Highly efficient visible-light photocatalyst of nitrogen-doped TiO2 nanoparticles sensitized by hematoporphyrin

• TiO2 and N-doped TiO2 nanoparticles were sensitized with HP and characterized in different ways.
• Degradation under visible light was promoted to about 1.7 and 4.2 times after sensitizing.
• Degradation efficiency of MO exceeds 88.5% after 180 min treatment in an efficient photoreactor.
• Apparent first order kinetic was relevant for MO photocatalytic degradation under visible light.
• The catalytic activity of the new hybrid nanocomposite was nearly the same after four times of recycling.

A novel hybrid nanocomposite based on N-doped TiO2 nanoparticles was prepared and sensitized with hematoporphyrin for visible light utilization. The product was characterized by thermogravimetric analysis (TGA), different thermal analysis (DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area analysis, UV–vis spectroscopy and field emission scanning electron microscopy (FE-SEM). The results showed that the N-doped TiO2 has smaller crystalline size and larger specific surface area than bare TiO2 particles. Surface oxygen defects, produced by nitrogen doping, would improve the advantage of hematoporphyrin placement and then facile electron exciting and transferring to the conduction band of N-doped TiO2. The crystal structure of N-doped TiO2 was not affected by the sensitizing; however, the surface area was significantly increased. Application of the hybrid nanocomposite exhibited higher visible-light absorption leading to an enhancement of about 1.7 and 4.2 times in photocatalytic degradation of methyl orange compared with N-doped TiO2 and just bare TiO2 utilization, respectively. The photocatalytic degradation of methyl orange with the products was demonstrated to follow first order kinetic model. The produced nanocomposite can be reused at least four times recycling without significant loss of activity.

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