1. Fuel Cell Laboratory; Korea Institute of Energy Research (KIER); 152, Gajeong-ro Yuseong-gu Daejeon 34129 Korea
2. Department of Chemical Engineering; Yonsei University; Seoul 120-749, 03722 Korea
3. Renewable Energy Engineering; University of Science and Technology (UST); 217, Gajeong Yuseong Daejeon 3411 Korea