| Summary: | Amorphous CeO<sub>2</sub>-TiO<sub>2</sub> nanoparticles synthesized by the H<sub>2</sub>O<sub>2</sub>-modified sol-gel method were investigated in terms of the Ce-<i>O</i>-Ce and Ti-<i>O</i>-Ti linkage, local structure, and redox properties. The decrease in the crystallinity of CeO<sub>2</sub>-TiO<sub>2</sub> by H<sub>2</sub>O<sub>2</sub> addition was confirmed. The metal–oxygen linkage analysis showed the difference in size of the metal–oxygen network between crystalline CeO<sub>2</sub>-TiO<sub>2</sub> and amorphous CeO<sub>2</sub>-TiO<sub>2</sub> due to the O<sub>2</sub><sup>2−</sup> formed by H<sub>2</sub>O<sub>2</sub>. The local structure of CeO<sub>2</sub>-TiO<sub>2</sub> was analyzed with an extended X-ray absorption fine structure (EXAFS), and the oscillation changes in the k space revealed the disordering of CeO<sub>2</sub>-TiO<sub>2</sub>. The decrease in Ce-O bond length and the Ce-O peak broadening was attributed to O<sub>2</sub><sup>2−</sup> interfering with the formation of the extended metal–oxygen network. The temperature-programmed reduction of the H<sub>2</sub> profile of amorphous CeO<sub>2</sub>-TiO<sub>2</sub> exhibited the disappearance of the bulk oxygen reduction peak and a low-temperature shift of the surface oxygen reduction peak. The H<sub>2</sub> consumption increased compared to crystalline CeO<sub>2</sub>-TiO<sub>2</sub>, which indicated the improvement of redox properties by amorphization.
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