Abstract:

The preparation of Mg₂FeH₆ nanocrystals and their hydrogen storage properties were reported. Mg₂FeH₆ nanocrystals were prepared by mechanical ball-milling the mixture of MgH₂ and Fe nanoparticles at room temperature under an argon atmosphere. The processing parameters(time, milling speed), crystal structure, morphologies, and hydrogen storage properties of the as-prepared Mg₂FeH₆ nanocrystals were investigated. The results show that the cubic Mg₂FeH₆ nanocrystals have a yield ratio around 91.4%, and a grain size between 10—30 nm in the powder. However, the agglomeration of particles are more serious. Mg₂FeH₆ nanocrystals show fast absorption/desorption kinetics. The desorption enthalpy and entropy for Mg₂FeH₆ are (-42.8±2) kJ/mol and (-72.0±3) J/(mol·K), respectively. At 503 K, the as-prepared Mg₂FeH₆ nanocrystals can release about 2.5%(mass fraction) hydrogen in 70 min under an initial hydrogen pressure of 6 kPa. Under 2 MPa hydrogen pressure, the rehydrogenation rate for the Mg₂FeH₆ decomposed product is fastZ)

Key words: Mg₂FeH₆ nanocrystal, Mechanical ball-milling, Hydrogen storage property