Anion-Mediated In Situ Reconstruction of the Bi 2 MoO 6 Precatalyst for Enhanced Electrochemical CO 2 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.