Method reveals secrets of bimetallic catalysts | November 27, 2017 Issue - Vol. 95 Issue 47 | Chemical & Engineering News
Volume 95 Issue 47 | p. 9 | Concentrates
Issue Date: November 27, 2017

Method reveals secrets of bimetallic catalysts

Single-molecule, single-particle imaging study quantifies catalytic enhancement
Department: Science & Technology
News Channels: Analytical SCENE, Materials SCENE
Keywords: Imaging, catalysis, catalyst, single-molecule
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A combination of electron microscopy (left) and fluorescence mapping (right) reveals the on a palladium nanorod with a spherical gold tip, the regions at the interface of the two metals are the most active catalytically (red and orange).
Credit: ACS Cent. Sci.
This electron micrograph (black and white) shows physical details of a palladium nanorod with a gold spherical tip. The colorful image shows which regions of the rod are the most active catalytically (orange and red).
 
A combination of electron microscopy (left) and fluorescence mapping (right) reveals the on a palladium nanorod with a spherical gold tip, the regions at the interface of the two metals are the most active catalytically (red and orange).
Credit: ACS Cent. Sci.

Nanoparticle catalysts containing two types of metals play an important role in petrochemical reforming, hydrogenation, and other industrial processes. Researchers have long known that the combination of metals leads to enhanced catalytic activity compared with the corresponding monometallic catalysts. Knowing the molecular level details that underpin the bimetallic enhancement could lead to even better catalysts—ones that use less energy and generate fewer by-products. But because of a lack of nanoparticle uniformity and difficulty tracking reactions on the nanometer scale, those details have remained hidden. Now they’re being exposed. Peng Chen of Cornell University and coworkers prepared palladium nanorods tipped with a gold sphere and used the catalysts to mediate a model photocatalytic reaction—reduction of nonfluorescent resazurin to fluorescent resorufin. By scrutinizing the system with electron microscopy and a fluorescence microscopy method that has single-molecule resolution, the team tracked thousands of reactions individually. In that way, they pinpointed with nanometer resolution, where on more than 50 particles, a reaction occurred (ACS Cent. Sci. 2017, DOI: 10.1021/acscentsci.7b00377). The data show that the nanoscale interface of the two metals is the catalytic hot spot: It’s about 50% more active than single-metal regions. Also, the most active facets of the monometallic catalysts are the best spots to form bimetallic interfaces.

 
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ISSN 0009-2347
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