Thermal- and photon-stimulated reactions of acetone co-adsorbed with oxygen on rutile TiO2(110) surface are studied with infrared reflection-adsorption spectroscopy (IRAS) combined with temperature programmed desorption and angle-resolved photon stimulated desorption. IRAS results show that n2-acetone diolate ((CH3)2COO) is produced via thermally-activated reactions between the chemisorbed oxygen with co-adsorbed acetone. Formation of acetone diolate is also consistent with 18O / 16O isotopic exchange experiments. During UV irradiation at 30 K, CH3 radicals are ejected from the acetone diolate with a distribution that is peaked at .-. +- 66 degrees from the surface normal along the azimuth (i.e. perpendicular to the rows of bridging oxygen and Ti5c ions). This distribution is also consistent with the orientation of the C–CH3 bonds in the n2-acetone diolate on TiO2(110). The acetone diolate peaks disappear from the IRAS spectra after UV irradiation and new peaks are observed and associated with n2-acetate. The data presented here demonstrate direct signatures of the proposed earlier 2-step mechanism for acetone photooxidation on TiO2(110)
Revised: July 28, 2015 |
Published: June 4, 2015
Citation
Petrik N.G., M.A. Henderson, and G.A. Kimmel. 2015.Insights into Acetone Photochemistry on Rutile TiO2(110). 1. Off-Normal CH3 Ejection from Acetone Diolate.Journal of Physical Chemistry C 119, no. 22:12262-12272.PNNL-SA-108620.doi:10.1021/acs.jpcc.5b02477