2-Propanol reactivity on in situ prepared Au(1 1 1)-supported TiO2 nanocrystals

The reactivity of 2-propanol with TiO2 nanocrystals supported on Au(1 1 1) was studied by temperature-programmed desorption (TPD) and scanning tunneling microscopy (STM). The nanocrystals, which are grown through oxidation of a Tisingle bondAu surface alloy, had an average height of 1 nm and width of 15 nm with a dominantly hexagonal morphology. The desorption of propanol and propanol-derived products from the TiO2 nanocrystal surfaces was observed in the 270–570 K temperature range and could be distinguished from desorption of propanol from the Au(1 1 1) surface below 270 K. With increasing propanol coverage, the TiO2-related TPD peaks were occupied before the appearance of any Au(1 1 1)-related peaks. Our calculations showed that the TiO2 nanocrystals were saturated at 0.4 ML of local propanol surface concentration, where 1 ML ≡ 5.2 × 1014 cm−2 refers to surface density of five-coordinated Ti atoms on rutile(1 1 0). Our TPD measurements showed that 61% of this adsorbed propanol desorbed molecularly at 310 K, while 23% dehydrated into propene and 6% dehydrogenated to form acetone, both products desorbing in the 370–570 K temperature range. The desorption temperatures of products from supported TiO2 nanocrystals were shown to depend strongly on the morphology of the nanocrystals.