Structural-Phase State and Morphology of a Composite Based on Magnesium Hydride and Magnesium Oxide Fabricated by Electric Arc Sputtering

This study investigates the effect of magnesium oxide, which is synthesized for the first time through electric arc sputtering, on the desorption temperature and activation energy of hydrogen from a composite based on magnesium hydride. Scanning electron microscopy determines the average particle size of the composite to be 297 nm, which is 33 times smaller than the particle size of magnesium hydride powder obtained under the same mechanical-synthesis parameters in a planetary ball mill. X-ray phase analysis does not reveal any additional phases in the synthesized sample, which confirms there is no catalytic adsorption or desorption reactions of hydrogen during the mechanical synthesis of magnesium hydride with the addition of magnesium oxide. The method of thermally stimulated desorption reveals a decrease in the peak desorption temperature of hydrogen from a composite based on magnesium oxide and magnesium hydride, compared to pure milled MgH₂, by 107, 124, and 127°C at heating rates of 8, 6, and 4°C/min, respectively. The activation energy for hydrogen desorption from the composite was 72 ± 1 kJ/mol, which is 82 kJ/mol lower than the activation energy for hydrogen desorption from magnesium hydride. This result confirms the positive effect of the noncatalytic additive on the kinetics of hydrogen desorption from magnesium hydride.