Nafion, cyclic voltammogram

Platinum was deposited on Nafion membrane by the method described earlier. Ibe cyclic voltammogram is shown in Fig. 2-i6 using 3 M H2SO4 as the electrolyte in the solution side of the membrane. The hydrogen adsorption—desorption features are not very well-defined probably because of some impurities. 

Figure 4.4 Cyclic voltammogram for the reduction and reoxidation of 6 nm Ti02 NPs immobilized in LbL films with Nafion. Scan rate, 100mVs . Electrolyte 0.1 M KCI. (i) 2 layers Ti02, (ii) 10 layers Ti02, (iii) 20 layers Ti02- From reference [57] with permission.

In Figure 2 is shown the decrease of the anodic peak current of the cyclic voltammograms at a sweep rate of 100 mV/s, which is proportional to the mediator loading in the Nafion-GOD film, as a function of time after the fully loaded Pt/Nafion-GOD-DMAFc, Pt/Nafion-GOD-ferrocene were respectively... 

Figure 2. Plots of anodic peak current of the cyclic voltammograms recorded at 100 mV/s vs time for the Nafion-GOD films fully loaded with ( O ) ClFc+, ( ) C6Fc+ and ( ) DMAFc, respectively in 0.1M phosphate buffer...

Figure 9. AFM images of TPSP-ZnO before (A)and after(B)GOD loading.(C) Cyclic voltammograms ofTPSP-ZnO/Nafion (a), GOD/Nafion (b)GOD/spherical ZnO/ Nafion (c) and GOD/TPSP-ZnO/Nalion (d) modified in 0.1M pH 7.0 PB at 0.1 Vs" ( Reprinted from Biosensors and Bioelectronics, 24, Z. Dai, G. Shao, J. Hong, J. Bao, J. Shen, Immobilization and direct electrochemistry of glucose oxidase on a tetragonal pyramid-shaped porous ZnO nanostructure for a glucose biosensor, 1288,1289, Copyrights (2009) with permission fom Elsevier.

Figure 3.26 Cyclic voltammograms (v = 50mVs 1) of a graphite electrode coated with a layer of Nafion (about 3.7 x 10-8 mol cm-2) incorporating H2TPP, before (curve a) and after conversion into Co(lll)TPP (curve b, see text) in Ar-purged 0.5 M H2S04. Also shown for comparison (curve c) is the response of about 10-8 mol cm 2 CoTPP adsorbed directly on the carbon surface, that is, no Nafion film.

Figure 3.27 Cyclic voltammogram (v = 5 mVs-1) of a Nafion film (about 2.4 x 10 7 mol crrT2) incorporating CoTPP recorded in a 0.5 M H2S04 solution containing 1 x 10-8 M Ru(NH3)63+ (see text for details).

The highest electronic resistances were observed at low Nafion loadings, indicating that the ionomer played a significant role as a binder [211], Meanwhile, kinetic losses pass throngh a minimnm correlated with the electrochemically active snrface area of the catalyst estimated from cyclic voltammograms [209] The higher the electrochemically active surface area, the lower the kinetic losses. This volcano type of cnrve reflects the optimnm in the metal utilization factor u. Below, we try to nnderstand how carbon properties may influence these characteristics. 

An Illustration of a PEC cell of this type, which operates in reverse, may be found in the work of Rubinstein and Bard (12). The well known duPont polymer Naflon was dip coated on a graphite electrode for this experiment, and then immersed in a solution of Ru(bpy)3Cl2 (bpy = 2,2 -bipyridine). Cyclic voltammograms of this treated electrode showed broad oxidative and reductive waves close to 1.2V vs NHE of the potential sweep, characteristic of the presence of the Ru(bpy)32" complex sequestered in the polymer film. However, when oxalate ion was added to the supporting electrolyte, which ion is only oxidized at higher potentials by plain Nafion, three effects were noted namely, an enhanced oxi-... 

Figure 13-7. Cyclic voltammogram at a Pt electrode coated with [MnTPP] in Nafion (A) and at a bare Pt electrode (B) in a phosphate buffer aqueous solution (pH 1.0) under Ar. Scan rate, 1 mV s . ...

Figure 7. Cyclic voltammograms of O2 reduction observed with the PXV coated BPG electrodes, in air-saturated solution of 0.2 M NaC104 (A and B), or 0.2 M CF3COONa (C), adjusted to pH = 6.5 with 50 mM phosphate buffer, at scanning rate of 100 mV/sec (A) bare (B) PXV-PSS (C) PXV-Nafion.

Fig. 24.3 Cyclic voltammogram of a 5 cm PEMFC with a PtA ulcan anode and cathode, Nafion 117 electrolyte 80 °C...

Figure L Cyclic voltammograms (100 mVs under N2) of CFP catalyst layer I Nafion 117 electrodes in 1 MH Ofaq). A. Pt on polyaniline/PSS B, Pt on polyaniline C Pt on polyaniline with Nafion (0.1 mg cm ) added to the catalyst layer. Pt loadings were all nominally ca. 0.2 mg cm . ...

Fig. 13. Subtracted cyclic voltammograms at a Nafion-coated carbon fiber electrode. All conditions are as in Fig. 12. (From ref. [29]).

Figure 1. A. Cyclic voltammograms recorded with a Nafion-coated pyrolytic graphite electrode containing 1.1 x 10" mole cm of sulfonate groups. The solid line was obtained witn the Nation coating alone the dashed line resulted after incorporation of 2.2 x 10" ° mole cm of CoP(py)4 in the coating.

We now examine a specific problem, the electrooxidation of catechol at a Nafion-coated electrode containing dispersed RUO2 particles. This work was recently published by Lyons and coworkers. Typical cyclic voltammograms recorded for the Ru02/Nafion composite material in 0.2 M H2SO4 are shown in Fig. 2.33. The broad nature of the current response across the entire potential window examined... 

Figure 11.27. Cyclic voltammograms to illustrate the eharge associated with hydrogen adsorption Qh and that associated with platinum oxide reduction Qo- Nafion 112 membrane Pt/C cathode catalyst T = 100 °C scan rate = 30 mV s [62]. (Reproduced by permission of ECS—The Electrochemical Society, from Xu H, Kunz R, Fenton JM. Investigation of platinum oxidation in PEM fuel cells at various relative humidities.)...

Figure 15.4. Comparison of cyclic voltammograms on Nafion electrol5de under N2 atmosphere. Scan rate = 100 mV/s [75]. (Reprinted from Electrochimica Acta, 49(21), Lee K, Ishihara A, Mitsushima S, Kamiya N, Ota K-I, Stabihty and electrocatal5dic activity for oxygen reduction in WC + Ta catalyst, 3479-85, 2004, with permission from Elsevier.)...

A three-electrode glass cell was used with the temperature maintained at 25 C. Current-potential curves of the ORR, cyclic voltammograms (CVs), and linear-sweep voltammograms, first for the noncontaminated condition, were obtained for the Nafion film covered platinum RDE. 

Figure 17 Spectra recorded at-0.90 V vs SCE during the 2nd, 4th, 6th, 8th and 10th cyclic voltammograms for an ITO/Nafion electrode in 0.1 mM 1,1 -dimethyl-4,4 -bipyridilium dichloride +0.2 M KCI (pH 5.5). The vertical arrows indicate absorbance increase with scan number. For a comparable experiment in the absence of Nafion, the maximum absorbance was <0.01. Reproduced with permission from Mortimer RJ and Dillingham JL (1997) Journal of the Electrochemical Soc/efy 144 1549-1553.

Fig. 2.19 Cyclic voltammograms of Os-(PVP)io (A) and Os-(PVP)io/Nafion B, C) modified electrodes in pH 6.9 PBS (A, B) and (B), + 1.0 x 10 M epinephrine (C) at a scan rate of 40 mV s Inset plot of logarithm of catalytic current versus epinephrine concentration. Figure reproduced from Ref. [9] with permission from Elsevier...

The concentration of FA inside the Nation membrane is very sensitive to the presence of other cations. Figure 2 shows cyclic voltammograms observed with the Nafion-coated GC electrode with 7.2 x 10" M FA and different concentrations of hexamethonium (autonomic ganglionic blocking drug) in the electrolyte solution. The addition of hexamethonium resulted in a decrease in the peak current for FA. This phenomenon clearly demonstrated that some FA initially trapped inside the Nation membrane is replaced by hexamethonium added to the electrolyte solution (Figure 3). 

In these measurements, cyclic voltammograms were recorded after 5 min immersion of the Nafion-coated electrode into the sample solution containing a specific amount of a drug. Hexamethonium, acetylcholine and neostigmine equilibrated fairly rapidly and a near equilibrium state was obtained after 5 min of immersion. Only small changes in the voltammetric peak current were observed on subsequent scans. However, ca. 30 min was necessary to reach a near equilibrium state for quinidine. These differences in the equilibration time seems to be mainly dependent on the size of the cation. For analytical purposes it is not necessary to obtain an equilibrium response. The same measurements were carried out using a number of Nafion-coated GC electrodes. The results were quite reproducible and the variation of the relative peak current under different runs were within 5%. When the Nafion-coated GC electrode used for these measurements... 

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