Carbon-felt electrodes

Furthermore, it was found that, although the catalytic efficiency measured in initial current was lower for 13, the latter was more stable. When carbon felt electrodes were coated with this polymer (approx. 1 x 10 mol on a 20x20x4 mm piece) the reduction of dibromostilbene was obtained on a mmol scale with only moderate da rease of mediator electroactivity The production of about 0.15 mmol of stilbene... 

Table 3. Electrocatalytic hydrogenations on carbon felt electrodes coated with polyviologen/Pd...

Controlled potential electrolysis of the substrates, at —1.4V vs. SCE, at a carbon felt electrode on which only 3.6x10" mol Bjj were immobilized (approx. 1 X 10 ° mol cm" ) resulted in the production of 76pmol of valeronitrile 16, corresponding to a turnover number of 2100 This example shows that the combination of inner sphere redox mediators and high surface electrodes is promising. 

Shen, Hao Ye, Lei Wu, Jianhua (1987) A method for dyeing wastewater treatment by a flowing type carbon-felt electrode, Huaning Baohu (Beijing) (1)15 Chem Abstr 106 (1987) 219043g... 

Electrocatalytic hydrogenation has the advantage of milder reaction conditions compared to catalytic hydrogenation. The development of various electrode materials (e.g., massive electrodes, powder cathodes, polymer film electrodes) and the optimization of reaction conditions have led to highly selective electrocatalytic hydrogenations. These are very suitable for the conversion of aliphatic and aromatic nitro compounds to amines and a, fi-unsaturated ketones to saturated ketones. The field is reviewed with 173 references in [158]. While the reduction of conjugated enones does not always proceed chemoselectively at a Hg cathode, the use of a carbon felt electrode coated with polyviologen/Pd particles provided saturated ketones exclusively (Fig. 34) [159]. 

A carbon felt electrode modified by electropolymer-ized methylene green has been implemented as the anode in an alcohol—O2 biofuel cell. The porous... 

Carbon fiber electrode - Edison produced the first carbon fibers by carbonization of cotton threads in 1879. Today polyacrylonitrile (as well as Rayon and various other organic precursors) is the most common precursor for carbon fiber formation [i]. Carbonization of polyacrylonitrile is carried out at 1500 °C to give highly electrically conducting fibers with 5-10 pm diameter. Fibers carbonized at up to 2500 °C are more graphitic with a carbon content of >99%. Carbon fiber-based materials have found many applications due to their exceptionally high tensile strength. In electrochemistry carbon fiber -> micro electrodes are very important in analytical detection [ii] and for in vivo electrochemical studies [iii]. Carbon fiber textiles are employed in - carbon felt electrodes. 

Carbon felt electrode -> carbon, and - carbon electrodes ... 

Graphite felt electrode -> carbon electrode, subentry -> carbon felt electrode... 

Three-dimensional electrode — This term is used for electrodes in which the electrode-solution interface is expanded in a three-dimensional way, i.e., the - electrode possesses a significantly increased surface area due to nonplanarity, so that it can be housed in a smaller volume. This can be achieved by constructing corrugated electrodes, reticulated electrodes, -> packed bed electrodes (see also - column electrodes), -> carbon felt electrodes, or fluidized bed electrodes. Three-dimensional electrodes are important for achieving high conversion rates in electrochemical reactions. Therefore they are especially important in technical electrochemistry, wastewater cleaning, and flow-through analytical techniques, e.g., - coulometry in flow systems. However, the - IR-drop within three-dimensional electrodes is an inherent problem. 

Electrochemical oxidation of the reduced form (NADH) of nicotinamide adenine dinucleotide and its analogs has been investigated [262] best results are obtained using a carbon felt electrode. The results are consistent with an ECE mechanism yielding the pyridinium salt. Indirect oxidation of NADH (and reduction of NAD" ) is treated in Chapters 27 and 29. 

Figure 4. Carbon felt electrode modified with poly-acrylic acid (PAA) under coimmobilization of HLADH, ferrocene derivatives, diaphorase (Dp), and NADH for the indirect electrochemical regeneration of NAD for enzymatic alcohol oxidation [22,112].

Erkoc, E. Yapici, S. Keskinler, B. Cakici, A. Akay, G. Effect of pulsed flow on the performance of carbon felt electrode. Chem. Eng. J. 

Figure 7.24 Electrochemical microflow reactor using a carbon felt electrode. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission...

Glassy carbon felt electrodes modified by electrodeposited poly(pyrrole-viologen) films containing electroprecipitated microparticles of precious metals like Pt, Pd, Rh or Ru have been shown to be suitable for the electrocatalytical hydrogenation of several organic substrates including benzonitrile, in acidic aqueous solution. Pd exhibited the highest current efficiency and yields for benzylamine formation when compared with Pt and Rh. 

Figure 8.27 shows the examined test reactions. In brief, molecular oxygen was electro-activated by the electropolymerized film of a manganese porphyrin deposited on graphite tissue and carbon felt electrodes. The supported catalyst was regenerated by controlled-potential electrolysis at = -0.5V/SCE. 

The previous systems for the recovery of metal ions have been primarily concerned with solutions containing only one metal ion. With mixed metal ion solutions there are thermodynamic and kinetic limitations which can effect the selectivity of the system and the final metal deposit. With some mixed metal ion solutions the difference in equilibrium potentials for the reactions can indicate that selective electrodeposition is probable, e.g. with solutions of zinc or cadmium and copper in dilute sulphuric acid solutions as used in fluidised bed electrolysis. Another example is the use of a flow-by carbon felt electrode in the extraction of Cu, Pb and Hg in a batch recirculating reactor [27]. The felt was of fibre diameter 1.1 x 10 m, with a porosity of 0.91 and a specific area of 2200 m By fixing the... 

Scheme 5 Pyrrole-substituted 4,4 -bipyridinium salt-modified carbon felt electrode.

Vatistas N, Marconi PF, Bartolozzi M (1991) Mass-transfer study of the carbon felt electrode. Electrochim Acta 36 339-343... 

Both reactions are reversible on the carbon felt electrodes that are used. An ion-selective membrane is used to separate the electrolytes in the positive and negative compartments of the cells. Cross-mixing of the reactants would result in a permanent loss in energy storage capacity for the system because of the resulting dilution of the active materials. Migration of other ions (mainly H ) to maintain electroneutrality, however, must be permitted. Thus, ion-selective membranes are required. 

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