Facile synthesis of TiO2/g-C3N4 nanosheet heterojunctions for efficient photocatalytic degradation of tartrazine under simulated sunlight

In this study, TiO2/g-C3N4 nanosheet heterojunctions were successfully fabricated via a facile hydrothermal process and demonstrated to be effective catalyst for tartrazine (TTZ) degradation. The synthesized catalyst was characterized by several analytical methods, including TEM, XRD, UV-DRS, BET, FT-IR, PL, XPS and a series of electrochemical characterizations. The photodegradation of tartrazine (TTZ) under simulated sunlight by TiO2/g-C3N4 is reported for the first time. The TiO2/g-C3N4 composites displayed more excellent photocatalytic performance than pure g-C3N4 and TiO2. The effect of initial TTZ concentration, catalyst dosage, pH and impurity ions on the degradation efficiency were systematically investigated. Under the optimal experimental conditions, the degradation rate still remained about 93% even after 4 cycles, confirming the relatively stable activity of TiO2/g-C3N4. Besides, the free radical scavenging experiments demonstrated that superoxide radical (•O2−) and photogenerated holes (h+) were indispensable active substances for the TTZ degradation. Meanwhile, ultraviolet–visible spectroscopy analysis evidenced that the azo bond (NN) in the TTZ molecule was destroyed during the photocatalytic reaction. Finally, the reaction mechanism and specific steps of TTZ degradation have been inferred in detail. This study provided a valuable reference for the application of composite heterojunction materials in the degradation of pollutants under solar light.