Chemist Lisa Utschig tests a container of photosynthetic proteins linked with platinum nanoparticles, which can produce hydrogen from sunlight. Tiny bubbles of hydrogen are visible in the container at right. Photo: Argonne National Laboratory
alga, hated by boaters and pool owners, may someday help provide us with the
raw machinery to power our appliances.
A group of
scientists at the U.S. Department of Energy’s Argonne National Laboratory, led
by chemist Lisa Utschig, has linked platinum nanoparticles with algae proteins,
commandeering photosynthesis to produce hydrogen instead. The system produces
hydrogen at a rate five times greater than the previous record-setting method.
you are considering the question ‘How do we get energy from the sun,’ you
always come back to photosynthesis,” Utschig said. “Photosynthesis
does it best. It’s been engineered over millions of years.”
and Tiede are part of Argonne’s Photosynthesis
Group, which has worked for fifty years to understand photosynthesis.
Photosynthesis built a green Earth out of the bare, meteor-blistered planet
which had sat empty for a billion years; it tipped the composition of the
atmosphere towards oxygen, allowing all kinds of life to blossom, including us.
chemistry group is part of a larger effort to develop efficient ways to produce
what are termed solar fuels. Most people think of solar panels when they think
of solar energy, but the energy that solar panels generate has to be used right
away—they directly create electricity, which can’t be stored easily.
alternative is solar fuels, which pull energy from the sun to create fuel that
can be stored for later, such as hydrogen. Hydrogen, a promising fuel in the
effort to reduce carbon dioxide emissions, is appealingly clean: when it’s
burned as fuel, water is the byproduct. But we have yet to discover a low-cost
way to manufacture large amounts of hydrogen.
we’ve been reverse-engineering photosynthesis,” said Argonne
chemist David Tiede, who co-authored the paper. “If we understand how
Nature does it, we can tweak the process to produce hydrogen.”
fuel efforts focus on a type of protein complex called Photosystem I, or PSI,
which is the first half of the photosynthetic duo found in all green plants.
strikes the PSI complex, it momentarily knocks an electron into an
“excited” state. The goal is to separate this electron from its home
atom—leaving behind a “hole” of positive charge—and channel it to an
artificial catalyst to make hydrogen. But the electron only remains excited for
the tiniest fraction of a second; the catalyst needs to grab it during this
co-author Nada Dimitrijevic, the team designed platinum nanoparticle catalysts.
These catalysts have a size and surface chemistry that allows them to stick to
PSI molecules at the point where the light-generated electrons accumulate. When
the modified platinum nanoparticles and PSI are mixed in water, the two link
platinum nanoparticles have the same size and surface charge as the molecule
that PSI would bind to naturally,” Tiede said.
the study design used platinum as a catalyst, which is too expensive to be
cost-effective, the research serves as proof-of-concept. Further studies hope
to improve the method’s efficiency, reliability, and economics.
“The next step we’ll take is experimenting with non-platinum
catalysts,” Utschig said. “Hopefully we can find a catalyst that can
be made with a cheaper metal, which would make the process much more attractive
on a large scale.”