The role of oxide in hydrogen absorption and desorption kinetics of MgH2-based material

MgH2-based hydrides have a very high affinity to oxygen, leading to the degradation of their hydrogen storage properties. Herein, we use MgO doping and air exposure methods to add oxygen to the MgH2-TiH2 materials, and the hydrogen storage properties of these materials are systematically investigated. The results show that MgO doping accelerates the ambient temperature absorption kinetics, impedes the Mg crystalline growth, and reduces the desorption temperature. In contrast, the air exposure significantly deteriorated the kinetics of MgH2-TiH2 under both ambient and high temperature. The hydrogenation kinetics of the air-exposed sample can be recovered under cycling. Our results indicate that the effect of MgO is highly dependent of the means to introduce MgO and the location of MgO in the matrix structure. Air-exposure is the main factor for the degradation of hydrogen storage properties, but the MgO doping positively affects the performance of the Mg-based hydride.