In situ preparation of nanocrystalline Ni@C and its effect on hydrogen storage properties of MgH2

Nanocrystalline Ni@C was fabricated by a self-template strategy using benzimidazole as the reductant and carbon precursor, and it exhibited remarkable catalytic effect on hydrogen storage performances of magnesium hydride (MgH2). It was found that MgH2-Ni@C composites exhibited relatively lower sorption temperature, faster sorption kinetics, and more stable cycling performance than that of pure-milled MgH2. The desorption peak temperature was lowered down to 283 degrees C, i.e. of more than 74 degrees C, with respect to pure Mg hydride. For MgH2-Ni@C composites, a total of 6.2 wt% hydrogen was absorbed within 1 h at 300 degrees C. No obvious loss in absorption amount of MgH2-Ni@C composites can be seen after six cycles. An activation energy (E-a) of 103 kJ mol(-1) for MgH2-Ni@C has been obtained, which exhibited an improved kinetics. The presence of in situ synthesized Ni@C prevented the nanograins sintering and agglomeration of MgH2 during cycling, which enhanced dehydrogenation and cycling stability of MgH2-Ni@C composite. The synergetic effect of Ni active species and carbon contributed to the reduced hydrogenation/dehydrogenation temperatures and enhanced kinetics. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.