Hydrogen Storage Properties of Zr-Based AB₂-x M_x Metal Hydrides Made by Hydriding Combustion Synthesis (HCS)

This study investigated the hydrogen storage properties of Zr-Based AB₂-xMx metal hybride made by HCS (Hydriding Combustion Synthesis). The materials were prepared by HCS 80 wt% AB₂-15 wt% Mg- 5 wt% Mm, HCS 80 wt% AB₂-20 wt% Mg and pure Zr-Based AB₂, These materials were activated at 298 K under 20 bar. Both HCS 80 wt% AB₂-20 wt% Mg and HCS 80 wt% AB₂-15 wt% Mg-5 wt% Mm were absorbed within 1 minute. In the case of the AB₂, it was perfectly absorbed within 6 minutes. Then, the materials were evaluated to obtain P-C-T (Pressure-Composition-Temperature) curves at 298K. As a result, the hydrogen storage capacity of HCS 80 wt% AB₂-20 wt% Mg, HCS 80 wt% AB₂-15 wt% Mg-5 wt% Mm and pure Zr-Based AB₂ were determined to be 1.2, 1.6 and 1.74 wt%, respectively. The activation energy and rate controlling step were calculated by the Johnson-Mehl Avrami equation. The activation energies of HCS 80 wt% AB₂-20 wt% Mg, HCS 80 wt% AB₂-15 wt% Mg-5 wt% Mm and pure Zr-Based AB₂ were 26.91, 20.45, and 60.41 kJ/mol, respectively. Also, the values of η in the Johnson-Mehl Avrami equation for HCS 80 wt% AB₂-20 wt% Mg, HCS 80 wt% AB₂-15 wt% Mg-5 wt% Mm and pure Zr-Based AB₂ are 0.60, 0.51, and 0.44. So, the rate controlling steps which indicate hydrogen storage mechanism are an one dimensional diffusion process.