# US 10,865,488 B2 · Method of producing graphene > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,865,488 B2 - Document ID: US10865488B2 - Status: Granted - Kind: B2 - Application number: 16/665,220 - Filed: 2019-10-28 - Published: 2020-03-26 - Granted: 2020-12-15 - Earliest claimed: 2014-02-14 - Assignees: Cambridge Enterprise Limited - Applicants: Cambridge Enterprise Limited - Inventors: Derek Fray; Ali Kamali - Web page: https://patentgrep.com/patent/US10865488B2 ## CPC - C25B 9/00: Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features - C01B 32/184: Preparation - C01B 32/19: by exfoliation - C25B 1/00: Electrolytic production of inorganic compounds or non-metals - C25B 1/135: Carbon - C25B 11/044: Impregnation of carbon - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - B82Y 40/00: Manufacture or treatment of nanostructures - C01B 2204/32: Size or surface area - Y10S 977/734: Fullerenes, i.e. graphene-based structures, such as nanohorns, nanococoons, nanoscrolls or fullerene-like structures, e.g. WS2 or MoS2 chalcogenide nanotubes, planar C3N4, etc. - Y10S 977/845: Purification or separation of fullerenes or nanotubes - C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B) - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A method of producing graphene sheets comprising the steps of, (a) forming a carbonaceous powder by electrochemical erosion of a graphite electrode in a molten salt comprising hydrogen ions, (b) recovering the resulting carbonaceous powder from the molten salt liquid, and (c) thermally treating the carbonaceous powder by heating the carbonaceous powder in a non-oxidising atmosphere to produce a thermally treated powder comprising graphene sheets. ## Claims ### Claim 1 A method of producing graphene sheets comprising the steps of, (a) forming a carbonaceous powder by electrochemical erosion of a graphite electrode in a molten salt comprising hydrogen ions, (b) recovering the resulting carbonaceous powder from the molten salt liquid, and (c) thermally treating the carbonaceous powder by heating the carbonaceous powder in a non-oxidising atmosphere to produce a thermally treated powder comprising graphene sheets. ### Claim 2 (depends on 1) A method according to claim 1 in which the molten salt comprises a halide salt of lithium, sodium or potassium. ### Claim 3 (depends on 1) A method according to claim 1 in which the temperature of the molten salt during the electrochemical erosion of the graphite electrode is greater than 800° C. ### Claim 4 (depends on 1) A method according to claim 1 in which the molten salt and the carbonaceous powder is recovered from the molten salt by a process comprising steps of cooling and solidifying the molten salt, and washing the solidified salt from the carbonaceous powder. ### Claim 5 (depends on 4) A method according to claim 4 further comprising the step of vacuum filtration of the washed carbonaceous material. ### Claim 6 (depends on 1) A method according to claim 1 in which the carbonaceous powder comprises a metal hydride compound prior to the step of thermal treatment, for example lithium hydride, the metal species in the metal hydride being derived from the molten salt. ### Claim 7 (depends on 1) A method according to claim 1 in which the carbonaceous powder is thermally treated by heating to a temperature of greater than 1,000° C., for example to 1250° C.+/−50° C., in a reducing atmosphere, for example, in a reducing gas atmosphere comprising a mixture of nitrogen and hydrogen. ### Claim 8 (depends on 1) A method according to claim 1 in which the carbonaceous powder is thermally treated by heating in a lower than atmospheric pressure environment. ### Claim 9 (depends on 1) A method according to claim 1 in which the graphene sheets are graphene nanosheets having lateral dimensions of greater than 200 nanometres. ### Claim 10 (depends on 1) A method according to claim 1 in which the current at the graphite electrode during electrochemical erosion of the electrode is greater than 0.5 A/cm2. ### Claim 11 (depends on 1) A method according to claim 1 in which graphene sheets are produced at a rate of greater than 1 kg per hour, per square metre of graphite electrode immersed in the ionic liquid. ### Claim 12 (depends on 1) A method according to claim 1 in which the graphite electrode is cathodic in polarity during electrochemical erosion. ### Claim 13 (depends on 1) A method according to claim 1 comprising the step of: (a) forming a carbonaceous powder by electrochemical erosion of two or more graphite electrodes in a molten salt comprising hydrogen ions, each of the two or more graphite electrodes alternately serving as a negative electrode in connection with a positive counter electrode for periods of time in order to effect the electrochemical erosion. ### Claim 14 A method of producing graphene sheets comprising the steps of: (a) forming a carbonaceous powder by electrochemical erosion of a graphite electrode in an ionic liquid, the ionic liquid comprising hydrogen ions, (b) recovering the resulting carbonaceous powder from the ionic liquid, and (c) thermally treating the carbonaceous powder by heating the carbonaceous powder in a non-oxidising or reducing atmosphere to produce a thermally treated powder comprising graphene sheets. ### Claim 15 A method of producing graphene sheets comprising the steps of: (a) forming a carbonaceous powder by electrochemical intercalation of a metallic species and a hydrogen species into a graphite electrode, the graphite electrode being arranged in contact with an electrolyte, the electrolyte comprising the metallic species and the hydrogen species, (b) recovering the resulting carbonaceous powder from the electrolyte, and (c) thermally treating the carbonaceous powder by heating the carbonaceous powder in a non-oxidising or reducing atmosphere to produce a thermally treated powder comprising graphene sheets. ### Claim 16 A method of producing graphene sheets comprising the steps of: (a) forming a carbonaceous powder by electrochemical erosion of a graphite electrode in a molten salt, in which electrochemical erosion of the graphite electrode is performed under an atmosphere comprising an inert gas and hydrogen, and (b) recovering the resulting carbonaceous powder, which comprises graphene sheets, from the molten salt. ### Claim 17 (depends on 16) A method according to claim 16 further comprising the step of: (c) thermally treating the carbonaceous powder by heating the carbonaceous powder in a non-oxidising atmosphere to produce a thermally treated powder comprising graphene sheets. ### Claim 18 (depends on 16) A method according to claim 16 in which the atmosphere comprises between 2 and 10 mole percent hydrogen and the inert gas is selected from the group consisting of argon and nitrogen. ### Claim 19 (depends on 18) A method according to claim 18, wherein the atmosphere is a dry atmosphere.