Recent Progress in Electrocatalytic CO₂ Reduction to Pure Formic Acid Using a Solid-State Electrolyte Device

The electrocatalytic CO2 reduction reaction (CO2RR) to formic acid has gained significant attention as a potential environmentally friendly approach to reducing CO2 emissions and producing carbon-neutral liquid fuels. However, several challenges must be addressed to achieve the production of high-purity and high-concentration formic acid through CO2RR. One major challenge is the formation of a formate mixture instead of pure formic acid in conventional reactors. This requires costly downstream purification and concentration processes to obtain pure formic acid. To overcome this problem, a three-compartment reactor design has been proposed where a solid-state electrolyte (SSE) is inserted between the anode and cathode compartments to recover pure formic acid directly. This reactor design involves the use of an anion exchange membrane (AEM) and a cation exchange membrane (CEM) to separate the anode and cathode compartments, and a center compartment filled with high-conductivity SSE to minimize ohmic resistance. Several studies have implemented this reactor design for continuous CO2RR and have reported remarkable improvements in the concentration and purity of the formic acid product. In this review, we summarize the recent progress of the SSE reactor design for CO2RR to produce pure formic acid (HCOOH) and propose further research to scale up this technology for industrial-scale applications in the future.