Abstract
Poly-o-phenylenediamine modified TiO2 nanocomposites were successfully synthesized via an ‘in situ’ oxidative polymerization method. The modified nanocomposites were characterized by BET, XRD, TEM, FT-IR, TGA, XPS, EA and UV-Vis DRS. The photocatalytic degradation of methylene blue was chosen as a model reaction to evaluate the photocatalytic activities of TiO2 and PoPD/TiO2. The results indicated that PoPD/TiO2 nanocomposites exhibited good photocatalytic activity and stability. The photocatalytic activity of PoPD/TiO2 increased as the initial pH increased because of electrostatic adsorption between the photocatalyst and MB as well as the generation of ·OH, whereas it exhibited an earlier increasing and later decreasing trend as the concentration of the photocatalyst increased owing to the absorption of visible light. The photocatalytic stability of the PoPD/TiO2 nanocomposite was dependent on the stability of its structure. Based on radical trapping experiments and ESR measurements, the origin of oxidizing ability of PoPD/TiO2 nanocomposites on photocatalytic degradation of MB was proposed, which taking into account of ·OH and ·O2− were the first and second important ROS, respectively. The possible photocatalytic mechanism and photocatalytic activity enhanced mechanism has been proposed, taking into account the photosensitization effect and synergetic effect of TiO2 with PoPD.
Highlights
Measurements, the origin of oxidizing ability of PoPD/TiO2 nanocomposites on photocatalytic degradation of methylene blue (MB) was proposed, which taking into account of ·OH and ·O2− were the first and second important reactive oxygen species (ROS), respectively
The modified photocatalysts were characterized by BET Test, X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Elemental Analysis (EA) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS)
The photocatalytic degradation of methylene blue (MB) was chosen as a model reaction to evaluate the photocatalytic activities of TiO2 and PoPD/TiO2
Summary
The PoPD/TiO2 nanocomposites can be excited to produce more electron-hole pairs under visible light illumination, which may result in higher photocatalytic activities. Electrons generated by conducting PoPD can be transferred to the conduction band of TiO2, enhancing charge separation and promoting the photocatalytic ability of the P/T(1/4). On the other hand, owing to the synergetic effect of the well-matched energy levels of TiO2 and PoPD, PoPD/TiO2 hinders the recombination of the hole and electron to generate more ROS that degrade MB. P/T(1/4) nanocomposites is capable of improving separation efficiency and effectively inhibit the electron-hole pair recombination
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