Fuel cell cathode metal oxide catalyst and preparation method thereof
By coating the metal oxide surface of the fuel cell cathode catalyst with nitrogen doped porous carbon layer, the problem of poor stability of the catalyst under acidic conditions is solved, and a fuel cell cathode catalyst with high activity and stability is achieved, which is suitable for proton exchange membrane fuel cells.
Patent Information
- Application Number
- CN202510176865.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-18
- Publication Date
- 2025-05-23
AI Technical Summary
The existing fuel cell cathode catalysts have poor stability under acidic conditions and have low catalytic activity, making it difficult to replace precious metal platinum.
Using metal oxides as precursors, a metal organic frame material is formed by coating a nitrogen-doped porous carbon layer on its surface, and a fuel cell cathode catalyst is prepared by annealing.
The catalyst's conductivity and activity are improved, and its stability under acidic conditions is enhanced. The limit current density can reach 5mA cm-2, the half-wave potential is 0.74V, and it only attenuates 10mV after 30,000 cycles of voltage.
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Figure CN120033262A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of fuel cell catalysts, and in particular relates to a fuel cell cathode metal oxide catalyst and a preparation method thereof. Background Art
[0002] The massive consumption of fossil fuels has led to serious environmental pollution and climate problems. Developing efficient conversion and storage technologies to make full use of sustainable clean energy is an indispensable option to reduce dependence on fossil fuels. As a sustainable energy conversion device, proton exchange membrane fuel cells have attracted widespread attention due to their high power generation efficiency, low operating temperature, and environmental friendliness.
[0003] Due to the slow kinetics of the oxygen reduction reaction and the strong acidic and oxidizing environment of the cathode, the high demand for precious metal platinum is one of the biggest challenges for the large-scale market penetration of proton exchange membrane fuel cells. The development of highly active and durable non-precious metal fuel cell catalysts is a current research focus and challenge. Conventional carbon materials are easily corroded under acidic conditions, while metal oxide materials are generally more stable under acidic conditions, but are limited by their conductivity, resulting in poor catalytic activity.
[0004] CN 115799538 A discloses a non-precious metal catalyst for oxygen reduction doped with multiple transition metals for fuel cells and a preparation method thereof. The method adopts a normal temperature solvent method and a high temperature cracking method, uses ZIF8 as a precursor, adds a transition metal organic compound during the synthesis process, and finally obtains a non-precious metal catalyst for oxygen reduction doped with multiple transition metals through high temperature cracking and acid treatment. The method is simple in process, and the obtained catalyst shows good performance in a proton exchange membrane fuel cell, but fails to solve the problem of poor stability of the non-precious metal catalyst.
[0005] Therefore, it is urgent to develop a new type of fuel cell cathode catalyst that has both catalytic activity and stability. Summary of the invention
[0006] The purpose of the present invention is to provide a fuel cell cathode catalyst having both catalytic activity and stability and to provide a fuel cell cathode metal oxide catalyst and a preparation method thereof.
[0007] The purpose of the present invention can be achieved by the following technical solutions:
[0008] The present invention first provides a fuel cell cathode metal oxide catalyst, wherein the catalyst uses a metal oxide as a precursor, and the surface of the metal oxide is coated with a nitrogen-doped porous carbon layer;
[0009] The porous carbon layer is formed by annealing a metal organic framework material, wherein the metal organic framework material is self-assembled after mixing a zinc source and an organic ligand;
[0010] The metal oxide includes Co 3 O 4 , CoO, Fe 2 O 3 One or more of .
[0011] Furthermore, the zinc source includes one or more of zinc sulfate, zinc nitrate, zinc chloride, zinc acetate, and zinc oxalate, preferably zinc nitrate hexahydrate.
[0012] Furthermore, the organic ligand includes at least one of 2-methylimidazole, 2-ethylimidazole, benzimidazole, terephthalic acid, and 2,5-dihydroxyterephthalic acid.
[0013] Furthermore, the mass ratio of the metal oxide to the organic ligand is (0.01-0.2):7.
[0014] Furthermore, the mass ratio of the zinc source to the organic ligand is (3-5):7.
[0015] The present invention also provides a method for preparing a fuel cell cathode metal oxide catalyst, the preparation method comprising the following steps:
[0016] S1: dissolving a metal oxide and an organic ligand in an organic solvent to obtain a precursor solution, and dissolving a zinc source in an organic solvent to obtain a zinc source solution;
[0017] S2: transferring the zinc source solution to the precursor solution for reaction, collecting the product, and obtaining a metal oxide material coated with a metal organic framework material;
[0018] S3: heat-treating the metal oxide material coated with the metal organic framework material in an inert gas atmosphere to obtain the fuel cell cathode metal oxide catalyst.
[0019] Furthermore, in step S1, the concentration of the organic ligand in the precursor solution is 10-30 g / L, and the concentration of the metal oxide is 0.01-1 g / L.
[0020] Furthermore, in step S1, the concentration of the zinc source in the zinc source solution is 5-20 g / L.
[0021] Furthermore, in step S2, the reaction is carried out at 20-30° C. and the reaction time is 1-12 h.
[0022] Furthermore, in step S2, the product is collected by centrifugation and dried after centrifugation.
[0023] Furthermore, in step S3, the temperature of the heat treatment is 900-1100° C., and the time of the heat treatment is 0.5-5 h.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] (1) The present invention can effectively improve the conductivity of metal oxides by introducing nitrogen-doped porous carbon layers, which is beneficial to improving the activity of catalysts. Metal oxides themselves have good corrosion resistance, so the obtained catalyst has excellent activity and stability and is an ideal fuel cell cathode catalyst.
[0026] (2) The catalyst prepared by the present invention can achieve a limiting current density of 5 mA cm in the oxygen reduction reaction test. -2 The half-wave potential is 0.74V, and it only decays by 10mV after 30,000 voltage cycles. It is a non-precious metal catalyst for the cathode of proton exchange membrane fuel cells with great application prospects.
[0027] (3) The present invention forms a metal organic framework material on the surface of a metal oxide by a room temperature reaction, and then obtains the catalyst by annealing. The entire preparation process is simple, the catalyst composition and structure can be flexibly controlled, it has good repeatability, and it is easy to prepare in large quantities, which is of great significance to the development of non-precious metal fuel cell catalysts. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 The figure is a schematic diagram of the preparation process of the cathode metal oxide catalyst of the fuel cell of the present invention.
[0029] Figure 2 The nitrogen isothermal adsorption-desorption curve and pore size distribution diagram of the catalyst obtained in Example 2 of the present invention.
[0030] Figure 3 It is a comparison chart of the test results of oxygen reduction polarization curves of the catalysts obtained in Examples 1-4 of the present invention and Comparative Examples 1 and 2.
[0031] Figure 4 It is a comparison chart of the test results of oxygen reduction polarization curves of the catalysts obtained in Examples 2, 5 and 6 of the present invention.
[0032] Figure 5 It is a comparison chart of the oxygen reduction polarization curve test results of the catalysts obtained in Example 2 and Examples 7-9 of the present invention.
[0033] Figure 6 The oxygen reduction polarization curve test results, electron transfer number and hydrogen peroxide yield of the catalyst obtained in Example 2 of the present invention and the commercial Pt / C catalyst in Comparative Example 3 are shown.
[0034] Figure 7 This is a comparison chart of the oxygen reduction polarization curve test results of the catalyst obtained in Example 2 of the present invention and the commercial Pt / C catalyst in Comparative Example 3 before and after 30,000 cycles of accelerated aging. DETAILED DESCRIPTION
[0035] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0036] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.
[0037] Embodiment 1:
[0038] This embodiment provides a fuel cell cathode metal oxide catalyst, the principle schematic diagram of the preparation process is as follows Figure 1 As shown, the specific preparation method is as follows:
[0039] (1) Add 7 g of 2-methylimidazole, 10 mg of cobalt tetraoxide and 150 ml of methanol to a 500 ml beaker, and add 4 g of zinc nitrate hexahydrate and 150 ml of methanol to a 250 ml beaker. Stir at 25°C for 15 min to obtain a uniform solution.
[0040] (2) The above-mentioned methanol solution of zinc nitrate hexahydrate is transferred to a methanol solution of 2-methylimidazole and cobalt oxide, and reacted at room temperature for 24 hours. The mixture is centrifuged three times with methanol, and then the solid is placed at 60° C. and vacuum dried for 8 hours to obtain a zinc-based metal organic framework-coated cobalt oxide material.
[0041] (3) The zinc-based metal organic framework-coated cobalt oxide material is placed in a tubular furnace, heated to 1000°C at a rate of 10°C / min under an argon atmosphere, kept warm for 1 hour, and then naturally cooled to room temperature to obtain a nitrogen-doped porous carbon layer-coated cobalt-based metal oxide fuel cell cathode catalyst.
[0042] Embodiment 2:
[0043] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (1) of this embodiment is:
[0044] 7 g of 2-methylimidazole, 50 mg of cobalt tetroxide and 150 ml of methanol were added to a 500 ml beaker, and 4 g of zinc nitrate hexahydrate and 150 ml of methanol were added to a 250 ml beaker. The mixture was stirred at 25° C. for 15 min to obtain a uniform solution.
[0045] Embodiment 3:
[0046] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (1) of this embodiment is:
[0047] 7 g of 2-methylimidazole, 100 mg of cobalt tetroxide and 150 ml of methanol were added to a 500 ml beaker, and 4 g of zinc nitrate hexahydrate and 150 ml of methanol were added to a 250 ml beaker. The mixture was stirred at 25° C. for 15 min to obtain a uniform solution.
[0048] Embodiment 4:
[0049] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (1) of this embodiment is:
[0050] 7 g of 2-methylimidazole, 200 mg of cobalt tetroxide and 150 ml of methanol were added to a 500 ml beaker, and 4 g of zinc nitrate hexahydrate and 150 ml of methanol were added to a 250 ml beaker. The mixture was stirred at 25° C. for 15 min to obtain a uniform solution.
[0051] Embodiment 5:
[0052] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (3) of this embodiment is:
[0053] In an argon atmosphere, the temperature was raised to 900°C at a rate of 10°C / min, kept at that temperature for 1 hour, and then naturally cooled to room temperature to obtain a nitrogen-doped porous carbon layer-coated cobalt-based metal oxide fuel cell cathode catalyst.
[0054] Embodiment 6:
[0055] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (3) of this embodiment is:
[0056] In an argon atmosphere, the temperature was raised to 1100°C at a rate of 10°C / min, kept at that temperature for 1 hour, and then naturally cooled to room temperature to obtain a nitrogen-doped porous carbon layer-coated cobalt-based metal oxide fuel cell cathode catalyst.
[0057] Embodiment 7:
[0058] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (3) of this embodiment is:
[0059] In an argon atmosphere, the temperature was raised to 1000°C at a rate of 10°C / min, kept at that temperature for 0.5h, and then naturally cooled to room temperature to obtain a nitrogen-doped porous carbon layer-coated cobalt-based metal oxide fuel cell cathode catalyst.
[0060] Embodiment 8:
[0061] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (3) of this embodiment is:
[0062] In an argon atmosphere, the temperature was raised to 1000°C at a rate of 10°C / min, kept at that temperature for 2 hours, and then naturally cooled to room temperature to obtain a nitrogen-doped porous carbon layer-coated cobalt-based metal oxide fuel cell cathode catalyst.
[0063] Embodiment 9:
[0064] This embodiment provides a fuel cell cathode metal oxide catalyst, which is different from the embodiment 1 in that step (3) of this embodiment is:
[0065] In an argon atmosphere, the temperature was raised to 1000°C at a rate of 10°C / min, kept at that temperature for 4 hours, and then naturally cooled to room temperature to obtain a nitrogen-doped porous carbon layer-coated cobalt-based metal oxide fuel cell cathode catalyst.
[0066] Comparative Example 1:
[0067] The basic steps are the same as those in Example 2, except that cobalt tetroxide is not added in step 1 of this comparative example.
[0068] Comparative Example 2:
[0069] The basic steps are the same as those in Example 2, except that 400 mg of cobalt tetroxide is added in step 1 of this comparative example.
[0070] Comparative Example 3:
[0071] This comparative example is a commercially available 20% Pt / C catalyst.
[0072] The catalyst obtained in Example 2 was subjected to a BET test. Figure 2 A and B are the nitrogen isothermal adsorption and desorption curves and pore size distribution diagrams, respectively. It has a large specific surface area and porosity of 959.5m 2 g -1 and 0.276cm 3 g -1 , which is beneficial to the improvement of catalyst performance.
[0073] The electrochemical performance of the catalysts obtained in Examples 1-4, Comparative Examples 1 and 2 was characterized respectively. The specific test method was as follows: 5 mg of catalyst, 30 μl of 5 wt% Nafion ionomer solution, 170 μl of water and 600 μl of isopropanol were used to prepare a catalyst slurry. After ultrasonic treatment for 2 hours, 20 μl was dripped onto the surface of the glassy carbon ring disk electrode. After natural drying, a uniform film was formed. The activity of the catalyst was then evaluated under a three-electrode system, in which the glassy carbon ring disk electrode loaded with the catalyst film was the working electrode, the counter electrode and the reference electrode were gold wire and Hg / Hg, respectively. 2 SO 4 Electrode, electrolyte is 0.1M HClO saturated with oxygen 4 The rotating disk electrode was rotated at 1600 rpm and the voltage range was 0 to 1.2 V vs. RHE at 10 mVs -1 Linear sweep voltammetry was performed to evaluate the performance of the catalyst.
[0074] Comparison of oxygen reduction polarization curve test results of the above catalysts Figure 3 As shown, it can be seen that the half-wave potentials of the catalysts obtained in Examples 1-4, Comparative Example 1 and Comparative Example 2 are 0.657, 0.758, 0.712, 0.685, 0.547 and 0.557 Vvs. RHE, respectively. Too little metal oxide content may lead to a reduction in the number of active sites, while too much metal oxide content may lead to a reduction in the conductivity of the catalyst. The performance of the catalyst obtained in Example 2 is better than the other five.
[0075] The electrochemical performance of the catalysts obtained in Example 2, Example 5 and Example 6 was characterized respectively, and the oxygen reduction polarization curve test results of the three were compared. Figure 4 It can be seen that the fuel cell catalysts prepared at an annealing temperature of 900-1100°C all have good catalyst activity, with an annealing temperature of 1000°C being the best.
[0076] The electrochemical performance of the catalysts obtained in Example 2 and Examples 7-9 was characterized respectively, and the oxygen reduction polarization curve test results of the four were compared. Figure 5 It can be seen that the fuel cell catalysts prepared under the annealing heat treatment time of 0.5-4h all have good catalytic activity, indicating that a reasonable heat treatment time can form a nitrogen-doped porous carbon layer on the surface of the metal oxide to ensure the catalytic activity of the catalyst, among which the annealing temperature of 1h is the best.
[0077] The electrochemical performance of the catalyst obtained in Example 2 and the commercial Pt / C catalyst in Comparative Example 3 was characterized. The test results of oxygen reduction polarization curves, electron transfer numbers and hydrogen peroxide yields of the two catalysts are shown in Figure 2. Figure 6As shown, it can be seen that the catalyst obtained in Example 2 has a performance close to that of commercial Pt / C, and the electron transfer number is close to 4, and the hydrogen peroxide yield is less than 10%.
[0078] The anti-aging performance of the catalyst obtained in Example 2 and the commercial Pt / C catalyst of Comparative Example 3 was characterized. The test results of the oxygen reduction polarization curves before and after 30,000 cycles of accelerated aging are shown in FIG. Figure 7 It can be seen that the catalyst prepared in Example 2 has very little performance loss after 30,000 cycles of accelerated aging, and the half-wave potential only decays by 10 mV, which is very close to the commercial Pt / C catalyst, indicating that the catalyst obtained in Example 2 has excellent stability and can be used as an ideal fuel cell cathode catalyst.
[0079] In summary, the present invention can effectively improve the conductivity of metal oxides by introducing a nitrogen-doped porous carbon layer, which is beneficial to improving the activity of the catalyst. The metal oxides themselves have good corrosion resistance, so the obtained catalyst has excellent activity and stability and is an ideal fuel cell cathode catalyst.
[0080] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.
Claims
1. A fuel cell cathode metal oxide catalyst, characterized in that: The catalyst uses a metal oxide as a precursor, and the surface of the metal oxide is coated with a nitrogen-doped porous carbon layer; The porous carbon layer is formed by annealing a metal organic framework material, wherein the metal organic framework material is self-assembled after mixing a zinc source and an organic ligand; The metal oxide includes one or more of Co3O4, CoO, and Fe2O3.
2. A fuel cell cathode metal oxide catalyst according to claim 1, characterized in that: The zinc source includes one or more of zinc sulfate, zinc nitrate, zinc chloride, zinc acetate, and zinc oxalate.
3. A fuel cell cathode metal oxide catalyst according to claim 1, characterized in that: The organic ligand includes at least one of 2-methylimidazole, 2-ethylimidazole, benzimidazole, terephthalic acid, and 2,5-dihydroxyterephthalic acid.
4. A fuel cell cathode metal oxide catalyst according to claim 1, characterized in that: The mass ratio of the metal oxide to the organic ligand is (0.01-0.2):
7.
5. A fuel cell cathode metal oxide catalyst according to claim 1, characterized in that: The mass ratio of the zinc source to the organic ligand is (3-5):
7.
6. A method for preparing a fuel cell cathode metal oxide catalyst according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1: dissolving a metal oxide and an organic ligand in an organic solvent to obtain a precursor solution, and dissolving a zinc source in an organic solvent to obtain a zinc source solution; S2: transferring the zinc source solution to the precursor solution for reaction, collecting the product, and obtaining a metal oxide material coated with a metal organic framework material; S3: heat-treating the metal oxide material coated with the metal organic framework material in an inert gas atmosphere to obtain the fuel cell cathode metal oxide catalyst.
7. The method for preparing a fuel cell cathode metal oxide catalyst according to claim 6, characterized in that: In step S1, the concentration of the organic ligand in the precursor solution is 10-30 g / L, and the concentration of the metal oxide is 0.01-1 g / L.
8. The method for preparing a fuel cell cathode metal oxide catalyst according to claim 6, characterized in that: In step S1, the concentration of the zinc source in the zinc source solution is 5-20 g / L.
9. The method for preparing a fuel cell cathode metal oxide catalyst according to claim 6, characterized in that: In step S2, the reaction is carried out at 20-30° C. for 1-12 hours; the product is collected by centrifugation and dried after centrifugation.
10. The method for preparing a fuel cell cathode metal oxide catalyst according to claim 6, characterized in that: In step S3, the temperature of the heat treatment is 900-1100° C., and the time of the heat treatment is 0.5-5 h.