Reactive Surface Structure Observed In Real Time | Chemical & Engineering News
Volume 92 Issue 5 | p. 26 | Concentrates
Issue Date: February 3, 2014

Reactive Surface Structure Observed In Real Time

High-energy X-rays and new detector permit atomic-level characterization under industrially relevant conditions
Department: Science & Technology
News Channels: Analytical SCENE, Materials SCENE
Keywords: surface, catalysis, X-ray, diffraction
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In the presence of CO and little O2, a palladium surface is covered in CO. At higher O2 concentrations, a PdO film forms concurrent with CO2 production (O = red, C = black, and Pd = green).
Credit: Science
This scheme shows how palladium can catalyze CO to carbon dioxide.
 
In the presence of CO and little O2, a palladium surface is covered in CO. At higher O2 concentrations, a PdO film forms concurrent with CO2 production (O = red, C = black, and Pd = green).
Credit: Science

To understand exactly how a catalytic material works or a surface corrodes, it helps to understand their structures and how they change during reactions. Typical techniques that enable structure determination with high resolution also require ultrahigh vacuum, however, making it difficult to watch materials change in real time under industrially relevant conditions. A group led by Johan Gustafson of Sweden’s Lund University has now demonstrated use of high-energy synchrotron X-rays and a larger-than-standard detector to study a palladium surface as it catalyzes oxidation of carbon monoxide to carbon dioxide (Science 2014, DOI: 10.1126/science.1246834). The approach does not require a vacuum and eliminates the need to move a detector around the sample to catch diffracted X-rays—the higher energy X-rays diffract at a smaller angle and can be caught in one place by the larger detector. Using a flow chamber, Gustafson collected diffraction data at intervals of 0.5 seconds as the team exposed the Pd to CO and O2. At high O2 concentrations, the researchers observed a PdO film grow over the surface as CO2 production commenced. The approach should also work to study buried structures or those at solid-liquid interfaces, the researchers say.

 
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