Activating dynamic Zn-ZnO interface with controllable oxygen vacancy in CO2 electroreduction for boosting CO production

Identification of the active sites for zinc oxide-derived catalysts and further elucidation of the catalytic mechanism for electrochemical CO2 reduction reaction (CO2RR) are limited by the dynamic structural evolution at real reaction conditions. Herein, we focus on the structural evolution of ZnO-T at the initial stage of CO2RR. ZnO-T undergoes in situ reduction to Zn within dozens of minutes, which is followed by reoxidation of the out layer. As a result, core-shell-like Zn@ZnO-T with controllable Zn-ZnO interfaces and oxygen vacancies is obtained depending on the temperature-controlled annealing and electrochemical pre-treatment. Zn-ZnO interfaces alter the energy band structure of ZnO layer, while oxygen vacancies modify the electron density of Zn sites. Thus, the obtained Zn@ZnO-T improves charge transfer, facilitates CO2 activation, and lowers energy barrier for *COOH and *CO intermediates formation. Expectedly, Zn@ZnO-T demonstrates excellent CO2RR performance for CO production with FE up to 92.1% at −1.2 V (vs. RHE) and a current density of −12.7 mA∙cm−2. In particular, Zn@ZnO-650 delivers a high FECO above 85% over a wide potential range from −1.0 to −1.3V (vs. RHE). This study provides a new compass for mechanistic investigation on relationship between intrinsic structure and catalytic performances, guiding the rational design of high-performance heterogeneous catalysts.