Voltammetric scan

Draw an EQCM (mass-potential) profile for a metal deposition-stripping process during a cycling voltammetric scanning. 

Waves I and II in Figure 2.81(b) are due to the formation of Cu(I) and Cu(II) surface oxides. Subsequent reduction of these films occurs during the cathodic sweep to give waves III and IV. The points A to D represent the potentials at which reflectivity data were collected during the voltammetric scan. The potential was ramped at lOmV/s until one of these potentials was reached, at which the scan was stopped for the duration of the data acquisition. The spectrum collected at A represents the condition of the electrode surface... 

Electrolysis of a solution of the catalyst at — 1.4 V to — 1.5 V vs. SCE in the absence of C02, giving le /Re atom, gave the sparingly soluble green dimer (as characterised by UV-visible, [R, nmr and elemental analysis on the isolated material) in agreement with the work of Lehn and colleagues (Hawecker, 1983) and showing that the first reduction is coupled to the formation of the dimer if chloride loss is allowed to occur. If the cyclic voltammetric scan was reversed when the potential reached —1.5 V, at a... 

In order to understand the meaning of such a sentence one must consider that the starting potential for a cyclic voltammetric scan must be selected on the basis of the zero-current condition, or to start from a potential value at which no electron transfer occurs at the working electrode. Even if one was wrong in the choice of the starting potential, i.e. one could have selected a potential at which an electrode process is taking place, it is very unlikely that one can realize it, in that the... 

In the experimental analysis the SW potential scan is preceded by a certain delay period (/delay) to allow the reactant to adsorb on the electrode surface. Besides, the reactant adsorbs additionally in the course of the voltammetric scan starting from the initial (Es) to the peak potential (fp). Thus, the total accumulation period (face)... 

In a systematical study, Golovin et al. investigated a series of metallocene derivatives in terms of their redox potentials, mass transport properties, and chemical and electrochemical stabilities in both electrochemical test cells and commercial-size AA rechargeable cells.Figure 43 shows the complete voltammetric scan of the ferrocene-containing elec-... 

This method involves electrochemical deposition of the MPc onto CNT-modified electrode surface by repetitive cycling in a concentrated MPc solution (1 mM) within a specific potential window. The first cyclic voltammetric scan is usually similar to subsequent scans, indicating the formation of monomeric species only. Ozoemena et al [11] found that on certain occasions, as reported recently [11] during the electro-deposition of CoTAPc onto a basal plane pyrolytic graphite electrode (BPPGE) pre-modified with SWCNT, both cathodic and anodic waves may decrease continually and then stabilizes at a certain scan (a process known as electrochemical adsorption or simply called electrosorption ). 

The potentials in Table 2 are referred to Ag/AgI in a medium of dmf + Bu4NI. While both the peaks are reversible or quasi-reversible in the cyclic voltammetric scans, the electrochemical reduction is carried out at the first peak, where an anion is generated. Dianion formation occurs at a more negative potential but is at a lower potential than the phosphonium salt. On controlling the potential of the electrode at the first reduction of the probase and carrying it to 2 F mol" the ylide is produced. 

A major advantage of carbon fiber electrodes is the possibility of using fast voltammetric scan rates (> 100 V/s) due to small electrode area [48]. Even though internal resistance can be significant for carbon fibers (see later), the... 

Instead of directly scanning the potential using a potentiostat, it is possible to indirectly achieve a voltammetric scan by coulostatic detection [26]. The potential of an electrode and the charge on that electrode are related according to... 

Fig. 7.6. Determination of cadmium (A) and lead (B) for increasing concentrations in 10 pgL-1 steps (b-e) concentration ranges of 10-40 (Cd) and 20-80 (Pb) pgL-1. Simultaneous determination of cadmium and lead (C) for increasing concentrations in 10 pgL-1 steps (Pb) and 20pgL-1steps (Cd). Also shown is the blank (a) and the corresponding calibration plots. Solutions 0.1 M acetate buffer (pH 4.5). Square-wave voltammetric scan with a frequency of 50 Hz, potential step of 20 mV, and amphtude of 25 mV. Deposition potential of —1.3 V during 120 s.

Detection The guanine oxidation peak was measured in an unstirred ABS using square-wave voltammetric scan (frequency — 200 Hz, step potential — 15 mV, amplitude = 40 mV),... 

Figure 8.3 illustrates cyclic voltammograms at a platinum (Pt) electrode for a dimethyl sulfoxide (Me2SO) solution that is saturated with H2 (1 atm). For each voltammogram the Pt electrode has been activated via preanodization at the indicated potential for 2 min prior to initiation of the voltammetric scan. 

Figure 11.13 Voltammetric scans at gold amalgam electrodes for the reduction of C02 in dimethyl sulfoxide (a) Pt, N2 (b) Pt, 1 mM C02 (c) Hg(Pt), N2 (d) Hg(Pt), 1 mM C02. Electrode area 0.215 cm2, supporting electrolyte 0.03 M (Et4N)C104, scan rate 0.05 V s 1.

Figure 6. Plot of E1/2 vs. SCE for the surface-confined acyl ferrocene thiol vs. pH (top) and plot of difference in cathodic current peak for surface-confined acyl ferrocenium and quinone vs. PH from two-terminal, voltammetric scans. All data are from voltammograms recorded at 500 mV/s in 1.0 M NaC104 in buffered solution. Reproduced with permission from ref. 1. Copyright 1991 American Association for the Advancment of Science.

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