Activity of faujasite supported gold monomer towards water gas shift reaction: hybrid density functional theory/molecular mechanics approach

Abstract

The activity of faujasite supported neutral and cationic gold monomer towards water gas shift reaction has been investigated with the hybrid density functional method. Our calculations indicate that CO adsorption on Auⁿ/FAU (n = 0, +1 and +3) in the presence of pre-adsorbed H₂O presents a favorable configuration for studying the water gas shift reaction. Occurrence of high barrier in dissociation of water and the endothermicity of the overall reaction observed in the cationic systems will diminish their activity towards water–gas shift reaction. The rate limiting step in Au⁺/FAU is the formation of a carboxyl intermediate. On the other hand, comparatively lower barriers and exothermicity of the reaction in Au⁰/FAU indicates it to be a better catalyst. The stability of all the species including the transition states with respect to the interacting species indicates no thermal activation in faujasite supported neutral Au monomer.