FeNi3 alloy doped carbon spheres for improving hydrogen storage performance of MgH2

MgH 2 is one of the ideal hydrogen storage materials because of its high hydrogen storage density, but the thermodynamic stability and slow kinetics of Mg/MgH 2 system hinder its practical application. Transition metal catalyst doping has become an important strategy to improve the hydrogen storage kinetics of MgH 2 . In this work, FeNi 3 @CS was prepared by solvothermal method with carbon spheres (CS) as the support, and introduced into Mg/MgH 2 system to prepare MgH 2 –FeNi 3 @CS composite. The initial dehydrogenation temperature of MgH 2 –FeNi 3 @CS composite is 565 K, which is 100 K lower than additive-free MgH 2 . At 423 K, MgH 2 –FeNi 3 @CS composite could absorb 4.5 wt% H 2 , while the hydrogen absorption capacity of MgH 2 without additives is only 2.0 wt%. After 10 cycles, the hydrogenation and dehydrogenation capacity could be maintained at 5.6 wt% and 4.5 wt%, respectively. In addition, the activation energy of MgH 2 –FeNi 3 @CS composite decreased by 52 kJ/mol compared with MgH 2 . FeNi 3 was in situ converted to Mg 2 NiH 4 and Fe after hydrogenation-ball milling, which were considered as the catalytic active substances in Mg/MgH 2 system. The synergistic catalysis of Mg 2 Ni/Mg 2 NiH 4 , Fe and carbon materials has a positive effect on improving the hydrogen storage performance of Mg/MgH 2 system.