Hydrogen storage characterization of Mg_(17)Ni_(1.5)Ce_(0.5)/5 wt. Graphite synthesized by mechanical milling and subsequent microwave sintering

摘要

Mg_(17)Ni_(1.5)Ce_(0.5)/5 wt. Graphite was synthesized by microwave sintering in the present work. Its pressure-composition-isotherm curves exhibit two plateaus corresponding to MgH_2 and Mg_2NiH_4 from 563 K to 623 K, and the hydrogen storage capacity is about 5.6 wt. at 593 K. Differential scanning calorimeter results reveal that its onset temperature and activation energy of desorption are 654.6 K and 107.41 kJ/mol, respectively, which are lower than those of MgH_2. Its rate-controlling step of the dehy driding reaction is the diffusion of hydrogen at lower temperature according to Chou model. As the catalyst and microwave absorbing agent, the addition of graphite is in favor of improving the hydrogen storage properties of the sample.