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Conversion of Solar Radiation into Chemical Energy

Conversion of Solar Radiation into Chemical Energy. E. Reguera CICATA-IPN, Unidad Legaria. Semana de la Ciencia en el IPN, 2013. “ The struggle for survival is the struggle for the energy availability ”. Ludwig Boltzmann.

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Conversion of Solar Radiation into Chemical Energy

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  1. Conversion of Solar RadiationintoChemicalEnergy E. Reguera CICATA-IPN, Unidad Legaria Semana de la Ciencia en el IPN, 2013 “Thestruggleforsurvivalisthestrugglefortheenergyavailability”. Ludwig Boltzmann

  2. Outline __________________________________________ • From Solar Radiation to Chemical Energy • Natural Photosynthesis Process • From Natural Photosynthesis to Fossil Fuels • Renewable Energies • Artificial Photosynthesis (APh) Products • Different Approaches • Use of Materials of Low Cost for APh • Summary

  3. 165,000 TeraWatts of sunlight hit the earth every day Current Global Energy Comsuption: 13 TW We only need to capture .02-.04% of solar radiation! • Lots of ‘big, fast & efficient’ problems • Light harvesting • Energy conversion • Energy transport • Energy storage …. • Nanotech will play a major role in meeting all of these!

  4. Natural Photosynthesis 2H2O  4H+ + 4e- +O2 DG = 237 kJ/mole Sugar from Sunlight + CO2 + H2O Natural Photosynthesis is a very complex process; its artificial reproduction involves large difficulties !!!

  5. Natural Photosynthesis: Process in presence of light 4Mn(II)  4Mn(III) + 4e-

  6. Process in absence of light

  7. The Natural Photosynthesis was already developed about 3 • billions of years ago; • The Natural Photosynthesis was first established in the aqueous • medium; • The evolved oxygen contributes to the formation of the ozone • shielding for UV radiation and to the appearance of an oxygen • rich atmosphere of our planet.

  8. Photosynthesis is also important for the environment preservation; it consumes CO2and releases O2

  9. Fossil Fuels: > 400 millions of years of solar into chemical energy conversion through Natural Photosyntesis That huge volume of accumulated chemical energy will be consumed by the human civilization in about 300 years !!!

  10. The Availability of Fossil Fuels: Global Scenario Peaks at about 2025 Shale gas and oil shift the peak about 50 years 2065 Assumes that 75% of each fossil fuel is burned for energy.

  11. World Population Projection Population with renewable energy Fit of population to available fossil-fuels energy 1950-2006.

  12. Renewable Energy Technologies: A Global Urgency Variable CharacterEnergy Storage Media are Required All these Sources are of Solar Nature

  13. How Much Land is Needed? • 12 kW/person x 8.3 billion people = 96 x 1012 watts ≈ 100 terawatts. Current = ~15 TW.) • Solar energy = ~342 watts/m2at surface. • Land area needed at 10% efficiency = ~2.8 x 106 km2. • Earth land area is ~1.48 x 108 km2. • So, ~2% of land is needed. Use roofs of buildings, parking lots, highways & railways (1.1 x 105 km2) for solar and use agriculture land and offshore sites for wind. http://arts.bev.net/RoperLDavid/

  14. Artificial Photosynthesis is the Solar into Chemical Energy Conversion H2O O2 CO2 H2, CH4 CH3OH N N H H C N H N O N N C H 3 2e- H2 2H2O + hu 4H2 +O2 “CO2 + 2H2O + hu  CH4 + 2O2” “CO2 + 2H2O + hu  CH3OH+ 3/2O2” “2CO2 + 3H2O + hu  C2H5OH+ 5/2O2” 2H+ 2H+ +1/2O2 H2O All these processes consume energy which is accumulated in the obtained products

  15. H2O  H2 + (1/2)O2 Eo = 1.23 eV H2O + CO2 (1/6)C6H12O6Eo = 1.24 eV H2 production involves the 99% of the harvested energy!!

  16. Why Artificial Photosynthesis is Needed? Chemical Energy (H2, CH4, CH3OH, C2H5OH) represents an Energy Storage support; The available mobile technologies are easily adaptable to Chemical Energy, e. g. using Fuel Cell devices; The captured CO2 from environmental emissions can be reduced, using sunlight and water, to CH4, CH3OH, C2H5OH; Bio-fuels must be ignored as an energy source option if potential foods are used in their production.

  17. Inverse Engineering of the Photosynthesis Process 4H+ + 4e- 2H2O cubane PSII 10 µ chlamydomonasmoewusii O Mn Mn O Mn O O Mn Mn O O O Mn Mn O Mn O O Water splitting in plants - photosynthesis 2H2O + hv → 4H+ + 4e- + O2 Modify the biochemistry of plants and bacteria - improve efficiency by a factor of 5–10 - produce a convenient fuel methanol, ethanol, H2, CH4 Wu, Dismukes et al, Inorg, Chem 43, 5795 (2004) Ferreira, et al, Science 303: 1831 (2004). Bio-Mimetic bacteria - hydrogenase catalyst for 2 H+ + 2e- H2 Tard et al, Nature 433, 610 (2005) Justice, Rauchfuss et al, J. Am. Chem. Soc.126, 13214 (2004) Alper, Science 299, 1686 (2003)

  18. Approaches in Progress for an Artificial Leaf: • Hydrogen production from water splitting; • 2) A complex process involving both water • splitting and CO2 capture and reduction: 2H2O + hu 4H2 +O2 “CO2 + 2H2O + hu  CH4 + 2O2” “CO2 + 2H2O + hu  CH3OH+ 3/2O2” “2CO2 + 3H2O + hu  C2H5OH+ 5/2O2”

  19. H2 Production using Sunlight

  20. Semiconductor base principle

  21. Creation of an analogue of Cubane for the OEC D. G.Nocera, Acc. Chem. Res. 2012

  22. Mn oxides and related nanostructures In addition to PSII, Mn nanostructures are found in bacterial and fungal redox reactions; as ocean and freshwater nodules, coatings on rock surfaces, hydrothermal veins, and dendrites

  23. Iron oxides for water splitting: scope and limitations Hematite (Fe2O3) and other iron oxides are earth-abundant with perspectives for artificial photosynthesis; Limitations: 1) Its conduction band is too low to drive H2 production; 2) The application of a bias potential is required to drive the oxidation reaction; 3) Ultrashort lifetime for the charge recombination process.

  24. Ternary Semiconductors: Tantalates, Vanadates, Oxinitrides, …. Ba5Ta4O15; BiVO4, N:Ta:TiO2 N-Ba5Ta4O15

  25. Use of MVS CoordinationCompoundsforWaterSplitting ne- hu 2e- H2 TA – L- TB 2H+ 2H+ +1/2O2 H2O Possiblecombinations: Mn, Fe, Co Mn2+ Mn3+, Mn4+ Fe2+ Fe3+, Fe4+ Co2+ Co3+ Example: Co3[Fe(CN)6]2 (Co2+)3-x(Co3+)x[(FeIII)2-x(FeII)x(CN)12] (Co2+)(Co3+)2[FeII(CN)6]2

  26. Engineering the photosynthesis process D. G.Nocera, Acc. Chem. Res. 2012

  27. An Artificial Leaf Eff.: 5 %

  28. In Summary: Nanostructures containing Mn, Fe and Co probably have the major opportunities in Artificial Photosynthesis; Ternary semiconductors (tantalates, vanadates, ….) are gaining interest by their response to visible light; Ru, Ir and Pt based materials must be considered as model systems; Efforts are required in materials science to obtain low cost semiconductor nanostructures conjugated to antenna compounds for an efficient solar radiation energy harvesting and their use for water splitting.

  29. Thank you for the attention!!! Thanks to the Organizing Committee for the opportunity to talk about this interesting subject. The Artificial Photosynthesis is a big challenge but also a great opportunity to do basic and applied science

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