Propene adsorption on gold particles on TiO2(110)

The adsorption of propene on rutile TiO2(110) and on gold islands dispersed on TiO2(110) [Au/TiO2(110)], both at 120 K, has been studied using temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and He low energy ion scattering spectroscopy (LEIS). Propene adsorbs on both TiO2(110) and Au/TiO2(110), with desorption peak temperatures at low coverage of similar to190 and similar to240 K, respectively. When only 16% of the TiO2(110) surface is covered by gold islands [16% Au/TiO2(110)], moderate propene doses populate both the 240 and 190 K TPD peaks, in that order. The 190 K peak, seen also without Au, is due to propene bound to bare Ti sites. The 240 K peak is attributed to propene adsorbed to Ti sites at the edges of gold islands. Tiny doses of propene to the 16% Au/TiO2(110) surface give this a 240 K TPD peak but no 190 K feature, showing that the propene is mobile on TiO2(110). A TPD feature at similar to 150 K, which is more prominent at higher Au coverages and higher propene doses, is due to propene bound only to metallic Au islands. Propene desorption shows additional intensity at 265-310 K when the gold islands are only one atom thick, due to propene adsorbed on 2D An islands or at Ti sites near their edges.