The use of geometrically well-defined electrodes is one of the key features of our experimental approach. By designing the geometry of the investigated electrochemical system, one obtains the ability to operate an electrochemical model cell in a highly defined manner. This is crucial for separating electrochemical elementary parameters (e.g. ionic and electronic conductivity, or interfacial and chemical capacitance) and for locating the origin of the rate-determining step of an electrode reaction. Due to their defined surface area, model electrodes are also an ideal platform for carrying out in-situ investigations of chemical processes on surfaces – e.g., for studying electrolysis reactions.
Geometrically well-defined microelectrodes allow the spatially resolved measurement of conductivity in inhomogeneous ceramics and enable the investigation of grain boundary properties. Moreover, microelectrodes are a powerful tool for the investigation of electrode kinetics since their modifiable shape allows to independently vary the triple phase boundary length and surface area of an electrode, which are potential reactions sites of electrode processes. At the same time, a large number of microelectrodes on a sample allows the corresponding statistical significance to be achieved.
Typically, our model-type electrodes consist of dense thin films, which are grown on single crystalline substrates by sputtering or pulsed laser deposition, and subsequently micro-patterned by photolithography and etching (either chemically or with Ar plasma). The ability to control each individual preparation step gives us the possibility to produce tailor-made model electrodes regarding material composition, size, geometry and microstructure that are optimised for answering a specific research question. Consequently, we also continuously optimise the methods and techniques for preparation of model-type electrochemical samples and develop novel preparation approaches and setups in our group.