Surface study of Pt-3d transition metal alloys, Pt3M (M = Ti, V), under CO oxidation reaction with ambient pressure x-ray photoelectron spectroscopy

Utilizing ambient pressure x-ray photoelectron spectroscopy, the surface segregation and the oxidation dynamics of platinum (Pt)-3d transition metal (M) alloys, Pt3M (M = Ti, V), are investigated. Under oxygen-rich conditions, i.e., P(CO)/P(O2) = 0.1, Pt3V surface forms Pt skin layer while Pt3Ti shows the presence of both Ti and Pt atoms. As temperature increases to 450 K, V atoms make surface segregation to form oxide while Ti atoms start to form various Ti oxides (Ti2O3 and TiOx) on the surface. When CO oxidation occurs at 600 K, the oxidation continues on both surfaces of Pt3M (M = Ti, V), showing the enhancement of TiOx for Pt3Ti and V2O5 and VOx for Pt3V. Also, during CO oxidation, a sign of pure metallic Pt state is found at Pt 4f spectra in both surfaces, suggesting the redistribution of electrons from the transition metals during the oxide formation.