WorldWideScience

Sample records for chemisorption

  1. Chemisorption And Precipitation Reactions

    Science.gov (United States)

    The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

  2. Refrigerator Based on Chemisorption

    Science.gov (United States)

    Jones, Jack A.

    1987-01-01

    Reversible chemical reaction generates pressurized oxygen for cooling. Concept for cryogenic refrigerator based on chemical absorption of oxygen by praseodymium/cerium oxide (PCO) compound. Refrigerator produces cryogenic liquid for cooling infrared sensors. Also used for liquefying air and separating oxygen from nitrogen in air. In chemisorption refrigerator, PCO alternately absorbs and desorbs oxygen depending on whether cooled or heated. One pair of compressors accepts oxygen while others releases it. Compressed oxygen liquefied when precooked and expanded.

  3. Oxygen chemisorption cryogenic refrigerator

    Science.gov (United States)

    Jones, Jack A. (Inventor)

    1987-01-01

    The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to provide a continuous flow of high pressure oxygen, multiple heat exchangers for precooling the oxygen, a Joule-Thomson expansion valve system for expanding the oxygen to partially liquefy it and a liquid oxygen pressure vessel. The primary novelty is that, while it was believed that once oxygen combined with an element or compound the reaction could not reverse to release gaseous oxygen, in this case oxygen will indeed react in a reversible fashion with certain materials and will do so at temperatures and pressures which make it practical for incorporation into a cryogenic refrigeration system.

  4. The chemisorptive bond basic concepts

    CERN Document Server

    Clark, Alfred

    1974-01-01

    The Chemisorptive Bond: Basic Concepts describes the basic concepts of the chemisorptive bond on solid surfaces from the simple analogies with ordinary chemical bonds to the quantum-mechanical approaches.This book is composed of 10 chapters and begins with discussions of simple formulas for correlating measurable quantities in chemisorptions and catalysis. The succeeding chapters deal with theories based on quantum-mechanical principles that describe the mutual interactions of atoms of the solid and foreign atoms on the surface. The remaining chapters consider the possible arrangements

  5. Modified Technique For Chemisorption Measurements

    Science.gov (United States)

    Schryer, David R.; Brown, Kenneth G.; Schryer, Jacqueline

    1989-01-01

    In measurements of chemisorption of CO on Pt/SnO2 catalyst observed that if small numbers of relatively large volumes of adsorbate gas are passed through sample, very little removal of CO detected. In these cases little or no CO has been chemisorbed on Pt/SnO2. Technique of using large number of small volumes of adsorbate gas to measure chemisorption applicable to many gas/material combinations other than CO on Pt/SnO2. Volume used chosen so that at least 10 percent of adsorbate gas removed during each exposure.

  6. N2 chemisorption to W-n nanoclusters : molecular versus dissociative chemisorption

    OpenAIRE

    Kim, Young Dok; Stolcic, Davor; Fischer, Matthias; Ganteför, Gerd

    2003-01-01

    Comparative studies on adsorption of atomic and molecular nitrogen indicate that in contrast to the previous results from tungsten bulk crystals, molecular chemisorption of N2 is more stable than dissociative ones on tungsten anion clusters consisting of 8 atoms or less. Our result provides a new aspect in chemisorption on metal clusters, namely the energetically preferred channel of chemisorption dissociative versus molecular might be different for metal clusters and bulk surfaces.

  7. CO Chemisorption at Metal Surfaces and Overlayers

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Morikawa, Y.; Nørskov, Jens Kehlet

    1996-01-01

    A database of ab initio calculations of the chemisorption energy of CO over Ni(111), Cu(111), Ru(0001), Pd(111), Ag(111), Pt(111), Au(111), Cu3Pt(111), and some metallic overlayer structures is presented. The trends can be reproduced with a simple model describing the interaction between the metal...... d states and the CO 2 pi* and 5 sigma states, renormalized by the metal sp continuum. Our model rationalizes the results by Rodriguez and Goodman [Science 257, 897 (1992)] showing a strong correlation between the CO chemisorption energy and the surface core level shift....

  8. Theory of hydrogen chemisorption on metals

    International Nuclear Information System (INIS)

    A theory of hydrogen chemisorption on metals is presented. Green's function is derived taking into account the coupling strength between metal and chemisorbed atom and the strength of the interatomic Coulomb repulsion, allowing the calculation of the local density of states at the adatom, especially for the limiting cases of strong and weak coupling

  9. Orbital-Specific Modeling of CO Chemisorption

    OpenAIRE

    Mason, Sara E.; Grinberg, Ilya; Rappe, Andrew M.

    2006-01-01

    We demonstrate that variations in molecular chemisorption energy on different metals, different surface terminations, and different strain conditions can be accounted for by orbital-specific changes in the substrate electronic structure. Our density functional theory data set, spanning three metals, two surface terminations, and five strain states, is fit to a single model based on tight binding. A crucial aspect of the model is decomposition of the $d$-band into contributions from the five $...

  10. CO Chemisorption at Metal Surfaces and Overlayers

    OpenAIRE

    Hammer, Bjørk; Morikawa, Y.; Nørskov, Jens Kehlet

    1996-01-01

    A database of ab initio calculations of the chemisorption energy of CO over Ni(111), Cu(111), Ru(0001), Pd(111), Ag(111), Pt(111), Au(111), Cu3Pt(111), and some metallic overlayer structures is presented. The trends can be reproduced with a simple model describing the interaction between the metal d states and the CO 2 pi* and 5 sigma states, renormalized by the metal sp continuum. Our model rationalizes the results by Rodriguez and Goodman [Science 257, 897 (1992)] showing a strong correlati...

  11. Reversible Chemisorption Gas-Gap Thermal Switch

    Science.gov (United States)

    Jones, Jack A.; Bard, Steven; Blue, Gary

    1991-01-01

    Gas/sorbent combinations provide means to turn heat-conduction paths on and off. Single-stage gas-gap thermal switch based on reversible chemisorption of hydrogen gas by ZrNiH. Two-stage gas-gap thermal switch based on reversible desorption of O2 from MnO2 in first stage, followed by absorption in Cu on zeolite in second stage. Requires relatively low power. Used in sorption refrigeration systems designed to operate for long times without maintenance.

  12. Chemisorption of Guanine on Cu(110)

    Science.gov (United States)

    Matos, Jeronimo; Kara, Abdelkader

    2011-03-01

    We use density functional theory (PBE) to calculate the adsorption of a guanine molecule on Cu(110). At saturation coverage, guanine adsorbs tilted with the oxygen atom strongly bound to one of the surface atoms at a height of 2.12 Å above this surface atom with a binding energy of 430 meV/molecule. The substrate top layer atoms show a buckling of 0.22 Å , while the molecule experiences a twist from the flat configuration in the gas phase. The dz 2 state of the copper atom -that is bound to the oxygen atom- presents an enhancement in its density near the Fermi level. We calculated a drop in the work function of 0.34 eV upon adsorption of guanine on Cu(110). These effects classify this system as chemisorption.

  13. Chemisorption of SO2 and Cl2 on indium oxide

    International Nuclear Information System (INIS)

    The mutual influence of SO2 and Cl2 during chemisorption on In2O3 surface has been studied. It is shown that SO2 molecules are adsorbed in a non-charged form and the amount of SO2 adsorbed decreases with temperature increase. Preliminary Cl2 chemisorption results in an abrupt decrease of SO2 sorption and change in SO2 bonding with indium oxide surface. In case of SO2 presorption a decrease in temperature of chloride formation during subsequent Cl2 chemisorption takes place. 8 refs.; 3 figs.; 1 tab

  14. Chemisorption of O and H on an Al-13 cluster

    Science.gov (United States)

    Patridge, H.; Bauschlicher, C. W., Jr.

    1986-01-01

    Chemisorption of oxygen and hydrogen atoms onto a 13 atom aluminum cluster is investigated theoretically. Oxygen atoms are found to remain on the outside of the cluster, and at low coverage, to expand the Al-Al bond length by 0.42 bohr. Hydrogen atoms penetrate into the cluster resulting in a sizeable, 0.57 bohr expansion at high coverage. The difference between chemisorption on aluminum and beryllium clusters is discussed.

  15. Summary Abstract: Chemisorption of water on Rh(111)

    OpenAIRE

    Zinck, J. J.; Weinberg, W. H.

    1980-01-01

    The chemisorption of H2O on the (111) surface of Rh has been studied by thermal desorption mass spectrometry and low-energy electron diffraction. In addition to the clean surface, the chemisorptive behavior of H2O has been examined when various coverages of oxygen, hydrogen, or carbon monoxide have been pre-adsorbed on the surface in the form of atomic oxygen, atomic hydrogen, and molecular CO.

  16. Direct dissociative chemisorption of propane on Ir(110)

    International Nuclear Information System (INIS)

    We have employed molecular beam techniques to investigate the initial probability of direct dissociative chemisorption, Pd, and the intrinsic trapping probability, ξ, of C3H8, C3D8, and (CH3)2CD2 on Ir(110) as a function of beam translational energy, Ei, from 1.5 to 59 kcal/mol. For C3H8 and (CH3)2CD2, a measurable (≥0.02) initial probability of direct dissociative chemisorption is observed above a beam energy of approximately 7 kcal/mol. For C3D8 this energy is roughly 10 kcal/mol. Above these energies the initial probability of direct chemisorption of each of the isotopomers of propane increases nearly linearly with Ei, approaching a value of approximately Pd=0.48 at Ei=52 kcal/mol for C3H8 and (CH3)2CD2, and Pd=0.44 at Ei=59 kcal/mol for C3D8. This kinetic isotope effect for the direct chemisorption of C3D8 relative to C3H8 is smaller than that expected for a mechanism of H (or D) abstraction by tunneling through an Eckart barrier, suggesting a contribution of C endash C bond cleavage to direct chemisorption. The lack of a kinetic isotope effect for the direct chemisorption of (CH3)2CD2 relative to C3H8 indicates that 1 degree C endash H bond cleavage dominates over 2 degree C endash H bond cleavage during the direct chemisorption of propane on Ir(110). The trapping behavior of each of these isotopomers of propane is approximately identical as a function of Ei, with ξ>0.9 at Ei=1.5 kcal/mol, ξ=0.3 at Ei=20 kcal/mol, and ξi=40 kcal/mol. copyright 1996 American Institute of Physics

  17. Commensurate Registry and Chemisorption at a Hetero-organic Interface

    Science.gov (United States)

    Stadtmüller, Benjamin; Sueyoshi, Tomoki; Kichin, Georgy; Kröger, Ingo; Soubatch, Sergey; Temirov, Ruslan; Tautz, F. Stefan; Kumpf, Christian

    2012-03-01

    We present evidence for a partly chemisorptive bonding between single monolayers of copper-II-phthalocyanine (CuPc) and 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) that are stacked on Ag(111). A commensurate registry between the two molecular layers and the substrate, i.e., a common crystallographic lattice for CuPc and PTCDA films as well as for the Ag(111) surface, indicates that the growth of the upper layer is dominated by the structure of the lower. Photoemission spectroscopy clearly reveals a gradual filling of the lowest unoccupied molecular orbital of PTCDA due to CuPc adsorption, which proves the chemisorptive character.

  18. A model for nitrogen chemisorption in ion thrusters

    Science.gov (United States)

    Wilbur, P. J.

    1979-01-01

    A theoretical model describing the formation of nitrogen species subject to chemisorption on ion thruster discharge chamber surfaces is presented. Molecules, atoms, atomic ions and molecular ions are identified as the important species in the analysis. Current densities of the atomic and molecular ions predicted by the model are compared to current densities measured in the beam of a SERT II thruster. The predicted and measured values of these two current densities are shown to agree within about + or - 100%. The mechanisms involved in the erosion of a surface subjected to simultaneous nitrogen chemisorption and sputter erosion by high energy ions are also discussed.

  19. Nature of Chemisorption on Titanium Carbide and Nitride

    OpenAIRE

    Ruberto, Carlo; Vojvodic, Aleksandra; Lundqvist, Bengt I.

    2005-01-01

    Extensive density-functional calculations are performed to understand atomic chemisorption on the TiC(111) and TiN(111) surfaces, in particular the calculated pyramid-shaped trends in the adsorption energies for second- and third-period adatoms. Our previously proposed concerted-coupling model for chemisorption on TiC(111) is tested against new results for adsorption on TiN(111) and found to apply on this surface as well, thus reflecting both similarities and differences in electronic structu...

  20. Chemisorption-Induced Resonance Frequency Shift of a Microcantilever

    International Nuclear Information System (INIS)

    The autonomy and property of atoms/molecules adsorbed on the surface of a microcantilever can be probed by measuring its resonance frequency shift due to adsorption. The resonance frequency change of a cantilever induced by chemisorption is theoretically studied. Oxygen chemisorbed on the Si(100) surface is taken as a representative example. We demonstrate that the resonant response of the cantilever is mainly determined by the chemisorption-induced bending stiffness variation, which depends on the bond configurations formed by the adsorbed atoms and substrate atoms. This study is helpful for optimal design of microcantilever-based sensors for various applications. (condensed matter: structure, mechanical and thermal properties)

  1. Dissociative chemisorption of N2 on Rhenium

    DEFF Research Database (Denmark)

    Billing, Gert D.; Guldberg, Annette; Henriksen, Niels Engholm;

    1990-01-01

    The dissociative chemisorption of nitrogen on the (0001) rhenium surface is studied at low impact energies, where tunnelling processes are important. A quantum-classical model is used in which two coordinates, the distance from the surface and the vibrational coordinate, are treated quantum...

  2. Chemisorption Techniques for the Determination of Metal Dispersion

    International Nuclear Information System (INIS)

    Chemisorption is an effective and un expensive analytical technique for characterizing and titrating active centers of the catalyst surface and for evaluating its activity with good approximation. The paper describes experimental procedures and the nature of information that can be obtained about active metal dispersion and area, diameter of active particles and isosteric heat of dispersion

  3. Theoretical study of chemisorption of CO on copper clusters

    International Nuclear Information System (INIS)

    The cluster size oscillations of the chemisorption energies are strongly effected by the geometry optimization of the clusters. This is found to be true for the case of CO absorbed on copper clusters of which this paper investigated using a correlated quantum chemical model approach

  4. Chemisorption of uranium hexa-fluoride on sodium fluoride pellets

    International Nuclear Information System (INIS)

    This paper comprises kinetics of chemical reaction or rather chemisorption of uranium hexafluoride gas on sodium fluoride pellets. The chemisorption is essentially irreversible at room temperature, while the process reverses at high temperature above 280 deg C. This chemisorption process was experimentally conducted in static condition at room temperature and its kinetics was studied. In the experiments, practically pure UF6 was used and the effects of gas pressure and weight of NaF pellets, were studied. In this heterogenous reaction, in which diffusion through ash layer is followed by chemical reaction, the reaction part is instantaneous and is first order with respect to gas concentration. Since the process of chemisorption is not only pure chemical reaction but also gas diffusion through ash layer, the rate constant depreciates with the percentage loading of UF6 on NaF pellets. The kinetic equation for the above process has been established for a particular size of NaF pellets and pellet porosity. (author)

  5. Indication of a size-dependent transition from molecular to dissociative chemisorption on clusters

    OpenAIRE

    Burkart, Stefan; Blessing, Nico; Ganteför, Gerd

    1999-01-01

    We report experimental indications for a size-dependent change of the chemical nature of chemisorption on small atomic clusters. We studied chemisorption of atomic hydrogen on negatively charged Tin- clusters using mass and photoelectron spectroscopy. Our experimental data support the assumption that for clusters with up to four Ti atoms, adsorption of intact H2 molecules is the energetically preferred configuration. For larger Tin clusters with n>4, dissociative hydrogen chemisorption is the...

  6. Model study in chemisorption: atomic hydrogen on beryllium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Bauschlicher, C.W. Jr.

    1976-08-01

    The interaction between atomic hydrogen and the (0001) surface of Be metal has been studied by ab initio electronic structure theory. Self-consistent-field (SCF) calculations have been performed using minimum, optimized minimum, double zeta and mixed basis sets for clusters as large as 22 Be atoms. The binding energy and equilibrium geometry (the distance to the surface) were determined for 4 sites. Both spatially restricted (the wavefunction was constrained to transform as one of the irreducible representations of the molecular point group) and unrestricted SCF calculations were performed. Using only the optimized minimum basis set, clusters containing as many as 22 beryllium atoms have been investigated. From a variety of considerations, this cluster is seen to be nearly converged within the model used, providing the most reliable results for chemisorption. The site dependence of the frequency is shown to be a geometrical effect depending on the number and angle of the bonds. The diffusion of atomic hydrogen through a perfect beryllium crystal is predicted to be energetically unfavorable. The cohesive energy, the ionization energy and the singlet-triplet separation were computed for the clusters without hydrogen. These quantities can be seen as a measure of the total amount of edge effects. The chemisorptive properties are not related to the total amount of edge effects, but rather the edge effects felt by the adsorbate bonding berylliums. This lack of correlation with the total edge effects illustrates the local nature of the bonding, further strengthening the cluster model for chemisorption. A detailed discussion of the bonding and electronic structure is included. The remaining edge effects for the Be/sub 22/ cluster are discussed.

  7. Commensurate registry and chemisorptions at a hetero-organic interface

    OpenAIRE

    Stadtmüller, B; Sueyoshi, T; Kichin, G.; Kröger, I.; Soubatch, S.; Temirov, R.; Tautz, F. S.; Kumpf, C.

    2012-01-01

    We present evidence for a partly chemisorptive bonding between single monolayers of copper-II-phthalocyanine (CuPc) and 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) that are stacked on Ag(111). A commensurate registry between the two molecular layers and the substrate, i.e., a common crystallographic lattice for CuPc and PTCDA films as well as for the Ag(111) surface, indicates that the growth of the upper layer is dominated by the structure of the lower. Photoemission spectroscopy c...

  8. Chemisorption kinetics of hydrogen on evaporated iron films

    Science.gov (United States)

    Shanabarger, M. R.

    1975-01-01

    An investigation is conducted of the kinetics of isothermal adsorption-desorption processes involving molecular hydrogen which is chemisorbed onto thin (20 to 50 A) polycrystalline Fe films at temperatures near 300 K. The results of the investigation indicate that chemisorption in the H2-Fe system occurs via a precursor state of molecularly adsorbed hydrogen. Contamination of the surface from unknown impurities in the gas phase is found to affect the number of available adsorption sites and to modify the prefactor for the absolute desorption rate constant for the precursor state.

  9. Chemisorption and catalytic decrease of sintering temperature for ceramics

    International Nuclear Information System (INIS)

    An explanation is suggested for a sintering temperature decrease in oxide ceramics (76%ZrO2, 19.8%Al2O3, 4.2Y2O3) during ceramic powder processing with carbon tetrachloride. It is shown that chemisorption on surface of powders to be compacted can affect both the density of compacts through a decrease of friction factor between powder particles and the kinetics of sintering through formation of additional vacancies in the process of chemisorbed substance dissolution over the bulk of particles. 6 refs

  10. Chemisorption and Reactions of Small Molecules on Small Gold Particles

    Directory of Open Access Journals (Sweden)

    Geoffrey C. Bond

    2012-02-01

    Full Text Available The activity of supported gold particles for a number of oxidations and hydrogenations starts to increase dramatically as the size falls below ~3 nm. This is accompanied by an increased propensity to chemisorption, especially of oxygen and hydrogen. The explanation for these phenomena has to be sought in kinetic analysis that connects catalytic activity with the strength and extent of chemisorption of the reactants, the latter depending on the electronic structure of the gold atoms constituting the active centre. Examination of the changes to the utilisation of electrons as particle size is decreased points to loss of metallic character at about 3 nm, as energy bands are replaced by levels, and a band gap appears. Detailed consideration of the Arrhenius parameters (E and ln A for CO oxidation points clearly to a step-change in activity at the point where metallic character is lost, as opposed to there being a monotonic dependence of rate on a physical property such as the fraction of atoms at corners or edges of particles. The deplorable scarcity of kinetic information on other reactions makes extension of this analysis difficult, but non-metallic behaviour is an unavoidable property of very small gold particles, and therefore cannot be ignored when seeking to explain their exceptional activity.

  11. Oxygen chemisorption compressor study for cryogenic J-T refrigeration

    Science.gov (United States)

    Jones, Jack A.; Blue, Gary D.

    1987-01-01

    Over twenty potentially reversible heat-powered oxide reactions have been studied and/or tested to determine their potential use as thermochemical oxygen compressors for cryogenic J-T LO2 refrigerators. One gas-solid compound family, Pr(1-n)Ce(n)O(x), proved to be completely reversible with fast kinetics for all pressure ranges tested below 650 C. With a heat-powered charcoal/methane physical adsorption upper stage and a Pr(1-n)Ce(n)O(x) chemisorption lower stage, temperatures should be attainable in the 55-80 K range for less power and over five times less weight than for charcoal/nitrogen sorption refrigeration systems. Total system power requirements with a hydride chemisorption lower stage (10 K to 7 K minimum) are about three times less than any mechanical refrigerator, and spacecraft refrigeration weights are about twenty times less. Due to the lack of wear-related moving parts in sorption refrigerators, life expectancy is at least ten years, and there essentially no vibration.

  12. Modelling of a chemisorption refrigeration and power cogeneration system

    International Nuclear Information System (INIS)

    Highlights: • An adsorption cogeneration was proposed and simulated for cooling and electricity. • A dynamic model was built and studied to demonstrate the variability of the system. • A dynamic model included the complex coupling of thermodynamic and chemical kinetic. • Mutual constrains between main components and optimisation methods were discussed. • The highest theoretical COP and exergy efficiency of cogeneration is 0.57 and 0.62. - Abstract: The present work for the first time explores the possibility of a small-scale cogeneration unit by combining solid–gas chemisorption refrigeration cycle and a scroll expander. The innovation in this work is the capability of producing refrigeration and electricity continuously and simultaneously without aggravating the energy scarcity and environmental impact. Individual modelling for each component, which has been validated by experimental data, was firstly investigated in order to identify the proper operation condition for the cogeneration mode achieving 1000 W power output. Subsequently, with the integrated modelling of two components the cogeneration performance was studied to demonstrate the viability of this concept. However, because of the mutual constraint between the chemisorption and the expansion when they link in series, the power output of the cogeneration mode was only around one third of the original expectation under the same condition identified in the individual modelling. Methods of improving the global performance including the selection of reactive mediums were also discussed and would be of referable value for the future practical investigation

  13. X-Ray Absorption Characterization of Supported Palladium Catalysts : A Comparison with Hydrogen Chemisorption

    OpenAIRE

    Zhang, G.; Habib, M; Vittoratos, S.

    1997-01-01

    X-ray absorption spectroscopy was used to characterize the supported palladium hydrocracking catalysts. Results with regard to the percentage of metal exposed are compared with those from hydrogen chemisorption measurements. Results from XAS indicate that hydrogen chemisorption has underestimated the metal dispersion. Possible explanations for this discrepancy are discussed.

  14. Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation

    Science.gov (United States)

    Jiang, Bin; Guo, Hua

    2016-03-01

    A fully coupled global nine-dimensional potential energy surface for the dissociative chemisorption of CO2 on Ni(100) is constructed from ˜18 000 density functional points. It reveals a complex reaction pathway dominated by two near iso-energetic transition states. The dissociation probabilities obtained by quasi-classical trajectories on the potential energy surface reproduced experimental trends, and indicate that vibrational excitations of CO2 significantly promote the dissociation. Using the sudden vector projection model, the behavior of the reactivity is rationalized by couplings with the reaction coordinate at each transition state. These results offer plausible rationalization for the observed enhancement of CO2 dissociation in non-thermal plasmas by metal surfaces.

  15. Quantum modelling of hydrogen chemisorption on graphene and graphite

    International Nuclear Information System (INIS)

    The chemisorption of hydrogen on graphene or graphite is studied within a quantum formalism involving a subsystem coupled to a phonon bath. The subsystem includes the hydrogen atom approaching the surface perpendicularly right on top of a carbon atom which puckers out of the surface. The bath includes the acoustic and optical phonon modes vibrating perpendicularly to the surface. Couplings between subsystem and bath are obtained with a periodic density functional theory calculation. Trapping probabilities are obtained as a function of the hydrogen atom kinetic energy. These results are discussed in the light of the experimental hydrogenation studies performed on graphite by Zecho et al. [J. Chem. Phys. 117, 8486 (2002)] and on graphene by Haberer et al. [Adv. Mater. 23, 4497 (2011)

  16. Chemisorption of CO on particulate deposits of platinum

    Science.gov (United States)

    Doering, D. L.; Poppa, H.; Dickinson, J. T.

    1982-01-01

    Morphology and CO chemisorption properties are studied as a function of particle size for the case of particulate Pt films, vapor-deposited onto ultrahigh vacuum-cleaved and heat-treated mica surfaces at a 200 C substrate temperature. The particles were found to be mostly irregular in shape and randomly-oriented, with two desorption peaks after CO absorption at 60 C: (1) an alpha peak, at 120 C, attributed to smooth particle surfaces, and (2) a beta peak, at about 175 C, attributed to particle edges and steps. Transmission electron microscopy showed that major changes occur in particle morphology during absorption-desorption cycling, so that the decrease in CO desorption flux may be interpreted as due to particle restructuring, rather than contamination by CO decomposition as in the cases of Ni or Pd on mica. Auger electron spectroscopy corroborates the lack of CO decomposition, even for the case of very small Pt particles.

  17. Dissociative chemisorption dynamics of small molecules on metal surfaces

    Institute of Scientific and Technical Information of China (English)

    JIANG Bin; XIE DaiQian

    2014-01-01

    Much progress has been achieved for both experimental and theoretical studies on the dissociative chemisorption of molecules on surfaces.Quantum state-resolved experimental data has provided unprecedented details for these fundamental steps in heterogeneous catalysis,while the quantitative dynamics is still not fully understood in theory.An in-depth understanding of experimental observations relies on accurate dynamical calculations,in which the potential energy surface and adequate quantum mechanical implementation are desired.This article summarizes the current methodologies on the construction of potential energy surfaces and the quantum mechanical treatments,some of which are promising for future applications.The challenges in this field are also addressed.

  18. Diffusion-controlled chemisorption transitions for (La,Sr)MnO3

    International Nuclear Information System (INIS)

    This paper considers the mechanism of oxygen interaction with the surface of oxide electrode materials, such as LSM, and surface related electrical properties. The mechanism involves rapid oxygen chemisorption, resulting in an increase of the surface charge, followed by slow oxygen incorporation, resulting in a shift of chemisorption equilibria and leading, in consequence, to a decrease of the surface charge. The latter process, involving transient chemisorption, is controlled by chemical diffusion. A good agreement between the chemical diffusion coefficient determined from work function and that determined by the manometric method is revealed. Copyright (1998) Australasian Ceramic Society

  19. The dissociative chemisorption of silane on the Si(111)7x7 surface

    International Nuclear Information System (INIS)

    Full text: The study of the interaction of silane with semiconducting substrates is of both fundamental and technological importance. This paper reports theoretical calculations of the initial stages of the dissociative chemisorption of silane on the Si(111)7x7 surface. The calculations have been performed within the periodic slab formalism using the extended Brenner empirical potential. The geometries and energetics of the different chemisorption structures are discussed, and compared with the existing experimental data

  20. Quantum-size effects on chemisorption properties: CO on Cu ultrathin films

    OpenAIRE

    Mouketo, L.; Binggeli, N.; M'Passi-Mabiala, B.

    2011-01-01

    We address, by means of ab-initio calculations, the origin of the correlation that has been observed experimentally between the chemisorption energy of CO on nanoscale Cu(001) supported films and quantum-size effects. The calculated chemisorption energy shows systematic oscillations, as a function of film thickness, with a periodicity corresponding to that of quantum-well states at the surface-Brillouin-zone center crossing the Fermi energy. We explain this trend based on the oscillations, wi...

  1. Molecular N-2 chemisorption-specific adsorption on step defect sites on Pt surfaces

    OpenAIRE

    Tripa, C. Emil; Zubkov, T.S.; Yates, John T.; Mavrikakis, Manos; Nørskov, Jens Kehlet

    1999-01-01

    Infrared reflection-absorption spectroscopy and density functional theory, within the generalized gradient approximation, were used to investigate both experimentally and theoretically N-2 chemisorption on stepped and smooth Pt surfaces. N-2 chemisorption was observed to occur only on the edge atoms of step defect sites in atop configuration by both methods. The calculated vibrational frequency of N-2 chemisorbed on Pt(112) step sites (2244 cm(-1)) is in good agreement with the frequency obse...

  2. Influence of chemisorption products of carbon dioxide and water vapour on radiolysis of tritium breeder

    International Nuclear Information System (INIS)

    Highlights: • Chemisorption products affect formation proceses of radiation-induced defects. • Radiolysis of chemisorption products increase amount of radiation-induced defects. • Irradiation atmosphere influence radiolysis of lithium orthosilicate pebbles. - Abstract: Lithium orthosilicate pebbles with 2.5 wt% excess of silica are the reference tritium breeding material for the European solid breeder test blanket modules. On the surface of the pebbles chemisorption products of carbon dioxide and water vapour (lithium carbonate and hydroxide) may accumulate during the fabrication process. In this study the influence of the chemisorption products on radiolysis of the pebbles was investigated. Using nanosized lithium orthosilicate powders, factors, which can influence the formation and radiolysis of the chemisorption products, were determined and described as well. The formation of radiation-induced defects and radiolysis products was studied with electron spin resonance and the method of chemical scavengers. It was found that the radiolysis of the chemisorption products on the surface of the pebbles can increase the concentration of radiation-induced defects and so could affect the tritium diffusion, retention and the released species

  3. Theoretical study of CO chemisorption on nickel and copper surfaces

    Science.gov (United States)

    Yu, H. L.

    1978-01-01

    A comparative study of the chemisorption of CO on Ni(001) and Cu(001) surfaces has been performed. The study is based on an analysis of the electronic structure of (M)5CO clusters obtained from self-consistent field X alpha scattered-wave calculations. The electron orbital formed principally by the 5 sigma orbital on CO was found to be mainly responsible for the bonding of the CO molecule to the metal surface for both the CO/Ni and CO/Cu systems. The different occupation of the antibonding 7 a sub 1 orbital in the two clusters is believed to be the major reason for the large difference observed in the measured heats of adsorption of CO on Ni and Cu surfaces. It was found also that metal atoms transfer electronic charge to the antibonding pi(asterisk)-like orbital of CO. A possible correlation between the amount of the charge transfered and the relative ease of dissociation of CO molecules on metal surfaces is discussed.

  4. Chemisorption studies of Pt/SnO2 catalysts

    Science.gov (United States)

    Brown, Kenneth G.; Ohorodnik, Susan K.; Vannorman, John D.; Schryer, Jacqueline; Upchurch, Billy T.; Schryer, David R.

    1990-01-01

    The low temperature CO oxidation catalysts that are being developed and tested at NASA-Langley are fairly unique in their ability to efficiently oxidize CO at low temperatures (approx. 303 K). The bulk of the reaction data that has been collected in the laboratory has been determined using plug flow reactors with a low mass of Pt/SnO2/SiO2 catalyst (approx. 0.1 g) and a modest flow rate (5 to 10 sc sm). The researchers have previously characterized the surface solely in terms of N2 BET surface areas. These surface areas have not been that indicative of reaction rate. Indeed, some of the formulations with high BET surface area have yielded lower reaction rates than those with lower BET surface areas. As a result researchers began a program of determining the chemisorption of the various species involved in the reaction; CO, O2 and CO2. Such a determination of will lead to a better understanding of the mechanism and overall kinetics of the reaction. The pulsed-reactor technique, initially described by Freel, is used to determine the amount of a particular molecule that is adsorbed on the catalyst. Since there is some reaction of CO with the surface to produce CO2, the pulsed reactor had to be coupled with a gas chromatograph in order to distinguish between the loss of CO that is due to adsorption by the surface and the loss that is due to reaction with the surface.

  5. DETERMINATION OF THE METAL PARTICLE SIZE OF SUPPORTED Pt, Rh, AND Ir CATALYSTS. A CALIBRATION OF HYDROGEN CHEMISORPTION BY EXAFS

    OpenAIRE

    Zon, van, JBAD Hans; Kip, BJ; Koningsberger, DC Diek; Prins, R Roel

    1986-01-01

    Hydrogen chemisorption measurements of highly dispersed Pt, Rh, and Ir catalysts yielded H/M values exceeding unity. These results cannot be used straightforwardly to determine the average metal particle size, because the H/M stoichiometry on the surface is unknown. EXAFS measurements were performed to determine the metal particle size and thereby, to calibrate the hydrogen chemisorption results. The high hydrogen chemisorption values can be explained best by assuming H/M surface stoichiometr...

  6. An investigation of the kinetics of hydrogen chemisorption on iron metal surfaces

    Science.gov (United States)

    Shanabarger, M. R.

    1982-01-01

    The isothermal kinetics of H2, H2S, and O2 chemisorption onto epitaxially grown (III) oriented Fe films were studied. The measurements were made using the techniques of chemisorption induced resistance change and Auger electron spectroscopy (for adsorbed sulfur and oxygen). Also the origin of the chemisorption induced resistance change for these systems and its applicability to kinetic measurements were established. The chemisorption kinetics were interpreted as dissociative chemisorption via an adsorbed molecular species. The applicable rate constants were established. In none of the studies were the rate constants observed to be coverage dependent. By comparing the temperature dependence of the rate constants with absolute rate theory, the binding energies and activation energies of all the kinetic processes were obtained for the H2/Fe system. The initial sticking coefficient was pressure dependent for both the H2/Fe and H2S/Fe systems. This results from the step between the adsorbed molecular state and the dissociated chemisorbed state being the rate limiting step for absorption at certain pressures and temperatures. Estimates were obtained for the temperature dependence of the rate constants for the O2/Fe system.

  7. Chemisorption-facilitated dislocation emission and motion, and induced nucleation of brittle nanocrack

    Institute of Scientific and Technical Information of China (English)

    宿彦京; 王燕斌; 褚武扬

    1997-01-01

    Using a special TEM constant deflection device, the change in dislocation configuration ahead of a loaded crack tip before and after adsorption of Hg atoms and the initiation of liquid metal-induced nanocracks (LMIC) have been observed. The results show that chemisorption of Hg atoms can facilitate dislocation emission, multiplication and motion. Nanocracks will be initiated in the dislocation-free zone (DFZ) or at the crack tip when chemisorption-facilitated dislocation emission, multiplication and motion reach a critical condition. On the basis of the available experimental evidence concerning liquid metal embnttlement (LME), a new mechanism for this phenomenon is considered. This involves the fact that the decrease in surface energy induced by chemisorption of Hg atoms results in a reduction in the critical stress intensity factors for dislocation emission and the resistance for dislocation motion. On the other hand, the plastic work and KIC will decrease with the decrease in the surface energy.

  8. Chemisorption and Diffusion of H on a Graphene Sheet and Single-Wall Carbon Nanotubes

    Science.gov (United States)

    Srivastava, Deepak; Dzegilenko, Fedor; Menon, Madhu

    2000-01-01

    Recent experiments on hydrogen storage in single wall nanotubes and nanotube bundles have reported large fractional weight of stored molecular hydrogen which are not in agreement with theoretical estimates based of simulation of hydrogen storage by physisorption mechanisms. Hydrogen storage in catalytically doped nanotube bundles indicate that atomic H might undergo chemisorption changing the basic nature of the storage mechanism under investigation by many groups. Using a generalized tight-binding molecular dynamics (GTBMD) method for reactive C-H dynamics, we investigate chemisorption and diffusion of atomic H on graphene sheet and C nanotubes. Effective potential energy surfaces (EPS) for chemisorption and diffusion are calculated for graphene sheet and nanotubes of different curvatures. Analysis of the activation barriers and quantum rate constants, computed via wave-packet dynamics method, will be discussed in this presentation.

  9. Chemisorption of Al and Ga on the GaAs (110) surface

    OpenAIRE

    Swarts, C. A.; Barton, J J; Goddard, W. A.; T. C. Mcgill

    1980-01-01

    We have studied the initial stages of the chemisorption of Al and Ga on the clean GaAs (110) surface by applying quantum chemical methods to small clusters representing Al or Ga on GaAs (110). These calculations suggest that at smallest coverages Al or Ga bind to a surface Ga atom; for higher coverages Al and the surface Ga interchange positions. We have obtained the binding energy, the chemical shifts of the Ga–3d, As–3d and Al–2p states, and the microscopic dipole associated with chemisorpt...

  10. Chemisorption-induced n-doping of MoS{sub 2} by oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Long; Wang, Ying; Wu, Yihong, E-mail: elewuyh@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117583 (Singapore); Shen, Lei, E-mail: shenlei@nus.edu.sg [Engineering Science Program, Faculty of Engineering, National University of Singapore, Singapore, Singapore 117579 (Singapore)

    2016-02-08

    Both chemisorption and physisorption affect the electronic properties of two-dimensional materials, such as MoS{sub 2}, but it remains a challenge to probe their respective roles experimentally. Through repeated in-situ electrical measurements of few-layer MoS{sub 2} field-effect transistors in an ultrahigh vacuum system with well-controlled oxygen partial pressure (6 × 10{sup −8} mbar–3 × 10{sup −7} mbar), we were able to study the effect of chemisorption on surface defects separately from physically adsorbed oxygen molecules. It is found that chemisorption of oxygen results in n-doping in the channel but negligible effect on mobility and on/off ratio of the MoS{sub 2} transistors. These results are in disagreement with the previous reports on p-doping and degradation of the device's performance when both chemisorption and physisorption are present. Through the analysis of adsorption-desorption kinetics and the first-principles calculations of electronic properties, we show that the experimentally observed n-doping effect originates from dissociative adsorption of oxygen at the surface defects of MoS{sub 2}, which lowers the conduction band edge locally and makes the MoS{sub 2} channel more n-type-like as compared to the as-fabricated devices.

  11. Raman and computational study of solvation and chemisorption of thiazole in silver hydrosol.

    Science.gov (United States)

    Muniz-Miranda, Maurizio; Pagliai, Marco; Muniz-Miranda, Francesco; Schettino, Vincenzo

    2011-03-21

    A SERS investigation combined with ab initio computational analysis involving Car-Parrinello molecular dynamics simulations and Density Functional Theory approach allows fundamental information to be obtained on the behaviour of thiazole in silver aqueous suspension where solvation and chemisorption processes competitively occur.

  12. First principles analysis of hydrogen chemisorption on Pd-Re alloyed overlayers and alloyed surfaces

    DEFF Research Database (Denmark)

    Pallassana, Venkataraman; Neurock, Matthew; Hansen, Lars Bruno;

    2000-01-01

    was developed to extend the Hammer-Norskov surface reactivity model [Surf. Sci. 343, 211 (1995)] to the analysis of bimetallic Pd-Re alloyed systems. The hydrogen chemisorption energies are correlated linearly to the surface d-band center, which is weighted appropriately by the d-band coupling matrix elements...

  13. Chemisorption-induced n-doping of MoS2 by oxygen

    Science.gov (United States)

    Qi, Long; Wang, Ying; Shen, Lei; Wu, Yihong

    2016-02-01

    Both chemisorption and physisorption affect the electronic properties of two-dimensional materials, such as MoS2, but it remains a challenge to probe their respective roles experimentally. Through repeated in-situ electrical measurements of few-layer MoS2 field-effect transistors in an ultrahigh vacuum system with well-controlled oxygen partial pressure (6 × 10-8 mbar-3 × 10-7 mbar), we were able to study the effect of chemisorption on surface defects separately from physically adsorbed oxygen molecules. It is found that chemisorption of oxygen results in n-doping in the channel but negligible effect on mobility and on/off ratio of the MoS2 transistors. These results are in disagreement with the previous reports on p-doping and degradation of the device's performance when both chemisorption and physisorption are present. Through the analysis of adsorption-desorption kinetics and the first-principles calculations of electronic properties, we show that the experimentally observed n-doping effect originates from dissociative adsorption of oxygen at the surface defects of MoS2, which lowers the conduction band edge locally and makes the MoS2 channel more n-type-like as compared to the as-fabricated devices.

  14. An investigation of the kinetics for hydrogen chemisorption on iron metal surfaces

    Science.gov (United States)

    Shanabarger, M. R.

    1980-01-01

    A quasi-isothermal approach was used to study the kinetics of hydrogen and hydrogen sulfide chemisorption onto iron film in an effort to understand the environmental degradation of steels. The coverage of chemisorbed hydrogen or chemisorbed sulfur was observed as a function of time for fixed conditions of substrate temperature. Auger electron spectroscopy was used to observe the sulfur and chemisorption-induced resistance change was employed to monitor hydrogen coverage. To compare the results obtained from studying the kinetics by two different techniques, the kinetics of oxygen chemisorption onto iron films was also studied. A reaction model utilized to interpret the H2/Fe2 chemisorption kinetics was applied to data from an earlier study on the desorption kinetics for H2 chemisorbed onto nicket films in the vicinity of the Curie temperature of the film. This analysis permitted a separation of the gross desorption process into individual components so that the influence of the magnetic phase transition on the rate constants could be determined.

  15. Chemisorption-induced n-doping of MoS2 by oxygen

    International Nuclear Information System (INIS)

    Both chemisorption and physisorption affect the electronic properties of two-dimensional materials, such as MoS2, but it remains a challenge to probe their respective roles experimentally. Through repeated in-situ electrical measurements of few-layer MoS2 field-effect transistors in an ultrahigh vacuum system with well-controlled oxygen partial pressure (6 × 10−8 mbar–3 × 10−7 mbar), we were able to study the effect of chemisorption on surface defects separately from physically adsorbed oxygen molecules. It is found that chemisorption of oxygen results in n-doping in the channel but negligible effect on mobility and on/off ratio of the MoS2 transistors. These results are in disagreement with the previous reports on p-doping and degradation of the device's performance when both chemisorption and physisorption are present. Through the analysis of adsorption-desorption kinetics and the first-principles calculations of electronic properties, we show that the experimentally observed n-doping effect originates from dissociative adsorption of oxygen at the surface defects of MoS2, which lowers the conduction band edge locally and makes the MoS2 channel more n-type-like as compared to the as-fabricated devices

  16. CHEMISORPTIONS OF ATOMIC OXYGEN AND ITS REPLACEMENT BY HYDROGEN ON THE DIAMOND (100) SURFACE STUDIED BY FIRST PRINCIPLES

    OpenAIRE

    Wang, Z. G.; X. T. ZU; J. L. NIE; H. Y. XIAO

    2006-01-01

    The initial oxidation process of a clean diamond (100) surface was studied by first-principles calculations. The O-bridge with C–O–C bond chemisorption, O-on-dimer chemisorption with epoxy structure, and O-on-top chemisorption with C=O bond structure are found to be stable on the diamond (100) surfaces. The epoxy structure is more stable than the O-bridge structure. The calculation also shows that the oxygen atom can be replaced by hydrogen in the oxidized diamond (100) surface.

  17. DFT-GGA errors in NO chemisorption energies on (111) transition metal surfaces: Possible origins and correction schemes

    OpenAIRE

    Huang, Xu; Mason, Sara E.

    2013-01-01

    Here we investigate whether well-known DFT-GGA errors in predicting the chemisorption energy ($E_{\\rm chem}$) of CO on transition metal surfaces manifest in analogous NO chemisorption systems. To verify the occurrence of DFT-GGA overestimation of the back-donation mechanism in NO Chemisorption, we use electronic structure analysis to show that the partially filled molecular NO 2$\\pi^{*}$ orbital rehybridizes with the transition metal $d$-band to form new bonding and anti-bonding states. We re...

  18. HCl chemisorption-induced drastic magneto-structural transformation in a layered cobalt-phosphonotriazolate coordination polymer.

    Science.gov (United States)

    Zhang, Weiquan; Wang, Dianpeng; Zhu, Lin; Zhai, Fupeng; Weng, Linhong; Sun, Jinyu; Ling, Yun; Chen, Zhenxia; Zhou, Yaming

    2016-07-14

    The chemisorption of gaseous HCl molecules in a two-dimensional coordination polymer results in subtle changes in its structure and instigates a drastic modification from antiferro- to ferromagnetic properties. PMID:27294584

  19. The effect of CO chemisorption on the metal surface CO/Ni(100)

    Science.gov (United States)

    Bauschlicher, Charles, W., jr.; Nelin, Constance J.

    1986-01-01

    The chemisorption of CO on Ni(100) is studied with a cluster model. The calculations suggest that chemisorption changes the nature of the Ni 3d orbitals. The open shell Ni 3d accepts charge from the Ni valence 4s4p orbitals, reducing the open shell 3d character on the Ni. The closed shell Ni 3d orbitals also mix with the Ni valence 4s4p orbitals and donate charge to the CO; thus helping to maintain the Ni 3d population near 9. These changes should affect the density of 3d states near the Fermi level and the surface magnetic moment. The variation in the bonding with the size of cluster is also discussed.

  20. CHEMISORPTION OF CO AND METHANATION ON Rh SURFACES AT LOW TEMPERATURE AND LOW PRESSURE, AN ATOM-PROBE FIM STUDY

    OpenAIRE

    W. Liu; Ren, D.; Bao, C.; Tsong, T.

    1987-01-01

    Pulsed-laser imaging atom-probe and high resolution voltage pulsed atom-probe were employed to study the chemisorption behavior of CO on rhodium surfaces at low temperature and low pressure. The results are consistent and interesting. Our results support dissociative chemisorption on stepped surfaces of Rh and the effect of the surface structures. We also carried out methanation on Rh surfaces under adverse conditions and identified the intermediates of methanation with an isotope exchange te...

  1. A molecular-beam study of the dissociative chemisorption of O2 on Ir(110)-(1×2)

    OpenAIRE

    Mullins, C B; Wang, Y.; Weinberg, W. H.

    1989-01-01

    The zero-coverage probability of dissociative chemisorption of O2 on Ir(110)-(1×2) has been measured using molecular-beam techniques for a wide range of incident kinetic energies, incident angles, and surface temperatures. The data indicate that a trapping-mediated mechanism is responsible for dissociative chemisorption at low energies, whereas at high energies a direct mechanism accounts for dissociative adsorption. Total energy scaling approximately describes the dissociative dynamics on th...

  2. Nanoparticle chemisorption printing technique for conductive silver patterning with submicron resolution

    OpenAIRE

    Yamada, Toshikazu; Fukuhara, Katsuo; Matsuoka, Ken; Minemawari, Hiromi; Tsutsumi, Jun'ya; Fukuda, Nobuko; Aoshima, Keisuke; Arai, Shunto; Makita, Yuichi; Kubo, Hitoshi; Enomoto, Takao; Togashi, Takanari; Kurihara, Masato; Hasegawa, Tatsuo

    2016-01-01

    Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of we...

  3. Nitrogen Chemisorption on alpha-Fe Nanoparticles studied by In situ Mossbauer Sepctroscopy

    DEFF Research Database (Denmark)

    Bødker, Franz; Chorkendorff, Ib; Mørup, Steen

    1997-01-01

    Carbon-supported metallic iron nanoparticles with an average diameter of 2.3 nm were studied by in situ Mossbauer spectroscopy at temperatures down to 5 K and with applied magnetic field up to 4 T. Nitrogen chemisorption at 300, 600 and 700 K on the iron particles was found only to affect the iron...... atoms in the surface layers, resulting in surface iron atoms bonded to nitrogen in a number of different types of environments....

  4. EXCHANGE-SPLITTING OF ADSORBATE-INDUCED BANDS IN CHEMISORPTION ON FERROMAGNETIC 3d-METALS

    OpenAIRE

    Schönhense, G.; Getzlaff, M.; Westphal, C; Heidemann, B.; Bansmann, J.

    1988-01-01

    The influence of the ferromagnetism of 3d-metal substrates upon the electronic states of "nonmagnetic" adsorbate overlayers like oxygen and sulphur has been investigated by means of photoelectron spinpolarization spectroscopy. The spectra reveal a substantial exchange splitting of the O 2p- and S 3p-derived bands in chemisorption on Fe and FeCo. This demonstrates the strong magnetic coupling of these species with the substrate.

  5. Chemisorption of atomic and molecular oxygen on Au and Ag cluster anions : discrimination of different isomers

    OpenAIRE

    Kim, Young Dok; Ganteför, Gerd; Sun, Qiang; Jena, Purusottam

    2004-01-01

    Structures of coinage metal clusters reacted with atomic and molecular oxygen were studied using Ultraviolet Photoelectron Spectroscopy and Density Functional Theory calculations. We show that O2 partially dissociates on Ag-2, and this dissociative chemisorption is a kinetically hindered step. For Au4O-2, in addition to the previously observed molecularly adsorbed oxygen, we are now able to synthesize a second isomer using atomic oxygen reagents, in which oxygen adsorbs dissociatively. We dem...

  6. Evolution of ConAl clusters and chemisorption of hydrogen on ConAl clusters

    International Nuclear Information System (INIS)

    The growth behavior of ConAl (n = 1–15) and the chemisorptions of hydrogen on the ground state geometries have been studied using the density functional theory (DFT) within the generalized gradient approximation (GGA). The growth pattern for ConAl is Al-substituted Con+1 clusters, and it keeps the similar frameworks of the most stable Con+1 clusters except for n = 2, 3, and 6. The Al atom substitutes the surface atom of the Con+1 clusters for n ≤ 13. Starting from n = 14, the Al atom completely falls into the center of the Co-frame. The dissociation energy, the second-order energy differences, and the HOMO–LUMO gaps indicate that the magic numbers of the calculated ConAl clusters are 7, 9, and 13, corresponding to the high symmetrical structures. To my knowledge, this is the first time that a systematic study of chemisorption of hydrogen on cobalt aluminum clusters. The twofold bridge site is identified to be the most favorable chemisorptions site for one hydrogen adsorption on ConAl (n = 1–6, 8, 10), and two hydrogen adsorption on ConAl (n = 1–7), while threefold hollow site is preferred for one hydrogen adsorption on ConAl (n = 7, 9, 11–15) and two hydrogen adsorption on ConAl (n = 8–10, 12–15) clusters. The ground state structure of two hydrogen adsorption on Co11Al is exceptional. In general, the binding energy of both H and 2H of ConAl (n = 1–12) is found to increase with the cluster size. And the result shows that large binding energies of the hydrogen atoms and large fragmentation energies for Co11AlH and Co12AlH make these species behaving like magic clusters.

  7. Isotope effects in trapping-mediated chemisorption of ethane and propane on Ir(110)

    International Nuclear Information System (INIS)

    We compare here recent results of molecular beam investigations of the initial probability of trapping-mediated C endash H and C endash D bond cleavage of C2H6, C2D6, C3H8, and C3D8 on Ir(110) at low beam translational energy and surface temperatures, TS, from 85 to 800 K. Each of these systems is highly reactive at low TS and displays decreasing reactivity with increasing TS. Measurements of the initial probability of trapping-mediated chemisorption for both ethane and propane reveal an isotope effect, which we attribute to zero-point energy differences, with the perhydrido-species exhibiting greater reactivity at a given TS. A difference in activation energies for desorption vs reaction (C endash D bond cleavage) for C2D6 has been found to be Ed endash Er=1.8±0.3 kcal/mol, cf. Ed endash Er=2.2 kcal/mol for C endash H bond cleavage of C2H6. For the trapping-mediated dissociative chemisorption of propane on Ir(110), Ed endash Er=4.2 kcal/mol for C endash H bond cleavage of C3H8, and Ed endash Er=3.2 kcal/mol for C endash D bond cleavage of C3D8. A quantitative analysis of the initial probability of trapping-mediated dissociative chemisorption of ethane and propane on Ir(110), within the context of a classical kinetic model of barrier crossing from the physically adsorbed state to the dissociatively chemisorbed state, provides the most reasonable description of the observed adsorption behavior. copyright 1996 American Institute of Physics

  8. Ca chemisorption on Cu(100) in the submonolayer regime: Metastable and stable adsorption phases

    OpenAIRE

    Rudolf, P.; Astaldi, C.; Bianco, A.; Modesti, S.

    1993-01-01

    Ca adsorption on Cu(100) has been studied by high-resolution electron energy-loss spectroscopy, work-function measurements, and low-energy electron diffraction as a function of coverage, up to one monolayer, at 110 and 300 K. At each coverage a condensed phase is formed at 110 K that irreversibly transforms into a dispersed phase upon heating. The 300-K data suggest that Ca occupies substitutional sites at this temperature. A comparison with the chemisorption of alkali metals is presented.

  9. Molecular cluster theory of CO chemisorption on a nickel /100/ surface

    Science.gov (United States)

    Ellis, D. E.; Baerends, E. J.; Adachi, H.; Averill, F. W.

    1977-01-01

    Self-consistent Hartree-Fock-Slater molecular cluster models for the chemisorption of carbon monoxide on a (100) transition metal surface are presented. Energy levels and charge distribution for the CO:Ni5 cluster in C sub 4v symmetry are obtained, and the variation of binding energies with height of the CO molecule above the surface of nickel is studied in detail. Comparison is made with experimental binding energy spectra and with the multiple-scattering results of Batra and Bagus. The redistribution in energy of free-atom valence levels is studied by means of local-densities-of-states diagrams.

  10. Molecular cluster theory for chemisorption of first row atoms on nickel /100/ surfaces

    Science.gov (United States)

    Ellis, D. E.; Adachi, H.; Averill, F. W.

    1976-01-01

    Self-consistent Hartree-Fock-Slater molecular cluster models for the chemisorption of first-row atoms on Ni(100) surfaces are presented. Energy levels and ground-state charge distributions are given for XNi5 clusters with the adatom X = H, C, N, O located in C4V symmetry at a fixed height of 2.0 au above the surface. The variation of properties with height was studied in detail for the case of oxygen. Theoretical results compare rather well with experimental photoelectron and energy-loss data. Local-densities-of-states diagrams are used to clarify the interaction between adsorbate levels and metal conduction bands.

  11. Tunneling electron induced chemisorption of copper phthalocyanine molecules on the Cu(111) surface

    International Nuclear Information System (INIS)

    The adsorption of up to one monolayer (ML) of copper phthalocyanine (CuPc) molecules on a room temperature Cu(111) surface has been studied using scanning tunneling microscopy (STM). Below 1 ML the molecules are in a fluid state and are highly mobile on the surface. At 1 ML coverage the molecules coalesce into a highly ordered 2D crystal phase. At sub-ML coverages, chemisorption of individual CuPc molecules can be induced through exposure to tunneling electrons at a tunneling bias voltage exceeding a threshold value. This tunneling electron induced effect has been exploited to perform molecular STM lithography

  12. Recognizing Physisorption and Chemisorption in Carbon Nanotubes Gas Sensors by Double Exponential Fitting of the Response.

    Science.gov (United States)

    Calvi, Andrea; Ferrari, Alberto; Sbuelz, Luca; Goldoni, Andrea; Modesti, Silvio

    2016-01-01

    Multi-walled carbon nanotubes (CNTs) have been grown in situ on a SiO 2 substrate and used as gas sensors. For this purpose, the voltage response of the CNTs as a function of time has been used to detect H 2 and CO 2 at various concentrations by supplying a constant current to the system. The analysis of both adsorptions and desorptions curves has revealed two different exponential behaviours for each curve. The study of the characteristic times, obtained from the fitting of the data, has allowed us to identify separately chemisorption and physisorption processes on the CNTs. PMID:27213387

  13. Absorption and Chemisorption of Small Levitated Single Bubbles in Aqueous Solutions

    OpenAIRE

    Alexander Tollkötter; Norbert Kockmann

    2014-01-01

    The absorption and chemisorption of small bubbles with N2 or CO2 were investigated experimentally in aqueous and alkaline solutions. Different bubble sizes were studied ranging from 0.1 to 2.5 mm in alkaline concentrations of 0.1 mM to 1 M NaOH. The experiments were conducted in a device consisting of a converging microchannel with a down flowing liquid. Levitation positions of single bubbles were optically characterized. A correlation was developed for the drag force coefficient, CD, includi...

  14. Chemisorption of hydrogen and oxygen atoms on a cobalt surface: A quantum chemical cluster model study

    International Nuclear Information System (INIS)

    The chemisorption of atomic hydrogen and oxygen on a cobalt surface has been studied on a five-atom cluster model using one-electron effective core potential (le- ECP) and all-electron calculations at the ab initio SCF and MCPF levels. Also, density functional calculations have been carried out. The different approaches are evaluated. The le- ECP has been compared to similar ECPS for nickel and copper. Our results indicate that this approach is valid also for cobalt. Different contributions to the cluster-adsorbate bonding energy are discussed. 31 refs., 1 fig., 1 tab

  15. Characteristics of synthesis and morphology of globular filtration-chemisorption membranes

    International Nuclear Information System (INIS)

    Conditions of synthesis, morphology and sorption properties towards iodine of globular filtration-chemisorption membranes produced by means of fast photo-induced copolymerization of compositions containing bifunctional cross-linker, vinylamide monomer and organic solvent are studied. Kinetic studied on iodine sorption, when aqueous solution containing 0.2 g of I2 and 8 g of KI in 200 ml of water is passed through the membrane permitted ascertaining that the adsorption complex consisted of two statistic segments of polyvinylamide and I3- ion

  16. Recognizing Physisorption and Chemisorption in Carbon Nanotubes Gas Sensors by Double Exponential Fitting of the Response

    Directory of Open Access Journals (Sweden)

    Andrea Calvi

    2016-05-01

    Full Text Available Multi-walled carbon nanotubes (CNTs have been grown in situ on a SiO 2 substrate and used as gas sensors. For this purpose, the voltage response of the CNTs as a function of time has been used to detect H 2 and CO 2 at various concentrations by supplying a constant current to the system. The analysis of both adsorptions and desorptions curves has revealed two different exponential behaviours for each curve. The study of the characteristic times, obtained from the fitting of the data, has allowed us to identify separately chemisorption and physisorption processes on the CNTs.

  17. Chemisorption and catalytic reactivity of cobalt and sulfur monolayers on ordered molybdenum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Knight, C.C.

    1992-03-01

    Complex Co/Mo sulfide catalysts are modelled by the chemisorption of layers on Mo single crystal surfaces. Growth and structure of overlayers on flat, stepped and kinked surfaces were investigated. Growth of Co overlayers on clean and S covered Mo surfaces was studied using AES and CO chemisorption; results reveal that Co grows as a flat monolayer on clean Mo surfaces. Co multilayers then form 3-D islands. When Co is deposited on S covered surfaces, the S overlayer migrates to the top; this topmost overlayer reduces CO adsorption capacity. While growth mode of Co overlayers are similar on flat and stepped surfaces, the number and type of ordered Co and S structures on flat and stepped surfaces are different. In the case of Co, an ordered (3 {times} 1) structure is formed on Mo(910) and (28,4,1) surfaces; this structure does not develop on clean (100) surface. Only one of two possible (3 {times} 1) Co domains are formed on Mo(910) and Mo(28,4,1) surfaces. These domains have one side of (3 {times} 1) unit cell parallel to the step edges, suggesting that Co adsorbs at the step edges. The (3 {times} 1) structure does not form on Mo(911) surface, indicating that step orientation can restrict formation of ordered overlayers. For chemisorbed S, only a subset of ordered overlayers on flat (100) surface nucleate on (910) and (911) and (28,4,1) surfaces. Ordered S overlayers also form domains that maximize the number of sulfur-step atom bonds. The adsorption and ordering of S overlayers on stepped and kinked Mo surfaces lead to doubling of step height and terrace width. Thiophene hydrodesulfurization (HDS) reactions were performed over Mo crystal surfaces modified by chemisorption of S, Co, C, and S + Co. The stepped and kinked Mo surfaces have reactivities greater than low Miller index (100) surface. Chemisorption of adsorbates decreased the thiophene HDS reactivity. Deposition of Co on Mo single crystal surfaces did not lead to increased HDS activity.

  18. The mechanism of chemisorption of hydrogen atom on graphene: Insights from the reaction force and reaction electronic flux

    International Nuclear Information System (INIS)

    At the PBE-D3/cc-pVDZ level of theory, the hydrogen chemisorption on graphene was analyzed using the reaction force and reaction electronic flux (REF) theories in combination with electron population analysis. It was found that chemisorption energy barrier is mainly dominated by structural work (∼73%) associated to the substrate reconstruction whereas the electronic work is the greatest contribution of the reverse energy barrier (∼67%) in the desorption process. Moreover, REF shows that hydrogen chemisorption is driven by charge transfer processes through four electronic events taking place as H approaches the adsorbent surface: (a) intramolecular charge transfer in the adsorbent surface; (b) surface reconstruction; (c) substrate magnetization and adsorbent carbon atom develops a sp3 hybridization to form the σC-H bond; and (d) spontaneous intermolecular charge transfer to reach the final chemisorbed state

  19. The mechanism of chemisorption of hydrogen atom on graphene: Insights from the reaction force and reaction electronic flux

    Energy Technology Data Exchange (ETDEWEB)

    Cortés-Arriagada, Diego, E-mail: dcortesr@uc.cl; Gutiérrez-Oliva, Soledad; Herrera, Bárbara; Soto, Karla; Toro-Labbé, Alejandro [Nucleus Millennium Chemical Processes and Catalysis, Laboratorio de Química Teórica Computacional (QTC), Departamento de Química-Física, Facultad de Química, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago (Chile)

    2014-10-07

    At the PBE-D3/cc-pVDZ level of theory, the hydrogen chemisorption on graphene was analyzed using the reaction force and reaction electronic flux (REF) theories in combination with electron population analysis. It was found that chemisorption energy barrier is mainly dominated by structural work (∼73%) associated to the substrate reconstruction whereas the electronic work is the greatest contribution of the reverse energy barrier (∼67%) in the desorption process. Moreover, REF shows that hydrogen chemisorption is driven by charge transfer processes through four electronic events taking place as H approaches the adsorbent surface: (a) intramolecular charge transfer in the adsorbent surface; (b) surface reconstruction; (c) substrate magnetization and adsorbent carbon atom develops a sp{sup 3} hybridization to form the σC-H bond; and (d) spontaneous intermolecular charge transfer to reach the final chemisorbed state.

  20. Quantum dynamics of polyatomic dissociative chemisorption on transition metal surfaces: mode specificity and bond selectivity.

    Science.gov (United States)

    Jiang, Bin; Yang, Minghui; Xie, Daiqian; Guo, Hua

    2016-06-27

    Dissociative chemisorption is the initial and often rate-limiting step in many heterogeneous processes. As a result, an in-depth understanding of the reaction dynamics of such processes is of great importance for the establishment of a predictive model of heterogeneous catalysis. Overwhelming experimental evidence has suggested that these processes have a non-statistical nature and excitations in various reactant modes have a significant impact on reactivity. A comprehensive characterization of the reaction dynamics requires a quantum mechanical treatment on a global potential energy surface. In this review, we summarize recent progress in constructing high-dimensional potential energy surfaces for polyatomic molecules interacting with transition metal surfaces based on the plane-wave density functional theory and in quantum dynamical studies of dissociative chemisorption on these potential energy surfaces. A special focus is placed on the mode specificity and bond selectivity in these gas-surface collisional processes, and their rationalization in terms of the recently proposed Sudden Vector Projection model. PMID:26100606

  1. Electron-hole pair effects in methane dissociative chemisorption on Ni(111)

    Science.gov (United States)

    Luo, Xuan; Jiang, Bin; Juaristi, J. Iñaki; Alducin, Maite; Guo, Hua

    2016-07-01

    The dissociative chemisorption of methane on metal surfaces has attracted much attention in recent years as a prototype of gas-surface reactions in understanding the mode specific and bond selective chemistry. In this work, we systematically investigate the influence of electron-hole pair excitations on the dissociative chemisorption of CH4/CH3D/CHD3 on Ni(111). The energy dissipation induced by surface electron-hole pair excitations is modeled as a friction force introduced in the generalized Langevin equation, in which the independent atomic friction coefficients are determined within the local-density friction approximation. Quasi-classical trajectory calculations for CH4/CH3D/CHD3 have been carried out on a recently developed twelve-dimensional potential energy surface. Comparing the dissociation probabilities obtained with and without friction, our results clearly indicate that the electron-hole pair effects are generally small, both on absolute reactivity of each vibrational state and on the mode specificity and bond selectivity. Given similar observations in both water and methane dissociation processes, we conclude that electron-hole pair excitations would not play an important role as long as the reaction is direct and the interaction time between the molecule and metal electrons is relatively short.

  2. Particle size effect for cobalt Fischer-Tropsch catalysts based on in situ CO chemisorption

    Science.gov (United States)

    Yang, Jia; Frøseth, Vidar; Chen, De; Holmen, Anders

    2016-06-01

    The cobalt particle size effect on activity and selectivity for CO hydrogenation was revisited on cobalt catalysts supported on a large variety of supports at 483 K, 1.85 bar, and H2/CO/Ar = 15/1.5/33.5 Nml/min. The size dependence of the activity and selectivity was analyzed in terms of site coverage and rate constants based on SSITKA experimental results. It was found that the Co particle size index estimated by the conventional method, namely, ex situ hydrogen chemisorption, could not correlate well the activity and selectivity as a function of the particle size index. The same holds for the site coverage of CO and intermediates leading to methane formation. However, the cobalt particle size index based on in situ CO chemisorption measured at 373 K provides a good correlation for turnover frequencies (TOFs) at reaction conditions. It was observed that TOF for CO conversion (TOFCO) increased with increasing particle size index of cobalt and SSITKA experiments showed that this was possibly due to increased site coverage of CO. The TOF for methane formation (TOFCH4) increased with particle size and remained constant at higher particle sizes possibly due to combined effect from the site coverage of intermediates leading to methane (θCHx) and the pseudo-first-order rate constant (kt). The results suggest that the support can play an important role for the size dependence of the activity and selectivity of CO hydrogenation on Co catalysts.

  3. Chemisorption of group-III metals on the Si(111) and Ge(111) surfaces: An ab initio study

    OpenAIRE

    Ricart, J M; Rubio Martínez, Jaime; Illas i Riera, Francesc

    1990-01-01

    Chemisorption of group-III metal adatoms on Si(111) and Ge(111) has been studied through the ab initio Hartree-Fock method including nonempirical pseudopotentials and using cluster models to simulate the surface. Three different high-symmetry sites (atop, eclipsed, and open) have been considered by using X4H9, X4H7, and X6H9 (X=Si,Ge) cluster models. In a first step, ideal surface geometries have been used. Metal-induced reconstruction upon chemisorption has also been taken into account. Equi...

  4. Impact-induced chemisorption of C2H2 on diamond(0 0 1) surfaces: a molecular dynamics simulation

    International Nuclear Information System (INIS)

    This paper reports some new observations in studying the interaction between hyperthermal C2H2 and diamond (0 0 1)-2x1 surface at room temperature by means of molecular dynamics simulations with the many-body hydrocarbon potential. Six types of chemisorption configurations have been observed, some of these are reported for the first time. Also, we have observed threshold effect and hydrogen atom dissociation in the chemisorption processes. All these facts are expected to be useful in setting experimental condition in diamond synthesis

  5. Decrease in the tension at the electrode-solution interface caused by a chemisorption interaction between solvent and metal

    International Nuclear Information System (INIS)

    On the basis of experimental data the values of decrease in liquid electrode interface tension in the maximum of electric capillary curve stemming from chemisorption interaction between water molecules and electrodes made of In-Ga and Cd-Ga alloys in reference to mercury electrode, were determined. The values obtained, equal to 0.59 and 0.65 μJ/cm2 respectively, are energy characteristic of a metal hydrophility. It is shown that chemisorption interaction of water molecules with In, Cd and Ga can not actually effect the composition of the surface layer in the above-mentioned alloys

  6. Chemisorption interaction between solvents and the gallium subgroup metals: a relationship with the ionization potential of the solvent molecules

    International Nuclear Information System (INIS)

    Experimental data characterizing chemisorption metal-solvent interaction on Ga-, (In-Ga)-, (Tl-Ga) - and Hg - electrodes in various solvents have been considered from the viewpoint of quantum-chemical notions of chemical bond formation. It is shown that there is a correlation between parameters characterizing chemisorption metal-solvent interaction on the electrodes and the change in the value of the first adiabatic ionization potential of the solvent molecule, as well as the change in electron energy on the metal Fermi level

  7. Molecular Adsorption Changes the Quantum Structure of Oxide-Supported Gold Nanoparticles: Chemisorption versus Physisorption.

    Science.gov (United States)

    Stiehler, Christian; Calaza, Florencia; Schneider, Wolf-Dieter; Nilius, Niklas; Freund, Hans-Joachim

    2015-07-17

    STM conductance spectroscopy and mapping has been used to analyze the impact of molecular adsorption on the quantized electronic structure of individual metal nanoparticles. For this purpose, isophorone and CO2, as prototype molecules for physisorptive and chemisorptive binding, were dosed onto monolayer Au islands grown on MgO thin films. The molecules attach exclusively to the metal-oxide boundary, while the interior of the islands remains pristine. The Au quantum well states are perturbed due to the adsorption process and increase their mutual energy spacing in the CO2 case but move together in isophorone-covered islands. The shifts disclose the nature of the molecule-Au interaction, which relies on electron exchange for the CO2 ligands but on dispersive forces for the organic species. Our experiments reveal how molecular adsorption affects individual quantum systems, a topic of utmost relevance for heterogeneous catalysis. PMID:26230817

  8. Absorption and Chemisorption of Small Levitated Single Bubbles in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Alexander Tollkötter

    2014-02-01

    Full Text Available The absorption and chemisorption of small bubbles with N2 or CO2 were investigated experimentally in aqueous and alkaline solutions. Different bubble sizes were studied ranging from 0.1 to 2.5 mm in alkaline concentrations of 0.1 mM to 1 M NaOH. The experiments were conducted in a device consisting of a converging microchannel with a down flowing liquid. Levitation positions of single bubbles were optically characterized. A correlation was developed for the drag force coefficient, CD, including wall effects based on the force equilibrium. A linear decrease of bubble diameters was identified with and without chemical reaction, which is referred to as a rigid bubble surface area. Measured Sherwood numbers agree well with the literature values for the investigated Reynolds number range.

  9. Nanoparticle chemisorption printing technique for conductive silver patterning with submicron resolution

    Science.gov (United States)

    Yamada, Toshikazu; Fukuhara, Katsuo; Matsuoka, Ken; Minemawari, Hiromi; Tsutsumi, Jun'ya; Fukuda, Nobuko; Aoshima, Keisuke; Arai, Shunto; Makita, Yuichi; Kubo, Hitoshi; Enomoto, Takao; Togashi, Takanari; Kurihara, Masato; Hasegawa, Tatsuo

    2016-04-01

    Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine-carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing.

  10. A tight-binding model of CO chemisorption on Pd/Ta(110) and similar systems

    International Nuclear Information System (INIS)

    Chemisorption of an isolated CO molecule at various adsorption sites above the epitaxial Pd overlayer on Ta(110), and on related systems, is studied by using a self-consistent tight-binding scheme. Basic assumptions of the model are discussed in detail. The σ donation and especially the π backdonation are generally a good deal reduced at the bimetallic surface as compared with the pure Pd(111) surface. Simultaneously, the bond between CO and the surface becomes weaker. However, for CO in the atop position the effect is considerably smaller than for sites with twofold or threefold coordination and the atop site can therefore become preferred. A simple bonding picture explaining the gross trends is suggested. Core-level shifts induced in surface atoms by the adsorption are briefly discussed. (authors)

  11. Quantum dynamics of water dissociative chemisorption on rigid Ni(111): An approximate nine-dimensional treatment

    Science.gov (United States)

    Jiang, Bin; Song, Hongwei; Yang, Minghui; Guo, Hua

    2016-04-01

    The quantum dynamics of water dissociative chemisorption on the rigid Ni(111) surface is investigated using a recently developed nine-dimensional potential energy surface. The quantum dynamical model includes explicitly seven degrees of freedom of D2O at fixed surface sites, and the final results were obtained with a site-averaging model. The mode specificity in the site-specific results is reported and analyzed. Finally, the approximate sticking probabilities for various vibrationally excited states of D2O are obtained considering surface lattice effects and formally all nine degrees of freedom. The comparison with experiment reveals the inaccuracy of the density functional theory and suggests the need to improve the potential energy surface.

  12. First-principles electronic functionalization of silicene and germanene by adatom chemisorption

    International Nuclear Information System (INIS)

    This study presents first-principles results on the electronic functionalization of silicene and germanene monolayers by means of chemisorption of adatom species H, Li, F, Sc, Ti, V. Three general adatom-monolayer configurations are considered, each having its distinct effect on the electronic structure, yielding metallic or semiconducting dispersions depending on the adatom species and configuration. The induced bandgap is a (in)direct Γ gap ranging from 0.2 to 2.3 eV for both silicene and germanene. In general the alternating configuration was found to be the most energetically stable. The boatlike and chairlike conformers are degenerate with the former having anisotropic effective carrier masses. The top configuration leads to the planar monolayer and predominately to a gapped dispersion. The hollow configuration with V adatoms retains the Dirac cone, but with strong orbital planar hybridization at the Fermi level. We also observe a planar surface state the Fermi level for the latter systems.

  13. Electrocatalytic conversion of products of chemisorption of simple iodoaromatic molecules on smooth platinum

    International Nuclear Information System (INIS)

    The role of iodine atom in electrocatalytic transformations of iodinated aromatic hydrocarbons, as well as the reasons of catalytic activity of hyper valent of iodinated aromatic hydrocarbons in various oxidizing processes were investigated. The curves of electrooxidation of the resulting chemisorption products in the C6H5I and C6H5IO solutions of the different concentration are presented. The oxidation product of C6H5IO is reduced easiest, than the oxidation product of C6H5I. It is noted that the reduction of the chemisorbed products of C6H5I is not available in the 0 - 0.4 V range of potentials. In the similar experiments with C6H5OI changing nature of the previously chemisorbed product occurs. It is proposed that break of the C-I bond is possible during the adsorption of C6H5IO

  14. Nanoparticle chemisorption printing technique for conductive silver patterning with submicron resolution

    Science.gov (United States)

    Yamada, Toshikazu; Fukuhara, Katsuo; Matsuoka, Ken; Minemawari, Hiromi; Tsutsumi, Jun'ya; Fukuda, Nobuko; Aoshima, Keisuke; Arai, Shunto; Makita, Yuichi; Kubo, Hitoshi; Enomoto, Takao; Togashi, Takanari; Kurihara, Masato; Hasegawa, Tatsuo

    2016-01-01

    Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine–carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing. PMID:27091238

  15. Chemisorption of NO on Pt-decorated graphene as modified nanostructure media: A first principles study

    Science.gov (United States)

    Rad, Ali Shokuhi; Abedini, Ehsan

    2016-01-01

    We used density functional theory calculations (DFT) to search the potential of pristine as well as Pt-decorated graphene sheets as adsorbent/gas sensors for NO by considering the electronic properties of NO on these two surfaces. We found much higher adsorption energy, higher charge transfer, lower connecting distance, and higher orbital hybridizing of NO gas molecule on Pt-decorated graphene than pristine graphene. We used orbital analysis including density of states as well as frontier molecular orbital study for NO-surface systems because of more understanding of the kind of interaction. Our results reveal physisorption of NO on pristine graphene with adsorption energy of -24 kJ mol-1while in contrast much higher adsorption energy of -199 kJ mol-1 is achieved upon adsorption of NO on Pt-decorated graphene which is in the range of chemisorption.

  16. Direct dissociative chemisorption of alkanes on Pt(111): Influence of molecular complexity

    International Nuclear Information System (INIS)

    The direct dissociative chemisorption of ethane, propane, n-butane, isobutane, and neopentane on Pt(111) was investigated as a function of the initial translational energy, ET, polar angle of incidence, θi, initial vibrational temperature, and surface temperature using supersonic molecular beam techniques. For each alkane, the initial probability for direct dissociative chemisorption scales with the initial normal energy of the alkanes, En=ET cos2 θi, and is independent of both the surface temperature and initial vibrational energy of the alkanes under the experimental conditions employed. Above initial normal energies of approximately 125 kJ/mol, at constant En, the dissociation probability decreases with increasing chain length of the C2-C4 linear alkanes; however, the dissociation probability of neopentane is greater than that of isobutane, and both isobutane and neopentane are more reactive than n-butane. By assuming that cleavage of primary C-H bonds is the dominant reaction pathway for all of the alkanes investigated here, the trends in reactivity are best explained by considering the differences in the steric factors for primary C-H bond cleavage for these alkanes. Secondary C-H bond cleavage does appear to contribute to the reactivity of propane and n-butane but only at the highest energies examined. Additionally, the reaction probabilities of each of these alkanes were estimated using a statistical model recently proposed by Ukrainstev and Harrison [J. Chem. Phys. 101, 1564 (1994)]. Assuming cleavage of only primary C-H bonds, the trends in reactivity for ethane, propane, n-butane, and isobutane were qualitatively reproduced by the statistical model; however, except for ethane, which was used to obtain the necessary parameters for the theory, there was poor quantitative agreement, and the predictions for neopentane were significantly lower than the measured values. The model also predicts that the dissociation probability is enhanced by increasing the

  17. Effect of particle size on the chemisorption and decomposition of carbon monoxide by palladium and nickel clusters

    Science.gov (United States)

    Doering, D. L.; Poppa, H.; Dickinson, J. T.

    1981-01-01

    The chemisorption of gases on well-defined, supported metal particles is a model for basic processes in heterogeneous catalysis. In this study, the chemisorption and decomposition of carbon monoxide on palladium and nickel particles was examined as a function of particle size. Particulate films with average particle sizes ranging from 1 to 10 nm were grown by vapor deposition on UHV-cleaved mica. Successive CO adsorption-desorption cycles resulted in the accumulation of carbon on the particles, which suppressed CO adsorption. The rate of carbon accumulation was strongly dependent on particle size and was higher for Ni than for Pd over the same size range. Carbon was removed from both metals by oxygen treatments at elevated temperatures. However, a mixture of CO and O2 was effective for monitoring the removal of carbon from palladium.

  18. Effect of van der Waals interactions on the chemisorption and physisorption of phenol and phenoxy on metal surfaces

    Science.gov (United States)

    Peköz, Rengin; Donadio, Davide

    2016-09-01

    The adsorption of phenol and phenoxy on the (111) surface of Au and Pt has been investigated by density functional theory calculations with the conventional PBE functional and three different non-local van der Waals (vdW) exchange and correlation functionals. It is found that both phenol and phenoxy on Au(111) are physisorbed. In contrast, phenol on Pt(111) presents an adsorption energy profile with a stable chemisorption state and a weakly metastable physisorbed precursor. While the use of vdW functionals is essential to determine the correct binding energy of both chemisorption and physisorption states, the relative stability and existence of an energy barrier between them depend on the semi-local approximations in the functionals. The first dissociation mechanism of phenol, yielding phenoxy and atomic hydrogen, has been also investigated, and the reaction and activation energies of the resulting phenoxy on the flat surfaces of Au and Pt were discussed.

  19. Adsorbate-adsorbate interactions and chemisorption at different coverage studied by accurate {\\em ab initio} calculations: CO on transition metal surfaces

    OpenAIRE

    Mason, Sara E.; Grinberg, Ilya; Rappe, Andrew M.

    2005-01-01

    We use density functional theory (DFT) with the generalized gradient approximation (GGA) and our first-principles extrapolation method for accurate chemisorption energies {[Mason {\\em et al.}, Phys. Rev. B {\\bf 69}, 161401R (2004)]} to calculate the chemisorption energy for CO on a variety of transition metal surfaces for various adsorbate densities and patterns. We identify adsorbate through-space repulsion, bonding competition, and substrate-mediated electron delocalization as key factors d...

  20. A Density Functional Study of Atomic Hydrogen and Oxygen Chemisorption on the Relaxed (0001) Surface of Double Hexagonal Close Packed Americium

    OpenAIRE

    Dholabhai, P. P.; Atta-Fynn, R.; A.K. Ray

    2009-01-01

    Ab initio total energy calculations within the framework of density functional theory have been performed for atomic hydrogen and oxygen chemisorption on the (0001) surface of double hexagonal packed americium using a full-potential all-electron linearized augmented plane wave plus local orbitals method. Chemisorption energies were optimized with respect to the distance of the adatom from the relaxed surface for three adsorption sites, namely top, bridge, and hollow hcp sites, the adlayer str...

  1. Theoretical studies on chemisorption of oxygen on β-Mo2C catalyst and its surface oxidation

    DEFF Research Database (Denmark)

    Shi, Xue-Rong; Wang, Shengguang; Hu, Jia;

    2012-01-01

    Oxygen chemisorption on β-Mo2C surface and its oxidation have been investigated by using the density functional theory with the periodic models. Two surfaces of (011) and (101) were chosen to perform the calculations and the most stable surface structures together with the energetics of oxygen...... the oxidation of β-Mo2C surface and lead a more negative reaction Gibbs free energy. High temperature and low oxidant pressure may hinder the surface oxidation process....

  2. Synthesis of vanadium-phosphorus oxide systems by joint chemisorption of phosphorus and vanadium oxychlorides on silica surface

    International Nuclear Information System (INIS)

    A new method of synthesis on silica of multilayer vanadium-phosphorus oxide systems containing vanadium in oxidation state (+4), which consists in joint chemisorption of phosphorus and vanadium oxychlorides, hydrolysis of surface chlorine-containing compounds by water steam and vanadium reduction by ammonia vapors, was suggested. The samples prepared were characterized by the method of ESR, IR spectroscopy and electron spectroscopy of diffuse reflection

  3. The chemisorption of H2O, HCOOH and CH3COOH on thin amorphous films of Al2O3

    Science.gov (United States)

    Lewis, B. F.; Weinberg, W. H.; Mosesman, M.

    1974-01-01

    Investigation of the irreversible chemisorption of water, formic acid and acetic acid on a thin amorphous aluminum oxide film, using inelastic tunneling spectroscopy. All of the tunnel junctions employed were Al-Al2O3-Pb junctions with the adsorbate on the Al2O3 surface between the Al2O3 and the Pb electrode. The results obtained include the finding that all Al2O3 surfaces prepared by oxidation of Al have free CH groups present on them.

  4. A Computational NMR Study for Chemisorption of Oxygen-doped on the Surface of Single-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    A. Ghasemi

    2012-08-01

    Full Text Available In this study computational Nuclear Magnetic Resonance (NMR study and chemisorptions are performed to investigate the electronic structure properties of arm-chair (4, 4 and zig-zag (5, 0 Single-Wall Carbon Nanotubes (SWCNTs. First-principles of Density Function Theory (DFT have applied in calculations on properties of molecular oxygen-doped (O-doped SWCNTs. The results show dramatic differences between two types, (5, 0 zigzag and (4, 4 arm chair, of carbon nano-tubes. Structural models are optimized and chemisorption energies are obtained to investigate the Nuclear Magnetic Resonance (NMR parameters for Odoped (5, 0 zigzag and (4, 4 armchair single-walled carbon nanotubes based on calculations using DFT. The chemical-shielding (σιι tensors were converted to isotropic chemical-shielding (iso and anisotropic chemicalshielding (Δσ and asymmetric (μj parameters of 17O and 13C atom for the optimized structures. We found that introduction oxygen does significantly change the structure of the SWCNT and thus the bonding mode of the structure is remarkably altered. Comparing the results of the zigzag and armchair models and calculated chemical shielding, electric filed gradient tensors at the sites of carbon reveal that O2 chemisorption has a dramatic effect on the electronic structure of SWCNTs.

  5. Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bruhn, Thomas [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr.36, D-10623 Berlin (Germany); Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Str.9, 12489 Berlin (Germany); Fimland, Bjørn-Ove [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); Vogt, Patrick, E-mail: patrick.vogt@tu-berlin.de [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstr.36, D-10623 Berlin (Germany)

    2015-03-14

    We report how the presence of electrophilic surface sites influences the adsorption mechanism of pyrrole on GaAs(001) surfaces. For this purpose, we have investigated the adsorption behavior of pyrrole on different GaAs(001) reconstructions with different stoichiometries and thus different surface chemistries. The interfaces were characterized by x-ray photoelectron spectroscopy, scanning tunneling microscopy, and by reflectance anisotropy spectroscopy in a spectral range between 1.5 and 5 eV. On the As-rich c(4 × 4) reconstruction that exhibits only nucleophilic surface sites, pyrrole was found to physisorb on the surface without any significant modification of the structural and electronic properties of the surface. On the Ga-rich GaAs(001)-(4 × 2)/(6 × 6) reconstructions which exhibit nucleophilic as well as electrophilic surface sites, pyrrole was found to form stable covalent bonds mainly to the electrophilic (charge deficient) Ga atoms of the surface. These results clearly demonstrate that the existence of electrophilic surface sites is a crucial precondition for the chemisorption of pyrrole on GaAs(001) surfaces.

  6. Relaxation of the chemical bond skin chemisorption size matter ZTP mechanics H2O myths

    CERN Document Server

    Sun, Chang Q

    2014-01-01

    The aim of this book is to explore the detectable properties of a material to the parameters of bond and non-bond involved and to clarify the interdependence of various properties. This book is composed of four parts; Part I deals with the formation and relaxation dynamics of bond and non-bond during chemisorptions with uncovering of the correlation among the chemical bond, energy band, and surface potential barrier (3B) during reactions; Part II is focused on the relaxation of bonds between atoms with fewer neighbors than the ideal in bulk with unraveling of the bond order-length-strength (BOLS) correlation mechanism, which clarifies the nature difference between nanostructures and bulk of the same substance; Part III deals with the relaxation dynamics of bond under heating and compressing with revealing of rules on the temperature-resolved elastic and plastic properties of low-dimensional materials; Part IV is focused on the asymmetric relaxation dynamics of the hydrogen bond (O:H-O) and the anomalous behav...

  7. Mode-selective chemistry on metal surfaces: The dissociative chemisorption of CH4 on Pt(111)

    Science.gov (United States)

    Guo, Han; Jackson, Bret

    2016-05-01

    A quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore CH4 dissociation on Pt(111). Computed sticking probabilities for molecules in the ground, 1v3 and 2v3, states are in very good agreement with the available experimental data, reproducing the variation in reactivity with collision energy and vibrational state. As was found in similar studies on Ni(100) and Ni(111), exciting the 1v1 symmetric stretch of CH4 is more effective at promoting the dissociative chemisorption of CH4 than exciting the 1v3 antisymmetric stretch. This behavior is explained in terms of symmetry, mode-softening, and nonadiabatic transitions between vibrationally adiabatic states. We find that the efficacies of the bending modes for promoting reaction are reasonably large, and similar to the 1v3 state. The vibrational efficacies for promoting reaction on Ni(111) are larger than for reaction on Pt(111), due to the larger nonadiabatic couplings. Our computed sticking probabilities are in good agreement with results from recent ab initio molecular dynamics and reactive force field studies.

  8. Cooperative Chemisorption-Induced Physisorption of CO2 Molecules by Metal-Organic Chains.

    Science.gov (United States)

    Feng, Min; Petek, Hrvoje; Shi, Yongliang; Sun, Hao; Zhao, Jin; Calaza, Florencia; Sterrer, Martin; Freund, Hans-Joachim

    2015-12-22

    Effective CO2 capture and reduction can be achieved through a molecular scale understanding of interaction of CO2 molecules with chemically active sites and the cooperative effects they induce in functional materials. Self-assembled arrays of parallel chains composed of Au adatoms connected by 1,4-phenylene diisocyanide (PDI) linkers decorating Au surfaces exhibit self-catalyzed CO2 capture leading to large scale surface restructuring at 77 K (ACS Nano 2014, 8, 8644-8652). We explore the cooperative interactions among CO2 molecules, Au-PDI chains and Au substrates that are responsible for the self-catalyzed capture by low temperature scanning tunneling microscopy (LT-STM), X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRAS), temperature-programmed desorption (TPD), and dispersion corrected density functional theory (DFT). Decorating Au surfaces with Au-PDI chains gives the interfacial metal-organic polymer characteristics of both a homogeneous and heterogeneous catalyst. Au-PDI chains activate the normally inert Au surfaces by promoting CO2 chemisorption at the Au adatom sites even at surface supported Au-PDI chains provide a platform for investigating the physical and chemical interactions involved in CO2 capture and reduction.

  9. Calorimetry, activity, and micro-FTIR analysis of CO chemisorption, titration, and oxidation on supported Pt

    Science.gov (United States)

    Sermon, Paul A.; Self, Valerie A.; Vong, Mariana S. W.; Wurie, Alpha T.

    1990-01-01

    The value of in situ analysis on CO chemisorption, titration and oxidation over supported Pt catalysts using calorimetry, catalytic and micro-FTIR methods is illustrated using silica- and titania-supported samples. Isothermal CO-O and O2-CO titrations have not been widely used on metal surfaces and may be complicated if some oxide supports are reduced by CO titrant. However, they can illuminate the kinetics of CO oxidation on metal/oxide catalysts since during such titrations all O and CO coverages are scanned as a function of time. There are clear advantages in following the rates of the catalyzed CO oxidation via calorimetry and gc-ms simultaneously. At lower temperatures the evidence they provide is complementary. CO oxidation and its catalysis of CO oxidation have been extensively studied with hysteresis and oscillations apparent, and the present results suggest the benefits of a combined approach. Silica support porosity may be important in defining activity-temperature hysteresis. FTIR microspectroscopy reveals the chemical heterogeneity of the catalytic surfaces used; it is interesting that the evidence with regard to the dominant CO surface species and their reactivities with regard to surface oxygen for present oxide-supported Pt are different from those seen on graphite-supported Pt.

  10. Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs(001) surfaces

    International Nuclear Information System (INIS)

    We report how the presence of electrophilic surface sites influences the adsorption mechanism of pyrrole on GaAs(001) surfaces. For this purpose, we have investigated the adsorption behavior of pyrrole on different GaAs(001) reconstructions with different stoichiometries and thus different surface chemistries. The interfaces were characterized by x-ray photoelectron spectroscopy, scanning tunneling microscopy, and by reflectance anisotropy spectroscopy in a spectral range between 1.5 and 5 eV. On the As-rich c(4 × 4) reconstruction that exhibits only nucleophilic surface sites, pyrrole was found to physisorb on the surface without any significant modification of the structural and electronic properties of the surface. On the Ga-rich GaAs(001)-(4 × 2)/(6 × 6) reconstructions which exhibit nucleophilic as well as electrophilic surface sites, pyrrole was found to form stable covalent bonds mainly to the electrophilic (charge deficient) Ga atoms of the surface. These results clearly demonstrate that the existence of electrophilic surface sites is a crucial precondition for the chemisorption of pyrrole on GaAs(001) surfaces

  11. Theoretical calculations of the Si(111)√3x√3R30 deg - B chemisorption system

    International Nuclear Information System (INIS)

    Full text: The plane wave pseudopotential density functional theory package fhi98md has been used to study the Si(111)√3x√3R30 deg - B chemisorption system. The minimum energy structure has been shown to be the B(S5) configuration in which the boron atoms occupy the second layer (S5) sites below the silicon surface. The calculated geometry for this B(S5) topology has been found to be in excellent agreement with recent experimental results. The electronic structure has also been calculated using the fhi98md program. By carefully analysing the nature of the wavefunctions in the vicinity of the Fermi energy we have been able to identify the surface states along the various symmetry directions of the Surface Brillouin Zone. We have found that there are two surface state bands below the Fermi energy with a splitting at the M point of 0.35 eV. This prediction, and the overall dispersion of the surface state bands, is in excellent agreement with the angle-resolved photoemission data. We also predict the occurrence of two surface state bands at the Γ-point. Only the upper of these two bands has so far been observed experimentally

  12. Water Chemisorption on aSputter Deposited Uranium Dioxide Film – Effect of Defects

    International Nuclear Information System (INIS)

    Uranium Dioxide (UO2) is mainly used as fuel for nuclear power plants for electricity generation and in the manufacturing of radioisotopes. Today more than ∼440 nuclear power plants are operating,generating a total capacity of ∼0.4 TW. Therefore,UO2 surface structure and reactions have been studied extensively(1). The two main corrosion threats to UO2 aremoisture and hydrogen. Moisture is mostly effective in atmospheric conditions (endless supply), and its reactivity can be further increased by radiation damage and radiolysis during long term storage.The enhanced oxidation and hydrogen formation can lead to a buildup of pressure and eventually a threat of breaching the storage container and a release of radioactive materials. Therefore, the safe disposal of UO2 spent fuel is crucial to environment safety. Previousstudies(2,3)had measured the effects of water adsorption on single crystal and thin film UO2 surfaces with high resolution X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). In the present study, the characteristics of water vapor chemisorption on a UO2 film, obtained by reactive sputter deposition, were studied over a temperature range of 300-500 K by combined measurements of direct recoil spectrometry (DRS) and XPS

  13. Scattering and recoiling imaging spectrometry (SARIS) study of chlorine chemisorption on Ni(1 1 0)

    International Nuclear Information System (INIS)

    The clean and chlorine chemisorbed Ni(1 1 0) surface has been investigated by scattering and recoiling imaging spectrometry (SARIS). Rare gas ion beams at 4 keV were scattered at different incident (α) and exit (β) angles along different azimuthal directions of the surface. The LEED pattern changed from a sharp (1x1) to a weak (3x1) after exposure to Cl2. The He+ images from the Cl/Ni surface exhibited very little differences compared to those of the clean surface. This is due to the high penetration depth of the He+ ions, which results in low surface sensitivity. The images obtained from the Cl/Ni surface with the heavier ions exhibited obvious changes due to their low penetration depths, which facilitates high surface sensitivity. Scattering and Recoiling Imaging Code (SARIC) simulations were carried out in order to interpret the perturbations induced by the chlorine adatoms. Different chemisorption sites for chlorine were tested. The results of the experiments and simulations agree that Cl atoms are chemisorbed in the short-bridge sites above the [1 1-bar 0] rows

  14. Surface Complexation at the TiO(2) (anatase)/Aqueous Solution Interface: Chemisorption of Catechol.

    Science.gov (United States)

    Rodríguez; Blesa; Regazzoni

    1996-01-15

    Catechol adsorbs at the TiO(2) (anatase)/aqueous solution interface forming inner-sphere surface complexes. The UV-visible differential reflectance spectrum of surface titanium-catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pK(a1), the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Gamma(max):N(S) (N(S) being the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH >/= pK(a1), the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO(2) suspended in indifferent electrolyte solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: identical withTiOH(1/3-) and identical withOH(1/3+). Although both surface groups undergo protonation-deprotonation reactions, only identical withTiOH(1/3-) are prone to chemisorption.

  15. Single-crystal adsorption calorimetry and density functional theory of CO chemisorption on fcc Co{110}.

    Science.gov (United States)

    Liao, Kristine; Fiorin, Vittorio; Gunn, David S D; Jenkins, Stephen J; King, David A

    2013-03-21

    Using single-crystal adsorption calorimetry (SCAC) and density functional theory (DFT), the interaction of carbon monoxide on fcc Co{110} is reported for the first time. The results indicate that adsorption is consistent with molecular chemisorption at all coverages. The initial heat of adsorption of 140 kJ mol(-1) is found in the range of heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. DFT adsorption energies are in good agreement with the experimental results, and comparison between SCAC and DFT for CO on other ferromagnetic surfaces is made. The calculated dissociation barrier of 2.03 eV implies that dissociation at 300 K is unlikely even at the lowest coverage. At high coverages during the adsorption-desorption steady state regime, a pre-exponential factor for CO desorption of 1.2 × 10(17) s(-1) is found, implying a localised molecular adsorbed state prior to desorption in contrast to what we found with Ni surfaces. This result highlights the importance of the choice of the pre-exponential factor in evaluating the activation energy for desorption.

  16. Chemisorption of Perfluorooctanoic Acid on Powdered Activated Carbon Initiated by Persulfate in Aqueous Solution.

    Science.gov (United States)

    Sun, Bo; Ma, Jun; Sedlak, David L

    2016-07-19

    Perfluorooctanoic acid (PFOA) is a perfluorocarboxylic acid that is difficult to treat by most conventional methods. As a result, it is often removed from solution by adsorption on powdered activated carbon (PAC), followed by incineration of the spent carbon. To provide a new approach for treatment, PFOA was exposed to sulfate radicals (SO4(-•)) produced by thermolysis of persulfate (S2O8(2-)) in the presence of PAC. Under acidic conditions, thermal activation of persulfate resulted in transformation of PFOA to shorter-chain-length perfluorinated compounds, as previously reported. However, when thermolysis of persulfate occurred under circumneutral pH conditions in the presence of PAC, a new removal pathway for PFOA was observed. Under these conditions, the removal of PFOA was attributable to chemisorption, a process in which PAC catalyzed persulfate decomposition and reacted with the transformation products to produce covalently bound PFOA. At PAC concentrations between 200 and 1000 mg/L and an initial PFOA concentration of 0.5 μM, covalent bonding resulted in removal of 10-40% of the PFOA. Under these conditions, the process resulted in removal of more than half of a more hydrophilic perfluoroalkyl acid (i.e., perfluorobutanoic acid, PFBA), which was greater than the amount of PFBA removed by physical adsorption on PAC. Although the high reaction temperatures (i.e., 80 °C) and relatively high doses of PAC used in this study may be impractical for drinking water treatment, this process may be applied to the treatment of these recalcitrant compounds in industrial wastewater, reverse osmosis concentrate, and other waters that contain high concentrations of PFOA and other perfluorocarboxylic acids. PMID:27336204

  17. A First Principle Comparative Study on Chemisorption of H2 on C60, C80, and Sc3N@C80 in Gas Phase and Chemisorption of H2 on Solid Phase C60

    OpenAIRE

    Hongtao Wang; Lijuan Chen; Yongkang Lv; Jianwen Liu; Gang Feng

    2014-01-01

    The chemisorptions of H2 on fullerenes C60 and C80, endofullerene Sc3C@C80 and solid C60 were comparatively studied. A chain reaction mechanism for dissociative adsorption of H2 on solid C60 is proposed under high pressure. The breaking of H–H bond is concerted with the formation of two C–H bonds on two adjacent C60 in solid phase. The adsorption process is facilitated by the application of high pressure. The initial H2 adsorption on two adjacent C60 gives a much lower barrier 1.36 eV in comp...

  18. Methane dissociative chemisorption and detailed balance on Pt(111): Dynamical constraints and the modest influence of tunneling

    International Nuclear Information System (INIS)

    A dynamically biased (d-) precursor mediated microcanonical trapping (PMMT) model of the activated dissociative chemisorption of methane on Pt(111) is applied to a wide range of dissociative sticking experiments, and, by detailed balance, to the methane product state distributions from the thermal associative desorption of adsorbed hydrogen with coadsorbed methyl radicals. Tunneling pathways were incorporated into the d-PMMT model to better replicate the translational energy distribution of the desorbing methane product from the laser induced thermal reaction of coadsorbed hydrogen and methyl radicals occurring near Ts = 395 K. Although tunneling is predicted to be inconsequential to the thermal dissociative chemisorption of CH4 on Pt(111) at the high temperatures of catalytic interest, once the temperature drops to 395 K the tunneling fraction of the reactive thermal flux reaches 15%, and as temperatures drop below 275 K the tunneling fraction exceeds 50%. The d-PMMT model parameters of (E0 = 58.9 kJ/mol, s = 2, ηv = 0.40) describe the apparent threshold energy for CH4/Pt(111) dissociative chemisorption, the number of surface oscillators involved in the precursor complex, and the efficacy of molecular vibrational energy to promote reaction, relative to translational energy directed along the surface normal. Molecular translations parallel to the surface and rotations are treated as spectator degrees of freedom. Transition state vibrational frequencies are derived from generalized gradient approximation-density functional theory electronic structure calculations. The d-PMMT model replicates the diverse range of experimental data available with good fidelity, including some new effusive molecular beam and ambient gas dissociative sticking measurements. Nevertheless, there are some indications that closer agreement between theory and experiments could be achieved if a surface efficacy less than one was introduced into the modeling as an additional dynamical

  19. Chemisorption of molecular oxygen on Cu(1 0 0): a Hartree¿Fock and density functional study

    OpenAIRE

    Torras Costa, Juan; Lacaze-Dufaure, C.; Russo, Beniamino; Ricart Pla, Josep Manel

    2001-01-01

    The interaction of molecular oxygen with the Cu(1 0 0) surface has been studied by using both Hartree–Fock and density functional methods in the framework of the cluster model approach. In this study, we have used the Cu8(6,2) cluster in order to simulate the O2 molecular adsorption on different high symmetry chemisorption sites (top–top, bridge–fourfold, bridge–top, fourfold–fourfold) on the Cu(1 0 0) surface. High level non-local density functional (NLSD) computations indicate that the more...

  20. XPS study of the chemisorption induced surface segregation in LaNi5 and ThNi5

    OpenAIRE

    Schlapbach, L.; Brundle, C. R.

    1981-01-01

    Surface segregation with the disproportionation into La and Th oxide plus precipitations of elemental Ni play an important role in the understanding of the easy hydrogen absorption of LaNi5 and of the catalytic properties of ThNi5. By means of core-level X-ray photoelectron spectroscopy we show that the chemisorption of O2, H2O, and H2 on LaNi 5 surfaces induces a strong, weak and no surface segregation, resp. Precoverage with SO2 blocks further segregation, whereas exposure to H2S does not. ...

  1. Molecular simulation of CO chemisorption on Co(0001) in presence of supercritical fluid solvent: A potential of mean force study

    Science.gov (United States)

    Asiaee, Alireza; Benjamin, Kenneth M.

    2016-08-01

    For several decades, heterogeneous catalytic processes have been improved through utilizing supercritical fluids (SCFs) as solvents. While numerous experimental studies have been established across a range of chemistries, such as oxidation, pyrolysis, amination, and Fischer-Tropsch synthesis, still there is little fundamental, molecular-level information regarding the role of the SCF on elementary heterogeneous catalytic steps. In this study, the influence of hexane solvent on the adsorption of carbon monoxide on Co(0001), as the first step in the reaction mechanism of many processes involving syngas conversion, is probed. Simulations are performed at various bulk hexane densities, ranging from ideal gas conditions (no SCF hexane) to various near- and super-critical hexane densities. For this purpose, both density functional theory and molecular dynamics simulations are employed to determine the adsorption energy and free energy change during CO chemisorption. Potential of mean force calculations, utilizing umbrella sampling and the weighted histogram analysis method, provide the first commentary on SCF solvent effects on the energetic aspects of the chemisorption process. Simulation results indicate an enhanced stability of CO adsorption on the catalyst surface in the presence of supercritical hexane within the reduced pressure range of 1.0-1.5 at a constant temperature of 523 K. Furthermore, it is shown that the maximum stability of CO in the adsorbed state as a function of supercritical hexane density at 523 K nearly coincides with the maximum isothermal compressibility of bulk hexane at this temperature.

  2. Theoretical studies on chemisorption of oxygen on β-Mo2C catalyst and its surface oxidation

    Science.gov (United States)

    Shi, Xue-Rong; Wang, Sheng-Guang; Hu, Jia; Qin, Zhangfeng; Wang, Jianguo

    2012-08-01

    Oxygen chemisorption on β-Mo2C surface and its oxidation have been investigated by using the density functional theory with the periodic models. Two surfaces of (011) and (101) were chosen to perform the calculations and the most stable surface structures together with the energetics of oxygen stepwise adsorption were identified. Thermodynamic effect of temperature and reactant pressure on the chemisorption and surface oxidation was investigated. The results suggest that the (101) surface is more active than the (011) surface towards the oxygen adsorption. The (101) surface can be fully oxidized by O2 at PO2/P0 of 10- 21-104 and temperature of 100-700 K. For the (011) surface with O2 as the oxidant, the most stable structure is that with 1/2 ML or 7/8 ML oxygen coverage, depending on the temperature and PO2/P0 value. The increase of gaseous oxidant pressure or decrease of temperature can enhance the oxidation of β-Mo2C surface and lead a more negative reaction Gibbs free energy. High temperature and low oxidant pressure may hinder the surface oxidation process.

  3. First-principles quantum dynamical theory for the dissociative chemisorption of H2O on rigid Cu(111).

    Science.gov (United States)

    Zhang, Zhaojun; Liu, Tianhui; Fu, Bina; Yang, Xueming; Zhang, Dong H

    2016-01-01

    Despite significant progress made in the past decades, it remains extremely challenging to investigate the dissociative chemisorption dynamics of molecular species on surfaces at a full-dimensional quantum mechanical level, in particular for polyatomic-surface reactions. Here we report, to the best of our knowledge, the first full-dimensional quantum dynamics study for the dissociative chemisorption of H2O on rigid Cu(111) with all the nine molecular degrees of freedom fully coupled, based on an accurate full-dimensional potential energy surface. The full-dimensional quantum mechanical reactivity provides the dynamics features with the highest accuracy, revealing that the excitations in vibrational modes of H2O are more efficacious than increasing the translational energy in promoting the reaction. The enhancement of the excitation in asymmetric stretch is the largest, but that of symmetric stretch becomes comparable at very low energies. The full-dimensional characterization also allows the investigation of the validity of previous reduced-dimensional and approximate dynamical models. PMID:27283908

  4. Use of carbon-14 for the study of elementary carbon exchange between methane and its chemisorption residues on metallic films

    International Nuclear Information System (INIS)

    After giving the results of the most recent work done with a view to providing a rational account of the exchanges between two gases in contact with a catalyst, the authors, using C14, proceed to study elementary exchange between methane and its chemisorption residues on molybdenum films. The surface is labelled in two ways: by chemisorption of C14H4 at different temperatures; or by exchange between C14H4 with a high specific activity and a metallic film previously treated with inactive methane. The C14 is counted in the form of CO2 in the Geiger region. The results show that the exchange rate is measurable from about 100o C onwards and that it reaches a maximum at about 250o C. Furthermore, the exchange is governed by laws which vary according to the prior treatment of the surface. On the basis of the results discussed, the authors suggest a methane displacement pattern which they compare with the CH4 and D2 exchange mechanisms suggested by Kemball. (author)

  5. Physisorption to chemisorption transition of NO2 on graphene induced by the interplay of SiO2 substrate and van der Waals forces: A first principles study

    International Nuclear Information System (INIS)

    Highlights: ► New mechanism of NO2 chemisorption on graphene is proposed. ► SiO2 changes the structures of graphene and enhances the NO2 adsorption. ► The physisorption to chemisorption transition can be induced by the interplay of substrate and van der Waals interactions. -- Abstract: The effect of SiO2 substrate and van der Waals interactions on the adsorption of NO2 molecule on graphene is studied using density functional theory. Contrary to physisorption on suspended graphene, both physisorption and chemisorption phenomena can be found, which are mainly caused by the covalent C–O bonds, the broken symmetry, and the local corrugations induced by SiO2. The electronic structures of the system are significantly influenced after NO2 adsorption, enhancing the detection of NO2. Interestingly, NO2 induces magnetization into graphene, and the spin polarization locates mainly on carbon atoms of graphene. The barrier of the transition from physisorption to chemisorption is about 0.05 eV, and this “pseudo barrier” can be overcome by van der Waals interactions. This work explains the experiments of graphene as gas sensors with high sensitivity, and supports new applications for electronic, spintronic devices.

  6. Empirical potential study of the dissociative chemisorption of Si2H6 on the Si(001)2x1 surface

    International Nuclear Information System (INIS)

    Full text: Two models have been proposed for the epitaxial growth of silicon on the Si(001)2x1 surface from the dissociation of disilane (Si2H6). Molecular dynamics simulations and potential energy calculations have been performed to investigate this dissociative chemisorption process. These calculations have been carried out using the extended Brenner (XB) empirical potential. The minimum energy atomic configurations for SiH3, SiH2 and H-Si-Si-H (Si2H2) species chemisorbed on the Si(001)2x1 surface have been determined. The chemisorption of SiH3 radicals has been observed to occur predominantly at the dangling bond sites of the Si(001) surface. The most stable SiH2 configurations are found to be the on-dimer and intra-row structures. Seven different Si2H2 chemisorption structures have been investigated and the on-dimer-B structure found to be the most energetically favourable. These theoretically predicted structures are discussed in the light of recent experimental studies and the proposed models for silicon epitaxial growth. Comparison of the results of these XB potential energy calculations with all-electron ab initio cluster calculations has also been made for a number of these different chemisorption structures

  7. A molecular dynamics study of the dissociative chemisorption Si2H6 on the Si(001):2x1 surface

    International Nuclear Information System (INIS)

    Full text: Molecular dynamics simulations have been carried out to investigate the dissociative adsorption of disilane (Si2H6) on the Si(001):2x1 surface using the improved empirical Brenner potential (IXB). A number of chemisorption sites and atomic configurations of the SiH, SiH2, SiH3 species chemisorbed on the Si(001):2x1 surface have been identified. The chemisorption of the SiH3, radicals was observed to occur predominantly on the dangling bond sites of the Si(001) surface. The chemisorption of the SiH2 species result in forming on-dimer and intra-row structures which were found to be most energetic and thermodynamic stable configurations. The three-fold bonding structure has been identified to be the most energetically favourable configuration for the chemisorption of the SiH radicals on Si(001). The comparison between the empirical molecular dynamics simulations and all electron ab initio cluster calculations for some of the atomic configurations discussed above is also presented

  8. Chemisorption of a thiol-functionalized ruthenium dye on zinc oxide nanoparticles: Implications for dye-sensitized solar cells

    Science.gov (United States)

    Singh, Jagdeep; Im, Jisun; Whitten, James E.; Soares, Jason W.; Steeves, Diane M.

    2010-09-01

    ZnO is an alternative to TiO 2-based dye-sensitized solar cells (DSSCs). Adsorption of cis-ruthenium-bis[2,2'-bipyridine]-bis[4-thiopyridine] onto ZnO nanorods has been studied using X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS). XPS indicates chemisorption with a surface density of ca. 1 × 10 15 molecules/cm 2, confirming the possibility of using thiol-terminated dyes for ZnO-based DSSC devices. The energy level diagram, based on UPS and absorbance spectroscopy, indicates that the LUMO of this dye is lower in energy than the ZnO conduction band edge, providing minimal enthalpic driving force for photovoltaic electron injection. However, optimization of thiol-functionalized Ru dyes could result in competitive ZnO-based DSSCs.

  9. Six-dimensional potential energy surface of the dissociative chemisorption of HCl on Au(111) using neural networks

    Institute of Scientific and Technical Information of China (English)

    LIU TianHui; FU BiNa; ZHANG Dong H

    2014-01-01

    We constructed a six-dimensional potential energy surface(PES)for the dissociative chemisorption of HCl on Au(111)using the neural networks method based on roughly 70000 energies obtained from extensive density functional theory(DFT)calculations.The resulting PES is accurate and smooth,based on the small fitting errors and good agreement between the fitted PES and the direct DFT calculations.Time-dependent wave packet calculations show that the potential energy surface is very well converged with respect to the number of DFT data points,as well as to the fitting process.The dissociation probabilities of HCl initially in the ground rovibrational state from six-dimensional quantum dynamical calculations are quite diferent from the four-dimensional fixed-site calculations,indicating it is essential to perform full-dimensional quantum dynamical studies for the title molecule-surface interaction system.

  10. Atomic and electronic structure of the Si(001)2x1-K chemisorption system at monolayer coverage

    International Nuclear Information System (INIS)

    Full text: It has been well established that the chemisorption of potassium on the Si (001) 2x1 surface leads to the so-called 'double-layer model' at one monolayer coverage. The plane wave pseudopotential density functional programs VASP and fhi98md have been used to optimise the geometry of this double-layer model. The resulting geometry has been found to be in excellent agreement with the experimental results. To identify the surface states of this double-layer model in the vicinity of the Fermi energy we have calculated the modulus squared of each wavefunction integrated over the surface unit cell. We have also calculated charge density contour plots over various planes containing the surface silicon and potassium atoms. The theoretically predicted dispersion of both the occupied and unoccupied surface states has been found to be in excellent agreement with the experimental data

  11. Chemisorption of sulfur on (100)Mo: growth of surface and volume sulfides, absolute calibration, thermodesorption of sulfur

    International Nuclear Information System (INIS)

    Physico-chemical processes following the chemisorption of sulfur on (100)Mo, that is: growth of the surface and volume sulfides, their thermo-stability, variation of emission and catalytic properties of the surface are studied using high resolution (δ E/E ≤ 0.1%) EOS with recording of spectra directly from the specimen highly heated up to T = 2000 K. The work of yield and bound energy of sulfur atom depending on the level of Mo surface population by S atoms are determined. It is shown that Mo exposure in H2S atmosphere under T = 300-2000 K does not result in accumulation of S atoms within the specimen volume. The absolute concentration of sulfur atoms in the surface sulfide is determined and it is shown that its stoichiometry is MoS. 31 refs., 5 figs

  12. Ab initio modeling of glass corrosion: Hydroxylation and chemisorption of oxalic acid at diopside and akermanite surfaces

    International Nuclear Information System (INIS)

    Using ab initio density functional theory, we have performed a systematic study of corrosion processes at pure and at hydroxylated surfaces of the silicate minerals diopside (CaMgSi2O6) and akermanite (Ca2MgSi2O7), serving as model systems for multicomponent glasses. The tendency of the cations to assume their ideal bulk coordination was identified as the driving force behind spontaneous surface relaxation and hydroxylation in an aqueous environment. Surface complexes formed after exposing the glass surfaces to oxalic acid form a protective hydrophobic layer on the surface and thus prevent the leaching of metal cations from the glass surface. This provides a description of the mechanism of glass corrosion inhibition at the atomic level: as the chemisorption energy of oxalic acid is larger than the physisorption energy of water, the former is the process that will actually occur.

  13. Density functional theory study of the chemisorption of CO on Ir/MgO(1 0 0)

    International Nuclear Information System (INIS)

    Density functional theory calculations have been used to study the adsorption of CO on the Ir/MgO(1 0 0). Substrate and adsorbate geometry relaxation, adsorption, energy and density of states are computed. Top and bridge adsorption sites for iridium atom deposition have been considered. The result indicated that the energetically most favorable sites are the top sites of the O atoms. CO adsorption on the Ir atom is then studied. Different adsorbate arrangements, perpendicular and parallel to the surface have been considered. Among them, the most stable CO chemisorption geometry, is that corresponding to the adsorbate perpendicular to the surface iridium atom and C-down oriented. Density of states and the CO stretching frequency analysis further found that the obvious charge transfer from adsorbate to the substrate.

  14. Chemisorption of single fluorine atoms on the surface of zigzag single-walled carbon nanotubes: A model calculation

    Energy Technology Data Exchange (ETDEWEB)

    Margulis, Vl.A. [Department of Physics, N.P. Ogarev Mordovian State University, Saransk 430000 (Russian Federation)]. E-mail: 612033@inbox.ru; Muryumin, E.E. [Department of Chemistry, N.P. Ogarev Mordovian State University, Saransk 430000 (Russian Federation)

    2007-03-01

    We report a model calculation of the chemisorption energies {delta}E{sub ads} of single fluorine atoms on the outer surface of zigzag single-walled carbon nanotubes (Z-SWCNTs) (p,0) with p ranging from 11 to 21. A simplified model based on an effective-mass theory is adopted to describe the electronic structure of the nanotubes. Chemisorption is treated within the Anderson-Newns approach, which takes account of Coulomb interaction between adsorbate electrons. Considering adsorption of an adatom directly on top of a surface carbon atom, we find that in the case of a fluorine atom bonded to the sidewall of the nanotubes, the absolute values of {delta}E{sub ads} are in the range 4.3-5.5eV for Z-SWCNTs with typical diameters of 0.86-1.66nm, larger {delta}E{sub ads} values being associated with semiconducting tubes. For the latter ones, {delta}E{sub ads} decreases rather significantly as the radius R of the tubes increases, tending towards the ''infinite'' radius graphene case, whereas for metallic tubes {delta}E{sub ads} slightly increases with increasing R. The localized acceptor states induced by a fluorine atom in the band gap of the semiconducting tubes are found to be responsible for such difference in the behaviour of {delta}E{sub ads} for the two above-mentioned types of tubes. The results obtained shed light on the possible mechanism of the atomic fluorine adsorption-induced hole-doping of the semiconducting tubes, which might significantly affect the transport properties of these tubes.

  15. Interaction of cyclobutane with the Ru(001) surface: Low-temperature molecular adsorption and dissociative chemisorption at elevated surface temperature

    International Nuclear Information System (INIS)

    We have studied the interaction of cyclobutane with the hexagonally close-packed Ru(001) surface. High-resolution electron energy loss spectroscopy (HREELS) has been used to identify the vibrational modes of both c-C4H8 and c-C4D8 adsorbed at 90 K as a function of cyclobutane exposure. We have observed a vibrational mode not observed in the gas phase at 2600 cm-1 (2140 cm-1) which is attributed to the strong interaction of the cyclobutane C endash H (C endash D) bonds with the ruthenium surface. Two different adsorption geometries for cyclobutane on Ru(001) have been proposed based on the dipolar activity of this softened C endash H mode. We have also measured the trapping-mediated dissociative chemisorption of both c-C4H8 and c-C4D8 at surface temperatures between 190 and 1200 K. The measured activation energies with respect to the bottom of the physically adsorbed well for c-C4H8 and c-C4D8 are 10thinsp090±180 and 10thinsp180±190 cal/mol, respectively. The trapping-mediated chemisorption of cyclobutane is believed to occur via C endash C bond cleavage, as judged by the absence of a kinetic isotope effect. The measured ratios of the preexponential factors for desorption relative to reaction of 21±2 and 47±4 for c-C4H8 and c-C4D8 respectively, are in the expected range considering the greater entropy gain associated with the transition state for desorption relative to the transition state for C endash C bond cleavage. copyright 1999 American Institute of Physics

  16. Investigation of the doped transition metal promotion effect on CO2 chemisorption on Ni (1 1 1)

    International Nuclear Information System (INIS)

    The chemisorption of CO2 on the pure Ni (1 1 1) and doped Ni (1 1 1) by transition metal (Co, Rh, Cr, Ce, La) were investigated by using the generalized gradient approximation (GGA) and the Perdew-Burke-Emzerhof (PBE) functional. The optimized structure of doped metal surface showed that Rh, Cr, Ce, La atoms upward shift from the surface of Ni (1 1 1) plane, while the atom radius of Co is the minimum offset which lead to the height is -0.03 Å. The ability of CO2 chemisorption follows the order of La/Ni (1 1 1) > Ce/Ni (1 1 1) > Cr/Ni (1 1 1) > Co/Ni (1 1 1) > pure Ni (1 1 1). It is exothermic when CO2 chemisorbed on Cr/Ni (1 1 1) Ce/Ni (1 1 1) and La/Ni (1 1 1), while it is endothermic on the Co/Ni (1 1 1) and pure Ni (1 1 1). CO2 molecular chemisorbed on all the metal surfaces are negatively charged, result from the electron transfer between the metal surfaces and the CO2 molecular. The transition metals La, Ce and Cr can promote the transformation of electron and make the C-O bonds longer than the pure Ni (1 1 1). We also analyzed the dissociation of CO2 on the Ni-based surface and found that the La/Ni (1 1 1) surface is the preference surface for the dissociation of CO2, which improved the ability to hinder carbon deposition.

  17. Role of different Pd/Pt ensembles in determining CO chemisorption on Au-based bimetallic alloys: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Ham, Hyung Chul, E-mail: hchahm@kist.re.kr [Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 (United States); Fuel Cell Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Manogaran, Dhivya [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712 (United States); Hwang, Gyeong S., E-mail: gshwang@che.utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 (United States); Han, Jonghee; Kim, Hyoung-Juhn; Nam, Suk Woo; Lim, Tae Hoon [Fuel Cell Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2015-03-30

    Graphical abstract: - Highlights: • Pd ensembles greatly reduce CO adsorption energy as compared to Pt ensembles. • The steeper potential energy surface of CO adsorption in Pd(1 1 1) than in Pt(1 1 1). • Switch of binding site preference in ensembles is key to determining CO adsorption. • Opposite electronic (ligand) effect in Pd and Pt ensemble. - Abstract: Using spin-polarized density functional calculations, we investigate the role of different Pd/Pt ensembles in determining CO chemisorption on Au-based bimetallic alloys through a study of the energetics, charge transfer, geometric and electronic structures of CO on various Pd/Pt ensembles (monomer/dimer/trimer/tetramer). We find that the effect of Pd ensembles on the reduction of CO chemisorption energy is much larger than the Pt ensemble case. In particular, small-sized Pd ensembles like monomer show a substantial reduction of CO chemisorption energy compared to the pure Pd (1 1 1) surface, while there are no significant size and shape effects of Pt ensembles on CO chemisorption energy. This is related to two factors: (1) the steeper potential energy surface (PES) of CO in Pd (1 1 1) than in Pt (1 1 1), indicating that the effect of switch of binding site preference on CO chemisorption energy is much larger in Pd ensembles than in Pt ensembles, and (2) down-shift of d-band in Pd ensembles/up-shift of d-band in Pt ensembles as compared to the corresponding pure Pd (1 1 1)/Pt (1 1 1) surfaces, suggesting more reduced activity of Pd ensembles toward CO adsorption than the Pt ensemble case. We also present the different bonding mechanism of CO on Pd/Pt ensembles by the analysis of orbital resolved density of state.

  18. Role of different Pd/Pt ensembles in determining CO chemisorption on Au-based bimetallic alloys: A first-principles study

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Pd ensembles greatly reduce CO adsorption energy as compared to Pt ensembles. • The steeper potential energy surface of CO adsorption in Pd(1 1 1) than in Pt(1 1 1). • Switch of binding site preference in ensembles is key to determining CO adsorption. • Opposite electronic (ligand) effect in Pd and Pt ensemble. - Abstract: Using spin-polarized density functional calculations, we investigate the role of different Pd/Pt ensembles in determining CO chemisorption on Au-based bimetallic alloys through a study of the energetics, charge transfer, geometric and electronic structures of CO on various Pd/Pt ensembles (monomer/dimer/trimer/tetramer). We find that the effect of Pd ensembles on the reduction of CO chemisorption energy is much larger than the Pt ensemble case. In particular, small-sized Pd ensembles like monomer show a substantial reduction of CO chemisorption energy compared to the pure Pd (1 1 1) surface, while there are no significant size and shape effects of Pt ensembles on CO chemisorption energy. This is related to two factors: (1) the steeper potential energy surface (PES) of CO in Pd (1 1 1) than in Pt (1 1 1), indicating that the effect of switch of binding site preference on CO chemisorption energy is much larger in Pd ensembles than in Pt ensembles, and (2) down-shift of d-band in Pd ensembles/up-shift of d-band in Pt ensembles as compared to the corresponding pure Pd (1 1 1)/Pt (1 1 1) surfaces, suggesting more reduced activity of Pd ensembles toward CO adsorption than the Pt ensemble case. We also present the different bonding mechanism of CO on Pd/Pt ensembles by the analysis of orbital resolved density of state

  19. A First Principle Comparative Study on Chemisorption of H2 on C60, C80, and Sc3N@C80 in Gas Phase and Chemisorption of H2 on Solid Phase C60

    Directory of Open Access Journals (Sweden)

    Hongtao Wang

    2014-01-01

    Full Text Available The chemisorptions of H2 on fullerenes C60 and C80, endofullerene Sc3C@C80 and solid C60 were comparatively studied. A chain reaction mechanism for dissociative adsorption of H2 on solid C60 is proposed under high pressure. The breaking of H–H bond is concerted with the formation of two C–H bonds on two adjacent C60 in solid phase. The adsorption process is facilitated by the application of high pressure. The initial H2 adsorption on two adjacent C60 gives a much lower barrier 1.36 eV in comparison with the barrier of adsorption on a single C60 (about 3.0 eV. As the stereo conjugate aromaticity of C60 is destructed by the initial adsorption, some active sites are created. Hence the successive adsorption becomes easier with much low barriers (0.6 eV. In addition, further adsorption can create new active sites for the next adsorption. Thus, a chain reaction path is formed with the initial adsorption dominating the whole adsorption process.

  20. Difference between potentials of zero charge in the absence of the metal-solvent chemisorption interaction of mercury and metals of the gallium subgroup

    International Nuclear Information System (INIS)

    The modern solution of the Volt problem is introduced. The difference values of the zero-charge potentials between Hg- and Ga-(In-Ga)- and (Tl-Ga)-electrodes in six solvents in the absence of the metal-solvent chemisorption interaction of mercury and the gallium subgroup metals are calculated. The errors of the calculated values and the possibility of their minimization are evaluated. It is shown, that the values obtained are determined by the metal nature alone

  1. Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) and PdML/Re(0001), ReML/Pd(111) pseudomorphic overlayers

    DEFF Research Database (Denmark)

    Pallassana, Venkataraman; Neurock, Matthew; Hansen, Lars Bruno;

    1999-01-01

    with the location of the d-band center of the bare metal surfaces, using a model developed by Hammer and N phi rskov. The DFT-computed adsorption energies were also analyzed on the basis of the density of states (DOS) at the Fermi level for the clean metal surfaces. The results indicate a clear correlation between...... the d-band center of the surface metal atoms and the hydrogen chemisorption energy. The further the d-band center is from the Fermi level, the weaker is the chemisorption bond of atomic hydrogen on the surface. Although the DOS at the Fermi level may be related to the location of the d-band, it does...... not appear to provide an independent parameter for assessing surface reactivity. The weak chemisorption of hydrogen on the Pd-ML/Re(0001) surface relates to substantial lowering of the d-band center of Pd, when it is pseudomorphically deposited as a monolayer on a Re substrate. [S0163-1829(99)00331-2]....

  2. Use of charge sensitivity analysis in diagnosing chemisorption clusters: Minimum-energy coordinate and Fukui function study of model toluene-[V2O5] systems

    International Nuclear Information System (INIS)

    Charge sensitivity analysis (CSA) is carried out for model toluene-vanadium pentoxide chemisorption complexes involving the two-pyramidal model of the active site on the (010)-V2O5 surface. Maps of the electrostatic potential around the adsorbate and the substrate cluster are used to rationalize energetical preferences of alternative perpendicular and parallel arrangements of the toluene ring relative to the pyramid bases, known from previous SCF MO studies. The minimum-energy coordinates (MEC) in the electron population space are determined from the CSA semiempirical, finite difference atomic hardness matrix for the actual SCF MO charges in the chemisorption clusters. They represent collective charge displacements which minimize the system energy per unit change in the oxidation state of a specified atom, thus providing a convenient diagnostic tool for testing the alternative charge rearrangements and range of perturbations due to the chemisorption bond or changes in the cluster environment. The MEC relaxed hardnesses diagnose mode stabilities and together with the MEC relaxed hardnesses diagnose mode stabilities and together with the MEC topologies identify the most probable locations of the adsorbate activation. Finally, the atomic Fukui function indices are used to explore trends in the distribution of the external charge transfer due to the system environment. 14 refs., 4 figs

  3. Selective chemisorption of graphene-like molecules on the Si(111) 7 x 7 surface: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Kiss, Janos; Gruhn, Thomas; Felser, Claudia [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universitaet, D-55099 Mainz (Germany)

    2011-07-01

    Graphene and porous graphene are very promising materials, which have been widely studied for electronic applications. Because of their improved properties, in the future it is expected, that graphene, porous graphene and graphene-like molecules will replace silicon. Despite its superior material properties, however, the field-effect transistors based on graphene or graphene nanoribbons build so far via top-down approaches have low on/off ratios. On the other hand, molecular nanotransistors build with precisely know atomic structures resembling graphene were synthesized only very recently. In order to pave the way towards the industrial fabrication of molecular nanotransistors, we have investigated the chemisorption of graphene-like molecules on the 7 x 7 reconstructed Si(111) surface via density functional theory (DFT) calculations. We found, that Si(111) is a very promising candidate to serve as substrate for the large-scale fabrication of coronene-based molecular transistors. Moreover, our calculations show, that various adsorbate molecules prefer specific binding sites on the Si(111) surface. By following the template of the Si(111) substrate, the molecules selectively adsorb and form a well defined two-dimensional grid with a 1 x 1 surface pattern.

  4. In situ analysis of CO during chemisorption and oxidation on graphite: Supported Pt by FTIR-microspectrometry

    Science.gov (United States)

    Self, Valerie A.; Sermon, Paul A.

    1990-01-01

    For chemisorption and oxidation on Pt/HOPG (highly-orientated pyrolytic) graphite, reflectance Fourier Transform Infrared (FTIR)-microspectrometry reveals a variable state and reactivity for CO. Even for model surface science systems, where surface heterogeneity is minimal, surface diffusion may be too slow relative to the reaction rate to avoid segregation of reactants into surface islands under steady-state conditions. Thus in CO oxidation on Pt (where the relevant surface diffusion coefficients are such that D sub O less than D sub CO) then reactant CO islands exists at the perimeters of which the surface reaction is thought to occur. Furthermore CO can chemisorb on metals in linear and bridge forms to extents which vary with precise faces predominantly exposed coverage, etc. Infrared has long been used to probe the nature of adsorbed CO on model film and heterogeneous surfaces, but it may now be that FTIR-microspectrometry will allow the state of this adsorbate and reactant to be investigated with a spatial resolution of 4.4 microns on model (and real) catalytic surfaces.

  5. Energy window effect in chemisorption of C36 on diamond (0 0 1)-(2x1) surface

    International Nuclear Information System (INIS)

    In this paper, the collision of a C36, with D6h symmetry, on diamond (0 0 1)-(2x1) surface was investigated using molecular dynamics (MD) simulation based on the semi-empirical Brenner potential. The incident kinetic energy of the C36 ranges from 20 to 150 eV per cluster. The collision dynamics was investigated as a function of impact energy Ein. The C36 cluster was first impacted towards the center of two dimers with a fixed orientation. It was found that when Ein was lower than 30 eV, C36 bounces off the surface without breaking up. Increasing Ein to 30-45 eV, bonds were formed between C36 and surface dimer atoms, and the adsorbed C36 retained its original free-cluster structure. Around 50-60 eV, the C36 rebounded from the surface with cage defects. Above 70 eV, fragmentation both in the cluster and on the surface was observed. Our simulation supported the experimental findings that during low-energy cluster beam deposition small fullerenes could keep their original structure after adsorption (i.e. the memory effect), if Ein is within a certain range. Furthermore, we found that the energy threshold for chemisorption is sensitive to the orientation of the incident C36 and its impact position on the asymmetric surface

  6. Dissociative chemisorption of methane on metal surfaces: Tests of dynamical assumptions using quantum models and ab initio molecular dynamics

    International Nuclear Information System (INIS)

    The dissociative chemisorption of methane on metal surfaces is of great practical and fundamental importance. Not only is it the rate-limiting step in the steam reforming of natural gas, the reaction exhibits interesting mode-selective behavior and a strong dependence on the temperature of the metal. We present a quantum model for this reaction on Ni(100) and Ni(111) surfaces based on the reaction path Hamiltonian. The dissociative sticking probabilities computed using this model agree well with available experimental data with regard to variation with incident energy, substrate temperature, and the vibrational state of the incident molecule. We significantly expand the vibrational basis set relative to earlier studies, which allows reaction probabilities to be calculated for doubly excited initial vibrational states, though it does not lead to appreciable changes in the reaction probabilities for singly excited initial states. Sudden models used to treat the center of mass motion parallel to the surface are compared with results from ab initio molecular dynamics and found to be reasonable. Similar comparisons for molecular rotation suggest that our rotationally adiabatic model is incorrect, and that sudden behavior is closer to reality. Such a model is proposed and tested. A model for predicting mode-selective behavior is tested, with mixed results, though we find it is consistent with experimental studies of normal vs. total (kinetic) energy scaling. Models for energy transfer into lattice vibrations are also examined

  7. Observing the Transition from Equatorial to Axial CO Chemisorption: Infrared Photodissociation Spectroscopy of Yttrium Oxide-Carbonyls.

    Science.gov (United States)

    Xie, Hua; Liu, Zhiling; Zhao, Zhi; Kong, Xiangtao; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-06-01

    A series of yttrium oxide-carbonyls are prepared via a laser vaporization supersonic cluster source in the gas phase and identified by mass-selected infrared photodissociation (IRPD) spectroscopy in the C-O stretching region and by comparing the observed IR spectra with those from quantum chemical calculations. For YO(CO)4(+), all four CO ligands prefer to occupy the equatorial site of the YO(+) unit, leading to a quadrangular pyramid with C4v symmetry. Two energetically nearly degenerate isomers are responsible for YO(CO)5(+), in which the fifth CO ligand is either inserted into the equatorial plane of YO(CO)4(+) or coordinated opposite the oxygen on the C4 axis. YO(CO)6(+) has a pentagonal bipyramidal structure with C5v symmetry, which includes five equatorial CO ligands and one axial CO ligand. The present IRPD spectroscopic and theoretical study of YO(CO)n(+) extends the first shell coordination number of CO ligands in metal monoxide carbonyls to six. The transition from equatorial to axial CO chemisorption in these yttrium oxide-carbonyls is fortunately observed at n = 5, providing new insight into ligand interactions and coordination for the transition metal oxides. PMID:27158889

  8. Parameter Estimation by Density Functional Theory for a Lattice-gas Model of Br and Cl Chemisorption on Ag(100)

    CERN Document Server

    Juwono, Tjipto; Rikvold, Per Arne; Wang, Sanwu

    2011-01-01

    We study Bromine and Chlorine chemisorption on a Ag(100) surface, using a lattice-gas model and the quantum-mechanical Density Functional Theory (DFT) method. In this model the Br and Cl ions adsorb at the fourfold hollow sites of the Ag(100) surface, which can be represented by a square lattice of adsorption sites. Five different coverages were used for each kind of adsorbate. For each adsorbate and coverage, we obtained the minimum-energy configuration, its energy, and its charge distribution. From these data we calculated dipole moments, lateral interaction energies, and binding energies. Our results show that for Br the lateral interactions obtained by fitting to the adsorption energies obtained from the DFT calculation are consistent with long-range dipole-dipole lateral interactions obtained using the dipole moments calculated from the DFT charge distribution. For Cl we found that, while the long-range dipole-dipole lateral interactions are important, short-range attractive interactions are also present...

  9. Chemisorptive removal of carbon dioxide from process streams using a reactive bubble column with simultaneous production of usable materials

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, P.; Ewert, G.; Roehm, H.J. [Department of Process and Environmental Engineering, Ruhr-University, Bochum (Germany)

    2006-09-15

    In the context of attempts to improve the protection of the environment, a novel process where the carbon dioxide reacts rapidly with almost 100 % conversion under mild conditions, is proposed. The chemisorptive process takes place in a slurry bubble column which operates with countercurrent flow, utilizing special solutions of primary long chain amines in a nonaqueous media. The product obtained is insoluble and separated by filtration. Because of its molecular structure, this product possesses tenside properties and can be used as an industrial additive. Typically the liquid phase consists of a mixture of hexadecylamine (C{sub 16}H{sub 33}NH{sub 2}) or dodecylamine (C{sub 12}H{sub 25}NH{sub 2}) in various concentrations with methanol or other alcohols as the solvent. Numerous parameters have been studied including different column heights, gas inlet compositions, gas flow rates and solvent type. Efficiencies of up to 99 % are achievable for CO{sub 2} absorption with methanol as the solvent. The second solvent examined, isopropanol, shows lower CO{sub 2} conversion rates. This can be attributed to its physical properties, mainly higher viscosity and hence, smaller mass transfer coefficient. In order to simulate real gas conditions, the influence of other sour gases, e.g., SO{sub 2} was also investigated experimentally. Because of coabsorption of the two gases, the CO{sub 2} efficiency was lower in this instance. In both solvents, the absorption efficiency with respect to SO{sub 2} is more than 99 % due to its high solubility and reactivity. A complex mathematical model has been developed and applied to describe the mass and enthalpy transport in the reactive bubble column. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  10. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    International Nuclear Information System (INIS)

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H2O, HOD, and D2O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D2O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate

  11. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Farjamnia, Azar; Jackson, Bret, E-mail: jackson@chem.umass.edu [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003 (United States)

    2015-06-21

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H{sub 2}O, HOD, and D{sub 2}O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D{sub 2}O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate.

  12. Ab initio cluster-model study of the on-top chemisorption of F and Cl on Si(111) and Ge(111) surfaces

    OpenAIRE

    Illas i Riera, Francesc; Rubio Martínez, Jaime; Ricart, J M

    1985-01-01

    The interaction of atomic F and Cl with Si4H9 and Ge4H9 cluster models has been studied by using ab initio pseudopotentials and basis sets of increasing complexity. The results show that the effect of d orbitals is important in order to reproduce the experimental findings. However, the use of polarization functions in the atoms which are directly involved in the chemisorption bond leads to results which are very close to those obtained using extended basis sets. The local nature of the chemis...

  13. An ab initio full potential fully relativistic study of atomic carbon, nitrogen, and oxygen chemisorption on the (111) surface of delta-plutonium

    OpenAIRE

    Atta-Fynn, Raymond; Ray, Asok K.

    2007-01-01

    Adsorption of carbon, nitrogen, and oxygen on the (111) surface of delta-Plutonium has been studied within the framework of density functional theory using the full-potential linear augmented plane wave plus local basis (FP-LAPW+lo) method. All adatoms prefer to bind at the higher coordinated hollow sites, with the chemisorption energies for C, N, and O being 6.539 eV, 6.714 eV, and 8.2 eV respectively. The work function and the surface Pu magnetic moments respectively increased and decreased...

  14. An ab initio cluster study of atomic oxygen chemisorption on Ga-rich GaAs(100) (2x1) and beta(4x2) surfaces

    OpenAIRE

    Mayo, Michael L.; Ray, Asok K.

    2003-01-01

    Ab initio self-consistent total energy calculations using second order Moller-Plesset perturbation theory and Hay-Wadt effective core potentials for gallium and arsenic have been used to investigate the chemisorption of atomic oxygen on the Ga-rich GaAs (100) (2 x 1) and beta(4 x 2) surfaces. Finite sized hydrogen saturated clusters with the experimental zinc-blende lattice constant of 5.654 angstroms and the energy optimized surface Ga dimer bond length of 2.758 angstroms have been used to m...

  15. Validity of the site-averaging approximation for modeling the dissociative chemisorption of H2 on Cu(111) surface: A quantum dynamics study on two potential energy surfaces

    International Nuclear Information System (INIS)

    A new finding of the site-averaging approximation was recently reported on the dissociative chemisorption of the HCl/DCl+Au(111) surface reaction [T. Liu, B. Fu, and D. H. Zhang, J. Chem. Phys. 139, 184705 (2013); T. Liu, B. Fu, and D. H. Zhang, J. Chem. Phys. 140, 144701 (2014)]. Here, in order to investigate the dependence of new site-averaging approximation on the initial vibrational state of H2 as well as the PES for the dissociative chemisorption of H2 on Cu(111) surface at normal incidence, we carried out six-dimensional quantum dynamics calculations using the initial state-selected time-dependent wave packet approach, with H2 initially in its ground vibrational state and the first vibrational excited state. The corresponding four-dimensional site-specific dissociation probabilities are also calculated with H2 fixed at bridge, center, and top sites. These calculations are all performed based on two different potential energy surfaces (PESs). It is found that the site-averaging dissociation probability over 15 fixed sites obtained from four-dimensional quantum dynamics calculations can accurately reproduce the six-dimensional dissociation probability for H2 (v = 0) and (v = 1) on the two PESs

  16. A low temperature oxygen chemisorption study of (VO/sub 2/P/sub 2/O/sub 7/ and V/sub 2/ O/sub 5/ catalysts

    International Nuclear Information System (INIS)

    Low temperature oxygen chemisorption (LTOC) has been applied to (VO)sub 2/P/sub 2/O/sub 7/ and V/sub 2/O/sub 5/ catalysts following reduction carbon monoxide as a means of determining the surface population of chemisorbed molecular oxygen. This latter measurement is taken to be equivalent to the surface population of anion vacancies, the oxygen being chemisorbed at the vacancies as O/sub 2/. The desorption activation energies for the molecular oxygen obtained for both catalysts were in the range 24-31 kJ mol showing the bonding to be in the lower limit of chemisorption. (author)

  17. Immobilization of bovine serum albumin on TiO 2 film via chemisorption of H 3PO 4 interface and effects on platelets adhesion

    Science.gov (United States)

    Weng, Y. J.; Hou, R. X.; Li, G. C.; Wang, J.; Huang, N.; Liu, H. Q.

    2008-02-01

    In the present study, bovine serum albumin (BSA) was successfully covalently immobilized on the surface of anatase TiO 2 film by a three-step method, i.e. application of H 3PO 4 chemisorption to increase surface -OH, which increases the amount of coupling 3-aminopropyl-triethoxylsilane (APTES), thus linking with BSA by imide bond using EDC/NHS/MES. There is no significant -OH group increase on rutile film when using the same method of phosphoric acid treatment, which suggest it is difficult for further chemical modification of the rutile film. After covalent immobilization of BSA on anatase film, an improved hemocompatibility of anti-platelet adhesion and aggregation in vitro could be recognized by LDH and SEM analysis. This study suggests BSA-immobilized anatase surface can serve as hemocompatibility material in vivo.

  18. Influence of preadsorbed oxygen on the sign and magnitude of the chemisorption-induced resistance change for H2 adsorption onto Fe films

    Science.gov (United States)

    Shanabarger, M. R.

    1986-01-01

    Measurements have been made of the chemisorption-induced resistance change for H2 adsorbed onto Fe film substrates predosed with fixed coverages of chemisorbed oxygen. The measurements were made at temperatures from 295 to 340 K and for estimated oxygen coverages of less than 0.1 monolayers. Two distinct resistance change components were observed in both the adsorption kinetics and the equilibrium isotherms: a positive component which is associated with the adsorption of H2 onto a clean Fe surface, and a negative component which was correlated with the presence of the chemisorbed oxygen. The resistance change isotherms can be fit with a model which assumes that each of the resistance change components result from dissociative chemisorbed hydrogen. Possible mechanisms for the chemisorbed-oxygen-induced negative resistance change are discussed.

  19. Ion photon-stimulated desorption as a tool to monitor the physisorption to chemisorption transition of benzene on Si(111) 7 x 7

    CERN Document Server

    Carbone, M; Casaletto, M P; Zanoni, R; Besnard-Ramage, M J; Comtet, G; Dujardin, G; Hellner, L

    2003-01-01

    We investigated the use of ion photodesorption as a tool to monitor the transition from the physisorbed to the chemisorbed state on a surface. The adsorption of benzene on Si(111) 7 x 7 in the temperature range 40-300 K is chosen as a prototype. The D sup + ion photodesorption yield was monitored as a function of temperature at various benzene exposures. Comparative measurements of the C 1s photoelectron yield in the same temperature range enable the physisorbed to chemisorbed state transition to be distinguished from that of the multilayer to the chemisorbed state. We find the onset at 110 K in the first case, and at 130-140 K in the second case. These results demonstrate that ion photodesorption is a potentially interesting method to identify physisorption to chemisorption transitions of adsorbed molecules on surfaces. (letter to the editor)

  20. Model catalyst studies of SMSI and the role of D-electrons in chemisorption and catalysis. Progress report, January 15, 1985-January 14, 1986

    International Nuclear Information System (INIS)

    Electron spectroscopic studies of the surface composition, electronic structure and chemisorption properties of model Rh/TiO2 catalysts fabricated on well characterized single-crystal supports have provided evidence that argues strongly against the simple charge transfer model of strong metal-support interaction that involves the transfer of electrons from surface Ti3+ ions that are created by high temperature reduction. The presence of surface Ti3+ ions does appear to be necessary in order to facilitate the migration of sub-oxides over the catalyst particles in the SMSI state, but hydrogen is not necessary if Ti3+ defect sites exist prior to high temperature annealing. A newly constructed electron beam evaporation source is now being used for in situ deposition of Rh onto TiO2 supports, giving greater control over catalyst loading and particle size. TEM studies of catalyst morphology, performed in parallel with the electron spectroscopic studies, are continuing. 3 figs

  1. Mode specificity for the dissociative chemisorption of H2O on Cu(111): a quantum dynamics study on an accurately fitted potential energy surface.

    Science.gov (United States)

    Liu, Tianhui; Zhang, Zhaojun; Fu, Bina; Yang, Xueming; Zhang, Dong H

    2016-03-16

    The mode-specific dynamics for the dissociative chemisorption of H2O on Cu(111) is first investigated by seven-dimensional quantum dynamics calculations, based on an accurately fitted potential energy surface (PES) recently developed by neural network fitting to DFT energy points. It is indicated that excitations in all three vibrational modes have a significant impact on reactivity, which are more efficacious than increasing the translational energy in promoting the reaction, with the largest enhancement for the excitation in the asymmetric stretching mode. There is large discrepancy between the six-dimensional reactivities with fixed azimuthal angles and seven-dimensional results, revealing that the 6D "flat surface" model cannot accurately characterize the reaction dynamics. The azimuthal angle-averaging approach is validated for vibrational excited states of the reactant, where the 7D mode-specific probability can be well reproduced by averaging the 6D azimuthal angle-fixed probabilities over 18 angles. PMID:26941197

  2. Chemisorption Mechanism of DNA on Mg/Fe Layered Double Hydroxide Nanoparticles: Insights into Engineering Effective SiRNA Delivery Systems.

    Science.gov (United States)

    Lu, Mingsheng; Shan, Zhi; Andrea, Kori; MacDonald, Bruce; Beale, Stefanie; Curry, Dennis E; Wang, Li; Wang, Shujun; Oakes, Ken D; Bennett, Craig; Wu, Wenhui; Zhang, Xu

    2016-03-22

    Layered double hydroxide nanoparticles (LDH NPs) have attracted interest as an effective gene delivery vehicle in biomedicine. Recent advances in clinic trials have demonstrated the efficacy of Mg/Fe LDHs for hyperphosphatemia treatment, but their feasibility for gene delivery has not been systematically evaluated. As a starting point, we aimed to study the interaction between oligo-DNA and Mg/Fe LDH NPs. Our investigation revealed the chemisorption mechanism of DNA on Mg/Fe LDH surfaces, wherein the phosphate backbone of the DNA polymer coordinates with the metal cations of the LDH lattice via the ligand-exchange process. This mechanistic insight may facilitate future gene delivery applications using Mg/Fe LDH NPs. PMID:26919981

  3. Ion photon-stimulated desorption as a tool to monitor the physisorption to chemisorption transition of benzene on Si(111) 7 x 7

    International Nuclear Information System (INIS)

    We investigated the use of ion photodesorption as a tool to monitor the transition from the physisorbed to the chemisorbed state on a surface. The adsorption of benzene on Si(111) 7 x 7 in the temperature range 40-300 K is chosen as a prototype. The D+ ion photodesorption yield was monitored as a function of temperature at various benzene exposures. Comparative measurements of the C 1s photoelectron yield in the same temperature range enable the physisorbed to chemisorbed state transition to be distinguished from that of the multilayer to the chemisorbed state. We find the onset at 110 K in the first case, and at 130-140 K in the second case. These results demonstrate that ion photodesorption is a potentially interesting method to identify physisorption to chemisorption transitions of adsorbed molecules on surfaces. (letter to the editor)

  4. Pentacene on Au(1 1 1), Ag(1 1 1) and Cu(1 1 1): From physisorption to chemisorption

    Science.gov (United States)

    Lu, Meng-Chao; Wang, Rong-Bin; Yang, Ao; Duhm, Steffen

    2016-03-01

    We measured the electronic and the molecular surface structure of pentacene deposited on the (1 1 1)-surfaces of coinage metals by means of ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction (LEED). Pentacene is almost flat-lying in monolayers on all three substrates and highly ordered on Au(1 1 1) and on Cu(1 1 1). On Ag(1 1 1), however, weak chemisorption leads to almost disordered monolayers, both, at room temperature and at 78 K. On Cu(1 1 1) pentacene is strongly chemisorbed and the lowest unoccupied molecular orbital becomes observable in UPS by a charge transfer from the substrate. On Ag(1 1 1) and Cu(1 1 1) multilayers adopt a tilted orientation and a high degree of crystallinity. On Au(1 1 1), most likely, also in multilayers the molecular short and long axes are parallel to the substrate, leading to a distinctively different electronic structure than on Ag(1 1 1) and Cu(1 1 1). Overall, it could be demonstrated that the substrate not only determines the geometric and electronic characteristics of molecular monolayer films but also plays a crucial role for multilayer film growth.

  5. Pentacene on Au(1 1 1), Ag(1 1 1) and Cu(1 1 1): From physisorption to chemisorption

    International Nuclear Information System (INIS)

    We measured the electronic and the molecular surface structure of pentacene deposited on the (1 1 1)-surfaces of coinage metals by means of ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction (LEED). Pentacene is almost flat-lying in monolayers on all three substrates and highly ordered on Au(1 1 1) and on Cu(1 1 1). On Ag(1 1 1), however, weak chemisorption leads to almost disordered monolayers, both, at room temperature and at 78 K. On Cu(1 1 1) pentacene is strongly chemisorbed and the lowest unoccupied molecular orbital becomes observable in UPS by a charge transfer from the substrate. On Ag(1 1 1) and Cu(1 1 1) multilayers adopt a tilted orientation and a high degree of crystallinity. On Au(1 1 1), most likely, also in multilayers the molecular short and long axes are parallel to the substrate, leading to a distinctively different electronic structure than on Ag(1 1 1) and Cu(1 1 1). Overall, it could be demonstrated that the substrate not only determines the geometric and electronic characteristics of molecular monolayer films but also plays a crucial role for multilayer film growth. (paper)

  6. Dissociative Chemisorption of an H2(v,j) Molecule on Rigid Ni (100) Surface: Dependence on Surface Topologies and Initial Rovibrational States of the Molecules

    Institute of Scientific and Technical Information of China (English)

    Meryem Evecen; Mustafa B(o)yükata; Mehmet (C)ivi; Ziya B. Güven(c)

    2005-01-01

    @@ The H2(v,j)+Ni(100) collision system has been studied to understand the effects of the surface sites and initial rovibrational states of the molecule on molecule-surface interactions, by a quasiclassical molecular dynamic simulation method. Dissociative adsorption of an H2 molecule on the rigid Ni(100) surface is investigated at topologically different three sites of the surface. Interaction between the molecule and Ni surface was described by a London-Eyring-Polani-Sato (LEPS) potential. Dissociative chemisorption probabilities of the H2(v, j) molecule on various sites of the surface are presented as a function of the translation energies between 0.001-1.0eV. The probabilities obtained at each collision site have unique behaviour. At lower collision energies, indirect processes enhance the reactivity, effects of the rotational excitations and impact sites on the reactivity are more pronounced. The results are compared with the available studies. The physical mechanisms underlying the results and quantum effects are discussed.

  7. Especiação e quimissorção de Pb(II em rejeito de caulim Speciation and chemisorption of Pb(II on kaolin waste

    Directory of Open Access Journals (Sweden)

    Marta Helena Tavares Pinheiro

    2013-01-01

    Full Text Available This study assesses the adsorption of Pb(II on natural kaolin waste (KRnatural and on that treated with 3 mol L-1 H2SO4 and HCl. Equilibrium and thermodynamic parameters were determined. The results indicate that the values of CEC, specific area and SiO2/Al2O3 ratio (4.6-6.0 cmol kg-1, 14.0-16.0 m² g-1 and 1.16-1.30, respectively vary only slightly for the adsorbents; the concentration of Pb2+ is much higher than that of other species (PbOH+ and Pb(OH2. The values of R L, ΔGº, ΔHº and ΔSº are typical of feasible, spontaneous, exothermic and ordered adsorption. The chemisorption on KRnatural is more feasible and ordered.

  8. Study on Chemisorption and Desorption of Hydrogen and Nitrogen on Ru-based Ammonia Synthesis Catalyst%钌基氨合成催化剂氢氮吸附性能的研究

    Institute of Scientific and Technical Information of China (English)

    祝一锋; 李小年; 高冬梅; 周春晖; 刘化章

    2003-01-01

    The effects of promoters K, Ba, Sm on the chemisorption and desorption of hydrogen and nitrogen,dispersion of metallic Ru and catalytic activity of active carbon (AC) supported ruthenium catalyst for ammoniasynthesis have been studied by means of pulse chromatography, temperature-programmed desorption, and activitytest. Promoters K, Ba and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly, andparticularly, potassium exhibited the best promotion on the activity because of the strong electronic donation tometallic Ru. Much higher activity can be obtained for Ru/AC catalyst with binary or triple promoters. The activityof Ru/AC catalyst is dependent on the adsorption of hydrogen and nitrogen. The high activity of catalyst could beascribed to strong dissociation of nitrogen on the catalyst surface. Strong adsorption of hydrogen would inhibit theadsorption of nitrogen, resulted in decrease of the catalytic activity. Ru/AC catalyst promoted by Sm2O3 showsthe best dispersion of metallic Ru, since the partly reduced SmOx on the surface modifies the morphology of activesites and favors the dispersion of metallic Ru. The activity of Ru/AC catalysts is in accordance to the correspondingamount of nitrogen chemisorption and the desorption activation energy of nitrogen. The desorption activation energyfor nitrogen decreases in the order of Ru>Ru-Ba>Ru-Sm>Ru-Ba-Sm>Ru-K>Ru-K-Sm>Ru-K-Ba>Ru-K-Ba-Sm,just opposite to the order of catalytic activity, suggesting that the ammonia synthesis over Ru-based catalyst iscontrolled by the step of dissociation of nitrogen.

  9. The effect of additives on the reactivity of palladium surfaces for the chemisorption and hydrogenation of carbon monoxide: A surface science and catalytic study. [LaMO/sub 3/(M = Cr, Mn, Fe, Co, Rh)

    Energy Technology Data Exchange (ETDEWEB)

    Rucker, T.G.

    1987-06-01

    This research studied the role of surface additives on the catalytic activity and chemisorptive properties of Pd single crystals and foils. Effects of Na, K, Si, P, S, and Cl on the bonding of CO and H and on the cyclotrimerization of acetylene on the (111), (100) and (110) faces of Pd were investigated in addition to role of TiO/sub 2/ and SiO/sub 2/ overlayers deposited on Pd foils in the CO hydrogenation reaction. On Pd, only in the presence of oxide overlayers, are methane or methanol formed from CO and H/sub 2/. The maximum rate of methane formation is attained on Pd foil where 30% of the surface is covered with titania. Methanol formation can be achieved only if the TiO/sub x//Pd surface is pretreated in 50 psi of oxygen at 550/sup 0/C prior to the reaction. The additives (Na, K, Si, P, S, Cl) affect the bonding of CO and hydrogen and the cyclotrimerization of acetylene to benzene by structural and electronic interactions. In general, the electron donating additives increase the desorption temperature of CO and increase the rate of acetylene cyclotrimerization and the electron withdrawing additives decrease the desorption temperature of CO and decrease the rate of benzene formation from acetylene.

  10. SrCl2-NH3化学吸附式制冷工质对吸附特性的研究%STUDY ON THE ADSORPTION CHARACTERISTICS OF SrCl2-NH3 CHEMISORPTION REFRIGERATION WORKING PAIR

    Institute of Scientific and Technical Information of China (English)

    陈砺; 谭盈科

    2001-01-01

    A study on the adsorption characteristics of the chemisorptionrefrigeration working pair using SrCl2 as adsorbent and NH3 as refrigerant was performed.The adsorption isotherms were obtained,the adsorpt i on isotherm equations were fit and the chemisorption mechanisms were discussed.T he results showed that SrCl2-NH3 is an excellent working pair in its larg e adsorption refrigeration capacity per unit weight of adsorbent and suitable fo r solar energy and low grade waste heat.%对以SrCl2为吸附剂、NH3为致冷剂所组成的化学吸附式制冷工质对的吸附性能进行了研究,得到了吸附等温线、回归出吸附等温方程并对化学吸附过程机理进行了探讨。研究结果表明,SrCl2-NH3工质对的吸附制冷量大,适宜太阳能或低品位余热驱动,是性能优良的工质对。

  11. Sauerstoff- und Stickstoff-Chemisorption an Metallclustern

    OpenAIRE

    Stolcic, Davor

    2003-01-01

    Anion Photoelectron Spectroscopy is a powerful tool for the investigation of the electronic structure of clusters. In this work three investigations are carried out with this method: Using photoelectron spectroscopy and first principle molecular orbital calculations the first observation of a metal-semiconductor transition with increasing number of Oxygen atoms in Tungsten oxide is observed. Tungsten oxide clusters with up to six Tungsten atoms and up to twelve Oxygen atoms were investigated....

  12. Chemisorption of CO on Pd particles supported on mica

    Science.gov (United States)

    Thomas, M.; Poppa, H.; Dickinson, J. T.; Pound, G. M.

    1978-01-01

    A UHV technique is presented for evaluating the adsorption-desorption properties of UHV vapor-deposited metal particles supported on insulating substrates. Desorption studies of CO from particulate and continuous Pd films supported on mica were performed. The desorption results indicate that: the CO desorption energies from the deposited metals are much lower than those from bulk single crystals; two desorption states exist for the vapor-deposited films; and the lower energy desorption peak of the vapor-deposited films is coverage dependent. Possible reasons for the difference between previously reported CO desorption studies on bulk substrates and the present results are discussed.

  13. Regularities in aluminium and indium chemisorption on chelating polymeric sorbents

    International Nuclear Information System (INIS)

    Complexation properties of synthesized polymer chelate sorbents: substituted of polystyrene-azo-pyrocatechol are investigated and correlations between pK'OH of functional groups of sorbents as well as pH50 values of chelation and constants of stability (lgKstab) are established for studying regularities of effect of structure and acid-base properties of functional groups of sorbents on the parameters of Al3+ and In3+ chemical sorption. Established correlations make it possible to predict the physicochemical parameters of sorbents and sorption of metal ions with the aim of separation and concentration of aluminium and indium micro account from the objects of different origin

  14. Surface studies of Cl2 chemisorption on CVD diamond

    International Nuclear Information System (INIS)

    The technique of X-ray photoelectron spectroscopy has been used to study the interactions of molecular chlorine with CVD diamond surfaces. Chlorine is found to adsorb onto the clean surface with a sticking probability of ∼0.001 at 25 deg C, although this can be enhanced by prehydrogenation of the surface. Adsorbed chlorine desorbs from the surface over a wide temperature range below 500 deg C. It can also be very efficiently etched away by atomic hydrogen. In this paper we present results obtained in the investigation, and discuss their implications in diamond growth mechanisms, in particular to the development of low temperature growth models using halogen-based precursors

  15. Sorption J-T refrigeration utilizing manganese nitride chemisorption

    Science.gov (United States)

    Jones, Jack; Lund, Alan

    1990-01-01

    The equilibrium pressures and compositions have been measured for a system of finely powdered manganese nitride and nitrogen gas at 650, 700, 800, and 850 C for various nitrogen loadings. Pressures ranged from less than 0.02 MPa at 650 C to 6.38 MPa at 850 C. Analysis of the test results has shown that under certain conditions Mn(x)N(y) could potentially be used in a triple regenerative sorption compressor refrigeration system, but the potential power savings are small compared to the increased complexity and reliability problems associated with very high temperature (above 950 C) pressurized systems.

  16. Chemisorption and reactions on clusters of nickel atoms

    Science.gov (United States)

    Waber, J. T.; Adachi, H.; Yu, T.

    1982-01-01

    The nucleation and growth of metallic clusters on a substantially amorphous substrate are discussed with emphasis on the geometrical and electronic structure of the clusters. Several clusters of different symmetry containing five to nine nickel atoms were studied. It was found that the energy range of primary d-like states is not significantly different from the width of the d-band states in nickel metal, as long as the interatomic distance is comparable to that in the bulk metal. The approach of one or more molecules to the cluster is examined using at the hydrogenation of acetylene and the dehydrogenation of ethylene as examples.

  17. Sequential oxygen atom chemisorption on surfaces of small iron Clusters

    International Nuclear Information System (INIS)

    We report photoelectron spectra of iron oxide clusters, FexOy- (x=1 endash 4, y=1 endash 6). For a given x, we find that the electron affinity increases with the number of O atoms, consistent with an increasing degree of oxidation. The results are interpreted based on charge transfer interactions between the Fex clusters and the O atoms, and provide key information about the oxide cluster structures, in which each O atom is suggested to locate on the surface of the clusters for the x=3 and 4 series. These clusters provide novel model systems to understand the electronic structure of bulk iron oxides. copyright 1996 The American Physical Society

  18. Electronic shell structure and chemisorption on gold nanoparticles

    OpenAIRE

    Larsen, Ask Hjorth; Kleis, Jesper; Thygesen, Kristian Sommer; Nørskov, J. K.; Jacobsen, Karsten Wedel

    2013-01-01

    We use density functional theory (DFT) to investigate the electronic structure and chemical properties of gold nanoparticles. Different structural families of clusters are compared. For up to 60 atoms we optimize structures using DFT-based simulated annealing. Cluster geometries are found to distort considerably, creating large band gaps at the Fermi level. For up to 200 atoms we consider structures generated with a simple EMT potential and clusters based on cuboctahedra and icosahedra. All t...

  19. Physisorption versus chemisorption of oxygen molecules on Ag(100)

    Science.gov (United States)

    Mehlhorn, Michael; Morgenstern, Karina

    2016-04-01

    We compare the adsorption of oxygen molecules on Ag(100) at 60 K and at 100 K. At both temperatures, the molecules form islands. Differences between the species adsorbed at the two temperatures in both low-temperature scanning tunneling microscopy and inelastic electron tunneling spectroscopy are attributed to two different adsorption states, a chemisorbed state after 100 K adsorption and a physisorbed state after 60 K adsorption.

  20. Role of Amine Functionality for CO2 Chemisorption on Silica.

    Science.gov (United States)

    Hahn, Maximilian W; Jelic, Jelena; Berger, Edith; Reuter, Karsten; Jentys, Andreas; Lercher, Johannes A

    2016-03-01

    The mechanism of CO2 adsorption on primary, secondary, and bibasic aminosilanes synthetically functionalized in porous SiO2 was qualitatively and quantitatively investigated by a combination of IR spectroscopy, thermogravimetry, and quantum mechanical modeling. The mode of CO2 adsorption depends particularly on the nature of the amine group and the spacing between the aminosilanes. Primary amines bonded CO2 preferentially through the formation of intermolecular ammonium carbamates, whereas CO2 was predominantly stabilized as carbamic acid, when interacting with secondary amines. Ammonium carbamate formation requires the transfer of the carbamic acid proton to a second primary amine group to form the ammonium ion and hence two (primary) amine groups are required to bind one CO2 molecule. The higher base strength of secondary amines enables the stabilization of carbamic acid, which is thereby hindered to interact further with nearby amine functions, because their association with Si-OH groups (either protonation or hydrogen bonding) does not allow further stabilization of carbamic acid as carbamate. Steric hindrance of the formation of intermolecular ammonium carbamates leads to higher uptake capacities for secondary amines functionalized in porous SiO2 at higher amine densities. In aminosilanes possessing a primary and a secondary amine group, the secondary amine group tends to be protonated by Si-OH groups and therefore does not substantially interact with CO2. PMID:26700549

  1. Active chemisorption sites in functionalized ionic liquids for carbon capture.

    Science.gov (United States)

    Cui, Guokai; Wang, Jianji; Zhang, Suojiang

    2016-07-25

    Development of novel technologies for the efficient and reversible capture of CO2 is highly desired. In the last decade, CO2 capture using ionic liquids has attracted intensive attention from both academia and industry, and has been recognized as a very promising technology. Recently, a new approach has been developed for highly efficient capture of CO2 by site-containing ionic liquids through chemical interaction. This perspective review focuses on the recent advances in the chemical absorption of CO2 using site-containing ionic liquids, such as amino-based ionic liquids, azolate ionic liquids, phenolate ionic liquids, dual-functionalized ionic liquids, pyridine-containing ionic liquids and so on. Other site-containing liquid absorbents such as amine-based solutions, switchable solvents, and functionalized ionic liquid-amine blends are also investigated. Strategies have been discussed for how to activate the existent reactive sites and develop novel reactive sites by physical and chemical methods to enhance CO2 absorption capacity and reduce absorption enthalpy. The carbon capture mechanisms of these site-containing liquid absorbents are also presented. Particular attention has been paid to the latest progress in CO2 capture in multiple-site interactions by amino-free anion-functionalized ionic liquids. In the last section, future directions and prospects for carbon capture by site-containing ionic liquids are outlined.

  2. Surface electronic structure and chemisorption of plutonium and uranium

    International Nuclear Information System (INIS)

    This paper reports that for the early actinides, uranium through plutonium, the direct overlap of the 5f orbitals and their hybridization with the s and d orbital give rise to narrow banding behavior for the 5f electrons. For the heavier actinides (from americium onward) the 5f electrons of the elemental solids remain localized and do not form a band. As the proportion of 5f to 6d and 7s electrons increases, the itinerant behavior of the 5f electrons gradually disappears. The change to localization is more dramatic between plutonium and americium. Surface f electrons tend to be somewhat more localized than those in the interior because of decreased opportunity for overlap and hybridization. It follows that the degree of localized f-electron behavior will be more conspicuous at the surface for any of the light actinides. Several experimentally accessible surface properties such as the work function are quite sensitive monitors of the degree of f-electron localization

  3. Electronic shell structure and chemisorption on gold nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Ask Hjorth; Kleis, Jesper; Thygesen, Kristian Sommer;

    2011-01-01

    We use density functional theory (DFT) to investigate the electronic structure and chemical properties of gold nanoparticles. Different structural families of clusters are compared. For up to 60 atoms we optimize structures using DFT-based simulated annealing. Cluster geometries are found to dist...

  4. Active chemisorption sites in functionalized ionic liquids for carbon capture.

    Science.gov (United States)

    Cui, Guokai; Wang, Jianji; Zhang, Suojiang

    2016-07-25

    Development of novel technologies for the efficient and reversible capture of CO2 is highly desired. In the last decade, CO2 capture using ionic liquids has attracted intensive attention from both academia and industry, and has been recognized as a very promising technology. Recently, a new approach has been developed for highly efficient capture of CO2 by site-containing ionic liquids through chemical interaction. This perspective review focuses on the recent advances in the chemical absorption of CO2 using site-containing ionic liquids, such as amino-based ionic liquids, azolate ionic liquids, phenolate ionic liquids, dual-functionalized ionic liquids, pyridine-containing ionic liquids and so on. Other site-containing liquid absorbents such as amine-based solutions, switchable solvents, and functionalized ionic liquid-amine blends are also investigated. Strategies have been discussed for how to activate the existent reactive sites and develop novel reactive sites by physical and chemical methods to enhance CO2 absorption capacity and reduce absorption enthalpy. The carbon capture mechanisms of these site-containing liquid absorbents are also presented. Particular attention has been paid to the latest progress in CO2 capture in multiple-site interactions by amino-free anion-functionalized ionic liquids. In the last section, future directions and prospects for carbon capture by site-containing ionic liquids are outlined. PMID:27243042

  5. Chemisorption of CO and Mechanism of CO Oxidation on Supported Platinum Nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Allian, Ayman D.; Takanabe, Kazuhiro; Fujdala, Kyle L.; Hao, Xianghong; Truex, Timothy J.; Cai, Juan; Buda, Corneliu; Neurock, Matthew; Iglesia, Enrique

    2011-03-30

    Kinetic, isotopic, and infrared studies on well-defined dispersed Pt clusters are combined here with first-principle theoretical methods on model cluster surfaces to probe the mechanism and structural requirements for CO oxidation catalysis at conditions typical of its industrial practice. CO oxidation turnover rates and the dynamics and thermodynamics of adsorption-desorption processes on cluster surfaces saturated with chemisorbed CO were measured on 1-20 nm Pt clusters under conditions of strict kinetic control. Turnover rates are proportional to O2 pressure and inversely proportional to CO pressure, consistent with kinetically relevant irreversible O2 activation steps on vacant sites present within saturated CO monolayers. These conclusions are consistent with the lack of isotopic scrambling in C16O-18O2-16O2 reactions, and with infrared bands for chemisorbed CO that did not change within a CO pressure range that strongly influenced CO oxidation turnover rates. Density functional theory estimates of rate and equilibrium constants show that the kinetically relevantO2 activation steps involve directO2* (or O2) reactions with CO* to form reactive O*-O-C*dO intermediates that decompose to form CO2 and chemisorbed O*, instead of unassisted activation steps involving molecular adsorption and subsequent dissociation of O2. These CO-assisted O2 dissociation pathways avoid the higher barriers imposed by the spin-forbidden transitions required for unassistedO2 dissociation on surfaces saturated with chemisorbed CO. Measured rate parameters for CO oxidation were independent of Pt cluster size; these parameters depend on the ratio of rate constants for O2 reactions with CO* and CO adsorption equilibrium constants, which reflect the respective activation barriers and reaction enthalpies for these two steps. Infrared spectra during isotopic displacement and thermal desorption with 12CO-13CO mixtures showed that the binding, dynamics, and thermodynamics of CO chemisorbed at saturation coverages do not depend on Pt cluster size in a range that strongly affects the coordination of Pt atoms exposed at cluster surfaces. These data and their theoretical and mechanistic interpretations indicate that the remarkable structure insensitivity observed for CO oxidation reactions reflects average CO binding properties that are essentially independent of cluster size. Theoretical estimates of rate and equilibriumconstants for surface reactions and CO adsorption show that both parameters increase as the coordination of exposed Pt atoms decreases in Pt201 cluster surfaces; such compensation dampens but does not eliminate coordination and cluster size effects on measured rate constants. The structural features and intrinsic non-uniformity of cluster surfaces weaken when CO forms saturated monolayers on such surfaces, apparently because surfaces and adsorbates restructure to balance CO surface binding and CO-CO interaction energies.

  6. Adsorbed hydrogen detection on a surface by slow electron energy loss, physisorption, chemisorption

    International Nuclear Information System (INIS)

    The use of Electron Energy Loss Spectroscopy (EELS) for the detection of hydrogen adsorbed on a surface is discussed. The principle of EELS is reminded and the experimental set up described. An overwiew of experimental results obtained on various substrates is given. It is shown that this method is able to determine the chemical form of hydrogen (physisorbed, chemisorbed, etc...). Furthermore the role of the surface dipole moment on hydrogen physisorption is outlined

  7. Long-range surface faceting induced by chemisorption of PTCDA on stepped Ag(111) surfaces

    Science.gov (United States)

    Schmitt, Stefan; Schöll, Achim; Umbach, Eberhard

    2016-01-01

    The organic molecule PTCDA preferentially adsorbs on steps of vicinal Ag(111) surfaces and bunches them to well defined facet planes. These depend on coverage and annealing temperature and are independent of the nominal step direction and angle of inclination of the unreconstructed initial surface. We study the development of the facets and present a map of all 16 types of facets in a stereographic triangle of 35° off the [111]-direction. The faceting mechanism is interpreted as orientational phase separation originating from different bonding strengths of PTCDA on various facets. The faceting drives the system to the minimum of its surface free energy.

  8. CO chemisorption and dissociation at high coverages during CO hydrogenation on Ru catalysts.

    Science.gov (United States)

    Loveless, Brett T; Buda, Corneliu; Neurock, Matthew; Iglesia, Enrique

    2013-04-24

    Density functional theory (DFT) and infrared spectroscopy results are combined with mechanism-based rate equations to assess the structure and thermodynamics of chemisorbed CO (CO*) and its activation during Fischer-Tropsch synthesis (FTS). CO* binding becomes weaker with increasing coverage on Ru(0001) and Ru201 clusters, but such decreases in binding energy occur at higher coverages on Ru201 clusters than on Ru(0001) surfaces (CO*/Ru = 1.55 to 0.75); such differences appear to reflect weaker repulsive interactions on the curved surfaces prevalent on small Ru201 clusters. Ru201 clusters achieve stable supramonolayer coverages (CO*/Ru > 1) by forming geminal dicarbonyls at low-coordination corner/edge atoms. CO* infrared spectra on Ru/SiO2 (~7 nm diameter) detect mobile adlayers that anneal into denser structures at saturation. Mechanism-based FTS rate equations give activation energies that reflect the CO*-saturated surfaces prevalent during catalysis. DFT-derived barriers show that CO* predominantly reacts at (111) terraces via H-assisted reactions, consistent with measured effects of H2 and CO pressures and cluster size effects on rates and O-rejection selectivities. Barriers are much higher for unassisted CO* dissociation on (111) terraces and low-coordination atoms, including step-edge sites previously proposed as active sites for CO* dissociation during FTS. DFT-derived barriers indicate that unassisted CO* dissociation is irreversible, making such steps inconsistent with measured rates. The modest activation barriers of H-assisted CO* dissociation paths remove a requirement for special low-coordination sites for unassisted CO* activation, which is inconsistent with higher rates on larger clusters. These conclusions seem generally applicable to Co, Fe, and Ru catalysts, which show similar FTS rate equations and cluster size effects. This study also demonstrates the feasibility and relevance of DFT treatments on the curved and crowded cluster surfaces where catalysis occurs.

  9. sup 1 H NMR studies of hydrogen and carbon monoxide chemisorption on the EUROPt-1 catalyst

    CERN Document Server

    Bouyssy, P X

    2001-01-01

    possible carbon monoxide-induced reorganisation of the surface sites available for hydrogen, following a carbon monoxide precoverage above a critical level. It also shows that carbon monoxide blocks hydrogen adsorption but not in the manner expected. No desorption of carbon monoxide was observed with gas phase infrared experiments even at hydrogen coverages approaching saturation. Secondly, to further the understanding of the dynamics of adsorbed hydrogen exchanging between the strongly bound and the weakly bound sites, proton relaxation NMR experiments were undertaken. T sub 1 and T sub 1 subrho measurements were carried out as a function of hydrogen coverage at room temperature and as a function of temperature at fixed hydrogen coverage. These experiments proved to be experimentally challenging and the data obtained do not show a clear enough trend to reach a significant conclusion as was firstly expected. A specially designed sup 1 H NMR probe, capable of holding a large quantity of catalyst sample for in ...

  10. NO Chemisorption on Cu/SSZ-13: a Comparative Study from Infrared Spectroscopy and DFT Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Renqin; McEwen, Jean-Sabin; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2014-11-07

    The locations and energies of Cu ions in a Cu/SSZ-13 zeolite catalyst were investigated by density functional theory (DFT) calculations. For 'naked' Cu2+ ions (i.e., Cu2+ ions with no ligands in their coordination spheres other than zeolite lattice oxygen atoms), the more energetically favorable sites are within a 6-membered ring. However, with the presence of various adsorbates, the energy difference between 6- and 8-membered ring locations greatly diminishes. Specifically, Cu2+ ions are substantially stabilized by -OH ligands (as [CuII(OH)]+), making the extra-framework sites in an 8-membered ring energetically more favorable than 6-membered ring sites. Under fully dehydrated high vacuum conditions with different Si/Al and Cu/Al ratios, three chemisorbed NO species coexist upon exposure of NO to Cu/SSZ-13: NO+, Cu2+-NO and Cu+-NO. The relative signal intensities for these bands vary greatly with Si/Al ratios. The vibrational frequency of chemisorbed NO was found to be very sensitive to the location of Cu2+ ions. On the one hand, with the aid from DFT calculations, the nature for these vibrations can be assigned in detail. On the other hand, the relative intensities for various Cu2+-NO species provide a good measure of the nature of Cu2+ ions as functions of Si/Al and Cu/Al ratios and the presence of humidity. These new findings cast doubt on the generally accepted proposal that only Cu2+ ions located in 6-membered rings are catalytically active for NH3-SCR.

  11. Chemisorption of CO and mechanism of CO oxidation on supported platinum nanoclusters

    KAUST Repository

    Allian, Ayman Daoud

    2011-03-30

    Kinetic, isotopic, and infrared studies on well-defined dispersed Pt clusters are combined here with first-principle theoretical methods on model cluster surfaces to probe the mechanism and structural requirements for CO oxidation catalysis at conditions typical of its industrial practice. CO oxidation turnover rates and the dynamics and thermodynamics of adsorption-desorption processes on cluster surfaces saturated with chemisorbed CO were measured on 1-20 nm Pt clusters under conditions of strict kinetic control. Turnover rates are proportional to O2 pressure and inversely proportional to CO pressure, consistent with kinetically relevant irreversible O2 activation steps on vacant sites present within saturated CO monolayers. These conclusions are consistent with the lack of isotopic scrambling in C16O-18O2-16O 2 reactions, and with infrared bands for chemisorbed CO that did not change within a CO pressure range that strongly influenced CO oxidation turnover rates. Density functional theory estimates of rate and equilibrium constants show that the kinetically relevant O2 activation steps involve direct O2* (or O2) reactions with CO* to form reactive O*-O-C*=O intermediates that decompose to form CO 2 and chemisorbed O*, instead of unassisted activation steps involving molecular adsorption and subsequent dissociation of O2. These CO-assisted O2 dissociation pathways avoid the higher barriers imposed by the spin-forbidden transitions required for unassisted O2 dissociation on surfaces saturated with chemisorbed CO. Measured rate parameters for CO oxidation were independent of Pt cluster size; these parameters depend on the ratio of rate constants for O2 reactions with CO* and CO adsorption equilibrium constants, which reflect the respective activation barriers and reaction enthalpies for these two steps. Infrared spectra during isotopic displacement and thermal desorption with 12CO- 13CO mixtures showed that the binding, dynamics, and thermodynamics of CO chemisorbed at saturation coverages do not depend on Pt cluster size in a range that strongly affects the coordination of Pt atoms exposed at cluster surfaces. These data and their theoretical and mechanistic interpretations indicate that the remarkable structure insensitivity observed for CO oxidation reactions reflects average CO binding properties that are essentially independent of cluster size. Theoretical estimates of rate and equilibrium constants for surface reactions and CO adsorption show that both parameters increase as the coordination of exposed Pt atoms decreases in Pt201 cluster surfaces; such compensation dampens but does not eliminate coordination and cluster size effects on measured rate constants. The structural features and intrinsic non-uniformity of cluster surfaces weaken when CO forms saturated monolayers on such surfaces, apparently because surfaces and adsorbates restructure to balance CO surface binding and CO-CO interaction energies. © 2011 American Chemical Society.

  12. Chemisorption of aromatic molecules on Si(100)-2x1. An HREELS study

    CERN Document Server

    Alkunshalie, T

    1998-01-01

    HREELS has been used to investigate the growth of ultra-thin organic film on Si(100)-2x1 by reactive coupling of polyimide precursors. 1,4- phenylenediamine and pyromelltic dianhydride were sequentially dosed on clean Si(100)-2x1 under ultra high vacuum conditions. The interfacial imidisation was initiated by thermal curing at 200 deg C. To simplify the analysis of the vibrational data, model compounds benzoic acid, aniline and phthalic anhydride were characterised first. HREEL spectra show that the model compounds absorb through dissociation of the functional group. The spectra also show that an oligimide chain has been formed which stands upright on the surface. The oligomer chain bonds to the silicon surface via a Si-(NH)-C linkage.

  13. Multidimensional effects in dissociative chemisorption: H2 on Cu and Ni surfaces

    DEFF Research Database (Denmark)

    Engdahl, C.; Lundqvist, Bengt; Nielsen, U.;

    1992-01-01

    It is shown that, in order to describe and understand the trends found experimentally for the variation of the H2 sticking probability with crystal face on Cu and Ni surfaces, the dynamics of all six molecular degrees of freedom must be included. The effective-medium theory is used to estimate th...

  14. H2 recombination on interstellar grains. [due to hydrogen atom chemisorption on graphite grains

    Science.gov (United States)

    Barlow, M. J.; Silk, J.

    1976-01-01

    From a consideration of relevant theoretical and experimental data it is concluded that H atoms (but not H2 molecules) will be chemisorbed on interstellar graphite grains, with H2 formation proceeding efficiently for graphite grain temperatures less than 70 K. It is argued that graphite grains will act as the principal sites for H2 formation, with a formation rate of about 4 to the minus 17th cu cm per sec. Heating by H2 molecules formed by surface recombination is analyzed in the context of the available experimental data, and a heating rate is derived and compared with other suggested cloud heating mechanisms. It is concluded that H2 recombination will provide the largest heat source in diffuse clouds if the albedo of interstellar dust in the 912-1200 A region is high (about 0.9), whereas if the albedo in this wavelength region is lower (about 0.5), photoelectron ejection from grains will tend to predominate, and can explain observed cloud temperatures with a carbon depletion factor of approximately 2, a factor attributable to a normal interstellar abundance of graphite grains.

  15. A proposal for the proper use of pseudopotentials in molecular orbital cluster model studies of chemisorption

    Science.gov (United States)

    Bagus, P. S.; Bauschlicher, C. W., Jr.; Nelin, C. J.; Laskowski, B. C.; Seel, M.

    1984-01-01

    The interaction of CO with Cu5, Ni5, and Al4 are treated as model systems for molecular adsorption on metal surfaces. The effect of the use of pseudopotentials for the metal atoms is studied by considering three types of clusters. In the first case, all of the metal electrons are explicitly included in the wave function; an all electron (AE) treatment. In the second case, the metal atom which directly interacts with the CO is described by AE but the remaining metal atoms include a pseudopotential for their core electrons. Finally, in the third case, all of the metal atoms in the cluster have a pseudopotential treatment for the core electrons. The AE cluster results are taken as reference values for the two pseudopotential treatments. The mixed cluster results are in excellent agreement with those of the all AE clusters; however, the results for the all pseudopotential cluster of Ni5CO or of Cu5CO are qualitatively different. The pseudopotential treatment for all of the metal atoms often leads to results that contain serious errors and it is not a reliable approach.

  16. Influence of hydrogen chemisorption kinetics on the interpretation of hydrogen transport through iron membranes

    Science.gov (United States)

    Shanabarger, M. R.; Taslami, A.; Nelson, H. G.

    1981-01-01

    The influence of a specific surface reaction on the transport of gas-phase hydrogen through iron membranes has been investigated on the basis of model calculations. The surface reaction involves an adsorbed molecular hydrogen precursor between the gas phase and the dissociated chemisorbed state. The calculations demonstrate that the surface reaction for the H2/Fe system makes significant contributions to the time delay associated with the transient hydrogen transport through iron membranes, even under conditions where the steady-state hydrogen transport is independent of the surface reaction. These contributions to the time delay are interpreted in terms of an effective diffusivity, which is a function of the pressure on the entrance side and the thickness of the membrane.

  17. The effects of cations and anions on hydrogen chemisorption at Pt

    Science.gov (United States)

    Huang, J. C.; Ogrady, W. E.; Yeager, E.

    1977-01-01

    Experimental evidence based on linear sweep voltammetry is presented to substantiate the view that ionic adsorption substantially shifts electrode potentials in addition to the relative heights of the hydrogen adsorption peaks. HClO4 and HF are chosen as better reference electrolytes for anion studies. The voltammetry curves for 0.1M HF and 0.1M HClO4 as well as the effect of adding successively increasing amounts of H2SO4 to these electrolytes are discussed. The measurements are also extended to alkaline solutions. Mechanisms whereby the addition of various cations and anions to electrolytes such as HF and HClO4 can induce changes in the structure of the hydrogen adsorption region in the voltammetry curves are identified: (1) blocking of sites by anion adsorption and coupling of hydrogen adsorption and anion desorption, (2) modification in the hydrogen adsorption energies for sites adjacent to adsorbed anions, (3) changes in the potential distribution across the interface, and (4) surface restructuring.

  18. Molecular Orbital Studies for Na Chemisorption on the Ga-stabilized GaAs(100) Surface

    International Nuclear Information System (INIS)

    Using the ASED-MO total energy calculations of the model clusters, we have investigated the adsorption site and the corresponding adsorption bond length of Na on the Ga-stabilized GaAs(100) surface. The bridge site (III) is the most stable site for the adsorption, and the distance between Na and the surface is 1.47 A. Our calculations suggest that this bridge site (III), the furthest one from the As atoms, is the most effective adsorption site of Na. It suggests that Na may interact more effectively with Ga than with As in the low Na coverage

  19. Metal compounds in zeolites as active components of chemisorption and catalysis. Quantum chemical approach

    International Nuclear Information System (INIS)

    A short review of possible catalitic active sites associated with various types of metal species in zoolite is presented. The structural and electronic peculiarity of aluminum ions in zeolite lattice and their distribution in the lattice are discussed on the basis of quantum chemical calculations in connection with the formation of Broensted activity of zeolites. Various molecular models of Lewis Acid Sites associated the extra-lattice oxide-hydroxide aluminum species have been investigated by means of density functional model cluster calculations using CO molecule as a probe. Probable ways of formation of the selective oxidation center in FeZSM-5 by decomposition of dinitrogen monoxide have been studied by ab-initio quantum chemical calculations. The immediate oxidizing site is reasonably represented by the binuclear iron-hydroxide cluster with peroxo-like fragment located between iron atoms. Various probable intermediates of the selective oxidation center formation resulted from interaction of a hydroperoxide molecule with a lattice titanium ion in titanium silicalite have been investigated by quantum chemical calculations. It was concluded that this reaction requires essential structural reconstruction in the vicinity of the titanium ion. Probability of this structural reconstruction is discussed. Possible reasons of an electron-deficient and electron-enriched state of metal particles entrapped in zoolite cavities are discussed. Also, various probable molecular models of such modified metal particles in zeolite are considered

  20. Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption

    Science.gov (United States)

    Kiuchi, Hisao; Shibuya, Riku; Kondo, Takahiro; Nakamura, Junji; Niwa, Hideharu; Miyawaki, Jun; Kawai, Maki; Oshima, Masaharu; Harada, Yoshihisa

    2016-03-01

    The characteristics of CO2 adsorption sites on a nitrogen-doped graphite model system (N-HOPG) were investigated by X-ray photoelectron and absorption spectroscopy and infrared reflection absorption spectroscopy. Adsorbed CO2 was observed lying flat on N-HOPG, stabilized by a charge transfer from the substrate. This demonstrated that Lewis base sites were formed by the incorporation of nitrogen via low-energy nitrogen-ion sputtering. The possible roles of twofold coordinated pyridinic N and threefold coordinated valley N (graphitic N) sites in Lewis base site formation on N-HOPG are discussed. The presence of these nitrogen species focused on the appropriate interaction strength of CO2 indicates the potential to fine-tune the Lewis basicity of carbon-based catalysts.

  1. Chemisorption of aromatic molecules on Si(100)-2x1. An HREELS study

    Energy Technology Data Exchange (ETDEWEB)

    Alkunshalie, T

    1998-07-01

    HREELS has been used to investigate the growth of ultra-thin organic film on Si(100)-2x1 by reactive coupling of polyimide precursors. 1,4- phenylenediamine and pyromelltic dianhydride were sequentially dosed on clean Si(100)-2x1 under ultra high vacuum conditions. The interfacial imidisation was initiated by thermal curing at 200 deg C. To simplify the analysis of the vibrational data, model compounds benzoic acid, aniline and phthalic anhydride were characterised first. HREEL spectra show that the model compounds absorb through dissociation of the functional group. The spectra also show that an oligimide chain has been formed which stands upright on the surface. The oligomer chain bonds to the silicon surface via a Si-(NH)-C linkage. (author)

  2. CHEMISORPTION OF SULFUR (IV) OXIDE BY WATER UNDER STATIC CONDITIONS. HENRY’S CONSTANT

    OpenAIRE

    Khoma, R. E.; Dlubovskiy, R. M.

    2015-01-01

    The absorption of sulfur (IV) oxide by water and aqueous solutions has the practical relevance as well as the theoretical interest. The mathematical model showing the relationship of effective Henry’s constant (HS(IV)*, М/Pa) with Henry’s constant (HSO2, М/Pа), and mole fractions of SO2-H2O, HSO3-, S2O5 (2-)  and SO32- is: where K1and K2– dissociation constants of “sulphurous acid” for the first and second degrees, respectively; K*– dimerization constant of hydrogensulfite ions; [H+] – hydrog...

  3. Chemisorption of oxygen and subsequent reactions on low index surfaces of β-Mo2C

    DEFF Research Database (Denmark)

    Shi, Xue Rong; Wang, Shengguang; Wang, Jianguo

    2016-01-01

    to the carbon vacancy were identified. We examined the effect of oxygen coverage on the morphology of β-Mo2C by plotting the equilibrium crystal shape. Thermodynamic effect of temperature and reactant or product pressure on the CO/CO2 desorption were investigated. The CO/CO2 desorption is more favorable...... at the saturated oxygen coverage than the low oxygen coverage thermodynamically. The subsequent oxygen diffusion to the carbon vacancy after CO/CO2 desorption may happen depending on the surfaces and oxygen coverage....

  4. Research of the behaviour of O chemisorption on the (110) surface of Rhx-Pt1-x alloy

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Zhang Guo-Ying; Wang Rui-Dan; Zhong Bo

    2006-01-01

    An atomic group model of the disordered binary alloy Rhx-Pt1-x has been constructed to investigate surface segregation. According to the model, we have calculated the electronic structure of the Rhx-Pt-x alloy surface by using the recursion method when O atoms are adsorbed on the Rhxx(110) surface under the condition of coverage 0.5. The calculation results indicate that the chemical adsorption of O changes greatly the density of states near the Fermi level, and the surface segregation exhibits a reversal behaviour. In addition, when x<0.3, the surface on which O is adsorbed displays the property of Pt; whereas when x> 0.3 it displays the property of Rh.

  5. Correlation of Chemisorption and Electronic Effects for Metal Oxide Interfaces: Transducing Principles for Temperature Programmed Gas Microsensors (Final Report)

    Energy Technology Data Exchange (ETDEWEB)

    S. Semancik; R. E. Cavicchi; D. L. DeVoe; T. J. McAvoy [National Institute of Standards and Technology (US)]|[University of Maryland (US)

    2001-12-21

    This Final Report describes efforts and results for a 3-year DoE/OST-EMSP project centered at NIST. The multidisciplinary project investigated scientific and technical concepts critical for developing tunable, MEMS-based, gas and vapor microsensors that could be applied for monitoring the types of multiple analytes (and differing backgrounds) encountered at DoE waste sites. Micromachined ''microhotplate'' arrays were used as platforms for fabricating conductometric sensor prototypes, and as microscale research tools. Efficient microarray techniques were developed for locally depositing and then performance evaluating thin oxide films, in order to correlate gas sensing characteristics with properties including composition, microstructure, thickness and surface modification. This approach produced temperature-dependent databases on the sensitivities of sensing materials to varied analytes (in air) which enable application-specific tuning of microsensor arrays. Mechanistic studies on adsorb ate transient phenomena were conducted to better understand the ways in which rapid temperature programming schedules can be used to produce unique response signatures and increase information density in microsensor signals. Chemometric and neural network analyses were also employed in our studies for recognition and quantification of target analytes.

  6. Correlation of Chemisorption and Electronic Effects for Metal Oxide Interfaces: Transducing Principles for Temperature Programmed Gas Microsensors

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Steve Semancik

    2002-01-03

    The spectrum of chemical monitoring problems faced by the Department of Energy at its hazardous waste sites is formidable. It is likely that a variety of existing types of instrumentation will be applied in the years ahead, with varying degrees of practicality and success. A tremendous impact could be realized, however, if instrumental methods could be supplemented by a low-cost, reliable sensing technology for continuous monitoring of a range of species, including, for example, volatile organics, chlorinated hydrocarbons, ammonia, and hydrogen. To meed the diverse gas and vapor monitoring needs at ODE hazardous waste sites, the sensing system must offer, inherently, and adaptability to match the wide variety of analytes and environmental conditions that well be encountered (in tank vapor spaces, and at locations with contaminated soil or groundwater.) The purpose of this project was to investigate scientific and technical concepts that could enable a MEMS-based chemical sensing technology (developed in its foundational form at NIST during early and mid 1990's) to be made tunable for multiple target analytes in differing types of backgrounds relevant to DOE waste storage and remediation

  7. Study of atomic and molecular oxygen chemisorption on BC3 nanotubes with Stone–Wales defects using density functional theory

    International Nuclear Information System (INIS)

    Highlights: • Atomic and molecular oxygen adsorption on BC3 nanotubes is studied by DFT methods. • Perfect BC3 nanotubes and four types of Stone-Wales defects are considered. • Adsorption of O is always exothermic, but for O2 it is sometimes endothermic. • Molecular oxygen is chemisorbed and produces spin-singlet states. • O2 adsorption on SW-CC-c system results in a half-metallic antiferromagnet. - Abstract: Density functional theory calculations are used to study the adsorption of chemical species including oxygen atom and oxygen molecule on the perfect and defective BC3 nanotubes. Stone–Wales topological defects with four different bond rotations have been examined. The adsorption of atomic oxygen is exothermic in all cases, while for the molecular oxygen, some sites showed endothermic adsorption. Comparative studies on the adsorption of these chemical species shows the maintenance of semiconductive behavior of nanotubes, except for one of the systems, the defected nanotube with a circumferential C–C bond rotation. In this system, the adsorption of molecular oxygen generates a half-metallic antiferromagnet. The results obtained in this paper are relevant for chemical sensing and spintronics applications

  8. FINAL REPORT. CORRELATION OF CHEMISORPTION AND ELECTRONIC EFFECTS FOR METAL OXIDE INTERFACES: TRANSDUCING PRINCIPLES FOR TEMPERATURE PROGRAMMED GAS MICROSENSORS

    Science.gov (United States)

    The spectrum of chemical monitoring problems faced by the Department of Energy (DOE) at its hazardous waste sites is formidable. It is likely that a variety of existing types of instrumentation will be applied in the years ahead, with varying degrees of practicality and success. ...

  9. CORRELATION OF CHEMISORPTION AND ELECTRONIC EFFECTS FOR METAL/OXIDE INTERFACES: TRANSDUCING PRINCIPLES FOR TEMPERATURE-PROGRAMMED GAS MICROSENSORS

    Science.gov (United States)

    The range of chemical monitoring problems faced by the Department of Energy (DOE) at its hazardous waste sites is formidable. It is likely that a variety of existing types of instrumentation will be applied in the years ahead, with varying degrees of practicality and success. A...

  10. Determination of the structural and chemisorption characteristics of granulated active charcoal on the basis of coconut shell

    Directory of Open Access Journals (Sweden)

    Milenković Dragan D.

    2004-01-01

    Full Text Available Wastewater purification and the acquirement of drinking water from water streams that are in most cases recipients of various industrial plants, present a significant problem nowadays. The structural characteristics of granulated active charcoal (GAC obtained by the carbonization of coconut shells and activated by steam are presented in this paper. The established kinetics of suspending cyanide from aqueous solution using GAC impregnated with copper(II acetate were studied and a mathematical model estabkusged by a regression - correlation analysis.

  11. Electronic energy transfer from molecules to metal and semiconductor surfaces, and chemisorption-induced changes in optical response of the nickel (111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Whitmore, P.M.

    1982-10-01

    The evolution of molecular excited states near solid surfaces is investigated. The mechanisms through which energy is transferred to the surface are described within a classical image dipole picture of the interaction. More sophisticated models for the dielectric response of the solid surface add important new decay channels for the energy dissipation. The predictions and applicability of three of these refined theories are discussed.

  12. Quantum and classical dynamics of water dissociation on Ni(111): A test of the site-averaging model in dissociative chemisorption of polyatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Bin [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Guo, Hua, E-mail: hguo@unm.edu [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2015-10-28

    Recently, we reported the first highly accurate nine-dimensional global potential energy surface (PES) for water interacting with a rigid Ni(111) surface, built on a large number of density functional theory points [B. Jiang and H. Guo, Phys. Rev. Lett. 114, 166101 (2015)]. Here, we investigate site-specific reaction probabilities on this PES using a quasi-seven-dimensional quantum dynamical model. It is shown that the site-specific reactivity is largely controlled by the topography of the PES instead of the barrier height alone, underscoring the importance of multidimensional dynamics. In addition, the full-dimensional dissociation probability is estimated by averaging fixed-site reaction probabilities with appropriate weights. To validate this model and gain insights into the dynamics, additional quasi-classical trajectory calculations in both full and reduced dimensions have also been performed and important dynamical factors such as the steering effect are discussed.

  13. Atomic-Level Organization of Vicinal Acid-Base Pairs through the Chemisorption of Aniline and Derivatives onto Mesoporous SBA15

    KAUST Repository

    Basset, Jean-Marie

    2016-06-09

    The design of novel heterogeneous catalysts with multiple adjacent functionalities is of high interest for heterogeneous catalysis. Herein, we report a method to obtain a majority bifunctional acid-base pairs on SBA15. Aniline reacts with SBA15 by opening siloxane bridges leading to N-phenylsilanamine-silanol pairs. In contrast with ammonia treated surfaces, the material is stable under air/moisture. Advanced solid state MAS NMR: 2D ¹H-¹H double-quantum, ¹H-¹³C HETCOR experiments and dynamic nuclear polarization enhanced ²⁹Si and ¹⁵N spectra demonstrate both the close proximity between the two moieties and the formation of a covalent Si-N surface bond and confirm the design of vicinal acid-base pairs. This approach was successfully applied to the design of a series of aniline derivatives bifunctional SBA15. A correlation of the substituents effects on the aromatic ring (Hammet parameters) on the kinetics of the model reaction of Knoevenagel is observed.

  14. Quantum and classical dynamics of water dissociation on Ni(111): A test of the site-averaging model in dissociative chemisorption of polyatomic molecules

    International Nuclear Information System (INIS)

    Recently, we reported the first highly accurate nine-dimensional global potential energy surface (PES) for water interacting with a rigid Ni(111) surface, built on a large number of density functional theory points [B. Jiang and H. Guo, Phys. Rev. Lett. 114, 166101 (2015)]. Here, we investigate site-specific reaction probabilities on this PES using a quasi-seven-dimensional quantum dynamical model. It is shown that the site-specific reactivity is largely controlled by the topography of the PES instead of the barrier height alone, underscoring the importance of multidimensional dynamics. In addition, the full-dimensional dissociation probability is estimated by averaging fixed-site reaction probabilities with appropriate weights. To validate this model and gain insights into the dynamics, additional quasi-classical trajectory calculations in both full and reduced dimensions have also been performed and important dynamical factors such as the steering effect are discussed

  15. Thermoelectric properties of nano-granular indium-tin-oxide within modified electron filtering model with chemisorption-type potential barriers

    Science.gov (United States)

    Brinzari, V.; Nika, D. L.; Damaskin, I.; Cho, B. K.; Korotcenkov, G.

    2016-07-01

    In this work, an approach to the numerical study of the thermoelectric parameters of nanoscale indium tin oxide (ITO, Sn contentchemisorption effect, and this can be observed despite of the degeneracy of the conduction band (CB). This hypothesis and the corresponding calculations are in good agreement with recent experimental studies [Brinzari et al. Thin Solid Films 552 (2014) 225].

  16. Practical method for highly accurate large-scale surface calculations. [of linearized muffin-tin orbital technique for chemisorption and magnetism

    Science.gov (United States)

    Fernando, G. W.; Cooper, B. R.; Ramana, M. V.; Krakauer, H.; Ma, C. Q.

    1986-01-01

    An accurate and efficient film linearized muffin-tin orbital (FLMTO) technique for surface electronic-structure calculations is presented which uses only 60-70 basis functions, as opposed to the 300 functions used in the linear augmented plane-wave method. Calculations for three different (3d and 4d) transition-metal films resulted in high quality results for five-layer slabs of Cu(001), Fe(001), and Ru(001), in addition to good results for the work functions and projected density of states. By retaining the LMTO small basis size, computer time and memory are reduced, making practical the study of systems with a larger number of atoms in the two-dimensional unit cell.

  17. Strong Lithium Polysulfide Chemisorption on Electroactive Sites of Nitrogen-Doped Carbon Composites For High-Performance Lithium–Sulfur Battery Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jiangxuan; Gordin, Mikhail; Xu, Terrence; Chen, Shuru; Yu, Zhaoxin; Sohn, Hiesang; Lu, Jun; Ren, Yang; Duan, Yuhua; wang, Donghai

    2015-03-27

    Despite the high theoretical capacity of lithium–sulfur batteries, their practical applications are severely hindered by a fast capacity decay, stemming from the dissolution and diffusion of lithium polysulfides in the electrolyte. A novel functional carbon composite (carbon-nanotube-interpenetrated mesoporous nitrogen-doped carbon spheres, MNCS/CNT), which can strongly adsorb lithium polysulfides, is now reported to act as a sulfur host. The nitrogen functional groups of this composite enable the effective trapping of lithium polysulfides on electroactive sites within the cathode, leading to a much improved electrochemical performance (1200 mAh g-1 after 200 cycles). The enhancement in adsorption can be attributed to the chemical bonding of lithium ions by nitrogen functional groups in the MNCS/CNT framework. Furthermore, the micrometer-sized spherical structure of the material yields a high areal capacity (ca. 6 mAh cm-2) with a high sulfur loading of approximately 5 mg cm-2, which is ideal for practical applications of the lithium–sulfur batteries.

  18. Strong Lithium Polysulfide Chemisorption on Electroactive Sites of Nitrogen-Doped Carbon Composites For High-Performance Lithium-Sulfur Battery Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jiangxuan [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering; Gordin, Mikhail L. [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering; Xu, Terrence [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering; Chen, Shuru [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering; Yu, Zhaoxin [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering; Sohn, Hiesang [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering; Lu, Jun [Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Div.; Ren, Yang [Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Div.; Duan, Yuhua [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Wang, Donghai [Pennsylvania State Univ., State College, PA (United States). Dept. of Mechanical and Nuclear Engineering

    2015-03-27

    Despite the high theoretical capacity of lithium–sulfur batteries, their practical applications are severely hindered by a fast capacity decay, stemming from the dissolution and diffusion of lithium polysulfides in the electrolyte. A novel functional carbon composite (carbon-nanotube-interpenetrated mesoporous nitrogen-doped carbon spheres, MNCS/CNT), which can strongly adsorb lithium polysulfides, is now reported to act as a sulfur host. The nitrogen functional groups of this composite enable the effective trapping of lithium polysulfides on electroactive sites within the cathode, leading to a much improved electrochemical performance (1200 mAhg-1after 200 cycles). The enhancement in adsorption can be attributed to the chemical bonding of lithium ions by nitrogen functional groups in the MNCS/CNT framework. Furthermore, the micrometer-sized spherical structure of the material yields a high areal capacity (ca.6 mAhcm-2) with a high sulfur loading of approximately 5 mgcm-2, which is ideal for practical applications of the lithium–sulfur batteries.

  19. Synergistically Enhanced Polysulfide Chemisorption Using a Flexible Hybrid Separator with N and S Dual-Doped Mesoporous Carbon Coating for Advanced Lithium-Sulfur Batteries.

    Science.gov (United States)

    Balach, Juan; Singh, Harish K; Gomoll, Selina; Jaumann, Tony; Klose, Markus; Oswald, Steffen; Richter, Manuel; Eckert, Jürgen; Giebeler, Lars

    2016-06-15

    Because of the outstanding high theoretical specific energy density of 2600 Wh kg(-1), the lithium-sulfur (Li-S) battery is regarded as a promising candidate for post lithium-ion battery systems eligible to meet the forthcoming market requirements. However, its commercialization on large scale is thwarted by fast capacity fading caused by the Achilles' heel of Li-S systems: the polysulfide shuttle. Here, we merge the physical features of carbon-coated separators and the unique chemical properties of N and S codoped mesoporous carbon to create a functional hybrid separator with superior polysulfide affinity and electrochemical benefits. DFT calculations revealed that carbon materials with N and S codoping possess a strong binding energy to high-order polysulfide species, which is essential to keep the active material in the cathode side. As a result of the synergistic effect of N, S dual-doping, an advanced Li-S cell with high specific capacity and ultralow capacity degradation of 0.041% per cycle is achieved. Pushing our simple-designed and scalable cathode to a highly increased sulfur loading of 5.4 mg cm(-2), the Li-S cell with the functional hybrid separator can deliver a remarkable areal capacity of 5.9 mAh cm(-2), which is highly favorable for practical applications. PMID:27225061

  20. Covalent functionalization of strained graphene

    OpenAIRE

    Boukhvalov, Danil W.; Son, Young-Woo

    2012-01-01

    Enhancement of the chemical activity of graphene is evidenced by first-principles modelling of chemisorption of the hydrogen, fluorine, oxygen and hydroxyl groups on strained graphene. For the case of negative strain or compression, chemisorption of the single hydrogen, fluorine or hydroxyl group is energetically more favourable than those of their pairs on different sublattices. This behaviour stabilizes the magnetism caused by the chemisorption being against its destruction by the pair form...

  1. Stanovení velikosti specifického povrchu palladia v hydrogenačních katalyzátorech chemisorpcí oxidu uhelnatého

    OpenAIRE

    Patera, J.; Krupka, J.; Pašek, J.; Paterová, I.; Jirátová, K.; Murafa, N. (Nataliya)

    2012-01-01

    An apparatus for dynamic chemisorption measurement was built and a reliable experimental methodology based on determination of the specific surface area of Pd (SPd) and the average particle size of Pd (dAV) in hydrogenation catalysts was developed using chemisorption of CO. Experimental conditions necessary for providing reproducibility of measured values were defined. The accuracy of the determination was verified by independent characterization techniques and by comparing chemisorption meas...

  2. Effects of steps and defects on O2 dissociation on clean and modified Cu(100)

    DEFF Research Database (Denmark)

    Hirsimaki, M.; Chorkendorff, Ib

    2003-01-01

    Dissociative chemisorption of O-2 on Cu(100), S/Cu(100) and Ag/Cu(100) surface alloy has been investigated by Auger electron spectroscopy (AES). A strong reduction in the initial O-2 chemisorption probability (S-0) from 0.05 to 7.4 x 10(-3) is observed already at an Ag coverage of 0.02 ML. Further...

  3. Adsorption-induced restructuring of gold nanochains

    DEFF Research Database (Denmark)

    Bahn, Sune Rastad; Lopez, Nuria; Nørskov, Jens Kehlet;

    2002-01-01

    The chemical properties of single-atomic chains of gold atoms are investigated using density functional calculations. The nanochains are shown to be unusually chemically active with strong chemisorption of oxygen atoms and carbon monoxide. The chemisorption energies vary significantly with the st......The chemical properties of single-atomic chains of gold atoms are investigated using density functional calculations. The nanochains are shown to be unusually chemically active with strong chemisorption of oxygen atoms and carbon monoxide. The chemisorption energies vary significantly...... with the strain/stress conditions for the chain. Oxygen atoms are found to energetically prefer to get incorporated into a chain forming a new type of gold-oxygen nanochain with a conductance of one quantum unit. We suggest that the long bond lengths observed in electron microscopy investigations of gold chains...

  4. Hydrogen adsorption on boron doped graphene: an {\\it ab initio} study

    OpenAIRE

    Miwa, R. H.; Martins, T B; Fazzio, A.

    2007-01-01

    The electronic and structural properties of (i) boron doped graphene sheets, and (ii) the chemisorption processes of hydrogen adatoms on the boron doped graphene sheets have been examined by {\\it ab initio} total energy calculations.

  5. A New Activation Method for Electroless Metal Plating:Palladium Laden via Bonding with Self—Assembly Monolayers

    Institute of Scientific and Technical Information of China (English)

    LiNaXU; JianHuiLIAO; 等

    2002-01-01

    A new activation method has been developed for electroless copper plating on silicon wafer based on palladium chemisorption on SAMs of APTS without SnCl2 sensitization and roughening condition.A closely packed electroless copper film with strong adhesion is successfully formed by AFM observation.XPS study indicates that palladium chemisorption occurred via palladium chloride bonding to the pendant amino group of the SAMs.

  6. A New Activation Method for Electroless Metal Plating: Palladium Laden via Bonding with Self-Assembly Monolayers

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new activation method has been developed for electroless copper plating on silicon wafer based on palladium chemisorption on SAMs of APTS without SnCl2 sensitization and roughening condition. A closely packed electroless copper film with strong adhesion is successfully fonned by AFM observation. XPS study indicates that palladium chemisorption occurred via palladium chloride bonding to the pendant amino group of the SAMs.

  7. Progress in surface and membrane science

    CERN Document Server

    Cadenhead, D A; Rosenberg, M D

    1975-01-01

    Progress in Surface and Membrane Science, Volume 9 covers the developments in surface and membrane science. The book discusses the physical adsorption of gases and vapors in micropores; the chemisorption theory; and the role of radioisotopes in the studies of chemisorption and catalysis. The text also describes the interaction of ions with monolayers; and the isolation and characterization of mycoplasma membranes. Chemists, physical chemists, and microbiologists will find the book useful.

  8. Reaction of tungsten anion clusters with molecular and atomic nitrogen

    OpenAIRE

    Kim, Young Dok; Stolcic, Davor; Fischer, Matthias; Ganteför, Gerd

    2003-01-01

    Ultraviolet photoelectron spectra for WnN-2 (n=1 8) clusters produced by addition of atomic and molecular nitrogen on W anion clusters are presented. Evidence is provided that molecular chemisorption of N2 is more stable than the dissociative one on tungsten anion clusters consisting of eight atoms or less, which is completely different from the results on tungsten bulk surfaces. A general tendency toward molecular chemisorption for small clusters can be explained by reduced charge transfer f...

  9. On adsorption of aluminium and methyl groups on silica for TMA/H2O process in atomic layer deposition of aluminium oxide nano layers

    Indian Academy of Sciences (India)

    Anu Philip; K Rajeev Kumar

    2010-04-01

    A detailed chemisorption mechanism is proposed for the atomic layer deposition (ALD) of aluminium oxide nano layers using trimethyl aluminum (TMA) and water as precursors. Six possible chemisorption mechanisms, complete ligand exchange, partial ligand exchange, simple dissociation, complete dissociation via ligand exchange, complete dissociation and association, are proposed and related parameters like ligand to metal ratio (L/M), concentrations of metal atoms and methyl groups adsorbed are calculated and compared against reported values. The maximum number of methyl groups that can get attached on the surface is calculated in a different way which yields a more realistic value of 6.25 per nm2 substrate area. The dependence of the number of metal atoms adsorbed on OH concentration is explained clearly. It is proposed that a combination of complete ligand exchange and complete dissociation is the most probable chemisorption mechanism taking place at various OH concentrations.

  10. Some problems in adsorption and calorimetric studies of the steps of catalytic processes

    Institute of Scientific and Technical Information of China (English)

    Victor E. Ostrovskii

    2004-01-01

    Principal side factors as well as technical and procedural peculiarities capable of distorting the results of measurements of adsorbed and desorbed amounts, of falsifying the nature of the processes proceeding in the systems under study, and of promoting artifacts in calorimetric and other studies of gas chemisorption on powders are considered. Modified techniques and procedures allowing the elimination of sources of side phenomena and artifacts and freeing traditional glass static adsorption apparatuses and experimental procedures from undesirable factors and peculiarities are proposed.Some available chemisorption and calorimetric data representing artifacts and also some data that are not artifacts but,due to imperfections of chemisorption techniques, show up as artifacts are presented and discussed. Several applications of the improved techniques and procedures to calorimetric and adsorption studies of the steps of catalytic processes proceeding on the basis of natural gas and of products of its processing are presented and discussed.

  11. Immobilization of Polymeric Luminophor on Nanoparticles Surface

    Science.gov (United States)

    Bolbukh, Yuliia; Podkoscielna, Beata; Lipke, Agnieszka; Bartnicki, Andrzej; Gawdzik, Barbara; Tertykh, Valentin

    2016-04-01

    Polymeric luminophors with reduced toxicity are of the priorities in the production of lighting devices, sensors, detectors, bioassays or diagnostic systems. The aim of this study was to develop a method of immobilization of the new luminophor on a surface of nanoparticles and investigation of the structure of the grafted layer. Monomer 2,7-(2-hydroxy-3-methacryloyloxypropoxy)naphthalene (2,7-NAF.DM) with luminophoric properties was immobilized on silica and carbon nanotubes in two ways: mechanical mixing with previously obtained polymer and by in situ oligomerization with chemisorption after carrier's modification with vinyl groups. The attached polymeric (or oligomeric) surface layer was studied using thermal and spectral techniques. Obtained results confirm the chemisorption of luminophor on the nanotubes and silica nanoparticles at the elaborated synthesis techniques. The microstructure of 2,7-NAF.DM molecules after chemisorption was found to be not changed. The elaborated modification approach allows one to obtain nanoparticles uniformly covered with polymeric luminophor.

  12. The chemistry of simple alkene molecules on Si(100)c(4 × 2): The mechanism of cycloaddition and their selectivities

    Science.gov (United States)

    Akagi, Kazuto; Yoshinobu, Jun

    2016-10-01

    The chemistry of simple alkene molecules on the Si(100) surface is reviewed with the newly-produced visual presentation by theoretical calculations. The early pioneering studies by the Kyoto Group and Pittsburgh group reported the di-σ bond formation and the precursor-mediated chemisorption for acetylene and ethylene on Si(100), respectively. Thereafter, these studies have been stimulating various studies of organic molecules on Si surfaces. Our recent studies have observed the precursor states for alkene chemisorption and elucidated the microscopic mechanisms of the di-σ bond formation (cycloaddition) with the help of theoretical calculations; the site-, stereo- and regio-selective chemisorption of simple alkene molecules on Si(100)c(4 × 2) has been established.

  13. Atomic and molecular adsorption on Rh(111)

    DEFF Research Database (Denmark)

    Mavrikakis, Manos; Rempel, J.; Greeley, Jeffrey Philip;

    2002-01-01

    A systematic study of the chemisorption of both atomic (H, O, N, S, C), molecular (N-2, CO, NO), and radical (CH3, OH) species on Rh(111) has been performed. Self-consistent, periodic, density functional theory (DFT-GGA) calculations, using both PW91 and RPBE functionals, have been employed...... to determine preferred binding sites, detailed chemisorption structures, binding energies, and the effects of surface relaxation for each one of the considered species at a surface coverage of 0.25 ML. The thermochemical results indicate the following order in the binding energies from the least to the most...

  14. Adsorption and collective paramagnetism

    CERN Document Server

    Selwood, Pierce W

    1962-01-01

    Adsorption and Collective Paramagnetism describes a novel method for studying chemisorption. The method is based on the change in the number of unpaired electrons in the adsorbent as chemisorption occurs. The method is applicable to almost all adsorbates, but it is restricted to ferromagnetic adsorbents such as nickel, which may be obtained in the form of very small particles, that is to say, to ferromagnetic adsorbents with a high specific surface. While almost all the data used illustratively have been published elsewhere this is the first complete review of the subject. The book is addresse

  15. Magnetism induced by single-atom defects in nanographites.

    OpenAIRE

    Yazyev, Oleg V.; Helm, Lothar

    2007-01-01

    We study from first principles the magnetism in graphene induced by single carbon atom defects. For two types of defects considered in our study, the hydrogen chemisorption defect and the vacancy defect, the magnetism due to the defect-induced extended states has been observed. Calculated magnetic moments are equal to 1 μB per hydrogen chemisorption defect and ∼1.5 μB per vacancy defect. The magnetic ordering is either ferromagnetic or antiferromagnetic, depending on whether the defects corre...

  16. Importance of the oxygen bond strength for catalytic activity in soot oxidation

    DEFF Research Database (Denmark)

    Christensen, Jakob M.; Grunwaldt, Jan-Dierk; Jensen, Anker D.

    2016-01-01

    (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation...... oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe2O3 and α-Cr2O3. Guided by an interpolation principle FeaCrbOx binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr2Ox binary oxide...

  17. Efficient Methanol Synthesis Catalysts: Long-Term Stability and Deactivation Phenomena

    OpenAIRE

    Fichtl, Matthias

    2014-01-01

    In this thesis the deactivation mechanism on different coprecipitated Cu/ZnO/Al2O3 methanol synthesis catalysts is evaluated. Transmission electron microcopy, X-ray diffraction, chemisorption methods and modeling techniques are applied to correlate the deactivation behavior with structural changes in the active catalyst. Updated models for the catalyst microstructure and deactivation behavior are presented.

  18. Hydrogen dissociation on metal surfaces

    NARCIS (Netherlands)

    Wijzenbroek, M.

    2016-01-01

    Dissociative chemisorption is an important reaction step in many catalytic reactions. An example of such a reaction is the Haber-Bosch process, which is used commercially to produce ammonia, an important starting material in the production of fertilisers. In theoretical descriptions of such chemical

  19. Scanning Tunneling Microscopic Observation of Adatom-Mediated Motifs on Gold-Thiol Self-assembled Monolayers at High Coverage

    DEFF Research Database (Denmark)

    Wang, Yun; Chi, Qijin; Hush, Noel S.;

    2009-01-01

    Self-assembled monolayers (SAMs) formed by chemisorption of a branched-chain alkanethiol, 2-methyl-1-propanethiol, on Au(111) surfaces were studied by in situ scanning tunneling microscopy (STM) under electrochemical potential control and analyzed using extensive density functional theory (DFT) c...

  20. Interactions between acid- and base-functionalized surfaces

    NARCIS (Netherlands)

    Giesbers, M.; Kleijn, J.M.; Cohen Stuart, M.A.

    2002-01-01

    In this paper we present an AFM force study on interactions between chemically modified surfaces. Surfaces with terminal groups of either NH2 or COOH were obtained by chemisorption of a silane-based compound (3-amino-propyltriethoxysilane) on silica or a thiol compound (11-mercapto undecanoic acid)

  1. Electrochemical reactions at surfaces. 1976-September, 1980 (citations from the NTIS Data Base). Report for 1976-September 1980

    Energy Technology Data Exchange (ETDEWEB)

    Cavagnaro, D.M.

    1980-10-01

    This bibliography covers electrode processes in aqueous solutions. The citations discuss battery electrode reactions, fuel cell reactions, electrochemical corrosion studies, catalyst reactions, chemisorption, theoretical analysis, electrical double layer, and measurement techniques. Also included are some molten salt processes. (This updated bibliography contains 148 citations, 23 of which are new entries to the previous edition.)

  2. Environmental chemistry of radioactive waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Duffield, J.R.; Williams, D.R.

    1986-09-01

    In this review the environmental chemistry problems associated with radioactive waste disposal are considered from the point of view of the threat to man of waste disposal, contamination pathways, the chemistry of waste containment, speciation of radio-isotopes, chemisorption, risk assessment and computerized simulation of waste disposal phenomena. A strategy for the future is discussed.

  3. Materials Down Select Decisions Made Within the Department of Energy Hydrogen Sorption Center of Excellence

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, Lin [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2009-11-30

    Technical report describing DOE's Hydrogen Sorption Center of Excellence investigation into various adsorbent and chemisorption materials and progress towards meeting DOE's hydrogen storage targets. The report presents a review of the material status as related to DOE hydrogen storage targets and explains the basis for the down select decisions.

  4. Long-Range Interfacial Electrochemical Electron Transfer of Pseudomonas aeruginosa Azurin-Gold Nanoparticle Hybrid Systems

    DEFF Research Database (Denmark)

    Jensen, Palle Skovhus; Chi, Qijin; Zhang, Jingdong;

    2009-01-01

    We have prepared a "hybrid" of the blue copper protein azurin (Pseudomonas aeruginosa) and a 3 nm gold nanoparticle (AuNP). The AuNP/azurin hybrid was assembled on a Au(111)-electrode surface in a two-step process. The AuNP was first attached to the Au(111) electrode via Au-S chemisorption of a 4...

  5. Chemisorbed and physisorbed structures for 1,10-phenanthroline and dipyrido[3,2-a : 2 ',3 '-c]phenazine on au(111)

    DEFF Research Database (Denmark)

    Cafe, P.F.; Larsen, Allan G.; Yang, W.R.;

    2007-01-01

    Scanning tunneling microscopy (STM) images of 1,10-phenanthroline (PHEN) and dipyrido[3,2-a:2',3'-c]phenazine (DPPZ) on Au(111) are recorded using both in situ and ex situ techniques. The images of PHEN depict regimes of physisorption and chemisorption, whereas DPPZ is only physisorbed. All physi...

  6. Reactive and nonreactive scattering of N-2 from Ru(0001): A six-dimensional adiabatic study

    DEFF Research Database (Denmark)

    Diaz, C.; Vincent, J.K.; Krishnamohan, G.P.;

    2006-01-01

    We have studied the dissociative chemisorption and scattering of N-2 on and from Ru(0001), using a six-dimensional quasiclassical trajectory method. The potential energy surface, which depends on all the molecular degrees of freedom, has been built applying a modified Shepard interpolation method...

  7. When Langmuir is too simple: H-2 dissociation on Pd(111) at high coverage

    DEFF Research Database (Denmark)

    Lopez, Nuria; Lodziana, Zbigniew; Illas, F.;

    2004-01-01

    Recent experiments of H-2 adsorption on Pd(111) [T. Mitsui et al., Nature (London) 422, 705 (2003)] have questioned the classical Langmuir picture of second order adsorption kinetics at high surface coverage requiring pairs of empty sites for the dissociative chemisorption. Experiments find that at...

  8. Interactions of hydrogen with alkali promoted Ru/SiO{sub 2} catalysts: A proton NMR study

    Energy Technology Data Exchange (ETDEWEB)

    Ozbay, U.D.

    1994-05-10

    Role of H spillover to the silica support was studied using chemisorption; a strongly bound component of spilled over H was found in the silica support which interfered with accurate measurements of active metal sites via volumetric strong H chemisorption. The volumetric chemisorption technique was modified so that measurement times were reduced from 12--36 h to 1 h. The active Ru surface was characterized means of changes in proton spin counts and NMR Knight shifts vs alkali loading. Na, K blocked the active surface of Ru metal, but Cs was pushed off by H chemisorption. The alkali promoters restricted H mobility on both metal surface and at the metal support interfaces; this is consistent with effects on Fischer-Tropsch synthesis. {sup 1}H NMR was used to study the effect of the active metal and promoter on support hydroxyl groups. The OH group density in the silica support decreased with metal and/or promoter loading, but not on a one-to-one basis; the exchange efficiency of the hydroxyls decreased with atomic size of the alkali metal. An additional downfield proton resonance was detected which was assigned to the alkali hydroxide species in the support.

  9. An Electrochemical and Raman Spectroscopy Study of the Surface Behaviour of Mononuclear Ruthenium and Osmium Polypyridyl Complexes Based on Pyridyl- and Thiophene-Based Linkers

    NARCIS (Netherlands)

    Halpin, Yvonne; Logtenberg, Hella; Cleary, Laura; Schenk, Stephan; Schulz, Martin; Draksharapu, Apparao; Browne, Wesley R.; Vos, Johannes G.

    2013-01-01

    The utility of a thiophene anchor unit as an alternative for thiols in the immobilisation of ruthenium and osmium complexes on gold and platinum is examined with special attention focused on the relative contributions of physi- and chemisorption of the complexes and the chemical stability of the thi

  10. Surface effects in metallic iron nanoparticles

    DEFF Research Database (Denmark)

    Bødker, Franz; Mørup, Steen; Linderoth, Søren

    1994-01-01

    Nanoparticles of metallic iron on carbon supports have been studied in situ by use of Mossbauer spectroscopy. The magnetic anisotropy energy constant increases with decreasing particle size, presumably because of the influence of surface anisotropy. Chemisorption of oxygen results in formation...

  11. The Electronic Structure Effect in Heterogeneous Catalysis

    DEFF Research Database (Denmark)

    Nilsson, A.; Pettersson, L. G. M.; Hammer, Bjørk;

    2005-01-01

    Using a combination of density functional theory calculations and X-ray emission and absorption spectroscopy for nitrogen on Cu and Ni surfaces, a detailed picture is given of the chemisorption bond. It is suggested that the adsorption bond strength and hence the activity of transition metal surf...

  12. Pt-Rh/g Al2O3 Influence of Catalyst Preparation Methods on Metallic Particle Dispersion and Size Distribution

    Directory of Open Access Journals (Sweden)

    N.M. da Fonseca

    1998-06-01

    Full Text Available - Pt-Rh/Al2O3 catalysts were prepared by successive incipient impregnations or coimpregnation. Characterization was achieved by H2 chemisorption and transmission electron microscopy. It was verified that method of preparation, ratio of metal weights and sequence of deposition are factors that result in very distinct catalysts.

  13. On the kinetics of oxidation of austenitic stainless steels AISI 304 and incoloy 800H

    NARCIS (Netherlands)

    Langevoort, J.C.; Hanekamp, L.J.; Gellings, P.J.

    1987-01-01

    The interaction of oxygen with clean surfaces of stainless steels has been studied by spectroscopic ellipsometry and AES. The reaction involves chemisorption and dissolution of oxygen into the surface of the metal via a place-exchange mechanism. Oxide thickening occurs via cation and anion migration

  14. Photocatalytic oxidation mechanism of alkanes in contact with titanium dioxide

    Science.gov (United States)

    Formenti, M.; Juillet, F.; Teichner, S. J.

    1977-01-01

    Isobutane was photooxidized on titanium dioxide between -16 and +180 C in tertiary butanol and acetone. The formation of tertiary butanol preceded the formation of acetone. Above 20 C the latter compound became clearly predominant. The reaction kinetics obeyed a steady state model of oxygen chemisorption with the involvement of isobutane in the physisorbed phase.

  15. Kinetics of the Low Pressure Chemical Vapor Deposition of Polycrystalline Germanium-Silicon Alloys from SiH4 and GeH4

    NARCIS (Netherlands)

    Holleman, J.; Kuiper, A.E.T.; Verweij, J.F.

    1993-01-01

    A Langmuir-Hinshelwood growth-rate equation is presented for the germanium-silicon (GeSi) alloy deposition fromGeH4 and SiH4 assuming dissociative chemisorption on a heterogeneous GeSi surface. Model parameters for the depositionkinetics have been extracted from measurements. The fit for the bond-en

  16. Understanding the Influence of the Pretreatment Procedure on Platinum Particle Size and Particle-Size Distribution for SiO2 Impregnated with [Pt2+(NH3)4](NO3-)2: A Combination of HRTEM Mass Spectrometry, and Quick EXAFS

    NARCIS (Netherlands)

    Koningsberger, D.C.; Oudenhuijzen, M.K.; Kooyman, P.J.; Tappel, B.; Bokhoven, J.A. van

    2002-01-01

    Using a combination of mass spectrometry, in situ quick extended X-ray absorption fine structure, high-resolution transmission electron microscopy, and hydrogen chemisorption, we studied the reactions taking place during different pretreatments of the catalyst precursor [Pt}2{}+{(NH{3}){4}](NO{3}}-{

  17. Modeling Mechanism and Growth Reactions for New Nanofabrication Processes by Atomic Layer Deposition.

    Science.gov (United States)

    Elliott, Simon D; Dey, Gangotri; Maimaiti, Yasheng; Ablat, Hayrensa; Filatova, Ekaterina A; Fomengia, Glen N

    2016-07-01

    Recent progress in the simulation of the chemistry of atomic layer deposition (ALD) is presented for technologically important materials such as alumina, silica, and copper metal. Self-limiting chemisorption of precursors onto substrates is studied using density functional theory so as to determine reaction pathways and aid process development. The main challenges for the future of ALD modeling are outlined.

  18. H{sub 2} formation in diffuse clouds: A new kinetic Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Wasim; Acharyya, Kinsuk [S. N. Bose National Centre for Basic Sciences, Salt Lake, Kolkata 700098 (India); Herbst, Eric [Departments of Chemistry, Astronomy, and Physics, University of Virginia, Charlottesville, VA 22904 (United States)

    2014-04-01

    We used the continuous-time random-walk Monte Carlo technique to study anew the formation of H{sub 2} on the surfaces of interstellar dust grains in diffuse interstellar clouds. For our study, we considered three different grain materials, olivine (a polycrystalline silicate), amorphous silicate, and amorphous carbon, as well as a grain temperature that depends on granular size. For some runs, we included temperature fluctuations. Four different granular surfaces were used, one 'flat' with one type of binding site due to physisorption, one 'rough' with five different types of physisorption binding sites due to lateral forces, and two with sites for chemisorption, one in which chemisorption sites are entered through precursor physisorption sites, and one in which chemisorption is direct but occurs with a barrier for the adsorption of the first hydrogen atom. We found that on flat and rough olivine surfaces, molecular hydrogen is formed at low efficiencies, with smaller grains contributing very little despite their large numbers due to high temperatures. For flat amorphous carbon and amorphous silicate surfaces, the efficiency increases, reaching unity for the largest grains. For models with barrierless chemisorption, the efficiency of formation of H{sub 2} is near unity at all grain sizes considered, while for direct chemisorption via a barrier, we found efficiencies of 0.13-0.6 depending upon the barrier, but independent of grain size. Treating the flat olivine and amorphous silicate surfaces with temperature fluctuations increases the efficiency of H{sub 2} formation.

  19. Removal of element mercury by medicine residue derived biochars in presence of various gas compositions

    International Nuclear Information System (INIS)

    Highlights: • Both physisorption and chemisorption of Hg0 occurred on the surface of M6WN5. • Chemisorption process was an absolute predominant route for Hg0 removal by M6WN5. • The effect of NO, H2O, SO2 and O2 on Hg0 removal by M6WN5 was investigated. • M6WN5 demonstrated to be a promising Hg0 sorbent in flue gas. - Abstract: Pyrolyzed biochars from an industrial medicinal residue waste were modified by microwave activation and NH4Cl impregnation. Mercury adsorption of different modified biochars was investigated in a quartz fixed-bed reactor. The results indicated that both physisorption and chemisorption of Hg0 occurred on the surface of M6WN5 which was modified both microwave and 5 wt.% NH4Cl loading, and exothermic chemisorption process was a dominant route for Hg0 removal. Microwave activation improved pore properties and NH4Cl impregnation introduced good active sites for biochars. The presence of NO and O2 increased Hg0 adsorption whereas H2O inhibited Hg0 adsorption greatly. A converse effect of SO2 was observed on Hg0 removal, namely, low concentration of SO2 promoted Hg0 removal obviously whereas high concentration of SO2 suppressed Hg0 removal. The Hg0 removal by M6WN5 was mainly due to the reaction of the C−Cl with Hg0 to form HgCl2, and the active state of C−Cl* groups might be an intermediate group in this process. Thermodynamic analysis showed that mercury adsorption by the biochars was exothermic process and apparent adsorption energy was 43.3 kJ/mol in the range of chemisorption. In spite of low specific surface area, M6WN5 proved to be a promising Hg0 sorbent in flue gas when compared with other sorbents

  20. On the behavior of Bronsted-Evans-Polanyi Relations for Transition Metal Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Vojvodic, Aleksandra

    2011-08-22

    Versatile Broensted-Evans-Polanyi (BEP) relations are found from density functional theory for a wide range of transition metal oxides including rutiles and perovskites. For oxides, the relation depends on the type of oxide, the active site and the dissociating molecule. The slope of the BEP relation is strongly coupled to the adsorbate geometry in the transition state. If it is final state-like the dissociative chemisorption energy can be considered as a descriptor for the dissociation. If it is initial state-like, on the other hand, the dissociative chemisorption energy is not suitable as descriptor for the dissociation. Dissociation of molecules with strong intramolecular bonds belong to the former and molecules with weak intramolecular bonds to the latter group. We show, for the prototype system La-perovskites, that there is a 'cyclic' behavior in the transition state characteristics upon change of the active transition metal of the oxide.

  1. Aromatization of n-hexane by platinum-containing molecular sieves. 1. Catalyst preparation by the vapor phase impregnation method

    Energy Technology Data Exchange (ETDEWEB)

    Suk Bong Hong; Mielczarski, E.; Davis, M.E. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States))

    1992-03-01

    A vapor phase impregnation method with Pt(acac){sub 2} has been developed and used to load Pt into aluminosilicate (KL, BaKL, NaY, CsNaY, cubic and hexagonal polytypes of faujasite, ZSM-12, and SSZ-24) and aluminophosphate (AlPO{sub 4}-5 and VPI-5) molecular sieves. Pt-containing molecular sieves are characterized by XRD,TPD, elemental analysis, {sup 13}C MAS NMR, TEM, and H{sub 2} chemisorption. {sup 13}C MAS NMR, TEM, and H{sub 2} chemisorption measurements reveal that Pt can be loaded into the micropores of molecular sieves with both charged and neutral frameworks. Pt impregnated into zeolites and aluminophosphates by this method does not migrate to the exterior surface of the molecular sieve catalysts at n-hexane aromatization reaction conditions of atmospheric pressure and temperatures between 460 and 510 C.

  2. Alkali promotion effect in Fischer-Tropsch cobalt-alumina catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Eliseev, O.L.; Tsapkina, M.V.; Davydov, P.E.; Kazantsev, R.V. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry; Belousova, O.S.; Lapidus, A.L. [Gubkin Russian State Univ. of Oil and Gas, Moscow (Russian Federation)

    2011-07-01

    Promoting Co-alumina Fischer-Tropsch synthesis catalysts with alkali and alkaline-earth metals was studied. XRD, oxygen titration and CO chemisorption were used for the characterization of the catalysts. The best results in terms of catalyst selectivity and long-chain alkanes content in synthesized products were obtained with K-promoted catalyst. Catalytic performance strongly depends on K:Co atomic ratio as well as preparation procedure. Effect of K loading on selectivities is non-linear with extreme point at K:Co=0.01. Significant increase in C{sub 5+} selectivity of K-promoted catalyst may be explained as a result of strong CO adsorption on the catalyst surface, as was confirmed in CO chemisorption experiments. (orig.)

  3. Surface effects of electrode-dependent switching behavior of resistive random-access memory

    KAUST Repository

    Ke, Jr Jian

    2016-09-26

    The surface effects of ZnO-based resistive random-access memory (ReRAM) were investigated using various electrodes. Pt electrodes were found to have better performance in terms of the device\\'s switching functionality. A thermodynamic model of the oxygen chemisorption process was proposed to explain this electrode-dependent switching behavior. The temperature-dependent switching voltage demonstrates that the ReRAM devices fabricated with Pt electrodes have a lower activation energy for the chemisorption process, resulting in a better resistive switching performance. These findings provide an in-depth understanding of electrode-dependent switching behaviors and can serve as design guidelines for future ReRAM devices.

  4. 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.

  5. Oxide Defect Engineering Enables to Couple Solar Energy into Oxygen Activation.

    Science.gov (United States)

    Zhang, Ning; Li, Xiyu; Ye, Huacheng; Chen, Shuangming; Ju, Huanxin; Liu, Daobin; Lin, Yue; Ye, Wei; Wang, Chengming; Xu, Qian; Zhu, Junfa; Song, Li; Jiang, Jun; Xiong, Yujie

    2016-07-20

    Modern development of chemical manufacturing requires a substantial reduction in energy consumption and catalyst cost. Sunlight-driven chemical transformation by metal oxides holds great promise for this goal; however, it remains a grand challenge to efficiently couple solar energy into many catalytic reactions. Here we report that defect engineering on oxide catalyst can serve as a versatile approach to bridge light harvesting with surface reactions by ensuring species chemisorption. The chemisorption not only spatially enables the transfer of photoexcited electrons to reaction species, but also alters the form of active species to lower the photon energy requirement for reactions. In a proof of concept, oxygen molecules are activated into superoxide radicals on defect-rich tungsten oxide through visible-near-infrared illumination to trigger organic aerobic couplings of amines to corresponding imines. The excellent efficiency and durability for such a highly important process in chemical transformation can otherwise be virtually impossible to attain by counterpart materials. PMID:27351805

  6. Effect of method of preparation on hydrodesulphurization activity of Co- or Ni-promoted MoS2/SBA-15 catalysts

    Indian Academy of Sciences (India)

    Shelu Garg; Kapil Soni; V V D N Prasad; Manoj Kumar; Thallada Bhaskar; J K Gupta; G Murali Dhar; C S Gopinath

    2014-03-01

    Ordered mesoporous material SBA-15 was synthesized and used as a support for the preparation of molybdenum sulphide catalysts through precipitation from homogeneous solution (PFHS) technique with the Mo content varying from 2-12 wt%. The prepared catalysts were evaluated for thiophene hydrodesulphurization catalytic activities at 400°RC. Catalysts prepared through PFHS method resulted in highly dispersed MoS2 catalysts, which were inferred from powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature oxygen chemisorptions (LTOC) and BET surface area analysis. The relationship between XPS intensity ratio, oxygen chemisorption and catalytic activities is discussed in terms of highly dispersed nano particles of MoS2 and its consequence in accommodating more promoted atoms at the edge sites.

  7. Oxide Defect Engineering Enables to Couple Solar Energy into Oxygen Activation.

    Science.gov (United States)

    Zhang, Ning; Li, Xiyu; Ye, Huacheng; Chen, Shuangming; Ju, Huanxin; Liu, Daobin; Lin, Yue; Ye, Wei; Wang, Chengming; Xu, Qian; Zhu, Junfa; Song, Li; Jiang, Jun; Xiong, Yujie

    2016-07-20

    Modern development of chemical manufacturing requires a substantial reduction in energy consumption and catalyst cost. Sunlight-driven chemical transformation by metal oxides holds great promise for this goal; however, it remains a grand challenge to efficiently couple solar energy into many catalytic reactions. Here we report that defect engineering on oxide catalyst can serve as a versatile approach to bridge light harvesting with surface reactions by ensuring species chemisorption. The chemisorption not only spatially enables the transfer of photoexcited electrons to reaction species, but also alters the form of active species to lower the photon energy requirement for reactions. In a proof of concept, oxygen molecules are activated into superoxide radicals on defect-rich tungsten oxide through visible-near-infrared illumination to trigger organic aerobic couplings of amines to corresponding imines. The excellent efficiency and durability for such a highly important process in chemical transformation can otherwise be virtually impossible to attain by counterpart materials.

  8. Adsorption of polyiodobenzene molecules on the Pt(111) surface using van der Waals density functional theory

    Science.gov (United States)

    Johnston, Karen; Pekoz, Rengin; Donadio, Davide

    2016-02-01

    Adsorption of aromatic molecules on surfaces is widely studied due to applications in molecular electronics. In this work, the adsorption of iodobenzene molecules on the Pt(111) surface has been studied using density functional theory. Iodobenzene molecules, with various numbers of iodine atoms, have two non-dissociative adsorption minima. One structure exhibits chemisorption between the ring and the surface (short-range) and the other structure exhibits chemisorption between the iodine ions and the surface (long-range). Both structures have a strong van der Waals interaction with the surface. In general, the adsorption energy increases as the number of iodine atoms increases. The dissociated structure of monoiodobenzene was investigated, and the dissociation barrier and the barrier between the short- and long-range states were compared.

  9. First-principles cluster expansion study of functionalization of black phosphorene via fluorination and oxidation

    Science.gov (United States)

    Nahas, Suhas; Ghosh, Barun; Bhowmick, Somnath; Agarwal, Amit

    2016-04-01

    Predicting the ground states for surface adsorption is a challenging problem because the number of degrees of freedom involved in the process is very high. Most of the studies deal with some specific arrangements of adsorbates on a given surface, but very few of them actually attempt to find the ground states for different adatom coverage. In this work, we show the effectiveness of the cluster expansion method to predict the "ground states" resulting from chemisorption of oxygen and fluorine atom on the surface of monolayer black phosphorus or phosphorene. For device applications, we find that in addition to band-gap tuning, controlled chemisorption can change the unique anisotropic carrier effective mass for both the electrons and holes and even rotate them by 90∘, which can be useful for exploring unusual quantum Hall effect and electronic devices based on phosphorene.

  10. Communication: Energy transfer and reaction dynamics for DCl scattering on Au(111): An ab initio molecular dynamics study

    Science.gov (United States)

    Kolb, Brian; Guo, Hua

    2016-07-01

    Scattering and dissociative chemisorption of DCl on Au(111) are investigated using ab initio molecular dynamics with a slab model, in which the top two layers of Au are mobile. Substantial kinetic energy loss in the scattered DCl is found, but the amount of energy transfer is notably smaller than that observed in the experiment. On the other hand, the dissociative chemisorption probability reproduces the experimental trend with respect to the initial kinetic energy, but is about one order of magnitude larger than the reported initial sticking probability. While the theory-experiment agreement is significantly improved from the previous rigid surface model, the remaining discrepancies are still substantial, calling for further scrutiny in both theory and experiment.

  11. Ethylene binding to Au/Cu alloy nanoparticles

    Science.gov (United States)

    Gammage, Michael D.; Stauffer, Shannon; Henkelman, Graeme; Becker, Michael F.; Keto, John W.; Kovar, Desiderio

    2016-11-01

    Weak chemisorption of ethylene has been shown to be an important characteristic in the use of metals for the separation of ethylene from ethane. Previously, density functional theory (DFT) has been used to predict the binding energies of various metals and alloys, with Ag having the lowest chemisorption energy amongst the metals and alloys studied. Here Au/Cu alloys are investigated by a combination of DFT calculations and experimental measurements. It is inferred from experiments that the binding energy between a Au/Cu alloy and ethylene is lower than to either of the pure metals, and DFT calculations confirm that this is the case when Au segregates to the particle surface. Implications of this work suggest that it may be possible to further tune the binding energy with ethylene by compositional and morphological control of films produced from Au-surface segregated alloys.

  12. Molecular Simulation Study on Interaction of Thiophene Sulfides with Transition Metals

    Institute of Scientific and Technical Information of China (English)

    Liu Yujian; Long Jun; Zhou Han; Zhu Yuxia; Da Zhijian

    2003-01-01

    The computer molecular simulation technique was applied to study the chemisorption of thiophene and tetramethylthiophene as the model sulfides on the simple oxides and complex oxides of some transition metals as the catalytic materials. The study disclosed that the thiophene sulfides could enter into chemisorption with metal oxides such as VO, ZnO, NiO and Zn-Al-spinel. This interaction could lead to thiophene molecular structure deformation to be in an activated adsorption state, which could help to promote the conversion of thiophene sulfides in the course of catalytic cracking. The VO with a valence of 2 could provide relatively strong selective adsorption sites for the conversion of thiophene sulfides to apparently transform the molecular structures and electron cloud states of such heterocyclic sulfur compounds such as thiophene and tetramethylthiophene into an activated adsorption state. The effect of this interaction was more pronounced with respect to tetramethylthiophene.

  13. Low metal loading catalysts used for the selective hydrogenation of styrene

    OpenAIRE

    Juan Badano; Cecilia Lederhos; Mónica Quiroga; Pablo L'Argentière; Fernando Coloma-Pascual

    2010-01-01

    A series of Group VIII metal catalysts was obtained for the semi-hydrogenation of styrene. Catalysts were characterized by Hydrogen Chemisorption, TPR and XPS. Palladium, rhodium and platinum low metal loading prepared catalysts presented high activity and selectivity (ca. 98%) during the semi-hydrogenation of styrene, being palladium the most active catalyst. The ruthenium catalyst also presented high selectivity (ca. 98%), but the lowest activity. For the palladium catalyst, the influence o...

  14. Surface thermodynamics

    International Nuclear Information System (INIS)

    Basic thermodynamics of a system consisting of two bulk phases with an interface. Solid surfaces: general. Discussion of experimental data on surface tension and related concepts. Adsorption thermodynamics in the Gibbsian scheme. Adsorption on inert solid adsorbents. Systems with electrical charges: chemistry and thermodynamics of imperfect crystals. Thermodynamics of charged surfaces. Simple models of charge transfer chemisorption. Adsorption heat and related concepts. Surface phase transitions

  15. Thermal Emissivity-Based Chemical Spectroscopy through Evanescent Tunneling.

    Science.gov (United States)

    Poole, Zsolt L; Ohodnicki, Paul R

    2016-04-01

    A new spectroscopic technique is presented, with which environmentalchemistry-induced thermal emissivity changes of thin films are extracted with high isolation through evanescent tunneling. With this method the hydrogen-induced emissivity changes of films of TiO2 , Pd-TiO2 , and Au-TiO2 , with properties of high conductivity, hydrogen chemisorption, and plasmonic activity, are characterized in the UV-vis and NIR wavelength ranges, at 1073 K.

  16. Dipole formation at metal/PTCDA interfaces: Role of the Charge Neutrality Level

    OpenAIRE

    Vazquez, H.; Oszwaldowski, R.; Pou, P.; Ortega, J.; Perez, R.; F. Flores; Kahn, A.

    2004-01-01

    The formation of a metal/PTCDA (3, 4, 9, 10-perylenetetracarboxylic dianhydride) interface barrier is analyzed using weak-chemisorption theory. The electronic structure of the uncoupled PTCDA molecule and of the metal surface is calculated. Then, the induced density of interface states is obtained as a function of these two electronic structures and the interaction between both systems. This induced density of states is found to be large enough (even if the metal/PTCDA interaction is weak) fo...

  17. Surface stress and large-scale self-organization at organic-metal interfaces

    OpenAIRE

    Pollinger, Florian

    2009-01-01

    Anhand von Modellsystemen wurde in dieser Arbeit die Bedeutung elastischer Wechselwirkungen an Organik-Metall Grenzflächen, insbesondere für die Selbstorganisierte Ausbildung periodisch facettierter Strukturen, untersucht. Die Änderung der Oberflächenspannung während der Ausbildung der Grenzfläche zwischen 3,4,9,10-Perylentetracarbonsäuredianhydrid (PTCDA) und Ag(111) wurde mit der Biegekristalltechnik gemessen. Es ist bekannt, dass dieses System durch eine chemisorptive Bindung bestimmt wird...

  18. Purification of ethanol for highly sensitive self-assembly experiments

    OpenAIRE

    Kathrin Barbe; Martin Kind; Christian Pfeiffer; Andreas Terfort

    2014-01-01

    Ethanol is the preferred solvent for the formation of self-assembled monolayers (SAMs) of thiolates on gold. By applying a thin film sensor system, we could demonstrate that even the best commercial qualities of ethanol contain surface-active contaminants, which can compete with the desired thiolates for surface sites. Here we present that gold nanoparticles deposited onto zeolite X can be used to remove these contaminants by chemisorption. This nanoparticle-impregnated zeolite does not only ...

  19. Bandgap Restructuring of the Layered Semiconductor Gallium Telluride in Air.

    Science.gov (United States)

    Fonseca, Jose J; Tongay, Sefaattin; Topsakal, Mehmet; Chew, Annabel R; Lin, Alan J; Ko, Changhyun; Luce, Alexander V; Salleo, Alberto; Wu, Junqiao; Dubon, Oscar D

    2016-08-01

    A giant bandgap reduction in layered GaTe is demonstrated. Chemisorption of oxygen to the Te-terminated surfaces produces significant restructuring of the conduction band resulting in a bandgap below 0.8 eV, compared to 1.65 eV for pristine GaTe. Localized partial recovery of the pristine gap is achieved by thermal annealing, demonstrating that reversible band engineering in layered semiconductors is accessible through their surfaces.

  20. Background, phenomenology, and motivation

    International Nuclear Information System (INIS)

    The authors discuss the background to the kinetics of adsorption and desorption after an elementary introduction to the problem of chemisorption in two limiting cases. Other topics discussed include the thermodynamics of adsorption, reaction mechanisms outside surfaces, and a case history of catalytic hydrogenation of carbon monoxide. Figures show the potential energy barrier as a function of an appropriate reaction coordinate, and bonding of carbon monoxide to platinum metal

  1. Nanoplasmonic structures for biophotonic applications: SERS overview

    International Nuclear Information System (INIS)

    Various nanoplasmonic devices were fabricated using top-down method such as electron beam lithography, electroplating and focused ion beam techniques. These substrates were investigated after depositing the molecules from dye to protein, using chemisorptions techniques. Theoretical simulations were also performed on these model nanostructures in order to understand the electrical field distribution. Furthermore, the future prospects of these nanostructures were also mentioned in this report. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Thermal Emissivity-Based Chemical Spectroscopy through Evanescent Tunneling.

    Science.gov (United States)

    Poole, Zsolt L; Ohodnicki, Paul R

    2016-04-01

    A new spectroscopic technique is presented, with which environmentalchemistry-induced thermal emissivity changes of thin films are extracted with high isolation through evanescent tunneling. With this method the hydrogen-induced emissivity changes of films of TiO2 , Pd-TiO2 , and Au-TiO2 , with properties of high conductivity, hydrogen chemisorption, and plasmonic activity, are characterized in the UV-vis and NIR wavelength ranges, at 1073 K. PMID:26901747

  3. Ni adatoms on Al{sub 2}O{sub 3} film probed by NO adsorption: a RAIRS study

    Energy Technology Data Exchange (ETDEWEB)

    Magkoev, T.T. [State Univ. of North Ossetia, Vladikavkaz (Russian Federation). Dept. of Physics; Murata, Y. [Univ. of Electro-Communications, Tokyo (Japan). Div. of Natural Sciences

    2001-01-01

    In this note we present an experimental result on reflection absorption infrared spectroscopy (RAIRS) of nitric oxide (NO) molecules adsorbed on nickel (Ni) adatoms on Al{sub 2}O{sub 3} film grown on Mo(110) crystal, which we interpret as the evidence for the formation of the chemisorption bond between Ni adatoms and Al{sub 2}O{sub 3} dominated by the oxide oxygen ion, rather than the aluminum ion. (orig.)

  4. Visible-light-induced water oxidation by a hybrid photocatalyst consisting of bismuth vanadate and copper(II) meso-tetra(4-carboxyphenyl)porphyrin.

    Science.gov (United States)

    Nakashima, Shu; Negishi, Ryo; Tada, Hiroaki

    2016-03-01

    Copper(II) meso-tetra(4-carboxyphenyl)porphyrin surface-modified monoclinic scheelite bismuth vanadate (CuTCPP/BiVO4) has been synthesized via a two-step route involving chemisorption of TCPP on BiVO4 and successive Cu(II) ion incorporation into the TCPP, and the surface modification drastically enhances the water oxidation to oxygen (O2) under visible-light irradiation (λ > 430 nm). PMID:26853997

  5. A Density Functional Study of O2 Adsorption on (100) Surface of gamma-Uranium

    OpenAIRE

    Huda, M. N.; A.K. Ray

    2004-01-01

    We have studied the chemisorption processes of O2 on the (100) surface of uranium using generalized gradient approximation to density functional theory. Dissociative adsorptions of O2 are significantly favored compared to molecular adsorptions. We found interstitial adsorption of molecular oxygen to be less probable, as no bound states were found in this case. Upon oxygen adsorption, O 2p orbitals is found to hybridize with U 5f bands, and part of the U 5f electrons become more localized. Als...

  6. The Role of the Coprecipitation Sequence of Salt Precursors on the Genesis of Cu-ZnO-Al2O3 Catalysts: Synthesis, Characterization and Activity for Low Temperature Shift Reaction

    OpenAIRE

    1998-01-01

    Cu-ZnO-Al2O3 catalysts for the low-temperature water-gas shift reaction were prepared using methods of direct and reverse coprecipitation. The catalysts obtained were characterized by DRX, TPR, XPS, N2O chemisorption, Hg-Porosimetry and BET surface area. It was observed that the precipitation sequence of the precursors led to significant differences in values of copper dispersion and consequently in the activity of the catalyst for the water-gas shift reaction.

  7. Halbleiternanopartikel-modifizierte Elektrode zum Nachweis von Substraten von NADH-abhängigen Enzymreaktionen

    OpenAIRE

    Schubert, Kirsten; Khalid, Waqas; Zhao, Yue; J. Parak, Wolfgang; Lisdat, Fred

    2010-01-01

    Es wurde ein Elektrodensystem entwickelt, das aufbauend auf Halbleiternanopartikeln (so genannte Quantenpunkte) die sensitive Detektion des Enzymkofaktors NADH (nicotinamide adenine dinucleotide) erlaubt. Kolloidale halbleitende CdSe/ZnS-Nanokristalle sind durch ein Dithiol über Chemisorption an Gold gebunden. Das Stromsignal kann durch die Beleuchtung der Quantenpunkt modifizierten Oberfläche beeinflusst werden. Durch Photoanregung entstehen Elektron-Loch- Paare in den Nanopartikeln, die als...

  8. THE RING OPENING REACTION OF AN EPOXY COMPOUND ON THE TOP OF CHEMISORBED CYSTAMINE STUDIED BY THE SERS TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    LU Yun; XUE Qi

    1994-01-01

    Metal foils for Raman scattering were prepared by HNO3 etching method. These foils were found to exhibit a strong SERS effect and excellent thermal stability. SERS spectra of cystamine have been taken to illustrate the usefulness of this sample preparation method in the studies of chemisorption. The ring opening reactions of an epoxy compound have been observed on the top of chemisorbed cystamine on silver foils.

  9. Modification of polymer (PET) surface reactivity by low energy ion bombardment

    Science.gov (United States)

    Bertrand, P.; De Puydt, Y.; Beuken, J.-M.; Lutgen, P.; Feyder, G.

    The surface of polyethylene terephtalate (PET) was studied by low energy He + ion scattering (ISS). Modifications of the surface composition induced by the He + and Ar + bombardments are observed. The ion bombardment causes surface damages with bond breaking and it results a highly activated surface for the chemisorption of nitrogen from the residual gas phase. Similar effects were observed on highly oriented pyrolytic graphite when analyzed in the same beam conditions.

  10. Hydrogen on graphene: Electronic structure, total energy, structural distortions and magnetism from first-principles calculations

    OpenAIRE

    Boukhvalov, D W; Katsnelson, M. I.; Lichtenstein, A. I.

    2008-01-01

    Density functional calculations of electronic structure, total energy, structural distortions, and magnetism for hydrogenated single-layer, bilayer, and multi-layer graphene are performed. It is found that hydrogen-induced magnetism can survives only at very low concentrations of hydrogen (single-atom regime) whereas hydrogen pairs with optimized structure are usually nonmagnetic. Chemisorption energy as a function of hydrogen concentration is calculated, as well as energy barriers for hydrog...

  11. (Electronic structure and reactivities of transition metal clusters)

    Energy Technology Data Exchange (ETDEWEB)

    1992-01-01

    The following are reported: theoretical calculations (configuration interaction, relativistic effective core potentials, polyatomics, CASSCF); proposed theoretical studies (clusters of Cu, Ag, Au, Ni, Pt, Pd, Rh, Ir, Os, Ru; transition metal cluster ions; transition metal carbide clusters; bimetallic mixed transition metal clusters); reactivity studies on transition metal clusters (reactivity with H{sub 2}, C{sub 2}H{sub 4}, hydrocarbons; NO and CO chemisorption on surfaces). Computer facilities and codes to be used, are described. 192 refs, 13 figs.

  12. Effect of Solution pH on the Removal of Paracetamol by Activated Carbon of Dende Coconut Mesocarp

    OpenAIRE

    Ferreira, R C; Couto Junior, O. M.; K. Q. Carvalho; P.A. Arroyo; M. A. S. D. Barros

    2015-01-01

    Activated carbon of dende coconut mesocarp was used to investigate the removal of paracetamol from water by adsorption. The results indicated that the retention of paracetamol was favored in activated carbon with neutral surface properties. The textural features and presence of a transport pores network contributed to ensuring the accessibility to the inner porosity, and the microporosity must be large enough to accommodate the paracetamol molecule. Chemisorption and mainly physisorption are ...

  13. Characterization, deactivation, and stabilization of cobalt oxide--molybdenum oxide--alumina

    International Nuclear Information System (INIS)

    The specific surface area of molybdena in reduced, alumina-supported catalysts of molybdena and cobalt-molybdena has been measured by the selective chemisorption of oxygen at low temperature on catalysts pre-reduced at high temperature. The amount of chemisorption was obtained from determining successive oxygen adsorption isotherms, at -1950C, on catalysts reduced and pumped at 5000C. The oxygen adsorption on pre-reduced (at 3500C), unsupported MoO3, 13.6 m2/ml(STP)O2 was used as calibrating standard for pre-reduced supported molybdena. For three supported catalysts, all of which contained about 15 percent MoO3 as prepared, the apparent fractional surface coverage was within the narrow range 0.24 to 0.28. The selective chemisorption of O2 (-1950C) and BET (-1950, N2) measurements on pre-sulfided and used synthoil catalyst showed lower values of total surface area as well as active area

  14. Adsorption on metal oxides Studies with the metastable impact electron spectroscopy

    CERN Document Server

    Krischok, S; Kempter, V

    2002-01-01

    An overview is given on the application of metastable impact electron spectroscopy, in combination with UPS, to the study of clean magnesia and titania surfaces and their interaction with metal atoms and small molecules. The mechanisms for metal adsorption on reducible (titania) and non-reducible (magnesia) substrates are different: while on titania the metal atom often bonds by electron transfer to Ti3d states, it is hybridization of the adsorbate and anion wavefunctions which accounts for the bonding on MgO. In the case of H sub 2 O, molecular adsorption takes place both on MgO and TiO sub 2; on the other hand, water-alkali coadsorption leads to hydroxide formation. In the case of CO sub 2 , chemisorption takes place in form of carbonate (CO sub 3) species. These originate from the CO sub 2 interaction with O sup 2 sup - surface anions. While for CaO chemisorption takes place at regular oxygen sites, for MgO this occurs at low-coordinated oxygen ions only; for TiO sub 2 chemisorption requires alkali coadsor...

  15. Characterization and functionalities of Pd/hydrotalcite catalysts

    Science.gov (United States)

    Naresh, Dhachapally; Kumar, Vanama Pavan; Harisekhar, Mitta; Nagaraju, Nekkala; Putrakumar, Balla; Chary, Komandur V. R.

    2014-09-01

    A series of palladium supported on calcined hydrotalcite (CHT) catalysts with varying palladium (Pd) loadings (1.0-8.0 wt%) were prepared by impregnation method. Their catalytic performance was evaluated for the reductive amination of phenol to aniline that showed a tremendous interest in the chemical industry. The catalysts were characterized by BET surface area, XRD, TEM, XPS, TPR of H2, TPD of CO2 and CO chemisorption. BET surface area decreased continuously with increase in Pd content. XRD results confirmed the changes in the crystalline phases with altering Pd content. TEM results showed the formation of fine particles at lower loadings and agglomerates at higher loadings. TPR profiles revealed that the reducibility increases with increase of Pd loading. CO2 TPD results illustrate the catalysts basicity increases with increase of Pd loading up to 4.0 wt% and decreases at higher loadings. Pd dispersion, metal area and crystallite sizes were determined by CO chemisorption method. Pd dispersion and metal area decreases with increase of Pd content and crystallite sizes. The results demonstrated that the Pd dispersion and basic properties are depending on the Pd loading. The catalytic performance clearly showed that the increase Pd loading the conversion of phenol increased up to 2.0 wt% and level off beyond the loading. The catalytic properties are well correlated with the active Pd sites determined by CO chemisorption, dispersion and basicity.

  16. Uranium uptake by the filamentous fungal biomass, Aspergillus fumigatus and mechanism of biosorption

    International Nuclear Information System (INIS)

    Uptake of uranium by Aspergillus fumigatus was investigated in a batch study. Previously, we had reported good uranium uptake capacity, i.e., 423 mg U/g by this fungal biomass. The objective of the present study was to investigate the uranium uptake and mechanism of biosorption by Aspergillus fumigatus. The metal uptake was rapid and 80% of metal ion could be removed within 4 minutes of contact time. Kinetic modeling indicated that the uptake of uranium followed Lagergren's pseudo-second order reaction indicating the process to be mediated through chemisorption mechanism. Further studies on isotherm modeling were carried out using D-R isotherm to confirm the same. The energy of biosorption obtained from D-R isotherm was found to be 14.4 kJ/mol. This energy corresponds to the energy of chemisorption (ion-exchange) which varies between 8-16 kJ/mol. All these results suggest that uranium uptake by Aspergillus fumigatus is mediated through chemisorptions mechanism. (author)

  17. Ga and As competition for thiolate formation at p-GaAs(1 1 1) surfaces

    International Nuclear Information System (INIS)

    Highlights: • SAMs of 4,4′-thio-bis-benzene-thiolate were formed at p-GaAs(1 1 1) surfaces. • Both As and Ga are involved in thiolate formation. • Only one SH group participates in the chemisorption bond. • Thiolate layer formed at GaAs(1 1 1)B is more stable than that formed at GaAs(1 1 1)A. • Terminal atoms control the chemisorption-and packing-forces joint action. -- Abstract: Self-assembled layers of 4,4′-thio-bis-benzene-thiolate spontaneously adsorbed on p-doped GaAs(1 1 1)A and GaAs(1 1 1)B electrodes were examined by EIS, XPS, and AFM investigations. XPS data provide evidence that (i) both As and Ga atoms are involved in the thiolate formation no matter which one is prevailing on the semiconducting surface and (ii) only one of the two thiol groups participates in the chemisorption bond. EIS and AFM results point to a more stable thiolate layer formed on the As-terminated surface than that formed on the Ga-terminated surface due to stronger self-assembling effects developed between the adsorbed species

  18. Biomolecular Interactions and Biological Responses of Emerging Two-Dimensional Materials and Aromatic Amino Acid Complexes.

    Science.gov (United States)

    Mallineni, Sai Sunil Kumar; Shannahan, Jonathan; Raghavendra, Achyut J; Rao, Apparao M; Brown, Jared M; Podila, Ramakrishna

    2016-07-01

    The present work experimentally investigates the interaction of aromatic amino acids viz., tyrosine, tryptophan, and phenylalnine with novel two-dimensional (2D) materials including graphene, graphene oxide (GO), and boron nitride (BN). Photoluminescence, micro-Raman spectroscopy, and cyclic voltammetry were employed to investigate the nature of interactions and possible charge transfer between 2D materials and amino acids. Graphene and GO were found to interact strongly with aromatic amino acids through π-π stacking, charge transfer, and H-bonding. Particularly, it was observed that both physi and chemisorption are prominent in the interactions of GO/graphene with phenylalanine and tryptophan while tyrosine exhibited strong chemisorption on graphene and GO. In contrast, BN exhibited little or no interactions, which could be attributed to localized π-electron clouds around N atoms in BN lattice. Lastly, the adsorption of amino acids on 2D materials was observed to considerably change their biological response in terms of reactive oxygen species generation. More importantly, these changes in the biological response followed the same trends observed in the physi and chemisorption measurements. PMID:27281436

  19. Immobilization of Polymeric Luminophor on Nanoparticles Surface.

    Science.gov (United States)

    Bolbukh, Yuliia; Podkoscielna, Beata; Lipke, Agnieszka; Bartnicki, Andrzej; Gawdzik, Barbara; Tertykh, Valentin

    2016-12-01

    Polymeric luminophors with reduced toxicity are of the priorities in the production of lighting devices, sensors, detectors, bioassays or diagnostic systems. The aim of this study was to develop a method of immobilization of the new luminophor on a surface of nanoparticles and investigation of the structure of the grafted layer. Monomer 2,7-(2-hydroxy-3-methacryloyloxypropoxy)naphthalene (2,7-NAF.DM) with luminophoric properties was immobilized on silica and carbon nanotubes in two ways: mechanical mixing with previously obtained polymer and by in situ oligomerization with chemisorption after carrier's modification with vinyl groups. The attached polymeric (or oligomeric) surface layer was studied using thermal and spectral techniques. Obtained results confirm the chemisorption of luminophor on the nanotubes and silica nanoparticles at the elaborated synthesis techniques. The microstructure of 2,7-NAF.DM molecules after chemisorption was found to be not changed. The elaborated modification approach allows one to obtain nanoparticles uniformly covered with polymeric luminophor. PMID:27090657

  20. Removal of element mercury by medicine residue derived biochars in presence of various gas compositions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guoliang [School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401 (China); College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Shen, Boxiong, E-mail: shenbx@nankai.edu.cn [School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401 (China); College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Li, Yongwang [College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Zhao, Bin [School of Chemical Engineering, Hebei University of Technology, Tianjin 300401 (China); Wang, Fumei; He, Chuan; Wang, Yinyin; Zhang, Min [College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China)

    2015-11-15

    Highlights: • Both physisorption and chemisorption of Hg{sup 0} occurred on the surface of M6WN5. • Chemisorption process was an absolute predominant route for Hg{sup 0} removal by M6WN5. • The effect of NO, H{sub 2}O, SO{sub 2} and O{sub 2} on Hg{sup 0} removal by M6WN5 was investigated. • M6WN5 demonstrated to be a promising Hg{sup 0} sorbent in flue gas. - Abstract: Pyrolyzed biochars from an industrial medicinal residue waste were modified by microwave activation and NH{sub 4}Cl impregnation. Mercury adsorption of different modified biochars was investigated in a quartz fixed-bed reactor. The results indicated that both physisorption and chemisorption of Hg{sup 0} occurred on the surface of M6WN5 which was modified both microwave and 5 wt.% NH{sub 4}Cl loading, and exothermic chemisorption process was a dominant route for Hg{sup 0} removal. Microwave activation improved pore properties and NH{sub 4}Cl impregnation introduced good active sites for biochars. The presence of NO and O{sub 2} increased Hg{sup 0} adsorption whereas H{sub 2}O inhibited Hg{sup 0} adsorption greatly. A converse effect of SO{sub 2} was observed on Hg{sup 0} removal, namely, low concentration of SO{sub 2} promoted Hg{sup 0} removal obviously whereas high concentration of SO{sub 2} suppressed Hg{sup 0} removal. The Hg{sup 0} removal by M6WN5 was mainly due to the reaction of the C−Cl with Hg{sup 0} to form HgCl{sub 2}, and the active state of C−Cl{sup *} groups might be an intermediate group in this process. Thermodynamic analysis showed that mercury adsorption by the biochars was exothermic process and apparent adsorption energy was 43.3 kJ/mol in the range of chemisorption. In spite of low specific surface area, M6WN5 proved to be a promising Hg{sup 0} sorbent in flue gas when compared with other sorbents.

  1. Novel Effective Catalyst for Elemental Mercury Removal from Coal-Fired Flue Gas and the Mechanism Investigation.

    Science.gov (United States)

    Chen, Wanmiao; Pei, Yang; Huang, Wenjun; Qu, Zan; Hu, Xiaofang; Yan, Naiqiang

    2016-03-01

    Mercury pollution from coal-fired power plants has drawn attention worldwide. To achieve efficient catalytic oxidation of Hg(0) at both high and low temperatures, we prepared and tested novel IrO2 modified Ce-Zr solid solution catalysts under various conditions. It was found that the IrO2/Ce0.6Zr0.4O2 catalyst, which was prepared using the polyvinylpyrrolidone-assisted sol-gel method, displayed significantly higher catalytic activity for Hg(0) oxidation. The mechanism of Hg(0) removal over IrO2/Ce0.6Zr0.4O2 was studied using various methods, and the Hg(0) oxidation reaction was found to follow two possible pathways. For the new chemisorption-regeneration mechanism proposed in this study, the adsorbed Hg(0) was first oxidized with surface chemisorbed oxygen species to form HgO; the HgO could desorb from the surface of catalysts by itself or react with adsorbed HCl to be release in the form of gaseous HgCl2. O2 is indispensable for the chemisorption process, and the doping of IrO2 could facilitate the chemisorption process. In addition, the Deacon reaction mechanism was also feasible for Hg(0) oxidation: this reaction would involve first oxidizing the adsorbed HCl to active Cl species, after which the Hg(0) could react with Cl to form HgCl2. Additionally, doping IrO2 could significantly improve the Cl yield process. In summary, the novel IrO2 modified catalyst displayed excellent catalytic activity for elemental mercury oxidation, and the proposed reaction mechanisms were determined reasonably. PMID:26815147

  2. Synthesis of Ag/ZnO nanostructures by different methods and investigation of their photocatalytic efficiency for 4-nitrophenol degradation

    Energy Technology Data Exchange (ETDEWEB)

    Divband, B., E-mail: baharakdivband@yahoo.com [Inorganic Chemistry Department, Faculty of Chemistry, University of Tabriz, C.P. 51664 Tabriz (Iran, Islamic Republic of); Khatamian, M., E-mail: khatamian@tabrizu.ac.ir [Inorganic Chemistry Department, Faculty of Chemistry, University of Tabriz, C.P. 51664 Tabriz (Iran, Islamic Republic of); Eslamian, G.R. Kazemi [Food Science and Technology Department, International Aras Campus, University of Tabriz (Iran, Islamic Republic of); Darbandi, M. [Experimental Physics, Faculty of Physics, Lotharstr. 1, University of Duisburg-Essen, Duisburg (Germany)

    2013-11-01

    In this paper, Ag/ZnO photocatalysts with different Ag loadings were prepared by photo reduction, chemical reduction and polyacrylamide-gel methods. The Ag/ZnO photocatalysts were characterized by XRD, SEM, TEM, EDS and DRUV–vis methods. The results of the photocatalytic degradation of 4-NP in aqueous suspensions showed that silver ions doping greatly improved the photocatalytic efficiency of ZnO nanocrystallites. The enhancement of photocatalytic activity is due to the fact that the modification of ZnO with an appropriate amount of Ag can increase the separation efficiency of photogenerated electrons and holes in ZnO, and the improvement of photo stability of ZnO is attributed to a considerable decrease of the surface defect sites of ZnO after the Ag loading. The chemisorptions of molecular oxygen and the chemisorption of atomic oxygen on Ag in the Ag/ZnO photocatalysts were observed. It was found that the metallic Ag in the Ag/ZnO photocatalysts does play a new role of O{sub 2} chemisorption sites except for electron acceptor, by which chemisorbed molecular oxygen reacts with photogenerated electrons to form active oxygen species, and thus facilitates the trapping of photogenerated electrons and further improves the photocatalytic activity of the Ag/ZnO photocatalysts. Also the method of preparation is regarded as important factors for determining photocatalysis. The best photocatalytic performance was exhibited for Ag/ZnO prepared by polyacrylamide gel method in comparison with chemical reduction and photo reduction method and the optimum Ag content was approximately 0.5%.

  3. Propane combustion over Pt/Al{sub 2}O{sub 3} catalysts with different crystalline structures of alumina

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jung Eun; Kim, Bo Bae; Park, Eun Duck [Ajou University, Suwon (Korea, Republic of)

    2015-11-15

    The effects of the crystalline phases (α-Al{sub 2}O{sub 3}, κ-Al{sub 2}O{sub 3}, δ-Al{sub 2}O{sub 3}, θ-Al{sub 2}O{sub 3}, η-Al{sub 2}O{sub 3}, and γ-Al{sub 2}O{sub 3}) of the alumina support of Pt/Al{sub 2}O{sub 3} catalysts on the catalyst activity toward propane combustion were examined. The catalysts were characterized by N{sub 2} physisorption, CO chemisorption, temperature-programmed reduction (TPR), temperature programmed oxidation (TPO), transmission electron microscopy (TEM), and infrared spectroscopy (IR) after CO chemisorption. The Pt dispersion of the catalysts (surface Pt atoms/total Pt atoms), measured via CO chemisorption, was more dependent on the crystalline structure of alumina than on the surface area of alumina. The highest catalytic activity for propane combustion was achieved with Pt/α-Al{sub 2}O{sub 3}, which has the lowest Brunauer, Emmett, and Teller (BET) surface area and Pt dispersion. The lowest catalytic activity for propane combustion was exhibited by Pt/γ-Al{sub 2}O{sub 3}, which has the highest BET surface area and Pt dispersion. The catalytic activity was confirmed to increase with increasing Pt particle size in Pt/δ-Al{sub 2}O{sub 3}. The apparent activation energies for propane combustion over Pt/α-Al{sub 2}O{sub 3}, Pt/κ- Al{sub 2}O{sub 3}, Pt/δ-Al{sub 2}O{sub 3}, Pt/θ-Al{sub 2}O{sub 3}, Pt/η-Al{sub 2}O{sub 3}, and Pt/γ-Al{sub 2}O{sub 3} were determined to be 24.7, 21.4, 24.3, 22.1, 24.0, and 19.1 kcal/mol, respectively.

  4. Dynamics of H2 dissociation on the close-packed (111) surface of the noblest metal: H2 + Au(111)

    Science.gov (United States)

    Wijzenbroek, Mark; Helstone, Darcey; Meyer, Jörg; Kroes, Geert-Jan

    2016-10-01

    We have performed calculations on the dissociative chemisorption of H2 on un-reconstructed and reconstructed Au(111) with density functional theory, and dynamics calculations on this process on un-reconstructed Au(111). Due to a very late barrier for dissociation, H2 + Au(111) is a candidate H2-metal system for which the dissociative chemisorption could be considerably affected by the energy transfer to electron-hole pairs. Minimum barrier geometries and potential energy surfaces were computed for six density functionals. The functionals tested yield minimum barrier heights in the range of 1.15-1.6 eV, and barriers that are even later than found for the similar H2 + Cu(111) system. The potential energy surfaces have been used in quasi-classical trajectory calculations of the initial (v,J) state resolved reaction probability for several vibrational states v and rotational states J of H2 and D2. Our calculations may serve as predictions for state-resolved associative desorption experiments, from which initial state-resolved dissociative chemisorption probabilities can be extracted by invoking detailed balance. The vibrational efficacy ηv=0→1 reported for D2 dissociating on un-reconstructed Au(111) (about 0.9) is similar to that found in earlier quantum dynamics calculations on H2 + Ag(111), but larger than found for D2 + Cu(111). With the two functionals tested most extensively, the reactivity of H2 and D2 exhibits an almost monotonic increase with increasing rotational quantum number J. Test calculations suggest that, for chemical accuracy (1 kcal/mol), the herringbone reconstruction of Au(111) should be modeled.

  5. Correlation between the acid-base properties of the La2O3 catalyst and its methane reactivity.

    Science.gov (United States)

    Chu, Changqing; Zhao, Yonghui; Li, Shenggang; Sun, Yuhan

    2016-06-28

    Density functional theory and coupled cluster theory calculations were carried out to study the effects of the acid-base properties of the La2O3 catalyst on its catalytic activity in the oxidative coupling of methane (OCM) reaction. The La(3+)-O(2-) pair site for CH4 activation is considered as a Lewis acid-Brönsted base pair. Using the Lewis acidity and the Brönsted basicity in the fluoride affinity and proton affinity scales as quantitative measures of the acid-base properties, the energy barrier for CH4 activation at the pair site can be linearly correlated with these acid-base properties. The pair site consisting of a strong Lewis acid La(3+) site and a strong Brönsted base O(2-) site is the most reactive for CH4 activation. In addition, the basicity of the La2O3 catalyst was traditionally measured by temperature-programmed desorption of CO2, but the CO2 chemisorption energy is better regarded as a combined measure of the acid-base properties of the pair site. A linear relationship of superior quality was found between the energy barrier for CH4 activation and the CO2 chemisorption energy, and the pair site favorable for CO2 chemisorption is also more reactive for CH4 activation, leading to the conflicting role of the "basicity" of the La2O3 catalyst in the OCM reaction. The necessity for very high reaction temperatures in the OCM reaction is rationalized by the requirement for the recovery of the most reactive acid-base pair site, which unfortunately also reacts most readily with the byproduct CO2 to form the very stable CO3(2-) species. PMID:27265027

  6. Effect of HNO{sub 3} treatment on the SO{sub 2} adsorption capacity of activated carbon prepared from Chinese low-rank coal

    Energy Technology Data Exchange (ETDEWEB)

    Hang Wenhui; Wang ling; Li Shurong [China Coal Research Institute, Beijing (China)

    1999-11-01

    SO{sub 2} removal from flue gas by activated carbon and HNO{sub 3} treated activated carbon from Chinese low-rank coal was studied. SO{sub 2} adsorption on activated carbon is mainly chemisorption. There was shown to be a correlation between adsorption capacity and the number of active sites on the carbon surface. HNO{sub 3} treatment transforms C-H bonds in activated carbon into active sites, for removal of SO{sub 2}. 2 figs., 2 tabs.

  7. Effect of porous polymer films (track membranes) on the isothermal evaporation kinetics of water

    Science.gov (United States)

    Novikov, S. N.; Ermolaeva, A. I.; Timoshenkov, S. P.; Korobova, N. E.; Goryunova, E. P.

    2016-06-01

    The kinetics of isothermal evaporation of distilled water that was in remote (10-15-mm) contact with porous polymer films (track membranes (TMs)) was studied by microgravimetry (derivatograph). When the H2O-TM system contained a disperse medium, the supramolecular structure of water changed, and the number of clusters (coherent domains) drastically decreased. The extraction of the light phase from liquid water was correlated with the chemisorption of H2O molecules containing the para-isomer of hydrogen, which predominantly form coherent domains of water.

  8. Production of negative hydrogen ions on metal grids

    Energy Technology Data Exchange (ETDEWEB)

    Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K. [Department of Electronic Device Engineering, Yamaguchi University, Ube 755-8611 (Japan)

    2015-03-15

    Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

  9. Nanosecond laser micro- and nanotexturing for the design of a superhydrophobic coating robust against long-term contact with water, cavitation, and abrasion

    Science.gov (United States)

    Emelyanenko, Alexandre M.; Shagieva, Farida M.; Domantovsky, Alexandr G.; Boinovich, Ludmila B.

    2015-03-01

    Existing and emerging applications of laser-driven methods make an important contribution to advancement in nanotechnological approaches for the design of superhydrophobic surfaces. In this study, we describe a superhydrophobic coating on stainless steel, designed by nanosecond IR laser treatment with subsequent chemisorption of fluorooxysilane for use in heavily loaded hydraulic systems. Coating characterization reveals extreme water repellency, chemical stability on long-term contact with water, and excellent durability of functional properties under prolonged abrasive wear and cavitation loads. The coating also demonstrates self-healing properties after mechanical damage.

  10. Roles of Lewis and Brnsted acid sites in NO reduction with ammonia on CeO_2-ZrO_2-NiO-SO_4~(2-) catalyst

    Institute of Scientific and Technical Information of China (English)

    司知蠢; 翁端; 吴晓东; 江洋

    2010-01-01

    Nickel and sulfate co-modified CeO2-ZrO2 catalysts were prepared by sol-gel method. The catalysts were characterized by XRD, FTIR, XPS, NH3 chemisorption and NH3-SCR activity tests. The results showed that the enhanced acidity of CeO2-ZrO2 catalysts by nickel and sulfate co-modification was responsible for the broadened temperature window and improved the selectivity to N2 in NH3-SCR deNOx. The introduction of nickel to CeO2-ZrO2 solid solutions resulted in more Ce3+ on surface of catalyst, leading to an in...

  11. Effects of Cerium Oxide on Ni/Al2O3 Catalysts for Decomposition of CH4 and C2H4

    Institute of Scientific and Technical Information of China (English)

    杨咏来; 李文钊; 徐恒泳

    2003-01-01

    Characteristics of carbon deposition of CH4 and C2H4 decomposition over supported Ni and Ni-Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal-semiconductor interaction (MScI) in the Ni-Ce catalyst, and the effect of MScI on the carbon deposition of CH4 decomposition is opposite to that of C2H4. A novel model of carbon deposition of CH4 or C2H4 decomposition was proposed.

  12. The Role of the Coprecipitation Sequence of Salt Precursors on the Genesis of Cu-ZnO-Al2O3 Catalysts: Synthesis, Characterization and Activity for Low Temperature Shift Reaction

    Directory of Open Access Journals (Sweden)

    R.T. Figueiredo

    1998-06-01

    Full Text Available Cu-ZnO-Al2O3 catalysts for the low-temperature water-gas shift reaction were prepared using methods of direct and reverse coprecipitation. The catalysts obtained were characterized by DRX, TPR, XPS, N2O chemisorption, Hg-Porosimetry and BET surface area. It was observed that the precipitation sequence of the precursors led to significant differences in values of copper dispersion and consequently in the activity of the catalyst for the water-gas shift reaction.

  13. Impact of incomplete metal coverage on the electrical properties of metal-CNT contacts: A large-scale ab initio study

    Science.gov (United States)

    Fediai, Artem; Ryndyk, Dmitry A.; Seifert, Gotthard; Mothes, Sven; Schroter, Michael; Claus, Martin; Cuniberti, Gianaurelio

    2016-09-01

    Using a dedicated combination of the non-equilibrium Green function formalism and large-scale density functional theory calculations, we investigated how incomplete metal coverage influences two of the most important electrical properties of carbon nanotube (CNT)-based transistors: contact resistance and its scaling with contact length, and maximum current. These quantities have been derived from parameter-free simulations of atomic systems that are as close as possible to experimental geometries. Physical mechanisms that govern these dependences have been identified for various metals, representing different CNT-metal interaction strengths from chemisorption to physisorption. Our results pave the way for an application-oriented design of CNT-metal contacts.

  14. NOM removal technologies – Norwegian experiences

    Directory of Open Access Journals (Sweden)

    H. Ødegaard

    2009-10-01

    Full Text Available The paper gives an overview of the methods for removal of natural organic matter (NOM, particularly humic substances (HS, in water with focus on the Norwegian experiences. It is demonstrated that humic substances may be removed by a variety of methods, such as; molecular sieving through nanofiltration membranes, coagulation with subsequent floc separation (including granular media or membrane filtration, oxidation followed by biofiltration and sorption processes including chemisorption (ion exchange and physical adsorption (activated carbon. All these processes are in use in Norway and the paper gives an overview of the operational experiences.

  15. NOM removal technologies – Norwegian experiences

    Directory of Open Access Journals (Sweden)

    H. Ødegaard

    2010-01-01

    Full Text Available The paper gives an overview of the methods for removal of natural organic matter (NOM in water, particularly humic substances (HS, with focus on the Norwegian experiences. It is demonstrated that humic substances may be removed by a variety of methods, such as; molecular sieving through nanofiltration membranes, coagulation with subsequent floc separation (including granular media or membrane filtration, oxidation followed by biofiltration and sorption processes including chemisorption (ion exchange and physical adsorption (activated carbon. All these processes are in use in Norway and the paper gives an overview of the operational experiences.

  16. Purification of ethanol for highly sensitive self-assembly experiments

    Directory of Open Access Journals (Sweden)

    Kathrin Barbe

    2014-08-01

    Full Text Available Ethanol is the preferred solvent for the formation of self-assembled monolayers (SAMs of thiolates on gold. By applying a thin film sensor system, we could demonstrate that even the best commercial qualities of ethanol contain surface-active contaminants, which can compete with the desired thiolates for surface sites. Here we present that gold nanoparticles deposited onto zeolite X can be used to remove these contaminants by chemisorption. This nanoparticle-impregnated zeolite does not only show high capacities for surface-active contaminants, such as thiols, but can be fully regenerated via a simple pyrolysis protocol.

  17. Benzimidazole as corrosion inhibitor for heat treated 6061 Al- SiCp composite in acetic acid

    Science.gov (United States)

    Chacko, Melby; Nayak, Jagannath

    2015-06-01

    6061 Al-SiCpcomposite was solutionizedat 350 °C for 30 minutes and water quenched. It was then underaged at 140 °C (T6 treatment). The aging behaviour of the composite was studied using Rockwell B hardness measurement. Corrosion behaviour of the underaged sample was studied in different concentrations of acetic acid and at different temperatures. Benzimidazole at different concentrations was used for the inhibition studies. Inhibition efficiency of benzimidazole was calculated for different experimental conditions. Thermodynamic parameters were found out which suggested benzimidazole is an efficient inhibitor and it adsorbed on to the surface of composite by mixed adsorption where chemisorption is predominant.

  18. Enhancement of Nitrite Reduction Kinetics on Electrospun Pd-Carbon Nanomaterial Catalysts for Water Purification.

    Science.gov (United States)

    Ye, Tao; Durkin, David P; Hu, Maocong; Wang, Xianqin; Banek, Nathan A; Wagner, Michael J; Shuai, Danmeng

    2016-07-20

    We report a facile synthesis method for carbon nanofiber (CNF) supported Pd catalysts via one-pot electrospinning and their application for nitrite hydrogenation. A mixture of Pd acetylacetonate (Pd(acac)2), polyacrylonitrile (PAN), and nonfunctionalized multiwalled carbon nanotubes (MWCNTs) was electrospun and thermally treated to produce Pd/CNF-MWCNT catalysts. The addition of MWCNTs with a mass loading of 1.0-2.5 wt % (to PAN) significantly improved nitrite reduction activity compared to the catalyst without MWCNT addition. The results of CO chemisorption confirmed that the addition of MWCNTs increased Pd exposure on CNFs and hence improved catalytic activity.

  19. Near field chemical speciation: the reaction of uranium and thorium with Hanford basalt and elevated pH

    International Nuclear Information System (INIS)

    The hydrolysis of radionuclides such as thorium and uranium and their subsequent chemisorption on Hanford basalt have been studied using a variety of techniques, including x-ray photoelectron and infrared spectroscopy. Data obtained to date indicate mixed complexes of uranium and thorium to be on the basalt surface, the complexes being radionuclide oxides, hydrated oxides (hydroxides), and carbonates. These findings are discussed with respect to their importance for input for models describing speciation and dissolution processes involving nuclear waste repository materials such as Hanford basalt. 5 figures, 2 tables

  20. Reactions of XeF/sub 2/ with thermally grown SiO/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Joyce, S.; Langan, J.G.; Steinfeld, J.I.

    1988-01-01

    The reactions of XeF/sub 2/ on thermally grown SiO/sub 2/ were studied. XeF/sub 2/ does not readily undergo a dissociative chemisorption on these surfaces. Damaging the oxide with 500-eV argon ions enhances this process significantly through the creation of active sites. XPS analysis of the resulting adlayer, together with molecular-orbital model calculations, reveal the presence of fluorine bound to both silicon and oxygen. The oxyfluoride species can be removed from the surface by annealing the crystal to 200 C.

  1. Enhancement of Nitrite Reduction Kinetics on Electrospun Pd-Carbon Nanomaterial Catalysts for Water Purification.

    Science.gov (United States)

    Ye, Tao; Durkin, David P; Hu, Maocong; Wang, Xianqin; Banek, Nathan A; Wagner, Michael J; Shuai, Danmeng

    2016-07-20

    We report a facile synthesis method for carbon nanofiber (CNF) supported Pd catalysts via one-pot electrospinning and their application for nitrite hydrogenation. A mixture of Pd acetylacetonate (Pd(acac)2), polyacrylonitrile (PAN), and nonfunctionalized multiwalled carbon nanotubes (MWCNTs) was electrospun and thermally treated to produce Pd/CNF-MWCNT catalysts. The addition of MWCNTs with a mass loading of 1.0-2.5 wt % (to PAN) significantly improved nitrite reduction activity compared to the catalyst without MWCNT addition. The results of CO chemisorption confirmed that the addition of MWCNTs increased Pd exposure on CNFs and hence improved catalytic activity. PMID:27387354

  2. Preparation and deployment of indigenous 125I- seeds for the treatment of prostate cancer: dawn of prostate brachytherapy in India

    International Nuclear Information System (INIS)

    'Permanent seed implantation' using 125I- seeds represents an effective treatment modality for prostate cancer. An innovative strategy to prepare and deploy 125I- seeds for treatment of prostate cancer has been evolved. Seeds prepared by chemisorptions of 125I on palladium coated silver wires were characterized and encased in titanium tubes by ND:YAG laser. Several batches of critically evaluated seeds exhibiting release of 125I were supplied to P.D. Hinduja Hospital, Mumbai for treatment of prostate cancer patients. Successful deployment of indigenous seeds in prostate brachytherapy has opened a new window for making prostate brachytherapy affordable to needy cancer patients. (author)

  3. VAPOR-PHASE CATALYTIC CONVERSION OF ETHANOL INTO 1,3-BUTADIENE ON Cr-Ba/MCM-41 CATALYSTS

    OpenAIRE

    N. La-Salvia; J. J. Lovón-Quintana; G.P. VALENÇA

    2015-01-01

    AbstractAl-MCM-41, 16%Ba/Al-MCM-41 and 1.4%Cr-16%Ba/Al-MCM-41 were used as catalysts in the vapor-phase catalytic conversion of ethanol. Physical-chemical properties of the catalysts and the effect of barium and chromium on the Al-MCM-41 activity and 1,3-butadiene yield were studied. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption (BET method), CO2chemisorption and Fourier transform infrared spectroscopy (FT-IR). When ethanol was completely converted on Al-MCM-41...

  4. Deactivation and Coke Accumulation during CO2/CH4 Reforming over Pt Catalysts

    OpenAIRE

    Bitter, J.H.; Seshan, K.; Lercher, J.A.

    2001-01-01

    The Deactivation of Pt catalysts used in the generation of synthesis gas via CO2/CH4 reforming depends strongly on the support and the metalparticle size. Methods of Physicochemical characterization such as X-ray absorption spectroscopy and hydrogen chemisorption suggest that carbon formation (most likely from methane) rather than sintering is the main cause of catalyst deactivation. The rate of carbon formation decreased in the order Pt/y-Al2O3 >> Pt/TiO2 > Pt/ZrO2. Carbon was formed on the ...

  5. Kondo effect in molecules with strong correlations

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmenko, Tetyana [Department of Physics, Ben-Gurion University, P.O. Box 653, Beer-Sheva 84105 (Israel)]. E-mail: tetyana@bgumail.bgu.ac.il; Kikoin, Konstantin [Department of Physics, Ben-Gurion University, P.O. Box 653, Beer-Sheva 84105 (Israel); Avishai, Yshai [Department of Physics, Ben-Gurion University, P.O. Box 653, Beer-Sheva 84105 (Israel)

    2005-04-30

    A theory of Kondo tunneling through molecules adsorbed on metallic substrate is constructed and the underlying physics is exposed. It is shown that in the case of weak chemisorption the sandwich-type molecules manifest a novel type of Kondo effect that has not been observed in magnetically doped bulk metals. The exchange Hamiltonian of these molecules unveils unusual dynamical SO(n) symmetries instead of conventional SU(2) symmetry. These symmetries can be experimentally realized and the specific value of n can be controlled by gate voltage.

  6. Kondo tunneling through real and artificial molecules.

    Science.gov (United States)

    Kikoin, K; Avishai, Y

    2001-03-01

    When an asymmetric double dot is hybridized with itinerant electrons, its singlet ground state and lowly excited triplet state cross, leading to a competition between the Zhang-Rice mechanism of singlet-triplet splitting in a confined cluster and the Kondo effect (which accompanies the tunneling through quantum dot under a Coulomb blockade restriction). The rich physics of an underscreened S = 1 Kondo impurity in the presence of low-lying triplet-singlet excitations is exposed and estimates of the magnetic susceptibility and the electric conductance are presented, together with applications for molecule chemisorption on metallic substrates.

  7. Radioelement studies in the oceans. Progress report, April 15, 1981-April 14, 1982

    International Nuclear Information System (INIS)

    Progress for the report period is reported under the following section headings: bibliographic summary - 1981; cruise reports and sampling activities; abstracts of reports published, submitted, or presented at meetings; and, brief summaries of work in progress. Research in progress includes the following studies: post-depositional chemistry of radionuclides: interstitial water composition and laboratory remobilizaton studies; thorium isotope studies in seawater; radionuclide measurements on samples from ocean weather ship MIKE, in the Norwegian Sea; counting technique optimization for Cs isotopes collected by chemisorption; Pu oxidation states in the Aleutian Trench water column; intercalibrations and standard materials; and radionuclides in deep water bathypelagic biota

  8. Preparation and catalytic performance of monolayer-dispersed Pd/Ni bimetallic catalysts for hydrogenation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pd/Ni bimetallic catalysts were prepared by replacement reactions,characterized by X-ray diffraction,CO chemisorption and H2 temperature-programmed desorption,and evaluated for hydrogenation of cyclohexene,styrene and acetone.The results show that Pd atoms are monolayer-dispersed on the Ni surface in these Pd/Ni catalysts.Consequently,Pd/Ni catalysts are much more active than Pd/Ni and Pd/γ-Al2O3 with the same Pd loading prepared by the conventional impregnation method.

  9. Materials for carbon dioxide separation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Qingqing

    2014-10-01

    The CO{sub 2} adsorption capacities at room temperature have been investigated by comparing carbon nanotubes, fullerene, graphenes, graphite and granular activated carbons. It turned out that the amount of the micropore surface area was dominating the CO{sub 2} adsorption ability. Another promising class of materials for CO{sub 2} capture and separation are CaO derived from the eggshells. Two aspects were studied in present work: a new hybrid materials synthesized by doping the CaTiO{sub 3} and the relationship between physisorption and chemisorption properties of CaO-based materials.

  10. Atomic arrangements and electronic properties of semiconductor surfaces and interfaces

    Science.gov (United States)

    Chadi, D. J.; Martin, R. M.

    1982-05-01

    The areas of research during the past 12 months have included: step-formation energies and domain orientation at Si(111) surfaces; the electronic structure of the Al-GaAs(110) surface chemisorption system; density-functional calculations of bulk properties of GaAs and of (100)GaAs-Ge interfaces; demonstration of the importance of correlation effects on the atomic and electronic structure of Si(111) surfaces; and derivation of an exact scaling law for the resistance of a thin wire for the one dimensional Anderson model containing Loth diagonal and off-diagonal disorder.

  11. Novel, High Activity Hydroprocessing Catalysts: Iron Group Phosphides

    OpenAIRE

    Wang, Xianqin

    2002-01-01

    A series of iron, cobalt and nickel transition metal phosphides was synthesized by means of temperature-programmed reduction (TPR) of the corresponding phosphates. The same materials, Fe2P, CoP and Ni2P, were also prepared on a silica (SiO2) support. The phase purity of these catalysts was established by x-ray diffraction (XRD), and the surface properties were determined by N2 BET specific surface area (Sg) measurements and CO chemisorption. The activities of the silica-supported catalysts...

  12. Heterogeneous fixation of N2: Investigation of a novel mechanism for formation of NO

    DEFF Research Database (Denmark)

    Zheng, Ying; Jensen, Anker Degn; Glarborg, Peter;

    2009-01-01

    Formation of NO initiated by heterogeneous fixation of N2 during pyrolysis is investigated experimentally and theoretically. The experiments were conducted with beech wood as well as with the pure biomass components cellulose, xylan, and lignin. The NO formation during char oxidation was recorded....... The experiments with pure materials show that the lignin char has the strongest ability to form NO from uptake of N2, while xylan char forms only small amounts of NO from N2. Density Functional Theory (DFT) calculations on model chars have revealed a number of chemisorption sites for N2, many of which are weakly...

  13. Study of calcium forms and their effect in carbon stabilization in fertile soils by FTIR and XPS

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, J.R.; Assis, K.L.S.; Calil, V.L.; Souza, K.R.; Beltrao, M.S.S.; Sena, L.A.; Archanjo, B.S.; Achete, C.A., E-mail: jraraujo@inmetro.gov.br [Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Duque de Caxias, RJ (Brazil). Divisao de Materiais e Metrologia

    2013-07-01

    Organic matter or black carbon atoms of Terra Preta de Indio (Amazonian Dark Earth) soils are composed of oxidized carbon groups as phenols, epoxide, carbonyl and carboxyl groups in their surface. At the pH of soil, carboxylate groups are deprotonated generating carboxylate anions leaving the surface of these soils with negative charges. Calcium cations can interact with oxidized carbon groups by chemisorption interactions lowering the total system energy. In this work, Terra Preta de Indio was examined by X-ray photoelectron spectroscopy and Infrared spectroscopy in order to correlate its organic fraction rich in calcium with calcium containing samples. (author)

  14. LETTER TO THE EDITOR: Variation of adatom to substrate charge transfer value along the first-row transition metal series on Mo(110)

    Science.gov (United States)

    Magkoev, T. T.; Christmann, K.; Lecante, P.; Moutinho, A. M. C.

    2002-04-01

    Adsorption of the first-row transition 3d metals (Ti-Cu) on the atomically clean Mo(110) surface in ultra-high-vacuum conditions has been studied by Auger electron spectroscopy and work function measurements (Anderson method). In this letter it is shown that adsorption behaviour of the metals under consideration systematically changes along the 3d series. The observed correlation between the systematic change of the dipole moments and the values of the charge transfer from adatom to substrate along the period leads us to the conclusion that the metal 3d orbitals play an important role in the formation of the chemisorption bond.

  15. Pt-Rh/g Al2O3 Benzene Hydrogenation Reaction as a Characterization Technique

    Directory of Open Access Journals (Sweden)

    N.M. da Fonseca

    1998-06-01

    Full Text Available Pt-Rh/Al2O3 catalysts prepared by successive incipient impregnations and coimpregnation were characterized by H2 chemisorption, temperature programmed reduction and benzene hydrogenation reaction in the vapor phase. The results showed that Rh plays the role of Pt reducting agent, which is very different from the effects of metal-metal interaction which appear mainly in solids with the highest metal contents. The most important parameter that results in bimetallic particles in the catalyst prepared by successive impregnation is the sequence of metal addition.

  16. Surface reactions of metal clusters. II. Reactivity surveys with D2, N2, and CO

    OpenAIRE

    Morse, M. D.; Gausic, M. E.; Heath, J. R.; Smalley, R. E.

    1985-01-01

    Reactions on the surface of a variety of transition metal clusters have been studied in the gas phase at near room temperature using a newly developed fast-flow reaction device. Initial examples of the use of this device are provided by survey studies of the reactivity of iron, cobalt, nickel, copper, and niobium clusters in contact with low concentrations of D2, N2 and CO. Dissociative chemisorption of D2 is found to occur with dramatic sensitivity to cluster size in the cases of iron, cobal...

  17. Linen Fire as Biosorbent to Remove Heavy Metal Ions From Wastewater Modeling

    Directory of Open Access Journals (Sweden)

    Ildar G. Shaikhiev

    2014-03-01

    Full Text Available The possibility of using linen fires – lnopererabotk i waste as a sorption material for the extraction of heavy metal ions from wastewater modeling. It is shown that treatment with acid solutions linen fires a low concentration increases the surface area of linen fires and thus sorption capacity for heavy metal ions. The values of the maximum sorption capacity ions Fe (III, Co (II, Ni (II and Zn (II under static and dynamic conditions. IR spectroscopy shows that along with the physical sorption process proceeds chemisorption.

  18. Kinetic for Adsorption of Dye Methyl Orange by the Modified Activated Carbon from Rice Husk

    Directory of Open Access Journals (Sweden)

    Muqing Qiu

    2015-08-01

    Full Text Available In this study, the modified activated carbon from rice husk is used as the low cost material to absorb dye Methyl Orange in aqueous solution. The effects of different process parameters like pH, initial dye concentration and contact time on the adsorption of dye are investigated. The kinetic data of adsorption studies are discussed by the pseudo first-order, pseudo second-order and intraparticle diffusion. The results were shown that the adsorption process is chemisorption, which involves a sharing of electrons between the adsorbate and the surface of the adsorbent.

  19. Sequential desorption energy of hydrogen from nickel clusters

    Energy Technology Data Exchange (ETDEWEB)

    Deepika,; Kumar, Rakesh, E-mail: rakesh@iitrpr.ac.in [Department of Physics, Indian Institute of Technology Ropar, Rupnagar-140001 (India); R, Kamal Raj. [Indian Institute of Science Education and Research Kolkata, Mohanpur-741246 (India); Kumar, T. J. Dhilip [Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar-140001 (India)

    2015-06-24

    We report reversible Hydrogen adsorption on Nickel clusters, which act as a catalyst for solid state storage of Hydrogen on a substrate. First-principles technique is employed to investigate the maximum number of chemically adsorbed Hydrogen molecules on Nickel cluster. We observe a maximum of four Hydrogen molecules adsorbed per Nickel atom, but the average Hydrogen molecules adsorbed per Nickel atom decrease with cluster size. The dissociative chemisorption energy per Hydrogen molecule and sequential desorption energy per Hydrogen atom on Nickel cluster is found to decrease with number of adsorbed Hydrogen molecules, which on optimization may help in economical storage and regeneration of Hydrogen as a clean energy carrier.

  20. Evaluation of the Catalytic Activity and Cytotoxicity of Palladium Nanocubes. The Role of Oxygen

    OpenAIRE

    Dahal, Eshan; Curtiss, Jessica; Subedi, Deepak; Chen, Gen; Houston, Jessica P.; Smirnov, Sergei

    2015-01-01

    Recently it has been reported that palladium nanocubes (PdNC) are capable of generating singlet oxygen without photo-excitation simply via chemisorption of molecular oxygen on its surface. Such a trait would make PdNC a highly versatile catalyst suitable in organic synthesis and a Reactive Oxygen Species (ROS) inducing cancer treatment reagent. Here we thoroughly investigated the catalytic activity of PdNC with respect to their ability to produce singlet oxygen and to oxidize 3,5,3′,5′-tetram...

  1. Tendências em modificação de eletrodos amperométricos para aplicações eletroanalíticas Trends in amperometric electrodes modification for electroanalytical applications

    Directory of Open Access Journals (Sweden)

    Arnaldo César Pereira

    2002-11-01

    Full Text Available The most relevant advances on the analytical applications of chemically modified electrodes (CME are presented. CME have received great attention due to the possibility of electrode surface modification including chemisorption, composite generation and polymer coating. In recent years, the interest in CME has increased overall to improve the sensitivity and selectivity of the electroanalytical probes, considering the electron mediator incorporation and the new conducting polymers development. The general procedures employed for the electrode modification and the operational characteristics of some electrochemical sensors are discussed.

  2. Electronic Properties of Hydrogen Storage Materials with Photon-in/Photon-out Soft-X-Ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jinghua

    2008-09-22

    The applications of resonant soft X-ray emission spectroscopy on a variety of carbon systems have yielded characteristic fingerprints. With high-resolution monochromatized synchrotron radiation excitation, resonant inelastic X-ray scattering has emerged as a new source of information about electronic structure and excitation dynamics. Photon-in/photon-out soft-X-ray spectroscopy is used to study the electronic properties of fundamental materials, nanostructure, and complex hydrides and will offer potential in-depth understanding of chemisorption and/or physisorption mechanisms of hydrogen adsorption/desorption capacity and kinetics.

  3. Trends in the exchange current for hydrogen evolution

    DEFF Research Database (Denmark)

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

    2005-01-01

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

  4. Influence of alumina binder content on catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone.

    Science.gov (United States)

    Kong, Xiangjin; Liu, Junhai

    2014-01-01

    The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N2 sorption, X-ray diffraction, H2-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst.

  5. Influence of alumina binder content on catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone.

    Directory of Open Access Journals (Sweden)

    Xiangjin Kong

    Full Text Available The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N2 sorption, X-ray diffraction, H2-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst.

  6. Creating, Varying, and Growing Single-Site Molecular Contacts

    Science.gov (United States)

    Siaj, Mohamed; McBreen, Peter H.

    2005-07-01

    The known range of chemisorption bonds forms the toolbox for the design of electrical contacts in molecular electronics devices. Double-bond contacts to technologically relevant materials would be attractive for a number of reasons. They are truly single-site, bonding to a single surface atom. They obviate the need for a thiol linkage, and they may be amenable to further modification through olefin-metathesis methodologies. We report olefin-metathesis methods for establishing, varying, and growing thermally stable double-bond contacts to molybdenum carbide, a conducting material.

  7. A quantitative method to discriminate between non-specific and specific lectin-glycan interactions on silicon-modified surfaces.

    Science.gov (United States)

    Yang, Jie; Siriwardena, Aloysius; Boukherroub, Rabah; Ozanam, François; Szunerits, Sabine; Gouget-Laemmel, Anne Chantal

    2016-02-15

    Essential to the success of any surface-based carbohydrate biochip technology is that interactions of the particular interface with the target protein be reliable and reproducible and not susceptible to unwanted nonspecific adsorption events. This condition is particularly important when the technology is intended for the evaluation of low-affinity interactions such as those typically encountered between lectins and their monomeric glycan ligands. In this paper, we describe the fabrication of glycan (mannoside and lactoside) monolayers immobilized on hydrogenated crystalline silicon (111) surfaces. An efficient conjugation protocol featuring a key "click"-based coupling step has been developed which ensures the obtention of interfaces with controlled glycan density. The adsorption behavior of these newly developed interfaces with the lectins, Lens culinaris and Peanut agglutinin, has been probed using quantitative IR-ATR and the data interpreted using various isothermal models. The analysis reveals that protein physisorption to the interface is more prevalent than specific chemisorption for the majority of washing protocols investigated. Physisorption can be greatly suppressed through application of a strong surfactinated rinse. The coexistence of chemisorption and physisorption processes is further demonstrated by quantification of the amounts of adsorbed proteins distributed on the surface, in correlation with the results obtained by atomic force microscopy (AFM). Taken together, the data demonstrates that the nonspecific adsorption of proteins to these glycan-terminated surfaces can be effectively eliminated through the proper control of the chemical structure of the surface monolayer combined with the implementation of an appropriate surface-rinse protocol.

  8. Vapor Phase Hydrogenation of Nitrobenzene to Aniline Over Carbon Supported Ruthenium Catalysts.

    Science.gov (United States)

    Srikanth, Chakravartula S; Kumar, Vanama Pavan; Viswanadham, Balaga; Srikanth, Amirineni; Chary, Komandur V R

    2015-07-01

    A series of Ru/Carbon catalysts (0.5-6.0 wt%) were prepared by impregnation method. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), CO-chemisorption, surface area and pore-size distribution measurements. The catalytic activities were evaluated for the vapor phase hydrogenation of nitrobenzene. The dispersion measured by CO-uptake values suggests that a decrease of dispersion is observed with increasing Ru loading on carbon support. These findings are well supported by the crystallite size measured from XRD measurements. XPS study reveals the formation of Ru0 after reduction at 573 K for 3 h. The catalysts exhibit high conversion/selectivity at 4.5 wt% Ru loading during hydrogenation reaction. The particle size measured from CO-chemisorption and TEM analysis are related to the TOF during the hydrogenation reaction. Ru/C catalysts are found to show higher conversion/selectivities during hydrogenation of nitrobenzene to aniline. PMID:26373150

  9. Kinetic, isotherm and thermodynamics investigation on adsorption of divalent copper using agro-waste biomaterials, Musa acuminata, Casuarina equisetifolia L. and Sorghum bicolor

    Directory of Open Access Journals (Sweden)

    Mokkapati Ramya Prasanthi

    2016-06-01

    Full Text Available Three novel and distinct agricultural waste materials, viz., Casuarinas fruit powder (CFP, sorghum stem powder (SSP and banana stem powder (BSP were used as low cost adsorbents for the removal of toxic copper(II from aqueous solutions. Acid treated adsorbents were characterized by SEM, EDX and FTIR. Different factors effecting adsorption capacity were analyzed and the efficiency order was BSP>SSP>CFP. Based on the extent of compatibility to Freundlich/Langmuir/D-R/Temkin adsorption isotherm and different models (pseudo-first and second order, Boyd, Weber’s and Elovich, chemisorption primarily involved in the case of CFP and SSP, whereas, simultaneous occurrence of chemisorption and physisorption was proposed in the case of BSP. Based on the observations, it was proposed that three kinetic stages involve in adsorption process viz., diffusion of sorbate to sorbent, intra particle diffusion and then establishment of equilibrium. These adsorbents have promising role towards removal of Cu(II from industrial wastewater to contribute environmental protection.

  10. Identifying Enclosed Chemical Reaction and Dynamics at the Molecular Level Using Shell-Isolated Miniaturized Plasmonic Liquid Marble.

    Science.gov (United States)

    Han, Xuemei; Lee, Hiang Kwee; Lee, Yih Hong; Hao, Wei; Liu, Yejing; Phang, In Yee; Li, Shuzhou; Ling, Xing Yi

    2016-04-21

    Current microscale tracking of chemical kinetics is limited to destructive ex situ methods. Here we utilize Ag nanocube-based plasmonic liquid marble (PLM) microreactor for in situ molecular-level identification of reaction dynamics. We exploit the ultrasensitive surface-enhanced Raman scattering (SERS) capability imparted by the plasmonic shell to unravel the mechanism and kinetics of aryl-diazonium surface grafting reaction in situ, using just a 2-μL reaction droplet. This reaction is a robust approach to generate covalently functionalized metallic surfaces, yet its kinetics remain unknown to date. Experiments and simulations jointly uncover a two-step sequential grafting process. An initial Langmuir chemisorption of sulfonicbenzene diazonium (dSB) salt onto Ag surfaces forms an intermediate sulfonicbenzene monolayer (Ag-SB), followed by subsequent autocatalytic multilayer growth of Ag-SB3. Kinetic rate constants reveal 19-fold faster chemisorption than multilayer growth. Our ability to precisely decipher molecular-level reaction dynamics creates opportunities to develop more efficient processes in synthetic chemistry and nanotechnology. PMID:27050645

  11. Kinetic and thermodynamics of the removal of Zn2+ and Cu2+ from aqueous solution by sulphate and phosphate-modified Bentonite clay

    International Nuclear Information System (INIS)

    The modification of pristine Bentonite clay with sulphate and phosphate anions was found to increase its cation-exchange capacity (CEC), adsorption capacity and overall pseudo-second order kinetic rate constant for the adsorption of Cu2+ and Zn2+. Modification with sulphate and phosphate anion decreased the specific surface area of pristine Bentonite clay. Phosphate-modified Bentonite clay was found to give the highest adsorption capacity for both metal ions. The adsorption process was observed to be endothermic and spontaneous in nature for both metal ions with Zn2+ being more adsorbed. Modification with phosphate anion increased the spontaneity of the adsorption process. The effective modification of pristine Bentonite clay with sulphate anion was confirmed from hypochromic shifts in the range of 13-18 cm-1 which is typical of physisorption while modification with phosphate anion was confirmed by its hyperchromic shifts typical of chemisorption in the infrared red region using Fourier transformed infrared spectroscopy (FTIR). Using the model efficiency indicator, kinetic data were found to show very strong fit to the pseudo-second order kinetic model implying that the adsorption of Cu2+ and Zn2+ were basically by chemisorption.

  12. Interaction of hydrogen with palladium clusters deposited on graphene

    International Nuclear Information System (INIS)

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H2 on Pd6 anchored on a graphene vacancy has been studied in detail

  13. The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors.

    Science.gov (United States)

    Jahandar Lashaki, Masoud; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

    2016-11-01

    The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials. PMID:27295065

  14. Improved sulfur-resistant ability on CO oxidation of Pd/Ce0.75Zr0.25O2 over Pd/CeO2-TiO2 and Pd/CeO2

    Institute of Scientific and Technical Information of China (English)

    沈美庆; 林放; 魏光曦; 王建强; 朱少春

    2015-01-01

    The influence of sulfation on Pd/Ce0.75Zr0.25O2, Pd/CeO2-TiO2 and Pd/CeO2 was investigated. Physical structure and chemical properties of different catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), CO chemisorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and X-ray fluorescence (XRF). After 10 h SO2 sulfation, it was found that the decrement on CO oxidation catalytic activity was limited on Pd/Ce0.75Zr0.25O2 compared to Pd/CeO2-TiO2 and Pd/CeO2. It demonstrated that Pd/Ce0.75Zr0.25O2 was more sulfur resistant compared to the other two catalysts. Af-ter sulfur exposure, catalyst texture was not much influenced as shown by N2 adsorption and XRD, and surface Pd atoms were poi-soned indicated by CO chemisorption results. Pd/Ce0.75Zr0.25O2 and Pd/CeO2-TiO2 exhibited less sulfur accumulation compared to Pd/CeO2 in the sulfation process. Furthermore, XPS results clarified that surface sulfur amount, especially surface sulfates amount on the sulfated catalysts was more crucial for the deactivation in sulfur containing environment.

  15. Tridentate benzylthiols on Au(111): control of self-assembly geometry.

    Science.gov (United States)

    Mezour, Mohamed A; Perepichka, Iryna I; Ivasenko, Oleksandr; Lennox, R Bruce; Perepichka, Dmitrii F

    2015-03-21

    A set of hexasubstituted benzene derivatives with three thiol groups in the 1, 3, 5 positions and varied aliphatic substituents in the 2, 4, 6 positions (Me3-BTMT, Et3-BTMT, ODe3-BTMT) has been synthesized and self-assembled on Au(111). The resulting self-assembled monolayers (SAMs) are characterized by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and electrochemistry. The molecular orientation and long-range order are affected by the “gear effect” of the hexasubstituted benzene ring and van der Waals interactions between the physisorbed alkyl chains drive. Me3-BTMT adopts a standing up orientation which results in the highest molecular surface density but also the lowest degree of chemisorption (1 to 2 Au–S bonds per molecule). In contrast, Et3-BTMT favors a lying down orientation with a greater number of surface-bonded thiol groups (2 to 3) per molecule, associated with the peculiar geometry of this molecule. Finally, ODe3-BTMT adsorbs mainly in a lying down orientation, forming the SAM with the highest degree of chemisorption (all thiol groups are gold-bonded) and the lowest molecular areal density. PMID:25695677

  16. Self-suspended permanent magnetic FePt ferrofluids

    KAUST Repository

    Dallas, Panagiotis

    2013-10-01

    We present the synthesis and characterization of a new class of self-suspended ferrofluids that exhibit remanent magnetization at room temperature. Our system relies on the chemisorption of a thiol-terminated ionic liquid with very low melting point on the surface of L10 FePt nanoparticles. In contrast, all types of ferrofluids previously reported employ either volatile solvents as the suspending media or superparamagnetic iron oxide nanoparticles (that lacks permanent magnetization) as the inorganic component. The ferrofluids do not show any sign of flocculation or phase separation, despite the strong interactions between the magnetic nanoparticles due to the strong chemisorption of the ionic liquid as evidenced by Raman spectroscopy and thermal analysis. Composites with high FePt loading (40 and 70. wt%) exhibit a pseudo solid-like rheological behavior and high remanent magnetization values (10.1 and 12.8. emu/g respectively). At lower FePt loading (12. wt%) a liquid like behavior is observed and the remanent and saturation magnetization values are 3.5 and 6.2. emu/g, respectively. The magnetic and flow properties of the materials can be easily fine tuned by controlling the type and amount of FePt nanoparticles used. © 2013 Elsevier Inc.

  17. Interaction of ester functional groups with aluminum oxide surfaces studied using infrared reflection absorption spectroscopy.

    Science.gov (United States)

    van den Brand, J; Blajiev, O; Beentjes, P C J; Terryn, H; de Wit, J H W

    2004-07-20

    The bonding of two types of ester group-containing molecules with a set of different oxide layers on aluminum has been investigated using infrared reflection absorption spectroscopy. The different oxide layers were made by giving typical surface treatments to the aluminum substrate. The purpose of the investigation was to find out what type of ester-oxide bond is formed and whether this is influenced by changes in the composition and chemistry of the oxide. The extent by which these bonded ester molecules resisted disbondment in water or substitution by molecules capable of chemisorption was also investigated. The ester groups were found to show hydrogen bonding with hydroxyls on the oxide surfaces through their carbonyl oxygens. For all oxides, the ester groups showed the same nu(C = O) carbonyl stretching vibration after adsorption, indicating very similar bonding occurs. However, the oxides showed differences in the amount of molecules bonded to the oxide surface, and a clear relation was observed with the hydroxyl concentration present on the oxide surface, which was determined from XPS measurements. The two compounds showed differences in the free to bonded nu(C = O) infrared peak shift, indicating differences in bonding strength with the oxide surface between the two types of molecules. The bonding of the ester groups with the oxide surfaces was found to be not stable in the presence of water and also not in the presence of a compound capable of chemisorption with the aluminum oxide surface. PMID:15248718

  18. Temperature-responsive self-assembled monolayers of oligo(ethylene glycol): control of biomolecular recognition.

    Science.gov (United States)

    Zareie, Hadi M; Boyer, Cyrille; Bulmus, Volga; Nateghi, Ebrahim; Davis, Thomas P

    2008-04-01

    Self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG)-tethered molecules on gold are important for various biorelevant applications ranging from biomaterials to bioanalytical devices, where surface resistance to nonspecific protein adsorption is needed. Incorporation of a stimuli-responsive character to the OEG SAMs enables the creation of nonfouling surfaces with switchable functionality. Here we present an OEG-derived structure that is highly responsive to temperature changes in the vicinity of the physiological temperature, 37 degrees C. The temperature-responsive solution behavior of this new compound was demonstrated by UV-vis and nuclear magnetic resonance spectroscopy. Its chemisorption onto gold(111), and the retention of responsive behavior after chemisorption have been demonstrated by surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS), and atomic force and scanning tunneling microscopy. The OEG-derived SAMs have been shown to reversibly switch the wettability of the surface, as determined by contact angle measurements. More importantly, SPR and AFM studies showed that the OEG SAMs can be utilized to control the affinity binding of streptavidin to the biotin-tethered surface in a temperature-dependent manner while still offering the nonspecific protein-resistance to the surface.

  19. Density Functional Theory with Modified Dispersion Correction for Metals Applied to Self-Assembled Monolayers of Thiols on Au(111

    Directory of Open Access Journals (Sweden)

    M. P. Andersson

    2013-01-01

    Full Text Available Using sound physical principles we modify the DFT-D2 atom pairwise semiempirical dispersion correction to density functional theory to work for metallic systems and in particular self-assembled monolayers of thiols on gold surfaces. We test our approximation for two functionals PBE-D and revPBE-D for lattice parameters and cohesive energies for Ni, Pd, Pt, Cu, Ag, and Au, adsorption energies of CO on (111 surfaces of Pd, Pt, Cu, Ag, and Au, and adsorption energy of benzene on Ag(111 and Au(111. Agreement with experimental data is substantially improved. We apply the method to self-assembled monolayers of alkanethiols on Au(111 and find reasonable agreement for PBE-D and revPBE-D for both physisorption of n-alkanethiols as well as dissociative chemisorption of dimethyl disulfide as an Au-adatom-dithiolate complex. By modifying the C6 coefficient for Au, we obtain quantitative agreement for physisorption and chemisorption for both PBE-D and revPBE-D using the same set of parameters. Our results confirm that inclusion of dispersion forces is crucial for any quantitative analysis of the thiol and thiolate bonds to the gold surface using quantum chemical calculations.

  20. Interaction of hydrogen with palladium clusters deposited on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, Julio A.; Granja, Alejandra; Cabria, Iván; López, María J. [Departamento de Física Teórica, Atómica y Optica, Universidad de Valladolid, 47011 Valladolid (Spain)

    2015-12-31

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H{sub 2} on Pd{sub 6} anchored on a graphene vacancy has been studied in detail.

  1. The role of adsorbed hydrogen species in the dehydrogenation and hydrocracking of saturated hydrocarbons on supported metal catalysts

    Science.gov (United States)

    Babenkova, L. V.; Naidina, I. N.

    1994-07-01

    The role of certain hydrogen absorption complexes in the dehydrogenation and hydrocracking of hydrocarbons on low-percentage one-component, (Pt, Pd/Al2O3) and bimetallic (Pd-Co, Pd-Ce, Pt-Co, Pt-Sn/Al2O3) catalysts is discussed. It is shown that the combination of metals in reduced forms and forms oxidised to different extents on the catalyst surfaces is responsible for their high capacity for the chemisorption of hydrogen, the wide range of its energetic inhomogeneity, and the high activity of the catalysts in the conversion of saturated hydrocarbons. Catalysts containing on the surface mainly sites for the type Hδ- chemisorption are the most active in the dehydrogenation of hydrocarbons, whereas specimens chemisorbing hydrogen mainly in the Hδ+ form are the most active in the hydrockracking of hydrocarbons. It is concluded that the strongly bound atomic hydrogen Hδ+ plays a dual role, since it not only participates directly in the dehydrogenation reaction but also promotes the reduction of the electron-deficient surface centres, which optimises the number of centres for the activation of C-H bonds. The bibliography includes 75 references.

  2. Cr(VI) sorption behavior from aqueous solutions onto polymeric microcapsules containing a long-chain quaternary ammonium salt: Kinetics and thermodynamics analysis

    Energy Technology Data Exchange (ETDEWEB)

    Barassi, Giancarlo; Valdes, Andrea; Araneda, Claudio; Basualto, Carlos; Sapag, Jaime; Tapia, Cristian [Laboratorio de Operaciones Unitarias, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Av. Vicuna Mackenna 20, Santiago (Chile); Valenzuela, Fernando, E-mail: fvalenzu@uchile.cl [Laboratorio de Operaciones Unitarias, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Av. Vicuna Mackenna 20, Santiago (Chile)

    2009-12-15

    This work studies the adsorption of Cr(VI) ions from an aqueous acid solution on hydrophobic polymeric microcapsules containing a long-chain quaternary ammonium salt-type extractant immobilized in their pore structure. The microcapsules were synthesized by adding the extractant Aliquat 336 during the in situ radical copolymerization of the monomers styrene (ST) and ethylene glycol dimethacrylate (EGDMA). The microcapsules, which had a spherical shape with a rough surface, behaved as efficient adsorbents for Cr(VI) at the tested temperatures. The results of kinetics experiments carried out at different temperatures showed that the adsorption process fits well to a pseudo-second-order with an activation energy of 82.7 kJ mol{sup -1}, confirming that the sorption process is controlled by a chemisorption mechanism. Langmuir's isotherms were found to represent well the experimentally observed sorption data. Thermodynamics parameters, namely, changes in standard free energy ({Delta}G{sup 0}), enthalpy ({Delta}H{sup 0}), and entropy ({Delta}S{sup 0}), are also calculated. The results indicate that the chemisorption process is spontaneous and exothermic. The entropy change value measured in this study shows that metal adsorbed on microcapsules leads to a less chaotic system than a liquid-liquid extraction system.

  3. Phase transition and vapochromism in molecular assemblies of a polymorphic zinc(II) Schiff-base complex.

    Science.gov (United States)

    Oliveri, Ivan Pietro; Malandrino, Graziella; Di Bella, Santo

    2014-09-15

    This paper reports for the first time the irreversible thermally induced phase transition, accompanied by color change, and the vapochromic behavior of an amphiphilic, Lewis acidic Zn(II) Schiff-base complex, through detailed X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, and optical absorption studies. The unprecedented irreversible phase transition for such kind of complexes is associated with a thermal, lamellar-to-hexagonal columnar structural transition, which involves a different arrangement of each molecular unit within the assembled structure, H- and J-type aggregates, respectively, responsible for the thermochromic behavior. The vapochromism, investigated either in powder samples or in thermally annealed cast films, is related to the formation of 1:1 adducts upon exposure to vapors of strong Lewis bases and implies dramatic optical absorption variations and naked-eye observation of the change in color from red-brown to red. The chemisorption process is fast, completely reversible, reproducible, and selective for amines. The reversible switching of the chemisorption-desorption process in cast films is demonstrated by successive cycles, amine exposure and subsequent heating, by monitoring the substantial optical absorption changes in the visible region. Vapochromism of this material can potentially be used to detect vapors of volatile amines. PMID:25148651

  4. Adsorption of oleic acid at sillimanite/water interface.

    Science.gov (United States)

    Kumar, T V Vijaya; Prabhakar, S; Raju, G Bhaskar

    2002-03-15

    The interaction of oleic acid at sillimanite-water interface was studied by adsorption, FT-IR, and zeta potential measurements. The isoelectric point (IEP) of sillimanite obtained at pH 8.0 was found to shift in the presence of oleic acid. This shift in IEP was attributed to chemisorption of oleic acid on sillimanite. Adsorption experiments were conducted at pH 8.0, where the sillimanite surface is neutral. The adsorption isotherm exhibited a plateau around 5 micromol/m2 that correspond to a monolayer formation. Adsorption of oleic acid on sillimanite, alumina, and aluminum hydroxide was studied by FT-IR. Chemisorption of oleic acid on the above substrates was confirmed by FT-IR studies. Hydroxylation of mineral surface was found to be essential for the adsorption of oleic acid molecules. These surface hydroxyl sites were observed to facilitate deprotonation of oleic acid and its subsequent adsorption. Thus protons from oleic acid react with surface hydroxyl groups and form water molecules. Based on the experimental results, the mechanism of oleic acid adsorption on mineral substrate was proposed. Free energy of adsorption was estimated using the Stern-Graham equation for a sillimanite-oleate system. PMID:16290466

  5. Diffusion and sorption of 32Si-labelled silica in the boom clay

    International Nuclear Information System (INIS)

    The long term corrosion rate of nuclear waste glass in a repository might be controlled by the steady-state diffusion of dissolved silica and would be enhanced by the sorption of silica onto clay minerals. Irreversible sorption and moderate retardation have been observed for dissolved silica in boom clay. Values of ηR between 10 and 20 have been determined by means of four flow-through migration experiments, while Kd in the range 20 to 100 cm3, g-1 have been measured by batch sorption tests with 32Si on fresh and slightly oxidized boom clay. As non specific interactions cannot explain the sorption of neutral Si(OH)4, or of negative silicate species (Donnan exclusion), onto negatively charged clay minerals other mechanisms must be invoked: i.a., the chemisorption of dissolved silica Si(OH)4 onto specific Lewis acid sites (Al3+, Fe3+) present at the clay surface. The suggested mechanism could be similar to this explaining the irreversible chemisorption of oxy-anions of weak acids (as phosphate, or borate) onto aluminum and iron hydroxides in soils. Ligand exchange of aqueous silica with a hydroxyl group of Al(OH)3 may form a hydroxy-aluminosilicate (HAS) surface complex. Gibbsite layers accessible on the basal plane of kaolinite and on the edges of illite and smectite are possible sorption sites for the dissolved silica in boom clay. Moreover, hydrous ferric oxide produced by pyrite oxidation significantly increases the extent of silica sorption. (orig.)

  6. Reduction of NO by CO using Pd-CeTb and Pd-CeZr catalysts supported on SiO2 and La2O3-Al2O3

    Institute of Scientific and Technical Information of China (English)

    Victor Ferrer; Dora Finol; Roger Solano; Alexander Moronta; Miguel Ramos

    2015-01-01

    The catalytic activity of Pd catalysts supported on Ce0.73Tb0.27Ox/SiO2,Ce0.6Zr0.4Ox/SiO2,Ce0.73Tb0.27Ox/La2O3-Al2O3 and Ce0.6Zr0.4Ox/La2O3-Al2O3 was studied using the reduction of NO by CO.The catalysts were characterized by X-ray fluorescence,surface area,X-ray diffraction,temperature-programmed reduction,CO chemisorption and oxygen storage capacity.Temperature-programmed reduction results indicated that Tb or Zr incorporation improves the reducibility and oxygen storage capacity.CO chemisorption data suggested the presence of large PdO particles due to the low CO/Pd ratio.No significant differences were obtained in light offtemperatures (TLight off) for all Pd catalysts and the most active was 1.5%Pd/Ce0.6Zr0.4Ox/SiO2.

  7. The effect of salinity on the sorption of cadmium ions from aqueous medium on Fe(III-sepiolite

    Directory of Open Access Journals (Sweden)

    Habish Amal Juma

    2015-01-01

    Full Text Available In this study, the sorption of cadmium ions onto sepiolite modified with hydrated iron(III oxide, Fe(III-sepiolite, has been investigated in natural seawater, artificial seawater, aqueous solution of NaCl of the same ionic strength as the seawater and distilled water. The sorption experiments were performed as a function of the initial solution pH value, the initial metal concentration and the equilibration time, using the batch method. The equilibrium sorption data were analyzed by the Langmuir, Freundlich and Sips isotherm models and the kinetics of sorption was analyzed using the pseudo-first-order and the pseudo-second-order kinetic models. The maximum sorption capacity and the strength of the sorbate-sorbent bonds at initial pH = 7 were found to decrease in the following order: distilled water > NaCl solution > artificial seawater > natural seawater. The values of parameter nS in the Sips model, which fitted the equilibrium sorption results best, showed that heterogeneity of the sorbent surface was the highest in distilled water and the lowest in natural seawater. The sorption kinetic data fitted well with the pseudo-second-order kinetic model, which suggests that the rate-limiting step in Cd2+ sorption onto Fe(III-sepiolite could be chemisorption. The low desorption percentage in both distilled water and 0.001 M HNO3 indicated that sorption occurred mainly by chemisorption mechanisms. [Projekat Ministarstva nauke republike srbije, br. III 45019

  8. ThermoEnergy Ammonia Recovery Process for Municipal and Agricultural Wastes

    Directory of Open Access Journals (Sweden)

    Alex G. Fassbender

    2001-01-01

    Full Text Available The Ammonia Recovery Process (ARP is an award-winning, low-cost, environmentally responsible method of recovering nitrogen, in the form of ammonia, from various dilute waste streams and converting it into concentrated ammonium sulfate. The ThermoEnergy Biogas System utilizes the new chemisorption-based ARP to recover ammonia from anaerobically digested wastes. The process provides for optimal biogas production and significantly reduced nitrogen levels in the treated water discharge. Process flows for the ammonia recovery and ThermoEnergy biogas processes are presented and discussed. A comparison with other techniques such as biological nitrogen removal is made. The ARP technology uses reversible chemisorption and double salt crystal precipitation to recover and concentrate the ammonia. The ARP technology was successfully proven in a recent large-scale field demonstration at New York City’s Oakwood Beach Wastewater Treatment Plant, located on Staten Island. This project was a joint effort with Foster Wheeler Environmental Corporation, the Civil Engineering Research Foundation, and New York City Department of Environmental Protection. Independent validated plant data show that ARP consistently recovers up to 99.9% of the ammonia from the city’s centrate waste stream (derived from dewatering of sewage sludge, as ammonium sulfate. ARP technology can reduce the nitrogen (ammonia discharged daily into local bodies of water by municipalities, concentrated animal farming operations, and industry. Recent advances to ARP enhance its performance and economic competitiveness in comparison to stripping or ammonia destruction technologies.

  9. Adsorptive removal of Congo red from aqueous solutions using crosslinked chitosan and crosslinked chitosan immobilized bentonite.

    Science.gov (United States)

    Huang, Ruihua; Zhang, Lujie; Hu, Pan; Wang, Jing

    2016-05-01

    Batch experiments were executed to investigate the removal of Congo red (CR) from aqueous solutions using the crosslinked chitosan (CCS) and crosslinked chitosan immobilized bentonite (CCS/BT composite). The CCS and CCS/BT composite were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The removal of CR was examined as a function of pH value of CR solution, contact time, and inorganic sodium salt and ionic strength. The equilibrium data of CCS and CCS/BT composite agreed well with the Langmuir model. The adsorption capacities of CCS and CCS/BT composite at 298K and natural pH value were 405 and 500mg/g, respectively. The kinetic data correlated well with the pseudo-second-order model. The adsorption of CR onto the CCS was mainly controlled by chemisorption while the adsorption of CR onto the CCS/BT composite was controlled by chemisorption and the electrostatic attraction. PMID:26820350

  10. Synthesis of PEG-Iodine-Capped Gold Nanoparticles and Their Contrast Enhancement in In Vitro and In Vivo for X-Ray/CT

    Directory of Open Access Journals (Sweden)

    Sun-Hee Kim

    2012-01-01

    Full Text Available We designed gold nanoparticles (AuNPs capped with iodine and polyethylene glycol (PEG to provide effective enhancement for X-ray CT imaging. The methoxy PEG-iodine-capped AuNPs were prepared through the chemisorption of iodine and substitution of methoxy PEG-SH onto the surface of gold nanoparticles, and severe aggregation in TEM was not observed. The binding energies of Au 4f7/2 and I 3d5/2 of the methoxy PEG-iodine-capped AuNPs were obtained as 84.1 eV and 619.3 eV, respectively. The binding energy shift of methoxy PEG-iodine-capped AuNPs would be resulted from the chemisorption between gold nanoparticles and iodine atoms. The methoxy PEG-iodine-capped AuNPs have higher enhancement compared to PEG-capped gold nanoparicles in the same amount of gold in vitro. After postinjection of methoxy PEG-iodine-capped AuNPs into the mice, dramatic contrast enhancement at the heart, aorta, liver, and kidney was observed, this was maintained up to 5 days, and there was no evidence of apparent toxicity. In conclusion, methoxy PEG-iodine-capped AuNPs might be a good candidate as a CT contrast agent for blood pool imaging, and this will also contribute to the prolongation of a blood circulation time for X-ray CT imaging.

  11. Nanocrystalline MgO supported nickel-based bimetallic catalysts for carbon dioxide reforming of methane

    Energy Technology Data Exchange (ETDEWEB)

    Meshkani, Fereshteh [Catalyst and Advanced Materials Research Laboratory, Chemical Engineering Department, Faculty of Engineering, University of Kashan, Kashan (Iran); Rezaei, Mehran [Catalyst and Advanced Materials Research Laboratory, Chemical Engineering Department, Faculty of Engineering, University of Kashan, Kashan (Iran); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan (Iran)

    2010-10-15

    Nanocrystalline magnesium oxide with high surface area and plate-like shape was employed as catalyst support for preparation of nickel-based bimetallic catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction (XRD), N{sub 2} adsorption (BET), Temperature programmed oxidation and desorption (TPO-TPD), Thermal gravimetric and differential thermal gravimetric (TGA-DTG), H{sub 2} chemisorption and Transmission and electron microscopies (TEM and SEM) analyses. CO{sub 2}-TPD data showed the high CO{sub 2} adsorption capacity of catalysts which improves the resistance of catalysts against the carbon formation. The H{sub 2} chemisorption results also indicated that the addition of Pt to nickel catalyst improved the nickel dispersion. The obtained results revealed that the prepared catalysts showed a high activity and stability during the reaction with a low amount of deposited carbon. Addition of Pt to nickel catalyst improved both the activity and resistivity against carbon formation. (author)

  12. Catalytic activity vs. size correlation in platinum catalysts of PEM fuel cells prepared on carbon black by different methods

    Energy Technology Data Exchange (ETDEWEB)

    Nores-Pondal, F.J.; Granada, M.; Corti, H.R. [Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), General Paz 1499, 1650 San Martin, Buenos Aires (Argentina); Vilella, I.M.J.; de Miguel, S.R.; Scelza, O.A. [Instituto de Investigaciones en Catalisis y Petroquimica (INCAPE), Facultad de Ingenieria Quimica (Universidad Nacional del Litoral) - CONICET, Santiago del Estero 2654, 3000 Santa Fe (Argentina); Troiani, H. [Departamento de Fisica, Centro Atomico Bariloche, Comision Nacional de Energia Atomica (CNEA), Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)

    2009-10-15

    In this work nanoparticulated platinum catalysts have been prepared on carbon Vulcan XC-72 using three methods starting with chloroplatinic acid as a precursor: (i) formic acid as a reductor agent; (ii) impregnation method followed by reduction in hydrogen atmosphere at moderated temperature; and (iii) microwave-assisted reduction in ethylene glycol. The catalytic and size studies were also performed on a commercial Pt catalyst (E-Tek, De Nora). The characterization of the particle size and distribution was performed by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characterizations of the catalytic and electrocatalytic properties of the catalysts were determined by studying the cyclohexane dehydrogenation reaction (CHD) and the behavior under cyclic voltammetry (CV) in sulfuric acid solutions. The measured electrochemical activity, along with the hydrogen chemisorption of the catalysts allows the estimation of effective particle sizes, which are much larger than those measured by TEM and XRD. The catalysts prepared by reduction with formic acid and ethylene glycol (microwave-assisted) show electrochemical activities very close to those of the commercial catalyst, and are almost insensitive to the Pt dispersion or Pt particle size. The chemical activity in CHD correlates well with the metallic dispersion determined by hydrogen chemisorption, indicating similar accesibility of H{sub 2} and cyclohexane to the catalyst surface. (author)

  13. Theoretical assessment of graphene-metal contacts.

    Science.gov (United States)

    Janthon, Patanachai; Viñes, Francesc; Kozlov, Sergey M; Limtrakul, Jumras; Illas, Francesc

    2013-06-28

    Graphene-metal contacts have emerged as systems of paramount importance in the synthesis of high-quality and large-size patches of graphene and as vital components of nanotechnological devices. Herein, we study the accuracy of several density functional theory methods using van der Waals functionals or dispersive forces corrections when describing the attachment of graphene on Ni(111). Two different experimentally observed chemisorption states, top-fcc and bridge-top, were put under examination, together with the hcp-fcc physisorption state. Calculated geometric, energetic, and electronic properties were compared to experimental data. From the calculations, one finds that (i) predictions made by different methodologies differ significantly and (ii) optB86b-vdW functional and Grimme dispersion correction seem to provide the best balanced description of stability of physisorption and chemisorption states, the attachment strength of the latter on Ni(111) surface, the graphene-Ni(111) separation, and the bandstructure of chemisorbed graphene. The collation suggests that accurate and affordable theoretical studies on technologies based on graphene-metal contacts are already at hand.

  14. Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

    Energy Technology Data Exchange (ETDEWEB)

    Jennifer Anne Harnisch

    2002-06-27

    The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performance both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol (BHT) SAMs. BHT chemisorbs to the gold surface in a previously unprecedented planar fashion. Carbon and gold substrates can be chemically altered by several methodologies resulting in new surface properties. The development of modification protocols and their application in the analytical arena is considered herein.

  15. Kinetic models for irreversible processes on a lattice

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, N.O.

    1979-04-01

    The development and application of kinetic lattice models are considered. For the most part, the discussions are restricted to lattices in one-dimension. In Chapter 1, a brief overview of kinetic lattice model formalisms and an extensive literature survey are presented. A review of the kinetic models for non-cooperative lattice events is presented in Chapter 2. The development of cooperative lattice models and solution of the resulting kinetic equations for an infinite and a semi-infinite lattice are thoroughly discussed in Chapters 3 and 4. The cooperative models are then applied to the problem of theoretically dtermining the sticking coefficient for molecular chemisorption in Chapter 5. In Chapter 6, other possible applications of these models and several model generalizations are considered. Finally, in Chapter 7, an experimental study directed toward elucidating the mechanistic factors influencing the chemisorption of methane on single crystal tungsten is reported. In this it differs from the rest of the thesis which deals with the statistical distributions resulting from a given mechanism.

  16. Nano-tribological characteristics of TiO2 films on 3-mercaptopropyl trimethoxysilane sulfonated self-assembled monolayer

    Indian Academy of Sciences (India)

    J Li; X H Sheng

    2009-10-01

    Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was used to prepare twodimensional self-assembled monolayer (SAM) on silicon substrate. The terminal –SH group was in situ oxidized to –SO3H group to endow the film with good chemisorption ability. Then TiO2 thin films were deposited on the oxidized MPTS–SAM to form composite thin films, making use of the chemisorption ability of the –SO3H group. Atomic force microscope (AFM) and contact angle measurements were used to characterize TiO2 films. Adhesive force and friction force of TiO2 thin films and silicon substrate were measured under various applied normal loads and scanning speed of AFM tip. Results showed that the friction force increased with applied normal loads and scanning speed of AFM tip. In order to study the effect of capillary force, tests were performed in various relative humidities. Results showed that the adhesive force of silicon substrate increases with relative humidities and the adhesive force of TiO2 thin films only increases slightly with relative humidity. Research showed that surfaces with more hydrophobic property revealed the lower adhesive and friction forces.

  17. Tungstophosphoric acid supported onto hydrous zirconia: Physicochemical characterization and esterification of 1° and 2° alcohol

    Indian Academy of Sciences (India)

    Pankaj Sharma; Anjali Patel

    2006-10-01

    The Keggin type heteropolyacid, 12-tungstophosphoric acid (PW), was supported onto hydrous zirconia (Z) by impregnation method and designated as ZH3. The ZH3 was calcinated at 300°C and 500°C and designated as ZH33 and ZH35, respectively. The resulting materials were characterized by FTIR, diffuse reflectance spectroscopy (DRS), XRD, surface area measurement (BET method) and particle size distribution. The surface morphology was studied by scanning electron microscopy. The acidity of all materials was evaluated by carrying out chemisorption of ammonia and esterification of 1° alcohol (-butanol) with different acids like formic acid, acetic acid and propionic acid and 2° alcohol (cyclohexanol, iso-butanol) with acetic acid. Above studies show the high dispersion of HPA in a non-crystalline form on the support as well as uniform distribution of particles of ZH3 which contains 30% 12-tungstophosphoric acid. It also shows that when ZH3 was calcinated at 500°C, it possesses highest acidity for both chemisorption of NH3 as well as esterification reactions.

  18. Modified energetics and growth kinetics on H-terminated GaAs (110)

    Energy Technology Data Exchange (ETDEWEB)

    Galiana, B. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Departamento de Física, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Madrid (Spain); Benedicto, M.; Díez-Merino, L.; Tejedor, P. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Lorbek, S.; Hlawacek, G.; Teichert, C. [Institut für Physik, Montanuniversität Leoben, Franz Josef St., 18A-8700 Leoben (Austria)

    2013-10-28

    Atomic hydrogen modification of the surface energy of GaAs (110) epilayers, grown at high temperatures from molecular beams of Ga and As{sub 4}, has been investigated by friction force microscopy (FFM). The reduction of the friction force observed with longer exposures to the H beam has been correlated with the lowering of the surface energy originated by the progressive de-relaxation of the GaAs (110) surface occurring upon H chemisorption. Our results indicate that the H-terminated GaAs (110) epilayers are more stable than the As-stabilized ones, with the minimum surface energy value of 31 meV/Å{sup 2} measured for the fully hydrogenated surface. A significant reduction of the Ga diffusion length on the H-terminated surface irrespective of H coverage has been calculated from the FFM data, consistent with the layer-by-layer growth mode and the greater As incorporation coefficient determined from real-time reflection high-energy electron diffraction studies. Arsenic incorporation through direct dissociative chemisorption of single As{sub 4} molecules mediated by H on the GaAs (110) surface has been proposed as the most likely explanation for the changes in surface kinetics observed.

  19. Modified energetics and growth kinetics on H-terminated GaAs (110)

    Science.gov (United States)

    Galiana, B.; Benedicto, M.; Díez-Merino, L.; Lorbek, S.; Hlawacek, G.; Teichert, C.; Tejedor, P.

    2013-10-01

    Atomic hydrogen modification of the surface energy of GaAs (110) epilayers, grown at high temperatures from molecular beams of Ga and As4, has been investigated by friction force microscopy (FFM). The reduction of the friction force observed with longer exposures to the H beam has been correlated with the lowering of the surface energy originated by the progressive de-relaxation of the GaAs (110) surface occurring upon H chemisorption. Our results indicate that the H-terminated GaAs (110) epilayers are more stable than the As-stabilized ones, with the minimum surface energy value of 31 meV/Å2 measured for the fully hydrogenated surface. A significant reduction of the Ga diffusion length on the H-terminated surface irrespective of H coverage has been calculated from the FFM data, consistent with the layer-by-layer growth mode and the greater As incorporation coefficient determined from real-time reflection high-energy electron diffraction studies. Arsenic incorporation through direct dissociative chemisorption of single As4 molecules mediated by H on the GaAs (110) surface has been proposed as the most likely explanation for the changes in surface kinetics observed.

  20. Molecular hydrogen formation on grain surfaces

    CERN Document Server

    Cazaux, S; Tielens, A G G M; Le Bourlot, J; Walmsley, M C

    2005-01-01

    We reconsider H2 formation on grain surfaces. We develop a rate equation model which takes into account the presence of both physisorbed and chemisorbed sites on the surface, including quantum mechanical tunnelling and thermal diffusion. In this study, we took into consideration the uncertainties on the characteristics of graphitic surfaces. We calculate the H2 formation efficiency with the Langmuir Hinshelwood and Eley Rideal mechanisms, and discuss the importance of these mechanisms for a wide range of grain and gas temperatures. We also develop a Monte Carlo simulation to calculate the H2 formation efficiency and compare the results to our rate equation models. Our results are the following: (1) Depending on the barrier against chemisorption, we predict the efficiency of H2 formation for a wide range of grain and gas temperatures. (2) The Eley-Rideal mechanism has an impact on the H2 formation efficiency at high grain and gas temperatures. (3) The fact that we consider chemisorption in our model makes the ...

  1. Self-suspended permanent magnetic FePt ferrofluids.

    Science.gov (United States)

    Dallas, Panagiotis; Kelarakis, Antonios; Sahore, Ritu; DiSalvo, Francis J; Livi, Sebastien; Giannelis, Emmanuel P

    2013-10-01

    We present the synthesis and characterization of a new class of self-suspended ferrofluids that exhibit remanent magnetization at room temperature. Our system relies on the chemisorption of a thiol-terminated ionic liquid with very low melting point on the surface of L10 FePt nanoparticles. In contrast, all types of ferrofluids previously reported employ either volatile solvents as the suspending media or superparamagnetic iron oxide nanoparticles (that lacks permanent magnetization) as the inorganic component. The ferrofluids do not show any sign of flocculation or phase separation, despite the strong interactions between the magnetic nanoparticles due to the strong chemisorption of the ionic liquid as evidenced by Raman spectroscopy and thermal analysis. Composites with high FePt loading (40 and 70 wt%) exhibit a pseudo solid-like rheological behavior and high remanent magnetization values (10.1 and 12.8 emu/g respectively). At lower FePt loading (12 wt%) a liquid like behavior is observed and the remanent and saturation magnetization values are 3.5 and 6.2 emu/g, respectively. The magnetic and flow properties of the materials can be easily fine tuned by controlling the type and amount of FePt nanoparticles used. PMID:23859815

  2. Microcalorimetry of oxygen adsorption on fcc Co{110}.

    Science.gov (United States)

    Liao, Kristine; Fiorin, Vittorio; Jenkins, Stephen J; King, David A

    2012-05-28

    The coverage dependent heats of adsorption and sticking probabilities for oxygen on fcc Co{110} have been measured at 300 K using single crystal adsorption calorimetry (SCAC). Initial adsorption is consistent with dissociative chemisorption at low coverage followed by oxide formation above 0.6 ML coverage. The initial heat of adsorption of 633 kJ mol(-1) is similar to heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. As the coverage increases, the heat of adsorption and sticking probability drop very rapidly up to the onset of oxidation. As already observed for other oxygen-metal surface systems, strong lateral adatom repulsions are responsible for the transition from the chemisorption regime to oxide film formation at higher coverage. The heat of oxide formation at the onset is 475 kJ mol(-1), which is consistent with the formation of CoO crystallites. The oxide film formation is discussed in terms of nucleation and island growth, and the Mott-Cabrera mechanisms, the latter being evidenced by the relatively constant heat of adsorption and sticking probability in contrast to the nickel and iron oxidation cases.

  3. Investigation of Tribological Behavior of Lanthanum-Based Thin Films Deposited on Sulfonated Self-Assembled Monolayer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    3-mercaptopropyl trimethoxysilane (MPTS) was prepared on glass substrate so as to form a two-dimensional self-assembled monolayer (SAM), and the terminal -SH group in the film was in situ oxidized to -SO3H group to confer good chemisorption ability to the film. Thus, lanthanum-based thin films were deposited on oxidized MPTS-SAM, making use of the chemisorption ability of -SO3H group. Atomic force microscopy (AFM) and X-ray photoelectron spectrometry (XPS) and contact angle measurements were used to characterize the thin films. The tribological properties of the as-prepared thin films sliding against a steel ball were evaluated on a friction and wear tester. Tribological experiment shows that the friction coefficient of glass substrate decreases from 0.8 to 0.08 after the rare earth (RE) self-assembled films (SAMs) are formed on its surface. And the RE self-assembled films have longer wear life (500 sliding passes). It is demonstrated that RE self-assembled film exhibits good wear-resistant property. The marked decrease in friction and the longer wear life of RE films are attributed to the excellent adhesion of the film to the substrate and to the special characteristics of the RE elements. The frictional behaviors of RE thin-films-coated silicon surface were sensitive to the applied load and the sliding velocity of the steel ball.

  4. The structure, energetics, and nature of the chemical bonding of phenylthiol adsorbed on the Au(111) surface: implications for density-functional calculations of molecular-electronic conduction.

    Science.gov (United States)

    Bilić, Ante; Reimers, Jeffrey R; Hush, Noel S

    2005-03-01

    The adsorption of phenylthiol on the Au(111) surface is modeled using Perdew and Wang density-functional calculations. Both direct molecular physisorption and dissociative chemisorption via S-H bond cleavage are considered as well as dimerization to form disulfides. For the major observed product, the chemisorbed thiol, an extensive potential-energy surface is produced as a function of both the azimuthal orientation of the adsorbate and the linear translation of the adsorbate through the key fcc, hcp, bridge, and top binding sites. Key structures are characterized, the lowest-energy one being a broad minimum of tilted orientation ranging from the bridge structure halfway towards the fcc one. The vertically oriented threefold binding sites, often assumed to dominate molecular electronics measurements, are identified as transition states at low coverage but become favored in dense monolayers. A similar surface is also produced for chemisorption of phenylthiol on Ag(111); this displays significant qualitative differences, consistent with the qualitatively different observed structures for thiol chemisorption on Ag and Au. Full contours of the minimum potential energy as a function of sulfur translation over the crystal face are described, from which the barrier to diffusion is deduced to be 5.8 kcal mol(-1), indicating that the potential-energy surface has low corrugation. The calculated bond lengths, adsorbate charge and spin density, and the density of electronic states all indicate that, at all sulfur locations, the adsorbate can be regarded as a thiyl species that forms a net single covalent bond to the surface of strength 31 kcal mol(-1). No detectable thiolate character is predicted, however, contrary to experimental results for alkyl thiols that indicate up to 20%-30% thiolate involvement. This effect is attributed to the asymptotic-potential error of all modern density functionals that becomes manifest through a 3-4 eV error in the lineup of the adsorbate and

  5. Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

    Directory of Open Access Journals (Sweden)

    M. C. Leuenberger

    2015-08-01

    Full Text Available It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i physisorption and (ii chemisorption. Physisorption is associated with lower binding energies in the order of 1–10 kJ mol−1 compared to chemisorption ranging from 100 to 1000 kJ mol−1. Furthermore, chemisorption forms only monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws, however, it can be influenced by hysteresis effects. In the present experiment we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. We proved the pressure effect on physisorption for CO2, CH4 and H2O by decanting one steel and two aluminium cylinders completely. The CO2 results for both cylinders are in excellent agreement with the pressure dependence of a monolayer adsorption model. However, adsorption on aluminium (2 and H2O was about 10 times less than on steel (2 amounts adsorbed (5.8 × 1019 CO2 molecules corresponds to about the five-fold monolayer adsorption indicating that the effective surface exposed for adsorption is significantly larger than the geometric surface area. Adsorption/desorption effects were minimal for CH4 and for CO. However, the latter dependence requires further attention since it was only studied on one aluminium cylinder with a very low mole fraction. In the climate chamber the cylinders were exposed to temperatures between −10 and +50 °C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO2 ranging from 0.0014 to 0.0184 ppm °C−1 for steel cylinders and −0.0002 to −0.0003 ppm °C−1 for aluminium cylinders. The reversed temperature dependence for aluminium cylinders

  6. Cyclic CO2 chemisorption–desorption behavior of Na2ZrO3: Structural, microstructural and kinetic variations produced as a function of temperature

    International Nuclear Information System (INIS)

    A structural, microstructural and kinetic analysis of the Na2ZrO3–CO2 system was performed over 20 chemisorption–desorption cycles. Different cyclic experiments were performed between 500 and 800 °C. Although the best results were obtained in Na2ZrO3 sample treated at 550 °C, all the samples treated between 500 and 700 °C presented good CO2 chemisorption efficiencies and stabilities. On the contrary, Na2ZrO3 sample treated at 800 °C presented a continuous decrement of the CO2 chemisorption. After 20 cycles all the samples presented a partial Na2ZrO3 decomposition, determined by the ZrO2 formation, which was associated to sodium sublimation. Additionally, the Na2ZrO3 microstructural analysis showed a systematic morphological evolution. It was microscopically observed that Na2ZrO3 particles tend to fracture due to the Na2CO3 formation. Later, after several cycles these tiny fractured particles sinter producing new polyhedral and dense Na2ZrO3–ZrO2 particles. Finally, an exhaustive kinetic analysis showed a high CO2 chemisorption–desorption stability at different temperatures. - Graphical abstract: A CO2 chemisorption–desorption analysis was performed in the Na2ZrO3–CO2 system. Different cyclic experiments were performed between 500 and 800 °C and the results showed high CO2 chemisorption efficiencies. Nevertheless the Na2ZrO3 composition and microstructure evolved during the cycles. Highlights: • Different CO2 chemisorption–desorption cycles were performed in the Na2ZrO3 phase. • Na2ZrO3 presents interesting microstructural changes depending on temperature. • At T≤550 °C, Na2ZrO3 presents the best cyclability due to microstructural factors. • At T≥600 °C, Na2ZrO3 presents a partial decomposition after 20 cycles. • Na2ZrO3 presents excellent CO2 cyclability properties

  7. Two-photon photoemission investigation of electronic and dynamical properties of alkali atoms adsorbed on noble metal surfaces

    Science.gov (United States)

    Sametoglu, Vahit

    We present a systematic time-resolved two-photon photoemission study of the electronic and dynamical properties of Li through Cs adsorbed on Cu(111) and Ag(111) surfaces. A fundamental problem in surface science is how to describe the electronic structure of a chemisorption interface based on the intrinsic properties of the interacting materials. Because of their simple s-electron structure, elements of the alkali atom group comprise paradigmatic adsorbates in many theories of chemisorption, whereas the complementary experimental studies are sparse and incomplete. Through a combination of spectroscopic and femtosecond time-resolved surface measurements, we are able to probe systematically the binding energies, symmetries, and electron and nuclear relaxation dynamics of the initially unoccupied alkali atom resonances. As a prelude, we study the two-photon photoemission process occurring at the bare Ag(111) surface. We develop a quantitative model for two-photon photoemission process, where the nonresonant and k-dependent two-photon absorption between the lower and upper sp-bands is modeled by the optical Bloch equations, and the angle-dependent intensities are described by the Fresnel equations. Our two-photon photoemission spectra of Li through Cs chemisorbed Cu(111) and Ag(111) surfaces reveal two resonances with the m = 0 and m = +/-1 symmetry ('m' is the projection of the orbital angular momentum 'l' onto the surface plane). For the m = 0 resonance, which is derived from the hybridization of the ns and npz orbitals of alkali atoms, we find a binding energy of 1.84--1.99 eV below the vacuum level, which is independent of the alkali atom period, and tunes with coverage in a universal manner. At 0.3--0.7 eV higher energy, we discover and identify the m = +/-1 resonance by its characteristic angular intensity distribution, which derives from the antisymmetry of the npx and npy orbitals. We implement a quantitative model for the alkali atom chemisorption based on the

  8. Gas adsorption and desorption effects on cylinders and their importance for long-term gas records

    Science.gov (United States)

    Leuenberger, M. C.; Schibig, M. F.; Nyfeler, P.

    2015-12-01

    It is well known that gases adsorb on many surfaces, in particular metal surfaces. There are two main forms responsible for these effects (i) physisorption and (ii) chemisorption. Physisorption is associated with lower binding energies in the order of 1-10 kJ mol-1, compared to chemisorption which ranges from 100 to 1000 kJ mol-1. Furthermore, chemisorption only forms monolayers, contrasting physisorption that can form multilayer adsorption. The reverse process is called desorption and follows similar mathematical laws; however, it can be influenced by hysteresis effects. In the present experiment, we investigated the adsorption/desorption phenomena on three steel and three aluminium cylinders containing compressed air in our laboratory and under controlled conditions in a climate chamber, respectively. Our observations from completely decanting one steel and two aluminium cylinders are in agreement with the pressure dependence of physisorption for CO2, CH4, and H2O. The CO2 results for both cylinder types are in excellent agreement with the pressure dependence of a monolayer adsorption model. However, mole fraction changes due to adsorption on aluminium (climate chamber, the cylinders were exposed to temperatures between -10 and +50 °C to determine the corresponding temperature coefficients of adsorption. Again, we found distinctly different values for CO2, ranging from 0.0014 to 0.0184 ppm °C-1 for steel cylinders and -0.0002 to -0.0003 ppm °C-1 for aluminium cylinders. The reversed temperature dependence for aluminium cylinders points to significantly lower desorption energies than for steel cylinders and due to the small values, they might at least partly be influenced by temperature, permeation from/to sealing materials, and gas-consumption-induced pressure changes. Temperature coefficients for CH4, CO, and H2O adsorption were, within their error bands, insignificant. These results do indicate the need for careful selection and usage of gas cylinders for

  9. Use of ultra-thin organic silane films for the improvement of gold adhesion to the silicon dioxide wafers for (bio)sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Ben Ali, M. [Institut Superieur des Sciences, Appliquees et de Technologies, Cite Taffela-Ebn Kaldoun, 4003-Tunisia (Tunisia); Laboratoire de Physique de Semi-conducteurs et Capteurs, IPEST la Marsa 2070 Tunis (Tunisia)], E-mail: mounirbenali@yahoo.com; Bessueille, F. [LSA, Universite Claude Bernard Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex (France); Chovelon, J.M. [IRCELYON, Universite Claude Bernard-Lyon 1.43 Bd du 11 novembre 1918 69622 Villeurbane Cedex (France); Abdelghani, A. [Laboratoire de Physique de Semi-conducteurs et Capteurs, IPEST la Marsa 2070 Tunis (Tunisia); Jaffrezic-Renault, N. [LSA, Universite Claude Bernard Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex (France); Maaref, M.A. [Laboratoire de Physique de Semi-conducteurs et Capteurs, IPEST la Marsa 2070 Tunis (Tunisia); Martelet, C. [AMPERE, Ecole Centrale de Lyon, 69134 Ecully Cedex (France)

    2008-07-01

    A mono-functional silane reagent, 3-mercaptopropyltrimethoxysilane (MPS) was used to modify the surface of silicon wafers. The structure of the SAMs formed with the MPS was investigated by contact angle measurements, ellipsometry, AFM, and X-ray photoelectron spectroscopy (XPS). The deposition of a metallic gold layer via ultra-high vacuum (UHV) evaporation reveals good adhesion properties on Au/MPS/SiO{sub 2}/Si structure. The 'chemisorption' between the SAM and the gold evaporated layer is confirmed by adhesion tests and optimum curing treatment is found 1 h at 100 deg. C). This very simple methodology, avoiding the usage of Cr and other metals as undercoating layers and could be proposed further for (bio)sensors applications.

  10. Separation of carbon dioxide from flue emissions using Endex principles

    CERN Document Server

    Ball, R

    2009-01-01

    In an Endex reactor endothermic and exothermic reactions are directly thermally coupled and kinetically matched to achieve intrinsic thermal stability, efficient conversion, autothermal operation, and minimal heat losses. Applied to the problem of in-line carbon dioxide separation from flue gas, Endex principles hold out the promise of effecting a carbon dioxide capture technology of unprecedented economic viability. In this work we describe an Endex Calcium Looping reactor, in which heat released by chemisorption of carbon dioxide onto calcium oxide is used directly to drive the reverse reaction, yielding a pure stream of carbon dioxide for compression and geosequestration. In this initial study we model the proposed reactor as a continuous-flow dynamical system in the well-stirred limit, compute the steady states and analyse their stability properties over the operating parameter space, flag potential design and operational challenges, and suggest an optimum regime for effective operation.

  11. Tribology in Gaseous Hydrogen

    Science.gov (United States)

    Sawae, Yoshinori; Sugimura, Joich

    Hydrogen is expected as a clean and renewable energy carrier for future environment-friendly society. Many machine elements in hydrogen energy systems should be operating within hydrogen gas and tribological behavior, such as friction and wear, of bearings and seals are affected by the hydrogen environment through some interactions between material surfaces and gaseous hydrogen, i.e., physisorption of hydrogen molecules and following chemisorptions of dissociated atoms on metal surfaces, formation of metal hydride and reduction of metal oxide layer by hydrogen atoms diffused into bulk. Therefore, friction and wear characteristics of tribomaterials in the hydrogen environment should be appropriately understood to establish a design guideline for reliable hydrogen utilizing systems. This paper reviews the current knowledge about the effect of hydrogen on friction and wear of materials, and then describes our recent progress of hydrogen research in the tribology field.

  12. Low metal loading catalysts used for the selective hydrogenation of styrene

    Directory of Open Access Journals (Sweden)

    Juan Badano

    2010-01-01

    Full Text Available A series of Group VIII metal catalysts was obtained for the semi-hydrogenation of styrene. Catalysts were characterized by Hydrogen Chemisorption, TPR and XPS. Palladium, rhodium and platinum low metal loading prepared catalysts presented high activity and selectivity (ca. 98% during the semi-hydrogenation of styrene, being palladium the most active catalyst. The ruthenium catalyst also presented high selectivity (ca. 98%, but the lowest activity. For the palladium catalyst, the influence of the precursor salt and of the reduction temperature on the activity and selectivity were studied. The following activity series was obtained: PdN-423 > PdCl-673 > PdCl-373> PtCl-673 > RhCl-673 >> RuCl-673. As determined by XPS, differences in activity could be attributed, at least in part, to electronic effects.

  13. Kinetics of ion beam deposition of carbon at room temperature

    International Nuclear Information System (INIS)

    Growth rates of carbon films grown by ion beam deposition using methane gas were measured in situ as a function of deposition conditions. The methane pressure dependence of the growth rate was used to measure the cross-section for charge exchange. Variations in deposition rate per incident energetic particle found for each ion energy were related to ion current density. It was found that rates of growth per incident energetic specie were (i) largest for the smallest current densities, (ii) decreased monotonically with increasing current density, and (iii) were consistently larger than can be explained by deposition directly from the energetic flux alone. These observations were interpreted in terms of irradiation-induced surface interactions which promote chemisorption of methane physisorbed from the ambient atmosphere. (orig.)

  14. Synthesis and growth kinetics of carbon nanocoils using Sn-Fe-O xerogel film catalyst

    International Nuclear Information System (INIS)

    Carbon nanocoils (CNCs) were synthesized by a chemical vapor deposition method using tin-iron-oxide (Sn-Fe-O) xerogel film catalyst. The Sn-Fe-O catalyst was prepared by a low-cost sol–gel method using stannous acetate and ferric acetate as precursors. The growth kinetics of CNCs were monitored by a thermogravimetric analyzer, and the experimental result was correlated using one-dimensional tip growth kinetic model. The kinetic model consists of three steps: (1) dissociative chemisorption of acetylene and formation of encapsulating carbon on a leading face of the catalyst, (2) diffusion and reduction of Sn-Fe-O catalyst in bulk structure, and (3) carbon cluster nucleation on a tailing face of the catalyst. (paper)

  15. Investigation of the oxidation of NO over platinum catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Despres, J.; Koebel, M.; Elsener, M.; Wokaun, A.

    2002-03-01

    The oxidation of NO to NO{sub 2} over Pt/SiO{sub 2} was investigated in the temperature range 150-450{sup o}C. Powdered catalysts were prepared by incipient wetness impregnation, followed by calcination and reduction. The feed gas typically contained oxygen, nitrogen monoxide, water and nitrogen. The concentration of NO in the feed was varied at constant concentration of O{sub 2} in order to study its influence on the reaction. A decrease of the conversion with increasing concentration of NO was observed. A similar study was performed with various oxygen concentrations at constant concentration of NO. Oxygen involved in the surface reaction originates from the dissociative chemisorption of O{sub 2} on the platinum surface. (author)

  16. Engineering Nanomaterial Surfaces for Biomedical Applications

    Science.gov (United States)

    Wang, Xin; Liu, Li-Hong; Ramström, Olof; Yan, Mingdi

    2014-01-01

    Nanomaterials, possessing unique physical and chemical properties, have attracted much interest and generated wide varieties of applications. Recent investigations of functionalized nanomaterials have expanded into the biological area, providing a versatile platform in biomedical applications such as biomolecular sensing, biological imaging, drug delivery and disease therapy. Bio-functions and bio-compatibility of nanomaterials are realized by introducing synthetic ligands or natural biomolecules onto nanomaterials, and combining ligand-receptor biological interactions with intrinsic nanomaterial properties. Common strategies of engineering nanomaterial surfaces involve physisorption or chemisorption of desired ligands. We developed a photochemically initiated surface coupling chemistry, bringing versatility and simplicity to nanomaterial functionalization. The method was applied to attach underivatized carbohydrates efficiently on gold and iron oxide nanoparticles, and the resulting glyconanoparticles were successfully used as a sensitive biosensing system probing specific interactions between carbohydrates and proteins as well as bacteria. PMID:19596820

  17. Sorption of indigo carmine by a Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge

    International Nuclear Information System (INIS)

    Indigo carmine removal from aqueous solution has been evaluated using Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl (CM). The adsorbents were characterized by scanning electron microscopy, BET surface area and X-ray diffraction. Sorption kinetics and isotherms were determined and the adsorption behaviors analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results obtained with the Fe-zeolitic material, while kinetic first order and Langmuir-Freundlich models were applied to the results from the carbonaceous materials. This indicates mechanisms of chemisorption and physic sorption, respectively, on the heterogeneous materials. The results indicate that the carbonaceous material from the pyrolysis of sewage sludge (sorption capacity 92.83 mg/g) is a better adsorbent of indigo carmine than the zeolitic material (sorption capacity 32.83 mg/g).

  18. The relationship between formate adsorption energy and electronic properties: A first principles density functional theory study

    Institute of Scientific and Technical Information of China (English)

    MORIKAWA; Yoshitada; NAKAMURA; Junji

    2009-01-01

    First principles density functional theory calculations have been performed for the chemisorption of formate adsorption on some metal surfaces. For the most stable adsorption site of short-bridge, the calculated formate adsorption energy follows the order of Au(110) < Ag(110) < Cu(110) < Pd(110) < Pt(110) < Ni(110) < Rh(110) < Fe(100) < Mo(100), and a clear linear correlation exists between the adsorption energy and the corresponding heat of formation of metal oxides. Moreover, it has been found that the formate adsorption energy for the transition metals can be correlated well with its d-band center (εd), and the IB Group metals can be described by the coupling matrix element square (Vad2).

  19. The relationship between formate adsorption energy and electronic properties:A first principles density functional theory study

    Institute of Scientific and Technical Information of China (English)

    MA HongYan; WANG GuiChang; MORIKAWA Yoshitada; NAKAMURA Junji

    2009-01-01

    First principles density functional theory calculations have been performed for the chemisorption of formate adsorption on some metal surfaces.For the most stable adsorption site of short-bridge,the calculated formate adsorption energy follows the order of Au(110) < Ag(110) < Cu(110) < Pd(110) < Pt(110)< Ni(110)< Rh(110)< Fe(100)< Mo(100),and a clear linear correlation exists between the adsorption energy and the corresponding heat of formation of metal oxides.Moreover,it has been found that the formate adsorption energy for the transition metals can be correlated well with its d-band center (εd),and the IB Group metals can be described by the coupling matrix element square (Vad2).

  20. A Novel Schiff Base of 3-acetyl-4-hydroxy-6-methyl-(2Hpyran-2-one and 2,2'-(ethylenedioxydiethylamine as Potential Corrosion Inhibitor for Mild Steel in Acidic Medium

    Directory of Open Access Journals (Sweden)

    Jonnie N. Asegbeloyin

    2015-05-01

    Full Text Available The corrosion inhibition activity of a newly synthesized Schiff base (SB from 3-acetyl-4-hydroxy-6-methyl-(2H-pyran-2-one and 2,2'-(ethylenedioxydiethylamine was investigated on the corrosion of mild steel in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopic techniques. Ultraviolet-visible (UV-vis and Raman spectroscopic techniques were used to study the chemical interactions between SB and mild steel surface. SB was found to be a relatively good inhibitor of mild steel corrosion in 1 M HCl. The inhibition efficiency increases with increase in concentration of SB. The inhibition activity of SB was ascribed to its adsorption onto mild steel surface, through physisorption and chemisorption, and described by the Langmuir adsorption model. Quantum chemical calculations indicated the presence of atomic sites with potential nucleophilic and electrophilic characteristics with which SB can establish electronic interactions with the charged mild steel surface.

  1. Sorption Kinetics for the Removal of Cadmium and Zinc onto Palm Kernel Shell Based Activated Carbon

    Directory of Open Access Journals (Sweden)

    Muhammad Muhammad

    2010-12-01

    Full Text Available The kinetics and mechanism of cadmium and zinc adsorption on palm kernel shell based activated carbons (PKSAC have been studied. A series of batch laboratory studies were conducted in order to investigate the suitability of palm kernel shell based activated carbon (PKSAC for the removal of cadmium (cadmium ions and zinc (zinc ions from their aqueous solutions. All batch experiments were carried out at pH 7.0 and a constant temperature of 30+-1°C using an incubator shaker that operated at 150 rpm. The kinetics investigated includes the pseudo first order, the pseudo-second order and the intraparticle diffusion models. The pseudo-second order model correlate excellently the experimental data, suggesting that chemisorption processes could be the rate-limiting step. Keywords: adsorption, cadmium, kinetics, palm kernel shell, zinc

  2. Ab Initio Studies on Hematite Surface and the Adsorption of Phosphate

    Directory of Open Access Journals (Sweden)

    Swati Chaudhury

    2014-01-01

    Full Text Available This investigation explores the ab initio DFT method for understanding surface structure of hematite and the nature and energetics of phosphate adsorption. Using the full potential linearized plane wave method (FP-LAPW, we derived the structure and energies of various magnetic forms of hematite. The antiferromagnetic (AFM form was observed to be the most stable. Hematite surfaces with Fe-termination, O-termination, or OH-termination were studied. The OH-terminated surface was the most stable. Stability of hematite surfaces follows the order OH-termination > Fe-termination > O-termination. Thus, surface reaction with hematite would occur with the OH at the surface and not with Fe atoms. The structure of phosphate adsorbed on hematite was derived. Bonding is through the H atom of the OH at the surface. An alternative mechanism of phosphate adsorption on hematite has been derived. Adsorption energy is high and suggests chemisorption rather than physisorption of phosphate on hematite.

  3. Perlite as a potential support for nickel catalyst in the process of sunflower oil hydrogenation

    Science.gov (United States)

    Radonjić, V.; Krstić, J.; Lončarević, D.; Jovanović, D.; Vukelić, N.; Stanković, M.; Nikolova, D.; Gabrovska, M.

    2015-12-01

    Investigation was conducted in order to elucidate the possibility of using perlite as support for preparation of nickel based precursor catalyst, potentially applicable in vegetable oil hydrogenation process. On three differently prepared expanded perlite, nickel catalyst precursors with identical Ni/SiO2 = 1.1 and Ni/Mg = 10/1 ratios were synthesized by precipitation-deposition method. Different techniques, SEM micrography, He-pycnometry, calcimetry, Hg-porosimetry, N2-physisorption, H2-chemisorption and temperature programmed reduction, were used for characterization of obtained samples. Determining the precursor texture, morphology and reducibility shows a successfully deposited nickel phase on perlite support with promising properties for vegetable oil hydrogenation. Chosen precursor was reduced and passivated in paraffin oil and the obtained catalyst showed significant catalytic activity in the test of sunflower oil hydrogenation.

  4. Correlation of acid-base properties of substituted polystyrene-azo-pyrocatechol and characteristics of their chelates with zirconium

    International Nuclear Information System (INIS)

    Acid-base and complexing properties of new synthesized polymeric chelate-forming sorbents (PCS) - substituents of polystyrene-azo-pyrocatechol - are investigated and quantitative correlations between pKOH of functional analytical group (FAG) of sorbent and Hammet constants for para-substituent and ΔpKOH-ΔpK50 correlations of zirconium chelate-forming and pKOH-lgKstb (Kstb - constant of stability of PCS complexes with zirconium) of polychelates to study regularities of effect of peculiarities of structure and acid-base properties of FAG on parameters of zirconium chemical sorption. Established correlations make it possible to predict quantitative physicochemical parameters of sorbents and zirconium chemisorption process with the aim of directed synthesis and application of PCS in concentrating processes

  5. van der Waals forces and confinement in carbon nanopores: Interaction between CH4, COOH, NH3, OH, SH and single-walled carbon nanotubes

    Science.gov (United States)

    Weck, Philippe F.; Kim, Eunja; Wang, Yifeng

    2016-05-01

    Interactions between CH4, COOH, NH3, OH, SH and armchair (n, n) (n = 4, 7, 14) and zigzag (n, 0) (n = 7, 12, 25) single-walled carbon nanotubes (SWCNTs) have been systematically investigated within the framework of dispersion-corrected density functional theory (DFT-D2). Endohedral and exohedral molecular adsorption on SWCNT walls is energetically unfavorable or weak, despite the use of C6 /r6 pairwise London-dispersion corrections. The effects of pore size and chirality on the molecule/SWCNTs interaction were also assessed. Chemisorption of COOH, NH3, OH and SH at SWCNT edge sites was examined using a H-capped (7, 0) SWCNT fragment and its impact on electrophilic, nucleophilic and radical attacks was predicted by means of Fukui functions.

  6. Adsorptive Thermodynamic Properties and Kinetics of trans-1,2- Cyclohexandiol onto AB-8 Resin

    Institute of Scientific and Technical Information of China (English)

    谢艳新; 侯丽丽; 杨倩; 蒋登高

    2012-01-01

    AB-8 resin was used as an adsorbent for the removal of trans-1,2-cyclohexandiol(CHD) from aqueous solutions.Batch experiments were carried out to investigate the effect of contact time and temperature on sorption efficiency.The adsorptive thermodynamic properties and kinetics of CHD from water onto AB-8 resin were studied.The Langmuir and Freundlich isotherm models were employed to discuss the adsorption behavior.Thermodynamic parameters such as G,H and S were calculated.The results indicate that the equilibrium data are perfectly represented by Langmuir isotherm model.Thermodynamic study reveals that it is an exothermic process in nature and mainly physical adsorption enhanced by chemisorption with a decrease of entropy process.The kinetics of CHD adsorption is well described by the pseudo second-order model.The adsorbed CHD can be eluted from AB-8 resin by 5% ethanol aqueous solution with 100% elution percentage.

  7. Use of ultra-thin organic silane films for the improvement of gold adhesion to the silicon dioxide wafers for (bio)sensor applications

    International Nuclear Information System (INIS)

    A mono-functional silane reagent, 3-mercaptopropyltrimethoxysilane (MPS) was used to modify the surface of silicon wafers. The structure of the SAMs formed with the MPS was investigated by contact angle measurements, ellipsometry, AFM, and X-ray photoelectron spectroscopy (XPS). The deposition of a metallic gold layer via ultra-high vacuum (UHV) evaporation reveals good adhesion properties on Au/MPS/SiO2/Si structure. The 'chemisorption' between the SAM and the gold evaporated layer is confirmed by adhesion tests and optimum curing treatment is found 1 h at 100 deg. C). This very simple methodology, avoiding the usage of Cr and other metals as undercoating layers and could be proposed further for (bio)sensors applications

  8. Decoration of gold nanoparticles with cysteine in solution: reactive molecular dynamics simulations.

    Science.gov (United States)

    Monti, Susanna; Carravetta, Vincenzo; Ågren, Hans

    2016-07-14

    The dynamics of gold nanoparticle functionalization by means of adsorption of cysteine molecules in water solution is simulated through classical reactive molecular dynamics simulations based on an accurately parametrized force field. The adsorption modes of the molecules are characterized in detail disclosing the nature of the cysteine-gold interactions and the stability of the final material. The simulation results agree satisfactorily with recent experimental and theoretical data and confirm previous findings for a similar system. The covalent attachments of the molecules to the gold support are all slow physisorptions followed by fast chemisorptions. However, a great variety of binding arrangements can be observed. Interactions with the adsorbate caused surface modulations in terms of adatoms and dislocations which contributed to strengthen the cysteine adsorption. PMID:27305447

  9. Ti-Si composite oxide-supported cobalt catalysts for CO2 hydrogenation

    Institute of Scientific and Technical Information of China (English)

    Jakrapan Janlamool; Piyasan Praserthdam; Bunjerd Jongsomjit

    2011-01-01

    In the present work,different silica-based supported cobalt (Co) catalysts were synthesized and used for CO2 hydrogenation for methanation.Different supports,such as SSP,MCM-41,TiSSP and TiMCM were used to prepare Co catalysts with 20 wt% Co loading.The supports and catalysts were characterized by means of N2 physisorption,XRD,SEM/EDX,XPS,TPR and CO chemisorption.It is found that after calcination of catalysts,Ti is present in the form of anatase.The introduction of Ti plays important roles in the properties of Co catalysts by.(i) facilitating the reduction of Co oxides species which are strongly interacted with support,(ii) preventing the formation of silicate compounds,and (iii) inhibiting the RWGS reaction.Based on CO2 hydrogenation,the CoTiMCM catalyst exhibites the highest activity and stability.

  10. ADSORPTION CHARACTERISTICS OF CHLOROPHENOLS FROM AQUATIC SYSTEMS BY HYPERCROSSLINKED RESINS MODIFIED WITH BENZOYL GROUP

    Institute of Scientific and Technical Information of China (English)

    Jing-ping Wang; Zheng-hao Fei

    2006-01-01

    A hypercrosslinked polymeric adsorbent (ZH-03) for adsorbing and removing chlorophenolic compounds from their aqueous solutions was studied, including the static adsorption. The equilibrium adsorption data were fit to Freundlich adsorption isothermic models to evaluate the model parameters. Thermodynamic studies on the adsorption of chlorophenolic compounds on ZH-03 indicated that there were chemisorption transitions for 2,4,6-trichlorophenol and physical adsorption processes for 2-chlorophenol and 2,6-chlorophenol, and ZH-03 showed the homogeneous nature of the adsorbent surface.Column adsorption for chlorophenols wastewater shows the advantages of the ZH-03 adsorbent for adsorbing the following chlorophenolic compounds as 2-chlorophenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol. Sodium hydroxide was used for desorpting chlorophenols from ZH-03 and showed excellent performance.

  11. Single-step synthesis of magnetic chitosan composites and application for chromate (Cr(VI)) removal

    Institute of Scientific and Technical Information of China (English)

    杨卫春; 唐琼芝; 董舒宇; 柴立元; 王海鹰

    2016-01-01

    Magnetic chitosan composites (Fe3O4@chitosan) were synthesized in one single-step, characterized and applied in Cr(VI) removal from water. With the increase of loading proportion of chitosan, Cr(VI) adsorption capacity of Fe3O4@chitosan composites increased from 10.771 to 21.040 mg/g. The optimum adsorption capacities of Cr(VI) on Fe3O4@chitosan-3 were found in a pH range of 3.0−5.0. Kinetic study results show that the adsorption process follows pseudo-second-order model, indicating that the rate-limiting step in the adsorption of Cr(VI) involves chemisorptions. Moreover, FT-IR spectra analysis confirms that the amine and hydroxyl groups of chitosan are predominantly responsible for binding. Results from this work demonstrate that the prepared Fe3O4@chitosan composites possess great potential in Cr(VI) removal from contaminated water.

  12. Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

    Directory of Open Access Journals (Sweden)

    Franziska Klitsche

    2015-05-01

    Full Text Available A common approach to generate tailored materials and nanoparticles (NPs is the formation of molecular monolayers by chemisorption of bifunctional anchor molecules. This approach depends critically on the choice of a suitable anchor group. Recently, bifunctional catecholates, inspired by mussel-adhesive proteins (MAPs and bacterial siderophores, have received considerable interest as anchor groups for biomedically relevant metal surfaces and nanoparticles. We report here the synthesis of new tripodal catecholates as multivalent anchor molecules for immobilization on metal surfaces and nanoparticles. The tripodal catecholates have been conjugated to various effector molecules such as PEG, a sulfobetaine and an adamantyl group. The potential of these conjugates has been demonstrated with the immobilization of tripodal catecholates on ZnO NPs. The results confirmed a high loading of tripodal PEG-catecholates on the particles and the formation of stable PEG layers in aqueous solution.

  13. Theoretical study of NO adsorbed on the surface of TiO2(110) cluster model

    Institute of Scientific and Technical Information of China (English)

    WANG Yang(汪洋); YANAGISAWA Yasunori

    2004-01-01

    The chemisorption properties of N18O adsorption on TiO2(110) surface were investigated by experimental and theoretical methods. The results of temperature programmed desorption (TPD) indicated that the temperatures of the three desorption peaks of the main N2 molecules were at (low) temperature of 230 K, 450 K, and (high) temperature of 980 K. This meant that N18O decomposed and recombined during the process of N2 desorption after N18O was exposed. Analysis of the stable combination and orbital theory calculation of the surface reaction of NO adsorption on the TiO2(110) cluster model showed that there was clear preference for the Ti-NO orientation.

  14. Theoretical study of NO adsorbed on the surface of TiO2(110) cluster model

    Institute of Scientific and Technical Information of China (English)

    汪洋; YANAGISAWAYasunori

    2004-01-01

    The chemisorption properties of N18O adsorption on TiO2(110) surface were investigated by experimental and theoretical methods. The results of temperature programmed desorption (TPD) indicated that the temperatures of the three desorption peaks of the main N2 molecules were at (low) temperature of 230 K, 450 K, and (high) temperature of 980 K. This meant that N18O decomposed and recombined during the process of N2 desorption after N18O was exposed. Analysis of thestable combination and orbital theory calculation of the surface reaction of NO adsorption on the TiO2(110) cluster modelshowed that there was clear preference for the Ti-NO orientation.

  15. A theoretical study of H{sub 2}S adsorption on graphene doped with B, Al and Ga

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Sheetal; Verma, A.S., E-mail: ajay_phy@rediffmail.com

    2013-10-15

    An effort has been made to exploit the adsorption potential of pure and doped graphene for H{sub 2}S molecule using density functional theory (DFT) modelling. Boron, aluminium and gallium atoms (IIIB) are used as dopant. For each pure and doped graphene system optimum position of adsorbed H{sub 2}S molecule is determined and adsorption energies are calculated. Further electronic properties are investigated by the analysis of Mulliken's charges and energy band-structures. The results indicate that H{sub 2}S molecule weakly binds to the pure graphene and boron doped graphene with small adsorption values; on the other hand aluminium doped graphene and gallium doped graphene have large adsorption energies values and binding distances typical for the chemisorptions. Local curvature in aluminium and gallium doped graphene is mainly responsible for the increased reactivity.

  16. Required catalytic properties for alkane production from carboxylic acids: Hydrodeoxygenation of acetic acid

    Institute of Scientific and Technical Information of China (English)

    Zhong; He; Xianqin; Wang

    2013-01-01

    The supported Pt catalysts(1 wt%)were prepared by the incipient impregnation method and analyzed using synchrotron-based X-ray diffraction,BET surface area,oxygen adsorption,CO pulse chemisorption,temperature-programmed desorption(TPD)of acetic acid,H2-TPD,NH3-TPD,O2-TPD,and H2-TPR.The reactivity of Pt-based catalysts was studied using a fixed bed reactor at 300 C and 4 MPa for hydrodeoxygenation of acetic acid,where Pt/TiO2 was very selective for ethane production.TPD experiments revealed that several conditions must be satisfied to achieve this high selectivity to ethane from acetic acid,such as Pt sites,moderate acidity,and medium metal-oxygen bond strength in the oxide support.This work provides insights in developing novel catalytic materials for hydrocarbon productions from various organics including bio-fuels.

  17. Electronic structure of disordered alloys, surfaces and interfaces

    CERN Document Server

    Turek, Ilja; Kudrnovský, Josef; Šob, Mojmír; Weinberger, Peter

    1997-01-01

    At present, there is an increasing interest in the prediction of properties of classical and new materials such as substitutional alloys, their surfaces, and metallic or semiconductor multilayers. A detailed understanding based on a thus of the utmost importance for fu­ microscopic, parameter-free approach is ture developments in solid state physics and materials science. The interrela­ tion between electronic and structural properties at surfaces plays a key role for a microscopic understanding of phenomena as diverse as catalysis, corrosion, chemisorption and crystal growth. Remarkable progress has been made in the past 10-15 years in the understand­ ing of behavior of ideal crystals and their surfaces by relating their properties to the underlying electronic structure as determined from the first principles. Similar studies of complex systems like imperfect surfaces, interfaces, and mul­ tilayered structures seem to be accessible by now. Conventional band-structure methods, however, are of limited use ...

  18. Accelerating the development of transparent graphene electrodes through basic science driven chemical functionalization.

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Calvin; Beechem Iii, Thomas Edwin; Ohta, Taisuke; Brumbach, Michael T.; Wheeler, David Roger; Veneman, Alexander; Gearba, I. Raluca; Stevenson, Keith J.

    2013-09-01

    Chemical functionalization is required to adapt graphenes properties to many applications. However, most covalent functionalization schemes are spontaneous or defect driven and are not suitable for applications requiring directed assembly of molecules on graphene substrates. In this work, we demonstrated electrochemically driven covalent bonding of phenyl iodoniums onto epitaxial graphene. The amount of chemisorption was demonstrated by varying the duration of the electrochemical driving potential. Chemical, electronic, and defect states of phenyl-modified graphene were studied by photoemission spectroscopy, spatially resolved Raman spectroscopy, and water contact angle measurement. Covalent attachment rehybridized some of the delocalized graphene sp2 orbitals to localized sp3 states. Control over the relative spontaneity (reaction rate) of covalent graphene functionalization is an important first step to the practical realization of directed molecular assembly on graphene. More than 10 publications, conference presentations, and program highlights were produced (some invited), and follow-on funding was obtained to continue this work.

  19. Catalisadores Ni/Al2O3 promovidos com molibdênio para a reação de reforma a vapor de metano Mo-Ni/AL2O3 catalysts for the methane steam reforming reaction

    Directory of Open Access Journals (Sweden)

    Silvia Sálua Maluf

    2003-03-01

    Full Text Available Mo-promoted Ni/Al2O3 catalysts for the methane steam reforming reaction were studied in this work. The Ni/Al2O3 catalysts were prepared by precipitation and molibdenum was added by impregnation up to 2%wt. The solids were tested using a micro-reactor under two H2Ov/C conditions and were characterized by ICP-OES, XRD, N2 adsoption, H2 chemisorption and TPR. NiO and NiAl2O4 phases were observed and the metallic area decreased with the increase of the Mo content. From the catalytic tests high stability was verified for H2Ov/C=4.0. On the other hand, only the catalyst containing 0,05% Mo stayed stable during 30 hours of the test at H2Ov/C=2.0.

  20. Synthesis of supported bimetallic nanoparticles with controlled size and composition distributions for active site elucidation

    Energy Technology Data Exchange (ETDEWEB)

    Hakim, Sikander H.; Sener, Canan; Alba Rubio, Ana C.; Gostanian, Thomas M.; O' neill, Brandon J; Ribeiro, Fabio H.; Miller, Jeffrey T.; Dumesic, James A

    2015-08-01

    Elucidation of active sites in supported bimetallic catalysts is complicated by the high level of dispersity in the nanoparticle size and composition that is inherent in conventional methods of catalyst preparation. We present a synthesis strategy that leads to highly dispersed, bimetallic nanoparticles with uniform particle size and composition by means of controlled surface reactions. We demonstrate the synthesis of three systems, RhMo, PtMo, and RhRe, consisting of a highly reducible metal with an oxophilic promoter. These catalysts are characterized by FTIR, CO chemisorption, STEM/EDS, TPR, and XAS analysis. The catalytic properties of these bimetallic nanoparticles were probed for the selective CO hydrogenolysis of (hydroxymethyl)tetrahydropyran to produce 1,6 hexanediol. Based on the characterization results and reactivity trends, the active sites in the hydrogenolysis reaction are identified to be small ensembles of the more noble metal (Rh, Pt) adjacent to highly reduced moieties of the more oxophilic metal (Mo, Re).

  1. Estudo microestrutural do catalisador Ni/gama-Al2O3: efeito da adição de CeO2 na reforma do metano com dióxido de carbono Microstructural study of Ni/gamma-Al2O3 catalyst: addition effects of CeO2 on carbon dioxide reforming of methane

    Directory of Open Access Journals (Sweden)

    Antoninho Valentini

    2003-10-01

    Full Text Available The carbon dioxide reforming of methane was carried out over nickel catalysts supported on the gamma-Al2O3/CeO2 system prepared by wet impregnation. With the increase of the CeO2 weight in the catalyst, a higher stability was observed in the catalytic activity, together with an excellent resistance to carbon deposition and a better Ni dispersion. The catalysts were characterized by means of surface area measurements, TPR, H2 chemisorption, XRD, SEM, EDX, XPS and TEM. An interaction between Ni and CeO2 was observed to the Ni/CeO2 sample after activation in a H2 atmosphere above 300 ºC. Such behavior has a significantly influence on the catalytic activity.

  2. Ni catalysts supported on nanocrystalline magnesium oxide for syngas production by CO2 reforming of CH4

    Institute of Scientific and Technical Information of China (English)

    Fereshteh Meshkani; Mehran Rezaei

    2011-01-01

    CO2 reforming of methane(CDRM)was carried out over MgO supported Ni catalysts with various Ni loadings.The preparation of MgO supported Ni catalysts via surfactant-assisted precipitation method led to the formation of a nanocrystalline carrier for nickel catalysts.The synthesized samples were characterized by XRD,N2 adsorption-desorption,H2 chemisorption,TPR,TPO and SEM techniques.It was found that the high catalytic activity and stability of the prepared catalysts could be attributable to high dispersion of reduced Ni species and basicity of support surface.In addition,the effect of feed ratio,nickel loading and GHSV on the catalytic performance of CDRM over the catalysts were investigated.

  3. Electron emission degradation of nano-structured sp2-bonded amorphous carbon films

    Institute of Scientific and Technical Information of China (English)

    Lu Zhan-Ling; Wang Chang-Qing; Jia Yu; Zhang Bing-Lin; Yao Ning

    2007-01-01

    The initial field electron emission degradation behaviour of original nano-structured sp2-bonded amorphous carbon films has been observed.which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot.The possible re.on for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating.For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film,a cluster model with a series of graphite(0001) basal surfaces has been presented,and the theoretical calculations have been performed to investigate work functions of graphite(0001) surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.

  4. Effect of La2O3 on Methanation of CO and CO2 over Ni-Mo/γ-Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A series of Ni-Mo/γ-Al2O3 methanation catalysts containing La2O3 were prepared by impregnation. The activities of catalysts for CO and CO2 methanation were investigated. The surface properties of the catalysts were studied by TEM, XPS and chemisorption of CO. The experimental results show that the addition of La2O3 increases the activities for the methanation of CO and CO2, the dispersity of nickel on catalysts, the active nickel surface area and the concentration of nickel atoms on the surface of Ni-Mo/γ-Al2O3 catalysts. At the same time, it also decreases the binding energy of Ni2P3/2 in catalysts.

  5. Adsorption of Fe on GaAs(100) Surface

    Institute of Scientific and Technical Information of China (English)

    WEI Shu-Yi; MA Li; WANG Jian-Guang; WANG Tian-Xing

    2003-01-01

    The adsorption of one monolayer Fe atoms on an ideal GaAs (100) surface is studied by using the self-consistent tight-binding linear muffin-tin orbital method. The Fe adatom chemisorption on Ga- and As-terminatedsurface are considered separately. A monolayer of S atoms is used to saturate the dangling bonds on one of the supercellsurfaces. Energies of adsorption systems of an Fe atom on different sites are calculated, and the charge transfers areinvestigated. It is found that Fe-As interaction is stronger than Fe-Ga interaction and Fe atoms prefer to be adsorbed onthe As-terminated surface. It is possible for the adsorbed Fe atoms to sit below the As-terminated surface resulting inan Fe-Ga-As mixed layer. The layer projected density states are calculated and compared with that of the clean surface.

  6. Half-oxidized phosphorene: band gap and elastic properties modulation

    International Nuclear Information System (INIS)

    Based on a first principles approach, we study structural, electronic and elastic properties, as well as stabilities of all possible half-oxidized phosphorene conformers. Stability analysis reveals that oxygen chemisorption is an exothermic process in the six configurations despite the formation of interstitial oxygen bridges in three of them. Electronic structure calculations show that oxidation induces a band gap modulation ranging between 0.54 and 1.57 eV in the generalized gradient approximation corrected to 1.19 and 2.88 eV using GW. The mechanical response of the conformers is sensitively dependent on direction and indicates that the new derivatives are incompressible materials and one configuration has an auxetic behavior. The present results provide a basis for tailoring the electronic and elastic properties of phosphorene via half oxidation. (paper)

  7. Magnetic behavior of iron-modified MCM-41 correlated with clustering processes from the wet impregnation method

    Science.gov (United States)

    Cuello, Natalia I.; Elías, Verónica R.; Winkler, Elin; Pozo-López, Gabriela; Oliva, Marcos I.; Eimer, Griselda A.

    2016-06-01

    Magnetic MCM-41 type mesoporous silica materials were synthetized and modified with different iron loadings by the wet impregnation method. The evolution of iron speciation, depending on the metal loading and associated with a particular magnetic behavior was investigated by M vs. H curves, FC-ZFC curves, EPR spectroscopy and other complementary techniques such as SEM, TEM, and chemisorption of pyridine followed by FT-IR studies. A superparamagnetic contribution was larger for the lower loadings suggesting the high dispersion of very small sized iron nanospecies. However, this contribution decreased with increasing metal loading due to the growth of magnetically blocked nanoparticles (hematite) on the outer surface. Finally, a bimodal size distribution for the superparamagnetic nanospecies could be inferred; then the anisotropy constant for this phase and the corresponding nanospecies sizes were estimated.

  8. Structure and properties of ultrathin iron films on Ru(10 overline10) : The formation of metastable surface phases of γ-Fe

    Science.gov (United States)

    Harrison, Kevin; Prince, Robert H.; Lambert, Richard M.

    1988-07-01

    The chemisorption and desorption of Fe at the (10 overline10) surface of Ru has been investigated by LEED, Auger spectroscopy, Δφ and thermal desorption measurements over a substrate temperature range of 300-900 K. The growth mode of the iron deposit was found to be strongly dependent on the temperature. At 300 K up to seven iron monolayers could be grown, these adopting the configuration of the fcc (111) plane of bulk γ-iron. The layers were metastable and heating of such films or deposition at elevated temperatures resulted in nucleation and growth of crystallites. Only a single Fe desorption peak ( Ed≈ 250 kJ mol-1) was observed over the whole coverage regime; this is assigned to the evaporation of iron atoms in contact with the ruthenium substrate, either pre-existing in the first monolayer or supplied from the Fe crystallites.

  9. Insight into biosorption equilibrium, kinetics and thermodynamics of crystal violet onto Ananas comosus (pineapple) leaf powder

    Science.gov (United States)

    Chakraborty, Sagnik; Chowdhury, Shamik; Saha, Papita Das

    2012-06-01

    Biosorption performance of pineapple leaf powder (PLP) for removal of crystal violet (CV) from its aqueous solutions was investigated. To this end, the influence of operational parameters such as pH, biosorbent dose, initial dye concentration and temperature were studied employing a batch experimental setup. The biosorption process followed the Langmuir isotherm model with high correlation coefficients ( R 2 > 0.99) at different temperatures. The maximum monolayer biosorption capacity was found to be 78.22 mg g-1 at 293 K. The kinetic data conformed to the pseudo-second-order kinetic model. The activation energy of the system was calculated as 58.96 kJ mol- 1 , indicating chemisorption nature of the ongoing biosorption process. A thermodynamic study showed spontaneous and exothermic nature of the biosorption process. Owing to its low cost and high dye uptake capacity, PLP has potential for application as biosorbent for removal of CV from aqueous solutions.

  10. Understanding the mechanism of CO2 capture by 1,3 di-substituted imidazolium acetate based ionic liquids.

    Science.gov (United States)

    Mao, James X; Steckel, Janice A; Yan, Fangyong; Dhumal, Nilesh; Kim, Hyung; Damodaran, Krishnan

    2016-01-21

    Efficient CO2 capture by ionic liquids needs a thorough understanding of underlying mechanisms of the CO2 interaction with ionic liquids, especially when it involves chemisorption. In this work we have systematically investigated the mechanism of CO2 capture by 1,3 di-substituted imidazolium acetate ionic liquids using density functional theory. Solvent effects are analyzed using QM/MM and QM/QM approaches with the help of molecular dynamics simulations and ONIOM methods. The investigation of different stepwise mechanisms shows that CO2 could be involved in the first step of the reaction mechanism, also a new two-step mechanism is proposed. The final stabilization step is analyzed and pointed out to be responsible for important experimentally-observed features of the reaction. PMID:26687108

  11. Unusual diffusing regimes caused by different adsorbing surfaces.

    Science.gov (United States)

    Guimarães, Veridiana G; Ribeiro, Haroldo V; Li, Quan; Evangelista, Luiz R; Lenzi, Ervin K; Zola, Rafael S

    2015-03-01

    A confined liquid with dispersed neutral particles is theoretically studied when the limiting surfaces present different dynamics for the adsorption-desorption phenomena. The investigation considers different non-singular kernels in the kinetic equations at the walls, where the suitable choice of the kernel can account for the relative importance of physisorption or chemisorption. We find that even a small difference in the adsorption-desorption rate of one surface (relative to the other) can drastically affect the behavior of the whole system. The surface and bulk densities and the dispersion are calculated when several scenarios are considered and anomalous-like behaviors are found. The approach described here is closely related to experimental situations, and can be applied in several contexts such as dielectric relaxation, diffusion-controlled relaxation in liquids, liquid crystals, and amorphous polymers. PMID:25633342

  12. Adsorption of dissolved Reactive red dye from aqueous phase onto activated carbon prepared from agricultural waste.

    Science.gov (United States)

    Senthilkumaar, S; Kalaamani, P; Porkodi, K; Varadarajan, P R; Subburaam, C V

    2006-09-01

    The adsorption of Reactive red dye (RR) onto Coconut tree flower carbon (CFC) and Jute fibre carbon (JFC) from aqueous solution was investigated. Adsorption studies were carried out at different initial dye concentrations, initial solution pH and adsorbent doses. The kinetic studies were also conducted; the adsorption of Reactive red onto CFC and JFC followed pseudosecond-order rate equation. The effective diffusion coefficient was evaluated to establish the film diffusion mechanism. Quantitative removal of Reactive red dye was achieved at strongly acidic conditions for both the carbons studied. The adsorption isotherm data were fitted well to Langmuir isotherm and the adsorption capacity were found to be 181.9 and 200 mg/g for CFC and JFC, respectively. The overall rate of dye adsorption appeared to be controlled by chemisorption, in this case in accordance with poor desorption studies.

  13. Luminescence of photoactivated pristine and Cr-doped MgAl2O4 spinel

    Science.gov (United States)

    Artemyeva, E. S.; Barinov, D. S.; Atitar, F. M.; Murashkina, A. A.; Emeline, A. V.; Serpone, N.

    2015-04-01

    This Letter reports a comparative study of the luminescence from pristine and Cr-doped MgAl2O4 spinel induced by different excitation mechanisms: photoluminescence (PhL), thermoluminescence (ThL) and Photo-Induced Chemisorption Luminescence (the PhICL phenomenon) to understand the mechanism of PhICL emission. Cr-doping alters the major pathway of physical relaxation through a luminescence pathway: quenching of the luminescence associated with intrinsic defects and appearance of the luminescence from Cr3+-states. The similarity between ThL and PhICL spectra suggest the mechanism of the PhICL phenomenon is due to electron transfer from the surface to the emission centers of luminescence; an energy transfer pathway is not precluded.

  14. Simulated structure and imaging of NTCDI on Si(1 1 1)-7 × 7 : a combined STM, NC-AFM and DFT study.

    Science.gov (United States)

    Jarvis, S P; Sweetman, A M; Lekkas, I; Champness, N R; Kantorovich, L; Moriarty, P

    2015-02-11

    The adsorption of naphthalene tetracarboxylic diimide (NTCDI) on Si(1 1 1)-7 × 7 is investigated through a combination of scanning tunnelling microscopy (STM), noncontact atomic force microscopy (NC-AFM) and density functional theory (DFT) calculations. We show that NTCDI adopts multiple planar adsorption geometries on the Si(1 1 1)-7 × 7 surface which can be imaged with intramolecular bond resolution using NC-AFM. DFT calculations reveal adsorption is dominated by covalent bond formation between the molecular oxygen atoms and the surface silicon adatoms. The chemisorption of the molecule is found to induce subtle distortions to the molecular structure, which are observed in NC-AFM images. PMID:25414147

  15. Effect of Y{sub 2}O{sub 3} addition to Rh/Al{sub 2}O{sub 3} catalysts on the autothermal reforming of methane; Efeito da adicao de Y{sub 2}O{sub 3} a catalisadores de Rh/Al{sub 2}O{sub 3} na reforma autotermica do metano

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Vanessa Monteiro; Cardoso, Gabriel Alexandre Lima; Coutinho, Ana Carla da S. Lomba S.; Passos, Fabio Barboza [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Engenharia Quimica e de Petroleo. Lab. de Reatores, Cinetica e Catalise (RECAT)]. E-mail: vanessafisqui@yahoo.com.br

    2008-07-01

    In this work, the effect of the addition of Y{sub 2}O{sub 3} (with 2%, 5% and 10% weight content) on Rh/{alpha}-Al{sub 2}O{sub 3} catalysts in the autothermal reforming reaction of methane to the production of hydrogen for fuel cells was investigated. The catalysts were characterized by the following techniques: N{sub 2} adsorption, H{sub 2} chemisorption, X-ray diffraction (XRD) and cyclohexane dehydrogenation reaction. The catalysts were also evaluated in the reaction of autothermal reforming. The catalyst with higher Y{sub 2}O{sub 3} content showed the best results both in the cyclohexane dehydrogenation rate and in the conversion of methane. (author)

  16. Removal of Cd (II) from water using the waste of jatropha fruit (Jatropha curcas L.)

    Science.gov (United States)

    Nacke, Herbert; Gonçalves, Affonso Celso; Coelho, Gustavo Ferreira; Schwantes, Daniel; Campagnolo, Marcelo Angelo; Leismann, Eduardo Ariel Völz; Junior, Élio Conradi; Miola, Alisson Junior

    2016-09-01

    The aim of this work was to evaluate the removal of Cd (II) from water using three biosorbents originated from the biomass of jatropha (bark, endosperm, and endosperm + tegument). For that, batch tests were performed to verify the effect of solution pH, adsorbent mass, contact time, initial concentration of Cd (II), and the temperature of the process. The adsorption process was evaluated by the studies of kinetics, isotherms, and thermodynamics. The ideal conditions of solution pH were 5.5 and 8 g L-1 of adsorbent mass of biosorbents by solution volume, with an equilibrium time of 60 min. According to the Langmuir model, the maximum adsorption capacity for bark, endosperm, and bark + endosperm of jatropha was, respectively, 29.665, 19.562, and 34.674 mg g-1, predominating chemisorption in monolayers. The biosorbents presented potential for the remediation of waters contaminated with Cd (II).

  17. On the Structure Sensitivity of Direct NO Decomposition over Low-Index Transition Metal Facets

    DEFF Research Database (Denmark)

    Falsig, Hanne; Shen, Juan; Khan, Tuhin Suvra;

    2014-01-01

    We present a study of the dissociative chemisorption of NO, O2, and N2 over close-packed, stepped, kinked, and open (fcc {111}, {211}, {311}, {532}, {100}, and {110}) transition metal facets using density functional theory (DFT). The offset of the Bronsted-Evans-Polanyi (BEP) relations suggest...... that the {111} surface is the least reactive, and that the {110} surface is the most reactive. This observation is verified by establishing volcano-relations based on mean-field microkinetic models for each facet, showing that the maximum rate over {110} is 4 orders of magnitude larger than the maximum {111...... of facet. This observation lends credibility to the approach of analyzing trends in catalytic reactivity over a single low-index facet, and assuming the experimentally observed activity trends are qualitatively well-described by such a single-facet analysis. Our study suggests that a key element...

  18. Reversible CO2 Capture by Conjugated Ionic Liquids through Dynamic Covalent Carbon-Oxygen Bonds.

    Science.gov (United States)

    Pan, Mingguang; Cao, Ningning; Lin, Wenjun; Luo, Xiaoyan; Chen, Kaihong; Che, Siying; Li, Haoran; Wang, Congmin

    2016-09-01

    The strong chemisorption of CO2 is always accompanied by a high absorption enthalpy, and traditional methods to reduce the absorption enthalpy lead to decreased CO2 capacities. Through the introduction of a large π-conjugated structure into the anion, a dual-tuning approach for the improvement of CO2 capture by anion-functionalized ionic liquids (ILs) resulted in a high capacity of up to 0.96 molCO2  mol-1IL and excellent reversibility. The increased capacity and improved desorption were supported by quantum chemical calculations, spectroscopic investigations, and thermogravimetric analysis. The increased capacity may be a result of the strengthened dynamic covalent bonds in these π-electron-conjugated structures through anion aggregation upon the uptake of CO2 , and the improved desorption originates from the charge dispersion of interaction sites through the large π-electron delocalization. These results provide important insights into effective strategies for CO2 capture. PMID:27458723

  19. Berberine as an Environmental-Friendly Inhibitor for Hot-Dip Coated Steels in Diluted Hydrochloric Acid

    Institute of Scientific and Technical Information of China (English)

    Hong Ju; Yulin Ju; Yan Li

    2012-01-01

    The inhibition effect of an excellent environmental-friendly corrosion inhibitor--berberine on hot-dip coated steels in the diluted HCI has been investigated by using quantum chemistry analysis, mass-loss tests, elec- trochemical measurements and scanning electron microscopy (SEM) observation. Calculation results show that berberine has a nearly planar structure with a number of active centers. The value of Mulliken charge, and the distribution of the highest occupied molecular orbital (HOMO) and the lower unoccupied molecular orbital (LUMO) imply that berberine has a good ability of electron exchange with metal surface. The test results indicate that inhibition efficiency (IE%) increases with the inhibitor concentration and the highest IE can reach 99%. Adsorption of berberine on the coating surface follows Langmuir adsorption isotherm with a single molecular layer by chemisorption.

  20. Photocatalytic degradation of carbofuran in TiO2 aqueous solution: kinetics using design of experiments and mechanism by HPLC/MS/MS.

    Science.gov (United States)

    Yang, Hai; Zhou, Shuolin; Liu, Huajie; Yan, Weiwei; Yang, Liping; Yij, Bing

    2013-08-01

    The photocatalytic degradation kinetics of carbofuran was optimized by central composite design based on response surface methodology for the first time. Three variables, TiO2 concentration, initial pH value and the concentration of carbofuran, were selected to determine the dependence of degradation efficiencies on independent variables. Response surface methodology modeling results indicated that the degradation efficiency of carbofuran was highly affected by the initial pH value and the concentration of carbofuran. Then nine degradation intermediates were detected by HPLC/MS/MS. The Frontier Electron Densities of carbofuran were calculated to predict the active sites on carbofuran attacked by hydroxyl radicals and photoholes. Point charges were used to elucidate the chemisorption pattern on TiO2 catalysts during the photocatalytic process. By combining the experimental results and calculation data, the photocatalytic degradation pathways of carbofuran were proposed, including the addition of hydroxyl radicals and the cleavage of the carbamate side chain.

  1. Influence of Preparation Methods of Nano Au/MCM-41 Catalysts for Vapor Phase Oxidation of Benzyl Alcohol.

    Science.gov (United States)

    Kumar, Ashish; Kumar, Vanama Pavan; Vishwanathan, Venkataraman; Chary, V R

    2015-12-01

    The Au/MCM-41 nano catalysts were synthesized from four different methods, viz., homogeneous deposition-precipitation, micro-emulsion, impregnation and polyol and their catalytic activities were tested for the vapor phase oxidation of benzyl alcohol to benzaldehyde. The physico-chemical properties of the catalysts were investigated by XRD, TEM, BET surface area, PSD, CO-chemisorption and XPS techniques. The effect of preparation methods, nature of the metal, support and the metal-support interaction in Au/MCM-41 catalysts were studied for the title reaction. The Au/MCM-41 catalysts synthesized from HDP method has shown higher and better catalytic activity as compared to the catalysts prepared by other methods. PMID:26682438

  2. Influence of the aluminium impregnation [ Al(NO33] in the beta zeolite over its acidity

    Directory of Open Access Journals (Sweden)

    Francisco José Sánchez Castellanos

    2010-04-01

    Full Text Available Beta zeolite was impregnated with [ Al(NO33], increasing the aluminium content in increments of 0.05% from 0.00% to 0.25%. A parallel treatment with 0.05% sulphuric acid was also performed; in both cases, methanol was used as solvent (disperse phase. Cation exchange capacity (CEC, ammonia chemisorption, infrared spectroscopy (FIT-IR, scanning electronic microscopy (SEM, X-Ray powder diffraction (XRD, atomic absorption spectroscopy (AAS, titration with sodium hydroxide and nitrogen physisorption at 77K were used to carry out the physical and chemical characterization of the catalysts. Futhermore, the catalysts were employed in the esterification of ethanol with acetic acid, to quantify the effect of aluminium impregnation over the beta zeolite.

  3. Adsorption of cyclic hydrocarbons on Pt and the interaction of the adsorbed species with hydrogen

    International Nuclear Information System (INIS)

    The adsorption of six-membered hydrocarbon cycles and cyclopentane and the interaction of hydrogen with the adsorbed layer on polycrystalline Pt-foil have been studied. The work function change (Δφ) was followed by a Kelvin probe and the C/Pt peak ratio was determined by Auger electron spectroscopy. Combining these two techniques made it possible to distinguish between chemisorption via σ-bonds and π-complex formation. Benzene and toluene adsorbed first as π-complex while cyclohexane showed initially a partial aromatization and a π-complex-like bonding to the surface. Excess hydrocarbon or addition of hydrogen transformed the π-complex into σ-bonded species. Cyclopentane adsorbed via σ-bonds and showed no significant hydrogen effect

  4. Study on Deactivation by Sulfur and Regeneration of Pd/C Catalyst in Hydrogenation of N-(3-nitro-4-methoxyphenyl) Acetamide

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qunfeng; L(U) Jinghui; MA Lei; LU Chunshan; LIU Wei; LI Xiaonian

    2013-01-01

    Deactivation of Pd/C catalyst often occurs in liquid hydrogenation using industrial materials.For instance,the Pd/C catalyst is deactivated severely in the hydrogenation of N-(3-nitro-4-methoxyphenyl) acetamide.In this study,the chemisorption of sulfur on the surface of deactivated Pd/C was detected by energy dispersive spectrometer and X-ray photoelectron spectroscopy.Sulfur compounds poison the Pd/C catalyst and increase the formation of azo deposit,reducing the activity of catalyst.We report a mild method to regenerate the Pd/C catalyst:wash the deposit by N,N-dimethylformamide and oxidize the chemisorbed sulfur by hot air.The regenerated Pd/C catalyst can be reused at least ten runs with stable activity.

  5. A study of the initial oxidation of evaporated thin films of aluminum by AES, ELS, and ESD

    Science.gov (United States)

    Bujor, M.; Larson, L. A.; Poppa, H.

    1982-01-01

    The room temperature, low pressure, oxidation of evaporated aluminum thin films has been studied by AES, ELS, and ESD. ESD was the most sensitive of the three methods to characterize a clean aluminum surface. Two oxidation stages were distinguished in the 0-3000 L oxygen exposure range. Between 0 and 50 L, the chemisorption of oxygen atoms was characterized by a fast decrease of the 67 eV AES Al peak and the 10 eV surface plasmon peak, and by a simultaneous increase of the oxygen AES and ESD signals. After 50 L, a change in slope in all AES and ESD signal variations was attributed to the slow growth of a thin layer of aluminum oxide, which after 3000 L was still only a few angstroms thick.

  6. Utilization of chemically modified citrus reticulata peels for biosorptive removal of acid yellow-73 dye from water

    International Nuclear Information System (INIS)

    Textile effluents contain several varieties of natural and synthetic dyes, which are non-biodegradable. Acid Yellow-73 is one of them. In this research work, adsorptive removal of this dye was investigated using chemically modified Citrus reticulata peels, in batch mode. It was noted that adsorption of dye on Citrus reticulata peels increased by increasing contact time and decreased in basic pH conditions. Langmuir and Freundlich isothermal models were followed by equilibrium data, but the first isotherm fitted the data better, showing that chemisorption occurred more as compared to physiosorption, showing maximum adsorption capacity 96.46 mg.g-1.L-1. The thermodynamic study showed that adsorption of Acid Yellow-73 on chemically modified Citrus reticulata peels was favorable in nature, following pseudo-second order kinetics. (author)

  7. Removal of dyes from aqueous solutions using activated carbon prepared from rice husk residue.

    Science.gov (United States)

    Li, Yaxin; Zhang, Xian; Yang, Ruiguang; Li, Guiying; Hu, Changwei

    2016-01-01

    The treatment of dye wastewater by activated carbon (AC) prepared from rice husk residue wastes was studied. Batch adsorption studies were conducted to investigate the effects of contact time, initial concentration (50-450 mg/L), pH (3-11) and temperature (30-70 °C) on the removal of methylene blue (MB), neutral red, and methyl orange. Kinetic investigation revealed that the adsorption of dyes followed pseudo-second-order kinetics. The results suggested that AC was effective to remove dyes, especially MB, from aqueous solutions. Desorption studies found that chemisorption by the adsorbent might be the major mode of dye removal. Fourier transform infrared results suggested that dye molecules were likely to combine with the O-H and P=OOH groups of AC. PMID:26942535

  8. Effects of surface features on sulfur dioxide adsorption on calcined NiAl hydrotalcite-like compounds.

    Science.gov (United States)

    Zhao, Ling; Li, Xinyong; Quan, Xie; Chen, Guohua

    2011-06-15

    The hydrotalcite-based NiAl mixed oxides were synthesized by coprecipitation and urea hydrolysis approaches and employed for SO₂ removal. The samples were well characterized by inductively coupled plasma (ICP) elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption/desorption isotherm analyses. The acid-base properties were characterized by pyridine chemisorption and CO₂ temperature-programmed desorption (TPD). The calcined NiAlO from the urea method showed excellent SO₂ adsorption and its adsorption equilibrium showed a type I isotherm, which significantly improved the adsorption performance for low-concentration SO₂. Both the physical structure and the acidic-basic sites were found to play important roles in the SO₂ adsorption process. In situ Fourier transform infrared spectroscopy (FTIR) investigation revealed that adsorbed SO₂ molecules formed surface bisulfite, sulfite, and bidentate binuclear sulfate. The mechanisms for SO₂ adsorption and transformation are discussed in detail. PMID:21609013

  9. Gas dynamics, optics and chemistry of an aircraft condensable wake

    Energy Technology Data Exchange (ETDEWEB)

    Grinats, E.S.; Kashevarov, A.V.; Stasenko, A.L. [Central Aerohydrodynamic Inst., Zhukovsky (Russian Federation)

    1997-12-31

    Prediction of the properties of a jet-and-vortex wake from an individual airplane is of great interest as the first step to assessment of the possible global changes in the atmosphere due to the world civil aviation. Several mathematical models of the different regions of an aircraft wake and corresponding numerical results are presented. The axisymmetric exhaust jet was simulated on the base of the well-known k-{epsilon} model of turbulence. Jet chemistry was investigated on the base of kinetic scheme of the gas phase reactions of enriched by including chemisorption by water droplets of several species and by taking into account of the photochemical processes. In the 3D far wake model, the numerical results for distribution of species exhausted by the engines and entrapped by the velocity field of two parallel vortices are shown. (R.P.) 7 refs.

  10. Hyperfine interaction in hydrogenated graphene

    Science.gov (United States)

    Garcia, Noel; Melle, Manuel; Fernandez-Rossier, Joaquin

    We study the hyperfine interaction of Hydrogen chemisorbed in graphene nanostructures with a gap in their spectrum, such as islands and ribbons. Chemisorption of Hydrogen on graphene results in a bound in-gap state that hosts a single electron localized around the adatom. Using both density functional theory and a four-orbital tight-binding model we study the hyperfine interaction between the hydrogen nuclear spin and the conduction electrons in graphene. We find that the strength of the hyperfine interaction decreases for larger nanostructures for which the energy gap is smaller. We then compare the results of the hyperfine interaction for large nanostructures with those of graphene 2D crystal with a periodic arrangement of chemisorbed Hydrogen atoms, obtaining very similar results. The magnitude of the hyperfine interaction is about 150 MHz, in line with that of Si:P. We acknowledge financial support by Marie-Curie-ITN 607904-SPINOGRAPH.

  11. Surface-Controlled Metal Oxide Resistive Memory

    KAUST Repository

    Ke, Jr-Jian

    2015-10-28

    To explore the surface effect on resistive random-access memory (ReRAM), the impact of surface roughness on the characteristics of ZnO ReRAM were studied. The thickness-independent resistance and the higher switching probability of ZnO ReRAM with rough surfaces indicate the importance of surface oxygen chemisorption on the switching process. Furthermore, the improvements in switching probability, switching voltage and resistance distribution observed for ReRAM with rough surfaces can be attributed to the stable oxygen adatoms under various ambience conditions. The findings validate the surface-controlled stability and uniformity of ReRAM and can serve as the guideline for developing practical device applications.

  12. Low-energy electron diffraction and density functional theory study of potassium adsorbed on Pb(1 0 0)

    International Nuclear Information System (INIS)

    Alkali metal adsorption systems provide important models for chemisorption. Low-energy electron diffraction experiments and density functional theory calculations were carried out for the adsorption of potassium on Pb(1 0 0). The stable structure for all submonolayer coverages was found to be the commensurate c(2   ×   2) structure, with potassium atoms located in substitutional sites in the top substrate layer. This structure is temperature activated and occurs for adsorption or annealing of the film above 200 K. This finding is consistent with an earlier theory that proposed that for substrates with low energies of vacancy formation, substitutional structures can be the most stable. The structural and vibrational parameters deduced from the experiment are in agreement with the calculated values, and these values fit well into and add to the database of alkali metal adsorption properties. (paper)

  13. Tailoring the surface properties and carrier dynamics in SnO2 nanowires.

    Science.gov (United States)

    Kar, Ayan; Stroscio, Michael A; Meyyappan, M; Gosztola, David J; Wiederrecht, Gary P; Dutta, Mitra

    2011-07-15

    We report a study of the role of mid-gap defect levels due to surface states in SnO(2) nanowires on carrier trapping. Ultrafast pump-probe spectroscopy provides carrier relaxation time constants that reveal the nature and positions of various defect levels due to the surface states which in turn provide details on how the carriers relax after their injection. The effect of oxygen annealing on carrier concentration is also studied through XPS valence band photoemission spectroscopy, a sensitive non-contact surface characterization technique. These measurements show that charge transfer associated with chemisorption of oxygen in different forms produces an upward band bending and leads to an increase in the depletion layer width by approximately 70 nm, thereby decreasing surface conductivity and forming the basis for the molecular sensing capability of the nanowires.

  14. Tailoring the surface properties and carrier dynamics in SnO{sub 2} nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kar, Ayan; Stroscio, Michael A; Dutta, Mitra [Electrical and Computer Engineering Department, University of Illinois, Chicago, IL 60607 (United States); Meyyappan, M [Center for Nanotechnology, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Gosztola, David J; Wiederrecht, Gary P, E-mail: dutta@ece.uic.edu [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2011-07-15

    We report a study of the role of mid-gap defect levels due to surface states in SnO{sub 2} nanowires on carrier trapping. Ultrafast pump-probe spectroscopy provides carrier relaxation time constants that reveal the nature and positions of various defect levels due to the surface states which in turn provide details on how the carriers relax after their injection. The effect of oxygen annealing on carrier concentration is also studied through XPS valence band photoemission spectroscopy, a sensitive non-contact surface characterization technique. These measurements show that charge transfer associated with chemisorption of oxygen in different forms produces an upward band bending and leads to an increase in the depletion layer width by approximately 70 nm, thereby decreasing surface conductivity and forming the basis for the molecular sensing capability of the nanowires.

  15. Synthesis and Understanding of Novel Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Stair, Peter C. [Northwestern University

    2013-07-09

    The research took advantage of our capabilities to perform in-situ and operando Raman spectroscopy on complex systems along with our developing expertise in the synthesis of uniform, supported metal oxide materials to investigate relationships between the catalytically active oxide composition, atomic structure, and support and the corresponding chemical and catalytic properties. The project was organized into two efforts: 1) Synthesis of novel catalyst materials by atomic layer deposition (ALD). 2) Spectroscopic and chemical investigations of coke formation and catalyst deactivation. ALD synthesis was combined with conventional physical characterization, Raman spectroscopy, and probe molecule chemisorption to study the effect of supported metal oxide composition and atomic structure on acid-base and catalytic properties. Operando Raman spectroscopy studies of olefin polymerization leading to coke formation and catalyst deactivation clarified the mechanism of coke formation by acid catalysts.

  16. Investigating the adsorption of H2O on ZnO nanoclusters by first principle calculations

    KAUST Repository

    Al-Sunaidi, Abdullah A.

    2011-04-01

    The interaction of a single H2O molecule on selected ZnO nanoclusters is investigated by carrying out calculations based on the density-functional theory at the hybrid-GGA (B97-2) level. These clusters have ring, drum, tube and bubble shapes and their physical properties like the binding energy and the band gap energy depend strongly on the shape and size of the cluster. Depending on the stability of the cluster, H2O show both chemisorption and dissociation on the surfaces of the clusters. We analyzed the effect of H2O adsorption on the properties of clusters of size n = 12 via the density of state, HOMO-LUMO orbitals and the changes in the IR frequencies. © 2011 Elsevier B.V. All rights reserved.

  17. Transition metal contacts to graphene

    Energy Technology Data Exchange (ETDEWEB)

    Politou, Maria, E-mail: Maria.Politou@imec.be; De Gendt, Stefan; Heyns, Marc [KU Leuven, 3001 Leuven (Belgium); imec, Kapeldreef 75, 3001 Leuven (Belgium); Asselberghs, Inge; Radu, Iuliana; Conard, Thierry; Richard, Olivier; Martens, Koen; Huyghebaert, Cedric; Tokei, Zsolt [imec, Kapeldreef 75, 3001 Leuven (Belgium); Lee, Chang Seung [SAIT, Samsung Electronics Co., Suwon 443-803 (Korea, Republic of); Sayan, Safak [imec, Kapeldreef 75, 3001 Leuven (Belgium); Intel Corporation, 2200 Mission College Blvd, Santa Clara, California 95054 (United States)

    2015-10-12

    Achieving low resistance contacts to graphene is a common concern for graphene device performance and hybrid graphene/metal interconnects. In this work, we have used the circular Transfer Length Method (cTLM) to electrically characterize Ag, Au, Ni, Ti, and Pd as contact metals to graphene. The consistency of the obtained results was verified with the characterization of up to 72 cTLM structures per metal. Within our study, the noble metals Au, Ag and Pd, which form a weaker bond with graphene, are shown to result in lower contact resistance (Rc) values compared to the more reactive Ni and Ti. X-ray Photo Electron Spectroscopy and Transmission Electron Microscopy characterization for the latter have shown the formation of Ti and Ni carbides. Graphene/Pd contacts show a distinct intermediate behavior. The weak carbide formation signature and the low Rc values measured agree with theoretical predictions of an intermediate state of weak chemisorption of Pd on graphene.

  18. Hydrogen Storage in Iron/Carbon Nano powder Composite Materials: Effect of Varying Spiked Iron Content on Hydrogen Adsorption

    International Nuclear Information System (INIS)

    This study investigates the effects of varying the spiked iron content of iron/carbon nano powder (Fe/CNP) composite materials on hydrogen storage capacity. Among four such samples, a maximum hydrogen uptake of approximately 0.48 wt % was obtained with 14 wt % of spiked iron under 37 atm and 300 K. This higher hydrogen uptake capacity was believed to be closely related to the physisorption mechanism rather than chemisorption. In this case, the formation of maghemite catalyzed the attraction of hydrogen molecules and the CNP skeleton was the principal absorbent material for hydrogen storage. However, as the iron content exceeded 14 wt %, the formation of larger and poorly dispersed maghemite grains reduced the available surface areas of CNP for the storage of hydrogen molecules, leading to decreased uptake. Our study shows that hydrogen uptake capacities can be improved by appropriately adjusting the surface polarities of the CNP with well dispersed iron oxides crystals.

  19. In Situ 3D Imaging of Catalysis Induced Strain in Gold Nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    Ulvestad, Andrew; Sasikumar, Kiran; Kim, Jong Woo; Harder, Ross; Maxey, Evan; Clark, Jesse N.; Narayanan, Badri; Deshmukh, Sanket; Ferrier, Nicola; Mulvaney, Paul; Sankaranarayanan, Subramanian K.R.S.; Shpyrko, Oleg G.

    2016-08-04

    Multielectron transfer processes are crucially important in energy and biological science but require favorable catalysts to achieve fast kinetics. Nanostructuring catalysts can dramatically improve their properties, which can be difficult to understand due to strain- and size-dependent thermodynamics, the influence of defects, and substrate-dependent activities. Here, we report three-dimensional (3D) imaging of single gold nanoparticles during catalysis of ascorbic acid decomposition using Bragg coherent diffractive imaging (BCDI). Local strains were measured in single nanoparticles and modeled using reactive molecular dynamics (RMD) simulations and finite element analysis (FEA) simulations. RMD reveals the pathway for local strain generation in the gold lattice: chemisorption of hydroxyl ions. FEA reveals that the RMD results are transferable to the nanocrystal sizes studied in the experiment. Our study probes the strain-activity connection and opens a powerful avenue for theoretical and experimental studies of nanocrystal catalysis.

  20. Synergistic Effects in Bimetallic Palladium-Copper Catalysts Improve Selectivity in Oxygenate Coupling Reactions.

    Science.gov (United States)

    Goulas, Konstantinos A; Sreekumar, Sanil; Song, Yuying; Kharidehal, Purnima; Gunbas, Gorkem; Dietrich, Paul J; Johnson, Gregory R; Wang, Y C; Grippo, Adam M; Grabow, Lars C; Gokhale, Amit A; Toste, F Dean

    2016-06-01

    Condensation reactions such as Guerbet and aldol are important since they allow for C-C bond formation and give higher molecular weight oxygenates. An initial study identified Pd-supported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO. PMID:27195582

  1. n-Dodecane Hydroconversion over Nickel Supported on Different Mesoporous Aluminosilicates

    Institute of Scientific and Technical Information of China (English)

    FANG, Ke-Gong(房克功); REN, Jie(任杰); SUN, Yu-Han(孙予罕)

    2004-01-01

    Several 2.0 wt% nickel catalysts supported on nanometer bimodal mesoporous aluminosilicate (NBMAS),AlHMS and AlMCM-41 were prepared by means of the wetness impregnation method. The characterization techniques such as Py-FTIR and H2 chemisorption showed that the amount of Bronsted acid sites decreased in the order of Ni/AlHMS>Ni/AlMCM-41 >Ni/NBMAS, while the nickel dispersion differed a little. In the catalytic n-dodecane hydroconversion, the highest conversion was obtained over Ni/NBMAS, and the lowest isomerization selectivity occurred over Ni/AlHMS. For the cracked products, the symmetrical carbon number distribution centered at C6 was obtained on the Ni/AlMCM-41 catalyst due to the well balanced metal/acid functions, whereas the Ni/AlHMS and Ni/NBMAS catalysts led to more C3-C5 and C1 +C11 products, respectively.

  2. A sensitive amperometric bromate sensor based on multi-walled carbon nanotubes/phosphomolybdic acid composite film

    International Nuclear Information System (INIS)

    An amperometric sensor for bromate was developed based on multi-walled carbon nanotubes (MWNTs)/phosphomolybdic acid (PMo12) composite film coated on a pyrolytic graphite (PG) electrode. MWNTs are dispersed in PMo12 aqueous solution through spontaneous and strong chemisorption between carbon and polyoxometalate, which results in a homogeneous MWNTs/PMo12 composite. Due to the unique electronic and electrocatalytic properties of MWNTs and PMo12, the combination of MWNTs and PMo12 results in a remarkable synergistic augmentation on the response current. The bromate sensor based on the PG/MWNTs/PMo12 electrode has excellent characteristics, such as a detection limit of 0.5 μM, a sensitivity of 760.9 μA mM-1 cm-2, a response time less than 2 s and a linear range from 5 μM to 15 mM

  3. PdZn catalysts prepared by washcoating microstructured reactors

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, P.; Schubert, K. [Forschungszentrum Karlsruhe GmbH, Institute for Micro Process Engineering, POB 3640, 76021 Karlsruhe (Germany); Liauw, M.A.; Emig, G. [University Erlangen-Nurnberg, LTC1, Egerlandstrasse 3, 91058 Erlangen (Germany)

    2004-08-30

    Methanol steam reforming is an option for dynamic hydrogen generation in automotive fuel cell systems. Microstructured reactors with small channels (100{mu}mx100{mu}m) are being studied. A washcoating procedure applying dispersed ZnO nanoparticles to the microchannel walls was adapted to the PdZn catalyst system. The catalyst layer showed no significant differences during X-ray diffraction and temperature-programmed oxidation and reduction experiments for examination of oxidation state and alloy formation compared with other PdZn systems reported in the literature. Chemisorption with different adsorbates and X-ray backscattering were used for gathering detailed information on PdZn dispersion, diameter and shape with respect to the preparation parameters. Catalytic experiments yielded a relationship between the catalyst properties and the catalytic activity, degradation and secondary reactions.

  4. Transformation of Heavy Metal Compounds during the Remediation of Contaminated Soils

    Directory of Open Access Journals (Sweden)

    Tatiana Minkina

    2011-03-01

    Full Text Available The effect of ameliorants, chalk, glauconite and semidecomposed cattle manure, on ordinary chernozem contaminated with Zn and Pb was studied in a long-term field experiment. The application of ameliorants significantly decreased the mobility of metals. Their effect depended on the ameliorant and was most significant at the simultaneous application of chalk and manure. This effect was presumably due to the strong binding of metals by carbonates through chemisorption and formation of lowsoluble Zn and Pb compounds and to the additional fixation in the form of complexes at the addition of organic material. The share of loosely bound metal compounds in the contaminated soils decreased to the level typical for the clean soils or even below. The general evolution of the transformation of metal compounds (from less to more firmly bound compounds accelerated by ameliorants remained for both metals.

  5. The inhibition effect and mechanism of L-cysteine on the corrosion of bronze covered with a CuCl patina

    International Nuclear Information System (INIS)

    Highlights: • CuCl patina was synthesized on bronze electrodes with electrochemical method. • L-cysteine was used as a green inhibitor for bronze covered with CuCl patina. • The inhibition efficiency reached above 90%. • The inhibition mechanism of L-cysteine on CuCl patina was investigated. - Abstract: CuCl patina was synthesized on bronze electrodes with electrochemical method. The inhibition effect and mechanism of L-cysteine (Cys) on bronze covered with CuCl patina have been studied with electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) techniques. The EIS results show that Cys stabilized the CuCl patina to a great extent. The hydrolysis reaction of CuCl was inhibited effectively and an inhibition efficiency of over 90% was achieved. The XPS analyses indicate that the chemisorption of Cys molecules on CuCl surface occurred through sulfur atom in thiol and nitrogen atom in amino group

  6. Electronic transport properties of BN sheet on adsorption of ammonia (NH3) gas.

    Science.gov (United States)

    Srivastava, Anurag; Bhat, Chetan; Jain, Sumit Kumar; Mishra, Pankaj Kumar; Brajpuriya, Ranjeet

    2015-03-01

    We report the detection of ammonia gas through electronic and transport properties analysis of boron nitride sheet. The density functional theory (DFT) based ab initio approach has been used to calculate the electronic and transport properties of BN sheet in presence of ammonia gas. Analysis confirms that the band gap of the sheet increases due to presence of ammonia. Out of different positions, the bridge site is the most favorable position for adsorption of ammonia and the mechanism of interaction falls between weak electrostatic interaction and chemisorption. On relaxation, change in the bond angles of the ammonia molecule in various configurations has been reported with the distance between NH3 and the sheet. An increase in the transmission of electrons has been observed on increasing the bias voltage and I-V relationship. This confirms that, the current increases on applying the bias when ammonia is introduced while a very small current flows for pure BN sheet.

  7. The orbital structure of {pi}-conjugated organic molecules on metal surfaces probed by angle-resolved photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Ziroff, Johannes; Wiessner, Michael; Forster, Frank; Schoell, Achim [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); Puschnig, Peter [University of Leoben, Chair of Atomistic Modelling and Design of Materials, A-8700 Leoben (Austria); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); FZ Karlsruhe, Gemeinschaftslabor fuer Nanoanalytik, D-76021 Karlsruhe (Germany)

    2010-07-01

    We present angle resolved photoemission spectra of monolayers of {pi}-conjugated molecules adsorbed on single-crystalline metal surfaces. Comparing the experimental k-dependant intensity distribution of the molecular states to DFT calculations for the free molecule allows to detect sophisticated modifications of the molecular orbitals at the interface. In case of the single-domain system PTCDA on Ag(110) the 2D emission pattern confirms that the now occupied interface state is mainly derived from the former LUMO-orbital. Moreover, a clear contribution of metal states is evident from additional intensity in normal emission. In the contrary, the structure of the molecular HOMO changes only slightly upon chemisorption on Ag surfaces. Additional data on other planar {pi}-conjugated organic molecules such as coronene or NTCDA demonstrates the potential of this approach in analysing the interaction at metal-organic interfaces in great detail.

  8. Structures and vibrational frequencies of CO adlayers on Rh(111) surface

    Institute of Scientific and Technical Information of China (English)

    XIAO; Haiyan(肖海燕); LAI; Wenzhen(赖文珍); XIE; Daiqian(谢代前); YAN; Guosen(鄢国森)

    2003-01-01

    Density functional theory calculations within the generalized gradient approximation (GGA) have been carried out to study the structural and vibrational properties of carbon monoxide adsorption on Rh(111) surface. The optimized geometries, adsorption energies and vibrational frequencies have been obtained and the preferred binding sites have been determined. The results show that at low coverage CO prefers to adsorb at top site and at high coverage one molecule occupies top site while the two other molecules occupy hcp and fcc hollow sites respectively. The investigation of the vibrational properties of CO chemisorption on Rh(111) shows that the top C-O stretching frequency increases along with the increase of the coverage. The site assignments, optimized geometries and calculated vibrational frequencies are found to be in good agreement with the experimental results.

  9. Electrochemical promotion of NO reduction by hydrogen on a platinum/polybenzimidazole catalyst

    DEFF Research Database (Denmark)

    Petrushina, Irina; Bandur, Viktor; Cappeln, Frederik Vilhelm;

    2003-01-01

    The electrochemical promotion of catalytic NO reduction by hydrogen was studied using a (NO, H-2, Ar), Pt polybenzimidazole (PBI)-H3PO4\\Pt, (H-2, Ar) fuel cell at 135degreesC. A mixture of NO/H-2/Ar was used as the working mixture at one electrode and a mixture of H-2/Ar was used as reference...... and 140 mL/min, respectively), NO reduction increased 20 times even without polarization compared to the high gas flow rate. The electrochemical promotion effect occurs at positive polarization with a maximum increase at approximately 0.08 V and with 1.5 times the zero polarization value. The promotion...... at the negative polarization can be attributed to the electrochemical production of the promoters. At low gas flow rates, a charge-induced change of the strength of chemisorptive bonds can take place....

  10. Corrosion Inhibitive Evaluation of an Environmentally Friendly Water-Base Acrylic Terpolymer on Mild Steel in Hydrochloric Acid Media

    Science.gov (United States)

    Azghandi, Mojtaba Vakili; Davoodi, Ali; Farzi, Gholam Ali; Kosari, Ali

    2013-12-01

    The corrosion inhibitive performance of an environmentally friendly water-base acrylic terpolymer [methyl methacrylate/Butyl Acrylate/Acrylic acid (ATP)] on mild steel in 1 M HCl was investigated by alternating current and direct current electrochemical techniques and the quantum chemical method. An efficiency of more than 97 pct was obtained with 0.8 mmol/L ATP. The increase in inhibitor concentration and immersion time has a positive effect, while the temperature influence is negligible on the inhibitor efficiency. The present terpolymer obeys the Langmuir isotherm, and thermodynamic calculation reveals a chemisorption type on the surface. Density functional calculations showed that the lone pairs of electrons of oxygen in the structure of three monomers are suitable sites to adsorb onto the metal surface. Finally, in the presence of ATP, a decrease in surface roughness and corrosion attacks was demonstrated by atomic force microscopy and optical microscopy examinations, respectively.

  11. Corrosion Inhibition Performance of Triazole Derivatives on Copper-Nickel Alloy in 3.5 wt.% NaCl Solution

    Science.gov (United States)

    Jiang, B.; Jiang, S. L.; Liu, X.; Ma, A. L.; Zheng, Y. G.

    2015-12-01

    This study investigates the performance of three triazole derivatives with different molecular structures as corrosion inhibitors for the copper-nickel alloy CuNi 90/10 in 3.5 wt.% NaCl solution. Inhibition behavior was systematically determined through electrochemical measurements, scanning electron microscopy, energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy. In addition, adsorption behavior and the inhibition mechanism were investigated via quantum chemical calculation and molecular dynamic simulation. Experimental results indicate that the three inhibitors with triazole rings and heteroatoms exhibited excellent corrosion inhibition capabilities on the copper-nickel alloy surface through physisorption and chemisorption. In particular, 3-amino-5-mercapto-1,2,4-triazole showed the best inhibition capability according to the concentration ranges considered in the experiments. The results of quantum chemical calculation agreed with the experimental findings.

  12. Dissociation of acetaldehyde on beta-Mo2C to yield ethylidene and oxo surface groups: a possible pathway for active site formation in heterogeneous olefin metathesis.

    Science.gov (United States)

    Siaj, Mohamed; Reed, Corey; Oyama, S Ted; Scott, Susannah L; McBreen, Peter H

    2004-08-11

    The dissociative adsorption of acetaldehyde on beta-Mo2C was studied using reflection absorption infrared spectroscopy. In contrast to what is observed for all metals previously studied, acetaldehyde undergoes selective carbonyl bond scission on the carbide surface. By comparison to calculated spectra, the surface product is identified as an oxo-ethylidene species. The study thus provides the first extended-range infrared spectrum of a propene metathesis initiator or propagator alkylidene. Aldehydes may be formed in the presence of olefins during the induction period of supported metal oxide olefin metathesis catalysts. Hence, the observed dissociative chemisorption of acetaldehyde suggests a possible answer to the question of how initiator sites are formed in heterogeneous olefin metathesis. This question has never been satisfactorily answered. In the proposed mechanism, aldehydes formed during the induction period subsequently react with the catalyst surface to generate alkylidene sites.

  13. Molybdenum carbide catalysed hydrogen production from formic acid - A density functional theory study

    Science.gov (United States)

    Luo, Qiquan; Wang, Tao; Walther, Guido; Beller, Matthias; Jiao, Haijun

    2014-01-01

    Density functional theory computations have been employed to investigate the decomposition of formic acid (HCO2H) into CO2 and hydrogen on the β-Mo2C(101) surface. The adsorption configurations and energies of the surface intermediates (HCO2H, CO2, CO, H2O, HCO2, CO2H, CHO, OH, O and H) have been systematically characterized. Among the different dissociation steps considered, our results showed the formate route (HCO2H → H + HCO2; HCO2 → H + CO2) is the minimum energy path for hydrogen formation and CO2 has very strong chemisorption. The adsorption and dissociation of formic acid on the Mo2C(101) surface have been compared with those of Pt group metals.

  14. The Effect of Nb Loading on Catalytic Properties of Ni/Ce0.75Zr0.25O2 Catalyst for Methane Partial Oxidation

    Institute of Scientific and Technical Information of China (English)

    Sitthiphong Pengpanich; Vissanu Meeyoo; Thirasak Rirksomboon; Johannes Schwank

    2007-01-01

    In this study,the effect of Nb loading on the catalytic activity of Ce0.75Zr0.25O2-supported Ni catalysts was studied for methane partial oxidation.The catalysts were characterized by BET,H2 chemisorption,XRD,TPR,TEM and tested for methane partial oxidation to syngas in the temperature range of 400-800 ℃ at atmospheric pressure.The results showed that the activity of methane partial oxidation on the catalysts was apparently dependent on Nb loading.It seemed that the addition of Nb lowered the catalytic activity for methane partial oxidation and increased the extent of carbon deposition.This might be due to the strong interaction between NiO and Nb-modified support and reduction of surfaceoxygen reducibility.

  15. AMMONIA AND COD REMOVAL FROM SYNTHETIC LEACHATE USING RICE HUSK COMPOSITE ADSORBENT

    Directory of Open Access Journals (Sweden)

    Azhar Abdul Halim

    2011-06-01

    Full Text Available Ammonia and chemical oxygen demand (COD were the most two problematic parameters in the landfill leachate. In this study, a new composite adsorbent derived from rice husk ash waste is evaluated with respect to its ability to remove these contaminants from synthetic leachate. Results indicate that the new composite adsorbent is able to adsorb both ammonia and COD. It has a higher adsorption capacity for ammonia (Q = 2.2578 mg/g and an almost equal adsorption capacity for COD (Q = 2.8893 when compared with commercially activated carbon. The adsorption kinetics of this new product for ammonia and COD were primarily represented by the pseudo second-order mechanism. The overall adsorption rate of the ammonia and COD adsorption processes appears to be determined by chemisorption process. The regenerated composite adsorbent indicated higher adsorption capacities of ammonia and COD, i.e. 12.9366 mg/g and 3.1162 mg/g, respectively.

  16. Electronic and energetic properties of FeCl{sub 3} and CrO{sub 3} interacting with single wall BN nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Serejo, J.A.S.; Guerini, S., E-mail: silvete.guerini@ufma.br

    2015-09-15

    Highlights: • The interaction between the BNNT and molecules occurs through chemical process. • The FeCl{sub 3} and CrO{sub 3} molecules are predicted to behave as an electron acceptor. • The binding energy is high, suggesting that the interaction is quite stable. - Abstract: Structural, electronic and energetic properties of FeCl{sub 3} and CrO{sub 3} interacting with (10,0) BN nanotube were obtained using ab initio calculation based on the density functional theory. It was found that the FeCl{sub 3} and CrO{sub 3} molecules behave as an electron acceptor in the presence of the BNNT in all the configurations studied. In a more stable configuration, the binding energy is much stronger, suggesting that the interaction is through a chemisorption regime.

  17. Consolidation of tin sulfide chalcogels and xerogels with and without adsorbed iodine

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J.; Pierce, David A.; Lepry, William C.; Kroll, Jared O.; Chun, Jaehun; Subrahmanyam, Kota S.; Kanatzidis, Mercouri G.; Alblouwy, Fares K.; Bulbule, Aneeruddha; Sabolsky, Edward

    2015-11-18

    Tin sulfide (Sn2S3) chalcogels are one of the most effective non-oxide aerogels evaluated to date for iodine gas capture. This is attributed to the fact that the Sn within the gel network has a strong affinity for chemisorption of iodine to form SnI4. This study demonstrates an approach for consolidating the raw and iodine-sorbed Sn2S3 chalcogels into a chalcogenide glass using GeS2 as a glass forming additive. The system with both iodine-sorbed and iodine-free Sn2S3 chalcogels provides better glass-forming characteristics than Sn-S or Sn-S-I alone, and the quantity of iodine measured in the bulk glass of the consolidated iodine-sorbed Sn2S3 chalcogel was at ~45 mass%. Additional experiments were also conducted using microwave sintering and hot isostatic pressing with Sn2S3 xerogels.

  18. Ultrasonic Extraction and TLC Determination of Glyphosate in the Spiked Red Soils

    Directory of Open Access Journals (Sweden)

    Sandra Babić

    2005-09-01

    Full Text Available Pesticides that get into soil bind mostly to its solid phase by physical or chemical processes. In the valley of the Neretva River the use of herbicides, especially of glyphosate is widespread and sometimes uncontrolled. In this work ultrasonic solvent extraction (USE followed by thin-layer chromatography (TLC was applied for determining glyphosate presence in soil. The experiments were conducted with two characterised soil types. The impact of soil composition on extraction efficiency is discussed. Chemical analysis showed that soil 1 contained much more iron and aluminium oxides than soil 2, which was richer in humic substances. Low glyphosate efficiency (ca 44 % in both soils could be attributed either to its binding to iron and aluminium oxides (soil 1, or to chemisorption on humic macromolecules (soil 2.

  19. Field-Assisted and Thermionic Contributions to Conductance in SnO Thick-Films

    Directory of Open Access Journals (Sweden)

    C. Malagù

    2009-01-01

    Full Text Available A deep analysis of conductance in nanostructured SnO2 thick films has been performed. A model for field-assisted thermionic barrier crossing is being proposed to explain the film conductivity. The model has been applied to explain the behavior of resistance in vacuum of two sets of nanostructured thick-films with grains having two well-distinct characteristic radii (=25 nm and =125 nm. In the first case the grain radius is shorter than the depletion region width, a limit at which overlapping of barriers takes place, and in the second case it is longer. The behavior of resistance in the presence of dry air has been explained through the mechanism of barrier modulation through gas chemisorption.

  20. Preparation of Palladium-Supported Periodic Mesoporous Organosilicas and their Use as Catalysts in the Suzuki Cross-Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Francisco J. Romero-Salguero

    2013-04-01

    Full Text Available Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt% were prepared by the incipient wetness method and subsequently reduced in an H2 stream at 200 °C. Both hydrogen chemisorption and temperature programmed reduction experiments revealed significant differences depending on the support. Pd2+ species were more reducible on the mesoporous organosilicas than on their silica counterpart. Also, remarkable differences on the particle morphology were observed by transmission electron microscopy. All Pd-supported samples were active in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic acid.

  1. A study of sulfonamides (used as corrosion inhibitor for the possibility to adsorption on steel

    Directory of Open Access Journals (Sweden)

    Andrei Sikachina

    2016-05-01

    Full Text Available The published work presents modeled using quantum chemistry package HyperChem version 8.0.7 using semiempirical method ZINDO/1 the adsorption process of organic compounds of the class of sulfonamides, such as iron (available in steel St3S in the amount of 97%. This approach, as will be shown, with high accuracy reflects the process of corrosion protection, with bacterial content by means of chemisorption of organic compounds on the metal surface with the formation of complex compounds. In the research process were obtained and analyzed: the composition of the complexes, a graph showing the dependence of the charge density per atom of iron, from corrosion rates.

  2. Influence of Rare Earth Doping on the Structural and Catalytic Properties of Nanostructured Tin Oxide

    Directory of Open Access Journals (Sweden)

    Maciel Adeilton

    2008-01-01

    Full Text Available AbstractNanoparticles of tin oxide, doped with Ce and Y, were prepared using the polymeric precursor method. The structural variations of the tin oxide nanoparticles were characterized by means of nitrogen physisorption, carbon dioxide chemisorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The synthesized samples, undoped and doped with the rare earths, were used to promote the ethanol steam reforming reaction. The SnO2-based nanoparticles were shown to be active catalysts for the ethanol steam reforming. The surface properties, such as surface area, basicity/base strength distribution, and catalytic activity/selectivity, were influenced by the rare earth doping of SnO2and also by the annealing temperatures. Doping led to chemical and micro-structural variations at the surface of the SnO2particles. Changes in the catalytic properties of the samples, such as selectivity toward ethylene, may be ascribed to different dopings and annealing temperatures.

  3. Thin film nanophase and nanocomposite fluorine-containing wear inhibitors

    Directory of Open Access Journals (Sweden)

    Yauheni Auchynnikau

    2015-12-01

    Full Text Available The paper examines features of the morphology and structure of thin films based on fluorine-containing oligomers modified by nanoparticles of different composition and obtaining technology. A classification of nanophase and nanocomposite thin film coatings is proposed. The oligomeric fluorine-containing components by using mortar technology develop thin-film coatings, comprising a quasi-crystalline nanophases in oligomeric matrix with high chemisorption activity to a metal substrate. Modifying of the oligomeric matrix by active components with uncompensated charge leads to the formation of ordered areas at the interface “low-dimensional filler-matrix”. In composites, containing synthetic polytetrafluoroethylene thermogas dynamic products, synergistic effect is realized due to thermodynamic compatibility of oligomeric polar and nonpolar components and high-molecular particles with uncompensated charge. This ensures the formation of coating with improved adhesion, deformation strength and tribological characteristics parameters.

  4. Experimental and quantum chemical characterization of the adsorption of some Schiff base compounds of phthaloyl thiocarbohydrazide on the mild steel in acid solutions

    International Nuclear Information System (INIS)

    Three derivatives of 2-[2-(hydrazinecarbonothioyl)hydrazinecarbonyl]benzoic acid (IL1) have been evaluated as new corrosion inhibitors for the corrosion of mild steel in 1 M HCl solutions using weight loss, polarization and electrochemical impedance spectroscopy (EIS) techniques. The adsorption of these compounds has been tested thermodynamically which was found to be of neither a typical physisorption nor a typical chemisorption mode. The thermodynamic functions (such as Ea, ΔHoads, ΔSoads and ΔGoads) of dissolution and adsorption processes have been evaluated. The polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the compounds was found to obey Langmuir's adsorption isotherm. In addition, quantum chemical calculations have been made to correlate inhibition efficiencies determined experimentally.

  5. Low metal loading catalysts used for the selective hydrogenation of styrene

    Energy Technology Data Exchange (ETDEWEB)

    Badano, Juan; Lederhos, Cecilia; Quiroga, Monica; L' Argentiere, Pablo [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Santa Fe (Argentina). Universidad Nacional del Litoral. Inst. de Investigaciones en Catalisis y Petroquimica; Coloma-Pascual, Fernando [Universidad de Alicante (Spain). Facultad de Ciencias. Servicios Tecnicos de Investigacion

    2010-07-01

    A series of Group VIII metal catalysts was obtained for the semi-hydrogenation of styrene. Catalysts were characterized by Hydrogen Chemisorption, TPR and XPS. Palladium, rhodium and platinum low metal loading prepared catalysts presented high activity and selectivity (ca. 98%) during the semi-hydrogenation of styrene, being palladium the most active catalyst. The ruthenium catalyst also presented high selectivity (ca. 98%), but the lowest activity. For the palladium catalyst, the influence of the precursor salt and of the reduction temperature on the activity and selectivity were studied. The following activity series was obtained: PdN-423 > PdCl-673 > PdCl-373> PtCl-673 > RhCl-673 >> RuCl-673. As determined by XPS, differences in activity could be attributed, at least in part, to electronic effects (author)

  6. Spatial, Hysteretic, and Adaptive Host-Guest Chemistry in a Metal-Organic Framework with Open Watson-Crick Sites.

    Science.gov (United States)

    Cai, Hong; Li, Mian; Lin, Xiao-Rong; Chen, Wei; Chen, Guang-Hui; Huang, Xiao-Chun; Li, Dan

    2015-09-01

    Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site-specific recognition takes advantage of cooperative spatial effects, as in local folding in protein-DNA binding. Herein, we report a new nucleobase-tagged metal-organic framework (MOF), namely ZnBTCA (BTC=benzene-1,3,5-tricarboxyl, A=adenine), in which the exposed Watson-Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson-Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host-guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine-thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed.

  7. Formation, phase composition, texture and catalytic properties of Co-MgO-alumino-calcium catalysts in synthesis of hydrocarbons from CO and H/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Lapidus, A.L.; Bruk, I.A.; Mal' tsev, V.V.; Iem, K.C.; Yakerson, V.I.; Golosman, Y.Z.; Mamayeva, I.A.; Kalacheva, N.B.; Danyushevskii, V.Y.; Nissenbaum, V.D.

    1981-01-01

    A study was made of the mechanism of formation of catalysts; a special feature of this mechanism is the interaction of components (calcium aluminates and basic carbonates of cobalt and magnesium); the carrier with a developed surface and the active component distributed on this surface are formed during this process. Catalysts show maximum selectivity in synthesis of liquid hydrocarbons from CO and H/sub 2/ with a degree of reduction of the metal of 65-84% and a dispersion (according to chemisorption of CO) of 6 x 10/sup -3/ - 10 x 10/sup -3/. Maximum yield of liquid hydrocarbons (114.1 g/nm/sup 3/) was obtained in the pressure of a system of 33Co-3MgO-64 talum treated with hydrogen at 550/sup 0/C.

  8. Transport Properties of Amine/Carbon Dioxide Reactive Mixtures and Implications to Carbon Capture Technologies.

    Science.gov (United States)

    Turgman-Cohen, Salomon; Giannelis, Emmanuel P; Escobedo, Fernando A

    2015-08-19

    The structure and transport properties of physisorbed and chemisorbed CO2 in model polyamine liquids (hexamethylenediamine and diethylenetriamine) are studied via molecular dynamics simulations. Such systems are relevant to CO2 absorption processes where nonaqueous amines are used as absorbents (e.g., when impregnated or grafted onto mesoporous media or misted in the gas phase). It is shown that accounting for the ionic speciation resulting from CO2 chemisorption enabled us to capture the qualitative changes in extent of absorption and fluidity with time that are observed in thermogravimetric experiments. Simulations reveal that high enough concentration of reacted CO2 leads to strong intermolecular ionic interactions and the arrest of molecular translations. The transport properties obtained from the simulations of the ionic speciated mixtures are also used to construct an approximate continuum-level model for the CO2 absorption process that mimics thermogravimetric experiments.

  9. Reversible CO2 Capture by Conjugated Ionic Liquids through Dynamic Covalent Carbon-Oxygen Bonds.

    Science.gov (United States)

    Pan, Mingguang; Cao, Ningning; Lin, Wenjun; Luo, Xiaoyan; Chen, Kaihong; Che, Siying; Li, Haoran; Wang, Congmin

    2016-09-01

    The strong chemisorption of CO2 is always accompanied by a high absorption enthalpy, and traditional methods to reduce the absorption enthalpy lead to decreased CO2 capacities. Through the introduction of a large π-conjugated structure into the anion, a dual-tuning approach for the improvement of CO2 capture by anion-functionalized ionic liquids (ILs) resulted in a high capacity of up to 0.96 molCO2  mol-1IL and excellent reversibility. The increased capacity and improved desorption were supported by quantum chemical calculations, spectroscopic investigations, and thermogravimetric analysis. The increased capacity may be a result of the strengthened dynamic covalent bonds in these π-electron-conjugated structures through anion aggregation upon the uptake of CO2 , and the improved desorption originates from the charge dispersion of interaction sites through the large π-electron delocalization. These results provide important insights into effective strategies for CO2 capture.

  10. Ambient carbon dioxide capture by different dimensional AlN nanostructures: A comparative DFT study

    Science.gov (United States)

    Esrafili, Mehdi D.; Nurazar, Roghaye; Nematollahi, Parisa

    2016-08-01

    Strong binding of an isolated carbon dioxide molecule over three different aluminium nitride (AlN) nanostructures (nanocage, nanotube and nanosheet) is verified using density functional calculations. Equilibrium geometries, electronic properties, adsorption energies and thermodynamic stability of each adsorbed configuration are also identified. Optimized configurations are shown at least one corresponding physisorption and chemisorption of CO2 molecule over different AlN nanostructures. Also, the effect of chirality on the adsorption of CO2 molecule is studied over two different finite-sized zigzag (6,0) and armchair (4,4) AlN nanotubes. It is found that the electronic properties of the Al12N12 nanocage are more sensitive to the CO2 molecule than other AlN nanostructures. This indicates the significant potential of Al12N12 nanocage toward the CO2 adsorption, fixation and catalytic applications in contrast to other AlN nanostructures.

  11. Kinetics and Mechanism of Adsorption of Phosphate on Fluorine-containing Calcium Silicate

    Institute of Scientific and Technical Information of China (English)

    ZHU Xinhua; ZHANG Zhao; SHEN Jun

    2016-01-01

    The nanowires-reticulated calcium silicate with a speciifc surface area more than 100 m2/g was prepared by a hydrothermal process using hydrated lime (Ca(OH)2, HL) and silica containing soluble lfuoride, which was a by-product of lfuorine industry, and the soluble lfuoride in raw silica was ifxed as CaSiF6 at the same time. The kinetic characteristics and mechanism of adsorbing phosphate by lfuorine-containing calcium silicate were investigated in the experiments of phosphorus (P) removal from aqueous solution. The results show that the prepared lfuorine-containing calcium silicate has excellent performance for adsorbing phosphate, the adsorption process appears to follow pseudo-second-order reaction kinetics and the process is mainly controlled by chemisorption. The product resulted from P adsorption is mainly composed of hydroxyapatite (HAP) and lfuorapatite (FAP), which are further used as adsorbents of heavy metal ion Cd2+ in aqueous solution and display excellent performance.

  12. ADSORPTION OF 4-METHYLANILINE IN AQUEOUS SOLUTION BY BENZOYL- CONTAINING POLYMERIC ADSORBENTS

    Institute of Scientific and Technical Information of China (English)

    Gen-cheng Zhang; Hai-suo Wu; Zheng-hao Fei

    2005-01-01

    New polymeric adsorbents (ZH-02, ZH-03) containing benzoyl group for adsorbing and removing 4-methylaniline from its aqueous solutions were prepared. Studies on the isotherms and the comparison of desorption conditions evidenced through the adsorption of 4-methylaniline in water onto ZH-02 and ZH-03, namely that there are chemisorption's transitions at a proper higher temperature. Mini-column adsorption studies of 4-methylaniline on XAD-4, ZH-02 and ZH-03 at 288 K show that the breakthrough capacities are 2.39, 2.99 and 3.19 mmol/g and the total capacities are 3.45, 3.92 and 4.35 mmol/g, respectively.

  13. Development and application of a quasi-continuously working system for measuring the immission of acid air pollutants like HCl, NO2 and SO2 using an absorber tube

    International Nuclear Information System (INIS)

    Main objective of this study during the report time is found to be the testing of different absorption materials for the simultaneous determination of acid gaseous pollutants like HCl, NO2 and SO2. These materials - so-called active collectors - were examined in laboratory-scale experiments using gas mixtures with various concentrations of the pollutants which should be chemisorbed by the active collectors. After eluation of the active collector and ion chromatographical analysis of the solutions informations about the absorption/desorption rate are obtained. In most cases adsorption were tested on which amino-functional groups are deposited by chemical reaction. The amino-groups act as reactive sites for the chemisorption of the acid gases. It can be observed that all tested materials are suitable for the measurement of HCl and SO2. Additionally some types of absorption materials are effective for the simultaneous absorption of HCl, SO2 and NO2. (orig.). 25 figs., 21 tabs., 66 refs

  14. Nitrogen-Doped Carbon Nanotube/Graphite Felts as Advanced Electrode Materials for Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Wang, Shuangyin; Zhao, Xinsheng; Cochell, Thomas; Manthiram, Arumugam

    2012-08-16

    Nitrogen-doped carbon nanotubes have been grown, for the first time, on graphite felt (N-CNT/GF) by a chemical vapor deposition approach and examined as an advanced electrode for vanadium redox flow batteries (VRFBs). The unique porous structure and nitrogen doping of N-CNT/GF with increased surface area enhances the battery performance significantly. The enriched porous structure of N-CNTs on graphite felt could potentially facilitate the diffusion of electrolyte, while the N-doping could significantly contribute to the enhanced electrode performance. Specifically, the N-doping (i) modifies the electronic properties of CNT and thereby alters the chemisorption characteristics of the vanadium ions, (ii) generates defect sites that are electrochemically more active, (iii) increases the oxygen species on CNT surface, which is a key factor influencing the VRFB performance, and (iv) makes the N-CNT electrochemically more accessible than the CNT. PMID:26295765

  15. Friction imprint effect in mechanically cleaved BaTiO{sub 3} (001)

    Energy Technology Data Exchange (ETDEWEB)

    Long, Christian J. [Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899 (United States); Maryland Nanocenter, University of Maryland, College Park, Maryland 20742 (United States); Ebeling, Daniel [Institute of Applied Physics, Justus Liebig University of Giessen, 35392 Giessen (Germany); Solares, Santiago D. [Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052 (United States); Cannara, Rachel J., E-mail: rcannara@intven.com [Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899 (United States)

    2014-09-28

    Adsorption, chemisorption, and reconstruction at the surfaces of ferroelectric materials can all contribute toward the pinning of ferroelectric polarization, which is called the electrical imprint effect. Here, we show that the opposite is also true: freshly cleaved, atomically flat surfaces of (001) oriented BaTiO{sub 3} exhibit a persistent change in surface chemistry that is driven by ferroelectric polarization. This surface modification is explored using lateral force microscopy (LFM), while the ferroelectric polarization is probed using piezoresponse force microscopy. We find that immediately after cleaving BaTiO{sub 3}, LFM reveals friction contrast between ferroelectric domains. We also find that this surface modification remains after the ferroelectric domain distribution is modified, resulting in an imprint of the original ferroelectric domain distribution on the sample surface. This friction imprint effect has implications for surface patterning as well as ferroelectric device operation and failure.

  16. Two stage sorption type cryogenic refrigerator including heat regeneration system

    Science.gov (United States)

    Jones, Jack A.; Wen, Liang-Chi; Bard, Steven

    1989-01-01

    A lower stage chemisorption refrigeration system physically and functionally coupled to an upper stage physical adsorption refrigeration system is disclosed. Waste heat generated by the lower stage cycle is regenerated to fuel the upper stage cycle thereby greatly improving the energy efficiency of a two-stage sorption refrigerator. The two stages are joined by disposing a first pressurization chamber providing a high pressure flow of a first refrigerant for the lower stage refrigeration cycle within a second pressurization chamber providing a high pressure flow of a second refrigerant for the upper stage refrigeration cycle. The first pressurization chamber is separated from the second pressurization chamber by a gas-gap thermal switch which at times is filled with a thermoconductive fluid to allow conduction of heat from the first pressurization chamber to the second pressurization chamber.

  17. Two-statge sorption type cryogenic refrigerator including heat regeneration system

    Science.gov (United States)

    Jones, Jack A. (Inventor); Wen, Liang-Chi (Inventor); Bard, Steven (Inventor)

    1989-01-01

    A lower stage chemisorption refrigeration system physically and functionally coupled to an upper stage physical adsorption refrigeration system. Waste heat generated by the lower stage cycle is regenerated to fuel the upper stage cycle thereby greatly improving the energy efficiency of a two-stage sorption refrigerator. The two stages are joined by disposing a first pressurization chamber providing a high pressure flow of a first refrigerant for the lower stage refrigeration cycle within a second pressurization chamber providing a high pressure flow of a second refrigerant for the upper stage refrigeration cycle. The first pressurization chamber is separated from the second pressurization chamber by a gas-gap thermal switch which at times is filled with a thermoconductive fluid to allow conduction of heat from the first pressurization chamber to the second pressurization chamber.

  18. Activation and micropore structure of carbon-fiber composites

    Energy Technology Data Exchange (ETDEWEB)

    Jagtoyen, M.; Derbyshire, F.; Kimber, G. [Univ. of Kentucky, Lexington, KY (United States). Center for Applied Energy Research

    1997-12-01

    Rigid, high surface area activated carbon fiber composites have been produced with high permeabilities for environmental applications in gas and water purification. The project involves a collaboration between the Oak Ridge National Laboratory (ORNL) and the Center for Applied Energy Research (CAER), University of Kentucky. The main focus of recent work has been to find a satisfactory means to uniformly activate large samples of carbon fiber composites to produce controlled pore structures. Processes have been developed using activation in steam and CO{sub 2}, and a less conventional method involving oxygen chemisorption and subsequent heat treatment. Another objective has been to explore applications for the activated composites in environmental applications related to fossil energy production.

  19. Development of nanostars as a biocompatible tumor contrast agent: toward in vivo SERS imaging

    Science.gov (United States)

    D’Hollander, Antoine; Mathieu, Evelien; Jans, Hilde; Vande Velde, Greetje; Stakenborg, Tim; Van Dorpe, Pol; Himmelreich, Uwe; Lagae, Liesbet

    2016-01-01

    The need for sensitive imaging techniques to detect tumor cells is an important issue in cancer diagnosis and therapy. Surface-enhanced Raman scattering (SERS), realized by chemisorption of compounds suitable for Raman spectroscopy onto gold nanoparticles, is a new method for detecting a tumor. As a proof of concept, we studied the use of biocompatible gold nanostars as sensitive SERS contrast agents targeting an ovarian cancer cell line (SKOV3). Due to a high intracellular uptake of gold nanostars after 6 hours of exposure, they could be detected and located with SERS. Using these nanostars for passive targeting after systemic injection in a xenograft mouse model, a detectable signal was measured in the tumor and liver in vivo. These signals were confirmed by ex vivo SERS measurements and darkfield microscopy. In this study, we established SERS nanostars as a highly sensitive contrast agent for tumor detection, which opens the potential for their use as a theranostic agent against cancer. PMID:27536107

  20. Adsorption of Anionic Dyes onto Chitosan-modified Diatomite

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ge-shan; XUE Hong-hai; TANG Xiao-jian; PENG Fei; KANG Chun-li

    2011-01-01

    The purpose of this work is to study the possibility of anionic dyes Reactive Red M-8B(RR)and Direct Green B(DG)adsorbed on chitosan-modified diatomite.The characteristics of adsorbent,adsorption isotherms and the influence of adsorption time,temperature and pH were researched in this work.The results show that the modified diatomite had a much better adsorption capability than the natural diatomite.The adsorption capacities of chitosan-modified diatomite for RR and DG were 94.46 and 137.0 mg/g,respectively.Both adsorption time and adsorption temperature provided a positive effect on the dye adsorption.Within the experimental pH range,the adsorbance was enhanced at lower pH but reduced sharply at high pH.On the basis of the experimental results and discussion,electrostatic attraction is considered as the main mechanism of this chemisorption.