Remarkable hydrogen storage properties at low temperature of Mg-Ni composites prepared by hydriding combustion synthesis and mechanical milling

Mg100-xNix (x = 0, 5, 10 and 20) composites with the main particle size below 400 nm were synthesized by hydriding combustion synthesis followed by mechanical milling (HCS + MM). XRD and TEM results of Mg100-xNix revealed that the products had the phases of MgH2, Mg2NiH4, Mg2NiH0.3 and Mg (Mg just for x = 0 and 5), with Mg-Ni hydrides distributing uniformly in the composites. DSC results of Mg100-xNix composites demonstrated that the hydrogen desorption peak for MgH2 in the Mg80Ni20 composite was decreased to 223.9/247.3 degrees C. With 5 at% Ni added, the Mg95Ni5 reached its saturated hydrogen absorption capacity of 5.80 wt% within 100 s at 473 K. As for Mg80Ni20, a hydrogen absorption of 3.70 wt% at 313 K and a desorption capacity of 1.84 wt% at 473 K could be obtained. The Mg2Ni distributing uniformly in Mg-Ni composites significantly facilitates hydrogen diffusion and improves the hydriding/ dehydriding kinetics and hydrogen storage capacity at low temperature. The amount of Ni is related greatly to the hydriding/dehydriding properties of Mg100-xNix, which makes the hydrogen storage capacity and hydriding/dehydriding kinetics remarkable. Besides, the excellent cycling stability was also obtained through the isothermal de/hydrogenation cycling kinetics measurement.