Anion-Mediated In Situ Reconstruction of the Bi 2 MoO 6 Precatalyst for Enhanced Electrochemical CO 2 Reduction over a Wide Potential Window.

Electrochemical CO2 reduction reaction (eCO2 RR) is a viable approach to achieve carbon neutrality. Bismuth-based electrocatalysts demonstrate exceptional selectivity in CO2 -to-formate conversion, but their reconstruction mechanisms during the eCO2 RR remain elusive. Herein, the reconstruction processes of bismuth molybdate (Bi2 MoO6 ) nanoplates are elucidated during the eCO2 RR. Operando and ex situ measurements reveal the in situ partial reduction of Bi2 MoO6 to Bi metal, forming Bi@Bi2 MoO6 at negative potentials. Meanwhile, CO3 2- ions in the electrolyte spontaneously exchange with MoO4 2- in Bi2 MoO6 . The obtained Bi@Bi2 MoO6 /Bi2 O2 CO3 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 Bi2 O2 CO3 , the prevention of excessive reduction to metal Bi significantly enhances long-term stability. Furthermore, the CO3 2- ion exchange process occurs in various 2D Bi-containing precatalysts, which should be emphasized in further studies.