[1] Guangxi Univ, Sch Chem & Chem Engn, Nanning 530004, Peoples R China
[2] Chinese Acad Sci, Beijing Inst Nanoenergy & Nanosyst, Beijing 101400, Peoples R China
[3] China Univ Petr, Unconvent Petr Res Inst, Beijing 100049, Peoples R China
[4] Georgia Inst Technol, Atlanta, GA 30332 USA