Tailoring electronic structure of bifunctional Cu/Ag layered electrocatalysts for selective CO2 reduction to CO and CH4

Nanostructured catalysts have been extensively demonstrated for electrochemical CO2 reduction. But, efforts to understand the mechanism of bimetallic catalysts have been limited. Here, we study electronic structures in bimetallic Cu/Ag layered catalysts to eliminate geometrical effects on the electrocatalytic characteristics. We found that the interfacial interaction between Cu and Ag affects the valence electronic states as confirmed by synchrotron radiation photoelectron spectroscopy and density functional theory calculation. The Ag adatom on Cu surface decreases charge density by forming an additional bond with Cu. As a result, the binding energy of CO intermediate increases on the surface. As the thickness of Ag layer increases, the effect of interfacial interaction of Cu/Ag gradually weakened and the center of d-states downshifted from 4.38 to 5.28 eV. The optimized Cu/Ag layered catalyst exhibited bifunctional catalytic selectivity with high CO faradaic efficiency (FE) = 89.1% at -0.8 V-RHE and high methane FE = 65.3% at -1.2 V-RHE.