Nanotechnology and Clean Energy

Transcription

1 Nanotechnology and Clean Energy Ir Prof. Michael K.H. Leung Associate Dean and Professor Director, Ability R&D Energy Research Centre School of Energy and Environment City University of Hong Kong 1

2 Outline 1. Nanotechnology 2. Nanostructured Photocatalyst 3. Photocatalytic Fuel Cell 4. Other Applications 5. Conclusion 2

3 Nanoscale Nanometer (nm) 10-9 m Human hair 10,000 nm Atoms nm 6 nm 6 nm 100nm 100 nm 3

4 Properties of Porous Material Large specific surface area Increase surface phenomena => higher reactivity Increase adsorptivity Facilitate light reflection => better utilization of light in photoactivation Facilitate electron transport 4

5 Photocatalysis TiO 2 + hν e - cb + h+ vb h + vb + H 2 O OH + H + h + vb + OH- OH e - cb + O 2 O - 2 Titanium dioxide (TiO 2 ) + vb - valence band cb - conduction band h + vb - hole OH - hydroxyl radical UV light 5

6 Solar Photocatalytic Water Purification Photocatalyst: P25 TiO 2 powder Recovery method: Sedimentation Light source: Solar light

7 Photocatalytic Air Purification Patent: Light-transmitting tubular-honeycomb photocatalytic reactor, Inventors: M.K.H. Leung, Y.C. Leung, W.C. Yam, P.S.P. Ng, L.L.P. Kwan, Hong Kong short-term patent, publication no.: , publication date: 10 Aug

8 Solar Photocatalytic Water Splitting Hydrogen Production Ref.: H 2 production (µmol) TiO 2 -NP-1-1.0Pt TiO 2 -NS-2-1.0Pt TiO 2 -NS-3-1.0Pt TiO 2 -NS-4-1.0Pt (b) Irradiation time (hours)

9 Material Fabrication by Anodization Anodization DC nm ~6.4 μm Ti F - containing EG solution Pt Anode: Ti Ti e - Ti H 2 O TiO 2 + 4H + Cathode: 2e - + 2H + H μm 2 μm Etching Process: TiO 2 + 4H + + 6F - [TiF 6 ] H 2 O XRD Intensity (a.u.) 2θ (degree) 9

10 Fabrication by Hydrothermal Process Temp. & Time Control 10

11 Various Nanostructures Nanotube Array Nanorod Array Nanosheet Nano-flower Hollow Sphere 6 nm 6 nm 100 nm 11

12 Modification of Nanomaterials CdS/TiO 2 nanorod Ag-Ag 2 S/TiO 2 nanotube Bi 2 O 3 /TiO 2 nanobelt Ref.: W. Fan, S. Jewell, Y. She and M. K. H. Leung, Physical Chemistry Chemical Physics, 2014, 16,

13 Fuel Cell Fuel cell converts hydrogen into electricity by electrochemical reactions. Water and heat are byproducts. Proton 13

14 Originally Designed by NASA for Space Applications Ref.: Features: Use available hydrogen fuel Produce drinkable water Effective hydrogen recycling 14

15 For Commercial Applications Reduce greenhouse gas emissions Reduce depletion of finite fossil fuels Hydrogen is clean and, in practice, it can be produced from water, which is abundant. Promote diverse, domestic, and sustainable energy resources Increase reliability and efficiency of electricity generation Hydrogen technologies can be viable with a transition from conventional technologies 15

16 (US$/kW) Capital Cost of Fuel Cell Ref.: U.S. DOE,

17 Mercedes-Benz plugin hydrogen fuel-cell Fuel Cell Cars BMW hydrogen fuel-cell vehicle Toyota Mirai GM Opel HydroGen4 Hyundai Tucson Fuel Cell Honda Clarity fuel cell 17

18 Stationary Electricity Supply 400-kW hydrogen fuel cell plant in Connecticut 200-kW natural gas fuel cell plant in Sydney Natural gas fuel cell plant in New Jersey 2.4-MW biogas fuel cell plant in San Diego 18

19 Photocatalytic Fuel Cell Effective wastewater treatment and simultaneous production of electricity Low-cost fabrication Environmental-friendly operation Ref.: Bin Wang, Hao Zhang, Xiao-Ying Lu, Jin Xuan, Michael K.H. Leung, Solar photocatalytic fuel cell using CdS TiO 2 photoanode and air-breathing cathode for wastewater treatment and simultaneous electricity production, Chemical Engineering Journal, Volume 253, 2014, Pages

20 Dye-Sensitized Solar Cell The dye-sensitized solar cell (DSSC) technology, taken as a new generation of photovoltaics, is a flexible, efficient and economical way to directly convert solar energy into electricity. 20

21 Thermoelectric Generator Recovery of waste heat from: Boilers Engines Geothermal sources 21

22 Conclusion Nanotechnology offers enormous opportunities to develop new materials that directly and/or indirectly enhance energy efficiency and promote the use of renewable energy. 22

23 Acknowledgements Funding Sources GRF ITF ECF SDF CityU Ability R&D Energy Research Centre 23

24 Acknowledgements 24

25 Thank You Ir Prof. Michael K.H. Leung School of Energy and Environment City University of Hong Kong tel: (852) Fax: (852)