CO spillover on CuO/ZnO p-n heterojunction facilitating the electrochemical reduction of carbon dioxide to ethylene

The electrochemical CO 2 reduction (ECO 2 R) driven by the renewable energy represents an effective approach to mitigate atmospheric CO 2 concentration and to achieve carbon neutrality. Zinc (Zn) and its oxides, being among the most abundant metal materials, are frequently employed in the generation of CO by ECO 2 R. Cooper and its oxides have the moderate *CO affinity which enables the C-C coupling reaction to produce the higher value C2+ products. In this work, we have developed the novel CuO/ZnO p-n heterojunction tandem catalyst using a straightforward solvothermal method. By optimizing the content of CuO/ZnO heterojunction, a maximum Faradaic efficiency of 37% for C 2 H 4 can be achieved in a gas diffusion flow cell, which is one of the highest among the Cu-Zn-based catalysts for ECO 2 R. Mechanism investigations illuminate that CuO/ZnO heterojunction interface enhances the adsorption of *CO 2 – intermediates facilitating the formation of *CO intermediates than pristine CuO, meanwhile weakens the adsorption of *H impeding the competitive hydrogen evolution reaction. Therefore, the spillover of CO from ZnO to CuO sites and the electrons rebalance on CuO/ZnO heterojunction interface promote the C-C coupling reaction rates, thus greatly enhances the selectivity for C 2 H 4 .