Electrode-electrolyte interface, static

II. Length and Time Scales at the Electrode-Electrolyte Interface HI. Static Structure of the Interface... 

Spectra measured using phase-sensitive detection when a periodic perturbation is applied frequency domain) as well as spectra measured as a function of time (a time domain) or any other state parameter of the system (e.g., a temperature, pressure, strain, distance, concentration domain) are referred to, by convention, as dynamic spectra to distinguish them from ordinary static (average) spectra. Dynamic spectra can offer an advanced opportunity for separating contributions of different subsystems to spectra of complex systems and quantifying the characteristic half-lives of these subsystems. This opportunity is especially valuable when complex spectra such as the spectra of electrode-electrolyte interfaces and biological films are interpreted. Below we will consider interpretation of dynamic IR spectra, while the technical side of the problem is discussed in Section 4.9. 

STATIC AND DYNAMIC STUDIES OF METAL ELECTRODE-ELECTROLYTE INTERFACE... 

In electrochemistry an electrode is an electronic conductor in 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 and ionic melts 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 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, and a carbon paste electrode). 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]. 

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