Synergistic Effects of Au and FeOx Nanocomposites in Catalytic NO Reduction with CO

Promotion of Au/TiO2 by FeOx addition is shown to result in a very strong enhancement of activity and selectivity in the NO reduction with CO. The nanocomposite Au-FeOx/TiO2 catalysts were prepared by deposition–precipitation (Au/TiO2) and subsequent impregnation (FeOx). Structural characterization of the nanocomposite catalysts using XRD, TEM, TPR, XPS, and DRIFTS revealed that they consist of titania-supported Au particles of about 4.4–4.8 nm size, which were partially covered with a thin layer of FeOx,, mainly made up of Fe2+ (FeO), in addition to a small fraction of Fe3+ (Fe2O3). In situ DRIFTS studies showed that, in comparison to Au/TiO2, on the Au-FeOx/TiO2 nanocomposites new adsorption sites were created, which led to enrichment of CO and NO molecules on the Au surface and at its interfaces with FeOx and TiO2. At the reaction temperature (250 °C), a new surface NO–CO complex, where both Fe and Au are proposed to be involved in the adsorptive interaction, was discovered. The titania-supported Au-FeOx nanocomposites considerably facilitated the formation of this complex and contributed to the striking enhancement of the catalytic performance (activity and selectivity) of the Au-based catalyst.