Titanium Dioxide-Tungsten Trioxide Composite Photocatalyst

Semiconductor-catalyzed photocatalytic degradation of organic pollutants has become an ideal technology for environmental pollution control due to its unique properties such as complete mineralization of various organic pollutants and no secondary pollution by direct use of sunlight at room temperature. At present, photocatalytic semiconductors, such as titanium dioxide, SnO₂, CdS and ZnO, are widely studied and used.

Compared with conventional photocatalysts, tungsten trioxide usually exhibits low photocatalytic activity, but it has many physical and chemical properties, such as easy purification, small band gap (2.2-2.8eV), and can effectively absorb ultraviolet and visible light. Therefore, tungsten trioxide has attracted wide attention in the field of photocatalysis. The preparation of composite catalysts by doping titanium dioxide into tungsten trioxide powders is currently highly recommended. The synthesis of such composite catalysts includes the following steps:

Step 1: Prepare yellowish tungsten trioxide powder:
Sodium tungstate was dissolved in 30 mL distilled water, stirred, and made into a solution. The solution was dripped with 4 mol/L hydrochloric acid until no new precipitation was produced in the upper solution. The yellowish tungsten trioxide powder was obtained by standing, filtering, washing, drying and scorching.

Step 2: Preparation of titanate colloid solution:
The solution of 5% Ti(0ch (CH₃)₂)₄ in ethanol was added to the hydrochloric acid solution with pH value of 1.5 dropwise, and then stirred for 0.5h to obtain titanate colloid solution.

Step 3: Preparation of titanium dioxide doped tungsten trioxide powder:
The pale yellow tungsten trioxide powder was added to the titanate colloid solution, stirred vigorously for 0.5 h at room temperature, dried in vacuum at 80 ℃ and placed in a muffle furnace, then burned at high temperature for 3 h to prepare titanium dioxide doped tungsten trioxide powder.

The results show that the titanium dioxide-tungsten trioxide composite photocatalyst prepared by colloidal impregnation of titanate has good thermal stability. Ti atoms enter the tungsten trioxide octahedron structure. Even after calcination at 550 ℃, the Ti-O-W bond does not break, and the components are still miscible at the molecular level. This shows that the photocatalytic performance of the product doped with titanium dioxide is obviously stronger than that of pure tungsten trioxide, and the photocatalytic performance is strongest when the doping ratio of titanium dioxide is about 5%.

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