Novel flake-like Z-Scheme Bi2WO6-ZnBi2O4 heterostructure prepared by sonochemical assisted hydrothermal procedures with enhanced visible-light photocatalytic activity

Abstract In this work, novel Bi2WO6-ZnBi2O4 p-n heterojunction was successfully synthesized through combination of sonochemical and hydrothermal procedures. The results revealed that the sonochemically prepared nanocomposites had spherical shape with amorphous structure which became crystalline particles with flak-like morphology after hydrothermal treatment. Bi2WO6-ZnBi2O4 nanocomposite with 20 wt% ZnBi2O4 content demonstrated the highest photocatalytic performance compared to the pure Bi2WO6 and ZnBi2O4 samples toward the degradation of Malachite Green (MG). This finding is associated with the efficient separation of photo-generated electron/hole pairs due to the formation of interfacial charge transfer between Bi2WO6 and ZnBi2O4. However, further ZnBi2O4 loading had no significant effect on the enhancement of photocatalytic activity of nanocomposite samples owing to the shielding effect of ZnBi2O4 against incident light. The obtained results were further verified by optical and photocurrent density measurements. Based on the obtained results from active species trapping experiments, electron spin resonance and Mott-Schottky calculations, the Z-scheme charge transfer pathway was proposed as the predominant mechanism for the photocatalytic reactions. Also, the photocatalytic degradation of 2,4-dichlorophenol, as a colorless model pollutant, was conducted on optimal composite sample to study the possible contribution of MG dye sensitization mechanism in the enhancement of photocatalytic efficiency.