Alternative Fuels Appropriate Catalysts

Basically, there are two methods to form the MEA of a PEM fuel cell. One alternative is using appropriate techniques to add the carbon-supported catalyst to a porous and conductive material, such as carbon cloth or carbon paper, called a gas diffusion layer (GDL). Normally, polytetrafluoroethylene (PTFE) and Nafion... 

This reaction provides a wide variety of hydrocarbons (Ci to 50-200) from synthesis gas, becoming a very attractive route for the production of clean fuels (LPG, gasoline, kerosene, and diesel) and a source of chemicals (namely, linear olefins) [42]. However, it is important to ensure an appropriate size and type of reactor due to its exothermicity (Af/R = -165kJ/mol). Mass transfer effects are also significant since catalyst pores are filled with liquid products (waxes and water) limiting the diffusion rate. Despite the gas phase of reactants, selectivity to C5+ seems to decrease notably for diffusion lengths exceeding 0.1-0.3mm. Therefore, MSRs have been proposed as a suitable alternative. 

Despite advancement in the development of direct methanol fuel cells (DMFCs), some restrictions still inhibit their large-scale commercialization. This chapter has discussed one of the primary constraints, that is, identification of appropriate membrane materials. Nafion membranes that dominate the market of polymer electrolyte membranes allow methanol permeation from the anode to the cathode side of a DMFC. This results in serious negative consequences. Three approaches have been pursued in order to resolve the methanol permeation problem. These include Nafion membranes modification, development of alternative membranes and provision of high activity anode catalysts or methanol tolerant cathode catalysts. All the three options have achieved certain degree of success in solving the problan. Of particular interest are the Nafion membranes modification and development of alternative membranes in which membranes with permeability values of 10 to 70 times lower than the pure Nafion membranes have been developed. In general, based on the tremendous research efforts being made to develop DMFCs membranes with the best qualities, we are optimistic that very soon the issue of methanol permeation shall become a history. 

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