Ampere-level CO2-to-formate electrosynthesis using highly exposed bismuth(110) facets modified with sulfur-anchored sodium cations

The high-rate electrosynthesis of formate from CO2 is challenging due to the insufficient active catalytic sites that can stabilize the *OCHO intermediate and suppress H2 formation at large-current density electrolysis. Herein, we developed the metallic bismuth nanosheets with highly exposed (110) facets modified with sulfur anions and sodium cations (i.e., Bi(110)-S-Na). Density functional theory calculations revealed that Bi(110) facets presented higher activity than Bi(012) for the formate pathway. In addition, the co -modification of sulfur anions and sodium cations improved Bi-Bi metallic bonds, enhanced electron localization of *OCHO, and facilitated water activation to form H*, which enabled the promotion of formate selectivity while suppressing H2 production. The Bi(110)S-Na catalyst exhibited one of the highest CO2-to-formate partial current densities of 2,505 mA center dot cm-2 with 83.5% faradaic efficiency. Our work suggests an attractive electrochemical reconstruction strategy to build highly exposed Bi(110) facets with surface modification toward efficient CO2-to-formate electrosynthesis.