Conversion of Solar Radiation into Chemical Energy E. Reguera E. Reguera CICATA-IPN, Unidad Legaria...
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Transcript of Conversion of Solar Radiation into Chemical Energy E. Reguera E. Reguera CICATA-IPN, Unidad Legaria...
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
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 .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!
Current Global Energy Comsuption: 13 TW
Sugar from Sunlight + CO2 + H2O
Natural Photosynthesis
Natural Photosynthesis is a very complex process; its artificial reproduction involves large difficulties !!!
2H2O 4H+ + 4e- +O2
DG = 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 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.
Photosynthesis is also important for the environment preservation; it consumes CO2 and releases O2
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 !!!
1900 1925 1950 1975 2000 2025 2050 2075 2100 2125 2150 2175 2200 2225 2250 2275 23000
50
100
150
200
250
300
Coal Energy Crude-Oil Energy Natural-Gas EnergyTotal Fossil Fuels Energy
year
10
^9
MB
tu
1980
2025
The Availability of Fossil Fuels: Global Scenario
Assumes that 75% of each fossil fuel is burned for energy.
2065
Peaks at about 2025
Shale gas and oil shift the peak about 50 years
190019251950197520002025205020752100212521502175220022252250227523000
1
2
3
4
5
6
7
8
0
50
100
150
200
250
300
350Population Fit to Energy
Population Projection (10^9) Population Fit Total Fossil Fuels Energy
year
10
^9 p
eo
ple
10
^9 M
Btu
Population without renewable energy
Fossil Fuels Energy
12 kW/person
World Population Projection
Fit of population to available fossil-fuels energy 1950-2006.
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 1012 watts ≈ 100 terawatts. Current = ~15 TW.)
Solar energy = ~342 watts/m2 at 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/
Artificial Photosynthesis is the Solar into Chemical Energy Conversion
2H2O + hu 4H2 +O2
“CO2 + 2H2O + hu CH4 + 2O2”
“CO2 + 2H2O + hu CH3OH + 3/2O2”
“2CO2 + 3H2O + hu C2H5OH + 5/2O2”All these processes consume energy which is accumulated in the obtained products
H2O
2e-
2H+ +1/2O2 2H+ H2
NC O
N C H3
NN
NN
HHH
CO2
H2, CH4
CH3OH
H2O
O2
H2O H2 + (1/2)O2 Eo = 1.23 eVH2O + CO2 (1/6)C6H12O6 Eo = 1.24 eV
H2 production involves the 99% of the harvested energy!!
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.
Inverse Engineering of the Photosynthesis Process
Mn
MnMn
Mn
O
OO
O
OO
Mn
Mn
MnMn
O
OO
O
2H2O 4H+ + 4e-
cubanePSII
Water splitting in plants - photosynthesis
2H2O + hv → 4H+ + 4e- + O2
Wu, Dismukes et al, Inorg, Chem 43, 5795 (2004)Ferreira, et al, Science 303: 1831 (2004).
H2 e-
H+
N Hd+O
OFe
S
FeS S
CC
CC C
Cys
[4Fe4S]
Od+HN
H2 e-
H+
N Hd+O
OFe
S
FeS S
CC
CC C
Cys
[4Fe4S]
Od+HN
Tard et al, Nature 433, 610 (2005)Justice, Rauchfuss et al, J. Am. Chem. Soc.126, 13214 (2004)
Alper, Science 299, 1686 (2003)
bacteria - hydrogenasecatalyst for
2 H+ + 2e- H2
10 µchlamydomonas moewusii
Modify the biochemistry of plants and bacteria
- improve efficiency by a factor of 5–10 - produce a convenient fuel methanol, ethanol, H2, CH4
Bio-Mimetic
Approaches in Progress for an Artificial Leaf:
2H2O + hu 4H2 +O2
“CO2 + 2H2O + hu CH4 + 2O2”
“CO2 + 2H2O + hu CH3OH + 3/2O2”
“2CO2 + 3H2O + hu C2H5OH + 5/2O2”
1) Hydrogen production from water splitting;
2) A complex process involving both water splitting and CO2 capture and reduction:
H2 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 (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.
Ternary Semiconductors:
N-Ba5Ta4O15
Tantalates, Vanadates, Oxinitrides, ….
Ba5Ta4O15; BiVO4, N:Ta:TiO2
H2O
H2
2H+ 2H+ +1/2O2
2e-
Co3[Fe(CN)6]2
(Co2+)3-x(Co3+)x[(FeIII)2-x(FeII)x(CN)12]
(Co2+)(Co3+)2[FeII(CN)6]2
Example:
TA – L- TB
hu ne-
Use of MVS Coordination Compounds for Water Splitting
Possible combinations: Mn, Fe, CoMn2+ Mn3+, Mn4+
Fe2+ Fe3+, Fe4+
Co2+ Co3+
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