1. School of Physics and Electronics, Hunan University, Changsha 410082, P. R. China
2. College of Materials Science and Engineering, Hunan Provincial Key Lab of Advanced Materials for New Energy Storage And Conversion, Hunan University of Science and Technology, Xiangtan, Hunan, 411201, P. R. China
3. College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, P. R. China
4. Fujian Strait Research Institute of Industrial Graphene Technologies, Quanzhou 362000, P.R. China