"A class of electrode reactions involving oxidation/reduction of two dissolved species. E.g., iron metal can exist in solution as a doubly positively charged (""ferrous"") ion or a triply positively charged (""ferric"") ion. Such a system is often called a ""redox couple,"" such as the ""ferrous/ferric"" couple. The ferric ions can be cathodically reduced to ferrous ions, or the ferrous ions can be anodically oxidized to ferric ions. With these reactions, an inert electrode is used that does not take part in any reactions under the conditions of the oxidation/reduction of the ions. This electrode then acts only as a source or sink of electrons; examples are: carbon, graphite, platinum, gold. Compare with a metal deposition/dissolution reaction where one of the reacting species is a solid metal and the other species is in solution. "
Meaning of REDOX REACTION in English
Electrochemistry English dictionary. Английский словарь электрохимии. 2012