Porous Tungsten Trioxide Nano Materials

Tungsten trioxide is a semiconductor nanomaterial with indirect band gap transition. It has good photoelectric and gas sensing properties. In order to make full use of the photoelectric properties of tungsten trioxide, porous tungsten trioxide nanomaterials with regular morphology and high specific surface area need to be prepared.

Electrochemical anodization is a low-cost method which can construct porous nanomaterials with adjustable pore size and regular morphology in a large area. Its basic principle is to use high purity metal as anode and another metal or carbon as cathode and put them into electrolyte. Under the action of applied electric field, the ions in electrolyte etch the metal surface of the anode and gradually accumulate into one. Metal oxides with definite morphology and structure.

Nano tungsten trioxide was prepared by electrochemical anodic oxidation method. The porous tungsten trioxide nano materials with uniform structure were prepared by self-assembly of molecule based on tungsten metal. The operation process was as follows:

The tungsten wafers were cut into 25 *50mm size, then sanded with 400 mesh, 600 mesh, 800 mesh, 1000 mesh and 1200 mesh sandpaper respectively, and connected with wires to form electrodes; the tungsten wafers were washed by ultrasonic wave in acetone, isopropanol, methanol and deionized water, and dried by nitrogen gas; 0.2wt% sodium fluoride (NaF) and 0.3% (V/V) hydrofluoric acid (HF) were mixed in a ratio of 1:1 and then poured into electricity. In the cell, the concentration of fluoride ion and hydrogen ion is 0.11mol/L and 0.086mol/L respectively.

With tungsten sheet as anode and platinum electrode as cathode, the temperature of the electrolyte is controlled to be constant at 20 +1 ℃. The oxidized tungsten sheet is first oxidized at 60V for 60 minutes, then oxidized at 40V for 30 minutes. The oxidized tungsten sheet is soaked in diluted hydrofluoric acid for several seconds and washed with deionized water. Finally, the electrolyte is burned at 450 ℃ for 4 hours in oxygen atmosphere. The self-assembled porous tungsten trioxide nanomaterials were prepared.

Porous tungsten trioxide nanomaterials have uniform pore distribution and regular morphology, forming self-assembled structure. Its crystal structure is monoclinic, and the growth of the crystal is preferential in the direction of (002) plane. The crystallization degree is very high. It has good photoelectrochemical characteristics and strong photocatalytic activity. It can be used as an efficient photocatalyst.

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