Hierarchical porous Li₂Mg(NH)₂@C nanowires with long cycle life towards stable hydrogen storage

Abstract

The hierarchical porous Li₂Mg(NH)₂@C nanowires full of micropores, mesopores, and macropores are successfully fabricated via a single-nozzle electrospinning technique combined with in-situ reaction between the precursors, i.e., MgCl₂ and LiN₃, under physical restriction upon thermal annealing. The explosive decomposition of LiN₃ well dispersed in the electrospun nanowires during carbothermal treatment induces a highly porous structure, which provides a favourable way for H₂ delivering in and out of Li₂Mg(NH) nanoparticles simultaneously realized by the space-confinement of the porous carbon coating. As a result, the thus-fabricatedLi₂Mg(NH)@C nanowires present significantly enhanced thermodynamics and kinetics towards hydrogen storage performance, e.g., a complete cycle of H2 uptake and release with a capacity close to the theoretical value at a temperature as low as 105°C. This is, to the best of our knowledge, the lowest cycling temperature reported to date. More interestingly, induced by the nanosize effects and space-confinement function of porous carbon coating, a excellently stable regeneration without apparent degradation after 20 de-/re-hydrogenation cycles at a temperature as low as 130°C was achieved for the as-prepared Li₂Mg(NH)₂@C nanowires.