An improved hydrogen storage performance of MgH2 enabled by core-shell structure Ni/Fe3O4@MIL

Magnesium hydride (MgH 2 ) with high gravimetric hydrogen storage capacity is considered as one of the most potential hydrogen storage materials ; however, its development has been plagued by the high operating temperature and slow kinetics. In this study, we have design and synthesize a core-shell Ni/Fe 3 O 4 @MIL additive to aid the (de)hydrogenation of MgH 2 /Mg system via the co-catalytic effect of in-situ formed Mg 2 NiH 4 /Mg 2 Ni and Fe. The initial dehydrogenation temperature significantly reduces from 613 K to 517 K, and the MgH 2 -Ni/Fe 3 O 4 @MIL composite can reabsorb 4.17 wt% H 2 within 3600 s under 3.0 MPa H 2 at 373 K. Remarkably, the dehydrogenation activation energy of the composite decreases by 61.77 kJ/mol compared to the pure MgH 2 (159.71 kJ/mol). Moreover, the composite also shows good cycling stability without distinct capacity decay after cycling twenty times. Studies show that during dehydrogenation and hydrogenation processes, the Mg 2 NiH 4 /Mg 2 Ni act as catalysts to induce hydrogen desorption/absorption of MgH 2 /Mg. Meanwhile, the unique core-shell structure of the Ni/Fe 3 O 4 @MIL not only provides reaction sites, but also prevents the agglomeration of nanoparticles and maintains stable catalytic activity. This study provides a new idea for designing stable transition metal heterogeneous catalytic system to improve hydrogen storage performance of MgH 2 .