Ab initio study for late steps of CO2 and CO electroreduction: from CHCO* toward C2 products on Cu and CuZn nanoclusters

Abstract

Electroreduction of CO₂ to C₂ products such as ethanol is motivated by its potential application to satisfy global energy demand in a more sustainable and renewable way. Cooper-based catalysts have exhibited highlighted performance in obtaining C₂ products, but large overpotentials and poor selectivity are still challenging. Herein, we employed density functional theory calculations and the computational hydrogen electrode model to study the impact of CuZn alloys on the mechanism and selectivity of CO₂ and CO electroreduction to C₂ products. On both clusters, the preferred pathway to ethanol and ethylene shares a common intermediate: CH₂CHO*. On Cu₅₅, ethanol formation would occur at lower electrode potential than the formation of ethylene, which agrees with experimental studies. Since Cu₄₂Zn₁₃ increases the Gibbs free energy change between CH₂CHO* and adsorbed acetaldehyde, the alloy exhibited lower selectivity toward ethanol than Cu₅₅ cluster. The role of Zn is mainly related to the stronger adsorption of the intermediates on Cu₄₂Zn₁₃ than in the Cu₅₅ group. Our results suggested that the d states of Zn are involved in the adsorption of intermediates, strengthening the interaction.