Cyclic potential

Similarly to the response at hydrodynamic electrodes, linear and cyclic potential sweeps for simple electrode reactions will yield steady-state voltammograms with forward and reverse scans retracing one another, provided the scan rate is slow enough to maintain the steady state [28, 35, 36, 37 and 38]. The limiting current will be detemiined by the slowest step in the overall process, but if the kinetics are fast, then the current will be under diffusion control and hence obey the above equation for a disc. The slope of the wave in the absence of IR drop will, once again, depend on the degree of reversibility of the electrode process. 

Hydrogen binds to As sites at the surface when the GaAs electrode is electron rich when the GaAs electrode is electron poor, the hydrogen adsorbates are replaced by OH species at the As sites. Changes in potential were determined by interrupting the cyclic potential scans every 100 ms for a lmn period at various... 

Again, application of the principle to the simple potential-step method appears trivial or superfluous. However, it is of quite great important for other types of potential control, namely double potential step, cyclic potential step [73], and especially the linear potential sweep method [21, 22, 73]. In all these techniques, sets of data Jf ( ) /f (f) E can be obtained, thus enabling kt(E) to be determined from eqn. (100). For more details, the reader is referred to the quoted textbooks. 

Fig. 6-6. RDE and HMRDE curves for quinhydrone at platinum. Curve A, RDE traces for cyclic potential scan of 1.00 pM quinhydrone in 0.02 M H2S04 at platinum disk electrode. Curve B, HMRDE traces for the solution in curve A. Curve B, HMRDE residual in 0.02 M H2S04. Conditions QU2 = 60 rpml/2. A 1/2 = 6 rpm1/2. /= 3 Hz, scan rate is 5 mV/s, averaging time constant is 3 s. From [67],...

Voltammetry with single and cyclic potential sweep was chosen as the electrochemical method of investigation. I - E curves were obtained with a PI-50-1 potentiostat in a polarization rate range of 0.005 -5- 0.1 V/s. Investigations were carried out in a temperature range of 500 850 °C and at a C02 pressure of 0.1 1.5 MPa. The temperature of the melt was maintained with accuracy to 2 °C. All... 

Fig. 13.4. Current vs. potential, charge vs potential and mass change vs potential curves for redox switching of a poly(thionine) film (r = 7.7 nmol cm-2) in aqueous O.i mol dm-3 acetic acid (pH = 2.9). The electrode was subject to a cyclic potential scan at 5 mV s l. (Adapted from Ref. [18] with permission.)...

Third, consider a triangular cyclic potential sweep under reversible (Nerns-tian) conditions for a planar electrode (Fig. 6.10), to derive a cyclic voltam-mogram (Fig. 6.11) In the Nemst expression, Eq. (6.19.14) a time-dependent potential is added E(t) = E(0) — vt, whence... 

Figure 2. PDEB spectnim of -Si in cyclic potential scan in 5mM CUSO4 + 0.5M H2SO4. (a) 3D representation (b), (c) orthogonal projections of (a) the same spectrum and (b) the spectrum of Si with nanoporous SiOj in 5mM CUSO4 + 0.5M H2SO4. Dark parts of the spectrum correspond to the cathodic scan, light parts - anodic scan. AC frequency ranged Hz to 585 Hz.

A complementary technique to EQCM is to monitor volume changes during cyclic potential sweeps—electromechanical analysis (EM A). This method is based on work by Pei and Inganas143149 and has been further developed at IPRI (see Chapter 3). The... 

Figure 6.1.3 a) Cyclic potential sweep, b) Resulting cyclic voltammogram. 

Figure 1. Cu UPD on Au. (a, b) PDEIS spectra, (a) cathodic, (b) anodic branch of the cyclic potential scan in O.IM H2SO4+10mM CUSO4 (c) cyclic voltammograms of Au in O.IM H2SO4+10mM CuSOa and O.IM HNOs+lOmM Cu(N03)2 (d-h) the dependencies of EEC parameters on potential (i) the EEC obtained from the PDEIS spectra. dE/dt = 2 mV/s.

C. Cyclic Potential Scan Steady-State Chronoabsorptometry... 

By cyclic potential scan steady-state chronoabsorptometry (CPS/ SSCA) OTTLSET, a steady-state absorbance-cyclic potential scan (A-F) curve at a certain wavelength is recorded. The two inflection points for the oxidation and reduction processes in the A-E curve correspond to... 

Other phenothiazine dyes, such as methylene green (MG), brilliant cresyl blue (BCB), janus green (JG), toluidine blue (TB), and azure A (AA), can also be immobilized on Pt electrode surfaces by adsorption and the cyclic potential scan method used to prepare MB CMEs." The MG, BCB, JG, TB, and AA CMEs were all found to facilitate effectively the electrochemical reactions of redox proteins and the modified... 

Figure 2. Variation of double layer pseudocapacitance (Qdi), inverses of the Warburg coefficient (An/ 2), and charge transfer resistance (/<-, ) in (a, c) Cd upd on bulk Te and (b, d) Cd upd on Te monolayer in cyclic potential scans. Concentrations of CdCb are shown in labels.

Fig. 2.8 Result of simultaneous measurement of current and change of reflectance during cyclic potential scan at 100 mV for a sub-monolayer of hemin on an HOPC electrode in 0.1 M Na2B407 aqueous solution. In part (a), potential, current, and dc reflectance change (ARjJ a a wavelength...

In a more recent work, Paik et al. described transport properties and stability of sulphonated porphyrin derivatives (3) in films of conducting polymers PPy and PEDOT films using EQCM . As expected, it was evidenced that such anions were not expelled from these polymer films by extensive potential cycles. The authors also analyzed the effects of potential cycling on PEDOT-H2-3 films obtained by two different modes of electropolymerization (i) at a constant current and (ii) with repeated cyclic potential sweeps. Figure 8.2 shows the results of potential cycles in 0.1 M NaCl solution for the two types of films (noted A and B, respectively). In both cases, the general feature of mass increases of the negative... 

Figure 8.2. Cyclic voltammetry and mass change of PEDOT-[H2-3] Aims in 0.1 M NaCl solution. (A) Film from galvanostatic polymerization (B) film from polymerization with cyclic potential. Potential sweep rate 50 mVs . Reprinted from ref. [50]. Copyright (2000), with permission from Elsevier.

Electrochemical methods for the preparation of anode electrocatalysts for DAFCs involve either the electrodeposition of one metal at a time, eventually followed by the electrodeposition of other metals, or the contemporaneons electrodeposition of two or more metals. Highly ordered Pd nanowires arrays (Fig. 5) have been prepared by template-electrodeposition on glassy carbon electrodes, while cyclic potential sweep techniqnes have been used to prepare Pd thin films on polyciystalline Pt or An substrates. Ni-Pd electrodes for methanol oxidation have been prepared by electrodeposition onto titaninm discs nsing a PdCl2/NiS04-7H20 bath." ... 

In this work, it will be demonstrated that simultaneous acquisition and analysis of impedance and gravimetric data in a single cyclic potential scan (Fig. 1) enables a detailed electrochemical characterization of dynamic non-stationary eleetrode/eleetrolyte interfaces. The combination of electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (EQCM) techniques is used to characterize the underpotential... 

Berkes, B., A. Maljusch, W. Schuhmann, and A. Bondarenko (2011). Simultaneous acquisition of impedance and gravimetric data in a cyclic potential scan for the characterization of nonstationary electrode/electrolyte interfaces. The Journal of Physical Chemistry C115, 9122-9130. 

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