Iron nitride / gallium nitride / carbon composite heterostructure material and preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy materials, and particularly relates to an iron nitride / gallium nitride / carbon composite heterostructure material and a preparation method and application thereof. In a protective atmosphere, the iron-containing raw material, the gallium-containing raw material and the nitrogen-containing organic compound are subjected to heat treatment, so that the iron-containing raw material and the gallium-containing raw material are subjected to reduction and nitridation reaction, an iron nitride phase and a gallium nitride phase are formed, meanwhile, a carbon phase is formed, and the iron nitride / gallium nitride / carbon composite heterostructure material is obtained. The nitrogen-containing organic compound is introduced under the inert atmosphere condition, so that the iron source and the gallium source are synchronously subjected to reduction and nitridation reactions in the heat treatment process, in-situ synergistic generation of iron nitride and gallium nitride is achieved, an iron nitride phase and a gallium nitride phase form a heterostructure interface on the nanoscale, and the performance of the device is improved. And a stable composite heterostructure is constructed under the confinement effect of a carbon phase, so that the problems that in the prior art, multi-phase materials are difficult to synergistically form, the interface effect is insufficient, the process condition is harsh and the like are solved.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials technology, specifically relating to an iron nitride / gallium nitride / carbon composite heterostructure material, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy, electronic information, and functional materials technologies, composite materials with multifunctional properties have attracted widespread attention in electrochemical energy devices, electromagnetic functional devices, and related fields. Among them, transition metal nitrides, due to their excellent electrical conductivity, chemical stability, and unique electronic structure, show promising application prospects in electrocatalysis, electromagnetic response, and magnetic materials.

[0003] Iron nitride materials (such as Fe4N, Fe3N, and Fe2N) possess noble metal-like electronic structure characteristics and high electrical conductivity, exhibiting certain catalytic activity in electrochemical processes such as oxygen reduction and oxygen evolution reactions. Simultaneously, iron-based materials inherently possess magnetic properties, making them potentially valuable in magnetic functions and electromagnetic control. However, existing iron nitride materials still have some shortcomings in practical applications: on the one hand, single iron nitride materials are prone to particle agglomeration and structural degradation under high-temperature treatment or long-term service conditions, affecting their stability; on the other hand, their electrical, magnetic, or electromagnetic properties are often limited by their single-phase structure, making it difficult to simultaneously meet the requirements of multifunctional applications.

[0004] To improve the stability and overall performance of iron nitride materials, current research attempts to combine them with carbon materials, such as graphitized carbon, carbon nanotubes, or graphene, to utilize the conductivity and structural support of carbon materials to suppress particle agglomeration and enhance electrical properties. However, simple physical mixing or coating methods often fail to form stable and effective interfacial structures between iron nitride and other functional phases, resulting in limited interfacial synergistic effects and thus limiting the improvement of the overall material performance. Summary of the Invention

[0005] The purpose of this invention is to provide an iron nitride / gallium nitride / carbon composite heterostructure material, its preparation method, and its applications. By introducing nitrogen-containing organic compounds under a protective atmosphere, the iron and gallium sources undergo simultaneous reduction and nitridation reactions during heat treatment, achieving in-situ synergistic generation of iron nitride and gallium nitride. A stable composite heterostructure is constructed under the confinement of the carbon phase, thereby overcoming the problems of difficulty in synergistic formation of multiphase materials, insufficient interfacial interaction, and harsh processing conditions in existing technologies.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] The first objective of this invention is to provide a method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material, comprising the following steps: In a protective atmosphere, iron-containing raw materials, gallium-containing raw materials, and nitrogen-containing organic compounds are heat-treated to induce reduction and nitriding reactions in the iron-containing and gallium-containing raw materials, forming iron nitride and gallium nitride phases, and simultaneously forming a carbon phase. The iron nitride and gallium nitride phases form a heterostructure interface at the nanoscale, and the carbon phase coats or connects to the outer surface of the iron nitride and / or gallium nitride phases, resulting in an iron nitride / gallium nitride / carbon composite heterostructure material. Among them, the nitrogen-containing organic compound is an organic compound that provides both nitrogen and carbon sources during the heat treatment process.

[0008] Furthermore, the iron nitride phase is at least one of Fe4N, Fe3N, and Fe2N.

[0009] Furthermore, the carbon phase is at least one of graphitized carbon, graphite-like carbon, carbon nanotubes, and carbon nanofibers.

[0010] Furthermore, the heat treatment temperature is 600℃~900℃, and the protective atmosphere is nitrogen or an inert gas.

[0011] Furthermore, the nitrogen-containing organic compounds are melamine and / or urea.

[0012] Furthermore, the molar ratio of Fe to Ga in the iron-containing and gallium-containing raw materials is 1:0.1–1.5, and the molar ratio of iron salt to nitrogen-containing organic compound is 1:5–50. The iron-containing raw material is an iron salt and / or iron hydroxide, and the gallium-containing raw material is a gallium salt and / or gallium hydroxide. Furthermore, the mixing methods for iron-containing and gallium-containing raw materials before heat treatment include: direct mixing with nitrogen-containing organic compounds, or mixing with nitrogen-containing organic compounds after forming a precursor through a precipitation reaction.

[0013] Furthermore, when iron-containing raw materials and gallium-containing raw materials undergo a precipitation reaction to form a precursor, the precipitant is at least one of urea, ammonia, and sodium hydroxide.

[0014] The second objective of this invention is to provide an iron nitride / gallium nitride / carbon composite heterostructure material, which is prepared using the above-described preparation method.

[0015] The third objective of this invention is to provide an application of the above-mentioned iron nitride / gallium nitride / carbon composite heterostructure material in electrocatalytic materials, electrochemical energy devices, electromagnetic wave absorbing materials, or magnetic materials.

[0016] Compared with the prior art, the present invention has the following advantages: This invention provides a preparation method in which iron-containing raw materials, gallium-containing raw materials, and nitrogen-containing organic compounds are heat-treated under a protective atmosphere to induce reduction and nitridation reactions in the iron-containing and gallium-containing raw materials. This achieves in-situ synergistic formation of iron nitride and gallium nitride in the same system, while simultaneously forming a carbon phase. This overcomes the problems of difficulty in synergistic formation of multiphase materials, insufficient interfacial interaction, and harsh process conditions in existing technologies. Specifically, the iron nitride and gallium nitride phases form a heterostructure interface at the nanoscale, and the carbon phase coats or connects to the outer surface of the iron nitride and / or gallium nitride phases, forming a composite heterostructure. By constructing the iron nitride / gallium nitride / carbon composite heterostructure, a stable heterostructure interface is formed inside the material, which is beneficial for… The process enhances the overall performance of materials in terms of electrical, magnetic, and electromagnetic responses by incorporating carrier transport, interface modulation, and synergistic effects of multiple physical properties. Carbon provides spatial confinement and coating for metal nitride particles, effectively suppressing particle agglomeration and structural degradation, and significantly improving the structural stability and service reliability of the materials. The preparation method introduces nitrogen-containing organic compounds in a protective atmosphere to achieve in-situ synergistic generation of iron nitride and gallium nitride in the same system, avoiding the dependence on ammonia or harsh process conditions in traditional gallium nitride preparation. The process is highly safe, simplified, has a wide process window, and is available from a wide range of raw material sources. The material composition and structure are adjustable, making it suitable for large-scale preparation and possessing good engineering application potential. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation process of the iron nitride / gallium nitride / carbon composite heterostructure material in Example 1 of the present invention.

[0018] Figure 2 The image shows the microstructure and elemental distribution of the iron nitride / gallium nitride / carbon composite heterostructure material in Example 1 of this invention. Figure 2 In the image, (a) is a scanning electron microscope image, (b) is a magnified view of (a), (c) is a transmission electron microscope image, (d) is a crystal phase region distribution map, and (e) is an energy-dispersive X-ray elemental distribution map.

[0019] Figure 3 The X-ray diffraction patterns are of the iron nitride / gallium nitride / carbon composite heterostructure materials of Examples 1 to 4 and the composite materials of Comparative Examples 1 to 2 of the present invention. Figure 3 (a) is a comparison diagram of Example 1 and Comparative Examples 1 to 2, (b) is a comparison diagram of samples with different ratios in Examples 1 to 4, and (c) is a comparison diagram of samples of Example 1 and Examples 7 to 9 at different temperatures.

[0020] Figure 4 The electrocatalytic performance diagrams are for the iron nitride / gallium nitride / carbon composite heterostructure material of Example 1 of the present invention, as well as the composite materials and commercial electrocatalytic materials of Comparative Examples 1 to 2. Figure 4(a) is the ORR linear sweep voltammetry (LSV) polarization curve of Example 1, Comparative Examples 1-2, and commercial Pt / C; (b) is the ORR Tafel curve corresponding to (a); (c) is the electron transfer number (n) and hydrogen peroxide yield of Example 1 and commercial ORR catalyst Pt / C in the ORR process; (d) is the ORR stability test curve of Example 1 and commercial ORR catalyst Pt / C under constant potential conditions; (e) is the linear sweep voltammetry (LSV) polarization curve of Example 1, Comparative Examples 1-2, and commercial OER catalyst RuO2 under oxygen evolution reaction (OER) conditions; and (f) is the OER Tafel curve corresponding to (e).

[0021] Figure 5 This is a power density diagram of a metal-air battery using a composite heterostructure material as an air electrode catalyst, as described in Example 1 of the present invention.

[0022] Figure 6 The figure shows the test results of the charge-discharge stability of the metal-air battery using the composite heterostructure material as the air electrode in Example 1 of the present invention under constant current conditions.

[0023] Figure 7 This is a graph showing the electromagnetic wave absorption performance of the composite heterostructure material in the 2GHz to 18GHz frequency band of Embodiment 1 of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0026] To improve the stability and overall performance of iron nitride materials, current research attempts to combine them with carbon materials, such as graphitized carbon, carbon nanotubes, or graphene, to utilize the conductivity and structural support of carbon materials to suppress particle agglomeration and enhance electrical properties. However, simple physical mixing or coating methods often fail to form stable and effective interfacial structures between iron nitride and other functional phases, resulting in limited interfacial synergistic effects and thus limiting the improvement of the overall material performance.

[0027] Gallium nitride (GaN), as an important group III-V semiconductor material, possesses a wide bandgap, good thermal stability, and chemical stability, and has been extensively studied in electronic devices, optoelectronic devices, and related functional materials. In composite material systems, the introduction of GaN holds promise for improving the overall performance of materials by modulating carrier behavior and interface electronic structure through heterostructure interfaces. However, current GaN preparation techniques typically rely on ammonia, plasma, or high-temperature, high-pressure conditions, resulting in complex processes, demanding equipment requirements, and certain safety and environmental risks. Furthermore, the formation conditions of GaN differ significantly from those of transition metal nitrides and carbon materials, making the synergistic formation and stable composite of GaN with iron nitride and carbon materials in the same system extremely challenging.

[0028] The purpose of this invention is to provide a novel material design and preparation approach that enables the synergistic construction of iron nitride, gallium nitride, and carbon materials under relatively mild and safe process conditions. This allows for the formation of stable heterogeneous interfaces within the materials, simultaneously enhancing their structural stability, electrical properties, magnetic characteristics, and electromagnetic response capabilities. This meets the application needs of various fields, including electrocatalysis, electrochemical energy devices, electromagnetic wave absorbing materials, and magnetic materials. Specifically:

[0029] A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: In a protective atmosphere, iron-containing raw materials, gallium-containing raw materials, and nitrogen-containing organic compounds are heat-treated to induce reduction and nitriding reactions in the iron-containing and gallium-containing raw materials, forming iron nitride and gallium nitride phases, and simultaneously forming a carbon phase. The iron nitride and gallium nitride phases form a heterostructure interface at the nanoscale, and the carbon phase coats or connects to the outer surface of the iron nitride and / or gallium nitride phases, resulting in an iron nitride / gallium nitride / carbon composite heterostructure material. Among them, the nitrogen-containing organic compound is an organic compound that provides both nitrogen and carbon sources during the heat treatment process.

[0030] It should be noted that the proportions of iron-containing raw materials, gallium-containing raw materials, and nitrogen-containing organic compounds in this invention can be adjusted according to the needs of actual application processes, thereby adjusting the relative content of the iron nitride phase and the gallium nitride phase. The iron nitride phase and the gallium nitride phase are dispersed in the form of nanoparticles, and the electronic, magnetic, or electromagnetic responses are synergistically regulated through the heterostructure interface, realizing the synergistic construction of iron nitride, gallium nitride, and carbon materials. A stable heterostructure interface is formed inside the material, satisfying the material's structural stability, electrical properties, magnetic characteristics, and electromagnetic response capabilities. This composite heterostructure material exhibits a synergistic enhancement effect in terms of electrical, magnetic, and electromagnetic responses, and is suitable for electrocatalytic materials, electrochemical energy devices, electromagnetic wave absorbing materials, magnetic materials, and related fields.

[0031] In this invention, the iron-containing raw material is a compound or combination thereof capable of undergoing reduction and nitridation reactions under a protective atmosphere heat treatment condition to provide iron, preferably an iron salt and / or iron hydroxide, etc.; the iron salt is, for example, at least one selected from ferric nitrate, ferric chloride, ferric sulfate, ferric acetate, ferric oxalate, ferric citrate, ammonium ferric salt, etc. In this invention, the gallium-containing raw material is a compound or combination thereof capable of undergoing reduction and nitridation reactions under a protective atmosphere heat treatment condition to provide gallium, preferably a gallium salt and / or gallium hydroxide, etc.; the gallium salt is, for example, at least one selected from gallium nitrate, gallium chloride, gallium sulfate, gallium acetate, etc. In some specific embodiments, the iron salt is ferric nitrate or ferric chloride, the gallium salt is gallium nitrate, the molar ratio of iron salt to gallium salt is 1:0.1 to 1.5, and the molar ratio of iron salt to nitrogen-containing organic compound is 1:5 to 50.

[0032] In this invention, by adjusting the amounts of iron-containing raw materials, gallium-containing raw materials, and nitrogen-containing organic compounds, the composition, particle size, and structural morphology of each phase in the resulting composite heterostructure material can be controlled. The composite heterostructure material includes an iron nitride phase, a gallium nitride phase, and a carbon phase. The iron nitride and gallium nitride phases form a heterostructure interface at the nanoscale, and the carbon phase coats or connects to the outer surface of the iron nitride and / or gallium nitride phases, forming a stable composite structure. Through the heterostructure interface and the spatial confinement effect of the carbon phase, the particle size, morphology, and dispersion state of the metal nitride are effectively controlled. The preparation method introduces a nitrogen-containing organic compound in a protective atmosphere to achieve in-situ synergistic generation of iron nitride and gallium nitride in the same system. This avoids the dependence on ammonia or harsh process conditions in traditional gallium nitride preparation processes. The process is highly safe, simplified, has a wide process window, uses widely available raw materials, and its composition and structure are adjustable, making it suitable for large-scale preparation and possessing good engineering application potential.

[0033] In some embodiments, the iron nitride phase may be selected from at least one of Fe4N, Fe3N, and Fe2N. The carbon phase may be selected from at least one of graphitized carbon, graphitic carbon, carbon nanotubes, and carbon nanofibers. The carbon phase provides spatial confinement for the iron nitride phase and / or the gallium nitride phase to regulate the size, morphology, and dispersion state of the iron nitride and gallium nitride particles.

[0034] In some embodiments, the heat treatment temperature is 600°C to 900°C, and the protective atmosphere is nitrogen or an inert gas. During the heat treatment process, the iron source and gallium source undergo a nitriding reaction under the action of the nitrogen source provided by the nitrogen-containing organic compound, and a carbon phase is formed at the same time, which plays a role in coating and confining the generated metal nitride particles, thereby constructing an iron nitride / gallium nitride / carbon composite heterostructure material.

[0035] In some embodiments, the nitrogen-containing organic compound may be selected from melamine, urea, or other organic compounds that can simultaneously provide a nitrogen source and a carbon source during heat treatment.

[0036] In some embodiments, the mixing of iron-containing and gallium-containing raw materials before heat treatment includes: direct mixing with a nitrogen-containing organic compound, or mixing with a nitrogen-containing organic compound after forming a precursor through a precipitation reaction. When the iron-containing and gallium-containing raw materials undergo a precipitation reaction to form a precursor, this can be achieved by adding urea, ammonia, sodium hydroxide, or a combination thereof.

[0037] This invention provides an iron nitride / gallium nitride / carbon composite heterostructure material, prepared using the method described above. By constructing the iron nitride / gallium nitride / carbon composite heterostructure, a stable heterostructure interface is formed within the material, which is beneficial for carrier transport, interface regulation, and synergistic effects on multiple properties. The carbon phase provides spatial confinement and coating for the metal nitride particles, effectively inhibiting particle aggregation and structural degradation, significantly improving the structural stability and service reliability of the material, thereby enhancing its comprehensive performance in electrical, magnetic, and electromagnetic response aspects. In electrocatalysis applications, the composite heterostructure material can be used in oxygen reduction reactions, oxygen evolution reactions, and as an air electrode in metal-air batteries; in electromagnetic and magnetic applications, it can be used in electromagnetic wave absorption, magnetic functional composite materials, or related devices.

[0038] The following specific examples will provide further explanation.

[0039] Example 1 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: S1. Precipitation method for preparing the precursor: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 1.5 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C, and maintain this temperature for 4 h. During this process, the urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0040] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0041] S3. Place the solid mixed precursor in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1The temperature was increased to 700℃ at a heating rate and held at that temperature for 2 hours. Then, it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material, named FeGa / C-0.75.

[0042] Example 2 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: S1. Preparation of the precursor by precipitation method: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 0.5 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C and maintain this temperature for 4 h. During this process, urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0043] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0044] S3. Place the solid mixed precursor in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a heating rate and held at that temperature for 2 hours, followed by natural cooling to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material, named FeGa / C-0.25.

[0045] Example 3 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: S1. Preparation of the precursor by precipitation method: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 1.0 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C and maintain this temperature for 4 h. During this process, urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0046] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0047] S3. Place the solid mixed precursor in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a heating rate and held at that temperature for 2 hours, followed by natural cooling to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material, named FeGa / C-0.5.

[0048] Example 4 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: S1. Preparation of the precursor by precipitation method: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 2.0 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C, and maintain this temperature for 4 h. During this process, urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0049] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0050] S3. Place the solid mixed precursor in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a heating rate and held at that temperature for 2 hours, followed by natural cooling to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material, named FeGa / C-1.

[0051] Example 5 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: S1. Direct mixing: Weigh 2.0 mmol of Fe(NO3)3·9H2O, 0.5 mmol of Ga(NO3)3·9H2O and 50 mmol of melamine, mix them and grind them thoroughly in a mortar to form a homogeneous mixture.

[0052] S2. Place the mixture in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a heating rate and held at that temperature for 2 hours. Then, it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material.

[0053] Example 6 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material includes the following steps: S1. Preparation of the precursor by precipitation method: Weigh 2.0 mmol of FeCl3·6H2O and 1.5 mmol of GaCl3, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C and maintain this temperature for 4 h. During this process, urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0054] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0055] S3. Place the solid mixed precursor in a tube furnace and heat it under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a heating rate and held at that temperature for 2 hours. Then, it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material.

[0056] Example 7 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material, differing from Example 1 in that the heat treatment temperature is 600℃, includes the following steps: S1. Precipitation method for preparing the precursor: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 1.5 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C, and maintain this temperature for 4 h. During this process, the urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0057] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0058] S3. Place the solid mixed precursor in a tube furnace and heat it under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 600℃ at a heating rate and held at that temperature for 2 hours. Then, it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material.

[0059] Example 8 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material, differing from Example 1 in that the heat treatment temperature is 800℃, includes the following steps: S1. Precipitation method for preparing the precursor: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 1.5 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C, and maintain this temperature for 4 h. During this process, the urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0060] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0061] S3. Place the solid mixed precursor in a tube furnace and heat it under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min-1 The temperature was increased to 800℃ at a heating rate and held at that temperature for 2 hours. Then, it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material.

[0062] Example 9 A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material, differing from Example 1 in that the heat treatment temperature is 900℃, includes the following steps: S1. Precipitation method for preparing the precursor: Weigh 2.0 mmol of Fe(NO3)3·9H2O and 1.5 mmol of Ga(NO3)3·9H2O, dissolve them in 300 mL of deionized water to form a clear and homogeneous mixed solution. Add 0.1 mol of urea to this solution under continuous magnetic stirring, heat to 90 °C, and maintain this temperature for 4 h. During this process, the urea gradually decomposes thermally, forming a yellow precipitate in the solution. After the reaction is complete, allow it to cool naturally to room temperature, collect the precipitate by centrifugation, wash repeatedly with deionized water, and then dry at 60 °C to obtain a yellow precursor powder.

[0063] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0064] S3. Place the solid mixed precursor in a tube furnace and heat it under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 900℃ at a heating rate and held at that temperature for 2 hours. Then, it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron nitride / gallium nitride / carbon composite heterostructure material.

[0065] Comparative Example 1 A method for preparing an iron / carbon composite material includes the following steps: S1. Precipitation method for preparing the precursor: 2.0 mmol of Fe(NO3)3·9H2O was dissolved in 300 mL of deionized water to form a clear and homogeneous mixed solution. 0.1 mol of urea was added to this solution under continuous magnetic stirring, and the mixture was heated to 90 °C and maintained at this temperature for 4 h. During this process, the urea gradually decomposed thermally, forming a yellow precipitate in the solution. After the reaction was complete, the solution was naturally cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was repeatedly washed with deionized water and then dried at 60 °C to obtain a yellow precursor powder.

[0066] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0067] S3. Place the solid mixed precursor in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a certain rate and held at that temperature for 2 hours. Then it was naturally cooled to room temperature in a nitrogen atmosphere to obtain an iron / carbon composite material, named Fe / C.

[0068] Comparative Example 2 A method for preparing a gallium / carbon composite material includes the following steps: S1. Precipitation method for preparing the precursor: 1.5 mmol of Ga(NO3)3·9H2O was dissolved in 300 mL of deionized water to form a clear and homogeneous mixed solution. 0.1 mol of urea was added to this solution under continuous magnetic stirring, and the mixture was heated to 90 °C and maintained at this temperature for 4 h. During this process, the urea gradually decomposed thermally, and a yellow precipitate formed in the solution. After the reaction was complete, the solution was naturally cooled to room temperature, and the precipitate was collected by centrifugation. The precipitate was repeatedly washed with deionized water and then dried at 60 °C to obtain a yellow precursor powder.

[0069] S2. Mix the precursor with 50 mmol of melamine and add 1 mL to 2 mL of anhydrous ethanol as a dispersant. Grind thoroughly in an agate mortar to form a uniform slurry. Then remove the anhydrous ethanol and continue grinding to obtain a uniform solid mixed precursor.

[0070] S3. Place the solid mixed precursor in a tube furnace under a nitrogen atmosphere (flow rate approximately 100 mL / min). -1 At 5℃·min -1 The temperature was increased to 700℃ at a certain heating rate and held at that temperature for 2 hours, followed by natural cooling to room temperature in a nitrogen atmosphere to obtain a gallium / carbon composite material, named Ga / C.

[0071] Figure 1 This is a flowchart illustrating the preparation process of the iron nitride / gallium nitride / carbon composite heterostructure material in Example 1 of the present invention. Figure 1As shown, the synergistic conversion of iron and gallium sources is achieved in the same reaction system through a combination of precursor construction and subsequent protective atmosphere heat treatment. During the heat treatment process, the iron and gallium sources undergo nitridation under the influence of nitrogen provided by nitrogen-containing organic compounds, simultaneously forming a carbon phase. This carbon phase coats and confines the generated metal nitride particles, thereby constructing an iron nitride / gallium nitride / carbon composite heterostructure material. This schematic diagram visually illustrates the synergistic formation process of iron nitride, gallium nitride, and the carbon phase in this invention, providing a foundation for the subsequent formation of the material's structure and properties.

[0072] The structural parameters of the iron nitride / gallium nitride / carbon composite heterostructure material in Example 1 and the composite materials in Comparative Examples 1 to 2 are shown in Table 1. In terms of structure, the materials in the examples can form metal nitride nanoparticles with controllable size and are effectively coated by the carbon phase, with a high metal mass fraction and stable composite structure characteristics; while in the comparative examples where there is no iron source or gallium source, it is difficult to construct a complete composite heterostructure.

[0073] Table 1. Structural parameters of metal particles and carbon layers in the composite materials of Examples 1-4 and Comparative Examples 1-2 Figure 2 The image shows the microstructure and elemental distribution of the iron nitride / gallium nitride / carbon composite heterostructure material in Example 1 of this invention. Figure 2 In the image, (a) is a scanning electron microscope (SEM) image, (b) is a magnified view of (a), (c) is a transmission electron microscope (TEM) image, (d) is a crystalline phase region distribution map, and (e) is an energy-dispersive X-ray diffraction (EDX) elemental distribution map. Figure 2 As shown in the scanning electron microscope (SEM) and transmission electron microscope (TEM) images, the material obtained in Example 1 consists of nanoscale metal nitride particles. These particles are relatively uniformly dispersed and are coated or connected by a carbon phase, forming a composite structure. TEM further reveals that different crystalline phase regions can be observed within individual particles, indicating that iron nitride and gallium nitride form a closely contacted heterostructure interface at the nanoscale. Energy-dispersive X-ray diffraction (EDXRD) elemental distribution maps show that iron, gallium, and nitrogen elements exhibit a relatively uniform spatial distribution in the material, indicating that iron nitride and gallium nitride achieve good composite and synergistic distribution within the carbon phase.

[0074] Figure 3 The X-ray diffraction patterns are of the iron nitride / gallium nitride / carbon composite heterostructure materials of Examples 1 to 4 and the composite materials of Comparative Examples 1 to 2 of the present invention. Figure 3 (a) is a comparison diagram of Example 1 and Comparative Examples 1 to 2; (b) is a comparison diagram of samples with different proportions from Examples 1 to 4; and (c) is a comparison diagram of samples from Examples 1 and Examples 7 to 9 at different temperatures. Figure 3As shown in (a), the sample of Example 1 (FeGa / C-0.75) simultaneously exhibits characteristic diffraction peaks of both iron nitride and gallium nitride. However, in the Fe / C sample without a gallium source and the Ga / C sample without an iron source, neither of these two nitride phases was observed simultaneously. This indicates that the synergistic introduction of iron and gallium sources is a crucial condition for constructing the composite heterostructure of this invention. Meanwhile, samples with different proportions are shown... Figure 3 As shown in (b), the relative peak intensities of the two phases change with the ratio, indicating that the phase composition of the material can be controlled by adjusting the ratio. Figure 3 As shown in (c), under the condition that the iron-gallium ratio remains unchanged, the intensity and shape of the diffraction peaks of the sample change with the increase of heat treatment temperature, indicating that the formation and degree of crystallization of the crystal phase are affected by the heat treatment temperature; among them, the intensity of the diffraction peaks related to iron nitride is significantly enhanced at 900℃. It should be noted that the intensity was normalized when the spectrum was drawn. Therefore, when the peak intensity of a certain crystal phase is significantly enhanced, the relative peak height of other crystal phases (such as gallium nitride) will decrease after normalization. This phenomenon reflects the trend of the relative diffraction intensity of different crystal phases and cannot be directly equated to the absolute content of gallium nitride phase by the change of relative peak height after normalization. In addition, further investigation of the iron / carbon composite material prepared by Comparative Example 1 (containing only iron raw materials) shows that under the same heat treatment conditions, it mainly forms iron carbide phase and carbon phase. No characteristic diffraction peaks of gallium nitride phase were detected in the X-ray diffraction test, and no iron nitride / gallium nitride heterostructure interface was formed in the material, indicating that it is difficult to construct the composite heterostructure described in this invention by introducing only an iron source. Further investigation of the gallium / carbon composite material prepared in Comparative Example 2 (containing only gallium raw materials) revealed that no obvious gallium-related crystalline phase (including gallium nitride) characteristic diffraction peaks were observed in X-ray diffraction tests. Only diffraction characteristics or weak, broad peaks of the carbon phase were observed, indicating that the gallium-related phases may exist in a form with low crystallinity / amorphous / very small grains or low content, and no iron nitride / gallium nitride heterostructure interface was formed. In summary, the synergistic introduction of iron and gallium sources is an important condition for achieving the in-situ synergistic generation of iron nitride and gallium nitride and constructing an iron nitride / gallium nitride / carbon composite heterostructure.

[0075] The iron nitride / gallium nitride / carbon composite heterostructure material of Example 1 and the composite materials of Comparative Examples 1 to 2 were used as catalysts for electrocatalysis, including the following steps: S1. Electrocatalytic testing system setup: A CHI760E electrochemical workstation was used, employing a three-electrode system for testing. A glassy carbon electrode with a rotating disk electrode (RDE) was used as the working electrode, an Hg / HgO electrode as the reference electrode, and a graphite rod as the counter electrode. All potentials were converted to the reversible hydrogen electrode (RHE) scale.

[0076] S2. Catalyst Ink Preparation and Electrode Preparation: 10 mg of catalyst (iron nitride / gallium nitride / carbon composite heterostructure material of Example 1, composite materials of Comparative Examples 1-2, and commercial electrocatalytic materials Pt / C or RuO2) were weighed and added to 20 μL of 5 wt% Nafion solution, followed by 980 μL of isopropanol / water mixed solvent (volume ratio 1:2). The mixture was ultrasonically dispersed to form a uniform catalyst ink. 10 μL of the ink was drop-coated multiple times onto the surface of a glassy carbon disk electrode and dried at room temperature to obtain a catalyst-loaded working electrode. The glassy carbon disk had a diameter of approximately 5.0 mm (area 0.1962 cm²) and a catalyst loading of approximately 0.5 mg·cm². -2 .

[0077] S3 and ORR polarization curve tests: in O2-saturated 0.1 mol·L⁻¹ -1 ORR activity was tested in KOH electrolyte using linear sweep voltammetry (LSV) at a scan rate of 5 mV·s. -1 The electrode rotation speed was 1600 rpm, and ORR polarization curves for different samples were obtained. ORR Tafel curve calculation: The Tafel curve was derived from the obtained ORR LSV polarization curves. The potential E was plotted against log(j), and the Tafel slope was obtained by fitting the linear region with low overpotential. Electron transfer number and H₂O₂ yield: RRDE was used in O₂-saturated 0.1 mol·L⁻¹ water. -1 The test was conducted in KOH at a scan rate of 5 mV·s. -1 The rotation speed was 1600 rpm; the Pt ring potential was fixed at 1.30 V (vs. RHE) to oxidize the H2O2 generated by the disk; the electron transfer number n and hydrogen peroxide yield were calculated according to the RRDE standard formula based on the disk current and ring current. ORR stability test: The stability was evaluated using chronoamperometry. The working electrode was tested for a long time at a constant potential of 0.6 V (vs. RHE) with an electrode rotation speed of 1600 rpm, and the change of relative current over time was recorded.

[0078] S4, OER polarization curve test: in N2 saturated 1.0 mol·L -1 In KOH electrolyte, OER activity was tested using LSV at a scan rate of 5 mV·s. -1 The electrode rotation speed was 1600 rpm. During the test, the solution resistance Rs was obtained through EIS, and 95% iR compensation was performed to correct the ohmic voltage drop caused by the solution resistance. The OER polarization curve was obtained, and 10 mA·cm⁻¹ was read. -2 Corresponding overpotential. From Figure 4The Tafel curve is calculated from the OER polarization curve obtained after iR compensation. The overpotential η (η=E−1.23V, the potential has been converted to RHE scale) is plotted against log(j), and the Tafel slope is obtained by fitting in the low overpotential linear region.

[0079] Figure 4 The electrocatalytic performance diagrams are for the iron nitride / gallium nitride / carbon composite heterostructure material of Example 1 of the present invention, as well as the composite materials and commercial electrocatalytic materials of Comparative Examples 1 to 2. Figure 4 In the diagram, (a) is the ORR linear sweep voltammetry (LSV) polarization curve for Example 1, Comparative Examples 1-2, and commercial Pt / C; (b) is the ORR Tafel curve corresponding to (a); (c) is the electron transfer number (n) and hydrogen peroxide yield curve for Example 1 and commercial ORR catalyst Pt / C during the ORR process; (d) is the ORR stability test curve for Example 1 and commercial ORR catalyst Pt / C under constant potential conditions; (e) is the linear sweep voltammetry (LSV) polarization curve for Example 1, Comparative Examples 1-2, and commercial OER catalyst RuO2 under oxygen evolution reaction (OER) conditions; and (f) is the OER Tafel curve corresponding to (e). Figure 4 As shown, the iron nitride / gallium nitride / carbon composite heterostructure material prepared in Example 1 exhibits good electrocatalytic activity and reaction kinetics in both oxygen reduction and oxygen evolution reactions (ORR), and outperforms Pt / C in ORR stability testing. Based on the aforementioned structural analysis, it can be concluded that the heterostructure interface formed by iron nitride and gallium nitride within the carbon phase confinement is beneficial for electron transport and interface regulation during the reaction process, contributing to improved stability / durability in electrochemical and device testing, thereby enhancing the material's bifunctional electrocatalytic performance and stability.

[0080] The electrochemical performance of the iron nitride / gallium nitride / carbon composite heterostructure material in Example 1 and the composite materials in Comparative Examples 1 and 2 are shown in Table 2. The materials in these examples exhibit higher reactivity and better kinetic characteristics in both the oxygen reduction reaction and the oxygen evolution reaction, indicating that the composite heterostructure formed by iron nitride and gallium nitride within the carbon phase confinement is beneficial for improving the overall electrocatalytic performance of the materials. These results demonstrate that the present invention achieves synergistic optimization of structure and performance through the synergistic introduction of iron and gallium sources and the construction of the composite heterostructure.

[0081] Table 2 Electrochemical properties of composite materials in Examples 1-6 and Comparative Examples 1-2 The composite heterostructure material prepared in Example 1 is used as an air electrode catalyst in a metal-air battery, comprising the following steps: S1. Preparation of air electrode: The material from Example 1 (FeGa / C-0.75) or the comparative catalyst (Pt / C+RuO2, mass ratio 1:1) was formulated into a catalyst ink; the catalyst ink was drop-coated onto a carbon paper substrate, and the catalyst loading was controlled to be 1.0 mg·cm³. -2 (Based on the total mass of the catalyst), and dried at room temperature to obtain an air electrode.

[0082] S2. Preparation of metal negative electrode and electrolyte: Take zinc sheet as metal negative electrode, use sandpaper to mechanically polish the surface of zinc sheet and rinse with deionized water; prepare electrolyte as 6.0M KOH + 0.2M Zn(CH3COO)2 aqueous solution.

[0083] S3. Battery assembly: The zinc negative electrode, electrolyte and the prepared air electrode are assembled in a zinc-air battery fixture (e.g., a PMMA battery fixture), with the catalyst layer of the air electrode facing the electrolyte and the other side of the air electrode exposed to ambient air to obtain oxygen.

[0084] S4. Discharge polarization curve and power density test: The discharge polarization curve was obtained using the linear sweep voltammetry (LSV) method at a scan rate of 5 mV·s. -1 The power density is calculated based on the discharge current and battery voltage. The power density calculation relationship is P=I×V / A, where I is the discharge current, V is the battery voltage, and A is the geometric area of ​​the air electrode.

[0085] S5. Charge / Discharge and Cycle Stability Testing: The battery is subjected to constant current charge / discharge testing to evaluate cycle stability; in some implementations, long-term cycle testing can be performed on the battery testing system: at 30 mA·cm -2 The current density is used to perform repeated constant current charge and discharge cycles, with each charge and discharge lasting 1 hour.

[0086] Figure 5 This is a power density diagram of a metal-air battery using a composite heterostructure material as an air electrode catalyst, as shown in Example 1 of the present invention. Figure 5 As shown, the metal-air battery constructed using the material of Example 1 can output a high power density, indicating that the composite heterostructure material can maintain good reactivity and energy output capability under actual device conditions. The results further demonstrate that the composite heterostructure material described in this invention not only performs well under electrochemical testing conditions but also possesses application potential at the device level.

[0087] Figure 6 The graph shows the charge-discharge stability test results of the metal-air battery using the material of Example 1 of the present invention as the air electrode under constant current conditions. Figure 6As shown, the battery maintains a relatively stable operating voltage during multiple charge-discharge cycles without significant performance degradation, indicating that the material in Example 1 has good structural stability and long-term operational reliability. Based on the material's structural characteristics, it can be inferred that the coating and confinement effect of carbon on the metal nitride particles, as well as the stable heterostructure interface formed by iron nitride and gallium nitride, helps to suppress structural degradation of the material during repeated charge-discharge cycles.

[0088] The composite heterostructure material of Example 1 was used to evaluate the electromagnetic wave absorption performance, including the following steps: S1) The composite heterostructure material of Example 1 was mixed with a non-conductive matrix such as paraffin / epoxy resin at a mass ratio of 30wt% to obtain a composite sample.

[0089] S2) Press / cast the composite sample into a ring-shaped specimen with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 2 mm.

[0090] S3) The electromagnetic parameters or S-parameters of the sample are tested in the 2GHz to 18GHz frequency band using a vector network analyzer to obtain the complex permittivity (εr) and complex permeability (μr). S4) Calculate the input impedance Z under different thicknesses d based on transmission line theory. in With reflection loss RL: .

[0091] .

[0092] In the formula, Z0 is the free space impedance. f Let c be the frequency and c be the speed of light.

[0093] Figure 7 This is a graph showing the electromagnetic wave absorption performance of the composite heterostructure material in Example 1 in the 2GHz–18GHz frequency band. Different colors correspond to different absorption layer thicknesses, and the reflection loss RL = -10dB is the effective absorption threshold. The curves are calculated from the complex permittivity / complex permeability. Figure 7 As shown, the material of Embodiment 1 of the present invention exhibits significant electromagnetic wave absorption characteristics in the range of 2 GHz to 18 GHz, and the position of the absorption peak can be adjusted with the thickness of the absorption layer. Using RL = −10 dB as the effective absorption threshold, a relatively wide effective absorption bandwidth (approximately 11.5 GHz to 15.8 GHz, with a bandwidth of approximately 4.35 GHz) can be obtained under suitable thickness conditions (approximately 7 mm to 8 mm), and the reflection loss is as low as approximately −43.7 dB at approximately 13.8 GHz, indicating that it has a strong electromagnetic wave attenuation capability.

[0094] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0095] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing an iron nitride / gallium nitride / carbon composite heterostructure material, characterized in that, Includes the following steps: In a protective atmosphere, iron-containing raw materials, gallium-containing raw materials, and nitrogen-containing organic compounds are heat-treated to induce reduction and nitriding reactions in the iron-containing and gallium-containing raw materials, forming iron nitride and gallium nitride phases, and simultaneously forming a carbon phase. The iron nitride and gallium nitride phases form a heterostructure interface at the nanoscale, and the carbon phase coats or connects to the outer surface of the iron nitride and / or gallium nitride phases, resulting in an iron nitride / gallium nitride / carbon composite heterostructure material. Among them, the nitrogen-containing organic compound is an organic compound that provides both nitrogen and carbon sources during the heat treatment process.

2. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 1, characterized in that, The iron nitride phase is at least one of Fe4N, Fe3N, and Fe2N.

3. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 1, characterized in that, The carbon phase is at least one of graphitized carbon, graphite-like carbon, carbon nanotubes, and carbon nanofibers.

4. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 1, characterized in that, The heat treatment temperature is 600℃~900℃, and the protective atmosphere is nitrogen or inert gas.

5. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 1, characterized in that, The nitrogen-containing organic compounds are melamine and / or urea.

6. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 1, characterized in that, The molar ratio of Fe to Ga in the iron-containing and gallium-containing raw materials is 1:0.1 to 1.5, and the molar ratio of iron salt to nitrogen-containing organic compound is 1:5 to 50. The iron-containing raw materials are iron salts and / or iron hydroxides, and the gallium-containing raw materials are gallium salts and / or gallium hydroxides.

7. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 1, characterized in that, The mixing methods for iron-containing and gallium-containing raw materials before heat treatment include: direct mixing with nitrogen-containing organic compounds, or mixing with nitrogen-containing organic compounds after forming a precursor through a precipitation reaction.

8. The method for preparing the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 7, characterized in that, When iron-containing raw materials and gallium-containing raw materials undergo a precipitation reaction to form a precursor, the precipitant is at least one of urea, ammonia, and sodium hydroxide.

9. A composite heterostructure material of iron nitride / gallium nitride / carbon, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the iron nitride / gallium nitride / carbon composite heterostructure material according to claim 9 in electrocatalytic materials, electrochemical energy devices, electromagnetic wave absorbing materials or magnetic materials.

Images