Electronic Delocalization of Bismuth Oxide Induced by Sulfur Doping for Efficient CO2 Electroreduction to Formate

Developing efficient electrocatalysts for electrochemical CO2 reduction (ECR) to fuels and chemicals with high product faradaic efficiency (FE) and current density is desirable but remains challenging. Herein, S-doped Bi2O3 electrocatalysts coupled with carbon nanotubes (S-Bi2O3-CNT) are synthesized for efficient ECR to formate. The obtained S-2-Bi2O3-CNT (with a S doping amount of 0.7 at. %) is highly active for formate production (FE > 90%) over a wide current density range (2.77-48.6 mA cm(-2)), and a maximum formate FE of 97.06% can be achieved at -0.9 V. The significantly enhanced selectivity and activity is originated from the fast electron transfer, enhanced CO2 adsorption, and more undercoordinated Bi sites induced by the S doping. More importantly, density functional theory calculations revealed that S doping can lead to an electronic delocalization of Bi, which benefits the binding of *CO2 and *HCOO for ECR, while significantly inhibiting the hydrogen evolution reaction via weakening the adsorption of *H, thus helping achieve high current density and FE. This work paves a promising way to tuning ECR activities at the atomic level.