Nitrogen-Doped Graphene-Supported Nickel Nanoparticles Reveal Low Dehydrogenation Temperature and Long Cyclic Life of Magnesium Hydrides.

Abstract

Magnesium hydride (MgH2) is a promising hydrogen storage candidate due to its large capacity; however, high dehydrogenation temperature and slow kinetic rates are the main bottlenecks. Herein, we proposed a strategy for designing nitrogen-doped graphene-supported Ni nanoparticles (NPs) (Ni@NC) to tackle these problems. The results showed that the MgH2 + 15 wt % Ni@NC nanocomposite reduced the on-set dehydrogenation temperature to 195 °C, which was 175 °C lower than pristine MgH2. In addition, MgH2 + 15 wt % Ni@NC achieved 1.7 and 6.5 wt % desorption capacities at 225 and 300 °C, respectively, while absorbing 5.5 wt % hydrogen at 100 °C. The MgH2 + 15 wt % Ni@NC nanocomposite showed high cyclic stability, achieving 98.0% capacity retention after 100 cycles at 270 °C with negligible loss in capacity. This remarkable hydrogen storage performance can be attributed to the homogeneous distribution of Ni NPs on N-doped graphene layers, in situ formed Mg2NiH2 NPs, and multiphasic regions, promoting the nucleation and growth process during hydrogenation/dehydrogenation, which stabilized and improved the cyclic stability. This strategy paves the way to developing high-performance MgH2 for large-scale applications.