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Frequently Asked Questions
Definition of Terms
Catalyst - A substance that promotes a chemical reaction. A layer of catalyst is sometimes added to gas diffusion electrodes to increase efficiency. E-TEK is a leader in the manufacture of high surface area catalysts and alloys and was the first to offer supported platinum catalysts.
ELAT® - The ELAT is a carbon cloth flow field that maximizes gas transport to the reactive zone while enabling water vapor and unreacted gases to move away from the zone. When coated with a noble metal catalyst, the ELAT can be used as a stand-alone electrode as well. Many customers use the ELAT coupled with proton exchange membranes for fuel cell applications.
Fuel Cell - A power generation device that combines hydrogen and oxygen to form water and electricity. Like batteries, fuel cells produce electricity through an electrochemical reaction, but they don't run down because they're supplied continuously with external fuel. Because they convert the chemical energy of a fuel directly into electricity, fuel cells are more efficient than combustion power sources. They have no moving parts, produce essentially zero pollutant emissions, and generate useful heat along with electricity. Fuel cells were invented more than a century ago, and have been used in spacecraft and military applications for years.
GDE - Gas Diffusion Electrode, a GDE, enables direct electronic transfer from a gas phase to or from the solid phase. The GDE also provides a path for ionic transfer, which is just as critical. Electrode assembly often begins with a conductive support such as carbon cloth, carbon paper, or metal mesh. A wet-proofing layer of carbon black is often added to this support or "web." Depending on the final use of the electrode, additional layers of wet-proofing are added. Lastly, a final catalyst layer may be applied. E-TEK excels at the construction of these assemblies, as well as the manufacture of specialty catalysts that provide facile electron transfer.
MEA - Membrane Electrode Assembly, an electrolyte membrane sandwiched between two gas diffusion electrodes. One electrode is positively charged (the anode); the other is negatively charged (the cathode). MEAs are the basic building blocks of fuel cells.
PEM - Proton Exchange Membrane. A membrane that allows hydrogen ions (protons) to travel between the cathode and anode of a fuel cell's membrane electrode assembly (see animation). PEM fuel cells are an especially promising and versatile type of fuel cell: they are compact and quick starting, giving them a compelling advantage in numerous applications. ETEK components help wring maximum performance from PEM fuel cells.
PEM Fuel Cell Animation - View a comprehensive guided tour of How a Fuel Cell Works.
Q: What sets E-TEK's products apart from the competition?
A: First, high performance. For example, the ELAT gas diffusion electrode is designed to maximize the transfer of hydrogen and oxygen gases as well as water vapor, which maximizes power output. The ELAT also provides an optimized interface for proton transport.
Second, superior reliability and durability. E-TEK components are designed and manufactured to withstand environmental and operational stresses. E-TEK products such as the ELAT and EFCG have operated in such corrosive environments as concentrated HCl saturated with chlorine, or concentrated phosphoric acid at over 150° C.
Third, customization with fast turnaround. We're proud of our roots as an innovative provider of custom components, and we retain the culture of a fast-moving startup. We'll provide the material for your initial product rollout or ramp-up, or specialty components for your R&D activities.
Q: Does E-TEK make fuel cells?
A: No, we don't make fuel cells, but our products can be described as the spark plugs for this next generation of energy engine. E-TEK components are the key building blocks of PEM fuel cells, an especially versatile type of fuel cell that can be used to generate electricity for home and businesses as well as provide propulsion for fuel-cell vehicles. See Links for fuel cell providers.
Q: What types of products does E-TEK offer?
A: E-TEK products include high-performance gas diffusion electrodes, membrane electrode assemblies, gas diffusion materials (carbon cloth and various types of carbon paper), and noble metal catalysts. We offer both Standard machine-made products for industry and Custom handmade product lines.
Q: What's the first step in obtaining custom components from E-TEK?
A: Look at our complete product list for Standard or Custom products, if you are still not finding what you need, please contact us. We would be happy to help you find the fuel cell components for your project.
Q: What is the standard wet-proofing on ELAT, carbon paper, EFCG electrodes, etc.?
A: Although that particular information is proprietary to E-TEK, we can provide wet-proofing from 10wt.% to 60wt.%.
Q: What are the specifications of the carbon black you offer for catalyst?
| Surface Area M2/gm. | Particle Size NM | Apparent Density Lbs./Cu.Ft. (Bulk) | |
| Vulcan XC-72 (Pellets) | 254 | 30 | 17 |
| Vulcan XC-72R (Fluffy) | 254 | 30 | 6 |
| BP 2000 | 1475 | 15 | 9.5 |
| Shawinigan Acetylene Black | 80 | 42 | 6.1 |
Q: What are the specifications on the various carbon cloths you offer?
| Cloth A | Cloth B | |
| Construction | Plain | Plain |
| Yarn Input | 2/27 | 2/10 |
| Count (W x F) | 48 x 44 yarns/in | 29 x 26 yarns/in |
| Areal Weight | 3.4 oz/yd2 | 6.5 oz/yd2 |
| Standard Widths * | 33 in | 42 in |
| Thickness | 15 mils | 26 mils |
| Density | 1.75 g/cc | 1.75 g/cc |
| Carbon Content | 99% | 99% |
| Oxidation Rate (% per hour) at 932F/500C | 1.0 | 1.0 |
| Surface Resistivity (ohms/square) | Outside: 0.30 Inside: 0.29 |
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| Cloth C | Cloth D | |
| Construction | 8 Harness Satin | 2 x 2 Basket |
| Yarn Input | 2/10 | 1.7 TPI Roving |
| Count (W x F) | 38 x 36 yarns/in | 12 x 12 yarns/in |
| Areal Weight | 8.5 oz/yd2 | 14.3 oz/yd2 |
| Standard Widths * | 33 in, 42 in | 42 in |
| Thickness | 40 mils | 62 mils |
| Density | 1.75 g/cc | 1.75 g/cc |
| Carbon Content | 99% | 99% |
| Oxidation Rate (% per hour) at 932F/500C | 1.0 | 1.0 |
| Surface Resistivity (ohms/square) | Outside: 0.30 Inside: 0.29 |
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Q: What is the porosity of your ELAT gas diffusers?
A: A detailed discussion of porosity is too complex to include here, but we refer you to a study performed by Springer et. al. at Los Alamos National Laboratory [Springer, Zawodzinski, Wilson, and Gottesfeld in "Proton Conducting Membrane Fuel Cells I" Gottesfeld, Halpert, and Landgrebe Editors, The Electrochemical Society Proceedings, Volume 95-23, page 137 (1995)]Q: Why do you offer different platinum loadings on carbon (for example 20, 30, 40% Pt on Vulcan XC-72)?
A: The weight of platinum on carbon ultimately influences platinum crystallite size, and ultimately the electrochemical metal surface area per gram of catalyst. Ample studies abound on the effect of platinum crystallite size and electrochemical activity for the E-TEK catalysts. For example, see Proceedings of the Symposium on Oxygen Electrochemistry, Proceedings Volume 95-26, Azdic, Anson, and Kinoshita Editors, 1995, The Electrochemical Society. Also see Genies, Faure, and Durand in "Electrochemical Reduction of Oxygen on Platinum Nanoparticles in Alkaline Media," Abstract 1078, The Electrochemical Society and The International Society of Electrochemistry Joint Meeting, Paris, 1997, Volume 97-2 Meeting Abstracts of The Electrochemical Society.
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