Atomic Insights into Pt-Confined FeO Model Catalyst: Surface Structure and NH3 Adsorption

Abstract

Iron oxides (FeO_x), a cost-effective and versatile transition metal oxide, are pivotal in heterogeneous catalysis due to their exceptional redox activity and tunable surface structures. In this study, the growth mechanisms of iron monoxide (FeO) thin films on Pt(100) substrate and the adsorption behaviors of NH₃ on these films are systematically investigated using low-temperature scanning tunneling microscopy (LT-STM) and X-ray photoelectron spectroscopy (XPS). Based on the FeO(111)/Pt(100) model system prepared by molecular beam epitaxy (MBE), the influence of the substrate on the atomic arrangement of Fe and O, surface structural stability, and NH₃ adsorption behavior of FeO thin films is investigated. Stoichiometric and oxygen-rich FeO(111) surfaces on Pt(100) are prepared by tuning overlayer thickness and characterized at the atomic scale via scanning tunneling microscopy (STM). In situ XPS experiments demonstrate nondissociative adsorption of NH₃ on the regular sites of FeO/Pt(100), but the unclosed FeO/Pt interfacial sites promote NH₃ dissociation into NH₂ species. Furthermore, this study reveals that the FeO-Pt(100) system exhibits an interfacial confinement effect analogous to that observed in the FeO-Pt(111) system. These findings provide theoretical guidance for the atomic-scale design of oxide-metal thin films and elucidate strategies to enhance the catalytic efficiency of environmental catalysts.