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

The urgent need to reduce CO₂ emissions has motivated the development of CO₂ capture and utilization technologies. An emerging application is CO₂ transformation into storage chemicals for clean energy carriers. Formic acid (FA), a valuable product of CO₂ reduction, is an excellent hydrogen carrier. CO₂ conversion to FA, followed by H₂ release from FA, are conventionally chemically catalyzed. Biocatalysts offer a highly specific and less energy-intensive alternative. CO₂ 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. H₂ production from formate is also catalyzed by several microorganisms possessing either formate hydrogenlyase or hydrogen-dependent CO₂ reductase complexes. Combination of these two processes can lead to a CO₂ -recycling cycle for H₂ production, storage, and release with potentially lower environmental impact than conventional methods.