Voltammetric techniques potential sweep electrochemical

By proper treatment of the linear potential sweep data, the voltammetric i-E (or i-t) curves can be transformed into forms, closely resembling the steady-state voltammetric curves, which are frequently more convenient for further data processing. This transformation makes use of the convolution principle, (A.1.21), and has been facilitated by the availability of digital computers for the processing and acquisition of data. The solution of the diffusion equation for semi-infinite linear diffusion conditions and for species O initially present at a concentration Cq yields, for any electrochemical technique, the following expression (see equations 6.2.4 to 6.2.6) ... 

Impedance spectroscopy differs from many of the voltammetric techniques discussed above, such as linear sweep and potential step methods, in that only a small perturbation (usually of sinusoidal form) is apphed to the electrochemical cell. In Chapter 2.6, Krause discusses impedance methods, introducing the basic... 

As it can provide some of the most basic electrochemical information related to the reactivity of the selected analyte (peak potential and peak current) most instruments that perform amperometry can also perform some of the most basic voltammetric techniques. These techniques determine the current as a function of the potential applied to the WE (in a conventional three-electrode cell) and can be performed with relatively simple instrumentation [105,106]. As different signals can be combined in the input ports of the instrument, multiple variations of the technique have been developed including cyclic voltammetry, linear sweep voltammetry, linear sweep stripping voltammetry, stripping voltammetry [107, 108], fast-scan cyclic voltammetry [109], square-wave voltammetry [110],and sinusoidal voltammetry [111]. 

In this section, we will show that the stationary responses obtained at microelectrodes are independent of whether the electrochemical technique employed was under controlled potential conditions or under controlled current conditions, and therefore, they show a universal behavior. In other words, the time independence of the I/E curves yields unique responses independently of whether they were obtained from a voltammetric experiment (by applying any variable on time potential), or from chronopotentiometry (by applying any variable on time current). Hence, the equations presented in this section are applicable to any multipotential step or sweep technique such as Staircase Voltammetry or Cyclic Voltammetry. 

The convolution technique offers a number of advantages in the treatment of linear sweep data (and perhaps also in other electrochemical techniques). For a reversible reaction in a cyclic voltammetric experiment, the curves of l(t) vs. E for the forward and backward scans superimpose, with l(t) returning to zero at sufficiently positive potentials [where Cr(0, 0 = 0]. This behavior has been verified experimentally (20, 25, 28) (Figure 6.13a). 

Recently new methods, based on petturbations on the linear sweep voltammetry response of the mediator in the presence of the protein," a mediated thin-layer voltammetry technique, cyclic voltammetric simulation apphed to an electrochemically mediated enzyme reaction" have been setded to gain information on the protein-mediator interactions. More recendy the Scanning Electrochemical Microscopy (SECM) was used to probe the red-ox activity of individual cells of purple bacteria, by using two groups of mediators (hydrophilic and hydrophobic species) in order to gain information on the dependence of measured rate constant on the formal potential of the mediator in solution. By this technique an evaluation of the intracellular potential was also performed. ... 

The Application of FTIR Spectrometers In essence, the routine use of FTIR spectrometers has meant that in situ infrared spectroscopic studies requiring high sensitivity, such as the study of adsorbed species, were no longer limited to the fast, reversible electrochemical systems dictated by lock-in detection techniques infrared spectra could be collected during a slow linear voltammetric sweep, during a series of potential steps to higher... 

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