Superior catalytic effect of facile synthesized LaNi4.5Mn0.5 submicro-particles on the hydrogen storage properties of MgH2

Abstract

Catalytic doping is an important strategy for enhancing the hydrogen storage performance of magnesium hydride. Hence, LaNi4.5Mn0.5 submicro-particles were successfully prepared via a facile wet chemical ball milling method. To further study the catalytic performance, various amount of as-received LaNi4.5Mn0.5 were introduced to MgH2 and the submicro-LaNi4.5Mn0.5 showed best catalytic effect on MgH2. Specifically, experimental results showed that LaNi4.5Mn0.5 submicro-particles modified MgH2 started to release hydrogen at 175 °C, about 150 °C lower than that of additive-free MgH2. At 300 °C, the composite could desorb 6.6 wt% H2 within 6 min. Moreover, the fully dehydrogenated sample could take up hydrogen at room temperature and 4.1 wt% H2 was charged within 10 min at 150 °C. The apparent activation energy of MgH2 for hydrogenation after doping submicro-LaNi4.5Mn0.5 was greatly reduced from 72.50 ± 2.70 to 16.63 ± 1.40 kJ/mol. Furthermore, a hydrogen capacity of 6.1 wt% was maintained after 10 cycles. The synergetic effects between the in-situ formed Mg2Ni/Mg2NiH4, Mn and LaH3 may contribute to the promoted hydrogen dissociation and diffusion along the Mg/MgH2 interface, thus reducing the energy barrier and enhancing the hydrogen storage performance of MgH2.