High‐Pressure Raman and Calorimetry Studies of Vanadium(III) Alkyl Hydrides for Kubas‐Type Hydrogen Storage

Abstract

Reversible hydrogen storage under ambient conditions has been identified as a major bottleneck in enabling a future hydrogen economy. Herein, we report an amorphous vanadium(III) alkyl hydride gel that binds hydrogen through the Kubas interaction. The material possesses a gravimetric adsorption capacity of 5.42 wt % H2 at 120 bar and 298 K reversibly at saturation with no loss of capacity after ten cycles. This corresponds to a volumetric capacity of 75.4 kgH2 m(-3) . Raman experiments at 100 bar confirm that Kubas binding is involved in the adsorption mechanism. The material possesses an enthalpy of H2 adsorption of +0.52 kJ mol(-1) H2 , as measured directly by calorimetry, and this is practical for use in a vehicles without a complex heat management system.

A manganese hydride molecular sieve for practical hydrogen storage under ambient conditions

“…3D) are endothermic and do not increase or decrease significantly with increased surface coverage. This supports the mechanism discussed at length previously and supported by computations and high-pressure Raman measurements [15][16][17] in which the 20-40 kJ mol À1 H 2 energy expected for Kubas binding of hydrogen 8,9 is offset by twisting of the material as the pressure increases to open up new binding sites. 26 A MOF has been reported that undergoes structural deformation on application of pressure and this deformation influences the adsorption properties.…”

“…This method of synthesizing a solid-state transition metal hydride from a metal alkyl has been reported previously by our group for Ti, Cr, and V systems. [14][15][16][17] The resulting black air sensitive solid (KMH-1 as synthesized) still contained hydrocarbon as evidenced by the infrared (IR) spectrum ( Fig. S1, ESI †) and because of this was hydrogenated in the solid state at 373 K and 85 bar for 4 hours to give KMH-1 after 1st hydrogenation.…”

“…This is also true for other transition-metal alkyl hydride materials previously reported by our group. [14][15][16][17] The Energy Dispersive X-ray Spectroscopy (EDS) for KMH-1 as synthesized ( Fig. S12 and Table S2, ESI †) and KMH-1 after 2nd hydrogenation ( Fig.…”

“…The enthalpy of hydrogen adsorption of KMH-1 after 2nd hydrogenation was measured directly using an isothermal calorimeter. In this set up 16 a hydrogen uptake measurement is conducted and the calorimeter collects the heat flow data simultaneously as the sample is dosed with hydrogen in increments up to 120 bar. To validate the results a calorimetric measurement of Carbon AX-21 at a similar level of 2 mmol total hydrogen adsorbed was also conducted.…”

“…28 Furthermore, while it is difficult to directly compare batteries and fuel cells, using an estimated price of 50 $ per kW for mass production of fuel cells, 29 the complete fuel cell energy storage system projects as roughly 3-4 times less expensive than the current price of about 200 $ per kW h for lithium batteries. 10 While high-pressure Raman measurements were used to confirm Kubas binding in closely analogous V, Cr, and Ti materials studied previously by our group, [14][15][16][17] inelastic neutron scattering (INS) is a generally considered to be a more informative technique to explore hydrogen binding. Thus, to probe the mechanism of hydrogen binding more deeply, INS studies were performed on a sample of KMH-1 after 2nd hydrogenation; the results are shown in Fig.…”