Interpretation of negative temperature dependence of hydriding reaction in LaNi5-Mg alloys by modified Chou model

A modified Chou model with parameters of temperature ( T ), initial hydrogen pressure ( P 0 ), enthalpy change (Δ H ) and entropy change (Δ S ) is proposed in consideration of thermodynamic driving force. The meaningful activation energy E v can be calculated for the negative temperature dependence of hydriding reaction in hydrogen storage materials. This model is verified by the hydriding/dehydriding experimental data of (LaNi 5 ) 1− x Mg x ( x   =   0, 0.018, 0.041, 0.063). The calculated results indicate that the hydriding kinetics of (LaNi 5 ) 1− x Mg x alloys are controlled by diffusion of hydrogen atom in hydride. The addition of small amount of magnesium improves the kinetic performance of LaNi 5 slightly. Furthermore, the modified Chou model was compared with the previous model that successfully explain the negative temperature depending hydrogenation reaction of Mg-based alloys. The fitting results show that the modified Chou model can describe the hydrogen absorption kinetic mechanism of negative temperature dependent materials more accurately.