PNNL

Abstract

The selectivity of trimethyl acetate (TMA) photodecomposition on TiO2(110) as a function of O2 pressure and TMA coverage was probed at room temperature (RT) using isothermal mass spectrometry (ISOMS) and scanning tunneling microscopy (STM). The selectivity of TMA photodecomposition on TiO2(110) is sensitive to the initial TMA coverage and the O2 pressure. TMA bridge bonds to the surface via the carboxylate end of the molecule in a manner consistent with the binding of other carboxylate species (e.g., formate and acetate) on TiO2 surfaces. Under all conditions, photodecomposition of TMA was initiated via hole reaction with the electron in carboxylate’s ? system resulting in opening of the O-C-O bond angle, and formation of CO2 and a t-butyl radical by cleavage of the C-C bond between these groups. The CO2 product desorbs from the surface at RT, but the t-butyl radical has several options for thermal chemistry. In ultrahigh vacuum (UHV), where the O2 partial pressure is