Improvement on hydrogen storage thermodynamics and kinetics of the as-milled SmMg11Ni alloy by adding MoS2

Abstract

In this experiment, the Mg-based hydrogen storage alloys SmMg11Ni and SmMg11Ni + 5 wt.% MoS2 (named SmMg11Ni-5MoS2) were prepared by mechanical milling. By comparing the structures and hydrogen storage properties of the two alloys, it could be found that the addition of MoS2 has brought on a slight change in hydrogen storage thermodynamics, an obvious decrease in hydrogen absorption capacity, an obvious catalytic action on hydrogen desorption reaction, and a lowered onset desorption temperature from 557 to 545 K. Additionally, the addition of MoS2 could dramatically improve the alloy in its hydrogen absorption and desorption kinetics. To be specific, the hydrogen desorption times of 3 wt.% H2 at 593, 613, 633 and 653 K were measured to be 1488, 683, 390 and 192 s respectively for the SmMg11Ni alloy, which were reduced to 938, 586, 296 and 140 s for the MoS2 catalyzed SmMg11Ni alloy at identical conditions. The activation energies of the alloys with and without MoS2 for hydrogen desorption are 87.89 and 100.31 kJ/mol, respectively. The 12.42 kJ/mol decrease is responsible for the ameliorated hydrogen desorption kinetics by adding catalyst MoS2.