Novel nanosized CexZr1−xO2, CexHf1−xO2 and CexTb1−xO2−δ solid solutions: Structural characteristics and catalytic performance

Nanosized ceria–zirconia, ceria–hafnia and ceria–terbia solid solutions were synthesized by a modified coprecipitation method and evaluated for oxygen storage/release capacity (OSC) and CO oxidation activity. The physicochemical characteristics were investigated by various techniques namely, XRD, Raman, XPS, ISS, UV–vis DRS, TEM and BET surface area. XRD and Raman results revealed formation of Ce0.75Zr0.25O2, Ce0.8Hf0.2O2 and Ce0.8Tb0.2O2−δ solid solutions typical of fluorite like cubic structure. Variation in the lattice parameter confirmed the successful incorporation of dopant cations into the ceria lattice. XPS measurements revealed that Ce is present in both 3+ and 4+ oxidation states in all samples. UV–vis DRS studies suggested the presence of Ce3+ ← O2− charge transfer transitions attributed to oxygen defects in all the samples. ISS measurements indicated surface enrichment of cerium in ceria–hafnia solid solutions. The ceria–hafnia solid solutions exhibited a high OSC and better CO oxidation activity among the investigated samples. Systematic investigation of these materials provided valid information about the key factors that control the catalytic efficiency of the solid solutions for OSC and CO oxidation.

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► CeO2−δ has been a crucial material in TWCs to reduce auto exhaust emissions.
► Physicochemical characteristics are efficiently improved in ceria-based mixed oxides.
► Hf4+ induced more Ce3+ ions in ceria lattice with consequent improvement in OSC.
► The enhanced CO oxidation activity of ceria–hafnia is ascribed to high OSC.
► Key parameters that control CO oxidation activity are discussed.