Potentiodynamic method

The electrocatalytic activity of novel redox films in regeneration of NAD/NADH has been investigated by means of chronoamperometry, hydrodynamic and potentiodynamic methods. In order to achieve the most efficient electrocatalytic properties indicated as both the highest heterogeneous rate constant and maximum sensitivity, the further optimization of electropolymerisation conditions has been made. 

Gegelova, N, B., Mudzhiri, Y. N., Knyazheva, V. M. and Topchiashvili, L. I., Determination of Intercrystalline Corrosion Tendency of Stainless Steel by Potentiodynamic Method , Zashch. Metal., 8, 420 (1972) C.A., 77, 121422n van der Horst, J. M. A., Grain Boundary Attack of 316L Stainless Steel in Ammonia-rich Environments , J. Electrochem. Soc., 119, 216C (1972)... 

According to the parameter controlled. When this is the potential, we speak of potentiostatic and potentiodynamic methods when it is the current, we speak of galvanostatic and galvanodynamic methods (galvanodynamic methods are rarely used) in the coulostatic method a certain amount of charge is delivered to the elecnode (e.g., from a capacitor) and the potential-time variation is followed. 

For the individual types of transient measuring techniques, special names exist but their terminology lacks uniformity. The potentiostatic techniques where the time-dependent current variation is determined are often called chronoamperometric, and the galvanostatic techniques where the potential variation is determined are called chronopotentiometric. For the potentiodynamic method involving linear potential scans, the term voltammetry is used, but this term is often used for other transient methods as well. 

The plot of the various reactants is most revealing. It is compared in Figure 6 with the radiotracer and potentiodynamic methods. It will be seen that there is a rough kind of agreement between the data here obtained and the radiotracer method data, though the potentiodynamic method is evidently less sensitive. On the other hand, the FTIR data distinguishes between the two, CO in the triple bond form and CO in the double bond form. 

The potential-independent CPT determined by the potentiodynamic method is defined as the lowest temperature at which pitting initiation occurs during a dynamic anodic polarization scan. ... 

The Cd/CdS electrode was also prepared in solutions containing cadmium sulfate and sodium thiosulfate using the potentiodynamic method [183]. The electrochemical behavior of such electrodes in electrolytes containing sulfide ions was studied. 

ASTM standards D-2776 (9) and G-59 (10) describe standard procedures for conducting polarization resistance measurements. Potentiodynamic (11), potential step, and current-step methods (12,13) have all been described to determine the linear E-i behavior of an electrode near Eco . The current step method has been cited to be faster than potentiodynamic methods and less susceptible to errors associated with drift in Econ. This issue will be discussed below. Regardless of the method used, independent determination of pa and pc is still required. 

Potentiodynamic sensors are based on the measurement of the current response of the working electrode under no mass transport limiting conditions. Potentiodynamic methods typically involve accumulation (or preconcentration) steps, such as in stripping voltammetry for analyzing trace metals in solution. 

PAn and polyheterocycles have been prepared frequently by many investigators using electrochemical methods for subsequent studies of their physical and chemical properties. Earlier studies on the characterization of these polymers used potentiostatic, potentiody-namic, and galvanostatic methods to grow the polymer films on the electrode surfaces for no special reasons [I6d,28]. The potentiodynamic method was claimed to produce films with superior adhesion, smoothness, and optical properties [28aj,l], but no clear reasons were given. However, Kitani et al [28h] could not see the difference in chemical and physical properties of PAn... 

In electrochemical experiments for the determination of the pitting potential one either controls the potential (potentiodynamic method) or, more rarely, the current (galvanostatic method). The composition and temperature of the electrolyte are selected such as to represent the real environment to which the metal will be exposed, but without the oxidant present, whose effect is simulated by the anodic polarization. 

F ure 7.49 Experimental determination of pitting potential (a) by the potentiodynamic method and (h) by the gavanostatic method. 

In the potentiodynamic method the film meets different potentials during the process and a more stable and homogeneous film is sometimes obtained. For example, polyaniline is commonly made by the potentiodynamic method in strongly acidic aqueous solution by scanning the potential back and forth between two values. The resulting film is flexible and compact and not powdery or flaky, as obtained by the galvanostatic method. 

A three-electrode cell with one or two compartments. If the potentiostatic or potentiodynamic method is used, a reference electrode is necessary. The reference electrode may be simply a silver wire, pseudoreference. Its potential is not particularly stable and it should be standardized before or after every use by measuring a cyclic voltammogram of ferrocene. The redox potential of the ferrocene-ferricinium couple is well known in all common solvents and hence this couple is generally used as a potential standard. 

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