A comparative study on the hydriding kinetics of Zr-based AB2 hydrogen storage alloys

Two kinetic models (Jander model and Chou model) are used to investigate the hydrogen absorption kinetic mechanism of Zr-based AB2 type Laves phase alloys (Ti0.1Zr0.9Mn0.9V0.1Fe0.5Co0.5, Ti0.1Zr0.9(Mn0.9V0.1)1.1Fe0.5Ni0.5 and Ti0.1Zr0.9Mn0.9V0.1Fe0.55Ni0.55). The analysis shows that the rate-controlling step is the diffusion process at high temperatures in the range from 673 K to 923 K with a low hydrogen concentration (solid solution phase). Both models can well describe the experimental data but Chou model is preferred. Chou model is simpler and easier to use for analyzing the experimental results. The activation energies calculated using Chou model with the least square method are 29.3 kJ/mol H2 for Ti0.1Zr0.9Mn0.9V0.1Fe0.5Co0.5, 43.8 kJ/mol H2 for Ti0.1Zr0.9(Mn0.9V0.1)1.1Fe0.5Ni0.5 and 48.5 kJ/mol H2 for Ti0.1Zr0.9Mn0.9V0.1Fe0.55Ni0.55, which are close to the values reported in the literature (28.3 kJ/mol H2 for Ti0.1Zr0.9Mn0.9V0.1Fe0.5Co0.5 and 40.3 ± 1.5 kJ/mol H2 for both Ti0.1Zr0.9(Mn0.9V0.1)1.1Fe0.5Ni0.5 and Ti0.1Zr0.9Mn0.9V0.1Fe0.55Ni0.55).