Improved hydrogen desorption properties of exfoliated graphite and graphene nanoballs modified MgH2

Magnesium hydride is a leading hydrogen storage material with high hydrogen content, however, suffers with sluggish kinetics. Several methods have been adopted to improve its kinetics, out of which, the addition of catalyst is an impressive way. Carbon materials have shown their promises as catalyst for several hydrogen storage materials. The present work is devoted to investigating the catalytic effects of exfoliated graphite and graphene nanoballs on dehydrogenation kinetics of MgH2. The lowest onset temperature of 282 °C is observed for graphene nanoballs modified MgH2 system. Exfoliated graphite mixed MgH2 desorbed hydrogen at onset temperature 301 °C which is also less than the dehydrogenation temperature of pure MgH2 (410 °C). The dehydrogenation kinetics has significantly improved by the addition of these catalysts as compared to the pure MgH2. The activation energy for the hydrogen desorption of MgH2 was reduced from 170 (pure MgH2) to 136 ± 2 and 140 ± 2 kJ/mol by the addition of exfoliated graphite and graphene nanoballs, respectively. The XRD results confirmed the presence of MgH2 after milling with exfoliated graphite and graphene nanoballs that indicates that there are no reactions during the milling thus both the additives are effective to improve the dehydrogenation as a catalyst.