Electron-Efficient Formate Electrosynthesis from CO₂ and Biomass-Derived Carbohydrates in a Zero-Gap Electrolyzer

Paired electrolysis is being actively developed for co-producing valuable chemicals by leveraging electron transfer at bipolar electrodes. In electrochemical CO₂ reduction to formate, if the reaction is coupled with oxygen evolution reaction, formate experiences severe crossover and oxidation to CO₂ over anode in membrane electrode assembly (MEA) electrolyzer. We reported a convergent electrolysis that produces formate at bipolar electrodes by coupling CO₂ reduction with biomass-derived carbohydrate (for example, glucose) oxidation, maximizing the electron efficiency toward formate (0.88 formate per e^-) and suppressing oxidation of crossed formate at anode. This convergent electrolysis shows low electricity consumption for formate production (76.5 Wh mol^-1 at 100 mA cm^-2), lower than that of conventional CO₂ reduction (180-350 Wh mol^-1). Furthermore, we extended the convergent electrolysis to acetate production by coupling electrochemical CO reduction with waste polylactic acid plastic oxidation. This work offers a framework for the rational design of paired electrolysis for low electricity consumption of chemical production.