1. State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, National Demonstration Center for Experimental Chemistry Education, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, China
2. Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China
3. Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV1067, Latvia