1. Graduate School of Human and Environmental Studies, Kyoto University, Sakyo‐ku, Kyoto 606‐8501, Japan
2. Department of Physical Chemistry, Norwegian University of Science and Technology, N‐7034 Trondheim, Norway
3. Center for Materials Science, University of Oslo, N‐0371 Oslo, Norway
4. Graduate School of Energy Science, Kyoto University, Sakyo‐ku, Kyoto 606‐8501, Japan