Interface-Confined FeO_x Adlayers Induced by Metal Support Interaction in Pt/FeO_x Catalysts

Active oxide nanolayers can be stabilized on noble metal surfaces through interface confinement effect in oxide/metal inverse catalysts. Here, using normal metal/oxide catalysts we show that Fe oxide nanolayers can be confined on Pt nanoparticles (NPs) when treating a Pt/FeO_x catalyst in Ar or H₂/O₂ atmospheres at elevated temperatures. Pt NPs partially covered with Fe oxide nanopatches are more active in CO oxidation than bare Pt NPs, while those with fully encapsulated Fe oxide shells in strong metal-support interaction (SMSI) state show much lower activity. Characterization results indicate that three steps play an important role in the formation of Fe oxide overlayers: Pt-aided reduction of interfacial Fe oxide, Pt alloying of interfacial Fe atoms, and surface segregation of alloyed Fe atoms onto surface of Pt NPs. Active surface oxides in so-called support-metal interface confinement (SMIC) state and fully encapsulated oxide layers in the SMSI state can be sequentially produced which depend on the treatment conditions.