Hummers' method
Hummers' method is a chemical process that can be used to generate
Graphite oxide
Graphite oxide is a compound of carbon, oxygen, and hydrogen where there is a ratio between 2.1 and 2.9 of carbon to oxygen. Graphite oxide is typically a yellowish solid. It is also known as graphene oxide when used to form unimolecular sheets.
Method
Hummers' method[1] was developed in 1958 as a safer, faster and more efficient method of producing graphite oxide. Before the method was developed, the production of graphite oxide was slow and hazardous to make because of the use of concentrated sulfuric and nitric acid. The Staudenmeier–Hoffman–Hamdi method[2] introduced the addition of potassium chlorate. However, this method had more hazards and produced one gram of graphite oxide to ten grams of potassium chlorate.[3]
The procedure starts with 100 g graphite and 50 g of sodium nitrate in 2.3 liters of sulfuric acid at 66 °C which is then cooled to 0 °C. 300 g of potassium permanganate is then added to the solution and stirred. Water is then added in increments until the solution is approximately 32 liters.
The final solution contains about 0.5% of solids to then be cleaned of impurities and dehydrated with phosphorus pentoxide.
Chemical equations and efficiency
The basic chemical reaction involved in the Hummers' method is the
Method | % Carbon | % Oxygen | % Water | % Ash | Carbon-to-oxygen atomic ratio |
---|---|---|---|---|---|
Hummers | 47.06 | 27.97 | 22.99 | 1.98 | 2.25 |
Staudenmeier | 52.112 | 23.99 | 22.2 | 1.90 | 2.89 |
Significance
The method has been taken up by many researchers and chemists who are interested in the use of graphite oxide for other purposes, because it is the fastest[4] conventional method of producing graphite oxide while maintaining a relatively high C/O ratio. When researchers and chemists are introducing a large quantity of graphite oxide within time limitations, Hummers' method is usually referenced in some form.
Modern variations
Graphite oxide captured the attention of the scientific community after the discovery of graphene in 2004. Many teams are looking into ways of using graphite oxide as a shortcut to mass production of graphene. So far, the materials produced by these methods have shown to have more defects than those produced directly from graphite. Hummers' method remains a key point of interest because it is an easy method of producing large quantities of graphite oxide.
Other groups have been focused on making improvements to the Hummers' method to make it more efficient and environmentally friendly. One such process is eliminating the use of NaNO3 from the process.[5][6] The addition of persufate (S2O82−) ensures the complete oxidation and exfoliation of graphite to yield suspensions of individual graphite oxide sheets. The elimination of nitrate is also advantageous as it stops the production of gases such as nitrogen dioxide and dinitrogen tetraoxide.
Future uses
Besides graphene, Hummers' method has become a point of interest in
See also
- Graphite Oxide
References
- ^ .
- ^ Ojha, Kasinath; Anjaneyulu, Oruganti; Ganguli, Ashok (10 August 2014). "Graphene-based hybrid materials: synthetic approaches and properties" (PDF). Current Science. 107 (3): 397–418. Retrieved 7 November 2014.
- ^ Murray-Smith, Robert. "How to make graphene oxide". YouTube. Retrieved 16 November 2014.
- ^ Ciszewski, Mateusz; Mianowski, Andrzej (2013). "Survey of graphite oxidation methods using oxidizing mixtures in inorganic acids". Chemik. 67 (4): 267–274. Retrieved 15 November 2014.
- .
- .
- S2CID 98775617.