Improvement of Hydrogen Desorption Characteristics of MgH2 With Core-shell Ni@C Composites

Abstract

Magnesium hydride (MgH2) has become popular to study in hydrogen storage materials research due to its high theoretical capacity and low cost. However, the high hydrogen desorption temperature and enthalpy as well as the depressed kinetics, have severely blocked its actual utilizations. Hence, our work introduced Ni@C materials with a core-shell structure to synthesize MgH2-x wt.% Ni@C composites for improving the hydrogen desorption characteristics. The influences of the Ni@C addition on the hydrogen desorption performances and micro-structure of MgH2 have been well investigated. The addition of Ni@C can effectively improve the dehydrogenation kinetics. It is interesting found that: i) the hydrogen desorption kinetics of MgH2 were enhanced with the increased Ni@C additive amount; and ii) the dehydrogenation amount decreased with a rather larger Ni@C additive amount. The additive amount of 4 wt.% Ni@C has been chosen in this study for a balance of kinetics and amount. The MgH2-4 wt.% Ni@C composites release 5.9 wt.% of hydrogen in 5 min and 6.6 wt.% of hydrogen in 20 min. It reflects that the enhanced hydrogen desorption is much faster than the pure MgH2 materials (0.3 wt.% hydrogen in 20 min). More significantly, the activation energy (EA) of the MgH2-4 wt.% Ni@C composites is 112 kJ mol−1, implying excellent dehydrogenation kinetics.

Electrocatalyst design for the conversion of energy molecules: electronic state modulation and mass transport regulation

“…Generally speaking, compressing the lattice on the surface of the shell is an effective means to improve the ORR activities of the catalysts. 95 However, the stretching of the Pt surface usually leads to excessive binding between the intermediate and the surface of the catalyst, which leads to the desorption difficulty of oxygen species and reduces the catalytic efficiency. Recently, a highly uniform PtPb/Pt core-shell nanoplate with a large biaxial tensile strain has attracted wide attention.…”