Tuning the local electronic structure of oxygen vacancies over copper-doped zinc oxide for efficient CO2 electroreduction

Oxygen vacancies in metal oxides can serve as electron trap centers to capture CO2 and lower energy barriers for the electrochemical CO2 reduction reaction (CO2RR). Under aqueous electrolytes, however, such charge-enriched active sites can be occupied by adsorbed hydrogen (H-*) and lose their effectiveness for the CO2RR. Here, we develop an efficient catalyst consisting of Cu-doped, defect-rich ZnO (Cu-ZnO) for the CO2RR, which exhibits enhanced CO Faradaic efficiency and current density compared to pristine ZnO. The introduced Cu dopants simultaneously stabilize neighboring oxygen vacancies and modulate their local electronic structure, achieving inhibition of hydrogen evolution and acceleration of the CO2RR. In a flow cell test, a current density of more than 45 mA cm(-2) and a CO Faradaic efficiency of > 80% is obtained for a Cu-ZnO electrocatalyst in the wide potential range of -0.76 V to -1.06 V vs. Reversible Hydrogen Electrode (RHE). This work opens up great opportunities for dopant-modulated metal oxide catalysts for the CO2RR.