1. Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong 999077, People’s Republic of China
2. Hong Kong Institute for Clean Energy, City University of Hong Kong, Hong Kong 999077, People’s Republic of China
3. Department of Chemistry, City University of Hong Kong, Hong Kong 999077, People’s Republic of China
4. Department of Chemistry, Korea University, Seoul 136-713, Korea
5. Center of Super-Diamond and Advanced Films, City University of Hong Kong, Hong Kong 999077, People’s Republic of China
6. School of Energy and Environment, City University of Hong Kong, Hong Kong 999077, People’s Republic of China
7. Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195-2120, United States