Facet-engineered surface and interface design of WO3/Bi2WO6 photocatalyst with direct Z-scheme heterojunction for efficient salicylic acid removal

WO3 ((0 0 1)) and WO3 ((0 0 1)&(1 1 0)) were initially grown on the surface of Bi2WO6 ((0 1 0)) nanoplates via simple hydrothermal route, respectively. Compared to WO3 ((0 0 1))/Bi2WO6, the developed WO3 ((0 0 1)&(1 1 0))/Bi2WO6 was endowed with the stronger interfacial interaction property. Moreover, the developed composite could present a broad visible light response at an absorption edge of 440 nm. Not only that, the optimized interfacial carriers were newly achieved, leading to the enhanced separation and transfer of photogenerated electron-hole pairs. The resulting WO3 ((0 0 1)&(1 1 0))/Bi2WO6 was implemented to salicylic acid removal (up to 74.5%) under visible light irradiation, demonstrating a kinetics of about 2.4 times faster than that of WO3 ((0 0 1))/Bi2WO6. The significantly improved photocatalysis of developed composite was attributed to the conversion from traditional heterojunction to Z-scheme heterojunction, thus, promoting the oxidation ability of photogenerated holes so as to engender abundant center dot OH. Ultimately, based on the analysis of energy band structures, the migration pathways of photogenerated carriers in composites was explained. Noticeably, it may open a new door towards the Z-scheme strategy of compound photocatalyst without any electronic mediators via controllable facet exposure engineering for highly photocatalysis.