Wide spectral response and enhanced photocatalytic activity of TiO2 continuous fibers modified with aminosilane coupling agents

• N–Si codoped TiO2 fibers modified with aminosilane coupling agents were prepared.
• N–Si codoping is responsible for a mesostructure and wide spectral response.
• γ-Aminopropyltriethoxysilane modified TiO2 fibers exhibit a higher photoactivity.
• The regenerated TiO2 fibers can be reused maintaining high photoactivity.

N–Si co-doped TiO2 continuous fibers were prepared by a modified sol–gel method combined with centrifugal spinning. Three aminosilane coupling agents, namely γ-aminopropyltriethoxysilane (APTES), γ-aminopropyltrimethoxysilane (APTMS) and N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES), were selected as novel different Si and N dopants. The fibers were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, and UV–vis diffuse reflectance spectroscopy (DRS). The results indicated that Si and N were incorporated into the lattice of TiO2. Si doping enhances surface area, delays the phase transformation from anatase to rutile and improves the UV photocatalytic activity, while N doping improves visible light absorption. In the case of APTES as a modifier at a Si/Ti molar ratio of 0.15, TiO2 fibers with a mixed crystalline phase at an anatase/rutile ratio of 77:23 and the largest Brunauer–Emmett–Teller (BET) specific surface area were obtained at 900 °C. It displayed the highest wide spectral responsive photoactivity, and the degradation rate of the azo dye reactive brilliant red X-3B in aqueous solution reached 96.6% for 90 min and 96.4% for 180 min under UV and visible light irradiation, respectively. In addition, the degradation efficiency was still maintained at >90% for 5 cycles. The resulting wide spectral responsive fibers possess enormous advantages in water treatment.