(345a) Novel and High Performance Electrodes with Nano-Hybrid Hydrocarbon Ionomers of Pemfc for Broad Temperature Range and Lower Humidity Condition

PEMFC (polymer electrolyte membrane fuel cell) especially for automobile is required high performance from the room temperature to 120 ^oC with low humidification. We succeeded to develop a novel nano-hybrid hydrocarbon MEA (membrane electrode assembly) operating at broad temperature range and make high three-phase boundaries in the catalyst layer. As a key point for the success, we invented a new method that the ionomer was ?capping' to the nano-sized proton conducting particle. This nano-hybrid proton conductor for the hybrid MEA was prepared from SPES (sulfonated poly (arylene ether sulfone)) ionomer and fully re-dispersible nanozirconia precursor powder in polar aprotic organic solvents. The nano-hybrid catalyst layer was fabricated with catalyst, nanohybrid electrolyte and DMF (N, N'-dimethylformamide) as a solvent. And in situ generation of zirconium hydrogen phosphate (ZrP) in the nano-hybrid matrix was carried out by treating with H₃PO₄. From the aspect of the structure of the catalyst layer, we controlled the size of nano-hybrid for higher utilization of catalyst and kept the high dispersibility for the proton conduction matrix via capping method which used the physical adsorption between the nano-zirconia precursor and SPES ionomer. The size of the hybrid proton conductor was confirmed by DLS (Dynamic Light Scattering) and the nano-structure change of the catalyst layer was observed by mercury porosimetry. The nano-hybrid MEA was developed by assembling the nano-hybrid electrodes and our original pore-filling membrane with the same nano-hybrid ionomer. The nanohybrid electrodes showed high utilization of catalyst by cyclic voltammetary in accordance with the concept without any leaching out of materials. The nano-hybrid ionomer MEA showed high fuel cell performances without using any perfluorosulfonicacid ionomers. For example, the power density of the MEA showed 285 mW/cm² with 720mA/ cm² at 100 ^oC, 1 atm and around 70 % humidity.