Ni-CNTs as an efficient confining framework and catalyst for improving dehydriding/rehydriding properties of MgH2

MgH2 is one of the most potential hydrogen storage material with a high gravimetric hydrogen storage capacity. however, its applications have been plagued by its high operating temperature and the relatively poor kinetics for releasing and absorbing hydrogen. In the present study, nanoconfinement or catalytic doping were introduced to improve de/rehydrogenation kinetic properties of MgH2. The MgH2@Ni-CNTs was fabricated by holding the MgH2 particles on the surface of the CNT-Ni. MgH2 supported by carbon nanotubes loaded with Ni nanoparticles (MgH2@Ni-CNTs) shows a superior H2 de/ab-sorption kinetics than that of MgH2. This nano-composite releases H2 at 250 °C with the dehydrogenation capacity of 7.29 wt% within 60 min. The dehydrogenation Ea of MgH2 in MgH2@Ni-CNTs is reduced to 74.8 kJ/mol by the confining and catalytic impact of Ni-CNTs. It also has a significant improvement on rehydriding kinetics, with a 7.20 wt% H2 absorption in 30 min even at a temperature as low as 200 °C. Moreover, the MgH2@Ni-CNTs also shows good cycling stability without distinct capacity decay after cycling ten times. Studies show that during dehydrogenation and hydrogenation processes, the CNTs-Ni act as confining framework and catalyst, can accelerate diffusion of hydrogen and prevent the Mg/MgH2 agglomeration. The application of this novel MgH2@Ni-CNTs extends the horizon of transition metallic catalyst and nanoconfinement, and offers a novel way to enhance the hydrogen storage property of the nanoconfined MgH2.