Sulfur boosting CO2 reduction activity of bismuth subcarbonate nanosheets via promoting proton-coupled electron transfer

Bismuth (Bi) based nanomaterials are attractive catalysts for electrochemical CO2 reduction to formate, while both high selectivity and high activity still need further investigation. Herein, we report a facile strategy, via introducing sulfur (S) atoms to modulate the electronic structure of two-dimensional (2D) bismuth subcarbonate Bi2O2CO3 (BiOC) nanosheets, to improve their catalytic activity meanwhile maintain high formate selectivity. The lower electronegativity of the substituted S than O enhances the local electron density around Bi active sites, promoting the proton-coupled electron transfer to the CO2 intermediate, and thus contributing to the superior CO2 reduction performance with the selectivity of formate >90% in a wide negative potential range and high partial current density up to 29.0 mA cm−2 at −0.9 vs RHE. This study provides an in-depth understanding on the design of advanced CO2 reduction electrocatalysts via heteroatom doping.