Shaowei Zhang, Xueyu Hu, Tianfu Liu, Hewei Liu, Yige Guo, Geng Zou, Wenwen Zhang, Xiaomin Zhang, Peng Zhang, Runsheng Yu, Yuefeng Song, Changrong Xia, Guoxiong Wang, Xinhe Bao
Abstract Tuning lattice oxygen activity in perovskite oxides (ABO 3 ) offers a promising approach to overcome the intrinsic trade‐off between catalytic activity and stability in redox reactions. However, precise modulation and mechanistic understanding of lattice oxygen activation remain elusive under high‐temperature CO 2 electrolysis conditions. Herein, a novel anion activation strategy is proposed by incorporating trace chloride ions (Cl − ) into the O‐sites of Sr 2 Fe 1.5 Mo 0.5 O 6−δ perovskite forming an oxychloride cathode. This Cl − substitution activates lattice oxygen reactivity by weakening Mo−O/Fe−O covalency, thereby facilitating the formation and redistribution of oxygen vacancies, accelerating bulk oxygen ion transport, enhancing CO 2 adsorption and carbonate intermediate formation, and ultimately promoting CO 2 reduction kinetics. As a result, the oxychloride cathode achieves a 60.2–80.8% enhancement in CO 2 ‐to‐CO electrolysis, reaching 2.02 A cm −2 at 800 °C and 1.5 V with ≈100% Faradaic efficiency, while maintaining exceptional stability of 500 h. This work establishes a new paradigm of O‐site anion engineering to unlock lattice oxygen activity for electrocatalytic reactions.