Transformed construction from type-II WO3/BaTiO3 heterojunction to Z-scheme WO3/Ba0.5Sr0.5TiO3 and WO3/SrTiO3 photocatalytic systems: Enhanced photocatalytic activity and mechanism insight.

In this study, type-II heterojunction WO 3 /BaTiO 3 and Z-scheme WO 3 /SrTiO 3 or WO 3 /Ba 0.5 Sr 0.5 TiO 3 nanocomposite photocatalysts were constructed for photodegradation of organic pollutants in wastewater under visible light. The photocatalytic performance of three WO 3 /titanate systems were estimated. Some influencing factors such as molar ratio of WO 3 and titanates, light irradiation time, catalyst dose, and initial concentration of organic pollutants on the photocatalytic activity were investigated. The stability and reusability of three WO 3 /titanates systems were examined. Moreover, the production of some radicals in the three WO 3 /titanates photocatalytic systems was demonstrated, and the three WO 3 /titanates photocatalytic reaction mechanisms were compared. The results reveal that the configurations of WO 3 /titanates photocatalytic systems are transformed from type-II heterojunction WO 3 /BaTiO 3 with lower activity to Z-scheme WO 3 /SrTiO 3 and WO 3 /Ba 0.5 Sr 0.5 TiO 3 with higher activity via the change of titanates. The WO 3 /titanate nanocomposites show higher photocatalytic activity at 3.0:1.0 M ratio of WO 3 and titanates, and WO 3 /Ba 0.5 Sr 0.5 TiO 3 nanoparticles have superior photocatalytic activity. The order of photocatalytic activity is as follows: WO 3 /Ba 0.5 Sr 0.5 TiO 3 > WO 3 /SrTiO 3 > WO 3 /BaTiO 3. Several organic pollutants, such as rhodamine B, methyl parathion, direct brilliant yellow-4R, and methylene blue, can be efficiently degraded using WO 3 /Ba 0.5 Sr 0.5 TiO 3 under visible light, and the RhB has higher degradation rate. After four cycles, WO 3 /titanate nanocomposites still have relatively high stability and reusability. •OH plays a major role in three WO 3 /titanates photocatalytic degradation. It is expected that the Z-scheme WO 3 /Ba 0.5 Sr 0.5 TiO 3 photocatalytic technology creates a good foreground for disposing of dyes and pesticides in water and wastewater. [ABSTRACT FROM AUTHOR]