Catalytic oxidation of carbon monoxide at cryogenic temperatures

• A Au/Titania catalyst has been developed active at cryogenic temperatures.
• CO oxidation is seen at temperatures as low as 120 K.
• Amorphous titanate sites appear to be required for this low T activity.
• A least two titania-adsorbed CO species are involved.
• A synergy was observed between the uptake of CO and O2 on the surface.

Although solid gold is often considered chemically inert, it has been shown that, in the form of nanometer-size particles, it is capable of promoting many catalytic reactions. This behavior is typified by the ease with which catalysts made out of gold nanoparticles dispersed on titania supports oxidize carbon monoxide to carbon dioxide around room temperature. Here, we report on a unique gold/titania-based catalyst that, in addition to such room temperature catalysis, displays a second active regime at much lower temperatures, as low as 120 K. We show that this new catalytic regime follows a mechanism different to that operative at room temperature, involving at least two titania-adsorbed CO species and a synergy between the uptake of CO and O2 on the surface. New titanate sites, formed upon treatment of catalysts made out of dispersing Au nanoparticles on amorphous titania with NaOH, appear to be responsible for the opening of this new reaction channel.

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