1. School of Chemistry South China Normal University Guangzhou 510000 P. R. China
2. Inner Mongolia Key Laboratory of Carbon Nanomaterials Nano Innovation Institute (NII) College of Chemistry and Materials Science Inner Mongolia University for Nationalities Tongliao 028000 P. R. China
3. State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of Chemistry Jilin University Changchun 130012 P. R. China
4. Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) Renewable Energy Conversion and Storage Center College of Chemistry Nankai University Tianjin 300071 P. R. China
5. Department of Physics Tsinghua University Beijing 100084 P. R. China