Subject: [Homestead] Hydrogen from Artificial Photosynthesis at Virginia Tech
Date: Tue, 31 Aug 2004 09:54:46 -0700
Means of extracting hydrogen from water continue to improve as an
economical alternative to fossil fuel, but research has to include how
to economically store it for vehicular use.
Molecular Assemblies Created To Convert Water To Hydrogen Gas
Blacksburg, Va. (Aug. 25, 2004) -- Wonder where the fuel will come from
for tomorrow's hydrogen-powered vehicles? Virginia Tech researchers are
developing catalysts that will convert water to hydrogen gas.
The research will be presented at the 228th American Chemical Society
National Meeting in Philadelphia August 22-26, 2004
Supramolecular complexes created by Karen Brewer's group at Virginia
Tech convert light energy (solar energy) into a fuel that can be
transported, stored, and dispensed, such as hydrogen gas.
The process has been called artificial photosynthesis, says Brewer,
associate professor of chemistry. "Light energy is converted to chemical
energy. Solar light is of sufficient energy to split water into hydrogen
and oxygen gas, but this does not happen on its own; we need a catalysts
to make this reaction occur."
One major challenge is to use light to bring together the multiple
electrons needed for fuel production reactions. Electrons are the
negatively charged particles that surround an atom's nucleus, allowing
atoms to react and form bonds.
Previous research has focused on collecting electrons using light
energy. The Brewer group has gone the next step and created molecular
machines that use light to bring electrons together (photoinitiated
electron collection) then deliver the electrons to the fuel precursor,
in this case, water, to produce hydrogen.
The researchers create a large molecular assembly called a
supramolecular complex. Light signals this molecular assembly or machine
to collect electrons and make them available for delivery to substrates.
Water is readily available and cheap, says Brewer, "but, so far, our
compound is expensive. The goal is to make it catalytic and to couple it
to oxygen production. We are working to build a supramolecular complex
that will initiate the collection and movement of electrons and bonding
of atoms without being destroyed in the process, so we don't have to
build another molecular machine every time we want to convert water to
hydrogen." Our systems do functioning catalytically but the efficiency
needs to be enhanced.
Mark Elvington, a graduate student in chemistry, will present the
research, "Photochemical reactivity of mixed-metal supramolecular
complexes: Applications as photochemical molecular devices," at 9:30
a.m., Wednesday, Aug. 25, at Pennsylvania Convention Center room113A.
Co-authors are Brewer, Elvington, and Ran Miao, also a Ph.D. student in
chemistry at Virginia Tech from Fudan University.