Preparation of Mg-Mg2Ni/C composite and its excellent hydrogen storage properties

Magnesium hydride (MgH2) is a promising hydrogen storage material with high weight and volume hydrogen capacity. However, higher operating temperature and reversible hydrogen capacity decay inhibit its wide application. To address these issues, Mg-Mg2Ni/C was obtained by ball milling magnesium and nickel-Metal Organic Framework (Ni-MOF), and following calcinations. Initial dehydrogenation temperature of the composite is 530 K, 70 K lower than that of MgH2, and the apparent activation energy of the composite is 77.6 +/- 2.1 kJ/mol, which is only 50% of MgH2. At 423 K, the hydrogen capacity of the composite is about 6 wt% within 3600 s, and keeps unchanged after ten cycles. The carbon material introduced by Ni-MOF inhibits the agglomeration of Mg, and Mg2Ni/Mg2NiH4 acts as a "hydrogen pump" in de/hydrogenation process. The carbon coating and "hydrogen pump" lead to the improvement of the ab/desorption kinetics and cycling stability. This attempt paves a potential way to achieve high performance Mg-based composite hydrogen storage materials.