Synthesis of TiO2/g-C3N5 heterojunction for photocatalytic degradation of methylene blue wastewater under visible light irradiation: Mechanism analysis

TiO2/g-C3N5 heterojunction is synthesized by the simple method, which is used in photocatalytic degradation methylene blue (MB) under visible light irradiation. The characterization analysis indicates that TiO2/g-C3N5 has good crystallinity, and the heterojunction between TiO2 and g-C3N5 is formed with good MB photocatalytic degradation performance. The MB photocatalytic degradation removal of the TiO2/g-C3N5 is 97.4 % at the concentration of 20 mg/L, which is significantly improved compared to the TiO2 and g-C3N5. The visible light adsorption ability and the separation of photogenerated carriers of the TiO2/g-C3N5 are improved, which is beneficial to the MB photocatalytic degradation. TiO2/g-C3N5 has good reusability with 95.8 % of the initial removal after 5 cycles. The capture experiment and electron paramagnetic resonance spectroscopy analysis indicate that the existence of the h+, O2− and OH involves in MB photocatalytic degradation process. MB photocatalytic mechanism of the TiO2/g-C3N5 is consistent with the direct Z scheme mechanism based on the band gap structure calculations.