Theoretical investigation on CO oxidation catalyzed by a copper nanocluster

Abstract

The mechanism of CO oxidation catalyzed by a 55-atom copper nanocluster was studied at the BVP86/DNP level with all-electron scalar relativity. Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms were studied in detail. Adsorption of O2 on the copper cluster was prior to that of CO. The ER mechanism included three pathways, i.e. the O2 dissociation, the O abstract from the O2-pre-adsorbed Cu55 cluster by the gaseous CO, and the insertion of CO into the O–O bond of the O2-precovered Cu55 cluster to form a carbonate-like intermediate to complete the CO oxidation. The LH mechanism was originated from the co-adsorption of CO and O2 on the Cu55 cluster and had three pathways to the final product. The reaction channels involving the O2 dissociation, the O-abstraction, and the insertion of CO into the O–O bond vied with each other. The commonly accepted LH mechanism via the peroxo-like intermediate was unfeasible because of the unstable co-adsorption of CO and O2 on the Cu55 cluster. After incorporating the entropy effect, the CO-assisted O2 dissociation pathway was the most feasible reaction channel above 250 K. The strong interaction of oxygen atom with the copper surface was in favour of the O2 dissociation step, and was adverse to the reaction of the atomic oxygen toward CO to form CO2.