In-situ catalyzation approach for enhancing the hydrogenation/dehydrogenation kinetics of MgH2 powders with Ni particles

Abstract

One practical solution for utilizing hydrogen in vehicles with proton-exchange fuel cells membranes is storing hydrogen in metal hydrides nanocrystalline powders. According to its high hydrogen capacity and low cost of production, magnesium hydride (MgH2) is a desired hydrogen storage system. Its slow hydrogenation/dehydrogenation kinetics and high thermal stability are the major barriers restricting its usage in real applications. Amongst the several methods used for enhancing the kinetics behaviors of MgH2 powders, mechanically milling the powders with one or more catalyst species has shown obvious advantages. Here we are proposing a new approach for gradual doping MgH2 powders with Ni particles upon ball milling the powders with Ni-balls milling media. This proposed is-situ method showed mutually beneficial for overcoming the agglomeration of catalysts and the formation of undesired Mg2NiH4 phase. Moreover, the decomposition temperature and the corresponding activation energy showed low values of 218 °C and 75 kJ/mol, respectively. The hydrogenation/dehydrogenation kinetics examined at 275 °C of the powders milled for 25 h took place within 2.5 min and 8 min, respectively. These powders containing 5.5 wt.% Ni performed 100-continuous cycle-life time of hydrogen charging/discharging at 275 °C within 56 h without failure or degradation.

Recent developments in the fabrication, characterization and implementation of MgH2-based solid-hydrogen materials in the Kuwait Institute for Scientific Research

“…The authors claimed that this fast kinetic behavior was attributed to the formation of a homogeneous nanocomposite system, in which nano-powders were adhered to all MgH 2 powders without exception. 83 The synthesized nanocomposite was able to perform 100 continuous cycle-life times of hydrogen charging/discharging at 275 C within 56 h without failure or degradation, as elucidated in Fig. 7c.…”

“…6k and l. MgH 2 /5.5 wt% Ni nanocomposite powders obtained aer a short RBM time (25 h) revealed low values for the decomposition temperature (218 C), at which the apparent activation energy (E a ) was 75 kJ mol À1 . 83 In addition, the hydrogenation (Fig. 7a)/dehydrogenation (Fig.…”

“…(a, d, g and j) STEM-BFIs; (b, e, h and k) Mg-Ka 1-2 ; and (c, f, i and l) Ni-La 1 for the powders obtained after different stages of RBM, using a milling media of Ni-balls 83. temperature of 200 C. For example, at this temperature the sample absorbed about 3.5 wt% H 2 within 500 s and approached 6.3 wt% H 2 aer about 2500 s, as shown inFig.…”

Effect of nanostructure Ni on the sorption properties of mechanical milled MgH2 for solid hydrogen storage materials

“…Many efforts have been done to improve the hydriding and dehydriding properties such as element substitution (metal or metal oxides) as catalyst in nanometer scale and modification of ball milling technique have been used to improve sorption and kinetics properties [2][3][4]. Recently, the reactive ball milling under hydrogen atmosphere was successfully introduced to prepare hydrogen storage materials [5][6][7][8]. Here, we report on MgH2 catalyzed with small amount of Ni in nanoparticles scale and the preparation was done by reactive ball milling under 10 bar hydrogen.…”

The role of nano-Ni catalyst in MgH2 obtained by reactive mechanical milling method for solid hydrogen storage application

“…Recently, Eskandarany et al 7 have showed a new approach for catalyzing MgH2 with nano-Ni by high energy reactive ball milling under 50 bar of hydrogen atmosphere. They found that the sorption kinetics was examined at 275 °C within 8 minutes and produced ~5 wt.% H2 for 25 h of milling time.…”