Nitrogen-Doped Carbon-Coated Bismuth Oxide for Highly Selective Electrochemical Reduction of Carbon Dioxide to Formate

Developing efficient and durable catalysts for the electrochemical reduction of CO2 （CO2RR） to formate remains a significant challenge， primarily due to the poor stability and limited exposure of active site in conventional Bi-based materials. Herein， we report a kind of N-doped carbon-encapsulated Bi2O3 catalyst synthesized via a hydrothermal process followed by high-temperature calcination. The catalyst calcined at 600 ℃ （Bi2O3-NC-600） exhibits uniform nanoflower-like morphology composed of hierarchically assembled nanosheets with abundant micropores， which effectively espouses more active sites and enhances intrinsic activity. This porous architecture also improves electrical conductivity and reduces charge-transfer resistance， leading to faster charge-transfer kinetics comparing with the catalyst without carbon encapsulation. Electrochemical measurements demonstrate that Bi2O3-NC-600 exhibits superior CO2RR performance with high selectivity， achieving a maximum formate Faradaic efficiency （FE） of 92.14% at -0.96 V（vs.RHE）. Moreover， long-term stability tests over 60 h reveal only negligible structural changes and a slight FE decay of 1.2%， confirming the outstanding durability of the catalyst. The enhanced performance originates from the N-doped carbon encapsulation， which stabilizes the whole structure of Bi2O3 and creates a synergetic effect between N and Bi that modulates the electronic properties of active site， thereby optimizing CO2RR catalytic activity. X-ray photoelectron spectroscopy （XPS） analysis further confirms the formation of Bi—N bonds， which can help anchor Bi species and suppress the dissolution during long-time reaction， contributing to the excellent stability. Furthermore， through carbon-mixing strategies， the current density of the catalyst can be enhanced without altering its selectivity， thereby increasing its practical applicability. This work demonstrates that N-doped carbon encapsulation not only boosts the intrinsic catalytic activity of Bi2O3， but also fundamentally enhances its structural stability， offering valuable insights for the rational design of highly selective and durable CO2RR catalysts.