Synthesis by reactive ball milling and cycling properties of MgH2-TiH2 nanocomposites: Kinetics and isotopic effects

Abstract MgH 2 , MgH 2 –TiH 2 nanocomposites and their deuterated analogues have been obtained by reactive ball milling and their kinetic and cycling hydrogenation properties have been analysed by isotope measurements and high-pressure differential scanning calorimetry (HP-DSC). Kinetics of material synthesis depends on both Ti-content and the isotopic nature of the gas. For pure Mg, the synthesis is controlled by isotope diffusion in Mg and therefore MgH 2 forms faster than MgD 2 . For the MgH 2 –TiH 2 nanocomposites, the synthesis is controlled by the efficiency of milling. Kinetics of reversible hydrogen/deuterium sorption in nanocomposites have been studied at 548 K. The rate limiting step is isotope diffusion for absorption and Mg/MgH 2 interface displacement for desorption. HP-DSC measurements demonstrate that the TiH 2 phase acts as a gateway for hydrogen sorption even in presence of MgO and provides abundant nucleation sites for Mg and MgH 2 phases. The 0.7MgH 2 –0.3TiH 2 nanocomposite exhibits steady hydrogen storage capacity after 100 cycles of absorption–desorption.