pH-Universal Electrocatalytic CO Reduction with Ampere-Level Current Density on Doping-Engineered Bismuth Sulfide.

The practical application of the electrocatalytic CO reduction reaction (CORR) to form formic acid fuel is hindered by the limited activation of CO 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 CORR 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 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 under acidic solutions. Notably, the current density can reach 700 mA cm while maintaining a FE of above 90 % in a membrane electrode assembly electrolyzer and operate stably for 150 h at 200 mA cm. 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.