Study On The Preparation And Photocatalytic Activity Of Bi₂WO₆/TiO₂

Environmental pollution is one of the problems to hinder human sustainable development, and the new green technology, photocatalysis, is expected to become an effective way to solve this crisis.The catalysts of bismuth, like Bi₂WO₆ as a representative of the narrow band system, has been demonstrated to be a visible-light or solar-light driven photocatalyst. Therefore, the development of this material is one of the key issues for researchers. TiO₂, as a kind of traditional wide-band-gap semiconductor, possseses unique advantages and excellent catalytic activity. In this paper, we reported the composites of the Bi₂WO₆ and TiO₂, aimed to prepare an kind of efficient visible-light or solar-light driven photocatalyst. Moreover, the catalysts were characterized by modern characterization techniques such as XRD, SEM, BET, Uv-vis and PL, in order to discuss the crystal phase, morphology, surface properties, solar absorption properties and optical properties. To evaluate the photocatalytic activities of the synthesized samples, the simulative Rhodamine B solution photodegradation were investigated under visible light irradiation. The main contents of this study related is as the following:?1? The Bi₂WO₆/TiO₂ heterostructure catalyst was synthesized by a facile hydro thermal step.The factors,such as the composite amount of TiO₂ precursor solution pH?hydrothermal reaction time and surfactant, were studied by series of experiments and characterization. The results showed that:when the composite maas amount of TiO₂ was 25%, the precursor solution was pH=5, the hydrothermal reaction time last 18 hours and used PVP as surfactants, the sample could be indexed to orthorhombic phased Bi₂WO₆ and mixed anatase and rutile phased TiO₂. It showed fluffy flower-like-sheet hollow porous structure and narrow gap-type internal pore structure, with a large specific surface area ?37.670 m2/g?. In addition, it possessed more efficient absorption of visible light ?Eg=2.82 eV? and the quite higher separation rate of light-generated electron-hole pairs.?2? Moreover, modified Bi₂WO₆/TiO₂ heterojunction catalyst powder using some suitable metal ions. The results indicated that:Fe³⁺ ions modified Bi₂WO₆/25%TiO₂ exhibited superior catalytic performance; the loading amount of Fe³⁺ ions has a great effect on light absorption properties and optical properties of Bi₂WO₆/TiO₂ heterostructure photocatalysts. Adjusting the loading mass amount of Fe³⁺ to 1.0%, the sample showed enhanced photocatalytic activity?reaction rate constant and stability. When the calcination temperature was 350? and the pH of precursor solution was 3, the specific surface area was greater than uncalcined one ?from 37.451m2/g to 42.991m2/g?. The absorption ability of visible-light was improved, the recombination rate of photoexcited electron-hole pairs was minimized greatly.?3? Adjusting the technology conditions, such as 1.0%Fe³⁺-Bi₂WO₆/25%TiO₂ catalyst dosage, initial pH and concentration of Rhodamine B solution, discuss influences on the degradation of Rhodamine B solution. The results indicated that:adding O.lg 1.0%Fe³⁺-Bi₂WO₆/25%TiO₂ photocatalysts powders to 100 mL initial solution Rhodamine B solution ?pH=7, C=20 mg/L? the degradation rate was up to 99.86% after 25 min.?4? Apparent kinetic model was established over the photocatalytic degradation reactions.In addition, the tentative photocatalytic mechanism was proposed over the Bi₂WO₆/25%TiO₂ and modified 1.0%Fe³⁺-Bi₂WO₆/25%TiO₂ heterostructure photocatalysts.