CO Oxidation on Single Transition Metal Atoms Supported on 2D ZnO: Role of Antibonding-State Center Shifts in Catalytic Efficiency

Catalytic oxidation is widely regarded as an effective method of eliminating CO pollutants. Given that single transition metal atoms supported on 2D ZnO monolayers have been successfully synthesized experimentally, we herein conduct a systematic study of CO oxidation on single transition metal atoms supported on 2D ZnO (TM₁/gZnO, TM = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt) using density functional theory. Our findings show that within the same period, a larger empty d-band ratio in a single transition metal atom enhances its adsorption of gas molecules on TM₁/gZnO. The common mechanisms for CO oxidation on TM₁/gZnO are the Langmuir-Hinshelwood and Eley-Rideal pathways, with Pt₁/gZnO emerging as the optimal single-atom catalyst due to its lowest rate-limiting adiabatic barriers in both mechanisms. We discover that the activation barrier height correlates closely with the upward shift of the antibonding-state center in the transition state relative to its preceding adsorption precursor; specifically, a greater upshift corresponds to a lower barrier. These insights deepen the understanding of CO oxidation mechanisms on supported single-atom catalysts and provide a predictive framework for designing efficient catalysts for CO oxidation.