6533b860fe1ef96bd12c3041

RESEARCH PRODUCT

From tungsten hexacarbonyl adsorption on TiO2(1 1 0) surface to supported tungsten oxide phases.

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Abstract Synchrotron-based photoemission spectroscopies were used to study the adsorption of tungsten hexacarbonyl on (1 1 0) TiO 2 surfaces: experiments using W4f and Ti2p intensities variations show that, at 140 K, the hexacarbonyl growth proceeds via a layer-by-layer mode. Moreover, it was evidenced using both core levels and valence band experiments that, after back to room temperature, W(CO) 6 desorbs without significant decomposition. However, low energy (500 eV) ion (Ar + ) irradiation can allow partial decomposition of tungsten hexacarbonyl molecules leading to sub-carbonyl tungsten molecules. The bonding of sub-carbonyl species to the TiO 2 surface was then stronger than the one of hexacarbonyl: these chemisorbed species do not desorb when going back to room temperature allowing a higher amount of metal to remain on the surface. Subsequent annealing gets rid of remaining carbonyl groups. This phenomenon leaves tungsten atoms at the TiO 2 surface. The annealing organizes these W atoms in the 400–600 K temperature range leading to WO x phases, which are almost free of carbon. The oxidation degree of these phases is strongly related to tungsten amount remaining at the surface.