Chapter 4 - Electrode potential

Abstract

The electronic conductor of an electrode may be either a metal or a semiconductor, and the electrolyte may be an aqueous solution, fused salt, solid electrolyte, or gaseous electrolyte. This chapter deals with metal and semiconductor electrodes in aqueous electrolytes. The electrode potential is one of the most important concepts in electrochemistry. It represents the energy level of electrons or ions in electrodes rather than simply the electrostatic potential of electrodes. The electrode potential can be defined not only by the energy level of electrons (the real potential of electrons) but also by the energy level of ions (the real potential of ions) in the electrode. The former is called the electronic electrode potential and the latter, the ionic electrode potential. For electrodes that have no electron energy levels in the energy range of general interest, such as ionic crystalline solid electrodes and membrane electrodes, only the concept of ionic electrode potential can be of practical significance. The electrode potential in the transfer equilibrium of redox electrons is characteristic of individual redox reactions but independent of the nature of the electrode materials. To measure the electrode potential, an electrochemical cell consisting of test electrode M and reference electrode M0 is used.