Pt/C/PTFE

Anode PTFE-bonded Pt black PTFE-bonded Pt/C PTFE-bonded Pt/C... 

Al Hot-pressed Pt black/PTFE layers B1 Ionomer - impregnated Pt/C//PTFE... 

A1) Applied and hot-pressed Pt /PTFE (A2) Electroless deposition of Pt on membrane (A3) Applied and hot-pressed Pt/C(or Pt)//ionomer within ionomer-impregnated carbon paper (A4) Alloy catalyst sputtered onto array of nanowhiskers and the catalyzed array embedded into the membrane surface (Bl) Pt/C//PTFE applied to substrate and impregnated with recast ionomer (B2) (Bl) + sputtered Pt layer (B3) Pt catalyst electrodeposited... 

Ionomer impregnation In the ionomer impregnation method described by Gottesfeld and Zawodzinski (1997) the catalytically active side of GDL is painted with solubilized PFSA in a mixture of lower aliphatic alcohols and water. To improve reproducibility of the GDL/catalyst assembly, the catalyst and ionomer are premixed before the catalyst layer is deposited, rather then ionomer impregnation of Pt/C//PTFE layer. 

Polarization curves for Hj/Oj fuel cells at 50°C, 1 atm pressure. Curve A Nation impregnated (brush coated) PTFE-bound electrode (0.35 mg/cm Pt loading) curve B PTFE-bound catalyst layer (Pt loading 4 mg/cm ) curve C PTFE-bound electrode (Pt loading 0.35 mg/cm. (Based on Ticianelli, E. A. et al. Journal of the Electrochemical Society 1988 135 2209-2214. By permission of The Electrochemical Society.)... 

Figure 14a is a typical TEM micrograph of Pt/C shadowed standard-size PTFE dispersion particles, (here sample G) with dark-field images of unshadowed particles in the insets typical BFDC micrographs of several standard-size DuPont dispersion particles are shown in Fig. 14b and c. The dark-field micrographs, taken with 100 reflections, are similar to the bright-held ones except... 

Fig. 25. Air cathode catalyst utilization for different types of catalyst layers in contact with ionomeric membranes. , Platinum black/PTFE (4 mg/cm ) ionomer-impregnated gas-diffusion electrodes (0.45 mg Pt/cm ) A, thin film of Pt/C//ionomer composite (0.13 mg Pt/cm ). The advantage of thin-film catalyst layers increases particularly at high current density (lower cell voltage) because transport limitations within the catalyst layer are minimized.

Fig. 23 Air cathode catalyst mass utilization (A mg-1 Pt) for different types of catalyst layers as developed chronologically for hydrogen/air PEFC. Squares PTFE-bonded Pt black at 4 mg Pt/cm2 circles ionomer-impregnated, PA- type electrodes (0.45 mg Pt/cm2) triangles thin-film Pt/C//ionomer composite (0.13 mg Pt/cm2). The relative advantage of thin-film catalyst layers is seen to increase with cell current density, as expected from the lower transport limitations involved (see Sect. 8.3.7.2.3) [10,11].

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. ... 

Membrane fuel cells have zero-gap electrodes on both sides of the membrane. Typically the electrodes are made of a carbon fiber mat impregnated with platinum on carbon (Pt/C) catalyst. To achieve an extended surface for the gas to be adsorbed and react and to maintain continuity for ionic transport, interpenetration of electrode and membrane is necessary. This is usually accomplished by impregnating the porous electrode with. Nafion solution. One assembly technique is to suspend the Pt/C in Nafion solution by sonication and spray it onto carbon paper. Then the membrane is hot pressed between the two impregnated electrodes [44]. Another approach is to make an aqueous suspension of three powders - Pt/C, carbon black, and PTFE - and spray it onto the carbon paper. Then 5% Nafion solution is applied by spraying or by floating the electrode on the Nafion solution, after which the membrane is pressed between the electrodes [45]. The Nafion solution serves as an adhesive as well as a means of extending the electrolyte into the structure of the porous electrode. 

Nowadays, the main type of H2 electrodes used in AFCs is a PTFE-bonded electrode with a Pt load of about 0.3 mg cm [12-14]. PAFCs employ H2-difiusion PTFE-bonded electrodes with Pt supported on carbon as catalyst for low loadings of O.l-l.O mg cm [15]. In contrast, PEFCs utilize H2 electrodes in which the catalyst (Pt/C) and the ionomer (Nafion ) are... 

Pozzio et al [66] studied the anodic oxidation of pure hydrogen on gas diffusion electrodes catalysed by Pt/C, Pt-Ru/C and Pt-Mo/C in aqueous H2SO4. The substrate was a carbon paper and the GDL was composed of a mixture of carbon and PTFE. Electrochemical measurements were carried out using a conventional three-electrode cell, where the GDE was moimted on a holder furnished with a metal ring current collector and hydrogen back feeding. 

Pt/C) and PTFE, only the Pt at the electrode-membrane interface has the potential to provide three-phase regions. The other Pt particles that are not in direct contact with the membrane are simply wasted. 

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