1. School of Chemical and Biomedical EngineeringNanyang Technological University 62 Nanyang Drive Singapore 637459 Singapore
2. Department of PhysicsSouthern University of Science and Technology Shenzhen 518055 China
3. Institute of Chemical and Engineering SciencesAgency for Science, Technology and Research (A*STAR) Singapore 627833 Singapore
4. Institute for New Energy Materials & Low-Carbon TechnologiesTianjin University of Technology Tianjin 300384 P. R. China
5. Present address: National Synchrotron Light Source IIBrookhaven National Laboratory Upton NY 11973 USA