Fabrication of graphene and large graphene electrodes

Abstract

The invention relates to the fabrication of large graphene electrodes. The conductivity is important for reducing energy consumption during electrolysis of water or operation of hydrogen fuel cells. Titanium electrodes are widely used, but their conductivity is only about 4% of copper. The conductivity of the graphene is 70% higher than that of copper, and the graphene is chemically stable under the condition that no metal ions exist in the electrolyte. By irradiating a mixture of a carbon dioxide gas and a hydrogen gas, a large amount of graphene can be easily produced, and then the graphene can be manufactured into a large electrode by the press molding.

Description

Technical Field

[0001] The field of the invention relates to the production and manufacture of electrodes, in particular to graphene electrodes.

[0002] This application claims priority to AU 2023901394 filed on May 9, 2023, the entire contents of which are incorporated herein by reference.

[0003] background

[0004] Monopolar water electrolysis is an advanced method for producing low-cost green hydrogen, as described in granted U.S. Patent 10,316,416. Although the energy required in the hydrolysis process has been significantly reduced from 53.4 kWh per kg in the early conventional hydrolysis process to 6.13 kWh per kg in monopolar electrolysis, the current required for electrolysis to produce hydrogen must follow Faraday's law, that is, 96484.3 coulombs (ampere-seconds) are required to produce 1 gram of hydrogen.

[0005] Solar power, the process of converting sunlight into electricity using photovoltaic cells or sunlight concentration systems, while clean, is limited by the availability of sunlight at any given location, which is about 10 hours per day. To supply hydrogen to a 200 megawatt (MW) fuel cell, 96 copper electrodes of 3 meters by 3 meters are required, each carrying about 200,000 amps. This requires a lot of copper, and the copper must be protected by a coating such as a ruthenium / iridium coating, and then platinum particles must be applied to the surface of the electrode.

[0006] The largest graphene manufacturer is Japan's Daikin, which makes about 80 tonnes of nanotube graphene per year. Another Australian manufacturer is the Graphene Manufacturing Group, which makes graphene-coated aluminium sheets for use in heat exchange equipment and aluminium graphene batteries. However, in the area of ​​interest, large electrolysis electrodes, there has been little, if any, work.

[0007] Conventionally, graphene can be produced from naturally occurring graphite by laborious processing methods. Alternatively, for example, it is known to split natural gas into graphene and hydrogen using electric plasma methods.

[0008]

[0009] However, there is a need to increase the scale-up of graphene production to make it more energy-efficient and suitable for widespread use. SUMMARY OF THE INVENTION

[0011] In some embodiments, the present invention relates to a method or system for producing graphene by exposing CO2 and hydrogen to a laser source. In some embodiments, CO2 and hydrogen are exposed to a laser source in a reaction chamber.

[0012] In some embodiments, the present invention relates to a method for converting a mixture of CO2 and hydrogen into graphene, which is provided by providing the mixture of CO2 and hydrogen into a reaction container, irradiating the mixture of CO2 and hydrogen with at least one laser beam to heat the mixture of CO2 and hydrogen, so as to convert the mixture of CO2 into graphene.

[0013] In some embodiments, the reaction vessel includes a catalyst, and the at least one laser beam heats the mixture of CO 2 and hydrogen with the catalyst to convert the mixture of CO 2 into graphene.

[0014] In some embodiments, at least one laser beam heats the surface of the catalyst to convert CO 2 in the mixture of CO 2 and hydrogen into graphene.

[0015] In some embodiments, the reaction vessel includes an additional heat source, such as an electric plasma source, a microwave energy source.

[0016] In some embodiments, a carbon raw material such as carbon paper or carbon from lignite is first molded with diamond-shaped holes before applying intense heat, such as from microwaves, lasers, or electric plasma.

[0017] In some embodiments, the mold may consist of a stationary bottom mold and a moving upper mold.

[0018] In some embodiments, the mold can be a set of rollers with indentations to create diamond-shaped holes in the electrode before intense heat is applied, such as from microwaves, lasers, or plasma.

[0019] A further aspect of the present invention is a method for forming a mesh electrode, the method comprising: preparing and assembling a plurality of sheets of conductive material to form a stack of sheets; compressing the stack of sheets using a press to produce a stack of compressed sheets, the press having a press plate having a surface having a pattern to press openings into the stack of compressed sheets to produce a stack of compressed sheets having a mesh pattern.

[0020] Other aspects of the present invention are that when the conductive material is carbon, a stack of compressed sheets having a mesh pattern is introduced into a reaction vessel and irradiated with laser radiation from a laser to heat the reaction vessel to a temperature in the range of 400°C to 900°C to convert the stack of compressed carbon sheets having a mesh pattern into a stack of graphene sheets having a mesh pattern.

[0021] Further forms of the invention will be apparent from the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present invention will now be better understood and apparent to those of ordinary skill in the art by reference to the written description, taken by way of example only, in conjunction with the accompanying drawings, in which:

[0024] FIG1 shows a schematic diagram of the present invention for producing graphene from a mixture of CO 2 and hydrogen using a laser according to some embodiments;

[0025] FIG2 shows a schematic diagram of the present invention for producing graphene from a mixture of CO 2 and hydrogen using a laser in combination with an additional heat source, according to some embodiments;

[0026] FIG3 shows a cross section of the electrode shown in FIG2 along AA;

[0027] FIG4a shows a side view of a linear reactor having multiple arrangements of laser emitting devices arranged to provide laser radiation of different wavelengths to a carbon sheet;

[0028] Fig. 4b is a plan view of the linear reactor shown in Fig. 4a;

[0029] FIG5 is a view of a press for producing a suitable pressed graphene paper material to form an electrode;

[0030] Fig. 6 is a view of a webbed embodiment produced by the press of Fig. 5 with an enlarged portion showing the webbed configuration;

[0031] FIG. 7 is a side view of a roller press for producing the graphene sheet of the present invention.

[0032] Details

[0033] The aim of the invention is to make graphene electrodes that are 10 to 30 mm thick, 500 to 1000 mm wide and 2000 to 3000 mm long. The electrodes will have diamond-shaped openings similar to expanded metal, so that the electrolyte can move through the electrode from one side of the electrode to the other with the help of a baffle.

[0034] Graphene electrodes can be made in 3 ways:

[0035] 1. As shown in Figures 1 and 2, fine particles of graphene are made by reacting methane or carbon dioxide and hydrogen in a chamber with a high-intensity laser or electric plasma. Fine graphene powder mixed with a suitable binder is placed in a mold to produce a graphene electrode. In the mold, the material is subjected to intense microwaves or lasers or electric plasma so that even the binder is converted into graphene. Carbon dioxide and hydrogen can be produced from my U.S. Patent 7,182,851 "Electrolytic Commercial Production of Hydrogen from Hydrocarbon Compounds" using lignite as a raw material.

[0036] 2. Another method is to use commercially available carbon papers of different thicknesses. The carbon papers can be laminated to the desired thickness of 10 to 30 mm. Diamond-shaped holes can be cut into the carbon paper before it is subjected to intense microwaves or lasers or electric plasma. Some suitable glue converted to graphene can be used to bond the carbon paper together.

[0037] 3. Other methods are to process lignite using my US patent 9,187,697 "Advanced Coal Upgrading Process for a Power Plant" where the lignite is subjected to microwave energy to produce gas, liquid and solid. The solid is almost pure carbon which becomes the raw material that is subjected to intense laser or microwave or plasma in a die with diamond shaped openings.

[0038] The production of carbon (graphene) can be achieved through the following reaction, although this requires significant amounts of energy, pressure and heat in conventional methods:

[0039]

[0040] Figure 1 shows the system / method of the present invention, wherein the reaction uses laser, high temperature (above 550°C) and pressure and a catalyst such as iron oxide, strontium oxide, etc. to convert CO2 into graphene powder according to one embodiment of the present invention.

[0041] The reactor 10 having an internal chamber 15 has an input conduit 20 through which a mixture of metered amounts of CO2 and hydrogen is supplied to the internal chamber 15. Gaseous CO2 30 and hydrogen 40 from a commercial supply source are supplied to a mixing chamber 50 in predetermined amounts, for example, in a ratio of 1:2 CO2:H2, and mixed for a predetermined amount of time before being directed to a gas compressor 60, which operates to compress the gas to a working state. Once compressed to the desired pressure, the compressed gas mixture of CO2 and H2 is then preheated to a predetermined temperature in a heater unit 70 and then supplied to the internal chamber 15 of the reactor 10.

[0042] In the internal chamber 15 of the reactor 10 there are a plurality of parallel arranged catalyst rods 75 , such as iron oxide, strontium oxide, etc., which are collinear with the longitudinal axis of the reactor 10 .

[0043] The laser source will be a laser that can be operated in either continuous or pulsed mode. The laser device may be a high power laser, for example but not limited to a gas laser such as a CO2 laser, an argon laser, a metal ion laser, a solid state laser that uses a crystal or glass rod "doped" with ions that provide the required energy state, or a combination of two or more such lasers. It may be preferred to select the laser source based on economic factors to keep production costs low. An example of an economical laser is a CO2 laser.

[0044] Located at the upper end 80 of the reactor 10 is a laser 100a configured to emit laser radiation, such as a CO2 laser. The laser 100a is directed to emit laser radiation downward and into the chamber 15 having the catalyst rods 75 to cause the reaction:

[0045]

[0046] Additional laser radiation emitting units 100b and 100c are positioned toward the lower end of the reaction vessel 10 to increase throughput.

[0047] Due to the internal temperature of the reaction, water is generated in the form of steam and is discharged through valve 110. Carbon material 130 in the form of graphene powder is then collected at the lower end 82 of reactor 10, away from the laser radiation source, and can be collected by conduit 140.

[0048] In certain embodiments, the laser will be configured to illuminate the catalyst surface inside the reactor to promote the conversion of CO2 to graphene.

[0049] In certain embodiments, the temperature of the catalyst or internal reactor chamber will be heated to about 400°C, about 450°C, about 500°C, about 550°C, about 600°C, about 650°C, about 700°C, about 750°C, about 800°C, about 850°C, about 900°C.

[0050] In some embodiments, the laser may be preset to illuminate the reactor chamber and catalyst for a predetermined period of time.

[0051] In some embodiments, the laser may be preset to irradiate the reactor chamber and / or catalyst for a predetermined period of time.

[0052] In some embodiments, the catalyst is iron oxide, strontium oxide, copper oxide, or a mixture thereof. In other embodiments, the catalyst is a metal catalyst such as aluminum, zinc, or magnesium.

[0053] Figure 2 shows a reactor using electric plasma and microwaves in addition to a high power laser.

[0054] The reactor 200 has an internal chamber 215 with an input conduit 220 through which a mixture of metered amounts of CO2 and hydrogen is supplied to the internal chamber 215. Gaseous CO2 230 and hydrogen 240 from a commercial supply source are supplied to a mixing chamber 250 in predetermined amounts, such as a ratio of 1:2 CO2:H2, and mixed for a predetermined amount of time before being directed to a gas compressor 260, which operates to compress the gas mixture to a working state. Once compressed to the desired pressure, the compressed gas mixture of CO2 and H2 is then preheated to a predetermined temperature in a heater unit 270 and then supplied to the internal chamber 215 of the reactor 200.

[0055] The laser source will be a laser that can be operated in either continuous or pulsed mode. The laser device may be a high power laser, for example but not limited to a gas laser such as a CO2 laser, an argon laser, a metal ion laser, a solid state laser that uses a crystal or glass rod "doped" with ions that provide the required energy state, or a combination of two or more such lasers. It may be preferred to select the laser source based on economic factors to keep production costs low. An example of an economical laser is a CO2 laser.

[0056] Located at the upper end 280 of the reactor 200 is a laser 300a configured to emit laser radiation, such as a CO2 laser. The laser 300a is directed to emit laser radiation downward and into the chamber 215 having the catalyst rods 275 to cause the reaction:

[0057]

[0058] Additional laser radiation emitting units 300b and 300c are positioned toward the lower end of the reaction vessel 200 to increase throughput.

[0059] Located in the center of the reaction vessel 200 is a high voltage electrode 320 having a positive electrode (anode) 330 surrounded by a negative electrode (cathode) 340 in the form of a hollow cylinder, which is operably connected to a power source 341. The CO2 / H2 mixture is drawn up 342 by convection, where it is exposed to a high pressure environment, and the mixture of carbon dioxide gas and hydrogen gas in the internal chamber of the high voltage electrode is subjected to a continuous arc between the two electrodes to heat the mixture of carbon dioxide gas and hydrogen gas in the interior 350 of the high voltage electrode 320. Carbon 330 in the form of graphene is collected at the lower end 282 of the reactor 200 and can be collected by conduit 340, while water vapor is exhausted through valve 320.

[0060] The mixture of carbon dioxide gas and hydrogen gas in the inner chamber of the high voltage electrode is subjected to a continuous electric arc between the two electrodes to heat the mixture of carbon dioxide gas and hydrogen gas.

[0061] FIG. 3 shows a cross section of the high voltage electrode 320 along AA of FIG. 2 .

[0062] In some embodiments, a microwave launch unit, such as a klystron microwave unit operating in the 8-14 GHz range, can be located on the lower end 282 of the reactor 200 to provide additional energy to the reactor chamber, the microwave launch unit operating through a quartz window or other suitable opening in the chamber 215 of the reactor 200.

[0063] The graphene powder obtained from the present reactor 10 or 200 can then be used to make graphene sheets, which in turn can then form electrodes.

[0064] For example, graphene can be applied to the sheet by electrodeposition, chemical vapor deposition (CVD) solution phase deposition, electroless deposition or hot pressing of a graphene-containing slurry onto the sheet. Techniques such as drop casting, spin coating, dip coating or spray coating can be used.

[0065] Graphene sheets can also be obtained by subjecting carbon paper to exposure to laser radiation in the presence of hydrogen, the carbon in the carbon paper being converted into graphene. Additionally, carbon from lignite can be used to form carbon paper.

[0066] As shown in Figures 4a and 4b, the carbon sheet 400 is fed to a linear reactor 410 having a plurality of laser emitting devices 420, 430, and 440. In some embodiments, the laser emitting devices are all identical laser emitting devices, such as CO2 lasers, each emitting laser radiation of the same or substantially the same wavelength. In other embodiments, the laser emitting devices 420, 430, and 440 can each be an independent laser emitting device, such as three independent CO2 lasers, each laser being tuned to provide laser radiation of a different wavelength. In yet other embodiments, the high power lasers are arranged from the lower frequency at the bottom to the highest frequency at the top. The laser can be pulsed or continuous.

[0067] In other embodiments, laser emitting device 420 emits radiation at about 532 nm (green), laser emitting device 430 emits radiation at about 589 nm (yellow), and laser emitting device 440 emits radiation at about 445 nm (blue). Laser irradiation of the carbon material on the carbon sheet converts the carbon into graphene to produce graphene sheet 460, which is then directed out of the linear reactor via flexible conduit 480.

[0068] According to FIG. 5 , the graphene powder obtained using the reactors 10 and 200 can be converted into sheets and then formed into electrodes.

[0069] Once the graphene sheets 460 are formed, they are bonded together using a conductive glue, for example, a glue containing silver, graphite, nickel, copper or other suitable conductive material. Such glues are known to those skilled in the art and can be purchased commercially, such as, but not limited to, MasterBond ® EP75-1. For example, a stack 500 of graphene sheets 460 is formed of layers stacked on top of each other and compacted using a press 510 having a moving plate 520 with an embossed mesh 530 and a stationary plate 540 with an embossed mesh 550, the moving plate 520 having peaks and valleys. The moving plate 520 is pressed against the stationary plate 540, compressing the stack 500, resulting in a diamond pattern on the consolidated / compressed stack 500 in a grid-like pattern, the compressed stack being about 12-16 mm thick. Depending on the size of the punch on the perforated plate, a die may also be used to form openings of appropriate size in the stack 500.

[0070] The consolidated / compressed stack 600 produced by the press 510 has a pattern with diamond-shaped openings 610 .

[0071] FIG. 7 shows another method of compressing the stack 500 with a roller press 650. The roller press 650 has an upper roller 660 and a lower roller 670, which work in combination to compress the stack 500 to a specified height by the counter-rotation of the rollers 660 and 670. The height between the rollers 660 and 670 (changing the roller gap) can be adjusted to provide a compressed stack 680. The upper roller 660 and the lower roller 670 each have a pattern on their surface, which is imprinted on the stack 500 when it is pulled in to produce the same mesh electrode structure 600 as shown in FIG. 6. These types of rollers have matching rotating cylinders, one with a series of protrusions (male mold) and the other with a series of indentations (female mold), which run in alignment with each other so that the male mold punches a shape out of the stack 500 during operation. In some embodiments, there may be a male mold that rotates against an anvil roller. Advantageously, the roller press 650 can produce mesh electrodes 600 of variable length, depending on the length of the stack 500 fed thereto.

[0072] In another embodiment, roller 650 can be used to compress a sheet of carbon paper, i.e., a paper of a paper-like material applied thereto by depositing one or more layers of carbon material on each surface thereof. For example, thin film deposition, liquid deposition, liquid / solution coating can be used to apply a layer of carbon material to both the upper and lower surfaces of a paper / similar film material, such as a polyethylene film, which is then cured / dried to form a carbon-coated / impregnated sheet. The cured / dried carbon-coated / impregnated sheets can then be stacked to form a stack of cured / dried carbon-coated / impregnated sheets, which are then fed to a press or roller press, similar to those of Figures 5 and 6, and compressed and embossed with a diamond mesh pattern to produce a carbon mesh sheet.

[0073] The carbon mesh sheet can then be subjected to intense heat using one or a combination of microwave laser, laser, electric plasma to convert the carbon material on the carbon mesh sheet into graphene, thereby producing a graphene mesh sheet that can be used as a graphene electrode.

[0074] In some embodiments, platinum particles may be applied to the surface of a graphene sheet produced by any of the methods described above.

[0075] The compacted electrode may be subjected to heat, laser, microwave to complete the curing of the glue. The glue used to consolidate the compacted material may include a curing agent, such as a thermal curing agent or a light curing agent, to facilitate the curing process.

[0076] Another aspect of the present invention is to dope graphene with metal ions such as hydrogen ions, copper ions, chromium ions and / or rare earth ions such as lanthanum ions and cerium ions. The addition of metal ions added to the graphene structure produces a graphene-metal hybrid structure, which allows electrons in the graphene-metal structure to move more freely, resulting in a higher current capacity of the doped graphene-metal hybrid structure.

[0077] As noted above, certain aspects of the invention include a method for converting carbon dioxide into graphene, the method comprising:

[0078] • injecting a mixture of carbon dioxide gas and hydrogen gas into a reaction vessel;

[0079] • the reaction vessel comprises a plurality of rods of catalytic material;

[0080] • irradiating the mixture of carbon dioxide gas and hydrogen gas with laser radiation from a laser to heat the reaction vessel to a temperature in the range of 400° C. to 900° C.;

[0081] • To convert CO2 gas mixture into solid graphene.

[0082] In some aspects, the plurality of catalytic material rods are rods made of a catalytic material of iron oxide or strontium oxide. The laser is a carbon dioxide laser, and in some aspects, the laser radiation is produced by a laser that is a continuous laser or a pulsed laser.

[0083] In some aspects, the mixture of carbon dioxide gas and hydrogen gas is preheated before being injected into the reaction vessel. The graphene produced by the conversion of the carbon dioxide gas mixture falls to the lower part of the reaction vessel under gravity for removal. In other aspects, the injection of the mixture of carbon dioxide gas and hydrogen gas into the reaction vessel can be performed continuously during the irradiation.

[0084] In a further aspect of the invention, the reaction vessel comprises a high voltage electrode. It may be a hollow cylindrical electrode with openings at both ends. The electrode comprises a positive anode core surrounded by a negative cathode cylinder. The mixture of carbon dioxide gas and hydrogen gas injected into the reaction vessel is sucked up and enters the internal chamber of the high voltage electrode. There, it is subjected to a continuous electric arc between the two electrodes to heat the mixture of carbon dioxide gas and hydrogen gas and leaves the hollow cylindrical electrode and is then irradiated by laser radiation from a laser in the presence of a catalytic rod.

[0085] In another embodiment of the invention, the electrodes can be made from borophene. Although little is known about borophene at this stage, early knowledge is that borophene also has high electrical conductivity, which makes it suitable as an electrode.

[0086] Borophene is an allotrope of carbon that can exist in two-dimensional and three-dimensional structures. Its structure has been observed to be similar to that of graphene and has a high electroactive surface area and high electron mobility.

[0087] As shown in FIGS. 5-7 , a borophene sheet or a borophene-doped sheet, such as a borophene-doped graphene sheet, may be prepared and subjected to a pressing and diamond-shaped hole patterning process.

Claims

1. A method for converting carbon dioxide into graphene, the method comprising: • injecting a mixture of carbon dioxide gas and hydrogen gas into a reaction vessel; • the reaction vessel comprises a plurality of rods of catalytic material; • irradiating the mixture of carbon dioxide gas and hydrogen gas with laser radiation from a laser to heat the reaction vessel to a temperature in the range of 400° C. to 900° C.; • To convert CO2 gas mixture into solid graphene powder.

2. The method of claim 2, wherein the plurality of catalytic material rods are rods made of a catalytic material of iron oxide or strontium oxide.

3. The method of any of the preceding claims, wherein the laser is a carbon dioxide laser.

4. The method of any of the preceding claims, wherein the laser radiation is generated by a laser that is a continuous laser or a pulsed laser.

5. The method of any one of the above claims, wherein the mixture of carbon dioxide gas and hydrogen gas is preheated before being injected into the reaction vessel.

6. The method of any one of the preceding claims, wherein the graphene produced by the conversion of the carbon dioxide gas mixture falls under gravity to a lower portion of the reaction vessel for removal.

7. The method of any one of the above claims, wherein the injection of the mixture of carbon dioxide gas and hydrogen gas into the reaction vessel can be continuous during the irradiation.

8. The method of any of the above claims, wherein the reaction vessel comprises a high voltage electrode.

9. The method of claim 8, wherein the electrode is a hollow cylindrical electrode.

10. The method of claim 9, wherein both ends of the cylindrical electrode are open.

11. The method of claim 10, wherein the electrode comprises a positive anode core surrounded by a negative cathode cylinder.

12. The method of claim 10, wherein the mixture of carbon dioxide gas and hydrogen gas injected into the reaction vessel is sucked up and enters an inner chamber of the high voltage electrode.

13. The method of claim 12, wherein the mixture of carbon dioxide gas and hydrogen gas in the inner chamber of the high voltage electrode is subjected to a continuous electric arc between two electrodes to heat the mixture of carbon dioxide gas and hydrogen gas.

14. The method of claim 13, wherein the heated mixture of carbon dioxide gas and hydrogen gas exits the hollow cylindrical electrode and is then irradiated by laser radiation from the laser in the presence of a catalytic rod, wherein the carbon dioxide gas mixture is converted into graphene.

15. The method of any one of claims 1 to 14, wherein graphene powder or carbon paper or carbon from lignite is fed to a set of cylindrical molds having valleys and peaks to form electrodes having diamond-shaped holes, and intense heat from microwaves or lasers or electric plasma is applied to form the graphene electrodes.

16. The method of any one of claims 1-14, wherein the graphene powder or carbon paper or carbon from lignite is molded with a fixed lower mold having valleys and peaks and a moving upper mold to form an electrode with desired thickness and diamond-shaped holes before applying intense heat using microwaves or lasers or electric plasma to produce graphene electrodes.

17. A method for forming a mesh electrode, the method comprising: preparing and assembling a plurality of sheets of conductive material to form a stack of sheets; The stack of sheets is compressed using a press having a press plate having a surface having a pattern to press openings into the stack of compressed sheets to produce a stack of compressed sheets having a web-like pattern.

18. The method of claim 17, wherein the platen is a pair of counter-rotating rollers.

19. The method of claim 17 or 18, wherein the conductive material is at least one selected from carbon, graphene, and borophene.

20. The method of claim 19, wherein when the conductive material is carbon, a stack of compressed sheets having a mesh pattern is introduced into a reaction vessel, irradiated with laser radiation from a laser to heat the reaction vessel to a temperature in the range of 400°C to 900°C to convert the stack of compressed carbon sheets having a mesh pattern into a stack of graphene sheets having a mesh pattern.

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