1. Department of Chemical Engineering, University of California, Davis, California, 95616, USA
2. School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
3. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
4. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
5. Department of Physics, University of Washington, Seattle, Washington 98195, USA
6. National Research Center for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China