Pyrolytic graphite disk electrode

Fig. 9 Schematic representation of LbL films of cyt P450 and CPR on pyrolydc graphite electrodes. Films are assembled electrostatically from CPR microsomes and pure cyt P450s on polyion bilayer surface of pyrolytic graphite disk electrodes...

Figure 7.5 (A) Oxygen reduction and hydrogen peroxide oxidation on a bare pyrolytic graphite disk-Pt ring electrode (B) Oxygen reduction and hydrogen peroxide oxidation on an oxidized pyrolytic graphite disk-Pt ring electrode in Oa-saturated 0.1 M KOH and (C) Proposed ORR mechanism. Potential scan rate 5 mV s ring potential 1.34 V vs 1 M NaOH//Hg/HgO. Reprinted with permission from Ref. 24.

The opportunity of obtaining direct electrochemistry of cytochrome c and other metalloproteins at various electrode materials such as modified gold and pyrolytic graphite has led to numerous reports of heterogeneous electron transfer rates and mechanisms between the protein and the electrode. In all the reports, Nicholson s method (37) was employed to calculate rate constants, which were typically within the range of 10" -10 cm sec with scan rates varying between 1 and 500 mV sec This method is based on a macroscopic model of the electrode surface that assumes that mass transport of redox-active species to and from the electrode occurs via linear diffusion to a planar disk electrode and that the entire surface is uniformly electroactive, i.e., the heterogeneous electron transfer reaction can take place at any area. 

Figure 3.9 (A) Dynamic polarization curves obtained using the pyrolytic graphite (PC) disk (A = 0.46 cm2) of a Pt PG RRDE recorded in 1.5 mM Co (111) (cyclam) in 0.5 M HCIO4 aqueous solutions,forw= 100,400,900 and 1600 rpm, where SSCE stands for a sodium chloride saturated calomel electrode. The corresponding ring currents obtained for Ering = 0.6 V are shown in the lower panel. (B) Plots of fJjTjc and /ring versus CO1 2.

The fabrication of copolymer multiheterolayers was carried out on a rotating highly oriented pyrolytic graphite (HOPG) disk electrode (working electrode 1000/r.p.m.) which leads to flat and sharp interfaces having a resolution of order Inm. The electrocopolymerization of a mixture of... 

Electrodes were prepared by attaching the cylindrical disk of basal plane pyrolytic graphite (BPG) (Union Carbide Co.) on the edge of stainless rod by conductive polymer paste, then they were sealed with heat-shrinkable olefin tube. All electrodes employed in this study had geometric area of 0.17 cm. Fresh electrode surfaces were produced by cleaving the disk of BPG with a scalpel. The polymers or polymer complexes were directly coated on the electrode by casting method as described previously. ... 

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... 

Figure 28. Reduction of O2 on high-pressure stress-annealed pyrolytic graphite in O2 saturated 1.0 A/KOH using a rotating disk electrode of area 0.20 cm. Solid curves edge orientation dashed line basal (cleavage) plane. Rotation rates in rpm s are indicated on curves. ...

Figure 31. O2 reduction on adsorbed layers of various transition metal tetrasulfonated phthalocyanines on the basal plane of stress-annealed pyrolytic graphite in O.lAfNaOH. Macrocyclic preadsorbed from aqueous 10 M MeTSPc solution. Rotating disk electrode. Rotation rate 4500 rpm. Disk area 0.20 cm. Potential scan rate (cathodic) 10 mV/sec. T =...

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