Hydrogen desorption behaviors of gamma-AlH3: Diverse decomposition mechanisms for the outer layer and the inner part of gamma-AlH3 particle

摘要

Aluminium hydride (AlH3) is a promising hydrogen storage material because it possesses a high theoretical hydrogen capacity of 10.01 wt%. However, the stability and decomposition mechanism of some AlH3 polymorphs (e.g., gamma-AlH3) still remain unclear. In this work, the hydrogen desorption behaviours of gamma-AlH3 with or without TiF3 addition were investigated by hydrogen desorption measurement and thermal analysis. It was revealed that the decompositions of the outer layer and the inner part of gamma-AlH3 particle follow diverse decomposition mechanisms. The outer layer of gamma-AlH3 particle tends to decompose directly, while the inner part of gamma-AlH3 particle prefers to first transform to more stable alpha-AlH3 and then decompose. TiF3 addition significantly lowers the temperature for the direct decomposition of outer layer gamma-AlH3 by about 30 degrees C but scarcely impacts the decomposition of inner part gamma-AlH3, which further confirms the decomposition mechanism of gamma-AlH3. It was suggested that the particle size plays an important role in the thermal stability of gamma-AlH3. The results of this work will help understanding the decomposition mechanisms of other AlH3 polymorphs for hydrogen storage. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.