Artificial Light Harvesting: Solution for Sustainable Energy and Fuel


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The Best Presentation Award in the 18th Chemistry Colloquium Competition at Memorial University

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Artificial Light Harvesting: Solution for Sustainable Energy and Fuel

  1. 1. Mohammad A. Halim The 18th Chemistry Colloquium Contest’2011 Artificial Light Harvesting: Solution for Sustainable Energy and Fuel February 3, 2011
  2. 2. Our Common Future Sustainable ....... “ ...that meets the needs of the present without compromising the ability of future generations to meet their own needs.... ” Brundtland, G. (Ed.), Our Common Future, Oxford Uni. Press., 1987. 2
  3. 3. Context Leif and Sharon, Acc. Chem. Res. 2009, 42, 1859-1860. IPCC(2007).... “ Warming in climate systems is unequivocal ” Environ. threat due to GHGs and geo-political problem 3 Major challenge is to develop renewable energy sources One hour solar energy can be used in one year Need to harvest less than 0.02% solar energy 34% 27% 23% 6% 10% Oil Coal Natural Gas Nuclear Renewable Source: Energy Outlook, 2010
  4. 4. Photosynthesis 4 Stochel et. al. Bioinorganic Photochemistry, Wiley, 2009. 6CO2 + 6H2O C6H12O6 + 6O2 Light Chlorophyll
  5. 5. PDB ID: 2AXT 5 Bacterial Photosystem Loll et. al. Nature 2005, 438, 1040-1044. Hu et. al. PNAS, 1998, 95, 5935-5941. Koepke et. al. Structure, 1996, 4, 581-597. Antenna/RC
  6. 6. 6 Artificial Photosynthesis Sunlight to electric power H2 fuel from water by using hydrogenage or Pt Carbon-based fuels by reduction of CO2 Antenna/RC complexes to harvest light Charge-separated systems Catalysts for water oxidation But no real systems yet exists, progress on necessary components Scope for Energy and Fuel Generation Basic Components Gust et. al. Acc. Chem. Res. 2009, 42, 1890-1898.
  7. 7. 7 Antenna/RC Complex Zn-based porphyrin and Ru-based polypyridyl complexes are frequently used as A/RC complex  similar properties like chlorophyll arrays in plants  high molar absorption coefficients  fast energy/e- transfer to other components Obvious candidate for LHAC are porphyrin arrays Konrad et. al. Chem. Rev. 2005, 105, 2647-2694.  Lifetime 380 ns  Product Yield 58%  Quantum Yield 24% Imahori et. al. JACS, 2001, 123, 6617-6628. Grätzel, M, J. Photochem. Photobio. C 2003, 4, 145-153.
  8. 8. Sensitizing Dye TiO2 film on FTOElectrolyte 3I-/I3 - Redox Couple Dye-Sensitized Solar Cell (DSC) (20 nm) Grätzel, M. Inorg. Chem. 2005, 44, 6841-6851. 8 DSCs received great attention as a low-cost alternative to silicon-based
  9. 9. 9 Operation Principle of DSC Grätzel, M. Inorg. Chem. 2005, 44, 6841-6851. Sensitizer (S) excitation by light Electron injection to the conduction band of TiO2 Recapture of the CB electrons by 3I-/I3 - to regenerate the S+
  10. 10. 10 IrO2.nH2O act as a water oxidation catalyst QE is 0.9% due to slow e- transfer from IrO2.nH2O to the dye Also back e- transfer from TiO2 to the dye is not effective Hydrogen Fuel Cell Justin et. al. JACS, 2009, 131, 926-927. Ru-complex act as a dye and molecular bridge Modified ps/ns
  11. 11. Epilogue 11 Natural photosynthesis process is highly complex and tough to mimic entirely Zn-porphyrin and Ru-polypyridyl frequently used as dye Ru-dye showed better performance in DSC and 11.18% efficient More studies need to develop dye, electrolyte and long-lasting cell Prospect of hydrogen fuel is promising but still in laboratory scale The Solar to Fuel and Back Again Symposium-2009 Imperial College, London “If the leaf can do it we can do it even better” “Nature took 2.7 billion years and we only spent 40 years”
  12. 12. 12 “Only Strong Passion Speeds up into the Success” “Saying” in Sanskrit....... Thanks ......