Improving Hydrogen Sorption Kinetics of the Mg(NH2)2-LiH System by the Tuning Particle Size of the Amide

Mg(NH2)(2) with three different particle sizes of 100, 500, and 2000 nm are obtained by a series of reactions between Mg, H-2, and NH3. The ammonia desorption temperature decreases with the particle size. In addition, the hydrogen desorption kinetics increases obviously with decreasing the particle size of amide after mixing with LiH. The desorption activation energy of the three mixed samples is 122.2, 134.7, and 182.0 kJ/mol with increasing the particle size. After dehydrogenation, the particle size of the product is similar to that of the amide before dehydrogenation. Due to the larger specific surface area and reduced diffusion distance, the absorption kinetics increases as well with decreasing the particle size. The relationship between particle size and hydrogen sorption kinetics is also discussed.