Determination of kinetic parameters and hydrogen desorption characteristics of MgH2-10 wt% (9Ni–2Mg–Y) nano-composite

Abstract

Hydrogen desorption kinetic parameters of MgH2 compounds were measured and compared with published gas solid reaction models. The compounds investigated in this study were as-received MgH2, ball milled MgH2, and MgH2 ball milled with 9Ni–2Mg–Y catalyst compound. It was determined that different models were necessary to fit the hydrogen desorption data collected at different temperatures on the same sample, indicating that desorption mechanisms changed with respect to temperature. Addition of (9Ni–2Mg–Y) alloy as a catalyst to MgH2 increased the hydrogen desorption capacity of MgH2 from zero (for as-received MgH2) to about 5 wt% at 350 °C within 500 s. The activation energy value was determined as 187 kJ/mol H2 for the as-received MgH2, 137 kJ/mol H2 for 20 h ball milled MgH2, and 62 kJ/mol H2 for 20 h ball milled MgH2-10 wt% (9Ni–2Mg–Y) nano-composite by the Arrhenius and Kissinger methods. Moreover, the integral heat of H2 desorption for the MgH2-10 wt% (9Ni–2Mg–Y) nano-composite was measured to be about 78 ± 0.5 kJ/mol H2 by adsorption micro-calorimetry consistent with the results of the Arrhenius and Kissinger methods.