Enhanced Formate Concentration via Alkaline CO 2 Electrolysis Using a Nickel Anode in a Zero–Gap Electrolyzer

High Resolution Image Download MS PowerPoint Slide The electrochemical reduction of CO 2 to formic acid is a promising route for decarbonizing the conventional industrial production of formic acid. Among the three most successful electrolyzers, the zero–gap (ZG) design stands out for its low cell complexity, making it particularly attractive for scalable applications. However, the low product concentration at the reactor outlet increases the cost of downstream purification processes, penalizing the ZG electrolyzer. This study addresses this technical challenge by using a ZG electrolyzer with an anionic exchange membrane (AEM) configuration, incorporating a PiperION AEM, a Bi 2 O 3 –coated gas diffusion electrode (GDE) as the cathode, and either a nickel mesh or IrO 2 –coated GDE as the anode electrode. Surprisingly, the nickel mesh outperformed the IrO 2 –coated GDE across the studied key performance indicators (KPs). At current densities of 50 and 100 mA cm –2, the cell operated with faradaic efficiencies ranging from 94.24 to 75.50%, low energy consumption values between 2.69 and 4.63 kWh kg –1 formate, and achieved the highest reported formate concentration (0.555 M) for a ZG cell design with an AEM configuration. Techno–economic analysis indicates a promising outlook for scalability using the presented ZG electrolyzer configuration with the nickel mesh.