High performance gas diffusion electrode of polymer electrolyte membrane fuel cells prepared by plasma polymerization

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Polymer electrolyte membrane fuel cells (PEMFC) have attracted much attention for use of batteries of electric vehicles. In PEMFC, gas diffusion electrodes have been used, and it is necessary to enhance the contact areas between electrode and electrolyte for the improvement of performance of PEMFC.In this work, we have aimed the development of high performance gas diffusion electrodes by plasma polymerization. Followings are the results of this work :1) Thin cation exchanger films fixed with sulfonic acid groups were prepared by plasma polymerization followed by hydrolysis of sulfonyl halide groups using benzenesulfonyl fluoride and benzenesulfonyl chloride, as starting material. Plasma polymer that formed at 3.5 W by using benzenesulfonyl fluoride after hydrolysis exhibits a cation-exchange capacity of 1.3 meq g^<-1>, which is comparable to those of commercially available cation exchange membranes.2) Perfluorinated polymer electrolytes have been prepared by using trifluoromethane sulfonic acid as ion exchange resources and octafluorocyclobutane as polymer bone. The resultant polymer electrolyte contains much fluorine atoms, and the ionic conductivity was determined to be in the order of 10^<-5> S / cm.3) By introducing Ar gas and water, the ionic conductivity of the resultant plasma polymer electrolytes was enhanced to be in the order of 10 -4 S / cm. This is probably due to the dilution of fluorine radicals prepared in plasma.