A direct Z-scheme polypyrrole/Bi2WO6 nanoparticles with boosted photogenerated charge separation for photocatalytic reduction of Cr(VI): Characteristics, performance, and mechanisms

Creating specific photoinduced carriers transport pathways is an important means of improving the photocatalytic performance. Here, we report a simple modification strategy: in-situ deposition of polypyrrole (PPy) onto Bi2WO6 (BWO) surface. The close contact between the interface of BWO and PPy as well as the appropriate band structure made it form a bult-in electric field, thus driving the direct Z-scheme charge transfer. The Cr(VI) reduction efficiency was 99.7% in 15 min under visible light irradiation, with the reduction rate constant reaching 0.221 min−1, which was about 19.2 times that of the bare BWO. The mechanism study showed that the Z-scheme heterojunction structure between PPy and BWO can effectively separate and transfer photogenerated charges, retain stronger redox ability of the system, and improve the photocatalytic performance. In addition, considering the complexity of the actual water environment, the effect of pH value and several substituted benzenes on the reduction of Cr(VI) were studied, and the relationship between the property and structure of substituted benzenes and Cr(VI) reduction rate were determined. We hope this work can provide a new sight toward designing a direct Z-scheme heterostructure and visible light photocatalytic activity of Cr(VI).