Sustainable Recycling of Formic Acid by Bio-Catalytic CO2 Capture and Re-Hydrogenation

Abstract

Formic acid (FA) is a promising reservoir for hydrogen storage and distribution. Its dehydrogenation releases CO2 as a by-product, which limits its practical application. A proof of concept for a bio-catalytic system that simultaneously combines the dehydrogenation of formic acid for H2, in-situ capture of CO2 and its re-hydrogenation to reform formic acid is demonstrated. Enzymatic reactions catalyzed by carbonic anhydrase (CA) and formate dehydrogenase (FDH) under ambient condition are applied for in-situ CO2 capture and re-hydrogenation, respectively, to develop a sustainable system. Continuous production of FA from stripped CO2 was achieved at a rate of 40% using FDH combined with sustainable co-factor regeneration achieved by electrochemistry. In this study, the complete cycle of FA dehydrogenation, CO2 capture, and re-hydrogenation of CO2 to FA has been demonstrated in a single system. The proposed bio-catalytic system has the potential to reduce emissions of CO2 during H2 production from FA by effectively using it to recycle FA for continuous energy supply.