Efficient TiO2/SubPc photocatalyst for degradation of organic dyes under visible light

In this work, H12SubPcB-Br (SubPc1) and p-hydroxybenzaldehyde were used for the synthesis of novel axially substituted subphthalocyanine H12SubPcB-OPhCHO (SubPc2). The photocatalyst hybrids TiO2/H12SubPcB-OPhCHO (TiO2/SubPc2) with different TiO2 amounts were obtained by a solvothermal method. The structure of SubPc2 was determined by single-crystal X-ray diffraction analysis and TiO2/SubPc2 was characterized by FT-IR, UV-vis, PXRD, SEM and XPS. Furthermore, the DFT and TD-DFT calculations were studied to analyze the electronic structure and optical properties of SubPc2. The photocatalytic degradation performance of all the samples was evaluated by analyzing the decomposition of methyl orange (MO), bromophenol blue (BB), methylene blue (MB) and acid magenta (AM) under visible light irradiation. It was demonstrated that SubPc2 acted in the role of sensitizer for pristine TiO2, and the optimal concentration was TiO2/SubPc2 = 25 : 1, and the calculated rate constant values were 0.68617 h−1, 1.41395 h−1, 1.00701 h−1 and 1.39237 h−1 for MO, BB, MB and AM, respectively. The enhancement of the photocatalytic performance of TiO2/SubPc2 was attributed to the extension of the photoactivity of the materials into the visible range and separation of the photogenerated electron–hole pairs. Moreover, the photocatalytic activity of the as-prepared composite was maintained at 90.11% after five cyclic stability degradation experiments, which was 4.5 times more when compared with the bare TiO2.