Fundamental Study on Mechanisms of Thermal Decomposition and Oxidation of Aluminum Hydride

MY Feng and HP Li and Q Mao and KH Luo and P Hellier, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 24436-24445 (2019).

DOI: 10.1021/acs.jpcc.9b07118

Aluminum hydride (AlH3) has great potential for a variety of propulsion and energy-storage applications. In this study, the ReaxFF reactive force field molecular dynamics simulation is employed to investigate the fundamental reaction mechanisms of thermal decomposition and oxidation of AlH3. The effects of an oxide layer and/or defect are examined, and the detailed process and mechanism of H-2 and H2O formation are illustrated. With the presence of an oxide layer, H-2 production of core-shell AlH3 during the thermal decomposition is slower than that of bare AlH3. As far as oxidation is concerned, any defect enhances the initiation of core-shell AlH3 oxidation and accelerates the oxidation at the early stage of the reaction. Additionally, the presence of O-2 promotes the production of OH. Both thermal decomposition and oxidation of core shell AlH3 show significant H2O production, and H2O is preferentially formed compared with H-2 at the beginning of the reaction. The results reveal that the structural evolution of core shell AlH3 during the thermal decomposition and oxidation proceeds in three distinctive stages, respectively. It is found that during the oxidation, dehydrogenation and oxidation proceed simultaneously although the oxidation rate is limited during the dehydrogenation period.

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