For electrocatalytic reduction of CO2 to CO,the stabilization of intermediate COOH* and the desorption of CO* are two key steps.Pd can easily stabilize COOH*,whereas the strong CO* binding to Pd surface results in severe poisoning,thus lowering catalytic activity and stability for CO2 reduction.On Ag surface,CO* desorbs readily,while COOH* requires a relatively high formation energy,leading to a high overpotential.In light of the above issues,we successfully designed the PdAg bimetallic catalyst to circumvent the drawbacks of sole Pd and Ag.The PdAg catalyst with Ag-terminated surface not only shows a much lower overpotential (-0.55 V with CO current density of 1 mNcm2) than Ag (-0.76 V),but also delivers a CO/H2 ratio 18 times as high as that for Pd at the potential of-0.75 V vs.RHE.The issue of CO poisoning is significantly alleviated on Ag-terminated PdAg surface,with the stability well retained after 4 h electrolysis at-0.75 V vs.RHE.Density functional theory (DFT) calculations reveal that the Ag-terminated PdAg surface features a lowered formation energy for COOH* and weakened adsorption for CO*,which both contribute to the enhanced performance for CO2 reduction.