Active Phase of FeOx/Pt Catalysts in Low-Temperature CO Oxidation and Preferential Oxidation of CO Reaction

The interface between metal and reducible oxide has attracted increasing interest in catalysis. The FeOx–Pt interface has been a typical example, which showed remarkable activity for the preferential oxidation of CO (PROX) at low temperatures. However, model catalytic studies under vacuum conditions or in high-pressure O-rich environment at 450 K have reported two different active phases with iron in two different valence states, invoking a possible pressure gap. To identify the active phase for low-temperature CO oxidation and PROX, it is necessary to investigate the stability and activity of FeO/Pt(111) under the realistic reaction conditions. We thus conducted an in situ study on FeO/Pt(111) from ultrahigh vacuum to the atmospheric pressure of reactant gases. Our study shows FeO islands were easily oxidized in 1 Torr O2 to form the trilayer FeO2 islands. However, the presence of 2 Torr CO could prevent the oxidation of FeO islands and lead to CO oxidation at the FeO/Pt(111) interface. The FeO/Pt(111) s...