The effect of a Ti-V-based BCC alloy as a catalyst on the hydrogen storage properties of MgH2
The effect of Ti0.4Cr0.15Mn0.15V0.3 (termed BCC due to the body centered cubic structure) alloy on the hydrogen storage properties of MgH2 was investigated. It was found that the hydrogenated BCC alloy showed superior catalysis properties compared to the quenched and ingot samples. As an example, the 1 h milled MgH2 + 20 wt.% hydrogenated BCC shows a peak temperature of dehydrogenation of about 294 °C. This is 16, 27 and 74 °C lower than those of MgH2 ball milled with quenched BCC, ingot BCC and an uncatalysed MgH2 sample, respectively. The hydrogenated BCC alloy is much easier to crush into small particles, and embed in MgH2 aggregates as revealed by X-ray diffraction and scanning electron microscope results. The BCC not only increases the hydrogen atomic diffusivity in the bulk Mg but also promotes the dissociation and recombination of hydrogen. The activation energy, Ea, for the dehydrogenation of the MgH2/hydrogenated BCC mixture was found to be 71.2 ± 5 kJ mol H2−1 using the Kissinger method. This represents a significant decrease compared to the pure MgH2 (179.7 ± 5 kJ mol H2−1), suggesting that the catalytic effect of the BCC alloy significantly decreases the activation energy of MgH2 for dehydrogenation by surface activation.
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