How to Prepare Tungsten Disulfide/Graphene Composite?

The preparation of composite of tungsten disulfide and graphene involves the four steps: the preparation of graphene oxide, the preparation of RGO, the preparation of tungsten disulfide and the preparation of composite of WS₂ and RGO. This is a simple preparation method with low cost.

The four preparation steps are as follow:

Step One: The preparation of graphene oxide (GO).

1. 2 g graphite and 1.2 g anhydrous sodium nitrate are stirred in 35 mL concentrated sulfuric acid slowly under the condition of ice bath.

2. Then 8 g potassium manganate is added and the mixture is fully stirred at 20°C for 30 minutes. 3. When the temperature is heated to 40°C, the mixture is stirred for 1 hour continuously.

4. During the mixing process, 50 mL distilled water is added and the new mixture is mixed for 30 minutes under 98°C. When the temperature is heated to 98°C, 20 mL hydrogen peroxide with a solvent ratio of 30% is added to the mixture until the solution turns bright yellow.

5. The yellow solution is stirred in deionized water and then dispersed by the ultrasonic. And then the precipitate is collected by centrifugation.

6. The centrifuged precipitate is washed by dilute hydrochloric acid and distilled water to eliminate SO4^2- and other ions.

7. Graphene oxide (GO) is successfully prepared.

Step Two: The preparation of RGO.

100 mg GO is dissolved and stirred in 100 mL distilled water. Then 1mL hydrazine hydrate (80%) is added to the mixture during the stir process. Then the mixed solution is transferred into a 100 mL PTFE lined stainless steel autoclave for 24-hour hydrothermal reaction at 180°C. When the mixture is cooled to room temperature, the product is collected. Then it is washed by deionized water and ethanol three times, dried in a vacuum oven at 60°C and crushed into powder. RGO is successfully prepared.

Step Three: The preparation of tungsten disulfide.

1 mmol WCl₆ and 4 mmol ammonium thioacetate (C₂H₅NS) are put into a beaker. And then 80 mL distilled water is added. The mixture is stirred in constant temperature water bath at 25°C for an hour. The mixed solution is transferred into a 100 mL PTFE lined stainless steel autoclave for 24-hour hydrothermal reaction at 180°C. When the solution is cooled to room temperature, the black product is obtained. The black product is washed and centrifuged by deionized water and ethanol repeatedly. Then it is dried in a vacuum oven at 60°C for 24 hours. The dried product is calcined in a tubular furnace filled with N₂ at 800°C for 2 hours, cooled and then milled.Tungsten disulfide is successfully prepared.

Step Four: The preparation of composite of WS₂ and RGO.

40 mg GO is dispersed in 80 mL distilled water and then stirred by ultrasonic for 24 hours. Then 1 mmol WCl₆ and 4 C₂H₅NS are added. And the mixture is stirred for 1 hour continuously. The pH value of the mixed solution is adjusted to 6 with 0.1 mol/L NaOH solution. Then it is transferred to a 100 mL PTFE lined stainless steel autoclave for 24-hour hydrothermal reaction at 180°C. And composite of WS2 and RGO is successfully prepared by the subsequent treatment of tungsten disulfide in Step Three.

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