1. State Key Laboratory for Advanced Metals and Materials, School of Materials Science and EngineeringUniversity of Science and Technology Beijing Beijing 100083 P. R. China
2. Department of Materials Science and Engineering, College of EngineeringPeking University Beijing 100871 P. R. China
3. Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
4. ENN Solar Energy Co., Ltd. Huaxiang Road 106 Langfang Hebei 065001 P. R. China