Lead electrode cyclic voltammograms

If the voltammetric scan is not reversed after the first oxidation, a second oxidation (Epa = 0.2-0.3 V) is observed (Figure 6c). This oxidation renders the lower potential oxidation irreversible (Epa = 0-0.1 V) and also leads to the observation of an irreversible reduction at negative potentials (Epc = —0.8 to —0.9 V). It has not been possible to measure accurately the number of electrons involved in either the second oxidation or in the coupled reduction process by coulometry due to the formation of films on the electrode surfaces. However, in comparison with that observed for the first oxidation, the peak currents are consistent with one- and two-electron processes, respectively. In spite of the irreversible nature of the cyclic voltammogram, continuous cycling be-... 

Fig. 9. (a) Simultaneous measurement of the cyclic voltammogram (upper trace) and the photocurrent (lower trace) of a lead electrode in 0.5 mol dm-3 H2S04. Wavelength, 340nm sweep rate, 20mVs 1. The photocurrent curves correspond to sweep reversal at different anodic limits. Note, in particular, the change in sign of the photocurrent on the reverse sweep, (b) Comparison of the anodic photocurrent spectrum ( ) with the absorption... 

Cyclic voltammograms for a lead electrode in H2SO4 solution. Anodic potential limit 1.45 V (vs Hg/Hg2S04) potential scan rate 10 mV s [52]. 

Cyclic voltammograms for a lead electrode in H2SO4 solution on polarization to potentials of... 

Electrochemical studies have revealed that indeed 6-hydroxydopamine is very easily oxidized. A cyclic voltammogram of 6-hydroxydopamine at a carbon paste electrode at pH 7 is shown in Figure 4. The evidence leads to the conclusion that peak la is a 2e-2H electrooxidation of 6-hydroxydopamine... 

Figure 4.27 Cyclic voltammogram of UPD of lead on a Ag(lll) surface. The reference potential is the Nemst potential of a lead/lead ion electrode in die same solution. 5 X 10 mol-dm-3 Pb(C104)2 + 5 X 10- mol-dm-2 NaC104 + 5 X lO mol-dm- HCIO4, 25 °C. Scan rate 0.42 mV-s-. (Reproduced with permission from Ref. [60], 1978, Elsevier.)...

Figure 4.27 shows a typical cyclic voltammogram of an UPD of lead on the crystallographic surfaces of a silver (111) single crystal. The cyclic voltammogram of lead UPD on silver (100) is shown in Figure 4.28. The current is plotted versus E — Eq, the potential referred to the Nemst potential of the lead electrode in the same solution. At E Eq < 0 the deposition of bulk lead would start. The diagram shows that a limited amount of lead is deposited at potentials that are more positive than the Nemst potential. The reason for this is an adsorption of the metal ions on the substrate metal.

Fig. II.1.25 (a) Schematic representation of the transfer of anion from the aqueous into the organic phase upon oxidation of Mn(II)TPP to Mn(III)TPP . (b) In the presence of the boronic acid B as a facilitator the tiansfer of the anion A leads to the formation of the complex AB in the oiganic phase, (c) Cyclic voltammograms [120] (scan rate 10 mVs ) for the oxidation and le-ieduction of 75 mM Mn(II)TPP dissolved in PPP (4-(3-phenylpropyl)-pyridine, 75 nL) and immobilised in the form of microdroplets onto a 4.9-mm diameter graphite electrode immersed in aqueous 0.1 M sodium lactate pH = 7.34. The presence of (i) 0 and (ii) 973 mM naphthyl-2-borDnic add is shown to cause a negative shift in the voltammetric response, (d) Plot of the midpoint potential versus the natural logarithm of the naphthyl-2-boronic add concentration in the microdroplets. Lines indicate calculated data [120] for reversible lactate-4)oronic add complex formation for three equilibrium constants...

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