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 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."
ABOUT THE RESEARCHERS
Maria Flytzani-Stephanopoulos has been active in the field of environmental catalysis for the past 20 years. In the early 1980s she was a member of the technical staff at the Jet Propulsion Laboratory in Pasadena, Calif., where she conducted research in autothermal and steam reforming of fuels for fuel cell applications and in coal gas desulfurization over regenerable mixed oxide sorbents. She also worked at MIT's chemical engineering department on novel catalysts for air pollution control prior to joining Tufts in 1994. Flytzani-Stephanopoulos has directed many projects sponsored by the government and industry, holds seven patents, has published more than 100 technical papers and has received several honors and awards, including three NASA certificates of recognition, a National Science Foundation career advancement award, a NASA achievement award, and the Raytheon Professorship in Pollution Prevention at Tufts. She is the North and South American editor of the journal Applied Catalysis B: Environmental.
Howard Saltsburg has been active in the field of surface science and catalysis for 40 years. He has published seminal works in molecular beam scattering, solid electrolyte aided studies of catalytic reactions, and the use of microelectronic fabrication techniques to create controlled structure catalysts. He is a research professor of chemical and biological engineering at Tufts and professor emeritus of chemical engineering at the University of Rochester.
Qi Fu is a doctoral student in chemical and biological engineering at Tufts who recently received the Outstanding Engineering Graduate Researcher award. This research will form a significant part of her dissertation. Her bachelor's and master's degrees are from East China University of Science and Technology, Shanghai, and from the Research Institute of Petroleum Processing, Beijing, People's Republic of China.
Tufts University, located on three Massachusetts campuses in Boston, Medford/Somerville, and Grafton, and in Talloires, France, is recognized among the premier research universities in the United States. Tufts enjoys a global reputation for academic excellence and for the preparation of students as leaders in a wide range of professions. A growing number of innovative teaching and research initiatives span all Tufts campuses, and collaboration among the faculty and students in the undergraduate, graduate and professional programs across the University's eight schools is widely encouraged.
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