In-situ grown iron carbide film electrode and preparation method and application thereof

Abstract

The application discloses an in-situ growth iron carbide film electrode and a preparation method and application thereof. An iron source solution is configured; a substrate material is added; the substrate is taken out and dried; the dried substrate is placed in a mixed powder of graphite powder and carbonate, and is heat treated in an inert gas atmosphere at a set temperature; the product is cooled to room temperature, ultrasonic cleaned and thoroughly dried to obtain an Fe3C film electrode in-situ grown on the substrate. The reaction solution and powder of the preparation method can be reused, the morphology and size of the Fe3C film can be controlled by the type and proportion of the iron source solution, the type of the carbonate and the temperature and time of the reaction process, the size of the Fe3C film in-situ grown on the substrate material is uniform, and the adhesion is strong. Meanwhile, the production process is simple and easy. The prepared Fe3C film / substrate can be directly used as an electrode material, and is expected to be applied in the fields of energy storage, ion exchange, catalysis or magnetic storage, information, energy and environment.

Description

Technical Field

[0001] This invention belongs to the field of thin film material preparation technology, specifically relating to an in-situ grown iron carbide thin film electrode, its preparation method, and its application. Background Technology

[0002] Clean energy is environmentally friendly and readily available in nature, but its supply is limited by time and location, making it unreliable for continuous and stable power generation. Therefore, developing novel energy conversion and storage devices to provide a continuous and stable power supply is essential. Supercapacitors, as a novel, highly efficient, and clean energy storage device, store charge based on rapid electrostatic adsorption or Faraday electrochemical processes on and near the surface of electrode materials. Although the charge storage mechanism is similar to that of traditional capacitors, their specific capacitance and energy density are increased by 100,000 times or more compared to traditional capacitors. Compared to batteries, supercapacitors can provide faster charge / discharge rates in minutes or even seconds, offering advantages such as high safety, long cycle life, wide operating temperature range, and environmental friendliness. However, their energy density is relatively low, making them suitable for applications such as high-energy pulses. How to design and develop electrode materials with high specific capacitance to improve their energy density is a key problem that urgently needs to be solved.

[0003] Iron (Fe), an abundant energy resource on Earth, is a vital force in structural materials. After oxygen, silicon, and aluminum, iron is the most abundant element in the Earth's crust. Iron-based compounds possess high theoretical specific capacitance, good redox activity, a wide operating window, and are environmentally friendly. Their cost advantages and energy storage potential make them one of the most promising electrode materials for industrialization. Iron-based compounds are diverse and widely used. Different iron-based compounds have their own advantages in physical properties, chemical properties, valence changes, environmental friendliness, and structural stability, showing great potential and prospects in information, energy, and environmental fields such as energy storage, ion exchange, catalysis, and magnetic storage. Among them, the nanoscale morphology of Fe3C possesses superior properties compared to its bulk form, attracting extensive research. Compared to nanopowders, nanofilms are typically grown directly on conductive substrates, exhibiting a higher specific mass of active material and eliminating intermediate processes such as coating. This significantly reduces manufacturing costs and time, greatly improves yield, and better meets industrialization needs. In addition, in the field of catalysis, nanofilms can better adapt to the recycling of application scenarios and avoid secondary pollution; in the field of magnetic storage, nanofilms can more accurately form micro-nano devices, improve the control precision and speed of storage devices, and effectively reduce power consumption.

[0004] The preparation of Fe3C is based on the consensus principle of iron reduction reaction, and is currently mainly achieved through a stepwise combination of one or more methods, such as solvothermal synthesis, sol-gel synthesis, sintering, and electrospinning. However, many synthesis processes produce Fe3C in powder form. For example, patent CN 120205189 A discloses an Fe3C catalyst, its preparation method, and its uses. This method involves hydrothermal aging of a prepared iron salt solution, followed by centrifugation, washing, and drying to obtain the catalyst precursor, which is then further reduced, carbonized, and decarbonized to finally obtain the Fe3C catalyst. This synthesis process requires multiple steps, involving multiple high-temperature reactions, resulting in high energy consumption, high production costs, and difficulty in control, which is not conducive to large-scale production. Therefore, although the solvothermal method combined with sintering and carbonization can obtain Fe3C, the product can only be synthesized into powder, the preparation conditions are complex and demanding, and the morphology and size are difficult to control, which is not conducive to industrial production. Similarly, patent CN 121342028 A discloses an ultra-small iron carbide nanoparticle, its preparation method, and its application. This method requires using mesoporous silica as a template and involves multiple steps including hydrothermal treatment with a dual iron source, high-temperature calcination, and etching to obtain ultra-small powdered iron carbide particles. Another example is patent CN 121155644 B, which discloses an in-situ formed FeO... x The Fe3C catalyst and its preparation method and application involve a complex multi-step process, resulting in a non-pure phase iron compound powder. Patent CN 112038635 B discloses a graphene-supported cementite particle composite cathode material for lithium-sulfur batteries and its preparation method. Although the resulting Fe3C-containing composite cathode material has applications in lithium-sulfur batteries, the electrochemically active material obtained is not pure phase Fe3C, and the product is in powder form, requiring additional coating and drying steps to form a usable electrode. Similarly, for example, the research work of Bo Wang et al. (…) International Journal of Biological Macromolecules 251 (2023) 126325 ), the research work of Shuge Dai et al. ( Journal of Power Sources 482 (2021) 228915 ), the research work of Xiaotong Wang et al. ( Chemical Engineering Journal 412 (2021) 128720 ), the research work of Gwan Hyeon Park et al. ( J. Mater. Chem. A, 2025, 13, 13028 ), the research work of Njemuwa Nwaji et al. ( ACS Appl. Mater. Interfaces 2023, 15, 34779−34788 ), the research work of Debendra Acharya et al. ( ACS Appl. Energy Mater. 2023, 6, 9196−9206The resulting products are Fe3C composite lignin powder, Fe2O3@Fe3C@C nanochain composite nickel-cobalt carbonate hydroxide hybrid microsphere powder, nitrogen-doped carbon shell coated Fe3C powder, nitrogen-doped carbon hybrid Fe3O4 / iron / Fe3C powder, Fe3C@NiCo2S4 powder, and Fe2O3 / porous carbon layer@Fe3C / electrospun porous carbon powder. When used as electrodes in electrochemical energy storage devices, these powder materials require multiple steps including slurry preparation, coating, drying, and pressing to obtain usable electrodes. It is important to note that although the products from these studies all contain Fe3C, none of them can directly produce pure-phase Fe3C nanofilms on a conductive substrate. Therefore, although the process based on the principle of iron reduction and combining solvothermal methods with multiple steps such as sintering, carbonization, and etching is a common method for obtaining Fe3C powder, the production process is complex and cumbersome, generates a large amount of waste, causes serious environmental pollution, and is costly. In particular, when used as an electrode, it often requires the addition of other binders and other substances, as well as subsequent processes such as coating, which is not conducive to industrialization.

[0005] While there are processes that can form Fe3C thin films, such as the electrospinning method for magnetic Fe3C-loaded hollow carbon-based nanofiber composite materials disclosed in patent CN 117604683 A, the preparation process is complex, and the electrospinning process itself has high equipment requirements. Another example is the nano-Fe3C particle composite carbon-based conductive film and its preparation method disclosed in CN 114974731 B. The preparation process requires equipment that can support the Joule reduction reaction of iron, which has high equipment requirements, requires a large amount of energy to be provided in a short time, and is energy-intensive. Furthermore, the choice of substrate can only be carbon-based conductive films, which lacks universality. However, the above methods cannot obtain high-performance supercapacitor electrode materials. Summary of the Invention

[0006] Compared with the traditional preparation techniques described above, the raw materials involved in the preparation method of this invention can be recycled, saving costs. Furthermore, the raw materials are non-toxic, consume less energy, and are environmentally friendly. Simultaneously, the preparation method of this invention is applicable to the direct in-situ growth of Fe3C thin films on various types of substrates. The resulting composite material can be directly used as an electrode material for supercapacitors and also has great potential in many other fields. Therefore, this invention not only provides a method for in-situ growth of Fe3C thin film electrode materials on substrates, but also eliminates the need for template agents and binders, reduces the number of steps, shortens the preparation cycle, and makes the production process easy to control, applicable to multiple substrates. By controlling the iron source reaction solution, the type and ratio of graphite powder and carbonate, and the reaction temperature and time, the nanomorphology, structure, size, and quality of Fe3C can be easily controlled. The resulting thin film can be directly used as an electrode for supercapacitors, exhibiting excellent performance, simple preparation, and facilitating industrialization.

[0007] The purpose of this invention is to provide a method for preparing an in-situ grown iron carbide thin film electrode, comprising the following steps: S1. Dissolve iron-containing salt and urea in water to obtain an iron source reaction solution; obtain and add the substrate to the iron source reaction solution and let it stand for a period of time; S2. Remove the substrate and dry it in an air atmosphere at a certain temperature for a period of time; S3. Thoroughly mix graphite powder and carbonate to form a mixed powder; fill the dried substrate into the mixed powder, heat from room temperature to the reaction temperature at a certain heating rate, and keep it at the temperature to allow it to react for a period of time; S4. The product from the S3 reaction is cooled to room temperature in the furnace, cleaned, and dried to obtain an Fe3C thin film electrode grown in situ on the substrate.

[0008] Preferably, the substrate is specifically carbon cloth, carbon felt, carbon paper, nickel foam, FTO conductive glass, titanium metal substrate, 304 stainless steel metal substrate, or copper metal substrate.

[0009] Preferably, the iron-containing salt is any one or a combination of nitrates, sulfates, chlorides, phosphates, acetates, and carbonates of the metallic element iron.

[0010] Preferably, in S1, the iron-containing salt and urea are dissolved in deionized water, and the mass ratio of the iron-containing salt, urea and deionized water in the iron source reaction solution is (100~0.01):1:(1000~20).

[0011] Preferably, in the mixed powder, the mass ratio of graphite powder to carbonate is (74-0.01):1.

[0012] Preferably, the step of adding the substrate to the iron source reaction solution and letting it stand for a period of time specifically means standing for 0.5 to 24 hours at a temperature range of 10 to 90°C.

[0013] Preferably, in step S4, the drying specifically includes drying for 0.5 to 24 hours at a temperature range of 10 to 90°C.

[0014] Preferably, in S3, the carbonate is sodium carbonate, potassium carbonate, or a mixture of both. By controlling the composition and ratio of the carbonate, the density of the Fe3C structure can be controlled: when the molar mass ratio of the two is 1:1, the Fe3C nanostructure formed is the sparsest; the further the molar mass ratio of the two deviates from 1:1, the denser the Fe3C nanostructure formed; when it is only sodium carbonate or only potassium carbonate, the Fe3C nanostructure formed is the densest.

[0015] Preferably, the step of heating from room temperature to the reaction temperature at a certain heating rate and holding the temperature to allow the reaction to proceed for a period of time specifically includes: the heating rate being 0.5~10 ℃ / min, the reaction temperature being 700~1200℃, and the reaction time being 0.5 hours~12 hours. Within the specified heating rate range, the nanostructure size and morphology of Fe3C can be adjusted by regulating the heating rate. The size of nanostructures can be increased by increasing the heating rate, resulting in polyhedral structures; the size of nanostructures can be reduced by decreasing the heating rate, resulting in sheet-like structures. Within the stated reaction temperature range, the degree of crystallinity of the Fe3C nanofilm can be controlled by adjusting the reaction temperature. The degree of crystallization is increased by increasing the reaction temperature; the degree of crystallization is decreased by decreasing the reaction temperature.

[0016] The present invention also provides an in-situ grown iron carbide thin film electrode prepared using the preparation method described above, and its application as a supercapacitor electrode.

[0017] The main advantages of this invention are as follows: (1) This invention enables the rapid and efficient preparation of Fe3C nanofilm materials on various substrates, which is easy to mass-produce; (2) The Fe3C thin film grown in situ on the substrate material has uniform size and strong adhesion. By controlling the ratio of the iron source reaction solution, the type and ratio of graphite powder and carbonate, and the reaction temperature and time, the nanomorphology, structure, size and quality of Fe3C can be easily controlled. Specifically, the phase composition and size of the product can be adjusted by controlling the ratio of the iron source reaction solution; the higher the mass of the reactants, the higher the quality of the product. The yield and density of Fe3C can be adjusted by controlling the type and ratio of graphite powder and carbonate; the higher the mass ratio of graphite powder to carbonate, the higher the yield of Fe3C. The density of the Fe3C structure can be controlled by controlling the composition and ratio of carbonate: when the molar mass ratio of the two is close to 1:1, the formed Fe3C nanostructure is the sparsest; the further the molar mass ratio deviates from 1:1, the denser the formed Fe3C nanostructure; when only sodium carbonate or only potassium carbonate is used, the formed Fe3C nanostructure is the densest. Adjusting the reaction temperature and time can control the morphology and size of the product. The growth of the nanostructure conforms to the crystal growth theory; the higher the temperature and the longer the time, the more complete the nucleation and growth, the easier it is to form a three-dimensional structure with a certain orientation, and the larger the size. (3) Compared with wet chemical synthesis combined with multi-step sintering, separation, carbonization and other steps, the synthesis method of the present invention is simple, has fewer steps and shorter cycle, low equipment requirements, and the reactants (iron source solution, graphite powder and carbonate powder in the preparation method) can be reused, with low cost, less pollutants and waste, and environmentally friendly. (4) The Fe3C nanofilm prepared by this invention has a uniform pure phase and can be used directly as an electrode of a supercapacitor. It is expected to be widely used in the fields of energy, information and environment, such as electrode materials, catalysts, ion exchange, magnetic storage, desulfurization and denitrification. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Some specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings indicate the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 Field emission scanning electron microscope image of the Fe3C nanosheets / carbon cloth prepared in Example 1.

[0019] Figure 2 Field emission scanning electron microscope image of the Fe3C nanonet / carbon cloth prepared in Example 2.

[0020] Figure 3 Field emission scanning electron microscope image of the Fe3C nanospheres / carbon cloth prepared in Example 3.

[0021] Figure 4 The X-ray diffraction pattern of the Fe3C nanostructure / carbon cloth prepared in Example 4 is shown.

[0022] Figure 5 The X-ray diffraction pattern of the Fe3C nanostructure / titanium sheet prepared in Example 5.

[0023] Figure 6 Cyclic voltammetry curves of the Fe3C nanostructure / titanium sheet and pure titanium sheet substrate prepared in Example 6 as electrodes of a supercapacitor.

[0024] Figure 7 The constant current charge-discharge curve of the Fe3C nanostructure / titanium sheet prepared in Example 7 as a supercapacitor electrode.

[0025] Figure 8 The image shows the areal capacitance data of the Fe3C nanostructure / carbon paper prepared in Example 8 as a supercapacitor electrode. Detailed Implementation

[0026] An in-situ grown Fe3C thin film and its preparation method are disclosed, achieving rapid and efficient preparation. The Fe3C thin film prepared by the method of this invention has controllable morphology, structure, size, and quality, is applicable to various substrates, has strong versatility, is simple to prepare, low in cost, low in energy consumption, and exhibits excellent performance. The method includes the following steps: (1) Clean the substrate and dry it thoroughly to obtain a clean substrate surface; (2) Dissolve the iron-containing salt and urea in a certain amount of deionized water at a certain mass ratio to prepare an iron source reaction solution. The mass ratio of the iron-containing salt, urea and deionized water is (100-0.01):1:(1000-20). (3) Add the substrate material prepared in step (1) to the solution in step (2), and let it stand at a certain temperature for a period of time so that the substrate is fully in contact with or fully wetted by the reaction solution. The temperature range for standing at a certain temperature for a period of time is 10~90℃, and the time range is 0.5~24 hours. (4) Take out the substrate from step (3) and dry it in an air atmosphere at a certain temperature for a period of time. The temperature range of the certain temperature is 10~90℃ and the time range of the time is 0.5~24 hours. (5) A certain mass ratio of graphite powder and carbonate is thoroughly mixed, with the mass ratio of graphite powder to carbonate being (74-0.01):1. Among them, the carbonate is sodium carbonate, potassium carbonate, or a mixture of the two. By controlling the composition and ratio of the carbonate, the density of the Fe3C structure is controlled: when the molar mass ratio of the two is close to 1:1, the Fe3C nanostructure formed is the sparsest; when the molar mass ratio of the two deviates further from 1:1, the Fe3C nanostructure formed is the densest; when it is only sodium carbonate or only potassium carbonate, the Fe3C nanostructure formed is the densest.

[0027] (6) The dried substrate from step (4) is embedded into the mixed powder from step (5) to form a reaction system; (7) In an inert gas atmosphere, the reaction system of step (6) is heated from room temperature to the reaction temperature at a certain heating rate, and kept at the temperature for a period of time. The heating rate ranges from 0.5 to 10 °C / min, the reaction temperature ranges from 700 to 1200 °C, and the reaction time ranges from 0.5 hours to 12 hours. By adjusting the reaction temperature and time, the morphology and size of the product can be controlled. The higher the temperature and the longer the time, the more complete the nucleation and growth, and the easier it is to form a three-dimensional structure with a certain orientation and the larger the size.

[0028] The size and morphology of the Fe3C nanostructure are adjusted by regulating the heating rate in step (7): increasing the heating rate increases the size of the nanostructure and makes the nanostructure form a polyhedral structure; decreasing the heating rate reduces the size of the nanostructure and makes the nanostructure form a sheet-like structure. The degree of crystallinity of Fe3C nanofilms can be controlled by adjusting the reaction temperature described in step (7): increasing the reaction temperature described in step (7) increases the degree of crystallinity; decreasing the reaction temperature described in step (7) decreases the degree of crystallinity. (8) Cool the product from step (7) to room temperature in the furnace and ultrasonically clean it with deionized water. (9) The cleaned product is thoroughly dried to obtain Fe3C thin film electrode material grown in situ on the substrate, which can be directly used as an electrode for supercapacitors.

[0029] The substrate is any one of carbon cloth, carbon felt, carbon paper, nickel foam, FTO conductive glass, titanium metal substrate, 304 stainless steel metal substrate, and copper metal substrate.

[0030] The iron-containing salt is one or more of the following: nitrate, sulfate, chloride, phosphate, acetate, or carbonate of the metallic element iron.

[0031] The present invention is further illustrated below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0032] Example 1

[0033] (1) Clean and thoroughly dry commercial carbon cloth to obtain clean commercial carbon cloth; (2) Dissolve 0.18 g ferric chloride and 18 g urea in 50 mL deionized water to prepare an iron source reaction solution; (3) Add the clean carbon cloth prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 80°C for 6 hours to allow the carbon cloth to be completely immersed in the reaction solution; (4) Take out the carbon cloth substrate from step (3) and dry it in an air atmosphere at 60°C for 12 hours; (5) Mix 10 g graphite powder and 0.5 g sodium carbonate thoroughly; (6) Fill the dried carbon cloth substrate from step (4) into the mixed powder from step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system from step (6) from room temperature to 700°C at a heating rate of 2°C / min, and keep it heated for 12 hours. The field emission scanning electron microscope image of the obtained Fe3C nanomaterial is shown below. Figure 1 As shown, the surface morphology observation results indicate that the nanomorphology is a fine, dense, sheet-like structure with a sheet thickness of approximately 0.5 nm.

[0034] Example 2

[0035] (1) Clean and thoroughly dry commercial carbon cloth to obtain clean commercial carbon cloth; (2) Dissolve 1 g of ferric chloride and 18 g of urea in 50 mL of deionized water to prepare an iron source reaction solution; (3) Add the clean carbon cloth prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 80°C for 4 hours to allow the carbon cloth to be completely immersed in the reaction solution; (4) Take out the carbon cloth substrate from step (3) and dry it in an air atmosphere at 60°C for 12 hours; (5) Mix 74 g of graphite powder and 1 g of potassium carbonate thoroughly; (6) Fill the dried carbon cloth substrate from step (4) into the mixed powder from step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system from step (6) from room temperature to 700°C at a heating rate of 2°C / min, and keep it heated for 12 hours. The field emission scanning electron microscope image of the obtained Fe3C nanomaterial is shown below. Figure 2 As shown, the surface morphology observation results indicate that the nanomorphology is a dense network structure with network pores having a diameter of approximately 80 nm.

[0036] Example 3

[0037] (1) Clean and thoroughly dry commercial carbon cloth to obtain clean commercial carbon cloth; (2) Dissolve 2 g ferric chloride and 18 g urea in 200 mL deionized water to prepare an iron source reaction solution; (3) Add the clean carbon cloth prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 80°C for 6 hours to allow the carbon cloth to be completely immersed in the reaction solution; (4) Take out the carbon cloth substrate from step (3) and dry it in an air atmosphere at 60°C for 12 hours; (5) Mix 10 g graphite powder and 0.5 g sodium carbonate thoroughly; (6) Fill the dried carbon cloth substrate from step (4) into the mixed powder from step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system from step (6) from room temperature to 700°C at a heating rate of 2°C / min, and keep it heated for 12 hours. The field emission scanning electron microscope image of the obtained Fe3C nanomaterial is shown below. Figure 3 As shown, the surface morphology observation results indicate that the nanomorphology is a sparse spherical structure with a diameter of approximately 100 nm.

[0038] Example 4

[0039] (1) Clean and thoroughly dry commercial carbon cloth to obtain clean commercial carbon cloth; (2) Dissolve 1 g of ferric chloride and 1 g of urea in 40 mL of deionized water to prepare an iron source reaction solution; (3) Add the clean carbon cloth prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 10°C for 24 hours to allow the carbon cloth to be completely immersed in the reaction solution; (4) Take out the carbon cloth substrate from step (3) and dry it in an air atmosphere at 60°C for 12 hours; (5) Mix 37 g of graphite powder, 0.25 g of sodium carbonate, and 0.25 g of potassium carbonate thoroughly; (6) Fill the dried carbon cloth substrate from step (4) into the mixed powder from step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system from step (6) from room temperature to 800°C at a heating rate of 5°C / min, and keep it heated for 12 hours. The X-ray diffraction pattern of the obtained product is as follows. Figure 4 As shown, the results indicate that Fe3C nanomaterials were grown in situ on commercial carbon cloth.

[0040] Example 5

[0041] (1) Clean the titanium sheet and dry it thoroughly to obtain a clean titanium sheet; (2) Dissolve 2 g of ferric chloride and 1 g of urea in 40 mL of deionized water to prepare an iron source reaction solution; (3) Add the clean titanium sheet prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 10°C for 24 hours to ensure that the titanium sheet is in complete contact with the reaction solution; (4) Take out the titanium sheet substrate from step (3) and dry it in an air atmosphere at 80°C for 1 hour; (5) Mix 37 g of graphite powder, 0.5 g of sodium carbonate, and 0.5 g of potassium carbonate thoroughly; (6) Fill the dried carbon cloth substrate from step (4) into the mixed powder from step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system from step (6) from room temperature to 1000°C at a heating rate of 5°C / min, and keep it heated for 12 hours. The X-ray diffraction pattern of the obtained product is as follows. Figure 5 As shown, the results indicate that Fe3C nanomaterials were grown in situ on a titanium sheet.

[0042] contrast Figure 4 and Figure 5 The curves show that by adjusting different preparation parameters and raw materials, this technology can grow Fe3C nanostructures in situ on various substrates. Comparing the relative peak intensities of the diffraction peaks, it can be seen that the crystallinity and quality of Fe3C nanostructures can be controlled by adjusting the preparation parameters. Higher reaction temperatures result in better product crystallinity. When the iron content in the iron source reaction solution is sufficient, more iron source leads to a more complete reaction and a higher product quality.

[0043] Example 6

[0044] (1) Clean the titanium sheet and dry it thoroughly to obtain a clean titanium sheet; (2) Dissolve 0.1 g of ferric chloride and 1.8 g of urea in 50 mL of deionized water to prepare an iron source reaction solution; (3) Add the clean titanium sheet prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 20°C for 1 hour to completely immerse the surface of the titanium sheet in the reaction solution; (4) Take out the titanium sheet substrate in step (3) and dry it in an air atmosphere at 60°C for 4 hours; (5) Mix 9 g of graphite powder and 1 g of potassium carbonate thoroughly; (6) Fill the dried titanium sheet substrate in step (4) into the mixed powder in step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system in step (6) from room temperature to 800°C at a heating rate of 5°C / min, keep it heated to react for 2 hours, and the resulting sample can be used directly as an electrode. The cyclic voltammetry results, along with clean pure titanium substrates, were tested in 1 M KOH electrolyte at a scan rate of 100 mV / s. Figure 6 As shown in the figure, the area of ​​the closed curves in the figure provides a direct comparison, revealing that the areal capacitance of the in-situ grown Fe3C thin film electrode is significantly higher than that of the pure titanium substrate. This indicates that the Fe3C thin film electrode grown in situ on the titanium substrate using this method has excellent prospects for electrochemical energy storage applications.

[0045] Example 7

[0046] (1) Clean the titanium sheet and dry it thoroughly to obtain a clean titanium sheet; (2) Dissolve 0.2 g of ferric chloride and 3.6 g of urea in 100 mL of deionized water to prepare an iron source reaction solution; (3) Add the clean titanium sheet prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 20°C for 2 hours to completely immerse the surface of the titanium sheet in the reaction solution; (4) Take out the titanium sheet substrate in step (3) and dry it in an air atmosphere at 60°C for 4 hours; (5) Mix 9 g of graphite powder and 1 g of potassium carbonate thoroughly; (6) Fill the dried titanium sheet substrate in step (4) into the mixed powder in step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system in step (6) from room temperature to 800°C at a heating rate of 5°C / min, and keep it heated to react for 2 hours. The resulting sample can be used directly as an electrode. It and a clean, pure titanium sheet substrate were electrolyzed in 1 M KOH electrolyte at concentrations of 1, 2, 3, 4, and 5 mA / cm². 2 A constant current charge-discharge test was performed on the current density, and the results are as follows: Figure 7 As shown in the figure, the good symmetry of the charging and discharging curves indicates that the Fe3C thin film electrode grown in situ on the titanium substrate has good charge-discharge reversibility; based on another cyclic voltammetry test result, a charge-discharge reversibility of 2 mV / s was calculated. -1Voltage scanning was performed at a certain speed, and the areal capacitance was calculated to be 258.4 mF / cm² based on the resulting cyclic volt-ampere curve. -2 , at 100 mV s -1 Voltage scanning was performed at a certain speed, and the areal capacitance was calculated to be 167.9 mF / cm² based on the resulting cyclic volt-ampere curve. -2 The good rate performance during rapid charge and discharge indicates that the energy obtained by this method has excellent prospects for electrochemical energy storage applications.

[0047] Example 8

[0048] (1) Clean the carbon paper and dry it thoroughly to obtain a clean carbon paper surface; (2) Dissolve 1 g of ferric chloride and 1 g of urea in 40 mL of deionized water to prepare an iron source reaction solution; (3) Add the clean carbon paper prepared in step (1) to the iron source reaction solution in step (2), and let it stand at 10°C for 24 hours to allow the carbon paper to be completely immersed in the reaction solution; (4) Take out the carbon paper substrate from step (3) and dry it in an air atmosphere at 60°C for 12 hours; (5) Mix 37 g of graphite powder, 0.25 g of sodium carbonate, and 0.25 g of potassium carbonate thoroughly; (6) Fill the dried carbon paper substrate from step (4) into the mixed powder from step (5) to form a reaction system; (7) In a nitrogen atmosphere, heat the reaction system from step (6) from room temperature to 800°C at a heating rate of 5°C / min, and keep it heated to react for 12 hours. The resulting sample can be used directly as an electrode. For electrodes in thin-film form, area is a more relevant reference than mass. The areal capacitance as a function of cyclic voltammetry scan rate is shown below. Figure 8 As shown, the results indicate that in 1 M KOH electrolyte, at 2 mV s -1 The voltage was scanned at a certain speed, and the areal capacitance was calculated to be 687.2 mF / cm² based on the resulting cyclic volt-ampere curve. -2 , at 100 mV s -1 Voltage scanning was performed at a certain speed, and the areal capacitance was calculated to be 616.1 mF / cm² based on the resulting cyclic volt-ampere curve. -2 This indicates that the Fe3C / carbon paper electrode prepared by this method has excellent rate performance and good prospects for electrochemical energy storage applications.

[0049] This invention prepares Fe3C nanofilms / substrates using low-cost, readily available raw materials. The reaction solution and powder can be reused, resulting in a wide range of applications. The preparation process is simple, efficient, and requires minimal equipment and environmental control. The obtained product can be directly used as a functional material, demonstrating significant potential in numerous fields. Unlike traditional methods that typically require multiple steps, specialized equipment, and often involve stepwise high-temperature sintering, carbonization, and decarburization, this invention offers rapid, efficient, and environmentally friendly synthesis. Therefore, this invention not only provides a method for in-situ growth of Fe3C nanofilms on a substrate but is also applicable to various substrates. By adjusting the type and amount of raw materials, reaction time, and temperature, the morphology, size, and quality of the Fe3C nanostructures can be easily controlled. The resulting film material can be directly used as a functional material, facilitating industrialization.

[0050] The embodiments and applications described above are specific implementations of the technical solutions of the present invention and are further detailed descriptions of the technical solutions of the present invention. However, the design concept of the present invention is not limited thereto. Any simple modifications, equivalent changes or improvements made to the present invention based on its technical essence should still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing an in-situ grown iron carbide thin film electrode, characterized in that, Includes the following steps: S1. Dissolve iron-containing salt and urea in water to obtain an iron source reaction solution; obtain and add the substrate to the iron source reaction solution and let it stand for a period of time; S2. Remove the substrate and dry it in an air atmosphere at a certain temperature for a period of time; S3. Thoroughly mix graphite powder and carbonate to form a mixed powder; fill the dried substrate into the mixed powder, heat from room temperature to the reaction temperature at a certain heating rate, and keep it at the temperature to allow it to react for a period of time; S4. The product from the S3 reaction is cooled to room temperature in the furnace, cleaned, and dried to obtain an Fe3C thin film electrode grown in situ on the substrate.

2. The preparation method according to claim 1, characterized in that, The substrate is specifically carbon cloth, carbon felt, carbon paper, nickel foam, FTO conductive glass, titanium metal substrate, 304 stainless steel metal substrate, or copper metal substrate.

3. The preparation method according to claim 1, characterized in that, The iron-containing salt is any one or a combination of nitrates, sulfates, chlorides, phosphates, acetates, and carbonates of the metallic element iron.

4. The preparation method according to claim 1, characterized in that, In S1, iron-containing salt and urea are dissolved in deionized water. In the iron source reaction solution, the mass ratio of iron-containing salt, urea and deionized water is (100~0.01):1:(1000~20).

5. The preparation method according to any one of claims 1, characterized in that, In the mixed powder, the mass ratio of graphite powder to carbonate is (74-0.01):

1.

6. The preparation method according to any one of claims 1-5, characterized in that, The step of adding the substrate to the iron source reaction solution and letting it stand for a period of time specifically refers to standing for 0.5 to 24 hours at a temperature range of 10 to 90°C.

7. The preparation method according to any one of claims 1-5, characterized in that, In S4, the drying specifically includes drying for 0.5 to 24 hours at a temperature range of 10 to 90°C.

8. The preparation method according to any one of claims 1-5, characterized in that, In S3, the carbonate is sodium carbonate, potassium carbonate, or a mixture of both. The density of the Fe3C structure is controlled by adjusting the composition and ratio of the carbonate: when the molar mass ratio of the two is 1:1, the Fe3C nanostructure is the sparsest; the further the molar mass ratio of the two deviates from 1:1, the denser the Fe3C nanostructure is; when it is only sodium carbonate or only potassium carbonate, the Fe3C nanostructure is the densest.

9. The preparation method according to claim 1, characterized in that, The process of heating from room temperature to the reaction temperature at a certain rate and holding the temperature to allow the reaction to proceed for a period of time specifically includes: the heating rate being 0.5~10 ℃ / min, the reaction temperature being 700~1200℃, and the reaction time being 0.5 hours~12 hours. Within the specified heating rate range, the nanostructure size and morphology of Fe3C can be adjusted by regulating the heating rate. The size of nanostructures can be increased by increasing the heating rate, resulting in polyhedral structures; the size of nanostructures can be reduced by decreasing the heating rate, resulting in sheet-like structures. Within the stated reaction temperature range, the degree of crystallinity of the Fe3C nanofilm can be controlled by adjusting the reaction temperature. The degree of crystallization is increased by increasing the reaction temperature; the degree of crystallization is decreased by decreasing the reaction temperature.

10. An in-situ grown iron carbide thin film electrode, characterized in that, It was prepared using the preparation method as described in claim 1.

11. The application of the in-situ grown iron carbide thin film electrode according to claim 10 as a supercapacitor electrode.

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