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 C-2 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-H-2) achieve C-2 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-H-2 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.