Metal (Ca, Cu, Zn)-modified defect-rich Bi nanosheets for electrocatalytic reduction of CO2 to HCOOH at high current density

Bismuth-based materials have emerged as promising electrocatalysts for the electrochemical reduction of carbon dioxide (eCO2RR) to HCOOH. However, it remains challenges to meet the practical application requirements and identify the active sites of bismuth-based catalysts in eCO2RR. Herein, bismuthate (MBi2O4, M = Ca, Cu, Zn) derived nanosheet-like electrocatalysts with metal-modified edge defects are developed. During electrochemical processes, MBi2O4 pre-catalyst undergoes surface reconstruction to expose more active Bi0 sites and to form abundant metal-modified edge defects, which facilitate the modulation of charge state of adjacent Bi sites and improve the adsorption of *OCHO intermediate, thereby enhancing the selectivity of eCO2RR towards HCOOH. The Ca-modified defect-rich Bi catalyst exhibits a maximum HCOOH Faradaic efficiency of 94.3 % at an industrially relevant current density of 400 mA cm−2, together with high stability/reproducibility of 55 h. This work proposes a new strategy for construction of Bi-based catalysts and explores its structural reconstruction mechanism during the electrocatalytic process, opening a new window for design of eCO2RR catalysts.