H 2 Production by Photosplitting of H 2 O Fasil Dejene

H2 Production by Photosplitting of H2O

Fasil Dejene

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 Nanoscience17 June 2009

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J mater Sci (2008) 43:5395-5429

Current primary H2 Sources

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Thermochemical, Hydrosol II plant, Almeria, Spain

Bayswater Power Station (New South Wales, Australia)


• Costly (€35,000/Kg)• Dirty although efficient (60-70%)• High temperature

H2 Production by Photosplitting of H2O

Artificial Bio-inspired Photoelectrochemical

Photo-Biological

4 "Energy & Nano" - Top Master Symposium in Nanoscience17 June 2009

NC

O

NCH3

NN N

N

HH

H

http://www.microscopy-uk.org.uk

Natural Photosynthesis

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Main Components Antenna Transport Reaction center OEC Acceptor


Artificial Photosynthesis

1. Antenna for Light Harvesting (Donor)

2. Reaction Center (Mediator)

3. Mn Clusters (catalysts)

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What is needed?

Artificial Leaf=1+2+3


Self-assembled antenna systems Two Routes

1 – Natural Antenna Systems

in a protein matrix

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Self-Assembly of Natural- Light Harvesting Bacteriochlorophylls of Green Sulfer Photosynthetic Bacteria

Saga et al, Biconjugate chem. (2006)


25nm

Self-assembled antennae Systems

2 – Artificial Antenna Systems

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Self-Assembled Discotic /Cylinderical Nanostructures of Perylene-3,4:9,10-bis(dicarboximide)

Sinks et al Chem. Mater., 2005


Reaction Center (Charge transfer) long-lived charge separated states Coupled to the antenna

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Water Splitting Cluster Acts as a catalyst Efficient catalyst Difficult to synthesize


J. Yano et.al., Science (2006)

Examples of an ‘Artificial Leaf’

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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


Cabtree & Lewis, Ame. Inst. Of Physics, (2007)

Another example

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http://www.fotomol.uu.se/Forskning/Biomimetics/fotosyntes/research2.shtm

•Low efficiency(<1%)

•Difficult to synthesize something which is not clearly known

synthetic Ru-Mn complex and Photosystem II


Photoelectrochemical

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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 Nanoscience17 June 2009

Photoelectrochemical

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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 Nanoscience17 June 2009

Catalysts

Nanoporous Nanotube Single Nanocrystal

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V.I.Bukhtiyarov Rus. Chem. Rev. (2001)

0 2 4 6 8 10

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

<d>, nm

TOF,

sec

-1


TOF is rate of a catalytic reaction, normalized to the number of surface atoms of active component

Size effect of Pt/-Al2O3 catalysts

Nanoporous ZnS as a Catalyst

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Angew. Chem. Int. Ed. 44, 5299-5303, 2005"Energy & Nano" - Top Master Symposium in Nanoscience17 June 2009

Carbon-Doped TiO2 Nanotube as a catalyst

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J.H. Park et al. Nano Lett., Vol. 6, No. 1, 2006"Energy & Nano" - Top Master Symposium in Nanoscience17 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


Next Joule Inc., US. Patent 6,060,026, (2000)US. Patent 6,361,660, (2000)

SiMetal

Metal oxide

Natural glass coat

Silicon nanocrystal coupled to metal and metal oxide catalysts

H2 + O2 bubble from solution

Photo-Biological

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U.S. DOE Report-H program"Energy & Nano" - Top Master Symposium in Nanoscience17 June 2009

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

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A. Melis, Int.Jour. Hydrogen 27,11-12,2002, 1217-1228

Smaller antenna systems allow better light penetration and increase saturation threshold

Summary Biological H2 Production

Bio-inspired H2 production Photoelectrochemical cell Low Efficiency Bio-Hybrid systems may improve the efficiency


E. Reisner et.al., Chem. Commun., 2009, 550–552Ru-TiO2-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 200921

Thank You

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H 2 Production by Photosplitting of H 2 O Fasil Dejene