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H 2 Production by Photosplitting of H 2 O

H 2 Production by Photosplitting of H 2 O. Fasil Dejene. Outline. Current Primary H 2 Production Mechanisms Natural Photosynthesis Photo-splitting of water Bio-inspired Semiconductor (Photoelectrochemical) Photo-Biological Summary. Current primary H 2 Sources.

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H 2 Production by Photosplitting of H 2 O

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  1. H2 Production by Photosplitting of H2O FasilDejene

  2. Outline • Current Primary H2 Production Mechanisms • Natural Photosynthesis • Photo-splitting of water • Bio-inspired • Semiconductor (Photoelectrochemical) • Photo-Biological • Summary "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  3. Current primary H2 Sources Bayswater Power Station (New South Wales, Australia) • Costly (€35,000/Kg) • Dirty although efficient (60-70%) • High temperature J mater Sci (2008) 43:5395-5429 Thermochemical, Hydrosol II plant, Almeria, Spain "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  4. H2 Production by Photosplitting of H2O Artificial Bio-inspired Photoelectrochemical Photo-Biological N N H H N C H N O N N C H 3 http://www.microscopy-uk.org.uk 4 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  5. Natural Photosynthesis • Main Components • Antenna • Transport • Reaction center • OEC • Acceptor "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  6. Artificial Photosynthesis • Antenna for Light Harvesting (Donor) • Reaction Center (Mediator) • Mn Clusters (catalysts) • What is needed? Artificial Leaf=1+2+3 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  7. Self-assembled antenna systems • Two Routes 1 – Natural Antenna Systems in a protein matrix Self-Assembly of Natural- Light Harvesting Bacteriochlorophylls of Green Sulfer Photosynthetic Bacteria 25nm Saga et al, Biconjugate chem. (2006) "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  8. Self-assembled antennae Systems 2 – Artificial Antenna Systems Self-Assembled Discotic /Cylinderical Nanostructures of Perylene-3,4:9,10-bis(dicarboximide) Sinks et al Chem. Mater., 2005 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  9. Reaction Center (Charge transfer) • long-lived charge separated states • Coupled to the antenna Water Splitting Cluster • Acts as a catalyst • Efficient catalyst • Difficult to synthesize J. Yano et.al., Science (2006) "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  10. Examples of an ‘Artificial Leaf’ Synthetic antenna-reaction center made up of hexaphenylbenzene –BPEA and Zn Porphyrin Porphyrin-fullerene based artificial photosynthetic reaction center A. L. Moore et al, l’actualite chimique, (2007) Cabtree & Lewis, Ame. Inst. Of Physics, (2007) "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  11. Anotherexample • Low efficiency(<1%) • Difficult to synthesize something which is not clearly known synthetic Ru-Mn complex and Photosystem II http://www.fotomol.uu.se/Forskning/Biomimetics/fotosyntes/research2.shtm "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  12. Photoelectrochemical • Honda-Fujishima Effect • Water splitting by TiO2 by UV light • Theoretical efficiency of 10% by using expensive materials Honda–Fujishima effect-water splitting using a TiO2 photoelectrode Fujishima & Honda, Nat., 1972, 238, 37. "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  13. Photoelectrochemical • What is needed? • Catalyst • Optimum Band gap • Visible and IR Honda–Fujishima effect-water splitting using a TiO2 photoelectrode Fujishima & Honda, Nat., 1972, 238, 37. "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  14. Catalysts • Nanoporous • Nanotube • Single Nanocrystal Size effect of Pt/-Al2O3 catalysts TOF, sec-1 TOFis rate of a catalytic reaction, normalized to the number of surface atoms of active component <d>, nm V.I.Bukhtiyarov Rus. Chem. Rev.(2001) "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  15. Nanoporous ZnS as a Catalyst Angew. Chem. Int. Ed.44, 5299-5303, 2005 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  16. Carbon-Doped TiO2 Nanotube as a catalyst J.H. Park et al. Nano Lett., Vol. 6, No. 1, 2006 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  17. Single Si Nanocrystal coupled to other metal oxides • Silicon nanocrystal excited by light to produce electrons (e-) and holes (h+) with energy greater than 2.3 electron volts greater than the parent bulk Si or metal oxide • Absorbs UV to Visible • 40% of solar spectrum used H2 + O2 bubble from solution Metal Natural glass coat Si Metal oxide Silicon nanocrystal coupled to metal and metal oxide catalysts Next Joule Inc., US. Patent 6,060,026, (2000) US. Patent 6,361,660, (2000) "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  18. Photo-Biological U.S. DOE Report-H program "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  19. Current Research DNA and Biomolecular Engineering (mutagenesis) Oxygen Stable Hydrogenase (gene deleting) [Fe]-hydrogenase –O2diffusion barriers (self assmebled membranes) Genetical truncating of Chlorophyll Semi-Permeable membrane for facilitated ejection of oxygen Smaller antenna systems allow better light penetration and increase saturation threshold A. Melis, Int.Jour. Hydrogen 27,11-12,2002, 1217-1228 19 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  20. Summary • Biological H2 Production • Bio-inspired H2 production • Photoelectrochemical cell • Low Efficiency • Bio-Hybrid systems may improve the efficiency Ru-TiO2-Hydrogenase E. Reisner et.al., Chem. Commun., 2009, 550–552 20 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

  21. Acknowledgements • I would like to thank my supervisor Prof. dr. Roberta Croce for helping me prepare this talk. "Energy & Nano" - Top Master Symposium in Nanoscience 2009

  22. Thank You "Energy & Nano" - Top Master Symposium in Nanoscience 2009

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