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

Abstract

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 (Ea = 96.58 kJ/mol H2), lower onset desorption temperature (Tonset = 200 °C) when compare to the commercial MgH2 (Ea = 142.27 kJ/mol H2, Tonset = 350 °C). Moreover, hydrogen absorption can be achieved at a temperature as low as 100 °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 °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.