Rational Design and Effective Control of Gold-Based Bimetallic Electrocatalyst for Boosting CO₂ Reduction Reaction: A First-Principles Study

Electrochemical CO₂ reduction reaction (CO₂RR) 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 CO₂RR properties due to its strong affinity to CO. Herein, Au−Pd bimetallic electrocatalysts with different metal ratio were firstly investigated on CO₂RR mechanism by using density functional theory. The Au monolayer over Pd substrate and single Pd atom on Au(111) were found to show better CO₂RR 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 CO₂RR 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 CH₃OH 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 CO₂RR reactivity descriptor than the common CO adsorption when establishing scaling relationship, which could avoid the fitting error caused by intermediate physisorption of CO.