An insight on the role of PVP in the synthesis of monoclinic WO3 with efficiently photocatalytic activity.

Nanoparticles of monoclinic WO3 were synthesized by a facile method using Na2WO4 as raw material and PVP 70 000 (polyvinylpyrrolidone) as surfactant and template. The effect of PVP on the structure and photocatalytic activity of the synthesized WO3 was discussed in detail. The prepared samples were characterized by XRD, SEM, FT-IR, UV-vis, XPS, PL techniques, and the results show that the visible light is strongly absorbed by the obtained samples, whose particle size varies from 38 to 85 nm. The photocatalytic properties of the resulted samples were evaluated using RhB in water as a target substance, and results illustrate that 30 mg l-1 of RhB can be efficiently photodegraded by nano WO3 under visible light irradiation. Based on the results of XPS, PL and photocalysis experiments, the reason of such improved photocatalytic efficiency may be attributed to the reducing activity of PVP, which leads to the formation of oxygen vacancies beneficial for the capture of photoelectrons and the generation of superoxide radicals. Furthermore, the results show that the photocatalytic efficiency is greatly influenced by the morphology of the synthesized WO3 samples, and the WO3 with a block-shaped morphology is an ideal photocatalyst for the degradation of RhB under visible light irradiation.