Tetsuji Shimohira

Development of a Method for Clarifying the Perfluorosulfonated Membrane Degradation Mechanism in a Fuel Cell Environment

A gas-phase H 2 O 2 exposure method in which a membrane was exposed to gaseous hydrogen peroxide to simulate the polymer electrolyte fuel cells (PEFC) environment was introduced to accelerate and assess membrane degradation. Gaseous hydrogen peroxide is able to degrade a membrane in the same manner as an actual fuel cell operation. This method is suitable for clarifying the membrane degradation mechanism because a membrane is degraded uniformly without contamination and mechanical degradation. The degradation mechanism of perfluorosulfonated membrane in a PEFC environment was investigated using the gas-phase H 2 O 2 exposure method. An increase in the number of carboxyl groups and a rapid drop of molecular weight in degraded membrane with time exposed to gaseous hydrogen peroxide was observed. We concluded that degradation of the perfluorosulfonated membrane was composed of the following two modes: (i) unzipping reaction at unstable polymer end groups and (ii) scission of main chains and forming new unstable polymer end groups at severed points. It is very likely that membranes can be degraded by hydrogen peroxide alone; ferrous ions are not necessary for membrane degradation.

Advances in Flemion Membranes for Chlor-Alkali Production

Updated advances of Asahi Glass’s membrane cell technology are described. Design concepts and advantages of the AZEC-F2 electrolyzer, basic properties and commercial experiences of Flemion 890 series (sulfonate base) membranes, features and economics of Fx-50 (a membrane for production of 50% caustic soda) are introduced.

Plenary) Development of PFSA Ionomers and Their Use in Fuel Cells

Perfluorosulfonic acid (PFSA) ionomers are desired to have higher proton conductivity even at elevated temperatures (95-120°C) and low relative humidity (RH) conditions so that the fuel cell systems especially in fuel cell vehicles (FCVs) can be compact, simple and lower cost through easy heat removal and humidifier less. For the ionomer in the cathode electrode, besides transporting the protons, it has to deliver high flux of oxygen to the platinum surface when operating at high current density using low platinum loading membrane electrode assembly (MEA). And for the microporous layer (MPL) on gas diffusion layer (GDL), ionomer was used as binder instead of hydrophobic resin such as polytetra-fluoroethylene (PTFE). It showed good performances in elevated temperatures and low RH conditions as well as in wet conditions through good water control. The design concepts as well as their cell performances are presented.