http://dx.doi.org/10.15344/2455-2372/2016/124
Abstract
In this paper, we present a statistic thermodynamic model quantitatively describing the pressurecomposition- isotherms (PCI) curve, which consists of hydrogen storage capacity, temperature, and equilibrium pressure in the hydriding and dehydriding (H/D) reactions, and a theoretical kinetic model to clarify the H/D kinetic mechanism of hydrogen storage alloys. The results of the calculations are well agreed with the experiments performed with La20.5MgNi78.5 and La15.5Mg6Ni78.5 alloys, their maximum hydrogen storage capacities and the hydride formation enthalpies at 303~333 K are 1.41 wt.% H2 and -31.64 kJ/mol H2 for La20.5MgNi78.5 and 1.31 wt.% H2 and -27.23 kJ/mol H2 for La15.5Mg6Ni78.5, respectively. A new diffusion kinetic model is proposed with the consideration of Pilling–Bedworth Ratio, i.e. hydrogen-induced volume change used for studying the hydrogen absorption reaction kinetics. The activation energies are calculated to be 31.25 kJ/mol H2 for La20.5MgNi78.5 and 24.24 kJ/mol H2 for La15.5Mg6Ni78.5, respectively.