期刊
ACS CATALYSIS
卷 5, 期 11, 页码 6463-6467出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.5b01819
关键词
scanning tunneling microscopy; ultraviolet photoelectron spectroscopy; trimethyl acetate; hydroxyl; TiO2
资金
- US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences
- DOE's Office of Biological and Environmental Research
The influence of reactant coverage on photochemical activity was explored using scanning tunneling microscopy (STM) and ultraviolet photoelectron spectroscopy (UPS). We observed diminished reactivity of carboxylate species (trimethyl acetate, TMA) on TiO2(110) as a function of increasing coverage. This effect was not linked to intermolecular interactions of TMA but to the accumulation of the coadsorbed bridging hydroxyls (HOb) deposited during (thermal) dissociative adsorption of the parent, trimethylacetic acid (TMAA). Confirmation of the hindering influence of HOb groups was obtained by the observation that HOb, species originated from H2O dissociation at O-vacancy sites have a similar hindering effect on TMA photochemistry. Though HOb's are photoinactive on TiO2(110) under ultrahigh vacuum conditions, UPS results show that these sites trap photoexcited electrons, which in turn likely (electrostatically) attract and neutralize photoexcited holes, thus suppressing the hole-mediated photoreactivity of TMA. This negative influence of surface hydroxyls on hole-mediated photochemistry is likely a major factor in other anaerobic photochemical processes on reducible oxide surfaces.
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