Tungstate Nanomaterials Preparation by Low Temperature Hydrothermal Method

Tungstate nanomaterials have been widely used in many fields, such as optics, electricity, magnetism, conductor/superconductor, catalysis, biology and so on. The synthesis methods of transition metal tungstate materials mainly include sol-gel method, copolymer-assisted synthesis method, inverted micelle soft template method, wet chemical method and solution synthesis method.

Some scholars have provided a low temperature hydrothermal preparation method for tungstic acid series nanometer photocatalytic materials. Include the following steps:

(1) Preparation of precursors:
A. Sodium tungstate (Na₂WO_4·2H₂O) and polyvinylpyrrolidone (PVP-30) were dissolved in 70 ml deionized water in proportion, and 4 mol/L hydrochloric acid solution was slowly added to the above mixed solution under sufficient stirring, and the pH was adjusted to 1.0.

B.After hydrothermal reaction, the precipitates were washed with deionized water and dried in vacuum for 12 hours at 80 C to obtain the precursor WO_3·0.33H₂O.

(2) Preparation of tungstate nanocrystalline photocatalyst:
A. The precursor prepared by weighing step (1) was added to 70 ml deionized water under magnetic stirring condition. After 10 minutes, 0.0569 g ammonium fluoride (NH₄F) was added to the above mixed solution, and the solution A was obtained by full stirring.

C.According to the stoichiometric ratio of different tungstates, the metal ion reactants were dissolved in nitric acid (HNO₃) solution with 3 mL concentration of 4 mol/L, and the solution B was obtained.

D.Mixing the solution A with solution B, adjusting the pH value of solution by 25% of the ammonia (NH_3·H₂O) for 7.

E.The mixed phase obtained from the above step C was transferred to a 100 ml polytetrafluoroethylene high-pressure reactor. After hydrothermal reaction, the tungstate nano-photocatalytic material was obtained by washing and drying.

Several nanostructured tungstate materials with controllable morphology can be prepared by adjusting parameters because of the advantages of simple process, simple operation and low cost.

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