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State-of-the-art palladium catalysts for fuel cells

Researchers have grappled with the challenge of creating palladium nanoparticles with enough active surface area, the essential property for them to function as catalysts in fuel cells, but until now this has involved obstacles that have been overcome by two Brown University researchers

Description of the process of using palladium in fuel cells
Description of the process of using palladium in fuel cells

Even small devices require energy, and a significant part of it comes from fuel cells. The smaller these devices become, the greater the urgency to find more efficient ways to please.

Over the past few years, chemists have discovered that the metal palladium is a preferred candidate for driving the primary energy of fuel cells - it is cheaper than another profitable fuel cell catalyst, platinum, and is more common.

But the researchers struggled with the challenge of creating palladium nanoparticles with enough active surface area, the essential characteristic for their function as catalysts in fuel cells, while trying to prevent these particles from clumping together during the chemical reaction that converts a fuel source into electricity. Two chemists from Brown University found a way to overcome these obstacles.

The researchers reported in the Journal of the American Chemical Society that they were able to produce palladium nanoparticles with a surface area XNUMX percent larger than commercial palladium particles. Also, the new catalyst remains unchanged for four times longer than the current one.

"This approach is extremely innovative. It works," said Vismadeb Mazumder, a chemistry graduate who co-authored the paper with chemistry professor Shouheng Sun. "The catalyst is twice as active, meaning you only need about half the energy to activate it. And it is four times more stable."

The researchers created nanoparticles with a diameter of 4.5 nanometers. They bonded the nanoparticles to a carbon surface at the anodic end of a direct formic acid fuel cell. So, the researchers did something new: they used weakly bound amine ligands to keep the nanoparticles separated while maintaining their original practical size. Thanks to the separation of the nanoparticles and their uniform size, they increased the available surface area on the carbon surface and increased the reaction efficiency of the fuel cell. "It just worked better," explained the researcher.

Another uniqueness of the ligands lies in the fact that they can be washed away from the carbon surface without risking the nature and activity of the individual palladium nanoparticles. This is an important improvement, according to the researcher, because previous attempts to remove bound converters resulted in the loss of the rigid structure of the nanoparticles, their clustering together, and ultimately - the loss of their catalytic activity.

The research team noted that in experiments that lasted about twelve hours, the new catalysts lost about sixteen percent of their surface area, compared to a sixty-four percent loss for commercial catalysts.

"We were able to reduce the decay rate of our catalyst thanks to our new approach," said the researcher. "We created high-quality palladium nanoparticles, fixed them efficiently to the substrate, and then removed the materials that stabilized them without harming the quality of the activity." The scientists of this study are now looking at a variety of other palladium-based catalysts to find ones that are more active and more stable, so that they can be used in future fuel cell applications.

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