1. Research Group for Nanoscale Structure and Function of Advanced Materials, Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakawa, Tokai, Ibaraki 319-1195, Japan
2. Innovation Research Center for Fuel Cells, The University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan
3. Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198, Japan
4. Laboratory for Environmental Chemistry, Paul Scherrer Institut, OFLB106, PSI, Forschungsstrasse 111, 5232 Villigen, Switzerland