Anion-Mediated In Situ Reconstruction of the Bi₂MoO₆ Precatalyst for Enhanced Electrochemical CO₂ Reduction over a Wide Potential Window

Electrochemical CO 2 reduction reaction (eCO 2 RR) is a viable approach to achieve carbon neutrality. Bismuth-based electrocatalysts demonstrate exceptional selectivity in CO 2 -to-formate conversion, but their reconstruction mechanisms during the eCO 2 RR remain elusive. Herein, the reconstruction processes of bismuth molybdate (Bi 2 MoO 6 ) nanoplates are elucidated during the eCO 2 RR. Operando and ex situ measurements reveal the in situ partial reduction of Bi 2 MoO 6 to Bi metal, forming Bi@Bi 2 MoO 6 at negative potentials. Meanwhile, CO 3 2– ions in the electrolyte spontaneously exchange with MoO 4 2– in Bi 2 MoO 6 . The obtained Bi@Bi 2 MoO 6 /Bi 2 O 2 CO 3 delivers a formate Faradaic efficiency (FE) of 95.2% at −1.0 V. Notably, high formate FEs (>90%) are maintained within a wide 500 mV window. Although computational calculations indicate a higher energy barrier for *OCHO formation on Bi 2 O 2 CO 3, the prevention of excessive reduction to metal Bi significantly enhances long-term stability. Furthermore, the CO 3 2– ion exchange process occurs in various 2D Bi-containing precatalysts, which should be emphasized in further studies.