transfer from the brookite conduction band to the anatase conduction band. On the other hand, a higher production of hydrogen in the presence of Evonik P25 is caused by a better charge separation in anatase-rutile than anatase-brookite phase compositions. TiO{sub 2}(M) appeared more active than TiO{sub 2}(E) in the

Hydrazine-hydrothermal method to synthesize three-dimensional chalcogenide framework for photocatalytic hydrogen generation

International Nuclear Information System (INIS)

Liu Yi; Kanhere, Pushkar D.; Wong, Chui Ling; Tian Yuefeng; Feng Yuhua; Boey, Freddy; Wu, Tom; Chen Hongyu; White, Tim J.; Chen Zhong; Zhang Qichun

2010-01-01

A novel chalcogenide, [Mn 2 Sb 2 S 5 (N 2 H 4 ) 3 ] (1), has been synthesized by the hydrazine-hydrothermal method. X-ray crystallography study reveals that the new compound 1 crystallizes in space group P1-bar (no. 2) of the triclinic system. The structure features an open neutral three-dimensional framework, where two-dimensional mesh-like inorganic layers are bridged by intra- and inter-layer hydrazine ligands. Both two Mn1 and Mn2 sites adopt distorted octahedral coordination. While two Sb1 and Sb2 sites exhibit two different coordination geometries, the Sb1 site is coordinated with three S atoms to generate a SbS 3 trigonal-pyramidal geometry, and the Sb2 site adopts a SbS 4 trigonal bipyramidal coordination geometry. It has an optical band gap of about ∼2.09 eV, which was deduced from the diffuse reflectance spectrum, and displays photocatalytic behaviors under visible light irradiation. Magnetic susceptibility measurements show compound 1 obeys the Curie-Weiss law in the range of 50-300 K. -- Graphical abstract: A novel chalcogenide, [Mn 2 Sb 2 S 5 (N 2 H 4 ) 3 ] (1), synthesized by hydrazine-hydrothermal method, has a band gap of about ∼2.09 eV and displays photocatalytic behaviors under visible light irradiation. Display Omitted

Low-temperature solid-state preparation of ternary CdS/g-C_3N_4/CuS nanocomposites for enhanced visible-light photocatalytic H_2-production activity

International Nuclear Information System (INIS)

Cheng, Feiyue; Yin, Hui; Xiang, Quanjun

2017-01-01

Highlights: • CdS/g-C_3N_4/CuS composite were synthesized by low-temperature solid-state method. • CdS/g-C_3N_4/CuS show enhanced visible-light photocatalytic H_2 evolution activity. • The enhanced photocatalytic H_2 production activity is due to the heterojunction. • Heterojunction between the components promote charge separation/transfer property. - Abstract: Low-temperature solid-state method were gradually demonstrated as a high efficiency, energy saving and environmental protection strategy to fabricate composite semiconductor materials. CdS-based multiple composite photocatalytic materials have attracted increasing concern owning to the heterostructure constituents with tunable band gaps. In this study, the ternary CdS/g-C_3N_4/CuS composite photocatalysts were prepared by a facile and novel low-temperature solid-state strategy. The optimal ternary CdS/g-C_3N_4/CuS composite exhibits a high visible-light photocatalytic H_2-production rate of 57.56 μmol h"−"1 with the corresponding apparent quantum efficiency reaches 16.5% at 420 nm with Na_2S/Na_2SO_3 mixed aqueous solution as sacrificial agent. The ternary CdS/g-C_3N_4/CuS composites show the enhanced visible-light photocatalytic H_2-evolution activity comparing with the binary CdS-based composites or simplex CdS. The enhanced photocatalytic activity is ascribed to the heterojunctions and the synergistic effect of CuS and g-C_3N_4 in promotion of the charge separation and charge mobility. This work shows that the low-temperature solid-state method is efficient and environmentally benign for the preparation of CdS-based multiple composite photocatalytic materials with enhanced visible-light photocatalytic H_2-production activity.

Indented Cu2MoS4 nanosheets with enhanced electrocatalytic and photocatalytic activities realized through edge engineering.

Science.gov (United States)

Chen, Bang-Bao; Ma, De-Kun; Ke, Qing-Ping; Chen, Wei; Huang, Shao-Ming

2016-03-07

Edges often play a role as active centers for catalytic reactions in some nanomaterials. Therefore it is highly desirable to enhance catalytic activity of a material through modulating the microstructure of the edges. However, the study associated with edge engineering is less investigated and still at its preliminary stage. Here we report that Cu2MoS4 nanosheets with indented edges can be fabricated through a simple chemical etching route at room temperature, using Cu2MoS4 nanosheets with flat ones as sacrifice templates. Taking the electrocatalytic hydrogen evolution reaction (HER), photocatalytic degradation of rhodamine B (RhB) and conversion of benzyl alcohol as examples, the catalytic activity of Cu2MoS4 indented nanosheets (INSs) obtained through edge engineering was comparatively studied with those of Cu2MoS4 flat nanosheets (FNSs) without any modification. The photocatalytic tests revealed that the catalytic active sites of Cu2MoS4 nanosheets were associated with their edges rather than basal planes. Cu2MoS4 INSs were endowed with larger electrochemically active surface area (ECSA), more active edges and better hydrophilicity through the edge engineering. As a result, the as-fabricated Cu2MoS4 INSs exhibited an excellent HER activity with a small Tafel slope of 77 mV dec(-1), which is among the best records for Cu2MoS4 catalysts. The present work demonstrated the validity of adjusting catalytic activity of the material through edge engineering and provided a new strategy for designing and developing highly efficient catalysts.

An efficient top-down approach for the fabrication of large-aspect-ratio g-C3N4 nanosheets with enhanced photocatalytic activities.

Science.gov (United States)

Tong, Jincheng; Zhang, Li; Li, Fei; Li, Mingming; Cao, Shaokui

2015-09-28

Graphitic carbon nitride (g-C3N4) nanosheets with large aspect ratios were fabricated from bulk g-C3N4 through an efficient top-down approach of moderate disintegration-exfoliation using diluted H2SO4 as an "efficient knife". By prior disintegration in a diluted H2SO4 solution, the exfoliation of bulk g-C3N4 was effectively accelerated. The as-prepared g-C3N4 nanosheets possess a two-dimensional (2D) thin-layer structure with seven-atom thickness, a large lateral size of about 1 μm, and a high specific surface area of 80 m(2) g(-1). Compared with the bulk precursor, the g-C3N4 nanosheets showed much higher efficiency of photogenerated charge transfer and separation, and consequently exhibited enhanced photocatalytic activity toward hydrogen evolution and pollutant decomposition under both full-sunlight and visible-light irradiation.

Enhanced visible light photocatalytic activity of g-C3N4 assisted by hydrogen peroxide

Science.gov (United States)

Chen, Quan-Liang; Liu, Yi-Ling; Tong, Li-Ge

2018-04-01

Water pollution has caused much attention nowadays. Photocatalysis as a kind of advanced oxidation technology has been widely studied in the field of environmental pollution control. As a stable non-metal photocatalyst, the photocatalytic activity of g-C3N4 assisted by H2O2 was investigated for the degradation of Rhodamine B (RhB) under visible light irradiation. The combination of g-C3N4 and H2O2 has much higher activity than that of pure g-C3N4 or H2O2. Neutral solution is preferred for the high phtotocatalytic activity of g-C3N4 with H2O2. The effect of the amount of catalyst, H2O2 concentration and RhB concentration was investigated. Photocatalytic mechanism study using radical scavenger showed free radicals {{{{O}}}2}- and · OH are the main active species. g-C3N4 assisted by H2O2 showed good photostability and repeatability after five cycles of degradation experiment.

Method and system for hydrogen evolution and storage

Science.gov (United States)

Thorn, David L.; Tumas, William; Hay, P. Jeffrey; Schwarz, Daniel E.; Cameron, Thomas M.

2012-12-11

A method and system for storing and evolving hydrogen (H.sub.2) employ chemical compounds that can be hydrogenated to store hydrogen and dehydrogenated to evolve hydrogen. A catalyst lowers the energy required for storing and evolving hydrogen. The method and system can provide hydrogen for devices that consume hydrogen as fuel.

Facile one-step hydrothermal synthesis toward strongly coupled TiO{sub 2}/graphene quantum dots photocatalysts for efficient hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Min, Shixiong, E-mail: sxmin@nun.edu.cn [School of Chemistry and Chemical Engineering, Beifang University of Nationalities, Yinchuan, 750021, Ningxia Province (China); Hou, Jianhua; Lei, Yonggang; Ma, Xiaohua [School of Chemistry and Chemical Engineering, Beifang University of Nationalities, Yinchuan, 750021, Ningxia Province (China); Lu, Gongxuan [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000 (China)

2017-02-28

Highlights: • TiO{sub 2}/GQDs composites were prepared by a facile one-step hydrothermal method. • GQDs were strongly coupled onto the surface of TiO{sub 2} nanoparticles by this method. • The TiO{sub 2}/GQDs showed enhanced light absorption and charge separation efficiency. • The TiO{sub 2}/GQDs exhibited higher photocatalytic H{sub 2} evolution activity than pure TiO{sub 2}. • GQDs play synergistic roles by acting as both photosensitizer and electron acceptor. - Abstract: The coupling of semiconductor photocatalysts with graphene quantum dots (GQDs) has been proven to be an effective strategy to enhance the photocatalytic and photoelectrical conversion performances of the resulted composites; however, the preparation of semiconductor/GQDs composites usually involves several time-inefficient and tedious post-treatment steps. Herein, we present a facile one-step hydrothermal route for the preparation of GQDs coupled TiO{sub 2} (TiO{sub 2}/GQDs) photocatalysts using 1,3,6-trinitropyrene (TNP) as the sole precursor of GQDs. During the hydrothermal process, TNP molecules undergo an intramolecular fusion to form GQDs, which simultaneously decorate on the surface of TiO{sub 2} nanoparticles, leading to a strong surface interaction between the two components. The effective coupling of GQDs on TiO{sub 2} can effectively extend the light absorption of the TiO{sub 2} to visible region and enhance the charge separation efficiency of TiO{sub 2}/GQDs composites as a result of GQDs acting as a photosensitizer and an excellent electron acceptor. These key advances make the TiO{sub 2}/GQDs photocatalyst highly active towards the H{sub 2} evolution reaction, resulting in 7 and 3 times higher H{sub 2} evolution rate and photocurrent response at optimal GQDs content than TiO{sub 2} alone, respectively. This study provides a new methodology for the development of high-performance GQDs modified semiconductor photocatalysts for energy conversion applications.

Hydrogen: it's now. Hydrogen, essential today, indispensable tomorrow. Power-to-Gas or how to meet the challenge of electricity storage. To develop hydrogen mobility. Hydrogen production modes and scope of application of the IED directive - Interview. Regulatory evolutions needed for an easier deployment of hydrogen energy technologies for a clean mobility. Support of the Community's policy to hydrogen and to fuel cells

International Nuclear Information System (INIS)

Mauberger, Pascal; Boucly, Philippe; Quint, Aliette; Pierre, Helene; Lucchese, Paul; Bouillon-Delporte, Valerie; Chauvet, Bertrand; Ferrari, Fabio; Boivin, Jean-Pierre

2015-01-01

Published by the French Association for Hydrogen and Fuel Cells (AFHYPAC), this document first outlines how hydrogen can reduce our dependence on fossil energies, how it supports the development of electric mobility to reduce CO 2 emissions by transports, how it enables a massive storage of energy as a support to renewable energies deployment and integration, and how hydrogen can be a competitiveness driver. Then two contributions address technical solutions, the first one being Power-to-Gas as a solution to energy storage (integration of renewable energies, a mean for massive storage of electricity, economic conditions making the first deployments feasible, huge social and economical benefits, necessity of creation of an adapted legal and economic framework), and the second one being the development of hydrogen-powered mobility (a major societal concern for air quality, strategies of car manufacturers in the world, necessity of a favourable framework, the situation of recharging infrastructures). Two contributions address the legal framework regarding hydrogen production modes and the scope of application of the European IED directive on industrial emissions, and the needed regulatory evolutions for an easier deployment of Hydrogen-energy technologies for a clean mobility. A last article comments the evolution of the support of European policies to hydrogen and fuel cells through R and d programs, presents the main support program (FCH JU) and its results, other European financing and support policy, and discusses perspectives, notably for possible financing mechanisms

Decomposition of water and production of H{sub 2} using semiconductor-photocatalytic effect induced by gamma ray from high radioactive waste

Energy Technology Data Exchange (ETDEWEB)

Wada, Y; Kawaguchi, K; Myouchin, M [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works

1996-12-31

The technology of the radiolytic decomposition of water leading to hydrogen production was demonstrated to explore a new field in the utilization of radiation and radioactive elements. The technology used consisted of a photoassisted catalytic method which has been generally investigated for photocatalysis using a semiconductor and light in an electrochemical study. In our study, gamma radiation from Co-60 was used instead of light, and a significant amount of evolved hydrogen was detected. Our preliminary experiments proved the possibility of converting the energy ionizing radiation (gamma radiation) into chemical energy (hydrogen) using a semiconductor-photocatalytic effect. (author).

Conversion of carbohydrate into hydrogen fuel by a photocatalytic process

Energy Technology Data Exchange (ETDEWEB)

Kawai, T; Sakata, T

1980-01-01

The conversion of carbohydrates into H by a photocatalytic process is described. Powders of RuO/sub 2/, TiO/sub 2/, and Pt (weight ratio 10:100:5) were dissolved in H/sub 2/O containing sugar, starch, or cellulose and irradiated with UV. The cellulose reaction was also performed in 6M NaOH. The RuO/sub 2/-TiO/sub 2/-Pt powder acts as an electrochemical microcell; light of energy larger than the band gap of TiO/sub 2/ produces electron-hole pairs which separate and produce redox reactions at the particle-solution interface. The gases evolved using H/sub 2/O were mainly H and CO/sub 2/. H and Na/sub 2/CO/sub 3/ or NaHCO/sub 3/ were produced on irradiation of the NaOH solution at increased rates with respect to reactions in water.

Platinum Group Metal-free Catalysts for Hydrogen Evolution Reaction in Microbial Electrolysis Cells.

Science.gov (United States)

Yuan, Heyang; He, Zhen

2017-07-01

Hydrogen gas is a green energy carrier with great environmental benefits. Microbial electrolysis cells (MECs) can convert low-grade organic matter to hydrogen gas with low energy consumption and have gained a growing interest in the past decade. Cathode catalysts for the hydrogen evolution reaction (HER) present a major challenge for the development and future applications of MECs. An ideal cathode catalyst should be catalytically active, simple to synthesize, durable in a complex environment, and cost-effective. A variety of noble-metal free catalysts have been developed and investigated for HER in MECs, including Nickel and its alloys, MoS 2 , carbon-based catalysts and biocatalysts. MECs in turn can serve as a research platform to study the durability of the HER catalysts. This personal account has reviewed, analyzed, and discussed those catalysts with an emphasis on synthesis and modification, system performance and potential for practical applications. It is expected to provide insights into the development of HER catalysts towards MEC applications. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A mathematical model for hydrogen evolution in an electrochemical cell and experimental validation

International Nuclear Information System (INIS)

Mahmut D Mat; Yuksel Kaplan; Beycan Ibrahimoglu; Nejat Veziroglu; Rafig Alibeyli; Sadiq Kuliyev

2006-01-01

Electrochemical reaction is largely employed in various industrial areas such as hydrogen production, chlorate process, electroplating, metal purification etc. Most of these processes often take place with gas evaluation on the electrodes. Presence of gas phase in the liquid phase makes the problem two-phase flow which is much knowledge available from heat transfer and fluid mechanics studies. The motivation of this study is to investigate hydrogen release in an electrolysis processes from two-phase flow point of view and investigate effect of gas release on the electrolysis process. Hydrogen evolution, flow field and current density distribution in an electrochemical cell are investigated with a two-phase flow model. The mathematical model involves solutions of transport equations for the variables of each phase with allowance for inter phase transfer of mass and momentum. An experimental set-up is established to collect data to validate and improve the mathematical model. Void fraction is determined from measurement of resistivity changes in the system due to the presence of bubbles. A good agreement is obtained between numerical results and experimental data. (authors)

Macroporous Inverse Opal-like MoxC with Incorporated Mo Vacancies for Significantly Enhanced Hydrogen Evolution.

Science.gov (United States)

Li, Feng; Zhao, Xianglong; Mahmood, Javeed; Okyay, Mahmut Sait; Jung, Sun-Min; Ahmad, Ishfaq; Kim, Seok-Jin; Han, Gao-Feng; Park, Noejung; Baek, Jong-Beom

2017-07-25

The hydrogen evolution reaction (HER) is one of the most important pathways for producing pure and clean hydrogen. Although platinum (Pt) is the most efficient HER electrocatalyst, its practical application is significantly hindered by high-cost and scarcity. In this work, an Mo x C with incorporated Mo vacancies and macroporous inverse opal-like (IOL) structure (Mo x C-IOL) was synthesized and studied as a low-cost efficient HER electrocatalyst. The macroporous IOL structure was controllably fabricated using a facile-hard template strategy. As a result of the combined benefits of the Mo vacancies and structural advantages, including appropriate hydrogen binding energy, large exposed surface, robust IOL structure and fast mass/charge transport, the synthesized Mo x C-IOL exhibited significantly enhanced HER electrocatalytic performance with good stability, with performance comparable or superior to Pt wire in both acidic and alkaline solutions.

Solar photocatalytic generation of hydrogen under ultraviolet-visible ...

Indian Academy of Sciences (India)

Administrator

solar energy has been regarded as an attractive solution to resolve the global energy ... simultaneous hydrogen production and H2S decomposi- tion is a highly ... of CdCO3 and ZnCO3 in dilute acetic acid at 60–70°C. Mixing slowly the hot ...

Photocatalytic hydrogen production using visible-light-responsive Ta{sub 3}N{sub 5} photocatalyst supported on monodisperse spherical SiO{sub 2} particulates

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaoming [Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), 4700 KAUST, Thuwal 23955-6900 (Saudi Arabia); School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Zhao, Lan [Advanced Nanofabrication, Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), 4700 KAUST, Thuwal 23955-6900 (Saudi Arabia); Domen, Kazunari [Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Takanabe, Kazuhiro, E-mail: kazuhiro.takanabe@kaust.edu.sa [Division of Physical Sciences and Engineering, KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), 4700 KAUST, Thuwal 23955-6900 (Saudi Arabia)

2014-01-01

photocatalytic activity measurements for H{sub 2} evolution from an aqueous methanol solution. The XRD results demonstrate the expected sequential formation of Ta{sub 2}O{sub 5} layers, followed by Ta{sub 3}N{sub 5} after nitridation on the Ta{sub 2}O{sub 5}/SiO{sub 2} composite. SEM and TEM observations indicate that the obtained Ta{sub 3}N{sub 5}/SiO{sub 2} sub-microspheres have a uniform size distribution with high crystallinity and an obvious core–shell structure. The presence of support maintained the intrinsic photocatalytic activity of Ta{sub 3}N{sub 5} nanoparticles, but it did drastically improve the dispersion of the photocatalysts in the solution. This study proposes the use of an inert support in photocatalytic reactors to improve ease of handling the powder photocatalyst for gas-phase photocatalysis and the suspension of the solution, controlling nature of light harvesting and degree of scattering of the photoreactor.

Co-axial heterostructures integrating palladium/titanium dioxide with carbon nanotubes for efficient electrocatalytic hydrogen evolution

Science.gov (United States)

Valenti, Giovanni; Boni, Alessandro; Melchionna, Michele; Cargnello, Matteo; Nasi, Lucia; Bertoni, Giovanni; Gorte, Raymond J.; Marcaccio, Massimo; Rapino, Stefania; Bonchio, Marcella; Fornasiero, Paolo; Prato, Maurizio; Paolucci, Francesco

2016-12-01

Considering the depletion of fossil-fuel reserves and their negative environmental impact, new energy schemes must point towards alternative ecological processes. Efficient hydrogen evolution from water is one promising route towards a renewable energy economy and sustainable development. Here we show a tridimensional electrocatalytic interface, featuring a hierarchical, co-axial arrangement of a palladium/titanium dioxide layer on functionalized multi-walled carbon nanotubes. The resulting morphology leads to a merging of the conductive nanocarbon core with the active inorganic phase. A mechanistic synergy is envisioned by a cascade of catalytic events promoting water dissociation, hydride formation and hydrogen evolution. The nanohybrid exhibits a performance exceeding that of state-of-the-art electrocatalysts (turnover frequency of 15000 H2 per hour at 50 mV overpotential). The Tafel slope of ~130 mV per decade points to a rate-determining step comprised of water dissociation and formation of hydride. Comparative activities of the isolated components or their physical mixtures demonstrate that the good performance evolves from the synergistic hierarchical structure.

Development of the work function approach to the underpotential deposition of metals. Application to the hydrogen evolution reaction

International Nuclear Information System (INIS)

Trasatti, S.

1975-01-01

A theory is developed for the underpotential deposition of metals. Concepts are then extended to oxygen and hydrogen adsorption. Analysis of results shows that, unlike oxygen adsorption, hydrogen adsorption in solution probably follows a different pattern with respect to the gas phase situation. The hydrogen evolution reaction is discussed in the light of the above findings and it is shown that usual concepts regarding the reactivity scale of metals towards hydrogen should be reconsidered taking into account solvent and entropy effects. The latters can account for the behaviour of sp-metals. The formers are important with transition metals. The final picture is consistent with the idea that M-H 2 O interactions are much stronger on transition than on sp-metals. (orig.) [de

Noble metals can have different effects on photocatalysis over metal-organic frameworks (MOFs): a case study on M/NH₂-MIL-125(Ti) (M=Pt and Au).

Science.gov (United States)

Sun, Dengrong; Liu, Wenjun; Fu, Yanghe; Fang, Zhenxing; Sun, Fangxiang; Fu, Xianzhi; Zhang, Yongfan; Li, Zhaohui

2014-04-14

M-doped NH2-MIL-125(Ti) (M=Pt and Au) were prepared by using the wetness impregnation method followed by a treatment with H2 flow. The resultant samples were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) analyses, N2-sorption BET surface area, and UV/Vis diffuse reflectance spectroscopy (DRS). The photocatalytic reaction carried out in saturated CO2 with triethanolamine (TEOA) as sacrificial agent under visible-light irradiations showed that the noble metal-doping on NH2-MIL-125(Ti) promoted the photocatalytic hydrogen evolution. Unlike that over pure NH2-MIL-125(Ti), in which only formate was produced, both hydrogen and formate were formed over Pt- and Au-loaded NH2-MIL-125(Ti). However, Pt and Au have different effects on the photocatalytic performance for formate production. Compared with pure NH2-MIL-125(Ti), Pt/NH2-MIL-125(Ti) showed an enhanced activity for photocatalytic formate formation, whereas Au has a negative effect on this reaction. To elucidate the origin of the different photocatalytic performance, electron spin resonance (ESR) analyses and density functional theory (DFT) calculations were carried out over M/NH2-MIL-125(Ti).The photocatalytic mechanisms over M/NH2-MIL-125(Ti) (M=Pt and Au) were proposed. For the first time, the hydrogen spillover from the noble metal Pt to the framework of NH2-MIL-125(Ti) and its promoting effect on the photocatalytic CO2 reduction is revealed. The elucidation of the mechanism on the photocatalysis over M/NH2-MIL-125(Ti) can provide some guidance in the development of new photocatalysts based on MOF materials. This study also demonstrates the potential of using noble metal-doped MOFs in photocatalytic reactions involving hydrogen as a reactant, like hydrogenation reactions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Noble metal nanoparticle-functionalized ZnO nanoflowers for photocatalytic degradation of RhB dye and electrochemical sensing of hydrogen peroxide

DEFF Research Database (Denmark)

Hussain, Muhammad; Sun, Hongyu; Karim, Shafqat

2016-01-01

Flower-like hierarchical Zinc oxide nanostructures synthesized by co-precipitation method have been hydrothermally functionalized with 8 nm Au NPs and 15 nm Ag nanoparticles. The photocatalytic and electrochemical performance of these structures are investigated. XPS studies show that the composite...... exhibits a strong interaction between noble metal nanoparticles (NPs) and Zinc oxide nanoflowers. The PL spectra exhibit UV emission arising due to near band edge transition and show that the reduced PL intensities of Au–ZnO and Ag–ZnO composites are responsible for improved photocatalytic activity arising...

Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production

Science.gov (United States)

Pang, Huan; Wei, Chengzhen; Li, Xuexue; Li, Guochang; Ma, Yahui; Li, Sujuan; Chen, Jing; Zhang, Jiangshan

2014-01-01

Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g-1 at 1.25 A g-1) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 μmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 μmol h-1.

Graphite oxide and molybdenum disulfide composite for hydrogen evolution reaction

Science.gov (United States)

Niyitanga, Theophile; Jeong, Hae Kyung

2017-10-01

Graphite oxide and molybdenum disulfide (GO-MoS2) composite is prepared through a wet process by using hydrolysis of ammonium tetrathiomolybdate, and it exhibits excellent catalytic activity of the hydrogen evolution reaction (HER) with a low overpotential of -0.47 V, which is almost two and three times lower than those of precursor MoS2 and GO. The high performance of HER of the composite attributes to the reduced GO supporting MoS2, providing a conducting network for fast electron transport from MoS2 to electrodes. The composite also shows high stability after 500 cycles, demonstrating a synergistic effect of MoS2 and GO for efficient HER.

Preparation of ZnO Nanoparticles and Photocatalytic H2 Production Activity from Different Sacrificial Reagent Solutions

Science.gov (United States)

Peng, Tian-you; Lv, Hong-jin; Zeng, Peng; Zhang, Xiao-hu

2011-08-01

ZnO nanoparticles were synthesized via a direct precipitation method followed by a heterogeneous azeotropic distillation and calcination processes, and then characterized by X-ray power diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption measurement. The effects of Pt-loading amount, calcination temperature, and sacrificial reagents on the photocatalytic H2 evolution efficiency from the present ZnO suspension were investigated. The experimental results indicate that ZnO nanoparticles calcined at 400 °C exhibit the best photoactivity for the H2 production in comparison with the samples calcined at 300 and 500 °C, and the photocatalytic H2 production efficiency from a methanol solution is much higher than that from a triethanolamine solution. It can be ascribed to the oxidization of methanol also contributes to the H2 production during the photochemical reaction process. Moreover, the photocatalytic mechanism for the H2 production from the present ZnO suspension system containing methanol solution is also discussed in detail.

Cobalt-Embedded Nitrogen-Rich Carbon Nanotubes Efficiently Catalyze Hydrogen Evolution Reaction at All pH Values

Czech Academy of Sciences Publication Activity Database

Zou, X.; Huang, X.; Goswami, A.; Silva, R.; Sathe, B. R.; Mikmeková, Eliška; Asefa, T.

2014-01-01

Roč. 53, č. 17 (2014), s. 4372-4376 ISSN 1433-7851 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : carbon nanotubes * cobalt nanoparticles * electrocatalysis * hydrogen evolution reaction * water splitting Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 11.261, year: 2014

Synthesis and visible-light-driven photocatalytic activity of p–n heterojunction Ag{sub 2}O/NaTaO{sub 3} nanocubes

Energy Technology Data Exchange (ETDEWEB)

Yang, Songbo [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Xu, Dongbo [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Biyi; Luo, Bifu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yan, Xu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013 (China); Xiao, Lisong, E-mail: xiaolisong123@sina.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Shi, Weidong, E-mail: swd1978@ujs.edu.cn [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

2016-10-15

Highlights: • We firstly report a facile way to prepare the visible-light-driven Ag{sub 2}O/NaTaO{sub 3}p–n heterojunction by chemical precipitation method. • The Ag{sub 2}O/NaTaO{sub 3} heterojunction shows the highest photocatalytic activity than the pure NaTaO{sub 3} and Ag{sub 2}O nanoparticles under visible light. • The enhancement of the heterojunction photocatalytic activity was discussed and the photocatalytic mechanism was tested in our paper. • In summary, we think that the Ag{sub 2}O/NaTaO{sub 3} heterojunction with the strong visible light absorption and efficient photocatalytic activity have been extended application in photocatalysis for organic dyes pollutants degradation and purification of water. - Abstract: The constructing of p–n heterojunction photocatalytic system has received much attention in environmental purification and hydrogen generation from water. In this study, an efficient visible-light-driven p–n heterojunction Ag{sub 2}O/NaTaO{sub 3} was successfully prepared by chemical precipitation method at room temperature. It showed an enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation, much higher than those of either individual Ag{sub 2}O or NaTaO{sub 3}. The reactive species scavenger results indicated the superoxide anion radicals (·O{sup 2−}) played key roles in RhB decoloration. From the experimental results and the relative band gap position of these semiconductors, a detailed possible photocatalytic mechanism of the Ag{sub 2}O/NaTaO{sub 3} heterojunction under visible light was proposed. The enhancement of the photocatalytic activity was attributed to the interfacial electronic interaction between NaTaO{sub 3} and Ag{sub 2}O and the high migration efficiency of photogenerated carriers.

Biomimetic hydrogen production

Energy Technology Data Exchange (ETDEWEB)

Krassen, Henning

2009-05-15

Hydrogenases catalyze the reduction of protons to molecular hydrogen with outstanding efficiency. An electrode surface which is covered with active hydrogenase molecules becomes a promising alternative to platinum for electrochemical hydrogen production. To immobilize the hydrogenase on the electrode, the gold surface was modified by heterobifunctional molecules. A thiol headgroup on one side allowed the binding to the gold surface and the formation of a self-assembled monolayer. The other side of the molecules provided a surface with a high affinity for the hydrogenase CrHydA1 from Chlamydomonas reinhardtii. With methylviologen as a soluble energy carrier, electrons were transferred from carboxy-terminated electrodes to CrHydA1 and conducted to the active site (H-cluster), where they reduce protons to molecular hydrogen. A combined approach of surface-enhanced infrared absorption spectroscopy, gas chromatography, and surface plasmon resonance allowed quantifying the hydrogen production on a molecular level. Hydrogen was produced with a rate of 85 mol H{sub 2} min{sup -1} mol{sup -1}. On a 1'- benzyl-4,4'-bipyridinum (BBP)-terminated surface, the electrons were mediated by the monolayer and no soluble electron carrier was necessary to achieve a comparable hydrogen production rate (approximately 50% of the former system). The hydrogen evolution potential was determined to be -335 mV for the BBP-bound hydrogenase and -290 mV for the hydrogenase which was immobilized on a carboxy-terminated mercaptopropionic acid SAM. Therefore, both systems significantly reduce the hydrogen production overpotential and allow electrochemical hydrogen production at an energy level which is close to the commercially applied platinum electrodes (hydrogen evolution potential of -270 mV). In order to couple hydrogen production and photosynthesis, photosystem I (PS1) from Synechocystis PCC 6803 and membrane-bound hydrogenase (MBH) from Ralstonia eutropha were bound to each other

Amorphous nickel/cobalt tungsten sulfide electrocatalysts for high-efficiency hydrogen evolution reaction

Energy Technology Data Exchange (ETDEWEB)

Yang, Lun [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Wu, Xinglong, E-mail: hkxlwu@nju.edu.cn [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Department of Physics, NingBo University, NingBo 315001 (China); Zhu, Xiaoshu [Center for Analysis and Testing, Nanjing Normal University, Nanjing 210093 (China); He, Chengyu; Meng, Ming; Gan, Zhixing [Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics and Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2015-06-30

Graphical abstract: - Highlights: • Amorphous nickel/cobalt tungsten sulfides were synthesized by a thermolytic process. • Amorphous NiWS and CoWS could realize hydrogen evolution efficiently. • Ni/Co promotion and annealing alter the porous structure and chemical bonding states. • Active sites on the surface of amorphous WS{sub x} are increased with Ni or Co doping. • Amorphous NiWS and CoWS have immense potentials in water splitting devices. - Abstract: The hydrogen evolution reaction (HER), an appealing solution for future energy supply, requires efficient and inexpensive electrocatalysts with abundant active surface sites. Although crystalline MoS{sub 2} and WS{sub 2} are promising candidates, their activity is dominated by edge sites. Amorphous tungsten sulfide prepared so far lacks the required active sites and its application has thus been hampered. In this work, nickel and cobalt incorporated amorphous tungsten sulfide synthesized by a thermolytic process is demonstrated to enhance the HER efficiency dramatically. The amorphous nickel tungsten sulfide (amorphous NiWS) annealed at 210 °C delivers the best HER performance in this system boasting a Tafel slope of 55 mV per decade and current density of 8.6 mA cm{sup −2} at 250 mV overpotential in a sustained test for 24 h. The introduction of Ni or Co into the catalyst and subsequent thermal treatment alters the porous structure and chemical bonding states thereby increasing the density of active sites on the surface.

CdS nanoparticles/CeO{sub 2} nanorods composite with high-efficiency visible-light-driven photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

You, Daotong; Pan, Bao; Jiang, Fan; Zhou, Yangen; Su, Wenyue, E-mail: suweny@fzu.edu.cn

2016-02-15

Graphical abstract: Coupling CdS with CeO{sub 2} can effectively improve the light-harvesting ability of wide-band gap CeO{sub 2} NRs as the photoinduced electrons on the conduction band of CdS are transfered to the conduction band of CeO{sub 2}. - Highlights: • Coupling CdS can effectively improve the light-harvesting ability of wide-band gap CeO{sub 2}. • CdS/CeO{sub 2} composites show high photocatalytic activity under visible light irradiation. • The mechanism of photocatalytic H{sub 2} evolution over CdS/CeO{sub 2} was proposed. - Abstract: Different mole ratios of CdS nanoparticles (NPs)/CeO{sub 2} nanorods (NRs) composites with effective contacts were synthesized through a two-step hydrothermal method. The crystal phase, microstructure, optical absorption properties, electrochemical properties and photocatalytic H{sub 2} production activity of these composites were investigated. It was concluded that the photogenerated charge carriers in the CdS NPs/CeO{sub 2} NRs composite with a proper mole ratio (1:1) exhibited the longest lifetime and highest separation efficiency, which was responsible for the highest H{sub 2}-production rate of 8.4 mmol h{sup −1} g{sup −1} under visible-light irradiation (λ > 420 nm). The superior photocatalytic H{sub 2} evolution properties are attributed to the transfer of visible-excited electrons of CdS NPs to CeO{sub 2} NRs, which can effectively extend the light absorption range of wide-band gap CeO{sub 2} NRs. This work provides feasible routes to develop visible-light responsive CeO{sub 2}-based nanomaterial for efficient solar utilization.

Microstructural evolution during hydrogen sorption cycling of Mg-FeTi nanolayered composites

Energy Technology Data Exchange (ETDEWEB)

Kalisvaart, W.P., E-mail: pkalisvaart@gmail.com [Chemical and Materials Engineering, University of Alberta and National Research Council Canada, National Institute for Nanotechnology, Edmonton, AB, T6G 2V4 (Canada); Kubis, Alan; Danaie, Mohsen; Amirkhiz, Babak Shalchi [Chemical and Materials Engineering, University of Alberta and National Research Council Canada, National Institute for Nanotechnology, Edmonton, AB, T6G 2V4 (Canada); Mitlin, David, E-mail: dmitlin@ualberta.ca [Chemical and Materials Engineering, University of Alberta and National Research Council Canada, National Institute for Nanotechnology, Edmonton, AB, T6G 2V4 (Canada)

2011-03-15

This paper describes the microstructural evolution of Mg-FeTi mutlilayered hydrogen storage materials during extended cycling. A 28 nm Mg-5 nm FeTi multilayer has comparable performance to a cosputtered material with an equivalent composition (Mg-10%Fe-10%Ti), which is included as a baseline case. At 200 deg. C, the FeTi layers act as a barrier, preventing agglomeration of Mg particles. At 300 deg. C, the initial structure of the multilayer is preserved up to 35 cycles, followed by fracturing of the Mg layers in the in-plane direction and progressive delamination of the FeTi layers as observed by electron microscopy. Concurrently, an increase in the Mg grain size was observed from 32 to 76 nm between cycles 35 and 300. As a result, the absorption kinetics deteriorate with cycling, although 90% of the total capacity is still absorbed within 2 min after as many as 300 cycles. The desorption kinetics, on the other hand, remain rapid and stable, and complete desorption of 4.6 wt.% H is achieved in 1.5 min at ambient desorption pressure. In addition to showing good hydrogen storage performance, multilayers are an excellent model system for studying the relation between microstructure and hydrogen absorption/desorption kinetics.

Microstructural evolution during hydrogen sorption cycling of Mg-FeTi nanolayered composites

International Nuclear Information System (INIS)

Kalisvaart, W.P.; Kubis, Alan; Danaie, Mohsen; Amirkhiz, Babak Shalchi; Mitlin, David

2011-01-01

This paper describes the microstructural evolution of Mg-FeTi mutlilayered hydrogen storage materials during extended cycling. A 28 nm Mg-5 nm FeTi multilayer has comparable performance to a cosputtered material with an equivalent composition (Mg-10%Fe-10%Ti), which is included as a baseline case. At 200 deg. C, the FeTi layers act as a barrier, preventing agglomeration of Mg particles. At 300 deg. C, the initial structure of the multilayer is preserved up to 35 cycles, followed by fracturing of the Mg layers in the in-plane direction and progressive delamination of the FeTi layers as observed by electron microscopy. Concurrently, an increase in the Mg grain size was observed from 32 to 76 nm between cycles 35 and 300. As a result, the absorption kinetics deteriorate with cycling, although 90% of the total capacity is still absorbed within 2 min after as many as 300 cycles. The desorption kinetics, on the other hand, remain rapid and stable, and complete desorption of 4.6 wt.% H is achieved in 1.5 min at ambient desorption pressure. In addition to showing good hydrogen storage performance, multilayers are an excellent model system for studying the relation between microstructure and hydrogen absorption/desorption kinetics.

Surface Functionalization of g-C 3 N 4 : Molecular-Level Design of Noble-Metal-Free Hydrogen Evolution Photocatalysts

KAUST Repository

Chen, Yin; Lin, Bin; Yu, Weili; Yang, Yong; Bashir, Shahid M.; Wang, Hong; Takanabe, Kazuhiro; Idriss, Hicham; Basset, Jean-Marie

2015-01-01

A stable noble-metal-free hydrogen evolution photocatalyst based on graphite carbon nitride (g-C3N4) was developed by a molecular-level design strategy. Surface functionalization was successfully conducted to introduce a single nickel active site

Photocatalyst based on titanium or iron semiconductors for the generation of hydrogen from water upon solar irradiation

OpenAIRE

Serra, Marco

2016-01-01

The objective of present thesis is to prepare and evaluate photocatalyst for hydrogen generation from water methanol mixture using solar light. This general objective has been accomplished by applying different methodology in material preparation as well as exploring the photocatalytic activity of novel semiconductors. In this way after a general introduction to the feed showing the relevance of solar fuels and in particular hydrogen generation, the...

Mace-like hierarchical MoS2/NiCo2S4 composites supported by carbon fiber paper: An efficient electrocatalyst for the hydrogen evolution reaction

Science.gov (United States)

Sun, Lan; Wang, Tao; Zhang, Long; Sun, Yunjin; Xu, Kewei; Dai, Zhengfei; Ma, Fei

2018-02-01

The rational design and preparation of earth-abundant, stable and efficient electrocatalysts for hydrogen production is currently the subject in extensive scientific and technological researches toward the future of a clean-energy society. Herein, a mace-like MoS2/NiCo2S4 hierarchical structure is designed and synthesized on carbon fiber paper via a facile hydrothermal method, and evaluated as electrocatalyst for hydrogen evolution reaction. In the MoS2/NiCo2S4/carbon fiber paper hierarchical structures, MoS2 nanosheets are dispersively distributed on the surface of NiCo2S4 nanowires, which provides an enlarged surface area, abundant interfaces and catalytic active sites. As for hydrogen evolution reaction, such MoS2/NiCo2S4/carbon fiber paper heterostructures give rise to a hydrogen evolution reaction catalytic current density of 10 mA cm-2 with a lower overpotential of 139 mV and a smaller Tafel slope of 37 mV·dec-1 than those of MoS2/carbon fiber paper and NiCo2S4/carbon fiber paper counterparts, exhibiting a prominent electrocatalytic performance. Moreover, the electrocatalytic properties change little after 5000 CV cycles and continual electrolysis for 12 h without obvious decay, respectively, demonstrating high durability and stability. The excellent hydrogen evolution reaction performances endow the hierarchical configuration MoS2/NiCo2S4/carbon fiber paper with promising alternative in HER and other related renewable energy fields.

Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand

International Nuclear Information System (INIS)

Kim, Hye-Jin; Leitch, Megan; Naknakorn, Bhanuphong; Tilton, Robert D.; Lowry, Gregory V.

2017-01-01

Highlights: • Reactivity of nZVI increased linearly with nZVI concentration above 10 g/L, but was non-linear below 10 g/L. • nZVI reactivity with PCE is more sensitive to solution redox potential than solution pH. • Mass transfer limits the reactivity of emplaced nZVI under typical groundwater flow velocity. • Lowering pH increases H_2 evolution from nZVI more than reactivity with PCE. • Design of nZVI remediation strategies should consider mass loading and flow velocity on performance and lifetime. - Abstract: The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW = 12 K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7 × 10"−"4 L hr"−"1 m"−"2) and hydrogen evolution rate constant (1.4 nanomol L hr"−"1 m"−"2) were independent of nZVI concentration above 10 g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10 g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H_2 evolution was explained by differences in pH and E_h at each nZVI mass loading; PCE reactivity increased when solution E_h decreased, and the H_2 evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5 g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime.

Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand

Energy Technology Data Exchange (ETDEWEB)

Kim, Hye-Jin [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Chemical Research Division, Environmental Health Research Department, National Institute of Environmental Research, Incheon 404-708 (Korea, Republic of); Leitch, Megan [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Naknakorn, Bhanuphong [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Tilton, Robert D. [Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Lowry, Gregory V., E-mail: glowry@cmu.edu [Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States); Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890 (United States)

2017-01-15

Highlights: • Reactivity of nZVI increased linearly with nZVI concentration above 10 g/L, but was non-linear below 10 g/L. • nZVI reactivity with PCE is more sensitive to solution redox potential than solution pH. • Mass transfer limits the reactivity of emplaced nZVI under typical groundwater flow velocity. • Lowering pH increases H{sub 2} evolution from nZVI more than reactivity with PCE. • Design of nZVI remediation strategies should consider mass loading and flow velocity on performance and lifetime. - Abstract: The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW = 12 K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7 × 10{sup −4} L hr{sup −1} m{sup −2}) and hydrogen evolution rate constant (1.4 nanomol L hr{sup −1} m{sup −2}) were independent of nZVI concentration above 10 g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10 g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H{sub 2} evolution was explained by differences in pH and E{sub h} at each nZVI mass loading; PCE reactivity increased when solution E{sub h} decreased, and the H{sub 2} evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5 g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime.

Temperature effect on the photoinduced reduction of methyl viologen with several sensitizers and the evolution of hydrogen from water

Energy Technology Data Exchange (ETDEWEB)

Nenadovic, M.T.; Micic, O.I.; Rajh, T.; Savic, D.

1983-01-01

Irradiation by visible light of an aqueous solution containing a photosensitizer, methyl viologen (MV/sup 2 +/) and ethylenediaminetetraacetic acid leads to the formation of the reduced form of methyl viologen (MV/sup +/). The quantum yield for the formation of MV/sup +/ depends strongly on the time during which the formation is observed owing to the reaction of MV/sup +/ with oxidative products and its reduction to MV/sup 0/. Proflavin, acridine yellow and ruthenium(II)tris(2,2-bipyridyl) were used as photosensitizers and showed the same ability to promote hydrogen evolution. When CdS was used as a sensitizer a factor of 10 less hydrogen was obtained than when the dyes were used. The redox catalysts platinum, Pt-TiO/sub 2/-RuO/sub 2/ and Pt-CdS in colloidal systems showed approximately the same activity towards the reduction of water. The reduction of MV/sup 2 +/ and the evolution of hydrogen were enhanced at higher temperatures (70/sup 0/C). The optimum conditions for water reduction on redox catalysts in colloidal system under continuous illumination are analysed.

Modification of molybdenum disulfide in methanol solvent for hydrogen evolution reaction

Science.gov (United States)

Niyitanga, Theophile; Jeong, Hae Kyung

2018-05-01

Molybdenum disulfide is a promising catalyst to replace the expensive platinum as an electrocatalyst but needs to be modified to present excellent electrocatalytic properties. Herein, we successfully modify molybdenum disulfide in methanol solvent for hydrogen evolution reaction by using a simple hydrothermal method. Overpotential reduced to -0.6 V from -1.5 V, and energy band gap decreased from 1.73 eV to 1.58 eV after the modification. The modified molybdenum disulfide also demonstrated lower resistance (42 Ω) at high frequency (1000 kHz) compared with that (240 Ω) of the precursor, showing that conductivity of the modified molybdenum disulfide has improved.

Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production

Science.gov (United States)

Pang, Huan; Wei, Chengzhen; Li, Xuexue; Li, Guochang; Ma, Yahui; Li, Sujuan; Chen, Jing; Zhang, Jiangshan

2014-01-01

Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g−1 at 1.25 A g−1) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 μmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 μmol h−1. PMID:24389929

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

KAUST Repository

Garcia Esparza, Angel T.; Shinagawa, Tatsuya; Ould-Chikh, Samy; Qureshi, Muhammad; Peng, Xuyuan; Wei, Nini; Anjum, Dalaver H.; Clo, Alain M.; Weng, Tsu-Chien; Nordlund, Dennis; Sokaras, Dimosthenis; Kubota, Jun; Domen, Kazunari; Takanabe, Kazuhiro

2017-01-01

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

An Oxygen-Insensitive Hydrogen Evolution Catalyst Coated by a Molybdenum-Based Layer for Overall Water Splitting

KAUST Repository

Garcia Esparza, Angel T.

2017-04-13

For overall water-splitting systems, it is essential to establish O2 -insensitive cathodes that allow cogeneration of H2 and O2 . An acid-tolerant electrocatalyst is described, which employs a Mo-coating on a metal surface to achieve selective H2 evolution in the presence of O2 . In operando X-ray absorption spectroscopy identified reduced Pt covered with an amorphous molybdenum oxyhydroxide hydrate with a local structural order composed of polyanionic trimeric units of molybdenum(IV). The Mo layer likely hinders O2 gas permeation, impeding contact with active Pt. Photocatalytic overall water splitting proceeded using MoOx /Pt/SrTiO3 with inhibited water formation from H2 and O2 , which is the prevailing back reaction on the bare Pt/SrTiO3 photocatalyst. The Mo coating was stable in acidic media for multiple hours of overall water splitting by membraneless electrolysis and photocatalysis.

Enhancement of olive mill wastewater biodegradation by homogeneous and heterogeneous photocatalytic oxidation

Energy Technology Data Exchange (ETDEWEB)

Badawy, M.I.; Gohary, F.El. [Water Pollution Research Department, National Research Centre (NRC), Dokki, Cairo 11312 (Egypt); Ghaly, M.Y., E-mail: ghalynrc@yahoo.com [Chemical Engineering and Pilot Plant Department, National Research Centre (NRC), Dokki, Cairo (Egypt); Ali, M.E.M. [Water Pollution Research Department, National Research Centre (NRC), Dokki, Cairo 11312 (Egypt)

2009-09-30

Olive mills wastewater (OMW) is characterized by its high organic content and refractory compounds. In this study, an advanced technology for the treatment of the recalcitrant contaminants of OMW has been investigated. The technique used was either photo-Fenton as homogeneous photocatalytic oxidation or UV/semi-conductor catalyst (such as TiO{sub 2}, ZrO{sub 2} and FAZA) as heterogeneous photocatalytic oxidation for treatment of OMW. For both the processes, the effect of irradiation time, amounts of photocatalysts and semi-conductors, and initial concentration of hydrogen peroxide has been studied. At the optimum conditions, photo-Fenton process achieved COD, TOC, lignin (total phenolic compounds) and total suspended solids (TSSs) removal values of 87%, 84%, 97.44% and 98.31%, respectively. The corresponding values for UV/TiO{sub 2} were 68.8%, 67.3%, 40.19% and 48.9%, respectively, after 80 min irradiation time. The biodegradability expressed by BOD{sub 5}/COD ratio for treated wastewater was ranged from 0.66 to 0.8 compared to 0.19 for raw wastewater indicating enhancement of biodegradation.

On the mechanism of hydrogen evolution catalysis by proteins: A case study with bovine serum albumin

Energy Technology Data Exchange (ETDEWEB)

Doneux, Th., E-mail: tdoneux@ulb.ac.b [Chimie Analytique et Chimie des Interfaces, Faculte des Sciences, Universite Libre de Bruxelles, Boulevard du Triomphe 2, CP 255, B-1050 Bruxelles (Belgium); Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno (Czech Republic); Ostatna, Veronika [Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno (Czech Republic); Palecek, Emil, E-mail: palecek@ibp.cz [Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno (Czech Republic)

2011-10-30

Highlights: > Proteins catalyse hydrogen evolution at mercury electrodes. > The adsorbed protein is the mediator and the buffer proton donor is the substrate. > The characteristics of the catalytic peak are connected to the protein properties. - Abstract: The catalysis of the hydrogen evolution reaction (HER) by proteins has been known for decades but was only recently found to be useful for electroanalytical purposes. The mechanism of the catalytic process is investigated at hanging mercury drop electrodes by cyclic voltammetry, with bovine serum albumin as a model system. It is shown that the catalyst is the protein in the adsorbed state. The influence of various parameters such as the accumulation time, scan rate or buffer concentration is studied, and interpreted in the framework of a surface catalytic mechanism. Under the experimental conditions used in the work, a 'total catalysis' phenomenon takes place, the rate of HER being limited by the diffusion of the proton donor. The adequacy of the existing models is discussed, leading to a call for the development of more refined models.

Photocatalytic hydrogen generation over Eosin Y-Sensitized TS-1 zeolite

International Nuclear Information System (INIS)

Zhang Xiaojie; Jin Zhiliang; Li Yuexiang; Li Shuben; Lu Gongxuan

2008-01-01

Eosin Y-sensitized TS-1 zeolite was studied for the photo-reduction of water into hydrogen driven by visible light (λ ≥ 420 nm). The optimal pH and weight ratio between Eosin Y and TS-1 zeolite is 7 and 1/8, respectively. In the presence of triethanolamine (TEA) as an electron donor, the highest rate of hydrogen generation and apparent quantum efficiency are 34 μmol h -1 and 9.4%, respectively, under visible light irradiation (λ ≥ 420 nm). Short-term stability test indicates that the catalyst is rather stable during 50 h photoreaction

Photocatalytic hydrogen generation over Eosin Y-Sensitized TS-1 zeolite

Energy Technology Data Exchange (ETDEWEB)

Zhang Xiaojie [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Tianshui Zhong Road 18, Lanzhou 730000 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100101 (China); Jin Zhiliang [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Tianshui Zhong Road 18, Lanzhou 730000 (China); Li Yuexiang [Department of Chemistry, Nanchang University, Nanjing Road 245, Nanchang 330047 (China); Li Shuben [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Tianshui Zhong Road 18, Lanzhou 730000 (China); Lu Gongxuan [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Tianshui Zhong Road 18, Lanzhou 730000 (China)], E-mail: gxlu@lzb.ac.cn

2008-05-30

Eosin Y-sensitized TS-1 zeolite was studied for the photo-reduction of water into hydrogen driven by visible light ({lambda} {>=} 420 nm). The optimal pH and weight ratio between Eosin Y and TS-1 zeolite is 7 and 1/8, respectively. In the presence of triethanolamine (TEA) as an electron donor, the highest rate of hydrogen generation and apparent quantum efficiency are 34 {mu}mol h{sup -1} and 9.4%, respectively, under visible light irradiation ({lambda} {>=} 420 nm). Short-term stability test indicates that the catalyst is rather stable during 50 h photoreaction.

Hg/HgO electrode and hydrogen evolution potentials in aqueous sodium hydroxide

Energy Technology Data Exchange (ETDEWEB)

Nickell, Ryan A.; Zhu, Wenhua H.; Payne, Robert U.; Cahela, Donald R.; Tatarchuk, Bruce J. [Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, 230 Ross Hall, Auburn University, Auburn, AL 36849 (United States)

2006-10-27

The Hg/HgO electrode is usually utilized as a reference electrode in alkaline solution such as for development of an alkaline hydrogen electrode. The reference electrode provides a suitable reference point but is available from few commercial vendors and suffers from inadequate documentation on potential in varying electrolytes. A new numerical method uses activity, activity coefficients, and a few correlated empirical equations to determine the potential values in both dilute and concentrated sodium hydroxide solutions at temperatures of 0-90{sup o}C and at concentrations of 0.100-12.8mol kg{sub H{sub 2}O}{sup -1}. The computed potentials of the Hg/HgO electrodes versus a normal hydrogen electrode (NHE) at 25{sup o}C and 1atm are 0.1634V for 0.100m, 0.1077V for 1.00m, and 0.0976V for 1.45m NaOH solutions. The Hg/HgO reduction potential further changes to -0.0751V versus NHE and hydrogen evolution potential changes to -0.9916V versus NHE in a solution of 30.0wt.% NaOH at 80{sup o}C. The calculated values are compared with the measured data at 25 and 75{sup o}C. The experimental data agree well with the numerical values computed from the theoretical and empirical equations. (author)

Graphitic Carbon-Based Nanostructures for Energy and Environmental Applications

Science.gov (United States)

Chan, Ka Long Donald

This thesis focuses on the synthesis and characterization of graphitic carbonbased photocatalytic nanostructures for energy and environmental applications. The preparation of carbon- and oxygen-rich graphitic carbon nitride with enhanced photocatalytic hydrogen evolution property was investigated. Composite materials based on graphene quantum dots were also prepared. These composites were used for photocatalytic degradation of organic pollutants and photoelectrocatalytic disinfection. The first part of this thesis describes a facile method for the preparation of carbon- and oxygen-rich graphitic carbon nitride by thermal condensation. Incorporation of carbon and oxygen enhanced the photoresponse of carbon nitride in the visible-light region. After exfoliation, the product was c.a. 45 times more active than bulk graphitic carbon nitride in photocatalytic hydrogen evolution under visible-light irradiation. In the second part, a simple approach to enhance the photocatalytic activity of red phosphorus was developed. Mechanical ball milling was applied to reduce the size of red phosphorus and to deposit graphene quantum dots (GQDs) onto red phosphorus. The product exhibited high visible-light-driven photocatalytic performance in the photodegradation of Rhodamine B. The incorporation of GQDs in titanium dioxide could also extend the absorption spectrum of TiO2 into the visible-light range. The third part of this thesis reports on the fabrication of a visible-light-driven composite photocatalyst of TiO2 nanotube arrays (TNAs) and GQDs. Carboxyl-containing GQDs were covalently coupled to amine-modified TNAs. The product exhibited enhanced photocurrent and high photoelectrocatalytic performance in the inactivation of E. coli under visible-light irradiation. The role of various reactive species in the photoelectrocatalytic process was investigated.

Functional carbon nitride materials - design strategies for electrochemical devices

Czech Academy of Sciences Publication Activity Database

Kessler, F. K.; Zheng, Y.; Schwarz, D.; Merschjann, C.; Schnick, W.; Wang, X.; Bojdys, Michael J.

2017-01-01

Roč. 2, č. 6 (2017), č. článku 17030. ISSN 2058-8437 Institutional support: RVO:61388963 Keywords : photocatalytic hydrogen evolution * visible light irradiation * triazine-based frameworks Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis)

Self-assembled monolayers of n-alkanethiols suppress hydrogen evolution and increase the efficiency of rechargeable iron battery electrodes.

Science.gov (United States)

Malkhandi, Souradip; Yang, Bo; Manohar, Aswin K; Prakash, G K Surya; Narayanan, S R

2013-01-09

Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

Self-Assembled Monolayers of n-Alkanethiols Suppress Hydrogen Evolution and Increase the Efficiency of Rechargeable Iron Battery Electrodes

Energy Technology Data Exchange (ETDEWEB)

Malkhandi, S; Yang, B; Manohar, AK; Prakash, GKS; Narayanan, SR

2013-01-09

Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

Electrocatalysis of the hydrogen evolution reaction by rhenium oxides electrodeposited by pulsed-current

International Nuclear Information System (INIS)

Vargas-Uscategui, Alejandro; Mosquera, Edgar; Chornik, Boris; Cifuentes, Luis

2015-01-01

Highlights: • Rhenium oxides were produced by means of pulsed current electrodeposition over ITO. • The electrocatalytic behavior of rhenium oxides electrodeposited over ITO was studied. • Electrodeposited rhenium oxides showed electrocatalytic behavior increasing the rate of the hydrogen evolution reaction. • The electrocatalysis behavior was explained considering the relative abundance of Re species on the surface of the electrodeposited material. - Abstract: Rhenium oxides are materials of interest for applications in the catalysis of reactions such as those occurring in fuel cells and photoelectrochemical cells. This research work was devoted to the production of rhenium oxide by means of pulsed current electrodeposition for the electrocatalysis of the hydrogen evolution reaction (HER). Rhenium oxides were electrodeposited over a transparent conductive oxide substrate (Indium Tin-doped Oxide – ITO) in an alkaline aqueous electrolyte. The electrodeposition process allowed the production of rhenium oxides islands (200–600 nm) with the presence of three oxidized rhenium species: Re"I"V associated to ReO_2, Re"V"I associated to ReO_3 and Re"V"I"I associated to H(ReO_4)H_2O. Electrodeposited rhenium oxides showed electrocatalytic behavior over the HER and an increase of one order of magnitude of the exchange current density was observed compared to the reaction taking place on the bare substrate. The electrocatalytic behavior varied with the morphology and relative abundance of oxidized rhenium species in the electrodeposits. Finally, two mechanisms of electrocatalysis were proposed to explain experimental results.

Microstructure and kinetics evolution in MgH2–TiO2 pellets after hydrogen cycling

International Nuclear Information System (INIS)

Mirabile Gattia, D.; Di Girolamo, G.; Montone, A.

2014-01-01

Highlights: • MgH 2 was ball milled with TiO 2 anatase phase and expanded graphite to prepare pellets. • Different pellets have been prepared at different compression load. • Pellets were repeatedly cycled under hydrogen pressure to simulate tank exercise and verify their stability. • The compression load highly affects the stability of the pellets to cycling. • Microstructural evolution of the particles due to cycling have been observed. - Abstract: The interest in Mg-based hydrides for solid state hydrogen storage is associated to their capability to reversibly absorb and desorb large amounts of hydrogen. In this work MgH 2 powder with 5 wt.% TiO 2 was ball milled for 10 h. The as-milled nanostructured powder was enriched with 5 wt.% of Expanded Natural Graphite (ENG) and then compacted in cylindrical pellets by cold pressing using different loads. Both the powder and the pellets were subjected to kinetic and thermodynamic tests using a Sievert’s type gas reaction controller, in order to study the microstructural and kinetic changes which took place during repeated H 2 absorption and desorption cycles. The pellets exhibited good kinetic performance and durability, even if the pressure of compaction revealed to be an important parameter for their mechanical stability. Scanning Electron Microscopy observations of as-prepared and cycled pellets were carried out to investigate the evolution of their microstructure. In turn the phase composition before and after cycling was analyzed by X-ray diffraction

Surface modification of g-C3N4 by hydrazine: Simple way for noble-metal free hydrogen evolution catalysts

KAUST Repository

Chen, Yin

2015-11-02

The graphitic carbon nitride (g-C3N4) usually is thought to be an inert material and it’s difficult to have the surface terminated NH2 groups functionalized. By modifying the g-C3N4 surface with hydrazine, the diazanyl group was successfully introduced onto the g-C3N4 surface, which allows the introduction with many other function groups. Here we illustrated that by reaction of surface hydrazine group modified g-C3N4 with CS2 under basic condition, a water electrolysis active group C(=S)SNi can be implanted on the g-C3N4 surface, and leads to a noble metal free hydrogen evolution catalyst. This catalyst has 40% hydrogen evolution efficiency compare to the 3 wt% Pt photo precipitated g-C3N4, with only less than 0.2 wt% nickel.

Surface modification of g-C3N4 by hydrazine: Simple way for noble-metal free hydrogen evolution catalysts

KAUST Repository

Chen, Yin; Lin, Bin; Wang, Hong; Yang, Yong; Zhu, Haibo; Yu, Weili; Basset, Jean-Marie

2015-01-01

The graphitic carbon nitride (g-C3N4) usually is thought to be an inert material and it’s difficult to have the surface terminated NH2 groups functionalized. By modifying the g-C3N4 surface with hydrazine, the diazanyl group was successfully introduced onto the g-C3N4 surface, which allows the introduction with many other function groups. Here we illustrated that by reaction of surface hydrazine group modified g-C3N4 with CS2 under basic condition, a water electrolysis active group C(=S)SNi can be implanted on the g-C3N4 surface, and leads to a noble metal free hydrogen evolution catalyst. This catalyst has 40% hydrogen evolution efficiency compare to the 3 wt% Pt photo precipitated g-C3N4, with only less than 0.2 wt% nickel.

Probing the Surface of Platinum during the Hydrogen Evolution Reaction in Alkaline Electrolyte

Energy Technology Data Exchange (ETDEWEB)

Stoerzinger, Kelsey A. [Physical; Favaro, Marco [Advanced; Joint; Chemical; Ross, Philip N. [Materials; Yano, Junko [Joint; Molecular; Liu, Zhi [State; Division; Hussain, Zahid [Advanced; Crumlin, Ethan J. [Advanced; Joint Center

2017-11-02

Understanding the surface chemistry of electrocatalysts in operando can bring insight into the reaction mechanism, and ultimately the design of more efficient materials for sustainable energy storage and conversion. Recent progress in synchrotron based X-ray spectroscopies for in operando characterization allows us to probe the solid/liquid interface directly while applying an external potential, applied here to the model system of Pt in alkaline electrolyte for the hydrogen evolution reaction (HER). We employ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify the oxidation and reduction of Pt-oxides and hydroxides on the surface as a function of applied potential, and further assess the potential for hydrogen adsorption and absorption (hydride formation) during and after the HER. This new window into the surface chemistry of Pt in alkaline brings insight into the nature of the rate limiting step, the extent of H ad/absorption and it’s persistence at more anodic potentials.

Increasing Solar Absorption for Photocatalysis with Black Hydrogenated Titanium Dioxide Nanocrystals

KAUST Repository

Chen, X.

2011-01-20

When used as a photocatalyst, titanium dioxide (TiO 2) absorbs only ultraviolet light, and several approaches, including the use of dopants such as nitrogen, have been taken to narrow the band gap of TiO 2. We demonstrated a conceptually different approach to enhancing solar absorption by introducing disorder in the surface layers of nanophase TiO 2 through hydrogenation. We showed that disorder-engineered TiO 2 nanocrystals exhibit substantial solar-driven photocatalytic activities, including the photo-oxidation of organic molecules in water and the production of hydrogen with the use of a sacrificial reagent.

Increasing Solar Absorption for Photocatalysis with Black Hydrogenated Titanium Dioxide Nanocrystals

KAUST Repository

Chen, X.; Liu, L.; Yu, P. Y.; Mao, S. S.

2011-01-01

When used as a photocatalyst, titanium dioxide (TiO 2) absorbs only ultraviolet light, and several approaches, including the use of dopants such as nitrogen, have been taken to narrow the band gap of TiO 2. We demonstrated a conceptually different approach to enhancing solar absorption by introducing disorder in the surface layers of nanophase TiO 2 through hydrogenation. We showed that disorder-engineered TiO 2 nanocrystals exhibit substantial solar-driven photocatalytic activities, including the photo-oxidation of organic molecules in water and the production of hydrogen with the use of a sacrificial reagent.

Photocatalytic hydrogen production on SOLECTRO {sup registered} titanium dioxide layers. Development and characterization of an efficient catalyst; Photokatalytische Wasserstoffgewinnung an SOLECTRO {sup registered} -Titandioxidschichten. Entwicklung und Charakterisierung eines geeigneten Katalysators

Energy Technology Data Exchange (ETDEWEB)

Saborowski, Sarah

2010-03-03

A catalyst for photocatalytic hydrogen production from methanol and water was developed on the basis of SOLECTRO {sup registered} titanium dioxide layers. A test facility was constructed in which several modified catalysts could be tested for this reaction. Detailed characterization of the electronic and optical characteristics of these catalysts made it possible to gain deeper insight into the processes involved in the reaction. (orig.) [German] Auf Basis der SOLECTRO {sup registered} -TiO{sub 2} -Schichten wurde ein Katalysator fuer die photokatalytische Wasserstoffdarstellung aus Methanol und Wasser entwickelt. Der Aufbau einer geeigneten Versuchsanlage ermoeglichte es, verschieden modifizierte Katalysatoren fuer diese Reaktion zu testen. Durch die ausfuehrliche Charakterisierung insbesondere der elektronischen und optischen Eigenschaften dieser Katalysatoren konnten vertiefende Erkenntnisse zu den waehrend der Reaktion ablaufenden Prozessen gewonnen werden. (orig.)

Photocatalytic materials and technologies for air purification.

Science.gov (United States)

Ren, Hangjuan; Koshy, Pramod; Chen, Wen-Fan; Qi, Shaohua; Sorrell, Charles Christopher

2017-03-05

Since there is increasing concern for the impact of air quality on human health, the present work surveys the materials and technologies for air purification using photocatalytic materials. The coverage includes (1) current photocatalytic materials for the decomposition of chemical contaminants and disinfection of pathogens present in air and (2) photocatalytic air purification systems that are used currently and under development. The present work focuses on five main themes. First, the mechanisms of photodegradation and photodisinfection are explained. Second, system designs for photocatalytic air purification are surveyed. Third, the photocatalytic materials used for air purification and their characteristics are considered, including both conventional and more recently developed photocatalysts. Fourth, the methods used to fabricate these materials are discussed. Fifth, the most significant coverage is devoted to materials design strategies aimed at improving the performance of photocatalysts for air purification. The review concludes with a brief consideration of promising future directions for materials research in photocatalysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Dodecahedral W@WC Composite as Efficient Catalyst for Hydrogen Evolution and Nitrobenzene Reduction Reactions.