Effect of hydrogen absorption/desorption cycling on hydrogen storage performance of LaNi4.25Al0.75

The effect of hydrogen absorption/desorption cycling on the hydrogen storage properties of LaNi4.25Al0.75 was investigated. The pressure-composition (PC) isotherms for absorption/desorption and absorption kinetics were measured at 363, 383 and 403 K, for both after initial activation and 1000 absorption/desorption cycles. The plateau pressures and storage capacity absorption kinetics were slightly changed after long-term cycles, while significant degradation of absorption kinetics was observed. Cycling could result in pulverization of the bulk alloy. The particle size distribution after 1000 cycles was narrower (0.36–103 μm) compared to that after initial activation (0.78–301 μm), with volume mean diameter decreasing from 34.81 to 11.34 μm. The change of hydrogen absorption/desorption properties of LaNi4.25Al0.75 over 1000 cycles has been explained by considering the disproportionation property of LaNi4.25Al0.75, the pulverization phenomena and the impurities from charging hydrogen employed in cycling.