Activated carbon electrodes voltammograms

Figure 2. Cyclic voltammograms of ferrl-/ ferro-cyanlde couple at an activated glassy carbon electrode at scan rates of a) 20, b) 50, and c) 100 mV s . See text for details.

Figure 3. Cyclic voltammograms of ascorbic acid at a freshly polished, active (a) and a deactivated (b) glassy carbon electrode surface. See text for details.

Figure 17.12 Direct electrocatal3ftic oxidation of D-fnictose at a glassy carbon electrode painted with a paste of Ketjen black particles modified with D-fructose dehydrogenase from a Gluconobacter species. The enzyme incorporates an additional heme center allowing direct electron transfer from the electrode to the flavin active site. Cyclic voltammograms were recorded at a scan rate of 20 mV s and at 25 + 2 °C and pH 5.0. Reproduced by permission of the PCCP Owner Societies, from Kamitaka et al., 2007.

Figure 3. Cyclic voltammograms in three-electrode cells for activated carbon andfor a-MnC>2 nH20 loaded with 15wt% of carbon nanotubes in 2 molL 1 KNO3 medium using Pt as...

Figure 4. Cyclic voltammogram of an asymmetric capacitor with activated carbon and a-MnOynHiO as positive and negative electrodes, respectively, in 2 mol L 1 KNOj medium.

Fig. 12 Cyclic voltammogram of [Mn202(phen)4] + in pH 4.5 phosphate buffer at an activated glassy carbon electrode i = 0.1 V s (reprinted with permission from Ref 97, Copyright 1992 American Chemical Society).

FIGURE 8.35 Comparative cyclic voltammograms of a-Mn02/CNTs composite and of activated carbon (Maxsorb, Kensai, SBET = 3487 m2 g-1) obtained with a three-electrode cell in 2 mol L"1 KNOs (pH = 6.4). (Adapted from Khomenko, V., et al., J. Power Sources, 153, 183, 2006.)... 

The various forms of adsorbed copper can alter the electrochemical behavior of modified carbon samples used as electrode materials (powdered working electrodes in cyclic voltammetry). Figures 45 and 46 show cyclic voltammograms (CVs) for powdered electrodes prepared from selected active carbon samples with and without preadsorbed copper recorded in solution, which do or do not contain Cu " ions. An aqueous solution of 0.5 M NaiS04 as background electrolyte was employed. The CV curves recorded in the solution containing copper ions exhibit a pair of cathodic and anodic peaks, the potentials of which are dependent on the carbon modification procedure and the electrolyte s pH. The estimated peak potentials and the midpoint potentials [formal potentials, Ef = ( p, — p,c)/2] are given in Table 13. 

One typical example of this behavior is the voltammogram of the ferro/ferricyanide couple (test reaction) that at carbon electrodes is less reversible than at noble metal electrodes. The kinetics of the test reaction in 1 M aqueous KCl was used as the reference to compare its electrochemical behavior on different carbon electrodes [20]. This electrochemical reaction occurs via an outer sphere mechanism and its rate depends on the electrolyte composition and can be increased by appropriate treatment of carbon electrodes, for instance, by application of a high current potential routine to electrodes of carbon fibers. Similar results have been obtained with glassy carbon surfaces that had been pretreated at 500°C under reduced pressure. An alternative activation method is based on careful electrode surface polishing [6]. 

Fig. 25. Comparative cyclic voltammograms in a three electrode cell using manganese oxide or activated carbon as working electrode in 2 mol L KNO3 aqueous electrolyte [107]. Reprinted with permission om V. Khomenko, E. Riprmundo-Pfflero and F. Bdguin, J. Power Sourc., 2005, in press.

Figure 8.17 Cyclic voltammograms (at 1 mVs" ) of two-electrode cells operating with activated carbons AAC 1 or AAC 2 in iodide/vanadium conjugated redox couples as electrolyte solutions [112].

Fig. 12.20 Three-electrode cyclic voltammograms with activated carbon (S50) or oxidized activated carbon (S50ox)-based electrodes in (a) pyrrolidinium nitrate and (b) pyrrolidinium formate vs the Ag/AgClsat, KClsat (PIL) reference electrode (Adapted from [71])...

Manganese Oxides, Fig.2 Cyclic voltammograms of (a) bimessite electrodes (-0.1 0.9 V) prepared by the electrochemical stimulation method and activated carbon... 

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