Performance conductive polymer electrodes

Modified electrodes for this analytical purpose have mostly been formed by electrode adsorption of the mediator systems on the electrode surface or by electropolymerization [24,116]. Recently, for example, NAD(P)H oxidations have been performed on platinum or gold electrodes modified with a monolayer of pyrroloquinoline quinone (PQQ) [117] or on poly(methylene blue)-modified electrodes with different dehydrogenases entrapped in a Nafion film for the amperometric detection of glucose, lactate, malate, or ethanol [118]. In another approach, carbon paste electrodes doped with methylene green or meldola blue together with diaphorase were used for the NADH oxidation [119]. A poly(3-methylthio-phene) conducting polymer electrode was efficient for the oxidation of NADH [120]. By electropolymerization of poly(aniline) in the presence of poly(vinylsulfonate) counterions. 

The immobilization of an active species into a conducting polymer layer allows one to obtain active electrodes for the reduction of various organic halides. Polypyrrole containing viologen electrodes appear to be active for the reduction of alkyl dibromide [177] or hexachloroacetone [178], Cobalt-bipyridyl-polypyrrole films are active electrodes for the reduction of alkyl chloride [107], The mechanism of this reaction is similar to that observed in the homogeneous phase. This confinns one of the major interests of the modified conductive polymer electrodes, i,e. the possibility of performing catalytic reactions with smaller amounts of active catalyst in comparison to homogeneous catalysis, and then to avoid problems related to the separation of products from the solution which contains this catalyst. 

Batteries This field is the first area where conducting polymers promise to have a big commercial impact. Batteries have several key components the electrodes allow for collection of current and transmission of power the cathode material becomes reduced when the anode material is oxidized and vice versa and the electrolyte provides a physical separation between the cathode and the anode, and provides a source of cations and anions to balance the redox reactions. Aside from picking the best conducting polymer available, there are many other issues, not related to conducting polymers, that affect battery performance, such as electrolyte stability and stability of the counter half-cell reaction (which is at least as important as the conducting-polymer electrode), and compatibility between the electrolyte and the materials. 

In electrical systems, it is common to describe the time to charge a capacitor using the product of resistance and capacitance, or RC. In designing and troubleshooting device performance, it is useful to consider the various time constants. In the case of symmetric conducting polymer electrodes that face each oflier, as shown in Fig. 6, with a capacitance, C, per electrode and a capacitance per volume of the polymer electrode, Cv> and assuming the ionic conductivity, a, electronic conductivity, the time constants are (Madden et al. 2002b) ... 

A considerable decrease in platinum consumption without performance loss was attained when a certain amount (30 to 40% by mass) of the proton-conducting polymer was introduced into the catalytically active layer of the electrode. To this end a mixture of platinized carbon black and a solution of (low-equivalent-weight ionomeric ) Nafion is homogenized by ultrasonic treatment, applied to the diffusion layer, and freed of its solvent by exposure to a temperature of about 100°C. The part of the catalyst s surface area that is in contact with the electrolyte (which in the case of solid electrolytes is always quite small) increases considerably, due to the ionomer present in the active layer. 

Cyclic voltammetry was performed with the ADH-NAD-MB/polypyrrole electrode in 0.1 M phosphate buffer (pH 8.5) at a scan rate of 5 mV s l. The corresponding substrate of ADH caused the anodic current at +0.35 V vs. Ag/AgCl to increase. These results suggest a possible electron transfer from membrane-bound ADH to the electrode through membrane-bound NAD and MB with the help of the conductive polymer of polypyrrole. 

The benefit of a hybrid phase for the intercalation-deintercalation of mobile species such as Li+ cations is well illustrated by the study of conductive polymers such as polyaniline or polypyrrole intercalated into a V2O5 framework as potential electrode materials in lithium batteries [34]. For PANI/V2O5, an oxidative post-treatment performed under an oxygen atmosphere allowed the authors to compare the conductivity attributed to the polymer, as in absence of reduced cations, there was no electronic hopping between ions, and the conductive state was due only to the... 

GC material was widely modified with conducting (or nonconducting) polymers in order to obtain an improved surface for DNA adsorption and detection. The initial approaches were performed by the physical attachment of nylon or nitrocellulose membranes on GC electrodes [51]. As explained, these membranes were extensively used in classical DNA analysis due to their well-known adsorption properties [33]. Other approaches were performed by the direct adsorption of the polymeric film on the GC surface. Finally, polymeric films were electrochemically grown on the GC substrate. These conducting polymers are particularly promising for the adsorption, but also for inducing electrical signals obtained from DNA interactions. 

If the surface of a metal or carbon electrode is covered with a layer of some functional material, the electrode often shows characteristics that are completely different from those of the bare electrode. Electrodes of this sort are generally called modified electrodes [9] and various types have been developed. Some have a mono-molecular layer that is prepared by chemical bonding (chemical modification). Some have a polymer coat that is prepared either by dipping the bare electrode in a solution of the polymer, by evaporating the solvent (ethanol, acetone, etc.) of the polymer solution placed on the electrode surface, or by electrolytic polymerization of the monomer in solution. The polymers of the polymer-modified electrodes are either conducting polymers, redox polymers, or ion-exchange polymers, and can perform various functions. The applications of modified electrodes are really limit-... 

Baldock, S.J., Fielden, P.R., Goddard, N.J., Prest, J.E., Brown, B.J.T., Integrated moulded polymer electrodes for performing conductivity detection on isota-chophoresis microdevices. J. Chromatogr. A 2003, 990, 11-22. 

In order to satisfy the industrial demand, the performance of supercapacitors must be improved and new solutions should be proposed. The development of new materials and new concepts has enabled important breakthroughs during the last years. In this forecast, carbon plays a central role. Due to its low cost, versatility of nanotextural and structural properties, high electrical conductivity, it is the main electrode component. Nanoporous carbons are the active electrode material, whereas carbon blacks or nanotubes can be used for improving the conductivity of electrodes or as support of other active materials, e.g., oxides or electrically conducting polymers. 

The use of electrochemically polymerized films to immobilize enzymes at electrode surfaces was reviewed by Bartlett and Cooper up to 1992 [24]. While a large variety of studies have been performed mainly using poly(pyrrole) as the conducting polymer, many problems still have to be solved, particularly with respect to the question of the speed of... 

Other conducting polymers can be investigated as supports for dispersing catalytic metallic particles. Shan and Pickup [21] used a composite of poly(3,4-ethylenedioxythiophene) and poly(styrene-4-sulfonate) (PEDOT/PSS) to disperse Pt particles. They compared the performances of such electrodes with carbon-supported Pt for the electroreduction of oxygen, and they found similar exchange... 

Nevertheless, as discussed here, it was demonstrated that fuel-cell electrodes can be obtained with dispersion of plurimetallic particles in an electron-conducting polymer. Actually, the performances of these electrodes remain lower than the state... 

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