A comparison of water–gas shift reaction on ZnO 101¯0 surface and 6Cu cluster deposited over ZnO 101¯0 surface using density functional theory studies

This work has presented a calculated study of the water–gas shift reaction (WGSR) performing on the models of ZnO 10 1 ¯ 0 only and six-atomic copper cluster deposited on the ZnO surfaces (6Cu/ZnO) using density functional theory (DFT). The most stable configurations of ZnO and 6Cu/ZnO surfaces were found and used for the mechanism calculations of WGSR. The carboxyl mechanism of WGSR was proposed to find the reaction pathway. Based on this pathway, WGSR occurred at the elementary reaction of COOH intermediate formation as the rate-controlling step on 6Cu/ZnO surface, and the elementary reaction of H–H association as the rate-controlling step on ZnO surface, in which the highest activation energies were calculated as 1.05 eV and 1.56 eV for 6Cu/ZnO and ZnO surfaces, respectively. These calculations indicated that the 6Cu/ZnO was more favorable and more effective than ZnO as a catalyst for WGSR. In addition, the nature of bonds of CO and H 2 O adsorption on ZnO and 6Cu/ZnO surfaces was also analyzed using the local density of states (LDOS) and electron density difference (EDD) methods. Graphical abstract