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Carbon, PTFE particle electrodes

The porous electrodes used in PAFCs are described extensively in the patent literature (6) see also the review by Kordesch (5). These electrodes contain a mixture of the electrocatalyst supported on carbon black and a polymeric binder, usually PTFE (about 30 to 50 wt%). The PTFE binds the carbon black particles together to form an integral (but porous) structure, which is supported on a porous carbon paper substrate. The carbon paper serves as a structural support for the electrocatalyst layer, as well as the current collector. A typical carbon paper used in PAFCs has an... [Pg.109]

A number of different methods exist for the production of catalyst layers [97-102]. They use variations in composition (contents of carbon, Pt, PFSI, PTFE), particle sizes and pds of highly porous carbon, material properties (e.g., the equivalent weight of the PFSI) as well as production techniques (sintering, hot pressing, application of the catalyst layer to the membrane or to the gas-diffusion layer, GDL) in order to improve the performance. The major goal of electrode development is the reduction of Pt and PFSI contents, which account for substantial contributions to the overall costs of a PEFC system. Remarkable progress in this direction has been achieved during the last decade [99, 100], At least on a laboratory scale, the reduction of the Pt content from 4.0 to 0.1 mg cm-2 has been successfully demonstrated. [Pg.479]

The PTFE-bonded electrode was introduced by Neidrach and Alford [11]. It consists of metal blacks or carbon supported metal catalysts that are hydrophilic, blended with fine particles of hydrophobic PTFE, that flow and bind the structure as a result of heat treatment during fabrication. Thanks to its physical properties, PTFE flows and penetrates the pores, thus allowing a good interfacial contact between catalyst and carbon and providing hydrophobic gas pores for reactants. [Pg.250]

The porous hydrophobic film of previous electrode designs has now been substituted with a new layer based on a mixture of particles of hydrophobic carbon and PTFE binder. This mixture is very similar in composition to the catalytic layer. This particular modification provides several advantages ... [Pg.135]

Pt-alloy catalysts, 40 132-133 PTFE-bonded carbon electrodes, 40 133-134 Pt microcrystal particle size on soot, 40 131-132... [Pg.109]

FIG. 21. Cross section through a commercial Prototech electrode fabricated from a carbon fabric impregnated with PTFE- bonded, Pt-catalyzed soot particles. The layer of light color below the electrode is the SiC matrix, determined to keep the electrolyte between the electrodes. [Pg.134]

Air diffusion electrodes In fuel cells and in air-breathing batteries, a mesoporous carbon electrode is made up of two layers an outer layer composed of carbon powder and a hydrophobic (nonwettable) binder, typically PTFE. This enables the access of gas to the inner layer, where the binder is selected to be both a hydrophilic (wettable) and an ion-conducting ionomer, to support (rather than impair if the binder was nonconducting) the ionic conductivity of the porous electrode. The catalyst particles are dispersed in-between the carbon particles. Thus, a very tortuous interface between the two layers is formed. The reacting gas approaches this interface, forming three phase points of contact providing a high active surface area. See also - air electrode. [Pg.527]

For polymer electrolyte membrane fuel cell (PEMFC) applications, platinum and platinum-based alloy materials have been the most extensively investigated as catalysts for the electrocatalytic reduction of oxygen. A number of factors can influence the performance of Pt-based cathodic electrocatalysts in fuel cell applications, including (i) the method of Pt/C electrocatalyst preparation, (ii) R particle size, (iii) activation process, (iv) wetting of electrode structure, (v) PTFE content in the electrode, and the (vi) surface properties of the carbon support, among others. ... [Pg.36]

Electrochemical-deposition Electrode. Vilambi-Reddy et al. [62] presented the early research on the electrochemical deposition electrode. They developed an electrochemical catalyzation (ECC) technique to deposit platinum catalyst particles selectively in the regions accessible to both ions and electrons. In the ECC technique, a hydrophobic porous carbon paper was first coated with dispersed carbon particles and PTFE to form a substrate. Then the Nafion ionomer was impregnated onto this carbon substrate. This substrate was then placed into a platinum acid-plating bath, along with a platinum counter electrode. One side of this substrate, without Nafion, was masked with a non-conducting film, which... [Pg.906]


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PTFE

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