Synergistic effects of ZnO in Cu-based catalysts for CO2 reduction: mechanistic insights into enhanced C2 product formation

• ZnO enhances Cu-based catalysts, improving CO 2 reduction and C 2 product formation. • DFT calculations show ZnO stabilizes key intermediates and promotes hydrogen spillover, facilitating efficient C − C coupling. • Oxygen vacancies in Cu-ZnO boost electron delocalization, charge transfer, and CO 2 activation. The electrochemical reduction of CO 2 (CO 2 RR) to multi-carbon products such as ethanol (C 2 H 5 OH) and ethylene (C 2 H 4 ) is a promising strategy for mitigating CO 2 emissions and producing valuable chemicals. In this study, we investigate the role of ZnO in enhancing the performance of Cu-based catalysts for CO 2 RR. Using both experimental and theoretical approaches, we demonstrate that ZnO incorporation significantly improves the catalytic efficiency of Cu by modifying its electronic structure, stabilizing key intermediates, and facilitating C–C coupling. DFT calculations show that ZnO stabilizes intermediates such as *CO and *HCOH, promoting their hydrogenation and enhancing C 2 product formation. The presence of oxygen vacancies (OVs) on the Cu-ZnO interface is found to facilitate proton-coupled electron transfer (PCET) and H-spillover, leading to improved catalytic performance. XPS and UV–Vis DRS analyses confirm that ZnO modifies the Cu surface, increasing the Cu 0 /Cu + species and narrowing the band gap, which enhances charge transfer and intermediate stabilization. The CZ catalyst exhibits significantly higher Faradaic efficiency for C 2 products compared to the Cu catalyst, as confirmed by experimental data. These findings highlight the importance of defect engineering in the design of more efficient catalysts for CO 2 reduction. This study provides valuable insights into optimizing Cu-based catalysts for sustainable CO 2 utilization and C 2 product formation.