Rotating linear sweep voltammetry

Recent studies describe the use of cyclic voltammetry in conjunction with controlled-potential coulometry to study the oxidative reaction mechanisms of benzofuran derivatives [115] and bamipine hydrochloride [116]. The use of fast-scan cyclic voltammetry and linear sweep voltammetry to study the reduction kinetic and thermodynamic parameters of cefazolin and cefmetazole has also been described [117]. Determinations of vitamins have been studied with voltammetric techniques, such as differential pulse voltammetry for vitamin D3 with a rotating glassy carbon electrode [118,119], and cyclic voltammetry and square-wave adsorptive stripping voltammetry for vitamin K3 (menadione) [120]. 

The last of these is the impedance which has been considered throughout this chapter. We now consider forced convection. For low frequencies the diffusion layer thickness due to the a.c. perturbation is similar to that of the d.c. diffusion layer in these cases convection effects will be apparent in the impedance expressions. For the rotating disc electrode these frequencies are lower than 40 Hz33. For higher frequencies where the two diffusion layers are of quite different thicknesses, the advantage of hydrodynamic electrodes is that transport is well defined with time, as occurs with linear sweep voltammetry. 

To obtain reproducible limiting currents rapidly, either (1) the solution or the electrode must be in continuous and reproducible motion or (2) a dropping mercury electrode must be used. Linear-sweep voltammetry in which the solution is stirred or the electrode is rotated is called hydrodynamic voltammetry. Voltammetry with the dropping mercury electrode is called polarography. 

Perez, J, E.R, Gonzalez, and E.A. Ticianelli, Oxygen electrocatalysis on thin porous coating rotating platinum electrodes. Electrochimica Acta, 1998, 44 pp. 1329-1339 Song, H,-K, H,-Y, Hwang, K.-H. Lee, and L.H, Dao, The effect of pore size distribution on the frequency dispersion of porous electrodes. Electrochimica Acta, 2000. 45 pp. 2241-2257 Srikumar, A, T.G. Stanford, and J.W, Weidner, Linear sweep voltammetry in flooded porous electrodes at low sweep rates. Journal of Electroanalytical Chemistry, 1998. 458 pp. 161-173... 

Figure 7.3 Linear sweep voltammetry for ORR of Pl/Au(111) (red line) and Pt(111) (blue line) electrodes measured in oxygen-saturated 0.1 M HCIO4 at a scan rate of 10 mV s with a rotation rate of 1600 rpm. Inset diffusion-corrected Tafel plot of the Pt(111) electrode obtained with a rotation rate of 1600 rpm. (For interpretation of the references to color in this figure legend, the reader is referred to the online version of this book.) Reprinted with permission from 4.

Cyclic voltammetry Square-wave voltammetry Staircase voltammetry Linear-sweep voltammetry Fast cyclic voltammetry Rotating disc voltammetry Stripping voltammetry Hydrodynamic voltammetry Direct current (d.c.) polarography Alternating current (a.c.) polarography Pulse polarography... 

Notes LSV linear sweep voltammetry. CV cyclic voltammetry, DCP direct current polarogra-phy, MEV steady-state voltammetry at microelectrodes, ChP chronopotentiometry, RDE rotating disc electrode, TEV voltammetry in tubular electrodes, kf and k, rate constants of irreversible follow-up and catalytic reactions, respectively cj, the bulk concentration of the catalyst Z k = kf + k, sum of the rate constants and drop time and transition time, respectively a radius of a hemispherical microelectrode, Xf length of the tubular electrode in the flow direction, co the angular rotation rate, Uf linear flow rate in a TE (7 = RT/(nFv) is the time required for the dimensionless potential shift nFdE/RT at the sweep rate v (Vs" ). 

Linear sweep voltammetry (LSV) in combination with a rotating disk electrode (RDE) is a widely used technique to study electrode kinetics. Different methods exist to extract the values of the process parameters from polarization curves. The Koutecky-Levich graphical method is frequently used to determine the mass transfer parameters (Diard et al., 1996) the slope of a plot of the inverse of the limiting current versus the inverse of the square root of the rotation speed of the rotating disk electrode is proportional to the diffusion coefficient. If more than one diffusing species is present, this method provides the mean diffusion coefficient of all species. The charge transfer current density is determined from the inverse of the intercept. In practical situations, however, the experimental observation of a limiting current... 

Linear sweep voltammetry in combination with a rotating disk electrode... 

The combination of linear sweep voltammetry with an RDE is a powerful tool to study electrochemical reactions. One limitation to the technique is the presence of gas in some electrochemical systems. The inverted rotating disk electrode (IRDE) is designed to tackle... 

Bioanalytical Systems BAS 100 and BAS lOOA Electrochemical Analyzers, a PAR 174 polarograph and a pulse generator-transient recorder combination were used for performing cyclic voltammetry, linear-sweep voltammetry, and chronocoulometry. Rotating-disc current-potential curves were recorded with a Tacussel model EDI electrode operating at rates of 100 to 2500 rpm. All measurements were made at ambient temperature (21 2 C) in a single-compartment cell employing saturated calomel (SCE) or saturated sodium chloride calomel (SSCE) reference electrodes and platinum discs as counter electrodes. 

Linear sweep voltammetry yields a current peak at a potential of 0.73 V vs. SCE for the oxidation of L-dopa in aqueous CFsCOONa (0.1 M, pH = 2) at a bare glassy-carbon electrode. This potential is close to that where IrCle " is oxidized and only a single, composite wave comprising currents from both the mediated and direct oxidation of L-dopa was observed in rotating-disc experiments when the glassy-carbon electrode was coated with a PVP-film in which IrCle had been incorporated. At potentials more positive than that required to convert IrCle to IrCle , current plateaus were recorded which were dependent on both electrode rotation rate, w, and on the L-dopa substrate concentration,... 

Our group also used diamond RDE electrodes for the determination of lead. The use of rotating electrodes showed that a factor of ca. 10 enhancement in the stripping current was realized. Linear sweep voltammetry curves for 2 nM lead solution using a RDE are shown in Fig. 16.16. The increase in the stripping peak current is evident with an increase in the rotation speed [45]. 

Methanol oxidation on CNF- and CNT-supported Pt-Ru particles in liquid electrolytes has been studied using cyclic voltammetry, chronoamperometry [13,231-237], and electrochemical impedance spectroscopy [236]. Rotating disk electrode and linear potential sweep voltammetry in liquid electrolytes were used to study the oxygen reduction reaction on Pt supported on CNTs and CNFs (see,... 

Strutwolf J, SchoeUer WW (1996) Linear and cyclic sweep voltammetry at a rotating disk electrode. A digital simulation. Electroanalysis 8 1034-1039... 

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