1. Key Laboratory of Coal Processing and Efficient UtilizationMinistry of EducationChina University of Mining & Technology Xuzhou Jiangsu 221116 P. R. China
2. State Key Laboratory of High‐efficiency Utilization of Coal and Green Chemical EngineeringNingxia University Yinchuan Ningxia 750021 P. R. China
3. Department of ChemistryPurdue University 560 Oval Drive West Lafayette IN 47907 USA
4. Low Carbon Energy InstituteChina University of Mining & Technology Xuzhou Jiangsu 221008 P. R. China