1. New Energy Research Institute; School of Environment and Energy; South China University of Technology; Guangzhou 510006 P. R China
2. Department of Materials Science and Engineering; College of Materials; Xiamen University; Xiamen Fujian 361005 P. R. China
3. Department of Chemistry; National Taiwan Normal University; Taipei 11677 Taiwan
4. Department of Mechanical Engineering; University of South Carolina; Columbia SC 29201 USA
5. School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta GA 30332-0245 USA