Hydrogen Production By Photosynthesis

http://www.osti.gov/energycitations/...sti_id=6660456

http://unisci.com/stories/20013/0823013.htm

Photosynthesis Redirected To Produce Hydrogen As Fuel

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.
Hydrogen's potential as a "clean" fuel cannot be fully realized until it can
be generated from renewable resources.

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.

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.

In the presence of an added electron donor, this "platinized complex" was
able to use visible light to produce hydrogen.

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.

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.

The UT/ORNL experiments uncoupled PSI from PSII, removing PSII and the
intervening complex and redirecting PSI reactions to produce molecular
hydrogen.

This is the first time platinized PSI has been used to generate hydrogen,
and represents the smallest nanoscale hydrogen-evolving system ever created.

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.

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.

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.