Physicochemical Characteristics and Catalytic Activity of Alumina-Supported Nanosized Ceria-Terbia Solid Solutions

Alumina-supported ceria-terbia solid solution (CeO2-TbO2/Al2O3 = 80:20:100 mol % based on oxides) has been synthesized and analyzed by means of different complementary techniques, namely, X-ray diffraction (XRD), Raman spectroscopy (RS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy (ISS), temperature programmed reduction/oxidation (TPR-TPO), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), BET surface area, and thermogravimetry (TG-DTA). The primary purpose of this investigation was to understand the structural and catalytic properties of ceria-terbia solid solutions dispersed over alumina support and their thermal stability. XRD studies revealed formation of ceria-terbia solid solutions without phase segregation up to the investigated temperature range of 1073 K. No specific inactive compounds were formed between the alumina support and cerium or terbium oxides. As revealed by TEM, the sizes of the Ce-Tb oxide are in the nanometer range (average size similar to 3.7-11.5 nm). The investigated combination catalyst exhibited a high specific surface area and better thermal stability. The RS measurements suggested the presence of oxygen vacancies due to defective structure formation. Both cerium and terbium are present in 3+ and 4+ oxidation states as per the XPS information. ISS studies revealed some surface enrichment of cerium in the extreme periphery of the catalyst surface. The solid solution particles are well distributed over the support surface. As a result of solid solution formation and high dispersion over the support, the reduction temperature of Ce-Tb mixed oxide is observed to be lower than its unsupported form inferring better redox properties. A significantly high OSC and CO oxidation activity is also exhibited by the alumina-supported Ce-Tb oxide system.