Performance and fuel cell applications of reacted ball-milled MgH2/5.3 wt% TiH2 nanocomposite powders

Abstract

The present study aimed to enhance the kinetics behavior and destabilize the thermal stability of MgH₂ powder by high-energy milling of Mg powder under 50 bar of H₂ for several hours using Ti-balls as the milling media. The results showed a monotonical increase in Ti content worn off the milling media and introduced into the milled powders. This gradual doping led to homogeneous distribution of fine Ti particles into the Mg/MgH₂ powder matrix without agglomeration or compositional fluctuations at the micro-level. During the activation stage of the powders, achieved at 350 °C/35 bar H₂ prior to hydrogenation kinetics measurements, elemental Ti reacted with H₂ to form fine TiH₂ particles. Our proposed in situ mechanically induced catalyzation approach was found to be mutually beneficial for decreasing the apparent activation energy of decomposition. In addition, introducing 5.3 wt% of TiH₂ to the MgH₂ powder obtained after 50 h led to the achievement of superior enhancement of gas uptake/release kinetics at relatively low temperatures. The nanocomposite MgH₂/5.3 TiH₂ powder possessed fast hydrogenation/dehydrogenation kinetics behaviors and revealed long cycle lifetimes. This system was successfully employed as a solid-state hydrogen source to charge the battery of a cell-phone device using an integrated Ti-tank/commercial proton exchange membrane-fuel cell system.