A High-Capacity, Reversible Liquid Organic Hydrogen Carrier: H₂-Release Properties and an Application to a Fuel Cell

Abstract

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-H2 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.

Hydrogen Production from Formic Acid Attained by Bimetallic Heterogeneous PdAg Catalytic Systems

“…gasification of biomass/biofuels and water splitting), it is mostly produced via steam reforming process, which indeed is not sustainable because it uses fossil fuels and CO 2 is produced [8]. Moreover, aside from that, there are also significant limitations related to its difficult storage and delivery [9], as well as safety issues derived from its high flammability and potential explosiveness [10]. A promising alternative to overcome those limitations is the production of H 2 from hydrogen carrier molecules.…”

A study on hydrogen uptake and release of a eutectic mixture of biphenyl and diphenyl ether

“…Therefore, mixing biphenyl and diphenylmethane to a eutectic composition allows the material to be liquid at ambient temperatures and still provides a high hydrogen storage capacity (6.9 wt%, 60 g-H 2 L −1 ). The hydrogenation reaction of 1 to a hydrogen-rich mixture 2 and the dehydrogenation of 2 to 1 were demonstrated successfully with a high conversion over 94% with the aid of proper catalysts [10,11] . DFT calculations indicated that dicyclohexylmethane requires a higher temperature (603 K) than bicyclohexyl (568 K) for complete dehydrogenation [11] .…”

“…The hydrogenation reaction of 1 to a hydrogen-rich mixture 2 and the dehydrogenation of 2 to 1 were demonstrated successfully with a high conversion over 94% with the aid of proper catalysts [10,11] . DFT calculations indicated that dicyclohexylmethane requires a higher temperature (603 K) than bicyclohexyl (568 K) for complete dehydrogenation [11] . The addition of diphenylmethane to biphenyl provides a clear advantage of 1 to be in a liquid phase but its hydrogen-rich analogue dicyclohexylmethane provides a drawback of 2, operating at a high reaction temperature upon H 2 release.…”

“…Although biphenyl contains a high gravimetric Scheme 1. (Top) A eutectic mixture of biphenyl and diphenylmethane employed in the previous study [10,11] . (Bottom) A eutectic mixture of biphenyl and diphenyl ether employed in this study.…”

“…Clot et al examined T G D =0 of various N-substituted heterocycles and showed that substitution of N on a 5-membered http://engine.scichina.com/doi/10.1016/j.jechem.2019.05.024 ring tends to be more effective in lowering T G D =0 value than on a 6-membered ring [15] . The values obtained for stepwise dehydrogenation of 10 to cyclohexyl phenyl ether (Entry 1), cyclohexyl phenyl ether to 9 (Entry 2), and 10 to 9 (Entry 3) are shown in [11] . Full thermochemical properties (i.e., reaction enthalpy and Gibbs free energy) of stepwise dehydrogenation of H 2 -rich form ( 6, 10 ) are also presented in Tables S3-S6.…”