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TRANSCRIPT
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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
Nanotechnology and Clean Energy
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Outline 1. Nanotechnology
2. Nanostructured Photocatalyst
3. Photocatalytic Fuel Cell
4. Other Applications
5. Conclusion
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Nanoscale • Nanometer (nm) – 10-9 m
• Human hair – 10,000 nm
• Atoms – 0.1 – 0.5 nm
100 nm100 nm
6 nm
6 nm
100nm
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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
Photocatalysis TiO2 + hν → e-
cb + h+vb
h+vb + H2O → OH· + H+
h+vb + OH- → OH·
e-cb + O2 → ·O2
- vb - valence band cb - conduction band h+
vb - hole OH· - hydroxyl radical Titanium dioxide
(TiO2)
+ UV light 5
Solar Photocatalytic Water Purification Photocatalyst: P25 TiO2 powder Recovery method: Sedimentation Light source: Solar light
Photocatalytic Air Purification
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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.: 1099477, publication date: 10 Aug 2007.
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00
50
100
150
200
250
300
350
H 2 pro
duct
ion
(µm
ol)
Irradiation time (hours)
TiO2-NP-1-1.0Pt TiO2-NS-2-1.0Pt TiO2-NS-3-1.0Pt TiO2-NS-4-1.0Pt
(b)
Solar Photocatalytic Water Splitting Hydrogen Production
Ref.:
Material Fabrication by Anodization
Anodization
DC + -
Ti Pt F- containing EG solution
Ti → Ti4+ + 4e- Ti4+ + 2H2O → TiO2 + 4H+
TiO2+ 4H+ + 6F- → [TiF6]2- + 2H2O
Anode: Cathode: 2e- + 2H+ → H2
Etching Process:
2θ (degree)
XRD
Inte
nsity
(a.u
.)
400 nm
2 μm
~6.4 μm
0.2 μm
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Various Nanostructures
100 nm100 nm
6 nm
6 nm
Nanotube Array Nanorod Array
Nanosheet Nano-flower Hollow Sphere
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Modification of Nanomaterials
Ag-Ag2S/TiO2 nanotube
CdS/TiO2 nanorod
Ref.: W. Fan, S. Jewell, Y. She and M. K. H. Leung, Physical Chemistry Chemical Physics, 2014, 16, 676-680.
Bi2O3/TiO2 nanobelt
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Proton
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Fuel Cell Fuel cell converts hydrogen into electricity by electrochemical reactions. Water and heat are byproducts.
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Originally Designed by NASA for Space Applications
Ref.: www.nasa.gov
Features: • Use available hydrogen fuel • Produce drinkable water • Effective hydrogen recycling
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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
Fuel Cell Cars
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Mercedes-Benz plug-in hydrogen fuel-cell BMW hydrogen
fuel-cell vehicle
Honda Clarity fuel cell
Hyundai Tucson Fuel Cell
GM Opel HydroGen4
Toyota Mirai
18 2.4-MW biogas fuel cell plant in San Diego Natural gas fuel cell plant in New Jersey
200-kW natural gas fuel cell plant in Sydney 400-kW hydrogen fuel cell plant in Connecticut
Stationary Electricity Supply
Photocatalytic Fuel Cell
19 Ref.: Bin Wang, Hao Zhang, Xiao-Ying Lu, Jin Xuan, Michael K.H. Leung, Solar photocatalytic fuel cell using CdS–TiO2 photoanode and air-breathing cathode for wastewater treatment and simultaneous electricity production, Chemical Engineering Journal, Volume 253, 2014, Pages 174-182.
• Effective wastewater treatment and simultaneous production of electricity • Low-cost fabrication • Environmental-friendly operation
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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.
Conclusion
Nanotechnology offers enormous opportunities to develop new materials that directly and/or indirectly enhance energy efficiency and promote the use of renewable energy.
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Acknowledgements
Funding Sources • GRF • ITF • ECF • SDF • CityU • Ability R&D Energy Research Centre
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Thank You Ir Prof. Michael K.H. Leung School of Energy and Environment City University of Hong Kong Email: [email protected] tel: (852)3442 4626 Fax: (852)3442 0688
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