Influence of TiO2 morphology on adsorption-photocatalytic efficiency of TiO2-graphene composites for methylene blue degradation

Solvothermal process had been used to obtain different morphological TiO2 and their graphene (GR) composites. The materials were characterized by X ray diffraction (XRD), field emission scanning electron microscopy (FESEM), fourier transform infrared spectroscopy (FTIR), brunauer-emment-teller (BET) and ultraviolet-visible diffuse reflectance (UV-vis DRS). FTIR revealed that the covalent bonds had been formed between Ti-O and carbon atoms at the surface of GR. The diameter of TiO2 nanorods (TNR) was 43-103 nm, and the length of TNR was 0.2-4.5 pm. The width of TiO2 nanosheets (TNS) was 50-180 nm, and the thickness of TNS was 6-18 nm Both of TNS and TNR were combined with GR in the form of agglomerates. The adsorption-photocatalytic activities of TiO2 nanorods (TNR), TiO2 nanosheets (TNS), TNR-GR and TNS-GR for methylene blue (MB) followed the order of TNS-GR > TNS > TNR-GR > TNR. The kinetic studies showed that the photocatalytic degradation process fitted well with the pseudo-first-order model. The band gaps of TNR-GR and TNS-GR had been decreased to 0.07 eV and 0.08 eV compared with that of TNR and TNS respectively, as measured from UV-vis DRS patterns. The decrement of the band gap was relative to the amount of Ti-O-C bonds between GR sheets and Ti-O broken bonds. Based on the proposed mechanism, the obtained result suggested the enhanced adsorption-photocatalytic property was attributed by Ti-O-C bands.