New catalysts may create more, cheaper hydrogen
ARGONNE, Ill. (Aug. 20, 2007) – A new class of catalysts created at the U.S.
Department of Energy's Argonne National Laboratory may help scientists and
engineers overcome some of the hurdles that have inhibited the production of
hydrogen for use in fuel cells.
Argonne chemist Michael Krumpelt and his colleagues in Argonne's Chemical
Engineering Division used "single-site" catalysts based on ceria
or lanthanum chromite doped with either platinum or ruthenium to boost hydrogen
production at lower temperatures during reforming. "We've made significant
progress in bringing the rate of reaction to where applications require it
to be," Krumpelt said.
Most hydrogen produced industrially is created through steam reforming. In
this process, a nickel-based catalyst is used to react natural gas with steam
to produce pure hydrogen and carbon dioxide.
These nickel catalysts typically consist of metal grains tens of thousands
of atoms in diameter that speckle the surface of metal oxide substrates. Conversely,
the new catalysts that Krumpelt developed consist of single atomic sites imbedded
in an oxide matrix. The difference is akin to that between a yard strewn with
several large snowballs and one covered by a dusting of flakes. Because some
reforming processes tend to clog much of the larger catalysts with carbon or
sulfur byproducts, smaller catalysts process the fuel much more efficiently
and can produce more hydrogen at lower temperatures.
Krumpelt's initial experiments with single-site catalysts used platinum in
gadolinium-doped ceria that, though it started to reform hydrocarbons at temperatures
as low as 450 degrees Celsius, became unstable at higher temperatures. As he
searched for more robust materials that would support the oxidation-reduction
reaction cycle at the heart of hydrocarbon reforming, Krumpelt found that if
he used ruthenium – which costs only one percent as much as platinum – in a
perovskite matrix, then he could initiate reforming at 450 degrees Celsius
and still have good thermal stability.
The use of the LaCrRuO3 perovskite offers an additional advantage over traditional
catalysts. While sulfur species in the fuel degraded the traditional nickel,
and to a lesser extent even the single-site platinum catalysts, the crystalline
structure of the perovskite lattice acts as a stable shell that protects the
ruthenium catalyst from deactivation by sulfur.
Krumpelt will present an invited keynote talk describing these results during
the 234th national meeting of the American
Chemical Society in Boston from
August 18 to 23. Seventeen other Argonne researchers will also present their
research.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology.
The nation's first national laboratory, Argonne conducts leading-edge basic
and applied scientific research in virtually every scientific discipline. Argonne
researchers work closely with researchers from hundreds of companies, universities,
and federal, state and municipal agencies to help them solve their specific
problems, advance America 's scientific leadership and prepare the nation for
a better future. With employees from more than 60 nations, Argonne is managed
by UChicago
Argonne, LLC for
the U.S.
Department of Energy's Office
of Science.
For more information, please
contact Steve McGregor (630/252-5580 or media@anl.gov)
at Argonne.
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