- Hydrogen holds great promise as the "green"
energy source of the future. Though ubiquitous, it rarely exists in a pure
form in nature. Present methods of producing hydrogen for fuel -- such
as extraction from natural gas -- are energy inefficient and polluting.
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- Hydrogen's potential as a "clean" fuel cannot
be fully realized until it can be generated from renewable resources.
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- In an article published in the June 2001 issue of Photochemistry
and Photobiology, researchers from the University of Tennessee's Center
for Environmental Biotechnology (CEB) and the Oak Ridge National Laboratory
(ORNL) demonstrate that photosynthesis -- the process that plants use to
make food from sunlight -- can be redirected to produce hydrogen.
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- The team of CEB researchers -- including undergraduate
student Jennifer Millsaps, UT/ORNL professor Elias Greenbaum and UT professor
Barry Bruce (biochemistry, cellular and molecular biology) -- extracted
intact photosynthetic complexes (Photosystem I) from spinach plants and
coated one side of each isolated complex with platinum atoms.
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- In the presence of an added electron donor, this "platinized
complex" was able to use visible light to produce hydrogen.
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- Photosynthesis results from the cooperation of two photosystems
called Photosystem I (PSI) and Photosystem II (PSII) that are coupled together
in the plant's chloroplast by an intermediary complex.
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- The green plant normally reduces carbon dioxide to carbohydrates
in PSI in a complex set of enzymatic reactions powered by the electrons
produced when water is split in PSII.
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- The UT/ORNL experiments uncoupled PSI from PSII, removing
PSII and the intervening complex and redirecting PSI reactions to produce
molecular hydrogen.
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- This is the first time platinized PSI has been used to
generate hydrogen, and represents the smallest nanoscale hydrogen-evolving
system ever created.
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- So far, diversion to hydrogen production must be supported
by feeding PSI a high-energy donor such as ascorbate. The next step is
to extract PSI and PSII separately, and then join them back together head
to toe, allowing PSII to directly supply PSI with electrons derived from
splitting water.
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- If done successfully, this nanoscale photosystem could
produce a constant supply of hydrogen and oxygen, a fuel that when burned
produces heat -- leaving only water as the waste product.
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- Jennifer Millsaps, the undergraduate student from Maryville
College who acted as lead author on the article, was supported by the Professional
Internship Program (PIP) of the Oak Ridge Institute of Science and Education
(ORISE). The research was supported by the U.S. Department of Energy.
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