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.
A novel, liquid‐phase hydrogen storage material was produced by mixing biphenyl (C12H10, solid) and diphenylmethane (C13H12, liquid) with a mass ratio (wt %) of 35:65. The eutectic mixture was proved to be liquid at ambient temperature with a viscosity of 3.0 cP at 25 °C and a vapor pressure of 1.4 Pa at 25 °C, which potentially meets the requirements for an efficient hydrogen storage system. A theoretical study using COSMO‐RS method further confirms that an optimum composition of biphenyl and diphenylmethane for the formation of eutectic mixture is 37:63 by mass, which is very close to the composition found experimentally. The eutectic mixture exhibited a superior activity for hydrogenation reactions conducted at 120 °C under 50 bar of H2 pressure in the presence of a Ru (5 wt %)/Al2O3 catalyst. Hydrogen uptake of the eutectic mixture tested was close to full conversion, which corresponds to 6.9 wt % and 60.1 g L−1 of gravimetric and volumetric hydrogen storage capacities, respectively.
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