Preparation and characterization of novel Ag/Ag2WO4/ZnWO4 heterojunctions with significantly enhanced sunlight-driven photocatalytic performance

In this paper, a series of Ag/Ag2WO4/ZnWO4 heterojunction photocatalysts were fabricated by a facile hydrothermal method. The specific surface area, structure, morphology and separation rate of photo-induced charge pairs of the as-prepared heterojunction photocatalysts were characterized by various experimental methods. The photocatalytic performance of heterojunction photocatalysts was evaluated by decolorization of rhodamine B (RhB) aqueous solution under simulated sunlight irradiation. The results reveal that Ag/Ag2WO4/ZnWO4 heterojunction photocatalysts exhibit higher specific surface area, separation efficiency of photo-induced charge pairs and photocatalytic performance than that of the reference ZnWO4. The photocatalytic evaluation results further illustrate that the sample with a molar ratio of Ag/Zn = 2% holds the highest activity. The trapping and ESR experiments illustrate that center dot O-2(-) is primary active free radicals in the degradation process of RhB, which can be attributed to the presence of Ag-0 in the heterojunctions. According to all the experimental results, a Z-scheme charge separation and transfer mechanism has been proposed to explain the relationship between the enhanced photocatalytic performance and the photoinduced carrier's separation and transfer process of Ag/Ag2WO4/ZnWO4 heterojunction photocatalyst.