Preparation of TiO2-Graphene Composite by a Two-Step Solvothermal Method and its Adsorption-Photocatalysis Property

TiO₂-graphene (TiO₂-GR) composites were successfully prepared by a two-step solvothermal method using titanium dioxide and natural graphite powder. X-ray diffraction (XRD) patterns showed that graphene oxide (GO) was prepared from natural flake graphite by a modified hydrothermal pressurized oxidation method. The results of Fourier transform infrared spectroscopy (FTIR) proved that TiO₂-GR composites were synthesized during the process of hydrothermal reaction while GO was changed into graphene. X-ray photoelectron spectroscopy (XPS) demonstrated that TiO₂ particles contacted closely with graphene via Ti–O–C bonds. The results of Raman spectra confirmed the existence of graphene in the TiO₂-GR composite. Scanning electron microscopy (SEM) images showed that TiO₂ particles were oval and grafted on the graphene sheet which was smooth with ripples. UV-visible diffuse reflectance spectra demonstrated that there was a red shift in the absorption edge of TiO₂-GR composite. The experimental results indicated that the TiO₂-GR composite had significantly adsorption-photocatalytic activity for the degradation of methylene blue (MB) dyes. The adsorption capacity (q ₘₐₓ) of TiO₂-6%GR-4h for MB was 41.32 mg ⋅ g⁻ ¹ calculated based on the Langmuir adsorption model, which was about 3.3 times the adsorption capacity of TiO₂. Adsorption kinetics studies showed that the adsorption process fit well with the pseudo-second-order model. It proved that the TiO₂-GR composites were more efficient than the pure TiO₂ in the field of environmental protection.