Decrypting the Electron-Withdrawing Effect of Au-Decorated Bi₂ O₃ for Efficient CO₂ -to-Formate Electroreduction

Although the electron-withdrawing effect of gold (Au) is highlighted in catalytic reactions, its enhancement mechanism for electron transport, especially in the electrochemical process, is still unclear. Herein, Au-decorated Bi₂ O₃ (Au-Bi₂ O₃ ) is proposed as a proof-of-concept to investigate the electron-withdrawing effect in the electrocatalytic CO₂ reduction reaction (eCO₂ RR) process. Evidence from in situ Raman spectra and in situ XRD tests reveals that, compared to Bi₂ O₃ , Bi species in Au-Bi₂ O₃ can be reduced to metallic Bi more rapidly and more easily driven by the electron-withdrawing effect of Au. The XPS tests after eCO₂ RR further validates the transformation from Bi³⁺ to Bi⁰ in Au-Bi₂ O₃ is more complete. Meanwhile, in the in situ Fourier transform infrared (FTIR) spectra, the key intermediates (CO₂ *^- and OCHO*^- ) appear at the more positive potential, indicating that metallic Bi is favorable for eCO₂ RR due to the lower energy barrier as corroborated by density function theory (DFT) calculations. Au don't directly participate in the conversion from CO₂ to formate as the reaction sites, but utilize the electron-withdrawing effect to motivate Bi-sites to deliver higher catalytic activity and higher selectivity to formate at a lower applied potential. This study not only has an insight into the electron-withdrawing effect of Au on the eCO₂ RR process, but also develops a new perspective for engineering electron-withdrawing effect in electrocatalysts for high-efficient CO₂ -to-formate conversion.