Carbon-polyethylene electrode

Fig.5. Peak potential evaluation as a function of pH. Trazodone = 1x10 M. methanol 20 %. Carbon polyethylene electrode A = first peak, B = second peak. Trazodone metabolite 1x10 " M, 20 % methanol. 

Cyclic voltammetry of the hexacyanoferrate(II/III) couple. Hexacyanoferrate(II) 5 x 10 M, 0.1 M KCl scan rate 20 mVs . a) Graphite spray electrode b) glassy carbon electrode c) carbon-polyethylene electrode d) carbon paste electrode. 

The modified supported powder electrodes used in the experiments hitherto described on the anodic activity of CoTAA are out of the question for practical application in fuel cells, as they do not have sufficient mechanical stability and their ohmic resistance is very high (about 1—2 ohm). For these reasons, compact electrodes with CoTAA were prepared by pressing or rolling a mixture of CoTAA, activated carbon, polyethylene, and PTFE powders in a metal gauze. The electrodes prepared in this way show different activities depending on the composition and the sintering conditions. Electrodes prepared under optimal conditions can be loaded up to about 40 mA/cm2 at a potential of 350 mV at 70 °C in 3 M HCOOH, with relatively good catalyst utilization (about 5 A/g) and adequate stability. 

Carbon composites have been developed as alternative materials for carbon paste electrodes because of the limited utility of the latter in most organic solvents. These composites include polyethylene/carbon black [49], Kel-F/graphite [50], carbon black immobilized in cross-hnked polyethylene [51], and epoxy/graphite [52]. A collection of for these materials is available [20]. Thus, for platinum = 0.24 cm/s, for pyrolytic graphites 0.002 <... 

The carbon paste electrodes were constructed from spectroscopic graphite (particle size <0.45 mm), which was mixed with nujol at a concentration of 1 g/ml and the necasary amount of moist clay to obtain a mass proportion of 10 %. This mixture was placed in a polyethylene tube with a geometric surface area of 1.6 mm. The connection was made with copper wire. 

In addition to aprotic solvents, films have been prepared in strong acid media. These preparations are carried out in polyethylene or polypropylene cells, using a platinum, gold or glassy carbon working electrode and a polymer-coated Ag/AgCI or Pd/H reference electrode [118,119]. Thus polypyrrole films have been prepared in aluminium chloride/ammonium chloride molten salts mixtures at room temperature [120,121]. 

Electroinactive polymers have also been utilized as supports for carbon-based electrodes assigned to voltammetric analysis. Such an electrode has been constructed by spraying a suspension of colloidal graphite in poly(methylmethacrylate) dissolved in butyl acetate onto a metallic support. A thin conductive film is obtained after drying . Another carbon-polymer electrode has been developed by mixing and heating at 150 C a mixture of carbon black and polyethylene in a ratio of 30 to 45% w/w. Thin disks are obtained by pressing the paste at 170 C under 200 kg cm 2 100,101. 

We have manufactured the graphite electrodes of plug type. An active mass (88wt% graphite, 10wt% carbon black and 2wt% PTFE) was pressed into a polyethylene plug of 11 mm inside diameter. We have studied... 

Transition-metal -phthalocyanines as catalysts in acid medium. To prevent carbonate formation by the carbon dioxide in the air or that produced by oxidation of carbonaceous fuels, an acid electrolyte is necessary hence it is important to find electrocatalysts for an acid medium. Independently of Jasinski, we were soon able to show 3>4> that under certain conditions the reduction of oxygen in dilute sulfuric acid proceeded better with phthalocyanines on suitable substrates than with platinum metal. The purified phthalocyanines were dissolved in concentrated sulfuric acid and precipitated on to the carbon substrate by addition of water. This coated powder was made into porous electrodes bound with polyethylene and having a geometrical surface of 5 cm2 (cf. Section 2.2.2.1.). The results obtained with compact electrodes of this type are shown in Fig. 6. 

Long-term tests on CoTMPP carbon electrodes with polyethylene as binder showed a drop in potential of about 5 mV per day, even after several hundred hours operation. 

Nickel hydrate, usually 5-10% cobalt added, serves as the active material and is mixed with a conductive carbon, e g., graphite. The active mass is mixed with an inert organic binder such as polyethylene or poly(tetrafluoroethyleiie) (TFE). The resultant mass is rolled into sheets on a compounding mill or pressed into electrodes as a dry powder on a nickel grid. 

Q. Yao, S. Yabuki and F. Mizutani, Preparation of a carbon paste/alcohol dehydrogenase electrode using polyethylene glycol-modified enzyme and oil-soluble mediator, Sens. Actuators B Chem., 65(1-3) (2000) 147-149. A. Morales, F. Cespedes, E. Martinez-Fabregas and S. Alegret, Ethanol amperometric biosensor based on an alcohol oxidase-graphite-polymer biocomposite, Electrochim. Acta, 43(23) (1998) 3575-3579. 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

In addition, various gel electrolytes were investigated for EDLC as well. Polyethylene oxide) (PEO)-, poly(acrylonitrile) (PAN)-, polymethylmethacrylate) (PMMA)- and poly(vinylidene flouride) (PVdF)-based gel electrolytes, which have been applied for secondary lithium batteries [5-7,50,51,64], were also studied as electrolyte systems for EDLC with carbon electrodes [65-68],... 

---