1. Institute for Materials Chemistry and Engineering, Kyushu University, Nishi-ku, Fukuoka, Fukuoka 819-0395, Japan
2. Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
3. Fuel Cell System Development Center, Toyota Motor Corporation, Mishuku, Susono, Shizuoka 410-1193, Japan