Reactivity and stabilization mechanisms of AlH3 crystals coated with polyvinylidene difluoride†

Aluminum hydride (AlH₃) is considered as one of the most promising high-energy hydrogen-storage fuels. Various studies have been conducted to improve its thermostability and compatibility with polar plasticizers. As frequently reported, polyvinylidene difluoride (PVDF) has inherent advantages as a coating agent of AlH₃ to improve its stability and compatibility. However, its optimal content and the interaction mechanisms with AlH₃ are still not clear. In this study, AlH₃ crystals coated with different contents of PVDF have been prepared and their thermochemical properties have been analyzed by using VST and DSC/TG techniques. In addition, the effect of PVDF on decomposition reaction pathways of AlH₃ and AlH₃@Al₂O₃ have been investigated using RMD simulations. It has been found that if the content of PVDF is less than 8%, it may enhance the stability of AlH₃. However, once the content is over 20%, the decomposition of AlH₃ would be promoted. In addition, even if PVDF can inhibit the initial dehydrogenation of AlH₃ during the induction period, once the fast exothermic reactions initiate, the corresponding energy barriers would be lowered with faster H₂ release.