Team:Tec Guadalajara/Chemistry

Mixing reagents

One of the most cost effective ways of producing graphene is through the reduction of graphene oxide into rGO (reduced graphene oxide).

In order to produce graphene from graphite we first need to separate the layer by oxidizing to form graphene oxide (GO). Hummer's method is the most common procedure to produce GO, in which graphite reacts with a mixture of sulphuric acid, sodium nitrate and potassium permanganate.

The problem with Hummer's method is that the reaction can get very violent if the temperature rises above 20 ºC. This is why other method have been developed recently like Tour's method which uses large quantities of potassium permanganate, and adding phosphoric acid combined with the sulphuric acid, instead of adding sodium nitrate.

After the oxidation, the layers of the graphite should be separated and the next step is to reduce the GO in order to get graphene. This is a crucial step that impacts on the quality of the final product. Reduction can be achieved though several chemical, thermal or electrochemical means; some examples are:

Graphene oxide

Reduced graphene oxide

  • Treating GO with hydrazine hydrate and maintaining the solution at 100 for 24 hours
  • Exposing GO to hydrogen plasma for a few seconds
  • Exposing GO to another form of strong pulse light, such as those produced by xenon flashtubes
  • Heating GO in distilled water at varying degrees for different lengths of time
  • Combining GO with an expansion-reduction agent such as urea and then heating the solution to cause the urea to release reducing gases, followed by cooling
  • Directly heating GO to very high levels in a furnace
  • Linear sweep voltammetry

Thermally reducing GO at temperatures of 1000 °C or more creates rGO that has been shown to have a very high surface area but the heating process damages the structure of graphene.

Reducing GO by using chemical reduction is a very scalable method, but unfortunately only using hydrazine, which is highly toxic and harmful to living organisms and the environment, the rGO results with enough quality in terms of surface and electronic conductivity.

We propose the use of D-isoascorbic acid, an organic molecule derived form glucose, as a substitute of hydrazine that enables the reduction of GO to rGO with comparable quality. The use of isoascorbic acid will avoid the complications of using hydrazine as a reducing agent enabeling the mass production of graphene.

Isoascorbic acid