E-TEK

MEAs used in this study were prepared in the following procedure [5]. The diffusion backing layers for anode and cathode were a Teflon-treated (20 wt. %) carbon paper (Toray 090, E-Tek) of 0.29 mm thickness. A thin diffusion layer was formed on top of the backing layer by spreading Vulcan XC-72 (85 wt. %) with PTFE (15 wt. %) for both anode and cathode. After the diffusion layers were sintered at a temperature of 360 C for 15 min., the catalyst layer was then formed with Pl/Ru (4 mg/cm ) and Nafion (1 mg/cm ) for anode and with Pt (4 mg/cm ) and Nafion (1 mg/cm ) for cathode. The prepared electrodes were placed either side of a pretreated Nafion 115 membrane and the assembly was hot-pressed at 85 kg/cm for 3 min. at 135 C. 

Table 1 shows that the physicochemical properties of the support material were modified by the pre-treatment process. The particle sizes. Dp, which are summarized in the Table 1 were calculated from the X-ray diffraction patterns of prepared catalysts and a commercial catalyst(30 wt% Pt-Ru/C E-TEK) by using Scherrer s equation. To avoid the interference from other peaks, (220) peak was used. All the prepared catalysts show the particle sizes of the range from 2.0 to 2.8nm. It can be thought that these values are in the acceptable range for the proper electrode performance[7]. For the prepared catalysts, notable differences are inter-metal distances(X[nm]) compared to commercial one. Due to their larger surface areas of support materials, active metals are apart from each other more than 2 3 times distance than commercial catalyst. Pt-Ru/SRaw has the longest inter-metal distances. 

Fig. 3. The effect of Nafion ionomer content on the MEA perfonnance. (a) E-TEK catalyst, (b) Pt-Ru/SRaw, (c) Pt-Ru/S700, (d) Pt-Ru/S900.

Recently, rhodium and ruthenium-based carbon-supported sulfide electrocatalysts were synthesized by different established methods and evaluated as ODP cathodic catalysts in a chlorine-saturated hydrochloric acid environment with respect to both economic and industrial considerations [46]. In particular, patented E-TEK methods as well as a non-aqueous method were used to produce binary RhjcSy and Ru Sy in addition, some of the more popular Mo, Co, Rh, and Redoped RuxSy catalysts for acid electrolyte fuel cell ORR applications were also prepared. The roles of both crystallinity and morphology of the electrocatalysts were investigated. Their activity for ORR was compared to state-of-the-art Pt/C and Rh/C systems. The Rh Sy/C, CojcRuyS /C, and Ru Sy/C materials synthesized by the E-TEK methods exhibited appreciable stability and activity for ORR under these conditions. The Ru-based materials showed good depolarizing behavior. Considering that ruthenium is about seven times less expensive than rhodium, these Ru-based electrocatalysts may prove to be a viable low-cost alternative to Rh Sy systems for the ODC HCl electrolysis industry. 

Figure 11. Tafel plots for methanol oxidation on (a) an E-Tek Pt-C electrode and (b) an E-Tek PtojRuoj-C electrode (1 M CH3OH in 0.5 M HQO4, 50 C, metal loading 0.1 mg cm" ).

Figure 7. Cyclic voltammetry polarization curves for MEA made with different Pt-Ru/C catalysts [25], 3M (Pt/Ru = 1 1), 3M (Pt/ Ru = 1 2) and 3 M (Pt/Ru = 2 1) represent the catalysts prepared using the unprotected metal nanoclusters as building blocks E-tek (Pt/ Ru = 1 1) represents the commercially available catalyst (C14-30). All the catalysts have the same total metal loading of 30wt.%.

For comparison, a 20wt% Pt/XC72 catalysts prepared commercially by E-TEK had an average diameter of 2.6 nm. The sputter deposited Pt had a standard deviation between 0.42 and 0.49 nm, whereas the commercial E-TEK catalyst has a standard deviation of 0.79 nm. Thus, the sputtering technique creates smaller and more uniformly dispersed Pt particles than those prepared chemically. It should be noted that the Pt/C samples having low loadings prepared via sputtering did not uniformly coat... 

The catalyst layer is the most expensive part of this fuel cell. It is made from a mixture of platinum, carbon powder, and PEM powder, bonded to a conductive carbon fiber cloth. We obtained ours from E-Tek Inc. The cost for an order of their ELAT catalyst cloth sheet includes a setup charge. So get together with others for a larger order if you want to keep costs down. We paid 360 for a piece of ELAT 15.2 centimeters by 15.2 centimeters [6 inches by 6 inches] including the 150 setup charge. This piece provides enough for about twelve disks. Each fuel cell requires two disks of ELAT and one larger disk of PEM to make the sandwich, so you can make six cells from this size... 

Two catalyst layer disks were punched from an E-Tek ELAT sheet. The sheet was placed on clean acrylic plastic and the disks were punched with a 3.8 centimeter (1.5 inch) arch punch and the mechanics hammer. 

ELAT Solid Polymer Electrolyte Electrode 20% Pt/C with 0.4 mg/cm2 Pt loading E-Tek, Inc., 1 Mountain Rd, Framingham Industrial Park, Framingham, MA 01701 508-879-0733... 

A real breakthrough towards the reliable industrial application of a catalyst is represented by the development of a new rhodium (Rh)-based catalyst, manufactured by the E-Tek division [3] of DeNora North America. This has demonstrated an ability to overcome substantially the above-mentioned problems of chemical attack. 

The first practical example of electrodes able to satisfy many of the characteristics required in the application of chlor-alkali electrolysis is a particular family of doublesided gas-diffusion electrodes introduced some years ago under the trade name of ESNS , by E-TEK Inc. (now a Division of DeNora North America). The dual function (electrode and separator) of this electrode structure was achieved with an accurate choice of the basic components. 

This technique yields a catalyst composed entirely of metal nanoparticles or nanocrystalline thin film, and it allows for control of size and distribution while eliminating the need for a dispersing and supporting medium. The obtained electrodes contained as little as 0.017 mg Pt/cm and performed as well as standard E-TEK electrodes (Pt loading 0.4 mg/cm ). The PLD technique may be of special interest as an alternative to the sputtering process in the production of micro fuel cells. 

Another important parameter that has to be taken into account when choosing the appropriate diffusion layer is the overall cost of the material. In the last few years, a number of cost analysis studies have been performed in order to determine fuel cell system costs now and in the future, depending on the power output, size of the system, and number of xmits. Carlson et al. [1] reported that in 2005 the manufacturing costs of diffusion layers (for both anode and cathode sides) corresponded to 5% of the total cost for an 80 kW direct hydrogen fuel cell stack (assuming 500,000 units) used in the automotive sector. The total value for the DLs was US 18.40 m-, which included two carbon cloths (E-TEK GDL LT 1200-W) with 27 wt% P ILE, an MPL with PTFE, and Cabot carbon black. Capital, manufacturing, tooling, and labor costs were included in the total. 

Scanning electron microscope pictures of typical carbon fiber cloths used in fuel cells (a) E-Tek carbon cloth "A" with no PTFE (reference bar indicates 500 pm) (b) E-Tek carbon cloth "A" with 20% PTFE (reference bar indicates 500 pm) (c) close-up view of the E-Tek carbon cloth "A" with 20% PTFE (reference bar indicates 50 pm). 

On the other hand, with the same amount of PTFE as the CFP, carbon cloth (E-TEK type A carbon cloth) performed better and was able to eject the gases within the DL more effectively, thus giving more access to the methanol. 

Oedegaard et al. [43] were also able to confirm that a fuel cell using CFP (TGP-H-090) as the anode DL achieved lower current densities than when the cell used CC (E-TEK type A CC) (see Figure 4.15). In addition, the currents were very unstable with the CFP because CO2 bubbles were blocking access of methanol to the CL. 

In DMFCs, Scott, Taama, and Argyropoulos [117] changed the PTFE content (from 0 to 40 wt%) of the anode DL (E-TEK type A CC) in order to observe how this affected the methanol and carbon dioxide transport through the DL. At very high levels of PTFE, the performance of the cell decreases due to an increase in resistance losses. On the other hand, when an untreated CC was used, the observed performance was the lowest of all the materials investigated. In this study it was concluded that the ideal amount of hydro-phobic agent for the anode DL is around 13-20 wt% (see Figure 4.17). 

Pt/Ru electrocatalysts are currently used in DMFC stacks of a few watts to a few kilowatts. The atomic ratio between Pt and Ru, the particle si2 e and the metal loading of carbon-supported anodes play a key role in their electrocatalytic behavior. Commercial electrocatalysts (e.g. from E-Tek) consist of 1 1 Pt/Ru catalysts dispersed on an electron-conducting substrate, for example carbon powder such as Vulcan XC72 (specific surface area of 200-250 m g ). However, fundamental studies carried out in our laboratory [13] showed that a 4 1 Pt/Ru ratio gives higher current and power densities (Figure 1.6). 

Figure 1.14 Fuel cell characteristics of a 25 cm DEFC recorded with a 30% Pt-Sn (90 10) catalyst. Influence of the working temperature. Anode catalyst, 1.5 mgcrn [30% Pt-Sn (90 10)/XC72] cathode catalyst, 2 mgcm (40% Pt/XC72 from E-TEK) membrane, Nafion 117 ethanol concentration, 1 M. ( ) 50°C ( ) 70°C (A) 90°C (T) 100°C ( ) 110°C.

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