Efficient metal overlayer catalysts on the Nb₂C monolayer for CO oxidation from first-principles screening

Based on the first-principles calculation, the configurations of different metal overlayers on the monolayer Nb₂C (MXene) (M_ML/Nb₂C) (M  =  Rh, Ir, Pd, Pt, Ag, Au) were studied aiming to find a kind of complex system with high CO-tolerance and high CO conversion efficiency. Combined with the stability of the composite systems and their adsorption properties on small gas molecules, Ag_ML/Nb₂C was screened out and further tested for CO oxidation reaction. By comparing the energy barriers of different reaction pathways, we concluded that CO oxidation reaction could be carried out on Ag_ML/Nb₂C var the LH mechanism with a small energy barrier of 0.35 eV. The rate-determining step was the oxidation of CO by the adsorbed oxygen atom. The Ag_ML/Nb₂C showed good activity for CO oxidation, which would provide a theoretical basis for designing the electrode material for the proton exchange membrane fuel cells (PEMFCs).