Stabilizing Undercoordinated Zn Active Sites through Confinement in CeO 2 Nanotubes for Efficient Electrochemical CO 2 Reduction

Zn-based catalysts hold great potential to replace the noble metal-based ones for CO reduction reaction (CO RR). Undercoordinated Zn (Zn ) 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 sites during CO reduction process. Herein, we present ZnO, Zn /ZnO and Zn as catalysts by varying the applied reduction potential. Theoretical studies reveal that Zn sites could suppress HER and HCOOH production to induce CO generation. And Zn /ZnO presents the highest CO selectivity (FE 70.9 % at -1.48 V vs. RHE) compared to Zn and ZnO. Furthermore, we propose a CeO nanotube with confinement effect and Ce /Ce redox to stabilize Zn species. The hollow core-shell structure of the Zn /ZnO/CeO catalyst enables to extremely expose electrochemically active area while maintaining the Zn sites with long-time stability. Certainly, the target catalyst affords a FE of 76.9 % at -1.08 V vs. RHE and no significant decay of CO selectivity in excess of 18 h.