Oxygen reduction catalyst as well as preparation method and application thereof
By using ZIF-12 as a precursor and combined with inorganic salt-assisted pyrolysis method, an efficient Co/N/C co-doped porous carbon oxygen reduction catalyst was prepared, which solved the problems of high prices, limited availability and poor stability of existing catalysts, and achieved efficient oxygen reduction catalytic effect, with wide application potential.
Patent Information
- Application Number
- CN202510153915.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-12
- Publication Date
- 2025-05-16
AI Technical Summary
Existing oxygen reduction catalysts such as Pt-based catalysts limit their large-scale commercial applications in renewable energy devices due to their high price, limited availability and poor stability.
An oxygen reduction catalyst preparation method for Co/N/C co-doped porous carbon catalyst prepared by ZIF-12 as a precursor and using an inorganic salt-assisted pyrolysis method is used. The method includes mixing components such as benzimidazole, solvent, ammonia water and cobalt salt to form ZIF-12, then mixing with inorganic salts and nitrogen-containing compounds, and carbonizing to obtain an oxygen reduction catalyst.
The prepared oxygen reduction catalyst has high oxygen reduction catalytic activity and good methanol tolerance. It can effectively replace precious metal Pt/C catalysts and is used in fuel cells or metal air batteries. It has broad application prospects and practical value.
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Figure CN120004241A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of battery catalysts, and in particular to an oxygen reduction catalyst and a preparation method and application thereof. Background Art
[0002] With the increasing concern about energy shortage, the development of renewable energy devices, such as metal-air batteries and fuel cells, has been extensively studied. Oxygen reduction reaction is a crucial reaction in these energy systems. Currently, the most advanced catalysts for the sluggish oxygen reduction reaction are still Pt-based catalysts. However, the high price, limited availability and poor stability of platinum have greatly hindered its large-scale commercial application. Therefore, it is necessary to develop cheap, efficient and stable non-precious metal catalysts. MOFs are porous supramolecular network materials self-assembled from metal ions and organic linkers. They have high specific surface area, good morphology, adjustable porosity and excellent chemical stability. They are widely used in storage, separation, biomedicine, adsorption and catalysis.
[0003] In recent years, MOFs have been considered as excellent precursors for the synthesis of MNC materials. Traditionally, MNC materials can be synthesized by pyrolysis of transition metal macrocyclic compounds or mixtures of carbon, nitrogen and metal precursors. However, the MNC materials obtained by these methods usually have the disadvantages of disordered structure and low specific surface area. Studies have shown that heteroatom doping can further enhance the oxygen reduction activity of MNC materials. The introduction of non-metallic heteroatom doping (S, P, B, etc.) in MNC can enhance the asymmetry of the charge density of C atoms, thereby improving the adsorption efficiency between oxygen atoms and carbon atoms. However, these synthesis schemes usually contain toxic reagents or cumbersome synthesis steps. Summary of the invention
[0004] Based on the technical problems existing in the background technology, the present invention proposes an oxygen reduction catalyst and a preparation method and application thereof.
[0005] The present invention provides a method for preparing an oxygen reduction catalyst, comprising the following steps:
[0006] S1, mixing benzimidazole, solvent, ammonia water and cobalt salt uniformly, centrifuging, washing and drying to obtain ZIF-12;
[0007] S2, after uniformly mixing the inorganic salt and the nitrogen-containing compound mixed solution, adding ZIF-12, stirring, drying, and grinding to obtain a mixture;
[0008] S3, carbonizing the mixture under a protective gas atmosphere, washing, and drying to obtain.
[0009] Preferably, in S1, the solvent is selected from one or more of methanol and toluene.
[0010] The role of methanol is to improve solubility, act as a reaction medium, and adjust the reaction rate. The role of toluene is to improve solubility, stabilize the reaction environment, and increase the reaction rate.
[0011] Preferably, in S1, the cobalt salt is selected from one or more of cobalt acetate tetrahydrate, cobalt chloride hexahydrate, and cobalt carbonate.
[0012] Preferably, in S1, the volume mass ratio of benzimidazole, solvent, ammonia water and cobalt salt is (12-18): (110-170): (0.5-1): (1-2) in terms of mL: mL: mL: g.
[0013] The volume-to-mass ratio of benzimidazole, solvent, ammonia water and cobalt salt within a certain range is helpful to improve the efficiency of oxygen reduction reaction, improve solubility and enhance catalytic activity. The role of ammonia water is to adjust pH value, chelate and improve solubility.
[0014] Preferably, in S1, the mixing temperature is 20-40° C. and the mixing time is 3-6 h.
[0015] Preferably, in said S1, the centrifugal speed is 5000-8000 r / min, the number of washings is 3-6 times, and the washing solvent is selected from one or more of methanol and ethanol.
[0016] The effect of centrifugal washing is to improve purity, control particle size and improve morphology.
[0017] Preferably, in S1, the drying is vacuum drying, the drying temperature is 60-100° C., and the drying time is 5-8 h.
[0018] Preferably, in S2, the inorganic salt is selected from one or more of sodium borate, sodium chloride and sodium fluoride.
[0019] The purpose of selecting different types of inorganic salts is to introduce different elements to increase active sites, optimize the electronic structure, and improve catalytic activity.
[0020] Preferably, in S2, the nitrogen-containing compound mixed solution is obtained by uniformly mixing the nitrogen-containing compound, N,N-dimethylformamide and water.
[0021] More preferably, the nitrogen-containing compound is selected from one or more of urea, imidazole, methylimidazole and dicyandiamide.
[0022] The role of nitrogen-containing compounds is to introduce nitrogen sources, improve conductivity, and adsorb oxygen.
[0023] More preferably, the mass volume ratio of the nitrogen-containing compound, N,N-dimethylformamide and water is (0.03-0.15):(3-5):2 in terms of g:mL:mL.
[0024] The mass-to-volume ratio of nitrogen-containing compounds, N,N-dimethylformamide and water within a certain range is helpful to improve the efficiency of oxygen reduction reaction and solubility.
[0025] More preferably, the molar ratio of the inorganic salt to the nitrogen-containing compound is (0.1-1):(0.5-1.5).
[0026] Preferably, in the S2, the mass ratio of the inorganic salt to the ZIF-12 is (0.004-0.2): (0.4-1.2).
[0027] Preferably, in S2, the stirring is heating stirring, and the heating temperature is 70-90°C.
[0028] Preferably, in S2, the stirring speed is 100-150 r / min.
[0029] Preferably, in S2, the particle size D50 after grinding is 2-3 μm.
[0030] Preferably, in S3, the protective gas is selected from one or more of nitrogen and argon.
[0031] Preferably, in S3, the carbonization treatment comprises heating the material to 700-1000° C. at a heating rate of 5-10° C. / min and carbonizing the material for 2-3 hours.
[0032] Preferably, in S3, washing includes acid washing and water washing.
[0033] More preferably, the pickling comprises washing with 0.3-0.7 mol / L dilute sulfuric acid.
[0034] The present invention also provides an oxygen reduction catalyst prepared by the above preparation method.
[0035] An application of the oxygen reduction catalyst or the oxygen reduction catalyst prepared by the preparation method in a fuel cell.
[0036] Preferably, the application method specifically comprises: applying the above oxygen reduction catalyst to the cathode of a fuel cell to carry out an oxygen reduction reaction.
[0037] The oxygen reduction catalyst provided by the present invention can significantly improve the reaction efficiency of the fuel cell, and improve the overall performance and energy conversion efficiency of the battery by accelerating the process of the oxygen reduction reaction.
[0038] The beneficial effects of the present invention are:
[0039] The present invention provides a simple and environmentally friendly inorganic salt-assisted pyrolysis method to prepare a Co / N / C co-doped porous carbon catalyst using ZIF-12 as a precursor. The prepared oxygen reduction catalyst has uniform morphology distribution, high oxygen reduction catalytic activity, and good methanol tolerance. It can replace the precious metal Pt / C catalyst as a catalytic material for use in fuel cells or metal-air batteries, and has broad application prospects and practical value. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Figure 1 This is a scanning electron microscope image of the oxygen reduction catalyst obtained in Example 1 of the present invention.
[0041] Figure 2 This is a comparison chart of ORR of the oxygen reduction catalysts of Examples 1-3 and Comparative Examples 1-4 in O2-saturated 0.1M KOH.
[0042] Figure 3 This is a graph showing the methanol tolerance of the oxygen reduction catalysts of Example 1 and Comparative Example 4 after methanol was added. DETAILED DESCRIPTION
[0043] The technical solution of the present invention is described in detail through specific embodiments.
[0044] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources.
[0045] Example 1
[0046] A method for preparing an oxygen reduction catalyst comprises the following steps:
[0047] S1. Dissolve 15 mL of benzimidazole in 75 mL of methanol and dissolve completely by ultrasonication; then add 60 mL of toluene and 0.84 mL of ammonia water and dissolve completely by ultrasonication, continue to add 6 mmol of cobalt acetate tetrahydrate, and then stir the mixed solution at 25°C for 4 hours; wash with methanol, centrifuge and separate the product at a speed of 6000 r / min, and dry in a vacuum oven at 80°C overnight to obtain purple solid ZIF-12;
[0048] S2, dissolving 0.5mmol sodium borate in a mixed solution of 60mL N,N-dimethylformamide solution containing 1mmol urea and water (2:1), ultrasonically dissolving completely, then adding 0.8g ZIF-12, stirring the mixed solution with a high temperature magnetic stirring at a speed of 120r / min and a temperature of 80°C until the solution forms a slurry, drying at 60°C, grinding evenly, and the particle size D50 after grinding is 2.5μm, to obtain a mixture;
[0049] S3. Put the mixture into a quartz boat, place it in a tube furnace, raise the temperature of the tube furnace to 800°C at a rate of 5°C / min under a nitrogen atmosphere for high-temperature carbonization for 2 hours, use 0.5 mol / L dilute sulfuric acid for acid washing, wash with deionized water and dry at 60°C to obtain an oxygen reduction catalyst.
[0050] Example 2
[0051] ZIF-12 was prepared by adopting step S1 of the method described in Example 1; 0.5 mmol sodium chloride was dissolved in a mixed solution of 60 mL of N,N-dimethylformamide solution containing 1 mmol urea and water (2:1), and completely dissolved by ultrasonication, and then 0.8 g ZIF-12 was added, and the mixed solution was subjected to high-temperature magnetic stirring at 80°C until the solution formed a slurry, dried at 60°C, and ground evenly to obtain a mixture; the mixture was placed in a quartz boat, placed in a tube furnace, and the temperature of the tube furnace was increased to 800°C at a rate of 8°C / min under a nitrogen atmosphere for high-temperature carbonization for 2 hours, and pickled with 0.5 mol / L dilute sulfuric acid, washed with deionized water and dried at 60°C to obtain an oxygen reduction catalyst.
[0052] Example 3
[0053] ZIF-12 was prepared by the method step S1 described in Example 1; 0.5 mmol sodium fluoride was dissolved in a mixed solution of 70 mL of N,N-dimethylformamide solution containing 1 mmol urea and water (2:1), and completely dissolved by ultrasonic treatment. Then 0.8 g ZIF-12 was added, and the mixed solution was magnetically stirred at 80° C. until the solution formed a slurry, dried at 60° C., and ground evenly to obtain a mixture; the mixture was placed in a quartz boat, placed in a tube furnace, and the temperature of the tube furnace was increased to 800° C. at a rate of 5° C. / min under a nitrogen atmosphere for high-temperature carbonization for 4 hours, and pickled with 0.5 mol / L dilute sulfuric acid, washed with deionized water and dried at 60° C. to obtain an oxygen reduction catalyst.
[0054] Comparative Example 1
[0055] ZIF-12 was prepared by the method step S1 described in Example 1; ZIF-12 was placed in a quartz boat, placed in a tube furnace, and the temperature of the tube furnace was raised to 800°C at a rate of 5°C / min under a nitrogen atmosphere for high-temperature carbonization for 2 hours, pickled with 0.5 mol / L dilute sulfuric acid, washed with deionized water and dried at 60°C to obtain an oxygen reduction catalyst.
[0056] Comparative Example 2
[0057] ZIF-12 was prepared by the method step S1 described in Example 1; 0.5 mmol sodium borate was dissolved in a mixed solution of 60 mL of N,N-dimethylformamide solution and water (2:1), and completely dissolved by ultrasonic treatment. Then 0.8 g ZIF-12 was added, and the mixed solution was magnetically stirred at 80° C. until the solution formed a slurry, dried at 60° C., and ground evenly to obtain a mixture; the mixture was placed in a quartz boat, placed in a tube furnace, and the temperature of the tube furnace was increased to 800° C. at a rate of 5° C. / min under a nitrogen atmosphere for high-temperature carbonization for 2 hours, and pickled with 0.5 mol / L dilute sulfuric acid, washed with deionized water and dried at 60° C. to obtain an oxygen reduction catalyst.
[0058] Comparative Example 3
[0059] ZIF-12 was prepared by the method step S1 described in Example 1; 0.8 g of ZIF-12 was dissolved in a mixed solution of 60 mL of N,N-dimethylformamide solution containing 1 mmol of urea and water (2:1), and completely dissolved by ultrasonic treatment. The mixed solution was then subjected to high-temperature magnetic stirring at 80°C until the solution formed a slurry, dried at 60°C, and ground evenly to obtain a mixture; the mixture was placed in a quartz boat, placed in a tubular furnace, and the temperature of the tubular furnace was increased to 800°C at a rate of 5°C / min under a nitrogen atmosphere for high-temperature carbonization for 2 hours, and pickled with 0.5 mol / L dilute sulfuric acid, washed with deionized water and dried at 60°C to obtain an oxygen reduction catalyst.
[0060] Comparative Example 4
[0061] The oxygen reduction catalyst was commercially available Pt / C.
[0062] The above oxygen reduction catalyst was subjected to electrochemical testing as follows: a three-electrode test was performed on a CHI660E instrument, with 0.1M KOH solution as the electrolyte, the test temperature was 25°C, and the silver chloride electrode, platinum wire electrode and glassy carbon electrode coated with the catalyst were used as the reference electrode, auxiliary electrode and working electrode, respectively. First, the glassy carbon electrode was polished with alumina and washed with deionized water. 5 mg of catalyst powder was dispersed in a mixture of 1.95 mL of water, 0.5 mL of ethanol and 50 μL of Nafion solution, and ultrasonic vibration was used for a certain period of time to fully mix it until the ink adhered to the bottle wall in the form of a watermark and no particles were visible to the naked eye. 30 μL of ink was transferred with a microinjector to the surface of the glassy carbon electrode. The catalyst loading on the glassy carbon electrode was 0.306 mg cm -2After the solvent evaporates, immerse it in an oxygen-saturated 0.1M KOH solution. During the electrochemical test, the open circuit potential is measured after oxygen is introduced for 20 minutes until the potential stabilizes and the oxygen reduction performance test is performed. Cyclic voltammetry is performed from the open circuit potential to the negative potential direction with a scanning speed of 5mV / s and a rotating disk electrode speed between 400-1600rpm. The linear sweep voltammogram (LSV) is used to evaluate the ORR performance of the catalyst. According to the following formula, all the potentials obtained in the experiment are converted to the reversible hydrogen electrode (RHE) scale:
[0063] E RHE =E (Ag / AgCl) +0.0591×pH+0.1967.
[0064] like Figure 1 As shown, Figure 1 is a scanning electron microscope image of the oxygen reduction catalyst obtained in Example 1 of the present invention, Figure 1 It can be seen that the prepared oxygen reduction catalyst has a regular tetrahedral structure and is evenly distributed. Figure 2 As shown, Figure 2 The ORR comparison diagram of the oxygen reduction catalysts of Examples 1-3 and Comparative Examples 1-4 in 0.1M KOH saturated with O2 is shown in FIG. Figure 2 It can be seen that the catalytic activity of the oxygen reduction catalyst prepared in Examples 1-3 is significantly better than that in Comparative Examples 1-3 and is equivalent to that in Comparative Example 4. Figure 3 As shown, Figure 3 The methanol tolerance graph of the oxygen reduction catalysts of Example 1 and Comparative Example 4 after adding 3 mL of methanol to 0.1 M KOH is shown in FIG. Figure 3 It can be seen that the methanol tolerance of the oxygen reduction catalyst prepared in Example 1 is significantly better than that in Comparative Example 4.
[0065] In summary, the oxygen reduction catalyst provided by the present invention has uniform morphology distribution, high oxygen reduction catalytic activity and good methanol tolerance, can replace the precious metal Pt / C catalyst as a catalytic material for use in fuel cells or metal-air batteries, and has broad application prospects and practical value.
[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A method for preparing an oxygen reduction catalyst, characterized in that: The following steps are involved: S1, mixing benzimidazole, solvent, ammonia water and cobalt salt uniformly, centrifuging, washing and drying to obtain ZIF-12; S2, after uniformly mixing the inorganic salt and the nitrogen-containing compound mixed solution, adding ZIF-12, stirring, drying, and grinding to obtain a mixture; S3, carbonizing the mixture under a protective gas atmosphere, washing, and drying to obtain.
2. The preparation method according to claim 1, characterized in that: In the S2, the nitrogen-containing compound mixed solution comprises a mixture of nitrogen-containing compounds, N,N-dimethylformamide and water; the nitrogen-containing compound is selected from one or more of urea, imidazole, methylimidazole and dicyandiamide; the molar ratio of the inorganic salt to the nitrogen-containing compound in the mixed solution is (0.1-1): (0.5-1.5).
3. The preparation method according to claim 2, characterized in that: The mass volume ratio of the nitrogen-containing compound, N,N-dimethylformamide and water is (0.03-0.15):(3-5):2 in terms of g:mL:mL.
4. The preparation method according to claim 1, characterized in that: In the S2, the inorganic salt is selected from one or more of sodium borate, sodium chloride, and sodium fluoride; the mass ratio of the inorganic salt to ZIF-12 is (0.004-0.2): (0.4-1.2).
5. The preparation method according to claim 1, characterized in that: In the S1, the solvent is selected from one or more of methanol and toluene; the cobalt salt is selected from one or more of cobalt acetate tetrahydrate, cobalt chloride hexahydrate, and cobalt carbonate; the volume mass ratio of benzimidazole, solvent, ammonia water, and cobalt salt is (12-18): (110-170): (0.5-1): (1-2) in mL: mL: mL: g.
6. The preparation method according to claim 1, characterized in that: In the S1, the centrifugal speed is 5000-8000 r / min, the number of washings is 3-6 times, the washing solvent is selected from one or more of methanol and ethanol; the drying is vacuum drying, the drying temperature is 60-100° C., and the drying time is 5-8 hours.
7. The preparation method according to claim 1, characterized in that: In the S3, the protective gas is selected from one or more of nitrogen and argon; the carbonization treatment includes heating to 700-1000°C at a heating rate of 5-10°C / min and carbonizing for 2-3h.
8. The preparation method according to claim 1, characterized in that: In the S3, washing includes acid washing and water washing; the acid washing includes washing with 0.3-0.7 mol / L dilute sulfuric acid.
9. An oxygen reduction catalyst, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the oxygen reduction catalyst according to claim 9 or the oxygen reduction catalyst prepared by the preparation method according to any one of claims 1 to 8 in a fuel cell.