Research on Chemical Intermediates

, Volume 43, Issue 9, pp 5041–5054 | Cite as

Photo-generated conduction-band and shallow-trap electrons from UV irradiation on ethanol-adsorbed TiO2 and N-TiO2: an in situ infrared study

  • Jiawei Liu
  • Long Zhang
  • Xuesi Yao
  • Steven S. C. Chuang
Article

Abstract

The dynamic behaviors of conduction-band electrons (\({\text{e}}_{CB}^{ - }\)) and shallow-trap electrons (\({\text{e}}_{ST}^{ - }\)) 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 \({\text{e}}_{CB}^{ - }\) and \({\text{e}}_{ST}^{ - }\), and the formation of acetate on TiO2 and the formation of acetate, formate, and formaldehyde on N-TiO2. Accumulated \({\text{e}}_{CB}^{ - }\) and \({\text{e}}_{ST}^{ - }\) 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 \({\text{e}}_{ST}^{ - }\) and generated \({\text{e}}_{ST}^{ - }\) and \({\text{e}}_{CB}^{ - }\) at a lower rate than TiO2. The average energy level of \({\text{e}}_{ST}^{ - }\) 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 \({\text{e}}_{CB}^{ - }\) and \({\text{e}}_{ST}^{ - }\) 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

Keywords

TiO2 N-doped TiO2 Conduction-band electrons Shallow-trap electrons Adsorbed ethanol FTIR Photocatalysis 

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Copyright information

© Springer Science+Business Media B.V. 2017

Authors and Affiliations

  • Jiawei Liu
    • 1
  • Long Zhang
    • 1
  • Xuesi Yao
    • 1
  • Steven S. C. Chuang
    • 1
  1. 1.Department of Polymer ScienceThe University of AkronAkronUSA

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