Electron-Efficient Co-Electrosynthesis of Formates from CO₂ and Methanol Feedstocks

The electrochemical conversion of CO₂ into valuable chemicals using renewable electricity shows significant promise for achieving carbon neutrality and providing alternative energy storage solutions. However, its practical application still faces significant challenges, including high energy consumption, poor selectivity, and limited stability. Here, we propose a hybrid acid/alkali electrolyzer that couples the acidic CO₂ reduction reaction (CO₂RR) at the cathode with alkaline methanol oxidation reaction (MOR) at the anode. This dual electro-synthesis cell is implemented by developing Bi nanosheets as cathode catalysts and oxide-decorated Cu₂Se nanoflowers as anode catalysts, enabling high-efficiency electron utilization for formate production with over 180 % coulombic efficiency and more than 90 % selectivity for both CO₂RR and MOR conversion. The hybrid acid/alkali CO₂RR-MOR cell also demonstrates long-term stability exceeding 90 hours of continuous operation, delivers a formate partial current density of 130 mA cm^-2 at a voltage of only 2.1 V, and significantly reduces electricity consumption compared to the traditional CO₂ electrolysis system. This study illuminates an innovative electron-efficiency and energy-saving techniques for CO₂ electrolysis, as well as the development of highly efficient electrocatalysts.