Production of graphene
A method for the production of graphene and graphite nanoplatelet structures having a thickness of less than 100 nm in an electrochemical cell, wherein the cell comprises: (a) a negative electrode which is graphitic; (b) a positive electrode which may be graphitic or another material; and (c) an electrolyte which is ions in a solvent where the cations are organic ions and metal ions; and wherein the method comprises the step of passing a current through the cell.
1. A method for the production of graphene and graphite nanoplatelet structures having a thickness of less than 100 nm in an electrochemical cell, wherein the cell comprises:
(a) a negative electrode which is graphitic;
(b) a positive electrode; and
(c) an electrolyte which comprises ions in a solvent, said ions comprising cations and anions, wherein the cations comprise organic ions and metal ions;
and wherein the method comprises the step of passing a current through the cell wherein the cations are intercalated into the negative electrode.
2. The method according to claim 1 , wherein the negative electrode comprises a layered graphite compound in which the cations can be intercalated.
3. The method according to claim 1 , wherein the negative electrode comprises a graphite compound that is selected from highly ordered pyrolytic graphite, natural graphite and synthetic graphite.
4. The method according to claim 1 , wherein the organic cations comprise alkylammonium cations.
5. The method according to claim 4 , wherein the alkylammonium cations comprise tetraalkyl ammonium cations.
6. The method according to claim 5 , wherein the alkylammonium cations are selected from tetrabutyl ammonium, tetraethylammonium and tetramethyl ammonium.
7. The method according to claim 4 , wherein the alkylammonium cations comprise trialkyl ammonium cations.
8. The method according to claim 7 , wherein the trialkylammonium cations are selected from tributyl ammonium, triethylammonium and trimethyl ammonium.
9. The method according to claim 4 , wherein the alkylammonium cations comprise dialkyl ammonium cations.
10. The method according to claim 9 , wherein the dialkylammonium cations are selected from dibutyl ammonium, diethylammonium and dimethyl ammonium.
11. The method according to claim 1 , wherein the metal cations are iron cations.
12. The method according to claim 1 , wherein the metal cations are tin cations.
13. The method according to claim 1 , wherein the metal cations are lithium cations.
14. The method according to claim 1 , wherein the electrolyte further comprises counter-ions selected from chloride, tetrafluoroborate, perchlorate and hexafluorophosphate.
15. The method according to claim 1 , which is carried out a temperature from 20° C. to 100° C.
16. The method according to claim 1 , wherein the graphene or graphite nanoplatelet structures having a thickness of less than 100 nm are separated from the electrolyte by at least one technique selected from:
(a) filtering;
(b) using centrifugal forces to precipitate the graphene or graphite nanoplatelet structures; and
(c) collecting the graphene or graphite nanoplatelet structures at the interface of two immiscible solvents.
17. The method according to claim 1 , wherein the graphene or graphite nanoplatelet structures having a thickness of less than 100 nm are electrochemically exfoliated from at least one electrode and wherein the method further comprises ultrasonicating the graphene or graphite nanoplatelet structures.
18. The method according to claim 1 , wherein, prior to the step of passing current through the cell, graphite at the negative electrode is functionalised electrochemically by oxidation in nitric acid or fluorination using hydrofluoric acid, and wherein the method comprises electrochemically exfoliating the graphene or graphite nanoplatelet structures having a thickness of less than 100 nm from at least one electrode.