The Facet Dependence of CO₂ Electroreduction Selectivity on a Pd₃Au Bimetallic Catalyst: A DFT Study

The electrochemical carbon dioxide reduction reaction (CO₂RR) has emerged as a promising approach to addressing global energy and environmental challenges. Alloys are of particular importance in these applications due to their unique chemical and physical properties. In this study, the possible mechanism of the C1 products from the electrochemical reduction of CO₂ on four different surfaces of Pd₃Au alloy bimetallic catalysts is predicted using the density functional theory. The differences in the number of d-band electrons and the charge distribution and morphology of the different surfaces result in differing catalytic activity and selectivity on the same surface. On different surfaces, Pd₃Au alloy bimetallic catalysts have different potential limiting steps in CO₂RR, resulting in differing selectivity. The Pd₃Au (100) surface has a good selectivity for HER, indicating that the increase in the net charge on the surface of the alloy improves the selectivity for HER. The Pd₃Au (211) surface, with a step structure, shows a good selectivity for methanol production from CO₂RR. In addition, an electronic structure analysis shows that the selectivity of the reactions involved in the conversion of adsorbates is determined by the difference between the center of the d-band on the top of the catalyst, where the reactant and the product are located. The results of this study may provide some theoretical basis for designing and developing more efficient and selective CO₂ reduction catalysts.