Stabilizing Undercoordinated Zn Active Sites through Confinement in CeO2 Nanotubes for Efficient Electrochemical CO2 Reduction

Zn-based catalysts hold great potential to replace the noble metal-based ones for CO2 reduction reaction (CO2RR). Undercoordinated Zn (Zn delta+) sites may serve as the active sites for enhanced CO production by optimizing the binding energy of *COOH intermediates. However, there is relatively less exploration into the dynamic evolution and stability of Zn delta+ sites during CO2 reduction process. Herein, we present ZnO, Zn delta+/ZnO and Zn as catalysts by varying the applied reduction potential. Theoretical studies reveal that Zn delta+ sites could suppress HER and HCOOH production to induce CO generation. And Zn delta+/ZnO presents the highest CO selectivity (FECO 70.9 % at -1.48 V vs. RHE) compared to Zn and ZnO. Furthermore, we propose a CeO2 nanotube with confinement effect and Ce3+/Ce4+ redox to stabilize Zn delta+ species. The hollow core-shell structure of the Zn delta+/ZnO/CeO2 catalyst enables to extremely expose electrochemically active area while maintaining the Zn delta+ sites with long-time stability. Certainly, the target catalyst affords a FECO of 76.9 % at -1.08 V vs. RHE and no significant decay of CO selectivity in excess of 18 h.