Electrochemical CO2 reduction reaction (CO2 RR) is an effective strategy converting CO2 to value-added products. Au is regarded as an efficient catalyst for electrochemical reduction of CO2 to CO, and the introduction of Pd can tune CO2 RR properties due to its strong affinity to CO. Herein, Au-Pd bimetallic electrocatalysts with different metal ratio were firstly investigated on CO2 RR mechanism by using density functional theory. The Au monolayer over Pd substrate and single Pd atom on Au(111) were found to show better CO2 RR selectivity against hydrogen evolution reaction (HER). Based on this, various single-atom catalysts on Au(111) and core-shell models with top Au monolayer were designed to study their CO2 RR performance. The results indicated that Pt, Cu, and Rh substrates below Au monolayer could enhance the activity and selectivity for CO production compared to pure Au, in which the limiting potential reduced from -0.74 to -0.63, -0.69, and -0.71 V, respectively. The single Pd embedded on Au(111) could adjust the adsorption strength, which provided an effective site to receive and further reduce CO to CH3 OH and CH4 at a low limiting potential of -0.61 V, and also avoided catalyst poisoning due to the over-strengthened CO adsorption caused by high Pd proportion on the surface. In addition, the adsorption energy of COOH was observed as a better CO2 RR reactivity descriptor than the common CO adsorption when establishing scaling relationship, which could avoid the fitting error caused by intermediate physisorption of CO.
Keywords: CO2 electrocatalytic reduction; bimetallic catalyst; density functional theory; electrochemistry; reactivity descriptor.
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