PHOTOELECTRON SPECTROMICROSCOPIC STUDY OF THE SPREADING BEHAVIOR OF MOO3 ON TITANIA AND ALUMINA MODEL SUPPORTS

The spreading of micron-sized MoO3 particles deposited on model suppor ts, alumina and titania thin films, has been studied by scanning photo emission spectromicroscopy. It was shown that Mo species released from the MoO3 crystals spread over the thin oxide film under conditions (h eating to 720 K for 6 h in air) similar to those used for catalysts on powdered supports. The changes in the surface morphology were followe d by elemental mapping and photoelectron spectroscopy from submicron s pots where the intensities and kinetic energies of the Mo 3d, Al 2p, T i 3d, and O 1s photoelectrons were used as fingerprints for the chemic al composition of the surface. The high spatial resolution when imagin g the spread phase on the laterally inhomogeneous samples made it poss ible to throw light onto the active transport mechanism of the wetting Mo oxide species during heat treatment of the model systems.