Preparation and Hydrogen Storage Properties of Mg2CoH5 Nanocrystals with 18-Electrons Structure
This paper reports on the preparation of Mg2CoH5 nanocrystals and their hydrogen storage properties. Mg2CoH5 nanocrystals have been synthesized by mechanical ball-milling the mixture of MgH2 and Co nanoparticles at room temperature under an argon atmosphere. The crystal structure, morphologies, and hydrogen storage properties of the as-prepared Mg2CoH5 nanocrystals are investigated. The results show that the tetragonal Mg2CoH5 nanocrystals (79%) are obtained by a ball-milling method at room temperature. The as-prepared Mg2CoH5 nanocrystals present a spherical shape with a well-proportioned particle size distribution around 80nm. Mg2CoH5 nanocrystals show fast absorption/desorption kinetics. The desorption enthalpy and entropy for Mg2CoH5 are -115.0 kJ·mol-1 H2 and -193.6.1 J·mol-1·K-1 H2, respectively. At 543 K, the hydrogen-desorbed sample can absorb about 1.5wt% hydrogen in 7 min only.