Compared with titanium oxide (TiO 2 ) and zirconium chloride (ZrCl 4 ), cerium oxide (CeO 2 ) significantly affects the dehydrogenation properties of lithium alanate (LiAlH 4 ). CeO 2 -doped LiAlH 4 samples obtained in different decomposition states were characterized by in situ X-ray diffraction, synchrotron radiation powder X-ray diffraction (PXD) data, and X-ray absorption fine structure (XAFS). PXD and XAFS analyses reveal that CeO 2 is present as a cubic CeO 2−x phase and behaves as a true catalyst. Ce 4+ reduction affects the ability of Li to donate its charge to AlH 4 , thereby weakening the Al–H bond and causing hydrogen to desorb at lower temperatures. Beyond 180 °C, approximately 50% of the O atoms of the CeO 2 catalyst are removed, which results in the formation of long-range disorder rhombohedral Ce 7 O 12 phase and an opposite effect on the dynamics.