1. Key Laboratory of Coal Science and Technology Ministry of Education and Shanxi Province Taiyuan University of Technology Taiyuan Shanxi 030024 P.R. China
2. State Key Laboratory of Physical Chemistry of Solid Surfaces College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 P.R. China
3. State Key Laboratory of Coal Conversion Institute of Coal Chemistry Chinese Academy of Sciences No.27 South Taoyuan Road Taiyuan Shanxi 030001 P.R. China