| Summary: | The hybrid hydrogen storage method consists of the combination of both solid-state metal hydrides and gas hydrogen storage. This method is regarded as a promising trade-off solution between the already developed high-pressure storage reservoir, utilized in the automobile industry, and solid-state storage through the formation of metal hydrides. Therefore, it is possible to lower the hydrogen pressure and to increase the hydrogen volumetric density. In this work, we design a non-stoichiometric AB<sub>2</sub> C14-Laves alloy composed of (Ti<sub>0.9</sub>Zr<sub>0.1</sub>)<sub>1.25</sub>Cr<sub>0.85</sub>Mn<sub>1.1</sub>Mo<sub>0.05</sub>. This alloy is synthesized by arc-melting, and the thermodynamic and kinetic behaviors are evaluated in a high-pressure Sieverts apparatus. Proper thermodynamic parameters are obtained in the range of temperature and pressure from 3 to 85 °C and from 15 to 500 bar: ΔH<sub>abs.</sub> = 22 ± 1 kJ/mol H<sub>2</sub>, ΔS<sub>abs.</sub> = 107 ± 2 J/K mol H<sub>2</sub>, and ΔH<sub>des.</sub> = 24 ± 1 kJ/mol H<sub>2</sub>, ΔS<sub>des.</sub> = 110 ± 3 J/K mol H<sub>2</sub>. The addition of 10 wt.% of expanded natural graphite (ENG) allows the improvement of the heat transfer properties, showing a reversible capacity of about 1.5 wt.%, cycling stability and hydrogenation/dehydrogenation times between 25 to 70 s. The feasibility for the utilization of the designed material in a high-pressure tank is also evaluated, considering practical design parameters.
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