Hydrogen storage in TiVCrMo and TiZrNbHf multiprinciple-element alloys and their catalytic effect upon hydrogen storage in Mg

Abstract

Hydrogen storage performance of nearly equimolar alloys TiVCrMo and TiZrNbH (HEA's) was studied. The alloys were prepared by repeated arc-melting in the form of single-phase alloys and as their multi-phase analogues prepared either by high-energy ball milling (HEBM) of the arc-melted ingots or by HEBM of pure elements. Besides these four-component experimental materials, also their mixtures with Mg were investigated that were prepared by HEBM with Mg (composition in both cases was Mg – 10 wt % HEA). Hydrogen sorption experiments were carried out in temperature interval between 240 °C and 380 °C under hydrogen-gas pressure up to 50 bars. Kinetic curves, temperature-programmed desorption spectra and concentration-pressure isotherms were measured. It was found that activation energy of hydrogen desorption, |Ea|, for materials with Mg was significantly decreased compared to pure Mg. Hydride formation enthalpy, ΔH, observed for all the materials under study was about the same as that for pure MgH2. Hydrogen absorption capacity in pure four-component HEA's was negligible; only hydrogen surface adsorption was detected. The capacity of mixtures of HEA's with Mg was between 3.5 and 6 wt % H2.