Local Structure and Redox Properties of Amorphous CeO₂-TiO₂ Prepared Using the H₂O₂-Modified Sol-Gel Method

Amorphous CeO₂-TiO₂ nanoparticles synthesized by the H₂O₂-modified sol-gel method were investigated in terms of the Ce-O-Ce and Ti-O-Ti linkage, local structure, and redox properties. The decrease in the crystallinity of CeO₂-TiO₂ by H₂O₂ addition was confirmed. The metal-oxygen linkage analysis showed the difference in size of the metal-oxygen network between crystalline CeO₂-TiO₂ and amorphous CeO₂-TiO₂ due to the O₂^2- formed by H₂O₂. The local structure of CeO₂-TiO₂ was analyzed with an extended X-ray absorption fine structure (EXAFS), and the oscillation changes in the k space revealed the disordering of CeO₂-TiO₂. The decrease in Ce-O bond length and the Ce-O peak broadening was attributed to O₂^2- interfering with the formation of the extended metal-oxygen network. The temperature-programmed reduction of the H₂ profile of amorphous CeO₂-TiO₂ exhibited the disappearance of the bulk oxygen reduction peak and a low-temperature shift of the surface oxygen reduction peak. The H₂ consumption increased compared to crystalline CeO₂-TiO₂, which indicated the improvement of redox properties by amorphization.