CHEMISTRY: Catalytic Obstacle Race

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Science  02 Aug 2002:
Vol. 297, Issue 5582, pp. 739a
DOI: 10.1126/science.297.5582.739a

Small metallic particles are often the active species in many industrial catalysts, but they can be “poisoned” during the catalytic process, either by contaminants in the reaction mixture or by a secondary reaction involving the reactants or products. Microscopic knowledge of the processes that lead to this poisoning is rare.

Schauermann et al. now provide detailed insights into how specific sites on metal nanoparticles differ in their catalytic activity and their resistance to poisoning for the decomposition of methanol on palladium particles. This reaction proceeds via two pathways. The dominant (and desired) pathway leads to the formation of carbon monoxide and molecular hydrogen, but the breakage of carbon-oxygen bonds can form unwanted adsorbed carbon species. Molecular beams and time-resolved reflection-adsorption infrared spectroscopy were used to show that steps and edges were poisoned preferentially in this system. Once all of the edge and step sites were covered with adsorbed carbon, the rate of adsorbed carbon formation decreased rapidly, leaving the larger flat facets of the particles free for the catalytic pathway. — JU

Angew. Chem. Int. Ed. 41, 2532 (2002).

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