Boosting Electrochemical Reduction of CO₂ at a Low Overpotential by Amorphous Ag‐Bi‐S‐O Decorated Bi⁰ Nanocrystals

Abstract

Bimetal-S-O composites have been rarely researched in electrochemical reduction of CO₂ . Now, an amorphous Ag-Bi-S-O decorated Bi⁰ catalyst derived from Ag_0.95 BiS_0.75 O_3.1 nanorods by electrochemical pre-treatment was used for catalyzing eCO₂ RR, which exhibited a formate FE of 94.3 % with a formate partial current density of 12.52 mA cm^-2 at an overpotential of only 450 mV. This superior performance was attributed to the attached amorphous Ag-Bi-S-O substance. S could be retained in the amorphous region after electrochemical pre-treatment only in samples derived from metal-S-O composites, and it would greatly enhance the formate selectivity by accelerating the dissociation of H₂ O. The existence of Ag would increase the current density, resulting in a higher local pH, which made the role of S in activating H₂ O more significantly and suppressed H₂ evolution more effectively, thus endowing the catalyst with a higher formate FE at low overpotentials.