Cerium oxide, or ceria, is a material widely used in industry and
catalysis. Catalytic systems consisting of active metals and cerium
oxide are used for example in automotive industry for oxidation of
CO and reduction of NOx in waste gases or as a cathode material
in the solid oxide fuel cells [1]. One of the most promising future
applications of cerium oxide is its use as an electrode material in
Proton Exchange Membrane Fuel Cells (PEMFC) [2,3].
The catalytic properties of cerium oxide originate from its
easy transformation from CeO2 to Ce2O3, which is accompanied
by a release of oxygen (so called Oxygen Storage
Capacity). During this process, the cerium atoms change their
oxidation state from Ce4þ to Ce3þ. This transition has a
relatively low activation energy, and can be reversed simply by
annealing the catalyst in oxygen-rich atmosphere [4].
The desired catalytic properties of cerium oxide can be
adjusted by suitable metal or oxide additives [5–8]. These
additives may induce partial reduction of the cerium oxide
either by creating oxygen vacancies at the surface or by
redistribution of electrons between the cerium atoms and the
additive. Tin, in particular, interacts very strongly with the
cerium oxide. Previously, it was shown, that deposition of
even a small amount of tin causes strong reduction of the
cerium oxide and leads to formation of the Sn–Ce–O mixed
oxide [9,10]. This mixed oxide exhibits greater catalytic
activity than the individual tin and cerium oxides [11]. Similar
behavior has also been observed for an inverse system, where
metallic cerium was deposited onto a flat tin dioxide surface
[12]. Formation of cerium-based mixed oxides was also
reported for aluminum [13] and tungsten