1. Department of Chemistry Tsinghua University Beijing 100084 P. R. China
2. Key Laboratory of Functional Inorganic Materials Chemistry (Heilongjiang University) Ministry of Education School of Chemistry and Materials Science International Joint Research Center for Catalytic Technology Harbin 150080 P. R. China
3. SUNCAT Center for Interface Science and Catalysis Department of Chemical Engineering Stanford University Stanford CA 94305 USA
4. Beijing Synchrotron Radiation Facility Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 P. R. China
5. Beijing National Center for Electron Microscopy and Laboratory of Advanced Materials Department of Materials Science and Engineering Tsinghua University Beijing 100084 P. R. China
6. Shanghai Synchrotron Radiation Facilities Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 P. R. China