Operando Converting BiOCl into BiO(CO)Cl 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 CO to formate. However, Bi-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 CORR conditions. A synthetic approach is developed to electrochemically convert BiOCl into Cl-containing subcarbonate (BiO(CO)Cl) under operando CORR conditions. The systematic operando spectroscopic studies depict that BiOCl is converted to BiO(CO)Cl via a cathodic potential-promoted anion-exchange process. The operando synthesized BiO(CO)Cl can tolerate - 1.0 V versus RHE, while for the wet-chemistry synthesized pure BiOCO, the formation of metallic Bi occurs at - 0.6 V versus RHE. At - 0.8 V versus RHE, BiO(CO)Cl can readily attain a FE- of 97.9%, much higher than that of the pure BiOCO (81.3%). DFT calculations indicate that differing from the pure BiOCO-catalyzed CORR, where formate is formed via a OCHO intermediate step that requires a high energy input energy of 2.69 eV to proceed, the formation of HCOO over BiO(CO)Cl has proceeded via a COOH intermediate step that only requires low energy input of 2.56 eV.