Cyclic voltammograms platinum surfaces

Fig. 8. Cyclic voltammograms of polyacetylene films on a platinum surface measured in acetonitrile containing 0.1 M Et4NBF4. Reproduced from [98],...

Figure 6. Cyclic voltammograms of a platinum disk-electrode modified with a film of the octanuclear dendrimer 2, measured in 0.1 M Bu NPFj/CHjClj. The surface coverage of electroactive ferrocenyl sites in the film is determined to be T = 2.01 x 10" mol cm . inset, scan rate dependence of the anodic peak current.

Fig. 8.7. Influence of electrode materials on cyclic voltammograms performed on skin surface at 50 mV s-1 (a) with a 50 pm diameter platinum electrode and (b) with a 50 pm diameter gold electrode.

Cyclic voltammograms were also performed with platinum microelectrodes on skin surface at regular time intervals of about 7 h. Figure 8.10 shows the typical curve giving the evolution of the anodic current at 0.9V/SCE as a function of time. A sinusoidal evolution was observed for the nine volunteers. Current values as well as the amplitude and the period of the variations were different for each subject. It has been verified that the amplitude of the current variations was significantly higher than the accuracy of the amperometric response. Consequently, the variation of the anodic current was actually due to a variation of the oxido-reductive properties of the skin and was not an artifact of the measurements. 

FIGURE 19 Cyclic voltammogram showing one complete anodic-cathodic sweep. The area under the hydrogen oxidation peaks is a measure of platinum surface area. 

Figure 8.2 Cyclic voltammograms for 5 mM solutions of Biyfnsted acids (114) in dimethylformamide (DMF) at a freshly surfaced platinum electrode (area 0.46 mm2). Scan rate 0.1 V s solutions contained 0.5 M tetraethylammonium perchlorate (TEAP).

Very thin films (ca. 10 nm) formed by electropolymerization can be used to effectively prevent signals due to interferences. Figure 1 shows a cyclic voltammogram for the electropolymerization of poly(l,3-DAB) onto a platinum ultramicroelectrode (25/un diameter). Note how the current decreases with each subsequent scan, indicating coverage of the electrode surface. 

Figure 5.3 Cyclic voltammogram of a spontaneously adsorbed [Os(bpy)2py(p3p)]2+ monolayer, obtained by using a scan rate of 50 V s 1, with a surface coverage of 9.5 x 10 n mol cnr2. The supporting electrolyte is 0.1 M TBABF4 in acetonitrile, and the radius of the platinum microelectrode is 25 xm. The cathodic currents are shown as up, while the anodic currents are shown as down. The complex is in the [Os(bpy)2py(p3p)]2+ form between +0.400 and —1.200 V the initial potential was 1.000 V. Reprinted with permission from R. J. Forster, Inorg. Chem., 35, 3394 (1996). Copyright (1996) American Chemical Society...

Figure 5.8 Cyclic voltammograms for the Os2+/3+ redox reaction within spontaneously adsorbed [Os(OMebpy)2(p3p)Cl]+ monolayers. From right to left, the electrode materials are platinum, gold, carbon and mercury. The scan rate is 50 Vs-1, with a surface coverage of 1.0 0.1 x 10-1° mol cm-2 the supporting electrolyte is aqueous 1.0 M NaC104. Reprinted with permission from R. J. Forster, P. J. Loughman and T. E. Keyes,/. Am. Chem. Soc., 122,11948 (2000). Copyright (2000) American Chemical Society...

Figure 2.9 Repetitive cyclic voltammograms illustrating the continuous growth of polyaniline on a platinum surface.

The cyclic voltammogram of [BMPJTfjN containing 0.1 molU1 SeCU on a platinum substrate at 25 °C is presented in Figure 6.14(a). At a potential of—750 mV vs. Pt a dark red deposit forms on the electrode surface, obviously passivating it. It is likely that this peak is correlated to the reduction of Se(IV) to the red phase of elemental Se. It cannot be excluded that the black phase is also formed. If the... 

Fig. 35 Cyclic voltammogram of platinum single-crystal surfaces in the hydrogen adsorption region in 0.5 M H2SO4 under nitrogen purging ...

The region of the cyclic voltammogram, corresponding to anodic removal of Hathermal desorption spectra of platinum catalysts. However, unlikely the thermal desorption spectra, the cyclic-voltammetric profiles for H chemisorbed on Pt are usually free of kinetic effects. In addition, the electrochemical techniques offer the possibility of cleaning eventual impurities from the platinum surface through a combined anodic oxidation-cathodic reduction pretreatment. Comparative gas-phase and electrochemical measurements, performed for dispersed platinum catalysts, have previously demonstrated similar hydrogen and carbon monoxide chemisorption stoichiometries at both the liquid and gas-phase interfaces (14). 

The Auger spectra for the carbon line can be used for checking the surface contamination that can be corroborated with the voltammograms [85]. Nevertheless, with the help of only cyclic voltammetry, we can observe and analyze easily a platinum surface that is free of the various atmospheric contaminants. Contamination is avoided because of the very short time required for the transfer of the sample from the flame treatment to the cell. This rather unusual requirement of quick transfer of the samples shows that voltammetry should be a good tool for the study of metallic surfaces in the presence of a defined and complex environment. 

---