Abstract
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 O22− 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 O22− 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.
Highlights
CeO2 -TiO2 nanoparticles have various properties depending on their crystallinity, and many studies have reported the improvement of the catalytic performance of CeO2 and TiO2 through amorphization [6,7]
CeO2 -TiO2 nanoparticles are synthesized by the sol-gel method, hydrothermal routes, and coprecipitation [9,10,11]
CeO2 -TiO2 nanoparticles were synthesized by the H2 O2 -modified sol-gel method
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. CeO2 is mainly used with other metal oxides because of its low redox property, specific surface area, and the thermal stability of pure CeO2. CeO2 -TiO2 nanoparticles have attracted much interest for use in various areas where oxidation/reduction reactions of cerium ions are important, such as de-NOx catalysts, photocatalysts, and water gas shift catalysts [3,4,5]. CeO2 -TiO2 nanoparticles are synthesized by the sol-gel method, hydrothermal routes, and coprecipitation [9,10,11]. It is important to understand the mechanism of hydrolysis and condensation reactions in terms of local structure in the sol-gel reaction and to reveal the relationship between structural properties and physicochemical properties. CeO2 -TiO2 nanoparticles were synthesized by the H2 O2 -modified sol-gel method. The relationship between the local structure and the redox properties was examined by H2 -temperature-programmed reduction
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