Influence of micro-amount O2 or N2 on the hydrogenation/dehydrogenation kinetics of hydrogen-storage material MgH2

Mg-based hydrogen-storage materials are regarded as promising hydrogen-storage alloys. However, in practical applications, Mg-based hydrogen-storage materials may be exposed to air or to a low-purity-gas environment with particularly oxygen as impurity. In this paper, the influence of a micro-amount of oxygen or nitrogen on the performance of adsorption/desorption of MgH2 hydrogen-storage material has been studied by placing samples in an argon-filled glove box (at atmospheric pressure) with 1000 ppm oxygen concentration. The hydrogen capacity and adsorption/desorption kinetics were measured by using a high-pressure and high-temperature gas-adsorption analyzer. The samples were characterized by X-ray diffraction. The activation energy for hydrogenation has been determined by means of the Arrhenius equation. It is found that the adsorption/desorption of MgH2 improves significantly by a micro-amount of oxygen, especially at high temperature.