1. Center for Nanochemistry (CNC), Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R. China
2. Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China
3. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China
4. School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
5. Tsinghua−Berkeley Shenzhen Institute (TBSI), Tsinghua University, Shenzhen 518055, P. R. China
6. Centre for Clean Environment and Energy, Griffith University, Gold Coast 4222, Australia