Pyrolytic graphite edge electrode

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... 

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]. 

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

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.)...

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.

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.

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. 

An important contribution towards understanding the electrochemical reactivity of graphene is that by Tsai et al. They compared naked basal (BPPG) and edge plane pyrolytic graphite (EPPG) electrodes with... 

Fig. 16.1 Cyclic voltammetric response of Boron-Doped Diamond (BDD), glassy carbon (GC), edge plane pyrolytic graphite (EPPG), basal plane pyrolytic graphite (BPPG) and highly ordered pyrolytic graphite (HOPG) electrodes in a 0.1 M KCl aqueous solution which has had 0.1 % ammonia bubbled through it for 4 min. The dashed line is the response of the electrode in the...

Figure 24 Square wave voltammograms recorded at an edge-oriented pyrolytic graphite electrode in buffered aqueous solutions of [3Fe-4S] aconitase. (a) pH 6.2 (b) pH 7.5 (c) pH 8.2. Scan rate 0.1 V s ...

---