IMPROVED PREPARATION PROCESS OF VERY-LOW-PLATINUM-LOADING ELECTRODES FOR POLYMER ELECTROLYTE FUEL-CELLS

We have previously reported a preparation process for the catalyst lay er of polymer electrolyte fuel cells (PEFCs) using perfluorosulfonate ionomer (PFSI) colloid. In this paper we report recent improvements in this method of preparation. In the present method, a carbon-supported platinum catalyst (Pt-C) was mixed with poor solvent for PFSI, and PF SI solution was added to this mixture. The colloidal PFSI formed was i mmediately adsorbed on Pt-C without coagulation. As a result, the reac tion area was increased, the internal resistance was decreased, and th e gaseous reactants were more readily supplied to the reaction area. W e also studied the influence of the carbon support on the microstructu re of the catalyst layer. We have found that the performance of a PEFC prepared by this process with optimum carbon support and with Very lo w platinum loading (0.1 mg/cm(2)) was superior to that prepared by our previous process with conventional carbon support and with a 0.5 mg/c m(2) platinum loading.