Tungsten Trioxide Preparation by One-step Hydrothermal Synthesis

Metal oxides play a key role in the development of many advanced functional materials and smart devices. Among many metal oxides, tungsten trioxide (WO₃) is a unique material. It is a N-type semiconductor with a wide range of crystal forms, band gap of 2.5-2.8eV, and has visible light response characteristics. Therefore, WO₃ can be used as light sensor devices, such as photochromic devices and transparent electrodes; at the same time, WO₃ can also be used as visible light photocatalyst, using photodynamic degradation of organic pollutants and heavy metal ions in sewage, which is environmentally friendly and economical; in indoor environment detection, WO₃ can be used as a gas sensor.

The synthesis method is very important for the final performance of tungsten trioxide. There are solid phase method and liquid phase method. The representative of liquid phase method is hydrothermal synthesis method. According to different academic research, hydrothermal synthesis methods can also be categorized. For example, some scholars have adopted a self-created hydrothermal synthesis method of tungsten trioxide. The synthesis process is one-step hydrothermal synthesis method. WO₃ with different morphology and photoelectric properties can be prepared by adjusting the concentration of sodium tungstate and the pH value of the precursor. The details are as follows:

(1)Sodium tungstate dihydrate and sodium chloride were added into water, and the pH value of the solution was adjusted to 1.5 by hydrochloric acid under magnetic stirring. The precursor solution was obtained by stirring for 1 h.

(2)Transfer the precursor solution to the reactor, react at 180 C for 24 hours, and then cool it to room temperature. The products are washed with distilled water and anhydrous ethanol in turn, dried after centrifugation, and WO₃ powder is obtained.

X-ray diffraction patterns of WO3 powders synthesized showed that WO₃ flower-like microspheres with particle size of 2-3 microns were obtained at pH=1.5. The samples were absorbed in visible light region, and the response to light extended to 480 nm. The peak response to light reached 350 mV, which had strong photoelectric response. WO₃ powders were used as catalysts to catalyze the degradation of 20mL when the amount of WO₃ was 0.02g. When the concentration of rhB was 10 mg/L, the degradation rate of rhB was 60% under mixed light irradiation for 1 hour.

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