Catalytic oxidation of carbon monoxide at cryogenic temperatures

Abstract

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 120K. 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.