Improving visible-light photocatalytic activity of N-doped TiO2 nanoparticles via sensitization by Zn porphyrin

In order to utilize visible light more efficiently in the photocatalytic reaction, N-doped TiO2 (N-TiO2) nanoparticles sensitized by Zn porphyrin including [tetrakis(4-carboxyphenyl)porphyrinato]zinc(II) (ZnTCPP) and [tetraphenyl-porphyrinato]zinc(II) (ZnTPP) were prepared, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectrometry (AAS), Fourier transform infrared spectroscopy (FT-IR) and UV-vis spectroscopy, etc. The characterization results show that the ZnTCPP is chemisorbed on the surface of TiO2 through an OCOTi bond; while the ZnTPP is physically adsorbed. N-TiO2 sensitized by Zn porphyrin exhibits higher absorption in the visible-light region and photocatalytic degradation efficiency of methylene blue under visible-light irradiation than N-TiO2 and TiO2 sensitized by ZnTCPP. Moreover, their visible-light photocatalytic mechanism was discussed.