New fuel cell catalyst uses 2 metals

May 14, 2009

Material scientists at Washington University in St. Louis have developed a technique for a bimetallic fuel cell catalyst that is efficient, robust and two to five times more effective than commercial catalysts. The novel technique eventually will enable a cost effective fuel cell technology, which has been waiting in the wings for decades, and should give a boost for cleaner use of fuels worldwide.

Younan Xia, Ph.D., the James M. McKelvey Professor of Biomedical Engineering at Washington University led a team of scientists at Washington University and the Brookhaven National Laboratory in developing a bimetallic catalyst comprised of a palladium core or "seed" that supports dendritic platinum branches, or arms, that are fixed on the nanostructure, consisting of a nine nanometer core and seven nanometer platinum arms. They synthesized the catalysts by sequentially reducing precursor compounds to palladium and platinum with L-ascorbic acid (that is, Vitamin C) in an aqueous solution. The catalysts have a high surface area, invaluable for a number of applications besides in fuel cells, and are robust and stable.

Xia and his team tested how the catalysts performed in the oxygen reduction reaction process in a fuel cell, which determines how large a current will be generated in an electrochemical system similar to the cathode of a fuel cell. They found that their bimetallic nanodendrites, at room temperature, were two-and-a-half times more effective per platinum mass for this process than the state-of-the-art commercial platinum catalyst and five times more active than the other popular commercial catalyst. At 60 C(the typical operation temperature of a fuel cell), the performance almost meets the targets set by the U.S. Department of Energy.

The Department of Energy has estimated for widespread commercial success the "loading" of platinum catalysts in a fuel cell should be reduced by four times in order to slash the costs. The Washington University technique is expected to substantially reduce the loading of platinum, making a more robust catalyst that won't have to be replaced often, and making better use of a very limited and very expensive supply of platinum in the world.

The study was published in Science on-line on May 14.

"There are two ways to make a more effective catalyst," Xia says. "One is to control the size, making it smaller, which gives the catalyst a higher specific surface area on a mass basis. Another is to change the arrangement of atoms on the surface. We did both. You can have a square or hexagonal arrangement for the surface atoms. We chose the hexagonal lattice because people have found that it's twice as good as the square one for the oxygen reduction reaction.

"We're excited by the technique, specifically with the performance of the new catalyst."

Xia says seeded growth has emerged recently as a good technique for precisely controlling the shape and composition of metallic nanostructures prepared in solutions. And it's the only technique that allowed Xia and his collaborators to come up with their unconventional shape.

"When you have something this small, the atoms tend to aggregate and that can reduce the surface area,' Xia says. "A key reason our technique works is the ability to keep the platinum arms fixed. They don't move around. This adds to their stability. We also make sure of the arrangement of atoms on each arm, so we increase the activity."

Xia and his collaborators are exploring the possibility of adding other noble metals such as gold to the bimetallic catalysts, making them trimetallic. Gold has been shown to oxidize carbon monoxide, making for even more robust catalysts that can resist the poisoning by carbon monoxide - a reduction byproduct of some fuels.

"Gold should make the catalysts more stable, durable and robust, giving yet another level of control," Xia says.

Washington University in St. Louis

Related Fuel Cell Articles from Brightsurf:

INRS researchers develop a new membraneless fuel cell
The research team of INRS (Institut national de la recherche scientifique) professor Mohamed Mohamedi has designed a green membraneless fuel cell that uses oxygen from the air.

Researchers advance fuel cell technology
Washington State University researchers have made a key advance in solid oxide fuel cells (SOFCs) that could make the highly energy-efficient and low-polluting technology a more viable alternative to gasoline combustion engines for powering cars.

Niobium used as catalyst in fuel cell
Glycerol fuel cell can replace batteries in cell phones and laptops, and could be used in future to run electric cars and supply power to homes.

Inside the fuel cell -- Imaging method promises industrial insight
Hydrogen-containing substances are important for many industries, but scientists have struggled to obtain detailed images to understand the element's behavior.

Selenium anchors could improve durability of platinum fuel cell catalysts
Researchers at the Georgia Institute of Technology have developed a new platinum-based catalytic system that is far more durable than traditional commercial systems and has a potentially longer lifespan.

Activity of fuel cell catalysts doubled
An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

More flexible nanomaterials can make fuel cell cars cheaper
A new method of increasing the reactivity of ultrathin nanosheets, just a few atoms thick, can someday make fuel cells for hydrogen cars cheaper, finds a new Johns Hopkins study.

Developed self-controlling 'smart' fuel cell electrode material
A research team led by Professor Kang Taek Lee in the Department of Energy Science and Engineering developed electrode material for a new form of high-performance solid oxide fuel cell.

Finally, a robust fuel cell that runs on methane at practical temperatures
Either exorbitantly expensive fuel or insanely hot temperatures have made fuel cells a boutique proposition, but now there's one that runs on cheap methane and at much lower temperatures.

New fuel cell concept brings biological design to better electricity generation
Fuel cells have long been viewed as a promising power source.

Read More: Fuel Cell News and Fuel Cell Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to