Boosting electrocatalytic CO₂ reduction by sulfur-modified bismuth nanosheets

Electrocatalytic reduction of CO 2 to formate represents a green and sustainable pathway for mitigating atmospheric CO 2 concentrations. Nevertheless, the practical implementation of CO 2 reduction reaction (CO 2 RR) still encounters critical obstacles, notably low current density and insufficient selectivity. Herein, we demonstrate a series of sulfur-modified bismuth nanosheets (S x -Bi NSs, where x represented the concentration of the electrolyte) synthesized via in situ electrochemical reduction. The optimized S 0.1 -Bi NSs catalyst exhibited tailored electronic structure modulation that simultaneously enhanced CO 2 adsorption capability and stabilized key reaction intermediates (*OCHO) while effectively suppressing the competing hydrogen evolution reaction (HER). Compared with pristine Bi NSs, S 0.01 -Bi NSs, and S 0.3 -Bi NSs, the S 0.1 -Bi NSs delivered superior catalytic performance across a broad potential window. Remarkably, at −1.1 V versus the reversible hydrogen electrode, they delivered a formate Faradaic efficiency (FE formate ) of 93.2% at a current density of 82.96 mA cm − 2 . Moreover, the catalyst maintained over 90% FEformate during a 30 h continuous operation, demonstrating exceptional operational stability.