DFT+U Study of the Adsorption and Oxidation of an Iron Oxide Cluster on CeO2 Support

Abstract

Highly dispersed small iron oxide clusters (FemOn) on CeO2 support effectively catalyze NO reduction by CO. However, their atomic structures and the reaction mechanism are still unclear, which prevent their further exploration and optimization. In this paper, the adsorption and oxidation of dispersed FemOn clusters on the CeO2(111) surface are studied using the DFT+U framework coupled with cluster expansion modeling to identify ground state configurations. Our results suggest under ambient conditions only the heavily oxidized FemOn clusters are stable. Under reaction conditions the NO reduction must be triggered by CO oxidation and FemOn reduction, followed by NO reduction on the reduced clusters. The reduction of FemOn is correlated with the simultaneous formation of Fe2+ and Ce3+, which is supported by recent operando X-ray absorption spectroscopy characterization. The reaction is likely to occur at the FemOn/CeO2 interface because of the weaker oxygen–metal bonding. Thus, the optimization of the interf...