1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
2. Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, 50 Nanyang Drive, Singapore 637553
3. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
4. Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
5. Institute of Materials Research & Engineering, A*STAR, 3 Research Link, Singapore 117602