A porous carbon catalyst embedded with high-density alloy nanoparticles and a preparation method and application thereof

Abstract

The application discloses a porous carbon catalyst embedded with high-density alloy nanoparticles and a preparation method and application thereof, and belongs to the technical field of fuel cell or water electrolysis catalytic materials. The porous carbon catalyst embedded with high-density alloy nanoparticles is a nitrogen and oxygen co-doped carbon carrier with a porous structure and partial graphitization, wherein high-density and high-crystallinity alloy nanoparticles are uniformly embedded, and the particle size distribution is below 6nm. The porous carbon catalyst embedded with high-density alloy nanoparticles significantly improves the dispersity and utilization rate of metal alloy nanoparticles, and improves the conductivity and stability of the carbon carrier, thereby effectively enhancing the catalytic activity of oxygen reduction reaction and oxygen evolution reaction in an alkaline medium, and having very excellent bifunctional oxygen catalytic performance, and having a wide application prospect in the field of renewable energy conversion and storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell or water electrolysis catalytic materials, in particular to a porous carbon catalyst embedded with high-density alloy nanoparticles and a preparation method and application thereof. BACKGROUND

[0002] In the green energy system represented by hydrogen energy and fuel cells, electrocatalytic reactions (such as cathode oxygen reduction reaction, ORR; anode oxygen evolution reaction, OER) are the key steps that limit the overall energy conversion efficiency and device performance. The existing commercial catalytic system mainly relies on the use of noble metal materials, such as platinum (Pt) for ORR, iridium (Ir) and ruthenium (Ru) oxides for OER. Although they exhibit excellent catalytic activity and stability, the high cost, resource scarcity and limited sustainability seriously restrict their promotion in large-scale applications.

[0003] In order to reduce the cost and improve the resource utilization, the research focus has gradually shifted to non-noble metal or low-noble metal electrocatalysts in recent years. Ruthenium-based alloys are widely concerned in the field of dual-function catalysis (i.e. ORR / OER activity) due to their unique electronic structure and catalytic reaction path regulation ability. By introducing a second metal (such as Fe, Ni, Cu, Pt, Pd, etc.) to form an alloy structure, the surface electronic state of ruthenium can be effectively regulated, the catalytic activity, selectivity and structural stability can be improved, and excessive oxidation and nanoparticle agglomeration can be further inhibited, thereby realizing more excellent electrocatalytic performance and service life. However, the simple metal alloy structure still faces problems such as uneven distribution of active sites, easy agglomeration of particles and poor long-term stability, and further structural optimization design is urgently needed. SUMMARY

[0004] The purpose of the present application is to provide a porous carbon catalyst embedded with high-density alloy nanoparticles and a preparation method and application thereof, in order to solve the problems existing in the prior art. The preparation method of the catalyst of the present application has high universality, and the structure of the prepared catalyst has high stability, can simultaneously realize very excellent oxygen reduction reaction and oxygen evolution reaction catalytic performance in alkaline medium, and has wide application prospect.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] One of the technical solutions of the present application: a preparation method of a porous carbon catalyst embedded with high-density alloy nanoparticles, comprising the following steps:

[0007] A pore-expanding agent is added to the block copolymer solution, and a micelle solution is obtained after mixing uniformly;

[0008] adding a first metal salt solution and a first initiator solution into a nitrogen-containing organic monomer solution under ice bath condition, mixing uniformly, then adding a second metal salt solution, the micelle solution and a second initiator solution in sequence, and obtaining a bimetallic ion coordinated polymer precursor after reaction;

[0009] carrying out two-step high-temperature carbonization on the bimetallic ion coordinated polymer precursor under inert atmosphere to obtain the porous carbon catalyst embedded with high-density alloy nanoparticles;

[0010] The mass content of the alloy nanoparticles is 15-35% of the porous carbon catalyst embedded with high-density alloy nanoparticles.

[0011] Further, the pore-expanding agent comprises mesitylene;

[0012] The block copolymer in the block copolymer solution comprises Pluronic F127 and / or Pluronic P123;

[0013] The concentration of the block copolymer solution is 0.015-0.045 g / mL;

[0014] The volume ratio of the block copolymer solution to the pore-expanding agent is 20:(0.35-1.05).

[0015] If the concentration of the block copolymer solution is too high, on the one hand, it will exceed the critical micelle concentration value, and the micelle template cannot be formed, and the porous structure cannot be formed in the catalyst; on the other hand, the content of the oxygen-containing functional groups in the polyethylene glycol segment in the solution is too high, which leads to too strong binding force of the metal ions, and the size of the metal nanoparticles formed is too large or even serious agglomeration. If the concentration of the block copolymer solution is too low, on the one hand, the micelle template formed will be too little, and the pore structure formed will be too little; on the other hand, the content of the oxygen-containing functional groups in the polyethylene glycol segment in the solution is insufficient, which leads to too few anchored metal nanoparticles.

[0016] Further, the nitrogen-containing organic monomer in the nitrogen-containing organic monomer solution comprises aniline and / or pyrrole;

[0017] The initiator in the first initiator solution and the second initiator solution is one or more of ammonium persulfate, sodium persulfate and potassium persulfate.

[0018] The concentration of the first initiator solution and the second initiator solution is 0.2 g / mL; and the solvent in the first initiator solution and the second initiator solution is a mixed solvent of ethanol and water.

[0019] The concentration of the first initiator solution and the second initiator solution is too high, which leads to too fast polymerization rate of the nitrogen-containing organic monomer, destroys the assembly process of the oligomer formed by the metal ions, the block polymer and the organic monomer, and finally reduces the content of the metal nanoparticles; and the concentration is too low, which leads to too slow polymerization rate and too long reaction time.

[0020] Further, the first metal salt in the first metal salt solution comprises ruthenium trichloride or chloroplatinic acid;

[0021] The second metal salt in the second metal salt solution comprises one or more of iron trichloride, cobalt chloride, nickel chloride or copper chloride.

[0022] Further, the molar ratio of the first metal salt to the second metal salt is 1:(0.5-2).

[0023] Further, the reaction time is 4-8h.

[0024] Further, the concentration of the nitrogen-containing organic monomer solution is 0.2-0.4mol / L; and the solvent in the nitrogen-containing organic monomer solution is a mixed solvent of ethanol and water.

[0025] The concentration of the first metal salt solution and the second metal salt solution is 0.01mol / L; and the solvent in the first metal salt solution and the second metal salt solution is water.

[0026] The concentration of the first metal salt solution and the second metal salt solution is too high, which is easy to cause hydrolysis of the solution itself, forms agglomerated alloy nanoparticles in the catalyst, and the concentration is too low, which leads to insufficient content of the anchored metal nanoparticles.

[0027] Further, the preparation method of the micelle solution comprises: dissolving the block copolymer in a mixed solvent of ethanol and water, then adding mesitylene, and uniformly mixing to obtain the micelle solution.

[0028] Further, the two-step high-temperature carbonization comprises: first, increasing the temperature to 350℃ at a temperature increasing rate of 1℃ / min, and keeping the temperature for 2h, and then increasing the temperature to 700-1000℃ (carbonization temperature) at a temperature increasing rate of 10℃ / min, and keeping the temperature for 2h.

[0029] Too high carbonization temperature is easy to make the metal components separate from the constraint of the carbon carrier (porous carbon), and significant agglomeration phenomenon occurs; and too low carbonization temperature leads to incomplete reduction of the metal ions and failure to form an alloy structure.

[0030] The second technical solution of the present application is a porous carbon catalyst embedded with high-density alloy nanoparticles, prepared by the above preparation method, wherein the porous carbon catalyst is a nitrogen and oxygen co-doped carbon carrier with a porous structure and partial graphitization, wherein uniform dispersed high-density and high-crystallinity alloy nanoparticles are embedded, and the particle size distribution is less than 6 nm.

[0031] When the first metal salt is ruthenium trichloride and the second metal salt is iron trichloride, the alloy nanoparticles in the porous carbon catalyst embedded with high-density alloy nanoparticles are ruthenium-iron alloy nanoparticles, which have high crystallinity, a chemical formula of Ru4Fe, a particle size of less than 6 nm, an average particle size of about 2.5 nm, and no obvious agglomeration phenomenon.

[0032] The carbon carrier of the present application is a porous carbon material, which has excellent electrical conductivity, high specific surface area and rich surface coordination sites, can not only provide an effective carrier to limit the migration of nanoparticles and regulate the spatial distribution thereof, but also can regulate the electronic structure through heteroatomic doping (such as nitrogen and oxygen), further improve the catalytic activity and selectivity of the catalyst material, solve the bottleneck problems of traditional metal alloy catalysts such as serious agglomeration and insufficient stability, realize high-efficiency and stable ORR / OER dual-function catalytic performance, and meet the actual application requirements of renewable energy conversion and storage devices.

[0033] The third technical solution of the present application is an application of the above porous carbon catalyst embedded with high-density alloy nanoparticles in an electrocatalytic oxygen reduction reaction.

[0034] Further, the electrocatalytic oxygen reduction reaction is an electrocatalytic oxygen reduction reaction in an alkaline medium.

[0035] The fourth technical solution of the present application is an application of the above porous carbon catalyst embedded with high-density alloy nanoparticles in an electrocatalytic oxygen evolution reaction.

[0036] Further, the electrocatalytic oxygen evolution reaction is an electrocatalytic oxygen evolution reaction in an alkaline medium.

[0037] The present application discloses the following technical effects:

[0038] (1) The porous carbon catalyst embedded with high-density alloy nanoparticles of the present application significantly improves the dispersibility and utilization rate of metal alloy nanoparticles, and improves the electrical conductivity and stability of the carbon carrier, thereby effectively enhancing the catalytic activity of the oxygen reduction reaction and the oxygen evolution reaction in an alkaline medium, and having very excellent dual-function oxygen catalytic performance, and having a broad application prospect in the field of renewable energy conversion and storage.

[0039] (2) The alloy nanoparticles in the porous carbon catalyst prepared by the present application have excellent dispersibility and crystallinity, the particle size distribution is below 6 nm, the average particle size is about 2.5 nm, and a high degree of size control is exhibited. In addition, the mass fraction of the alloy nanoparticles in the catalyst is as high as 15-35%, and the catalyst has high active site density and high loading characteristics.

[0040] (3) In the preparation method of the present application, Pluronic F127 and / or Pluronic P123 are used as non-ionic surfactants, and spherical micelles are formed in the mixed system of alcohol and water, which act as soft templates to guide the polymerization of organic monomers, and then the templates are removed by high-temperature carbonization to form a porous carbon framework structure, thereby significantly improving the specific surface area of the catalyst and effectively solving the problems of limited number of active sites of single-atom catalysts and easy carbon coating. On the other hand, the oxygen-containing functional groups on the polyethylene glycol segments of the hydrophilic ends of Pluronic F127 and / or Pluronic P123 can effectively anchor metal ions, and finally form a high content of oxygen-doped atoms in the carbon carrier, thereby improving the loading and dispersibility of the alloy nanoparticles.

[0041] (4) In the preparation method of the present application, nitrogen-containing organic monomers, non-ionic surfactant micellar templates and bimetallic ions are designed to be assembled synchronously, so that the metal ions can be uniformly anchored in the precursor network at the early stage of synthesis. The rich nitrogen source and oxygen-containing groups further enhance the coordination ability and anchoring stability of the metal ions, and also give high metal loading, which ensures that the alloy nanoparticles are uniformly embedded in the carbon carrier after carbonization, and significantly improves the structural stability and catalytic performance.

[0042] (5) The preparation method of the present application has good universality, which is not only suitable for the construction of RuFe alloy, but also can be extended to the preparation of porous carbon supported catalysts of other ruthenium-based or platinum-based alloy systems, and has wide material design space and application potential. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0044] Figure 1 X-ray diffraction spectra of RuFe@NOC-R1, RuFe@NOC-R2, RuFe@NOC-R3 and RuFe@NOC-R4 prepared in Examples 1-4;

[0045] Figure 2X-ray diffraction patterns of catalysts prepared for Example 3 and Comparative Examples 1-3, wherein a is Ru@NOC prepared for Comparative Example 1, b is RuFe@NOC-R3 prepared for Example 3, RuFe@NOC-nF prepared for Comparative Example 2 and RuFe / NOC prepared for Comparative Example 3;

[0046] Figure 3 SEM images of catalysts prepared for Examples 1-4, wherein a is RuFe@NOC-R1 prepared for Example 1, b is RuFe@NOC-R2 prepared for Example 2, c is RuFe@NOC-R3 prepared for Example 3 and d is RuFe@NOC-R4 prepared for Example 4;

[0047] Figure 4 High-angle annular dark-field image of RuFe@NOC-R2 prepared for Example 2;

[0048] Figure 5 Elemental mapping image of RuFe@NOC-R2 prepared for Example 2;

[0049] Figure 6 TEM images of RuFe@NOC-R2 prepared for Example 2, wherein a is a low magnification TEM image, b and c are higher magnification TEM images and d is a high resolution lattice image;

[0050] Figure 7 Particle size distribution histogram and its Gaussian fitting curve of Ru-Fe alloy nanoparticles in RuFe@NOC-R2 prepared for Example 2;

[0051] Figure 8 Thermogravimetric analysis curve of RuFe@NOC-R2 prepared for Example 2;

[0052] Figure 9 Performance comparison curves of different catalyst materials for electrocatalytic oxygen reduction reaction in alkaline medium, wherein a is the comparison results of RuFe@NOC-R1 prepared for Example 1, RuFe@NOC-R2 prepared for Example 2, RuFe@NOC-R3 prepared for Example 3 and RuFe@NOC-R4 prepared for Example 4, b is the comparison results of RuFe@NOC-R3 prepared for Example 3 and Ru@NOC prepared for Comparative Example 1, RuFe@NOC-nF prepared for Comparative Example 2 and RuFe / NOC prepared for Comparative Example 3;

[0053] Figure 10 Electron transfer number and H2O2 byproduct yield curves of porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared for Examples 1-4 for electrocatalytic oxygen reduction reaction in alkaline medium;

[0054] Figure 11 Comparison results of the initial state and polarization curves of RuFe@NOC-R3 prepared for Example 3 after undergoing 10,000, 20,000 cycles of ADT potential cycles in the electrocatalytic oxygen reduction reaction in alkaline medium;

[0055] Figure 12 Comparison curves of the performance of the porous carbon catalysts embedded with high-density ruthenium-iron alloy nanoparticles prepared for Examples 1-4 in the electrocatalytic oxygen evolution reaction in alkaline medium and the overpotential required at different current densities, wherein a is the comparison curves of the performance of the electrocatalytic oxygen evolution reaction, and b is the overpotential required at different current densities;

[0056] Figure 13 Tafel curves of the porous carbon catalysts embedded with high-density ruthenium-iron alloy nanoparticles prepared for Examples 1-4 in the electrocatalytic oxygen evolution reaction in alkaline medium;

[0057] Figure 14 Comparison curves of the performance of the catalysts prepared for Examples 3-4 and Comparative Examples 1-3 in the electrocatalytic oxygen evolution reaction in alkaline medium, wherein a is RuFe@NOC-R3, RuFe@NOC-R4 prepared for Examples 3-4 and Ru@NOC prepared for Comparative Example 1, and b is RuFe@NOC-R3 prepared for Example 3, RuFe@NOC-nF and RuFe / NOC prepared for Comparative Examples 2-3. DETAILED DESCRIPTION

[0058] Various exemplary embodiments of the present application will now be described in detail, with reference to the figures. The detailed description is not to be considered to limit the application in any way, but rather to explain certain aspects, features, and embodiments of the application.

[0059] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, for a range of values of a variable being disclosed, every intervening value of the variable, to the extent it does not expressly exclude the intervening textual description of a variable that ranges between any other stated values or intervening values of said variable, in combination, is also specifically disclosed. Each smaller range between any other stated or intervening value of a variable is also specifically disclosed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also specifically disclosed.

[0060] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In the case of conflict between the present specification and any document incorporated by reference, the present specification will control.

[0061] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0062] It is intended that all such additional applications be considered as falling within the scope of the present application. It is also contemplated that various combinations of the elements described herein can be employed.

[0063] It should be noted that the present application does not describe in detail the conventional means in the art, and is not the focus of the present application.

[0064] Example 1

[0065] A method for preparing a porous carbon catalyst RuFe@NOC-R1 embedded with high-density ruthenium-iron alloy nanoparticles:

[0066] (1) 0.5 mmol of ruthenium trichloride trihydrate was weighed and dissolved in 50 mL of deionized water, and ultrasonically treated until completely dissolved to obtain solution A;

[0067] 0.5 mmol of iron trichloride hexahydrate was weighed and dissolved in 50 mL of deionized water, and ultrasonically treated until completely dissolved to obtain solution B;

[0068] 2.0 g of ammonium persulfate was dissolved in 5 mL of a mixed solvent of deionized water and 5 mL of anhydrous ethanol, and ultrasonically treated until completely dissolved to obtain initiator solution C.

[0069] (2) 0.6 g of triblock copolymer Pluronic F127 was dissolved in 10 mL of a mixed solvent of deionized water and 10 mL of anhydrous ethanol, and stirred at room temperature for 0.5 h, then 0.69 mL of mesitylene was added, and continued to be stirred at room temperature for 5 h to obtain a micellar solution.

[0070] (3) 0.8 mL of aniline (ANI, 8.8 mmol) was dispersed in 10 mL of a mixed solvent of deionized water and 20 mL of anhydrous ethanol, and ultrasonically dispersed uniformly, then placed in an ice bath, 6 mL of solution A was added, stirred for 0.5 h, then 0.2 mL of initiator solution C was added, and pre-polymerization was carried out for 0.5 h; then 3 mL of solution B was added, and continued to be stirred for 0.5 h, then all the micellar solution prepared in step (2) was added, and stirred for 0.5 h, finally 9.8 mL of remaining initiator solution C was added to the system, and continued to be stirred for 6 h, and then centrifuged, freeze-dried to obtain a polymer precursor coordinated with ruthenium-iron bimetallic ions, wherein the molar ratio of ruthenium and iron metal ions in the feed was 1:0.5.

[0071] (4) Put the polymer precursor of ruthenium-iron bimetallic ion coordination into a corundum boat, and send it into a tube furnace to perform two-step high-temperature carbonization under the protection of continuously introduced inert gas: first, increase the temperature to 350°C at a rate of 1°C / min, and keep the temperature for 2 h to complete the preliminary carbonization of the polymer; then, increase the temperature to 900°C at a rate of 10°C / min, and keep the temperature for 2 h to realize the formation of alloy nanoparticles and the construction of the carbon carrier structure; naturally cool to room temperature to obtain a porous carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles, RuFe@NOC-R1.

[0072] Example 2

[0073] A preparation method of a porous carbon catalyst RuFe@NOC-R2 embedded with high-density ruthenium-iron alloy nanoparticles:

[0074] (1) Take 0.5 mmol of ruthenium trichloride trihydrate and dissolve it in 50 mL of deionized water, and ultrasonically treat it until it is completely dissolved to obtain solution A;

[0075] Take 0.5 mmol of iron trichloride hexahydrate and dissolve it in 50 mL of deionized water, and ultrasonically treat it until it is completely dissolved to obtain solution B;

[0076] Dissolve 2.0 g of ammonium persulfate in 5 mL of a mixed solvent of deionized water and 5 mL of anhydrous ethanol, and ultrasonically treat it until it is completely dissolved to obtain initiator solution C.

[0077] (2) Take 0.6 g of triblock copolymer Pluronic F127 and dissolve it in 10 mL of a mixed solvent of deionized water and 10 mL of anhydrous ethanol, and stir it at room temperature for 0.5 h, then add 0.69 mL of mesitylene, and continue to stir it at room temperature for 5 h to obtain a micellar solution.

[0078] (3) Disperse 0.8 mL of aniline (ANI, 8.8 mmol) in 10 mL of a mixed solvent of deionized water and 20 mL of anhydrous ethanol, and ultrasonically disperse it uniformly, then place it in an ice bath, add 6 mL of solution A to it, stir it for 0.5 h, then add 0.2 mL of initiator solution C, and perform a pre-polymerization reaction for 0.5 h; then add 6 mL of solution B, continue to stir it for 0.5 h, then add all the micellar solution prepared in step (2), stir it for 0.5 h, and finally add the remaining 9.8 mL of initiator solution C to the system, and continue to stir it for 6 h, then perform centrifugal separation, and freeze-dry it to obtain a polymer precursor of ruthenium-iron bimetallic ion coordination, wherein the molar ratio of the ruthenium and iron metal ions in the feed is 1:1.

[0079] (4) Put the polymer precursor of ruthenium-iron bimetallic ion coordination into a corundum boat, and send it into a tube furnace to perform two-step high-temperature carbonization under the protection of continuously introduced inert gas: first, increase the temperature to 350°C at a rate of 1°C / min, and keep the temperature for 2 h to complete the preliminary carbonization of the polymer; then, increase the temperature to 900°C at a rate of 10°C / min, and keep the temperature for 2 h to realize the formation of alloy nanoparticles and the construction of the carbon carrier structure; naturally cool to room temperature to obtain a porous carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles, RuFe@NOC-R2.

[0080] Example 3

[0081] A preparation method of a porous carbon catalyst RuFe@NOC-R3 embedded with high-density ruthenium-iron alloy nanoparticles:

[0082] (1) Take 0.5 mmol of ruthenium trichloride trihydrate and dissolve it in 50 mL of deionized water, and ultrasonically treat it until it is completely dissolved to obtain solution A;

[0083] Take 0.5 mmol of iron trichloride hexahydrate and dissolve it in 50 mL of deionized water, and ultrasonically treat it until it is completely dissolved to obtain solution B;

[0084] Dissolve 2.0 g of ammonium persulfate in 5 mL of a mixed solvent of deionized water and 5 mL of anhydrous ethanol, and ultrasonically treat it until it is completely dissolved to obtain initiator solution C.

[0085] (2) Take 0.6 g of triblock copolymer Pluronic F127 and dissolve it in 10 mL of a mixed solvent of deionized water and 10 mL of anhydrous ethanol, and stir it at room temperature for 0.5 h, then add 0.69 mL of mesitylene, and continue to stir it at room temperature for 5 h to obtain a micellar solution.

[0086] (3) Disperse 0.8 mL of aniline (ANI, 8.8 mmol) in 10 mL of a mixed solvent of deionized water and 20 mL of anhydrous ethanol, and ultrasonically disperse it uniformly, then place it in an ice bath, add 6 mL of solution A to it, stir it for 0.5 h, then add 0.2 mL of initiator solution C, and perform a pre-polymerization reaction for 0.5 h; then add 9 mL of solution B, continue to stir it for 0.5 h, then add all the micellar solution prepared in step (2), stir it for 0.5 h, and finally add the remaining 9.8 mL of initiator solution C to the system, and continue to stir it for 6 h, and then perform centrifugal separation and freeze-drying to obtain a polymer precursor of ruthenium-iron bimetallic ion coordination, wherein the molar ratio of the ruthenium and iron metal ions in the feed is 1:1.5.

[0087] (4) Put the polymer precursor of ruthenium-iron bimetallic ion coordination into a corundum boat, and send it into a tube furnace to perform two-step high-temperature carbonization under the protection of continuously introduced inert gas: first, heat it to 350℃ at a heating rate of 1℃ / min, and keep it for 2h to complete the preliminary carbonization of the polymer; then, heat it to 900℃ at a heating rate of 10℃ / min, and keep it for 2h to realize the formation of alloy nanoparticles and the construction of the carbon carrier structure; naturally cool it to room temperature to obtain a porous carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles, RuFe@NOC-R3.

[0088] Example 4

[0089] A preparation method of a porous carbon catalyst RuFe@NOC-R4 embedded with high-density ruthenium-iron alloy nanoparticles:

[0090] (1) Take 0.5mmol of ruthenium trichloride trihydrate and dissolve it in 50mL of deionized water, and ultrasonically treat it until it is completely dissolved to obtain solution A;

[0091] Take 0.5mmol of iron trichloride hexahydrate and dissolve it in 50mL of deionized water, and ultrasonically treat it until it is completely dissolved to obtain solution B;

[0092] Dissolve 2.0g of ammonium persulfate in 5mL of a mixed solvent of deionized water and 5mL of anhydrous ethanol, and ultrasonically treat it until it is completely dissolved to obtain initiator solution C.

[0093] (2) Take 0.6g of triblock copolymer Pluronic F127 and dissolve it in 10mL of a mixed solvent of deionized water and 10mL of anhydrous ethanol, and stir it at room temperature for 0.5h, then add 0.69mL of mesitylene, and continue to stir it at room temperature for 5h to obtain a micellar solution.

[0094] (3) Disperse 0.8mL of aniline (ANI, 8.8mmol) in 10mL of a mixed solvent of deionized water and 20mL of anhydrous ethanol, and ultrasonically disperse it uniformly, then place it in an ice bath, add 3mL of solution A to it, stir it for 0.5h, then add 0.2mL of initiator solution C, and perform a pre-polymerization reaction for 0.5h; then add 6mL of solution B, continue to stir it for 0.5h, then add all the micellar solution prepared in step (2), stir it for 0.5h, and finally add the remaining 9.8mL of initiator solution C to the system, and continue to stir it for 6h, then centrifugally separate it, and freeze-dry it to obtain a polymer precursor of ruthenium-iron bimetallic ion coordination, wherein the molar ratio of the ruthenium and iron metal ions in the feed is 1:2.

[0095] (4) The polymer precursor coordinated with ruthenium-iron bimetallic ions is placed in a corundum boat and sent into a tube furnace, and two-step high-temperature carbonization is performed under the protection of continuously introduced inert gas: first, the temperature is raised to 350°C at a rate of 1°C / min, and the polymer is preliminarily carbonized by maintaining the temperature for 2h; then, the temperature is raised to 900°C at a rate of 10°C / min, and the formation of alloy nanoparticles and the construction of the carbon carrier structure are realized by maintaining the temperature for 2h; the product is naturally cooled to room temperature to obtain a porous carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles, RuFe@NOC-R4.

[0096] Comparative Example 1

[0097] A preparation method of a porous carbon catalyst embedded with metal ruthenium nanoparticles Ru@NOC, which is different from Example 3 only in that no iron source is added:

[0098] (1) 0.5 mmol of ruthenium trichloride trihydrate is weighed and dissolved in 50 mL of deionized water, and ultrasonic treatment is performed until complete dissolution to obtain solution A;

[0099] 2.0 g of ammonium persulfate is dissolved in a mixed solvent of 5 mL of deionized water and 5 mL of anhydrous ethanol, and ultrasonic treatment is performed until complete dissolution to obtain initiator solution C.

[0100] (2) 0.6 g of triblock copolymer Pluronic F127 is weighed and dissolved in a mixed solvent of 10 mL of deionized water and 10 mL of anhydrous ethanol, and stirring is performed at room temperature for 0.5h, then 0.69 mL of mesitylene is added, and stirring is continued at room temperature for 5h to obtain a micellar solution.

[0101] (3) 0.8 mL of aniline (ANI, 8.8 mmol) is dispersed in a mixed solvent of 10 mL of deionized water and 20 mL of anhydrous ethanol, and ultrasonic dispersion is performed until uniform, then 6 mL of solution A is added under ice bath conditions, stirring is performed for 0.5h, then 0.2 mL of initiator solution C is added, and pre-polymerization is performed for 0.5h; then the entire micellar solution prepared in step (2) is added, stirring is performed for 0.5h, and finally the remaining 9.8 mL of initiator solution C is added to the system, and stirring is continued for 6h; after centrifugal separation and freeze-drying, a polymer precursor coordinated with ruthenium metal ions is obtained.

[0102] (4) The polymer precursor coordinated with ruthenium metal ions is placed in a corundum boat and sent into a tube furnace, and two-step high-temperature carbonization is performed under the protection of continuously introduced inert gas: first, the temperature is raised to 350°C at a rate of 1°C / min, and the polymer is preliminarily carbonized by maintaining the temperature for 2h; then, the temperature is raised to 900°C at a rate of 10°C / min, and the formation of metal nanoparticles and the construction of the carbon carrier structure are realized by maintaining the temperature for 2h; the product is naturally cooled to room temperature to obtain a porous carbon catalyst embedded with metal ruthenium nanoparticles, Ru@NOC.

[0103] Comparative Example 2

[0104] A preparation method of a carbon catalyst embedded with ruthenium-iron alloy nanoparticles RuFe@NOC-nF, which is different from Example 3 only in that no block copolymer Pluronic F127 (surfactant F127) is added, and no porous structure is formed:

[0105] (1) 0.5 mmol of ruthenium trichloride trihydrate was weighed into 50 mL of deionized water, and ultrasonic treatment was performed until complete dissolution to obtain solution A;

[0106] 0.5 mmol of iron trichloride hexahydrate was weighed into 50 mL of deionized water, and ultrasonic treatment was performed until complete dissolution to obtain solution B;

[0107] 2.0 g of ammonium persulfate was dissolved in a mixed solvent of 5 mL of deionized water and 5 mL of anhydrous ethanol, and ultrasonic treatment was performed until complete dissolution to obtain initiator solution C.

[0108] (2) 0.8 mL of aniline (ANI, 8.8 mmol) was dispersed in a mixed solvent of 20 mL of deionized water and 30 mL of anhydrous ethanol, and after ultrasonic dispersion, it was placed in an ice bath. 6 mL of solution A was added, stirred for 0.5 h, and then 0.2 mL of initiator solution C was added, and a pre-polymerization reaction was performed for 0.5 h; then 9 mL of solution B was added, and stirring was continued for 0.5 h; finally, the remaining 9.8 mL of initiator solution C was added to the system, and stirring was continued for 6 h. After centrifugal separation and freeze-drying, a polymer precursor coordinated with ruthenium-iron bimetallic ions was obtained, and the molar ratio of ruthenium and iron metal ions in the feed was 1:1.5.

[0109] (4) The polymer precursor coordinated with ruthenium-iron bimetallic ions was placed in a corundum boat and sent into a tube furnace, and two-step high-temperature carbonization was performed under the protection of continuous inert gas: first, the temperature was raised to 350°C at a rate of 1°C / min, and the polymer was preliminarily carbonized for 2 h; then the temperature was raised to 900°C at a rate of 10°C / min, and the alloy nanoparticles were formed and the carbon carrier structure was constructed for 2 h; and then the temperature was naturally cooled to room temperature. A carbon catalyst embedded with ruthenium-iron alloy nanoparticles, RuFe@NOC-nF, was obtained.

[0110] Comparative Example 3

[0111] A preparation method of a porous carbon catalyst RuFe / NOC loaded with ruthenium-iron alloy nanoparticles, which is different from Example 3 only in that the polymerization of the nitrogen-containing organic monomer is completed first, and then the metal ions are added for reaction:

[0112] (1) Take 0.5 mmol of ruthenium trichloride trihydrate and dissolve it in 50 mL of deionized water, and ultrasonic treatment until completely dissolved to obtain solution A;

[0113] Take 0.5 mmol of iron trichloride hexahydrate and dissolve it in 50 mL of deionized water, and ultrasonic treatment until completely dissolved to obtain solution B;

[0114] Dissolve 2.0 g of ammonium persulfate in 5 mL of deionized water and 5 mL of anhydrous ethanol mixed solvent, and ultrasonic until completely dissolved to obtain initiator solution C.

[0115] (2) Take 0.6 g of triblock copolymer Pluronic F127 and dissolve it in 10 mL of deionized water and 10 mL of anhydrous ethanol mixed solvent, and stir at room temperature for 0.5 h, then add 0.69 mL of mesitylene, and continue to stir at room temperature for 5 h to obtain a micellar solution.

[0116] (3) Disperse 0.8 mL of aniline (ANI, 8.8 mmol) in 10 mL of deionized water and 20 mL of anhydrous ethanol mixed solvent, and ultrasonic dispersion until uniform, then place in an ice bath, add all the micellar solution prepared in step (2), and add 10 mL of initiator solution C to it, carry out polymerization reaction for 6 h, then add 6 mL of solution A, and then add 9 mL of solution B, continue to stir for 6 h, and then centrifugal separation, freeze-drying to obtain a polymer precursor coordinated with ruthenium and iron bimetallic ions, wherein the molar ratio of ruthenium and iron metal ions is 1:1.5.

[0117] (4) Place the polymer precursor coordinated with ruthenium and iron bimetallic ions in a corundum boat, and send it into a tube furnace to carry out two-step high-temperature carbonization under the protection of continuous inert gas: first, heat to 350℃ at a heating rate of 1℃ / min, and keep the temperature for 2 h to complete the preliminary carbonization of the polymer; then heat to 900℃ at a heating rate of 10℃ / min, and keep the temperature for 2 h to realize the formation of alloy nanoparticles and the construction of carbon carrier structure; naturally cool to room temperature to obtain a porous carbon catalyst loaded with ruthenium-iron alloy nanoparticles, RuFe / NOC.

[0118] Effect Example 1

[0119] The catalyst materials prepared in Examples 1-4 and Comparative Examples 1-3 were analyzed by X-ray diffraction spectrum (XRD), scanning electron microscope (SEM), high-angle annular dark field image (HAADF), transmission electron microscope (TEM), and thermogravimetric analyzer (TGA).

[0120] (1) X-ray diffraction spectrum analysis

[0121] The X-ray diffraction patterns of RuFe@NOC-R1, RuFe@NOC-R2, RuFe@NOC-R3, and RuFe@NOC-R4 prepared in Examples 1-4 are shown below. Figure 1 The X-ray diffraction pattern of Ru@NOC prepared in Comparative Example 1 is shown in Figure 1. Figure 2 Figure a shows the X-ray diffraction patterns of RuFe@NOC-nF and RuFe / NOC prepared in Comparative Examples 2-3. Figure 2 Image b.

[0122] from Figure 1 As can be seen, the porous carbon catalysts with embedded high-density ruthenium-iron alloy nanoparticles prepared in Examples 1-4 all exhibit significant broad diffraction peaks at approximately 25.2°, corresponding to the diffraction signal of the carbon support, indicating that they have a certain degree of graphitization structure. The diffraction peaks appearing at approximately 38.6°, 44.5°, 58.4°, and 70.8° are highly matched with the standard card (PDF#40-1147) of Ru4Fe alloy, and these diffraction peaks are generally broad, indicating that nanoscale Ru4Fe alloy particles have been successfully formed in the catalyst.

[0123] from Figure 2 As shown in Figure a, the porous carbon catalyst with embedded ruthenium nanoparticles prepared in Comparative Example 1 also exhibits a significant broad diffraction peak at approximately 25.2°, reflecting the partial graphitization characteristics of the carbon support. It shows a diffraction peak at approximately 44.5° consistent with the standard card for metallic Ru (PDF#06-0663), with a relatively broad peak shape, indicating the successful formation of metallic Ru nanoparticles in the catalyst. Compared to the catalysts prepared in Examples 1-4, this catalyst did not show diffraction signals corresponding to the Ru4Fe alloy at 38.6°, 58.4°, and 70.8°, verifying the difference in its metal composition. Figure 2 As shown in Figure b, the catalysts prepared in Comparative Examples 2-3 all exhibit a broad diffraction peak at approximately 25.2°, which matches the diffraction characteristics of the carbon substrate, indicating that they possess a certain degree of graphitized ordered structure. The diffraction peaks at approximately 38.6°, 44.5°, 58.4°, and 70.8° highly match the characteristic peak positions of the standard card (PDF#40-1147) for Ru4Fe alloy, and all show a relatively obvious broadening phenomenon, indicating the formation of nanoscale Ru4Fe alloy particles. However, compared with the catalyst prepared in Example 3, the intensity of the diffraction peak at 44.5° of the catalysts prepared in Comparative Examples 2-3 is significantly reduced, indicating that the absence of surfactant F127 during the synthesis process and the time-separated carbon source assembly-metal ion coordination process (i.e., completing the polymerization of nitrogen-containing organic monomers first, and then adding metal ions for reaction) both significantly reduce the loading of alloy nanoparticles in the catalyst.

[0124] (2) SEM analysis

[0125] The SEM images of the catalysts prepared in Examples 1-4 are shown in Figure 3 , Figure 3 In the figures, Figure a is RuFe@NOC-R1 prepared in Example 1, Figure b is RuFe@NOC-R2 prepared in Example 2, Figure c is RuFe@NOC-R3 prepared in Example 3, and Figure d is RuFe@NOC-R4 prepared in Example 4.

[0126] As can be seen from Figure 3 , the porous carbon catalysts embedded with high-density ruthenium-iron alloy nanoparticles prepared in Examples 1-4 have very similar morphologies, and the carbon support presents an irregular block structure with a rough surface, and no obvious metal particle exposure is observed.

[0127] (3) TEM analysis

[0128] The high-angle annular dark-field image of RuFe@NOC-R2 prepared in Example 2 is shown in Figure 4 .

[0129] As can be seen from Figure 4 , in the porous carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles prepared in Example 2, the carbon support has a porous structure, and the high-density ruthenium-iron alloy ultrafine nanoparticles are uniformly anchored in the carbon support without obvious agglomeration, indicating good metal particle dispersion.

[0130] (4) The elemental mapping image of RuFe@NOC-R2 prepared in Example 2 is shown in Figure 5 .

[0131] As can be seen from Figure 5 , in the porous carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles prepared in Example 2, the four elements of N, O, Ru and Fe are uniformly distributed on the carbon substrate. Among them, the uniform doping of N and O elements reflects the double-doping characteristics of the carbon support, while the Ru and Fe elements are highly dispersed in the carbon matrix, proving that the ruthenium-iron alloy nanoparticles are successfully embedded in the porous carbon structure and have good dispersion due to the rich anchoring sites provided by the carbon support.

[0132] (5) The TEM image of RuFe@NOC-R2 prepared in Example 2 is shown in Figure 6 , Figure 6 In the figures, Figure a is a low-magnification TEM image, Figures b and c are higher-magnification TEM images, and Figure d is a high-resolution lattice image.

[0133] As can be seen from Figure 6As can be seen from the results, the porous carbon catalyst with high-density ruthenium-iron alloy nanoparticles embedded in Example 2 generated high-density ruthenium-iron alloy ultrafine nanoparticles with a particle size of less than 6 nm. The high-resolution analysis results further showed that these nanoparticles had clear lattice stripes and a crystal plane spacing of 0.216 nm, corresponding to the (101) crystal plane of Ru4Fe alloy, indicating that they have high crystallinity.

[0134] (6) Particle size distribution analysis

[0135] The particle size distribution histogram and Gaussian fitting curve of the ruthenium-iron alloy nanoparticles in RuFe@NOC-R2 prepared in Example 2 are shown in the figure. Figure 7 .

[0136] from Figure 7 As can be seen, in the porous carbon catalyst with embedded high-density ruthenium-iron alloy nanoparticles prepared in Example 2, the particle size distribution of the ruthenium-iron alloy nanoparticles is below 6 nm, with an average particle size of 2.5 nm, which shows the characteristics of concentrated size distribution and small particle size.

[0137] (7) Metal loading analysis

[0138] Thermogravimetric analysis curve of RuFe@NOC-R2 prepared in Example 2 is shown in the figure. Figure 8 .

[0139] from Figure 8 As can be seen from the above, the porous carbon catalyst with embedded high-density ruthenium-iron alloy nanoparticles prepared in Example 2 exhibits significant mass loss in the temperature range of approximately 300-420℃, corresponding to the oxidative decomposition process of the porous carbon support; the final residual mass stabilizes at approximately 21.3%, indicating that the mass fraction of the ruthenium-iron alloy component in the catalyst is approximately 21%.

[0140] Example 2

[0141] To evaluate the electrocatalytic performance of the catalyst materials prepared in Examples 1-4 and Comparative Examples 1-3 of this invention, electrocatalytic oxygen reduction and oxygen evolution reaction performance tests were conducted using an electrochemical workstation. The specific methods are as follows:

[0142] (1) The oxygen reduction reaction (ORR) performance test was carried out in 0.1M KOH aqueous solution using a three-electrode system. The working electrode was a rotating disk electrode (RDE, 3mm in diameter) or a rotating ring electrode (RRDE, 4mm in diameter, 7mm outer diameter and 5mm inner diameter of the ring electrode) loaded with catalyst material. The reference electrode was a saturated Ag / AgCl electrode, and the counter electrode was a carbon rod.

[0143] Preparation of working electrode: First, mix 10mg of catalyst material, 900μL of isopropanol and 100μL of Nafion solution, and ultrasonically disperse for 30min to obtain catalyst ink. Then, take 15μL or 25μL of this ink and uniformly drop it onto the surface of RDE or RRDE, and let it air dry for later use.

[0144] To evaluate the catalyst stability, accelerated durability testing (ADT) was conducted using a three-electrode system. The working electrode was an RRDE electrode (load-to-polarization curve test) supporting the catalyst material, the reference electrode was a saturated Ag / AgCl electrode, and the counter electrode was a carbon rod. The tests were performed under a saturated Ar atmosphere. Cyclic voltammetry (CV) was used to perform 10,000 and 20,000 ADT cycles within the potential range of -0.3–0.1 V (0.67–1.07 V vs. RHE), respectively, at a scan rate of 50 mV / s. The polarization curves before and after each cycle were measured to compare the changes in catalyst performance.

[0145] (2) The oxygen evolution reaction (OER) performance test was carried out in 1.0M KOH aqueous solution using a three-electrode system, with a glassy carbon electrode (3mm in diameter) loaded with catalyst material as the working electrode, a saturated Ag / AgCl electrode as the reference electrode, and a carbon rod as the counter electrode.

[0146] Preparation of working electrode: First, mix 10mg of catalyst material, 900μL of isopropanol and 100μL of Nafion solution, and ultrasonically disperse for 30min to obtain catalyst ink. Then, take 4μL of the ink and uniformly drop it onto the surface of glassy carbon electrode, and let it air dry for later use.

[0147] Unless otherwise specified in this test, all operating procedures are conventional methods well known to those skilled in the art.

[0148] The performance comparison curves of different catalyst materials in the electrocatalytic oxygen reduction reaction (ORR) in alkaline media are shown below. Figure 9 , Figure 9 In the figure, Figure a shows RuFe@NOC-R1 prepared in Example 1, RuFe@NOC-R2 prepared in Example 2, RuFe@NOC-R3 prepared in Example 3, and RuFe@NOC-R4 prepared in Example 4; Figure b shows RuFe@NOC-R3 prepared in Example 3, Ru@NOC prepared in Comparative Example 1, RuFe@NOC-nF prepared in Comparative Example 2, and RuFe / NOC prepared in Comparative Example 3.

[0149] from Figure 9 As shown in Figure a, the porous carbon catalysts with embedded high-density ruthenium-iron alloy nanoparticles prepared in Examples 1-4 exhibit excellent ORR catalytic activity in alkaline media. At a rotation speed of 1600 RPM, all catalyst materials exhibited high onset potentials (E0).onset ), half-wave potential (E 1 / 2 ) and limiting current density (J L ), see Table 1. Among them, the catalyst material prepared in Example 3 has the highest E 1 / 2 , which is 0.85 V, and the J L at 0.4 V reaches -5.67 mA cm -2 , close to the theoretical limit value -6.0 mA cm -2 . In contrast, the porous carbon catalyst embedded with metal ruthenium nanoparticles prepared in Comparative Example 1 has poor catalytic activity, with E 1 / 2 of about 0.74 V and J L at 0.4 V of only -5.28 mA cm -2 . The results show that the ORR activity of Ru4Fe alloy nanoparticles is significantly better than that of metal Ru nanoparticles, and the introduction of Fe element effectively promotes the adsorption and dissociation process of oxygen molecules, thereby enhancing the overall catalytic performance. From the b chart of Figure 9 , it can be seen that the catalytic activity of the carbon catalyst embedded with ruthenium-iron alloy nanoparticles prepared in Comparative Example 2 and the carbon catalyst embedded with high-density ruthenium-iron alloy nanoparticles prepared in Example 3 is different, which shows that F127 and mesitylene can further optimize the microstructure of the catalyst in the structure formation process of the catalyst, play a key role in the template and regulation, help to form a more favorable pore structure and active site distribution for the ORR reaction, enhance the exposure and utilization efficiency of the active site, and increase the metal loading, thereby synergistically improving the overall catalytic performance; and the catalytic activity of the porous carbon catalyst loaded with ruthenium-iron alloy nanoparticles prepared in Comparative Example 3 is poor, which shows that changing the order of adding raw materials, separating the polymerization of organic monomers and the coordination process of metal ions in time, makes it difficult for the metal to penetrate into the interior of the carbon carrier, and the metal cannot be uniformly dispersed, the combination tightness and uniformity of the metal and the carbon carrier are insufficient, thereby reducing the number of ORR active sites on the surface of the catalyst and limiting the distribution, hindering the oxygen adsorption and reduction process, and thus reducing the ORR performance.

[0150] The electron transfer number and hydrogen peroxide yield curves obtained by rotating ring-disk electrode (RRDE) test in step (1) are shown in Figure 10 .

[0151] From Figure 10As can be seen from the results, the porous carbon catalysts with embedded high-density ruthenium-iron alloy nanoparticles prepared in Examples 1-4 all exhibited high reaction selectivity in alkaline media, with electron transfer numbers ranging from 3.7 to 4.0 and H2O2 yields controlled within the range of 0-15%. Among them, the catalyst prepared in Example 3 showed the best performance, with the highest electron transfer number and the lowest H2O2 byproduct yield, as detailed in Table 1. Therefore, the electrocatalytic oxygen reduction of the porous carbon catalyst with embedded ruthenium-iron alloy nanoparticles mainly generates water through a direct four-electron reaction pathway, exhibiting both high activity and high selectivity.

[0152] The polarization curves of RuFe@NOC-R3 prepared in Example 3 during the electrocatalytic oxygen reduction reaction in alkaline medium at the initial state and after 10,000 and 20,000 cycles of ADT potential are shown in the figure. Figure 11 .

[0153] from Figure 11 As can be seen, the RuFe@NOC-R3 prepared in Example 3 exhibits excellent long-term cycling stability in alkaline media. After 10,000 ADT cycles, its half-wave potential decreased by only about 6 mV, and after 20,000 ADT cycles, the half-wave potential decreased by only about 13.5 mV. This indicates that the catalyst exhibits minimal electrochemical performance degradation during long-term cycling and can maintain relatively stable catalytic activity. Therefore, the RuFe@NOC-R3 catalyst possesses excellent long-term cycling stability in alkaline media and has great potential in related electrochemical applications.

[0154] Table 1. Comparison of ORR performance parameters of catalysts prepared in Examples 1-4 and Comparative Examples 1-3

[0155]

[0156] The performance comparison curves of different catalyst materials for the electrocatalytic oxygen evolution reaction in alkaline media and the overpotentials required at different current densities are shown in the figure. Figure 12 , Figure 12 In the figure, Figure a shows the performance comparison curves of the electrocatalytic oxygen evolution reaction, and Figure b shows the overpotential required at different current densities.

[0157] from Figure 12 As can be seen, the porous carbon catalysts with embedded high-density ruthenium-iron alloy nanoparticles prepared in Examples 1-4 exhibit excellent oxygen evolution activity in alkaline media, producing oxygen from a potential of approximately 1.5 V. The catalyst prepared in Example 3 shows similar activity at 10, 20, and 50 mA cm⁻¹. -2 The overpotentials at the same current densities were 330, 358 and 420 mV, respectively; the catalyst prepared in Example 4 exhibited the best activity, with overpotentials of 310, 332 and 380 mV at the same current densities.

[0158] Tafel curves of the porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared in Examples 1-4 for electrocatalytic oxygen evolution reaction in alkaline medium are shown in FIG. 1. Figure 13 .

[0159] As can be seen from FIG. 1, the porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared in Examples 1-4 have very fast kinetics for electrocatalytic OER reaction in alkaline medium, with Tafel slopes in the range of 40-65 mV dec-1, indicating that the reaction process has a lower energy barrier. -1 Figure 13

[0160] Performance comparison curves of the porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared in Examples 3-4 (RuFe@NOC-R3, RuFe@NOC-R4) and the porous carbon catalyst embedded with metal Ru nanoparticles prepared in Comparative Example 1 (Ru@NOC) for electrocatalytic oxygen evolution reaction in alkaline medium are shown in FIG. 2. Figure 14 .

[0161] As can be seen from FIG. 2a, the porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared in Examples 3 and 4 have much better OER performance in alkaline medium than the porous carbon catalyst embedded with metal Ru nanoparticles prepared in Comparative Example 1, indicating that Ru4Fe alloy nanoparticles have a significant advantage in promoting water molecule adsorption and dissociation, and the synergistic effect of Fe element significantly enhances the overall oxygen evolution performance. Figure 14 As can be seen from FIG. 2b, the porous carbon catalyst embedded with high-density Ru-Fe alloy nanoparticles prepared in Example 3 has much better OER performance in alkaline medium than the catalysts prepared in Comparative Examples 2-3, indicating that the absence of surfactant F127 in the synthesis process makes it impossible to form a porous structure in the catalyst, and the separation of the carbon source assembly and metal ion coordination process in time significantly reduces the loading of alloy nanoparticles, which leads to a significant reduction in the number of active sites available on the catalyst surface and severely limits their distribution, making it impossible for them to fully play a catalytic role in the OER reaction.

[0162] Figure 14 In summary, the porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared in Examples 1-4 all exhibit excellent bifunctional oxygen catalytic performance in alkaline medium, with high oxygen reduction and oxygen evolution activity, and have the potential to be used as high-performance bifunctional electrocatalysts in the fields of zinc-air batteries, water splitting, and other energy conversion.

[0163] In summary, the porous carbon catalysts embedded with high-density Ru-Fe alloy nanoparticles prepared in Examples 1-4 all exhibit excellent bifunctional oxygen catalytic performance in alkaline medium, with high oxygen reduction and oxygen evolution activity, and have the potential to be used as high-performance bifunctional electrocatalysts in the fields of zinc-air batteries, water splitting, and other energy conversion.

[0164] ​​​The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A method for preparing a porous carbon catalyst embedded with high-density alloy nanoparticles, characterized in that, Includes the following steps: A pore-expanding agent is added to the block copolymer solution, and the mixture is homogeneous to obtain a micelle solution. Under ice bath conditions, a first metal salt solution and a first initiator solution are added to a nitrogen-containing organic monomer solution and mixed evenly. Then, a second metal salt solution, the micelle solution, and the second initiator solution are added sequentially. After the reaction, a polymer precursor coordinated by bimetallic ions is obtained. The polymer precursor coordinated with bimetallic ions was subjected to two-step high-temperature carbonization under an inert atmosphere to obtain the porous carbon catalyst embedded with high-density alloy nanoparticles. The mass content of the alloy nanoparticles is 15-35% of the porous carbon catalyst with embedded high-density alloy nanoparticles. The block copolymer in the block copolymer solution includes Pluronic F127 and / or Pluronic P123; The nitrogen-containing organic monomers in the nitrogen-containing organic monomer solution include aniline and / or pyrrole; The first metal salt in the first metal salt solution includes ruthenium trichloride or chloroplatinic acid; The second metal salt in the second metal salt solution includes one or more of ferric chloride, cobalt chloride, nickel chloride, or copper chloride; The two-step high-temperature carbonization process includes: first, heating to 350°C at a heating rate of 1°C / min and holding the temperature for 2 hours; then heating to 700-1000°C at a heating rate of 10°C / min and holding the temperature for 2 hours.

2. The preparation method according to claim 1, characterized in that, The pore-expanding agent includes mesitylene; And / or, the concentration of the block copolymer solution is 0.015-0.045 g / mL; And / or, the volume ratio of the block copolymer solution to the pore expander is 20:(0.35-1.05).

3. The preparation method according to claim 1, characterized in that, The initiators in the first initiator solution and the second initiator solution are one or more of ammonium persulfate, sodium persulfate, and potassium persulfate.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the first metal salt to the second metal salt is 1:(0.5-2).

5. The preparation method according to claim 1, characterized in that, The reaction time is 4-8 hours.

6. A porous carbon catalyst with embedded high-density alloy nanoparticles prepared by the preparation method according to any one of claims 1-5, characterized in that, The porous carbon catalyst is a nitrogen and oxygen co-doped carbon support with a porous structure and partial graphitization, in which uniformly dispersed high-density, highly crystalline alloy nanoparticles are embedded, with a particle size distribution below 6 nm.

7. The application of the porous carbon catalyst with embedded high-density alloy nanoparticles as described in claim 6 in the electrocatalytic oxygen reduction reaction.

8. The application of the porous carbon catalyst with embedded high-density alloy nanoparticles as described in claim 6 in the electrocatalytic oxygen evolution reaction.

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