Voltammogram linear sweep

Figures 2.16(a) and (b) show the linear sweep voltammogram and cyclic voltammogram that would be expected from an electroactive adsorbed species assuming that ...

Figure 2.19 Linear sweep voltammograms of a platinum electrode immersed in N -saturated 0.5 M H2SO t showing the anodic stripping of adsorbed CO. The CO was adsorbed from the CO-saturated electrolyte for 10 minutes at the designated potential. The scan rate was 1 mV s The adsorption potential was (a) 0.05 V and (b) 0.4 V vs. NHE. Note the different electrode potential scales for the two plots. From Kunimatsu et at. (1986).

Figure 3.8 Current-potential linear sweep voltammogram and the differential reflectivity change in the hydrogen adsorption region at fixed wavelengths (a) 2.34 pm and (b) 1.93 pm. The sweep rate was 15mVs with a square wave modulation of lOmV at 8.5 Hz. From Bewick et al.

Figures 3.8(a) and (b) show the linear sweep voltammograms and concomitant reflectivity changes monitored at 2.34pm (4273cm-1) and 1.93pm (5181cm-1), Under the conditions employed the reflectivity change was obtained as (l/R)(AR/d ). This gives spectra in which an increase in reflectivity results in a negative value of (l/R)-(AR/d ) and a decrease in reflectivity (i.e, absorption) gives a positive response.

The relative electrochemical stability of AICI4 and AECE is best illustrated in the series of linear sweep voltammograms shown in Figure 5, in 52 m/o AlCE-NaCI melt... 

Fig. 31. Linear sweep voltammograms recorded at a sweep rate of 100 mV s 1 on a polished tungsten electrode in (---) 66.7 m/o AlCl3-NaCl and (—) 66.7 m/o AlCl3-NaCl containing 225 mmol L 1 Ti2+ at 150 °C [177],...

The potential of the working electrode is ramped at a scan rate of v. The resultant trace of current against potential is termed a voltamnu ram. In linear-sweep voltammetry (LSV), the potential of the working electrode is ramped from an initial potential Ei to a final potential Ef (cf. Figure 6.2). Figure 6.12 shows a linear-sweep voltammogram for the reduction of a solution-phase analyte, depicted as a function of scan rate. Note that the jc-axis is drawn as a function of overpotential (equation (6.1)), and that the peak occurs just after = 0. 

Figure 6.12 Linear-sweep voltammogram for the reduction reaction, O - - ne" —> R, at a solid electrode, shown as a function of the scan rate u. The solution was under diffusion control, which was achieved by adding inert electrolyte and maintaining a still solution during potential ramping. Note that the x-axis has been normalized to , that is, thex-axis represents an overpotential. Reproduced from Greef, R., Peat, R., Peter, L.M., Pletcher, D. and Robinson, J., Instrumental Methods in Electrochemistry, Ellis Horwood, Chichester, 1990, with permission of Profes.sor D. Pletcher, Department of Chemistry, University of Southampton, Southampton, UK.

The forward half of the CV is identical to a linear-sweep voltammogram. The back half of the CV represents the reverse electron-transfer processes occurring at the working electrode if the peak on the forward limb of the CV represents the oxidation reaction, Fe + -> Fe -I- e, then the reverse limb represents the reduction reaction, Fe e Fe. V/e can gain much information if the peak current of the reverse limb is smaller than the peak current during the forward part of the cycle (see next section). Such information cannot be obtained in a LSV experiment because no reverse limb is traversed. 

Figure 5.15 Stability change of a SAM of propane thiol on Au/ mica by UPD of a series of metals. The linear sweep voltammograms were recorded in 0.5 M KOH at a scan rate ofO.l V/s. The electrode area was 0.36 cmf In the case of Cu UPD no desorption is discernible since the stability is increased to such an extent that the desorption peak shifts negative beyond the range shown into the region of hydrogen evolution. Reproduced with permission from Ref [202].

Fig. 14 Linear sweep voltammograms for UPD of Bi on three low-index gold surfaces in 0.1 M HCIO4 containing 2.5 mM Bi203. Scan rate ...

Figure 6.20. Experimental linear sweep voltammogram of carbon-supported high surface area nanoparticle electrocatalyst in oxygen-saturated perchloric acid electrolyte (room temperature). Solid curve pure Pt dashed curve Pt50Co50 alloy electrocatalyst. Inset a blow up of the kinetically controlled ORR regime. Inset b comparison of the specific (Pt surface area normalized) current density of the Pt and the Pt alloy catalyst for ORR at 0.9 V.

This method is sometimes abbreviated to LSV. In this method, a static indicator electrode (A cm2 in area) is used and its potential is scanned at constant rate v (V s-1) from an initial value ( ) in the positive or negative direction (Fig. 5.18). A typical linear sweep voltammogram is shown in Fig. 5.19. In contrast to DC polar-ography, there is no limiting current region. After reaching a peak, the current decreases again.9 For a reversible reduction process, the peak current ip (A) is expressed by Eq. (5.26), where D and C are the diffusion coefficient (cm2 s 1) and the concentration (mol cm-3) of the electroactive species ... 

Fig. 5. The effect of double layer charging current on linear sweep voltammograms at different sweep rates. Reprinted with permission from ref. 21.

Cross-linked with BSA using glutaraldehyde Copper-plated SPCE 26.7 Peak in linear sweep voltammogram at 150 mV Kumar and Zen [31]... 

One redox species is chemically insensitive with respect to variation in E1/2, e.g. a ferrocene derivative, and serves as an internal reference in a linear sweep voltammogram. The second species is chemically sensitive, e.g. a pH sensitive quinone or a CO sensitive ferraazetine derivative, which has an E1/2 that varies with the changes in the chemical environment. A linear sweep voltammogram thus shows two waves, one for the reference molecule and one for the indicator molecule. The shift for the indicator wave along the potential or current axis provides a method for analyte detection. Surface derivitization, proof-of-structure, and proof-of-concept sensor functions are demonstrated. 

Scheme I. Concept of a two-terminal microsensor showing two possible idealized responses to a species L which binds to the indicator molecule M. A) The linear sweep voltammograms reveal a difference between the current peaks for oxidizing the reference molecule, R, and M or M-L. The position of the current peak along the potential axis, V, is variable and depends on the concentration of L. B) The linear sweep voltammograms reveal a decrease in amplitude for the current peak assigned to M and proportional growth of a new current peak assigned to M-L.

Fig. 9.2. Normalized linear sweep voltammogram for a reversible reduction at a planar electrode, using values from Table 9.1. E = Epl2 when / = /p/2.

Fig. 9.4. Linear sweep voltammogram for an irreversible system (O + ne —> R). In cyclic voltammetry, on inverting the sweep direction, one obtains only the continuation of current decay (-------------------).

Almost all the analysis of cyclic and linear sweep voltammograms has been done through peak currents and peak potentials. Unless digital simulation and curve-fitting by parameter adjustment is carried out, all the information contained in the rest of the wave is ignored this brings problems of accuracy and precision. Besides this, a kinetic model has to be proposed before the results can be analysed. 

Fig. 9.12. Linear sweep voltammograms at a rotating-disc electrode for different sweep rates and for the same rotation speed—reversible reaction (from Ref. 15...

Fig. 11.4. Typical linear sweep voltammogram (LSV) data for the ICA film in background electrolyte LSV data is recorded (a) initially after film formation (b) after cycling and repeated holding first at a potential corresponding to complete oxidation (1 hour) and then at a potential for complete reduction of the film (1 hour) for an overall period of 2 days (c) same as (b) but for 5 days (d) in 0.1 M NaCI04 rather than 0.1 M LiCI04. The voltage sweep rate was 2.5 mV/s"1 in all cases.

Theoretical linear sweep voltammogram for a reversible charge transfer and a planar electrode, using the dimensionless auxiliary function x at) of Table 6.3. The half-wave potential Ey2 and the half-peak potential p/2 (scan-dependent) are shown. 

Figure 13.7 shows typical linear sweep voltammograms (LSV) obtained using a Ti mesh-supported Pd cathode in 0.05 M sodium sulphate solutions with or without pentachlorophenol (PCP) and 2,4-dichlorophenol (DCP). 

Fig. 13.7 Linear sweep voltammograms for electrochemical HDH of pentachlorophenol (PCP) and 2,4-dichlorophenol (DCP) on a Ti mesh-supported Pd cathode (2mgPdcm-2, 4cm2). Cell H-cell divided by a Nation 117 membrane. Anode Pt mesh (lOcm2). Catholyte 0.05MNa2S04 (pH 3) solution without (blank) or with saturated PCP and DCP. Anolyte 0.05 M Na2S04 (pH 3) solution. Scan rate 5 mV s-1. Temperature 21.5 0.5°C...

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