Renewable Hydrogen Production and Storage Via Enzymatic Interconversion of CO₂ and Formate with Electrochemical Cofactor Regeneration

The urgent need to reduce CO 2 emissions has motivated the development of CO 2 capture and utilization technologies. An emerging application is CO 2 transformation into storage chemicals for clean energy carriers. Formic acid (FA), a valuable product of CO 2 reduction, is an excellent hydrogen carrier. CO 2 conversion to FA, followed by H 2 release from FA, are conventionally chemically catalyzed. Biocatalysts offer a highly specific and less energy‐intensive alternative. CO 2 conversion to formate is catalyzed by formate dehydrogenase (FDH), which usually requires a cofactor to function. Several FDHs have been incorporated in bioelectrochemical systems where formate is produced by the biocathode and the cofactor is electrochemically regenerated. H 2 production from formate is also catalyzed by several microorganisms possessing either formate hydrogenlyase or hydrogen‐dependent CO 2 reductase complexes. Combination of these two processes can lead to a CO 2 ‐recycling cycle for H 2 production, storage, and release with potentially lower environmental impact than conventional methods.