Method and apparatus for producing carbon materials incorporating additives - Patents.com

Abstract

A method for producing carbon materials from one or more carbon-containing feed gases is provided. [Solution] The process includes providing an electrolytic cell comprising an anode 130, a cathode 140, and a reaction vessel configured to contain a molten electrolyte, the cathode being disposed at least at the bottom of the reaction vessel; supplying molten electrolyte 150 into the reaction vessel such that an electric current passes between the anode and the cathode through the molten electrolyte, the additive being configured as a layer coating on a surface of the cathode at the bottom of the reaction vessel such that the additive is on the surface of the cathode and is disposed in contact with the molten electrolyte; and applying a voltage between the anode and the cathode while supplying one or more carbon-containing feedstock gases to the molten electrolyte, thereby producing a carbon material.

Description

[Technical field]

[0001] The present disclosure generally relates to the production of carbon materials incorporating additives using a carbon-containing gas as a feed gas. [Background technology]

[0002] Carbon materials in different forms, such as powders and dispersions, are becoming increasingly important in the manufacture of energy storage devices (e.g., supercapacitors, batteries, fuel cells and other energy storage systems) due to their electrical and mechanical properties.

[0003] For example, transition metal nitrogen doped carbon materials (MNCs) have been attracting attention as promising candidates to replace Pt catalysts in solid polymer electrolyte membrane fuel cells (PEMFCs) because the doped carbon materials have low cost and high electrocatalytic activity. In recent years, many reports have shown that carbon nanomaterials co-doped with copper and nitrogen are efficient and durable electrocatalysts. Catalysts containing Cu-Nx sites supported on a carbon matrix, also known as single atom catalysts (SACs), reduce oxygen through a four-electron pathway. Cu-N x A site consists of a copper atom surrounded by x nitrogen atoms (mainly x=2, 3, 4). Transition metal macrocycles such as metal phthalocyanines and porphyrins are often used to prepare SACs. These molecules have a metal atom bonded to four nitrogen atoms, and therefore serve as active sites for MNC catalysts. N-doped carbon encapsulated copper particles (Cu@NC) are another group of Cu-NC catalysts. The carbon shell protects the metal particles from corrosion and oxidation and controls the electronic interaction with the adsorbate in the oxygen reduction reaction (ORR). Moreover, the activity of MNC materials is partially attributed to the nitrogen moieties in the carbon lattice, with pyridinic-N and graphitic-N being the most suitable species for effective oxygen reduction.

[0004] Molten salt CO2 capture and electrochemical conversion (MSCC-ET) has recently emerged as an attractive method for producing carbon-based materials. In this process, carbonate-containing molten salts are converted into solid carbon and O2, which absorbs CO2 from the atmosphere. 2- ions. Using MSCC-ET, carbon nanotubes, carbon spheres, and graphite have been successfully synthesized. The morphology of carbon materials derived from CO2 can be changed according to the electrolysis conditions. For example, carbon nanotubes, carbon spheres, and graphite have been successfully synthesized using MSCC-ET.

[0005] In "Controlled Growth of Unusual Nanocarbon Allotropes by Molten Electrolysis of CO2" (Catalysts 2022, 12, 125), Liu et al. disclose a method to synthesize carbon materials by electrolysis using a molten carbonate electrolyte and discuss the effect of different metal and metal oxide additives in the molten electrolyte on the resulting nanocarbon morphology.

[0006] In "Nickel and Nitrogen-Doped Bifunctional ORR and HER Electrocatalysts Derived from CO2" (ACS Sustainable Chem. Eng. 2022, 10, 1, 134-145), Remmel et al. disclose the synthesis of nickel- and nitrogen-co-doped carbon materials by electrolysis using a molten carbonate electrolyte containing NiO as an additive, followed by N-doping with DCDA and PVP. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method and an apparatus for producing a carbon material incorporating an additive using a carbon-containing gas as a raw material gas. [Means for solving the problem]

[0008] According to one embodiment of the present invention, there is provided a method for producing carbon materials from one or more carbon-containing feed gases, the method comprising the steps of: providing an electrolysis cell comprising an anode, a cathode, and a reaction vessel configured to contain a molten electrolyte, the cathode being disposed at least at a bottom of the reaction vessel; providing a molten electrolyte in the reaction vessel such that an electric current passes between the anode and the cathode through the molten electrolyte, the additive being configured as a layer coating on the surface of the cathode at the bottom of the reaction vessel such that the additive is on the surface of the cathode and is disposed in contact with the molten electrolyte; and Applying a voltage between the anode and the cathode while supplying one or more carbon-containing feedstock gases to the molten electrolyte, thereby producing the carbon material.

[0009] This method allows for the production of carbon materials with additives incorporated into the carbon network during carbon formation from a carbon-containing feed gas such as CO2. By configuring the additive as a layer that coats the surface of the cathode, the carbon material can be formed through a layer of additive, embedding the additive into the carbon network of the forming carbon material. This results in a good dispersion of the additive in the carbon material formed at the cathode. This method also allows for the incorporation of the additive into the carbon matrix without requiring an additional doping step after the synthesis of the carbon material to incorporate the additive into the carbon network.

[0010] The electrolysis cell includes a reaction vessel configured to contain a molten electrolyte, and a cathode is disposed at least at the bottom of the reaction vessel such that the additive-coated surface of the cathode is disposed within the molten electrolyte when the molten electrolyte is contained within the reaction vessel. This provides a suitable configuration for coating a wide range of additive materials onto the surface of the cathode. For example, the additive material in powder form can be spread across the surface of the cathode to coat the surface, thereby incorporating the additive into the carbon material formed on the cathode surface during electrolysis.

[0011] It will be appreciated that the reaction vessel may have any suitable shape suitable for containing the molten electrolyte. The reaction vessel may be any three-dimensional structure that defines a cavity capable of containing the molten electrolyte. The reaction vessel may be, for example, substantially cubic or substantially cylindrical. The reaction vessel preferably includes a substantially flat interior bottom surface on which the cathode is disposed.

[0012] The cathode may define at least a portion of the inner bottom surface of the reaction vessel, or may define the entire inner bottom surface of the reaction vessel. The cathode may form at least the bottom of the reaction vessel (particularly the substantially flat inner bottom surface of the reaction vessel), and in some embodiments, the entire reaction vessel (i.e., the reaction vessel is formed of a cathode material such that the reaction vessel functions as the cathode during the electrolysis process). In other words, the cathode may be molded to form the reaction vessel (i.e., the cathode is the reaction vessel). Thus, the molten electrolyte may be contained within the cathode, and the additive may be configured as a layer coating the inner bottom surface of the cathode. This provides a suitable configuration in which the additive may be provided as a layer coating the surface of the cathode to be disposed between the cathode and the molten electrolyte.

[0013] The additive may have a density at the reaction temperature that is greater than the density of the molten electrolyte. Thus, the additive may be coated onto the cathode simply by placing the additive on the cathode located at the bottom of the reaction vessel. Due to the relative densities of the additive and the molten electrolyte, the additive remains coated onto the cathode by gravity during the synthesis process. This keeps the additive adjacent to the cathode during the synthesis process, allowing for effective incorporation of the additive into the carbon material formed at the cathode. The additive may be placed into the reaction vessel to coat the cathode surface (e.g., by spreading the additive material over the entire surface of the cathode) before the electrolyte is added to the reaction vessel. The molten electrolyte may be placed into the reaction vessel first (by melting the electrolyte and then adding it to the reaction vessel, or by melting the electrolyte in the reaction vessel), and then the additive may be added to the molten electrolyte and allowed to settle to the bottom of the reaction vessel by gravity to coat the cathode surface before electrolysis is performed.

[0014] The additive may comprise a metal, particularly at least one of copper, cobalt, nickel, aluminum, and titanium, which may be an elemental metal or a metal compound.

[0015] The additive may include a metal complex, such as a transition metal complex. The metal complex may be a macrocyclic metal complex. The metal complex may be an MN x moieties, where M is a metal and optionally x=2, 3 or 4, i.e., M x The moiety consists of a metal atom surrounded by x nitrogen atoms. The additive may include a metal phthalocyanine or metal porphyrin complex. The additive may include a metal complex selected from the group consisting of copper phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, aluminum phthalocyanine, and titanium phthalocyanine, or any combination thereof.

[0016] In some embodiments, the loading of the additive on the surface of the cathode is between 1 and 20 mg cm -2In one embodiment, the additive is copper phthalocyanine, and the loading of copper phthalocyanine on the surface of the cathode is in the range of 2 to 8 mg cm. -2 In particular, the range of 4 mg cm -2 may be also possible.

[0017] The electrolyte may include a carbonate base. The electrolyte may include Na2CO3, Li2CO3, K2CO3, BaCO3, CaCO3, or any combination thereof. In one embodiment, the electrolyte includes a eutectic mixture of Na2CO3, Li2CO3, and K2CO3. Providing a eutectic mixture of salts reduces the melting point of the electrolyte and therefore allows the synthesis to be carried out at lower temperatures. This increases the specific surface area of ​​the synthesized material and improves the microporosity, which in turn improves the electrocatalytic performance of the carbon material.

[0018] The electrolyte may be heated to a temperature of from 400° C. to 900° C. to melt the electrolyte and maintain it in a molten state.

[0019] Applying a voltage between the anode and the cathode can be performed by a power supply adapted to provide a current of 12,000 to 24,000 amperes (A), for example 4,000 A, to the device. According to an embodiment of the present disclosure, the applied direct current density is 100 A m -2 to 20,000 (preferably 6,000) A m -2 For example, when using a direct current (DC) power source or rectifier, the positive (+) terminal is connected to one or more anodes and the negative (-) terminal is connected to one or more cathodes. High current density and low voltage allow slower growth of the carbon material and therefore improved structure of the carbon material can be achieved. Renewable energy sources such as solar, wind, and hydroelectric power can be used as the power source.

[0020] The carbon-containing feed gas may include one or a combination of CO2, CH4, and CO. The carbon-containing feed gas preferably includes CO2. The feed gas may be, for example, at least one of flue gas or industrial exhaust gas containing one or more of CO, CO2, or CH4. By using feed gas such as flue gas and industrial exhaust gas or other waste gas containing CO2, environmental damage can be reduced. For example, CO2 may be industrial waste CO2 or exhaust CO2 from heavy industrial sources, and is used as a feedstock for producing carbon materials according to the present disclosure.

[0021] The carbon-containing feed gas may be provided to the electrolysis cell by any suitable means. The feed gas may be present in the atmosphere of the electrolysis cell such that the electrolyte is in fluid communication with the atmosphere containing the feed gas. For example, if the carbon-containing feed gas is CO2, the electrolyte may be open to air such that CO2 naturally present in the air is captured in the molten electrolyte during the electrolysis process. Alternatively, the atmosphere of the electrolysis cell may be controlled to contain a higher CO2 concentration than the natural concentration of CO2 present in the air. For example, exhaust gas, industrial gas or other carbon-containing exhaust gas may be introduced into the atmosphere of the electrolysis cell such that the electrolyte is in fluid communication with the exhaust gas so that CO2, CH4 and / or CO can be captured in the molten electrolyte during the electrolysis process. Other feed gases may be provided as well. Alternatively or additionally, the carbon-containing feed gas may be directly introduced into the molten electrolyte during the electrolysis process, for example, by feeding the gas to the molten electrolyte via a tube. The feed gas may be bubbled into the molten electrolyte.

[0022] By selecting the appropriate cathode material, additional dopants can be incorporated into the carbon material. For example, the cathode may include at least one metal selected from iron, nickel and chromium, or any combination thereof. By incorporating such dopant metals during synthesis, the electrocatalytic properties of the material can be further optimized and improved without the need for an additional doping step. In some embodiments, the cathode may include stainless steel. Alternatively, the cathode may be formed of an inert cathode material, such that the only dopants incorporated into the carbon material come from additives. The cathode may include at least one of graphite or silicon carbide.

[0023] The method may further include removing the carbon material from the cathode. Subsequent steps may then be carried out on the recovered carbon material. For example, the method may include a subsequent nitrogen doping step, particularly when the additive is MN x It is beneficial to include metal complexes with the moiety, which increases the basicity of the carbon support, thereby modifying the electronic properties of the carbon support and enhancing the activity of the metal-nitrogen active sites in the material for the oxygen reduction reaction, thereby improving the electrocatalytic properties of the carbon material.

[0024] The nitrogen doping step may include pyrolyzing a mixture of the carbon material recovered from the cathode and a nitrogen-containing doping agent. The nitrogen-containing doping agent may include at least one of polyvinylpyrrolidone and dicyandiamide.

[0025] According to another aspect of the present invention, there is provided a carbon material obtainable by the above method. The carbon material may contain graphite as a carbon allotrope.

[0026] According to another aspect of the present invention, there is provided an apparatus for producing carbon materials from one or more carbon-containing feed gases, the apparatus comprising: a reaction vessel configured to contain a molten electrolyte; anode; a cathode disposed at least at a bottom of the reaction vessel; a power source for applying a voltage between the anode and the cathode; and A heating unit configured to heat the reaction vessel to maintain the electrolyte in a molten state.

[0027] In this configuration, the apparatus can be configured to provide a layer of additive coating the surface of the cathode by placing the additive material at the bottom of the reaction vessel so as to cover the cathode. As described above with respect to the method of the present disclosure, the carbon material can be formed by electrolysis using a molten electrolyte and a carbon-containing feed gas, thereby forming the carbon material through a layer of additive material, so that the additive material is embedded in the carbon network of the carbon material as it is formed. As a result, the additive is well dispersed in the carbon material formed at the cathode. This apparatus also facilitates the incorporation of the additive into the carbon matrix without the need for an additional doping step after the synthesis of the carbon material. This apparatus provides a suitable configuration that allows a wide range of additive materials to be coated onto the surface of the cathode.

[0028] As discussed above in connection with the methods of the present disclosure, it will be appreciated that the reaction vessel may have any suitable shape suitable for containing the molten electrolyte. The reaction vessel may be any three-dimensional structure that defines a cavity capable of containing the molten electrolyte. The reaction vessel may, for example, be substantially cubic or cylindrical. The reaction vessel preferably includes a substantially flat interior bottom surface on which the cathode is disposed.

[0029] The cathode may define at least a portion of the inner bottom surface of the reaction vessel. The cathode may form at least the bottom of the reaction vessel, and in some embodiments, the entire reaction vessel (i.e., the reaction vessel is formed of the cathode material such that the reaction vessel becomes the cathode during the electrolysis process). In certain embodiments, the cathode may be molded to form the reaction vessel (i.e., the cathode is the reaction vessel). Thus, the molten electrolyte may be contained within the cathode, and the additive may be configured as a layer coating the inner bottom surface of the cathode. This provides a suitable configuration in which the additive may be configured as a layer coating the surface of the cathode and disposed between the cathode and the molten electrolyte. This configuration is particularly beneficial when the additive has a density higher than the density of the molten electrolyte, for example, as described above.

[0030] The device may include an additive configured as a layer coating the surface of the cathode at the bottom of the reaction vessel.

[0031] The apparatus may include a gas supply unit configured to supply one or more feed gases to the molten electrolyte in the reaction vessel. The gas supply unit may be configured to supply the gas continuously during operation of the apparatus. The gas supply unit may include a means for uniformly diffusing the feed gas into the electrolyte. Such a means for diffusing the feed gas may be a feed gas pipe disposed in the reaction vessel. Optionally, the gas supply unit includes an electrolyte mixing means for uniformly diffusing the CO2 gas into the electrolyte. The electrolyte mixing means allows the gas to be uniformly dissolved and distributed in the electrolyte. Slow mass transport in the reaction vessel creates oxide concentration gradients, which accelerates anode corrosion. The electrolyte mixing means may be an S-shaped tube with holes and disposed in the electrolysis cell chamber in the electrolyte. When the feed gas is pumped through the S-shaped tube in the molten electrolyte, bubbles of the feed gas can be generated in the electrolyte to mix the electrolyte. Other suitable means for directly introducing the feed gas into the molten electrolyte will occur to those skilled in the art. [Brief description of the drawings]

[0032] Non-limiting embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a block diagram illustrating an apparatus for producing carbon materials from one or more feed gases. FIG. 2 is a schematic diagram of the electrolysis cell of the apparatus of FIG. FIG. 3 is a flow chart illustrating an example of a method for producing a carbon material. 4A-4C are SEM images of the carbon material produced according to the method of FIG. 4D and 4E are bright field TEM images of carbon materials produced according to the method of FIG. 4F and 5A are HAADF-STEM images of carbon materials produced according to the method of FIG. 5B, 5C and 5D are STEM-EDX images of carbon materials produced according to the method of FIG. 6A, 7A and 8A are HAADF-STEM images of carbon materials produced according to the method of FIG. 6B-6E, 7B-7E and 8B-8E are STEM-EDX images of carbon materials produced according to the method of FIG. FIG. 9 shows the X-ray diffraction pattern of the carbon material produced according to the method of FIG. FIG. 10A is a graph showing the polarization curve of a carbon material produced according to the method of FIG. FIG. 10B is a graph showing the Tafel slope of the carbon material produced according to the method of FIG. 11A-11C are graphs showing Koutecky-Levich plots for oxygen reduction of the carbon material produced according to the method of FIG. FIG. 12 is a graph showing the X-ray diffraction pattern of another carbon material produced according to the method of FIG. 13 and 14 are graphs showing the polarization curves of another carbon material produced according to the method of FIG. 15A-15D are SEM images of another carbon material.

[0033] 1, a block scheme is shown illustrating an apparatus 100 for producing carbon materials from one or more feed gases according to the present disclosure. The apparatus 100 comprises an electrolytic cell 120, a power source 170, a heating unit 180, and an optional gas supply unit 190.

[0034] Referring to Figure 2, a schematic diagram of the electrolysis cell 120 of Figure 1 is shown. The electrolysis cell 120 comprises an anode 130 and a cathode 140. The cathode 140 is shaped to form a reaction vessel that contains layers of molten electrolyte 150 and additive 160.

[0035] The anode 130 is insertable into an interior space defined by the cathode 140 so as to be disposed within the molten electrolyte 150 contained within the cathode 140. Alternatively, the anode 130 may be in a fixed position relative to the cathode 140, which allows the anode 130 to be immersed in the molten electrolyte 150 during use. The anode 130 and cathode 140 are connected via a power supply 170 so that a voltage can be applied to the anode 140 and cathode 150.

[0036] It will be appreciated that the reaction vessel may be formed in any suitable shape capable of containing the molten electrolyte 150. In the illustrated embodiment, the reaction vessel defined by the cathode 140 has a substantially cuboid or rectangular shape so as to adopt a "basket" shape, although other shapes, such as a cylinder, may also be adopted. A variety of other suitable cathode shapes will occur to those skilled in the art.

[0037] 2, gas supply unit 180 (if present) may be disposed within the interior space defined by cathode 140, either in a fixed position or insertably therein. Gas supply unit 180 may take the form of one or more tubes positioned to direct gas directly to electrolyte 150 contained within a reaction vessel defined by cathode 140.

[0038] Alternatively or additionally, a carbon-containing feedstock gas may be introduced into the atmosphere 200 of the electrolysis cell such that it is in fluid communication with the molten electrolyte 150. In this manner, the feedstock gas may be entrained in the molten electrolyte during the electrolysis process.

[0039] Figure 3 is a flow chart illustrating an example of a method for producing a carbon material according to the present disclosure, which is described with further reference to the apparatus shown generally in Figures 1 and 2. The exemplary method includes the following steps:

[0040] S1: Providing an electrolysis cell 120 comprising an anode 130 and a cathode 140, the cathode 140 being shaped to form a reaction vessel containing a molten electrolyte 150.

[0041] S2: Placing a layer of additive 160 on the bottom of the reaction vessel defined by the cathode 140 so as to cover the inner bottom surface 142 of the cathode 140.

[0042] S3: Providing an electrolyte 150 in a reaction vessel defined by the cathode 140 and bringing the electrolyte 150 into a molten state by operation of a heating unit 180, wherein the additive 160 is selected to have a density higher than the density of the molten electrolyte 150 at the reaction temperature, thereby maintaining the additive 160 on the inner bottom surface 142 of the cathode 140.

[0043] S4: A step of applying a voltage between the anode 130 and the cathode 140 by operating the power source 170 while maintaining the molten electrolyte 150 in equilibrium with the CO2-containing atmosphere 200, thereby producing a carbon material on the inner bottom surface 142 of the cathode 140.

[0044] S5: Removing the carbon material from the cathode 140.

[0045] S6: A process of further doping the synthesized carbon material.

[0046] In the described example, the electrolyte 150 is melted in the reaction vessel defined by the cathode 140 in step S3. However, alternatively, the electrolyte 150 may be brought to a molten state outside the reaction vessel and then transferred into the reaction vessel by suitable means. In either case, the heating unit 180 is configured such that the electrolyte 150 in the reaction vessel defined by the cathode 140 is heated to a temperature sufficient to maintain the electrolyte 150 in a molten state during electrolysis.

[0047] In the described example, the additive 160 is selected to have a density greater than that of the molten electrolyte 150 at the reaction temperature, thereby maintaining the additive 160 on the inner bottom surface 142 of the cathode 140 by gravity. This provides a suitable configuration for maintaining a layer of the additive 160 on the surface of the cathode 140 during the electrolysis reaction. However, it will be understood that the surface of the cathode 140 may be coated with the additive 160 by other means as would occur to one skilled in the art.

[0048] At least in the described example, steps S2 and S3 may be performed in any order. In particular, if, as in the described example, additive 160 is selected to have a higher density than molten electrolyte 150, additive 160 may alternatively be placed in the reaction vessel after the molten electrolyte and allowed to settle to the bottom interior surface 142 of cathode 140 prior to the electrolysis reaction.

[0049] In step S4, in the described example, a carbon-containing feedstock gas (CO in this case) is supplied to the molten electrolyte 150 by maintaining the molten electrolyte 150 in equilibrium with a CO2-containing atmosphere 200. However, the carbon-containing feedstock gas may alternatively or additionally be supplied by any gas supply unit 190, which may take any suitable form for introducing gas into the molten electrolyte 150, as described above.

[0050] In the described example, step S6 may in particular be a nitrogen doping step. In particular, a mixture of the carbon material recovered from the cathode and a nitrogen-containing doping agent (e.g., polyvinylpyrrolidone or dicyandiamide) may be subjected to pyrolysis. It will be understood that step S6 is optional, depending on the carbon material produced and the desired application.

[0051] An example of the method for producing a carbon material according to the present disclosure will be described below. EXAMPLES

[0052] Example 1 Synthesis of carbon materials A DC01 steel "basket" reactor was used as the cathode, with a layer of copper phthalocyanine (CuPc) as the additive. The CuPc was spread evenly on the bottom of the cathode, and the inside bottom surface of the cathode was coated with CuPc, after which the cathode was filled with a eutectic mixture of Li2CO3, Na2CO3, and K2CO3 (>99.5%, Lach-Ner) as the electrolyte. The basket was then placed in a heating device, and the electrolyte mixture was heated to 450°C. A graphite rod was used as the anode, and placed in the molten electrolyte. The electrodes were then connected to a power source, and a voltage of 4 V was applied between the electrodes for 2 hours.

[0053] Three different materials were synthesized by coating the inner bottom surface of the cathode basket with 50 mg, 100 mg, and 200 mg of CuPc, which corresponds to 2, 4, and 8 mg cm of the inner bottom surface area of ​​the cathode. -2 (Hereafter, the synthesized materials are referred to as CO2-Cu 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0 (See also:

[0054] After the synthesis was completed, 5 M HCl was added, the mixture was sonicated for 30 min, and left at room temperature for 3 days to remove carbonates and soluble impurities, after which the carbon material was filtered and dried.

[0055] Nitrogen doping of carbon materials The synthesized materials were then further doped with nitrogen. First, 50 mg of each sample of carbon material was sonicated in ethanol with 5 mg of polyvinylpyrrolidone (PVP) and 1 g of dicyandiamide (DCDA) for 2 h. The mixture was then dried and placed in a ceramic boat. The boat was then placed in a quartz tube and then in a furnace. The furnace was purged with Ar and heated to 800 °C. The materials were pyrolyzed for 1 h, cooled and removed from the furnace.

[0056] result During the synthesis, carbon materials are produced by electrolysis of carbonate salts to produce lithium oxide and solid carbon. [ka]

[0057] Carbon is deposited inside a steel reactor vessel, which acts as a cathode during the electrolysis process, incorporating CuPc (known to be stable up to 500 °C) into the carbon network. The steel reactor vessel also serves as a source of Fe doping, as iron is dissolved in the carbonate during carbon deposition. The low synthesis temperature (and high deposition voltage) also helps to form a porous carbon network, which allows better access to the active sites for both CO2 and oxygen reduction.

[0058] Because the carbonates are in equilibrium with the surrounding atmosphere, CO2 is incorporated into the electrolyte, thereby regenerating Li2CO3, enabling a continuous process. [ka]

[0059] To more strongly incorporate CuPc into the carbon lattice, increase the basicity and nitrogen doping level of the carbon material, and homogenize the carbon material, CuPc was suspended in ethanol and pyrolyzed in the presence of DCDA and PVP (see the nitrogen doping step above).

[0060] 4A to 4C show the CO2-Cu prepared as above. 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0 Figure 4A shows the SEM images of the respective carbon materials. The images show that the materials are highly porous. Flakes of graphitic carbon are more evident at the locations of low CuPc incorporation (Figure 4A). At higher CuPc contents, a more amorphous and porous network is formed (Figure 4B and Figure 4C). At lower CuPc contents (Figure 4A), large flakes of graphitic carbon (d>1 μm) are visible. Increasing the CuPc content in the reaction vessel reduced the size of these flakes.

[0061] Figures 4D and 4E show the CO2-Cu 4.0 Bright-field TEM images of the material show the coexistence of graphitic flakes and porous carbon material. Figure 4F is a HAADF-STEM image of the CO2-Cu100 material, showing that the copper is well-dispersed on the surface of the catalyst (visible as bright dots). While most of the copper is dispersed at the atomic level on the surface of the material, Figure 4F also shows the presence of small metal particles.

[0062] STEM-EDX analysis was performed to elucidate whether the particulate phase originated from CuPc or the steel cathode. 4.0Further HAADF-STEM images of the material showing the presence of two nanoparticles within the carbon network. Figure 5B, Figure 5C and Figure 5D are STEM-EDX images showing the chemical distribution of nitrogen (Figure 5B), copper (Figure 5C) and iron (Figure 5D). As can be seen, the distribution of Cu and N is uniform throughout the material, indicating successful uniform incorporation of Cu from CuPc and N from CuPc and DCDA. The STEM-EDX mapping image of Fe (Figure 5D) shows Fe concentrated in the nanoparticles, indicating that the particle phase in the material originates from the steel cathode, rather than from decomposition of CuPc and the formation of copper particles. Thus, this result indicates that CuPc was successfully incorporated into the carbon network as an additive without decomposition. It will be appreciated that other metal dopants can be introduced by using cathodes of different metals, or the central metal in the additive (Cu in this example) can be kept as the only metal dopant by using an inert cathode.

[0063] 6A to 8E show the CO2-Cu prepared according to Example 1. 2.0 (Figure 6A-6E), CO2-Cu 4.0 (Figure 7A-7E) and CO2-Cu 8.0 (FIGS. 8A-8E) provide further STEM-EDX analysis of carbon materials. FIGS. 6A, 7A, and 8A show the structure of CO2-Cu, 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0HAADF-STEM images of the materials. The corresponding STEM-EDX elemental mapping images show the chemical distribution of carbon (Figures 6B, 7B, 8B), nitrogen (Figures 6C, 7C, 8C), copper (Figures 6D, 7D, 8D) and iron (Figures 6E, 7E, 8E) in the carbon materials. For all materials, uniform incorporation of Cu from CuPc and N from CuPc and DCDA was observed, indicating that CuPc was successfully incorporated as an additive into the carbon network without decomposition. All materials also show incorporation of Fe, indicating that the Fe particle phase originates from the steel cathode.

[0064] CO2-Cu 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0 The materials were further analyzed by X-ray photoelectron spectroscopy. The surface elemental composition of each material is shown in Table 1. 2.0 ) loading is 2 mg cm -2 In the case of 4 mg cm, no copper was detected on the surface of the material. This indicates that the copper content on the surface of the material was insufficient for detection by XPS, even though the STEM-EDX mapping analysis above confirmed copper in the material. -2 and 8mg cm -2 At high loadings of 0.3 and 0.2 at.%, the copper content at the surface of the material was 0.3 and 0.2 at.%, respectively. This indicates that increasing the CuPc loading above a threshold level allows copper to be incorporated into the bulk of the material without increasing the surface (electrocatalytic) content. The effect of Cu on the nitrogen content was also demonstrated by XPS data, where a CuPc loading of 4 mg cm -2 Then, CO2-Cu 4.0 The nitrogen content of is 14.5 at.%, which is much higher than the other samples, leading to improved ORR activity as described below. The increased nitrogen content is related to the basicity of the catalyst material, which is known to be an important descriptor of electrocatalytic activity. A higher degree of iron incorporation from the steel basket is also observed, which further increases the activity. The Fe content is associated with a higher CO2-Cu content than the other materials. 4.0The CuPc loading is much higher in the sample, indicating the optimum loading for Fe uptake from the steel cathode.

[0065] [Table 1]

[0066] Figure 9 shows the CO2-Cu 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0 Powder X-ray diffraction patterns of the materials are shown. Graphitized carbon was observed in all three patterns with a (002) diffraction peak at 26.8°2θ. The X-ray diffraction patterns confirm the findings from the microscopy images. Up to the optimum CuPc content, the catalyst material becomes more amorphous (the peak intensity of graphite (002) at 26.8°2θ is reduced to that of CO2-Cu). 4.0 CO2-Cu 2.0 The graphite peak intensity at 26.8°2θ (002) is lower than that of the CO2-Cu alloy, and then becomes more graphitized again during the pyrolysis process (the graphite peak intensity at 26.8°2θ (002) is higher than that of the CO2-Cu alloy). 8.0 CO2-Cu 4.0 Fe impurities from the steel basket used as the cathode were also seen in the diffraction pattern, which may also affect the graphitization and porosity of the material.

[0067] To measure the electrocatalytic activity of the synthesized materials, the rotating disk electrode (RDE) method was employed. First, 2 mg of material and 3 μl of QAPS-S per mg of carbon were mixed. 14 A 1 ml suspension containing the ionomer solution was prepared. The suspension was then pipetted onto a glassy carbon disk electrode that had been polished with 1 μl and 0.3 μl of alumina slurry prior to the experiment, and the residues were removed by successive sonication in isopropanol and Milli-Q water. The catalyst loading was 0.2 mg cm. -2The measurements were carried out in a five-neck electrochemical cell in a 0.1 M KOH solution saturated with oxygen. A graphite rod was used as the counter electrode and a silver / silver chloride electrode (Ag / AgCl) was utilized as the reference electrode. The polarization curves were recorded using a Gamry potentiostat 1010E at a sweep rate of 1.667 mV s -1 The potentials were measured in the range of 0.05 V to -1.15 V vs Ag / AgCl. The rotation speeds of the working electrode were 400, 800, 1200, 1600, 1900, 2400, and 3600 rpm. The speeds were controlled by an OrigaTrod device. The recorded potentials were later converted to the reversible hydrogen electrode (RHE). Table 2 shows the kinetic current density, Tafel slopes, and mass activity of the catalyst derived from CO2 at 0.8 and 0.9 V vs RHE.

[0068] FIG. 10A shows the electrocatalyst CO2-Cu. 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0 The polarization curves of the materials measured in 0.1 M KOH by RDE at 1600 rpm are shown. 4.0 The material showed the best performance, with an onset potential of 0.927 V vs RHE and a mass activity of 31.2 A g at 0.8 V vs RHE. -1 Lower copper loadings resulted in more positive onset potentials and lower mass activities, while higher loadings reduced these values ​​as well.

[0069] Figure 10B shows the CO2-Cu 2.0 , CO2-Cu 4.0 and CO2-Cu 8.0 The Tafel slope of the material is shown. 4.0 The material is the most active catalyst for ORR, but the Tafel slope is 76.1 mV dec -1 With increasing potential, the -1 CO2-Cu 8.0The Tafel slope of the catalyst is 67.9 mV dec -1 and the average Tafel slope of Pt / C (60 mV dec -1 The similarity of the Tafel slope values ​​between the catalysts indicates that the rate-determining step and reaction mechanism are the same.

[0070] [Table 2]

[0071] 11A to 11C show the CO2-Cu 2.0 (Figure 11A), CO2-Cu 4.0 (Figure 11B) and CO2-Cu 8.0 (Figure 11C) The Coutecky-Levich plot of oxygen reduction in the material is shown. The plot was derived based on the ORR data obtained at different rotation speeds. Each inset in Figure 11A to Figure 11C shows the number of transferred electrons per O2 molecule. The number of transferred electrons, n, was calculated using the following equation:

number

[0072] For all materials, at more negative potentials the n value was approximately 4, indicating a four-electron oxygen reduction process. However, at more positive potentials the calculated value of electrons transferred was approximately 3.4-3.5, indicating that a certain amount of H2O2 was produced during the reduction. H2O2 is an undesirable product as it causes degradation of fuel cell components, reduces current efficiency, and impedes the overall performance of the fuel cell. Nevertheless, electrochemical testing demonstrated high electrocatalytic activity of the materials synthesized according to the methods of the present disclosure.

[0073] Example 2 Six additional carbon materials were synthesized by the same electrolytic method as described above for Example 1, except that zinc phthalocyanine (ZnPc), cobalt(II) phthalocyanine (Co(II)Pc), nickel phthalocyanine (NiPc), aluminum chloride phthalocyanine (AlPcCl), and titanium(IV) dichloride phthalocyanine (Ti(IV)PcCl2) were used instead of CuPc. Each additive was added at a concentration of 4 mg cm relative to the surface area of ​​the inner bottom surface of the reaction vessel defined by the cathode. -2 The carbon material produced is referred to as CO2-Zn 4.0 , CO2-Co 4.0 , CO2-Ni 4.0 , CO2-Al 4.0 and CO2-Ti 4.0 Refer to:

[0074] Figure 12 shows the CO2-Zn 4.0 , CO2-Co 4.0 , CO2-Ni 4.0 , CO2-Al 4.0 , and CO2-Ti 4.0 Figure 1 shows the powder X-Ray Diffraction pattern of the carbon material. The XRD pattern showed peaks corresponding to the graphite planes (002) and (004) at 2θ equal to 26.8 and 54.6, respectively. Other peaks were attributed to the presence of iron oxide in the material, which appeared due to corrosion of the cathode.

[0075] FIG. 13 shows the CO2-Zn measured using the same rotating disk electrode method as described above for Example 1. 4.0 , CO2-Co 4.0 , CO2-Ni 4.0 , CO2-Al 4.0 and CO2-Ti 4.0 Figure 1 shows the ORR polarization curves of the materials. Small differences in the electrocatalytic activity of the synthesized materials were observed. Analysis of the polarization curves using the Coutecky-Revitch equation revealed that all the materials catalyzed the ORR via an indirect 2+2 electron pathway.

[0076] Next, CO2-Zn was synthesized by pyrolysis with DCDA and PVP by the same process as described above for the carbon material of Example 1. 4.0 , CO2-Co 4.0 , CO2-Ni 4.0 and CO2-Al 4.0 The material was doped with nitrogen. The N-doped material is hereafter referred to as CO2-N-Zn 4.0 , CO2-N-Co 4.0 , CO2-N-Ni 4.0 and CO2-N-Al 4.0 Figure 14 shows a comparison of the polarization curves of carbon materials before and after nitrogen doping at a rotation speed of 1600 rpm for Co (Figure 14A), Zn (Figure 14B), Al (Figure 14C), and Ni (Figure 14E). As can be seen, a significant increase in ORR activity was observed for all materials after doping with nitrogen.

[0077] Figure 15 shows the CO2-Co 4.0 (Figure 15A), CO2-Al 4.0 (Figure 15B), CO2-Ni 4.0 (Figure 15C) and CO2-Zn 4.0 (Figure 15D) is an SEM image showing the difference in morphology.

[0078] All optional and preferred features and modifications of the described embodiments and dependent claims can be used in all aspects of the invention taught herein. Moreover, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments, are mutually combinable and interchangeable.

Claims

1. 1. A method for producing a carbon material incorporating an additive from one or more carbon-containing feed gases, the method comprising the steps of: providing an electrolysis cell comprising an anode and a cathode shaped to form a reaction vessel containing a molten electrolyte; providing a molten electrolyte in the reaction vessel such that a current passes between the anode and the cathode through the molten electrolyte, the additive being configured as a layer coating a bottom inner surface of the cathode; and Applying a voltage between the anode and the cathode while supplying one or more carbon-containing feed gases to the molten electrolyte, thereby producing a carbon material incorporating the additive.

2. The method of claim 1 , wherein the additive has a density greater than a density of the molten electrolyte.

3. 3. The method of claim 1, wherein the additive is disposed in the reaction vessel so as to cover the bottom inner surface of the cathode prior to adding the electrolyte to the reaction vessel.

4. 3. The method of claim 1 or 2, wherein the electrolyte is placed in the reaction vessel and then melted, or is melted and then placed in the reaction vessel, prior to the addition of the additive.

5. 3. The method of claim 1 or 2, wherein the additive comprises at least one of copper, cobalt, nickel, aluminum, titanium, or iron.

6. The method of claim 1 or 2, wherein the additive comprises a metal complex.

7. The metal complex is MN x 7. The method of claim 6, wherein the moiety is a cyclic alkyl group, M is the metal, and x=2, 3, or 4.

8. The method of claim 1 or 2, wherein the additive comprises a metal phthalocyanine or a metal porphyrin complex.

9. 3. The method of claim 1 or 2, wherein the additive comprises a metal complex selected from the group consisting of copper phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, aluminum phthalocyanine, and titanium phthalocyanine, or any combination thereof.

10. The loading of the additive on the surface of the cathode is between 1 and 20 mg cm -2 The method according to claim 1 or 2, wherein the range is

11. The additive is copper phthalocyanine, and the loading of the copper phthalocyanine on the surface of the cathode is 2 to 8 mg cm -2 The method according to claim 1 or 2, wherein the range is

12. The method of claim 1 or 2, wherein the electrolyte comprises a carbonate base.

13. The electrolyte is Na 2 CO 3 , Li 2 CO 3 , K 2 CO 3 , BaCO 3 , CaCO 3 or any combination thereof.

14. The electrolyte is Na 2 CO 3 , Li 2 CO 3 and K. 2 CO 3 3. The method of claim 1 or 2, comprising a mixture of:

15. The method according to claim 1 or 2, wherein the electrolyte is heated to a temperature of between 400°C and 900°C.

16. The raw gas is CO 2 , C.H. 4 and CO.

17. 3. The method of claim 1 or 2, wherein the feed gases are present in the atmosphere of the electrolytic cell and / or the one or more feed gases are introduced directly into the molten electrolyte.

18. 3. The method of claim 1 or 2, wherein the cathode comprises at least one metal selected from iron, nickel and chromium, or any combination thereof.

19. 3. The method of claim 1 or 2, further comprising removing the additive-incorporated carbon material from the cathode, and subsequently doping the additive-incorporated carbon material with nitrogen.

20. 20. The method of claim 19, wherein the nitrogen doping step comprises pyrolyzing a mixture of the additive-incorporated carbon material and a nitrogen-containing doping agent.

21. 21. The method of claim 20, wherein the nitrogen-containing doping agent comprises at least one of polyvinylpyrrolidone and dicyandiamide.

22. The method of claim 1 or 2, wherein the carbon material incorporating the additive comprises graphite as a carbon allotrope.

23. 1. An apparatus for producing a carbon material incorporating an additive from one or more carbon-containing feed gases, comprising: anode; a cathode configured to be shaped to form a reaction vessel for containing a molten electrolyte, the cathode being configured with a layer of additive coating a bottom interior surface of the reaction vessel; a power source for applying a voltage between the anode and the cathode; and a heating unit configured to heat the reaction vessel to maintain the electrolyte in a molten state.

24. 24. The apparatus of claim 23, further comprising a gas supply unit configured to supply one or more feed gases to the molten electrolyte in the reaction vessel.

25. 25. The device of claim 23 or 24, wherein the additive comprises a metal complex.

26. 25. The device of claim 23 or 24, wherein the additive comprises a metal complex selected from the group consisting of copper phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, aluminum phthalocyanine and titanium phthalocyanine, or any combination thereof.

27. 25. The apparatus of claim 23 or 24, wherein the cathode comprises at least one metal selected from iron, nickel and chromium, or any combination thereof.

28. 25. Apparatus according to claim 23 or 24, wherein the cathode is made of steel.

Images