|
This finding could have potential cost savings of
millions of dollars in the materials required to commercialize the
fuel cell technology.
The research will be published in the July 3, 2003 edition of "Science Express," the online version of the journal
Science that provides rapid electronic publication of timely and
important research papers. The article also will be published in
Science later this summer.
A fuel cell consists of two electrodes sandwiched
around an electrolyte. Hydrogen fed to the one electrode (anode)
passes through the electrolyte in the form of protons and combines
with oxygen on the other electrode (cathode) making water and
producing heat. Electricity is generated in the process. A fuel cell
will produce energy in the form of electricity and heat as long as
fuel and oxygen are supplied. To produce fuel-cell quality hydrogen,
an important step involves the removal of any by-product carbon
monoxide, which poisons the fuel cell anode catalyst.
"A lot of people have spent a lot of time studying
the properties of gold and platinum nanoparticles that are used to
catalyze the reaction of carbon monoxide with water to make hydrogen
and carbon dioxide," said Maria Flytzani-Stephanopoulos, professor of
chemical and biological engineering at Tufts and the lead researcher
of the project. "We find that for this reaction over a cerium oxide
catalyst carrying the gold or platinum, metal nanoparticles are not
important. Only a tiny amount of the precious metal in non metallic
form is needed to create the active catalyst. Our finding will help
researchers find a cost-effective way to produce clean energy from
fuel cells in the near future"
She and her two colleagues, doctoral student Qi Fu
and research professor Howard Saltsburg, were funded by a $300,000
three-year grant from the National Science Foundation, and have filed
a provisional patent for their research. Their cutting-edge work in
catalytic fuel processing to generate hydrogen for fuel cell
applications is one of the major undertakings at Tufts' Science and
Technology Center at the University's Medford campus.
The Tufts researchers' article is based on the "water-gas
shift" reaction they use to make hydrogen from water and carbon
monoxide over cerium oxide loaded with gold or platinum. Typically, a
loading of 1-10 weight percent of gold or other precious metals is
used to make an effective catalyst. But the Tufts team discovered that,
after stripping the gold with a cyanide solution, the catalyst was
just as active with a slight amount of the gold remaining – one-tenth
the normal amount used.
According to Flytzani-Stephanopoulos, "This finding
is significant because it shows that metallic nanoparticles are mere 'spectator
species' for some reactions, such as the water-gas shift. The
phenomenon may be more general, since we show that it also holds for
platinum and may also hold true for other metals and metal oxide
supports, such as titanium and iron oxide."
She adds, "It opens the way for new catalyst
designs so more hydrogen can be produced with less precious metal.
This can pave the way for cost-effective clean energy production from
fuel cells in the near future."
Fuel cells currently are being used on a trial
basis in some buses, cars and even hotels, but they're expensive. It
may take up to 10 years until the technology is used in transportation
and by the general population. (Since the 1960s, one type of fuel cell
has powered NASA's spacecrafts.)
"We've raised the issue of now having to look back
and see if less precious metal may be used in other similar
applications," said Saltsburg. There's much more to be done, and
that's what makes the research exciting." |
