Kinetics and mechanism of hydrogen release from isothermal decomposition of AlH₃

Aluminum trihydride is an ideal hydrogen storage material. Aluminum trihydride is prone to dehydrogenate in ambient atmosphere due to its low chemical and thermal stability. Therefore, its thermal stability has become the focus of attention during production, use, transportation, and storage. In this paper, the pressure curve of the gas produced during the thermal decomposition of AlH₃ with time at 333–373 K was obtained using an isothermal thermal decomposition gas measurement device. The isothermal thermal decomposition kinetic parameters of AlH₃ were calculated using Arrhenius equation and mode matching method. The results show that the decomposition of AlH₃ can be divided into three stages. The time required for AlH₃ to reach a certain decomposition depth at different temperatures was obtained from Semenov equation. At room temperature, the time required for the decomposition depth of AlH₃ (purity>99%) to reach 0.1% is 224.7 days in a vacuum environment. Furthermore, the possible decomposition mechanism of AlH₃ was proposed by X-ray diffraction, gas chromatography, and transmission electron microscopy.