Presentation on theme: "Conversion of Solar Radiation into Chemical Energy E. Reguera E. Reguera CICATA-IPN, Unidad Legaria CICATA-IPN, Unidad Legaria Semana de la Ciencia en."— Presentation transcript:
Conversion of Solar Radiation into Chemical Energy E. Reguera E. Reguera CICATA-IPN, Unidad Legaria CICATA-IPN, Unidad Legaria Semana de la Ciencia en el IPN, 2013 Semana de la Ciencia en el IPN, 2013 “The struggle for survival is the struggle for the energy availability”. Ludwig Boltzmann Ludwig Boltzmann
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
165,000 TeraWatts of sunlight hit the earth every day We only need to capture % of solar radiation! Lots of ‘big, fast & efficient’ problems Light harvesting Light harvesting Energy conversion Energy conversion Energy transport Energy transport Energy storage …. Energy storage …. Nanotech will play a major role in meeting all of these! Current Global Energy Comsuption: 13 TW
Sugar from Sunlight + CO 2 + H 2 O Natural Photosynthesis Natural Photosynthesis is a very complex process; its artificial reproduction involves large difficulties !!! 2H 2 O 4H + + 4e - +O 2 G = 237 kJ/mole
Natural Photosynthesis: Process in presence of light 4Mn(II) 4Mn(III) + 4e -
Process in absence of light
The Natural Photosynthesis was already developed about 3 The Natural Photosynthesis was already developed about 3 billions of years ago; billions of years ago; The Natural Photosynthesis was first established in the aqueous The Natural Photosynthesis was first established in the aqueous medium; medium; The evolved oxygen contributes to the formation of the ozone The evolved oxygen contributes to the formation of the ozone shielding for UV radiation and to the appearance of an oxygen shielding for UV radiation and to the appearance of an oxygen rich atmosphere of our planet. rich atmosphere of our planet.
Photosynthesis is also important for the environment preservation; it consumes CO 2 Photosynthesis is also important for the environment preservation; it consumes CO 2 and releases O 2
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 !!!
The Availability of Fossil Fuels: Global Scenario Assumes that 75% of each fossil fuel is burned for energy Peaks at about 2025 Shale gas and oil shift the peak about 50 years
World Population Projection Fit of population to available fossil-fuels energy Population with renewable energy
Renewable Energy Technologies: A Global Urgency Variable Character Energy Storage Media are Required All these Sources are of Solar Nature
How Much Land is Needed? 12 kW/person x 8.3 billion people = 96 x watts ≈ 100 terawatts. Current = ~15 TW.) Solar energy = ~342 watts/m 2 at surface. Land area needed at 10% efficiency = ~2.8 x 10 6 km 2. Earth land area is ~1.48 x 10 8 km 2. So, ~2% of land is needed. Use roofs of buildings, parking lots, highways & railways (1.1 x 10 5 km 2 ) for solar and use agriculture land and offshore sites for wind.
Artificial Photosynthesis is the Solar into Chemical Energy Conversion 2H 2 O + h 4H 2 +O 2 “CO 2 + 2H 2 O + h CH 4 + 2O 2 ” “CO 2 + 2H 2 O + h CH 3 OH + 3/2 O 2 ” “2CO 2 + 3H 2 O + h C 2 H 5 OH + 5/2 O 2 ” All these processes consume energy which is accumulated in the obtained products H2OH2O 2e- 2H + + 1/2 O 2 2H + HH2HH2 CO 2 H 2, CH 4 CH 3 OH H2OH2OH2OH2O O2O2O2O2
H 2 O H 2 + (1/2)O 2 E o = 1.23 eV H 2 O + CO 2 (1/6)C 6 H 12 O 6 E o = 1.24 eV H 2 production involves the 99% of the harvested energy!!
Why Artificial Photosynthesis is Needed? Chemical Energy (H 2, CH 4, CH 3 OH, C 2 H 5 OH) represents an Energy Storage support; The available mobile technologies are easily adaptable to Chemical Energy, e. g. using Fuel Cell devices; The captured CO 2 from environmental emissions can be reduced, using sunlight and water, to CH 4, CH 3 OH, C 2 H 5 OH; Bio-fuels must be ignored as an energy source option if potential foods are used in their production.
Inverse Engineering of the Photosynthesis Process Mn Mn Mn Mn O O O O O O Mn Mn Mn Mn O O O O 2H 2 O 4H + + 4e - cubanePSII Water splitting in plants - photosynthesis 2H 2 O + hv → 4H + + 4e - + O 2 Wu, Dismukes et al, Inorg, Chem 43, 5795 (2004) Ferreira, et al, Science 303: 1831 (2004). Tard et al, Nature 433, 610 (2005) Justice, Rauchfuss et al, J. Am. Chem. Soc.126, (2004) Alper, Science 299, 1686 (2003) bacteria - hydrogenase catalyst for 2 H + + 2e - H 2 10 µ chlamydomonas moewusii Modify the biochemistry of plants and bacteria - improve efficiency by a factor - improve efficiency by a factor of 5–10 of 5–10 - produce a convenient fuel - produce a convenient fuel methanol, ethanol, H 2, CH 4 methanol, ethanol, H 2, CH 4 Bio-Mimetic
Approaches in Progress for an Artificial Leaf: 2H 2 O + h 4H 2 +O 2 “CO 2 + 2H 2 O + h CH 4 + 2O 2 ” “CO 2 + 2H 2 O + h CH 3 OH + 3/2 O 2 ” “2CO 2 + 3H 2 O + h C 2 H 5 OH + 5/2 O 2 ” 1)Hydrogen production from water splitting; 2) A complex process involving both water splitting and CO 2 capture and reduction : splitting and CO 2 capture and reduction :
H 2 Production using Sunlight
Semiconductor base principle
Creation of an analogue of Cubane for the OEC D. G.Nocera, Acc. Chem. Res. 2012
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
Iron oxides for water splitting: scope and limitations Hematite (Fe 2 O 3 ) and other iron oxides are earth-abundant with perspectives for artificial photosynthesis; Limitations: 1) Its conduction band is too low to drive H 2 production; 2) The application of a bias potential is required to drive the oxidation reaction; the oxidation reaction; 3) Ultrashort lifetime for the charge recombination process.
Ternary Semiconductors: N-Ba 5 Ta 4 O 15 Tantalates, Vanadates, Oxinitrides, …. Ba 5 Ta 4 O 15 ; BiVO 4, N:Ta:TiO 2
H2OH2O HH2HH2 2H + 2H + + 1/2 O 2 2e- Co 3 [Fe(CN) 6 ] 2 (Co 2+) 3-x (Co 3+ ) x [(Fe III ) 2-x (Fe II ) x (CN) 12 ] (Co 2+) 3-x (Co 3+ ) x [(Fe III ) 2-x (Fe II ) x (CN) 12 ] (Co 2+ )(Co 3+ ) 2 [Fe II (CN) 6 ] 2 (Co 2+ )(Co 3+ ) 2 [Fe II (CN) 6 ] 2 Example: T A – L- T B hhhh ne - Use of MVS Coordination Compounds for Water Splitting Possible combinations: Mn, Fe, Co Mn 2+ Mn 3+, Mn 4+ Fe 2+ Fe 3+, Fe 4+ Co 2+ Co 3+
Engineering the photosynthesis process D. G.Nocera, Acc. Chem. Res. 2012
An Artificial Leaf Eff.: 5 %
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.
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