THE REACTION-KINETICS OF HYDROGEN STORAGE IN MG2NI

The reaction kinetics of the hydrogen storage in Mg2Ni was investigated by the method of initial rates in the two-phase coexistence region of α- and β-phase hydrides. The experiments of the hydriding reaction were made in the temperature range from 553 to 613 K and at the pressure difference (P0 - Peq) range from 1.5 to 3.0 atm, where P0 and Peq are the initial hydrogen pressure of the reaction and the equilibrium hydrogen pressure at an experimental temperature respectively. To avoid possible non-isothermality due to the large heat of reaction, the rates were measured during the initial stage of each run which insures the isothermal condition of a fixed temperature. It was found that the shrinking unreacted core model could be applied for the analysis of the kinetic data. The rate control step was changed during the hydriding reaction from the chemical reaction of the hydrogen atom with α-phase hydride to the diffusion of hydrogen atom through β-phase, while both the chemical reaction and the diffusion of hydrogen atom influenced the rate in the intermediate step of the reaction. © 1990.