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05/01/2006 10:29 AM cathode Hydrogen fuel cell. The actual fuel cell stack is the layered cubic structure in the center of the image Hydrogen Air Air Water Electrolyte O,+4H* + 4de"=—» 2H_O On the anode side, hydrogen diffuses to the anode catalyst where it dissociates into protons and electrons. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have travelled through the external circuit) and protons to form water. In this example, the only waste product is water vapor and/or liquid water. In addition to pure hydrogen, there are hydrogen-carrying fuels for fuel cells, including diesel, methanol (see DMFC) and chemical hydrides, the waste product with this type of fuels is carbon dioxide. Voltage A typical fuel cell produces about 0.8 volts, to create enough voltage the cells are layered and combined in series and parallel into the so called "Fuel Cell Stack." The number of cells used is usually greater than 45 and varies with design. Materials The materials used in fuel cells differ by type. See Types of fuel cells. fuel «s channeled fed tow plates to the anode on one side of the fuel cell whale Oxygen fom the ar Channeled to the cathode on the other side of the col Hyorogen 1.The electrode/bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum or palladium) for higher efficiency. 2.carbon paper. 3/4.The electrolyte could be ceramic or a membrane. Example: The construction of the Low temperature fuel cell PEMFC: 1. Bipolarplate as electrode with in-milled gas channel structure, fabricated from conductive plastics (enhanced with carbon nanotubes for more conductivity); 2. Porous carbon papers; 3. Reactive layer, usually on the polymer membrane applied. Page 2 of 8 Fuel cell - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Fuel_cell