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 2 reduction reaction (CO 2 RR). Undercoordinated Zn (Zn δ+ ) 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 δ+ sites during CO 2 reduction process. Herein, we present ZnO, Zn δ+ /ZnO and Zn as catalysts by varying the applied reduction potential. Theoretical studies reveal that Zn δ+ sites could suppress HER and HCOOH production to induce CO generation. And Zn δ+ /ZnO presents the highest CO selectivity (FE CO 70.9 % at −1.48 V vs. RHE) compared to Zn and ZnO. Furthermore, we propose a CeO 2 nanotube with confinement effect and Ce 3+ /Ce 4+ redox to stabilize Zn δ+ species. The hollow core–shell structure of the Zn δ+ /ZnO/CeO 2 catalyst enables to extremely expose electrochemically active area while maintaining the Zn δ+ sites with long‐time stability. Certainly, the target catalyst affords a FE CO of 76.9 % at −1.08 V vs. RHE and no significant decay of CO selectivity in excess of 18 h.