Study on the hydrogen storage properties of the dual active metals Ni and Al doped graphene composites.

Abstract The graphene nanosheets are synthesized by modified Hummer's method, based on which the dual active metals Ni and Al doped graphene composites are prepared through in-suit reaction and self-assembly with high-temperature reduction process. The molecular structure, morphology and specific surface area of graphene nanosheets are characterized systematically. The phase composition, surface morphology and hydrogen storage properties of dual active metals Ni and Al doped graphene composites are further investigated by X-ray diffraction, scanning electron microscopy and gas reaction controller. Results show that the graphene nanosheets have typical graphene feature, whose transparent graphene edges can be observed clearly, and the specific surface area is as high as 604.2 m2 g−1. The Ni and Al doped graphene composites are composed with Ni, Al and C phases, which have high hydrogen storage capacity and excellent hydriding/dehydriding stabilities. The maximum hydrogen storage uptake of such composites is up to 5.7 wt% at 473 K, and the dehydriding efficiency is high as 96%∼97% at the dehydriding temperature of 380 K. The hydrogen adsorption and desorption rate control step of the Ni and Al doped graphene composites is complied to the nucleation and two-dimensional growth mechanism. Highlights • The maximum hydrogen storage uptake of the Ni/Al/graphene composites is up to 5.7 wt%. • The Ni/Al/graphene composites have excellent hydriding/dehydriding stabilities. • We first analyze the hydrogen desorption mechanism of Ni/Al/graphene composites. • We use JMA equation to simulate the hydrokinetic and hydrogen release reaction. [ABSTRACT FROM AUTHOR]