Voltammograms ring-disk

Figure 6 Steady state rotating ring-disk voltammograms of (A) compound (42) (B) compound (43) and (C) a Ru-bridged polymer of (43) each adsorbed to a graphite working electrode. Disk current shows reduction of 02 while ring current reveals the presence of H202 simultaneously reoxidised at the ring anode poised at +1.0 V (reproduced with permission of the American Chemical Society from Acc. Chem. Res., 1997, 30, 437-444).

Pseudo-first-order rate constants, ki (normalized to unit substrate concentration [S]), were determined from measurements with a glassy-carbon-glassy-carbon ring-disk electrode that was rotated at 900 rev min (Ref. 19), or from the ratio ( anodic/ cathodic cyclic voltammogram of O2 in the... 

Figure 1.16. Cyclic voltammograms under N2 (A,C) and rotating ring-disk current-potential curves in aqueous air-saturated pH 7 buffers (B,D) of 2FeCu and 2Fe-only directly adsorbed on a graphite electrode (A,B) and as a 0.7% (mol) suspension in a 1-/rm-thick phosphadytilcholine film on the electrode surface (C.D). The rapid charge transfer within the films of adsorbed catalysts is supported by the linear dependence of the peak currents on the scan rate. The non-ideal shape of the peaks is due to cooperative behavior of the catalytic films as a whole. The Fe / and Cu / potentials are the same in the adsorbed catalysts (A) but separate when the catalysts are in the lipid film (C). Autooxidation of the catalyst-02 complex is the major source of ring-detectable byproducts (see below) and accounts for the potential-dependent selectivity of electrode-adsorbed catalysts (B). The measured collection efficiency of the ring electrode toward H2O2 in these experiments was 15%.

Fig. 7.8 (A) Examples of dicobalt cofacial bisporphyrins DPX diporphyiin xanthene (a) DPD diporphyrin dibenzofuran (b) DPXM diporphyrin xanthene methoxyaryl (c) DPDM diporphyrin dibenzofuran methoxyaryl (d). (B) Rotating ring-disk voltammograms of O2 reduction at pyrolytic graphite disks modified with (a), (b), (c), and (d) [48]...

Figure 7.63 Disk voltammograms and luminescence intensity vs potential of an n-GaAs (ring disk electrode (RDE)) in the presence of 10" M Ce at pH 1 at two different rotation velocities 9 Hz (dashed) and 25 Hz (solid lines) scan rate lOmVs (after [85]).

Figure 11.18 Linear cyclic voltammograms of a FePc/C disk electrode and corresponding oxidation current of a Pt ring electrode maintained at 1.2 V vs. RHE, recorded at 2500 rev min in an 02-saturated 0.5 M H2SO4 electrolyte (temperature 20 °C, sweep rate 5 mV s ).

Fig. 35. Disk and ring voltammograms recorded during the oxidation of thin-layer Co-Al electrodeposits from a Pt-RRDE in pure 60.0 m/o AlCl3-EtMeImCl melt. These deposits were produced with a charge density of 425 mC cm 2 in melt containing 5.00 mmol L-1 M Co(II) at the following deposition potentials (—) 0.200, (—) 0.100, and ( ) 0 V. During stripping, the disk electrode was scanned at 0.002 V s 1, and Er was held at 0.500 V. The angular velocity of the RRDE was 104.7 rad s 1. Adapted from Mitchell et al. [44] by permission of The Electrochemical Society.

Figure 3.13 Electrochemical oxidation of HOOH and reduction of its products at GC electrodes in MeCN (0.1 M TEAP) (a) linear-sweep anodic voltammograms for (A) 0, (B) 0.3, (C) 1.7, and (D) 3.3 mM HOOH (scan rate 2 V min-1 electrode area, 0.46 cm2) (b) rotated-ring electrode cathodic voltammogram (scan rate 10 mV s-1) of the product from the oxidation of 4 mM HOOH at the rotated-disk electrode (rotation rate 1600 rpm) for (A) ED disconnected, and (B) En = +2.6 V versus SCE (c) rotated-ring electrode cathodic voltammogram (scan rate 10 mV s-1) of the products from the oxidation of 1 mM HOOH at the rotated-disk electrode (rotation rate 4900 rpm) for (A) disconnected and (B) ED = +2.6 V versus SCE.

Figure 7.1 (A) Disk and ring currents during oxygen reduction on (A) Pt(111), (B) Pt(IOO), and (C) Pt(110) facets, respectively, in 0.1 M Oa-saturated KOH aqueous solution at a potential sweep rate of 50 mV s (ring potential = 1.15 V (RHE)). Cyclic voltammograms in the insets (a) are recorded in KOH aqueous solution without dissolved oxygen. Reprinted with permission from Ref. 2.

Figures. Top Cyclic voltammogram for Cu UPD on a Pt(lll) disk electrode. Bottom Ring electrode currents recorded with the ring being potentiostated at -0.275 V. Insert Charges on the disk,, and the ring, Qj. electrode.

Figure 2.10. RRDE voltammograms for O2 reduction at the PDDA/MWCNTs/GC (curve 1) and bare GC (curve 2) disk electrodes in 02-saturated 0.10 M KOH solution. Curves 1 and 2 represent the current for the oxidation of HO2 produced at the corresponding disk electrodes. Potential scan rate 10 mV/s electrode rotating rate 400 rpm. The Pt ring electrode was polarized at +0.50 V for the oxidation of HO2 [16]. (Reprinted with permission from Langmuir 2004 20 8781-5. Copyright 2004 American Chemical Society.)...

The basic idea of this technique is that a linear potential sweep (of low rate) is applied to the disk electrode, while cyclic voltammograms (of a relatively high sweep rate) are measured at the ring. The results of such experiments can lead to the creation of a 3D map , which may reveal the electroactive intermediates or products that are formed in the electrode process(es) taking place on the disk. The applicability of the proposed technique is demonstrated here by considering the oxygen reduction process at the gold 0.5 mol dm sulphuric acid electrode as an illustrative model reaction. 

Figure 3. Controlling waveforms of the disk and ring electrodes while the disk potential is slowly swept towards cathodic values, a multitude of cyclic voltammograms are obtained from the ring with a high sweep rate.

The experiment was carried out as follows The disk electrode was slowly polarized from 600 to -600 mV vs. SCE (at a sweep rate of 0.25 mV/s), while the cyclic voltammograms of the ring were recorded at a sweep rate of 100 mV/s between the potential limits of 1450 and -550mV (Figure 3). The electrode was rotated at 1000 rpm during the experiment. 

The approach that Cadle and Bruekenstein used for the deteetion of the soluble gold species was based on the measurement of cyclic voltammograms at the disk electrode, while holding the ring at sulEciently negative potentials. The technique presented in [19] will be discussed below, and it will be demonstrated how the sensitivity and the applicability of the RRDE detection can be extended by the applieation of dual dynamic perturbations. 

Figure 7. (a) Cyclic voltammograms measured on the disk electrode between vertices of 1400 and -500 mV at a sweep-rate of 50 mV/s. (c) The ring current is recorded in parallel with measuring the CVs of the disk. A segment of the measured ring current is shown as a function of the disk potential in (b). Rotation rate 500 min. ... 

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