Fabrication of g-C3N4/Bi2WO6 as a direct Z-scheme excellent photocatalyst

To improve the photocatalytic efficiency of Bi2WO6, two types of g-C3N4 nanomaterial, g-C3N4 quantum dots and g-C3N4 nanosheets, were incorporated with Bi2WO6 to construct two kinds of g-C3N4/Bi2WO6 Z-scheme photocatalysts with excellent photocatalytic activity. The results showed that the g-C3N4 quantum dots were uniformly distributed over the whole surface of Bi2WO6, inhibited the Bi2WO6 sheets from growing, and resulted in high specific surface area and more active sites. Conversely, the stronger electrostatic interaction between g-C3N4 and Bi2WO6 nanosheets led to the formation of a dense and uniform flower-like structure with small specific surface area. All the g-C3N4/Bi2WO6 composites showed higher photocatalytic activities than pure Bi2WO6. The g-C3N4 quantum dots/Bi2WO6 composite showed better photocatalytic activities towards the degradation of organic dyes, such as methylene blue and acid fuchsin, while the g-C3N4 nanosheets/Bi2WO6 composite showed better photocatalysis decomposition of antibiotics including ciprofloxacin and tetracycline. The enhanced photocatalytic activity of the g-C3N4/Bi2WO6 composites under sunlight irradiation could be ascribed to a Z-scheme mechanism based on the radical trapping experiments and electron spin resonance, thereby revealing that the holes played a major role in photocatalytic performance.