1. School of Energy and Environment City University of Hong Kong Tat Chee Avenue, Kowloon Hong Kong P. R. China
2. Department of Civil Engineering The University of Hong Kong Pokfulam Hong Kong P. R. China
3. Key Laboratory of Renewable Energy Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 510640 P. R. China
4. State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of Chemistry Jilin University 2699 Qianjin Street Changchun 130012 P. R. China
5. Australian Synchrotron ANSTO 800 Blackburn Rd Clayton Victoria 3168 Australia