1. Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario M5S 3G8, Canada
2. Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada
3. Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan, R.O.C.
4. School of Materials Science and Engineering and Key Laboratory of Efficient Utilization of Low and Medium Grade Energy, Ministry of Education, Tianjin University, Tianjin 300350, P. R. China