1. School of Chemistry and Chemical Engineering North Minzu University Yinchuan 750021 P. R. China
2. State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering Ningxia University Yinchuan 750021 P. R. China
3. Ningxia Key Laboratory of Solar Chemical Conversion Technology North Minzu University Yinchuan 750021 P. R. China
4. Key Laboratory for Chemical Engineering and Technology State Ethnic Affairs Commission North Minzu University Yinchuan 750021 P. R. China