1. School of Materials Science and Engineering; Nanyang Technological University; 50 Nanyang Avenue Singapore 639798 Singapore
2. Institute of Materials Research and Engineering; A*STAR (Agency for Science, Technology and Research); 2 Fusionopolis Way Innovis #08-03 Singapore 138634 Singapore
3. Energy Research Institute (ERI@N); Interdisciplinary Graduate School; Nanyang Technological University; 50 Nanyang Drive Singapore 639798 Singapore