Graphite edge pyrolytic

Figure 17.7 Electrocatalysis of O2 reduction by Pycnoporus cinnabarinus laccase on a 2-aminoanthracene-modified pyrolytic graphite edge (PGE) electrode and an unmodified PGE electrode at 25 °C in sodium citrate buffer (200 mM, pH 4). Red curves were recorded immediately after spotting laccase solution onto the electrode, while black curves were recorded after exchanging the electrochemical cell solution for enzyme-fiiee buffer solution. Insets show the long-term percentage change in limiting current (at 0.44 V vs. SHE) for electrocatalytic O2 reduction by laccase on an unmodified PGE electrode ( ) or a 2-aminoanthracene modified electrode ( ) after storage at 4 °C, and a cartoon representation of the probable route for electron transfer through the anthracene (shown in blue) to the blue Cu center of laccase. Reproduced by permission of The Royal Society of Chemistry fi om Blanford et al., 2007. (See color insert.)...

Typical cyclic voltammogram at 0.3mV/s of a hydrogenase film adsorbed at a pyrolytic graphite edge electrode immersed in a pH 9.00 hydrogen-saturated solution at 45°C and rotating... 

It is important to point out that not all redox systems will exhibit electrocatalytic activity when probed on high-density edge CNT electrodes or edge pyrolytic graphite. Such phenomenon depends on the particular mechanism of the redox system ]2]. It is important to recall that among the redox species there are some of them whose... 

Figure 3. Steady state polarization curves in KF-2HF at 90 C O layer plane of pyrolytic graphite, edge plane of pyrolytic graphite...

Flavocytochrome c3 (EC 1.3.99.1) isolated from Shewanella frigidimarina is a unique fumarate reductase of 63.8 kDa MW in a single subunit composed of two domains. The active site is located in the flavin domain. The heme domain contains four c-type hemes, each with a bis-His axial ligation. It has been proposed that this domain is similar to cytochrome c3 from Desulfovibrio desulfuricans. On pyrolytic graphite (edge) electrodes in the presence of polymyxin the single redox centres were examined. Fumarate addition is followed by a catalytic current [108]. 

Figure 4-2. Cartoons of the ways in which proteins are attached to electrodes for protein film voltammetry. (A) Pyrolytic graphite edge (PGE) electrode. (B) SAM modified metal electrode. (C) Layer-by-layer polyion adsorption. (D) Electrode confined bilayers.

Thus, SNIFTIRS is an extremely versatile technique, especially when it is realised that virtually any electrode may be employed providing it is IR reflective, e.g. metals, doped semiconductors, basal plane and edge pyrolytic graphite, and glassy carbon, etc. As yet, its applications have only been touched upon, but it is expected that the technique is, and will continue to be, an increasingly powerful tool in the hands of the electrochemist. 

Figure 4.7 Current—potential curves for 02-saturated 1 M KOH solution on high-pressure-annealed pyrolytic graphite — edge plane, — basal plane. Reprinted from Ref. 24, with permission from Elsevier.

The voltammetry of cytochrome c at the pyrolytic graphite edge showed a marked pH dependence [91]. Analysis of the reduction current measured at a rotating-disk electrode as a function of pH showed that this was virtually abolished under acid conditions. A plot of log(ima, — i/imax) against pH was linear (slope 1.5) between pH 4.2 and 7.0 and yielded an effective pK of 5.6. A similar set of measurements on the reduction of Fe(CN)g under conditions of low ionic... 

Fig. 2 Reversible voltammograms for (top row) a diffusing redox couple reacting at a planar macroelectrode at which the entire surface is interactive (bottom row) a diffusing couple reacting at a microelectrode, or a macroelectrode at which most of the surface is blocked to protein interaction. Theoretical voltammograms are shown at the center, while the right hand side shows actual results obtained for cytochrome c at a polished pyrolytic graphite edge plane (top) or basal plane electrode, (bottom) showing the effect of the density of interactive sites on the electrode.

Fig. 7 Voltammetry of a film of yeast cytochrome c peroxidase adsorbed on a pyrolytic graphite edge electrode.

Figure 2.9. Current-potential curves for 02-saturated 1 M KOH solution on high pressure annealed pyrolytic graphite — edge plane, — basal plane [22]. (Reprinted from Electrochimica Acta, 15(6), Morcos 1. and Yeager E., Kinetic studies of the oxygen— peroxide couple on pyrolytic graphite, 953-75, 1970, with permission from Elsevier.)...

Hirst and coworkers reported DET of formate dehydrogenase (from Syntrophobacter fumaroxidans) which reversibly interconverted formate and CO2 at a pyrolytic graphite edge (PGE) electrode. With an applied potential of —0.41 V (vs. SHE), the formate dehydrogenase hioelectrode exhibited approximately 102% faradaic efficiency for the reduction of CO2 to formate at pH 6.5. 

Pyrolytic graphite edge None <.55 0.12 <70 Cytochrome C peroxidase was used free in solution 16... 

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