MOF-derived Ni3Fe/Ni/NiFe2O4@C for enhanced hydrogen storage performance of MgH2

Abstract

Magnesium hydride (MgH₂) is an important material for hydrogen (H₂) storage and transportation owing to its high capacity and reversibility. However, its intrinsic properties have considerably limited its industrial application. In this study, the NiFe-800 catalyst as metal-organic framework (MOF) derivative was first utilized to promote the intrinsic properties of MgH₂. Compared to pure MgH₂, which releases 1.24 wt% H₂ in 60 min at 275 °C, the MgH₂-10 NiFe-800 composite releases 5.85 wt% H₂ in the same time. Even at a lower temperature of 250 °C, the MgH₂-10 NiFe-800 composite releases 3.57 wt% H₂, surpassing the performance of pure MgH₂ at 275 °C. Correspondingly, while pure MgH₂ absorbs 2.08 wt% H₂ in 60 min at 125 °C, the MgH₂-10 NiFe-800 composite absorbs 5.35 wt% H₂ in just 1 min. Remarkably, the MgH₂-10 NiFe-800 composite absorbs 2.27 wt% H₂ in 60 min at 50 °C and 4.64 wt% H₂ at 75 °C. This indicates that MgH₂-10 NiFe-800 exhibits optimum performance with excellent kinetics at low temperatures. Furthermore, the capacity of the MgH₂-10 NiFe-800 composite remains largely stable after 10 cycles. Moreover, the Mg₂Ni/Mg₂NiH₄ acts as a “hydrogen pump”, providing effective diffusion channels that enhance the kinetic process of the composite during cycling. Additionally, Fe⁰ facilitates electron transfer and creates hydrogen diffusion channels and catalytic sites. Finally, carbon (C) effectively prevents particle agglomeration and maintains the cyclic stability of the composites. Consequently, the synergistic effects of Mg₂Ni/Mg₂NiH₄, Fe⁰, and C considerably improve the kinetic properties and cycling stability of MgH₂. This work offers an effective and valuable approach to improving the hydrogen storage efficiency in the commercial application of MgH₂.