2. Electrodes with Immobilized Particles and Droplets: Three-Phase Electrodes

It is a common feature of electrodes with immobilized particles and droplets that three phases are in close contact with each other, i.e., each phase having an interface with the two other phases. This situation exists also in most of the so-called surface-modified or film electrodes, many battery and fuel cell electrodes, electrodes of the second kind, etc. In fact, the majority of surface-modified electrodes consist of arrays of particles that partially cover the electrode surface. It would be far beyond the scope of this book to include all chemical and electrochemical techniques to deposit films on electrodes. Here we shall deal only with electrodes where the particles or droplets have been mechanically attached with the aim of studying their electrochemistry. Before going into the details in Chaps. 5 and 6, we now like to outline the specificity of three-phase electrodes.