Improved hydrogen storage kinetic properties of magnesium-based materials by adding Ni2P

Abstract

Nickel phosphide (Ni2P) is synthesized via a hydrothermal method, and it is introduced into magnesium hydride (MgH2) to enhance the hydrogen storage performance of magnesium-based materials. For this purpose, magnesium powders are hydrogenated into MgH2, and MgH2-x wt% Ni2P (x = 0, 0.5, 1, 3, 5, 10) composites are prepared by mechanical ball milling method. X-ray diffraction analysis results show that the chemical structure of Ni2P in the MgH2–Ni2P composites does not change during ball milling process, and it can irreversibly decompose and react with MgH2 to form Mg2NiH4 and Mg3P2 during hydrogenation process. The addition of Ni2P significantly decreases the dehydrogenation temperature of MgH2, but it slightly decreases the hydrogen storage capacity of the composites. Also, the hydrogen absorption and desorption kinetics of the composites are greatly improved with the increase of Ni2P content. Moreover, the dehydrogenation activation energies of these composites are evaluated by using Arrhenius equation. The dehydrogenation activation energy values of MgH2 can be reduced to 63.5 ± 3.4 kJ mol−1 by adding 10 wt% of Ni2P. The hydrogenation cycling performance of the MgH2–Ni2P composites are also studied, and the results show that the composites have good phase structure and micromorphology stability during hydrogenation cyclings.