Oxygen Vacancy Tuning toward Efficient Electrocatalytic CO2 Reduction to C2H4

Electrochemical reduction of carbon dioxide (CO2) is a promising approach to solve both renewable energy storage and carbon-neutral energy cycles, while the capability of selective reduction to C2+ products has still been quite limited. In this work, partially reduced copper oxide nanodendrites with rich surface oxygen vacancies (CuOx-Vo) are developed, serving as excellent Lewis base sites for enhanced CO2 adsorption and subsequent electrochemical reduction. Theoretical calculations reveal that these oxygen vacancy-rich CuOx surfaces provide strong binding affinities to the intermediates of *CO and *COH, but weak affinity to *CH2, thus leading to efficient formation of C2H4. As a result, the partially reduced CuOx nanodendrites exhibit one of the highest C2H4 production Faradaic efficiencies of 63%. The electrochemical stability test further shows that the C2H4 Faradaic efficiency strongly depends on the oxygen vacancy density in CuOx, which can further be regenerated for several cycles, thus suggesting the critical role of oxygen vacancies for the C-2 product selectivity.