The PDF analysis with TEM, XPS and Raman spectroscopy indicates the formation of homogenous Rh _x Ce _1−x O _2−δ nanocrystalline solid solutions.

We applied a method of plasma arc synthesis to study effects of modification of the fluorite phase of ceria by tin ions. By sputtering active components (Pt, Ce, Sn) together with carbon from a graphite electrode in a helium ambient we prepared samples of complex highly defective composite PtCeC and PtCeSnC oxide particles stabilized in a matrix of carbon. Subsequent high-temperature annealing of the samples in oxygen removes the carbon matrix and causes the formation of active catalysts Pt/CeO_x and Pt/CeSnO_x for CO oxidation. In the presence of Sn, X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM) show formation of a mixed phase CeSnO_x and stabilization of more dispersed species with a fluorite-type structure. These factors are essential for the observed high activity and thermic stability of the catalyst modified by Sn. X-Ray Photoelectron Spectroscopy (XPS) reveals the presence of both Pt²⁺ and Pt⁴⁺ ions in the catalyst Pt/CeO_x, whereas only the state Pt²⁺ of platinum could be detected in the Sn-modified catalyst Pt/CeSnO_x. Insertion of Sn ions into the Pt/CeO_x lattice destabilizes/reduces Pt⁴⁺ cations in the Pt/CeSnO_x catalyst and induces formation of strikingly high concentration (up to 50% at.) of lattice Ce³⁺ ions. Our DFT calculations corroborate destabilization of Pt⁴⁺ ions by incorporation of cationic Sn in Pt/CeO_x. The presented results show that modification of the fluorite lattice of ceria by tin induces substantial amount of mobile reactive oxygen partly due to affecting geometric parameters of ceria by tin ions.

In this work, the reaction properties of mixed silver-nickel oxide AgNiO₂ were investigated in the reaction of CO oxidation ranging from room temperature up to 350 °C. X-ray photoelectron spectroscopy revealed the presence of a single oxidized silver state and the combination of Ni²⁺ and Ni³⁺ species on the surface of the as-prepared mixed oxide. It was established that AgNiO₂ was able to interact with CO at room temperature. It was accompanied by the simultaneous titration of the lattice (O²⁻-like) and weakly charged (O⁻-like) oxygen species. The interaction with CO below 100 °C resulted in the accumulation of carbonate-like species on the AgNiO₂ surface. Above 150 °C, the surface structure of mixed oxide was found to be disrupted, resulting in the formation of individual particles of metallic silver and oxidized nickel.