Cyclic Voltammetry Background

Cyclic voltanunetry (CV) is an electrochemical technique in which a three-electrode system is used and the applied potential (between the working and reference electrodes) is changed linearly using a triangular wave form between a negative (cathodic). 

FIGURE 7.12 Potential-time dependences used in CV. and Ej arc. respectively, a negative (cathodic) and a positive (anodic) turnaround potentials. 

and a positive (anodic) tum-around value, 2, which are usually in an aqueous solution between the hydrogen and oxygen equihbrium electrode potentials (Hgure 7.12). 

FIGURE 7.13 Current density-potential dependences in the CV of a theoretical reversible electrochemical reaction O + ne = R. 

The limiting current density on the RDE can be estimated if the Nemst diffusion layer thickness and the bulk concentration of the electrochemically active species are known. 

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Figure 4.28 The anodic scan section of cyclic voltammetry for pyrrhotite electrode in different pH buffer solution at potential scan of 10 mV/s (Background solution buffer solution plus 0.1 mol/L KNO3, DDTC 10" mol/L)...

Figure 3.15 (a) Cyclic voltammetry of SWNT-modified electrodes where the tubes were cut for 2 h and either randomly dispersed or vertically aligned. CVs are recorded relative to an Ag/AgCI reference electrode in 1 mM l<3Fe(CN)6 in a background electrolyte of 0.05 M KH2PO4 and 0.05 M KCI at pH 7.0 at lOOmV/s. The y-axis shows the current normalized to the anodic peak... 

Detection limits obtained with the DME are restricted by a relatively large background current due to the constantly changing electrode area. Also, a stationary electrode is required for stripping experiments and for mechanistic studies employing cyclic voltammetry. Thus, many applications require a stationary or hanging mercury drop electrode (HMDE). 

Fig. 14.34. Voltammetry of epinephrine. Background (A, solid line) and signal containing (A, dashed line) currents generated during fast-scan cyclic voltammetry (300 V/s) at a carbon fiber microelectrode r = 5 pm). A background subtracted cyclic voltammogram (B) is produced from the traces shown in A. (Reprinted from Wightman, et al. Chemical Communication, Interface, 5(3) 22, Fig. 2,1996. Reproduced by permission of the Electrochemical Society, Inc.)...

The various forms of adsorbed copper can alter the electrochemical behavior of modified carbon samples used as electrode materials (powdered working electrodes in cyclic voltammetry). Figures 45 and 46 show cyclic voltammograms (CVs) for powdered electrodes prepared from selected active carbon samples with and without preadsorbed copper recorded in solution, which do or do not contain Cu " ions. An aqueous solution of 0.5 M NaiS04 as background electrolyte was employed. The CV curves recorded in the solution containing copper ions exhibit a pair of cathodic and anodic peaks, the potentials of which are dependent on the carbon modification procedure and the electrolyte s pH. The estimated peak potentials and the midpoint potentials [formal potentials, Ef = ( p, — p,c)/2] are given in Table 13. 

Figure 3.33 Simultaneous cyclic voltammetry charge determined from a coulometric analysis (v = 100 mVs-1, left ordinate) and reflectance of the voltammetric peak as a function of the (A, = 440nm, smoothed, right ordinate) background corrected AR/R based on the optical...

Of the three SECM modes that can be used to study electrode reaction mechanisms—the TG/SC, feedback, and SG/TC modes—the former is the most powerful for measuring rapid kinetics. With this approach, fast followup and sandwiched chemical reactions can be characterized under steady-state conditions, which are difficult to study even with rapid transient techniques such as fast scan cyclic voltammetry or double potential step chronoamperometry, where extensive corrections for background currents are often mandatory (44). At present, first- and second-order rate constants up to 105 s 1 and 1010 M 1 s, respectively, should be measurable with SECM. The development of smaller tip and substrate electrodes that can be placed closer together should facilitate the detection and characterization of electrogenerated species with submirosecond lifetimes. In this context, the introduction of a fabrication procedure for spherical UMEs with diameters... 

The performances of PtSn/C electrocatalysts for ethanol eletro-oxidation are shown in Fig. 3. The anodic cyclic voltammetry responses were plotted after subtracting the backgrounds currents [12,13] and the currents values were normalized per gram of platinum, considering that ethanol adsorption and dehydrogenation occur only on platinum sites at room... 

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