A method of producing carbon materials from feedstock gases

Abstract

A method of producing carbon materials from one or more carbon- containing feedstock gases by melting one or more electrolytes inside a reactor chamber, adding from 0.03 wt% to 2 wt% catalyst of the total electrolyte mass at a dosage rate from 16.7 ppm hour-1 to 1100 ppm hour-1, providing one or more feedstock gases into the molten electrolyte in the reactor chamber with a flow rate comprising at least 4.2 standard cm3 min-1 A-1 mass equivalent of CO2, and applying a direct current density in the range from 100 A m-2 up to 20 000 A m-2 to one or more anodes and one or more cathodes.

Description

[0001] A METHOD OF PRODUCING CARBON MATERIALS

[0002] FROM FEEDSTOCK GASES

[0003] TECHNICAL FIELD

[0004] The present disclosure relates generally to production of carbon materials, and more specifically, to methods for producing carbon materials from feedstock gases.

[0005] BACKGROUND

[0006] Carbon materials in different forms such as powders and dispersions are increasingly important in the production of energy storage devices (e.g., supercapacitors, batteries, fuel cells and other energy storage systems) due to their electrical and mechanical properties. There are different methods and systems known for producing carbon materials such as graphite, graphene, carbon nanotubes, carbon nanofibers, carbon nanospheres or other carbon materials. One of the known methods is for example chemical vapour deposition (CVD) method, which is the current industry standard to produce carbon nanotubes. The CVD method uses 800 MWh energy to produce 1 ton of carbon nanotubes. Thus, the energy usage for producing carbon materials is huge and this makes production very expensive. Thus, there is a need to reduce energy consumption in the production of carbon materials. Furthermore, the CVD method uses a fossil fuel-based feedstock which makes the method harmful to the environment.

[0007] US20220388847 Licht et al. proposes a method of synthesising helical carbon nanostructures via an electrolysis reaction using a molten carbonate electrolyte and carbon-containing input between electrodes of a reaction vessel. Liu et al in "Controlled Growth of Unusual Nanocarbon Allotropes by Molten Electrolysis of CO2" Catalysts 2022, 12, 125 relates to a similar technology as above, further disclosing the effect of different additives in the molten electrolyte on the resulting nano-carbon morphology.

[0008] Laasonen et al in "Insights into carbon production by CO2 reduction in molten salt electrolysis in coaxial-type reactor" disclose a coaxial-type reactor used for reducing CO2 to carbon using various electrolytes and no catalyst, with the purpose of studying the voltage-current characteristics of molten salt electrolysis of CO2.

[0009] Other disclosures which relate to technological background only can be found in:

[0010] "Controlled Transition Metal Nucleated Growth of Carbon Nanotubes by Molten Electrolysis of CO2", Xinye Liu et al., Catalysts 2022, 12, 137.

[0011] "Overview of CO2 capture and electrolysis technology in molten salts: operational parameters and their effects", Qiuji Zhu et al., Ind Chem. Mater., 2023, 1, 595617.

[0012] The present application seeks to provide an improved method of producing carbon from carbon-containing feedstock gases.

[0013] SUMMARY OF INVENTION

[0014] In accordance with a first aspect of the invention, there is provided a method of producing carbon materials from feedstock gases as defined in the appended independent claim to which reference is made. Advantageous features are set out in the appended dependent claims.

[0015] According to a preferred embodiment of the present disclosure, there is provided a method of producing carbon materials, wherein the method comprising following steps: melting one or more electrolytes inside a reactor chamber, adding from 0.03 wt% to 2 wt% catalyst of the total electrolyte mass at a dosage rate from 16.7 ppm hour1to 1100 ppm hour1(preferably from 16.7 ppm hour1to 500 ppm hour1, most preferably from 16.7 ppm hour1to 277.8 ppm hour1) providing one or more feedstock gases into the molten electrolyte in the reactor chamber with a flow rate comprising at least 4.2 standard cm3min1A1mass equivalent of CO2, applying a direct current density in the range from 100 A rrr2up to 20 000 A rrr2(preferably up to 6 000 A rrr2) to a one or more anodes and one or more cathodes. The advantage of the method according to the present disclosure is that the catalyst reaches the cathode more efficiently and in a controlled way, providing carbon nanotube growth nucleation centres and resulting in higher-grade carbon nanotube morphology.

[0016] The method enables efficient increase of the production of carbon materials per year in tons, wherein at the same time reducing the amount of emitted CO2. Additionally, the present method enables the production of carbon materials in controlled ways to achieve morphology suitable for energy storage devices. The produced materials can be used for producing carbonaceous powders, carbonaceous dispersions, oxidized carbon powders, heteroatom-enriched powders which are used for electrical vehicle batteries, stationary energy storages (e.g., lithium-ion batteries, lithium iron phosphate batteries, sodium-ion batteries, lithiumsilicon batteries). DETAILED DESCRIPTION OF EMBODIMENTS

[0017] The following detailed description illustrates preferred embodiments of the present disclosure and ways in which they can be implemented.

[0018] A device suitable for carrying out the present invention includes a reactor chamber adapted to accommodate one or more electrolytes selected from at least one of an alkaline or one or more alkaline-earth electrolytes, a one or more anodes arranged in an 3D structure, a one or more cathodes, a power source for applying an electric current to the one or more anodes and the one or more cathodes, a heating unit configured to heat the reactor chamber to melt the one or more electrolytes, a gas supply unit configured to provide one or more feedstock gases into a molten electrolyte in the reactor chamber.

[0019] However, the skilled person will appreciate that any suitable conventional device can be used.

[0020] The device may be a modular device, wherein two or more devices are configured to work in a system of producing carbon materials from one or more feedstock gases. The device can be connected to a factory or to a production network that emits feedstock gases.

[0021] The reactor chamber of the device is adapted to accommodate one or more electrolytes selected from at least one of an alkaline or one or more alkaline-earth electrolytes and may have a round or square cross-section. The reactor chamber is made of nickel alloy, which optionally may be coated with NiCoCrAI[Ta, Hf, Si]Y, AI2O3 coatings to improve corrosion resistance or ceramic tiles like AI2O3.

[0022] According to a preferred method of the present disclosure the reactor chamber is used for electrolysis, purification and functionalisation with heteroatoms. The reactor chamber comprises a metal vessel adapted to accommodate the electrolyte media (consisting of one or the combination of lithium, potassium, sodium carbonate or halides or any mixture thereof). In particular, the reactor chamber is adapted to accommodate one or more electrolytes including at least one of an alkaline or one or more alkaline earth electrolytes. According to a preferred embodiment the one or more electrolytes comprise from 90% up to 100% of carbonate electrolyte. The carbonate electrolyte is preferably selected to be at least one of Na2CO3, IJ2CO3, K2CO3, BaCO3, CaCOs, SrCO3. The electrolyte may be formed of a eutectic mixture of a plurality of carbonates.

[0023] According to the preferred embodiments of the present disclosure, the one or more electrolytes further comprises a catalyst which is at least one selected from Fe2O3, U2O, LiOH, NiO, ZnO, CT2O3, Ni or others. The amount of catalyst in the electrolyte may be from 0.03 wt% up to 10 wt% (preferably from 0.03 wt% to 2wt%, more preferably from 0.03 wt% to 1.5wt%, even more preferably from 0.03 wt% to lwt%, most preferably from 0.03 wt% to 0.5 wt%). The catalysts enable controlled structures of the particles of carbon materials to be obtained. E.g., Fe2O3 enables straight or predominantly entangled carbon nanotubes to be obtained. The catalyst is preferably added before and during the step of applying a direct current density, although it may be added only during that step. Adding the metal oxides, e.g., Fe2O3 (preferably at 0.1 %wt) with a continuous controlled linear dosing regime throughout the synthesis process to the electrolyte further enables nucleation centres to be generated.

[0024] Optionally, the reactor chamber comprises nickel metal alloy. The benefit of the reactor chamber comprising the nickel metal alloy is that it enables low impurity levels and uniform carbon morphology to be achieved. The power source for applying an electric current to the one or more anodes and the one or more cathodes is preferably adapted to provide to the device 12 000 - 24 000 ampere (A) current. E.g., 4 000 A. According to the preferred embodiments of the present disclosure, the applied direct current density is in the range from 100 A rrr2up to 20 000 (preferably 6 000) A rrr2. E.g., when using a direct current (DC) power supply or rectifier the positive (+) terminal is connected to the one or more anode(s) and negative (-) terminal connected to the one or more cathode(s). The high current density and low voltage enables slower growth of carbon material and thus to achieve better structure of the carbon material. As a power source, renewable energy such as solar, wind, hydro etc. power can be used.

[0025] In the preferred embodiments of the present disclosure the heating unit is configured to heat the one or more electrolytes inside the reactor chamber to a temperature from 400 °C to 900 °C. In the case of a lithium carbonate electrolyte, the preferred range is from 730 °C to 800 °C. The heating unit may be one or more insulated industrial ovens for heating the reactor chamber. The heating unit enables the melt salt to be obtained in the reactor chamber. The reactor chamber may be heated to e.g., 770 °C to melt the electrolyte (e.g., lithium carbonate).

[0026] The gas supply unit for providing one or more feedstock gases into a molten electrolyte in the reactor chamber is configured to provide the gas continuously when the device is running. The gas supply unit may comprise means to diffuse the feedstock gases evenly into the electrolyte. Such means to diffuse the feedstock gases may be piping of the feedstock gases arranged in the reactor chamber. Optionally, the gas supply unit comprises electrolyte mixing means to diffuse the CO2 gas evenly into the electrolyte. The electrolyte mixing means enable the gas to be dissolved and distributed in the electrolyte evenly. Slow mass transport in the rector creates a concentration gradient for oxides, leading to faster corrosion of the anode. The electrolyte mixing means may be an S- shaped tube comprising holes and arranged in the reactor chamber inside the electrolyte. If the feedstock gas is pumped through the S-shaped tube inside the electrolyte it generates feedstock gas bubbling in the electrolyte and enables the electrolyte to be mixed.

[0027] According to the preferred embodiments of the present disclosure, the one or more feedstock gases comprise at least one of an exhaust gas or industrial gas comprising one or more of CO, CO2 or CH4. Using feedstock gases such as exhaust gases and industrial flue gases or other waste gases comprising CO2 enables environmental damage to be reduced. For example, the CO2 may be industrial waste CO2 or exhaust CO2 from heavy industry emitters, which according to the present disclosure is used as the feedstock for producing carbon materials.

[0028] The method may be carried out by a device comprising a heating unit (e.g., a furnace), a reactor chamber, one or more anodes arranged in a 3D structure, a gas supply unit and a power source.

[0029] The electrodes and electrolytes (e.g., lithium carbonate, potassium carbonate, sodium carbonate or lithium, potassium or sodium halides or any mixture thereof) are inserted in the reactor chamber. The electrodes are connected to the power source and as the current is applied to the electrodes, the electrolysis process initiates. The power source provides the electrodes with electrons to split the electrolyte into solid carbon and dissolved alkali metal oxide, with a current input in the range of 12 000 - 24 000 A and direct current density is in the range from 100 A rrr2up to 20 000 A rrr2. Direct current of the power source positive (+) terminal is connected to the anode and negative (-) terminal connects to the one or more cathodes. The specific current density used per cathode surface area may be e.g., 0.08 A cm-3- 0.16 A cm-3.

[0030] The electrodes and the electrolytes are ideally heated up to a temperature from 450 °C to 850 °C. Lithium carbonate is preferably used as an electrolyte. The heating unit is heated to 770 °C to melt the electrolyte and iron(III) oxide Fe2O3 catalyst (at 0.1 wt%) is added to the electrolyte salt to generate nucleation centres.

[0031] The oxide anions migrate onto the one or more anodes, where they are oxidized into gaseous oxygen. At the same time, the electrolyte readily absorbs CO2. The electrochemical process is initiated by the molten electrolyte and applied potential to the electrodes. In the process the CO2 molecule is separated into C and O2. Oxygen is evolved and is optionally vented out from the reactor chamber by a ventilation system. At the same time the carbon is collected at the one or more cathodes of the electrodes.

[0032] Concentrated CO2 is bubbled through an S-shaped gas supply unit which sits close to the bottom of the reactor chamber and has holes in the bottom side of the tube. The flow rate of CO2 preferably needs to be at least 4.2 standard cm3min1A’1.

[0033] The maximum flow is limited by bubbling, which would, if too intense, decrease the contact area between the electrolyte and the electrodes. As the current is applied to the electrodes, the electrolysis process initiates. Carbon transforms from Li2CO3 to carbon material such as multi-walled carbon nanotubes (MWCNT) and deposits onto the cathode.

[0034] The process is a four-electron reduction. The transformation also produces Li2O and O2 gas, which is bubbled out from the molten electrolyte. The produced Li2O on the other hand reacts immediately with incoming CO2 acting as a carbon capture to produce U2CO3. Thus, the process is CO2 and electrical energy dependent, which are the only consumables in the process.

[0035] At the beginning of the process the electrolyte including additives is preferably melted by the heating unit in which the reactor chamber sits. After the electrolyte is in a molten state the CO2 flow is turned on with a mass flow controller (MFC) and the electrodes are lowered into the molten electrolyte. Thereafter, the current from the power supply is turned on, which commences the electrolysis electrochemical transformation process. The MWCNT preferably grows on the cathode with a rate of about 0.12 g A1h’1. The resistive heating taking place between the anode and cathode releases excess heat to the molten electrolyte which keeps it molten, therefore the heating unit extra heating is required only at the beginning to melt the electrolyte salt and during the times when the electrolysis current is switched off.

[0036] The method may further comprise adding additives to the electrolyte, e.g., electrolyte dopant additives containing dopant heteroatoms such as N, S, B, Fe, Mn, Co, Ni, Zn, P, Cu, Cr, Ti. Adding the additives enables the inclusion of controlled quantities of metal oxides into the electrolyte, which act as catalysts instead of impurities from electrodes.

[0037] In a preferred embodiment, the one or more feedstock gases are bubbled into the molten electrolyte in the reactor chamber. The bubbled gas enables it to be mixed in the molten electrolyte and directed to the electrodes.

[0038] The method according to the preferred embodiments of the present disclosure thus produces carbon materials such as carbon nanotubes (CNT), carbon nanospirals, carbon nanospheres, carbon nanofibers (CNF), carbon nanoflakes, multi-walled carbon nanotubes (MWCNT), oxidized multiwall carbon nanotubes (OMWCNT).

[0039] Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments construed in conjunction with the appended claims that follow.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the embodiments of the disclosure are shown in the drawings, with references to the following diagrams wherein:

[0042] Figure 1 shows a block scheme illustrating an embodiment of a device for producing carbon materials from one or more feedstock gases according to the present disclosure;

[0043] Figure 2 shows a schematic illustration of an embodiment of a device for carrying out the present invention;

[0044] Figures 3A and 3B show SEM images comparing carbon nanostructures formed from the addition of catalyst in bulk compared to a controlled dosing regime;

[0045] Figure 4 shows an SEM image of a carbon nanotubes formed in accordance with the invention; and Figure 5 shows an SEM image of a graphitic carbon flakes formed in accordance with the invention.

[0046] DETAILED DESCRIPTION OF THE DRAWINGS

[0047] Referring to Figure 1, there is shown a block scheme illustrating an embodiment of a device for producing carbon materials from one or more feedstock gases according to the present disclosure. The device comprises a reactor chamber 120, a power source 160, a heating unit 170 and a gas supply unit 180.

[0048] Referring to Figure 2, there is shown a schematic illustration of an embodiment of a device according to the present disclosure. The device comprises a heating unit 170 having a drainage opening 123, a reactor chamber 120 insertable to the heating unit 170, wherein the reactor chamber 120 comprises a drainage 125 and a gas supply unit 180, an electrode interface having a first frame 128 with sockets for anodes mounting and a second frame 130 with cathode sockets for cathodes mounting, sheet anodes 140 arranged in an 3D structure adapted to be mountable to the sockets of the first frame 128, multiple cathodes 150 adapted to be mountable to the sockets of the second frame 130 and a cover of the furnace 132.

[0049] The gas supply unit 180 is arranged in the reactor chamber 120. The anodes 140 arranged in the 3D structure mounted to the first frame 128 are insertable to the vessel of the one or more electrolytes 124, wherein when the anodes 140 arranged in the 3D structure are inserted to the reactor chamber 120, the pipeline of the gas supply unit 180 is arranged in the reactor chamber 120. The multiple cathodes 131 mounted to the second frame 130 are insertable to the reactor chamber 120. Referring to Figure 3A, there is shown an SEM image of the morphology of carbon nanotubes mixed with carbon black resulting from a bulk catalyst addition method. Figure 3B shows an SEM image of the morphology of carbon nanotubes mixed with carbon black resulting from a controlled catalyst dosing method of the present invention.

[0050] WORKED EXAMPLES

[0051] Comparative Example 1

[0052] Carbon nanomaterials were synthesized within an Inconel 600 vessel, securely positioned within a stainless steel safety vessel. The Inconel 600 vessel was filled with high purity Li2CO3 (>99%,) supplemented with 0.1 wt% of Fe2O3 (purity >96%, Sigma Aldrich, Germany) which was added in bulk in one go at the beginning of the process. An Inconel 600 anode and a Monel 400 cathode were positioned approximately 1-2 cm above the bottom of the reactor. Electrolysis was initiated by applying a direct current electrical program determined by precise cathode surface area measurements. A controllable power supply was utilized to regulate the applied current over time. Pressurised CO2 (>98% purity) was guided into the bottom of molten salt with constant flow (4.2 standard cm3min1A1mass equivalent) which was maintained by the mass flow controller. The synthesis duration was set at 18 hours.

[0053] Upon completion of the reaction, the carbon product was removed from the cathode. The collected material underwent electrolyte demineralization, involving a wash with 10M HCI to eliminate excess electrolyte and metal impurities. Subsequent steps included water wash neutralization, vacuum filtration and drying in an oven for 12 hours at 60°C.

[0054] The results are shown in Figure 3A. Example 2

[0055] In another experiment, carbon nanomaterials were synthesized within an Inconel 600 vessel, securely positioned within a stainless steel safety vessel. The Inconel 600 vessel was filled with high purity U2CO3 (>99%). The electrolyte was allowed to melt overnight, ensuring homogeneity and complete moisture removal.

[0056] An Inconel 600 anode and a Monel 400 cathode were positioned approximately 1-2 cm above the bottom of the reactor. Electrolysis was initiated by applying a direct current electrical program determined by precise cathode surface area measurements. A controllable power supply was utilized to regulate the applied current over time. Pressurised CO2 (>98% purity) was guided into the bottom of molten salt with constant flow (4.2 standard cm3min-1A-1mass equivalent) which was maintained by the mass flow controller. One hour before the electrosynthesis starts, the controlled dosing of the Fe2O3 started with a constant rate at mass dosage rate 52.6 ppm hour1to reach the total catalyst amount 0.1 wt% of the total molten electrolyte mass until the end of the synthesis. The synthesis duration was set at 18 hours.

[0057] Upon completion of the reaction, the carbon product was removed from the cathode. The collected material underwent electrolyte demineralization, involving a wash with 10M HCI to eliminate excess electrolyte and metal impurities. Subsequent steps included water wash neutralization, vacuum filtration and drying in an oven for 12 hours at 60°C.

[0058] The results are shown in Figure 3B.

[0059] As seen from the SEM image results of the first experiment (Figure 3A), if the catalyst is added in bulk in one go, the end carbon product morphology is not clear multi-walled carbon nanotubes (MWCNTs). Rather, a mixture of spherical carbon (carbon black [CB] / nano-onions) start to slightly grow further, i.e. lower grade mixture of

[0060] CB / MWCNTs. The reason for this is that the majority of the Fe2O3 catalyst drops to the bottom of the reactor vessel. This was detectable even by slightly stirring the molten electrolyte mixture with an alumina rod, with a higher viscosity noticeable at the bottom of the mixture. As the catalyst drops to the bottom, the Fe2O3 does not reach the cathode efficiently anymore to act as a carbon nanotube growth nucleation centre.

[0061] With the controlled dosing method of the second experiment, the SEM image results in Figure 3B demonstrate that adding the Fe2O3 catalyst in a controlled constant manner throughout the whole synthesis process obtains a carbon product with a clearer MWCNTs morphology.

[0062] The suitable range of Fe2O3 is determined to be from 0.03 wt% to 2 wt% of the total electrolyte mass at a dosage rate from 16.7 ppm hour1to 1100 ppm hour1in the reactor vessel by the end of the 18 hour synthesis. If the concentration of the Fe2O3 catalyst gets too high, it alters the end carbon product morphology once again to lower grade carbon.

[0063] The following examples were carried out using the process as described in Examples 1 and 2, with the following specific process parameters:

[0064] Example 3

[0065] Electrolyte: U2CO3

[0066] Additive: 0.1wt% Fe2O3 from total electrolyte mass

[0067] Dosing rate: 41.7 ppm hour1

[0068] Temperature: 750°C

[0069] Current density: 0.08 A cm-2of cathode submerged surface area CO2 bubbling rate: 5 standard cm3min1A1 A purification process was carried out in HCI until total dissolution of solidified electrolyte was achieved.

[0070] The results are shown in Fig. 4. The SEM image shows pure and clearly defined MWCNT formation.

[0071] Example 4

[0072] Electrolyte: Li2CO3 / Na2CO3 / K2CO3 carbonates eutectic mixture, 43.5 / 31.5 / 25. Owt%

[0073] Additive: 1.3wt% LiOH from total electrolyte mass Dosing rate: 541.7 ppm hour1Temperature: 600°C

[0074] Current density: 0.2 A cm-2of cathode submerged surface area CO2 bubbling rate: 4.8 standard cm3min1A1

[0075] A purification process was carried out in HCI until total dissolution of solidified electrolyte was achieved.

[0076] The results are shown in Fig. 5. With an electrolyte composition of Li2CO3 / Na2CO3 / K2CO3 carbonates forms a eutectic mixture with significantly lower melting point at around 400°C. In this experiment LiOH was used as an additive with a dosing rate of 541.7 ppm hour1. This additive dosing method yields graphitic flake-like structures as seen in the SEM image.

[0077] In molten salt CO2 capture and electrochemical transformation processes, alkaline earth metal carbonates such as BaCOs, CaCOs and SrCOs behave similarly to other alkali metal carbonates like Li2COs, Na2COs and K2CO3. This expectation arises from their comparable ionic structures and melting points, which influence their roles as electrolytes in high-temperature molten salt applications. Similarly, catalysts such as U2O, NiO, ZnO, Cr20s and Ni function comparably to Fe2Os or LiOH in these processes due to their shared transition metal oxide characteristics, facilitating analogous catalytic mechanisms in CO2 electrochemical conversion. Evidence for said interchangeability of the electrolytes and catalysts can be found in "Overview of CO2 capture and electrolysis technology in molten salts: operational parameters and their effects", Zhu et al., Ind. Chem. Mater., 2023, 1, 595-617.

[0078] All optional and preferred features and modifications of the described embodiments and dependent claims are usable in all aspects of the invention taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another. The disclosures in UK patent application number 2319842.7, from which this application claims priority, and in the abstract accompanying this application are incorporated herein by reference.

Claims

CLAIMS1. A method of producing carbon material from one or more carbon- containing feedstock gases, the method comprising the following steps:(a) melting one or more electrolytes inside a reactor chamber,(b) adding a catalyst to the molten electrolyte, wherein the catalyst is added from 0.03 wt% to 2 wt% of the total electrolyte mass at a dosage rate from 16.7 ppm hour1to 1100 ppm hour1,(c) adding one or more feedstock gases to the molten electrolyte at a flow rate of at least 4.2 standard cm3min1A1mass equivalent of CO2,(d) applying a direct current density in the range from 100 A rrr2up to 20 000 A rrr2to one or more anodes and one or more cathodes in contact with the molten electrolyte.

2. A method as claimed in claim 1 wherein the catalyst is Fe2O3, Li2O,LiOH, NiO, ZnO, Cr20s, Ni, or any combination thereof.

3. A method as claimed in claim 1 or 2 wherein the catalyst is Fe2O3.

4. A method as claimed in any preceding claim wherein the electrolyte includes a carbonate-group.

5. A method as claimed in any preceding claim wherein the electrolyte includes Na2CO3, Li2CO3, K2CO3, BaCOs, CaCOs, SrCOs or any combination thereof.

6. A method as claimed in any preceding claim wherein the electrolyte includes Li2CO3.

7. A method as claimed in any preceding claim, wherein the one or more electrolytes is heated to a temperature from 400 °C to 900 °C.

8. A method as claimed in any preceding claim, wherein the one or more electrolytes comprises from 90 % to 100 % carbonate-group- containing electrolyte.

9. A method as claimed in any preceding claim, wherein the feedstock gas is one or a combination of CO2, CH4 and CO.

10. A method as claimed in any preceding claim, wherein the feedstock gas is CO2.

11. A method as claimed in any preceding claim further comprising removing the carbon material from the one or more cathodes.

12. A method as claimed in any preceding claim, wherein the one or more feedstock gases are bubbled into the molten electrolyte.

13. A method as claimed in any preceding claim, wherein the dosage rate is substantially linear.

14. Carbon material obtainable by means of a method as claimed in any preceding claim.

15. An electric battery including carbon material as claimed in claim 14.

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