1. College of Chemistry and Chemical Engineering; Guangzhou University; Guangzhou 510006 P. R. China
2. College of Chemistry and Chemical Engineering; Northwest Normal University; Lanzhou 730070 P. R. China
3. Guangzhou Key Lab. for Surface Chemistry of Energy Materials New Energy Research Institute; South China University of Technology; Guangzhou 510006 P. R. China
4. International Research Center for Renewable Energy State Key Lab. of Multiphase Flow in Power Engineering; Xi'an Jiaotong University Xi'an; 710049 Shanxi P. R. China
5. Department of Applied Physics; CINVESTAV-IPN; Merida 97310 Mexico
6. School of Environmental Science and Engineering; Shanghai Jiao Tong University; Shanghai 200240 P. R. China
7. Department of Chemistry and Biochemistry; San Diego State University; San Diego CA 92182 USA