a
School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive, Singapore 637457, Singapore
E-mail: xwlou@ntu.edu.sg
b
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
c
Energy Research Institute @ NTU, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore