Iridium-Catalyzed Continuous Hydrogen Generation from Formic Acid and Its Subsequent Utilization in a Fuel Cell: Toward a Carbon Neutral Chemical Energy Storage

This study represents a notable step toward a potentially carbon neutral energy storage solution based on formic acid as a hydrogen/energy carrier. A catalytic system derived from IrCl3 and 1,3-bis(2'-pyridylimino)-isoindoline (IndH) in the presence of aqueous sodium formate showed high selectivity and robustness for hydrogen generation from formic acid (FA) at 90-100 degrees C under both high and moderate pressure conditions suppressing the formation of CO impurity. Being a solid substance, the catalyst can be recovered by a simple filtration, if necessary. Furthermore, addition of neat formic acid is sufficient to reuse the catalyst and maintain a constant flow of H-2 and CO2 mixture and the stable performance of a coupled fuel cell. The easy to recycle catalyst did not show any loss of activity after 20 days of continuous use, and similar activity was observed even a year after the original preparation. The reactor for formic acid decomposition provided a one to one ratio of a H-2/CO2 mixture that was coupled to a hydrogen/air proton exchange membrane (PEM) fuel cell to demonstrate a stable and continuous conversion of chemical energy to electricity. This integrated system embodies the first example of an indirect formic acid fuel cell, which can function, without the requirement of applying inert conditions and feed gas purification, for extended periods of time.