The synergistic effects of the Cu–CeO2(111)catalysts on the adsorption and dissociation of water molecules

Abstract

The interaction of water molecules with the Cu–CeO₂(111) catalyst (Cu/CeO₂ and Cu_0.08Ce_0.92O₂) is studied systematically by using the DFT+U method. Although both molecular and dissociative adsorption states of water are observed on all the considered Cu–CeO₂(111) systems, the dissociation is preferable thermodynamically. Furthermore, the dissociation of water molecule relates to the geometric structure (e.g. whether or not there are oxygen vacancies; whether or not the reduced substrate retains a fluorite structure) and the electronic structure (e.g. whether or not there is reduced cerium, Ce³⁺) of the substrate.

In addition, the adsorption of water molecules induces variations of the electronic structure of the substrate, especially for Cu/CeO_2−x(111)-B (a Cu atom adsorbed symmetrically above the vacancy of the reduced ceria) and highly reduced Cu_0.08Ce_0.92O₂(111), i.e. the Cu_0.08Ce_0.92O_2−x(111)-h. The variations of electronic structure promote the dissociation of water for the highly reduced system Cu_0.08Ce_0.92O_2−x(111)-h. More importantly, the improvement of WGS reaction by Cu-ceria is expected to be by the associative route through different intermediates.