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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/CeOx and Pt/CeSnOx 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 CeSnOx 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/CeOx, whereas only the state Pt2+ of platinum could be detected in the Sn-modified catalyst Pt/CeSnOx. Insertion of Sn ions into the Pt/CeOx lattice destabilizes/reduces Pt4+ cations in the Pt/CeSnOx 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/CeOx. 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.

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Composites based on graphene and nanosized silicon have recently been of interest in various applications. This paper reports a new method of synthesising a graphene-nano silicon composite material by spraying a mixture of quartz-graphite using an electric arc. The structure and composition of the materials obtained depends on the synthesis conditions. The quality of the graphene structure depends on the concentration of quartz in the load. Higher SiO 2 content leads to the production of more structured graphene. In this case, silicon is present in the materials in the form of carbide nanoparticles deposited on graphene planes. When sputtering pure quartz contained in the cavity of the graphite anode, silicon whiskers form during the synthesis process. The content of the silicon structure depends on the arc current and the sputtering rate of the anode material. The mechanisms that lead to the formation of the graphene structure and silicon whiskers in the condensation process of the products of the electric arc spraying of the anode material are considered.