Synergistic Effects of Au and FeO_<i>x</i> Nanocomposites in Catalytic NO Reduction with CO

Abstract

Promotion of Au/TiO₂ by FeO_<i>x</i> addition is shown to result in a very strong enhancement of activity and selectivity in the NO reduction with CO. The nanocomposite Au-FeO_<i>x</i>/TiO₂ catalysts were prepared by deposition–precipitation (Au/TiO₂) and subsequent impregnation (FeO_<i>x</i>). 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 FeO_x,, 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-FeO_<i>x</i>/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 FeO_<i>x</i> 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-FeO_<i>x</i> 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