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

Electrochemical CO₂ reduction reaction (eCO₂RR) 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 eCO₂RR remain elusive. Herein, the reconstruction processes of bismuth molybdate (Bi₂MoO₆) nanoplates are elucidated during the eCO₂RR. Operando and ex situ measurements reveal the in situ partial reduction of Bi₂MoO₆ to Bi metal, forming Bi@Bi₂MoO₆ at negative potentials. Meanwhile, CO₃^2- ions in the electrolyte spontaneously exchange with MoO₄^2- in Bi₂MoO₆. The obtained Bi@Bi₂MoO₆/Bi₂O₂CO₃ 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 Bi₂O₂CO₃, 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.