Theoretical Insights into Mechanisms of Electrochemical Reduction of CO2 to Ethylene Catalyzed by Pd3Au

Abstract Electrochemical reduction of CO2 has attracted wide attention because of its promising application prospects in carbon dioxide recovery and the fuel industry, which is helpful to solve the global energy crisis and carbon emission problems. Pd-Au alloy is a copper-free catalyst that can reduce CO2 to multi-carbon products. A mechanistic understanding of the process is crucial to the discovery of new efficient catalysts. In this work, we examine the CO2 →C2H4 electrocatalytic pathway on Pd3Au (111) using density functional theory (DFT) calculations. Results show that the COH* coupled with CO* to generate OHCCO* intermediate is the rate-limiting step of ethylene on Pd3Au (111) surface, instead of the previously proposed CO* dimerization mechanism on Cu catalysis. The reduction of CO2* to CO*, the limiting potential is 0.64 V, and the rate-limiting step is the reduction of CO2* to COOH* with the kinetic barrier is 0.62 eV at 0 V vs RHE, indicating that the rate-limiting step for CO2 reduction to ethylene occurs after CO formation. The calculations show that Pd3Au (111) is more favorable for CO* hydrogenation to COH* instead of CO* hydrogenation to CHO*. And the adsorption energy date also suggesting that the COH* is more stable than CHO* on Pd3Au (111). Our results also indicate the solvation effect and CO* hydrogenation is beneficial to the formation of the C-C bond.