Voltammetry double layer capacity effect

Analytical applications of electrochemistry, where the objectives are well defined, have fared better. There is a long list of papers going back twenty years on the applications of computers and then microprocessors. Reviews of this subject appear in the Fundamental Reviews sction of Analytical Chemistry (see refs. 8 and 9). In general, the aim in electroanalytical methods is to avoid interfering effects, such as the ohmic loss and the double layer capacity charging, and to use the Faradaic response peak current-potential curve as an analytical tool. Identification of the electroactive species is achieved by the position of the response peak on the potential axis and "pattern recognition , and quantitative analysis by peak shape and height. A recent development is squarewave voltammetry [10]. 

Electrochemical techniques such as chronocoulometry, integrated cyclic voltammetry curves, or differentiating double-layer capacity measurements as a function of bulk concentrations can be used to estimate FA however, these types of determinations may still be in error since they measure the total number of surface species, while the number of molecules at active sites which exhibit both the EM and CT effects may be much smaller. Thus, the estimates of Gsers 10 to 10 found at pretreated Ag, for example, may err on the low side if special active sites are involved in SERS. It has been estimated that only 3% of the surface sites are SERS active. " ... 

The double-layer structure at the electro-chemically polished and chemically treated Cd(OOOl), Cd(lOlO), Cd(1120), Cd(lOh), and Cd(1121) surface electrodes was studied using cyclic voltammetry, impedance spectroscopy, and chronocoulometry [9, 10]. The limits of ideal polarizahility, Epzc, and capacity of the inner layer were established in the aqueous surface inactive solutions. The values of iipzc decrease, and the capacity of the inner layer increases, if the superficial density of atoms decreases. The capacity of metal was established using various theoretical approximations. The effective thickness of the thin metal layer increases in the sequence of planes Cd(1120) < Cd(lOiO) < Cd(OOOl). It was also found that the surface activity of C104 was higher than that of F anions [10]. 

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