Fig. 3: In situ spectroscopy.
From: The dynamics of overlayer formation on catalyst nanoparticles and strong metal-support interaction
APXPS (650 eV photon energy) at 600 °C of the Pt 4f peak with respective peak fittings (Donjac–Sunjic for a, c and Gaussian–Lorentian for b): after the first H2 (0.15 mbar) exposure at 600 °C (a), the Pt signal intensity decreased by 50% after exposure to 1 mbar O2 (b); a subsequent switch to H2 (c) increased the signal intensity but total intensity remained low. NEXAFS spectra of the Ti L2,3 edge (d) acquired during the in situ XPS set-up. The second peak (eg) exhibits specific peak shapes for different TiO2 polymorphs and oxidation state. Under O2 at 600 °C characteristics of titania rutile are visible. Under H2 the lack of this feature is characteristic of Ti2O3 or amorphous titania. Depth profiling (e) under H2 at 600 °C (blue) and after the switch to O2 (orange). The probing depth was calculated based on the inelastic mean free path of photoelectrons in titania. The results indicate that a titania layer covered the platinum nanoparticles and that this layer is thicker while dosing oxygen. Error bars in e were calculated by Gaussian error propagation of the standard deviation of the Pt 4f and Ti2p peak fitting.
