Stability and Effects of Subsurface Oxygen in Oxide-Derived Cu Catalyst for CO2 Reduction

Oxide-derived copper (OD-Cu) catalysts are promising candidates for the electrochemical CO2 reduction reaction (CO2RR) due to the enhanced selectivity toward ethylene over methane evolution, which has been linked to the presence of subsurface oxygen (Osb). In this work, Osb is investigated with theoretical methods. Although Osb is unstable in slab models, it becomes stabilized within a “manually” reduced OD-Cu nanocube model which was calculated by self-consistent charge density functional tight binding (SCC-DFTB). The results obtained with SCC-DFTB for the full nanocube were confirmed with subcluster models extracted from the nanocube, calculated with both density functional theory (DFT) and SCC-DFTB. The higher stability of Osb in the nanocube is attributed to the disordered structure and greater flexibility. The adsorption strength of CO on Cu(100) is enhanced by Osb withdrawing electron density from the Cu atom, resulting in reduction of the σ-repulsion. Hence, the coverage of CO may be increased, facilitating its dimerization.