Visible light active dye-sensitizing titanium dioxide/graphene composites with excellent photocatalytic activity

TiO2/rGO (TG) composites were synthesized using a hydrothermal reduction method, with titanium dioxide and graphene as the starting materials. Subsequently, dye-sensitizing titanium dioxide/graphene photocatalytic composites, named DTG and APTG, were prepared by covalently attaching C.I. Direct Black 17 or C.I. Acid Violet 3 dye onto TG. The composites were characterized using FTIR, TEM, UV-vis DRS, EDS, and Raman spectroscopy. The EDS surface scanning results of APTG and D2.70TG composites have shown that Ti and S atoms are uniformly distributed on the graphene sheets. The presence of characteristic peaks for S2p and N1s near 166 eV and 399 eV in D2.70TG and APTG was intensified compared to those of TG composites. The grafting rate reached its peak when the amount of C.I. Direct Black 17 was 2.70 and the fixed amount of TG was 0.1 g. The UV-vis diffuse reflectance spectroscopy study results demonstrated a shift in the response range to visible light after dye modification for DTGs and APTG. Photocatalytic experiments showed that D2.70TG was capable of removing over 99% of MB within 1 hour. Furthermore, after 5 cycles of photocatalytic experiments, the removal rate of MB remained at above 95%.