Semiconductor Photocatalytic Material-Yellow Tungsten Oxide

What is tungsten oxide?

Tungsten trioxide is a light yellow triclinic powder crystal. When the temperature is higher than 740degC, it turns into orange tetragonal crystals, which return to the original state after cooling. It is stable in air, with a melting point of 1473degC, a boiling point higher than 1750degC, and a relative density of 7.16.

Tungsten trioxide is the most stable kind of tungsten oxide. It is insoluble in water and inorganic acids other than hydrofluoric acid. It can be dissolved in hot concentrated sodium hydroxide solution and ammonia water to form soluble tungstate. When the temperature is higher than 650, it can be reduced by H2 and can be decreased by C to obtain tungsten powder at 1000~1100.

Yellow tungsten oxide is a typical n-type semiconductor material. It is considered a photocatalytic semiconductor material with excellent development potential due to its high solar energy utilization, well visible light responsiveness and strong light corrosion resistance. It has been widely used in the fields of photolysis of water to produce hydrogen and catalytic degradation of organic pollutants.

The higher photo-generated electron-hole recombination efficiency on the surface of WO3 semiconductor is one of the main factors affecting its photocatalytic performance, which limits the industrial application of yellow tungsten oxide in the field of photocatalysis. However, because photocatalytic technology is considered to be one of the effective means to solve environmental pollution and energy crisis, photocatalytic reactions using semiconductors such as WO3 as catalysts have received widespread attention and aroused great interest from governments and scientists of various countries.

A method for improving the photocatalytic performance of yellow tungsten oxide

Researchers have proposed a method to improve the photocatalytic performance of yellow tungsten oxide-building a heterogeneous junction. This is currently one of the effective techniques to improve the electron-hole separation efficiency of photocatalysts. Through this method, the yellow tungsten oxide photocatalyst exhibits higher photocatalytic activity than a single crystal phase in the photocatalytic degradation of aquatic hydrogen production and pollutant degradation reactions. In recent years, people have successfully constructed heterogeneous junctions such as WO3/WO3*H2O.

WO3 is a polycrystalline phase material with a variety of crystal structures including orthorhombic phase (m-WO3), hexagonal phase (h-WO3), monoclinic phase and tetragonal phase. Among them, m-WO3 has a suitable bandwidth and good visible light response, so it is widely used in the field of photocatalysis. Moreover, the conduction band and valence band of h-WO3 are lower than those of m-WO3, so it is possible to construct monoclinic/hexagonal heterogeneous junctions (m-WO3/h-WO3) in WO3 materials. Improve the photocatalytic performance of WO3.

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