The decomposition and chemistry of Ru3(CO)12 on TiO2(1Â 1Â 0) studied with X-ray photoelectron spectroscopy and temperature programmed desorption

The decomposition process of triruthenium dodecacarbonyl (Ru3(CO)12) on single crystal TiO2(1 1 0) has been investigated using synchrotron-based high resolution photoemission spectroscopy and temperature programmed desorption (TPD). Ruthenium carbonyl adsorbs molecularly on TiO2(1 1 0) at 100 K. When dosing at room temperature, the molecule dissociatively adsorbs forming a Ru3(CO)m (m ⩽ 10) species on the surface. TPD spectra for ruthenium carbonyl dosed at 100 K and 300 K are quite different in peak numbers and shape, indicating that the ruthenium carbonyl decomposition is sensitive to the preparation procedure. Both TPD and photoemission demonstrate that around 700 K, the decarbonylation process is completed yielding almost pure Ru particles. A small amount of CO adsorbs on the obtained Ru particles after large CO exposures (60-100 L) at 300 K. The Ru particles can be oxidized to form RuO2 at 600 K with an O2 pressure of ∼1 × 10−6 Torr (>400 L exposure). In addition, the chemical activity of the Ru metal particles dispersed on TiO2(1 1 0) has also been examined with SO2 and compared to that of a Ru(0 0 1) single crystal. SO2 is easily decomposed by the Ru particles at room temperature, producing S and O adatoms. SO4 is the main product of the reaction of SO2 with the titania support, and the presence of the Ru particles favors a SO4,ads → Sads + nOads + mO2,gas transformation at elevated temperature.