1. Beijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences Beijing 100083 P. R. China
2. College of Nanoscience and TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
3. School of MaterialsSun Yat‐sen University Guangzhou 510275 P. R. China
4. Center on Nanoenergy ResearchSchool of Physical Science and TechnologyGuangxi University Nanning 530004 P. R. China
5. School of Materials Science and EngineeringGeorgia Institute of Technology Atlanta GA 30332 USA