Evaluating Bicarbonate Electrolyzer Configurations for Energy‐Efficient Formate Production

Reactive carbon capture (RCC) by direct conversion of CO2 capture solutions has emerged as a promising alternative to gas-fed electrolyzers. Leveraging bicarbonate electrolyzers (BEs), RCC eliminates energy-intensive steps such as CO2 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 CO2 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 CO2 recycling. Even with 100% CO2 utilization enabled by recycling systems, RCCC remains competitive. With potential improvements in BE performance, RCCC emerges as a promising strategy for converting CO2 into formate efficiently.