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Hydrogen Adsorption and Sulfur Binding on Pd, Cu, Au and Their Alloys by Density Functional Theory

Author: HuangYongLi
Tutor: LiuZhiPing
School: Beijing University of Chemical Technology
Course: Chemical Engineering
Keywords: Density functional theory Adsorption on the surface of the metal A hydrogen atom A sulfur atom Palladium alloy membrane Resistance to sulfur toxicity
CLC: O647.3
Type: Master's thesis
Year: 2008
Downloads: 186
Quote: 0
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Abstract


Palladium alloy film not only has a high hydrogen permeation rate of hydrogen permeation selectivity , but also has good chemical and thermal stability concern in the membrane reactor , hydrogen separation and purification . Since hydrogen is an important intermediate in many catalytic reactions , sulfur is a common reaction of the film poisoning loss of activity of impurity gases , hydrogen and sulfur atoms and thus to study the adsorption properties of palladium and its alloys , for the understanding of the mechanism of surface reactions , analysis adsorbed nature has important theoretical significance and potential applications . In this paper, density functional theory of atoms adsorbed on the metal surface in the field of surface science , mainly includes two parts: the hydrogen atoms in the Pd , Cu , Au ( 111 ) alloy surface adsorption ; sulfur atoms in the Pd , Cu Au ( 111 ) and its alloy surface adsorption . The systematic study of hydrogen and sulfur atoms in the metal Pd , Au , Cu alloy PDM 3 < / sub > , the PD 2 < / sub > M 2 and Pd < Sub > 3 < / sub > M ( 111 ) adsorption ( M = Au , Cu ) coverage of 0.25 the most stable adsorption sites , binding energy , as well as before and after adsorption surface relaxation . Hydrogen and sulfur are the most stable adsorption and Pd , Cu , followed by Au adsorption weakest in three pure metal (111) surface , the most stable adsorption sites are fcc bit . Pd - Au alloy having a larger lattice constant the Pd 3 < / sub > the Au alloy Hydrogen binding can be even greater than the pure Pd , in addition , hydrogen and sulfur on the surface of the Pd - M alloy adsorption are reduced with the increase of the M component , while the most stable adsorption varies with the metal species and the change in the composition . Adsorption according to the calculated binding energy , it is found that compared with the Pd-Cu alloy , Pd - Au alloy , the Au content is low (<0.25mol/mol) , hydrogen , and sulfur adsorption binding energy decreases slowly , while the Au content is more when high ( > 0.5mol/mol ) , the value decreased rapidly, and this indicates that the gold content of 0.25 ~ 0.5mol/mol Pd - Au alloy may remain similar for hydrogen permeation performance than the Pd-Cu alloy having a better resistance to sulfur toxicity.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > The physical chemistry of surface phenomena > Adsorption
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