Dehydrogenation behavior and mechanism of LiAlH4 adding nano-CeO2 with different morphologies
Chunmin Zhang, Long Liang, Shaolei Zhao, Zhijian Wu, Shaohua Wang, Dongming Yin, Qingshuang Wang, Limin Wang, Chunli Wang, Yong Cheng
Abstract
Complex hydride LiAlH 4 , as a hydrogen storage material, possesses high theoretical hydrogen storage capacity (10.5 wt.%). However, highly efficient additives are urgently required to modify its thermal stability and sluggish kinetics. Some additives exhibit unique morphology-dependent characteristics. Herein, the efficient rare earth oxide nano-CeO 2 additives with different morphologies (nanoparticles, nanocubes, and nanorods) are prepared by the hydrothermal method, and the intrinsic properties are characterized. The three different morphologies of nano-CeO 2 , which are different in the Ce 3+ content and specific surface area, are added to LiAlH 4 to improve the dehydrogenation behavior. The LiAlH 4 -CeO 2 -nanorod composite exhibits the optimal dehydrogenation behavior, which begins to desorb hydrogen at 76.6 °C with a hydrogen capacity of 7.17 wt.%, and 3.83 wt.% hydrogen is desorbed within 30 min at 140 °C. The dehydrogenation process of the composites demonstrates that hydrogen release is facilitated by the in-situ formed CeH 2.73 and the facile transition between the oxidation states of Ce 4+ and Ce 3+ . Combined with density functional theory calculations, the addition of nano-CeO 2 can weaken the Al-H bond and accelerate the decomposition of [AlH 4 ] 4− tetrahedron, which is consistent with the reduction of the decomposition activation energy.