Fabrication of FeWO₄@ZnWO₄/ZnO Heterojunction Photocatalyst: Synergistic Effect of ZnWO₄/ZnO and FeWO₄@ZnWO₄/ZnO Heterojunction Structure on the Enhancement of Visible-Light Photocatalytic Activity

One-dimensional FeWO 4 @ZnWO 4 /ZnO heterojunction photocatalysts were prepared by a two-step hydrothermal method. The heterojunction structure was formed through the dispersing of FeWO 4 nanoparticles on the surface of ZnWO 4 /ZnO nanorods. The FeWO 4 @ZnWO 4 /ZnO photocatalyst possessed strong visible light absorption capacity. The photocatalytic activities of the prepared photocatalysts were evaluated by degradation of rhodamine B (RhB), methylene blue (MB), and phenol under visible light irradiation. Remarkably, the FeWO 4 @ZnWO 4 /ZnO composite showed superior photocatalytic activity than that of individual FeWO 4 and ZnWO 4 /ZnO substrate. The enhanced photocatalytic activity could be attributed to the interfacial transportation of photogenerated holes between FeWO 4 and ZnWO 4 /ZnO substrate, leading to more effective separation and faster transfer of carriers in the heterostructures, which was confirmed by photocurrent responses and photoluminescence spectral analysis. Radical trapping experiments indicated that hydroxyl radicals ( • OH) are the major reactive species. Moreover, a possible mechanism for the excellent photocatalytic activity of FeWO 4 @ZnWO 4 /ZnO composites was proposed.