Dehydrogenation behavior and mechanism of LiAlH_(4) adding nano-CeO_(2)with different morphologies

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℃ with a hydrogen capacity of 7.17 wt.%,and 3.83 wt.%hydrogen is desorbed within 30 min at 140℃.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.