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 (FEHCOO– = 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.