1. Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan
2. Materials Science Research Group, Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST Kansai), Ikeda 563-8577, Japan
3. Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Ibaraki 567-0047, Japan