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Summary
Prompt production of bismuth subcarbonate (Bi2O2CO3) intermediate is crucial for high-efficiency formate production and preservation of the bismuth-oxygen (Bi-O) structures during electrochemical CO2 reduction re-action (CO2RR) catalyzed by Bi-based catalyst. In this work, we investigate the CO2RR performance of bismuth oxyhalide (BiOX, including BiOCl, BiOBr and BiOI) catalysts with nanosheet-assembling microsphere morphology and develop an effective strategy of engineering BiOI-derived Bi2O2CO3 through dynamic ion ex-change reaction to promote formate production from CO2RR. Among investigated BiOX catalysts with nanosheet-assembling microsphere morphology, BiOI exhibits the highest ion exchange rate due to the large interlayer spacing and low binding energy between [Bi2O2]2+ layer and I- ion. The produced BiOI-derived Bi2O2CO3 in-herits the large interlayer spacing of BiOI and thus facilitates diffusion of HCO3- ions to promote CO2RR for formate production. By comparison with BiOCl and BiOBr, BiOI exhibits better CO2RR performance, achieving faradaic efficiency of 98 % with a current density of 42.0 mA cm- 2 and excellent long-term durability. Mech-anism studies demonstrate that the sufficient supply of HCO3- ions resulted from large interlayer spacing of BiOI-derived Bi2O2CO3 significantly promotes formate production and, in turn, improves the resistance of Bi-O structures to electroreduction. This work provides a deep insight into the mechanism of BiOX-catalyzed CO2RR for formate production, opening up new opportunities for developing high-performance CO2RR catalysts.
