SiO2 stabilized Pt/C cathode catalyst for proton exchange membrane fuel cells

International Nuclear Information System (INIS)

Zhu Tong; Du Chunyu; Liu Chuntao; Yin Geping; Shi Pengfei

2011-01-01

This paper describes the preparation of SiO 2 stabilized Pt/C catalyst (SiO 2 /Pt/C) by the hydrolysis of alkoxysilane, and examines the possibility that the SiO 2 /Pt/C is used as a durable cathode catalyst for proton exchange membrane fuel cells (PEMFCs). TEM and XRD results revealed that the hydrolysis of alkoxysilane did not significantly change the morphology and crystalline structure of Pt particles. The SiO 2 /Pt/C catalyst exhibited higher durability than the Pt/C one, due to the facts that the silica layers covered were beneficial for reducing the Pt aggregation and dissolution as well as increasing the corrosion resistance of supports, although the benefit of silica covering was lower than the case of Pt/CNT catalyst. Also, it was observed that the activity of the SiO 2 /Pt/C catalyst for the oxygen reduction reaction was somewhat reduced compared to the Pt/C one after the silica covering. This reduction was partially due to the low oxygen kinetics as revealed by the rotating-disk-electrode measurement. Silica covering by hydrolysis of only 3-aminopropyl trimethoxysilane is able to achieve a good balance between the durability and activity, leading to SiO 2 /Pt/C as a promising cathode catalyst for PEMFCs.

Synthesis and characterization of the Pt/SiO2 nanocomposite by the sol-gel method

Directory of Open Access Journals (Sweden)

A. Salabat

2011-01-01

Full Text Available The silica supported platinum nanoparticles was synthesized by using the sol-gel method. The possibility of using diamminedinitro platinum (II as Pt precursor and effect of metal precursor concentration on the final Pt nanoparticle size was investigated. A stable silica sol was prepared via hydrolysis of tetraethyl orthosilicate (TEOS as a metal alcoxide and condensation reaction. Subsequently, diamminedinitro platinum (II was added to sol to form the Pt/silica sol. After drying and calcination of the sol, the Pt/SiO2 nanocpmposite has been obtained. Crystallographic information and crystalline size of the synthesized Pt/SiO2 were determined by X-ray diffraction (XRD method. Morphology of the nanoparticles and hydrogen-bonding interaction between silanol groups and amine ligands were characterized by SEM and Fourier transform infrared (FTIR spectra, respectively. Transmission Electron Microscopy (TEM was employed in evaluating the distribution and size of the platinum nanoparticles in the silica.

A new approach for the detection of ethylene using silica-supported palladium complexes.

Science.gov (United States)

Cabanillas-Galán, Patricia; Farmer, Linda; Hagan, Terence; Nieuwenhuyzen, Mark; James, Stuart L; Lagunas, M Cristina

2008-10-06

The coordination of olefins to square-planar Pd(II) and Pt(II) complexes containing 2,9-dimethylphenanthroline ( L1) often involves a change of color associated with a change of geometry at the metal center. In order to obtain suitable colorimetric detectors for ethylene gas, a series of new Pd(II) and Pt(II) compounds with a range of 2,9-disubstituted phenanthroline ligands [2,9-di- n-butyl-1,10-phenanthroline ( L2), 2,9-di- s-butyl-1,10-phenanthroline ( L3), 2,9-diphenyl-1,10-phenanthroline ( L4), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine, L5)] have been prepared and their reactivity toward ethylene investigated both in solution and after depositing the detector compounds on a variety of solid supports. The Pd(II) complex [PdCl 2( L2)] supported on silica undergoes a clear color change upon exposure to ethylene, while remaining stable toward air and water, and forms the basis for new simple colorimetric detectors with potential applications in ethylene pipe-leak detection and the monitoring of fruit ripening. Encouragingly, the detector is able to discriminate between fruit at different stages of ripening. The response of the detector to other volatiles was also examined, and specific color changes were also observed upon exposure to aromatic acetylenes. The crystal structures of four new derivatives, including the ethylene-Pt(II) complex [PtCl 2(C 2H 4)( L2)], are also described.

A Highly Stable and Magnetically Recyclable Nanocatalyst System: Mesoporous Silica Spheres Embedded with FeCo/Graphitic Shell Magnetic Nanoparticles and Pt Nanocatalysts.

Science.gov (United States)

Kim, Da Jeong; Li, Yan; Kim, Yun Jin; Hur, Nam Hwi; Seo, Won Seok

2015-12-01

We have developed a highly stable and magnetically recyclable nanocatalyst system for alkene hydrogenation. The materials are composed of mesoporous silica spheres (MSS) embedded with FeCo/graphitic shell (FeCo/GC) magnetic nanoparticles and Pt nanocatalysts (Pt-FeCo/GC@MSS). The Pt-FeCo/GC@MSS have superparamagnetism at room temperature and show type IV isotherm typical for mesoporous silica, thereby ensuring a large enough inner space (surface area of 235.3 m(2)  g(-1), pore volume of 0.165 cm(3)  g(-1), and pore diameter of 2.8 nm) to undergo catalytic reactions. We have shown that the Pt-FeCo/GC@MSS system readily converts cyclohexene into cyclohexane, which is the only product isolated and Pt-FeCo/GC@MSS can be seperated very quickly by an external magnetic field after the catalytic reaction is finished. We have demonstrated that the recycled Pt-FeCo/GC@MSS can be reused further for the same hydrogenation reaction at least four times without loss in the initial catalytic activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous Catalytic Hydrodeoxygenation of Guaiacol over Pt/SiO2 and Pt/H-MFI-90

Directory of Open Access Journals (Sweden)

Melanie Hellinger

2015-07-01

Full Text Available Hydrodeoxygenation of guaiacol in the presence of 1-octanol was studied in a fixed-bed reactor under mild conditions (50–250 °C over platinum particles supported on silica (Pt/SiO2 and a zeolite with framework type MFI at a Si/Al-ratio of 45 (Pt/H-MFI-90. The deoxygenation selectivity strongly depended on the support and the temperature. Both guaiacol and octanol were rapidly deoxygenated in the presence of hydrogen over Pt/H-MFI-90 at 250 °C to cyclohexane and octane, respectively. In contrast, Pt/SiO2 mostly showed hydrogenation, but hardly any deoxygenation activity. The acidic sites of the MFI-90 support lead to improved deoxygenation performance at the mild temperature conditions of this study. Significant conversions under reaction conditions applied already occurred at temperatures of 200 °C. However, during long-term stability tests, the Pt/H-MFI-90 catalyst deactivated after more than 30 h, probably due to carbon deposition, whereas Pt/SiO2 was more stable. The catalytic activity of the zeolite catalyst could only partly be regained by calcination in air, as some of the acidic sites were lost.

Periodically Arranged Arrays of Dendritic Pt Nanospheres Using Cage-Type Mesoporous Silica as a Hard Template.

Science.gov (United States)

Kani, Kenya; Malgras, Victor; Jiang, Bo; Hossain, Md Shahriar A; Alshehri, Saad M; Ahamad, Tansir; Salunkhe, Rahul R; Huang, Zhenguo; Yamauchi, Yusuke

2018-01-04

Dendritic Pt nanospheres of 20 nm diameter are synthesized by using a highly concentrated surfactant assembly within the large-sized cage-type mesopores of mesoporous silica (LP-FDU-12). After diluting the surfactant solution with ethanol, the lower viscosity leads to an improved penetration inside the mesopores. After Pt deposition followed by template removal, the arrangement of the Pt nanospheres is a replication from that of the mesopores in the original LP-FDU-12 template. Although it is well known that ordered LLCs can form on flat substrates, the confined space inside the mesopores hinders surfactant self-organization. Therefore, the Pt nanospheres possess a dendritic porous structure over the entire area. The distortion observed in some nanospheres is attributed to the close proximity existing between neighboring cage-type mesopores. This new type of nanoporous metal with a hierarchical architecture holds potential to enhance substance diffusivity/accessibility for further improvement of catalytic activity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tin-Platinum catalysts interactions on titania and silica

International Nuclear Information System (INIS)

Nava, N.; Del Angel, P.; Salmones, J.; Baggio-Saitovitch, E.; Santiago, P.

2007-01-01

Pt-Sn was supported on titania and silica, and the resulting interactions between the components in prepared samples and the resulting interactions between the components before and after treatment with hydrogen were characterized by Moessbauer spectroscopy, X-ray diffraction, Rietveld refinement, high-resolution transmission electron microscopy (HRTEM) and catalytic tests data. Results show the presence of Pt and SnO 2 after calcinations, and Pt 3 Sn, PtSn and PtSn 3 after reduction. Rietveld analysis shows that some Ti 4+ are replaced by Sn 4+ atoms in the titania structure. Finally, HRTEM and the practically absence of activity observed confirms that metallic platinum is encapsulated

A Robust Fiber Bragg Grating Hydrogen Gas Sensor Using Platinum-Supported Silica Catalyst Film

Directory of Open Access Journals (Sweden)

Marina Kurohiji

2018-01-01

Full Text Available A robust fiber Bragg grating (FBG hydrogen gas sensor for reliable multipoint-leakage monitoring has been developed. The sensing mechanism is based on shifts of center wavelength of the reflection spectra due to temperature change caused by catalytic combustion heat. The sensitive film which consists of platinum-supported silica (Pt/SiO2 catalyst film was obtained using sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica precursor solution. The atom ratio of Si : Pt was fixed at 13 : 1. A small amount of this solution was dropped on the substrate and dried at room temperature. After that, the film was calcined at 500°C in air. These procedures were repeated and therefore thick hydrogen-sensitive films were obtained. The catalytic film obtained by 20-time coating on quartz glass substrate showed a temperature change 75 K upon exposure to 3 vol.% H2. For realizing robust sensor device, this catalytic film was deposited and FBG portion was directly fixed on titanium substrate. The sensor device showed good performances enough to detect hydrogen gas in the concentration range below lower explosion limit at room temperature. The enhancement of the sensitivity was attributed to not only catalytic combustion heat but also related thermal strain.

Synthesis of Pt-Sn core-shell nanoparticles deposited on SBA-15 modified

Energy Technology Data Exchange (ETDEWEB)

Alvarez-Contreras, L.; Alonso-Lemus, I. [Centro de Investigacion en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnologia (Mexico); Botte, G. G. [Ohio University, Center for Electrochemical Engineering Research, Department of Chemical and Biomolecular Engineering (United States); Verde-Gomez, Y., E-mail: ysmaelverde@yahoo.com [Instituto Tecnologico de Cancun (Mexico)

2013-07-15

A novel one-step synthesis method to prepare Pt-Sn bimetallic nanoparticles supported on mesoporous silica with high surface area (SBA-15, 700 m{sup 2}/g) and narrow pore size distribution (around 9.5 nm) was developed. Tin incorporation plays an important dual role, to create active sites into the silica walls that serve as particles anchors center, and to grow Pt-Sn core-shell nanoparticles. High-resolution transmission and scanning electron microscopy, and X-ray diffraction pattern confirm the formation of the Pt-Sn core-shell type nanoparticles ( Almost-Equal-To 1-10 nm). The metal loading was 2.2 and 2.3 wt% for Pt and Sn, respectively. Electron microscopy results show that the metal nanoparticles were deposited not only on the matrix, but also inside of it. Structural, textural, and morphological features of the SBA-15 were slightly affected after the nanoparticles deposition, maintaining its high surface area. The results obtained suggest that Pt-Sn on SBA-15 could be attractive material for several catalytic applications, due to the narrow particle size distribution achieved (from 1 to 10 nm) the high dispersion on the support, as well as the Pt-Sn alloy developed.Graphical Abstract.

Characterization of Pt catalysts supported in mixed oxides

International Nuclear Information System (INIS)

Perez H, R.; Garcia C, M.A.; Gomez C, A.; Diaz, G.

1999-01-01

The catalytic supports TiO 2 , ZrO 2 and TiO 2 -ZrO 2 were prepared by the sol-gel technique. The incorporation of Pt to the supports was by the classical impregnation method. The catalytic materials were characterized (Pt/TiO 2 , Pt/ZrO 2 and Pt/TiO 2 -ZrO 2 ) by diverse techniques to determine: the texture (BET), evolution of the catalytic materials synthesised after drying and calcination (Infrared spectroscopy) and by Thermogravimetric analysis. (Author)

Selective and regular localization of accessible Pt nanoparticles inside the walls of an ordered silica: Application as a highly active and well-defined heterogeneous catalyst for propene and styrene hydrogenation reactions

KAUST Repository

Boualleg, Malika; Norsic, Sé bastien; Baudouin, David; Sayah, Reine; Quadrelli, Elsje Alessandra; Basset, Jean-Marie; Candy, Jean Pierre; Dé lichè re, Pierre; Pelzer, Katrin; Veyre, Laurent; Thieuleux, Chloé

2011-01-01

We describe here an original methodology related to the "build-the-bottle-around-the-ship" approach yielding a highly ordered silica matrix containing regularly distributed Pt nanoparticles (NPs) located inside the silica walls, Pt@{walls}SiO2. The starting colloidal solution of crystalline Pt nanoparticles was obtained from Pt(dba)2 (dba = dibenzylidene acetone) and 3-chloropropylsilane. The resulting nanoparticles (diameter: 2.0 ± 0.4 nm determined by HRTEM) resulted hydrophilic. The NPs present in the THF colloidal solution were incorporated inside the walls of a highly ordered 2D hexagonal mesoporous silica matrix via sol-gel process using a templating route with tetraethylorthosilicate, TEOS, as the silica source, and block copolymer (EthyleneOxide) 20(PropyleneOxide)70(EthyleneOxide)20 (Pluronic P123) as the structure-directing agent. Low-temperature calcination of the crude material at 593 K led to the final solid Pt@{walls}SiO2. Characterization by IR, HRTEM, BF-STEM and HAADF-STEM, SAXS, WAXS, XRD, XPS, H2 chemisorption, etc. of Pt@{walls}SiO2 confirmed the 2D hexagonal structuration and high mesoporosity (870 m2/g) of the material as well as the presence of stable 2-nm-sized crystalline Pt(0) NPs embedded inside the walls of the silica matrix. The material displayed no tendency to NPs sintering or leaching (Pt loading 0.3 wt.%) during its preparation. Pt@{walls}SiO2 was found to be a stable, selective and highly active hydrogenation catalyst. The catalytic performances in propene hydrogenation were tested under chemical regime conditions in a tubular flow reactor (278 K, propene/H2/He = 20/16/1.09 cm3/min, P tot = 1 bar) and were found superior to those of an homologous solid containing Pt NPs along its pore channels Pt@{pores}SiO2 and to those of a classical industrial catalysts Pt/Al2O3, (TOF = 2.3 s-1 vs. TOF = 0.90 and 0.92 s-1, respectively, calculated per surface platinum atoms). Pt@{walls}SiO2 also catalyzes fast and selective styrene

Selective and regular localization of accessible Pt nanoparticles inside the walls of an ordered silica: Application as a highly active and well-defined heterogeneous catalyst for propene and styrene hydrogenation reactions

KAUST Repository

Boualleg, Malika

2011-12-01

We describe here an original methodology related to the "build-the-bottle-around-the-ship" approach yielding a highly ordered silica matrix containing regularly distributed Pt nanoparticles (NPs) located inside the silica walls, Pt@{walls}SiO2. The starting colloidal solution of crystalline Pt nanoparticles was obtained from Pt(dba)2 (dba = dibenzylidene acetone) and 3-chloropropylsilane. The resulting nanoparticles (diameter: 2.0 ± 0.4 nm determined by HRTEM) resulted hydrophilic. The NPs present in the THF colloidal solution were incorporated inside the walls of a highly ordered 2D hexagonal mesoporous silica matrix via sol-gel process using a templating route with tetraethylorthosilicate, TEOS, as the silica source, and block copolymer (EthyleneOxide) 20(PropyleneOxide)70(EthyleneOxide)20 (Pluronic P123) as the structure-directing agent. Low-temperature calcination of the crude material at 593 K led to the final solid Pt@{walls}SiO2. Characterization by IR, HRTEM, BF-STEM and HAADF-STEM, SAXS, WAXS, XRD, XPS, H2 chemisorption, etc. of Pt@{walls}SiO2 confirmed the 2D hexagonal structuration and high mesoporosity (870 m2/g) of the material as well as the presence of stable 2-nm-sized crystalline Pt(0) NPs embedded inside the walls of the silica matrix. The material displayed no tendency to NPs sintering or leaching (Pt loading 0.3 wt.%) during its preparation. Pt@{walls}SiO2 was found to be a stable, selective and highly active hydrogenation catalyst. The catalytic performances in propene hydrogenation were tested under chemical regime conditions in a tubular flow reactor (278 K, propene/H2/He = 20/16/1.09 cm3/min, P tot = 1 bar) and were found superior to those of an homologous solid containing Pt NPs along its pore channels Pt@{pores}SiO2 and to those of a classical industrial catalysts Pt/Al2O3, (TOF = 2.3 s-1 vs. TOF = 0.90 and 0.92 s-1, respectively, calculated per surface platinum atoms). Pt@{walls}SiO2 also catalyzes fast and selective styrene

Synthesis and characterization of titanium oxide supported silica materials

Science.gov (United States)

Schrijnemakers, Koen

2002-01-01

Titania-silica materials are interesting materials for use in catalysis, both as a catalyst support as well as a catalyst itself. Titania-silica materials combine the excellent support and photocatalytic properties of titania with the high thermal and mechanical stability of silica. Moreover, the interaction of titania with silica leads to new active sites, such as acid and redox sites, that are not found on the single oxides. In this Ph.D. two recently developed deposition methods were studied and evaluated for their use to create titanium oxide supported silica materials, the Chemical Surface Coating (CSC) and the Molecular Designed Dispersion (MDD). These methods were applied to two structurally different silica supports, an amorphous silica gel and the highly ordered MCM-48. Both methods are based on the specific interaction between a titanium source and the functional groups on the silica surface. With the CSC method high amounts of titanium can be obtained. However, clustering of the titania phase is observed in most cases. The MDD method allows much lower titanium amounts to be deposited without the formation of crystallites. Only at the highest Ti loading very small crystallites are formed after calcination. MCM-48 and silica gel are both pure SiO2 materials and therefore chemically similar to each other. However, they possess a different morphology and are synthesized in a different way. As such, some authors have reported that the MCM-48 surface would be more reactive than the surface of silica gel. In our experiments however no differences could be observed that confirmed this hypothesis. In the CSC method, the same reactions were observed and similar amounts of Ti and Cl were deposited. In the case of the MDD method, no difference in the reaction mechanism was observed. However, due to the lower thermal and hydrothermal stability of the MCM-48 structure compared to silica gel, partial incorporation of Ti atoms in the pore walls of MCM-48 took place

Tin-Platinum catalysts interactions on titania and silica

Energy Technology Data Exchange (ETDEWEB)

Nava, N. [Instituto Mexicano del Petroleo Lazaro Cardenas 152, 07730 Mexico, D.F. (Mexico)], E-mail: tnava@imp.mx; Del Angel, P. [Instituto Mexicano del Petroleo Lazaro Cardenas 152, 07730 Mexico, D.F. (Mexico); Salmones, J. [Instituto Politecnico Nacional-ESIQIE UPALM, 07738 Mexico, D.F. (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, Brasil (Brazil); Santiago, P. [Instituto de Fisica, UNAM, Mexico, D. F., 04510 Mexico (Mexico)

2007-09-30

Pt-Sn was supported on titania and silica, and the resulting interactions between the components in prepared samples and the resulting interactions between the components before and after treatment with hydrogen were characterized by Moessbauer spectroscopy, X-ray diffraction, Rietveld refinement, high-resolution transmission electron microscopy (HRTEM) and catalytic tests data. Results show the presence of Pt and SnO{sub 2} after calcinations, and Pt{sub 3}Sn, PtSn and PtSn{sub 3} after reduction. Rietveld analysis shows that some Ti{sup 4+} are replaced by Sn{sup 4+} atoms in the titania structure. Finally, HRTEM and the practically absence of activity observed confirms that metallic platinum is encapsulated.

Synthesis of Supported NiPt Bimetallic Nanoparticles, Methods for Controlling the Surface Coverage of Ni Nanoparticles With Pt, Methods Of Making NiPt Multilayer Core-Shell Structures and Application of the Supported Catalysts for CO2 Reforming

KAUST Repository

Li, Lidong; Anjum, Dalaver H.; Zhou, Lu; Laveille, Paco; Basset, Jean-Marie

2015-01-01

Embodiments of the present disclosure provide for supported Ni/Pt bimetallic nanoparticles, compositions including supported NiPt nanoparticles, methods of making supported NiPt nanoparticles, methods of using supported NiPt nanoparticles

Synthesis of Supported NiPt Bimetallic Nanoparticles, Methods for Controlling the Surface Coverage of Ni Nanoparticles With Pt, Methods Of Making NiPt Multilayer Core-Shell Structures and Application of the Supported Catalysts for CO2 Reforming

KAUST Repository

Li, Lidong

2015-06-25

Embodiments of the present disclosure provide for supported Ni/Pt bimetallic nanoparticles, compositions including supported NiPt nanoparticles, methods of making supported NiPt nanoparticles, methods of using supported NiPt nanoparticles, and the like.

Effect of support on hydro-metathesis of propene: A comparative study of W(CH 3 ) 6 anchored to silica vs. silica-alumina

KAUST Repository

Tretiakov, Mykyta; Samantaray, Manoja; Saidi, Aya; Basset, Jean-Marie

2018-01-01

Hydro-metathesis of propene was carried out by using well-defined W(CH3)6 supported on silica and silica-alumina. It was observed that W(CH3)6 supported silica-alumina catalyst is much better (TON 4577) than the silica supported catalyst (TON 2104

Pt and PtRu nanoparticles supported on N-doped carbons as electrocatalysts for methanol electro oxidation

Energy Technology Data Exchange (ETDEWEB)

Pereira, Viviane Santos; Silva, Julio Cesar Martins; Oliveira Neto, Almir; Spinace, Estevam Vitorio, E-mail: viviane_sp_saopaulo@yahoo.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2016-07-01

Full text: Methanol is a liquid transportation fuel that can be produced from fossil or renewable resources. Fuel cells employing methanol directly as fuel (Direct Methanol Fuel Cell - DMFC) are very attractive as power source for portable, mobile and stationary applications [1]. PtRu/C electrocatalyst has been considered the best electrocatalyst for methanol electro-oxidation, however, its performance is strongly dependent on the method of preparation and on the characteristics of the carbon support. N-doped carbons with different N contents (1, 2 and 5 wt%) were prepared by thermal treatment of carbon with urea at 800 deg C. Pt and PtRu nanoparticles were supported on N-doped carbons by coreduction of Pt(IV) and Ru(III) ions using an alcohol-reduction process [2]. The obtained materials were characterized by Energy Dispersive X-ray spectroscopy, X-ray diffraction, Transmission electron microscopy and Cyclic Voltammetry. Pt and PtRu nanoparticles supported on N-doped carbons showed superior performance for methanol electro-oxidation when compared to the materials supported on non-modified carbon and to Pt/C and PtRu/C commercial electrocatalysts. Pt/C and PtRu/C prepared with the carbon modified with 2.5 wt% of N content showed the best activities. (author) [1] Y. Zhou, K. Neyerlin, T.S. Olson, S. Pylypenko, J. Bult, H.N. Dinh, T. Gennett, Z. Shao and R. O'Hayre, Energy Environ. Sci. 3, 1437 (2010); [2] E.V. Spinace, A.Oliveira Neto, T.R.R. Vasconcellos, M. Linardi, J. Power Sources 137, 17 (2004)

Metal Phosphate-Supported Pt Catalysts for CO Oxidation

Directory of Open Access Journals (Sweden)

Xiaoshuang Qian

2014-12-01

Full Text Available Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2 have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO46(OH2, denoted as Ca-P-O here also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP atomic emission spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectron spectroscopy (XPS, and H2 temperature-programmed reduction (H2-TPR. This work furnishes a new catalyst system for CO oxidation and other possible reactions.

SELECTIVE HYDROGENATION OF CINNAMALDEHYDE WITH Pt AND Pt-Fe CATALYSTS: EFFECTS OF THE SUPPORT

Directory of Open Access Journals (Sweden)

A.B. da Silva

1998-06-01

Full Text Available Low-temperature reduced TiO2-supported Pt and Pt-Fe catalysts are much more active and selective for the liquid–phase hydrogenation of cinnamaldehyde to unsaturated cinnamyl alcohol than the corresponding carbon-supported catalysts. High-temperature reduced catalysts, where the SMSI effect should be present, are almost inactive for this reaction. There is at present no definitive explanation for this effect but an electronic metal-support interaction is most probably involved.

Electro-oxidation of Ethanol on Carbon Supported PtSn and PtSnNi Catalysts

Directory of Open Access Journals (Sweden)

Nur Hidayati

2016-03-01

Full Text Available Even though platinum is known as an active electro-catalyst for ethanol oxidation at low temperatures (< 100 oC, choosing the electrode material for ethanol electro-oxidation is a crucial issue. It is due to its property which easily poisoned by a strong adsorbed species such as CO. PtSn-based electro-catalysts have been identified as better catalysts for ethanol electro-oxidation. The third material is supposed to improved binary catalysts performance. This work presents a study of the ethanol electro-oxidation on carbon supported Pt-Sn and Pt-Sn-Ni catalysts. These catalysts were prepared by alcohol reduction. Nano-particles with diameters between 2.5-5.0 nm were obtained. The peak of (220 crystalline face centred cubic (fcc Pt phase for PtSn and PtSnNi alloys was repositioned due to the presence of Sn and/or Ni in the alloy. Furthermore, the modification of Pt with Sn and SnNi improved ethanol and CO electro-oxidation. Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th November 2015; Revised: 1st February 2016; Accepted: 1st February 2016 How to Cite: Hidayati, N., Scott, K. (2016. Electro-oxidation of Ethanol on Carbon Supported PtSn and PtSnNi Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 10-20. (doi:10.9767/bcrec.11.1.394.10-20 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.394.10-20

Carbon supported nanoparticles Pt Ru (Pt Ru/C electrocatalysts) prepared using electron beam irradiation; Preparacao de nanoparticulas de PtRu suportadas em carbono (eletrocatalisadores PtRu/C) utilizando feixe de eletrons

Energy Technology Data Exchange (ETDEWEB)

Silva, Dionisio F. da; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Programa de Celulas a Combustivel], e-mail: espinace@ipen.br, e-mail: dfsilva@ipen.br

2006-07-01

Carbon-supported Pt Ru (electrocatalysts PtRu/C nanoparticles) were prepared submitting a water/ethylene glycol mixture containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The PtRu/C electrocatalysts were characterized by EDX, XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C ETEK electrocatalyst at ambient temperature. (author)

Mechanistic studies of formic acid oxidation at polycarbazole supported Pt nanoparticles

International Nuclear Information System (INIS)

Moghaddam, Reza B.; Pickup, Peter G.

2013-01-01

Highlights: •A polycarbazole support decreases the accumulation of adsorbed intermediates on Pt during formic acid oxidation. •Polycarbazole causes a bilayer of Cu to form on Pt nanoparticles during Cu underpotential deposition. •XPS suggests that both of these effects are due to electron donation from the metal (Pt or Cu) into the polymer π-system. -- Abstract: Mechanistic aspects of the promotion of formic acid oxidation at Pt nanoparticles supported on a thin layer of polycarbazole (PCZ) have been investigated by voltammetry and X-ray photoelectron spectroscopy (XPS). The Pt nanoparticles were drop coated onto a glassy carbon (GC) electrode coated with a ca. 9 nm layer of electrochemically deposited polycarbazole. After 500 s of formic acid oxidation at 0 V vs. SCE, the current at a GC/PCZ/Pt electrode was 25 times higher than at a GC/Pt electrode. Voltammetry in formic acid free H 2 SO 4 following potentiostatic oxidation of formic acid revealed that there was less accumulation of adsorbed intermediates for the polycarbazole supported Pt nanoparticles than for those deposited directly onto the glassy carbon with, 50% more Pt sites remaining available for the GC/PCZ/Pt electrode relative to the GC/Pt electrode. Independent CO stripping experiments revealed only slight differences, while Cu underpotential deposition surprisingly resulted in the deposition of a ca. two-fold excess of Cu on the polycarbazole supported particles. This observation was supported by XPS which also revealed a second Cu signal at a higher binding energy, suggesting electron donation into the conjugated π system of the polymer. Such an interaction of Pt with the polycarbazole may be responsible for its higher activity for formic acid oxidation

Characterization of Pt catalysts supported in mixed oxides; Caracterizacion de catalizadores de Pt soportado en oxidos mixtos

Energy Technology Data Exchange (ETDEWEB)

Perez H, R.; Garcia C, M.A.; Gomez C, A.; Diaz, G. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

2000-07-01

The catalytic supports TiO{sub 2}, ZrO{sub 2} and TiO{sub 2}-ZrO{sub 2} were prepared by the sol-gel technique. The incorporation of Pt to the supports was by the classical impregnation method. The catalytic materials were characterized (Pt/TiO{sub 2}, Pt/ZrO{sub 2} and Pt/TiO{sub 2}-ZrO{sub 2}) by diverse techniques to determine: the texture (BET), evolution of the catalytic materials synthesised after drying and calcination (Infrared spectroscopy) and by Thermogravimetric analysis. (Author)

Nitrogen: Unraveling the Secret to Stable Carbon-Supported Pt-Alloy Electrocatalysts

Science.gov (United States)

2013-10-01

release; distribution is unlimited. Nitrogen: unraveling the secret to stable carbon-supported Pt- alloy electrocatalysts The views, opinions and/or...Nitrogen: unraveling the secret to stable carbon-supported Pt-alloy electrocatalysts Report Title Nitrogen functionalities significantly improve...design and optimization of next generation high performance catalyst materials. Nitrogen: unraveling the secret to stable carbon-supported Pt-alloy

Pd-Pt Catalysts on Mesoporous SiO2-Al2O3 with Superior Activity for HDS of 4,6-Dimethyldibenzothiophene: Effect of Metal Loading and Support Composition

Czech Academy of Sciences Publication Activity Database

Vít, Zdeněk; Gulková, Daniela; Kaluža, Luděk; Kupčík, Jaroslav

2015-01-01

Roč. 179, DEC 2015 (2015), s. 44-53 ISSN 0926-3373 R&D Projects: GA ČR GAP106/11/0902 Institutional support: RVO:67985858 ; RVO:61388980 Keywords : Pd-Pt catalyst * mesoporous silica-alumina * 4,6-DMDBT Subject RIV: CF - Physical ; Theoretical Chemistry ; CA - Inorganic Chemistry (UACH-T) Impact factor: 8.328, year: 2015

Methanol Electro-Oxidation on Pt-Ru Alloy Nanoparticles Supported on Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Yangchuan Xing

2009-09-01

Full Text Available Carbon nanotubes (CNTs have been investigated in recent years as a catalyst support for proton exchange membrane fuel cells. Improved catalyst activities were observed and attributed to metal-support interactions. We report a study on the kinetics of methanol electro-oxidation on CNT supported Pt-Ru alloy nanoparticles. Alloy catalysts with different compositions, Pt53Ru47/CNT, Pt69Ru31/CNT and Pt77Ru23/CNT, were prepared and investigated in detail. Experiments were conducted at various temperatures, electrode potentials, and methanol concentrations. It was found that the reaction order of methanol electro-oxidation on the PtRu/CNT catalysts was consistent with what has been reported for PtRu alloys with a value of 0.5 in methanol concentrations. However, the electro-oxidation reaction on the PtRu/CNT catalysts displayed much lower activation energies than that on the Pt-Ru alloy catalysts unsupported or supported on carbon black (PtRu/CB. This study provides an overall kinetic evaluation of the PtRu/CNT catalysts and further demonstrates the beneficial role of CNTs.

Syntheses of carbon porous materials with varied pore sizes and their performances as catalyst supports during methanol oxidation reaction

International Nuclear Information System (INIS)

Lo, An-Ya; Hung, Chin-Te; Yu, Ningya; Kuo, Cheng-Tzu; Liu, Shang-Bin

2012-01-01

Highlights: ► CPMs with varied pore sizes (1–400 nm) were replicated from various porous silicas by CVI method. ► MOR activities of Pt/CPM electrocatalysts increase with increasing pore size of CPM support. ► Microporous CPMs are favorable supports for Pt in terms of catalytic performance and CO-tolerance. -- Abstract: Carbon porous materials (CPMs) with extended ranges of pore size and morphology were replicated using various porous silicas, such as zeolites, mesoporous silicas, and photonic crystals, as templates by means of chemical vapor infiltration (CVI) method. The micro-, meso-, and macro-porous carbons so fabricated were adopted as supports for the metal (Pt) catalyst for direct methanol fuel cells (DMFCs), and the supported Pt/CPM electrocatalysts were characterized by a variety of different spectroscopic/analytical techniques, viz. transmission electron microscopy (TEM), Raman, X-ray photoelectron spectroscopy (XPS), gas physisorption/chemisorption analyses, and cyclic voltammetry (CV). That these Pt/CPMs were found to exhibit superior electrocatalytic activities compared to the commercial Pt/XC-72 with a comparable Pt loading during methanol oxidation reaction (MOR) is attributed to the presence of Pt nanoparticles (NPs; typically 1–3 nm in size) that are highly dispersed in the CPMs, facilitating an improved tolerance for CO poisoning. While the MOR activity observed for various Pt/CPMs tend to increase with increasing pore size of the carbon supports, Pt catalyst supported on carbon substrates possessing microporosities was found to have superior stability in terms of tolerance for CO poisoning than those with greater pore size or having meso- and macroporosities.

Effect of support on hydro-metathesis of propene: A comparative study of W(CH 3 ) 6 anchored to silica vs. silica-alumina

KAUST Repository

Tretiakov, Mykyta

2018-03-27

Hydro-metathesis of propene was carried out by using well-defined W(CH3)6 supported on silica and silica-alumina. It was observed that W(CH3)6 supported silica-alumina catalyst is much better (TON 4577) than the silica supported catalyst (TON 2104). We demonstrated that the present catalysts are much better than the previously reported (tantalum hydride/KCC-1, TON 786) catalyst. For the first time, we observed the formation of n-decane from propene, which enables us to think of using cheaper raw materials and converting them to petroleum range alkanes using hydro-metathesis reaction.

Tuning metal support interactions enhances the activity and durability of TiO2-supported Pt nanocatalysts

International Nuclear Information System (INIS)

Hsieh, Bing-Jen; Tsai, Meng-Che; Pan, Chun-Jern; Su, Wei-Nien; Rick, John; Chou, Hung-Lung; Lee, Jyh-Fu; Hwang, Bing-Joe

2017-01-01

Highlights: • The coverage of TiO x on Pt can be modified by thermal and fluoric acid treatments. • Strong metal support interaction (SMSI) can be testified by electrochemical method. • For the first time, the SMSI effect is observed at 200 °C with supporting TEM images. • Increased activity and stability are attributed to stronger SMSI. • This tunable approach is valid for other oxide supported catalysts, e.g. Pt/Nb-TiO 2 . - Abstract: A facile approach to enhance catalytic activity and durability of TiO 2 -supported Pt nanocatalysts by tuning strong metal support interaction (SMSI) is investigated in this work. No need for a high temperature treatment, the strong metal-support interaction (SMSI) in TiO 2 -supported Pt can be induced at 200° C by H 2 reduction. Moreover, electrochemical methods (methanol oxidation reaction and cyclic voltammetry) are first reported ever to be effective characterization tools for the coverage state caused by SMSI. In addition, the SMSI has also been confirmed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and Transmission Electron Microscopy. It is found that the encapsulation of TiO 2-x species on the surface Pt clusters was induced and modified by thermal reduction and fluoric acid treatment. The catalytic activity and durability of the TiO 2 -supported Pt nanocatalysts are strongly dependent of the state of SMSI. The proposed SMSI-tunable approach to enhance the ORR activity and stability is also proved applicable to Pt/Ti 0.9 Nb 0.1 O 2 nanocatalysts. We believe that the reported approach paves the way for manipulating the activity and stability of other TiO 2 -supported metal nanocatalysts. Furthermore, the suggested electrochemical methods offer facile and effective ways to verify the presence of coverage state before combining with other physical analysis.

Well-defined single-site monohydride silica-supported zirconium from azazirconacyclopropane

KAUST Repository

Hamzaoui, Bilel

2015-01-13

The silica-supported azazirconacyclopropane ≡SiOZr(HNMe2)(η2-NMeCH2)(NMe2) (1) leads exclusively under hydrogenolysis conditions (H2, 150°C) to the single-site monopodal monohydride silica-supported zirconium species ≡SiOZr(HNMe2)(NMe2)2H (2). Reactivity studies by contacting compound 2 with ethylene, hydrogen/ethylene, propene, or hydrogen/propene, at a temperature of 200°C revealed alkene hydrogenation.

Well-defined single-site monohydride silica-supported zirconium from azazirconacyclopropane

KAUST Repository

Hamzaoui, Bilel; El Eter, Mohamad; Abou-Hamad, Edy; Chen, Yin; Pelletier, Jeremie; Basset, Jean-Marie

2015-01-01

The silica-supported azazirconacyclopropane ≡SiOZr(HNMe2)(η2-NMeCH2)(NMe2) (1) leads exclusively under hydrogenolysis conditions (H2, 150°C) to the single-site monopodal monohydride silica-supported zirconium species ≡SiOZr(HNMe2)(NMe2)2H (2). Reactivity studies by contacting compound 2 with ethylene, hydrogen/ethylene, propene, or hydrogen/propene, at a temperature of 200°C revealed alkene hydrogenation.

Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO2 reforming of methane

KAUST Repository

Biausque, Gregory; Laveille, Paco; Anjum, Dalaver H.; Caps, Valerie; Basset, Jean-Marie

2015-01-01

Embodiments of the present disclosure provide for NiPt nanoparticles, compositions and supports including NiPt nanoparticles, methods of making NiPt nanoparticles, methods of supporting NiPt nanoparticles, methods of using NiPt nanoparticles, and the like.

Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO2 reforming of methane

KAUST Repository

Biausque, Gregory

2015-09-24

Embodiments of the present disclosure provide for NiPt nanoparticles, compositions and supports including NiPt nanoparticles, methods of making NiPt nanoparticles, methods of supporting NiPt nanoparticles, methods of using NiPt nanoparticles, and the like.

From photoluminescence emissions to plasmonic properties in platinum nanoparticles embedded in silica by ion implantation

Energy Technology Data Exchange (ETDEWEB)

Bornacelli, J., E-mail: jhbornacelli@gmail.com [Instituto de Física, Universidad Nacional Autónoma de México, 04510 México D.F. (Mexico); Silva-Pereyra, H.G. [IPICyT, Division de Materiales Avanzados, Camino a la presa San Jose 2055, San Luis Potosi, S.L.P. 78216 (Mexico); Rodríguez-Fernández, L. [Instituto de Física, Universidad Nacional Autónoma de México, 04510 México D.F. (Mexico); Avalos-Borja, M. [IPICyT, Division de Materiales Avanzados, Camino a la presa San Jose 2055, San Luis Potosi, S.L.P. 78216 (Mexico); Centro de Nanociencias y Nanotecnologia – Universidad Nacional Autónoma de México, A. Postal 2681, Ensenada, B.C. (Mexico); Oliver, A. [Instituto de Física, Universidad Nacional Autónoma de México, 04510 México D.F. (Mexico)

2016-11-15

We have studied photoluminescence emission and optical absorption from platinum nanoparticles (Pt-nps) embedded in a silica matrix obtained by ion implantation. The Pt ions were implanted at 2 MeV and the nanoclusters were nucleated after thermal treatment at 600, 800, and 1100 °C under two different atmospheres: argon gas and a reducing atmosphere compound of H{sub 2} and N{sub 2}. The luminescent spectrum is broader (400–600 nm) and is peaked at 530 nm, but its intensity decreases as the annealing temperature increases. However, at high annealing temperatures, a Mie resonance at 220 nm emerges in the absorption spectrum. We then observed a transition between two optical properties in a system of Pt-nps embedded in silica: from molecule-like properties such as photoluminescence emission to localized surface plasmon absorption. - Highlights: • Photoluminescence (PL) from ion-implanted Pt-nps in silica have been demonstrated. • PL properties depend on the temperature and atmosphere used to form Pt-nps in silica. • PL is quenched for samples with larger Pt-nps, however a Mie resonance appear. • Transition from molecule-like to bulk-like properties of Pt-nps in silica is reveled.

A Silica-Supported Monoalkylated Tungsten Dioxo Complex Catalyst for Olefin Metathesis

KAUST Repository

Maity, Niladri

2018-02-15

A well-defined silica-supported monoalkylated tungsten dioxo complex [(Si-O-)W(=O)(CH-Bu)] was prepared by treatment of highly dehydroxylated silica (SiO: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt][W(=O)(CH-Bu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.

A Silica-Supported Monoalkylated Tungsten Dioxo Complex Catalyst for Olefin Metathesis

KAUST Repository

Maity, Niladri; Barman, Samir; Minenkov, Yury; Ould-Chikh, Samy; Abou-Hamad, Edy; Ma, Tao; Qureshi, Ziyauddin; Cavallo, Luigi; D'Elia, Valerio; Gates, Bruce C.; Basset, Jean-Marie

2018-01-01

A well-defined silica-supported monoalkylated tungsten dioxo complex [(Si-O-)W(=O)(CH-Bu)] was prepared by treatment of highly dehydroxylated silica (SiO: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt][W(=O)(CH-Bu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.

Preparation of Mesoporous Silica-Supported Palladium Catalysts for Biofuel Upgrade

Directory of Open Access Journals (Sweden)

Ling Fei

2012-01-01

Full Text Available We report the preparation of two hydrocracking catalysts Pd/CoMoO4/silica and Pd/CNTs/CoMoO4/silica (CNTs, carbon nanotubes. The structure, morphologies, composition, and thermal stability of catalysts were studied by X-ray diffraction (XRD, scanning electron microscopy (SEM, Raman spectroscopy, transmission electron microscopy (TEM, energy-dispersive X-ray (EDX, and thermogravimetric analysis (TGA. The catalyst activity was measured in a Parr reactor with camelina fatty acid methyl esters (FAMEs as the feed. The analysis shows that the palladium nanoparticles have been incorporated onto mesoporous silica in Pd/CoMoO4/silica or on the CNTs surface in Pd/CNTs/CoMoO4/silica catalysts. The different combinations of metals and supports have selective control cracking on heavy hydrocarbons.

Tuning the Chemoselective Hydrogenation of Nitrostyrenes Catalyzed by Ionic Liquid-Supported Platinum Nanoparticles

DEFF Research Database (Denmark)

Beier, Matthias Josef; Andanson, Jean-Michel; Baiker, Alfons

2012-01-01

Pt nanoparticles (NPs) in the range of 1.7–3.4 nm were synthesized in an ionic liquid (IL). Subsequent immobilization on various solid supports (silica, alumina, titania, carbon nanotubes (CNTs)) in some cases proved to be beneficial. These catalysts exhibited excellent performance in the chemose......Pt nanoparticles (NPs) in the range of 1.7–3.4 nm were synthesized in an ionic liquid (IL). Subsequent immobilization on various solid supports (silica, alumina, titania, carbon nanotubes (CNTs)) in some cases proved to be beneficial. These catalysts exhibited excellent performance...

Aminopropyl-Silica Hybrid Particles as Supports for Humic Acids Immobilization

Directory of Open Access Journals (Sweden)

Mónika Sándor

2016-01-01

Full Text Available A series of aminopropyl-functionalized silica nanoparticles were prepared through a basic two step sol-gel process in water. Prior to being aminopropyl-functionalized, silica particles with an average diameter of 549 nm were prepared from tetraethyl orthosilicate (TEOS, using a Stöber method. In a second step, aminopropyl-silica particles were prepared by silanization with 3-aminopropyltriethoxysilane (APTES, added drop by drop to the sol-gel mixture. The synthesized amino-functionalized silica particles are intended to be used as supports for immobilization of humic acids (HA, through electrostatic bonds. Furthermore, by inserting beside APTES, unhydrolysable mono-, di- or trifunctional alkylsilanes (methyltriethoxy silane (MeTES, trimethylethoxysilane (Me3ES, diethoxydimethylsilane (Me2DES and 1,2-bis(triethoxysilylethane (BETES onto silica particles surface, the spacing of the free amino groups was intended in order to facilitate their interaction with HA large molecules. Two sorts of HA were used for evaluating the immobilization capacity of the novel aminosilane supports. The results proved the efficient functionalization of silica nanoparticles with amino groups and showed that the immobilization of the two tested types of humic acid substances was well achieved for all the TEOS/APTES = 20/1 (molar ratio silica hybrids having or not having the amino functions spaced by alkyl groups. It was shown that the density of aminopropyl functions is low enough at this low APTES fraction and do not require a further spacing by alkyl groups. Moreover, all the hybrids having negative zeta potential values exhibited low interaction with HA molecules.

SiO2-supported Pt particles studied by electron microscopy

International Nuclear Information System (INIS)

Wang, D.; Penner, S.; Su, D.S.; Rupprechter, G.; Hayek, K.; Schloegl, R.

2003-01-01

Regularly grown Pt particles supported by amorphous SiO 2 were heated in hydrogen at 873 K after an oxidising treatment. The morphological and structural changes were studied by electron microscopy. Platinum silicides Pt 3 Si with L1 2 (Cu 3 Au) structure, monoclinic Pt 3 Si and tetragonal Pt 12 Si 5 were identified after the treatment. The mechanisms of coalescence of the particles and the formation of irregular large particles are suggested. A topotactic structural transformation accompanied with the migration of Si from the substrate to the particles are suggested to take place during Pt 3 Si formation

Mass transport in thin supported silica membranes

NARCIS (Netherlands)

Benes, Nieck Edwin

2000-01-01

In this thesis multi-component mass transport in thin supported amorphous silica membranes is discussed. These membranes are micro-porous, with pore diameters smaller than 4Å and show high fluxes for small molecules (such as hydrogen) combined with high selectivities for these molecules with respect

Porous graphene supported Pt catalysts for proton exchange membrane fuel cells

International Nuclear Information System (INIS)

Cheng, Kun; He, Daping; Peng, Tao; Lv, Haifeng; Pan, Mu; Mu, Shichun

2014-01-01

Graphene nanosheet (GNS) has a remarkably high ratio of surface area to thickness and intense inter-sheet aggregation, which heavily resist mass diffusion in vertical orientation. Here, we establish a fast-speed mass diffusion passage by creating pores in GNS, and the corresponding Pt catalyst (Pt/rPGO) displays 15.5 times mass diffusion rate than that of the pristine GNS supported Pt catalyst (Pt/rGO). Thus, the Pt/rPGO catalyst exhibits 1.5 times increase in Pt mass activity toward oxygen reduction reaction compared with the Pt/rGO. Significantly, after H 2 thermal treatment, the mass activity of the Pt/rPGO further increases to 1.9 times that of the Pt/rGO, and its electrochemical stability is also greatly improved

Silica-supported silicotungstic acid: A study by X-ray photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Berry, Frank J.; Derrick, Glyn R. [Department of Chemistry and Analytical Sciences, Robert Hooke Building, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); Marco, Jose F. [Instituto de Quimica -Fisica ' Rocasolano' , Consejo Superior de Investigaciones Cientificas, Serrano 119, 28006 Madrid (Spain); Mortimer, Michael [Department of Chemistry and Analytical Sciences, Robert Hooke Building, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom)], E-mail: m.mortimer@open.ac.uk

2009-04-15

W 4f and O 1s X-ray photoelectron spectra for silicotungstic acid, H{sub 4}SiW{sub 12}O{sub 40}, in pure and silica-supported form are reported. W 4f XP spectra for the supported acid are analysed in terms of contributions from two W(VI) spin-orbit doublets arising from tungsten atoms in terminal W=O bonds some of which directly interact with the silica surface. At low loading (3.2 wt.%) significant changes in the relative contributions and binding energies of the two spin-orbit doublets are taken as evidence of a strong interaction of individual [SiW{sub 12}O{sub 40}]{sup 4-} anions with highly active sites on the silica surface. It is suggested that selective ordering of silanol groups can occur on the silica surface in order to accommodate the adsorption of individual [SiW{sub 12}O{sub 40}]{sup 4-} anions.

Optimum Pt and Ru atomic composition of carbon-supported Pt-Ru alloy electrocatalyst for methanol oxidation studied by the polygonal barrel-sputtering method

International Nuclear Information System (INIS)

Hiromi, Chikako; Inoue, Mitsuhiro; Taguchi, Akira; Abe, Takayuki

2011-01-01

Highlights: → The sputtered Pt and Ru form the Pt-Ru alloy nanoparticles on the carbon support. → The deposited Pt-Ru alloy particles have uniform Pt:Ru atomic ratios. → The optimum Pt:Ru ratio of the Pt-Ru/C for methanol oxidation is 58:42 at.% at 25 deg. C. → The optimum Pt:Ru ratio of 58:42 shifts to 50:50 at.% at 40 and 60 deg. C. → The polygonal barrel-sputtering method is useful to prepare the DMFC anode catalyst. - Abstract: The optimum Pt and Ru atomic composition of a carbon-supported Pt-Ru alloy (Pt-Ru/C) used in a practical direct methanol fuel cell (DMFC) anode was investigated. The samples were prepared by the polygonal barrel-sputtering method. Based on the physical properties of the prepared Pt-Ru/C samples, the Pt-Ru alloy was found to be deposited on a carbon support. The microscopic characterization showed that the deposited alloy forms nanoparticles, of which the atomic ratios of Pt and Ru (Pt:Ru ratios) are uniform and are in accordance with the overall Pt:Ru ratios of the samples. The formation of the Pt-Ru alloy is also supported by the electrochemical characterization. Based on these results, methanol oxidation on the Pt-Ru/C samples was measured by cyclic voltammetry and chronoamperometry. The results indicated that the methanol oxidation activities of the prepared samples depended on the Pt:Ru ratios, of which the optimum Pt:Ru ratio is 58:42 at.% at 25 deg. C and 50:50 at.% at 40 and 60 deg. C. This temperature dependence of the optimum Pt:Ru ratio is well explained by the relationship between the methanol oxidation reaction process and the temperature, which is reflected in the rate-determining steps considered from the activation energies. It should be noted that at 25-60 deg. C, the Pt-Ru/C with Pt:Ru = 50:50 at.% prepared by our sputtering method has the higher methanol oxidation activity than that of a commercially available sample with the identical overall Pt:Ru ratio. Consequently, the polygonal barrel-sputtering method

Design of supported bi-metallic nanoparticles based on Platinum and Palladium using Surface Organometallic Chemistry (SOMC)

KAUST Repository

Al-Shareef, Reem A.

2017-01-01

Well-defined silica supported bimetallic catalysts Pt100-x Pdx (where x is the molar ratio of Pd) are prepared by Surface Organometallic Chemistry (SOMC) via controlled decomposition of Pd2(allyl)2Cl2 on Pt/SiO2. For comparison purposes, Pt100-x Pdx

Ethanol electrooxidation on novel carbon supported Pt/SnOx/C catalysts with varied Pt:Sn ratio

International Nuclear Information System (INIS)

Jiang, L.; Colmenares, L.; Jusys, Z.; Sun, G.Q.; Behm, R.J.

2007-01-01

Novel carbon supported Pt/SnO x /C catalysts with Pt:Sn atomic ratios of 5:5, 6:4, 7:3 and 8:2 were prepared by a modified polyol method and characterized with respect to their structural properties (X-ray diffraction (XRD) and transmission electron microscopy (TEM)), chemical composition (XPS), their electrochemical properties (base voltammetry, CO ad stripping) and their electrocatalytic activity and selectivity for ethanol oxidation (ethanol oxidation reaction (EOR)). The data show that the Pt/SnO x /C catalysts are composed of Pt and tin oxide nanoparticles with an average Pt particle diameter of about 2 nm. The steady-state activity of the Pt/SnO x /C catalysts towards the EOR decreases with tin content at room temperature, but increases at 80 deg. C. On all Pt/SnO x /C catalysts, acetic acid and acetaldehyde represent dominant products, CO 2 formation contributes 1-3% for both potentiostatic and potentiodynamic reaction conditions. With increasing potential, the acetaldehyde yield decreases and the acetic acid yield increases. The apparent activation energies of the EOR increase with tin content (19-29 kJ mol -1 ), but are lower than on Pt/C (32 kJ mol -1 ). The somewhat better performance of the Pt/SnO x /C catalysts compared to alloyed PtSn x /C catalysts is attributed to the presence of both sufficiently large Pt ensembles for ethanol dehydrogenation and C-C bond splitting and of tin oxide for OH generation. Fuel cell measurements performed for comparison largely confirm the results obtained in model studies

Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

International Nuclear Information System (INIS)

Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang; Gao, Ziwei

2015-01-01

A successive anchoring of Ti(NMe 2 ) 4 , cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, 13 C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, 13 C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated

Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

Energy Technology Data Exchange (ETDEWEB)

Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang, E-mail: gfzhang@snnu.edu.cn; Gao, Ziwei, E-mail: zwgao@snnu.edu.cn

2015-01-15

A successive anchoring of Ti(NMe{sub 2}){sub 4}, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, {sup 13}C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, {sup 13}C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated.

Adsorption and oxidation of acetaldehyde on carbon supported Pt, PtSn and PtSn-based trimetallic catalysts by in situ Fourier transform infrared spectroscopy

Science.gov (United States)

Beyhan, Seden; Léger, Jean-Michel; Kadırgan, Figen

2013-11-01

The adsorption and oxidation of acetaldehyde on carbon supported Pt, Pt90Sn10 and Pt80Sn10M10 (M = Ni, Co, Rh, Pd) catalysts have been investigated by using in situ Fourier transform infrared (FTIR) spectroscopy. The result revealed that Pt90Sn10/C catalyst is not very efficient for the conversion of acetaldehyde to CO2 due to the weak adsorption of acetaldehyde in the presence of Sn. However, the addition of a third metal to Pt--Sn facilitates the C-C bond cleavage of acetaldehyde. It seems that acetaldehyde is adsorbed dissociatively on the surface of Pt80Sn10Ni10/C, Pt80Sn10Co10/C, Pt80Sn10Rh10/C catalysts, producing CH3 and CHO adsorbate species, which can be further oxidized to CO2. However, the pathway forming CO2 for Pt80Sn10Pd10/C catalyst mainly originates from the oxidation of CH3CO species. Thus, the presence of third metal in the PtSn catalyst has a strong impact upon the acetaldehyde adsorption behaviour and its reaction products.

The role of support and promoter on the oxidation of sulfur dioxide using platinum based catalysts

DEFF Research Database (Denmark)

Koutsopoulos, Sotiris; Rasmussen, Søren Birk; Eriksen, Kim Michael

2006-01-01

The catalytic oxidation of SO2 to SO3 was studied over platinum based catalysts in the absence and the presence of dopants. The active metal was supported on silica gel or titania (anatase) by impregnation. The activities of the silica supported catalysts were found to follow the order PtRh/SiO2 ...

Glycerol valorization: dehydration to acrolein over silica-supported niobia catalysts

NARCIS (Netherlands)

Shiju, N.R.; Brown, D.R.; Wilson, K.; Rothenberg, G.

2010-01-01

The catalytic dehydration of glycerol to acrolein is investigated over silica-supported niobia catalysts in a continuous fixed-bed gas-phase reactor. Various supported niobia catalysts are prepared and characterized using surface analysis and spectroscopic methods (XRD, UV-Vis, XPS, N2 adsorption),

CTAB assisted microwave synthesis of ordered mesoporous carbon supported Pt nanoparticles for hydrogen electro-oxidation

International Nuclear Information System (INIS)

Zhou, Jian-Hua; He, Jian-Ping; Ji, Ya-Jun; Dang, Wang-Juan; Liu, Xiao-Lei; Zhao, Gui-Wang; Zhang, Chuan-Xiang; Zhao, Ji-Shuang; Fu, Qing-Bin; Hu, Huo-Ping

2007-01-01

Mesoporous carbon with ordered hexagonal structure derived from the co-assembly of triblock copolymer F127 and resol was employed as the carbon support of Pt catalysts for hydrogen electro-oxidation. Structural characterizations revealed that the mesoporous carbon exhibited large surface area and uniform mesopores. The Pt nanoparticles supported on the novel mesoporous carbon were fabricated by a facile CTAB assisted microwave synthesis process, wherein CTAB was expected to improve the wettability of carbon support as well as the dispersion of Pt nanoparticles. X-ray diffraction and transmission electron microscopy were applied to characterize the Pt catalysts. It was found that the Pt nanoparticles were uniform in size and highly dispersed on the mesoporous carbon supports. The cyclic voltammograms in sulfuric acid demonstrated that the electrochemical active surface area of Pt catalysts prepared with CTAB was two times than that without CTAB

Moessbauer spectroscopic characterisation of catalysts obtained by interaction between tetra-n-butyl-tin and silica or silica supported rhodium

International Nuclear Information System (INIS)

Millet, J.M.M.; Toyir, J.; Didillon, B.; Candy, J.P.; Nedez, C.; Basset, J.M.

1997-01-01

Moessbauer spectroscopy at 78 K was used to study the interaction between tetra-n-butyl-tin and the surfaces of silica or silica supported rhodium. At room temperature, the tetra-n-butyl-tin was physically adsorbed on the surfaces. After reaction under hydrogen at 373 K, the formation of grafted organometallic fragments on the Rh surface was confirmed whereas with pure silica, ≡SiO-Sn(n-C 4 H 9 ) 3 moieties were observed. After treatment at 523 K, the rhodium grafted organometallic species was completely decomposed and there was formation of a defined bimetallic RhSn compound

Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

Science.gov (United States)

Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang; Gao, Ziwei

2015-01-01

A successive anchoring of Ti(NMe2)4, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1‧-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, 13C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands.

Sol-gel synthesis of iron catalysers supported on silica and titanium for selectively oxidising methane to formaldehyde

OpenAIRE

Carlos Alberto Guerrero Fajardo; Francisco José Sánchez Castellanos; Anne Cécile Roger; Claire Courson

2010-01-01

Iron materials supported on silica were prepared by the sol-gel method for evaluating catalytic activity in selective o-xidation of methane to formaldehyde. Four catalysts were prepared, one corresponding to the silica support (catalyst 1S), another to the titanium support (catalyst 1T) and two more having 0.5% weight iron loads, one for the silica su-pport (catalyst 2FS) and the last one the titanium support (catalyst 2FT). The higher BET areas were 659 and 850 m2/g for catalysts 1S and 2FS,...

Preparation of supported PtRu/C electrocatalyst for direct methanol fuel cells

International Nuclear Information System (INIS)

Jiang Luhua; Sun Gongquan; Zhao Xinsheng; Zhou Zhenhua; Yan Shiyou; Tang Shuihua; Wang Guoxiong; Zhou Bing; Xin Qin

2005-01-01

In this work, high-surface supported PtRu/C were prepared with Ru(NO)(NO 3 ) 3 and [Pt(H 2 NCH 2 CH 2 NH 2 ) 2 ]Cl 2 as the precursors and hydrogen as a reducing agent. XRD and TEM analyses showed that the PtRu/C catalysts with different loadings possessed small and homogeneous metal particles. Even at high metal loading (40 wt.% Pt, 20 wt.% Ru) the mean metal particle size is less than 4 nm. Meanwhile, the calculated Pt crystalline lattice parameter and Pt (2 2 0) peak position indicated that the geometric structure of Pt was modified by Ru atoms. Among the prepared catalysts, the lattice parameter of 40-20 wt.% PtRu/C contract most. Cyclic voltammetry (CV), chronoamperometry (CA), CO stripping and single direct methanol fuel cell tests jointly suggested that the 40-20 wt.% PtRu/C catalyst has the highest electrochemical activity for methanol oxidation

Study of carbon-supported bimetallic PtCu nanoparticles by ASAXS

International Nuclear Information System (INIS)

Bulat, N.V.; Avakyan, L.A; Pryadchenko, V.V.; Srabionyan, V.V.; Belenov, S.V.; Bugaev, L.A.

2017-01-01

Bimetallic platinum-copper nanoparticles on carbon support are studied as a perspective electrochemical catalyst by anomalous small-angle X-ray scattering near the Pt absorption L 3 -edge. The simultaneous fitting of several diffraction patterns measured at different photon energies lead to a satisfactory agreement between experimental and model curves in the assumption of core-shell structure of the particles with Pt-rich shell and Cu-rich core. It is shown that the average size of as prepared nanoparticles is about 6 nm with distribution spread of about ±2 nm and with thickness of Pt-rich shell approximately 1.6 nm. After annealing at 350o C the average size of the particles increased by two times with additional enlargement of the Pt-rich shell thickness. (paper)

Effects of Cu over Pd based catalysts supported on silica or niobia

Directory of Open Access Journals (Sweden)

Roma M.N.S.C.

2000-01-01

Full Text Available Palladium and palladium-copper catalysts supported on silica and niobia were characterized by H2 chemisorption and H2-O2 titration. Systems over silica were also analyzed by transmission electron microscopy and EXAFS. The metallic dispersion decreased from 20% to 7% when the content of Pd was increased from 0.5wt.-% to 3wt.-% in monometallic catalysts. The addition of 3 wt.-% Cu to obtain Pd-Cu catalysts caused a remarkable capacity loss of hydrogen chemisorption. TPR analysis suggested an interaction between the two metals and EXAFS characterization of the catalyst supported on silica confirmed the formation of Pd-Cu alloy. Pd/Nb2O5 catalysts showed turnover numbers higher than those obtained with the Pd/SiO2 systems in the cyclohexane dehydrogenation. However, the bimetallic catalysts showed very low turnover numbers.

Is carbon-supported Pt-WOx composite a CO-tolerant material?

International Nuclear Information System (INIS)

Maillard, F.; Peyrelade, E.; Soldo-Olivier, Y.; Chatenet, M.; Chainet, E.; Faure, R.

2007-01-01

Pt-WO x /C composite materials elaborated via a two-step impregnation/electrochemical reduction method have been characterized and tested for the electrooxidation of CO/H 2 mixtures. TEM and EDS measurements revealed that WO x covered imperfectly the C particles. Nanometer-sized or agglomerated Pt particles were found on the WO x /C surface. XRD measurements revealed the absence of diffraction peaks characteristic of crystalline WO x and could indicate that this material is amorphous. No evidence of alloying between the Pt and W was observed. A significant improvement toward the electrooxidation of a CO ads monolayer was observed for the composite material compared to pure Pt/C electrocatalyst, which is evidenced by a new electrooxidation peak at 0.55V versus RHE (v=0.02Vs -1 ). As the electrical charge below this electrooxidation peak is sweep rate dependant, it is probably associated to the electrooxidation of CO ads on Pt sites at the interface with the WO x /C support. The performance of the Pt-WO x /C material for the electrooxidation of CO/H 2 mixtures was tested by polarization curves under steady-state conditions (0.001Vs -1 ) or potentiostatic measurements under fuel cell relevant conditions and compared with that of commercial 20wt% Pt/C and Pt-Ru/C materials

Noncovalently functionalized graphitic mesoporous carbon as a stable support of Pt nanoparticles for oxygen reduction

Energy Technology Data Exchange (ETDEWEB)

Shao, Yuyan; Zhang, Sheng; Kou, Rong; Wang, Chongmin; Viswanathan, Vilayanur; Liu, Jun; Wang, Yong; Lin, Yuehe [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Wang, Xiqing; Dai, Sheng [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2010-04-02

We report a durable electrocatalyst support, highly graphitized mesoporous carbon (GMPC), for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. GMPC is prepared through graphitizing the self-assembled soft-template mesoporous carbon (MPC) under high temperature. Heat-treatment at 2800 C greatly improves the degree of graphitization while most of the mesoporous structures and the specific surface area of MPC are retained. GMPC is then noncovalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) and loaded with Pt nanoparticles by reducing Pt precursor (H{sub 2}PtCl{sub 6}) in ethylene glycol. Pt nanoparticles of {proportional_to}3.0 nm in diameter are uniformly dispersed on GMPC. Compared to Pt supported on Vulcan XC-72 carbon black (Pt/XC-72), Pt/GMPC exhibits a higher mass activity towards oxygen reduction reaction (ORR) and the mass activity retention (in percentage) is improved by a factor of {proportional_to}2 after 44 h accelerated degradation test under the potential step (1.4-0.85 V) electrochemical stressing condition which focuses on support corrosion. The enhanced activity and durability of Pt/GMPC are attributed to the graphitic structure of GMPC which is more resistant to corrosion. These findings demonstrate that GMPC is a promising oxygen reduction electrocatalyst support for PEM fuel cells. The approach reported in this work provides a facile, eco-friendly promising strategy for synthesizing stable metal nanoparticles on hydrophobic support materials. (author)

Carbon-Supported PtRuMo Electrocatalysts for Direct Alcohol Fuel Cells

Directory of Open Access Journals (Sweden)

José L.G. Fierro

2013-10-01

Full Text Available The review article discusses the current status and recent findings of our investigations on the synthesis and characterization of carbon-supported PtRuMo electrocatalysts for direct alcohol fuel cells. In particular, the effect of the carbon support and the composition on the structure, stability and the activity of the PtRuMo nanoparticles for the electrooxidation of CO, methanol and ethanol have been studied. Different physicochemical techniques have been employed for the analysis of the catalysts structures: X-ray analytical methods (XRD, XPS, TXRF, thermogravimetry (TGA and transmission electron microscopy (TEM, as well as a number of electrochemical techniques like CO adsorption studies, current-time curves and cyclic voltammetry measurements. Furthermore, spectroscopic methods adapted to the electrochemical systems for in situ studies, such as Fourier transform infrared spectroscopy (FTIRS and differential electrochemical mass spectrometry (DEMS, have been used to evaluate the oxidation process of CO, methanol and ethanol over the carbon-supported PtRuMo electrocatalysts.

Electro-oxidation of ethanol and ethylene glycol on carbon-supported nano-Pt and -PtRu catalyst in acid solution

International Nuclear Information System (INIS)

Chatterjee, Moitrayee; Chatterjee, Abhik; Ghosh, Susanta; Basumallick, I.

2009-01-01

Present paper reports kinetics of electro-oxidation of ethanol (EtOH) and ethylene glycol (EG) onto Pt and PtRu nanocatalysts of different compositions in the temperature range of 298-318 K. These catalysts have been characterized by SEM, EDX, XRD, CV and amperometry. It has been observed that apparent activation energies for oxidation of EtOH and EG pass through a minimum at about 15-20 at.% of Ru in the PtRu alloy catalysts. Anodic peak current vs. composition curve also shows a maximum around this composition. The results have been explained by a geometric model, which proposes requirement of an ensemble of three Pt atoms with an adjacent Ru atom onto PtRu surface for an efficient electro-oxidation of EtOH or EG. This is further supported from statistical data analysis of probability of occurrence of such ensembles onto PtRu alloy surface. Present results also suggest that electro-oxidation of EG onto nano-PtRu catalyst surfaces follows a different path from that of EtOH at alloy composition less than 15 at.% of Ru.

Electro-oxidation of ethanol and ethylene glycol on carbon-supported nano-Pt and -PtRu catalyst in acid solution

Energy Technology Data Exchange (ETDEWEB)

Chatterjee, Moitrayee; Chatterjee, Abhik; Ghosh, Susanta [Electrochemical Laboratory, Department of Chemistry, Visva-Bharati University, Santiniketan 731235 (India); Basumallick, I., E-mail: ibasumallick@yahoo.co.u [Electrochemical Laboratory, Department of Chemistry, Visva-Bharati University, Santiniketan 731235 (India)

2009-12-01

Present paper reports kinetics of electro-oxidation of ethanol (EtOH) and ethylene glycol (EG) onto Pt and PtRu nanocatalysts of different compositions in the temperature range of 298-318 K. These catalysts have been characterized by SEM, EDX, XRD, CV and amperometry. It has been observed that apparent activation energies for oxidation of EtOH and EG pass through a minimum at about 15-20 at.% of Ru in the PtRu alloy catalysts. Anodic peak current vs. composition curve also shows a maximum around this composition. The results have been explained by a geometric model, which proposes requirement of an ensemble of three Pt atoms with an adjacent Ru atom onto PtRu surface for an efficient electro-oxidation of EtOH or EG. This is further supported from statistical data analysis of probability of occurrence of such ensembles onto PtRu alloy surface. Present results also suggest that electro-oxidation of EG onto nano-PtRu catalyst surfaces follows a different path from that of EtOH at alloy composition less than 15 at.% of Ru.

Architecture-dependent surface chemistry for Pt monolayers on carbon-supported Au.

Science.gov (United States)

Cheng, Shuang; Rettew, Robert E; Sauerbrey, Marc; Alamgir, Faisal M

2011-10-01

Pt monolayers were grown by surface-limited redox replacement (SLRR) on two types of Au nanostructures. The Au nanostructures were fabricated electrochemically on carbon fiber paper (CFP) by either potentiostatic deposition (PSD) or potential square wave deposition (PSWD). The morphology of the Au/CFP heterostructures, examined using scanning electron microscopy (SEM), was found to depend on the type of Au growth method employed. The properties of the Pt deposit, as studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and cyclic voltammetry (CV), were found to depend strongly on the morphology of the support. Specifically, it was found that smaller Au morphologies led to a higher degree of cationicity in the resulting Pt deposit, with Pt(4+) and Pt(2+) species being identified using XPS and XAS. For fuel-cell catalysts, the resistance of ultrathin catalyst deposits to surface area loss through dissolution, poisoning, and agglomeration is critical. This study shows that an equivalent of two monolayers (ML) is the low-loading limit of Pt on Au. At 1 ML or below, the Pt film decreases in activity and durability very rapidly due to presence of cationic Pt. © 2011 American Chemical Society

Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO.sub.2 reforming of methane

KAUST Repository

Biausque, Gregory; Laveille, Paco; Anjum, Dalaver H.; Caps, Valerie; Basset, Jean-Marie

2015-01-01

Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO.sub.2 reforming of methane

Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO.sub.2 reforming of methane

KAUST Repository

Biausque, Gregory

2015-04-28

Methods to synthesize NiPt bimetallic nanoparticles by a reversed-phase microemulsion, deposition of NiPt bimetallic nanoparticles on a support, and application of the supported catalyst for CO.sub.2 reforming of methane

Ethanol electrooxidation on novel carbon supported Pt/SnO{sub x}/C catalysts with varied Pt:Sn ratio

Energy Technology Data Exchange (ETDEWEB)

Jiang, L. [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany); Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian (China); Colmenares, L.; Jusys, Z. [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany); Sun, G.Q. [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian (China)], E-mail: gqsun@dicp.ac.cn; Behm, R.J. [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany)], E-mail: juergen.behm@uni-ulm.de

2007-12-01

Novel carbon supported Pt/SnO{sub x}/C catalysts with Pt:Sn atomic ratios of 5:5, 6:4, 7:3 and 8:2 were prepared by a modified polyol method and characterized with respect to their structural properties (X-ray diffraction (XRD) and transmission electron microscopy (TEM)), chemical composition (XPS), their electrochemical properties (base voltammetry, CO{sub ad} stripping) and their electrocatalytic activity and selectivity for ethanol oxidation (ethanol oxidation reaction (EOR)). The data show that the Pt/SnO{sub x}/C catalysts are composed of Pt and tin oxide nanoparticles with an average Pt particle diameter of about 2 nm. The steady-state activity of the Pt/SnO{sub x}/C catalysts towards the EOR decreases with tin content at room temperature, but increases at 80 deg. C. On all Pt/SnO{sub x}/C catalysts, acetic acid and acetaldehyde represent dominant products, CO{sub 2} formation contributes 1-3% for both potentiostatic and potentiodynamic reaction conditions. With increasing potential, the acetaldehyde yield decreases and the acetic acid yield increases. The apparent activation energies of the EOR increase with tin content (19-29 kJ mol{sup -1}), but are lower than on Pt/C (32 kJ mol{sup -1}). The somewhat better performance of the Pt/SnO{sub x}/C catalysts compared to alloyed PtSn{sub x}/C catalysts is attributed to the presence of both sufficiently large Pt ensembles for ethanol dehydrogenation and C-C bond splitting and of tin oxide for OH generation. Fuel cell measurements performed for comparison largely confirm the results obtained in model studies.

Silica-supported Preyssler Nanoparticles as New Catalysts in the ...

African Journals Online (AJOL)

A new and efficient method for the preparation of 4(3H)-quinazolinones from the condensation of anthranilic acid, orthoester and substituted anilines, in the presence of catalytic amounts of silica-supported Preyssler nanoparticles is reported. The catalyst performs very well in comparison with other catalysts reported before.

Effect of Particle Morphology on the Ripening of Supported Pt Nanoparticles

DEFF Research Database (Denmark)

Simonsen, Søren Bredmose; Chorkendorff, Ib; Dahl, Søren

2012-01-01

To improve the understanding of sintering in diesel and lean-burn engine exhaust after-treatment catalysts, we examined oxygen-induced sintering in a model catalyst consisting of Pt nanoparticles supported on a planar, amorphous Al2O3 substrate. After aging at increasing temperatures, a transmiss......To improve the understanding of sintering in diesel and lean-burn engine exhaust after-treatment catalysts, we examined oxygen-induced sintering in a model catalyst consisting of Pt nanoparticles supported on a planar, amorphous Al2O3 substrate. After aging at increasing temperatures...

Bimetallic Ag-Pt Sub-nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts

Energy Technology Data Exchange (ETDEWEB)

Negreiros, Fabio R. [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Halder, Avik [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Yin, Chunrong [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Singh, Akansha [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Barcaro, Giovanni [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Sementa, Luca [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Tyo, Eric C. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Bartling, Stephan [Institut für Physik, Universität Rostock, Rostock Germany; Meiwes-Broer, Karl-Heinz [Institut für Physik, Universität Rostock, Rostock Germany; Seifert, Sönke [X-ray Science Division, Argonne National Laboratory, Lemont IL USA; Sen, Prasenjit [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Nigam, Sandeep [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Majumder, Chiranjib [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Fukui, Nobuyuki [East Tokyo Laboratory, Genesis Research Institute, Inc., Ichikawa Chiba 272-0001 Japan; Yasumatsu, Hisato [Cluster Research Laboratory, Toyota Technological Institute: in, East Tokyo Laboratory, Genesis Research Institute, Inc. Ichikawa, Chiba 272-0001 Japan; Vajda, Stefan [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Nanoscience and Technology Division, Argonne National Laboratory, Lemont IL USA; Institute for Molecular Engineering, University of Chicago, Chicago IL USA; Fortunelli, Alessandro [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Materials and Process Simulation Center, California Institute of Technology, Pasadena CA USA

2017-12-29

A combined experimental and theoretical investigation of Ag-Pt sub-nanometer clusters as heterogeneous catalysts in the CO -> CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size-selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first-principles simulations at realistic coverage. Insitu GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano-aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O-2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species.

Activity of carbon supported Pt3Ru2 nanocatalyst in CO oxidation

Directory of Open Access Journals (Sweden)

KSENIJA DJ. POPOVIĆ

2009-08-01

Full Text Available The electrocatalytic activity of Pt3Ru2/C nanocatalyst toward the electro-oxidation of bulk CO was examined in acid and alkaline solution at ambient temperature using the thin-film, rotating disk electrode (RDE method. The catalyst was characterized by XRD analysis. The XRD pattern revealed that the Pt3Ru2/C catalyst consisted of two structures, i.e., Pt–Ru-fcc and Ru-hcp (a solid solution of Ru in Pt and a small amount of Ru or a solid solution of Pt in Ru. Electrocatalytic activities were measured by applying potentiodynamic and steady state techniques. The oxidation of CO on the Pt3Ru2/C catalyst was influenced by pH and anions from the supporting electrolytes. The Pt3Ru2/C was more active in alkaline than in acid solution, as well as in perchloric than in sulfuric acid. Comparison of CO oxidation on Pt3Ru2/C and Pt/C revealed that the Pt3Ru2/C was more active than Pt/C in acid solution, while both catalysts had a similar activity in alkaline solution.

Characterization of a surface modified carbon cryogel and a carbon supported Pt catalyst

Directory of Open Access Journals (Sweden)

BILJANA M. BABIĆ

2007-08-01

Full Text Available A carbon cryogel, synthesized by carbonization of a resorcinol/formaldehyde cryogel and oxidized in nitric acid, was used as catalyst support for Pt nano-particles. The Pt/C catalyst was prepared by a modified polyol synthesis method in an ethylene glycol (EG solution. Characterization by nitrogen adsorption showed that the carbon cryogel support and the Pt/C catalyst were mesoporous materials with high specific surface areas (SBET > 400 m2 g-1 and large mesoporous volumes. X-Ray diffraction of the catalyst demonstrated the successful reduction of the Pt precursor to metallic form. TEM Images of the Pt/C catalyst and Pt particle size distribution showed that the mean Pt particle size was about 3.3 nm. Cyclic voltammetry (CV experiments at various scan rates (from 2 to 200 mV s-1 were performed in 0.5 mol dm-3 HClO4 solution. The large capacitance of the oxidized carbon cryogel electrode, which arises from a combination of the double-layer capacitance and pseudocapacitance, associated with the participation of surface redox-type reactions was demonstrated. For the oxidized carbon cryogel, the total specific capacitance determined by 1/C vs. ν0.5 extrapolation method was found to be 386 F g-1. The hydrogen oxidation reaction at the investigated Pt/C catalyst proceeded as an electrochemically reversible, two-electron direct discharge reaction.

Structure and chemical composition of supported Pt-Sn electrocatalysts for ethanol oxidation

International Nuclear Information System (INIS)

Jiang Luhua; Sun Gongquan; Sun Shiguo; Liu Jianguo; Tang Shuihua; Li Huanqiao; Zhou Bing; Xin Qin

2005-01-01

Carbon supported PtSn alloy and PtSnO x particles with nominal Pt:Sn ratios of 3:1 were prepared by a modified polyol method. High resolution transmission electron microscopy (HRTEM) and X-ray microchemical analysis were used to characterize the composition, size, distribution, and morphology of PtSn particles. The particles are predominantly single nanocrystals with diameters in the order of 2.0-3.0 nm. According to the XRD results, the lattice constant of Pt in the PtSn alloy is dilated due to Sn atoms penetrating into the Pt crystalline lattice. While for PtSnO x nanoparticles, the lattice constant of Pt only changed a little. HRTEM micrograph of PtSnO x clearly shows that the change of the spacing of Pt (1 1 1) plane is neglectable, meanwhile, SnO 2 nanoparticles, characterized with the nominal 0.264 nm spacing of SnO 2 (1 0 1) plane, were found in the vicinity of Pt particles. In contrast, the HRTEM micrograph of PtSn alloy shows that the spacing of Pt (1 1 1) plane extends to 0.234 nm from the original 0.226 nm. High resolution energy dispersive X-ray spectroscopy (HR-EDS) analyses show that all investigated particles in the two PtSn catalysts represent uniform Pt/Sn compositions very close to the nominal one. Cyclic voltammograms (CV) in sulfuric acid show that the hydrogen ad/desorption was inhibited on the surface of PtSn alloy compared to that on the surface of the PtSnO x catalyst. PtSnO x catalyst showed higher catalytic activity for ethanol electro-oxidation than PtSn alloy from the results of chronoamperometry (CA) analysis and the performance of direct ethanol fuel cells (DEFCs). It is deduced that the unchanged lattice parameter of Pt in the PtSnO x catalyst is favorable to ethanol adsorption and meanwhile, tin oxide in the vicinity of Pt nanoparticles could offer oxygen species conveniently to remove the CO-like species of ethanolic residues to free Pt active sites

Enhancement of ethanol oxidation at Pt and PtRu nanoparticles dispersed over hybrid zirconia-rhodium supports

Science.gov (United States)

Rutkowska, Iwona A.; Koster, Margaretta D.; Blanchard, Gary J.; Kulesza, Pawel J.

2014-12-01

A catalytic material for electrooxidation of ethanol that utilizes PtRu nanoparticles dispersed over thin films of rhodium-free and rhodium-containing zirconia (ZrO2) supports is described here. The enhancement of electrocatalytic activity (particularly in the potential range as low as 0.25-0.5 V vs. RHE), that has been achieved by dispersing PtRu nanoparticles (loading, 100 μg cm-2) over the hybrid Rh-ZrO2 support composed of nanostructured zirconia and metallic rhodium particles, is clearly evident from comparison of the respective voltammetric and chronoamperometric current densities recorded at room temperature (22 °C) in 0.5 mol dm-3 H2SO4 containing 0.5 mol dm-3 ethanol. Porous ZrO2 nanostructures, that provide a large population of hydroxyl groups in acidic medium in the vicinity of PtRu sites, are expected to facilitate the ruthenium-induced removal of passivating CO adsorbates from platinum, as is apparent from the diagnostic experiments with a small organic molecule such as methanol. Although Rh itself does not show directly any activity toward ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH. It has also been found during parallel voltammetric and chronoamperometric measurements that the hybrid Rh-ZrO2 support increases activity of the platinum component itself toward ethanol oxidation in the low potential range.

Graphitized nanodiamond supporting PtNi alloy as stable anodic and cathodic electrocatalysts for direct methanol fuel cell

International Nuclear Information System (INIS)

Wang, Yongjiao; Zang, Jianbing; Dong, Liang; Pan, Hong; Yuan, Yungang; Wang, Yanhui

2013-01-01

Highlights: • The graphitized nanodiamond (GND) showed a higher oxidation-resistance than XC-72. • The PtNi/GND electrocatalytic exhibited greater stability than PtNi/XC-72. • The PtNi/GND had a better catalytic activity for MOR and ORR than Pt/GND. -- Abstract: Surface graphitized nanodiamond (GND) with a diamond core covered by a graphitic carbon shell was prepared by annealing ND at the temperature of 1300 °C in a vacuum of 10 −3 Pa. PtNi electrocatalysts were prepared by a microwave heating polyol method using the prepared GND as a support. The composition and morphology of the PtNi electrocatalysts supported on GND (PtNi/GND) were characterized by X-ray diffraction, transmission electron microscopy and energy dispersion spectra. The results showed that nano-scaled PtNi alloy particles with an atomic ratio of approximately 1:1 were uniformly deposited on the GND through co-reduction process. The electrocatalytic activities of the PtNi/GND electrocatalysts for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) were investigated by cyclic voltammetry, chronoamperometry and linear sweep voltammetry. The PtNi/GND exhibited better electrocatalytic activities than the Pt/GND either for MOR and ORR. In comparison with traditional carbon support Vulcan XC-72, GND showed higher oxidation-resistance, and consequently led to greater stability for the PtNi/GND than PtNi/XC-72

Unsaturated Fatty Acid Esters Metathesis Catalyzed by Silica Supported WMe5

KAUST Repository

Riache, Nassima; Callens, Emmanuel; Talbi, Karima; Basset, Jean-Marie

2015-01-01

Metathesis of unsaturated fatty acid esters (FAEs) by silica supported multifunctional W-based catalyst is disclosed. This transformation represents a novel route towards unsaturated di-esters. Especially, the self-metathesis of ethyl undecylenate

Constrained Geometry Organotitanium Catalysts Supported on Nanosized Silica for Ethylene (co)Polymerization.

Science.gov (United States)

Li, Kuo-Tseng; Wu, Ling-Huey

2017-05-05

Supported olefin polymerization catalysts can prevent reactor-fouling problems and produce uniform polymer particles. Constrained geometry complexes (CGCs) have less sterically hindered active sites than bis-cyclopentadienyl metallocene catalysts. In the literature, micrometer-sized silica particles were used for supporting CGC catalysts, which might have strong mass transfer limitations. This study aims to improve the activity of supported CGC catalysts by using nanometer-sized silica. Ti[(C₅Me₄)SiMe₂(N t Bu)]Cl₂, a "constrained-geometry" titanium catalyst, was supported on MAO-treated silicas (nano-sized and micro-sized) by an impregnation method. Ethylene homo-polymerization and co-polymerization with 1-octene were carried out in a temperature range of 80-120 °C using toluene as the solvent. Catalysts prepared and polymers produced were characterized. For both catalysts and for both reactions, the maximum activities occurred at 100 °C, which is significantly higher than that (60 °C) reported before for supported bis-cyclopentadienyl metallocene catalysts containing zirconium, and is lower than that (≥140 °C) used for unsupported Ti[(C₅Me₄)SiMe₂(N t Bu)]Me₂ catalyst. Activities of nano-sized catalyst were 2.6 and 1.6 times those of micro-sized catalyst for homopolymerization and copolymerization, respectively. The former produced polymers with higher crystallinity and melting point than the latter. In addition, copolymer produced with nanosized catalyst contained more 1-octene than that produced with microsized catalyst.

Electrochemical evaluation of Pt-Based binary catalysts on various supports for the direct methanol fuel cell

CSIR Research Space (South Africa)

Khotseng, L

2016-01-01

Full Text Available Ru/MoO(sub2) > PtSn/TiO(sub2) > PtRu/TiO(sub2). It was also observed that catalysts supported on MWCNTs were more active than those supported on metal oxides. Furthermore, catalysts supported on MWCNTs proved to be more stable than all the other supported...

Pt supported on nanosized oxides for electrocatalyst used in polymer electrolyte fuel cells

DEFF Research Database (Denmark)

Banu, N.; Serban, E. C.; Marinescu, A.

2011-01-01

Even though Pt is a standard catalyst for fuel cells, new advanced materials with low activation energy and high specific surface area are required. Researches proved that conducting oxides are the emerging candidates as support for Pt catalysts targeting replacement of nanocarbons. This paper pr...

Wettability of modified silica layers deposited on glass support activated by plasma

Energy Technology Data Exchange (ETDEWEB)

Terpiłowski, Konrad, E-mail: terpil@umcs.pl [Department of Physical Chemistry – Interfacial Phenomena, Faculty of Chemistry, Maria Curie-Sklodowska University, Lublin (Poland); Rymuszka, Diana [Department of Physical Chemistry – Interfacial Phenomena, Faculty of Chemistry, Maria Curie-Sklodowska University, Lublin (Poland); Goncharuk, Olena V.; Sulym, Iryna Ya.; Gun’ko, Vladimir M. [Chuiko Institute of Surface Chemistry, National Academy of Science of Ukraine, Kiev (Ukraine)

2015-10-30

Highlights: • New modified silica materials synthesis. • Support surface plasma activation. • Apparent surface free energy determination. • Equilibrium contact angle calculation. - Abstract: Fumed silica modified by hexamethyldisilazane [HDMS] and polydimethylsiloxane [PDMS] was dispersed in a polystyrene/chloroform solution. To increase adhesion between deposited silica layers and a glass surface, the latter was pretreated with air plasma for 30 s. The silica/polystyrene dispersion was deposited on the glass support using a spin coater. After deposition, the plates were dried in a desiccator for 24 h. Water advancing and receding contact angles were measured using the tilted plate method. The apparent surface free energy (γ{sub S}) was evaluated using the contact angle hysteresis approach. The surface topography was determined using the optical profilometry method. Contact angles changed from 59.7° ± 4.4 (at surface coverage with trimethylsilyl groups Θ = 0.14) to 155° ± 3.1 at Θ = 1. The value of γ{sub S} decreased from 51.3 ± 2.8 mJ/m{sup 2} (for the sample at the lowest value of Θ) to 1.0 ± 0.4 mJ/m{sup 2} for the most hydrophobic sample. Thus, some systems with a high degree of modification by HDMS showed superhydrophobicity, and the sliding angle amounted to about 16° ± 2.1.

Carbon nanotubes-supported PtAu-alloy nanoparticles for electro-oxidation of formic acid with remarkable activity

International Nuclear Information System (INIS)

Bai Yancui; Zhang Weide; Chen Caihong; Zhang Jiaqi

2011-01-01

Research highlights: → Electro-oxidation of HCOOH over PtAu at lower potential, higher peak current. → The stability of the PtAu catalyst is high. → Au in the PtAu catalyst promotes utilization of Pt. - Abstract: PtAu-alloy nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) were successfully prepared by simultaneous reduction of H 2 PtCl 6 .6H 2 O and HAuCl 4 .3H 2 O with sodium borohydride as a reducing reagent and sodium citrate as a stabilizing reagent. The morphology and composition of the composite catalyst were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The results show that the PtAu alloy nanoparticles with an average diameter of about 3.5 nm and narrow size distribution are supported on MWCNTs. Electrocatalytic oxidation of formic acid at the PtAu/MWCNTs nanocomposite electrode was investigated in a solution containing 0.50 M H 2 SO 4 as a supporting electrolyte and 0.50 M formic acid by cyclic voltammogram and chronoamperometry. The results demonstrate that the PtAu/MWCNTs catalyst exhibits higher activity and stability for electro-oxidation of formic acid than the commercial Pt/C catalyst, reflecting by its lower onset potential (-0.05 V), oxidation mainly occurring in low potential range of -0.05 ± 0.65 V and higher peak current density of 3.12 mA cm -2 . The result of CO stripping voltammetry discloses that gold in the PtAu/MWCNTs nanocomposite enhances the catalytic activity and stability.

Characterization and evaluation of Pt-Ru catalyst supported on multi-walled carbon nanotubes by electrochemical impedance

Energy Technology Data Exchange (ETDEWEB)

Ocampo, A.L.; Miranda-Hernandez, M.; Sebastian, P.J. [Centro de Investigacion en Energia-UNAM, Temixco, 62580 Morelos (Mexico); Morgado, J.; Montoya, J.A. [IMP, Eje Central Lazaro Cardenas 152, 07730 D.F. Mexico (Mexico)

2006-10-06

In this work the authors present the results of a systematic characterization and evaluation of the carbon nanotube supported Pt-Ru (Pt-Ru/CNT) for its use as methanol oxidation catalyst. Its activity was compared with that of Pt and Pt-Ru catalysts supported on Vulcan and synthesized from carbonyl precursors, and another commercial Pt-Ru catalyst. The cyclic voltammetry, CO stripping and electrochemical impedance techniques were employed to determine the electrocatalytic activity of the catalysts. The electrochemical studies were performed in 0.5M H{sub 2}SO{sub 4} containing different concentrations of methanol (0.05-1M). The results showed a noticeable influence of the catalyst support (CNT) on the performance of the catalyst for CO oxidation. The electrochemical impedance studies allowed us to separate the different steps in the methanol oxidation reaction and to control these steps or reactions by varying the applied potential and the methanol concentration. At low methanol concentration and potentials the de-hydrogenation of methanol predominated. But, at high potential and methanol concentrations, the CO oxidation predominated. These results allowed us to clearly describe at what potential and concentration ranges the bi-functional effect of Ru becomes evident. Our results indicated that the CO oxidation occurs both on Pt and Ru. Compared to other catalysts, Pt-Ru supported on carbon nanotubes showed superior catalytic activity for CO and methanol oxidation. (author)

The electrocatalytic properties of carbon supported PtRu/C nanoalloys in oxidation of small organic molecules: Comparison with Pt/C catalyst

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Lović Jelena D.

2012-01-01

Full Text Available The electrocatalytic activity of carbon supported PtRu/C catalysts, with different composition, toward the electrooxidation of methanol, CO and formic acid were examined in acid and alkaline solution at ambient temperature using thin-film rotating disk electrode (RDE method and compared with activity of Pt/C. The catalysts were characterized by XRD, AFM and STM techniques. XRD pattern revealed that PtRu-1/C catalyst is consisted of two structures e.g. Pt-Ru-fcc and Ru-hcp (the solid solution of Ru in Pt and the small amount of Ru or solid solution of Pt in Ru, as opposed to PtRu-2/C catalyst which is consisted of one structure mostly, Pt-Ru-fcc. According to STM images, PtRu as well as Pt, particles size were between 2 and 6 nm, which is in a good agreement with the mean particles size determined by XRD. To establish the activity and stability of the catalysts potentiodynamic and quasi steady-state measurements were performed. It was found that the activity of Pt and PtRu for CO and methanol oxidation is a strong function of pH of solution. The kinetics are much higher in alkaline than in acid solution and the difference between Pt/C and PtRu/C is much less pronounced in alkaline media. Results presented in this work indicate that activity of PtRu catalysts depends on catalyst composition, e.g. on Pt/Ru atomic ratio, as well as on alloying degree of catalysts. Comparison of CO, methanol and formic acid oxidation on PtRu-2/C, PtRu-1/C and Pt/C catalysts revealed that PtRu-2/C is the most active one. It was shown that the PtRu-2/C catalyst, due to fact that it is consisted of only one phase, with high alloying degree, through the bifunctional mechanism improved by electronic effect, achieve the activity two times higher related to PtRu-1/C in the oxidation of all organic molecules investigated, and about three times higher compared to Pt/C in the oxidation of methanol and CO, and five times higher in formic acid oxidation.

N-Doped Carbon Xerogels as Pt Support for the Electro-Reduction of Oxygen

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Cinthia Alegre

2017-09-01

Full Text Available Durability and limited catalytic activity are key impediments to the commercialization of polymer electrolyte fuel cells. Carbon materials employed as catalyst support can be doped with different heteroatoms, like nitrogen, to improve both catalytic activity and durability. Carbon xerogels are nanoporous carbons that can be easily synthesized in order to obtain N-doped materials. In the present work, we introduced melamine as a carbon xerogel precursor together with resorcinol for an effective in-situ N doping (3–4 wt % N. Pt nanoparticles were supported on nitrogen-doped carbon xerogels and their activity for the oxygen reduction reaction (ORR was evaluated in acid media along with their stability. Results provide new evidences of the type of N groups aiding the activity of Pt for the ORR and of a remarkable stability for N-doped carbon-supported Pt catalysts, providing appropriate physico-chemical features.

Particle size effect of redox reactions for Co species supported on silica

International Nuclear Information System (INIS)

Chotiwan, Siwaruk; Tomiga, Hiroki; Katagiri, Masaki; Yamamoto, Yusaku; Yamashita, Shohei; Katayama, Misaki; Inada, Yasuhiro

2016-01-01

Conversions of chemical states during redox reactions of two silica-supported Co catalysts, which were prepared by the impregnation method, were evaluated by using an in situ XAFS technique. The addition of citric acid into the precursor solution led to the formation on silica of more homogeneous and smaller Co particles, with an average diameter of 4 nm. The supported Co 3 O 4 species were reduced to metallic Co via the divalent CoO species during a temperature-programmed reduction process. The reduced Co species were quantitatively oxidized with a temperature-programmed oxidation process. The higher observed reduction temperature of the smaller CoO particles and the lower observed oxidation temperature of the smaller metallic Co particles were induced by the higher dispersion of the Co oxide species, which apparently led to a stronger interaction with supporting silica. The redox temperature between CoO and Co 3 O 4 was found to be independent of the particle size. - Graphical abstract: Chemical state conversions of SiO 2 -supported Co species and the particle size effect have been analyzed by means of in situ XAFS technique. The small CoO particles have endurance against the reduction and exist in a wide temperature range. Display Omitted - Highlights: • The conversions of the chemical state of supported Co species during redox reaction are evaluated. • In operando XAFS technique were applied to measure redox properties of small Co particles. • A small particle size affects to the redox temperatures of cobalt catalysts.

Polymerization of Methyl Methacrylate with Samarocene Complex Supported on Mesoporous Silica

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

Samarocene complex was supported on a series of mesoporous silica with various pore sizes. Polymerization of methyl methacrylate (MMA) by these catalysts provide highly syndiotactic PMMAs with higher molecular weights compared with those obtained by solution polymerization with homogeneous catalyst system.

Citric acid induced promoted dispersion of Pt on the support and enhanced catalytic activities for a Pt-based catalyst

Science.gov (United States)

Cheng, Tianqiong; Wang, Jianli; Wang, Suning; Cui, Yajuan; Zhang, Hailong; Yan, Shuang; Yuan, Shandong; Chen, Yaoqiang

2017-12-01

Citric acid (CA), as the chelating agent, was introduced to obtain the enhanced Pt dispersion and catalytic activities for the Pt-based catalysts supported on oxygen-storage material. The role and content of CA were investigated systematically. It was found that the citric acid-assisted catalysts showed better Pt dispersion and smaller nanoparticle size of Pt. Thus, the catalyst had lower reduction temperature, preferable thermostability and possessed more oxidation state of Pt species under the oxidation atmosphere. The citric acid-induced fresh catalysts were excellent to convert CO and the corresponding aged ones exhibited higher activities for the elimination of all the target pollutants. Among the aged catalysts, P2-a (the mole ratio of Pt/CA is 2:1) presented the best performance. Particularly, compared with the reference sample (Pc-a), the light-off temperatures (T50) of NO, HC and CO for P2-a decreased by 39 °C, 42 °C and 72 °C, respectively, and the full-conversion temperatures (T90) of NO, HC and CO for P2-a decreased by 44 °C, 44 °C and 48 °C, respectively. Therefore, this work provides a facile and valid method to manufacture advanced catalysts for purification of the vehicle exhaust in the future.

Influence of surface morphology on methanol oxidation at a glassy carbon-supported Pt catalyst

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S. STEVANOVIC

2008-08-01

Full Text Available Platinum supported on glassy carbon (GC was used as a model system for studying the influence of the surface morphology of a Pt catalyst on methanol oxidation in alkaline and acidic solutions. Platinum was deposited by the potential step method on GC samples from H2SO4 + H2PtCl6 solution under the same conditions with loadings from 10 to 80 mg cm-2. AFM and STM images of the GC/Pt electrodes showed that the Pt was deposited in the form of 3D agglomerates composed of spherical particles. Longer deposition times resulted in increased growth of Pt forms and a decrease in the specific area of the Pt. The real surface area of Pt increased with loading but the changes were almost negligible at higher loadings. Nevertheless, both the specific and mass activity of platinum supported on glassy carbon for methanol oxidation in acidic and in alkaline solutions exhibit a volcanic dependence with respect to the platinum loading. The increase in the activity can be explained by the increasing the particle size with the loading and thus an increase in the contiguous Pt sites available for adsorption and decomposition of methanol. However, the decrease in the activity of the catalyst with further increase of loading and particle size after reaching the maximum is related to the decrease of active sites available for methanol adsorption and their accessibility as a result of more close proximity and pronounced coalescence of the Pt particles.

Chemoselective Hydrogenation with Supported Organoplatinum(IV) Catalyst on Zn(II)-Modified Silica

Energy Technology Data Exchange (ETDEWEB)

Camacho-Bunquin, Jeffrey [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Ferrandon, Magali [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Sohn, Hyuntae [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Yang, Dali [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Liu, Cong [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Ignacio-de Leon, Patricia Anne [Energy Sciences Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Perras, Frédéric A. [Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50010, United States; Pruski, Marek [Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50010, United States; Department of Chemistry, Iowa State University, 2416 Pammel Drive, Ames, Iowa 50011, United States; Stair, Peter C. [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States; Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States; Delferro, Massimiliano [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States

2018-02-22

Well-defined organoplatinum(IV) sites were grafted on a Zn(II)-modified SiO2 support via surface organometallic chemistry in toluene at room temperature. Solid-state spectroscopies including XAS, DRIFTS, DRUV-Vis, and solid-state (SS)NMR enhanced by dynamic nuclear polarization (DNP), as well as TPR-H2 and TEM techniques revealed highly dispersed (methylcyclopentadi-enyl)methylplatinum(IV) sites on the surface ((MeCp)PtMe/Zn/SiO2, 1). In addition, computational modelling suggests that the surface reaction of (MeCp)PtMe3 with Zn(II)-modified SiO2 support is thermodynamically favorable (ΔG = -12.4 kcal/mol), likely due to the increased acidity of the hydroxyl group, as confirmed by NH3-TPD and DNP-enhanced 17O{1H} SSNMR. In situ DRIFTS and XAS hydrogenation experiments reveal the formation of a surface Pt(IV)-H upon hydrogenolysis of Pt-Me groups. The heterogenized organoplatinum(IV)-H sites catalyze the selective partial hydrogenation of 1,3-butadiene to butenes (up to 95%) and the reduction of nitrobenzene derivatives to anilines (up to 100%) with excellent tolerance of reduction-sensitive func-tional groups (olefin, carbonyl, nitrile, halogens) under mild reaction conditions.

Pt/MOx/SiO2, Pt/MOx/TiO2, and Pt/MOx/Al2O3 Catalysts for CO Oxidation

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Hongmei Qin

2015-04-01

Full Text Available Conventional supported Pt catalysts have often been prepared by loading Pt onto commercial supports, such as SiO2, TiO2, Al2O3, and carbon. These catalysts usually have simple metal-support (i.e., Pt-SiO2 interfaces. To tune the catalytic performance of supported Pt catalysts, it is desirable to modify the metal-support interfaces by incorporating an oxide additive into the catalyst formula. Here we prepared three series of metal oxide-modified Pt catalysts (i.e., Pt/MOx/SiO2, Pt/MOx/TiO2, and Pt/MOx/Al2O3, where M = Al, Fe, Co, Cu, Zn, Ba, La for CO oxidation. Among them, Pt/CoOx/SiO2, Pt/CoOx/TiO2, and Pt/CoOx/Al2O3 showed the highest catalytic activities. Relevant samples were characterized by N2 adsorption-desorption, X-ray diffraction (XRD, transmission electron microscopy (TEM, H2 temperature-programmed reduction (H2-TPR, X-ray photoelectron spectroscopy (XPS, CO temperature-programmed desorption (CO-TPD, O2 temperature-programmed desorption (O2-TPD, and CO2 temperature-programmed desorption (CO2-TPD.

Effect of Support Pretreatment Temperature on the Performance of an Iron Fischer–Tropsch Catalyst Supported on Silica-Stabilized Alumina

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Kamyar Keyvanloo

2018-02-01

Full Text Available The effect of support material pretreatment temperature, prior to adding the active phase and promoters, on Fischer–Tropsch activity and selectivity was explored. Four iron catalysts were prepared on silica-stabilized alumina (AlSi supports pretreated at 700 °C, 900 °C, 1100 °C or 1200 °C. Addition of 5% silica to alumina made the AlSi material hydrothermally stable, which enabled the unusually high support pretreatment temperatures (>900 °C to be studied. High-temperature dehydroxylation of the AlSi before impregnation greatly reduces FeO·Al2O3 surface spinel formation by removing most of the support-surface hydroxyl groups leading to more effectively carbided catalyst. The activity increases more than four-fold for the support calcined at elevated temperatures (1100–1200 °C compared with traditional support calcination temperatures of <900 °C. This unique pretreatment also facilitates the formation of ε′-Fe2.2C rather than χ-Fe2.5C on the AlSi support, which shows an excellent correlation with catalyst productivity.

Crumpled rGO-supported Pt-Ir bifunctional catalyst prepared by spray pyrolysis for unitized regenerative fuel cells

Science.gov (United States)

Kim, In Gyeom; Nah, In Wook; Oh, In-Hwan; Park, Sehkyu

2017-10-01

Three-dimensional (3D) crumpled reduced graphene oxide supported Pt-Ir alloys that served as bifunctional oxygen catalysts for use in untized regenerative fuel cells were synthesized by a facile spray pyrolysis method. Pt-Ir catalysts supported on rGO (Pt-Ir/rGOs) were physically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to observe change in composition by heat treatment, alloying, and morphological transition of the catalysts. Their catalytic activities and stabilities for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) conditions were electrochemically investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), potential cycling and hold tests on the rotating disk electrode (RDE). Pt-Ir/rGO with no post heat-treatment (Pt-Ir/rGO_NP) showed a lower activity for ORR and OER although metal nanoparticles decorated on the support are relatively small. However, Pt-Ir/rGO showed remarkably enhanced activity following heat treatment, depending on temperature. Pt-Ir/rGO heat-treated at 600 °C after spray pyrolysis (Pt-Ir/rGO_P600) exhibited a higher activity and stability than a commercially available Pt/C catalyst kept under the ORR condition, and it also revealed a comparable OER activity and durability versus the commercial unsupported Ir catalyst.

Core-shell structural nanodiamond@TiN supported Pt nanoparticles as a highly efficient and stable electrocatalyst for direct methanol fuel cells

International Nuclear Information System (INIS)

Zhao, Yuling; Wang, Yanhui; Dong, Liang; Zhang, Yan; Huang, Junjie; Zang, Jianbing; Lu, Jing; Xu, Xipeng

2014-01-01

Highlights: • Core-shell structural nanodiamond@TiN was used as a novel support for Pt catalysts. • The ND@TiN support possessed a high electrochemical stability than carbon black. • The Pt/ND@TiN showed a higher catalytic activity for MOR and ORR than the Pt/C. • The Pt/ND@TiN demonstrated a much better durability compared with the Pt/C. - Abstract: A novel core-shell support material was designed with nanodiamond (ND) as core possessed excellent stability and TiN as shell improved the conductivity of support. The nano-TiN shell was decorated on the surface of ND by annealing TiO 2 in nitrogen atmosphere, and the obtained ND@TiN was employed to support Pt nanoparticles (NPs). The ND@TiN support and Pt/ND@TiN electrocatalyst were characterized by X-ray diffraction and transmission electron microscopy. ND particles were coated uniformly by the TiN layer and Pt NPs with a mean size of 4.2 nm were highly dispersed on the surface of ND@TiN. The electrochemical results confirmed that the ND@TiN support possessed a much more stability than the carbon black and exhibited a bigger background current density than the ND. The Pt/ND@TiN catalyst showed higher catalytic activity and better stability in methanol oxidation and oxygen reduction reactions compared with the Pt/C and Pt/ND

Improving the stability and ethanol electro-oxidation activity of Pt catalysts by selectively anchoring Pt particles on carbon-nanotubes-supported-SnO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Li, J.J.; Wang, J.S.; Zhao, J.H.; Song, C.Y.; Wang, L.C. [School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou (China); Guo, X. [Department of Chemistry, Tsinghua University, Beijing (China)

2012-10-15

To improve the stability and activity of Pt catalysts for ethanol electro-oxidation, Pt nanoparticles were selectively deposited on carbon-nanotubes (CNTs)-supported-SnO{sub 2} to prepare Pt/SnO{sub 2}/CNTs and Pt/CNTs was prepared by impregnation method for reference study. X-ray diffraction (XRD) was used to confirm the crystalline structures of Pt/SnO{sub 2}/CNTs and Pt/CNTs. The stabilities of Pt/SnO{sub 2}/CNTs and Pt/CNTs were compared by analyzing the Pt size increase amplitude using transmission electron microscopy (TEM) images recorded before and after cyclic voltammetry (CV) sweeping. The results showed that the Pt size increase amplitude is evidently smaller for Pt/SnO{sub 2}/CNTs, indicating the higher stability of Pt/SnO{sub 2}/CNTs. Although both catalysts exhibit degradation of electrochemical active surface area (EAS) after CV sweeping, the EAS degradation for the former is lower, further confirming the higher stability of Pt/SnO{sub 2}/CNTs. CV and potentiostatic current-time curves were recorded for ethanol electro-oxidation on both catalysts before and after CV sweeping and the results showed that the mass specific activity of Pt/CNTs increases more than that of Pt/SnO{sub 2}/CNTs, indicating that Pt/CNTs experiences more severe evolution and is less stable. The calculated area specific activity of Pt/SnO{sub 2}/CNTs is larger than that of Pt/CNTs, indicating SnO{sub 2} can co-catalyze Pt due to plenty of interfaces between SnO{sub 2} and Pt. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The effect of antimony-tin and indium-tin oxide supports on the catalytic activity of Pt nanoparticles for ammonia electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Silva, Júlio César M. [Department of Chemical & Biological Engineering, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada); Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP (Brazil); Piasentin, Ricardo M.; Spinacé, Estevam V.; Neto, Almir O. [Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Cidade Universitária, CEP 05508-900, São Paulo, SP (Brazil); Baranova, Elena A., E-mail: elena.baranova@uottawa.ca [Department of Chemical & Biological Engineering, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada)

2016-09-01

Platinum nanoparticles supported on carbon (Pt/C) and carbon with addition of ITO (Pt/C-ITO (In{sub 2}O{sub 3}){sub 9}·(SnO{sub 2}){sub 1}) and ATO (Pt/C-ATO (SnO{sub 2}){sub 9}·(Sb{sub 2}O{sub 5}){sub 1}) oxides were prepared by sodium borohydride reduction method and used for ammonia electro-oxidation reaction (AmER) in alkaline media. The effect of the supports on the catalytic activity of Pt for AmER was investigated using electrochemical (cyclic voltammetry and chronoamperometry) and direct ammonia fuel cell (DAFC) experiments. X-ray diffraction (XRD) showed Pt peaks attributed to the face-centered cubic (fcc) structure, as well as peaks characteristic of In{sub 2}O{sub 3} in ITO support and cassiterite SnO{sub 2} phase of ATO support. According to transmission electron micrographs the mean particles sizes of Pt over carbon were 5.4, 4.9 and 4.7 nm for Pt/C, Pt/C-ATO and Pt/C-ITO, respectively. Pt/C-ITO catalysts showed the highest catalytic activity for ammonia electrooxidation in both electrochemical and fuel cell experiments. We attributed this to the presence of In{sub 2}O{sub 3} phase in ITO, which provides oxygenated or hydroxide species at lower potentials resulting in the removal of poisonous intermediate, i.e., atomic nitrogen (N{sub ads}) and promotion of ammonia electro-oxidation. - Highlights: • Oxide support effect on the catalytic activity of Pt towards ammonia electro-oxidation. • Direct ammonia fuel cell (DAFC) performance using Pt over different supports as anode. • Pt/C-ITO shows better catalytic activity for ammonia oxidation than Pt/C and Pt/C-ATO.

Effects of the Electrodeposition Time in the Synthesis of Carbon-Supported Pt(Cu and Pt-Ru(Cu Core-Shell Electrocatalysts for Polymer Electrolye Fuel Cells

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Griselda Caballero-Manrique

2016-08-01

Full Text Available Pt(Cu/C and Pt-Ru(Cu/C electrocatalysts with core-shell structure supported on Vulcan Carbon XC72R have been synthesized by potentiostatic deposition of Cu nanoparticles on the support, galvanic exchange with Pt and spontaneous deposition of Ru species. The duration of the electrodeposition time of the different species has been modified and the obtained electrocatalysts have been characterized using electrochemical and structural techniques. The High Resolution Transmission Electron Microscopy (HRTEM, Fast Fourier Transform (FFT and Energy Dispersive X-ray (EDX microanalyses allowed the determining of the effects of the electrodeposition time on the nanoparticle size and composition. The best conditions identified from Cyclic Voltammetry (CV corresponded to onset potentials for CO and methanol oxidation on Pt-Ru(Cu/C of 0.41 and 0.32 V vs. the Reversible Hydrogen Electrode (RHE, respectively, which were smaller by about 0.05 V than those determined for Ru-decorated commercial Pt/C. The CO oxidation peak potentials were about 0.1 V smaller when compared to commercial Pt/C and Pt-Ru/C. The positive effect of Cu was related to its electronic effect on the Pt shells and also to the generation of new active sites for CO oxidation. The synthesis conditions to obtain the best performance for CO and methanol oxidation on the core-shell Pt-Ru(Cu/C electrocatalysts were identified. When compared to previous results in literature for methanol, ethanol and formic acid oxidation on Pt(Cu/C catalysts, the present results suggest an additional positive effect of the deposited Ru species due to the introduction of the bifunctional mechanism for CO oxidation.

Characteristics of supported nano-TiO2/ZSM-5/silica gel (SNTZS): Photocatalytic degradation of phenol

International Nuclear Information System (INIS)

Zainudin, Nor Fauziah; Abdullah, Ahmad Zuhairi; Mohamed, Abdul Rahman

2010-01-01

Photocatalytic degradation of phenol was investigated using the supported nano-TiO 2 /ZSM-5/silica gel (SNTZS) as a photocatalyst in a batch reactor. The prepared photocatalyst was characterized using XRD, TEM, FT-IR and BET surface area analysis. The synthesized photocatalyst composition was developed using nano-TiO 2 as the photoactive component and zeolite (ZSM-5) as the adsorbents, all supported on silica gel using colloidal silica gel binder. The optimum formulation of SNTZS catalyst was observed to be (nano-TiO 2 :ZSM-5:silica gel:colloidal silica gel = 1:0.6:0.6:1) which giving about 90% degradation of 50 mg/L phenol solution in 180 min. The SNTZS exhibited higher photocatalytic activity than that of the commercial Degussa P25 which only gave 67% degradation. Its high photocatalytic activity was due to its large specific surface area (275.7 m 2 /g), small particle size (8.1 nm), high crystalline quality of the synthesized catalyst and low electron-hole pairs recombination rate as ZSM-5 adsorbent was used. The SNTZS photocatalyst synthesized in this study also has been proven to have an excellent adhesion and reusability.

Robust non-carbon titanium nitride nanotubes supported Pt catalyst with enhanced catalytic activity and durability for methanol oxidation reaction

International Nuclear Information System (INIS)

Xiao, Yonghao; Zhan, Guohe; Fu, Zhenggao; Pan, Zhanchang; Xiao, Chumin; Wu, Shoukun; Chen, Chun; Hu, Guanghui; Wei, Zhigang

2014-01-01

By the combination of solvothermal alcoholysis and post-nitriding method, titanium nitride nanotubes (TiN NTs), with high surface area, hollow and interior porous structure are prepared successfully and used at a support for Pt nanoparticles. The TiN NTs supported Pt (Pt/TiN NTs) catalyst displays enhanced activity and durability towards methanol oxidation reaction (MOR) compared with the commercial Pt/C (E-TEK) catalyst. X ray diffraction (XRD), nitrogen adsorption/desorption, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) measurements are performed to investigate the physicochemical properties of the synthesized catalyst. SEM and TEM images reveal that the wall of the TiN NTs is porous and Pt nanoparticles supported on the dendritic TiN nanocrystals exhibit small size and good dispersion. Effects of inherent corrosion-resistant, tubular and porous nanostructures and electron transfer due to the strong metal–support interactions of TiN NTs contribute to the enhanced catalytic activity and stability of Pt/TiN NTs towards the MOR

Radiolytic synthesis of carbon-supported PtRu nanoparticles using high-energy electron beam: effect of pH control on the PtRu mixing state and the methanol oxidation activity

International Nuclear Information System (INIS)

Ohkubo, Yuji; Kageyama, Satoru; Seino, Satoshi; Nakagawa, Takashi; Kugai, Junichiro; Nitani, Hiroaki; Ueno, Koji; Yamamoto, Takao A.

2013-01-01

Electrode catalysts composed of carbon-supported PtRu nanoparticles (PtRu/C) for use as a direct methanol fuel cell anode were synthesized by the reduction of precursor ions in an aqueous solution via irradiation with a high-energy electron beam. The effect of pH control in the precursor solution on the PtRu mixing state and the methanol oxidation activity was studied in order to enhance the catalytic activity for methanol oxidation. The PtRu/C structures were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray fluorescence spectrometry, and X-ray diffraction and X-ray absorption fine structure techniques. The methanol oxidation activity was evaluated by linear sweep voltammetry. The initial pH of the precursor solution has little influence on the average grain size for the metal particles (approximately 3.5 nm) on the carbon particle supports, but the dispersibility of the metal particles, PtRu mixing state, and methanol oxidation activity differed. The maintenance of a low pH in the precursor solution gave the best dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles, whereas, a high pH gave the best PtRu mixing state and the highest oxidation current although a low dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles was obtained. The PtRu mixing state strongly correlated with the methanol oxidation current. In addition, a high pH was more effective for PtRu mixing when using an electron beam irradiation reduction method, because the complexation reaction of the chelating agents was improved, which resulted in an enhancement of the catalytic activity for methanol oxidation.

Radiolytic synthesis of carbon-supported PtRu nanoparticles using high-energy electron beam: effect of pH control on the PtRu mixing state and the methanol oxidation activity

Energy Technology Data Exchange (ETDEWEB)

Ohkubo, Yuji, E-mail: okubo@mit.eng.osaka-u.ac.jp; Kageyama, Satoru; Seino, Satoshi; Nakagawa, Takashi; Kugai, Junichiro [Osaka University, Graduate School of Engineering (Japan); Nitani, Hiroaki [High Energy Accelerator Research Organization (KEK), Institute of Materials Structure Science (Japan); Ueno, Koji [Japan Electron Beam Irradiation Service Ltd (Japan); Yamamoto, Takao A. [Osaka University, Graduate School of Engineering (Japan)

2013-05-15

Electrode catalysts composed of carbon-supported PtRu nanoparticles (PtRu/C) for use as a direct methanol fuel cell anode were synthesized by the reduction of precursor ions in an aqueous solution via irradiation with a high-energy electron beam. The effect of pH control in the precursor solution on the PtRu mixing state and the methanol oxidation activity was studied in order to enhance the catalytic activity for methanol oxidation. The PtRu/C structures were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray fluorescence spectrometry, and X-ray diffraction and X-ray absorption fine structure techniques. The methanol oxidation activity was evaluated by linear sweep voltammetry. The initial pH of the precursor solution has little influence on the average grain size for the metal particles (approximately 3.5 nm) on the carbon particle supports, but the dispersibility of the metal particles, PtRu mixing state, and methanol oxidation activity differed. The maintenance of a low pH in the precursor solution gave the best dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles, whereas, a high pH gave the best PtRu mixing state and the highest oxidation current although a low dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles was obtained. The PtRu mixing state strongly correlated with the methanol oxidation current. In addition, a high pH was more effective for PtRu mixing when using an electron beam irradiation reduction method, because the complexation reaction of the chelating agents was improved, which resulted in an enhancement of the catalytic activity for methanol oxidation.

Pt Catalyst Supported within TiO2 Mesoporous Films for Oxygen Reduction Reaction

International Nuclear Information System (INIS)

Huang, Dekang; Zhang, Bingyan; Bai, Jie; Zhang, Yibo; Wittstock, Gunther; Wang, Mingkui; Shen, Yan

2014-01-01

In this study, dispersed Pt nanoparticles into mesoporous TiO 2 thin films are fabricated by a facile electrochemical deposition method as electro-catalysts for oxygen reduction reaction. The mesoporous TiO 2 thin films coated on the fluorine-doped tin oxide glass by screen printing allow a facile transport of reactants and products. The structural properties of the resulted Pt/TiO 2 electrode are evaluated by field emission scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. Cyclic voltammetry measurements are performed to study the electrochemical properties of the Pt/TiO 2 electrode. Further study demonstrates the stability of the Pt catalyst supported within TiO 2 mesoporous films for the oxygen reduction reaction

Preparation and Properties of Nano Dy/TiO2 Films Supported on High Silica Fiber

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HUANG Feng-ping

2017-07-01

Full Text Available In order to improve the photocatalytic degradation performance and stability of nano TiO2, Dy doped TiO2 supported on high silica glass fiber was prepared by microwave-sol method combined with dip-coating method. The samples were analyzed by XRD,SEM,PL,EDS,XPS and other equipments for phase composition of films,surface topography, surface elements and the stability of films. And the effects of pretreatment solution and coating method on the high-silica fiber film were investigated.In addition, the photocatalytic performance of the sample has been investigated by degrading methylene blue. The results show that the catalytic stability of Dy doping TiO2 nanofilms supported on high silica glass fiber can be improved and the degradation of methyl orange can reach 94% in 30min after 5 times of coating treatment.

MnO2/CNT supported Pt and PtRu nanocatalysts for direct methanol fuel cells.

Science.gov (United States)

Zhou, Chunmei; Wang, Hongjuan; Peng, Feng; Liang, Jiahua; Yu, Hao; Yang, Jian

2009-07-07

Pt/MnO2/carbon nanotube (CNT) and PtRu/MnO2/CNT nanocomposites were synthesized by successively loading hydrous MnO2 and Pt (or PtRu alloy) nanoparticles on CNTs and were used as anodic catalysts for direct methanol fuel cells (DMFCs). The existence of MnO2 on the surface of CNTs effectively increases the proton conductivity of the catalyst, which then could remarkably improve the performance of the catalyst in methanol electro-oxidation. As a result, Pt/MnO2/CNTs show higher electrochemical active surface area and better methanol electro-oxidation activity, compared with Pt/CNTs. As PtRu alloy nanoparticles were deposited on the surface of MnO2/CNTs instead of Pt, the PtRu/MnO2/CNT catalyst shows not only excellent electro-oxidation activity to methanol with forward anodic peak current density of 901 A/gPt but also good CO oxidation ability with lower preadsorbed CO oxidation onset potential (0.33 V vs Ag/AgCl) and peak potential (0.49 V vs Ag/AgCl) at room temperature.

Influence of Support Material of PtSnNiGa/C Electrocatalysts for Ethanol Oxidation

Directory of Open Access Journals (Sweden)

Deise M Santos

2017-07-01

Full Text Available Ethanol is a promising alternative source for fuel cells due to its low toxicity and high power density. However, the cleavage of the C-C bond, CO poisoning, and low electrocatalyst stability are still considered crucial issues. To overcome this limitation, binary, ternary and quaternary electrocatalysts have been investigated along with new carbon supports. This paper presents a physicochemical and electrochemical investigation of quaternary PtSnNiGa/C electrocatalysts supported on Vulcan XC72 and Printex-L6 carbons and also a carbon produced by natural gas pyrolysis in an Argon plasma torch (Black Plasma. The electrochemical characterization was performed through cyclic voltammetry, chronoamperometry, chronopotentiometry and electrochemical impedance spectroscopy in the presence of ethanol 1.0 mol L-1. Energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscopy were also carried out for physicochemical characterization. The electrochemical results show that the quaternary electrocatalysts supported on Vulcan XC72 and Printex-L6 carbons display a high current normalized by Pt mass and are more stable than the electrocatalyst supported on Black Plasma. In addition, the quaternary electrocatalysts with reduced Pt loading display better electrocatalytic activity towards the EOR compared to high Pt loading electrocatalysts. DOI: http://dx.doi.org/10.17807/orbital.v9i3.949 

Hydrogenation of tetralin in the presence of dibenzothiophene and quinoline on Pt-Pd/SiO{sub 2}-Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Gutierrez, O.Y.; Yu, Y.; Jentys, A.; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Dept. of Chemistry and Catalysis Research Center

2012-07-01

Three Pt-Pd catalysts with 0.3 and 0.5 wt.% of Pt and Pd, respectively, were supported on amorphous silica alumina with Al{sub 2}O{sub 3}:SiO{sub 2} wt.% ratios of 20:80, 30:70 and 55:45. The materials were characterized by physisorption of N{sub 2}, TEM, X-ray absorption spectroscopy and adsorption of pyridine and CO followed by IR spectroscopy. The EXAFS fitting and IR characterization showed that bimodal distributions of monometallic Pd and bimetallic Pt-Pd particles. The bimetallic particles in all catalysts have a Pt-rich core and a Pd-rich shell. However, the degree of alloying and proportion of exposed Pt increases with increasing concentration of Lewis acid sites (LAS) in the support, probably because the LAS are good anchoring sites for Pt species. The activity of the catalysts for the hydrogenation of tetralin in the presence of DBT and quinoline, and the corresponding selectivity to cis-decalin increase with the proportion of exposed Pt. Therefore, in the presence of DBT and quinoline the morphology of bimetallic clusters is the parameter determining its hydrogenation performance. (orig.)

Enhancement of Degradation and Dechlorination of Trichloroethylene via Supporting Palladium/Iron Bimetallic Nanoparticles onto Mesoporous Silica

Directory of Open Access Journals (Sweden)

Jianjun Wei

2016-07-01

Full Text Available This study is aimed to prevent the agglomeration of Pd/Fe bimetallic nanoparticles and thus improve the efficiency toward degradation and dechlorination of chlorinated organic contaminants. A mesoporous silica with a primary pore diameter of 8.3 nm and a specific surface area of 688 m2/g was prepared and used as the host of Pd/Fe nanoparticles. The Pd/Fe nanoparticles were deposited onto or into the mesoporous silica by reduction of ferrous ion and hexachloropalladate ion in aqueous phase. Batch degradation and dechlorination reactions of trichloroethylene were conducted with initial trichloroethylene concentration of 23.7 mg/L, iron loading of 203 or 1.91 × 103 mg/L and silica loading of 8.10 g/L at 25 °C. Concentration of trichloroethylene occurs on the supported Pd/Fe nanoparticles, with trichloroethylene degrading to 56% and 59% in 30 min on the supported Pd/Fe nanoparticles with weight percentage of palladium to iron at 0.075% and 0.10% respectively. The supported Pd/Fe nanoparticles exhibit better dechlorination activity. When the supported Pd/Fe nanoparticles with a weight percentage of palladium to iron of 0.10% were loaded much less than the bare counterpart, the yield of ethylene plus ethane in 10 h on them was comparable, i.e., 19% vs. 21%. This study offers a future approach to efficiently combine the reactivity of supported Pd/Fe nanoparticles and the adsorption ability of mesoporous silica.

Pt nanoparticles supported over Ce-Ti-O: the solvothermal and photochemical approaches for the preparation of catalytic materials

International Nuclear Information System (INIS)

Silva, Adrian M. T.; Machado, Bruno F.; Gomes, Helder T.; Figueiredo, Jose L.; Drazic, Goran; Faria, Joaquim L.

2010-01-01

Ce-Ti-O supports with different Ce/Ti molar ratios were synthesized by the solvothermal method using hexadecyltrimethylammonium bromide. Pt nanoparticles were then supported by photochemical deposition. The shape, size, and structure of these materials were analyzed by high-resolution transmission electron microscopy. The single CeO 2 support was also prepared, consisting of agglomerated cubic particles ranging from ∼3 to 8 nm. When titania was combined with ceria, a nanostructured architecture was produced, evidencing the strong influence of Ti in the support structure. Photodeposition of Pt nanoparticles is more efficient on Ce-Ti-O supports than in pristine CeO 2 . Crystalline Pt nanoparticles (mainly of ∼2 to 4 nm) were detected. The catalytic properties of the materials were tested in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. It was observed that Pt supported on Ce-Ti-O is more active and selective than Pt on CeO 2 or TiO 2 separately. The catalyst with 40 mol% Ce leads to total conversion of cinnamaldehyde in a few minutes; however, higher selectivity toward the desired product (cinnamyl alcohol) was obtained with higher amounts of Ce (50 mol%).

In situ TEM study of the coarsening of carbon black supported Pt nanoparticles in hydrogen

DEFF Research Database (Denmark)

Simonsen, Søren Bredmose; Wang, Yan; Jensen, Jens Oluf

2017-01-01

The control of sizes and shapes of nanostructures is of tremendous importance for the catalytic activity in electrochemistry and in catalysis more generally. However, due to relatively large surface free energies, nanostructures often sinter to form coarser and more stable structures that may...... not have the intended physicochemical properties. Pt is known to be a very active catalyst in several chemical reactions and for example as carbon supported nanoparticles in fuel cells. The presentation focusses on coarsening mechanisms of Pt nanoparticles supported on carbon black during exposure...... to hydrogen. By means of in situ transmission electron microscopy (TEM), Pt nanoparticle coarsening was monitored in 6 mbar 20 % H2/Ar while ramping up the temperature to ca. 900 °C. Time-resolved TEM images directly reveal that separated ca. 3 nm sized Pt nanoparticles in the pure hydrogen environment...

Synthesis of honeycomb-like mesoporous nitrogen-doped carbon nanospheres as Pt catalyst supports for methanol oxidation in alkaline media

Science.gov (United States)

Zhang, Yunmao; Liu, Yong; Liu, Weihua; Li, Xiying; Mao, Liqun

2017-06-01

This paper reports the convenient synthesis of honeycomb-like mesoporous nitrogen-doped carbon spheres (MNCS) using a self-assembly strategy that employs dopamine (DA) as a carbon and nitrogen precursor and a polystyrene-b-poly(ethylene oxide) (PS173-b-PEO170) diblock copolymer as a soft template. The MNCS have large BET surface areas of up to 554 m2 g-1 and high nitrogen contents of up to 6.9 wt%. The obtained MNCS are used as a support for Pt catalysts, which promote methanol oxidation in alkaline media. The MNCS-supported Pt (Pt/MNCS) catalyst has a larger electrochemically active surface area (ESA) (89.2 m2 g-1) than does a commercially available Vulcan XC-72R supported Pt/C catalyst. Compared to the Pt/C catalyst, Pt/MNCS displays a higher peak current density (1007 mA mg-1) and is more stable during methanol oxidation. These improvements are attributed to the honeycomb-like porous structure of the MNCS and the introduction of nitrogen to the carbon support. The MNCS effectively stabilize Pt nanoparticles and assuage the agglomeration of the nanoparticles, suggesting that MNCS are potential and promising application as electrocatalyst supports in alkaline direct methanol fuel cells.

Ceria Supported Pt/PtO-Nanostructures: Efficient Photocatalyst for Sacrificial Donor Assisted Hydrogen Generation under Visible-NIR Light Irradiation

Czech Academy of Sciences Publication Activity Database

Manwar, N.R.; Chilkalwar, A.A.; Nanda, K.K.; Chaudhary, Y.S.; Šubrt, Jan; Rayalu, S.S.; Labhsetwar, N.K.

2016-01-01

Roč. 4, č. 4 (2016), s. 2323-2332 ISSN 2168-0485 Institutional support: RVO:61388980 Keywords : Pt/Ceria * Photocatalysis * Water splitting * Visible-NIR light Subject RIV: CA - Inorganic Chemistry Impact factor: 5.951, year: 2016

The emergence of nonbulk properties in supported metal clusters: negative thermal expansion and atomic disorder in Pt nanoclusters supported on gamma-Al2O3.

Science.gov (United States)

Sanchez, Sergio I; Menard, Laurent D; Bram, Ariella; Kang, Joo H; Small, Matthew W; Nuzzo, Ralph G; Frenkel, Anatoly I

2009-05-27

The structural dynamics-cluster size and adsorbate-dependent thermal behaviors of the metal-metal (M-M) bond distances and interatomic order-of Pt nanoclusters supported on a gamma-Al(2)O(3) are described. Data from scanning transmission electron microscopy (STEM) and X-ray absorption spectroscopy (XAS) studies reveal that these materials possess a dramatically nonbulklike nature. Under an inert atmosphere small, subnanometer Pt/gamma-Al(2)O(3) clusters exhibit marked relaxations of the M-M bond distances, negative thermal expansion (NTE) with an average linear thermal expansion coefficient alpha = (-2.4 +/- 0.4) x 10(-5) K(-1), large static disorder and dynamical bond (interatomic) disorder that is poorly modeled within the constraints of classical theory. The data further demonstrate a significant temperature-dependence to the electronic structure of the Pt clusters, thereby suggesting the necessity of an active model to describe the cluster/support interactions mediating the cluster's dynamical structure. The quantitative dependences of these nonbulklike behaviors on cluster size (0.9 to 2.9 nm), ambient atmosphere (He, 4% H(2) in He or 20% O(2) in He) and support identity (gamma-Al(2)O(3) or carbon black) are systematically investigated. We show that the nonbulk structural, electronic and dynamical perturbations are most dramatically evidenced for the smallest clusters. The adsorption of hydrogen on the clusters leads to an increase of the Pt-Pt bondlengths (due to a lifting of the surface relaxation) and significant attenuation of the disorder present in the system. Oxidation of these same clusters has the opposite effect, leading to an increase in Pt-Pt bond strain and subsequent enhancement in nonbulklike thermal properties. The structural and electronic properties of Pt nanoclusters supported on carbon black contrast markedly with those of the Pt/gamma-Al(2)O(3) samples in that neither NTE nor comparable levels of atomic disorder are observed. The Pt

Supported 3-D Pt nanostructures: the straightforward synthesis and enhanced electrochemical performance for methanol oxidation in an acidic medium

International Nuclear Information System (INIS)

Li, Zesheng; Ji, Shan; Pollet, Bruno G.; Shen, Pei Kang

2013-01-01

Noble metal nanostructures with branched morphologies [i.e., 3-D Pt nanoflowers (NFs)] by tri-dimensionally integrating onto conductive carbon materials are proved to be an efficient and durable electrocatalysts for methanol oxidation. The well-supported 3-D Pt NFs are readily achieved by an efficient cobalt-induced/carbon-mediated galvanic reaction approach. Due to the favorable nanostructures (3-D Pt configuration allowing a facile mass transfer) and supporting effects (including framework stabilization, spatially separate feature, and improved charge transport effects), these 3-D Pt NFs manifest much higher electrocatalytic activity and stability toward methanol oxidation than that of the commercial Pt/C and Pt-based electrocatalysts

Supported 3-D Pt nanostructures: the straightforward synthesis and enhanced electrochemical performance for methanol oxidation in an acidic medium

Energy Technology Data Exchange (ETDEWEB)

Li, Zesheng [Sun Yat-sen University, The State Key Laboratory of Optoelectronic Materials and Technologies, and Guangdong Province Key Laboratory of Low-carbon Chemistry and Energy Conservation, School of Physics and Engineering (China); Ji, Shan; Pollet, Bruno G. [University of the Western Cape, South African Institute for Advanced Materials Chemistry (SAIAMC) (South Africa); Shen, Pei Kang, E-mail: stsspk@mail.sysu.edu.cn [Sun Yat-sen University, The State Key Laboratory of Optoelectronic Materials and Technologies, and Guangdong Province Key Laboratory of Low-carbon Chemistry and Energy Conservation, School of Physics and Engineering (China)

2013-10-15

Noble metal nanostructures with branched morphologies [i.e., 3-D Pt nanoflowers (NFs)] by tri-dimensionally integrating onto conductive carbon materials are proved to be an efficient and durable electrocatalysts for methanol oxidation. The well-supported 3-D Pt NFs are readily achieved by an efficient cobalt-induced/carbon-mediated galvanic reaction approach. Due to the favorable nanostructures (3-D Pt configuration allowing a facile mass transfer) and supporting effects (including framework stabilization, spatially separate feature, and improved charge transport effects), these 3-D Pt NFs manifest much higher electrocatalytic activity and stability toward methanol oxidation than that of the commercial Pt/C and Pt-based electrocatalysts.

Synergy between Two Metal Catalysts: A Highly Active Silica Supported Bimetallic W/Zr Catalyst for Metathesis of n-Decane

KAUST Repository

Samantaray, Manoja; Dey, Raju; Kavitake, Santosh Giridhar; Abou-Hamad, Edy; Bendjeriou-Sedjerari, Anissa; Hamieh, Ali Imad Ali; Basset, Jean-Marie

2016-01-01

A well-defined, silica supported, bimetallic precatalyst [≡Si-O-W(Me)5 ≡Si-O-Zr(Np)3](4) has been synthesized for the first time via successively grafting two organometallic complexes [W(CH3)6 (1) followed by ZrNp4 (2)] on a single silica support

Plasma-induced synthesis of Pt nanoparticles supported on TiO{sub 2} nanotubes for enhanced methanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Su, Nan [College of Materials Science and Engineering, Nanjing Tech University, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); The Synergetic Innovation Center for Advanced Materials, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Hu, Xiulan, E-mail: whoxiulan@163.com [College of Materials Science and Engineering, Nanjing Tech University, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); The Synergetic Innovation Center for Advanced Materials, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China); Zhang, Jianbo; Huang, Huihong; Cheng, Jiexu; Yu, Jinchen; Ge, Chao [College of Materials Science and Engineering, Nanjing Tech University, Xin-Mo-Fan Road No. 5, 210009, Nanjing, Jiangsu (China)

2017-03-31

Highlights: • Pt nanoparticles are synthesized by plasma sputtering in water. • Pt/C/TiO{sub 2} nanotubes shows better mass activity and CO-poisoning tolerance than Pt/C. • TiO{sub 2} nanotubes are more suitable for support materials than TiO{sub 2} small particles. • The metal-support interactions between Pt and TiO{sub 2} nanotubes are detected by XPS. - Abstract: A Pt/C/TiO{sub 2} nanotube composite catalyst was successfully prepared for enhanced methanol electro-oxidation. Pt nanoparticles with a particle size of 2 nm were synthesized by plasma sputtering in water, and anatase TiO{sub 2} nanotubes with an inner diameter of approximately 100 nm were prepared by a simple two-step anodization method and annealing process. Field-emission scanning electron microscopy images indicated that the different morphologies of TiO{sub 2} synthesized on the surface of Ti foils were dependent on the different anodization parameters. The electrochemical performance of Pt/C/TiO{sub 2} catalysts for methanol oxidation showed that TiO{sub 2} nanotubes were more suitable for use as Pt nanoparticle support materials than irregular TiO{sub 2} short nanorods due to their tubular morphology and better electronic conductivity. X-ray photoelectron spectroscopy characterization showed that the binding energies of the Pt 4f of the Pt/C/TiO{sub 2} nanotubes exhibited a slightly positive shift caused by the relatively strong interaction between Pt and the TiO{sub 2} nanotubes, which could mitigate the poisoning of the Pt catalyst by CO{sub ads}, and further enhance the electrocatalytic performance. Thus, the as-obtained Pt/C/TiO{sub 2} nanotubes composites may become a promising catalyst for methanol electro-oxidation.

Sintering of oxide-supported Pt and Pd nanoparticles in air studied by in situ TEM

DEFF Research Database (Denmark)

Simonsen, Søren Bredmose

This thesis presents a fundamental study of the sintering of supported nanoparticles in relation to diesel oxidation catalysts. The sintering of supported nanoparticles is an important challenge in relation to this catalyst, as well as many other catalyst systems, and a fundamental understanding...... of Pt, Pd and bimetallic Pt-Pd nanoparticles supported on a flat and homogeneous Al2O3 or SiO2 surface. By using in situ TEM on the planar model catalysts it was possible to directly monitor the detailed dynamical changes of the individual nanoparticles during exposure to oxidizing conditions...

Preparation and characterization of multi-walled carbon nanotube (MWCNTs)-supported Pt-Ru catalyst for methanol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Yang Chunwei [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: cw.yang@hit.edu.cn; Wang Dianlong; Hu Xinguo; Dai Changsong [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Zhang Liang [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)

2008-01-10

Multi-walled carbon nanotubes (MWCNTs) as a support of PtRu catalyst nanocomposites were prepared by colloid method in this work. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) all indicate that ultrasonic treatment can effectively functionalize MWCNTs, endowing them with groups that can act as nucleation sites which can favor well-dispersed deposition of PtRu clusters on their surface. The PtRu/MWCNTs catalysts have a high and homogeneous dispersion of spherical PtRu metal particles with a narrow particle-size distribution. From XPS tests, in PtRu/MWCNTs catalysts Ru can weaken the out-shell electrons of Pt because a part of Ru form alloy with Pt. The remnant Ru exists in oxidation and provides abundant oxygen to nearby Pt, as accelerated desorption and oxidation of intermediate products of methanol oxidation at surface of Pt. By a series of electrochemistry measurements, the PtRu/MWCNTs catalysts display significantly higher performance than the PtRu/XC-72 catalysts. Finally, schematic procedures for the oxidation of MWCNTs and synthesis of PtRu/MWCNTs catalysts were given.

Preparation and characterization of multi-walled carbon nanotube (MWCNTs)-supported Pt-Ru catalyst for methanol electrooxidation

International Nuclear Information System (INIS)

Yang Chunwei; Wang Dianlong; Hu Xinguo; Dai Changsong; Zhang Liang

2008-01-01

Multi-walled carbon nanotubes (MWCNTs) as a support of PtRu catalyst nanocomposites were prepared by colloid method in this work. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) all indicate that ultrasonic treatment can effectively functionalize MWCNTs, endowing them with groups that can act as nucleation sites which can favor well-dispersed deposition of PtRu clusters on their surface. The PtRu/MWCNTs catalysts have a high and homogeneous dispersion of spherical PtRu metal particles with a narrow particle-size distribution. From XPS tests, in PtRu/MWCNTs catalysts Ru can weaken the out-shell electrons of Pt because a part of Ru form alloy with Pt. The remnant Ru exists in oxidation and provides abundant oxygen to nearby Pt, as accelerated desorption and oxidation of intermediate products of methanol oxidation at surface of Pt. By a series of electrochemistry measurements, the PtRu/MWCNTs catalysts display significantly higher performance than the PtRu/XC-72 catalysts. Finally, schematic procedures for the oxidation of MWCNTs and synthesis of PtRu/MWCNTs catalysts were given

Diamond nanoparticles as a support for Pt and PtRu catalysts for direct methanol fuel cells.

Science.gov (United States)

La-Torre-Riveros, Lyda; Guzman-Blas, Rolando; Méndez-Torres, Adrián E; Prelas, Mark; Tryk, Donald A; Cabrera, Carlos R

2012-02-01

Diamond in nanoparticle form is a promising material that can be used as a robust and chemically stable catalyst support in fuel cells. It has been studied and characterized physically and electrochemically, in its thin film and powder forms, as reported in the literature. In the present work, the electrochemical properties of undoped and boron-doped diamond nanoparticle electrodes, fabricated using the ink-paste method, were investigated. Methanol oxidation experiments were carried out in both half-cell and full fuel cell modes. Platinum and ruthenium nanoparticles were chemically deposited on undoped and boron doped diamond nanoparticles through the use of NaBH(4) as reducing agent and sodium dodecyl benzene sulfonate (SDBS) as a surfactant. Before and after the reduction process, samples were characterized by electron microscopy and spectroscopic techniques. The ink-paste method was also used to prepare the membrane electrode assembly with Pt and Pt-Ru modified undoped and boron-doped diamond nanoparticle catalytic systems, to perform the electrochemical experiments in a direct methanol fuel cell system. The results obtained demonstrate that diamond supported catalyst nanomaterials are promising for methanol fuel cells.

Preparation of SnO{sub 2}-CNTs supported Pt catalysts and their electrocatalytic properties for ethanol oxidation

Energy Technology Data Exchange (ETDEWEB)

Pang, H.L.; Lu, J.P. [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Chen, J.H. [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)], E-mail: chenjinhua@hnu.cn; Huang, C.T.; Liu, B.; Zhang, X.H. [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)

2009-03-30

SnO{sub 2}-carbon nanotubes (CNTs) composites were prepared by sol-gel method, and characterized by scanning electron microscopy and X-ray diffraction. Due to high stability in diluted acidic solution, SnO{sub 2}-CNTs composites were selected as the catalyst support and second catalyst for ethanol electrooxidation. The electrocatalytic properties of the SnO{sub 2}-CNTs supported platinum (Pt) catalyst (Pt/SnO{sub 2}-CNTs) for ethanol oxidation have been investigated by typical electrochemical methods. Under the same mass loading of Pt, the Pt/SnO{sub 2}-CNTs catalyst shows higher electrocatalytic activity and better long-term cycle stability than Pt/SnO{sub 2} catalyst. Additionally, the effect of the mass ratio of CNTs to SnO{sub 2} on the electrocatalytic activity of the electrode for ethanol oxidation was investigated, and the optimum mass ratio of CNTs to SnO{sub 2} in the Pt/SnO{sub 2}-CNTs catalyst is 1/6.3.

Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

International Nuclear Information System (INIS)

Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

2011-01-01

The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO 2 ) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO 2 ). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO 2 /TiO 2 ) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO 2 -Degussa P25 catalyst is detected.

Synthesis, characterization, and photocatalytic properties of core/shell mesoporous silica nanospheres supporting nanocrystalline titania

Science.gov (United States)

Cendrowski, K.; Chen, X.; Zielinska, B.; Kalenczuk, R. J.; Rümmeli, M. H.; Büchner, B.; Klingeler, R.; Borowiak-Palen, E.

2011-11-01

The facile bulk synthesis of silica nanospheres makes them an attractive support for the transport of chemical compounds such as nanocrystalline titanium dioxide. In this contribution we present a promising route for the synthesis of mesoporous silica nanospheres (m-SiO2) with diameter in range 200 nm, which are ideal supports for nanocrystalline titanium dioxide (TiO2). The detailed microscopic and spectroscopic characterizations of core/shell structure (m-SiO2/TiO2) were conducted. Moreover, the photocatalytic potential of the nanostructures was investigated via phenol decomposition and hydrogen generation. A clear enhancement of photoactivity in both reactions as compared to commercial TiO2-Degussa P25 catalyst is detected.

Effect of Al content on the gas-phase dehydration of glycerol over silica-alumina-supported silicotungstic acid catalysts

International Nuclear Information System (INIS)

Kim, Yong Tae; You, Su Jin; Park, Eun Duck; Jung, Kwangdeog

2012-01-01

The gas-phase dehydration of glycerol to acrolein was carried out over silicotungstic acid (H 4 SiW 12 O 40 ·xH 2 O, HSiW) catalysts supported on SiO 2 , η-Al 2 O 3 , and silica-alumina with different Al contents. The HSiW catalysts supported on silica-alumina showed higher glycerol conversions and acrolein yields during the initial 2 h at 315.deg.C than did SiO 2 - and η-Al 2 O 3 -supported HSiW catalysts. Among the tested catalysts, HSiW/Si 0.9 Al 0.1Ox exhibited the highest space-time yield during the initial 2 h. The loaded HSiW species can change the acid types and suppress the formation of carbonaceous species on Al-rich silica-alumina. The deactivated HSiW supported on silica-alumina can be fully regenerated after calcination in air at 500.deg.C. As long as the molar ratio between water and glycerol was in the range of 2-11, the acrolein selectivity increased significantly with increasing water content in the feed, while the surface carbon content decreased owing to the suppression of heavy compounds

Remarkable support effect on the reactivity of Pt/In2O3/MOx catalysts for methanol steam reforming

Science.gov (United States)

Liu, Xin; Men, Yong; Wang, Jinguo; He, Rong; Wang, Yuanqiang

2017-10-01

Effects of supports over Pt/In2O3/MOx catalysts with extremely low loading of Pt (1 wt%) and In2O3 loadings (3 wt%) are investigated for the hydrogen production of methanol steam reforming (MSR) in the temperature range of 250-400 °C. Under practical conditions without the pre-reduction, the 1Pt/3In2O3/CeO2 catalyst shows the highly efficient catalytic performance, achieving almost complete methanol conversion (98.7%) and very low CO selectivity of 2.6% at 325 °C. The supported Pt/In2O3 catalysts are characterized by means of Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), high-resolution transmission microscopy (HRTEM), temperature programmed reduction with hydrogen (H2-TPR), CO pulse chemisorption, temperature programmed desorption of methanol and water (CH3OH-TPD and H2O-TPD). These demonstrate that the nature of catalyst support of Pt/In2O3/MOx plays crucial roles in the Pt dispersion associated by the strong interaction among Pt, In2O3 and supporting materials and the surface redox properties at low temperature, and thus affects their capability to activate the reactants and determines the catalytic activity of methanol steam reforming. The superior 1Pt/3In2O3/CeO2 catalyst, exhibiting a remarkable reactivity and stability for 32 h on stream, demonstrates its potential for efficient hydrogen production of methanol steam reforming in mobile and de-centralized H2-fueled PEMFC systems.

Negligible degradation upon in situ voltage cycling of a PEMFC using an electrospun niobium-doped tin oxide supported Pt cathode.

Science.gov (United States)

Savych, Iuliia; Subianto, Surya; Nabil, Yannick; Cavaliere, Sara; Jones, Deborah; Rozière, Jacques

2015-07-14

Novel platinum-catalysed, corrosion-resistant, loose-tube-structured electrocatalysts for proton exchange membrane fuel cells have been obtained using single-needle electrospinning associated with a microwave-assisted polyol method. Monodisperse platinum particles supported on Nb-SnO2 demonstrated higher electrochemical stability than conventional Pt/C electrodes during ex situ potential cycling and comparable activity in the oxygen reduction reaction. In situ fuel cell operation under accelerated stress test conditions of a membrane electrode assembly elaborated using a Pt/C anode and Pt/Nb-SnO2 cathode confirmed that the voltage loss is significantly lower for the novel cathode than for an MEA prepared using conventional Pt/C supported electrocatalysts. Furthermore, the Nb-SnO2 stabilised the supported platinum nanoparticles against dissolution, migration and reprecipitation in the membrane. Pt/Nb-SnO2 loose-tubes constitute a mitigation strategy for two known degradation mechanisms in PEMFC: corrosion of the carbon support at the cathode, and dissolution of Pt at high cell voltages.

Silica from triethylammonium tris (oxalato) silicate (IV) thermal decomposition

International Nuclear Information System (INIS)

Ferracin, L.C.; Ionashiro, M.; Davolos, M.R.

1990-01-01

Silica can be obtained from differents precursors by differents methods. In this paper it has been investigated the thermal decomposition of triethylammonium tris (oxalato) silicate (IV) to render silica. Among the trisoxalato-complexes of silicon preparation methods reviewed it has been used the Bessler's one with the reflux adaptaded in microwave oven. Thermal decomposition analysis of the compound has been made by TG-DTG and DTA curves. Silica powders obtained and heated between 300 to 900 0 C in a oven were characterized by infrared vibrational spectroscopy, X-ray powder difraction and nitrogen adsorption isotherm (BET). The triethylammonium tris (oxalato) silicate (IV) thermal decomposition takes place at 300 0 C and the silica powder obtained is non cristalline with impurities that are eliminated with heating at 400 0 C. (author) [pt

Characteristics of supported nano-TiO{sub 2}/ZSM-5/silica gel (SNTZS): Photocatalytic degradation of phenol

Energy Technology Data Exchange (ETDEWEB)

Zainudin, Nor Fauziah; Abdullah, Ahmad Zuhairi [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Penang (Malaysia); Mohamed, Abdul Rahman, E-mail: chrahman@eng.usm.my [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Penang (Malaysia)

2010-02-15

Photocatalytic degradation of phenol was investigated using the supported nano-TiO{sub 2}/ZSM-5/silica gel (SNTZS) as a photocatalyst in a batch reactor. The prepared photocatalyst was characterized using XRD, TEM, FT-IR and BET surface area analysis. The synthesized photocatalyst composition was developed using nano-TiO{sub 2} as the photoactive component and zeolite (ZSM-5) as the adsorbents, all supported on silica gel using colloidal silica gel binder. The optimum formulation of SNTZS catalyst was observed to be (nano-TiO{sub 2}:ZSM-5:silica gel:colloidal silica gel = 1:0.6:0.6:1) which giving about 90% degradation of 50 mg/L phenol solution in 180 min. The SNTZS exhibited higher photocatalytic activity than that of the commercial Degussa P25 which only gave 67% degradation. Its high photocatalytic activity was due to its large specific surface area (275.7 m{sup 2}/g), small particle size (8.1 nm), high crystalline quality of the synthesized catalyst and low electron-hole pairs recombination rate as ZSM-5 adsorbent was used. The SNTZS photocatalyst synthesized in this study also has been proven to have an excellent adhesion and reusability.

Nanostructured electrocatalyst for fuel cells : silica templated synthesis of Pt/C composites.

Energy Technology Data Exchange (ETDEWEB)

Stechel, Ellen Beth; Switzer, Elise E.; Fujimoto, Cy H.; Atanassov, Plamen Borissov; Cornelius, Christopher James; Hibbs, Michael R.

2007-09-01

Platinum-based electrocatalysts are currently required for state-of-the-art fuel cells and represent a significant portion of the overall fuel cell cost. If fuel cell technology is to become competitive with other energy conversion technologies, improve the utilization of precious metal catalysts is essential. A primary focus of this work is on creating enhanced nanostructured materials which improve precious-metal utilization. The goal is to engineer superior electrocatalytic materials through the synthesis, development and investigation of novel templated open frame structures synthesized in an aerosol-based approach. Bulk templating methods for both Pt/C and Pt-Ru composites are evaluated in this study and are found to be limited due to the fact that the nanostructure is not maintained throughout the entire sample. Therefore, an accurate examination of structural effects was previously impossible. An aerosol-based templating method of synthesizing nanostructured Pt-Ru electrocatalysts has been developed wherein the effects of structure can be related to electrocatalytic performance. The aerosol-based templating method developed in this work is extremely versatile as it can be conveniently modified to synthesize alternative materials for other systems. The synthesis method was able to be extended to nanostructured Pt-Sn for ethanol oxidation in alkaline media. Nanostructured Pt-Sn electrocatalysts were evaluated in a unique approach tailored to electrocatalytic studies in alkaline media. At low temperatures, nanostructured Pt-Sn electrocatalysts were found to have significantly higher ethanol oxidation activity than a comparable nanostructured Pt catalyst. At higher temperatures, the oxygen-containing species contribution likely provided by Sn is insignificant due to a more oxidized Pt surface. The importance of the surface coverage of oxygen-containing species in the reaction mechanism is established in these studies. The investigations in this work present

An Investigation of Methyl Viologen Functionalized Reduced Graphene Oxide: Chitosan as a Support for Pt Nanoparticles Towards Ethanol Electrooxidation

Science.gov (United States)

Ekrami-Kakhki, Mehri-Saddat; Farzaneh, Nahid; Abbasi, Sedigheh; Beitollahi, Hadi; Ekrami-Kakhki, Seyed Ali

2018-05-01

In this research, graphene oxide was prepared by a modified Hummers' method, and then functionalized with 1, 1'-dimethyl-4, 4'-bipyridinium dichloride (MV), and chitosan (CH) to get a MV-RGO-CH support. Pt nanoparticles were prepared on this support to get Pt/MV-RGO-CH catalyst. The morphology and microstructure of Pt/MV-RGO-CH catalyst were characterized with transmission electron microscopy image and X-ray diffraction analysis. The electrocatalytic activity of the prepared catalyst towards ethanol oxidation was investigated by carbon monoxide stripping voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The effects of some experimental parameters such as scan rate, ethanol concentration, and temperature were investigated for ethanol electrooxidation at Pt/MV-RGO-CH catalyst. Durability of the catalyst was also investigated. The electrocatalytic performance of Pt/MV-RGO-CH catalyst for ethanol oxidation was compared with those of Pt/CH and Pt/MV-RGO catalysts. The higher electrocatalytic performance of Pt/MV-RGO-CH than Pt/CH and Pt/MV-RGO catalysts towards ethanol electrooxidation indicated that Pt/MV-RGO-CH could be a promising catalyst for application in direct ethanol fuel cells.

Highly effective and CO-tolerant PtRu electrocatalysts supported on poly(ethyleneimine) functionalized carbon nanotubes for direct methanol fuel cells

International Nuclear Information System (INIS)

Cheng, Yi; Jiang, San Ping

2013-01-01

A highly efficient and CO tolerant PtRu electrocatalysts supported on amino-rich, cationic poly(ethyleneimine) polyelectrolyte functionalized multi-walled carbon nanotubes (PtRu/PEI-MWCNTs) has been developed. The catalysts were characterized by thermogravimetric analysis, Raman spectroscopy, cyclic voltammograms, CO stripping, chronoamperometry, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The PtRu particles with average size ∼2.5 nm are well dispersed on PEI-MWCNTs. The peak current for the methanol oxidation reaction on 40% PtRu/PEI-MWCNTs is 636mAmg Pt −1 , 5.7 times higher than 112mA mg Pt −1 measured on the 40% PtRu supported on acid treated MWCNTs (PtRu/AO-MWCNTs) under identical conditions. PtRu/PEI-MWCNTs catalysts exhibit a superior electrocatalytic activity and stability for the methanol oxidation reaction due to its high tolerance toward CO poisoning as compared with PtRu/AO-MWCNTs for direct methanol fuel cells

Pt-Ru nanoparticles supported on functionalized carbon as electrocatalysts for the methanol oxidation

International Nuclear Information System (INIS)

Salgado, J.R.C.; Fernandes, J.C.S.; Botelho do Rego, A.M.; Ferraria, A.M.; Duarte, R.G.; Ferreira, M.G.S.

2011-01-01

Highlights: → The functionalized carbon using acid solutions contains surface oxygenated groups. → Uniform dispersion of PtRu nanoparticles on the carbon surface was achieved. → Physical analysis showed the formation of PtRu alloy catalysts on functionalized carbon. → PtRu alloy catalysts on functionalized carbon enhanced the methanol oxidation rate. - Abstract: Platinum-ruthenium alloy electrocatalysts, for methanol oxidation reaction, were prepared on carbons thermally treated in helium atmosphere or chemically functionalized in H 2 O 2 , or in HNO 3 + H 2 SO 4 or in HNO 3 solutions. The functionalized carbon that is produced using acid solutions contains more surface oxygenated functional groups than carbon treated with H 2 O 2 solution or HeTT. The XRD/HR-TEM analysis have showed the existence of a higher alloying degree for Pt-Ru electrocatalysts supported on functionalized carbon, which present superior electrocatalytic performance, assessed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, as compared to electrocatalysts on unfunctionalized carbon. It also was found that Pt-Ru alloy electrocatalysts on functionalized carbon improve the reaction rate compared to Pt-Ru on carbons treated with H 2 O 2 solution and thermally. A mechanism is discussed, where oxygenated groups generated from acid functionalization of carbon and adsorbed on Pt-Ru electrocatalysts are considered to enhance the electrocatalytic activity of the methanol oxidation reaction.

Facial synthesis of porous hematite supported Pt catalyst and its photo enhanced electrocatalytic ethanol oxidation performance

International Nuclear Information System (INIS)

Kang, Shuai; Shen, Pei Kang

2015-01-01

Graphical Abstract: A porous α-Fe 2 O 3 supported Pt catalyst has been synthesized by a facial thermal treatment assisted precipitation method and the materials show a illumination enhanced performance for ethanol oxidation. Display Omitted -- Highlights: •A porous α-Fe 2 O 3 supported Pt catalyst has been synthesized for the first time. •With the addition of α-Fe 2 O 3 , the current density of Pt/C grows about 51% under illumination and 32% in the dark compared with unsupported catalyst. •The current increases under illuminationin chronoamperometric experiments at a given potential of 0.7 V due to the photons from light provide energy for CO stripping. •This work demostrates an optical strategy to accelerate electrode reactions towards ethanol oxidation reaction. -- Abstract: The porous α-Fe 2 O 3 supported Pt catalyst is synthesized by a facial thermal treatment assisted precipitation method. The particle size of Pt is less than 3 nm. The pore diameters of α-Fe 2 O 3 particles are concentrated to 2.46 nm in a mesooporous scale. Its electrochemical performance is tested. The ethanol oxidation current of the Pt/Fe 2 O 3 catalsyt obviously improves under illumination, compared with that in the dark, during the optical switching operation. Moreover, with the addition of α-Fe 2 O 3 , the ethanol oxidation current of Pt/C grows about 51% under illumination and 32% in the dark; the onset potential shifts negtively for about 20 mV. This work demostrates an optical strategy which can be a potential alternative to accelerate electrode reactions towards ethanol oxidation reaction

Kinetic study of methanol oxidation on carbon-supported PtRu electrocatalyst

International Nuclear Information System (INIS)

Gojkovic, S.Lj.; Vidakovic, T.R.; Durovic, D.R.

2003-01-01

Methanol electrooxidation was investigated on the carbon-supported PtRu electrocatalyst (1:1 atomic ratio) in acid media. X-ray diffraction measurement indicated alloying of Pt and Ru. Cyclic voltammetry of the sample reflects the amount of Ru in the catalyst and its ability to adsorb OH radicals. Tafel plots for the oxidation of 0.02-3 M methanol in the solutions containing 0.05-1 M HClO 4 and in the temperature range 27-40 deg. C showed reasonably well-defined linear region with the slope of about 115 mV dec -1 at the low currents, irrespective of the experimental conditions employed. Reaction order with respect to methanol was found to be 0.5. A correlation between methanol oxidation rate and pseudocapacitive current of OH adsorption on Ru sites was established. It was proposed that bifunctional mechanism is operative with the reaction between methanol residues adsorbed on Pt sites and OH radicals adsorbed on Ru sites as the rate-determining step

Selective oxidation of propylene to acrolein by silica-supported bismuth molybdate catalysts

DEFF Research Database (Denmark)

Duc, Duc Truong; Ha, Hanh Nguyen; Fehrmann, Rasmus

2011-01-01

Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (β-Bi2Mo2O9) w...

The influence of boron dopant on the electrochemical properties of graphene as an electrode material and a support for Pt catalysts

International Nuclear Information System (INIS)

Bo, Xiangjie; Li, Mian; Han, Ce; Guo, Liping

2013-01-01

Highlights: •More defective sites in graphene after the doping of boron atoms. •Fine dispersion of Pt nanoparticles supported on boron-doped graphene. •Low electron transfer resistance at boron-doped graphene. •High performance of boron-doped graphene as an electrode material or a support for Pt catalysts. -- Abstract: Boron-doped graphene (BGR) is prepared by thermal annealing of graphene oxide (GO) in the presence of boric acid. More defective sites are introduced into GR accompanied by the doping of boron. Low electron transfer resistance towards redox probe is observed at BGR. The BGR modified electrode can effectively distinguish the anodic peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The defective sites of BGR can also act as anchoring sites for the deposition of Pt nanoparticles. When used as a support for Pt electrocatalysts, Pt nanoparticles with an average diameter of 3.2 nm are deposited on BGR. The doping of boron into GR facilitates the dispersion of Pt nanoparticles and increases the utilization efficiency of Pt nanoparticles. The Pt/BGR exhibits significant catalytic activity towards the oxidation of methanol. The results demonstrate that BGR is a good support for Pt catalysts or an electrode material compared with the undoped GR

Electrocatalytic Activity for CO, MeOH, and EtOH Oxidation on the Surface of Pt-Ru Nanoparticles Supported by Metal Oxide

Directory of Open Access Journals (Sweden)

Kwang-Sik Sim

2011-01-01

Full Text Available This paper describes the electrocatalytic activity for CO, MeOH, and EtOH oxidation on the surface of Pt-Ru nanoparticles supported by metal oxide (Nb-TiO2-H prepared for use in a fuel cell. To prepare Nb-TiO2-supported Pt-Ru nanoparticles, first, the Nb-TiO2 supports were prepared by sol-gel reaction of titanium tetraisopropoxide with a small amount of the niobium ethoxide in polystyrene (PS colloids. Second, Pt-Ru nanoparticles were then deposited by chemical reduction of the Pt4+ and Ru3+ ions onto Nb-TiO2 supports (Pt-Ru@Nb-TiO2-CS. Nb element was used to reduce electrical resistance to facilitate electron transport during the electrochemical reactions on a fuel cell electrode. Finally, the Pt-Ru@Nb-TiO2-H catalysts were formed by the removal of core-polystyrene ball from Pt-Ru@TiO2-CS at 500∘C. The successfully prepared Pt-Ru electrocatalysts were confirmed via TEM, XPS, and ICP analysis. The electrocatalytic efficiency of Pt-Ru nanoparticles was evaluated via CO, MeOH, and EtOH oxidation for use in a direct methanol fuel cell (DMFC. As a result, the Pt-Ru@Nb-TiO2-H electrodes showed high electrocatalytic activity for the electrooxidation of CO, MeOH, and EtOH.

Ultra-large bandwidth hollow-core guiding in all-silica bragg fibers with nano-supports

DEFF Research Database (Denmark)

Vienne, Guillaume; Xu, Yong; Jakobsen, Christian

2004-01-01

We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in t...... in this new class of Bragg fibers exceeds that of other hollow-core fibers reported in the literature. With only three rings of silica cladding layers, these Bragg fibers achieve propagation loss of the order of 1 dB/m....

Electrochemical fabrication of clean dendritic Au supported Pt clusters for electrocatalytic oxidation of formic acid

International Nuclear Information System (INIS)

Xia Yue; Liu Jun; Huang Wei; Li Zelin

2012-01-01

Highlights: ► A smooth Au surface was rebuilt into clean dendrite via square wave potential pulses. ► It was performed in blank H 2 SO 4 solution without Au(III) species and other additives. ► Dendritic Au provided certain advantage for dispersing Pt due to its unique structure. ► Pt-decorated dendritic Au demonstrated high activity for the HCOOH electrooxidation. - Abstract: We report here the fabrication of clean dendritic gold (DG) directly on a smooth Au electrode via square wave potential pulses (SWPPs) in a blank H 2 SO 4 solution containing no Au(III) species and additives. The effects of potential range, frequency and duration time of SWPPs and H 2 SO 4 concentration on the construction of DG were systematically investigated. A possible mechanism was proposed to explain the growth of DG. The whole process was templateless and surfactantless, and therefore effectively avoided possible contaminations that occurred in other synthetic routes. Further, the prepared DG electrode functioned as a scaffold to support electrodeposited Pt clusters, producing Pt-decorated DG (Pt-DG) electrodes. The electrocatalytic properties of Pt-DG electrodes with various Pt loadings were examined for the oxidation of formic acid. The low Pt loading Pt-DG demonstrated different electrochemical behavior from that on Pt-decorated smooth gold (Pt-SG) and on Pt-decorated gold nanoparticles because there were more defect sites like steps and edges on the DG surface. Ensemble effect, as well as electronic effect, accounts for the improved electrocatalytic activity of low Pt loading Pt-DG.

Methanol and ethanol electrooxidation on Pt and Pd supported on carbon microspheres in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei; Cheng, Liqiang; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Shen, Peikang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2007-05-15

Noble metal (Pt, Pd) electrocatalysts supported on carbon microspheres (CMS) are used for methanol and ethanol oxidation in alkaline media. The results show that noble metal electrocatalysts supported on carbon microspheres give better performance than that supported on carbon black. It is well known that palladium is not a good electrocatalyst for methanol oxidation, but it shows excellently higher activity and better steady-state electrolysis than Pt for ethanol electrooxidation in alkaline media. The results show a synergistic effect by the interaction between Pd and carbon microspheres. The Pd supported on carbon microspheres in this paper possesses excellent electrocatalytic properties and may be of great potential in direct ethanol fuel cells. (author)

A three-site Langmuir adsorption model to elucidate the temperature, pressure, and support dependence of the hydrogen coverage on supported Pt particles

NARCIS (Netherlands)

Ji, Y.; Koot, V.; van der Eerden, A.M.J.; Weckhuysen, B.M.; Koningsberger, D.C.; Ramaker, D.E.

2007-01-01

The three-site adsorption model, previously developed to describe H adsorption on small Pt particles, was used to gain insight into dependence of hydrogen coverage on temperature, pressure, and support ionicity. The three sites, in order of decreasing PtH bond strength, involve H in an atop, a

Uniform Au@Pt core-shell nanodendrites supported on molybdenum disulfide nanosheets for the methanol oxidation reaction

Science.gov (United States)

Su, Shao; Zhang, Chi; Yuwen, Lihui; Liu, Xingfen; Wang, Lihua; Fan, Chunhai; Wang, Lianhui

2015-12-01

Herein, we presented a facile seeded growth method to prepare high-quality three-dimensional (3D) Au@Pt bimetallic nanodendrite-decorated molybdenum disulfide (MoS2) nanosheets (Au@Pt/MoS2). Transmission electron microscopy (TEM) and high-resolution TEM exhibited that Au@Pt core-shell nanostructures were dispersed onto the surface of MoS2 nanosheets. More importantly, the thickness of the Pt shell of the Au@Pt bimetallic nanodendrites on the surface of the MoS2 nanosheets could be easily tuned via simply changing the synthesis parameters, such as the concentration of H2PtCl6, reaction time and temperature, which greatly influence the catalytic ability of Au@Pt/MoS2 nanohybrids. Both cyclic voltammetry (CV) and chronoamperometry (CA) demonstrated that the as-prepared Au@Pt/MoS2 nanohybrids possessed much higher electrocatalytic activity and stability than Pt/MoS2 or commercial Pt/C catalyst. The peak current mass density of the selected Au@Pt/MoS2 was 6.24 A mg-1, which was 3389 and 20.3 times those of Pt/C (0.00184 A mg-1) and Pt/MoS2 (0.307 A mg-1), respectively. The presented method may be a facile approach for the synthesis of MoS2-supported bimetallic nanocomposites, which is significant for the development of high performance MoS2-based sensors and catalysts.Herein, we presented a facile seeded growth method to prepare high-quality three-dimensional (3D) Au@Pt bimetallic nanodendrite-decorated molybdenum disulfide (MoS2) nanosheets (Au@Pt/MoS2). Transmission electron microscopy (TEM) and high-resolution TEM exhibited that Au@Pt core-shell nanostructures were dispersed onto the surface of MoS2 nanosheets. More importantly, the thickness of the Pt shell of the Au@Pt bimetallic nanodendrites on the surface of the MoS2 nanosheets could be easily tuned via simply changing the synthesis parameters, such as the concentration of H2PtCl6, reaction time and temperature, which greatly influence the catalytic ability of Au@Pt/MoS2 nanohybrids. Both cyclic voltammetry (CV

Synthesis and characterization of supported Pt and Pt alloys nanoparticles used for the catalytic oxidation of sulfur dioxide

DEFF Research Database (Denmark)

Koutsopoulos, Sotiris; Eriksen, Kim Michael; Fehrmann, Rasmus

2006-01-01

pressure in the temperature range of 250–700 °C. The effect of doping the active metal with rhodium and palladium was also studied. The catalytic activities of the supported catalysts were found to follow the order Pt–Pd/CPG > Pt–Rh/CPG > Pt/CPG. A significant synergistic effect of the Pt–Pd alloy...

thesis of high-purity carbon nanotubes over alumina and silica supported bimetallic catalysts

Directory of Open Access Journals (Sweden)

Sanja Ratković

2009-10-01

Full Text Available Carbon nanotubes (CNTs were synthesized by a catalytic chemical vapor deposition method (CCVD of ethylene over alumina and silica supported bimetallic catalysts based on Fe, Co and Ni. The catalysts were prepared by a precipitation method, calcined at 600 °C and in situ reduced in hydrogen flow at 700 °C. The CNTs growth was carried out by a flow the mixture of C2H4 and nitrogen over the catalyst powder in a horizontal oven. The structure and morphology of as-synthesized CNTs were characterized using SEM. The as-synthesized nanotubes were purified by acid and basic treatments in order to remove impurities such as amorphous carbon, graphite nanoparticles and metal catalysts. XRD and DTA/TG analyses showed that the amounts of by-products in the purified CNTs samples were reduced significantly. According to the observed results, ethylene is an active carbon source for growing high-density CNTs with high yield but more on alumina-supported catalysts than on their silica- supported counterparts. The last might be explained by SMSI formed in the case of alumina-supported catalysts, resulting in higher active phase dispersion.

Simulation from the first principal theory on the effect of supporting silica on graphene and the new composite material

CSIR Research Space (South Africa)

Kiarii, EM

2017-07-01

Full Text Available Silica has been used as support material with many photocatalytic materials. In this study, silica polymorphs on graphene and epoxy graphene were studied using Density Functional Theory (DFT) to determine the interfacial and optical properties...

An anodic alumina supported Ni-Pt bimetallic plate-type catalysts for multi-reforming of methane, kerosene and ethanol

KAUST Repository

Zhou, Lu

2014-05-01

An anodic alumina supported Ni-Pt bimetallic plate-type catalyst was prepared by a two-step impregnation method. The trace amount 0.08 wt% of Pt doping efficiently suppressed the nickel particle sintering and improved the nickel oxides reducibility. The prepared Ni-Pt catalyst showed excellent performance during steam reforming of methane, kerosene and ethanol under both 3000 h stationary and 500-time daily start-up and shut-down operation modes. Self-activation ability of this catalyst was evidenced, which was considered to be resulted from the hydrogen spillover effect over Ni-Pt alloy. In addition, an integrated combustion-reforming reactor was proposed in this study. However, the sintering of the alumina support is still a critical issue for the industrialization of Ni-Pt catalyst. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Microwave heated polyol synthesis of carbon supported PtAuSn/C nanoparticles for ethanol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Zhu, Hong; Han, Kefei [School of Science, State key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Liu, Yingli; Chang, Zhaorong [College of Chemistry and Environmental Science, Henan Normal University, Xinxiang, Henan (China); Shen, Liangbo [Beijing No.4 High School, Beijing (China); Wei, Yongsheng; Guo, Zhijun (School of Science Beijing Jiaotong University Beijing P. R. China); Wang, Haijiang [Institute for Fuel Cell Innovation, National Research Council of (Canada)

2010-04-15

Carbon-supported PtAuSn/C nanoparticle catalyst was synthesized by a microwave-assisted polyol process. The process is a quick process that only requires a few minutes to complete. The catalyst thus obtained was characterized by transmission electron microscopy and X-ray diffraction analysis. The electrochemical performance of the catalyst, for the ethanol oxidation reaction, was also investigated. The results indicated that the PtAuSn/C catalyst was uniformly dispersed on carbon and was in the nano-size range. The electrochemical measurements indicated that PtAuSn/C nanoparticle catalyst synthesized by the microwave-assisted polyol method demonstrated a significantly higher electrochemically active area and higher catalytic activity than Pt/C for the ethanol oxidation reaction. (author)

N, P-codoped Mesoporous Carbon Supported PtCox Nanoparticles and Their Superior Electrochemical toward Methanol Oxidation

Science.gov (United States)

Cui, Hangjun; Li, Yueming; Liu, Shimin

2018-03-01

In this report, a novel strategy by using the N, P co-doped mesoporous carbon structure as catalyst support to enhance the electrochemical catalytic activity of Pt-based catalysts is proposed. The as-synthesized PtCox@N, P-doped mesoporous carbon nanocomposties have been studied as an anode catalyst toward methanol oxidation, exhibiting greatly improved electrochemical activity and stability compared with Pt@mesoporous carbon. The synergistic effects of N, P dual-doping and porous carbon structure help to achieve better electron transport at the electrode surface, which eventually leads to greatly enhanced catalytic activity compared to the pristine Pt/mesoporous carbon.…

Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

KAUST Repository

Merle, Nicolas; Le Qué mé ner, Fré dé ric; Bouhoute, Yassine; Szeto, Kai C.; De Mallmann, Aimery; Barman, Samir; Samantaray, Manoja; Delevoye, Laurent; Gauvin, Ré gis M.; Taoufik, Mostafa; Basset, Jean-Marie

2016-01-01

The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

Well-Defined Molybdenum Oxo Alkyl Complex Supported on Silica by Surface Organometallic Chemistry: A Highly Active Olefin Metathesis Precatalyst

KAUST Repository

Merle, Nicolas

2016-12-05

The well-defined silica-supported molybdenum oxo alkyl species (SiO−)MoO(CH Bu) was selectively prepared by grafting of MoO(CH Bu)Cl onto partially dehydroxylated silica (silica) using the surface organometallic chemistry approach. This surface species was fully characterized by elemental analysis and DRIFT, solid-state NMR, and EXAFS spectroscopy. This new material is related to the active species of industrial supported MoO/SiO olefin metathesis catalysts. It displays very high activity in propene self-metathesis at mild (turnover number = 90 000 after 25 h). Remarkably, its catalytic performance outpaces those of the parent imido derivative and its tungsten oxo analogue.

The Effect of Support on Advanced Pt-based Cathodes towards the Oxygen Reduction Reaction. State of the Art

International Nuclear Information System (INIS)

Luo, Yun; Alonso-Vante, Nicolas

2015-01-01

Graphical abstract: TOC: This mini-review summarizes advanced Pt catalysts towards enhanced ORR activity and stability. Tunable ORR activity and stability can be achieved in tailoring Pt active center, depending on nature of supporting materials. - Highlights: • Substrate effect leads to ORR activity and stability enhancement of catalyst centers. • Carbon-based materials and oxide-carbon composite influences favorably the Pt electronic environment. • Pt surface modification induced via ligand effect, geometric effect, metal-substrate strong interaction, and interaction of rare earth oxide and Pt surface atoms. • Sources for enhancement of ORR activity and stability were identified. - Abstract: This work summarizes the advanced materials developed by various research groups for improving the stability of platinum (Pt), and Pt-based catalysts center toward the oxygen reduction reaction (ORR) in acid medium. The ORR stability enhancement of Pt catalytic center can be classified according to the different nature of the supporting materials, namely, carbon-, oxide-based-, and oxide-carbon composites. The enhancement and stability of a catalytic center can be related to either its electronic modification induced by a strong interaction with the support, another metal (alloy), or to geometric effects. In addition, other parameters come into play, the size, the morphology of the catalytic center, the temperature, the dispersion, and mass loading, along with the measuring methods. This mini-review mainly focusses on the stability improvement, depending on the substrate nature. This latter can be further modified via functionalization or by the chemical interaction nature between the substrate and catalyst.

Silica-Supported Co3O4 Nanoparticles as a Recyclable Catalyst for Rapid Degradation of Azodye

Directory of Open Access Journals (Sweden)

Ali Baghban

2016-10-01

Full Text Available In this paper, silica nanoparticles with particle size of ~ 10-20 nm were selected as a support for the synthesis of Co3O4 nanoparticles by impregnation of silica nanoparticles in solution of Co(II in a specific concentrations and then calcination to 800 oC. This nanocomposite was then, used as a catalyst for oxidative degradation of methyl orange (MO with ammonium persulfate in aqueous media. Effect of pH, temperature, contact time, amount of oxidant and catalyst were studied in the presence of manuscript. Scanning electron microscope (SEM, electron dispersive spectroscopy (EDS, FT-IR, and ICP-AES analyses were used for analysis of silica-supported Co3O4 (Co3O4/SiO2. Treating MO with ammonium persulfate in the presence of Co3O4/SiO2 led to complete degradation of MO under the optimized conditions. Also, the catalyst exhibited recyclability at least over 10 consecutive runs. Copyright © 2016 BCREC GROUP. All rights reserved Received: 12nd December 2015; Revised: 27th January 2016; Accepted: 27th January 2016 How to Cite: Baghban, A., Doustkhah, E., Rostamnia, S., Aghbash, K.O. (2016. Silica-Supported Co3O4 Nanoparticles as a Recyclable Catalyst for Rapid Degradation of Azodye. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (3: 284-291 (doi:10.9767/bcrec.11.3.568.284-291 Permalink/DOI: http://doi.org/10.9767/bcrec.11.3.568.284-291

Facile synthesis of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide with enhanced electrocatalytic properties

Science.gov (United States)

Li, Shan-Shan; Zheng, Jie-Ning; Ma, Xiaohong; Hu, Yuan-Yuan; Wang, Ai-Jun; Chen, Jian-Rong; Feng, Jiu-Ju

2014-05-01

A simple and facile method is developed for one-pot preparation of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide (PtPd/RGO) at room temperature, without using any seed, organic solvent, or complex apparatus. It is found that octylphenoxypolyethoxyethanol (NP-40) as a soft template and its amount are critical to the formation of PtPd garlands. The as-prepared nanocomposites are further applied to methanol and ethanol oxidation with significantly enhanced electrocatalytic activity and better stability in alkaline media.A simple and facile method is developed for one-pot preparation of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide (PtPd/RGO) at room temperature, without using any seed, organic solvent, or complex apparatus. It is found that octylphenoxypolyethoxyethanol (NP-40) as a soft template and its amount are critical to the formation of PtPd garlands. The as-prepared nanocomposites are further applied to methanol and ethanol oxidation with significantly enhanced electrocatalytic activity and better stability in alkaline media. Electronic supplementary information (ESI) available: Experimental section, Fig. S1-S12 and Tables S1 and S2. See DOI: 10.1039/c3nr06808k

PtRu catalysts supported on heteropolyacid and chitosan functionalized carbon nanotubes for methanol oxidation reaction of fuel cells.

Science.gov (United States)

Cui, Zhiming; Li, Chang Ming; Jiang, San Ping

2011-09-28

A simple self-assembly approach has been developed to functionalize carbon nanotubes (CNTs) with chitosan (CS) and heteropolyacids (HPAs) of phosphomolybdic acid (H(3)PMo(12)O(40), HPMo) and phosphotungstic acid (H(3)PW(12)O(40), HPW). The non-covalent functionalization method, which introduces homogenous surface functional groups with no detrimental effect on graphene structures of CNTs, can be carried out at room temperature without the use of corrosive acids. The PtRu nanoparticles supported on HPAs-CS-CNTs have a uniform distribution and much smaller size as compared to those of the PtRu nanoparticles supported on conventional acid treated CNTs (PtRu/AO-CNTs). The onset and peak potentials for CO(ad) oxidation on PtRu/HPAs-CS-CNTs catalysts are more negative than those on PtRu/AO-CNTs, indicating that HPAs facilitate the electro-oxidation of CO. The PtRu/HPMo-CS-CNTs catalyst has a higher electrocatalytic activity for methanol oxidation and higher tolerance toward CO poisoning than PtRu/HPW-CS-CNTs. The better electrocatalytic enhancement of HPMo on the PtRu/HPAs-CS-CNTs catalyst is most likely related to the fact that molybdenum-containing HPAs such as HPMo have more labile terminal oxygen to provide additional active oxygen sites while accelerating the CO and methanol oxidation in a similar way to that of Ru in the PtRu binary alloy system.

Synthesis and separation properties of an α-alumina-supported high-silica MEL membrane

NARCIS (Netherlands)

Kosinov, N.; Hensen, E.J.M.

2013-01-01

A thin high-silica MEL membrane was synthesized on a porous a-alumina hollow fiber support by a secondary growth approach. The membrane quality was evaluated by permporometry, single-gas permeation and butane isomer separation. Comparison of the pervaporation performance of MEL membranes with a MFI

Hydrophilic nano-silica coating agents with platinum and diamond nanoparticles for denture base materials.

Science.gov (United States)

Yoshizaki, Taro; Akiba, Norihisa; Inokoshi, Masanao; Shimada, Masayuki; Minakuchi, Shunsuke

2017-05-31

Preventing microorganisms from adhering to the denture surface is important for ensuring the systemic health of elderly denture wearers. Silica coating agents provide high hydrophilicity but lack durability. This study investigated solutions to improve the durability of the coating layer, determine an appropriate solid content concentration of SiO 2 in the silica coating agent, and evaluate the effect of adding platinum (Pt) and diamond nanoparticles (ND) to the agent. Five coating agents were prepared with different SiO 2 concentrations with/without Pt and ND additives. The contact angle was measured, and the brush-wear test was performed. Scanning electron microscopy was used to investigate the silica coating layer. The appropriate concentration of SiO 2 was found to be 0.5-0.75 wt%. The coating agents with additives showed significantly high hydrophilicity immediately after coating and after the brush-wear test. The coating agents with/without additives formed a durable coating layer even after the brush-wear test.

Electrocatalytic properties of carbon-supported Pt-Ru catalysts with the high alloying degree for formic acid electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Chen, Yu.; Zhou, Yiming; Tang, Yawen; Lu, Tianhong [College of Chemistry and Environmental Science, Nanjing Normal University, Nanjing 210097 (China)

2010-07-01

A series of carbon-supported bimetallic Pt-Ru catalysts with high alloying degree and different Pt/Ru atomic ratio have been prepared by a chemical reduction method in the H{sub 2}O/ethanol/tetrahydrofuran (THF) mixture solvent. The structural and electronic properties of catalysts are characterized using X-ray reflection (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). The electrooxidation of formic acid on these Pt-Ru nanoparticles are investigated by using cyclic voltammetry, chronoamperometry and CO-stripping measurements. The results of electrochemical measurements illustrate that the alloying degree and Pt/Ru atomic ratio of Pt-Ru catalyst play an important role in the electrocatalytic activity of the Pt-Ru/C catalyst for formic acid electrooxidation due to the bifunctional mechanism and the electronic effect. Since formic acid is an intermediate in the methanol electrooxidation on Pt electrode in acidic electrolyte, the observation provides an additional fundamental understanding of the structure-activity relationship of Pt-Ru catalyst for methanol electrooxidation. (author)

Silica gel-Supported Palladium Catalyst for the Acyl Sonogashira Reaction

Energy Technology Data Exchange (ETDEWEB)

Hossain, Shahin; Park, Jihoon; Park, Minkyu; Jin, Myungjong [Inha Univ., Incheon (Korea, Republic of)

2013-06-15

We have demonstrated an efficient and eco-friendly procedure for the synthesis of ynones using silica supported thiol-palladium complex as a recyclable catalyst under copper free mild reaction conditions. The material was synthesized by post grafting of 3-mercaptopropyltrimethoxysilane on amorphous silica and subsequently Pd(II) attached onto thiol groups. This synthetic method has notable advantages because it involves easily available, less costly and produces an easily recyclable catalyst in high yields of the products. The mild reaction conditions encouraged us to further extension for the development of novel multicomponent reactions. Thus we have explained the three component synthesis of pyrazoles in one-pot fashion with good yields. Specifically, this simple procedure for the ynone synthesis and this approach to synthesize N-containing heterocycles may be valuable tool in future. The acyl Sonogashira reaction between acyl chlorides and terminal alkynes is one of the most useful method for the preparation of ynones which are important intermediates to prepare versatile pharmaceutically and biologically active heterocyclic compounds such as pyrroles, pyrazoles, furans, furanones, isoxazoles, pyrimidines, quinolines, indolizidinones.

Silica gel-Supported Palladium Catalyst for the Acyl Sonogashira Reaction

International Nuclear Information System (INIS)

Hossain, Shahin; Park, Jihoon; Park, Minkyu; Jin, Myungjong

2013-01-01

We have demonstrated an efficient and eco-friendly procedure for the synthesis of ynones using silica supported thiol-palladium complex as a recyclable catalyst under copper free mild reaction conditions. The material was synthesized by post grafting of 3-mercaptopropyltrimethoxysilane on amorphous silica and subsequently Pd(II) attached onto thiol groups. This synthetic method has notable advantages because it involves easily available, less costly and produces an easily recyclable catalyst in high yields of the products. The mild reaction conditions encouraged us to further extension for the development of novel multicomponent reactions. Thus we have explained the three component synthesis of pyrazoles in one-pot fashion with good yields. Specifically, this simple procedure for the ynone synthesis and this approach to synthesize N-containing heterocycles may be valuable tool in future. The acyl Sonogashira reaction between acyl chlorides and terminal alkynes is one of the most useful method for the preparation of ynones which are important intermediates to prepare versatile pharmaceutically and biologically active heterocyclic compounds such as pyrroles, pyrazoles, furans, furanones, isoxazoles, pyrimidines, quinolines, indolizidinones

Carbon nanocages: a new support material for Pt catalyst with remarkably high durability.

Science.gov (United States)

Wang, Xiao Xia; Tan, Zhe Hua; Zeng, Min; Wang, Jian Nong

2014-03-24

Low durability is the major challenge hindering the large-scale implementation of proton exchange membrane fuel cell (PEMFC) technology, and corrosion of carbon support materials of current catalysts is the main cause. Here, we describe the finding of remarkably high durability with the use of a novel support material. This material is based on hollow carbon nanocages developed with a high degree of graphitization and concurrent nitrogen doping for oxidation resistance enhancement, uniform deposition of fine Pt particles, and strong Pt-support interaction. Accelerated degradation testing shows that such designed catalyst possesses a superior electrochemical activity and long-term stability for both hydrogen oxidation and oxygen reduction relative to industry benchmarks of current catalysts. Further testing under conditions of practical fuel cell operation reveals almost no degradation over long-term cycling. Such a catalyst of high activity, particularly, high durability, opens the door for the next-generation PEMFC for "real world" application.

Further studies on hydration of alkynes by the PtCl4-CO catalyst

Energy Technology Data Exchange (ETDEWEB)

Israelsohn, Osnat; Vollhardt, K. Peter C.; Blum, Jochanan

2002-01-18

Under CO atmosphere, between 80 and 120 C, a glyme solution of PtCl{sub 4} forms a carbonyl compound that promotes hydration of internal as well as terminal alkynes to give aldehyde-free ketones. The catalytic process depends strongly on the electronic and steric nature of the substrates. Part of the carbonyl functions of the catalyst can be replaced by phosphine ligands. Chiral DIOP reacts with the PtCl{sub 4}-CO compound to give a catalyst that promotes partial kinetic resolution of a racemic alkyne. Replacement of part of the CO by polystyrene-bound diphenylphosphine enables to attach the catalyst to the polymeric support. Upon entrapment of the platinum compound in a silica sol-gel matrix, it reacts as a partially recyclable catalyst. A reformulated mechanism for the PdCl{sub 4}-CO catalyzed hydration is suggested on the basis of the present study.

Preparation and characterization of Pt/C and Pt-Ru/C electrocatalysts for direct ethanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Liu, Zhaolin; Ling, Xing Yi; Su, Xiaodi; Lee, Jim Yang; Gan, Leong Ming [Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore)

2005-09-26

Nano-sized Pt and Pt-Ru colloids are prepared by a microwave-assisted polyol process, and transferred to a toluene solution of decanthiol. Vulcan XC-72 is then added to the toluene solution to adsorb the thiolated Pt and Pt-Ru colloids. Transmission electron microscopy examinations show nearly spherical particles and narrow size distributions for both supported and unsupported metals. The carbon-supported Pt and Pt-Ru nanoparticles are activated by thermal treatment to remove the thiol stabilizing shell. All Pt and Pt-Ru catalysts (except Pt{sub 23}-Ru{sub 77}) give the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Pt{sub 23}-Ru{sub 77} alloy is more typical of the hexagonal close packed (hcp) structure. The electro-oxidation of liquid ethanol on these catalysts is investigated at room temperature by cyclic voltammetry. The results demonstrate that the alloy catalyst is catalytically more active than pure platinum. Preliminary tests on a single cell of a direct ethanol fuel cell (DEFC) indicate that a Pt{sub 52}-Ru{sub 48}/C anode catalyst gives the best electrocatalytic performance among all the carbon-supported Pt and Pt-Ru catalysts. (author)

PtNi alloy nanoparticles supported on carbon-doped TiO2 nanotube arrays for photo-assisted methanol oxidation

International Nuclear Information System (INIS)

He, Huichao; Xiao, Peng; Zhou, Ming; Liu, Feila; Yu, Shujuan; Qiao, Lei; Zhang, Yunhuai

2013-01-01

To develop anode catalysts for photo-assisted direct methanol fuel cell (PDMFC), carbon-doped TiO 2 nanotube arrays-supported PtNi alloy nanoparticles with different Pt/Ni atomic ratio (PtNi/C-TiO 2 NTs) prepared by pulsed electrodeposition method are evaluated as catalysts for photo-assisted methanol oxidation. The cyclic voltammetry (CV) and chronoamperometry results show that the PtNi/C-TiO 2 NTs prepared at t onPt :t onNi : = 10:7 (t on is the current-on time) with a Pt:Ni atomic ratio of 6.1:5.7 presents the highest catalytic activity for methanol oxidation both in the dark and under illumination. In addition, according to the results obtained from the CO stripping voltammetry and electrochemical impedance spectroscopy (EIS) tests, it was found that the light play an accelerative role in the oxidation of methanol on PtNi/C-TiO 2 NTs under illumination. The effect of illumination which enhancing the catalytic activity of PtNi/C-TiO 2 NTs are attributed to (1) methanol and the intermediates be oxidized directly on C-TiO 2 NTs for the light-induced catalytic effect; (2) more abundant oxygen-donating species be produced on C-TiO 2 NTs in the presence of light; (3) less CO ads adsorbing on catalysts due to the presence of stronger metal–support interactions between PtNi alloy nanoparticles and C-TiO 2 NTs under illumination

Cooperative catalysis by silica-supported organic functional groups

OpenAIRE

Margelefsky, Eric L.; Zeidan, Ryan K.; Davis, Mark E.

2008-01-01

Hybrid inorganic–organic materials comprising organic functional groups tethered from silica surfaces are versatile, heterogeneous catalysts. Recent advances have led to the preparation of silica materials containing multiple, different functional groups that can show cooperative catalysis; that is, these functional groups can act together to provide catalytic activity and selectivity superior to what can be obtained from either monofunctional materials or homogeneous catalysts. This tutorial...

Mesoporous Silica Supported Au Nanoparticles with Controlled Size as Efficient Heterogeneous Catalyst for Aerobic Oxidation of Alcohols

Directory of Open Access Journals (Sweden)

Xuefeng Chu

2015-01-01

Full Text Available A series of Au catalysts with different sizes were synthesized and employed on amine group functionalized ordered mesoporous silica solid supports as catalyst for the aerobic oxidation of various alcohols. The mesoporous silica of MCM-41 supported Au nanoparticles (Au-1 exhibited the smallest particle size at ~1.8 nm with superior catalytic activities owing to the confinement effect of the mesoporous channels. Au-1 catalyst is also very stable and reusable under aerobic condition. Therefore, this presented work would obviously provide us a platform for synthesizing more size-controlled metal catalysts to improve the catalytic performances.

Three-dimensional structure of Au nanoparticles supported on amorphous silica and carbon substrates

International Nuclear Information System (INIS)

Bruma, A; Li, Z Y

2012-01-01

Scanning Transmission Electron Microscope (STEM) has been employed to study the three-dimensional structure of gold (Au) nanoparticles deposited by means of thermal evaporation in high vacuum on amorphous silica (a-SiO 2 ) and amorphous carbon (a-C) supports. By performing quantitative analysis on the evolution of the high angle annular dark field (HAADF) images, we studied the influence of the nature and the temperature of support on the growth mode of gold nanoparticles.

Electrocatalytic activity of Pt and PtCo deposited on Ebonex by BH reduction

International Nuclear Information System (INIS)

Slavcheva, E.; Nikolova, V.; Petkova, T.; Lefterova, E.; Dragieva, I.; Vitanov, T.; Budevski, E.

2005-01-01

The method of borohydride reduction (BH) has been applied to synthesize Pt and PtCo nanoparticles supported on Magneli phase titanium oxides, using Pt and Co ethylenediamine complexes as metal precursors. The phase composition of the synthesized catalysts, their morphology and surface structure were studied by physical methods for bulk and surface analysis, such as electron microprobe analysis (EMPA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and BET technique. The catalytic activity towards oxygen evolution reaction in alkaline aqueous solution was investigated using the common electrochemical techniques. It was found that PtCo/Ebonex facilitates essentially the oxygen evolution which starts at lower overpotentials and proceeds with higher rate compared to both the supported Pt and unsupported PtCo catalysts. The observed effect is prescribed to metal-metal and metal-support interactions. The Ebonex possesses a good electrical conductivity and corrosion resistance at high anodic potentials and despite its low surface area is considered as a potential catalyst carrier for the oxygen evolution reaction

Carbon supported Pt-NiO nanoparticles for ethanol electro-oxidation in acid media

Science.gov (United States)

Comignani, Vanina; Sieben, Juan Manuel; Brigante, Maximiliano E.; Duarte, Marta M. E.

2015-03-01

In the present work, the influence of nickel oxide as a co-catalyst of Pt nanoparticles for the electro-oxidation of ethanol in the temperature range of 23-60 °C was investigated. The carbon supported nickel oxide and platinum nanoparticles were prepared by hydrothermal synthesis and microwave-assisted polyol process respectively, and characterized by XRD, EDX, TEM and ICP analysis. The electrocatalytic activity of the as-prepared materials was studied by cyclic voltammetry and chronoamperometry. Small metal nanoparticles with sizes in the range of 3.5-4.5 nm were obtained. The nickel content in the as-prepared Pt-NiO/C catalysts was between 19 and 35 at.%. The electrochemical experiments showed that the electrocatalytic activity of the Pt-NiO/C materials increase with NiO content in the entire temperature range. The apparent activation energy (Ea,app) for the overall ethanol oxidation reaction was found to decrease with NiO content (24-32 kJ mol-1 at 0.3 V), while for Pt/C the activation energy exceeds 48 kJ mol-1. The better performance of the Pt-NiO/C catalysts compared to Pt/C sample is ascribed to the activation of both the C-H and O-H bonds via oxygen-containing species adsorbed on NiO molecules and the modification of the surface electronic structure (changes in the density of states near the Fermi level).

Combined TEM and NC-AFM study of Al2O3-supported Pt nanoparticles

DEFF Research Database (Denmark)

Jensen, Thomas Nørregaard; Simonsen, Søren Bredmose; Chorkendorff, Ib

Sintering, the growth of large particles at the expense of smaller ones, is one of the main causes of catalysts deactivation, since the physicochemical properties of a nanoparticle may depend strongly on its size, shape and composition. For application as heterogeneous catalysts, the nanoparticle...... kinks and edges often play an important role for the catalytic activity. In order to preserve these sites, it is important to stabilize the supported nanoparticles with sizes of a few nanometers during operational conditions at often high temperatures and in the relevant gas environments. A prototypical...... nanocatalyst system for studying coarsening consists of Pt nanoparticles supported on an Al2O3 material which is relevant as an oxidation catalyst in diesel and lean-burn engine exhaust after-treatment technologies. In this study we address the effect on sintering of the shape of Pt nanoparticles supported...

Pt-Fe catalyst nanoparticles supported on single-wall carbon nanotubes: Direct synthesis and electrochemical performance for methanol oxidation

Science.gov (United States)

Ma, Xiaohui; Luo, Liqiang; Zhu, Limei; Yu, Liming; Sheng, Leimei; An, Kang; Ando, Yoshinori; Zhao, Xinluo

2013-11-01

Single-wall carbon nanotubes (SWCNTs) supported Pt-Fe nanoparticles have been prepared by one-step hydrogen arc discharge evaporation of carbon electrode containing both Pt and Fe metal elements. The formation of SWCNTs and Pt-Fe nanoparticles occur simultaneously during the evaporation process. High-temperature hydrogen treatment and hydrochloric acid soaking have been carried out to purify and activate those materials in order to obtain a new type of Pt-Fe/SWCNTs catalyst for methanol oxidation. The Pt-Fe/SWCNTs catalyst performs much higher electrocatalytic activity for methanol oxidation, better stability and better durability than a commercial Pt/C catalyst according to the electrochemical measurements, indicating that it has a great potential for applications in direct methanol fuel cells.

Graphene–poly(5-aminoindole) composite film as Pt catalyst support for methanol electrooxidation in alkaline medium

International Nuclear Information System (INIS)

Yue, Ruirui; Zhang, Qiang; Wang, Caiqin; Du, Yukou; Yang, Ping; Xu, Jingkun

2013-01-01

Highlights: • Electropolymerization of 5-aminoindole (AIn) in the presence of graphene (GE). • Significant catalytic effect of GE on the polymerization of AIn. • PAIn/GE/GC used as Pt catalyst support. • The enhanced catalytic activity of Pt/PAIn/GE/GC for methanol electrooxidation. -- Abstract: 5-Aminoindole (AIn) was electropolymerized on graphene (GE) modified glass carbon (GC) electrode in 0.5 M H 2 SO 4 aqueous solution containing 0.01 M AIn. Because of the catalytic effect of GE, the polymerization efficiency of AIn and the electrochemical activity of as-formed poly(5-aminoindole) (PAIn) were significantly improved on GE/GC electrode as compared to that on the bare GC electrode. The prepared PAIn/GE/GC electrode was used as substrate for Pt particle electrodeposition. SEM, EDX and Raman spectral were used to characterize the prepared electrodes. Electrocatalytic experiments demonstrate that the Pt/PAIn/GE/GC electrode possesses high catalytic activity toward methanol electrooxidation in alkaline medium, due to the good dispersion of Pt particles on PAIn/GE/GC and the electronic interactions between the metal particles and the polymer matrixes. Thus, PAIn can be a promising alternative for polymeric catalyst support in direct alcohol fuel cells

Sol-gel synthesis of iron catalysers supported on silica and titanium for selectively oxidising methane to formaldehyde

Directory of Open Access Journals (Sweden)

Carlos Alberto Guerrero Fajardo

2008-01-01

Full Text Available Iron materials supported on silica were prepared by the sol-gel method for evaluating catalytic activity in selective o-xidation of methane to formaldehyde. Four catalysts were prepared, one corresponding to the silica support (catalyst 1S, another to the titanium support (catalyst 1T and two more having 0.5% weight iron loads, one for the silica su-pport (catalyst 2FS and the last one the titanium support (catalyst 2FT. The higher BET areas were 659 and 850 m2/g for catalysts 1S and 2FS, respectively while catalysts 1T and 2FT displayed areas of 65 and 54 m2/g, respec-tively. Scanning and transmission electronic microscopy displayed an amorphous structure in the silica-supported materials while titanium-supported materials displayed dense materials having defined structure. X-ray diffraction confirmed the silica’s amorphous structure in 1S and 2FS catalysts and displayed the 1T and 2FT catalysts’ anatase structure. The programmed temperature reduction for the 1S and 2FS catalysts did not display reducible species, while displaying hydrogen consumption peaks related to Fe3O4 reduction to α-Fe via FexO route for 1T and 2FT ca-talysts. The electronic spectroscopy X-ray photo confirmed the Fe(III specie as having 710.6 e.V binding energy for both 2FS and 2FT catalysts. Catalytic activity was carried out at atmospheric pressure in a quartz reactor, reaction mixture as CH4/O2/N2 =7.5/1/4 at 400-800°C temperature range. The reaction products were analysed by gas chromatography on Hayesep R and T columns using 5Å molecular screening. The best response for selective oxida-tion of methane to formaldehyde was displayed by the 2FS catalyst with 3.4% mol methane conversion at 650°C, 11.9% mol formaldehyde selectivity and 0.0211 g HCHO/Kg catalyst yield.

Nonalloyed carbon-supported PtRu catalysts for PEMFC applications

NARCIS (Netherlands)

Papageorgopoulos, D.C.; Heer, de M.P.; Keijzer, M.; Pieterse, J.A.Z.; Bruijn, de F.A.

2004-01-01

PtRu(1:1)/C catalysts were prepared by a process that was claimed previously to lead to nonalloyed Pt and Ru particles, using twodifferent precursors, Ru nitrosyl nitrate and Ru chloride hydrate. Both X-ray diffraction and characterization by cyclic voltammetrypoint toward Pt and Ru being present as

Nonalloyed carbon-supported PtRu catalysts for PEMFC applications

NARCIS (Netherlands)

Papageorgopoulos, D.C.; De Heer, M.P.; Keijzer, M.; Pieterse, J.A.Z.; de Bruijn, F. A.

2004-01-01

PtRu(1:1)/C catalysts were prepared by a process that was claimed previously to lead to non-alloyed Pt and Ru particles, using two different precursors, Ru nitrosyl nitrate and Ru chloride hydrate. Both X-ray diffraction and characterization by cyclic voltammetry point toward Pt and Ru being present

Cooperative effect by monopodal silica-supported niobium com-plexes pairs enhancing catalytic cyclic carbonate production

KAUST Repository

D'Elia, Valerio

2015-05-07

Recent discoveries highlighted the activity and the intriguing mechanistic features of NbCl5 as a molecular catalyst for the cycloaddition of CO2 and epoxides under ambient conditions. This has inspired the preparation of novel silica supported Nb-species by reacting a molecular niobium precursor [NbCl5•OEt2] with silica dehydroxylated at 700 °C (SiO2-700) or at 200 oC (SiO2-200) to generate diverse surface complexes. The product of the reaction between SiO2-700 and [NbCl5•OEt2] was identified as a monopodal supported surface species [≡SiONbCl4•OEt2] (1a). The reactions of SiO2-200 with the niobium precursor, according to two different protocols, generated surface complexes 2a and 3a presenting significant, but different, populations of the monopodal surface complex along with bipodal [(≡SiO)2NbCl3•OEt2]. 93Nb SSNMR spectra of 1a-3a and 31P SSNMR on their PMe3 derivatives (1b-3b) led to the unambiguous assignment of 1a as a single site, monopodal Nb-species while 2a and 3a were found to present two distinct surface-supported components, with 2a being mostly monopodal [≡SiONbCl4•OEt2] and 3a being mostly bipodal [≡S ONbCl3•OEt2]. Double-quantum/single-quantum 31P NMR correlation experiment carried out on 2b supported the existence of vicinal Nb centers on the silica surface for this species. 1a-3a were active heterogeneous catalysts for the synthesis of propylene carbonate from CO2 and propylene oxide under mild catalytic conditions; the performance of 2a was found to significantly surpass that of 1a and 3a. With the support of a systematic DFT study carried out on model silica surfaces, the observed differences in catalytic efficiency were correlated with an unprece-dented cooperative effect between two neighboring Nb centers on the surface of 2a. This is in an excellent agreement with our previous discoveries regarding the mechanism of the NbCl5 catalyzed cycloaddition in the homogeneous phase.

Cooperative effect by monopodal silica-supported niobium com-plexes pairs enhancing catalytic cyclic carbonate production

KAUST Repository

D'Elia, Valerio; Dong, Hailin; Rossini, Aaron J; Widdifield, Cory M.; Vummaleti, Sai V. C.; Minenkov, Yury; Poater, Albert; Abou-Hamad, Edy; Pelletier, Jeremie D. A.; Cavallo, Luigi; Emsley, Lyndon; Basset, Jean-Marie

2015-01-01

Recent discoveries highlighted the activity and the intriguing mechanistic features of NbCl5 as a molecular catalyst for the cycloaddition of CO2 and epoxides under ambient conditions. This has inspired the preparation of novel silica supported Nb-species by reacting a molecular niobium precursor [NbCl5•OEt2] with silica dehydroxylated at 700 °C (SiO2-700) or at 200 oC (SiO2-200) to generate diverse surface complexes. The product of the reaction between SiO2-700 and [NbCl5•OEt2] was identified as a monopodal supported surface species [≡SiONbCl4•OEt2] (1a). The reactions of SiO2-200 with the niobium precursor, according to two different protocols, generated surface complexes 2a and 3a presenting significant, but different, populations of the monopodal surface complex along with bipodal [(≡SiO)2NbCl3•OEt2]. 93Nb SSNMR spectra of 1a-3a and 31P SSNMR on their PMe3 derivatives (1b-3b) led to the unambiguous assignment of 1a as a single site, monopodal Nb-species while 2a and 3a were found to present two distinct surface-supported components, with 2a being mostly monopodal [≡SiONbCl4•OEt2] and 3a being mostly bipodal [≡S ONbCl3•OEt2]. Double-quantum/single-quantum 31P NMR correlation experiment carried out on 2b supported the existence of vicinal Nb centers on the silica surface for this species. 1a-3a were active heterogeneous catalysts for the synthesis of propylene carbonate from CO2 and propylene oxide under mild catalytic conditions; the performance of 2a was found to significantly surpass that of 1a and 3a. With the support of a systematic DFT study carried out on model silica surfaces, the observed differences in catalytic efficiency were correlated with an unprece-dented cooperative effect between two neighboring Nb centers on the surface of 2a. This is in an excellent agreement with our previous discoveries regarding the mechanism of the NbCl5 catalyzed cycloaddition in the homogeneous phase.

Preparation and characterization of Pt/C and Pt sbnd Ru/C electrocatalysts for direct ethanol fuel cells

Science.gov (United States)

Liu, Zhaolin; Ling, Xing Yi; Su, Xiaodi; Lee, Jim Yang; Gan, Leong Ming

Nano-sized Pt and Pt sbnd Ru colloids are prepared by a microwave-assisted polyol process, and transferred to a toluene solution of decanthiol. Vulcan XC-72 is then added to the toluene solution to adsorb the thiolated Pt and Pt sbnd Ru colloids. Transmission electron microscopy examinations show nearly spherical particles and narrow size distributions for both supported and unsupported metals. The carbon-supported Pt and Pt sbnd Ru nanoparticles are activated by thermal treatment to remove the thiol stabilizing shell. All Pt and Pt sbnd Ru catalysts (except Pt 23sbnd Ru 77) give the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Pt 23sbnd Ru 77 alloy is more typical of the hexagonal close packed (hcp) structure. The electro-oxidation of liquid ethanol on these catalysts is investigated at room temperature by cyclic voltammetry. The results demonstrate that the alloy catalyst is catalytically more active than pure platinum. Preliminary tests on a single cell of a direct ethanol fuel cell (DEFC) indicate that a Pt 52sbnd Ru 48/C anode catalyst gives the best electrocatalytic performance among all the carbon-supported Pt and Pt sbnd Ru catalysts.

Characterization of platinized and unplatinized cerium dioxide and other cerium containing catalyst supports

International Nuclear Information System (INIS)

Daniel, D.W.

1984-01-01

The adsorption of CO on platinized cerium dioxide has been investigated by FTIR (Fourier Transform Infrared Spectroscopy). Four active surface sites and two adsorption geometries were found for the oxidized catalyst. Although the metallic sites and both geometries, linear and bridged, were retained upon reduction the two cationic sites were not. During stepwise desorption, CO dissociates leaving behind adsorbed carbon inhibiting readsorption. At elevated temperatures CeO 2 oxidizes Pt. The large decrease in CO adsorption resulting from high temperature reduction was reversed by reoxidation. XPS (X-ray Photoelectron Spectroscopy) data provided no evidence of encapsulation and XRD (X-ray Diffraction) showed the retention of a constant particle size. The results were interpreted as electronic metal-support interaction. The addition of H 2 or D 2 to adsorbed CO at 25 0 C caused spillover of the CO onto the support and a decrease in CO band frequency. When O 2 was added to preadsorbed CO a new band associated with oxygen and CO coadsorbed on a single Pt atom appeared. Carbon dioxide dissociation at room temperature is proposed to occur via a Langmuir-Hinshelwood mechanism. CO adsorption on platinized titania, silica, ceria/titania, ceria/silica, and cerium titanate has also been studied by the same techniques. The adsorption/desorption behavior of the cerium/titania and the single oxide systems paralleled that of Pt/CeO 2

Evaluation of the Scaffolding Effect of Pt Nanowires Supported on Reduced Graphene Oxide in PEMFC Electrodes

Directory of Open Access Journals (Sweden)

Peter Mardle

2018-01-01

Full Text Available The stacking and overlapping effect of two-dimensional (2D graphene nanosheets in the catalyst coating layer is a big challenge for their practical application in proton exchange membrane fuel cells (PEMFCs. These effects hinder the effective transfer of reactant gases to reach the active catalytic sites on catalysts supported on the graphene surface and the removal of the produced water, finally leading to large mass transfer resistances in practical electrodes and poor power performance. In this work, we evaluate the catalytic power performance of aligned Pt nanowires grown on reduced graphene oxide (rGO (PtNW/rGO as cathodes in 16-cm2 single PEMFCs. The results are compared to Pt nanoparticles deposited on rGO (Pt/rGO and commercial Pt/C nanoparticle catalysts. It is found that the scaffolding effect from the aligned Pt nanowire structure reduces the mass transfer resistance in rGO-based catalyst electrodes, and a nearly double power performance is achieved as compared with the Pt/rGO electrodes. However, although a higher mass activity was observed for PtNW/rGO in membrane electrode assembly (MEA measurement, the power performance obtained at a large current density region is still lower than the Pt/C in PEMFCs because of the stacking effect of rGO.

Examining the rudimentary steps of the oxygen reduction reaction on single-atomic Pt using Ti-based non-oxide supports

DEFF Research Database (Denmark)

Tak, Young Joo; Yang, Sungeun; Lee, Hyunjoo

2018-01-01

C(100)-supported single Pt atoms. The O2 and OOH* dissociation processes on Pt/TiN(100) are determined to be non-activated (i.e. "barrier-less" dissociation) while an activation energy barrier of 0.19 and 0.51eV is found for these dissociation processes on Pt/TiC(100), respectively. Moreover, the series...

Nanoparticles of Pt and Ag supported in meso porous SiO2: characterization and catalytic applications

International Nuclear Information System (INIS)

Espinosa, M.E.; Perez H, R.; Perez A, M.; Mondragon G, G.; Arenas A, J.

2004-01-01

The surface properties of catalysts of Pt and Ag supported in conventional SiO 2 hey have been studied through reduction reactions of N 2 O with H 2 which is a sensitive reaction to the structure. In our case it was used a meso porous ceramic support of SiO 2 of great surface area (1100 m 2 /gr), where it is caused a high dispersion of the metallic nanoparticles of Pt and Ag, the total charge of the active phase in the meso porous support was of 3% in weight. The catalysts show a variation in the percentages of conversion of N 2 O depending on the size and dispersion of the metallic phases. (Author)

Effective adsorption/electrocatalytic degradation of perchlorate using Pd/Pt supported on N-doped activated carbon fiber cathode

Energy Technology Data Exchange (ETDEWEB)

Yao, Fubing; Zhong, Yu [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yang, Qi, E-mail: yangqi@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wang, Dongbo, E-mail: dongbowang@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Chen, Fei; Zhao, Jianwei; Xie, Ting; Jiang, Chen; An, Hongxue; Zeng, Guangming; Li, Xiaoming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)

2017-02-05

Highlights: • Pd/Pt-NACF served as an adsorption/electrocatalysis electrode to reduce perchlorate. • The possible mechanisms involved in the reaction process were explained. • The reusability and stability of Pd/Pt-NACF bifunctional material was evaluated. - Abstract: In this work, Pd/Pt supported on N-doped activated carbon fiber (Pd/Pt-NACF) was employed as the electrode for electrocatalytic degradation of perchlorate through adsorption/electroreduction process. Perchlorate in solution was firstly adsorbed on Pd/Pt-NACF and then reduced to non-toxic chloride by the catalytic function of Pd/Pt at a constant current (20 mA). Compared with Pd/Pt-ACF, the adsorption capacity and electrocatalytic degradation efficiency of Pd/Pt-NACF for perchlorate increased 161% and 28%, respectively. Obviously, positively charged N-functional groups on NACF surface enhanced the adsorption capacity of Pd/Pt-NACF, and the dissociation of hydrogen to atomic H* by the Pd/Pt nanostructures on the cathode might drastically promote the electrocatalytic reduction of perchlorate. The role of atomic H* in the electroreduction process was identified by tertiary butanol inhibition test. Meanwhile, the perchlorate degradation performance was not substantially lower after three successive adsorption/electrocatalytic degradation experiments, demonstrating the electrochemical reusability and stability of the as-prepared electrode. These results showed that Pd/Pt-NACF was effective for electrocatalytic degradation of perchlorate and had great potential in perchlorate removal from water.

One-pot synthesis of reduced graphene oxide supported PtCuy catalysts with enhanced electro-catalytic activity for the methanol oxidation reaction

International Nuclear Information System (INIS)

Peng, Xinglan; Zhao, Yanchun; Chen, Duhong; Fan, Yanfang; Wang, Xiao; Wang, Weili; Tian, Jianniao

2014-01-01

The outstanding performance PtCu y (y = 1,2,3) alloy nanoparticles supported on reduced graphene oxide (rGO) have been synthesized by a facile, efficient, one-pot hydrothermal synthesis approach. The as-prepared PtCu y /rGO catalysts are comprehensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy. Cyclic voltammetry, CO-stripping voltammetry and chronoamperometry results reveal that the PtCu y /rGO catalysts have higher electro-catalytic activity, more negative onset oxidative potential, more excellent tolerance ability for CO poisoning and enhanced stability for the electro-oxidation of methanol compared to pure Pt/rGO. As far as the as-made PtCu y /rGO catalysts are concerned, the PtCu 2 /rGO exhibits the highest electro-catalytic activity. The mechanism of the promoting effect of Cu on Pt is explained based on the electronic modification effect. The nature of interfacial interactions between the Pt-Cu active metal phase and the rGO supporting materials is crucial to achieving high performance

Phase behavior of methane hydrate in silica sand

International Nuclear Information System (INIS)

Sun, Shi-Cai; Liu, Chang-Ling; Ye, Yu-Guang; Liu, Yu-Feng

2014-01-01

Highlights: • Hydrate p-T trace in coarse-grained sediment is consistent with that in bulk water. • Fine-grained sediment affects hydrate equilibrium for the depressed water activity. • Hydrate equilibrium in sediment is related to the pore size distribution. • The application of hydrate equilibrium in sediment depends on the actual condition. -- Abstract: Two kinds of silica sand powder with different particle size were used to investigate the phase behavior of methane hydrate bearing sediment. In coarse-grained silica sand, the measured temperature and pressure range was (281.1 to 284.2) K and (5.9 to 7.8) MPa, respectively. In fine-grained silica sand, the measured temperature and pressure range was (281.5 to 289.5) K and (7.3 to 16.0) MPa, respectively. The results show that the effect of coarse-grained silica sand on methane hydrate phase equilibrium can be ignored; however, the effect of fine-grained silica sand on methane hydrate phase equilibrium is significant, which is attributed to the depression of water activity caused by the hydrophilicity and negatively charged characteristic of silica particle as well as the pore capillary pressure. Besides, the analysis of experimental results using the Gibbs–Thomson equation shows that methane hydrate phase equilibrium is related to the pore size distribution of silica sand. Consequently, for the correct application of phase equilibrium data of hydrate bearing sediment, the geological condition and engineering requirement should be taken into consideration in gas production, resource evaluation, etc

Preparation of Mesoporous SBA-16 Silica-Supported Biscinchona Alkaloid Ligand for the Asymmetric Dihydroxylation of Olefins

Directory of Open Access Journals (Sweden)

Shaheen M. Sarkar

2014-01-01

Full Text Available Optically active cinchona alkaloid was anchored onto mesoporous SBA-16 silica and the as-prepared complex was used as a heterogeneous chiral ligand of osmium tetraoxide for the asymmetric dihydroxylation of olefins. The prepared catalytic system provided 90–93% yield of vicinal diol with 92–99% enantioselectivity. The ordered mesoporous SBA-16 silica was found to be a valuable support for the cinchona alkaloid liganded osmium catalyst system which is frequently used in chemical industries and research laboratories for olefin functionalization.

Ordered cubic nanoporous silica support MCM-48 for delivery of poorly soluble drug indomethacin

Science.gov (United States)

Zeleňák, Vladimír; Halamová, Dáša; Almáši, Miroslav; Žid, Lukáš; Zeleňáková, Adriána; Kapusta, Ondrej

2018-06-01

Ordered MCM-48 nanoporous silica (SBET = 923(3) m2·g-1, VP = 0.63(2) cm3·g-1) with cubic Ia3d symmetry was used as a support for drug delivery of anti-inflammatory poorly soluble drug indomethacin. The delivery from parent, unmodified MCM-48, and 3-aminopropyl modified silica carrier was studied into the simulated body fluids with the pH = 2 and pH = 7.4. The studied samples were characterized by thermal analysis (TG/DTG-DTA), N2 adsorption/desorption, infrared spectroscopy (FT-IR), powder XRD, SEM, HRTEM methods, measurements of zeta potential (ζ) and dynamic light scattering (DLS). The determined content of indomethacin in pure MCM-48 was 21 wt.% and in the amine-modified silica MCM-48A-I the content was 45 wt.%. The release profile of the drug, in the time period up to 72 h, was monitored by TLC chromatographic method. It as shown, that by the modification of the surface, the drug release can be controlled. The slower release of indomethacin was observed from amino modified sample MCM-48A-I in the both types of studied simulated body fluids (slightly alkaline intravenous solution with pH = 7.4 and acidic gastric fluid with pH = 2), which was supported and explained by zeta potential and DLS measurements. The amount of the released indomethacin into the fluids with various pH was different. The maximum released amount of the drug was 97% for sample containing unmodified silica, MCM-48-I at pH = 7.4 and lowest released amount, 57%, for amine modified sample MCM-48A-I at pH = 2. To compare the indomethacin release profile four kinetic models were tested. Results showed, that that the drug release based on diffusion Higuchi model, mainly governs the release.

High-temperature catalytic reforming of n-hexane over supported and core-shell Pt nanoparticle catalysts: role of oxide-metal interface and thermal stability.

Science.gov (United States)

An, Kwangjin; Zhang, Qiao; Alayoglu, Selim; Musselwhite, Nathan; Shin, Jae-Youn; Somorjai, Gabor A

2014-08-13

Designing catalysts with high thermal stability and resistance to deactivation while simultaneously maintaining their catalytic activity and selectivity is of key importance in high-temperature reforming reactions. We prepared Pt nanoparticle catalysts supported on either mesoporous SiO2 or TiO2. Sandwich-type Pt core@shell catalysts (SiO2@Pt@SiO2 and SiO2@Pt@TiO2) were also synthesized from Pt nanoparticles deposited on SiO2 spheres, which were encapsulated by either mesoporous SiO2 or TiO2 shells. n-Hexane reforming was carried out over these four catalysts at 240-500 °C with a hexane/H2 ratio of 1:5 to investigate thermal stability and the role of the support. For the production of high-octane gasoline, branched C6 isomers are more highly desired than other cyclic, aromatic, and cracking products. Over Pt/TiO2 catalyst, production of 2-methylpentane and 3-methylpentane via isomerization was increased selectively up to 420 °C by charge transfer at Pt-TiO2 interfaces, as compared to Pt/SiO2. When thermal stability was compared between supported catalysts and sandwich-type core@shell catalysts, the Pt/SiO2 catalyst suffered sintering above 400 °C, whereas the SiO2@Pt@SiO2 catalyst preserved the Pt nanoparticle size and shape up to 500 °C. The SiO2@Pt@TiO2 catalyst led to Pt nanoparticle sintering due to incomplete protection of the TiO2 shells during the reaction at 500 °C. Interestingly, over the Pt/TiO2 catalyst, the average size of Pt nanoparticles was maintained even after 500 °C without sintering. In situ ambient pressure X-ray photoelectron spectroscopy demonstrated that the Pt/TiO2 catalyst did not exhibit TiO2 overgrowth on the Pt surface or deactivation by Pt sintering up to 600 °C. The extraordinarily high stability of the Pt/TiO2 catalyst promoted high reaction rates (2.0 μmol · g(-1) · s(-1)), which was 8 times greater than other catalysts and high isomer selectivity (53.0% of C6 isomers at 440 °C). By the strong metal-support interaction

Mesoporous Pt and Pt/Ru alloy electrocatalysts for methanol oxidation

Energy Technology Data Exchange (ETDEWEB)

Franceschini, Esteban A. [Grupo de Celdas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Planes, Gabriel A. [Departamento de Quimica, Facultad de Ciencias Exactas, Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto, Agencia Postal No 3, 5800, Rio Cuarto (Argentina); Williams, Federico J. [Departamento de Quimica Inorganica, Analitica y Quimica-Fisica, INQUIMAE CONICET, Facultad Ciencias Exactas y Naturales, Pabellon 2, Ciudad Universitaria, Buenos Aires (Argentina); Soler-Illia, Galo J.A.A. [Gerencia de Quimica, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Corti, Horacio R. [Grupo de Celdas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Departamento de Quimica Inorganica, Analitica y Quimica-Fisica, INQUIMAE CONICET, Facultad Ciencias Exactas y Naturales, Pabellon 2, Ciudad Universitaria, Buenos Aires (Argentina)

2011-02-15

Mesoporous Pt and Pt/Ru catalysts with 2D-hexagonal mesostructure were synthesized using a triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (Pluronic F127 {sup registered}) template, on a gold support. Large electrochemical surface areas were observed for the catalysts prepared at high overpotentials. Compared to the Pt catalyst, the Pt/Ru alloy containing 3 at% of Ru exhibited lower onset potential and more than three times the limit mass activity for methanol oxidation. This behavior is assigned to the larger pore size of the mesoporous Pt and Pt/Ru catalysts obtained with this template that seems to improve the methanol accessibility to the active sites compared to those obtained using lyotropic liquid crystals. (author)

Plasma-induced synthesis of Pt nanoparticles supported on TiO2 nanotubes for enhanced methanol electro-oxidation

Science.gov (United States)

Su, Nan; Hu, Xiulan; Zhang, Jianbo; Huang, Huihong; Cheng, Jiexu; Yu, Jinchen; Ge, Chao

2017-03-01

A Pt/C/TiO2 nanotube composite catalyst was successfully prepared for enhanced methanol electro-oxidation. Pt nanoparticles with a particle size of 2 nm were synthesized by plasma sputtering in water, and anatase TiO2 nanotubes with an inner diameter of approximately 100 nm were prepared by a simple two-step anodization method and annealing process. Field-emission scanning electron microscopy images indicated that the different morphologies of TiO2 synthesized on the surface of Ti foils were dependent on the different anodization parameters. The electrochemical performance of Pt/C/TiO2 catalysts for methanol oxidation showed that TiO2 nanotubes were more suitable for use as Pt nanoparticle support materials than irregular TiO2 short nanorods due to their tubular morphology and better electronic conductivity. X-ray photoelectron spectroscopy characterization showed that the binding energies of the Pt 4f of the Pt/C/TiO2 nanotubes exhibited a slightly positive shift caused by the relatively strong interaction between Pt and the TiO2 nanotubes, which could mitigate the poisoning of the Pt catalyst by COads, and further enhance the electrocatalytic performance. Thus, the as-obtained Pt/C/TiO2 nanotubes composites may become a promising catalyst for methanol electro-oxidation.

Nitriles at Silica Interfaces Resemble Supported Lipid Bilayers.

Science.gov (United States)

Berne, Bruce J; Fourkas, John T; Walker, Robert A; Weeks, John D

2016-09-20

Nitriles are important solvents not just for bulk reactions but also for interfacial processes such as separations, heterogeneous catalysis, and electrochemistry. Although nitriles have a polar end and a lipophilic end, the cyano group is not hydrophilic enough for these substances to be thought of as prototypical amphiphiles. This picture is now changing, as research is revealing that at a silica surface nitriles can organize into structures that, in many ways, resemble lipid bilayers. This unexpected organization may be a key component of unique interfacial behavior of nitriles that make them the solvents of choice for so many applications. The first hints of this lipid-bilayer-like (LBL) organization of nitriles at silica interfaces came from optical Kerr effect (OKE) experiments on liquid acetonitrile confined in the pores of sol-gel glasses. The orientational dynamics revealed by OKE spectroscopy suggested that the confined liquid is composed of a relatively immobile sublayer of molecules that accept hydrogen bonds from the surface silanol groups and an interdigitated, antiparallel layer that is capable of exchanging into the centers of the pores. This picture of acetonitrile has been borne out by molecular dynamics simulations and vibrational sum-frequency generation (VSFG) experiments. Remarkably, these simulations further indicate that the LBL organization is repeated with increasing disorder at least 20 Å into the liquid from a flat silica surface. Simulations and VSFG and OKE experiments indicate that extending the alkyl chain to an ethyl group leads to the formation of even more tightly packed LBL organization featuring entangled alkyl tails. When the alkyl portion of the molecule is a bulky t-butyl group, packing constraints prevent well-ordered LBL organization of the liquid. In each case, the surface-induced organization of the liquid is reflected in its interfacial dynamics. Acetonitrile/water mixtures are favored solvent systems for separations

Catalyst Architecture for Stable Single Atom Dispersion Enables Site-Specific Spectroscopic and Reactivity Measurements of CO Adsorbed to Pt Atoms, Oxidized Pt Clusters, and Metallic Pt Clusters on TiO2.

Science.gov (United States)

DeRita, Leo; Dai, Sheng; Lopez-Zepeda, Kimberly; Pham, Nicholas; Graham, George W; Pan, Xiaoqing; Christopher, Phillip

2017-10-11

Oxide-supported precious metal nanoparticles are widely used industrial catalysts. Due to expense and rarity, developing synthetic protocols that reduce precious metal nanoparticle size and stabilize dispersed species is essential. Supported atomically dispersed, single precious metal atoms represent the most efficient metal utilization geometry, although debate regarding the catalytic activity of supported single precious atom species has arisen from difficulty in synthesizing homogeneous and stable single atom dispersions, and a lack of site-specific characterization approaches. We propose a catalyst architecture and characterization approach to overcome these limitations, by depositing ∼1 precious metal atom per support particle and characterizing structures by correlating scanning transmission electron microscopy imaging and CO probe molecule infrared spectroscopy. This is demonstrated for Pt supported on anatase TiO 2 . In these structures, isolated Pt atoms, Pt iso , remain stable through various conditions, and spectroscopic evidence suggests Pt iso species exist in homogeneous local environments. Comparing Pt iso to ∼1 nm preoxidized (Pt ox ) and prereduced (Pt metal ) Pt clusters on TiO 2 , we identify unique spectroscopic signatures of CO bound to each site and find CO adsorption energy is ordered: Pt iso ≪ Pt metal atoms bonded to TiO 2 and that Pt iso exhibits optimal reactivity because every atom is exposed for catalysis and forms an interfacial site with TiO 2 . This approach should be generally useful for studying the behavior of supported precious metal atoms.

Isolated Pt Atoms Stabilized by Amorphous Tungstenic Acid for Metal-Support Synergistic Oxygen Activation.

Science.gov (United States)

Zhang, Qian; Qin, Xixi; Duanmu, Fanpeng; Ji, Huiming; Shen, Zhurui; Han, Xiaopeng; Hu, Wenbin

2018-06-05

Oxygen activation plays a crucial role in many important chemical reactions such as organics oxidation and oxygen reduction. For developing highly active materials for oxygen activation, herein, we report an atomically dispersed Pt on WO3 nanoplates stabilized by in-situ formed amorphous H2WO4 out-layer and the mechanism for activating molecular oxygen. Experimental and theoretical studies demonstrate that the isolated Pt atoms coordinated with oxygen atoms from [WO6] and water of H2WO4, consequently leading to optimized surface electronic configuration and strong metal support interaction (SMSI). In exemplified reactions of butanone oxidation sensing and oxygen reduction, the atomic Pt/WO3 hybrid exhibits superior activity than those of Pt nanoclusters/WO3 and bare WO3 as well as enhanced long-term durability. This work will provide insight on the origin of activity and stability for atomically dispersed materials, thus promoting the development of highly efficient and durable single atom-based catalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled Synthesis of Pt Nanowires with Ordered Large Mesopores for Methanol Oxidation Reaction

Science.gov (United States)

Zhang, Chengwei; Xu, Lianbin; Yan, Yushan; Chen, Jianfeng

2016-08-01

Catalysts for methanol oxidation reaction (MOR) are at the heart of key green-energy fuel cell technology. Nanostructured Pt materials are the most popular and effective catalysts for MOR. Controlling the morphology and structure of Pt nanomaterials can provide opportunities to greatly increase their activity and stability. Ordered nanoporous Pt nanowires with controlled large mesopores (15, 30 and 45 nm) are facilely fabricated by chemical reduction deposition from dual templates using porous anodic aluminum oxide (AAO) membranes with silica nanospheres self-assembled in the channels. The prepared mesoporous Pt nanowires are highly active and stable electrocatalysts for MOR. The mesoporous Pt nanowires with 15 nm mesopores exhibit a large electrochemically active surface area (ECSA, 40.5 m2 g-1), a high mass activity (398 mA mg-1) and specific activity (0.98 mA cm-2), and a good If/Ib ratio (1.15), better than the other mesoporous Pt nanowires and the commercial Pt black catalyst.

Mesoporous Silica-Supported Sulfonyldiamine Ligand for Microwave-Assisted Transfer Hydrogenation

Directory of Open Access Journals (Sweden)

Shaheen M. Sarkar

2015-01-01

Full Text Available N-Sulfonyl-1,2-diamine ligands, derived from 1,2-diaminocyclohexane and 1,2-diaminopropane, were immobilized onto mesoporous SBA-15 silica. The SBA-15-supported sulfonyldiamine-Ru complex was prepared in situ under microwave heating at 60 W for 3 min. The prepared sulfonyldiamine-Ru complex was used as an efficient catalyst for the transfer hydrogenation of ketones to the corresponding secondary alcohols. The heterogeneous complex showed extremely high catalytic activity with 99% conversion rate under microwave heating condition. The complexes were regenerated by simple filtration and reused two times without significant loss of activity.

Preparation, surface characterization and performance of a Fischer-Tropsch catalyst of cobalt supported on silica nanosprings

International Nuclear Information System (INIS)

Kengne, Blaise-Alexis Fouetio; Alayat, Abdulbaset M.; Luo, Guanqun; McDonald, Armando G.; Brown, Justin; Smotherman, Hayden; McIlroy, David N.

2015-01-01

Graphical abstract: - Highlights: • Determined that the reduction of Co nanoparticles on silica nanosprings 200 °C higher than the reduction temperature of Co in a solgel support. • The high reduction temperature of Co supported on silica nanosprings is attributed to the heat transfer properties of the nanosprings due to their high surface area. Co-silica nanospring Fischer-Tropsch catalyst can be used to produce drop in fuels such as JP-4. - Abstract: The reduction of cobalt (Co) catalyst supported on silica nanosprings for Fischer-Tropsch synthesis (FTS) has been monitored by X-ray photoelectron spectroscopy (XPS) and compared to FT catalytic activity. The cobalt is present in the starting catalyst as a Co 3 O 4 spinel phase. A two-step reduction of Co 3 O 4 to CoO and then to Co 0 is observed, which is consistent with the results of H 2 -temperature programmed reduction. During the reduction the two steps occur concurrently. The deconvolution of the Co 2p core level state for the catalyst reduced at 385 °C and 1.0 × 10 −6 Torr of H 2 revealed signatures of Co 0 , CoO, and Co 3 O 4 . The reduction saturates at a Co o concentration of approximately 41% after 20 h, which correlates with the activity and lifetime of the catalyst during FTS testing. Conversely, at 680 °C and 10 Torr of H 2 , the catalyst is completely reduced after 10 h. The evolution of the Co d-band at the Fermi level in the valence band XPS spectrum definitively verifies the metallic phase of Co. FTS evaluation of the Co/NS catalyst reduced at 609 °C showed higher production rate (3-fold) of C 6 -C 17 hydrocarbons than the catalyst reduced at 409 °C and is consistent with the XPS analysis.

Facile synthesis of porous Pt-Pd nanospheres supported on reduced graphene oxide nanosheets for enhanced methanol electrooxidation

Science.gov (United States)

Li, Shan-Shan; Lv, Jing-Jing; Hu, Yuan-Yuan; Zheng, Jie-Ning; Chen, Jian-Rong; Wang, Ai-Jun; Feng, Jiu-Ju

2014-02-01

In this study, a simple, facile, and effective wet-chemical strategy was developed in the synthesis of uniform porous Pt-Pd nanospheres (Pt-Pd NSs) supported on reduced graphene oxide nanosheets (RGOs) under ambient temperature, where octylphenoxypolye thoxyethanol (NP-40) is used as a soft template, without any seed, organic solvent or special instruments. The as-prepared nanocomposites display enhanced electrocatalytic activity and good stability toward methanol oxidation, compared with commercial Pd/C and Pt/C catalysts. This strategy may open a new route to design and prepare advanced electrocatalysts for fuel cells.

Tunable and selective hydrogenation of furfural to furfuryl alcohol and cyclopentanone over Pt supported on biomass-derived porous heteroatom doped carbon.

Science.gov (United States)

Liu, Xiuyun; Zhang, Bo; Fei, Benhua; Chen, Xiufang; Zhang, Junyi; Mu, Xindong

2017-09-21

The search for and exploitation of efficient catalytic systems for selective conversion of furfural into various high value-added chemicals remains a huge challenge for green synthesis in the chemical industry. Here, novel Pt nanoparticles supported on bamboo shoot-derived porous heteroatom doped carbon materials were designed as highly active catalysts for controlled hydrogenation of furfural in aqueous media. The porous heteroatom doped carbon supported Pt catalysts were endowed with a large surface area with a hierarchical porous structure, a high content of nitrogen and oxygen functionalities, a high dispersion of the Pt nanoparticles, good water dispersibility and reaction stability. Benefiting from these features, the novel Pt catalysts displayed a high activity and controlled tunable selectivity for furfural hydrogenation to produce furfuryl alcohol and cyclopentanone in water. The product selectivity could be easily modulated by controlling the carbonization temperature of the porous heteroatom doped carbon support and the reaction conditions (temperature and H 2 pressure). Under mild conditions (100 °C, 1 MPa H 2 ), furfuryl alcohol was obtained in water with complete conversion of the furfural and an impressive furfuryl alcohol selectivity of >99% in the presence of Pt/NC-BS-500. A higher reaction temperature, in water, favored rearrangement of the furfural (FFA) with Pt/NC-BS-800 as the catalyst, which resulted in a high cyclopentanone yield of >76% at 150 °C and 3 MPa H 2 . The surface properties and pore structure of the heteroatom doped carbon support, adjusted using the carbonization temperature, might determine the interactions between the Pt nanoparticles, carbon support and catalytic reactants in water, which in turn could have led to a good selectivity control. The effect of different reaction temperatures and reaction times on the product selectivity was also explored. Combined with exploration of the distribution of the reaction products, a

H2 splitting on Pt, Ru and Rh nanoparticles supported on sputtered HOPG

DEFF Research Database (Denmark)

Fiordaliso, Elisabetta Maria; Murphy, Shane; Nielsen, R.M.

2012-01-01

The equilibrium hydrogen exchange rate between adsorbed and gas phase hydrogen at 1bar is measured for Pt, Ru and Rh nanoparticles supported on a sputtered HOPG substrate. The particles are prepared by Electron Beam Physical Vapor Deposition and the diameter of the particles varies between 2 and ...

High activity of cubic PtRh alloys supported on graphene towards ethanol electrooxidation.

Science.gov (United States)

Rao, Lu; Jiang, Yan-Xia; Zhang, Bin-Wei; Cai, Yuan-Rong; Sun, Shi-Gang

2014-07-21

Cubic PtRh alloys supported on graphene (PtxRhy/GN) with different atomic ratio of Pt and Rh were directly synthesized for the first time using the modified polyol method with Br(-) for the shape-directing agents. The process didn't use surface-capping agents such as PVP that easily occupy the active sites of electrocatalysts and are difficult to remove. Graphene is the key factor for cubic shape besides Br(-) and keeping catalysts high-dispersed. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of these electrocatalysts. The results showed that they were composed of homogeneous cubic PtRh alloys. Traditional electrochemical methods, such as cyclic voltammetry and chronoamperometry, were used to investigate the electrocatalytic properties of PtxRhy/GN towards ethanol electrooxidation. It can be seen that PtxRhy/GN with all atomic ratios exhibited high catalytic activity, and the most active one has a composition with Pt : Rh = 9 : 1 atomic ratio. Electrochemical in situ FTIR spectroscopy was used to evaluate the cleavage of C-C bond in ethanol at room temperature in acidic solutions, the results illustrated that Rh in an alloy can promote the split of C-C bond in ethanol, and the alloy catalyst with atomic ratio Pt : Rh = 1 : 1 showed obviously better performance for the C-C bond breaking in ethanol and higher selectivity for the enhanced activity of ethanol complete oxidation to CO2 than alloys with other ratios of Pt and Rh. The investigation indicates that high activity of PtxRhy/GN electrocatalyst towards ethanol oxidation is due to the specific shape of alloys and the synergistic effect of two metal elements as well as graphene support.

Biogenic porous silica and silicon sourced from Mexican Giant Horsetail (Equisetum myriochaetum) and their application as supports for enzyme immobilization.

Science.gov (United States)

Sola-Rabada, Anna; Sahare, Padma; Hickman, Graham J; Vasquez, Marco; Canham, Leigh T; Perry, Carole C; Agarwal, Vivechana

2018-06-01

Porous silica-based materials are attractive for biomedical applications due to their biocompatibility and biodegradable character. In addition, inorganic supports such as porous silicon are being developed due to integrated circuit chip compatibility and tunable properties leading to a wide range of multidisciplinary applications. In this contribution, biosilica extracted from a rarely studied plant material (Equisetum Myriochaetum), its conversion to silicon and the potential for both materials to be used as supports for enzyme immobilization are investigated. E. myriochaetum was subject to conventional acid digestion to extract biogenic silica with a% yield remarkably higher (up to 3 times) than for other Equisetum sp. (i.e. E. Arvense). The surface area of the isolated silica was ∼400 m 2 /g, suitable for biotechnological applications. Biogenic silicon was obtained by magnesiothermic reduction. The materials were characterized by SEM-EDX, XRD, FT-IR, ICP-OES, TGA and BET analysis and did not contain significant levels of class 1 heavy elements (such as Pb, Cd, Hg and As). Two commercial peroxidases, horseradish peroxidase (HRP) and Coprinus cinereus peroxidase (CiP) were immobilized onto the biogenic materials using three different functionalization routes: (A) carbodiimide, (B) amine + glutaraldehyde and (C) amine + carbodiimide. Although both biogenic silica and porous silicon could be used as supports differences in behaviour were observed for the two enzymes. For HRP, loading onto biogenic silica via the glutaraldehyde immobilization technique (route B) was most effective. The loading of CiP showed a much higher peroxidase activity onto porous silicon than silica functionalized by the carbodiimide method (route A). From the properties of the extracted materials obtained from Equisetum Myriochaetum and the immobilization results observed, these materials appear to be promising for industrial and biomedical applications. Copyright © 2018 Elsevier

Perceived Organizational Support, Job Satistaction Dan Organizational Citizenship Behavior Pada PT. Bank Maluku Cabang UTAMA Kota Ambon

OpenAIRE

Waileruny, Hulawa Theresia

2014-01-01

Penelitian ini dilakukan untuk menguji Perceived Organizational Support, Job Satisfaction dan Organizational Citizenship Behavior pada PT. Bank Maluku Cabang Utama Kota Ambon. Sampel yang digunakan dalam penelitian ini berjumlah 103 orang karyawan PT. Bank Maluku Cabang Utama Kota Ambon. Penelitian ini menggunakan pendekatan kuantitatif, data penelitian diperoleh melalui kuesioner penelitian yang telah diisi oleh responden. Metode pengolahan data dilakukan dengan menggunakan validitas, relia...

Vertically aligned carbon nanotubes/carbon fiber paper composite to support Pt nanoparticles for direct methanol fuel cell application

Science.gov (United States)

Zhang, Jing; Yi, Xi-bin; Liu, Shuo; Fan, Hui-Li; Ju, Wei; Wang, Qi-Chun; Ma, Jie

2017-03-01

Vertically aligned carbon nanotubes (VACNTs) grown on carbon fiber paper (CFP) by plasma enhanced chemical vapor deposition is introduced as a catalyst support material for direct methanol fuel cells (DMFCs). Well dispersed Pt nanoparticles on VACNTs surface are prepared by impregnation-reduction method. The VACNTs on CFP possess well-maintained alignment, large surface area and good electrical conductivity, which leading to the formation of Pt particles with a smaller size and enhance the Pt utilization rate. The structure and nature of resulting Pt/VACNTs/CFP catalysts for methanol oxidation are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning electron microscope (SEM). With the aid of VACNTs, well-dispersed Pt catalysts enable the reversibly rapid redox kinetic since electron transport efficiently passes through a one-dimensional pathway, which leads to enhance the catalytic activity and Pt utilization rate. Compared with the Pt/XC-72/CFP electrode, the electrochemical measurements results display that the Pt/VACNTs/CFP catalyst shows much higher electrocatalytic activity and better stability for methanol oxidation. In addition, the oxidation current from 200 to 1200 s decayed more slowly for the Pt/VACNTs/CFP than that of the Pt/XC-72/CFP catalysts, indicating less accumulation of adsorbed CO species. All those results imply that the Pt/VACNTs/CFP has a great potential for applications in DMFCs.

SiC nanocrystals as Pt catalyst supports for fuel cell applications

DEFF Research Database (Denmark)

Dhiman, Rajnish; Morgen, Per; Skou, E.M.

2013-01-01

A robust catalyst support is pivotal to Proton Exchange Membrane Fuel Cells (PEMFCs) to overcome challenges such as catalyst support corrosion, low catalyst utilization and overall capital cost. SiC is a promising candidate material which could be applied as a catalyst support in PEMFCs. Si...... on the nanocrystals of SiC-SPR and SiC-NS by the polyol method. The SiC substrates are subjected to an acid treatment to introduce the surface groups, which help to anchor the Pt nano-catalysts. These SiC based catalysts have been found to have a higher electrochemical activity than commercially available Vulcan...... based catalysts (BASF & HISPEC). These promising results signal a new era of SiC based catalysts for fuel cell applications....

Determination of silica in silicates by differential spectrophotometry as α-molybdosilicic acid

International Nuclear Information System (INIS)

Ohlweiler, O.A.; Meditsch, J.O.; Silva, S.

1980-01-01

A method for determining silica in silicates by differential spectrophotometry, using β-molybdosilic acid, is described. The sample is attacked by a mixture of boron trioxide and lithium carbonate (10:1). α-molydbosilicic acid is developed in a buffered solution (pH approximatelly 3.9) containing acetic acid and sodium acetate. The analytical procedure involves a series of preliminary steps which were previously elaborated for the gravimetric determination of silica as oxine molybdosilicate and which account for the removal of phosphorus, titanium and zirconium through ion exchange resins. (C.L.B.) [pt

Las bases del PT: ideología versus personalismo en su apoyo electoral Sources of PT: ideology versus personalism in its electoral support

Directory of Open Access Journals (Sweden)

David SAMUELS

2011-01-01

-bidi-font-family: 'BFHAF J+ Simoncini Garamond';">y sus electores aún son más importantes que los vínculos ideológicos entre los demás partidos brasileños y sus respectivos electores.

pt; margin: 0cm 0cm 9.85pt;">pt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">This article explores data from the pt; mso-bidi-font-family: 'BFHAF K+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">Estudo Eleitoral Brasileiro pt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">in order to research the bases of support to the pt; mso-bidi-font-family: 'BFHAF K+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">Partido dos Trabalhadores pt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">(pt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">PTpt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">, who reached the Presidency of Brazil in 2002. The results show that pt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">PTpt; mso-bidi-font-family: 'BFHAF J+ Simoncini Garamond'; mso-ansi-language: EN-GB;" lang="EN-GB">’s voters are more identified with the leadership of Luiz Inácio Lula da Silva, the current president and the

Ultrasonically treated multi-walled carbon nanotubes (MWCNTs) as PtRu catalyst supports for methanol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Yang, Chunwei; Hu, Xinguo; Wang, Dianlong; Dai, Changsong [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Zhang, Liang; Jin, Haibo [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Agathopoulos, Simeon [Department of Materials Science and Engineering, University of Ioannina, GR-451 10 Ioannina (Greece)

2006-09-29

In the quest of fabricating supported catalysts, experimental results of transmission electron microscopy, Raman and infrared spectroscopy indicate that ultrasonic treatment effectively functionalizes multi-walled carbon nanotubes (MWCNTs), endowing them with groups that can act as nucleation sites which can favor well-dispersed depositions of PtRu clusters on their surface. Ultrasonic treatment seems to be superior than functionalization via regular refluxing. This is confirmed by the determination of the electrochemistry active surface area (ECA) and the CO-tolerance performance of the PtRu catalysts, measured by adsorbed CO-stripping voltammetry in 0.5M sulfuric acid solution, and the real surface area of the PtRu catalysts, evaluated by Brunauer-Emmett-Teller (BET) measurements. Finally, the effectiveness for methanol oxidation is assessed by cyclic voltammetry (CV) in a sulfuric acid and methanol electrolyte. (author)

Raman Spectroscopy and Electrochemical Investigations of Pt Electrocatalyst Supported on Carbon Prepared through Plasma Pyrolysis of Natural Gas

Directory of Open Access Journals (Sweden)

Tereza Cristina Santos Evangelista

2015-01-01

Full Text Available Physicochemical and electrochemical characterisations of Pt-based electrocatalysts supported on carbon (Vulcan carbon, C1, and carbon produced by plasma pyrolysis of natural gas, C2 toward ethanol electrooxidation were investigated. The Pt20/C180 and Pt20/C280 electrocatalysts were prepared by thermal decomposition of polymeric precursors at 350°C. The electrochemical and physicochemical characterisations of the electrocatalysts were performed by means of X-ray diffraction (XRD, transmission electron microscope (TEM, Raman scattering, cyclic voltammetry, and chronoamperometry tests. The XRD results show that the Pt-based electrocatalysts present platinum metallic which is face-centered cubic structure. The results indicate that the Pt20/C180 electrocatalyst has a smaller particle size (10.1–6.9 nm compared with the Pt20/C280 electrocatalyst; however, the Pt20/C280 particle sizes are similar (12.8–10.4 nm and almost independent of the reflection planes, which suggests that the Pt crystallites grow with a radial shape. Raman results reveal that both Vulcan carbon and plasma carbon are graphite-like materials consisting mostly of sp2 carbon. Cyclic voltammetry and chronoamperometry data obtained in this study indicate that the deposition of Pt on plasma carbon increases its electrocatalytic activity toward ethanol oxidation reaction.

Direct hydrothermal synthesis of iron-containing mesoporous silica SBA-15 : potential as a support for gold nanoparticles

NARCIS (Netherlands)

Li, Y.; Guan, Y.; Santen, van R.A.; Kooyman, P.J.; Dugulan, A.I.; Li, C.; Hensen, E.J.M.

2009-01-01

The preparation of mesoporous silica SBA-15 with high iron loadings (14-90 wt % Fe2O3) as a suitable support for gold nanoparticles to be used in CO oxidation catalysis has been investigated. The support materials were prepared by a direct hydrothermal two-step pH adjusting method which consisted of

Controlled interactions between anhydrous keggin-type heteropolyacids and silica support: Preparation and characterization of well-defined silica-supported polyoxometalate species

KAUST Repository

Grinenval, Eva

2010-11-11

Anhydrous Keggin-type phosphorus heteropolyacids were deposited on partially dehydroxylated silica by using the surface organometallic chemistry (SOMC) strategy. The resulting solids were characterized by a combination of physicochemical methods including IR, Raman, 1D and 2D 1H, and 31P MAS NMR, electron microscopy experiments and density functional theory (DFT) calculations. It is shown that the main surface species is [ - Si(OH...H+)]2[H+]1[PM 12O403-] where the polyoxometalate is linked to the support by proton interaction with two silanols. Two other minor species (10% each) are formed by coordination of the polyoxometalate to the surface via the interaction between all three protons with three silanol groups or via three covalent bonds formed by dehydroxylation of the above species. Comparison of the reactivity of these solids and of compounds prepared by a classical way shows that the samples prepared by the SOMC approach contain ca. 7 times more acid sites. © 2010 American Chemical Society.

Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

KAUST Repository

Dey, Raju

2016-08-19

A method for the synthesis of a homogeneous cationic tungsten(VI)penta-methyl complex [(WMe5)(+)(C6F5)(3)BMe-] from neutral tungstenhexamethyl (WMe6) and a silica supported cationic tungstentetramethyl complex [( Si-O-)WMe4+ (C6F5)(3)BMe-] from a neutral silica supported tungstenpentamethyl complex [( Si-O-)WMe5] is described. In both cases a direct demethylation using the B(C6F5)(3) reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe5)(+)(C6F5)(3)BMe-] shows moderate activity whereas the supported cationic complex [( Si-O-)WMe4+(C6F5)(3)BMe-] exhibits good activity in olefin metathesis reactions.

Synthesis and characterization of a homogeneous and silica supported homoleptic cationic tungsten(vi) methyl complex: application in olefin metathesis

KAUST Repository

Dey, Raju; Samantaray, Manoja; Poater, Albert; Hamieh, Ali Imad Ali; Kavitake, Santosh Giridhar; Abou-Hamad, Edy; Callens, Emmanuel; Emwas, Abdul-Hamid M.; Cavallo, Luigi; Basset, Jean-Marie

2016-01-01

A method for the synthesis of a homogeneous cationic tungsten(VI)penta-methyl complex [(WMe5)(+)(C6F5)(3)BMe-] from neutral tungstenhexamethyl (WMe6) and a silica supported cationic tungstentetramethyl complex [( Si-O-)WMe4+ (C6F5)(3)BMe-] from a neutral silica supported tungstenpentamethyl complex [( Si-O-)WMe5] is described. In both cases a direct demethylation using the B(C6F5)(3) reagent was used. The aforesaid complexes were characterized by liquid or solid state NMR spectroscopy. Interestingly, the homogeneous cationic complex [(WMe5)(+)(C6F5)(3)BMe-] shows moderate activity whereas the supported cationic complex [( Si-O-)WMe4+(C6F5)(3)BMe-] exhibits good activity in olefin metathesis reactions.

Preparation of ethylene/1-hexene copolymers from ethylene using a fully silica-supported tandem catalyst system

NARCIS (Netherlands)

Karbach, Fabian F.; Macko, Tibor; Duchateau, Robbert

2016-01-01

A silica-supported tandem catalyst system, capable of producing ethylene/1-hexene copolymers from ethylene being the single monomer, has been investigated. As tandem couple a phenoxyimine titanium catalyst for ethylene trimerization was combined with a metallocene catalyst for α-olefin

Recent progress of ordered mesoporous silica-supported chiral metallic catalysts

Directory of Open Access Journals (Sweden)

LIU Rui

2013-02-01

Full Text Available Recently,ordered silica-based mesoporous chiral organometallics-functionalized heterogeneous catalysts have attracted extensive research interest due to their excellent properties,such as easy preparation,high activity and convenient recycle.This review mainly summarizesthe generally prepared strategy and the silica-based organometallics-functionalized heterogeneous catalysts reported in the literatures.

Synergistic Effect of Nitrogen Doping and MWCNT Intercalation for the Graphene Hybrid Support for Pt Nanoparticles with Exemplary Oxygen Reduction Reaction Performance

Directory of Open Access Journals (Sweden)

Kang Fu

2018-04-01

Full Text Available The potential of graphene–multi-walled-carbon nanotube (G-M hybrids prepared by the one-pot modified Hummers method followed by thermal annealing has been demonstrated by employing one as an electrocatalyst support for oxygen reduction reaction (ORR. N doping effectively modified the electronic structure of the G-M hybrid support, which was beneficial for the uniform distribution of Pt nanoparticles, and ORR activities were further improved. The newly prepared Pt/N-G-M catalyst demonstrated higher electrochemical activity than Pt/G-M and Pt/G catalysts. Even compared with commercial 20 wt % Pt/C (JM20, Pt/N-G-M delivered a better half-wave potential and mass activity. In terms of the durability test, Pt/N-G-M maintained 72.7% of its initial electrochemical active surface area (ECSA after 2000 repeated potential cycles between 0 and 1.2 V in acidic media in relation to the 44.4% retention for JM20. Moreover, the half-wave potential for Pt/N-G-M showed only a minimal change, significantly superior to the 139 mV of loss for JM20. It is expected that Pt/N-G-M can be the potential candidate as a highly efficient and durable catalyst if utilized in proton exchange membrane fuel cells (PEMFCs.

Direct methanol fuel cell with extended reaction zone anode: PtRu and PtRuMo supported on graphite felt

Energy Technology Data Exchange (ETDEWEB)

Bauer, Alex; Gyenge, Elod L.; Oloman, Colin W. [Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, BC (Canada)

2007-05-15

Pressed graphite felt (thickness {proportional_to}350 {mu}m) with electrodeposited PtRu (43 g m{sup -2}, 1.4:1 atomic ratio) or PtRuMo (52 g m{sup -2}, 1:1:0.3 atomic ratio) nanoparticle catalysts was investigated as an anode for direct methanol fuel cells. At temperatures above 333 K the fuel cell performance of the PtRuMo catalyst was superior compared to PtRu. The power density was 2200 W m{sup -2} with PtRuMo at 5500 A m{sup -2} and 353 K while under the same conditions PtRu yielded 1925 W m{sup -2}. However, the degradation rate of the Mo containing catalyst formulation was higher. Compared to conventional gas diffusion electrodes with comparable PtRu catalyst composition and load, the graphite felt anodes gave higher power densities mainly due to the extended reaction zone for methanol oxidation. (author)

Direct methanol fuel cell with extended reaction zone anode: PtRu and PtRuMo supported on graphite felt

Science.gov (United States)

Bauer, Alex; Gyenge, Előd L.; Oloman, Colin W.

Pressed graphite felt (thickness ∼350 μm) with electrodeposited PtRu (43 g m -2, 1.4:1 atomic ratio) or PtRuMo (52 g m -2, 1:1:0.3 atomic ratio) nanoparticle catalysts was investigated as an anode for direct methanol fuel cells. At temperatures above 333 K the fuel cell performance of the PtRuMo catalyst was superior compared to PtRu. The power density was 2200 W m -2 with PtRuMo at 5500 A m -2 and 353 K while under the same conditions PtRu yielded 1925 W m -2. However, the degradation rate of the Mo containing catalyst formulation was higher. Compared to conventional gas diffusion electrodes with comparable PtRu catalyst composition and load, the graphite felt anodes gave higher power densities mainly due to the extended reaction zone for methanol oxidation.

Phosphate-Doped Carbon Black as Pt Catalyst Support: Co-catalytic Functionality for Dimethyl Ether and Methanol Electro-oxidation

DEFF Research Database (Denmark)

Yin, Min; Huang, Yunjie; Li, Qingfeng

2014-01-01

). The supported Pt catalysts show significant improvement in catalytic activity towards the direct oxidation of methanol and DME, attributable to the enhanced adsorption and dehydrogenation of methanol and DME, as well as the presence of activated OH species in the catalysts. The latter is demonstrated......Niobium-phosphate-doped (NbP-doped) carbon blacks were prepared as the composite catalyst support for Pt nanoparticles. Functionalities of the composite include intrinsic proton conductivity, surface acidity, and interfacial synergistic interactions with methanol and dimethyl ether (DME...... to facilitate the removal of CO intermediates formed during the oxidation reactions....

Electrocatalysis of the hydrogen oxidation in the presence of CO on RhO{sub 2}/C-supported Pt nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Freitas, K.S.; Lopes, P.P. [Instituto de Quimica de Sao Carlos, USP, C.P. 780, Sao Carlos, SP 13560-970 (Brazil); Ticianelli, E.A., E-mail: edsont@iqsc.usp.b [Instituto de Quimica de Sao Carlos, USP, C.P. 780, Sao Carlos, SP 13560-970 (Brazil)

2010-12-15

This work presents a study on the kinetics of the hydrogen oxidation reaction (HOR) in the absence and in the presence of CO in ultra thin porous layer and in PEM fuel cell electrodes formed with Pt supported on RhO{sub 2}/C substrates. Together with the electrochemical measurements, the structural and electronic properties of these catalysts were characterized, enabling to correlate their structural and electronic properties with the HOR kinetics. The results show that the presence of Rh oxides leads to an emptying of the Pt 5d band and a consequent reduction of the back-donation of electrons from Pt to CO, weakening the Pt-CO bond and diminishing the CO degree of coverage on Pt, leaving more sites available to HOR. These changes in the electronic spectra do not lead to any perceptible change in the kinetics or the reaction of pure hydrogen. Also, the formation of CO{sub 2} monitored by the MS experiments in the fuel cell anode outlet indicates that the bifunctional mechanism is also operative, but the major CO tolerance is achieved by the electronic effect induced by the RhO{sub 2} support.

Synthesis Of Silver Nanoparticles Supported On Silica Using As Antifungal Agent By Gamma Irradiation

International Nuclear Information System (INIS)

Nguyen Thi Kim Lan; Nguyen Tue Anh; Dang Van Phu; Vo Kim Lang; Nguyen Thuy Khanh; Nguyen Quoc Hien

2011-01-01

Silver nanoparticles supported on silica (Ag nano/SiO 2 ) were prepared by gamma Co-60 irradiation method. The formation of Ag nano doped on silica particles was confirmed by the UV-Vis spectroscopy. The size of silver nanoparticles was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) which showed the particle size of Ag nano to be in range of 15-30 nm for Ag + concentration 10 mM. In addition, antifungal activity of Ag nano/SiO 2 was tested against Aspergillus niger var Tieghn by plate count method. The results indicated that the antifungal efficiency of Ag nano/SiO 2 was about 64, 71, 81, 82 and 96% at the concentrations of Ag nanoparticles of 30, 50, 70, 100 and 150 ppm respectively. (author)

Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water

Science.gov (United States)

Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

2016-06-01

Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m2 g-1 were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction.

Highly selective hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on g-C3N4 nanosheets catalysts in water.

Science.gov (United States)

Chen, Xiufang; Zhang, Ligang; Zhang, Bo; Guo, Xingcui; Mu, Xindong

2016-06-22

Graphitic carbon nitride nanosheets were investigated for developing effective Pt catalyst supports for selective hydrogenation of furfural to furfuryl alcohol in water. The nanosheets with an average thickness of about 3 nm were synthesized by a simple and green method through thermal oxidation etching of bulk g-C3N4 in air. Combined with the unique feature of nitrogen richness and locally conjugated structure, the g-C3N4 nanosheets with a high surface area of 142 m(2) g(-1) were demonstrated to be an excellent supports for loading small-size Pt nanoparticles. Superior furfural hydrogenation activity in water with complete conversion of furfural and high selectivity of furfuryl alcohol (>99%) was observed for g-C3N4 nanosheets supported Pt catalysts. The large specific surface area, uniform dispersion of Pt nanoparticles and the stronger furfural adsorption ability of nanosheets contributed to the considerable catalytic performance. The reusability tests showed that the novel Pt catalyst could maintain high activity and stability in the furfural hydrogenation reaction.

Preparation of PtSn/C, PtRu/C, PtRh/C, PtRuRh/C and PtSnRh/C electrocatalysts using an alcohol-reduction process for methanol and ethanol oxidation; Preparacao e caracterizacao de eletrocatalisadores PtRu, PtSn, PtRh, PtRuRh e PtSnRh para oxidacao direta de alcoois em celulas a combustivel tipo PEM utilizando a metodologia da reducao por alcool

Energy Technology Data Exchange (ETDEWEB)

Dias, Ricardo Rodrigues

2009-07-01

In this work, Pt/C, PtRh (90:10), PtRh/C (50:50), PtSn/C (50:50), PtRu (50:50)/C, PtRuRh/C (50:40:10) and PtSnRh/C (50:40:10) were prepared by an alcohol-reduction process with metal loading of 20 wt.% using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), SnCl{sub 2}.2H{sub 2}O (Aldrich),and RhCl{sub 2}.XH{sub 2}O (Aldrich) as metals sources and Vulcan XC72 as support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry (CV). The electro-oxidation of ethanol was studied by CV, chronoamperomety at room temperature in acid medium and tests at 100 deg C on a single cell of a direct methanol or ethanol fuel cell. The EDX analysis showed that the metal atomic ratios of the obtained electrocatalysts were similar to the nominal atomic ratios used in the preparation. The diffractograms of electrocatalysts prepared showed four peaks at approximately 2{theta} =40 deg, 47 deg, 67 deg and 82 deg, which are associated with the (111), (200), (220) and (311) planes, respectively, of a face cubic-centered (fcc) structure characteristic of platinum and platinum alloys. The average crystallite sizes using the Scherrer equation and the calculated values were in the range of 2-3 nm. For Pt Sn/C and PtSnRh/C two additional peaks were observed at 2 = 34 deg and 52 deg that were identified as a SnO{sub 2} phase. Pt Sn/C (50:50) and PtSnRh/C (50:40:10) electro catalyst showed the best performance for ethanol oxidation at room temperature. For methanol oxidation at room temperature Pt Ru/C, Pt Sn/C and PtRuRh/C electrocatalysts showed the best performance. Tests at 100 deg C on a single cell of a direct ethanol fuel cell PtSnRh/C showed the best performance, for methanol oxidation PtRuRh/C showed the best performance. (author)

Immobilization of β-glucosidase onto mesoporous silica support: Physical adsorption and covalent binding of enzyme

Directory of Open Access Journals (Sweden)

Ivetić Darjana Ž.

2014-01-01

Full Text Available This paper investigates β-glucosidase immobilization onto mesoporous silica support by physical adsorption and covalent binding. The immobilization was carried out onto micro-size silica aggregates with the average pore size of 29 nm. During physical adsorption the highest yield of immobilized β-glucosidase was obtained at initial protein concentration of 0.9 mg ml-1. Addition of NaCl increased 1.7-fold, while Triton X-100 addition decreased 6-fold yield of adsorption in comparison to the one obtained without any addition. Covalently bonded β-glucosidase, via glutaraldehyde previously bonded to silanized silica, had higher yield of immobilized enzyme as well as higher activity and substrate affinity in comparison to the one physically adsorbed. Covalent binding did not considerably changed pH and temperature stability of obtained biocatalyst in range of values that are commonly used in reactions in comparison to unbounded enzyme. Furthermore, covalent binding provided biocatalyst which retained over 70% of its activity after 10 cycles of reuse. [Projekat Ministarstva nauke Republike Srbije, br. III 45021

Mesoporous silica nanoparticles for biomedical and catalytical applications

Energy Technology Data Exchange (ETDEWEB)

Sun, Xiaoxing [Iowa State Univ., Ames, IA (United States)

2011-01-01

Mesoporous silica materials, discovered in 1992 by the Mobile Oil Corporation, have received considerable attention in the chemical industry due to their superior textual properties such as high surface area, large pore volume, tunable pore diameter, and narrow pore size distribution. Among those materials, MCM-41, referred to Mobile Composition of Matter NO. 41, contains honeycomb liked porous structure that is the most common mesoporous molecular sieve studied. Applications of MCM-41 type mesoporous silica material in biomedical field as well as catalytical field have been developed and discussed in this thesis. The unique features of mesoporous silica nanoparticles were utilized for the design of delivery system for multiple biomolecules as described in chapter 2. We loaded luciferin into the hexagonal channels of MSN and capped the pore ends with gold nanoparticles to prevent premature release. Luciferase was adsorbed onto the outer surface of the MSN. Both the MSN and the gold nanoparticles were protected by poly-ethylene glycol to minimize nonspecific interaction of luciferase and keep it from denaturating. Controlled release of luciferin was triggered within the cells and the enzymatic reaction was detected by a luminometer. Further developments by varying enzyme/substrate pairs may provide opportunities to control cell behavior and manipulate intracellular reactions. MSN was also served as a noble metal catalyst support due to its large surface area and its stability with active metals. We prepared MSN with pore diameter of 10 nm (LP10-MSN) which can facilitate mass transfer. And we successfully synthesized an organo silane, 2,2'-Bipyridine-amide-triethoxylsilane (Bpy-amide-TES). Then we were able to functionalize LP10-MSN with bipyridinyl group by both post-grafting method and co-condensation method. Future research of this material would be platinum complexation. This Pt (II) complex catalyst has been reported for a C-H bond activation reaction as an

Preparation, surface characterization and performance of a Fischer-Tropsch catalyst of cobalt supported on silica nanosprings

Energy Technology Data Exchange (ETDEWEB)

Kengne, Blaise-Alexis Fouetio [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States); Alayat, Abdulbaset M. [Environmental Science Program, University of Idaho, Moscow, ID 83844-3006 (United States); Luo, Guanqun [Department of Forest, Rangeland & Fire Sciences, University of Idaho, Moscow, ID 83844-1132 (United States); McDonald, Armando G. [Environmental Science Program, University of Idaho, Moscow, ID 83844-3006 (United States); Department of Forest, Rangeland & Fire Sciences, University of Idaho, Moscow, ID 83844-1132 (United States); Brown, Justin; Smotherman, Hayden [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States); McIlroy, David N., E-mail: dmcilroy@uidaho.edu [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States)

2015-12-30

Graphical abstract: - Highlights: • Determined that the reduction of Co nanoparticles on silica nanosprings 200 °C higher than the reduction temperature of Co in a solgel support. • The high reduction temperature of Co supported on silica nanosprings is attributed to the heat transfer properties of the nanosprings due to their high surface area. Co-silica nanospring Fischer-Tropsch catalyst can be used to produce drop in fuels such as JP-4. - Abstract: The reduction of cobalt (Co) catalyst supported on silica nanosprings for Fischer-Tropsch synthesis (FTS) has been monitored by X-ray photoelectron spectroscopy (XPS) and compared to FT catalytic activity. The cobalt is present in the starting catalyst as a Co{sub 3}O{sub 4} spinel phase. A two-step reduction of Co{sub 3}O{sub 4} to CoO and then to Co{sup 0} is observed, which is consistent with the results of H{sub 2}-temperature programmed reduction. During the reduction the two steps occur concurrently. The deconvolution of the Co 2p core level state for the catalyst reduced at 385 °C and 1.0 × 10{sup −6} Torr of H{sub 2} revealed signatures of Co{sup 0}, CoO, and Co{sub 3}O{sub 4}. The reduction saturates at a Co{sup o} concentration of approximately 41% after 20 h, which correlates with the activity and lifetime of the catalyst during FTS testing. Conversely, at 680 °C and 10 Torr of H{sub 2}, the catalyst is completely reduced after 10 h. The evolution of the Co d-band at the Fermi level in the valence band XPS spectrum definitively verifies the metallic phase of Co. FTS evaluation of the Co/NS catalyst reduced at 609 °C showed higher production rate (3-fold) of C{sub 6}-C{sub 17} hydrocarbons than the catalyst reduced at 409 °C and is consistent with the XPS analysis.

A comparative investigation of metal-support interactions on the catalytic activity of Pt nanoparticles for ethanol oxidation in alkaline medium

Science.gov (United States)

Godoi, Denis R. M.; Villullas, Hebe M.; Zhu, Fu-Chun; Jiang, Yan-Xia; Sun, Shi-Gang; Guo, Junsong; Sun, Lili; Chen, Rongrong

2016-04-01

The effects of interactions of Pt nanoparticles with hybrid supports on reactivity towards ethanol oxidation in alkaline solution are investigated. Studies involve catalysts with identical Pt nanoparticles on six hybrid supports containing carbon powder and transition metal oxides (TiO2, ZrO2, SnO2, CeO2, MoO3 and WO3). In situ X-ray absorption spectroscopy (XAS) results evidence that metal-support interactions produce changes in the Pt 5d band vacancy, which appears to determine the catalytic activity. The highest and lowest activities are observed for Pt nanoparticles on hybrid supports containing TiO2 and CeO2, respectively. Further studies are presented for these two catalysts. In situ FTIR reflection spectroscopy measurements, taken using both multi-stepped FTIR spectroscopy (MS-FTIR) and single potential alteration FTIR spectroscopy (SPA-FTIR), evidence that the main product of ethanol oxidation is acetate, although signals attributed to carbonate and CO2 indicate some differences in CO2 production. Fuel cell performances of these catalysts, tested in a 4.5 cm2 single cell at different temperatures (40-90 °C) show good agreement with data obtained by electrochemical techniques. Results of this comprehensive study point out the possibility of compensating a reduction of noble metal load with an increase in activity promoted by interactions between metallic nanoparticles and a support.

Carbon-supported ternary PtSnIr catalysts for direct ethanol fuel cell

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, J.; Kokoh, K.B.; Coutanceau, C.; Leger, J.-M. [Equipe Electrocatalyse, UMR 6503 CNRS, Universite de Poitiers, 40 avenue du Recteur Pineau 86022 Poitiers Cedex (France); Dos Anjos, D.M. [Equipe Electrocatalyse, UMR 6503 CNRS, Universite de Poitiers, 40 avenue du Recteur Pineau 86022 Poitiers Cedex (France); Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 780, 13560-970 Sao Carlos, SP (Brazil); Olivi, P.; De Andrade, A.R. [Departamento de Quimica da Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Av. Bandeirantes, 3900, 14040-901 Ribeirao Preto, SP (Brazil); Tremiliosi-Filho, G. [Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 780, 13560-970 Sao Carlos, SP (Brazil)

2007-08-01

Binary PtIr, PtSn and ternary PtSnIr electrocatalysts were prepared by the Pechini-Adams modified method on carbon Vulcan XC-72, and these materials were characterized by TEM and XRD. The XRD results showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of solid solutions between the metals Pt/Ir and Pt/Sn. However, the increase in Sn loading promoted phase separation, with the formation of peaks typical of cubic Pt{sub 3}Sn. The electrochemical investigation of these different electrode materials was carried out as a function of the electrocatalyst composition, in a 0.5 mol dm{sup -3} H{sub 2}SO{sub 4} solution, with either the presence or the absence of ethanol. Cyclic voltammetric measurements and chronoamperometric results obtained at room temperature showed that PtSn/C and PtSnIr/C displayed better electrocatalytic activity for ethanol electrooxidation compared to PtIr/C and Pt/C, mainly at low potentials. The oxidation process was also investigated by in situ infrared reflectance spectroscopy, to identify the adsorbed species. Linearly adsorbed CO and CO{sub 2} were found, indicating that the cleavage of the C-C bond in the ethanol substrate occurred during the oxidation process. At 90 C, the Pt{sub 89}Sn{sub 11}/C and Pt{sub 68}Sn{sub 9}Ir{sub 23}/C electrocatalysts displayed higher current and power performances as anode materials in a direct ethanol fuel cell (DEFC). (author)

Dual-functional Pt-on-Pd supported on reduced graphene oxide hybrids: peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic.

Science.gov (United States)

Zhang, Xiahong; Wu, Genghuang; Cai, Zhixiong; Chen, Xi

2015-03-01

In this study, a facile hydrothermal method was developed to synthesize Pt-on-Pd supported on reduced graphene oxide (Pt-on-Pd/RGO) hybrids. Because of the synergistic effect between Pt-on-Pd and RGO, the obtained Pt-on-Pd/RGO had superior peroxidase-mimic activities in H2O2 reduction and TMB oxidation. The reaction medium was optimized and a sensing approach for H2O2 was developed with a linear range from 0.98 to 130.7 μM of H2O2. In addition, the characteristic of electrocatalytic oxidation of methanol was investigated. The peak current density value, j(f), for the Pt-on-Pd/RGO hybrid (328 mA mg(Pt)(-1)) was about 1.85 fold higher than that of commercial Pt black (177 mA mg(Pt)(-1)) and, also, more durable electrocatalytic activity could be obtained. For the first time, the dual-functional Pt-on-Pd/RGO with peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic was reported. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

Directory of Open Access Journals (Sweden)

John Meynard M. Tengco

2016-06-01

Full Text Available Carbon-supported bimetallic Pt-Co cathode catalysts have been previously identified as higher activity alternatives to conventional Pt/C catalysts for fuel cells. In this work, a series of Pt-Co/C catalysts were synthesized using electroless deposition (ED of Pt on a Co/C catalyst prepared by modified charge enhanced dry impregnation. X-ray diffraction (XRD and scanning transmission electron microscopy (STEM characterization of the base catalyst showed highly dispersed particles. A basic ED bath containing PtCl62− as the Pt precursor, dimethylamine borane as reducing agent, and ethylenediamine as stabilizing agent successfully targeted deposition of Pt on Co particles. Simultaneous action of galvanic displacement and ED resulted in Pt-Co alloy formation observed in XRD and energy dispersive X-ray spectroscopy (XEDS mapping. In addition, fast deposition kinetics resulted in hollow shell Pt-Co alloy particles while particles with Pt-rich shell and Co-rich cores formed with controlled Pt deposition. Electrochemical evaluation of the Pt-Co/C catalysts showed lower active surface but much higher mass and surface activities for oxygen reduction reaction compared to a commercial Pt/C fuel cell catalyst.

Preparation of the vulcan XC-72R-supported Pt nanoparticles for the hydrogen evolution reaction in PEM water electrolysers

International Nuclear Information System (INIS)

Nguyen, Huy Du; Nguyen, T Thuy Luyen; Nguyen, Khac Manh; Ha, Thuc Huy; Nguyen, Quoc Hien

2015-01-01

Pt nanoparticles on vulcan XC-72R support (Pt/vulcan XC-72R) were prepared by the impregnation–reduction method. The Pt content, the morphological properties and the electrochemical catalysis of the Pt/vulcan XC 72R materials have been investigated by ICP-OES analysis, FESEM, TEM, and cyclic voltammetry. These materials were then used as catalyst for hydrogen evolution reaction at the cathode of proton exchange membrane (PEM) water electrolysers. The best catalyst was Pt/vulcan XC-72R prepared by the impregnation–reduction method which is conducted in two reducing steps with the reductants of sodium borohydride and ethylene glycol, respectively. The current density of PEM water electrolysers reached 1.0 A cm"−"2 when applying a voltage of 2.0 V at 25 °C. (paper)

Nitrogen Doped Graphene Supported Pt Nanoflowers as Electrocatalysts for Oxidation of Formaldehyde.

Science.gov (United States)

Xie, Aijuan; Zhou, Wenting; Luo, Shiping; Chen, Yu; Zhou, Xiaoqing; Chao, Yao

2017-02-01

A facile Pt nanoflowers/nitrogen-doped graphene (PtNFs/NG) electrocatalyst was prepared via depositing Pt nanoflowers (PtNFs) onto the nitrogen-doped graphene (NG) matrix with urea as the nitrogen source and PtNFs/NG modified glassy carbon electrode (GCE) was prepared by electro-chemical method. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscope, X-ray photoelectron spectroscopy (XPS) and Scanning electron microscope (SEM) were used to characterize the resulting composites. Also oxidation of formaldehyde on the resulting PtNFs/NG modified electrode was investigated. The influence of deposition time, electrodeposition potential and formaldehyde concentration on electrooxidation of formaldehyde was detected, the experimental results indicate the high performance of PtNFs/NG catalyst for formaldehyde oxidation is at electrodeposition time of 300 s with the applied potential of −0.3 V. Electrochemical process, electrocatalytic stability and chronoamperometry were also inspected, it was indicated that formalde-hyde oxidation reaction on the PtNFs/NG electrode is diffusion-controlled and PtNFs/NG exhibits a high catalytic activity, stability as well as excellent poisoning-tolerance towards formaldehyde oxidation, which is attributed to the synergistic effect of PtNFs and NG. It turns out that PtNFs/NG can be used in direct liquid-feed fuel cells as a promising alternative catalyst.

Chromium containing silica: effect of ultrasonic and purification methods on color products

International Nuclear Information System (INIS)

Martines, M.A.U.; Jafelicci Junior, M.; Davolos, M.R.

1990-01-01

Chromium containing silica has numerous applications, such as: fiber-optics, luminescent materials, catalysts and pigments. In paint and ceramic pigments, chromate and dichromate ions, and silica are largely used. In this paper, it has been investigated the effect of pH, heating methods, and ultrasonic stirring on chromium oxidation states coprecipitated with silica. The material has been obtained from the coprecipitation of an aqueous diluted sodium silicate solution and acid chromium nitrate solution, purified by extractions and dialysis, and dried with microwave oven. Products have been characterized by X-ray powder diffraction, infrared vibrational spectroscopy and nitrogem adsorption isotherm (BET). Coprecipitates are non cristalline and the specific surface area value for sample obtained by conventional heating is smaller than the one for sample obtained by ultrasonic method. It is possible to obtain silica with different colors from blue due to the Cr(III), to yellow due to the Cr (VI), depending on the precipitation, purification and drying methods. (author) [pt

Sustainable green catalysis by supported metal nanoparticles.

Science.gov (United States)

Fukuoka, Atsushi; Dhepe, Paresh L

2009-01-01

The recent progress of sustainable green catalysis by supported metal nanoparticles is described. The template synthesis of metal nanoparticles in ordered porous materials is studied for the rational design of heterogeneous catalysts capable of high activity and selectivity. The application of these materials in green catalytic processes results in a unique activity and selectivity arising from the concerted effect of metal nanoparticles and supports. The high catalytic performances of Pt nanoparticles in mesoporous silica is reported. Supported metal catalysts have also been applied to biomass conversion by heterogeneous catalysis. Additionally, the degradation of cellulose by supported metal catalysts, in which bifunctional catalysis of acid and metal plays the key role for the hydrolysis and reduction of cellulose, is also reported. Copyright 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Preparation of PtSn/C, PtRu/C, PtRh/C, PtRuRh/C and PtSnRh/C electrocatalysts using an alcohol-reduction process for methanol and ethanol oxidation

International Nuclear Information System (INIS)

Dias, Ricardo Rodrigues

2009-01-01

In this work, Pt/C, PtRh (90:10), PtRh/C (50:50), PtSn/C (50:50), PtRu (50:50)/C, PtRuRh/C (50:40:10) and PtSnRh/C (50:40:10) were prepared by an alcohol-reduction process with metal loading of 20 wt.% using H 2 PtCl 6 .6H 2 O (Aldrich), SnCl 2 .2H 2 O (Aldrich),and RhCl 2 .XH 2 O (Aldrich) as metals sources and Vulcan XC72 as support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry (CV). The electro-oxidation of ethanol was studied by CV, chronoamperomety at room temperature in acid medium and tests at 100 deg C on a single cell of a direct methanol or ethanol fuel cell. The EDX analysis showed that the metal atomic ratios of the obtained electrocatalysts were similar to the nominal atomic ratios used in the preparation. The diffractograms of electrocatalysts prepared showed four peaks at approximately 2θ = 40 0 , 47 0 , 67 0 and 82 0 , which are associated with the (111), (200), (220) and (311) planes, respectively, of a face cubic-centered (fcc) structure characteristic of platinum and platinum alloys. The average crystallite sizes using the Scherrer equation and the calculated values were in the range of 2–3 nm. For PtSn/C and PtSnRh/C two additional peaks were observed at 2θ = 34 0 and 52 0 that were identified as a SnO 2 phase. PtSn/C (50:50) and PtSnRh/C (50:40:10) electrocatalyst showed the best performance for ethanol oxidation at room temperature. For methanol oxidation at room temperature PtRu/C, PtSn/C and PtRuRh/C electrocatalysts showed the best performance. Tests at 100 deg C on a single cell of a direct ethanol fuel cell PtSnRh/C showed the best performance, for methanol oxidation PtRuRh/C showed the best performance. (author)

Wrinkling of graphene membranes supported by silica nanoparticles on substrates

Science.gov (United States)

Yamamoto, Mahito; Cullen, William; Fuhrer, Michael; Einstein, Theodore; Department of Physics, University of Maryland Team

2011-03-01

The challenging endeavor of modulating the morphology of graphene via a patterned substrate to produce a controlled deformation has great potential importance for strain engineering the electronic properties of graphene. An essential step in this direction is to understand the response of graphene to substrate features of known geometry. Here we employ silica nanoparticles with a diameter of 10-100 nm to uniformly decorate Si O2 and mica substrates before depositing graphene, to promote nanoscale modulation of graphene geometry. The morphology of graphene on this modified substrate is then characterized by atomic force spectroscopy. We find that graphene on the substrate is locally raised by the supporting nanoparticles, and wrinkling propagates radially from the protrusions to form a ridge network which links the protrusions. We discuss the dependence of the wrinkled morphology on nanoparticle diameter and graphene thickness in terms of graphene elasticity and adhesion energy. Supported by NSF-MRSEC, Grant DMR 05-20471

Electro-oxidation of methanol and ethanol using PtRu/C, PtSn/C and PtSnRu/C electrocatalysts prepared by an alcohol-reduction process

Science.gov (United States)

Neto, Almir Oliveira; Dias, Ricardo R.; Tusi, Marcelo M.; Linardi, Marcelo; Spinacé, Estevam V.

PtRu/C, PtSn/C and PtSnRu/C electrocatalysts were prepared by the alcohol reduction process using ethylene glycol as the solvent and reduction agent and Vulcan Carbon XC72 as the support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry. The electrochemical oxidation of methanol and ethanol were studied by chronoamperometry using a thin porous coating technique. The PtSn/C electrocatalyst prepared by this methodology showed superior performance compared to the PtRu/C and PtSnRu/C electrocatalysts for methanol and ethanol oxidation at room temperature.

Bimetallic magnetic PtPd-nanoparticles as efficient catalyst for PAH removal from liquid media

Science.gov (United States)

Zanato, A. F. S.; Silva, V. C.; Lima, D. A.; Jacinto, M. J.

2017-11-01

Monometallic Pd- and bimetallic PtPd-nanoparticles supported on a mesoporous magnetic magnetite@silica matrix resembling a core-shell structure (Fe3O4@mSiO2) have been fabricated. The material was characterized by transmission electron microscope (TEM), high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectra (XPS), energy dispersive spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS). The catalysts were applied in the removal of anthracene from liquid phase via catalytic hydrogenation. It was found that anthracene as a model compound could be completely converted into the partially hydrogenated species by the monometallic and bimetallic solids. However, during the recycling study the bimetallic material (Fe3O4@mSiO2PtPd-) showed an enhanced activity towards anthracene removal compared with the monometallic materials. A single portion of the PtPd-based catalyst can be used up to 11 times in the hydrogenation of anthracene under mild conditions (6 atm of H2, 75 °C, 20 min). Thanks to the presence of a dense magnetic core, the catalysts were capable of responding to an applied external magnetic field and once the reaction was completed, catalyst/product separation was straightforward.

Microwave sinthesys and characterization of Pt and Pt-Rh-Sn electrocatalysts for ethanol oxidation

Directory of Open Access Journals (Sweden)

Jovanović Vladislava M.

2011-01-01

Full Text Available Carbon supported Pt and Pt-Rh-Sn catalysts were synthesized by microwave-polyol method in ethylene glycol solution and investigated for the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition by employing XRD, STM and EDX techniques. STM analysis indicated rather uniform particles and particle size of below 2 nm for both catalysts. XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of face centered cubic crystal structure (fcc of platinum and another related to graphite like structure of carbon support Vulcan XC-72R. However, in XRD pattern of the Pt-Rh-Sn/C catalyst diffraction peaks for Pt, Rh or Sn cannot be resolved, indicating an extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts should be attributed to the advantages of microwave assisted modified polyol process in ethylene glycol solution. Pt-Rh- Sn/C catalyst is highly active for the ethanol oxidation with the onset potential shifted for more than 150 mV to negative values and with currents nearly 5 times higher in comparison to Pt/C catalyst. The stability tests of the catalysts, as studied by the chronoamperometric experiments, reveal that the Pt-Rh-Sn/C catalyst is evidently less poisoned then Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst is most probably promoted by bifunctional mechanism and the electronic effect of alloyed metals.

Hydrogenation of Phenol over Pt/CNTs: The Effects of Pt Loading and Reaction Solvents

OpenAIRE

Feng Li; Bo Cao; Wenxi Zhu; Hua Song; Keliang Wang; Cuiqin Li

2017-01-01

Carbon nanotubes (CNTs)-supported Pt nanoparticles were prepared with selective deposition of Pt nanoparticles inside and outside CNTs (Pt–in/CNTs and Pt–out/CNTs). The effects of Pt loading and reaction solvents on phenol hydrogenation were investigated. The Pt nanoparticles in Pt–in/CNTs versus Pt–out/CNTs are smaller and better dispersed. The catalytic activity and reuse stability toward phenol hydrogenation both improved markedly. The dichloromethane–water mixture as the reaction solvent,...

PT AND PT/NI "NEEDLE" ELETROCATALYSTS ON CARBON NANOTUBES WITH HIGH ACTIVITY FOR THE ORR

Energy Technology Data Exchange (ETDEWEB)

Colon-Mercado, H.

2011-11-10

Platinum and platinum/nickel alloy electrocatalysts supported on graphitized (gCNT) or nitrogen doped carbon nanotubes (nCNT) are prepared and characterized. Pt deposition onto carbon nanotubes results in Pt 'needle' formations that are 3.5 nm in diameter and {approx}100 nm in length. Subsequent Ni deposition and heat treatment results in PtNi 'needles' with an increased diameter. All Pt and Pt/Ni materials were tested as electrocatalysts for the oxygen reduction reaction (ORR). The Pt and Pt/Ni catalysts showed excellent performance for the ORR, with the heat treated PtNi/gCNT (1.06 mA/cm{sup 2}) and PtNi/nCNT (0.664 mA/cm{sup 2}) showing the highest activity.

A theoretical understanding on the CO-tolerance mechanism of the WC(0001) supported Pt monolayer: Some improvement strategies

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xilin [College of Physics and Materials Science, Henan Normal University, Xinxiang, 453007 (China); Lu, Zhansheng [College of Physics and Materials Science, Henan Normal University, Xinxiang, 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Henan Province (China); Yang, Zongxian, E-mail: yzx@henannu.edu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang, 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Henan Province (China)

2016-12-15

Highlights: • The mechanism of CO tolerance and oxidation on Pt{sub ML}/WC(0001) is clarified. • The high tolerance of Pt{sub ML}/WC(0001) to CO originate from the weak adsorption. • The minimum energy path and the rate-determining step are identified. • The activity of Pt{sub ML}/WC(0001) to CO oxidation is comparable to that of Pt(111). • Some probable strategies are proposed to improve the activity of Pt{sub ML}/WC(0001). - Abstract: The deposition of platinum on the tungsten carbide (Pt/WC) have been achieved and proved with high stability, activity and CO-tolerance toward some reactions in experiments. Although a lot of experimental efforts have been focused on understanding the activity, stability and CO-tolerance of Pt/WC, the relevant theoretical works related to the CO-tolerance mechanism are still scarce. In current study, the adsorption and oxidation of CO on the Pt monolayer supported on WC(0001) surface (Pt{sub ML}/WC(0001)) are investigated using density functional theory calculations. It is found that the oxidation of CO on Pt{sub ML}/WC(0001) proceeds preferably along the Langmuir-Hinshelwood mechanism. The energy barrier of 1.06 eV for the rate-determining step of OOCO formation is almost equal to that (1.05 eV) for CO oxidation by atomic O on Pt(111), while the adsorption energy of 1.59 eV for CO on Pt{sub ML}/WC(0001) is smaller than that on Pt(111) (1.85 eV), indicating that the high resistance to CO poisoning of Pt{sub ML}/WC(0001) may originate from the weak interaction between them. To further improve the CO tolerance, some probable strategies are proposed based on the relevant kinetics results. The current results are helpful to understanding the origin of the highly resistant to CO poisoning of Pt{sub ML}/WC(0001) and rationally designing catalysts to improve the CO oxidation activity.

Influence of potassium on the competition between methane and ethane in steam reforming over Pt supported on yttrium-stabilized zirconia.

NARCIS (Netherlands)

Graf, P.O.; Mojet, Barbara; Lefferts, Leonardus

2008-01-01

effect of addition of potassium to Pt supported on yttrium-stabilized zirconia (PtYSZ) catalyst for steam reforming of methane, ethane and methane/ethane mixtures was explored. Addition of potassium has a positive effect on preferential steam reforming of methane in mixtures of methane and ethane

Preparation of PtSn/C, PtRu/C, PtRh/C, PtRuRh/C and PtSnRh/C electrocatalysts using an alcohol-reduction process for methanol and ethanol oxidation; Preparacao e caracterizacao de eletrocatalisadores PtRu, PtSn, PtRh, PtRuRh e PtSnRh para oxidacao direta de alcoois em celulas a combustivel tipo PEM utilizando a metodologia da reducao por alcool

Energy Technology Data Exchange (ETDEWEB)

Dias, Ricardo Rodrigues

2009-07-01

In this work, Pt/C, PtRh (90:10), PtRh/C (50:50), PtSn/C (50:50), PtRu (50:50)/C, PtRuRh/C (50:40:10) and PtSnRh/C (50:40:10) were prepared by an alcohol-reduction process with metal loading of 20 wt.% using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), SnCl{sub 2}.2H{sub 2}O (Aldrich),and RhCl{sub 2}.XH{sub 2}O (Aldrich) as metals sources and Vulcan XC72 as support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry (CV). The electro-oxidation of ethanol was studied by CV, chronoamperomety at room temperature in acid medium and tests at 100 deg C on a single cell of a direct methanol or ethanol fuel cell. The EDX analysis showed that the metal atomic ratios of the obtained electrocatalysts were similar to the nominal atomic ratios used in the preparation. The diffractograms of electrocatalysts prepared showed four peaks at approximately 2θ = 40{sup 0}, 47{sup 0}, 67{sup 0} and 82{sup 0}, which are associated with the (111), (200), (220) and (311) planes, respectively, of a face cubic-centered (fcc) structure characteristic of platinum and platinum alloys. The average crystallite sizes using the Scherrer equation and the calculated values were in the range of 2–3 nm. For PtSn/C and PtSnRh/C two additional peaks were observed at 2θ = 34{sup 0} and 52{sup 0} that were identified as a SnO{sub 2} phase. PtSn/C (50:50) and PtSnRh/C (50:40:10) electrocatalyst showed the best performance for ethanol oxidation at room temperature. For methanol oxidation at room temperature PtRu/C, PtSn/C and PtRuRh/C electrocatalysts showed the best performance. Tests at 100 deg C on a single cell of a direct ethanol fuel cell PtSnRh/C showed the best performance, for methanol oxidation PtRuRh/C showed the best performance. (author)

Particle size effects of sulfonated graphene supported Pt nanoparticles on ethanol electrooxidation

International Nuclear Information System (INIS)

Sun, Chia-Liang; Tang, Jui-Shiang; Brazeau, Nicolas; Wu, Jhing-Jhou; Ntais, Spyridon; Yin, Chung-Wei; Chou, Hung-Lung; Baranova, Elena A.

2015-01-01

Highlights: • Pt colloidal nanoparticles with five mean diameters are synthesized. • Size-selected Pt nanoparticles are loaded on sulfonated graphene (sG). • Sulfonic acid functional groups atop graphene donate charge to Pt. • Pt-sG catalysts are used for ethanol oxidation reaction (EOR). • Pt-sG(2.5 nm) has the highest peak current density in EOR. - Abstract: Fuel cells are promising alternative in automobile and stationary power generation. Direct ethanol fuel cells (DEFCs) offer significant advantages due to the non-toxicity and renewability of ethanol as well as its high power density. Development of the efficient catalysts for ethanol oxidation reaction (EOR) has attracted great attention and represents one of the major challenges in electrocatalysis. Graphene, one-atom thick nanocarbon materials, has attracted much attention recently in a variety of applications. The sulfonation of graphene is able to make it hydrophilic, which enhances its dispersibility in aqueous solvents. Furthermore, sulfonation increases the adsorption and uniform distribution of the Pt nanoparticles, which increases both the electrocatalytic activity and the durability. In this study, theoretical calculations demonstrated that the sulfonate functional group can donate charge to Pt, enhanced the adsorption energy of Pt, and then reduce the adsorption energy of CO on Pt. Then experimentally five kinds of Pt/sulfonated-graphene (Pt/sG) catalysts were synthesized via the control of pH values during the preparation of five-selected colloidal nanoparticles. Among all catalysts, Pt-sG(2.5 nm) has the highest peak current density in EOR

Effects of K and Pt promoters on the performance of cobalt catalyst supported on CNTs

International Nuclear Information System (INIS)

Zabidi, Noor Asmawati Mohd; Ali, Sardar; Subbarao, Duvvuri

2014-01-01

This paper presents a comparative study on the effects of incorporation of potassium (K) and platinum (Pt) as promoters on the physicochemical properties of cobalt catalyst. The catalyst was prepared by a wet impregnation method on a CNTs support. Samples were characterized using transmission electron microscopy (TEM), H 2 -temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) techniques. Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H 2 /CO = 2v/v and space velocity, SV of 12 L/g.h for 5 hours. The K-promoted and Pt-promoted Co catalysts have different physicochemical properties and catalytic performances compared to that of the un-promoted Co catalyst. XPS analysis revealed that K and Pt promoters induced electronic modifications as exhibited by the shifts in the Co binding energies. Incorporation of 0.06 wt% K and 0.06 wt% Pt in Co/CNTs catalyst resulted in an increase in the CO conversion and C 5+ selectivity and a decrease in methane selectivity. Potassium was found to be a better promoter for Co/CNTs catalyst compared to platinum

Effects of K and Pt promoters on the performance of cobalt catalyst supported on CNTs

Energy Technology Data Exchange (ETDEWEB)

Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Ali, Sardar, E-mail: alikhan-635@yahoo.com [Centralized Analytical Laboratory, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my [Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2014-10-24

This paper presents a comparative study on the effects of incorporation of potassium (K) and platinum (Pt) as promoters on the physicochemical properties of cobalt catalyst. The catalyst was prepared by a wet impregnation method on a CNTs support. Samples were characterized using transmission electron microscopy (TEM), H{sub 2}-temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) techniques. Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H{sub 2}/CO = 2v/v and space velocity, SV of 12 L/g.h for 5 hours. The K-promoted and Pt-promoted Co catalysts have different physicochemical properties and catalytic performances compared to that of the un-promoted Co catalyst. XPS analysis revealed that K and Pt promoters induced electronic modifications as exhibited by the shifts in the Co binding energies. Incorporation of 0.06 wt% K and 0.06 wt% Pt in Co/CNTs catalyst resulted in an increase in the CO conversion and C{sub 5+} selectivity and a decrease in methane selectivity. Potassium was found to be a better promoter for Co/CNTs catalyst compared to platinum.

Strategic Alliance Between PT Dirgantara Indonesia and Airbus Millitary (a Case Study of PT Dirgantara Indonesia)

OpenAIRE

Indriyanto, Reza Relen; Wandebori, Harimukti; Astuti, Novika Candra

2013-01-01

PT Dirgantara Indonesia (PT DI) is one of the aircraft manufacturing companies in Indonesia. The tight of competition in aerospace industry needs to improve its performance to gain niche market. Therefore, Ministry State of Own Enterprises has instructed PT Perusahaan Pengelola Aset (PT PPA) and PT DI to restructure and revitalize company with supported by Airbus Military as a strategic alliance partner, in order to increase the performance of production capacity, aircraft sales, and financia...

Synthesis of magnetic CoPt/SiO{sub 2} core-shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Seto, Takafumi [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Koga, Kenji [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Takano, Fumiyoshi [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Akinaga, Hiroyuki [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Orii, Takaaki [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Hirasawa, Makoto [Research Consortium for Synthetic Nano-Function Materials Project (SYNAF), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Murayama, Mitsuhiro [National Institute for Material Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2007-04-15

Core-shell nanoparticles composed of ferromagnetic cobalt platinum cores covered by non-magnetic silica shells were synthesized by laser ablating a composite target in a helium background gas. The average diameter of the CoPt core was controlled by adjusting the CoPt/SiO{sub 2} ratio of the ablation target. The particles were also classified in the gas phase using an electrical mobility classifier. The present method successfully synthesized nearly monodispersed nanoparticles with an average core diameter of 2.5nm. This article describes the synthesis of the core-shell nanoparticles and investigates their magnetic properties.

Electro-oxidation of methanol and ethanol using PtRu/C, PtSn/C and PtSnRu/C electrocatalysts prepared by an alcohol-reduction process

Energy Technology Data Exchange (ETDEWEB)

Neto, Almir Oliveira; Dias, Ricardo R.; Tusi, Marcelo M.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN/SP, Av. Prof. Lineu Prestes 2242, Cidade Universitaria, CEP 05508-900 Sao Paulo, SP (Brazil)

2007-03-30

PtRu/C, PtSn/C and PtSnRu/C electrocatalysts were prepared by the alcohol reduction process using ethylene glycol as the solvent and reduction agent and Vulcan Carbon XC72 as the support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry. The electrochemical oxidation of methanol and ethanol were studied by chronoamperometry using a thin porous coating technique. The PtSn/C electrocatalyst prepared by this methodology showed superior performance compared to the PtRu/C and PtSnRu/C electrocatalysts for methanol and ethanol oxidation at room temperature. (author)

Electrocatalytic oxidation of methanol on (Pb) lead modified by Pt, Pt-Ru and Pt-Sn microparticles dispersed into poly(o-phenylenediamine) film

Energy Technology Data Exchange (ETDEWEB)

Golikand, Ahmad Nozad; Maragheh, Mohammad Ghannadi; Irannejad, Leila [Jaber Ibn Hayan Research Lab., Atomic Energy Organization of Iran (AEOI), Tehran (Iran); Golabi, Seyed Mehdi [Electroanalytical Chemistry Lab., Faculty of Chemistry, University of Tabriz, Tabriz (Iran)

2005-08-18

The electrocatalytic oxidation of methanol at a (Pb) lead electrode modified by Pt, Pt-Ru and Pt-Sn microparticles dispersed into poly(o-phenylenediamine) (PoPD) film has been investigated using cyclic voltammetry as analytical technique and 0.5M sulfuric acid as supporting electrolyte. It has been shown that the presence of PoPD film increases considerably the efficiency of deposited Pt and Pt alloys microparticles toward the electrocatalytic oxidation of methanol. The catalytic activity of Pt particles is further enhanced when Ru and especially Sn, is co-deposited in the polymer film. The effects of various parameters such as concentration of methanol, medium temperature as well as the long term stability of modified electrodes have also been investigated. (author)

Structural and luminescence properties of europium(III)-doped zirconium carbonates and silica-supported Eu3+-doped zirconium carbonate nanoparticles

International Nuclear Information System (INIS)

Sivestrini, S.; Riello, P.; Freris, I.; Cristofori, D.; Enrichi, F.; Benedetti, A.

2010-01-01

The synthesis, morphology and luminescence properties of europium(III)-doped zirconium carbonates prepared as bulk materials and as silica-supported nanoparticles with differing calcination treatments are reported. Transmission electron microscopy and X-ray diffraction analyses have, respectively, been used to study the morphology and to quantify the atomic amount of europium present in the optically active phases of the variously prepared nanomaterials. Rietveld analysis was used to quantify the constituting phases and to determinate the europium content. Silica particles with an approximate size of 30 nm were coated with 2 nm carbonate nanoparticles, prepared in situ on the surface of the silica core. Luminescence measurements revealed the role of different preparation methods and of europium-doping quantities on the optical properties observed.

Silica-supported, single-site titanium catalysts for olefin epoxidation. A molecular precursor strategy for control of catalyst structure.

Science.gov (United States)

Jarupatrakorn, Jonggol; Don Tilley, T

2002-07-17

A molecular precursor approach involving simple grafting procedures was used to produce site-isolated titanium-supported epoxidation catalysts of high activity and selectivity. The tris(tert-butoxy)siloxy titanium complexes Ti[OSi(O(t)Bu)(3)](4) (TiSi4), ((i)PrO)Ti[OSi(O(t)Bu)(3)](3) (TiSi3), and ((t)BuO)(3)TiOSi(O(t)Bu)(3) (TiSi) react with the hydroxyl groups of amorphous Aerosil, mesoporous MCM-41, and SBA-15 via loss of HO(t)Bu and/or HOSi(O(t)Bu)(3) and introduction of titanium species onto the silica surface. Powder X-ray diffraction, nitrogen adsorption/desorption, infrared, and diffuse reflectance ultraviolet spectroscopies were used to investigate the structures and chemical natures of the surface-bound titanium species. The titanium species exist mainly in isolated, tetrahedral coordination environments. Increasing the number of siloxide ligands in the molecular precursor decreases the amount of titanium that can be introduced this way, but also enhances the catalytic activity and selectivity for the epoxidation of cyclohexene with cumene hydroperoxide as oxidant. In addition, the high surface area mesoporous silicas (MCM-41 and SBA-15) are more effective than amorphous silica as supports for these catalysts. Supporting TiSi3 on the SBA-15 affords highly active cyclohexene epoxidation catalysts (0.25-1.77 wt % Ti loading) that provide turnover frequencies (TOFs) of 500-1500 h(-1) after 1 h (TOFs are reduced by about half after calcination). These results demonstrate that oxygen-rich siloxide complexes of titanium are useful as precursors to supported epoxidation catalysts.

Unsaturated Fatty Acid Esters Metathesis Catalyzed by Silica Supported WMe5

KAUST Repository

Riache, Nassima

2015-11-14

Metathesis of unsaturated fatty acid esters (FAEs) by silica supported multifunctional W-based catalyst is disclosed. This transformation represents a novel route towards unsaturated di-esters. Especially, the self-metathesis of ethyl undecylenate results almost exclusively on the homo-coupling product whereas with such catalyst, 1-decene gives ISOMET (isomerization and metathesis olefin) products. The olefin metathesis in the presence of esters is very selective without any secondary cross-metathesis products demonstrating that a high selective olefin metathesis could operate at 150 °C. Additionally, a cross-metathesis of unsaturated FAEs and α-olefins allowed the synthesis of the corresponding ester with longer hydrocarbon skeleton without isomerisation.

In Situ Synthesis and Characterization of Polyethyleneimine-Modified Carbon Nanotubes Supported PtRu Electrocatalyst for Methanol Oxidation

Directory of Open Access Journals (Sweden)

Xi Geng

2015-01-01

Full Text Available PtRu bimetallic nanoparticles were successfully synthesized on polyethyleneimine- (PEI- functionalized multiwalled carbon nanotubes (MWCNTs via an effective and facile polyol reduction approach. Noncovalent surface modification of MWCNTs with PEI was confirmed by FTIR and zeta potential measurements. The morphology, crystalline structure, and composition of the hybrid material were characterized by transmission electron microscopy (TEM, scanning electron microscopy (SEM, X-ray powder diffraction (XRD, and energy dispersive X-ray spectroscopy (EDX, respectively. According to SEM and TEM observations, PtRu nanoparticles with narrow size distribution were homogeneously deposited on PEI-MWCNTs. Cyclic voltammetry tests demonstrated that the as-prepared PtRu/PEI-MWCNTs nanocomposite had a large electrochemical surface area and exhibited enhanced electrocatalytic activity towards methanol oxidation in comparison with oxidized MWCNTs as catalyst support. PEI-functionalized CNTs, as useful building blocks for the assembly of Pt-based electrocatalyst, may have great potential for applications such as direct methanol fuel cell (DMFC.

Controlled synthesis of carbon-supported Pt{sub 3}Sn by impregnation-reduction and performance on the electrooxidation of CO and ethanol

Energy Technology Data Exchange (ETDEWEB)

Garcia-Rodriguez, S.; Pena, M.A.; Fierro, J.L.G.; Rojas, S. [Grupo Energia y Quimica Sostenibles, Instituto de Catalisis y Petroleoquimica, CSIC, C/Marie Curie 2, E-28049 Madrid (Spain)

2010-09-01

The paper discusses experimental features relevant to the synthesis of carbon-supported Pt{sub 3}Sn nanosized particles by impregnation-reduction of the salt precursors in carbon. Colloidal techniques are proposed as the most suitable ones for obtaining carbon-supported nanosized Pt{sub 3}Sn particles. In most cases, the electrocatalysts obtained have a wide range of Pt and Sn phases, including bimetallic ones. The synthesis of similar materials by impregnating readily available precursors such as SnCl{sub 2} and H{sub 2}PtCl{sub 6} yields Pt-enriched catalyst precursors. In order to obtain electrocatalysts with the desired Pt:Sn = 3 atomic stoichiometry, it is necessary to eliminate chloride ions prior to thermal treatments. Microscopy characterization and thermal stability studies of the fresh and treated bimetallic materials reveal that if such ions are present, Sn is eliminated as volatile SnCl{sub x} species at around 120-130 C. Chloride elimination is achieved by ageing the catalyst precursor in water to ensure the complete hydrolysis of the SnCl{sub 2} precursor. This treatment should be performed once SnCl{sub 2} has been deposited on the carbon to avoid the formation of large Sn-oxide aggregates. A further thermal treatment in hydrogen results in the formation of the desired Pt{sub 3}Sn intermetallic phase. The performance of the Pt{sub 3}Sn/C samples in the CO and ethanol electrooxidation reaction has been studied by means of electrochemical techniques. The electrocatalysts prepared by the impregnation-reduction approach match the performance of the state-of-the-art Pt{sub 3}Sn samples prepared by colloidal techniques. (author)

Cu(II) recognition materials: Fluorophores grafted on mesoporous silica supports

International Nuclear Information System (INIS)

Kledzik, Krzysztof; Orlowska, Maja; Patralska, Dorota; Gwiazda, Marcin; Jezierska, Julia; Pikus, Stanislaw; Ostaszewski, Ryszard; Klonkowski, Andrzej M.

2007-01-01

There were designed and synthesized naphthalene and pyrene derivatives consisting of fluorophore group and of receptor fragment with donor N and O atoms. These fluorosensors were covalently attached by grafting carboxyl group to surfaces of silica xerogel or mesoporous silicas (MCM-41 and MCM-48) functionalized either with 3-aminopropyl or 3-glycidoxypropyl groups. The pyrene derivatives 2 and 3 covalently grafted on MCM-48 silica functionalized with 3-aminopropyl groups are potential recognition elements of a fluorescence chemical sensor. Fluorescence emission of the prepared recognition materials is quenched specifically owing to photoinduced electron transfer (PET) effect after coordination reactions with Cu(II) ions. Moreover, both the materials exhibit selectivity for Cu(II) ions in aqueous solutions in presence of such metal ions as: alkali, alkaline earth and transition. During UV irradiation the studied recognition elements undergo slowly photochemical degradation

Solid-State NMR and DFT Studies on the Formation of Well-Defined Silica-Supported Tantallaaziridines: From Synthesis to Catalytic Application

KAUST Repository

Hamzaoui, Bilel

2016-01-27

Single-site, well-defined, silica-supported tantallaaziridine intermediates [≡Si-O-Ta(η2-NRCH2)(NMe2)2] [R=Me (2), Ph (3)] were prepared from silica-supported tetrakis(dimethylamido)tantalum [≡Si-O-Ta(NMe2)4] (1) and fully characterized by FTIR spectroscopy, elemental analysis, and 1H,13C HETCOR and DQ TQ solid-state (SS) NMR spectroscopy. The formation mechanism, by β-H abstraction, was investigated by SS NMR spectroscopy and supported by DFT calculations. The C-H activation of the dimethylamide ligand is favored for R=Ph. The results from catalytic testing in the hydroaminoalkylation of alkenes were consistent with the N-alkyl aryl amine substrates being more efficient than N-dialkyl amines. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural Stability of Light-harvesting Protein LH2 Adsorbed on Mesoporous Silica Supports.

Science.gov (United States)

Shibuya, Yuuta; Itoh, Tetsuji; Matsuura, Shun-ichi; Yamaguchi, Akira

2015-01-01

In the present study, we examined the reversible thermal deformation of the membrane protein light-harvesting complex LH2 adsorbed on mesoporous silica (MPS) supports. The LH2 complex from Thermochromatium tepidum cells was conjugated to MPS supports with a series of pore diameter (2.4 to 10.6 nm), and absorption spectra of the resulting LH2/MPS conjugates were observed over a temperature range of 273 - 313 K in order to examine the structure of the LH2 adsorbed on the MPS support. The experimental results confirmed that a slight ellipsoidal deformation of LH2 was induced by adsorption on the MPS supports. On the other hand, the structural stability of LH2 was not perturbed by the adsorption. Since the pore diameter of MPS support did not influence the structural stability of LH2, it could be considered that the spatial confinement of LH2 in size-matches pore did not improve the structural stability of LH2.

Role of Pt(0) in bimetallic (Pt,Fe)-FER catalysts in the N2O decomposition

Czech Academy of Sciences Publication Activity Database

Tabor, Edyta; Jíša, Kamil; Nováková, Jana; Bastl, Zdeněk; Vondrová, Alena; Závěta, K.; Sobalík, Zdeněk

2013-01-01

Roč. 165, JAN 2013 (2013), s. 40-47 ISSN 1387-1811 R&D Projects: GA ČR GA203/09/1627 Institutional support: RVO:61388955 Keywords : bimetallic Pt,Fe- FER * Pt- FER * Pt(0) clusters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.209, year: 2013

Enhancement of the catalytic activity of Pt nanoparticles toward methanol electro-oxidation using doped-SnO2 supporting materials

Science.gov (United States)

Merati, Zohreh; Basiri Parsa, Jalal

2018-03-01

Catalyst supports play important role in governing overall catalyst activity and durability. In this study metal oxides (SnO2, Sb and Nb doped SnO2) were electrochemically deposited on titanium substrate (Ti) as a new support material for Pt catalyst in order to electro-oxidation of methanol. Afterward platinum nanoparticles were deposited on metal oxide film via electro reduction of platinum salt in an acidic solution. The surface morphology of modified electrodes were evaluated by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX) techniques. The electro-catalytic activities of prepared electrodes for methanol oxidation reaction (MOR) and oxidation of carbon monoxide (CO) absorbed on Pt was considered with cyclic voltammetry. The results showed high catalytic activity for Pt/Nb-SnO2/Ti electrode. The electrochemical surface area (ECSA) of a platinum electro-catalyst was determined by hydrogen adsorption. Pt/Nb-SnO2/Ti electrode has highest ECSA compared to other electrode resulting in high activity toward methanol electro-oxidation and CO stripping experiments. The doping of SnO2 with Sb and Nb improved ECSA and MOR activity, which act as electronic donors to increase electronic conductivity.

An extraordinarily stable catalyst: Pt NPs supported on two-dimensional Ti3C2X2 (X = OH, F) nanosheets for oxygen reduction reaction.

Science.gov (United States)

Xie, Xiaohong; Chen, Siguo; Ding, Wei; Nie, Yao; Wei, Zidong

2013-10-03

High dispersion Pt nanoparticles supported on 2D Ti3C2X2 (X = OH, F) nanosheets are presented and electro-chemical measurements confirm that the Pt/Ti3C2X2 catalyst shows enhanced durability and improved ORR activity compared with the commercial Pt/C catalyst.

Understanding the Effects of Surface Chemistry and Microstructure on the Activity and Stability of Pt Electrocatalysts on Non-Carbon Supports

Energy Technology Data Exchange (ETDEWEB)

Mustain, William [Univ. of Conneticut, Storrs, CT (United States)

2015-02-12

The objective of this project is to elucidate the effects of the chemical composition and microstructure of the electrocatalyst support on the activity, stability and utilization of supported Pt clusters.

Poisoning Experiments Aimed at Discriminating Active and Less-Active Sites of Silica-Supported Tantalum Hydride for Alkane Metathesis

KAUST Repository

Saggio, Guillaume; Taoufik, Mostafa; Basset, Jean-Marie; Thivolle-Cazat, Jean

2010-01-01

Only 50% of the silica-supported tantalum hydride sites are active in the metathesis of propane. Indeed, more than 45% of the tantalum hydride can be eliminated by a selective oxygen poisoning of inactive sites with no significant decrease

Enhanced Efficiency of Dye-Sensitized Solar Counter Electrodes Consisting of Two-Dimensional Nanostructural Molybdenum Disulfide Nanosheets Supported Pt Nanoparticles

Directory of Open Access Journals (Sweden)

Chao-Kuang Cheng

2017-10-01

Full Text Available This paper reports architecturally designed nanocomposites synthesized by hybridizing the two-dimensional (2D nanostructure of molybdenum disulfide (MoS2 nanosheet (NS-supported Pt nanoparticles (PtNPs as counter electrodes (CEs for dye-sensitized solar cells (DSSCs. MoS2 NSs were prepared using the hydrothermal method; PtNPs were subsequently reduced on the MoS2 NSs via the water–ethylene method to form PtNPs/MoS2 NSs hybrids. The nanostructures and chemical states of the PtNPs/MoS2 NSs hybrids were characterized by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Detailed electrochemical characterizations by electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel-polarization measurement demonstrated that the PtNPs/MoS2 NSs exhibited excellent electrocatalytic activities, afforded a higher charge transfer rate, a decreased charge transfer resistance, and an improved exchange current density. The PtNPs/MoS2 NSs hybrids not only provided the exposed layers of 2D MoS2 NSs with a great deal of catalytically active sites, but also offered PtNPs anchored on the MoS2 NSs enhanced I3− reduction. Accordingly, the DSSCs that incorporated PtNPs/MoS2 NSs CE exhibited an outstanding photovoltaic conversion efficiency (PCE of 7.52%, which was 8.7% higher than that of a device with conventional thermally-deposited platinum CE (PCE = 6.92%.

Kinetic and Thermodynamics of Methylene Blue Adsorption onto Zero Valent Iron Supported on Mesoporous Silica

Directory of Open Access Journals (Sweden)

Atyaf Khalid Hameed

2016-08-01

Full Text Available Zero valent iron supported on mesoporous silicanano particles (NZVI/MSNs was prepared by the aqueous phase borohydride reduction methods. Prior to the reduction, mesoporous silica nanoparticles (MSNs were prepared through the activation of fumed silica with concentrated HCl by refluxing at 90 °C. FTIR, XRD, FESEM, EDX and BET were used to characterize theadsorbents prepared. BET surface areas of MSNs, NZVI, and NZVI/MSNs were 126, 41, and 72 m2/g for, respectively. The performance of NZVI/MSNs as adsorbent was examined by adsorption of methylene blue (MB, performed in series of batch experiments. In the kinetic studies, pseudo first order and pseudo second order kinetic models were examined. The pseudo second order equation provided the best fit with the experimental data. Thermodynamic studies indicated that the adsorption process is endothermic with ΔH° was 90.53 kJ/mol. Positive ΔS° (300 J/mol and negative ΔG° (-6.42 kJ/mol was recorded, indicating the spontaneous of the adsorption process and naturally favorable. Copyright © 2016 BCREC GROUP. All rights reserved Received: 5th March 2016; Revised: 18th March 2016; Accepted: 18th March 2016 How to Cite: Hameed, A.K., Dewayanto, N., Dongyun, D., Nordin, M.R., Mohd Hasbi Ab. Rahim, M.H.A. (2016. Kinetic and Thermodynamics of Methylene Blue Adsorption onto Zero Valent Iron Supported on Mesoporous Silica. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (2: 250-261 (doi:10.9767/bcrec.11.2.443.250-261 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.2.443.250-261

Analisa Kadar Silika Pada Air Umpan Ketel Dan Air Boiler Dengan Alat Lovibond Di Pks PT. Perkebunan Nusantara IV Dolok Ilir

OpenAIRE

Simamora, Evi Novita F.

2016-01-01

Analysis was performed on a silica content of boiler feed water and boiler water at the PKS PT. PTPN IV Dolok Ilir. Samples taken from the boiler feed water tank heated while the boiler water sample taken from the heating pipes in the boiler drum. Silica content in the sample is determined by comparison with a reagent Ammonium molybdat, HCL 1: 1, and oxalic acid. The determinations were performed over a period of 18 to 27 February 2015. The results showed that the silica content of boiler fee...

Application of a Heterogeneous Chiral Titanium Catalyst Derived from Silica-Supported 3-Aryl H8-BINOL to Enantioselective Alkylation and Arylation of Aldehydes.

Science.gov (United States)

Akai, Junichiro; Watanabe, Satoshi; Michikawa, Kumiko; Harada, Toshiro

2017-07-07

A 3-aryl H 8 -BINOL was grafted on the surface of silica gel using a hydrosilane derivative as a precursor, and the resulting silica-supported ligand (6 mol %) was employed in the enantioselective alkylation and arylation of aldehydes in the presence of Ti(O i Pr) 4 . The reactions using Et 2 Zn, Et 3 B, and aryl Grignard reagents all afforded the corresponding adducts in high enantioselectivities and yields. The silica-immobilized titanium catalyst could be reused up to 14 times without appreciable deterioration of the activity.

Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports

Energy Technology Data Exchange (ETDEWEB)

Stanger, Keith James [Iowa State Univ., Ames, IA (United States)

2003-01-01

The tethered, chiral, chelating diphosphine rhodium complex, which catalyzes the enantioselective hydrogenation of methyl-α-acetamidocinnamate (MAC), has the illustrated structure as established by ³¹P NMR and IR studies. Spectral and catalytic investigations also suggest that the mechanism of action of the tethered complex is the same as that of the untethered complex in solution. The rhodium complexes, [Rh(COD)H]₄, [Rh(COD)₂]⁺BF₄^-, [Rh(COD)Cl]₂, and RhCl₃• 3H₂O, adsorbed on SiO₂ are optimally activated for toluene hydrogenation by pretreatment with H₂ at 200 C. The same complexes on Pd-SiO₂ are equally active without pretreatments. The active species in all cases is rhodium metal. The catalysts were characterized by XPS, TEM, DRIFTS, and mercury poisoning experiments. Rhodium on silica catalyzes the hydrogenation of fluorobenzene to produce predominantly fluorocyclohexane in heptane and 1,2-dichloroethane solvents. In heptane/methanol and heptane/water solvents, hydrodefluorination to benzene and subsequent hydrogenation to cyclohexane occurs exclusively. Benzene inhibits the hydrodefluorination of fluorobenzene. In DCE or heptane solvents, fluorocyclohexane reacts with hydrogen fluoride to form cyclohexene. Reaction conditions can be chosen to selectively yield fluorocyclohexane, cyclohexene, benzene, or cyclohexane. The oxorhenium(V) dithiolate catalyst [-S(CH₂)₃s-]Re(O)(Me)(PPh₃) was modified by linking it to a tether that could be attached to a silica support. Spectroscopic investigation and catalytic oxidation reactivity showed the heterogenized catalyst's structure and reactivity to be similar to its homogeneous analog. However, the immobilized catalyst offered additional advantages of recyclability, extended stability, and increased resistance to deactivation.

Gold Nanoparticles Supported on Fibrous Silica Nanospheres (KCC-1) as Efficient Heterogeneous Catalysts for CO Oxidation

KAUST Repository

Qureshi, Ziyauddin S.; Sarawade, Pradip B.; Hussain, Irshad; Zhu, Haibo; Al-Johani, Hind; Anjum, Dalaver H.; Hedhili, Mohamed N.; Maity, Niladri; D'Elia, Valerio; Basset, Jean-Marie

2016-01-01

Gold nanoparticles (Au NPs) of different sizes were supported on fibrous silica nanospheres (KCC-1) by various methods. The size and the location of the Au NPs on the support were found to depend on the preparation method. The KCC-1-supported Au NPs were thoroughly characterized by using HR-TEM, XRD, X-ray photoelectron spectroscopy, UV, and Brunauer-Emmett-Teller surface area measurements and were applied in catalysis for the oxidation of CO. The catalytic performance is discussed in relation to the morphological properties of KCC-1. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold Nanoparticles Supported on Fibrous Silica Nanospheres (KCC-1) as Efficient Heterogeneous Catalysts for CO Oxidation

KAUST Repository

Qureshi, Ziyauddin S.

2016-04-13

Gold nanoparticles (Au NPs) of different sizes were supported on fibrous silica nanospheres (KCC-1) by various methods. The size and the location of the Au NPs on the support were found to depend on the preparation method. The KCC-1-supported Au NPs were thoroughly characterized by using HR-TEM, XRD, X-ray photoelectron spectroscopy, UV, and Brunauer-Emmett-Teller surface area measurements and were applied in catalysis for the oxidation of CO. The catalytic performance is discussed in relation to the morphological properties of KCC-1. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pt/Au nanoalloy supported on alumina and chlorided alumina: DFT and experimental analysis

Science.gov (United States)

Sharifi, N.; Falamaki, C.; Ghorbanzadeh Ahangari, M.

2018-04-01

Density functional theory (DFT) was used to explore the adsorption of Pt/Au nanoalloy onto a pure and chlorided γ-Al2O3(110) surface, which has been applied in numerous catalytic reactions. First, we considered the adsorption properties of Pt clusters (n ≤ 5) onto the Al2O3(110) surface to determine the most stable Pt cluster on alumina surface in reforming processes. After full structural relaxations of Pt clusters at various configurations on alumina, our computed results expressed that the minimum binding energy (‑5.67 eV) is accrued for Pt4 cluster and the distance between the nearest Pt atom in the cluster to the alumina surface is equal to 1.13 Å. Then, we investigated the binding energies, geometries, and electronic properties of adsorbed Aun clusters (n ≤ 6) on the γ-Al2O3(110) surface. Our studied showed that Au5 was the most thermodynamically stable structure on γ-Al2O3. Finally, we inspected these properties for adsorbed Au clusters onto the Pt4-decorated alumina (Aun/Pt4-alumina) system. The binding energy of the Au4/Pt4-alumina system was ‑5.01 eV, and the distance between Au4 cluster and Pt4-alumina was 1.33 Å. The Au4/Pt4alumina system was found to be the most stable nanometer-sized catalyst design. At last, our first-principles calculations predicted that the best position of embedment Cl on the Au4/Pt4-alumina.

Iron supported on bioinspired green silica for water remediation.

Science.gov (United States)

Alotaibi, Khalid M; Shiels, Lewis; Lacaze, Laure; Peshkur, Tanya A; Anderson, Peter; Machala, Libor; Critchley, Kevin; Patwardhan, Siddharth V; Gibson, Lorraine T

2017-01-01

Iron has been used previously in water decontamination, either unsupported or supported on clays, polymers, carbons or ceramics such as silica. However, the reported synthesis procedures are tedious, lengthy (involving various steps), and either utilise or produce toxic chemicals. Herein, the use of a simple, rapid, bio-inspired green synthesis method is reported to prepare, for the first time, a family of iron supported on green nanosilica materials (Fe@GN) to create new technological solutions for water remediation. In particular, Fe@GN were employed for the removal of arsenate ions as a model for potentially toxic elements in aqueous solution. Several characterization techniques were used to study the physical, structural and chemical properties of the new Fe@GN. When evaluated as an adsorption platform for the removal of arsenate ions, Fe@GN exhibited high adsorption capacity (69 mg of As per g of Fe@GN) with superior kinetics (reaching ∼35 mg As per g sorbent per hr) - threefold higher than the highest removal rates reported to date. Moreover, a method was developed to regenerate the Fe@GN allowing for a full recovery and reuse of the adsorbent in subsequent extractions; strongly highlighting the potential technological benefits of these new green materials.

Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

Science.gov (United States)

Firdosy, Samad A.; Ravi, Vilupanur A.; Valdez, Thomas I.; Kisor, Adam; Narayan, Sri R.

2013-01-01

Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

TiO2 supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

International Nuclear Information System (INIS)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri; Subrahmanyam, Machiraju

2010-01-01

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO 2 under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO 2 /E-Si is found to be highly active for isoproturon degradation.

Thermally stable silica-coated hydrophobic gold nanoparticles.

Science.gov (United States)

Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

2009-01-01

We have successfully developed a method for silica coating on hydrophobic dodecanethiol-protected Au nanoparticles with coating thickness ranging from 10 to 40 nm. The formation of silica-coated Au nanoparticles could be accomplished via the preparation of hydrophilic Au nanoparticle micelles by cationic surfactant encapsulation in aqueous phase, followed by hydrolysis of tetraethylorthosilicate on the hydrophilic surface of gold nanoparticle micelles. Silica-coated Au nanoparticles exhibited quite high thermal stability, that is, no agglomeration of the Au cores could be observed after annealing at 600 degrees C for 30 min. Silica-coated Au nanoparticles could serve as a template to derive hollow nanoparticles. An addition of NaCN solution to silica-coated Au nanoparticles led the formation of hollow silica nanoparticles, which were redispersible in deionized water. The formation of the hollow silica nanoparticles results from the mesoporous structures of the silica shell and such a mesoporous structure is applicable to both catalyst support and drug delivery.

Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen

KAUST Repository

Al-Shareef, Reem A.; Harb, Moussab; Saih, Youssef; Ould-Chikh, Samy; Roldan, Manuel A.; Anjum, Dalaver H.; Guyonnet, Elodie Bile; Candy, Jean-Pierre; Jan, Deng-Yang; Abdo, Suheil F.; Aguilar-Tapia, Antonio; Proux, Olivier; Hazemann, Jean-Louis; Basset, Jean-Marie

2018-01-01

Well-defined silica supported bimetallic catalysts Pt100-x Pdx were prepared by Surface Organometallic Chemistry (SOMC) and Ionic-Exchange (IE) methods. For all investigated catalysts, iso-butane reaction with hydrogen under differential conditions led to the formation of methane and propane, n-butane, and traces of iso-butylene. The total reaction rate decreased with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the experimental results in combination with DFT calculations suggested a selective coverage of Pt (1 0 0) surface by agglomerated Pd atoms like “islands”, assuming that each metal roughly keeps its intrinsic catalytic properties with relatively small electron transfer from Pt to Pd in the case of Pt-rich sample and from Pd to Pt in the case of Pd-rich sample. For the PtPd catalysts prepared by IE, the catalytic behavior could be explained by the formation of a surface alloy between Pt and Pd in the case of Pd-rich sample and by the segregation of a small amount of Pd on the surface in the case of Pt-rich sample, as demonstrated by TEM, EXAFS and DFT. The catalytic results were explained by a structure activity relationship based on the proposed mechanism of CH bond and CC bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen

KAUST Repository

Alshareef, Reem Abdul aziz Hamed

2018-04-25

Well-defined silica supported bimetallic catalysts Pt100-x Pdx were prepared by Surface Organometallic Chemistry (SOMC) and Ionic-Exchange (IE) methods. For all investigated catalysts, iso-butane reaction with hydrogen under differential conditions led to the formation of methane and propane, n-butane, and traces of iso-butylene. The total reaction rate decreased with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the experimental results in combination with DFT calculations suggested a selective coverage of Pt (1 0 0) surface by agglomerated Pd atoms like “islands”, assuming that each metal roughly keeps its intrinsic catalytic properties with relatively small electron transfer from Pt to Pd in the case of Pt-rich sample and from Pd to Pt in the case of Pd-rich sample. For the PtPd catalysts prepared by IE, the catalytic behavior could be explained by the formation of a surface alloy between Pt and Pd in the case of Pd-rich sample and by the segregation of a small amount of Pd on the surface in the case of Pt-rich sample, as demonstrated by TEM, EXAFS and DFT. The catalytic results were explained by a structure activity relationship based on the proposed mechanism of CH bond and CC bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

Poisoning Experiments Aimed at Discriminating Active and Less-Active Sites of Silica-Supported Tantalum Hydride for Alkane Metathesis

KAUST Repository

Saggio, Guillaume

2010-10-04

Only 50% of the silica-supported tantalum hydride sites are active in the metathesis of propane. Indeed, more than 45% of the tantalum hydride can be eliminated by a selective oxygen poisoning of inactive sites with no significant decrease in the global turnover. Conversely, cyclopentane induces no such selective poisoning. Hence, the active tantalum hydride sites that show greater resistance to oxygen poisoning correspond to the νTa-H bands of higher wavenumbers, particularly that at 1860cm-1. These active tantalum hydride sites should correspond to tris- or monohydride species relatively far from silica surface oxygen atoms. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sintering of Pt nanoparticles via volatile PtO_2: Simulation and comparison with experiments

International Nuclear Information System (INIS)

Plessow, Philipp N.; Abild-Pedersen, Frank

2016-01-01

It is a longstanding question whether sintering of platinum under oxidizing conditions is mediated by surface migration of Pt species or through the gas phase, by PtO_2(g). Clearly, a rational approach to avoid sintering requires understanding the underlying mechanism. A basic theory for the simulation of ripening through the vapor phase has been derived by Wynblatt and Gjostein. Recent modeling efforts, however, have focused entirely on surface-mediated ripening. In this work, we explicitly model ripening through PtO_2(g) and study how oxygen pressure, temperature, and shape of the particle size distribution affect sintering. On the basis of the available data on α-quartz, adsorption of monomeric Pt species on the support is extremely weak and has therefore not been explicitly simulated, while this may be important for more strongly interacting supports. Our simulations clearly show that ripening through the gas phase is predicted to be relevant. Assuming clean Pt particles, sintering is generally overestimated. This can be remedied by explicitly including oxygen coverage effects that lower both surface free energies and the sticking coefficient of PtO_2(g). Additionally, mass-transport limitations in the gas phase may play a role. Using a parameterization that accounts for these effects, we can quantitatively reproduce a number of experiments from the literature, including pressure and temperature dependence. Lastly, this substantiates the hypothesis of ripening via PtO_2(g) as an alternative to surface-mediated ripening.

Enhanced Electrocatalytic Activity of Pt Particles Supported on Reduced Graphene Oxide/Poly(3,4-ethylenedioxythiophene RGO/PEDOT Composite towards Ethanol Oxidation

Directory of Open Access Journals (Sweden)

Juanito Raphael F. Foronda

2013-01-01

Full Text Available Catalysts in fuel cells are normally platinum based because platinum exhibits high electrocatalytic activity towards ethanol oxidation in acidic medium. However, bulk Pt is expensive and rare in nature. To reduce the consumption of Pt, a support material or matrix is needed to disperse Pt on its surface as micro- or nanoparticles with potential application as anode material in direct ethanol fuel cells (DEFCs. In this study, a composite material consisting of platinum particles dispersed on reduced graphene oxide/poly(3,4-ethylenedioxythiophene (RGO/PEDOT support was electrochemically prepared for ethanol oxidation in sulfuric acid electrolyte. PEDOT, a conductive polymer, was potentiodynamically polymerized from the corresponding monomer, 0.10 M EDOT in 0.10 M HClO4 electrolyte. The PEDOT-modified electrode was used as a substrate for exfoliated graphene oxide (EGO which was prepared by electrochemical exfoliation of graphite from carbon rod of spent batteries and subsequently reduced to form RGO. The Pt/RGO/PEDOT composite gave the highest electrocatalytic activity with an anodic current density of 2688.7 mA·cm−2 at E = 0.70 V (versus Ag/AgCl towards ethanol oxidation compared to bare Pt electrode and other composites. Scanning electron microscopy (SEM revealed the surface morphology of the hybrid composites while energy dispersive X-ray (EDX confirmed the presence of all the elements for the Pt/RGO/PEDOT composite.

Nanoparticles of Pt and Ag supported in meso porous SiO{sub 2}: characterization and catalytic applications; Nanoparticulas de Pt y Ag soportadas en SiO{sub 2} mesoporosa: caracterizacion y aplicaciones cataliticas

Energy Technology Data Exchange (ETDEWEB)

Espinosa, M.E.; Perez H, R.; Perez A, M.; Mondragon G, G. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Arenas A, J. [IFUNAM, A.P. 20-364, 01000 Mexico D.F. (Mexico)

2004-07-01

The surface properties of catalysts of Pt and Ag supported in conventional SiO{sub 2} hey have been studied through reduction reactions of N{sub 2}O with H{sub 2} which is a sensitive reaction to the structure. In our case it was used a meso porous ceramic support of SiO{sub 2} of great surface area (1100 m{sup 2}/gr), where it is caused a high dispersion of the metallic nanoparticles of Pt and Ag, the total charge of the active phase in the meso porous support was of 3% in weight. The catalysts show a variation in the percentages of conversion of N{sub 2}O depending on the size and dispersion of the metallic phases. (Author)

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.

Science.gov (United States)

Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

2014-03-01

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of sulfonated carbon nanofiber-supported Pt on performance of Nafion {sup registered} -based self-humidifying composite membrane for proton exchange membrane fuel cell

Energy Technology Data Exchange (ETDEWEB)

Hung, T.F. [Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, 200 Chung Pei Rd., Chung-Li, 32023 (China); Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617 (China); Liao, S.H.; Li, C.Y.; Chen-Yang, Y.W. [Department of Chemistry and Center for Nanotechnology, Chung Yuan Christian University, 200 Chung Pei Rd., Chung-Li, 32023 (China)

2011-01-01

In the present study, the Nafion {sup registered} -based self-humidifying composite membrane (N-SHCM) with sulfonated carbon nanofiber-supported Pt (s-Pt/CNF) catalyst, N-s-Pt/CNF, is successfully prepared using the solution-casting method. The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) images of N-s-Pt/CNF indicate that s-Pt/CNF is well dispersed in the Nafion {sup registered} matrix due to the good compatibility between Nafion {sup registered} and s-Pt/CNF. Compared with those of the non-sulfonated Pt/CNF-containing N-SHCM, N-Pt/CNF, the properties of N-s-Pt/CNF, including electronic resistivity, ion-exchange capacity (IEC), water uptake, dimensional stability, and catalytic activity, significantly increase. The maximum power density of the proton exchange membrane fuel cell (PEMFC) fabricated with N-s-Pt/CNF operated at 50 C under dry H{sub 2}/O{sub 2} condition is about 921 mW cm{sup -2}, which is approximately 34% higher than that with N-Pt/CNF. (author)

Hydrogen sulfide removal from hot coal gas by various mesoporous silica supported Mn2O3 sorbents

International Nuclear Information System (INIS)

Zhang, Z.F.; Liu, B.S.; Wang, F.; Wang, W.S.; Xia, C.; Zheng, S.; Amin, R.

2014-01-01

Graphical abstract: - Highlights: • Mn 2 O 3 /KIT-1 presented the best desulfurization performance at 600–850 °C. • High sulfur capacity of Mn 2 O 3 /KIT-1 correlated closely with 3-D channel of KIT-1. • Desulfurization character depended strongly on framework structure of sorbents. • High steam content suppressed greatly the occurrence of sulfidation reaction. - Abstract: A series of 50 wt% Mn 2 O 3 sorbents was prepared using various mesoporous silica, MCM-41, HMS, and KIT-1 as support. The influence of textural parameters of mesoporous silica, especially type of channel on the desulfurization performance of Mn 2 O 3 sorbents was investigated at 600–850 °C using hot coal gas containing 0.33 vol.% H 2 S. The fresh and used sorbents were characterized by means of N 2 -adsorption, x-ray diffraction (XRD), high resolution transmission microscopy (HRTEM) and H 2 temperature- programmed reduction (H 2 -TPR) techniques. The results confirmed that the manganese oxide was dispersed highly in regular pore channel of the mesoporous supports due to high surface area. Compared with the Mn 2 O 3 /diatomite, all mesoporous silica supported Mn 2 O 3 sorbents exhibited high breakthrough sulfur capacity and a sharp deactivation rate after the breakthrough point. Compared to Mn 2 O 3 /MCM-41 and Mn 2 O 3 /HMS sorbent, the Mn 2 O 3 /KIT-1 showed better desulfurization performance because of the 3D wormhole-like channel. The high sulfur capacity of the Mn 2 O 3 /KIT-1 sorbent was maintained during the eight consecutive desulfurization-regeneration cycles. The Mn 2 O 3 /KIT-1 still presented high desulfurization activity when hot coal gas contained low steam (<5%)

The Use of C-MnO2 as Hybrid Precursor Support for a Pt/C-MnxO1+x Catalyst with Enhanced Activity for the Methanol Oxidation Reaction (MOR

Directory of Open Access Journals (Sweden)

Alessandro H.A. Monteverde Videla

2015-07-01

Full Text Available Platinum (Pt nanoparticles are deposited on a hybrid support (C-MnO2 according to a polyol method. The home-made catalyst, resulted as Pt/C-MnxO1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C. The synthesized catalyst is characterized by means of FESEM, XRD, ICP-MS, XPS and μRS analyses. MnO2 is synthesized and deposited over a commercial grade of carbon (Vulcan XC72 by facile reduction of potassium permanganate in acidic solution. Pt nanoparticles are synthesized on the hybrid support by a polyol thermal assisted method (microwave irradiation, followed by an annealing at 600 °C. The obtained catalyst displays a support constituted by a mixture of manganese oxides (Mn2O3 and Mn3O4 with a Pt loading of 19 wt. %. The electro-catalytic activity towards MOR is assessed by RDE in acid conditions (0.5 M H2SO4, evaluating the ability to oxidize methanol in 1 M concentration. The synthesized Pt/C-MnxO1+x catalyst shows good activity as well as good stability compared to the commercial Pt/C based catalyst.

Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports

Directory of Open Access Journals (Sweden)

Bernay Cifuentes

2015-11-01

Full Text Available CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51 at a gaseous space velocity of 70,600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H2 yield above 600 °C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

Carbon monoxide adsorption studies on Ru:Mn bimetallic catalysts supported on alumina, silica and titania supported for the determination of metal surface area overview

International Nuclear Information System (INIS)

Hussain, S.T.

1992-01-01

Supported Ru: Mn bimetallic samples were studied using CO-chemisorption on alumina, silica and titania supports for the determination of active metal site/metal surface area. The data indicates the presence of Mn on the surface of Ru. With the increase of Mn loadings a decrease in the CO adsorption occurred indicating that presence of Mn masks the active sites responsible for Co-adsorption. On the titania supported system reduced at high and low temperature the CO-chemisorption data suggest the unusual behaviour. This behaviour is possibly caused due to creation of new active surface sites. (author)

Sonochemical synthesis and characterization of Pt/CNT, Pt/TiO2, and Pt/CNT/TiO2 electrocatalysts for methanol electro-oxidation

International Nuclear Information System (INIS)

Bedolla-Valdez, Z.I.; Verde-Gómez, Y.; Valenzuela-Muñiz, A.M.; Gochi-Ponce, Y.; Oropeza-Guzmán, M.T.; Berhault, Gilles; Alonso-Núñez, G.

2015-01-01

Highlights: • Pt/CNT/TiO 2 electrocatalyst was successfully prepared by the sonochemical method. • The electrocatalyst Pt/CNT/TiO 2 was synthesized without heat treatments, additives or surfactants. • The TiO 2 -Pt interaction improves the CO-tolerance of Pt/CNT/TiO 2 , as well as the electrocatalyst stability. • Low amount of multi-walled carbon nanotubes increases the current density of Pt/CNT/TiO 2 significantly compared to Pt/TiO 2 . - Abstract: Pt electrocatalyst supported on composite formed of multi-walled carbon nanotubes and titanium oxide (CNT/TiO 2 ) was successfully synthesized by a sonochemical method without heat treatments, surfactants or additives. This electrocatalyst could be used for direct methanol fuel cells (DMFC) applications. For comparison, Pt/CNT and Pt/TiO 2 electrocatalysts were prepared as reference samples. Structural properties and morphology of the synthesized materials were examined by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and their specific surface areas were determined by the Brunauer-Emmett-Teller method. The Pt and acid-treated CNT contents were analyzed by inductively coupled plasma atomic emission spectroscopy and thermogravimetric analysis, respectively. The electrochemical properties of the synthesized electrocatalysts were evaluated by cyclic voltammetry (CV) and chronoamperometry in a three-electrode cell at room temperature. The evaluation performed using electrochemical techniques suggests that TiO 2 promotes the CO-tolerance due to TiO 2 -Pt interaction. The CV tests demonstrated that 6 wt.% of acid-treated CNT increases significantly the current density when Pt selectively interacts with TiO 2 .

TiO{sub 2} supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

Energy Technology Data Exchange (ETDEWEB)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, Andhra Pradesh (India); Subrahmanyam, Machiraju, E-mail: subrahmanyam@iict.res.in [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, Andhra Pradesh (India)

2010-03-15

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO{sub 2} under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO{sub 2}/E-Si is found to be highly active for isoproturon degradation.

Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

KAUST Repository

Song, Hyon Min

2015-01-13

The synthesis and magnetic behavior of matrix-supported Pd and PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal columnal packing is selected as a template, and the impregnation method with thermal annealing is used to obtain supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary to the general belief that smaller Pd NPs or cluster size particles have higher magnetization, matrix-supported Pd NPs in this study maintain the highest magnetization with room temperature ferromagnetism when the size is the largest. (2) Twin boundaries along with stacking faults are more pronounced in these large Pd NPs and are believed to be the reason for this high magnetization. Similarly, supported PdO NPs were prepared under air conditions with different heating rates. Their phase is tetragonal (P42/mmc) with cell parameters of a = 3.050 Å and c = 5.344 Å, which are slightly larger than in the bulk phase (a = 3.03 Å, c = 5.33 Å). Faster heating rate of 30 °C/min also produces larger particles and larger magnetic hysteresis loop, although magnetization is smaller and few twin boundaries are observed compared to the supported metallic Pd NPs.

Exploring the Potential of Different-Sized Supported Subnanometer Pt Clusters as Catalysts for Wet Chemical Applications

KAUST Repository

Rondelli, Manuel

2017-05-10

The use of physicochemical preparation techniques of metal clusters in the ultrahigh vacuum (UHV) allows for high control of cluster nuclearity and size distribution for fundamental studies in catalysis. Surprisingly, the potential of these systems as catalysts for organic chemistry transformations in solution has not been explored. To this end, single Pt atoms and Pt clusters with two narrow size distributions were prepared in the UHV and applied for the hydrogenation of p-chloronitrobenzene to p-chloroaniline in ethanol. Following the observation of very high catalytic turnovers (approaching the million molecules of p-nitroaniline formed per Pt cluster) and of size-dependent activity, this work addresses fundamental questions with respect to the suitability of these systems as heterogeneous catalysts for the conversion of solution-phase reagents. For this purpose, we employ scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS) characterization before and after reaction to assess the stability of the clusters on the support and the question of heterogeneity versus homogeneity in the catalytic process.

Effect of heat treatment on stability of gold particle modified carbon supported Pt-Ru anode catalysts for a direct methanol fuel cell

International Nuclear Information System (INIS)

Li Xiaowei; Liu Juanying; Huang Qinghong; Vogel, Walter; Akins, Daniel L.; Yang Hui

2010-01-01

Carbon supported Au-PtRu (Au-PtRu/C) catalysts were prepared as the anodic catalysts for the direct methanol fuel cell (DMFC). The procedure involved simple deposition of Au particles on a commercial Pt-Ru/C catalyst, followed by heat treatment of the resultant composite catalyst at 125, 175 and 200 o C in a N 2 atmosphere. High-resolution transmission electron microscopy (HR-TEM) measurements indicated that the Au nanoparticles were attached to the surface of the Pt-Ru nanoparticles. We found that the electrocatalytic activity and stability of the Au-PtRu/C catalysts for methanol oxidation is better than that of the PtRu/C catalyst. An enhanced stability of the electrocatalyst is observed and attributable to the promotion of CO oxidation by the Au nanoparticles adsorbed onto the Pt-Ru particles, by weakening the adsorption of CO, which can strongly adsorb to and poison Pt catalyst. XPS results show that Au-PtRu/C catalysts with heat treatment lead to surface segregation of Pt metal and an increase in the oxidation state of Ru, which militates against the dissolution of Ru. We additionally find that Au-PtRu/C catalysts heat-treated at 175 o C exhibit the highest electrocatalytic stability among the catalysts prepared by heat treatment: this observation is explained as due to the attainment of the highest relative concentration of gold and the highest oxidation state of Ru oxides for the catalyst pretreated at this temperature.

Performance PtSnRh electrocatalysts supported on carbon-Sb2O5.SbO2 for the electro-oxidation of ethanol, prepared by an alcohol-reduction process

International Nuclear Information System (INIS)

Castro, Jose Carlos

2013-01-01

PtSnRh electrocatalysts supported on carbon-Sb 2 O 5 .SnO 2 , with metal loading of 20 wt%, were prepared by an alcohol-reduction process, using H 2 PtCl 6 .6H 2 O (Aldrich), RhCl 3 .xH 2 O (Aldrich) and SnCl 2 .2H 2 O (Aldrich), as source of metals; Sb 2 O 5 .SnO 2 (ATO) and carbon Vulcan XC72, as support; and ethylene glycol as reducing agent. The electrocatalysts obtained were characterized physically by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diffractograms showed which PtSnRh/C-ATO electrocatalysts had FCC structure of Pt and Pt alloys, besides several peaks associated with SnO 2 and ATO. The average sizes of crystallites were between 2 and 4 nm. TEM micrographs showed a good distribution of the nanoparticles on the support. The average sizes of particles were between 2 and 3 nm, with good agreement for the average size of the crystallites. The performances of the electrocatalysts were analyzed by electrochemical techniques and in real conditions of operation using single direct ethanol fuel cell. In the chronoamperometry at 50 deg C, the electrocatalysts with carbon (85 wt%) and ATO (15 wt%) support, showed the best activity, and the atomic proportions which achieved the best results were PtSnRh(70:25:05) e (90:05:05). PtSnRh(70:25:05)/85C+15ATO electrocatalysts showed the best performance in a direct ethanol fuel cell. (author)

Radiolytic Preparation of Electrocatalysts with Pt-Co and Pt-Sn Nanoparticles for a Proton Exchange Membrane Fuel Cell

Directory of Open Access Journals (Sweden)

Sang Kyum Kim

2014-01-01

Full Text Available Nanosized Pt-Sn/VC and Pt-Co/VC electrocatalysts were prepared by a one-step radiation-induced reduction (30 kGy process using distilled water as the solvent and Vulcan XC72 as the supporting material. While the Pt-Co/VC electrodes were compared with Pt/VC (40 wt%, HiSpec 4000, in terms of their electrocatalytic activity towards the oxidation of H2, the Pt-Co/VC electrodes were evaluated in terms of their activity towards the hydrogen oxidation reaction (HOR and compared with Pt/VC (40 wt%, HiSpec 4000, Pt-Co/VC, and Pt-Sn/VC in a single cell. Additionally, the prepared electrocatalyst samples (Pt-Co/VC and Pt-Sn/VC were characterized by transmission electron microscopy (TEM, scanning electron microscope (SEM, thermogravimetric analysis (TGA, X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, electrochemical surface area (ECSA, and fuel cell polarization performance.

Silica-Supported Catalyst for Enantioselective Arylation of Aldehydes under Batch and Continuous-Flow Conditions.

Science.gov (United States)

Watanabe, Satoshi; Nakaya, Naoyuki; Akai, Junichiro; Kanaori, Kenji; Harada, Toshiro

2018-05-04

A silica-supported 3-aryl H 8 -BINOL-derived titanium catalyst exhibited high performance in the enantioselective arylation of aromatic aldehydes using Grignard and organolithium reagents not only under batch conditions but also under continuous-flow conditions. Even with a simple pipet reactor packed with the heterogeneous catalyst, the enantioselective production of chiral diarylmethanols could be achieved through a continuous introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The pipet reactor could be used repeatedly in different reactions without appreciable deterioration of the activity.

Pt coating on flame-generated carbon particles

International Nuclear Information System (INIS)

Choi, In Dae; Lee, Dong Geun

2008-01-01

Carbon black, activated carbon and carbon nanotube have been used as supporting materials for precious metal catalysts used in fuel cell electrodes. One-step flame synthesis method is used to coat 2-5nm Pt dots on flame-generated carbon particles. By adjusting flame temperature, gas flow rates and resident time of particles in flame, we can obtain Pt/C nano catalyst-support composite particles. Additional injection of hydrogen gas facilitates pyrolysis of Pt precursor in flame. The size of as-incepted Pt dots increases along the flame due to longer resident time and sintering in high temperature flame. Surface coverage and dispersion of the Pt dots is varied at different sampling heights and confirmed by Transmission Electron Microscopy (TEM), Energy Dispersive Spectra (EDS) and X-Ray Diffraction (XRD). Crystallinity and surface bonding groups of carbon are investigated through X-ray Photoelectron Spectroscoy (XPS) and Raman spectroscopy

Experimental and DFT study of thiol-stabilized Pt/CNTs catalysts.

Science.gov (United States)

Li, L; Chen, S G; Wei, Z D; Qi, X Q; Xia, M R; Wang, Y Q

2012-12-28

Using a combination of experiments and density functional theory (DFT) calculations, we explored the mechanisms of the stabilization effect of the thiolized (-SH) group on the Pt/SH-CNTs catalyst. Pt particles supported on the hydroxyl functionalized CNTs (Pt/OH-CNTs) are synthesized as a baseline for comparison. Experimentally, the platinum on OH-CNTs has a stronger tendency for aggregation than that on SH-CNTs. The differences in the oxidation resistance, migration activation energy, and corrosion resistance between the Pt/SH-CNTs and Pt/OH-CNTs are calculated using DFT. The DFT calculations indicate that the -SH group enhances the oxidation resistance of the Pt cluster and CNTs and restricts Pt migration on the CNTs. DFT calculations also suggest that the enhanced stability of Pt/SH-CNTs originates from the increased interaction between Pt and SH-CNTs and the depressed d-band center of the Pt NPs. Thus, the functional groups on the CNTs used for stabilization of supported Pt NPs should provide a deposit and anchor site for Pt NPs and maintain the perfect structure of CNTs rather than destroying it.

Synergy between Two Metal Catalysts: A Highly Active Silica Supported Bimetallic W/Zr Catalyst for Metathesis of n-Decane

KAUST Repository

Samantaray, Manoja

2016-06-01

A well-defined, silica supported, bimetallic precatalyst [≡Si-O-W(Me)5 ≡Si-O-Zr(Np)3](4) has been synthesized for the first time via successively grafting two organometallic complexes [W(CH3)6 (1) followed by ZrNp4 (2)] on a single silica support. Surprisingly, multiple quantum NMR characterization demonstrates that W and Zr species are in close proximity to each other. Hydrogenation of this bimetallic catalyst at room temperature showed the easy formation of Zirconium hydride, probably facilitated by tungsten hydride which was formed at this temperature. This bimetallic W/Zr hydride precatalyst proved to be more efficient (TON: 1436) than the monometallic W hydride (TON: 650) in metathesis of n-decane at 150 0C. This synergy between Zr and W suggests that the slow step of alkane metathesis is the C-H bond activation which occurs on Zr. The produced olefin resulting from a ß–H elimination undergoes easy metathesis on W.

Au and AuCu Nanoparticles Supported on SBA-15 Ordered Mesoporous Titania-Silica as Catalysts for Methylene Blue Photodegradation

Directory of Open Access Journals (Sweden)

Isabel Barroso-Martín

2018-05-01

Full Text Available The photocatalytic degradation of methylene blue (MB dye has been performed under UV irradiation in aqueous suspension, employing photocatalysts based on Au (1.5 wt % and AuCu (Au/Cu = 1, 2.0 wt %, and supported on SBA-15-ordered mesoporous silica, with and without titania (Si/Ti = 3, in order to evaluate the versatility of this mesoporous support in this type of reaction of great impact from the environmental point of view. Samples were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, N2 adsorption-desorption at −196 °C, and X-ray photoelectron spectroscopy (XPS, so as to study their structural, optical, and chemical properties. All the prepared catalysts were found to be active in the test reaction. The bimetallic AuCu-based catalysts attained very high MB degradation values, in particular AuCu/SBA-15 titania-silica sample reached 100% of dye oxidation after the monitored reaction period (120 min.

H2-splitting on Pt/Ru alloys supported on sputtered HOPG

DEFF Research Database (Denmark)

Fiordaliso, Elisabetta Maria; Dahl, Søren; Chorkendorff, Ib

2011-01-01

to strain and ligand effects, caused by the compression of the surface due to the presence of the larger Pt atoms in the neighboring Ru atoms. The apparent energy of desorption at equilibrium, Eapp, for the three Pt-Ru systems is found to decrease with an increasing amount of Ru in the alloys...

Synthesis and evaluation of Pt-alloys supported on MWCNTS as ethylene glycol-tolerant ORR cathodes

Energy Technology Data Exchange (ETDEWEB)

Morales-Acosta, D.; Arriaga, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo, Queretaro (Mexico); Alvarez-Contreras, L. [Centro de Investigacion en Materiales Avanzados S. C., Chihuahua, Chihuahua (Mexico); Fraire Luna, S.; Rodriguez Varela, F.J. [Cinvestav, Unidad Saltillo, Ramos Arizpe, Coahuila (Mexico)]. E-mail: javier.varela@cinvestav.edu.mx

2009-09-15

In this work, a Pt-Co/MWCNT alloy (atomic ratio 70:30) was synthesized and evaluated as oxygen reduction reaction (ORR) cathode for Direct Ethylene Glycol Fuel Cells (DEGFC) applications. The alloy showed good performance for the ORR in acid medium, while in the presence of 0.125M EG (C{sub 2}H{sub 6}O{sub 2}) the MWCNTs-supported electrocatalyst showed a very high selectivity for the cathodic reaction and a high degree of tolerance to the organic fuel, i.e., a very small shift in the onset potential for the ORR, Eonset, and no peak current densities associated to the oxidation of EG, a detrimental effect of organic fuels normally observed in the case of Pt-alone electrocatalysts. [Spanish] En este trabajo, se sintetizo y evaluo una aleacion Pt-Co/NTCMP (razon atomica 70/30) como catodo de reaccion de reduccion de oxigeno (RRO) para aplicaciones de celdas de combustible de glicol de etileno directo (CCGED). La aleacion mostro buen desempeno para la RRO en medio acido, en tanto que la presencia de 0.125M de GE (C{sub 2}H{sub 6}O{sub 2}) del electrocatalizador soportado por NTCMP mostro una muy alta selectividad para la reaccion catodica y un alto grado de tolerancia al combustible organico, es decir, un corrimiento muy pequeno del potencial de inicio para la RRO, Einicio, y no densidades de corriente asociadas a la oxidacion del GE, efecto perjudicial de los combustibles organicos que se observa en el caso del electrocatalizadores solo de Pt.

Palladium nanoparticles supported on fibrous-structured silica nanospheres (KCC-1): An efficient and selective catalyst for the transfer hydrogenation of alkenes

KAUST Repository

Qureshi, Ziyauddin; Sarawade, Pradip; Albert, Matthias; D'Elia, Valerio; Hedhili, Mohamed Nejib; Kö hler, Klaus; Basset, Jean-Marie

2015-01-01

An efficient palladium catalyst supported on fibrous silica nanospheres (KCC-1) has been developed for the hydrogenation of alkenes and α,β-unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high-resolution TEM, chemisorption) with analogous mesoporous (MCM-41, SBA-15) silica-supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC-1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC-1-supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.

Palladium nanoparticles supported on fibrous-structured silica nanospheres (KCC-1): An efficient and selective catalyst for the transfer hydrogenation of alkenes

KAUST Repository

Qureshi, Ziyauddin

2015-01-09

An efficient palladium catalyst supported on fibrous silica nanospheres (KCC-1) has been developed for the hydrogenation of alkenes and α,β-unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high-resolution TEM, chemisorption) with analogous mesoporous (MCM-41, SBA-15) silica-supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC-1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC-1-supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.

Oxygen reduction reaction on a highly-alloyed Pt-Ni supported carbon electrocatalyst in acid solution

CSIR Research Space (South Africa)

Zheng, H

2010-08-31

Full Text Available Alloyed electrocatalysts such as PtNi/C[1-2], PtCo/C[3], PtCr/C[4], PtFe/C [5-6], and non-alloyed Pt-TiO2/C were reportedly investigated for methanol tolerance during Oxygen reduction reaction (ORR). The high methanol tolerance...

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

International Nuclear Information System (INIS)

Abolghasemi, Mir Mahdi; Yousefi, Vahid; Rafiee, Ezzat

2014-01-01

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL −1 and a dynamic range as wide as from 0.001 to 100 ng mL −1 . Under optimum conditions, the repeatability for one fiber (n = 3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction. (author)

Low Pt content of carbon supported Pt-Ni-TiO2 nanotube electrocatalysts for direct methanol fuel cell

Energy Technology Data Exchange (ETDEWEB)

Jiang, Q.Z; Wu, X.; Ma, Z.F. [Shanghai Jiao Tong Univ., Shanghai, (China). Dept. of Chemical Engineering

2008-07-01

Interest in titanium oxide (TiO2) nanomaterial is growing due to their special characteristics for optics, catalysis, and photoelectricity conversion. In this study, the anatase/rutile crystalline of TiO2 nanoparticles was synthesized by co-deposition. TiO2 nanotubes were then obtained by microwave irradiations. This paper described the mechanism to fabricate TiO2 nanotubes. The conditions for preparing TiO2 nanotubes by microwave irradiation were optimized. Electrocatalysts were then prepared on the basis of the synthesized TiO2 nanotube. Their performances were investigated by the electro-oxidation of methanol. When Pt electrocatalysts were doped with a certain content of TiO2 nanotubes, they had more electrocatalytic activity for methanol electro-oxidation, particularly if the second transition metal, such as Ni, was added into the electrocatalyst. The electrocatalysts contained 5 and 10 wt per cent of Pt and Ni respectively. The 10 wt per cent TiO2 nanotubes showed better activities than any other catalysts for methanol electro-oxidation. According to XRD and TEM results, the size of nanoparticles of Pt became smaller after adding TiO2 nanotubes into the catalysts. It was concluded that here might be some interactions between Pt, Ni, and TiO2 nanotubes.

Hydrothermal stability of silica, hybrid silica and Zr-doped hybrid silica membranes

NARCIS (Netherlands)

ten Hove, Marcel; Luiten-Olieman, Mieke W.J.; Huiskes, Cindy; Nijmeijer, Arian; Winnubst, Louis

2017-01-01

Hybrid silica membranes have demonstrated to possess a remarkable hydrothermal stability in pervaporation and gas separation processes allowing them to be used in industrial applications. In several publications the hydrothermal stability of pure silica or that of hybrid silica membranes are

Fumed silica. Fumed silica

Energy Technology Data Exchange (ETDEWEB)

Sukawa, T.; Shirono, H. (Nippon Aerosil Co. Ltd., Tokyo (Japan))

1991-10-18

The fumed silica is explained in particulate superfineness, high purity, high dispersiveness and other remarkable characteristics, and wide application. The fumed silica, being presently produced, is 7 to 40nm in average primary particulate diameter and 50 to 380m{sup 2}/g in specific surface area. On the surface, there coexist hydrophilic silanol group (Si-OH) and hydrophobic siloxane group (Si-O-Si). There are many characteristics, mutually different between the fumed silica, made hydrophobic by the surface treatment, and untreated hydrophilic silica. The treated silica, if added to the liquid product, serves as agent to heighten the viscosity, prevent the sedimentation and disperse the particles. The highest effect is given to heighten the viscosity in a region of 4 to 9 in pH in water and alcohol. As filling agent to strengthen the elastomer and polymer, and powder product, it gives an effect to prevent the consolidation and improve the fluidity. As for its other applications, utilization is made of particulate superfineness, high purity, thermal insulation properties and adsorption characteristics. 2 to 3 patents are published for it as raw material of quartz glass. 38 refs., 16 figs., 4 tabs.

SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions

KAUST Repository

Qureshi, Ziyauddin

2017-01-05

Synthesis, structure, and olefin metathesis activity of a surface complex [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten(VI) oxytetrachloride generated the tungsten oxo imidazolin-2-iminato chloride complex [ImDippNW(═O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(≡Si-O-)W(═O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.

SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions

KAUST Repository

Qureshi, Ziyauddin; Hamieh, Ali Imad Ali; Barman, Samir; Maity, Niladri; Samantaray, Manoja; Ould-Chikh, Samy; Abou-Hamad, Edy; Falivene, Laura; D’ Elia, Valerio; Rothenberger, Alexander; Llorens, Isabelle; Hazemann, Jean-Louis; Basset, Jean-Marie

2017-01-01

Synthesis, structure, and olefin metathesis activity of a surface complex [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten(VI) oxytetrachloride generated the tungsten oxo imidazolin-2-iminato chloride complex [ImDippNW(═O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(≡Si-O-)W(═O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.

Polyethyleneimine-loaded bimodal porous silica as low-cost and high-capacity sorbent for CO{sub 2} capture

Energy Technology Data Exchange (ETDEWEB)

Witoon, Thongthai, E-mail: fengttwi@ku.ac.th [National Center of Excellence for Petroleum, Petrochemicals and Advance Material, Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand)

2012-11-15

In this work, bimodal (meso-macro) porous silicas with different mesopore diameters synthesized by using rice husk ash as a low-cost silica source and chitosan as a natural template were used as a polyethyleneimine (PEI) support for CO{sub 2} capture. Unimodal porous silica supports with equivalent mesopore diameters to bimodal porous silica supports have been prepared for purpose of comparison. Effects of different PEI contents (10, 20, 30, 40 and 50 wt%) on CO{sub 2} sorption capacity have been systematically investigated. The porous silica supports and the PEI-loaded porous silica supports were characterized by N{sub 2}-sorption analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analysis. CO{sub 2} sorption measurements of all PEI-loaded porous silica supports were performed at different adsorption temperatures (60, 75, 85, 90, 95 and 105 Degree-Sign C). At low PEI contents (10-20 wt%), the CO{sub 2} sorption of all adsorbents was found to decrease as a function of adsorption temperature, which was a characteristic of a thermodynamically-controlled regime. A transition from the thermodynamically-controlled regime to a kinetically-controlled regime was found when the PEI content was increased up to 30 wt% for PEI-loaded unimodal porous silicas and 40 wt% for PEI-loaded bimodal porous silicas. At high PEI contents (40-50 wt%), the CO{sub 2} capturing efficiency of the PEI-loaded bimodal porous silicas was found to be considerably greater than that of the PEI-loaded unimodal porous silicas, indicating that most of the amine groups of PEI molecules loaded on the unimodal porous silica supports was useless, and thus the appeared macroporosity of the bimodal porous silica supports could provide a higher effective amine density to adsorb CO{sub 2}. Highlights: Black-Right-Pointing-Pointer PEI-impregnated bimodal porous silica as low-cost sorbent for CO{sub 2} capture. Black-Right-Pointing-Pointer Macropores enhances

Fast Synthesis of Pt Nanocrystals and Pt/Microporous La2O3 Materials Using Acoustic Levitation

Science.gov (United States)

Yu, Yinkai; Qu, Shaohua; Zang, Duyang; Wang, Liuding; Wu, Hongjing

2018-02-01

Usually, we must use an appropriate support material to keep the metal species stable and finely dispersed as supported metal nanoparticles for industry application. Therefore, the choice of support material is a key factor in determining the dispersion and particle size of the noble metal species. Here, we report the synthesis of a single-atom Pt material in the solution and supported Pt nanoclusters on microporous La2O3 by a one-step acoustic levitation method without any pretreatment/modification of raw oxide. We have strongly contributed to the synthetic methodology of the surface/interfacial heterogeneous catalysts in this study, and this finding could open another door for synthesis of supported metal nanoparticles on porous materials for environmental catalysis.

Well-defined silica supported bipodal molybdenum oxo alkyl complexes: a model of the active sites of industrial olefin metathesis catalysts

KAUST Repository

Merle, Nicolas

2017-09-25

A well-defined, silica-supported molybdenum oxo alkyl species, ([triple bond, length as m-dash]SiO-)2Mo([double bond, length as m-dash]O)(CH2tBu)2, was prepared by the selective grafting of Mo([double bond, length as m-dash]O)(CH2tBu)3Cl onto a silica partially dehydroxylated at 200 °C using a rigorous surface organometallic chemistry approach. The immobilized bipodal surface species, partly resembling the active species of industrial MoO3/SiO2 olefin metathesis catalysts, exhibited excellent functional group tolerance in conjunction with its high activity in homocoupling, self and ring closing olefin metathesis.

Well-defined silica supported bipodal molybdenum oxo alkyl complexes: a model of the active sites of industrial olefin metathesis catalysts

KAUST Repository

Merle, Nicolas; Le Qué mé ner, Fré dé ric; Barman, Samir; Samantaray, Manoja; Szeto, Kai C.; De Mallmann, Aimery; Taoufik, Mostafa; Basset, Jean-Marie

2017-01-01

A well-defined, silica-supported molybdenum oxo alkyl species, ([triple bond, length as m-dash]SiO-)2Mo([double bond, length as m-dash]O)(CH2tBu)2, was prepared by the selective grafting of Mo([double bond, length as m-dash]O)(CH2tBu)3Cl onto a silica partially dehydroxylated at 200 °C using a rigorous surface organometallic chemistry approach. The immobilized bipodal surface species, partly resembling the active species of industrial MoO3/SiO2 olefin metathesis catalysts, exhibited excellent functional group tolerance in conjunction with its high activity in homocoupling, self and ring closing olefin metathesis.

Ultraviolet-Visible (UV-Vis) Microspectroscopic System Designed for the In Situ Characterization of the Dehydrogenation Reaction Over Platinum Supported Catalytic Microchannel Reactor.

Science.gov (United States)

Suarnaba, Emee Grace Tabares; Lee, Yi Fuan; Yamada, Hiroshi; Tagawa, Tomohiko

2016-11-01

An ultraviolet visible (UV-Vis) microspectroscopic system was designed for the in situ characterization of the activity of the silica supported platinum (Pt) catalyst toward the dehydrogenation of 1-methyl-1,4-cyclohexadiene carried out in a custom-designed catalytic microreactor cell. The in situ catalytic microreactor cell (ICMC) with inlet/outlet ports was prepared using quartz cover as the optical window to facilitate UV-Vis observation. A fabricated thermometric stage was adapted to the UV-Vis microspectrophotometer to control the reaction temperature inside the ICMC. The spectra were collected by focusing the UV-Vis beam on a 30 × 30 µm area at the center of ICMC. At 393 K, the sequential measurement of the spectra recorded during the reaction exhibited a broad absorption peak with maximum absorbance at 260 nm that is characteristic for gaseous toluene. This result indicates that the silica supported Pt catalyst is active towards the dehydrogenation of 1-methyl-1,4-cyclohexadiene at the given experimental conditions. The onset of coke formation was also detected based on the appearance of absorption bands at 300 nm. The UV-Vis microspectroscopic system developed can be used further in studying the mechanism of the dehydrogenation reaction. © The Author(s) 2016.

Hydrogenation and hydrodeoxygenation of difurfurylidene acetone to liquid alkanes over Raney Ni and the supported Pt catalysts

International Nuclear Information System (INIS)

Li, Yuping; Huang, Xiaoming; Zhang, Qian; Chen, Lungang; Zhang, Xinghua; Wang, Tiejun; Ma, Longlong

2015-01-01

Highlights: • The C_8−C_1_4 alkane yield of 82.9% was obtained in the two-step hydrogenation/HDO process. • Protonation effect from methanol solvent increased F_2A conversion in the two-step process. • The rate-determining step was acyl C=O bond hydrogenation in the first step of F_2A hydrogenation. • The acidic centers from SiO_2−ZrO_2 activated the acyl and oxygen atoms of intermediates. • Acidity of SiO_2−ZrO_2 and Pt active centers of 1 wt%Pt/SiO_2−ZrO_2 resulted stable HDO performance. - Abstract: Direct HDO process for difurfurylidene acetone dimer (F_2A) conversion to liquid alkanes (C_8−C_1_4) at 260 °C in a batch reactor was investigated over different material supported 1 wt%Pt catalysts, including SAPO-11, HZSM-5, SiO_2−Al_2O_3, MCM-22, and home-made SiO_2−ZrO_2. C_8−C_1_4 alkanes of 55.8% was obtained over the optimized 1 wt%Pt/SiO_2−ZrO_2 due to its proper pore size of 9.0 nm and moderate acidic centers, together with more than 10% carbon yield of the oxygenated hydrocarbons, including C_1_1−C_1_3 chain alcohols & ketones and the hydrogenated F_2A dimers with furan ring (H-F_2A dimers). To improve the liquid alkane yield, a two-step process for F_2A conversion was also investigated, which included low-temperature hydrogenation at 50 °C over Raney Ni catalyst in a batch reactor and the subsequent high-temperature hydrodeoxygenation (HDO) at 280 °C over 1 wt%Pt/SiO_2−ZrO_2 in a fixed-bed reactor. The selectivity of 1,5-di(tetrahydro-2-furanyl)-3-pentanol (II-c) was the highest of 83.0% among the hydrogenated intermediates of H-F_2A dimers due to the protonation effect of methanol as the solvent and the hydrogenation of C=C bonds by Ni active centers. In the same time, the high content of this saturated alcohol H-dimer of II-C increased the solubility and stability of the intermediates in methanol solvent. High carbon yield of C_8−C_1_4 alkanes of 82.9%(mol) was obtained after oxygen atom removal from H-F_2A dimers via

Extrudate versus Powder Silica Alumina as Support for Re2O7 Catalyst in the Metathesis of Seed Oil-Derivatives – A Comparison

Directory of Open Access Journals (Sweden)

Bassie B. Marvey

2009-01-01

Full Text Available Self- and cross-metathesis of fatty acid methyl esters (FAMEs was investigated using a silica alumina supported Re2O7 catalyst. Although a 3 wt% Re2O7/SiO2-Al2O3/SnBu4 is already active for the metathesis of unsaturated FAMEs, the results have shown that particle size of silica alumina support has a profound influence on its activity and selectivity. Consequently, high substrate conversions coupled with improved product yields (for mono- and diesters and reaction rates were obtained upon using powder, as opposed to extrudate silica alumina as the support material. Diesters are platform compounds for the synthesis of polymers and fragrances. In this paper a comparative outline of the influence of particle size of silica alumina (extrudate versus powder on catalytic performance of a 3 wt% Re2O7/SiO2-Al2O3/SnBu4 for self- and cross-metathesis of FAMEs is made. Low surface area and diffusion constraints associated with extrudates were identified as some of the factors leading to low catalytic activity and selectivity.

Successive heterolytic cleavages of H2 achieve N2 splitting on silica-supported tantalum hydrides: A DFT proposed mechanism

KAUST Repository

Solá ns, Xavier Luis; Chow, Catherine; Gouré , Eric; Kaya, Yasemin; Basset, Jean-Marie; Taoufik, Mostafa; Quadrelli, Elsje Alessandra; Eisenstein, Odile

2012-01-01

DFT(B3PW91) calculations have been carried out to propose a pathway for the N2 cleavage by H2 in the presence of silica-supported tantalum hydride complexes [(≡ SiO)2TaHx] that forms [(≡SiO)2Ta(NH)(NH2)] (Science2007, 317, 1056). The calculations

Synthesis of PtSn nanostructured catalysts supported over TiO{sub 2} and Ce-doped TiO{sub 2} particles for the electro-oxidation of ethanol

Energy Technology Data Exchange (ETDEWEB)

Alvarez, A.E. [Instituto de Ingeniería Electroquímica y Corrosión (INIEC), CONICET, Universidad Nacional del Sur. Av. Alem 1253, Bahía Blanca B8000CPB (Argentina); Gravina, A.N. [Departamento de Química, INQUISUR, CONICET, Universidad Nacional del Sur, Av. Alem 1253, Bahía Blanca B8000CPB (Argentina); Sieben, J.M., E-mail: jmsieben@uns.edu.ar [Instituto de Ingeniería Electroquímica y Corrosión (INIEC), CONICET, Universidad Nacional del Sur. Av. Alem 1253, Bahía Blanca B8000CPB (Argentina); Messina, P.V. [Departamento de Química, INQUISUR, CONICET, Universidad Nacional del Sur, Av. Alem 1253, Bahía Blanca B8000CPB (Argentina); Duarte, M.M.E. [Instituto de Ingeniería Electroquímica y Corrosión (INIEC), CONICET, Universidad Nacional del Sur. Av. Alem 1253, Bahía Blanca B8000CPB (Argentina)

2016-09-15

Highlights: • PtSn particles supported on TiO2 and Ce-doped TiO2 were evaluated as catalysts for EOR. • PtSn/TiO2 showed better mass current and higher TON than PtSn/Ce–TiO2 materials. • The activity for EOR decreased markedly with increasing Ce content in the TiO2. - Abstract: PtSn/TiO2 and PtSn/Ce-doped TiO2 catalysts were synthesized and evaluated for ethanol electro-oxidation in acid media. Titanium dioxide and Ce-doped TiO2 nanoparticles were prepared by hydrothermal method followed by calcination at 923 K. Bimetallic PtSn catalysts supported on the oxide materials were synthesized by microwave assisted reduction in ethylene glycol (EG). The structural properties of the resulting materials were evaluated via TEM and XRD, and the compositions were assessed by EDX and ICP-AES analysis. PtSn nanoparticles of about 3–4 nm were deposited on TiO2 and Ce–TiO2 particles. It was found that the catalyst composition is scarcely influenced by the cerium content in the mixed oxides while the electrochemical surface area per unit mass decreases upon the incorporation of Ce in the anatase lattice. The electrochemical tests pointed out that the electrocatalytic activity for ethanol oxidation decreases markedly as the Ce content increases. The results indicate that the presence of cerium in the titanium dioxide crystalline network induces local structural and electronic modifications, thereby leading to a reduction of the crystallinity, surface conductivity and the amount of OH species adsorbed on the surface of the oxide support.

Nano-Pt/C electrocatalysts: synthesis and activity for alcohol oxidation

International Nuclear Information System (INIS)

Huong Nguyen, Thi Giang; Anh Pham, Thi Van; Phuong, Thi Xuan; Binh Lam, Thi Xuan; Tran, Van Man; Thoa Nguyen, Thi Phuong

2013-01-01

Nano-sized platinum electrocatalysts on a carbon support (Pt/C) have been synthesized by the polyol reduction method under microwave irradiation using ethylene glycol (EG) as the reductant and carbon vulcan XC-72R as the support material. The physical characteristics of the Pt/C materials were analyzed using transmission electron microscopy and Brunauer–Emmet–Teller nitrogen adsorption theory. The glycerol and EG electro-oxidation in alkaline media on the Pt/C catalysts was investigated with cyclic voltammetry and chronoamperometry. The particle size of Pt on carbon was about 3.0 nm. The catalytic activity for the alcohol electro-oxidation of Pt/C materials synthesized in various pH values (7.9–9.5) was found to be significantly higher than that of commercial Pt/C (Aldrich Sigma, 10 wt% Pt/activated carbon). The Pt/C catalyst synthesized in pH 9.5 showed the best electrochemical behavior. At all the synthesized Pt/C electrodes, compared with glycerol, the oxidation rate of EG was about ten times higher. (paper)

Synthesis and physicochemical properties of Zr-MCM-41 mesoporous molecular sieves and Pt/H3PW12O40/Zr-MCM-41 catalysts

International Nuclear Information System (INIS)

Chen, L.F.; Wang, J.A.; Norena, L.E.; Aguilar, J.; Navarrete, J.; Salas, P.; Montoya, J.A.; Del Angel, P.

2007-01-01

For the first time, modifications of the surface and framework of Si-MCM-41 by depositing a heteropolyacid on the surface and by introducing foreign Zr 4+ ions into the framework are investigated. The Zr-modified Si-MCM-41 mesoporous materials (hereafter referred as WSZn, n=Si/Zr=25, 15, 8, 4) were synthesized through a surfactant-templated preparation approach, using low-cost fumed silica as the Si precursor. After impregnation with 25 wt% of H 3 PW 12 O 40 , the surface Broensted acidity of the Pt/H 3 PW 12 O 40 /WSZn catalysts was greatly enhanced by 2-10 times relative to the bare WSZn support. Two kinds of supported heteropolyacids were formed: (i) bulk-like heteropolyacid crystals with unchanged Keggin structures, and (ii) highly dispersed heteropolyacid with distorted Keggin units. The formation of various kinds of heteropolyacid structures is closely related to the interaction between the heteropolyanions and the hydroxyl groups in the host support. - Graphical abstract: Modifications of the surface and framework of Si-MCM-41 by depositing a heteropolyacid on the surface and by introducing foreign Zr 4+ ions into the framework are investigated. Broensted acidity of the Pt/H 3 PW 12 O 40 /Zr-MCM-41 catalysts was greatly enhanced by 2-10 times relative to the bare Zr-MCM-41 support

Molecular and Silica-Supported Molybdenum Alkyne Metathesis Catalysts: Influence of Electronics and Dynamics on Activity Revealed by Kinetics, Solid-State NMR, and Chemical Shift Analysis.

Science.gov (United States)

Estes, Deven P; Gordon, Christopher P; Fedorov, Alexey; Liao, Wei-Chih; Ehrhorn, Henrike; Bittner, Celine; Zier, Manuel Luca; Bockfeld, Dirk; Chan, Ka Wing; Eisenstein, Odile; Raynaud, Christophe; Tamm, Matthias; Copéret, Christophe

2017-12-06

Molybdenum-based molecular alkylidyne complexes of the type [MesC≡Mo{OC(CH 3 ) 3-x (CF 3 ) x } 3 ] (MoF 0 , x = 0; MoF 3 , x = 1; MoF 6 , x = 2; MoF 9 , x = 3; Mes = 2,4,6-trimethylphenyl) and their silica-supported analogues are prepared and characterized at the molecular level, in particular by solid-state NMR, and their alkyne metathesis catalytic activity is evaluated. The 13 C NMR chemical shift of the alkylidyne carbon increases with increasing number of fluorine atoms on the alkoxide ligands for both molecular and supported catalysts but with more shielded values for the supported complexes. The activity of these catalysts increases in the order MoF 0 molecular and supported species. Detailed solid-state NMR analysis of molecular and silica-supported metal alkylidyne catalysts coupled with DFT/ZORA calculations rationalize the NMR spectroscopic signatures and discernible activity trends at the frontier orbital level: (1) increasing the number of fluorine atoms lowers the energy of the π*(M≡C) orbital, explaining the more deshielded chemical shift values; it also leads to an increased electrophilicity and higher reactivity for catalysts up to MoF 6 , prior to a sharp decrease in reactivity for MoF 9 due to the formation of stable metallacyclobutadiene intermediates; (2) the silica-supported catalysts are less active than their molecular analogues because they are less electrophilic and dynamic, as revealed by their 13 C NMR chemical shift tensors.

Corrugation of Phase-Separated Lipid Bilayers Supported by Nanoporous Silica Xerogel Surfaces

Energy Technology Data Exchange (ETDEWEB)

Goksu, E I; Nellis, B A; Lin, W; Satcher Jr., J H; Groves, J T; Risbud, S H; Longo, M L

2008-10-30

Lipid bilayers supported by substrates with nanometer-scale surface corrugations holds interest in understanding both nanoparticle-membrane interactions and the challenges of constructing models of cell membranes on surfaces with desirable properties, e.g. porosity. Here, we successfully form a two-phase (gel-fluid) lipid bilayer supported by nanoporous silica xerogel. Surface topology, diffusion, and lipid density in comparison to mica-supported lipid bilayers were characterized by AFM, FRAP, FCS, and quantitative fluorescence microscopy, respectively. We found that the two-phase lipid bilayer follows the xerogel surface contours. The corrugation imparted on the lipid bilayer results in a lipid density that is twice that on a flat mica surface. In direct agreement with the doubling of actual bilayer area in a projected area, we find that the lateral diffusion coefficient (D) of lipids on xerogel ({approx}1.7 {micro}m{sup 2}/s) is predictably lower than on mica ({approx}4.1 {micro}m{sup 2}/s) by both FRAP and FCS techniques. Furthermore, the gel-phase domains on xerogel compared to mica were larger and less numerous. Overall, our results suggest the presence of a relatively defect-free continuous two-phase bilayer that penetrates approximately midway into the first layer of {approx}50 nm xerogel beads.

Direct esterification of olive-pomace oil using mesoporous silica supported sulfonic acids

Directory of Open Access Journals (Sweden)

F. Alrouh

2017-02-01

Full Text Available Mesoporous silica MCM-41 and SBA-15 containing propyl sulfonic acid groups were synthesized according to the literature and were characterized by X-ray diffraction, N2 adsorption and the H+ exchange capacities of the sulfonic acid groups were titrated. The esterification reaction of glycerol with olive-pomace oil has been carried out by using prepared functionalized mesoporous silica (MCM-41 and SBA-15 as catalysts. It has been monitored by GC two fatty acids (palmitic and oleic acids as reactants in olive-pomace oil and their related monoacylglycerols (Glycerol monopalmitate GMP and monooleate GMO as reaction product. The catalytic activities of the functionalized mesoporous silica were compared with commercial catalysts, these included homogeneous catalysts (p-toluenesulfonic acid and heterogeneous catalysts (Amberlyst-15. The total yield of monoacylglycerols (GMO + GMP was nearly 40%. Remarkably, we found that MCM-41-SO3H was recycled at least 3 times without any loss of activity.

CoPt/TiN films nanopatterned by RF plasma etching towards dot-patterned magnetic media

Science.gov (United States)

Szívós, János; Pothorszky, Szilárd; Soltys, Jan; Serényi, Miklós; An, Hongyu; Gao, Tenghua; Deák, András; Shi, Ji; Sáfrán, György

2018-03-01

CoPt thin films as possible candidates for Bit Patterned magnetic Media (BPM) were prepared and investigated by electron microscopy techniques and magnetic measurements. The structure and morphology of the Direct Current (DC) sputtered films with N incorporation were revealed in both as-prepared and annealed state. Nanopatterning of the samples was carried out by means of Radio Frequency (RF) plasma etching through a Langmuir-Blodgett film of silica nanospheres that is a fast and high throughput technique. As a result, the samples with hexagonally arranged 100 nm size separated dots of fct-phase CoPt were obtained. The influence of the order of nanopatterning and anneling on the nanostructure formation was revealed. The magnetic properties of the nanopatterned fct CoPt films were investigated by Vibrating Sample Magnetometer (VSM) and Magnetic Force Microscopy (MFM). The results show that CoPt thin film nanopatterned by means of the RF plasma etching technique is promising candidate to a possible realization of BPM. Furthermore, this technique is versatile and suitable for scaling up to technological and industrial applications.

Analysis of Human Resources Readiness Through ADKAR, Management Commitment and Specific Competence Approach in Support Transformational Era PT KAI

OpenAIRE

Febriwan, Muhamad; Bangun, Yuni Ros

2013-01-01

PT Kereta Api Indonesia performs the transformation towards the service orientation in order to keep survive in its business environment. Human resources readiness of supporting the transformation is determinative without it, the company will fail in transformation and pursuing the business target. This applied ADKAR (awareness, desire, knowledge, ability and reinforcement), management commitment (organization support, reward, empowerment and training) and specific competencies (hospitality c...

Use of graphene supported on aminopropyl silica for microextraction of parabens from water samples.

Science.gov (United States)

Fumes, Bruno Henrique; Lanças, Fernando Mauro

2017-03-03

This paper describes the synthesis, characterization and use of graphene supported on aminopropyl silica through covalent bonds (Si-G) as a sorbent for microextraction by packed sorbent (MEPS). Five parabens (methyl, ethyl, propyl, butyl and benzyl) present in water matrices were used as model compounds for this evaluation. The Si-G phase was compared to other sorbents used in MEPS (C18 and Strata™-X) and also with graphene supported on primary-secondary amine (PSA) silica, where Si-G showed better results. After this, the MEPS experimental parameters were optimized using the Si-G sorbent. The following variables were optimized through univariate experiments: pH (4,7 and 10), desorption solvent (ACN:MeOH (50:50), ACN:H 2 O (40:60), MeOH and ACN) and ionic strength (0, 10 and 20% of NaCl). A factorial design 2 6-2 was then employed to evaluate other variables, such as the sample volume, desorption volume, sampling cycles, wash cycles and desorption cycles, as well as the influence of NaCl% on the extraction performance. The optimized method achieved a linear range of 0.2-20μg/L for most parabens; weighted calibration models were employed during the linearity evaluation to reduce the absolute sum of the residue values and improve R 2 , which ranged from 0.9753 to 0.9849. The method's accuracy was 82.3-119.2%; precision, evaluated as the coefficient of variance for intraday and interday analysis, ranged from 1.5 to 19.2%. After evaluation of the figures of merit, the method was applied to the determination of parabens in water samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation of Ag@mSiO{sub 2} and Pt@mSiO{sub 2}nano composites using trioctylmethyl ammonium hydrogen phthalate (TOMAHP) ionic liquid as reaction medium

Energy Technology Data Exchange (ETDEWEB)

Biswas, Sujoy, E-mail: sujoyb@barc.gov.in [Chemical Engineering Group, Bhabha Atomic Research Centre, Mumbai 400085 (India); Dasgupta, Kinshuk [Materials Group, Bhabha Atomic Research Centre, Mumbai 400085 (India); Bahadur, Jitendra [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Tewari, Raghavendra [Materials Group, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mazumder, Subhasish [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2016-09-15

A novel one step green chemistry approach utilizing trioctylmethyl ammonium hydrogen phthalate (TOMAHP), task specific ionic liquid has been attempted for synthesis of Ag and Pt nanoparticles supported on silica (Ag@mSiO{sub 2} and Pt@mSiO{sub 2}). Structure, size distribution and morphology of these nano-composite particles were evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), small angle neutron scattering (SANS) as well as small angle X-ray scattering (SAXS) techniques. The XRD results show that Ag/Pt metal nanoparticles deposited on to SiO{sub 2} surface are face center cubic (fcc) in nature. The TEM and SAXS/SANS results show the morphology and size distributions of Ag and Pt nanoparticles loaded on to the surface of SiO{sub 2}. It has been found that Ag nanoparticles are well dispersed on to the SiO{sub 2} surface and are quite monodisperse in size, whereas Pt nanoparticles are quite polydisperse in size and forms aggregate or chain like structure on SiO{sub 2} surface containing primary nanoparticles of typical size range 3–7 nm. The stability of nanoparticles, which controls its dispersion on SiO{sub 2} substrate, has been discussed. - Graphical abstract: Mechanism for Ag@mSiO{sub 2} and Pt@mSiO{sub 2} nano composites in TOMAHP ionic liquid medium. - Highlights: • Novel methods for preparation of Pt@SiO{sub 2} and Ag@SiO{sub 2} nano composite in functionalized ionic liquid. • Pt@SiO{sub 2} and Ag@SiO{sub 2} nano composite are characterized using XRD, TEM as well as small angle x-ray scattering techniques. • The sizes of nano composite is <10 nm in size. • The method is simple one step, green chemical reduction method to prepare SiO{sub 2} support nano catalyst.

Ferrocenyl-doped silica nanoparticles as an immobilized affinity support for electrochemical immunoassay of cancer antigen 15-3

International Nuclear Information System (INIS)

Hong Chenglin; Yuan Ruo; Chai Yaqin; Zhuo Ying

2009-01-01

The aim of this study is to elaborate a simple and sensitive electrochemical immunoassay using ferrocenecarboxylic (Fc-COOH)-doped silica nanoparticles (SNPs) as an immobilized affinity support for cancer antigen 15-3 (CA 15-3) detection. The Fc-COOH-doped SNPs with redox-active were prepared by using a water-in-oil microemulsion method. The use of colloidal silica could prevent the leakage of Fc-COOH and were easily modified with trialkoxysilane reagents for covalent conjugation of CA 15-3 antibodies (anti-CA 15-3). The Fc-COOH-doped SNPs were characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The fabrication process of the electrochemical immunosensor was demonstrated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Under optimal conditions, the developed immunosensor showed good linearity at the studied concentration range of 2.0-240 U mL -1 with a coefficient 0.9986 and a detection limit of 0.64 U mL -1 at S/N = 3

Ferrocenyl-doped silica nanoparticles as an immobilized affinity support for electrochemical immunoassay of cancer antigen 15-3.

Science.gov (United States)

Hong, Chenglin; Yuan, Ruo; Chai, Yaqin; Zhuo, Ying

2009-02-09

The aim of this study is to elaborate a simple and sensitive electrochemical immunoassay using ferrocenecarboxylic (Fc-COOH)-doped silica nanoparticles (SNPs) as an immobilized affinity support for cancer antigen 15-3 (CA 15-3) detection. The Fc-COOH-doped SNPs with redox-active were prepared by using a water-in-oil microemulsion method. The use of colloidal silica could prevent the leakage of Fc-COOH and were easily modified with trialkoxysilane reagents for covalent conjugation of CA 15-3 antibodies (anti-CA 15-3). The Fc-COOH-doped SNPs were characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The fabrication process of the electrochemical immunosensor was demonstrated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Under optimal conditions, the developed immunosensor showed good linearity at the studied concentration range of 2.0-240 UmL(-1) with a coefficient 0.9986 and a detection limit of 0.64 UmL(-1) at S/N=3.

In situ synthesis of copper nanoparticles on SBA-16 silica spheres

Directory of Open Access Journals (Sweden)

Asma Tufail Shah

2016-07-01

Full Text Available A chemical method for in situ synthesis of copper nanoparticles on SBA-16 silica spheres under ambient conditions has been reported. The silica support has been introduced into copper precursor solution before chemical reduction. Metal ions diffuse into mesopores (pore diameter 5–7 nm of silica where in situ reduction by hydrazine leads to formation of nanoparticles. These mesopores act as nanoreactor and their walls prevent metal particle’s agglomeration by providing a physical barrier. The obtained copper nanoparticles have been investigated by electron microscopy, X-ray diffraction, UV–Visible spectroscopy, Fourier transform Infra-red spectroscopy and thermogravimetric analyzer. SEM, TEM and UV–Visible spectroscopic images revealed that nanosized particles have been successfully synthesized by this method. Thermogravimetric investigations revealed that copper nanoparticles impregnated on silica were thermally more stable compared to unsupported nanoparticles. Silica not only helps in maintaining the particle size but also makes nanoparticles stable at high temperatures due to its thick pore walls. Macro sized silica support also makes separation/handling of nanoparticles easy and simple.

A density functional theory study of a silica-supported zirconium monohydride catalyst for depolymerization of polyethylene

Energy Technology Data Exchange (ETDEWEB)

Mortensen, J.J.; Parrinello, M.

2000-04-06

A silica-supported zirconium hydride catalyst for depolymerization of polyethylene is studied using density functional theory (DFT) together with a generalized gradient approximation (GGA) for the exchange and correlation energy. The (100) and (111) surfaces of {beta}-cristobalite are used as two possible models of a silica surface. Based on the experimental surface structure determined by J. Corker et al., they propose a detailed atomic model of the zirconium monohydride that is believed to be the active site for depolymerization of polyolefins. The model of the zirconium monohydride on the (100) surface is found to be very stable and the structure is in good agreement with extended X-ray absorption fine structure (EXAFS) measurements. Depolymerization of a small polyolefin chain (C{sub 3}H{sub 8}) was carried out to give CH{sub 4} and C{sub 2}H{sub 6} by addition of H{sub 2}. The rate-limiting step is a {beta}-methyl transfer to the zirconium atom, and the activation energy is 29 kcal/mol on the (100) surface.

Methanol oxidation catalysis and substructure of PtRu bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nitani, Hiroaki; Nakagawa, Takashi; Ono, Takahiro; Honda, Yusuke; Koizumi, Akiko; Seino, Satoshi; Yamamoto, Takao A. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Daimon, Hideo; Kurobe, Yukiko [Development and Technology Division, Hitachi Maxell Ltd., 6-20-1 Kinunodai, Tsukubamirai, Ibaraki 300-2496 (Japan)

2007-07-15

Catalytic material of PtRu nanoparticles supported on carbon (PtRu/C) for direct methanol fuel cells was synthesized by a polyol reduction method. Addition of phosphorus was effective for downsizing PtRu particles and improving their catalytic activity. The activity obtained was six times of that of a commercial catalysis. The samples were analyzed by techniques of X-ray absorption fine structure (XAFS) at Pt L{sub III}-edge and Ru K-edge, transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF). These results indicated a core-shell structure consisting of a Pt-rich core and Ru-rich shell. By examining coordination numbers determined by XAFS analysis, we found a clear correlation between the catalytic activity and the Pt-Ru atomic pair frequency occurring on the particle surface, which supports the 'bi-functional mechanism'. (author)

Pt, Co–Pt and Fe–Pt alloy nanoclusters encapsulated in virus capsids

International Nuclear Information System (INIS)

Okuda, M; Eloi, J-C; Jones, S E Ward; Schwarzacher, W; Verwegen, M; Cornelissen, J J L M

2016-01-01

Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl 4 ] − by NaBH 4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co–Pt and Fe–Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid. (paper)

Shape resonances and EXAFS scattering in the $Pt L_{2,3}$ XANES from a Pt electrode

CERN Document Server

O'Grady, W E

1999-01-01

Atomic hydrogen and oxygen adsorption on a platinum electrode in H /sub 2/SO/sub 4/ and HClO/sub 4/ electrolytes were studied by Pt L /sub 23/ XANES. The Pt electrode was formed of highly dispersed 1.5-3.0 nm particles supported on $9 carbon. A difference procedure utilizing the L/sub 2/ and L/sub 3/ spectra at various applied voltages was used to isolate the electronic and geometric effects in the XANES spectra. At 0.54 V (relative to RHE) the Pt electrode in $9 HClO/sub 4/ is assumed to be "clean". By taking the difference between the spectra at 0.0 and 0.54 V, the Pt-H antibonding state (electronic effect) is isolated and found to have a Fano-resonance line shape. In addition, a $9 significant Pt-H EXAFS scattering (geometric effect) was found for photon energies 0 to 20 eV above the edge. The difference between the spectra at 1.14 and 0.54 V allows isolation of the Pt-O antibonding state and the Pt-O EXAFS $9 scattering. (7 refs).

Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes

Energy Technology Data Exchange (ETDEWEB)

Molina, J.; Fernandez, J.; Rio, A.I. del; Bonastre, J. [Departamento de Ingenieria Textil y Papelera, EPS de Alcoy, Universitat Politecnica de Valencia, Plaza Ferrandiz y Carbonell s/n, 03801 Alcoy (Spain); Cases, F., E-mail: fjcases@txp.upv.es [Departamento de Ingenieria Textil y Papelera, EPS de Alcoy, Universitat Politecnica de Valencia, Plaza Ferrandiz y Carbonell s/n, 03801 Alcoy (Spain)

2012-06-15

The electrochemical characterization of two organic dyes (amaranth and procion orange MX-2R) has been performed on Pt electrodes and Pt electrodes coated with polyaniline and dispersed Pt. Electrodes with different Pt loads have been synthesized and characterized obtaining that a load of 300 {mu}g cm{sup -2} was the optimum one. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was employed to observe the distribution and morphology of the Pt nanoparticles. The electroactivity of the electrodes has also been characterized by means of scanning electrochemical microscopy (SECM). The chemical characterization of Pt dispersed Pani coated Pt electrodes (Pt-Pani-Pt) was performed by means of X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of the dyes has been performed by means of cyclic voltammetry. Voltammograms have shown that the presence of the dyes diminishes characteristic Pt oxidation and reduction peaks. However, redox processes due to the dyes, appeared in the voltammograms. The different species responsible of these redox processes were generated in the vicinity of the electrode and were not adsorbed on the electrode surface since after stirring, the different redox processes disappeared. Characterization with different scan rates showed that redox processes of both dyes were controlled by diffusion.

Electrochemical and structural characterization of carbon-supported Pt-Pd bimetallic electrocatalysts prepared by electroless deposition

Energy Technology Data Exchange (ETDEWEB)

Ohashi, Masato; Beard, Kevin D.; Ma Shuguo; Blom, Douglas A.; St-Pierre, Jean; Van Zee, John W. [Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Monnier, John R., E-mail: monnier@cec.sc.ed [Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

2010-10-01

Electrochemical and structural characteristics of various Pt-Pd/C bimetallic catalysts prepared by electroless deposition (ED) methods have been investigated. Structural analysis was conducted by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Monometallic Pt or Pd particles were not detected by EDS, indicating the ED methodology formed only bimetallic particles. The size of the Pt-Pd bimetallic particles was smaller than those of a commercially available Pt/C catalyst. The morphology of the Pt on Pd/C catalysts was identified and corresponded to Pd particles partially encapsulated by Pt. The electrochemical characteristics of the lowest Pd loading catalyst (7.0% Pt on 0.5% Pd/C) for the oxygen reduction reaction (ORR) have been investigated by the rotating ring disk electrode technique. The electrochemical activity was equal or lower than the commercially available Pt/C catalyst; however, the amount of hydrogen peroxide observed at the ring was reduced by the Pd, suggesting that such a catalyst has the potential to decrease ionomer degradation in applications. The Pt on Pd/C catalysts also show a higher tolerance to ripening induced by potential cycling. Therefore, catalyst suitability cannot be judged solely by its initial performance; information related to specific degradation mechanisms is also needed for a more complete assessment.

Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

Directory of Open Access Journals (Sweden)

Raimondo Maggi

2016-10-01

Full Text Available Converting biomass into value-added chemicals holds the key to sustainable long-term carbon resource management. In this context, levulinic acid, which is easily obtained from cellulose, is valuable since it can be transformed into a variety of industrially relevant fine chemicals. Here we present a simple protocol for the selective esterification of levulinic acid using solid acid catalysts. Silica supported sulfonic acid catalysts operate under mild conditions and give good conversion and selectivity with stoichiometric amounts of alcohols. The sulfonic acid groups are tethered to the support using organic tethers. These tethers may help in preventing the deactivation of the active sites in the presence of water.

Single Site Silica Supported Tetramethyl Niobium by the SOMC Strategy: Synthesis, Characterization and Structure-Activity Relationship in Ethylene Oligomerization Reaction

KAUST Repository

Hamieh, Ali Imad Ali

2017-06-06

Silica supported Tetramethyl niobium complex [(≡SiO)NbMe4] 2 has been isolated by surface alkylation of [(≡SiO-)NbCl3Me] 1 with dimethyl zinc in pentane. 1 can be easily synthesized by grafting of NbCl3Me2 on to the surface of partially dehydroxylated silica by the SOMC strategy. Precise structural analysis was carried out by the FTIR, advance solid state NMR, elemental analysis and mass balance techniques (gas quantification after treating 2 with degassed water) . Complex 1 was found to be active in the ethylene oligomerization to produce up to C30, whereas to our surprise complex 2 selectively dimerizes ethylene into 1-butene in the absence of a co-catalyst at the same conversion levels.

Single Site Silica Supported Tetramethyl Niobium by the SOMC Strategy: Synthesis, Characterization and Structure-Activity Relationship in Ethylene Oligomerization Reaction

KAUST Repository

Hamieh, Ali Imad Ali; Dey, Raju; Nekoueishahraki, Bijan; Samantaray, Manoja; Chen, Yin; Abou-Hamad, Edy; Basset, Jean-Marie

2017-01-01

Silica supported Tetramethyl niobium complex [(≡SiO)NbMe4] 2 has been isolated by surface alkylation of [(≡SiO-)NbCl3Me] 1 with dimethyl zinc in pentane. 1 can be easily synthesized by grafting of NbCl3Me2 on to the surface of partially dehydroxylated silica by the SOMC strategy. Precise structural analysis was carried out by the FTIR, advance solid state NMR, elemental analysis and mass balance techniques (gas quantification after treating 2 with degassed water) . Complex 1 was found to be active in the ethylene oligomerization to produce up to C30, whereas to our surprise complex 2 selectively dimerizes ethylene into 1-butene in the absence of a co-catalyst at the same conversion levels.

High surface area synthesis, electrochemical activity, and stability of tungsten carbide supported Pt during oxygen reduction in proton exchange membrane fuel cells

Science.gov (United States)

Chhina, H.; Campbell, S.; Kesler, O.

The oxidation of carbon catalyst supports to carbon dioxide gas leads to degradation in catalyst performance over time in proton exchange membrane fuel cells (PEMFCs). The electrochemical stability of Pt supported on tungsten carbide has been evaluated on a carbon-based gas diffusion layer (GDL) at 80 °C and compared to that of HiSpec 4000™ Pt/Vulcan XC-72R in 0.5 M H 2SO 4. Due to other electrochemical processes occurring on the GDL, detailed studies were also performed on a gold mesh substrate. The oxygen reduction reaction (ORR) activity was measured both before and after accelerated oxidation cycles between +0.6 V and +1.8 V vs. RHE. Tafel plots show that the ORR activity remained high even after accelerated oxidation tests for Pt/tungsten carbide, while the ORR activity was extremely poor after accelerated oxidation tests for HiSpec 4000™. In order to make high surface area tungsten carbide, three synthesis routes were investigated. Magnetron sputtering of tungsten on carbon was found to be the most promising route, but needs further optimization.

High surface area synthesis, electrochemical activity, and stability of tungsten carbide supported Pt during oxygen reduction in proton exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Chhina, H. [Automotive fuel cell corporation, 9000 Glenlyon Parkway, Burnaby, BC (Canada); Department of Mechanical and Industrial Engineering, 5 King' s College Road, University of Toronto, Toronto, Ontario (Canada); Campbell, S. [Automotive fuel cell corporation, 9000 Glenlyon Parkway, Burnaby, BC (Canada); Kesler, O. [Department of Mechanical and Industrial Engineering, 5 King' s College Road, University of Toronto, Toronto, Ontario (Canada)

2008-04-15

The oxidation of carbon catalyst supports to carbon dioxide gas leads to degradation in catalyst performance over time in proton exchange membrane fuel cells (PEMFCs). The electrochemical stability of Pt supported on tungsten carbide has been evaluated on a carbon-based gas diffusion layer (GDL) at 80 C and compared to that of HiSpec 4000 trademark Pt/Vulcan XC-72R in 0.5 M H{sub 2}SO{sub 4}. Due to other electrochemical processes occurring on the GDL, detailed studies were also performed on a gold mesh substrate. The oxygen reduction reaction (ORR) activity was measured both before and after accelerated oxidation cycles between +0.6 V and +1.8 V vs. RHE. Tafel plots show that the ORR activity remained high even after accelerated oxidation tests for Pt/tungsten carbide, while the ORR activity was extremely poor after accelerated oxidation tests for HiSpec 4000 trademark. In order to make high surface area tungsten carbide, three synthesis routes were investigated. Magnetron sputtering of tungsten on carbon was found to be the most promising route, but needs further optimization. (author)

Design criteria for stable Pt/C fuel cell catalysts

Directory of Open Access Journals (Sweden)

Josef C. Meier

2014-01-01

Full Text Available Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3–4 nm and two Pt@HGS catalysts with different particle size, 1–2 nm and 3–4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS. All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.

Electrochemical stability of subnanometer Pt clusters

DEFF Research Database (Denmark)

Quinson, Jonathan; Röefzaad, Melanie; Deiana, Davide

2018-01-01

In the present work, the degradation of size-selected Pt nanoclusters is studied under electrochemical conditions. This model catalyst mimics carbon supported Pt nanoclusters and nanoparticles typically employed in proton exchange membrane fuel cells (PEMFCs). Insight into the early stage...... of degradation is given by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and confirmed by transmission electron microscopy (TEM). In contrast to common assumptions, it is demonstrated that even extremely small Pt clusters exhibit a remarkable stability under electrochemical...... - is observed. In light of the findings reported, developing highly-dispersed subnanometer Pt clusters as catalyst for PEMFCs is a realistic approach provided the operation conditions are suitably adjusted. Furthermore, mitigation strategies to improve the stability of few-atoms catalyst under electrochemical...

Surface enrichment of Pt in stable Pt-Ir nano-alloy particles on MgAl 2 O 4 spinel in oxidizing atmosphere

Energy Technology Data Exchange (ETDEWEB)

Li, Weizhen; Nie, Lei; Chen, Ying; Kovarik, Libor; Liu, Jun; Wang, Yong

2017-04-01

With the capability of MgAl2O4 spinel {111} nano-facets in stabilizing small Rh, Ir and Pt particles, bimetallic Ir-Pt catalysts on the same support were investigated, aiming at further lowering the catalyst cost by substituting expensive Pt with cheaper Ir in the bulk. Small Pt-Ir nano-alloy particles (< 2nm) were successfully stabilized on the spinel {111} nano-facets as expected. Interestingly, methanol oxidative dehydrogenation (ODH) rate on the surface Pt atoms increases with oxidizing aging but decreases upon reducing treatment, where Ir is almost inactive under the same reaction conditions. Up to three times enhancement in Pt exposure was achieved when the sample was oxidized at 800 °C in air for 1 week and subsequently reduced by H2 for 2 h, demonstrating successful surface enrichment of Pt on Pt-Ir nano-alloy particles. A dynamic stabilization mechanism involving wetting\

Controllable fabrication of Pt nanocatalyst supported on N-doped carbon containing nickel nanoparticles for ethanol oxidation.

Science.gov (United States)

Yu, Jianguo; Dai, Tangming; Cao, Yuechao; Qu, Yuning; Li, Yao; Li, Juan; Zhao, Yongnan; Gao, Haiyan

2018-08-15

In this paper, platinum nanoparticles were deposited on a carbon carrier with the partly graphitized carbon and the highly dispersive carbon-coated nickel particles. An efficient electron transfer structure can be fabricated by controlling the contents of the deposited platinum. The high resolution transmission electron microscopy images of Pt 2 /Ni@C N-doped sample prove the electron transfer channel from Pt (1 1 1) crystal planes to graphite (1 0 0) or Ni (1 1 1) crystal planes due to these linked together crystal planes. The Pt 3 /Ni@C N-doped with low Pt contents cannot form the electron transfer structure and the Pt 1 /Ni@C N-doped with high Pt contents show an obvious aggregation of Pt nanoparticles. The electrochemical tests of all the catalysts show that the Pt 2 /Ni@C N-doped sample presents the highest catalytic activity, the strongest CO tolerance and the best catalytic stability. The high performance is attributed to the efficient electronic transport structure of the Pt 2 /Ni@C N-doped sample and the synergistic effect between Pt and Ni nanoparticles. This paper provides a promising method for enhancing the conductivity of electrode material. Copyright © 2018 Elsevier Inc. All rights reserved.

Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

NARCIS (Netherlands)

Keller, D.E.; Visser, T.; Soulimani, F.; Koningsberger, D.C.; Weckhuysen, B.M.

2007-01-01

The effect of hydration on the molecular structure of silica-supported vanadium oxide catalysts with loadings of 1–16 wt.% V has been systematically investigated by infrared, Raman, UV–vis and EXAFS spectroscopy. IR and Raman spectra recorded during hydration revealed the formation of V–OH groups,

Ethylene glycol oxidation on Pt and Pt-Ru nanoparticle decorated polythiophene/multiwalled carbon nanotube composites for fuel cell applications

International Nuclear Information System (INIS)

Selvaraj, Vaithilingam; Alagar, Muthukaruppan

2008-01-01

A novel supporting material containing polythiophene (PTh) and multiwalled carbon nanotubes (MWCNTs) (PTh-CNTs) is prepared by in situ polymerization of thiophene on carbon nanotubes using FeCl 3 as oxidizing agent under sonication. The prepared polythiophene/CNT composites are further decorated with Pt and Pt-Ru nanoparticles by chemical reduction of the corresponding metal salts using HCHO as reducing agent at pH = 11 (Pt/PTh-CNT and Pt-Ru/PTh-CNT). The fabricated composite films decorated with nanoparticles were investigated towards the electrochemical oxidation of ethylene glycol (EG). The presence of carbon nanotubes in conjugation with a conducting polymer produces a good catalytic effect, which might be due to the higher electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces, which allows higher dispersion of Pt and Pt-Ru nanoparticles. Such nanoparticle modified PTh-CNT electrodes exhibit better catalytic behavior towards ethylene glycol oxidation. Results show that Pt/PTh-CNT and Pt-Ru/PTh-CNT modified electrodes show enhanced electrocatalytic activity and stability towards the electro-oxidation of ethylene glycol than the Pt/PTh electrodes, which shows that the composite film is more promising for applications in fuel cells

MENINGKATKAN KAPASITAS LOADING MESIN PRESS 1000T PADA PROSES PRESS BRACKET SUPPORT AIR TANK DENGAN METODE PDCA DI PT. XYZ

Directory of Open Access Journals (Sweden)

Renty Anugerah Mahaji Puteri

2016-01-01

Full Text Available Agar proses produksi bisa berjalan dengan lancar, diperlukan improvement. Dalam pembahasan ini, improvement yang akan dilakukan terkait dengan proses pembentukan part bracket support air tank. Adapun metode yang digunakan pada penelitian ini adalah PDCA (Plan Do Check Action. Metode ini diangkat penulis sebagai metode yang paling cocok untuk diterapkan pada perusahaan yang bergerak di bidang otomotif seperti PT. XYZ ini. Yang menjadi titik fokus dari improvement yang akan dilakukan saat ini adalah dies untuk part bracket support air tank. Produk ini dianggap cocok untuk menjadi bahan improvement karena merupakan new project. Sehingga dapat melakukan improvement yang ekstrim sekalipun tanpa harus mengganggu produksi yang sedang berlangsung. Untuk itu penyesuaian atau rekayasa terhadap dies dari part tersebut akan dilaksanakan guna mencapai hasil atau target yang diinginkan.Adapun hasil yang diharapkan dari penelitian ini adalah tercukupinya kapasitas mesin untuk melakukan proses – proses yang harus dilakukan untuk pembuatan part bracket support air tank. Selain itu, kualitas dari produk yang dibuat juga menjadi item yang harus tetap dijaga. Karena kualitas dari produk yang dibuat akan menjaga kepercayaan customer terhadap PT. XYZ.

Pretreatments of porous silica for improving the activity of a nickel-loaded catalyst

Energy Technology Data Exchange (ETDEWEB)

Arai, M.; Ikushima, Y.; Nishiyama, Y.

1986-02-01

Nickel catalysts supported on porous silicas treated with water, ethanol, and 1-butanol were found to be more active than that supported on untreated silica for ethane hydrogenolysis and furan hydrogenation. To elucidate the reason for the activation, some surface properties of the treated silicas were examined. The treatments decreased the surface area and increased the volume of the macropores, the surface density of hydroxyl groups, and the heat of immersion in water per unit surface area. The state of nickel on the support was examined by temperature programed desorption (TPD) of hydrogen, X-ray diffraction (XRD), and scanning electron microscopy/X-ray microanalysis. The dispersion measured by XRD was not appreciably altered by the treatments, but the TPD showed more hydrogen desorbed above 150/sup 0/C from nickel on the treated supports. The activation of nickel by pretreatment of the support was ascribed to the increase of those nickel atoms which dispersed finely over the support by the increased number of surface hydroxyl groups. This was based on the number of hydroxyl groups per unit surface area. The nickel catalyst supported on the pretreated silicas showed greater thermal stability. 16 references, 5 figures, 1 table.

Dicationic ionic liquid mediated fabrication of Au@Pt nanoparticles supported on reduced graphene oxide with highly catalytic activity for oxygen reduction and hydrogen evolution

Science.gov (United States)

Shi, Ya-Cheng; Chen, Sai-Sai; Feng, Jiu-Ju; Lin, Xiao-Xiao; Wang, Weiping; Wang, Ai-Jun

2018-05-01

Ionic liquids as templates or directing agents have attracted great attention for shaping-modulated synthesis of advanced nanomaterials. In this work, reduced graphene oxide supported uniform core-shell Au@Pt nanoparticles (Au@Pt NPs/rGO) were fabricated by a simple one-pot aqueous approach, using N-methylimidazolium-based dicationic ionic liquid (1,1-bis(3-methylimadazoilum-1-yl)butylene bromide, [C4(Mim)2]2Br) as the shape-directing agent. The morphology evolution, structural information and formation mechanism of Au@Pt NPs anchored on rGO were investigated by a series of characterization techniques. The obtained nanocomposites displayed superior electrocatalytic features toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) compared with commercial Pt/C catalyst. This approach provides a novel route for facile synthesis of nanocatalysts in fuel cells.

Ruthenium-platinum bimetallic catalysts supported on silica: characterization and study of benzene hydrogenation and CO methanation

Energy Technology Data Exchange (ETDEWEB)

Chakrabarty, D.K.; Rao, K.M.; Sundararaman, N.; Chandavar, K.

1986-12-15

Ru-Pt/SiO/sub 2/ bimetallic catalysts with varying Ru:Pt ratio have been prepared and studied with the aim to establish if they contain coclusters or isolated ruthenium and platinum particles. X-ray diffraction studies show that individual crystallites of ruthenium and platinum are present and no coclusters are formed. Metal dispersion has been determined by hydrogen chemisorption and surface composition of the catalysts has been obtained from XPS. It was found that preoxidation of the catalysts prior to reduction is essential for good platinum dispersion. The experimental turnover number (TN) for benzene hydrogenation on the bimetallic catalysts agrees very well with that of the weighted average on the individual metal catalysts and this may be taken as a kinetic evidence for the absence of coclusters. Carbon monoxide methanation activity of the bimetallic catalysts is quite similar to that of the supported platinum catalyst. 6 refs., 6 figs., 2 tabs.

Isomerization-cracking of n-octane on catalysts based on heteropolyacid H{sub 3}Pw{sub 12}O{sub 40} and heteropolyacid supported on zirconia and promoted with Pt and Cs

Energy Technology Data Exchange (ETDEWEB)

Manuele, Debora L.; Torres, Gerardo C.; Benitez, Viviana M.; Badano, Juan M.; Yori, Juan C.; Sepulveda, Jorge H., E-mail: jsepulve@fiq.unl.edu.ar [Universidad Nacional de Litoral, Santa Fe (Argentina). Instituto de Investiaciones en Catalisis y Petroquimica. Consejo Nacional de Investigaciones Cientificas y Tecnicas

2013-10-01

Isomerization-cracking of n-octane was studied using H{sub 3}PW{sub 12}O{sub 40} (HPA) and HPA supported on zirconia and promoted with Pt and Cs. The addition of Pt and Cs to the supported HPA did not modify the Keggin structure. The Pt addition to the supported HPA did not substantially modify the total acidity; however, the Broensted acidity increased significantly. Cs increased the total acidity and Broensted acidity. A linear relation was observed between the n-C{sub 8} total conversion and Broensted acidity. The most adequate catalysts for performing isomerization and cracking to yield high research octane number (RON) are those with higher values of Broensted acidity. (author)

Electrochemical oxidation of methanol on Pt/(RuxSn1-xO2 nanocatalyst

Directory of Open Access Journals (Sweden)

Krstajić Mila N.

2013-01-01

Full Text Available The Ru-doped SnO2 powder, (RuxSn1-xO2, with the Sn:Ru atomic ratio of 9:1 was synthesized and used as a support for Pt nanoparticles (30 mass% loading. The (RuxSn1-xO2 support and Pt/(RuxSn1-xO2 catalyst were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM. (RuxSn1-xO2 was found to be two-phase material consisting of probably solid solution of RuO2 in SnO2 and pure RuO2. The average Pt particle size determined by TEM was 5.3 nm. Cyclic voltammetry of Pt/(RuxSn1-xO2 indicated good conductivity of the sup-port and displayed usual features of Pt. The results of the electrochemical oxidation of COads and methanol on Pt/(RuxSn1-xO2 were compared with those on commercial Pt/C and PtRu/C catalysts. Oxidation of COads on Pt/(RuxSn1-xO2 starts at less positive potentials than on PtRu/C and Pt/C. Potentiodynamic polarization curves and chronoamperometric curves of methanol oxidation indicated higher initial activity of Pt/(RuxSn1-xO2 catalyst compared to PtRu/C, but also a greater loss in the current density over time. Potentiodynamic stability test of the catalysts revealed that deactivation of the Pt/(RuxSn1-xO2 and Pt/C was primarily caused by the poisoning of Pt surface by the methanol oxidation residues, which mostly occurred during the first potential cycle. In the case of PtRu/C the poisoning of the surface was minor and deactivation was caused by the PtRu surface area loss. [Projekat Ministarstva nauke Republike Srbije, br. ON-172054

The effect of potassium addition to Pt supported on YSZ on steam reforming of mixtures of methane and ethane

NARCIS (Netherlands)

Graf, P.O.; Mojet, Barbara; Lefferts, Leonardus

2009-01-01

The influence of potassium addition on Pt supported on yttrium-stabilized zirconia (YSZ) was studied with FT-IR CO adsorption and CO-FT-IR-TPD, in order to understand the effect of potassium on the performance of the catalyst in reforming of mixtures of methane and ethane. Potassium modification of

Hydrogen sulfide removal from hot coal gas by various mesoporous silica supported Mn{sub 2}O{sub 3} sorbents

Energy Technology Data Exchange (ETDEWEB)

Zhang, Z.F.; Liu, B.S., E-mail: bingsiliu@tju.edu.cn; Wang, F.; Wang, W.S.; Xia, C.; Zheng, S.; Amin, R.

2014-09-15

Graphical abstract: - Highlights: • Mn{sub 2}O{sub 3}/KIT-1 presented the best desulfurization performance at 600–850 °C. • High sulfur capacity of Mn{sub 2}O{sub 3}/KIT-1 correlated closely with 3-D channel of KIT-1. • Desulfurization character depended strongly on framework structure of sorbents. • High steam content suppressed greatly the occurrence of sulfidation reaction. - Abstract: A series of 50 wt% Mn{sub 2}O{sub 3} sorbents was prepared using various mesoporous silica, MCM-41, HMS, and KIT-1 as support. The influence of textural parameters of mesoporous silica, especially type of channel on the desulfurization performance of Mn{sub 2}O{sub 3} sorbents was investigated at 600–850 °C using hot coal gas containing 0.33 vol.% H{sub 2}S. The fresh and used sorbents were characterized by means of N{sub 2}-adsorption, x-ray diffraction (XRD), high resolution transmission microscopy (HRTEM) and H{sub 2} temperature- programmed reduction (H{sub 2}-TPR) techniques. The results confirmed that the manganese oxide was dispersed highly in regular pore channel of the mesoporous supports due to high surface area. Compared with the Mn{sub 2}O{sub 3}/diatomite, all mesoporous silica supported Mn{sub 2}O{sub 3} sorbents exhibited high breakthrough sulfur capacity and a sharp deactivation rate after the breakthrough point. Compared to Mn{sub 2}O{sub 3}/MCM-41 and Mn{sub 2}O{sub 3}/HMS sorbent, the Mn{sub 2}O{sub 3}/KIT-1 showed better desulfurization performance because of the 3D wormhole-like channel. The high sulfur capacity of the Mn{sub 2}O{sub 3}/KIT-1 sorbent was maintained during the eight consecutive desulfurization-regeneration cycles. The Mn{sub 2}O{sub 3}/KIT-1 still presented high desulfurization activity when hot coal gas contained low steam (<5%)

Silica Nephropathy

Directory of Open Access Journals (Sweden)

N Ghahramani

2010-06-01

Full Text Available Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2 is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600–7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents.

“Single-” and “multi-core” FePt nanoparticles: from controlled synthesis via zwitterionic and silica bio-functionalization to MRI applications

Energy Technology Data Exchange (ETDEWEB)

Kostevšek, Nina, E-mail: nina.kostevsek@ijs.si; Šturm, Sašo [Jožef Stefan Institute, Department for Nanostructured Materials (Slovenia); Serša, Igor; Sepe, Ana [Jožef Stefan Institute, Department for Condensed Matter Physics (Slovenia); Bloemen, Maarten; Verbiest, Thierry [KU Leuven, Department of Chemistry (Belgium); Kobe, Spomenka; Žužek Rožman, Kristina [Jožef Stefan Institute, Department for Nanostructured Materials (Slovenia)

2015-12-15

The value of the magnetization has a strong influence on the performance of nanoparticles that act as the contrast agent material for MRI. In this article, we describe processing routes for the synthesis of FePt nanoparticles of different sizes, which, as a result, exhibit different magnetization values. “Single-core” FePt nanoparticles of different sizes (3–15 nm) were prepared via one-step or two-step synthesis, with the latter exhibiting twice the magnetization (m{sub (1.5T)} = 14.5 emu/g) of the nanoparticles formed via the one-step synthesis (m{sub (1.5T)} < 8 emu/g). Furthermore, we propose the synthesis of “multi-core” FePt nanoparticles by changing the ratio between the two surfactants (oleylamine and oleic acid). The step from smaller “single-core” FePt nanoparticles towards the larger, “multi-core” FePt nanoparticles (>20 nm) leads to an increase in the magnetization m{sub (1.5T)} from 8 to 19.5 emu/g, without exceeding the superparamagnetic limit. Stable water suspensions were prepared using two different approaches: (a) functionalization with a biocompatible, zwitterionic, catechol ligand, which was used on the FePt nanoparticles for the first time, and (b) coating with SiO{sub 2} shells of various thicknesses. These FePt-based nanostructures, the catechol- and SiO{sub 2}-coated “single-core” and “multi-core” FePt nanoparticles, were investigated in terms of the relaxation rates. The higher r{sub 2} values obtained for the “multi-core” FePt nanoparticles compared to that for the “single-core” ones indicate the superiority of the “multi-core” FePt nanoparticles as T{sub 2} contrast agents. Furthermore, it was shown that the SiO{sub 2} coating reduces the r{sub 1} and r{sub 2} relaxation values for both the “single-core” and “multi-core” FePt nanoparticles. The high r{sub 2}/r{sub 1} ratios obtained in our study put FePt nanoparticles near the top of the list of candidate materials for use in MRI

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes.

Science.gov (United States)

Hassan, Ayaz; Ticianelli, Edson A

2018-01-01

Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC) anodes are revised for the following catalyst systems: (1) a carbon supported PtMo electrocatalyst submitted to heat treatments; (2) Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C); (3) ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4) Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC) Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes

Directory of Open Access Journals (Sweden)

AYAZ HASSAN

2018-04-01

Full Text Available ABSTRACT Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC anodes are revised for the following catalyst systems: (1 a carbon supported PtMo electrocatalyst submitted to heat treatments; (2 Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C; (3 ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4 Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Synthesis and characterization of fluorescence-labelled silica core-shell and noble metal-decorated ceria nanoparticles

Directory of Open Access Journals (Sweden)

Rudolf Herrmann

2014-12-01

Full Text Available The present review article covers work done in the cluster NPBIOMEM in the DFG priority programme SPP 1313 and focuses on synthesis and characterization of fluorescent silica and ceria nanoparticles. Synthetic methods for labelling of silica and polyorganosiloxane/silica core–shell nanoparticles with perylenediimide derivatives are described, as well as the modification of the shell with thiol groups. Photometric methods for the determination of the number of thiol groups and an estimate for the number of fluorescent molecules per nanoparticles, including a scattering correction, have been developed. Ceria nanoparticles decorated with noble metals (Pt, Pd, Rh are models for the decomposition products of automobile catalytic converters which appear in the exhaust gases and finally interact with biological systems including humans. The control of the degree of agglomeration of small ceria nanoparticles is the basis for their synthesis. Almost monodisperse agglomerates (40 ± 4–260 ± 40 nm diameter can be prepared and decorated with noble metal nanoparticles (2–5 nm diameter. Fluorescence labelling with ATTO 647N gave the model particles which are now under biophysical investigation.

Low Pt content Pt-Ru-Ir-Sn quaternary catalysts for anodic methanol oxidation in DMFC

Energy Technology Data Exchange (ETDEWEB)

Neburchilov, Vladimir; Wang, Haijiang; Zhang, Jiujun [Institute for Fuel Cell Innovation, National Research Council (Canada)

2007-07-15

In this communication we report our research work on low Pt content Pt-Ru-Ir-Sn quaternary catalysts for use in DMFC anodes. The carbon-supported quaternary metal alloy catalyst was synthesized according to the solution reduction method and was deposited onto a carbon fiber paper or a carbon aerogel nanofoam to form the anode for direct methanol fuel cells. The Pt loading of the electrode is 0.1 mg/cm{sup 2}. The testing results from a three-electrode electrochemical cell show that the simultaneous use of higher Ir (25-35 wt.%) and Sn (10 wt.%) content gives satisfactory stability and higher activity for methanol oxidation than the commercially available E-TEK anode (80%[0.5Pt 0.5Ru]/C on carbon cloth). Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), and Bruner-Emmett-Teller method (BET) measurements were carried out to characterize the composition, structure, morphology, and surface area of the developed catalysts. (author)

Electronic structures of PtCu, PtAg, and PtAu molecules: a Dirac four-component relativistic study

International Nuclear Information System (INIS)

Abe, Minori; Mori, Sayaka; Nakajima, Takahito; Hirao, Kimihiko

2005-01-01

Relativistic four-component calculations at several correlated levels have been performed for diatomic PtCu, PtAg, and PtAu molecules. The ground state spectroscopic constants of PtCu were calculated using the four-component MP2 method, and show good agreement with experiment. We also performed calculations on the experimentally unknown species, PtAg and PtAu, and the mono-cationic systems, PtCu + , PtAg + , and PtAu + . The low-lying excited states of these diatomic molecules were also investigated using the four-component multi-reference CI method

Design of Pt/Carbon Xerogel Catalysts for PEM Fuel Cells

Directory of Open Access Journals (Sweden)

Nathalie Job

2015-01-01

Full Text Available The design of efficient catalytic layers of proton exchange membrane fuel cells (PEMFCs requires the preparation of highly-loaded and highly-dispersed Pt/C catalysts. During the last few years, our work focused on the preparation of Pt/carbon xerogel electrocatalysts, starting from simple impregnation techniques that were further optimized via the strong electrostatic adsorption (SEA method to reach high dispersion and a high metal weight fraction. The SEA method, which consists of the optimization of the precursor/support electrostatic impregnation through an adequate choice of the impregnation pH with regard to the support surface chemistry, leads to very well-dispersed Pt/C samples with a maximum 8 wt.% Pt after drying and reduction under H2. To increase the metal loading, the impregnation-drying-reduction cycle of the SEA method can be repeated several times, either with fresh Pt precursor solution or with the solution recycled from the previous cycle. In each case, a high dispersion (Pt particle size ~3 nm is obtained. Finally, the procedure can be simplified by combination of the SEA technique with dry impregnation, leading to no Pt loss during the procedure.

An Efficient Solvent-Free Protocol for the Synthesis of 1-Amidoalkyl-2-naphthols using Silica-Supported Molybdatophosphoric Acid

Directory of Open Access Journals (Sweden)

Abdolkarim Zare

2010-01-01

Full Text Available A highly efficient, green and simple solvent-free method for the synthesis of 1-amidoalkyl-2-naphthols via one-pot multi-components condensation of 2-naphthol, aromatic aldehydes and amides in the presence of catalytic amount of silica-supported molybdatophosphoric acid (H3PMo12O40.xH2O/SiO2, 3.17 mol% is described. The reactions proceed rapidly and the title compounds are produced in high to excellent yields.

Perencanaan Enterprise Architecture Pada Perusahaan Manufaktur PT. Z

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