Enhanced photoelectric property and visible activity of nitrogen doped TiO2 synthesized from different nitrogen dopants

N doped TiO2 nano-particles were synthesized through simple sol–gel reactions from different nitrogen dopants. The resulting materials were characterized by X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) and surface photovoltage spectroscopy (SPS). Furthermore, the photoelectric property and activity enhanced mechanism were investigated in detail. It was found that the introduction of N dopants could effectively inhibit the crystal growth of TiO2 nano-particles, enhance the light absorption in visible region, possess more surface hydroxyl groups and separate the photoinduced charge carriers. The effects of dopants on the photocatalytic activity for the degradation of rhodamine B (RhB) were investigated in detail. It is clearly demonstrated that the photocatalytic activity of image nano-particle was higher than that of image and undoped TiO2. The enhanced photocatalytic activity could be attributed to the smaller crystal size, more hydroxyl groups on surface of the catalyst, stronger light absorption in visible region and higher separation efficiency of photoinduced charge carriers.