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

摘要

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.