engleski

Electrodes and Electrolytes

In electrochemistry an electrode is the entire assembly of an electronic conductor in intimate contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution, however solid electrolytes can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In analytical voltammetry the analyte is usually dissolved in an electrolyte solution, and, when both the oxidized and the reduced forms are soluble in the solution, this, in electrochemistry, is called a redox electrode. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g.: a rotating disk electrode, or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g.: a mercury film electrode, an enzyme electrode, a carbon paste electrode etc.). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9]

electrodes, electrolytes

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