Image courtesy of Brookhaven National Laboratory
Electron microscope image of new catalyst structure showing a single layer of platinum coating a palladium nanoparticle.
Utilizing the ability to create and characterize catalytic structures on the nanoscale, researchers have developed a platinum monolayer catalyst with a palladium-gold alloy core that retained nearly 70 percent of reactivity after 200,000 cycles of testing.
The significant improvement in durability and performance of these catalysts enable design of fuel-cell-powered vehicles that use no more platinum than is currently used for emission control on vehicles powered by internal combustion engines.
Platinum catalysts are the most expensive and least durable component of fuel-cell technology. Before fuel-cell-powered vehicles can hit the road, scientists will have to find a way to protect the platinum catalysts from the wear and tear of stop-and-go driving and to reduce the amount of platinum needed in the electrodes. Platinum electrocatalysts are used to speed up the oxidation and reduction reactions involved in the process of converting hydrogen and oxygen into water and producing electricity. But these reactions also degrade the catalyst through platinum loss, eventually destroying the fuel cell. Brookhaven National Laboratory research has developed a new electrocatalyst that uses only a single layer of platinum over a palladium core and is much more durable than traditional platinum based catalysts. In the new catalyst, palladium in the core interacts with the platinum shell to accelerate the desired fuel oxidation and reduction reactions, but slows the undesired oxidation (corrosion) of platinum itself. In the process, some of the palladium is dissolved, but only slowly, and the overall durability is improved. The platinum is almost unaffected, except for a small contraction of the platinum monolayer that makes the catalyst even more active and increases the stability of the particles. Reactivity of the platinum monolayer/palladium core catalyst also remains extremely high. It is reduced by merely 37 percent after 100,000 cycles, compared to simpler platinum-carbon catalysts, which lose nearly 70 percent of their reactivity after much shorter cycling times. Applied research activities included joint development of the catalyst for automotive applications with Toyota Motor Corp. Brookhaven scientists received an R&D 100 Award for this new technology in 2012 and it is now commercially licensed.
Basic Research: DOE Office of Science, Office of Basic Energy Sciences
Follow-on Applied R&D: DOE Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program; and Toyota Motor Corporation
K. Sasaki et al. "Core-Protected Platinum Monolayer Shell High-Stability Electrocatalysts for Fuel-Cell Cathodes," Angewandte Chemie Int. Ed. 49 8602 (2010).
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