Synthesis and Characterization of Nanostructured Ce0.8M0.2O2−δ (M = Sm, Eu, and Gd) Solid Solutions for Catalytic CO Oxidation

In the present study nanosized Sm3+, Eu3+, and Gd3+ doped ceria (Ce0.8M0.2O2−δ, M = Sm, Eu, and Gd) catalytic systems were synthesized by coprecipitation method. The prepared samples were characterized by X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, transmission electron microscopy (TEM), Raman spectroscopy, UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), and temperature programmed reduction (TPR) and finally evaluated for CO oxidation studies. The XRD results suggested that lattice expansion occurred with the introduction of trivalent dopants into the ceria lattice and confirms the formation of solid solutions. Raman spectra corroborated the existence of oxygen defects. TEM results indicate the presence of nanocrystalline nature of the prepared catalysts. TPR analysis revealed that trivalent dopants decreased the surface reduction temperature of the pure ceria by minimum 141 and maximum 249 K. From the activity studies, it was noticed that for pure ceria the observed T50 is 613 K, at this temperature doped ceria exhibited minimum 75 % CO conversion. The above characterization studies demonstrate that trivalent dopants successfully tuned the structural and catalytic properties of pure ceria. Among the examined samples, Ce0.8Sm0.2O2−δ material improved the CO oxidation activity much better than other samples.