One-Pot Ethyl Acetate Production from Ethanol Photooxidation on Rutile TiO2(110): Strong Photon Energy Dependence

Ethyl acetate (EA) production from sequential ethanol (EtOH) photooxidation on a rutile­(R)-TiO2(110) surface has been investigated by the temperature-programmed desorption (TPD) method at 355 and 266 nm. Significant EA product is detected under 266 nm irradiation, which is most likely to be formed via cross-coupling of primary dissociation products, aldehyde (CH3CHO) and ethoxy groups. On the contrary, EA formation at 355 nm is negligible. In addition, the initial rate of EA formation from EtOH at 266 nm is nearly 2 orders of magnitude faster than that at 355 nm. Quantitative analysis suggests that EA formation from sequential EtOH photooxidation on R-TiO2(110) is strongly dependent on photon energy or the energy of hot holes. This experimental result raises doubt about the traditional photocatalysis model on TiO2 where charge carriers relax to their respective band edges prior to charge transfer to adsorbates during the photocatalytic process, leading to no dependence on photon energy in TiO2 photocatalysis.