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Delta XANES technique helps study operation of fuel cell catalysts

A research group at The George Washington University in the US have developed a new analytical tool that helps to shed light on new catalysts that hopefully will alleviate some of the many problems that remain with modern fuel cells.

The Delta X-ray Absorption Near Edge Structure technique (Delta XANES) helps us to understand why some catalysts in fuel cells work better than others, why some get poisoned more than others, and why some deteriorate more than others.

In catalyst research, X-ray Absorption Spectroscopy (XAS) measures the amount of light absorbed by the studied sample such as metal catalysts (the absorption coefficient). An intense X-ray beam, such as that coming from a synchrotron, is needed to conduct XAS. The Extended X-ray Absorption Fine Structure (EXAFS) in the absorption coefficient can provide structural information about the sample utilizing a procedure developed over the last 25 years.

The new Delta XANES technique isolates the absorption component coming from chemisorption of atoms or molecules on a sample, by taking the difference between the XANES with and without the chemisorbed species, and thereby provides adsorbate information.

Dr David Ramaker, the research group leader in the Department of Chemistry, believes that the new Delta XANES technique now makes it possible to see things that have never been observed before in operating fuel cells.

The method enables both the determination of atomic and molecular adsorption sites and coverage on small metal nanoparticles, and correlation of that with the structural information obtained from EXAFS. Both techniques can be applied to very complex systems such as in electrochemical cells, operating fuel cells and catalysts under reaction conditions.

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