Photosynthesis is one of nature's most important processes. Aside from
producing oxygen, this natural process converts solar to chemical energy by
transforming atmospheric carbon dioxide and water into sugar molecules to
provide plants with needed food and energy to survive.

Scientists have tried to artificially replicate this energy conversion
process to produce environmentally friendly and sustainable fuels such as
hydrogen and methanol. Mimicking the process has been challenging to
scientists as artificial photosynthesis requires the creation of a molecular
system that absorbs light, transports and separates electrical charge, and
catalyzes
[www.isaaa.org]
fuel-producing reactions. All are complicated processes that must operate
synchronously to achieve high energy-conversion efficiency.

A team of researchers led by chemists from the U.S. Department of Energy's
(DOE) Brookhaven National Laboratory and Virginia Tech has designed two
photocatalysts that combine individual components for light absorption,
charge separation, or catalysis into a single "supramolecule." Each
supramolecule is made up of multiple light-harvesting ruthenium (Ru) metal
ions connected to a single catalytic center of rhodium (Rh) metal ions. The
researchers found that the supramolecule with six Ru centers and one Rh
center was seven times more efficient than the other, cycling 300 times to
produce hydrogen for 10 hours. The larger of the supramolecules was slightly
electron-deficient, making it more receptive to electrons needed for
synthetic photosynthesis.

[www.bnl.gov]