Electron trapping fluorine stabilizing Bi–O motif for pH-universal CO2 electroreduction to formate at industrial-level current density

Abstract

The generation of economically valuable chemicals through electrocatalytic CO₂ reduction reaction (CO₂RR) is a highly attractive strategy for achieving the carbon cycle. Bismuth (Bi) is a prospective element due to the high selectivity for formate. Researches demonstrate the Bi–O bonds have a significant effect on the key *OCHO intermediate. Herein, we report a F-doped catalyst that displays remarkable performance in generating formate in pH-universal electrolytes. Specifically, the as-prepared F-Bi/BOC@GO achieves formate Faradaic efficiencies (FE_formate) around 95% in a wide range of pH from 1 to 13.6. Furthermore, at an industrial level, current density of 200 mA cm⁻², the F-Bi/BOC@GO catalyst shows a much more stable FE_formate than the catalyst without introducing F. In situ Raman reveals that the doped F can greatly improve the stability of Bi–O bonds during the electroreduction process. DFT calculations further demonstrate that fluorine doping raises the energy barrier for oxygen desorption from Bi–O motifs, thus enhancing the stability of active sites. Combined with X-ray photoelectron spectroscopy (XPS), the doped F acts as an electron trapping, which may direct electrons towards Bi–Bi bonds, thus protecting the key Bi–O motif. This work reveals the critical role of fluorine in stabilizing Bi–O active centers across a wide pH range, maintaining high formate Faradaic efficiency for a longer time than the catalyst without fluorine introduction.