Synthesis of Z-scheme Ag4V2O7/Ag3VO4/GO nanocomposites for photocatalytic degradation of DDT under visible light

Abstract

The direct Z-scheme Ag₄V₂O₇/Ag₃VO₄/GO (AVGZ) nanostructure was successfully synthesized using a hydrothermal method with microwave-assisted techniques. The obtained AVGZ catalyst was characterized by XRD, TEM, EDX, UV-Vis, PL, and XPS methods. The characterization results showed that under controlled pH conditions, the orderly stacking of vanadium oxide tetrahedron formed Ag₄V₂O₇ nanoparticles (NPs) on the surface of Ag₃VO₄ nanorods (with a diameter of 50–200 nm). Interestingly, the AVGZ exhibited absorbance in the visible light region at 470–550 nm wavelengths. The photocatalytic performance of AVGZ was evaluated by the degradation of dichloro-diphenyl-trichloroethane (DDT) under LED visible light irradiation. Compared to the Ag₃VO₄/Ag₄V₂O₇ nanostructure material, AVGZ showed much higher activity in the degradation of DDT under the same reaction conditions. The optimal conditions were determined to be a catalyst concentration of 0.5 g L⁻¹, pH 6.0, and reaction time of 4 hours, achieving a DDT degradation efficiency of 95.46%, according to the analysis using the response surface methodology (RSM) based on the central composite design (CCD) method. The DDT degradation efficiency was higher compared to Ag₃VO₄/GO (89.4%) and Ag₃VO₄ (82.1%), respectively. Scavenging experiments were conducted to study the photocatalytic mechanism using the spin trapping technique (EPR). The results indicated that ·OH and ·O₂⁻ radicals were the primary oxidizing agents in the photocatalytic reaction process on the AVGZ catalyst. The formation of a heterojunction and the addition of GO accelerated electron–hole pair separation, enhancing the durability and efficiency of the photocatalysts. Furthermore, the Z-scheme mechanism of the AVGZ photocatalyst was also proposed, demonstrating its potential application for DDT degradation under LED visible light.