CeOx/TiO₂-Supported Copper Cluster for the Water–Gas Shift Reaction: Active Site Identification Based on MF-MKM Modeling

The composite support strategy is of great significance in regulating the reaction performance of catalysts. In this paper, the water–gas shift reaction catalyzed by copper clusters supported on the TiO2 and CeOx–TiO2 mixed support was studied comparatively. The introduction of a Ce2Ox overlayer increases the adsorption energy of oxygen-containing species due to the conversion of adsorption sites from metals to the Cu8–CeOx interface. It is more advantageous to react on copper clusters on the Cu/TiO2 surface, mainly through the redox mechanism. The reaction on the Cu/CeOx–TiO2 surface is more advantageous at the Cu8–CeOx interface, also through the redox mechanism. Microkinetic analysis shows that the addition of the CeOx support significantly enhances the performance of the water–gas shift reaction. The reason for the high activity of the Cu/CeOx–TiO2 catalyst is that the rate-determining step changes from H2O dissociation to OH dissociation. Fundamentally, the Ce site on the Cu8/CeOx interface activates H2O and promotes the decomposition of H2O. As CeOx can promote H2O dissociation largely, the excessive OH* results in surface poisoning and reduced C–O (or H2) formation, and the appropriate concentration of OH* is better for WGSR due to the balance of O–H bond activation and C–O (or H–H) bond formation, so the Cu–Ce–Ti model with the OH* ligand maybe the candidate of the active site for Cu/CeOx/TiO2. OH self-promoting reaction mechanism offers new insights into the fundamental role of surface adsorbed OH intermediate in WGSR. This article reveals the essence of the composite oxide support strategy in improving reaction performance, pointing out a new direction for regulating reaction performance.