LAUSR

The dynamic behaviors of conduction-band electrons ($${\text{e}}_{CB}^{ - }$$eCB-) and shallow-trap electrons ($${\text{e}}_{ST}^{ - }$$eST-) generated from UV irradiation on ethanol-adsorbed TiO2 and N-TiO2 have been studied by in situ Fourier transform infrared spectroscopy (FTIR) in a diffuse reflectance mode at 300 K and 0.1 MPa. UV irradiation on ethanol-adsorbed TiO2 resulted in the breaking of C–H bond of ethanol, the transfer of electrons from ethanol to the photo-generated holes on TiO2 and N-TiO2, the accumulation of $${\text{e}}_{CB}^{ - }$$eCB- and $${\text{e}}_{ST}^{ - }$$eST-, and the formation of acetate on TiO2 and the formation of acetate, formate, and formaldehyde on N-TiO2. Accumulated $${\text{e}}_{CB}^{ - }$$eCB- and $${\text{e}}_{ST}^{ - }$$eST- are manifested by broad and featureless IR absorbance spectra, which can be fitted into two models for estimation of their relative concentrations. N-doping onto TiO2 produced a higher population of $${\text{e}}_{ST}^{ - }$$eST- and generated $${\text{e}}_{ST}^{ - }$$eST- and $${\text{e}}_{CB}^{ - }$$eCB- at a lower rate than TiO2. The average energy level of $${\text{e}}_{ST}^{ - }$$eST- was determined to be 0.30 eV for TiO2 and 0.26 eV for N-TiO2 below the conduction band. Upon terminating UV irradiation, the IR intensity of accumulated $${\text{e}}_{CB}^{ - }$$eCB- and $${\text{e}}_{ST}^{ - }$$eST- showed a gradual decay in a time scale of minutes. This study demonstrated that the recombination of photo-generated electrons and holes can be a slow process on TiO2 and N-TiO2 in the presence of adsorbed ethanol under ambient conditions.Graphical Abstract