A thin film electrode consists of a layer of impermeable material separated from the electrode by a thin space (of the order of micrometers). Thin films can be found in a wide range of applications, for example, in electronic devices, optical coatings, and electrochemical cells. This Demonstration shows the use of cyclic voltammetry to characterize a thin film electrode.
The electrode (red) is separated from the film (black) by a very thin space of width . The potential varies with time as shown in the potential-time diagram. The current-potential diagram is the cyclic voltammogram for a thin film with different values of .
When this distance is decreased, the film will block the diffusion of electroactive reactant to the electrode, which decreases the current.
For small , the concentration can be regarded as independent of distance from the electrode. The concentration is then dependent only on the time (or the applied potential). When the reactant is mostly consumed, so that its concentration is small, the color of the solution becomes lighter.