1. Nanoelectrochemical Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, Section 4, #43, Keelung Road, Taipei 106, Taiwan, Republic of China, Department of Materials Science and Engineering and Center for Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, and National Synchrotron Radiation Research Center, #101, Hsin-Ann Road, Science-Based Industrial Park, Hsinchu 30077, Taiwan, Republic of China