Hydrogen absorption/desorption kinetics of magnesium nano-nickel composites synthesized by dry particle coating technique

Dry particle coating technique was utilized for coating nano-nickel on magnesium particles. The objectives of this study were to evaluate the effects of the nanocatalyst (Ni) on the hydrogen absorption and desorption kinetics of the Mg-based composite (Mg–Ni). Hydrogen absorption curves plotted as a function of time showed that composites processed for longer periods of time exhibited significantly higher hydrogen absorption rates. With increased coating time, the catalyst was more evenly distributed over the Mg surface, resulting in the formation of a composite with increased hydrogen capacity and kinetics. Meanwhile, no significant morphology change in the composites was observed. A change in the hydrogen absorption rate as a function of time was observed. This change in rate implies a change in the rate limiting mechanism from chemical absorption on the Mg particle to diffusion into the Mg particle. TGA results showed that lower coating speeds resulted in lower initial desorption temperatures as well as steeper desorption rates. Higher heating rates resulted in faster reaction rates and therefore reduced hydrogen absorption time and increased hydrogen storage capacity.