Nanotechnology and Clean Energy Ir Prof. Michael K.H. Leung - - PowerPoint PPT Presentation

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Nanotechnology and Clean Energy Ir Prof. Michael K.H. Leung - - PowerPoint PPT Presentation

Jan 04, 2024 687 likes •948 views

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 1 Outline 1. Nanotechnology 2.

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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 nm 100 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
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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

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Solar Photocatalytic Water Purification

Photocatalyst: P25 TiO2 powder Recovery method: Sedimentation Light source: Solar light

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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.

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0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 50 100 150 200 250 300 350

H2 production (µmol) 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.:

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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 Intensity (a.u.)

400 nm 2 μm

~6.4 μm

0.2 μm 9

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Fabrication by Hydrothermal Process

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  • Temp. & Time

Control

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Various Nanostructures

100 nm 100 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

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Capital Cost of Fuel Cell

Ref.: U.S. DOE, 2012

(US$/kW)

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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

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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

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Photocatalytic Fuel Cell

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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

  • f photovoltaics, is a flexible, efficient and economical way to directly

convert solar energy into electricity.

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Thermoelectric Generator

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Recovery of waste heat from:

  • Boilers
  • Engines
  • Geothermal sources
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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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Acknowledgements

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Thank You

Ir Prof. Michael K.H. Leung School of Energy and Environment City University of Hong Kong Email: mkh.leung@cityu.edu.hk tel: (852)3442 4626 Fax: (852)3442 0688

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