Controllable preparation of three-dimensional porous WO₃ with enhanced visible light photocatalytic activity via a freeze-drying method

Three dimensional porous WO₃ was fabricated by a novel freeze-drying method using a polyvinyl alcohol (PVA)/phosphotungstic acid (H₃PW₁₂O₄₀) aqueous solution as the precursor followed by calcination. Results revealed that WO₃ interconnected porous structures have channels of 3–10 µm and wall thicknesses of about 0.68 µm. Interestingly, the morphology and porous structure of WO₃ samples can be well controlled by the amount of PVA and calcination temperature. To further demonstrate their potential application in photocatalysis, their photocatalytic activities for the photodegradation of Rhodamine B under visible light irradiation were investigated. It was found that the highest photocatalytic activity was obtained by using the WO₃ porous sample which prepared by fixing the addition amount of PVA at 7.5% (relative to solvent) and the calcination temperature at 800 °C. The enhanced photocatalytic performance of WO₃ can be attributed to the combined effects of increased surface area, the interconnected macroporous as well as the enhanced crystal quality.