MgH2 confinement in MOF-derived N-doped porous carbon nanofibers for enhanced hydrogen storage

Magnesium hydride (MgH2) is one of the most promising hydrogen storage materials, while the high desorption temperature and sluggish kinetics hamper its further commercialization. Herein, a novel MOF-derived 1D N-doped hierarchically porous carbon nanofiber (pCNF) is firstly prepared and used as the scaffold for self-assembly of MgH2/Ni nanoparticles (NPs). The resultant MgH2/Ni@pCNF nanocomposites show faster desorption kinetics (E-a = 96.58 kJ/mol H-2), lower onset desorption temperature (T-onset = 200 degrees C) when compare to the commercial MgH2 (E-a = 142.27 kJ/mol H-2, T-onset = 350 degrees C). Moreover, hydrogen absorption can be achieved at a tem(p)erature as low as 100 degrees C with a capacity of 2.2 wt% within 120 min. Additionally, the composites exhibit excellent cycling stability with a capacity retention over 95.4% after 10 complete re-/dehydriding cycles at 300 degrees C. In-situ HRTEM observations of the desorption process combined with XPS and XRD indicate that the synergistic effects from nanoconfinement of Mg/MgH2 in pCNF, electron-donating ability of N atoms and the "hydrogen pump " function of Mg2Ni/Mg2NiH4 account for the unprecedent hydrogen storage properties. The strategy of using the MOF-derived 1D pCNF as support for nanoparticles provides a new approach for fabricating nanostructured energy materials with enhanced performances.