A High-Capacity, Reversible Liquid Organic Hydrogen Carrier: H ₂ -Release Properties and an Application to a Fuel Cell

Hydrogen storage in the form of a liquid chemical is an important issue that can bridge the gap between sustainable hydrogen production and utilization with a fuel cell, which is one of the essential sectors in the hydrogen economy. Herein, the application of a potential liquid organic hydrogen carrier, consisting of biphenyl and diphenylmethane, is demonstrated as a safe and economical hydrogen storage material. The presented material is capable of a reversible storage and release of molecular hydrogen with 6.9 wt % and 60 g-H ₂ L ^-1 of gravimetric and volumetric hydrogen storage capacities, respectively, presenting superior properties as a hydrogen carrier. Equilibrium conversion and the required enthalpies of dehydrogenation are calculated using a density functional theory. Experimentally, dehydrogenation conversion of greater than 99% is achieved, producing molecular hydrogen with greater than 99.9% purity, with negligible side reactions; this is further confirmed by nuclear magnetic resonance spectroscopy. Less than 1% of the material is lost after cyclic tests of hydrogenation and dehydrogenation were conducted consecutively nine times. Finally, a dehydrogenation system is designed and operated in conjunction with a polymer electrolyte membrane fuel cell that can generate greater than 0.5 kW of electrical power in a continuous manner, proving its capability as a promising liquid organic hydrogen carrier.