Artificial photosynthesis: If plants can do it, why can

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Artificial photosynthesis If plants can do it,
why cant we?

• Mercer University School of Engineering
• Professional Practices, Dr. Davis
• D. Hodges

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The Natural Process What is Actually Happening?

• In nature, plants use photosynthesis to convert
  sunlight and carbon dioxide into oxygen and a
  carbohydrate food source.
• Chlorophyll is a vital piece of this process. It
  captures the energy of sunlight and allow it to
  be used to power the complex chemical reactions
  inside the plant.
• Plants then use this energy to make a compound
  called NADPH repeatedly cycle
• between its two forms in
• order to bind oxygen to
• the carbon of carbon
• dioxide in order to create
• various forms of
• carbohydrates.
• These carbohydrates are
• a very efficient source of
• chemical energy.

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Reproducing a Natural Process Easy, Right?

• The true challenge
• Splitting the water
• This reaction consists of two parts First, the
  water molecule is split into an oxygen molecule
  and a loose proton and electron. This reaction is
  driven, artificially, at least, by a hydride
  catalyst. Scientists are trying to determine the
  material that will best serve its purpose as the
  catalyst for this reaction. Second, the loose
  protons and electrons form a hydrogen molecule.
  The molecule that performs this in nature has
  been isolated, but it does not perform the same
  in laboratories as it does in plants.

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Making fuel from carbon dioxide

• In order to maximize the efficiency of this
  process, carbon dioxide must behave similar to a
  liquid. This is being accomplished by heating the
  gas to a high temperature under high pressure.
  This
• makes reactions
• involving the carbon
• dioxide much faster,
• cleaner, and more
• efficient.

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The Uses of Reproducing the Process

• Food Resources
• Plants use photosynthesis for food, so if we are
  able to reproduce the process, we could use it to
  create a food supply limited only by the amount
  of sunlight, even in the most barren of tundra
  and driest of deserts.
• Fuel Resources
• Since the food produced is a hydrocarbon, we
  could manipulate the process to make various
  fuels with this process. These can range
• from simple fuels such as
• natural gas to more
• complex molecules such
• as gasoline and even
• jet fuel.

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How useful will this actually be?

• Once the process is perfected, even 3rd world
  countries could become self-sufficient for both
  food and fuel. The only
• requirement will be sunlight,
• a resource that is universally
• abundant, and whatever
• catalysts and chemicals are
• developed for use in the
• process. The possibilities for
• its use are endless

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But will it ever actually get there?

• Right now, the research being conducted uses
  extremely expensive materials and is not very
  efficient. Any true benefit from this research
  appears to be several
• years, possibly even
• decades away, but
• new advances are
• constantly pouring in,
• and progress is
• accelerating towards
• a promising future.

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References

• Photosynthesis. (n.d.). Retrieved March 24, 2008,
  from http//en.wikipedia.org/wiki/Photosynthesis
• Snyder, Kendra. (2007). New Developments in
  Artificial Photosynthesis. Retreived March 23,
  2008, from Brookhaven National Laboratories Web
  site, http//www.bnl.gov/bnlweb/pubaf/pr/PR_displa
  y.asp?prID07-31
• Beardsley, Tim. (1998). Catching the Rays.
  Scientific American, 278(3) 25
• Rodriguez, Jose A. and Hbrek, Jan. (2007,
  December 17). Water-Gas Shift Mechanism
  Revealed. Chemical Engineering News, 85(51) 23
• Jacoby, Mitch. (2007, October 8). Turning Water
  Into Fuel. Chemical Engineering News, 85(41) 9
• Gust, Devens and Moore, Thomas A. (1989, April
  7). Mimicking Photosynthesis. Science, 244,
  35-41
• Penner-Hahn, James E. and Yocum, Charles F.
  (2005, November 11). BIOCHEMISTRY The
  Photosynthesis Oxygen Clock Gets a New Number.
  Science, 310, 982-983