Solid Bi₂O₃-derived nanostructured metallic bismuth with high formate selectivity for the electrocatalytic reduction of CO₂

CO₂ electrochemical reduction (CO₂ER) is an important research area for carbon neutralization. However, available catalysts for CO₂ reduction are still characterized by limited stability and activity. Recently, metallic bismuth (Bi) has emerged as a promising catalyst for CO₂ER. Herein, we report the solid cathode electroreduction of commercial micronized Bi₂O₃ as a straightforward approach for the preparation of nanostructured Bi. At −1.1 V versus reversible hydrogen electrode in a KHCO₃ aqueous electrolyte, the resulting nanostructure Bi delivers a formate current density of ~40 mA·cm⁻² with a current efficiency of ~86%, and the formate selectivity reaches 97.6% at −0.78 V. Using nanosized Bi₂O₃ as the precursor can further reduce the primary particle sizes of the resulting Bi, leading to a significantly increased formate selectivity at relatively low overpotentials. The high catalytic activity of nanostructured Bi is attributable to the ultrafine and interconnected Bi nanoparticles in the nanoporous structure, which exposes abundant active sites for CO₂ electrocatalytic reduction.