Electrochemical carbon dioxide reduction on copper–zinc alloys: ethanol and ethylene selectivity analysis

Abstract

The electrochemical conversion of CO₂ to ethanol and ethylene is an environmentally and economically promising method for addressing global climate change in a carbon-neutral society. Ethanol is desirable because of its high energy density. However, ethanol production is less favored than ethylene production on Cu catalysts. Alloys have gained prominence as a catalyst that enhances ethanol selectivity. In this study, metallic CuZn alloys with different Zn contents (Cu, Cu₉Zn₁, Cu₃Zn₁, and Cu₂Zn₁) were fabricated by co-sputtering Cu and Zn. A maximum ethanol/ethylene ratio of 9.2 was achieved on Cu₂Zn₁, which is 11 times higher than that of the Cu catalyst. Furthermore, we prepared Cu₉Zn₁ on polytetrafluoroethylene (PTFE), which achieved an ethanol partial density of approximately 93 mA cm⁻² at −0.76 V vs. RHE. Cu₉Zn₁/PTFE exhibited stable ethanol production with ∼25% faradaic efficiency and ∼11% full-cell energy efficiency of ethanol over a period of 7 h in a membrane electrode assembly system. The remarkable ethanol selectivity of the CuZn catalysts was attributed to the local atomic arrangement, which was supported by density functional theory calculations.