Improved hydrogen storage properties of Ti-doped Mg⁹⁵Ni₅ powder produced by hydriding combustion synthesis

Ti was added to Mg-Ni alloy (Mg⁹⁵Ni₅) by a novel hydriding combustion synthesis (HCS) process. The effect of Ti on hydrogen absorption/desorption kinetics of Mg⁹⁵Ni₅ was investigated. The results showed that Ti had superior catalytic effects on hydrogen storage properties of Mg⁹⁵Ni₅, which required only 80 s to reach its saturated hydrogen absorption capacity of 6.29 wt% at 473 K and released 5.49 wt% hydrogen within 900 s at 553 K. Based on an Arrhenius analysis, the activation energy of the hydrogen desorption process was 80.8 kJ mol^-1 for the main phase of MgH₂ in the Ti-doped Mg⁹⁵Ni₅. The excellent hydriding/dehydriding properties were related to the existence of TiH_1.924, which improved the efficiency of mechanical milling and was helpful in the refinement of the crystallite size of MgH₂, resulting in more fresh surface area and grain boundary area. Besides, it was thought to restrain the Mg particles from growth during the hydrogenation/dehydrogenation cycles.