Electrochemically Formed Defect-Rich Bismuthene–Bismuth Oxycarbonate Nanosheets Promote Selective Reduction of CO₂ to Formic Acid

Formic acid has a high hydrogen storage capacity and is a valuable chemical for industrially important reactions. The industrial production of formic acid proceeds through the carbonylation of methanol to form methyl formate and its subsequent hydrolysis. This process requires high temperature and pressure, and it relies on the use of fossil fuels. In this context, the electrochemical reduction of CO₂ to HCOOH as the selective C₁ product has emerged as an efficient technique for carbon fixation. Herein, we report the electrochemical transformation of bismuth phytate to active catalyst bismuthene-bismuth oxycarbonate nanosheets under cathodic CO₂ reduction conditions. The electrochemically derived catalyst showed an atomic-level thickness (6.5 nm) with a highly disordered structure. The catalyst reduced CO₂ to HCOOH as the major product with a faradaic efficiency of >94%, and the selectivity of formic acid formation was found to be >97% under optimized conditions. Further, the catalyst demonstrates durability, maintaining a constant current density over 6 h. The two-dimensional nanosheet morphology, atomic-level thickness, and highly disordered structure of the active catalyst provide high selectivity for the formic acid formation.