Efficient electroreduction of carbon dioxide to formate enabled by bismuth nanosheets enriched dual V vacancy.

The electrocatalytic reduction of carbon dioxide (COER) into formate presents a compelling solution for mitigating dependence on fossil energy and green utilization of CO. Bismuth (Bi) has been gaining recognition as a promising catalyst material for the COER to formate. The performance of Bi catalysts (named as Bi-V) can be significantly improved when they possess single metal atom vacancy. However, creating larger-sized metal atom vacancies within Bi catalysts remains a significant challenge. In this work, Bi nanosheets with dual V vacancy (Bi-DV) were synthesized utilizing in situ electrochemical transformation, using BiOBr nanosheets with triple vacancy associates (VVV, V and V denote the Bi and O vacancy, respectively) as a template. The obtained Bi-DV achieved higher COER activity than Bi-V, showing Faradaic efficiency for formate production of >92% from -0.9 to -1.2 V in an H-type cell, and the partial current density of formate reached up to 755 mA/cm in a flow cell. The comprehensive characterizations coupled with density functional theory calculations demonstrate that the dual V vacancy on the surface of Bi-DV expedite the reaction kinetics toward COER, by reducing the thermodynamic barrier of *OCHO intermediate formation. This research provides critical insights into the potential of large atom vacancies to enhance electrocatalysis performance.