In situ constructed oxygen vacancy-rich Bi2O2CO3 nanosheets derived from BiOI for efficient electrochemical CO2 reduction to formate

Abstract

The electrochemical CO₂ reduction reaction (CO₂RR) to value-added chemicals, such as formate, represents a promising strategy to achieve carbon neutrality and store renewable energy. However, many electrocatalysts exhibit limited faradaic efficiency for formate (FE_HCOO⁻) at high current densities due to the high activation barrier of CO₂ and the competing hydrogen evolution reaction (HER). Bismuth-based materials have emerged as efficient catalysts for formate production, yet the precise control of their microstructures remains a challenge. Herein, we prepared ultrathin and oxygen vacancy-rich Bi₂O₂CO₃ nanosheets (denoted as BOC_R) by reconstructing bismuth oxyiodide (BiOI) nanosheets through an in situ electrochemical anion-exchange approach. The engineered BOC_R catalyst achieved a high FE_HCOO⁻ of >89% across a broad current density range (−50 to −200 mA cm⁻²) and reached a maximum FE_HCOO⁻ of 96.2% at −100 mA cm⁻² along with excellent durability for >17 h in a flow cell. In situ attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and density functional theory (DFT) calculations revealed that the superior CO₂RR performances of BOC_R were the rationalized outcome of abundant oxygen vacancies (V_O), which accelerated electron transfer kinetics during the CO₂RR process, enhanced the adsorption of the key intermediates (*OCHO), and thus promoted the formation of formate products. The work provides some new insight into the design and synthesis of Bi-based electrocatalysts containing abundant oxygen vacancies for highly efficient CO₂ reduction to produce formate.