Electrocatalytic reduction of CO2 with enhanced C2 liquid products activity by the synergistic effect of Cu single atoms and oxygen vacancies

Electrochemical conversion of CO₂ to high energy density multi-carbon liquid phase fuels such as ethanol offers a promising strategy to realize carbon neutrality. However, the selectivity of value-added C₂ liquid products is still deemed unsatisfactory currently due to the high overpotential, poor selectivity, and the difficulty of the C–C coupling process. Herein, we report that Cu single atoms (SAs) on hydrogen reduced UIO66-NH₂ (named Cu SAs/UIO-H₂) achieve C₂ liquid products Faraday efficiency (FE) of 58.62% and ethanol FE of 46.28% at a low potential of –0.66 V versus the reversible hydrogen electrode. The ethanol FE of Cu SAs/UIO-H₂ is 9.61 times higher than UIO66-NH₂. Moreover, the experimental results and theoretical calculations demonstrate that Cu SAs and oxygen vacancies (OVs) synergistically promote the generation of *HCCOH intermediate, thus accelerating the formation of ethanol. This work offers deeper understanding at the atomic scale for designing high-performance electrocatalysts for CO₂ conversion to valuable liquid fuels.