1. State Key Laboratory of Heavy Oil Processing,College of Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, P. R. China
2. Institute of New Energy, China University of Petroleum (East China), Qingdao 266580, P. R. China
3. School of Materials Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, P. R. China