Photocatalytic degradation of organic compounds by 2-ethylimidazole-treated titania under visible light illumination

Titania modified by 2-ethylimidazole (2-EI) (denoted as 2-EI-TiO2) demonstrated visible light photocatalytic activity for the degradation of organic compounds. 2-EI-TiO2 was a bright brown powder that exhibited similar crystallinity and morphology with the control TiO2. A diffuse reflectance spectrum indicated that 2-EI-TiO2 absorbs visible light of all wavelengths. X-ray photoelectron spectroscopy (XPS) confirmed the cationic state of nitrogen species (e.g. Ti-O-N) on the surface of 2-EI-TiO2. Visible light-illuminated 2-EI-TiO2 degraded 10 M 4-chlorophenol (4-CP) by approximately 85% in 4 h. The photochemical activity of 2-EI-TiO2 was selective in targeting the organic compound. The repeated use of 2-EI-TiO2 decreased the photocatalytic activity for the 4-CP degradation. Experiments using radical scavengers and oxidant probes revealed that the oxidation by photogenerated holes is responsible for the degradation of organic compounds by illuminated 2-EI-TiO2 and the role of •OH is negligible.