Tungsten Oxide Semiconductor Photocatalyst

The narrow band gap (about 2.7eV) of WO₃ makes it have better absorption in visible light area, which is obviously superior to the traditional TiO₂ photocatalyst, but it also has the disadvantages of high carrier recombination rate and low visible light photocatalytic activity. The separation efficiency of photogenerated electron hole pair of WO₃ can be improved by the control of graphene recombination, crystal structure and morphology, and then the photocatalytic activity can be improved.

Graphene can be tightly wrapped on the surface of nano semiconductor oxide, and its thickness can be achieved by controlling the amount of graphene input. In addition, graphene special wrapping way retains the adsorption capacity of semiconductor oxide, which is conducive to the mass transfer of reaction process. In general, the introduction of graphene is conducive to photogenesis. The separation of electron hole pair can improve the physical structure and light absorption performance of semiconductor catalyst, so as to expand its absorption range in visible light and improve the efficiency of photocatalysis.

The results show that the hollow microsphere tungsten oxide can be obtained by calcining SrWO₄ microsphere immersed in concentrated nitric acid. In a certain range, with the increase of calcination temperature, the crystal size and pore diameter of the catalyst will increase correspondingly, and the photocatalytic activity will increase. The precursor of tungsten oxide is synthesized by coprecipitation method with H₄2N₁₀O₄2W12 · xH₂O and NH₂CONH₂ as raw materials, and then calcined at different temperatures. The results showed that the catalyst calcined at 500 ℃ showed the best photocatalytic activity, and the degradation effect of Congo red (CR), rhodamine (RHB) and indigo carmine (IC) was enhanced under UV irradiation.

WO₃ / TiO₂ composite film and single TiO₂ film (p-tio2) were prepared by micro arc oxidation method. The surface of the two films is rough and porous, but the number of holes in WO₃ / TiO₂ film is more and the distribution is more uniform. Compared with p-tio2 film, WO₃ / TiO2 film has a wider light absorption range, a better separation effect between photogenerated electrons and holes, a higher surface acidity, and a strong ability to adsorb organic matters and hydroxyl groups. The high photocatalytic activity of WO₃ / TiO₂ film is due to its high specific surface area, better electron hole separation effect and higher surface acidity.

Tungsten oxide nanowires were synthesized by electrospinning. The smooth WO₃ nanowires, which are composed of small grains, exhibit high activity in the degradation of rhodamine under the visible light with the wavelength of 420 nm. Electrospinning is an effective way to synthesize new visible light catalysts at present because of its simple operation and strong controllability.

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