Sn interaction with the CeO2(111) system: Bimetallic bonding and ceria reduction

Abstract A tin layer 0.8 nm thick was deposited onto the CeO 2 (1 1 1) surface by molecular beam deposition at a temperature of 520 K. The interaction of tin with cerium oxide (ceria) was investigated by X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS) and resonant photoelectron spectroscopy (RPES). The strong tin–ceria interaction led to the formation of a homogeneous bulk Ce–Sn–O mixed oxide system. The bulk compound formation is accompanied by partial Ce 4+ → Ce 3+ reduction, observed as a giant 4f resonance enhancement of the Ce 3+ species. CeO 2 and SnO 2 oxides were formed after oxygen treatment at 520 K. The study proved the existence of strong Ce–Sn interaction and charge transfer from Sn to the Ce–O complex that lead to a weakening of the cerium–oxygen bond, and consequently, to the formation of oxygen deficient active sites on the ceria surface. This behavior can be a key for understanding the higher catalytic activity of the SnO x /CeO x mixed oxide catalysts as compared with the individual pure oxides.