Synergistic interaction and mechanistic evaluation of NO oxidation catalysis on Pt/Fe2O3 cubes

Abstract

Supported platinum particles with the help of strong metal-support interaction (SMSI) could boost catalytic performance. Pt/Fe2O3 cubes were synthesized byin situreductions of platinum precursors over Fe2O3 cubes, tested for catalytic oxidation of NO, and further characterized by different techniques. The catalytic tests showed that Pt/Fe2O3 cubes exhibited a dramatically enhanced catalytic activity of NO oxidation in comparison to Fe2O3 cubes, Pt/SiO2, and physical mixture of Fe2O3 cubes and Pt/SiO2, suggesting a synergistic interaction between Pt particles and Fe2O3 cubes. Pt particles not only triggered the generation of surface oxygen vacancy sites on Fe2O3 cubes, but also increased the amount of chemically adsorbed O2 at the surface oxygen vacancy sites. The rigorous kinetic study of NO oxidation described a specific reaction pathway following the Langmuir-Hinshelwood mechanism over Pt/Fe2O3 cubes. The dissociation of O2* to O* assisted by NO* was recognized as the rate-determining step of NO oxidation, which might be further promoted by the O* spillover from the Pt particles to the surface oxygen vacancy sites at the supporting Fe2O3 cubes. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed that abundant nitrates formed on the surface of Pt/Fe2O3 cubes, which suggested that the adsorbed NO2 could transform to surface nitrate species.