Synthesis of multi-walled carbon nanotubes/TiO₂ composites and their photocatalytic performance

TiO₂ is widely used in environmental pollution management, new energy conversion and sensors, etc. Broadening the spectral response range of nano-TiO₂ proves to be an effective research method to improve the photocatalytic performance of TiO₂ as the separation efficiency of electron-positron pair photoproduction can improve a lot. In this paper, multi-walled carbon nanotubes and isopropyl titanate are used as raw materials to synthesize TiO₂ photocatalyst supported on carbon nanotubes by sol-gel method. The catalyst is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman and ultraviolet-visible diffuse reflection spectrum (UV-vis DRS), etc. The photocatalytic degradation of methylene blue by 365 nm ultraviolet irradiation is observed to study the effect of different contents of TiO₂ loaded on carbon nanotubes on the photocatalytic activity of TiO₂. The experimental results show that the photocatalytic effect of TiO₂ has improves a lot when 2% TiO₂ is loaded on the carbon nanotube and its degradation rate of methylene blue reaches 90.6 %. After carbon nanotubes are loaded with TiO₂, their specific surface area, absorption capacity of visible light, photocurrent intensity, the lifetime of photogenerated electrons all increase. At the same time, the close interfacial contact between carbon nanotubes and TiO₂ causes the shortening of Ti-O bonds, which facilitates the separation of photogenerated electrons and holes, producing a large number of active groups such as h⁺, ·OH and super-oxygen free radicals that can effectively improve the photocatalytic properties of TiO₂.