Copper-stabilized bismuth subcarbonate electrocatalysts for durable large-scale formate production at kilowatt power

Electrochemical CO2 reduction (CO2RR) to formate offers a sustainable route for decarbonization, yet achieving both high catalytic selectivity and stability remains challenging. Herein, we achieve a high formate Faradaic efficiency of 92.5% and full-cell energy efficiency of 53.8% at 30 A in a 100 cm2 alkaline membrane electrode assembly (MEA) electrolyzer based on the designed bismuth subcarbonate stabilized with copper (Cu@BOC) catalyst. The electrolyzer demonstrates durable electrolysis at 30 A for 130 h, producing a formate yield of 98.5 mol in 24.5 L of electrolyte (4.02 M). In situ electrochemical spectroscopy measurements reveal the critical role of Cu dopants in stabilizing the catalyst structure from self-reduction, enhancing *OCHO adsorption, and suppressing the competitive hydrogen evolution. A scale-up coupled electrolysis system achieves a molar-scale formate production rate of 10.5 mol h−1 at 2.1 kW and 100 A with a 5 × 100 cm2 MEA electrolyzer stack. This rationally designed coupling electrosynthesis system with efficient formate production performance should significantly accelerate practical industrial applications of CO2RR to formate. Electrochemical CO2 reduction to formate with both high catalytic selectivity and stability remains challenging. Here, the authors report high-performance CO2 electroreduction for molar-scale formate electrosynthesis at kilowatt-scale power by stabilizing bismuth subcarbonate with copper.