A nitrogen-rich polyimide / metal monatomic composite material, a preparation method and application thereof

Abstract

This invention provides a nitrogen-rich polyimide / metal single-atom composite material, its preparation method, and its application. First, a nitrogen-rich polyamic acid solution is obtained through chemical polymerization and coated onto a support material. Gradient-temperature thermal imidization is then performed to obtain the nitrogen-rich polyimide / support composite material. Next, metal single atoms are anchored onto the nitrogen-rich polyimide / support composite material using an impregnation method, ultimately obtaining the nitrogen-rich polyimide / metal single-atom composite material coated on the support material. The nitrogen and oxygen atoms on the prepared nitrogen-rich polyimide / metal single-atom composite material provide stable anchoring sites for the metal single atoms. Simultaneously, the strongly electron-deficient nitrogen-rich structure helps promote surface charge accumulation and increases the local reactant concentration near the metal active sites, thereby significantly improving the material's stability and catalytic activity.

Description

Technical Field

[0001] This invention belongs to the field of polymer nanocomposite technology, and in particular relates to a nitrogen-rich polyimide / metal single-atom composite material, its preparation method and application. Background Technology

[0002] Polyimide is a class of special engineering plastics with excellent molding and processing properties, high mechanical strength, and good thermal stability. It is widely used in many important sectors of the national economy, including catalysis, thermal conductivity, electronic devices, electromagnetic shielding and absorption, and electrochemical energy storage. To further improve its performance, polyimide is composited with metals to obtain polyimide / metal nanoparticle composites, which can achieve further performance enhancement. However, metal nanoparticles, especially noble metal nanoparticles (such as platinum, ruthenium, and iridium), are expensive, which significantly increases the cost of composite materials. Compared with metal nanoparticles, single metal atoms have high metal atom utilization, which can reduce the cost of composite materials while achieving excellent catalytic activity. Compared with polyimide / metal single-atom composites without nitrogen-rich structures, nitrogen-rich polyimide / metal single-atom composites utilize nitrogen and oxygen atoms on the surface of nitrogen-rich polyimide materials to immobilize metal single atoms, prevent single-atom migration and aggregation, and achieve excellent chemical stability. In addition, the strongly electron-deficient nitrogen-rich structure can also promote charge accumulation on the surface of nitrogen-rich polyimide / metal single-atom composites, increase the local reactant concentration near the metal single atoms, and thus achieve better catalytic activity. Summary of the Invention

[0003] To address the problems and shortcomings of existing technologies, this invention provides a nitrogen-rich polyimide / metal single-atom composite material, its preparation method, and its application. The metal single atoms can be more stably anchored on the nitrogen-rich polyimide support, achieving superior catalytic performance.

[0004] The first aspect of this invention is to provide a method for preparing a nitrogen-rich polyimide / metal single-atom composite material, the method comprising the following steps: (i) Dissolve nitrogen-rich diamine monomer in organic solvent I, add dianhydride monomer under nitrogen atmosphere, stir in an ice-water bath, and allow to stand to react to prepare nitrogen-rich polyamic acid solution; (ii) The obtained nitrogen-rich polyamic acid solution was subjected to solvent exchange and freeze-drying to obtain nitrogen-rich polyamic acid solid; the obtained freeze-dried nitrogen-rich polyamic acid solid was dissolved in organic solvent II and drop-coated onto a conductive carrier, and subjected to gradient heating thermal imidization treatment to prepare nitrogen-rich polyimide / carrier composite material. (iii) The metal precursor salt is dissolved in a mixed solution of water and ethanol to obtain a metal precursor salt solution, and then drop-coated onto a nitrogen-rich polyimide / carrier composite material. Metal single atoms are anchored onto the nitrogen-rich polyimide / carrier composite material by impregnation to obtain a nitrogen-rich polyimide / metal single atom composite material on a conductive carrier material.

[0005] In one implementation, in step (i), the molar ratio of the nitrogen-rich diamine monomer and the dianhydride monomer used in the reaction is 1.0:1.0-1.0:1.2.

[0006] In one embodiment, in step (i), the nitrogen-rich diamine monomer comprises 3,6-diaminopyridazine or 2,5-diaminopyridine, preferably 3,6-diaminopyridazine.

[0007] In one embodiment, in step (i), the dianhydride monomer includes one or more of pyromellitic dianhydride, pyromellitic dianhydride, biphenyl dianhydride, benzophenone tetracarboxylic dianhydride, hexafluorodianhydride, pyromellitic ether dianhydride, or benzophenone tetracarboxylic dianhydride, preferably pyromellitic dianhydride.

[0008] In one embodiment, the organic solvent I includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, preferably N,N-dimethylformamide.

[0009] In one implementation, in step (ii), the exchange solvent used for solvent exchange includes one or more of ultrapure water or ethanol, preferably ultrapure water.

[0010] In one embodiment, in step (ii), the nitrogen-rich polyimide solid is first rapidly frozen in liquid nitrogen for 100-300 s to -10-50 °C, and then freeze-dried in a vacuum freeze dryer with a vacuum degree of 10-100 Pa for 24-72 h.

[0011] In one embodiment, in step (ii), the solid content of the nitrogen-rich polyamic acid solid dissolved in organic solvent II is 5%-15%.

[0012] In one embodiment, in step (ii), the organic solvent II for dissolving the freeze-dried nitrogen-rich polyamic acid solid includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide.

[0013] In one implementation, the amount of nitrogen-rich polyamic acid solution added in step (ii) is 5-40 μL / cm. 2 .

[0014] In one implementation, the conductive carrier material in step (ii) includes one of carbon cloth, carbon paper, carbon fiber, or carbon felt.

[0015] In one implementation, the temperature nodes of the stepped heating in step (ii) are sequentially 50 ℃, 70 ℃, 100 ℃, and 200 ℃, with a heating rate of 4-7 ℃ / min and a holding time of 60-120 min at each temperature point.

[0016] In one implementation, the heating rate of the stepped temperature rise in step (ii) is 5 °C / min, and each temperature node is held for 1 h.

[0017] In one implementation, step (ii) involves a gradient heating thermal imidization process in a tube furnace or muffle furnace.

[0018] In one implementation, the concentration of the metal precursor salt described in step (iii) is 0.025-0.05 mg / μL.

[0019] In one implementation, the metal precursor salt in step (iii) is a halide, sulfate, carbonate, or nitrate of a metal ion, wherein the metal ion includes any one or more of platinum, ruthenium, iridium, iron, cobalt, copper, molybdenum, or nickel.

[0020] In one implementation, the ratio of water to ethanol in the water and ethanol mixture used to dissolve the metal precursor salt in step (iii) is 1.0:1.0-1.0:2.0.

[0021] In one implementation, the impregnation method described in step (iii) specifically includes: after drop-coating a metal precursor salt solution onto a nitrogen-rich polyimide / carrier composite material, annealing it at 100 °C in an argon atmosphere in a tube furnace at a heating rate of 2-5 °C / min; after the temperature drops to room temperature, drying it with dimethyl sulfoxide, and then annealing it at 350 °C in a hydrogen-argon mixed atmosphere in a tube furnace at a heating rate of 2-5 °C / min, holding each temperature point for 120-180 min.

[0022] In one implementation, the metal used in the impregnation step of step (iii) includes any one of platinum, ruthenium, iridium, iron, cobalt, copper, molybdenum, or nickel.

[0023] On the other hand, the present invention also provides a nitrogen-rich polyimide / metal single-atom composite material prepared by the above method.

[0024] In one embodiment, the loading of the metal single atom in the nitrogen-rich polyimide / metal single atom composite material is 0.015 wt% to 2.500 wt%.

[0025] In one embodiment, the nitrogen-rich polyimide / metal single-atom composite material is used in a 0.5 M H₂SO₄ electrolyte at a current density of 10 mA / cm². 2 The overpotential is below 250 mV.

[0026] Furthermore, in one embodiment, the nitrogen-rich polyimide / metal single-atom composite material is used in a 0.5 MH2SO4 electrolyte at a current density of 10 mA / cm². 2 The overpotential is below 220 mV.

[0027] Furthermore, in one embodiment, the nitrogen-rich polyimide / metal single-atom composite material is used in a 0.5 MH2SO4 electrolyte at a current density of 10 mA / cm². 2 The overpotential is below 200 mV.

[0028] On the other hand, the present invention also provides an application of the above preparation method or an application of a nitrogen-rich polyimide / metal single-atom composite material, such as applications in catalysis, thermal conductivity, electronic devices, electromagnetic wave shielding and absorption, electrochemical energy storage and other fields.

[0029] Compared with the prior art, the beneficial effects of the present invention are: 1. The method for preparing nitrogen-rich polyimide / metal single-atom composite materials used in this invention is simple and easy to operate. By introducing different precursor metals, nitrogen-rich polyimide / metal single-atom composite materials with different metals exhibiting atomic and dispersed properties can be obtained.

[0030] 2. Compared with existing carbon materials / metal single-atom composite materials, the nitrogen-rich polyimide support prepared in this invention has unique advantages in anchoring single atoms due to its strong molecular designability, excellent electrochemical stability under acidic conditions, and tunable electronic properties.

[0031] 3. Compared to existing polyimide / metal single-atom composite materials, the nitrogen-rich polyimide material surface used in the nitrogen-rich polyimide / metal single-atom composite material prepared in this invention can be used to fix metal single atoms, preventing the migration and aggregation of single atoms, thus exhibiting excellent resistance to chemical / electrochemical corrosion. Furthermore, the strongly electron-deficient nitrogen-rich structure can also promote charge accumulation on the surface of the nitrogen-rich polyimide / metal single-atom composite material, increasing the local reactant concentration near the metal single atoms, thereby achieving excellent catalytic activity. Attached Figure Description

[0032] Figure 1 The diagram shows the iridium single-atom coordination structure in the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1.

[0033] Figure 2 The infrared spectrum of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 is shown.

[0034] Figure 3 This is a spherical aberration electron microscope image of the nitrogen-rich polyimide / iridium single-atom composite material of Example 1.

[0035] Figure 4 The X-ray photoelectron spectroscopy (XPS) spectra of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 are shown in Figure a. Figure a is the high-resolution spectrum of nitrogen, and Figure b is the high-resolution spectrum of iridium.

[0036] Figure 5 The X-ray absorption spectrum of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 is shown in Figure a. Figure a shows the near-edge absorption spectrum of X-rays, and Figure b shows the extended edge absorption spectrum of X-rays.

[0037] Figure 6 The graph shows the iridium single-atom content in the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1.

[0038] Figure 7 Linear sweep voltammetry curves of the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1.

[0039] Figure 8 The bar chart shows the mass activity of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 and the nitrogen-free polyimide / iridium single-atom composite material in Comparative Example 1.

[0040] Figure 9 The pulse voltammetry curves and linear graphs of total charge versus potential are shown for the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1.

[0041] Figure 10 This is a chronopotential analysis diagram of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments and comparative examples are only a part of the implementation of the present invention, and not all of the 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.

[0043] Unless otherwise specified, all reagents used in the embodiments of this invention can be purchased commercially.

[0044] The present invention provides accompanying drawings of the characterization test results of Example 1 and Comparative Example 1. Other embodiments all use the same characterization test method. Those skilled in the art can directly and without doubt determine the content of the embodiments of the present invention through the characterization test method provided by the present invention.

[0045] Example 1: Preparation of nitrogen-rich polyimide / iridium single-atom composite material (1) Weigh 2.20 g (0.02 mol) of 3,6-diaminopyridazine using a balance and add it to a three-necked flask, followed by 47.0 g of N,N-dimethylformamide. Stir and keep nitrogen gas flowing through the flask to purge air and ensure the reaction system is under a nitrogen atmosphere. After the 3,6-diaminopyridazine has completely dissolved, slowly add 4.36 g (0.02 mol) of pyromellitic dianhydride. Continue stirring under an ice-water bath until a pale yellow, viscous, nitrogen-rich polyamic acid solution is obtained.

[0046] (2) The obtained nitrogen-rich polyamic acid solution was poured into a large amount of stirred ultrapure water for solvent exchange. After filtration, it was rapidly frozen in liquid nitrogen for 120 s at -30 ℃, and then freeze-dried in a vacuum freeze dryer at a vacuum degree of 10 Pa for 24 h to obtain nitrogen-rich polyamic acid solid. 0.50 g of nitrogen-rich polyamic acid solid was weighed into a blue-mouthed bottle, and 10.00 g of N,N-dimethylformamide was added to control the solid content at 5%. The nitrogen-rich polyamic acid was completely diluted by heating at 50 ℃ and magnetic stirring. A 0.5 × 1.0 cm sample was then cut. 2 Carbon paper of various sizes serves as a carrier for nitrogen-rich polyamic acid solutions.

[0047] (3) Take 10 μL of the nitrogen-rich polyamic acid solution obtained in step (2) and drop it onto both sides of the carbon paper. Place the obtained carbon paper into a muffle furnace for gradient heating thermal imidization. The temperature nodes are 50 ℃, 70 ℃, 100 ℃, and 200 ℃ respectively, the heating rate is 5 ℃ / min, and each temperature node is held for 1 h to complete the preparation of nitrogen-rich polyimide / carbon paper composite substrate.

[0048] (4) Weigh 5 mg of iridium tetrachloride and dissolve it in a mixed solution of 200 μL of water and ethanol (water: ethanol = 1:1). Coat the iridium tetrachloride solution onto the nitrogen-rich polyimide / carbon paper composite material prepared in step (3). Place it in a tube furnace for hydrogen-argon reduction. The temperature nodes of the gradient heating are 100 ℃ and 350 ℃, the heating rate is 2 ℃ / min, and each temperature node is held for 2 h to complete the preparation of nitrogen-rich polyimide / iridium metal single-atom composite material.

[0049] Example 2: Preparation of nitrogen-rich polyimide / iridium single-atom composite material (1) Weigh 2.18 g (0.02 mol) of 2,5-diaminopyridine using a balance and add it to a three-necked flask, followed by 47.0 g of N,N-dimethylformamide. Stir and keep nitrogen gas flowing through the flask to purge air and ensure the reaction system is under a nitrogen atmosphere. After the 2,5-diaminopyridine has completely dissolved, slowly add 4.36 g (0.02 mol) of pyromellitic dianhydride. Continue stirring under ice-water bath conditions until a pale yellow, viscous, nitrogen-rich polyamic acid solution is obtained.

[0050] (2) The obtained nitrogen-rich polyamic acid solution was poured into a large amount of stirred ultrapure water for solvent exchange. After filtration, it was rapidly frozen in liquid nitrogen for 120 s at -30 ℃, and then freeze-dried in a vacuum freeze dryer with a vacuum degree of 10 Pa for 24 h to obtain nitrogen-rich polyamic acid solid. 0.50 g of nitrogen-rich polyamic acid solid was weighed into a blue-mouthed bottle, and 10.00 g of N,N-dimethylformamide was added to control the solid content to 5%. The nitrogen-rich polyamic acid was completely diluted by heating at 50 ℃ and magnetic stirring. A 0.5 × 1.0 cm sample was then cut. 2 Carbon paper of various sizes serves as a carrier for nitrogen-rich polyamic acid solutions.

[0051] (3) Take 10 μL of the mixed solution obtained in step (2) and drop it onto both sides of the carbon paper. Place the obtained carbon paper into a muffle furnace for gradient heating thermal imidization. The temperature nodes are 50 ℃, 70 ℃, 100 ℃, and 200 ℃ respectively, the heating rate is 5 ℃ / min, and each temperature node is held for 1 h to complete the preparation of nitrogen-rich polyimide / carbon paper composite substrate.

[0052] (4) Weigh 5 mg of iridium tetrachloride and dissolve it in a mixed solution of 200 μL of water and ethanol (water: ethanol = 1:1). Coat the iridium tetrachloride solution onto the nitrogen-rich polyimide / carbon paper composite material prepared in step (3). Place it in a tube furnace for hydrogen-argon reduction. The temperature nodes of the gradient heating are 100 ℃ and 350 ℃, the heating rate is 2 ℃ / min, and each temperature node is held for 2 h to complete the preparation of nitrogen-rich polyimide / iridium metal single-atom composite material.

[0053] Example 3: Preparation of nitrogen-rich polyimide / ruthenium single-atom composite material (1) Weigh 2.20 g (0.02 mol) of 3,6-diaminopyridazine using a balance and add it to a three-necked flask, followed by 47.0 g of N,N-dimethylformamide. Stir and keep nitrogen gas flowing through the flask to purge air and ensure the reaction system is under a nitrogen atmosphere. After the 3,6-diaminopyridazine has completely dissolved, slowly add 4.36 g (0.02 mol) of pyromellitic dianhydride. Continue stirring under an ice-water bath until a pale yellow, viscous, nitrogen-rich polyamic acid solution is obtained.

[0054] (2) The obtained nitrogen-rich polyamic acid solution was poured into a large amount of stirred ultrapure water for solvent exchange. After filtration, it was rapidly frozen in liquid nitrogen for 120 s at -30 ℃, and then freeze-dried in a vacuum freeze dryer with a vacuum degree of 10 Pa for 24 h to obtain nitrogen-rich polyamic acid solid. 0.50 g of nitrogen-rich polyamic acid solid was weighed into a blue-mouthed bottle, and 10.00 g of N,N-dimethylformamide was added to control the solid content to 5%. The nitrogen-rich polyamic acid was completely diluted by heating at 50 ℃ and magnetic stirring. A 0.5 × 1.0 cm sample was then cut. 2 Carbon paper of various sizes serves as a carrier for nitrogen-rich polyamic acid solutions.

[0055] (3) Take 10 μL of the mixed solution obtained in step (2) and drop it onto both sides of the carbon paper. Place the obtained carbon paper into a muffle furnace for gradient heating thermal imidization. The temperature nodes are 50 ℃, 70 ℃, 100 ℃, and 200 ℃ respectively, the heating rate is 5 ℃ / min, and each temperature node is held for 1 h to complete the preparation of nitrogen-rich polyimide / carbon paper composite substrate.

[0056] (4) Weigh 5 mg of ruthenium trichloride and dissolve it in a mixed solution of 200 μL of water and ethanol (water: ethanol = 1:1). Coat the ruthenium trichloride solution onto the nitrogen-rich polyimide / carbon paper composite material prepared in step (3). Place it in a tube furnace for hydrogen-argon reduction. The temperature nodes of the gradient heating are 100 ℃ and 350 ℃, the heating rate is 2 ℃ / min, and each temperature node is held for 2 h to complete the preparation of nitrogen-rich polyimide / ruthenium metal single-atom composite material.

[0057] Comparative Example 1: Preparation of polyimide / iridium single-atom composite materials without nitrogen-rich structures (1) Weigh 2.16 g (0.02 mol) of p-phenylenediamine using a balance and add it to a three-necked flask, followed by 47.0 g of N,N-dimethylformamide. Stir and keep nitrogen gas flowing through the flask to purge air and ensure the reaction system is under a nitrogen atmosphere. After the p-phenylenediamine has completely dissolved, slowly add 4.36 g (0.02 mol) of pyromellitic dianhydride. Continue stirring under an ice-water bath until a pale yellow viscous polyamic acid solution is obtained.

[0058] (2) The obtained nitrogen-rich polyamic acid solution was poured into a large amount of stirred ultrapure water for solvent exchange. After filtration, it was rapidly frozen in liquid nitrogen for 120 s at -30 ℃, and then freeze-dried in a vacuum freeze dryer with a vacuum degree of 10 Pa for 24 h to obtain solid polyamic acid. 0.50 g of solid polyamic acid was weighed into a blue-mouthed bottle, and 10.00 g of N,N-dimethylformamide was added to control the solid content at 5%. The polyamic acid was completely diluted by heating at 50 ℃ and stirring with a magnetic stirrer. A 0.5 × 1.0 cm sample was then cut. 2 Carbon paper of various sizes serves as a carrier for the polyamic acid solution.

[0059] (3) Take 10 μL of the mixed solution obtained in step (2) and drop it onto both sides of the carbon paper. Place the obtained carbon paper into a muffle furnace for gradient heating thermal imidization. The temperature nodes are 50 ℃, 70 ℃, 100 ℃, and 200 ℃ respectively. The heating rate is 5 ℃ / min. Hold at each temperature node for 1 h to complete the preparation of the polyimide / carbon paper composite substrate.

[0060] (4) Weigh 5 mg of iridium tetrachloride and dissolve it in a 200 μL mixed solution of water and ethanol (water: ethanol = 1:1). Coat the iridium tetrachloride solution onto the polyimide / carbon paper composite material prepared in step (3). Place it in a tube furnace for hydrogen-argon reduction. The temperature nodes of the gradient heating are 100 ℃ and 350 ℃, the heating rate is 2 ℃ / min, and each temperature node is held for 2 h to complete the preparation of polyimide / iridium metal single-atom composite material.

[0061] Performance testing of the polyimide / iridium single-atom composite material obtained in the examples like Figure 1 These are schematic diagrams of the iridium single-atom coordination structures in the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1. It can be seen that in the nitrogen-rich polyimide / iridium single-atom composite material, the iridium single atom coordinates with the nitrogen and oxygen atoms in the nitrogen-rich polyimide material; in the nitrogen-free polyimide / iridium single-atom composite material, the iridium single atom coordinates with the carbon and oxygen atoms in the nitrogen-free polyimide material.

[0062] like Figure 2 The infrared spectrum of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 is shown, revealing the typical infrared characteristic peaks of the nitrogen-rich polyimide. This confirms that the iridium single-atom support is the nitrogen-rich polyimide polymer.

[0063] like Figure 3 The image shown is a spherical aberration electron microscope image of the nitrogen-rich polyimide / iridium single-atom composite material of Example 1. It can be seen that iridium single atoms are dispersed on the surface of the nitrogen-rich polyimide material, confirming that the iridium single atoms are anchored on the nitrogen-rich polyimide material.

[0064] like Figure 4 The image shown is an X-ray photoelectron spectrum of the nitrogen-rich polyimide / iridium single-atom composite material of Example 1, which shows that the nitrogen-rich polyimide / iridium single-atom composite material contains nitrogen and iridium elements.

[0065] like Figure 5 The X-ray absorption spectrum of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 is shown. A clear iridium-oxygen peak can be seen, but no iridium-iridium peak was observed, confirming that the metal components in the prepared nitrogen-rich polyimide / iridium single-atom composite material are all single atoms.

[0066] like Figure 6 The figures show that the iridium metal single-atom contents loaded on the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1 are 1.828% and 1.915%, respectively, achieving essentially equivalent loading effects. This demonstrates that the introduction of the nitrogen-rich structure does not affect the loading rate of the metal single atoms.

[0067] like Figure 7 The figure shows the linear sweep voltammetry curves of the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1. As can be seen from the figure, the prepared nitrogen-rich polyimide / iridium single-atom composite material, in 0.5 M H₂SO₄ electrolyte, at a current density of 10 mA / cm², exhibits excellent performance. 2 The overpotential was as low as 198 mV. The prepared polyimide / iridium single-atom composite material without nitrogen-rich structures was tested in 0.5 M H2SO4 electrolyte at a current density of 10 mA / cm². 2 The overpotential was 283 mV, confirming that the nitrogen-rich polyimide / iridium single-atom composite material has excellent electrocatalytic activity.

[0068] like Figure 8 The bar charts for the mass activity of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1 and the nitrogen-free polyimide / iridium single-atom composite material in Comparative Example 1 show that the nitrogen-rich polyimide single-atom composite material has superior mass activity at the same potential.

[0069] like Figure 9 The figures show the pulse voltammetry curves and the linear graph of total charge versus potential for the nitrogen-rich polyimide / iridium single-atom composite material of Example 1 and the nitrogen-free polyimide / iridium single-atom composite material of Comparative Example 1. As can be seen from Figure b, the slope of the nitrogen-rich polyimide / iridium single-atom composite material is higher, indicating that charge accumulation has occurred on its surface, increasing the local reactant concentration near the iridium single atoms, thereby enhancing the catalytic activity.

[0070] like Figure 10 This is a chronopotential analysis chromatogram of the nitrogen-rich polyimide / iridium single-atom composite material in Example 1. The chromopotential analysis shows that the prepared nitrogen-rich polyimide / iridium single-atom composite material exhibits high chronopotential at 10 mA cm⁻¹. -2 Stable operation for 200 h under current density and 0.5 M H2SO4 electrolyte, with potential decay within 20 mV, confirms that nitrogen-rich polyimide materials have excellent electrochemical stability.

[0071] The embodiments and comparative examples described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-rich polyimide / metal single-atom nanocomposite material, characterized in that, Includes the following steps: (i) Dissolve the nitrogen-rich diamine monomer in organic solvent I, add the dianhydride monomer under a nitrogen atmosphere, stir in an ice-water bath, and allow the reaction to stand to prepare a nitrogen-rich polyamic acid solution; the nitrogen-rich diamine monomer includes 3,6-diaminopyridazine or 2,5-diaminopyridine. (ii) The obtained nitrogen-rich polyamic acid solution was subjected to solvent exchange and freeze-drying to obtain nitrogen-rich polyamic acid solid; the obtained nitrogen-rich polyamic acid solid was dissolved in organic solvent II and drop-coated onto a conductive carrier, and subjected to gradient heating thermal imidization treatment to prepare nitrogen-rich polyimide / carrier composite material. (iii) A metal precursor salt is dissolved in a mixed solution of water and ethanol to obtain a metal precursor salt solution, which is then drop-coated onto a nitrogen-rich polyimide / carrier composite material. Metal single atoms are anchored onto the nitrogen-rich polyimide / carrier composite material by an impregnation method to obtain a nitrogen-rich polyimide / metal single-atom composite material on a conductive carrier material. The metal precursor salt is a halide, sulfate, carbonate, or nitrate of a metal ion, and the metal ion includes any one or more of platinum, ruthenium, iridium, iron, cobalt, copper, molybdenum, or nickel.

2. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, In step (i), the molar ratio of the added diamine monomer and dianhydride monomer is 1.0:1.0-1.0:1.

2.

3. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, In step (i), The dianhydride monomer comprises one or more of pyromellitic dianhydride, biphenyltetracarboxylic anhydride, benzophenone tetracarboxylic anhydride, and hexafluorodianhydride; and / or The organic solvent I mentioned in step (i) includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

4. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, In step (ii), the exchange solvent used for solvent exchange includes one or more of ultrapure water or ethanol; In the freeze-drying step, the nitrogen-rich polyimide solid is first rapidly frozen in liquid nitrogen for 100-300 s to -10-50 °C, and then freeze-dried in a vacuum freeze dryer with a vacuum degree of 10-100 Pa for 24-72 h. The nitrogen-rich polyamic acid solid dissolved in organic solvent II has a solid content of 5%-15%, and / or The organic solvent II for dissolving the freeze-dried nitrogen-rich polyamic acid solid includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide.

5. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, The coating concentration of the nitrogen-rich polyamic acid solution in step (ii) is 5-40 μL / cm. 2 , and / or The conductive carrier material includes any one of carbon cloth, carbon paper, carbon fiber, or carbon felt.

6. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, The order of the temperature nodes in the gradient heating thermal imidization in step (ii) is: 50 ℃, 70 ℃, 100 ℃, 200 ℃, with a heating rate of 4-7 ℃ / min and a holding time of 60-120 min for each temperature node.

7. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, The concentration of the metal precursor salt in step (iii) is 0.025-0.05 mg / μL; and / or In the water and ethanol mixed solution used to dissolve the metal precursor salt, the ratio of water to ethanol is 1.0:1.0-1.0:2.

0.

8. The method for preparing a nitrogen-rich polyimide / metal single-atom composite material according to claim 1, characterized in that, In step (iii), the impregnation method specifically includes: after drop-coating the metal precursor salt solution onto the nitrogen-rich polyimide / carrier composite material, annealing it at 100 °C in an argon atmosphere in a tube furnace, with a heating rate of 2-5 °C / min and a holding time of 120-180 min; after the temperature drops to room temperature, washing with dimethyl sulfoxide, drying, and then annealing it at 350 °C in a hydrogen-argon mixed atmosphere in a tube furnace, with a heating rate of 2-5 °C / min and a holding time of 120-180 min.

9. A nitrogen-rich polyimide / metal single-atom composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The use of the nitrogen-rich polyimide / metal single-atom composite material according to claim 9 includes applications in catalysis, electronic devices, electromagnetic shielding and absorption, antibacterial and biomedical or electrochemical energy storage.

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