Frontier methods reveal the workings of nanocatalysts.
Instruments with extraordinary capabilities enable scientists at Oak Ridge National Laboratory to capture images of catalysts only a billionth of a meter wide. Their efforts may lead to a better understanding of the relationship between nanocatalyst structures and functions. This knowledge in turn could spawn improvements in catalysts that make the development and manufacture of thousands of industrial products—including fuels, pharmaceuticals and polymers—both possible and profitable.
At ORNL's nanoscience center, chemist Zili Wu bombards samples with photon beams to monitor catalysts at work. Wu's process combines optical imaging—infrared, Raman and X-ray diffraction spectroscopy—with mass spectroscopy. The technique, operando imaging, makes it possible for scientists to watch catalysts while they operate. The technology also enables researchers to determine which chemical species are generated, and in what quantities, at a reactive surface.
Using operando spectroscopy, the researchers study gold nanocatalysts that turn carbon monoxide into carbon dioxide. The work may aid fuel cell research because the industrial process that generates hydrogen to power proton exchange membranes also produces carbon monoxide, which even in trace amounts can poison electrode catalysts in fuel cells.
In another case of extreme imaging, the Department of Energy's Transmission Electron Aberration-Corrected Microscope project aims to meet a challenge posed in 1959 by physicist Richard Feynman, who lamented the lack of a powerful electron microscope. In 2009, scientists hope to deliver an instrument for imaging atomic-scale order, electronic structure and dynamics of individual nanostructures.
"We can resolve two objects separated by a distance about one million times smaller than the diameter of a human hair," says materials scientist Andrew Lupini, whose aberration-corrected scanning transmission electron microscopes rectify the unavoidable imperfections of round lenses. "We can 'see' individual atoms and obtain spectra from single nanoparticles." Such fine detail may guide industrial engineers in optimizing catalyst support structures and preparation methods.—Dawn Levy
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