Ceria-based materials have a lot of potential uses in many applications such as catalysts in gas sensors, electrolyte and catalytic interfacial layer in solid oxide fuel cells, etc. There are many ways to synthesize ceria compounds: physical techniques (Atomic Layer Deposition, Sputtering), chemical methods (chemical bath deposition, hydrothermal, sol-gels processes) and electrochemical process.

Electrodeposition is an interesting cheap method which can be done at ambient pressure and rather low temperature (less than 100°C). Moreover, it allows the control of the film thickness, in situ. Electrodeposition of ceria is based on the reduction of an oxygen precursor to form hydroxide ions nearby the electrode. Consecutively higher is the pH in the vicinity of the electrode. In the presence of Ce(III) ions in the solution, cerium oxide is thus directly formed on the electrode by precipitation with hydroxide ions.

Depending on the nature of the electrolyte (aqueous or organic), the temperature (from room temperature to 60°C), ranging the solution acidity level (4<pH<8), the imposed potential value (0.7 to 1 V/SCE) and the duration of deposition (20min<t<2h), different ceria thin films features such as thickness, colour, crystallinity, were obtained. This work focused on finding the best conditions (especially pH and oxygen sources) to synthesize adherent, thin and homogeneous films of ceria onto stainless steel for high temperature fuel cell applications.

The optimized deposition conditions lead to homogeneous and covering films. The microstructure and the crystallinity of the ceria thin layers were characterized by SEM and XRD measurements. Electrochemical microscopy (SECM) was used as a unique tool to study the morphology and homogeneity of the films as well as their electronic characteristics. Finally, electrochemical characterisations such as impedance spectroscopy were performed and more precisely impedance spectroscopy under air atmosphere.

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