1. Center for Functional Nanomaterials, Energy & Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, United States
2. National Synchrotron Light Source II, Energy & Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, United States
3. Key Lab of Materials Physics, Anhui Key Lab of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, P. R. China
4. Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, P. R. China
5. Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
6. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States