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

Abstract

Identification of the active sites of zinc oxide-derived catalysts and further elucidation of their catalytic mechanism for electrochemical CO₂ reduction reaction (CO₂RR) are limited by the dynamic structural evolution at real reaction conditions. Herein, we focused on the structural evolution of ZnO-T at the initial stage of CO₂RR. ZnO-T underwent in situ reduction to Zn within dozen of minutes, which was followed by reoxidation of the outer layer. As a result, core–shell-like Zn@ZnO-T with controllable Zn–ZnO interfaces and oxygen vacancies was obtained via temperature-controlled annealing and electrochemical pre-treatment. Zn–ZnO interfaces altered the energy band structure of ZnO layer, while the oxygen vacancies modified the electron density of Zn sites. Thus, the obtained Zn@ZnO-T improved the charge transfer, facilitated CO₂ activation, and lowered the energy barrier for *COOH and *CO intermediate formation. Expectedly, Zn@ZnO-T demonstrated 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 delivered a high FE_CO above 85% over a wide potential range from −1.0 to −1.3 V (vs. RHE). This study provides a new direction for mechanistic investigations on the relationship between intrinsic structure and catalytic performance, guiding the rational design of high-performance heterogeneous catalysts.