Self‐Refreshing Bi‐Based Active Sites for Efficient and Durable Electrochemical CO ₂ Reduction

Abstract The electrochemical CO ₂ reduction reaction (eCO ₂ RR) performance of Bi‐based catalysts is significantly hindered by the limited active sites and uncontrollable reconstruction, leading to the challenges of simultaneous wide‐potential‐window efficiency and prolonged durability. To address this, a novel design is presented for self‐refreshing active sites through rational engineering of a pre‐catalyst, a basic bismuth nitrate (BBN) nanosheet. During eCO ₂ RR operation, the pre‐catalyst undergoes systematic phase evolution of initial transition into bismuth oxycarbonate (Bi ₂ O ₂ CO ₃ ) at low potentials (<−0.9 V) followed by reduction to metallic Bi at high potentials (>−0.9 V). Notably, when the eCO ₂ RR terminates, the metallic Bi phase spontaneously reconstructs back to Bi ₂ O ₂ CO ₃ by re‐oxidation of CO ₂ in the electrolyte, establishing a closed‐loop self‐refreshing cycle. This unique self‐refreshing mechanism endows the catalyst with three distinct advantages: i) differential active sites of Bi ₂ O ₂ CO ₃ and metallic Bi phases enable synergistically efficient formate selectivity (> 90%) across a wide potential window (−0.5–−1.4 V); ii) phase‐dependent adsorption properties optimize CO ₂ activation and intermediate stabilization; iii) self‐repairing capability through reversible phase transitions significantly enhances operational durability (>1200 h). This work sheds new light on designing advanced high‐performance nanomaterials toward practical eCO ₂ RR applications.