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The design of promising heterogeneous catalysts is an urgent task for protecting the environment from automotive exhaust pollutants. In this work, the catalytic efficiency of nanosized Ce–Sm and Ce–Sm/γ-Al2O3 samples synthesized using economical coprecipitation and deposition coprecipitation methods, respectively, was investigated for diesel soot oxidation. The physicochemical properties of the synthesized materials were systematically analyzed by means of XRD, BET surface area, Raman spectroscopy, TG-DTA, FT-IR spectroscopy, HRTEM, ICP-OES, XPS, and UV-vis DRS techniques. XRD studies confirmed the formation of nanocrystalline single-phase Ce–Sm oxide solid solutions. HRTEM images showed the presence of small-sized nanocrystals (∼4–15 nm) in the synthesized samples. The Ce–Sm/γ-Al2O3 sample exhibited remarkable thermal stability compared with the Ce–Sm oxide and CeO2 samples, as evidenced by an insignificant variation in the crystallite size and BET surface area with high temperature thermal treatments. Owing to the disparity in the oxidation state of Sm3+ and Ce4+, abundant oxygen vacancies were formed in both the Ce–Sm and Ce–Sm/γ-Al2O3 samples. Interestingly, the oxygen vacancy concentration substantially decreased with increased calcination temperature, attributed to the high level of order of the samples. The catalytic activity results revealed that both the Ce–Sm and Ce–Sm/γ-Al2O3 samples show excellent soot oxidation performance compared with pristine CeO2 due to the presence of abundant oxygen vacancies and superior BET surface area. A 50% soot conversion was achieved at ∼690, 697 and 835 K with the Ce–Sm, Ce–Sm/γ-Al2O3 and CeO2 samples calcined at 773 K, respectively. It was found that the soot oxidation efficiency of the Ce–Sm and Ce–Sm/γ-Al2O3 samples strongly depends on the calcination temperature. Despite its trivial activity difference with respect to the Ce–Sm sample, the outstanding thermal stability of the Ce–Sm/γ-Al2O3 sample is vital in view of the practical working conditions of diesel engines.

A nanocrystalline Ce-Sm-oxide solid solution, with an excellent redox property and remarkable oxygen storage/release capacity, has been synthesized by means of a simple and highly practicable coprecipitation method. To understand the thermal and textural stability, the synthesized catalyst was subjected to calcination at various temperatures (773-1073 K). Physicochemical characterization was achieved using XRD, HRTEM, BET surface area, Raman, ICP-OES, XPS, TG-TDA, UV-vis DRS, TPR, and FTIR techniques, and the catalytic performance was evaluated for the oxidation of CO. Coprecipitation of Ce 4+ and Sm3+ ions through ultra-high dilute solutions provided the single phase Ce0.6Sm0.4O2-δ solid solution in the nanoscale range, as confirmed by XRD and TEM studies. Raman studies revealed two types of lattice defects, namely, oxygen vacancies and MO8 complex defects due to disparity in the oxidation state and ionic radius of Sm3+ and Ce4+, respectively. Calculations made from XPS atomic ratios (Ce/Sm) and Raman band intensity ratios (A D1/AF2g) indicated migration of Sm from the bulk to the surface at elevated temperatures that caused a negative effect on the oxygen vacancy concentration. The doping of Sm3+ into the ceria lattice effectively enhanced the reduction behaviour of ceria by shifting the surface and bulk reduction to lower temperatures. Remarkably, Sm-incorporation showed an optimistic influence on the oxygen storage ability and CO oxidation efficiency of ceria attributed to profound lattice defects and enhanced bulk oxygen mobility. The salient features of physicochemical characterization versus catalytic CO oxidation efficiency of Ce-Sm-oxide solid solutions have been elaborated in this article. Refereed/Peer-reviewed