Process for the preparation of graphene
The present invention relates to a process for the preparation of graphene which can be used in the development of graphene paper or films, graphene-based composites and articles for nanoelectronics, nanocomposites, batteries, supercapacitors, hydrogen storage and bioapplications. This process comprises reducing purified exfoliated graphite oxide in the presence of a base.
1. A process for the preparation of a stable graphene dispersion which comprises reducing a graphene oxide dispersion by adding a reducing agent in the presence of a base.
2. The process according to claim 1 , in which the graphene dispersion is solution-processable.
3. The process according to claim 1 , in which the graphene dispersion is water-based.
4. The process according to claim 1 , in which the reducing agent is an inorganic or organic reducing agent.
5. The process according to claim 4 , in which the inorganic reducing agent is hydrazine or NaBH 4 .
6. The process according to claim 5 , in which the hydrazine is added in an amount of 1.0 to 7.0 g of 35% hydrazine per gram of graphene oxide.
7. The process according to claim 4 , in which the organic reducing agent is hydroquinone, dimethylhydrazine or N,N′-diethylhydroxylamine.
8. The process according to claim 1 , in which the base is a water soluble inorganic or organic base.
9. The process according to claim 8 , in which the water soluble inorganic base is ammonia, sodium hydroxide, or potassium hydroxide.
10. The process according to claim 9 , in which the ammonia is added in an amount of 7.0 to 20.0g of 28% ammonia per gram of graphene oxide.
11. The process according to claim 8 , in which the water soluble organic base is methylamine ethanolamine, dimethylamine or trimethylamine.
12. The process according to claim 1 , in which the graphene oxide is prepared by chemical oxidation of graphite to form graphite oxide which is then purified and exfoliated.
13. The process according to claim 12 , in which the graphite oxide is purified by dialysis, filtration, centrifugation or washing with water.
14. The process according to claim 12 , in which the graphite oxide is exfoliated by ultrasonication or mechanical stirring.
15. The process according to claim 1 , in which a water immiscible liquid is added before or during the reduction.
16. The process according to claim 1 , in which the reducing agent is in the form of a solution.
17. The process according to claim 1 , in which the base is in the form of a solution.
18. The process according to claim 1 , in which the graphene oxide is present in the dispersion at a concentration of less than 0.5mg/mL.
19. The process according to claim 5 , in which the hydrazine is added in an amount of 1.5 to 5.0 g of 35% hydrazine per gram of graphene oxide.
20. The process according to claim 5 , in which the hydrazine is added in an amount of 1.5 to 2.5 g of 35% hydrazine per gram of graphene oxide.
21. The process according to claim 9 , in which the ammonia is added in an amount of 8.0 to 16.0 g of 28% ammonia per gram of graphene oxide.
22. The process according to claim 9 , in which the ammonia is added in an amount of 10.0 to 13.0 g of 28% ammonia per gram of graphene oxide.
23. The process according to claim 1 , in which the base is added to increase the pH of the graphene oxide dispersion to 6 or greater.
24. The process according to claim 23 , in which the pH of the graphene oxide dispersion is 9 to 11.