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 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June

J mater Sci (2008) 43: Current primary H 2 Sources 3 Thermochemical, Hydrosol II plant, Almeria, Spain Bayswater Power Station (New South Wales, Australia) "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009 Costly (€35,000/Kg) Dirty although efficient (60-70%) High temperature

H 2 Production by Photosplitting of H 2 O  Artificial  Bio-inspired  Photoelectrochemical  Photo-Biological 4 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June

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

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

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

Self-assembled antennae Systems 2 – Artificial Antenna Systems 8 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

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

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

Another example 11 Low efficiency(<1%) Difficult to synthesize something which is not clearly known synthetic Ru-Mn complex and Photosystem II "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

Photoelectrochemical 12  Honda-Fujishima Effect  Water splitting by TiO 2 by UV light  Theoretical efficiency of 10% by using expensive materials Honda–Fujishima effect-water splitting using a TiO 2 photoelectrode Fujishima & Honda, Nat., 1972, 238, 37. "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

Photoelectrochemical 13  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

Catalysts  Nanoporous  Nanotube  Single Nanocrystal 14 V.I.Bukhtiyarov Rus. Chem. Rev. (2001), nm TOF, sec -1 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009 TOF is rate of a catalytic reaction, normalized to the number of surface atoms of active component Size effect of Pt/  -Al 2 O 3 catalysts

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

Carbon-Doped TiO 2 Nanotube as a catalyst 16 J.H. Park et al. Nano Lett., Vol. 6, No. 1, 2006 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009

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 17 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009 Next Joule Inc., US. Patent 6,060,026, (2000) US. Patent 6,361,660, (2000) Si Metal Metal oxide Natural glass coat Silicon nanocrystal coupled to metal and metal oxide catalysts H 2 + O 2 bubble from solution

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

Current Research  DNA and Biomolecular Engineering (mutagenesis)  Oxygen Stable Hydrogenase (gene deleting)  [Fe]-hydrogenase –O 2 diffusion barriers (self assmebled membranes)  Genetical truncating of Chlorophyll  Semi-Permeable membrane for facilitated ejection of oxygen 19 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009 A. Melis, Int.Jour. Hydrogen 27,11-12,2002, Smaller antenna systems allow better light penetration and increase saturation threshold

Summary  Biological H 2 Production  Bio-inspired H 2 production  Photoelectrochemical cell  Low Efficiency  Bio-Hybrid systems may improve the efficiency 20 "Energy & Nano" - Top Master Symposium in Nanoscience 17 June 2009 E. Reisner et.al., Chem. Commun., 2009, 550–552 Ru-TiO 2 -Hydrogenase

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

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