pH‐Universal Electrocatalytic CO 2 Reduction with Ampere‐Level Current Density on Doping‐Engineered Bismuth Sulfide

The practical application of the electrocatalytic CO 2 reduction reaction (CO 2 RR) to form formic acid fuel is hindered by the limited activation of CO 2 molecules and the lack of universal feasibility across different pH levels. Herein, we report a doping‐engineered bismuth sulfide pre‐catalyst (BiS‐1) that S is partially retained after electrochemical reconstruction into metallic Bi for CO 2 RR to formate/formic acid with ultrahigh performance across a wide pH range. The best BiS‐1 maintains a Faraday efficiency (FE) of ~95 % at 2000 mA cm −2 in a flow cell under neutral and alkaline solutions. Furthermore, the BiS‐1 catalyst shows unprecedentedly high FE (~95 %) with current densities from 100 to 1300 mA cm −2 under acidic solutions. Notably, the current density can reach 700 mA cm −2 while maintaining a FE of above 90 % in a membrane electrode assembly electrolyzer and operate stably for 150 h at 200 mA cm −2 . In situ spectra and density functional theory calculations reveals that the S doping modulates the electronic structure of Bi and effectively promotes the formation of the HCOO* intermediate for formate/formic acid generation. This work develops the efficient and stable electrocatalysts for sustainable formate/formic acid production.