Synthesis of α-AlH3 by organic liquid reduction method and its hydrogen desorption performance

Abstract

Aluminum hydride (AlH3) is considered to be a promising hydrogen storage material due to its moderate dehydrogenation temperature and high hydrogen desorption capacity. However, AlH3 has multiple crystal forms, and it is difficult to prepare a single crystalline, which restricted the development of this material. In this study, a new organic liquid reduction method was used to prepare pure α-AlH3. The synthesis process includes two steps: primary reduction reaction in ether and subsequent desolvation reaction in toluene. The effects of reaction conditions on product composition were discussed in detail. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were used to characterize the crystal structure and morphology of reaction products. Research results show that the final product is composed of α-AlH3 and γ-AlH3. The composition proportion of α-AlH3/γ-AlH3 can be adjusted by controlling reaction conditions. Through comparison and analysis, an optimal synthetic condition has been gained to obtain pure α-AlH3. The dehydrogenation performance of the obtained pure α-AlH3 were studied through thermal analysis methods. It is found that the α-AlH3 has a hydrogen desorption capacity of about 9.6 wt% below 200 °C. The dehydrogenation activation energy was also evaluated by using Kissinger and Friedman methods. This study provides a more simple and efficient method for synthesising pure α-AlH3, and also offers some reference for the future research of AlH3.