1. Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, Anhui 230031, China
2. Key Laboratory of Photovoltaic and Energy Conservation Materials, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
3. Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
4. College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, P. R. China
5. Guangdong Provincial Key Laboratory of Petrochemical Pollution Process and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming Guangdong, 525000, P. R. China