Adsorption-Enhanced Bismuth Oxide Efficiently Convert CO₂ to Formate Over a Wide Potential Window

Electrochemical conversion of carbon dioxide (CO₂) into high-value-added chemicals using clean energy is a processing method to reduce carbon emissions and store energy. The unsatisfactory adsorption and activation of CO₂ suppress electrochemical reduction over a narrow potential window. Herein, we synthesized CO₂ adsorption-enhanced bismuth oxide nanosheets (syn-Bi₂O₃) using a one-pot low-temperature water bath method. The syn-Bi₂O₃ exhibited marked Faradic efficiency (FE_formate) over 94% in a wide potential window from -0.43 to -1.31 V versus RHE in the flow cell, and demonstrated an appreciable FE_formate of 94.5% at a partial current density of 661.9 mA cm^-2. The in situ spectroscopy and theoretical calculation unraveled the distinct formate production performance of the syn-Bi₂O₃ catalyst, which was contributed by its adsorption of CO₂ and promoting the subsequent formation of intermediates. Furthermore, coupled with the simulated solar cell with the 4 layer 3-cell stacks, the solar to formate and overall solar-to-fuel reach 19.34% and 20.23% with over 0.21 A, respectively. This work provides insights into the practical application of electrochemical CO₂ reduction for formate production driven by solar energy.