Hydrogen storage performances of the as-milled REMg11Ni (RE = Sm, Y) alloys catalyzed by CeO2

Abstract

The addition of catalysts and rare earth elements is considered to be very effective methods to enhance the hydrogenation/dehydrogenation properties of Mg and Mg-based hydrides. In this paper, the REMg11Ni+ 5 wt% CeO2 (RE = Sm, Y) (named REMg11Ni-5CeO2 (RE = Sm, Y)) alloys were fabricated through ball milling. The phase composition and structure of the as-milled alloys were investigated in detail. The isothermal hydrogen storage thermodynamics and kinetics of the as-milled alloys were measured by using an automatically Sievert apparatus. Non-isothermal dehydrogenation performance of the alloys was investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) at different heating rates. The results revealed that all the as-milled alloys were the nanocrystalline and amorphous structure. The RE = Y alloy had a faster hydriding rate and a lower onset hydrogen desorption temperature than the RE = Sm alloy. The superior property of the RE = Y alloy depended on the decrease of the dehydrogenation activation energy. By means of the measurement of Pressure-Composition-Isotherm (P-C-T) curves, the thermodynamic parameters of the REMg11Ni-5CeO2 (RE = Sm, Y) alloys were calculated, and the dehydrogenation enthalpy change was 74.86 kJ/mol for the RE = Sm alloy and 73.75 kJ/mol for the RE = Y alloy, respectively.