| The key part of Proton Exchange Membrane Fuel Cells (PEMFC) is membrane electrode assembly (MEA), where mass transfer processes and electrochemical reactions proceed simultaneously. The accurate, systematic and in-deepth acquaintance with MEA has not been obtained yet. So a comprehensive study about MEA is completely necessary.In the thesis, we proposed a random lattice model of MEA The lattice model randomly occupied by three kinds of particles, Pt/C, Nafion and PTFE (poly-tetra -fluoro-ethylene), was generated on a computer by the means of Monte Carlo method. It was supposed that current was only produced on those catalysts which have not only channels of electrons via carbon but also have channels of proton via Nafion. The purpose of the work, in a word, is to find how many catalysts , Pt/C, with such a two-types channels . A labyrinth channel and a arithmetic of non-then-back random walk(NTBRW) were established and performed. The simulation program was written by C and MATLAB on the base of arithmetic of non-then-back random walk. Utilization of catalyst was obtained by statistical algorithm of NTBRW. We also discussed the effect the of structure and fabrication techniques of MEA on utilization of catalysts.The following results have been concluded:(1) The utilization could be improved through reduction of the catalyst layer thickness, especially, the utilization would be severely worsen if the thickness exceeds 10 μm. (2) There is an optimum loading of Nafion corresponding to certain loading of catalysts. For instance, the utilization of Pt is 85.7% and 51.2% for 60% Pt/C and 10% Pt/C, respectively.(3) The thickness of an electrode could be reduction and the utilization of catalyst could be increased by using catalyst with a high ratio of catalyst Pt to substrate carbon. Finally, the influces of effective surface on the reaction rate of oxygen reduction is discussed by means of the established mathematical model.
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