Chronoamperometry, chronocoulometry

If for potentiostatic conditions one applies a potential jump AE, starting at the equilibrium potential (e.g., in the case of a metal electrode from the Nemst potential to a deposition 

The dependence of a selected concentration value on the square root of time is typical for diffusion-controlled processes (Tamman s law). 

The equation for the dependence of the current upon time derived from the concentrationtime dependence is called the Cottrell equation  

In the current-time diagram a peak usually occurs at the beginning. The initial rise of the current with time is limited by the charging of the double layer capacitance to build up the selected deposition potential. 

Integration of the current gives the development of charge with time 

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Appropriate electroanalytical procedures to verify the one or other case have been given in the references of this section. The main techniques are cyclic voltammetry, chronoamperometry, chronocoulometry, and rotating disk voltammetry. The last one appears to be best suited since constant mass transport in the film is a very important feature as outlined aixive Table 2 gives examples for... 

R.W. Murray, Chronoamperometry, Chronocoulometry and Chronopoten-tiometry, Physical Methods of Chemistry. Electrochemical Methods. A. Weissberger and B.W. Rossiter eds, Vol. 2. Wiley Interscience, New York, 1986. 

Potential step method Chronoamperometry Chronocoulometry Voltage pulse method Pulse polarography Differential pulse polarography... 

It is important to recognize that the Nernst equation is valid only at the equilibrium condition, determined by specifying i, = 0. Most electrochemical techniques (chronoamperometry, chronocoulometry, voltammetry, etc.) involve nonequilibrium conditions and therefore cannot be expected to exhibit a Nernstian response unless the rates are very fast and equilibrium is quickly reestablished at the surface. 

The electroanalytical techniques chronoamperometry, chronocoulometry, and chronoabsorptometry are all based on the same excitation function of one or more potential steps that are applied to an electrode immersed in a nonstirred solution. The system response is thus identical for all three techniques. They differ only in the data domain of the monitored response. Consequently, the common excitation aspect is dealt with here, whereas each monitored response is considered individually in subsequent sections. 

Many of the electroanalytical techniques that are routinely employed in conventional solvents, such as, chronoamperometry, chronocoulometry, chronopotentiometry, coulometry, cyclic (stationary electrode) voltammetry, rotating electrode voltammetry, and pulse voltammetry, have also been applied to molten salts. Some of these techniques are discussed next with special attention to their employment in molten salts. References to noteworthy examples appearing in the literature are included. Background information about these techniques is available elsewhere in this book. 

Diffusion current is usually measured in the case of several transient electrochemical methods, e.g., in chronoamperometric and chronocoulometric experiments (see chronoamperometry, -> chronocoulometry, -> Cottrell equation) as well as it determines the shape of... 

For decades the electrochemical techniques, i.e., potential, current, or charge step methods such as - chronoamperometry, - chronocoulometry, - chrono-potentiometry, coulostatic techniques were consid-... 

The quartz crystal nanobalance (QCN) can be combined with practically any electrochemical methods, such as cyclic voltammetry, chronoamperometry, chronocoulometry, potentiostatic, galvanostatic, rotating disc electrode [11], or potentiometric measurements. The EQCN can be further combined with other techniques, e.g., with UV-Vis spectroscopy [12], probe beam deflection (PBD) [13], radiotracer [14], atomic force microscopy (AEM) [15], and scanning electrochemical microscopy (SECM) [16]. The concept and the instrumentation of... 

Note that the slope of the absorbancetime plot allows the determination of the (usually) unknown extinction coefficient r for the electrogenerated species, providing that c and Dq are known. No knowledge of the electrogenerated species diffusion coefficient Dr is necessary. Usually the concentration is known and it is a simple matter to determine Dq from a chronoamperometry, chronocoulometry, or ultramicroelectrode experiment. If both c and Do are unknown, then they can be obtained from a potential step experiment at an ultramicroelectrode [47, 48]. 

Chronoamperometry, chronocoulometry, and chronopotentiometry belong to the family of step techniques [1-4]. In chronoamperometry the current, while in chronocoulometry the charge is measured as a function of time after application of a potential step perturbation. In the case of chronopotentiometry, a current step is applied, and the change of the potential with time is detected. 

Chronoamperometry, Chronocoulometry, and Chronopotentiometry, Fig. 1 Typical waveform of the potential step (a) and the respective chronoam-perometric response (b)... 

Chronoamperometry, Chronocoulometry, and Chronopotentiometry, Fig. 4 Chronocoulometric charge versus (time) plot in the absence (1) and in the presence (2) of adsorption. The dashed, horiztmtal line represents the charge response in the absence of reactant. This representation is sometimes referred to as Anson plot in the literature... 

Routine electrochemical characterization, including cyclic voltammetry, chronoamperometry, chronocoulometry, (Chapters 3 and 4) ... 

Atomic Force Microscopy Chronoamperometry Chronocoulometry Cyclic Voltammogram Chronovoltabsorptometry Degenerate Four-Wave Mixing Differential Pulse Voltammetry Differential Scanning Calorimetry Electron Energy Loss Spectroscopy Explanation Extended HUckel... 

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