Understanding the effects of cluster restructuring on water gas shift reaction over Cu/TM (TM = Cu, Ni and Pt) under high concentration of CO

Abstract

Ambient pressure and resulting cluster restructuring have been proved to influence water gas shift reaction (WGSR), but the intrinsic role that high concentration of CO and cluster surface play during WGSR is still elusive. In this work, the rationale behind the dual effects of CO concentration and cluster condensation on WGSR over Cu-based bimetallic alloys is theoretically revealed using density functional theory (DFT) approach. The results demonstrate that the additional adsorption of CO molecules inhibits WGSR thermodynamically and kinetically. Specifically, the increase of concentration weakens the molecule adsorption (CO and water-related molecules) and hinders the development of intermediate evolutions in WGSR, while the cluster restructuring simultaneously raises the activation energy of water dissociation. The charge density difference and Bader distribution provide electronic support for the above conclusions. Furthermore, Cu/Ni is considered as the preferential catalyst under high concentration of CO, not only because of the remarkable adsorption capacity, but also the fine structure-catalytic stability. The selection of cluster shape and energy-temperature characteristics of intermediates are also introduced, enriching the understanding of group reactivity on copper based catalysts.