Electrochemistry - Preliminaries to the study of electrolysis

An electrochemical process consists of all the phenomena associated with the production of an electrical charge transfer across the interface formed by bringing an "electrode" into contact with an "electrolyte", i.e. an electronic conductor (metal, graphite, etc.) and an ionic conductor (conductor by migration of ions, instead of electrons: aqueous or non-aqueous ionic solutions, ionized molten salts, certain ionic solids). This type of interface is therefore referred to as an electrochemical interface.

The main effect of this charge transfer, which corresponds to the passage of an electric current through the electrochemical interface, is to produce a chemical transformation known as an electrochemical reaction (or electrode reaction). As the electrolyte is a medium in which there are no "free" electrons, the transfer of electrons (e ^– , elementary negative charges) from the electrode to the electrolyte requires a substance located close to the interface to capture the electrons released by the electrode and fix them, corresponding to the reduction of the electron-accepting substance (oxidant). This transformation can be symbolized by :

For electron transfer to take place in the opposite direction, from the electrolyte to the electrode, electrons must conversely be supplied to the electrode by a substance acting as an electron donor (reductant), also located near the interface. This process corresponds to oxidation, symbolized by :

Substances (oxidizing or reducing agents) that react in this way are called electroactive.