Fuel cells are electricity generators which convert chemical energy of hydrogen directly to electricity by means of electrochemical oxidation and reduction reactions. While the operation of them is similar to batteries without any mechanical parts, the electricity generation is continuous as the case in mechanical electricity generators. In a typical fuel cell, gaseous fuels are fed continuously to the anode compartment (negative electrode) and an oxidant (i.e., oxygen in air) is fed continuously to the cathode compartment (positive electrode); the electrochemical reactions take place at the electrodes to produce an electric current.

 Fuel cells attract interests in the last decades as electrical generators from micro power scales to hundreds of kilowatts power scales. There are many types classified by the operation temperature and the electrolyte used. Among the available types, proton exchange membrane (PEM) fuel cells are the most attracted ones. PEM fuel cells are very suitable for portable power generating systems. There is a potential for 100W portable power generators or storages like batteries. The main disadvantages of the energy storage devices such as batteries are their long charging time and low energy densities (energy stored/weight). Using a fuel cell system eliminates the long charging time and increases energy density for larger amount of energy storages.

 A single fuel cell produces electricity at 0.5-0.7V on maximum rated power load conditions. In order to produce electricity useful for many applications, many cells must be connected in series to form a fuel cell stack. Fuel cells are in the research and development phase and many studies are conducted on various parts of them. Especially the component development has been intensively studied by researchers all around the world. However, the studies for the development of fuel cell stack are relatively limited. There are few prototypes developed by companies. New design and prototypes are necessary for future applications.

In order to achieve a PEM fuel cell system, the most important part is the development of stack and stack components. The stack components are bipolar plates, seals, gaskets and membrane electrode assembly (MEA) which consists of proton exchange membrane, electro-catalyst and gas diffusion layer, and compression end plates.

Bipolar plates are the physical backbone of a fuel cell stack. They conduct the electrons produced by the reaction, distribute the reactants on the active area of the MEA and exchanges heat generated by the reaction with a suitable cooling medium such as air or water. The material of a bipolar plate must have some important properties such as high electrical and heat conductivity, chemical stability, easy and cheap manufacturability. Non-metal, metal and composite materials are used as bipolar plate material. As non-metal material, graphite is widely used for manufacturing of bipolar plates. It has a perfect chemical resistance. Its electrical and thermal conductivity is acceptable. However, it has high manufacturing cost since graphite bipolar plates can be manufactured by computer numeric control (CNC) machining only. Metals have very high electrical and thermal conductivity in bulk. However, the chemical resistance of the metals is not enough to be used in a fuel cell. The contact interface between the bipolar plate and gas diffusion layer loses its electrical conductivity rapidly. In order to prevent the surface from corrosion, some corrosion resistant conductive coatings are applied to the surface of the bipolar plates. Another method of bipolar plate manufacturing is the molding of composite blends such as chemically stable polymer and conductive fillers. As a binder resin, thermoplastics such as polyvinylidene fluoride, polypropylene, polyethylene and thermosets such as, epoxy, phenolic, furan resins and vinyl esters might be used [2].

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