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Artificial Photosynthesis as a Next Generation Power Source
Terms to Know Watt
Unit of power defined as one joule-second Mole
Measurement of amount of atoms/molecules in a system Joule
Unit of energy Prefix “Giga”Billion Prefix “Mega”Million Prefix “Kilo”Thousand
Photolysis Splitting by light
Photoelectrochemistry Study of light and electricity interaction with chemical substances Photoelectrochemical Cell=Photocatalytic Cell
Photocatalytic Water Splitting Splitting of water with the help of light and catalysts
Quick Facts Highest solar-to-power conversion
efficiency for a Photovoltaic Cell (Solar Panel) to date 20% Efficiency
Average amount of energy the Earth receives from the Sun per day 550 Terawatts (200 Petawatts per year)
The entire US uses 3.163 Terawatts per year The entire world uses 16.16 Terawatts per year
Photo-powered Cells vs. Petroleum Engine
Photo-powered Easily controlled reaction Very efficient energy conversion (Fuel Cell) No heat Clean Renewable Works almost limitlessly No need for refueling
Petroleum Explosive Lost energy during energy conversion (Combustion) Heat Emissions Non-renewable Needs regular refueling
Clearly Photo-powered systems are better
Quick Review of Photosynthesis Photosynthesis
6 Carbon Dioxide + 6 Water>>> Glucose+ 6 Oxygen
Requires energy Takes place in Chloroplasts of Plant Cells Light to Chemical Energy Light reactions produce Oxygen
Thylakoid Membrane Dark reactions produce Glucose
Stroma
Quick Review of Cellular Respiration Cellular Respiration
6 Oxygen + Glucose >>> ATP (Energy) + 6 Carbon Dioxide + 6 Water
Produces energy Takes place in Mitochondria of Cells Chemical to Usable Chemical Three Steps
Glycolysis: Sugar Breaking Krebs Cycle: Carbon Dioxide and ATP Production Electron Transport Chain: Water and ATP Production
Ways to Use Energy from Photosynthesis Glucose Fuel Cells
Efficient Direct Conversion of Chemical Energy to Usable Energy Provides reusable products Requires expensive catalysts (for now) such as Platinum
Cellular Respiration Efficient ATP produced will have to be converted into Usable Energy Provides reusable products Complicated to synthetically reproduce
Combustion Inefficient: Heat loss Direct conversion of Chemical Energy to Usable Energy Provides reusable products Simple reaction
Photosynthesis vs. Photocatalysis Photosynthesis
Produces Glucose and Oxygen Glucose and Oxygen combustion produces 3204 kilojoules per
mole Energy per Weight=17.8 kilojoules per gram Less weight efficient Easily found in nature
Photocatalysis Produces Hydrogen and Oxygen
Hydrogen and Oxygen combustion produces 286 kilojoules per mole
Energy per Weight=283 kilojoules per gram Very weight efficient Still being researched
Photosynthesis and electrochemistry vs. Photovoltaics
Photosynthesis/Photoelectrochemistry Convert sunlight directly to easily stored chemical
compounds Shorter Lifespan Easily adapted to current engines Still being researched technology
Photovoltaic Converts sunlight into electricity which then needs to
converted to chemical energy for storage Longer Lifespan Can not be easily adapted to current engines Well-established technology
Typical Photosynthesis Cell
Light 6(CO2)+6(H2O)
Photosynthetic Cell
C6H12O6+6(H2O)
Fuel Cell
ENERG
Y
Storage
Candidates for Artificial Photosynthesis Microalgae
Converts Carbon Dioxide and Water into Lipids at high efficiencies
Nostoc Punctiforme (Cyanobacteria) Converts Nitrogen gas into Ammonia and releases Hydrogen,
both of which can be used to create energy NAPD+/ NADPH Coenzyme System
Based off the Calvin Cycle, produces Carbohydrates which can be used to create energy
Ribulose-Bisphosphate Carboxylase (RuBisCO) Rather slow enzyme that reduces Carbon Dioxide, works in mild
conditions Blue Dimer
Catalyst based off those found in natural photosynthesis, evolves oxygen from water
Detailed Look into Blue Dimer Blue Dimer is a photocatalyst that produces
protons (H+) ions and O2 molecules from water It mimics the light reactions of Natural
Photosynthesis For it to be properly used, the Hydrogen ions
would have to be converted to H2 molecules It is much more efficient in terms of energy
production than RuBisCO systems or Microalgae To provide an even greater efficiency, the Triad
Approach could be utilized
Triad Approach
Typical Photoelectrochemical Cell
Photocatalyst
Light 2(H20)
2(H2)+O2Fuel Cell
ENERG
Y
Storage
Candidate Catalysts for Photoelectrochemical Cells Most Catalysts come from Transition Metals (D-Block) of
Periodic Table Candidates for PEC Cells are:
Vanadium Dioxide (VO2) 1.416 moles of hydrogen/gram catalyst/hour 405
kilojoules/gram/hour Sodium Tantalate (NaTaO3)
1180 millimoles/gram/hour 33 kilojoules/gram/hour Titanium Dioxide (TiO2)
180 millimoles/gram/hour 5 kilojoules/gram/hour Cadmium Compounds (Cd)
Various Rates, Highest Achieved: 14 moles/gram/hour 4 Megajoules/gram/hour
Detailed Look at VO2 System Vanadium Dioxide provides the best ratio of price to efficiency
$20 per pound 183 Megajoules per pound (Enough to power 36 houses for a day)
Vanadium Dioxide would be deposited on silicon chips via sol-gel method
Using a design similar to a solar panel, VO2 would break down a constant stream of water that would flow over it
The Hydrogen gas produced would exit via a tube at the top of the panel
Hydrogen could be stored indefinitely Hydrogen could then be catalyzed with oxygen in a fuel cell,
releasing energy Oxygen would be produced by a different catalyst, such as
Ruthenium Dioxide (RuO2)
Vanadium Dioxide Photoreactor Cell
Fuel Cell
Fuel Cell
VO2
RuO2
Basic Fuel Cell
A Final Recap Photosynthesis and Photoelectrochemistry
use light from the sun to produce chemical compounds that store energy
Stored chemical energy can be released by various methods, allowing the energy to be used
Products of the release of energy can be used to form more energy-storing compounds
Global ImpactPhotosynthetic Cells and PEC Cells, once
perfected, will provide a cheap, accessible, clean, and renewable power source. Currently the best technology is either the Blue Dimer Catalyst or the VO2 catalyst. The Photocells will help with Global Climate Change as no they will reduce CO2 emissions. Over time, once they have been incorporated into everyday infrastructure such as cars, gas stations, and power plants, they could very well make gasoline and other fossil fuels obsolete.
Other Research Metabolic Engineering
Used to modify the metabolism of organisms Research is being done into altering RuBisCO so as to make it more efficient
Fuel Cells Used to release energy from fuel Use precious and expensive metals Research being done to lower price and raise efficiency of these
Ultraviolet Upconverters Light ranges from low energy (infrared) to high energy (Ultraviolet) Most catalysts work better with higher light energies, and most sunlight
comes in lower energies UV Upconverters take photons with lower energies and convert them into a
proton with high energy Chromera Velia
Photosynthetic Protista Very good at converting sunlight into chemical energy using a different form
of RuBisCO Unfortunately, C. Velia still uses most of its produced energy
Bibliography- Primary Sources Only1. Faunce, Thomas. "Artificial Photosynthesis as a Frontier Technology for Energy Sustainability."Energy &
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3. “Revealing How Nature Uses Sunlight to Split Water” The Royal Society n.d. Web. 16. http://www.jstor.org/stable/20208513
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10. Ellis, R. John. "Biochemistry: Tackling Unintelligent Design." Nature Journal. Nature, n.d. Web. 16 May 2013. http://www.nature.com/nature/journal/v463/n7278/full/463164a.html
11. "Artificial Photosynthesis: Biomimetic Approaches to Solar Energy Conversion and Storage."ScienceDirect.com. Science Direct, n.d. Web. 16 May 2013. http://www.sciencedirect.com/science/article/pii/S0958166910000649
12. "A Hydrogen-producing, Hydrogenase-free Mutant Strain of Nostoc Punctiforme ATCC 29133." ScienceDirect.com. Science Direct, n.d. Web. 16 May 2013. http://www.sciencedirect.com/science/article/pii/S0360319902001210
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Bibliography-Non-Primary Sources1. "Artificial Photosynthesis." Wikipedia. Wikimedia Foundation,
14 May 2013. Web. 16 May 2013. http://en.wikipedia.org/wiki/Artificial_photosynthesis
2. Wolfram|Alpha: Computational Knowledge Engine. Wolfram Alpha, n.d. Web. 16 May 2013. http://www.wolframalpha.com/
3. "Artificial Photosynthesis Project Aims to Create Hydrogen Fuel." Wired. Conde Nast Digital, 20 Jan. 0013. Web. 16 May 2013. http://www.wired.com/autopia/2013/01/photosynthesis-hydrogen/
4. "Metabolic Engineering." Wikipedia. Wikimedia Foundation, 15 May 2013. Web. 16 May 2013. http://en.wikipedia.org/wiki/Metabolic_engineering