Ni-Doped Carbon Nanotube-Mg(BH4)2 Composites for Hydrogen Storage

Borohydride magnesium is widely studied as a promising hydrogen storage material due to its high gravimetric and volumetric density (14.9 wt % and 112 g/L, respectively). Different types of catalysts play a good catalytic role in enhancing the hydrogen desorption rates in borohydride systems. In the present paper, multiwalled carbon nanotubes supported Ni (Ni/MWCNTs) were synthesized by a chemical reduction method, and the catalyst was introduced into Mg(BH4)(2) to enhance the dehydrogenation kinetics. The effect of Ni/MWCNTs on the microstructural evolution and hydrogen storage properties of Mg(BH4)(2) is studied. The Mg(BH4)(2)-5wt% Ni/MWCNTs (95M@5NiMWCNTs) sample exhibits the best hydrogen storage performance; it starts to release hydrogen at 93 degrees C, which is 113 degrees C lower than that of the primary Mg(BH4)(2) sample. Moreover, it takes only 3600 s to desorb hydrogen completely at 300 degrees C, showing a significant improvement on hydrogen desorption kinetics. In comparison with the primary Mg(BH4)(2) sample, the dehydriding apparent activation energy of the 95M@5Ni(3)MWCNTs(2) sample is significantly lowered to 119.5 kJ mol(-1). Transmission electron microscopy analysis exhibits that the striking improvement of dehydriding properties of Mg(BH4)(2) is mainly due to the synergistic catalysis of Ni and MWCNTs. This work provides a new method for designing and synthesizing high-performance catalysts in borohydride hydrogen storage materials, which is potentially utilized as a hydrogen supplier for hydrogen fuel cells.