Annick Hubin

Modeling and Quantification of Electrochemical Reactions in RDE (Rotating Disk Electrode) and IRDE (Inverted Rotating Disk Electrode) Based Reactors

Whether it is for the design of a new electrochemical reactor or the optimization of an existing electrochemical process, it is of primordial importance to have the possibility to predict the behavior of a system. For example, the process of electrogalvanization of steel on an industrial scale would not be possible without knowing the main and side reactions taking place during the deposition of zinc on the metallic surface. However, understanding their mechanism is only the first point. The characteristic parameters of the reaction need to be identified and quantified in order to obtain a correct reactor design and to achieve the optimal operating conditions. Nowadays, part of the technological know-how still relies on best practice guidance, most often gained from years of experience with trial and error. Condensing those findings into empirical models may help to control some of the process parameters and make predictions of the system behavior within a small operation window. The problem, however, is that such a model acts as a black box and that a profound comprehension of the physical and electrochemical phenomena will fail to come.

Towards a nano-scale electrochemical and spectroscopic characterization of organic layers on oxide surfaces

Department of Solid State Physics and Magnetism, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium The presented works prepares the ground for galvanic deposition of metallic overlayers on metal oxide surfaces functionalized by phosphonic acid monolayers. In view of this goal, it is necessary to control the most important factors of the electrodeposition process (e.g. flatness and uniformity of distribution). Because of these requirements, in this work, we study the morphology and the interaction between PO(OH)

Use of in-situ spectroscopic ellipsometry to study the behavior of metallic surfaces in different solutions

Visible spectroscopic ellipsometry is applied to monitor in-situ the behaviour of metal and metal oxides in various aqueous solutions. Ellipsometry measures the change in polarisation state upon reflection on a sample and is widely used for the determination of the optical properties of surfaces and thin films. The technique has the advantage that no reference measurements are needed. The use of in-situ ellipsometry in the fields of electrochemistry and corrosion is illustrated by means of three cases. These show the possibilities to obtain film thickness, film refractive index, and the surface roughness of the metal. The first case is related to oxide films on aluminium. For the native oxide (several nm thick) on the metal the roughening of the substrate as well as the changes in oxide film thickness can be observed independently. On thicker oxides (> 100 nm), it is possible to independently determine in-situ the refractive index and thickness of the oxide, as well as the interface roughness. This was shown in a study of the effect of aggressive solution son aluminium/aluminium oxide surface. The second case concerns the electrochemical polishing process of copper. A good coincidence is achieved between the interface roughness and layer thickness from ellipsometry and the expected surface structure for the different electrochemical conditions. A last example shows the possibility of ellipsometry to study the copper corrosion in an aggressive solution. For this case, the thickness and the refractive index of the corrosion film can only be obtained in that part of the spectrum where the oxide is transparent. The degree of corrosion protection was characterised by monitoring the protective film thickness.