A RAMAN AND XPS INVESTIGATION OF SUPPORTED MOLYBDENUM OXIDE THIN-FILMS .2. REACTIONS WITH HYDROGEN-SULFIDE

Surface characterization of supported molybdenum oxide thin films is u ndertaken following sulfidation treatments with H2S. Surface character ization is carried out by in situ and ex situ laser Raman spectroscopy (LRS) and X-ray photoelectron spectroscopy (XPS). Sulfidation of thin -film molybdenum oxides supported on planar alumina and graphite produ ces two sulfides species: MoS2 and a reduced form with a binding energ y lower than MoS2. The S(2p) spectra also show polysulfide species at higher binding energies to MoS2. Sulfidation of thicker, octahedral Mo O3 thin films results only in MoS2. Extensive prereduction of octahedr al MoO2 prior to sulfidation is shown not to be important in the conve rsion of oxide to sulfide phases.