1. Division of Advanced Materials Engineering, Research Center for Advanced Materials Development, Engineering College, Chonbuk National University, 664-14 Deokjin-dong 1-ga, Deokjin-gu, Jeonju, Jeonbuk 561-756, Republic of Korea
2. Advanced Functional Materials Research Center, Korea Institute of Science and Technology, PO Box 131, Cheongryang, Seoul 130-650, Republic of Korea
3. Department of Hydrogen and Fuel Cells Engineering, Specialized Graduate School, Chonbuk National University, Chonbuk, 561-756, Republic of Korea