Robust Bi Metal–Organic Framework-Derived Catalyst for the Selective Electroreduction of CO2 to Formate at Current Densities up to 1 A cm–2 in Gas Diffusion Electrodes

Electrochemical reduction of CO₂ to useful products requires selective and stable catalysts that can be easily synthesized and are cost-effective. In this work, we investigate the Bi CAU-17 metal–organic framework (MOF) synthesized by a novel and scalable method to generate in situ highly active Bi₂O₂CO₃ catalyst for CO₂ electroreduction to formate in either KHCO₃ or KOH electrolytes. The Bi CAU-17-derived catalyst provides high faradaic efficiencies toward formate (FE_HCOO^– = 85–100%) at current densities up to 1 A cm^–2 in a gas diffusion electrode with a low catalyst loading (0.5 mg cm^–2). Comparative experiments between commercial and in situ generated Bi₂O₂CO₃ from Bi CAU-17 showed that the latter has superior catalytic performance at high current densities (>300 mA cm^–2) and with stable activity after 26 h of continuous electrolysis at 200 mA cm^–2 in the pH range 8–14. These results highlight the importance of generating in situ active Bi/Bi–O sites that promote the selective reduction of CO₂ to formate.