Dehydriding properties of γ-AlH3

AlH3 is a promising hydrogen storage material due to its high hydrogen capacity (10 wt%) and relatively low dehydriding temperature. In this work, gamma-AlH3 was prepared by organometallic synthesis method and the effects of ball milling on dehydriding properties of gamma-AlH3 were investigated systematically. Experimental results shows that as-prepared gamma-AlH3 releases about 8.3 wt% of hydrogen in the temperature range of 130-160 degrees C at a heating rate of 2 degrees C/min. Ball milling significantly improves the dehydriding behavior of gamma-AlH3. DSC-MS analysis reveals that the dehydriding temperature of gamma-AlH3 ball-milled for 10 h decreases by around 30 degrees C. In addition, the dehydriding activation energy of gamma-AlH3 ball-milled for 2 h decreased from 87 to 68 kJ/mol. Isothermal dehydriding measurements demonstrate that duration needed to release 90% hydrogen for as-prepared gamma-AlH3 is 280 min, but it takes only 82 min after ball milled for 10 h to release the same amount of hydrogen. Moreover, the dehydriding path of gamma-AlH3 is changed by ball milling. As-prepared gamma-AlH3 transforms to alpha-AlH3 before dehydriding, while ball-milled gamma-AlH3 prefers to dehydride directly without firstly transforming to alpha-AlH3. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.