Evaluating Bicarbonate Electrolyzer Configurations for Energy‐Efficient Formate Production

Abstract Reactive carbon capture (RCC) by direct conversion of CO ₂ capture solutions has emerged as a promising alternative to gas‐fed electrolyzers. Leveraging bicarbonate electrolyzers (BEs), RCC eliminates energy‐intensive steps such as CO ₂ regeneration and pressurization. Additionally, BEs prevent failures like carbonate salt deposition common in gas‐fed systems. However, intrinsic challenges in BEs, such as higher cell voltages and lower faradaic efficiencies (FEs), result in greater energy consumption during electrolysis compared to gas‐fed electrolyzers. To evaluate whether an RCC chain (RCCC) is more energy‐efficient for formate production than a gas‐fed carbon chain (GFCC), the study optimizes the BE configuration and compares it to a valorization chain requiring a pure, pressurized CO ₂ stream for gas‐fed electrolyzers. This study shows the most efficient BE setup employs a cation exchange membrane paired with a buffer layer, achieving a FE for formate of ≈75% at a current density of 100 mA cm⁻ ² and a cell potential of 3.1 V. Using this optimized BE, the RCCC demonstrates an energetic advantage over GFCCs in scenarios without CO ₂ recycling. Even with 100% CO ₂ utilization enabled by recycling systems, RCCC remains competitive. With potential improvements in BE performance, RCCC emerges as a promising strategy for converting CO ₂ into formate efficiently.