Preparation of porous nitrogen-doped titanium dioxide microspheres and a study of their photocatalytic, antibacterial and electrochemical activities

Nitrogen-doped titanium dioxide (N-doped TiO2) microspheres with porous structure were prepared via the nitrogen-assisted glow discharge plasma technique at room temperature for the first time. The samples were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption measurement, UV–Vis diffuse reflectance spectra, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The results indicated that the plasma treatment did not affect the porous structure of the TiO2 microspheres. With the plasma treatment, the N contents in the samples increased. During the photocatalytic degradation of methylene blue under simulative sunlight irradiation, the sample after plasma treatment for 60 min (N-TiO2-60) exhibited higher photocatalytic activity than those of the TiO2 microspheres, P25 and other N-doped TiO2 microspheres. Furthermore, the N-TiO2-60 showed excellent antibacterial activities towards Escherichia coli under visible irradiation. These should be attributed to the enhancement of the visible light region absorption for TiO2 after N-doping. Electrochemical data demonstrated that the N-doping not only enhanced the electrochemical activity of TiO2, but also improved the reversibility of Li insertion/extraction reactions and the rate behavior of TiO2 during charge–discharge cycles.