Theoretical insight into the electrocatalytic reduction of CO2 with different metal ratios and reaction mechanisms on palladium–copper alloys

Abstract

Environmental impacts of continued CO₂ production have led to an increased need for new methods of CO₂ removal and energy development. Electrochemical reduction of CO₂ has been shown to be a good method through recent studies. Alloys are of special interest for these applications, because of their unique chemical and physical properties that allow for highly active surfaces. Here, Pd_nCu_m (m + n = 15 and n > m) bimetallic electrocatalysts were used for systematic studies to understand the effect of the composition of Pd and Cu on the electrochemical reduction of CO₂ to CO. In particular, the Pd–Cu alloy with the Pd/Cu = 2/1 atomic ratio (i.e., Pd₁₀Cu₅) has the best catalytic effect, particularly true at the step of the hydrogenation of CO₂ to COOH, and the Pd₁₀Cu₅ catalyst is better than most known electrodes. With the energetic analysis of the proposed reaction pathways over the Pd₁₀Cu₅ catalyst, the limiting voltages for CO₂ reduction to CH₃OH, CH₄, and CH₃CH₂O have been compared. Most importantly, the kinetic model analysis showed that the rate constant values indicate that the probability of generating C₂H₅OH on the Pd₁₀Cu₅ catalyst is greater than that of CH₃OH or CH₄. The findings revealed in this study may shed some light on the design of cost-effective and efficient electrocatalysts for CO₂ conversion to CO or to other useful hydrocarbons.