Penn State researchers have used an ink jet printer in a successful search for an improved fuel-cell catalyst material.

Fuel cells operate like chemical batteries, using the intrinsic free energy of hydrogen or hydrocarbon fuels to produce electricity in a continuous catalytic process. The new catalyst, a quaternary alloy containing platinum, ruthenium, osmium, and iridium, is 40 percent better at its job (depending on power demand) than the best-known current catalyst, a platinum-ruthenium alloy, according to the researchers. It also functions particularly well under high-current/high-power conditions, researchers said.

"The hydrogen fuel cells that have flown on space missions since Gemini are not practical for most applications on Earth because they use catalysts and electrolytes that work only with very pure hydrogen, which is expensive to make and is hard to store and transport," said Thomas E. Mallouk, professor of chemistry at Penn State and a member of the research group. "Nobody wants to carry a tank of compressed hydrogen with their laptop computer, and they would prefer not to have one in their car. Their problems have motivated our research on fuel cells that run on renewable liquid fuel," he said.

Methanol fuel cells have always faced a problem in that the oxidation of methyl alcohol in the cell poisons the catalytic electrode surface. "The platinum catalysts that work so well in hydrogen fuel cells are basically useless for methanol," explained Eugene S. Smotkin, associate professor of chemical and environmental engineering at the Illinois Institute of Technology in Chicago. "They do not absorb water, which is needed to oxidize away the carbon monoxide that builds up on the platinum surface. That is why platinum alloys containing elements that bind the oxygen atom in water are much better catalysts."

To search for an improved catalyst, team members loaded a common ink jet printer with liquid-metal solutions instead of ink. The researchers then used a computer to print out characters on carbon paper. Each character was printed out with different combinations of the metals in the printer. The scientists then converted the metal solutions to metal salt form. When the carbon paper was connected up in an electrical circuit, the characters lit up. The researchers knew the catalyst materials that glowed at the lowest positive voltage would be the most promising catalysts. This unique approach enabled a large number of candidate catalysts to be evaluated relatively rapidly.

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