Operando Converting BiOCl into Bi2O2(CO3)xCly for Efficient Electrocatalytic Reduction of Carbon Dioxide to Formate

Bismuth-based materials (e.g., metallic, oxides and subcarbonate) are emerged as promising electrocatalysts for converting CO2 to formate. However, Bi-o-based electrocatalysts possess high overpotentials, while bismuth oxides and subcarbonate encounter stability issues. This work is designated to exemplify that the operando synthesis can be an effective means to enhance the stability of electrocatalysts under operando CO2RR conditions. A synthetic approach is developed to electrochemically convert BiOCl into Cl-containing subcarbonate (Bi2O2(CO3)(x)Cl-y) under operando CO2RR conditions. The systematic operando spectroscopic studies depict that BiOCl is converted to Bi2O2(CO3)(x)Cl-y via a cathodic potential-promoted anion-exchange process. The operando synthesized Bi2O2(CO3)(x)Cl-y can tolerate - 1.0 V versus RHE, while for the wet-chemistry synthesized pure Bi2O2CO3, the formation of metallic Bi-o occurs at - 0.6 V versus RHE. At - 0.8 V versus RHE, Bi2O2(CO3)(x)Cl-y can readily attain a FEHCOO- of 97.9%, much higher than that of the pure Bi2O2CO3 (81.3%). DFT calculations indicate that differing from the pure Bi2O2CO3-catalyzed CO2RR, where formate is formed via a (OCHO)-O-* intermediate step that requires a high energy input energy of 2.69 eV to proceed, the formation of HCOO- over Bi2O2(CO3)(x)Cl-y has proceeded via a (COOH)-C-* intermediate step that only requires low energy input of 2.56 eV.

Automated summary

This study demonstrates that operando synthesis can enhance the stability of electrocatalysts for CO2 conversion to formate. By converting BiOCl into Cl-containing subcarbonate under operando conditions, the synthesized catalyst exhibits improved stability and higher formate yield compared to pure Bi2O2CO3.