Covalent organic framework-derived low-load Pt / C catalyst as well as preparation method and application thereof

Abstract

The invention discloses a covalent organic framework-derived low-load Pt / C catalyst as well as a preparation method and application thereof, and belongs to the field of electro-catalysis. According to the invention, a covalent organic framework material coordinated with platinum metal salt is used as a precursor, and the low-load integrated Pt / C nano material is synthesized through a simple carbonization method in a mixed atmosphere of argon / ammonia gas. Compared with commercial Pt / C with the mass fraction being 20%, the Pt / C nano material prepared through the method has the oxygen reduction performance far higher than that of the commercial Pt / C and the stability performance superior to that of the commercial Pt / C. Due to the high nitrogen content and the porous characteristic of the catalyst, the catalytic performance and the stability of the catalyst are superior to those of commercial Pt / C, and the obtained covalent organic framework-derived low-load Pt / C catalyst shows excellent oxidation-reduction catalytic performance. And after 10000 cycles, the catalytic activity is attenuated. The method is easy to operate and high in controllability and has certain universality.

Description

Technical Field

[0001] The present invention relates to a covalent organic framework-derived low-loading Pt / C catalyst, a preparation method thereof, and an application thereof, belonging to the technical field of electrocatalysis. Background Art

[0002] With the acceleration of the industrialization process and the increasingly severe environmental and energy problems, more and more countries around the world have begun to pay attention to clean, efficient, and safe energy conversion technologies. A fuel cell is an energy device that converts chemical energy in small molecule fuels such as ethanol, methanol, hydrogen, and formic acid into electrical energy, and has advantages such as high efficiency, safety, and environmental protection. Since the concept of fuel cells was first proposed in the 1840s of the 18th century, it has experienced more than 170 years of development. The working efficiency and power density of fuel cells often depend on the selection of electrolyte and catalyst materials, among which the role of the catalyst is crucial, and to a certain extent, it determines the development of fuel cell technology. The carbon-supported platinum-based catalyst is regarded as the most ideal catalytic material in fuel cells due to its excellent catalytic performance and occupies an important position in the application of fuel cells. However, its high cost and scarce resources limit its large-scale commercial application to a certain extent. Therefore, reducing the platinum loading while improving its catalytic activity and stability is crucial for promoting the development of fuel cells.

[0003] Existing commercial platinum-carbon catalysts have a high loading, with a mass fraction of platinum loading ≥ 20%, and need to undergo carbon loading treatment, resulting in high costs and limited catalytic activity and stability.

[0004] In view of the above problems, the present application is specifically proposed. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a covalent organic framework-derived low-loading Pt / C catalyst, a preparation method thereof, and an application thereof. The method of the present invention has a simple process and relatively low cost. The prepared low-loading Pt / C catalytic material has excellent redox activity and stability, shows a half-wave potential of 0.90 V under acidic conditions, which is much higher than the half-wave potential of commercial Pt / C (0.84 V), and shows signs of attenuation only after 10,000 cycles, and can be applied to the field of fuel cells.

[0006] The first object of the present invention is to provide a preparation method of a covalent organic framework-derived low-loading Pt / C catalyst, including the following steps: S1: Add a platinum metal salt and a covalent organic framework precursor to an ethanol solution, and after sufficient reflux condensation, obtain a covalent organic framework precursor coordinated with platinum metal ions; S2: Pyrolyze the covalent organic framework precursor coordinated with platinum metal ions under the atmosphere of a mixed gas of argon and ammonia, and cool down to obtain a derived low-loading Pt / C catalyst.

[0007] Preferably, the preparation method of the covalent organic framework in step S1 is specifically as follows: Select 15.00 mg (0.024 mmol) of tetrakis(4-formylphenyl)pyrene and 7.58 mg (0.048 mmol) of 1,4-phenylenediacetonitrile as reaction monomers, add them to a sealed glass tube containing a mixed solution of 1 ml of 1 / 5 volume of mesitylene / 1,4-dioxane and 0.1 mL of 4 M NaOH, heat to 90 °C, and react for 3 days to obtain a covalent organic framework.

[0008] Preferably, the covalent organic framework is sp 2 covalent organic framework.

[0009] Preferably, the mass ratio of the platinum metal salt to the covalent organic framework in step S1 is 0.1 - 0.4.

[0010] Preferably, the platinum metal salt is chloroplatinic acid, sodium chloroplatinate, or potassium chloroplatinate.

[0011] Preferably, the pyrolysis treatment conditions in step S2 are: pyrolyze for 2 - 4 h, the temperature is 900 - 1000 °C, and the heating rate is 2 - 5 °C / min.

[0012] Preferably, the volume ratio of argon to ammonia in step S2 is 10:1.

[0013] With the above technical solution, under a mixed atmosphere, using a platinum metal salt and a covalent organic framework as precursors, after sufficient reflux condensation, the covalent organic framework precursor coordinated with platinum metal ions is extracted using a rotary evaporator, and the above precursor is pyrolyzed in a tube furnace at a certain temperature. After the pyrolysis is completed, a low-loading Pt / C catalyst derived from the covalent organic framework is obtained.

[0014] The second object of the present invention is to provide a Pt / C catalyst with a loading amount prepared by the above method. The mass fraction of platinum in the low-loading Pt / C catalyst is 8% - 12%.

[0015] The third object of the present invention is to provide the application of the above low-loading Pt / C catalyst in cathode materials, fuel cells, or fuel cell-driven devices.

[0016] The beneficial effects of the present invention: (1) The present invention uses a covalent organic framework material as a precursor to directly prepare an integrated catalyst with a low Pt content supported on carbon, which can avoid the secondary carbon carrier loading process in the preparation of platinum-based nanocatalysts by the traditional nano-hydrothermal method.

[0017] (2) Due to its high nitrogen content and porous properties, the catalyst of the present invention has better catalytic performance and stability than commercial Pt / C. In particular, when the mass ratio of chloroplatinic acid to covalent organic framework precursor is 0.2, heated to 900 °C at a heating rate of 5 °C / min, with a pyrolysis time of 3 h, the covalent organic framework-derived low-loading Pt / C catalyst obtained after cooling shows excellent redox catalytic performance. After 10,000 cycles, the catalytic activity begins to decay. Description of the Drawings

[0018] Figure 1 It is the structure diagram of the covalent organic framework precursor used in the present invention.

[0019] Figure 2 They are transmission electron microscopy (TEM) pictures of Pt / C (named Pt / C-N-900, Pt / C-N-950, and Pt / C-N-1000 respectively) prepared at different temperatures under an argon / ammonia mixed atmosphere as obtained in Examples 1-3, where Figure 2 a is Pt / C-N-900, Figure 2 b is Pt / C-N-950, Figure 2 c is Pt / C-N-1000.

[0020] Figure 3 They are X-ray diffraction patterns of Pt / C-N-900, Pt / C-N-950, and Pt / C-N-1000 prepared in Examples 1-3.

[0021] Figure 4 They are the platinum contents in the samples of Pt / C-N-900, Pt / C-N-950, and Pt / C-N-1000 prepared in Examples 1-3.

[0022] Figure 5 They are oxygen reduction polarization curves of Pt / C-N-900, Pt / C-N-950, Pt / C-N-1000, and commercial Pt / C prepared in Examples 1-3.

[0023] Figure 6 They are the stability test results of Pt / C-N-900, Pt / C-N-950, Pt / C-N-1000, and commercial Pt / C prepared in Examples 1-3.

[0024] Figure 7 They are the power density results of Pt / C-N-900 and commercial Pt / C prepared in Example 1 tested in an H2-O2 fuel cell.

[0025] Figure 8 They are TEM pictures of the samples prepared by pyrolysis in different gas atmospheres.

[0026] Figure 9 TEM image of the sample prepared with platinum acetylacetonate as the platinum source in Example 5.

[0027] Figure 10 TEM image of the sample prepared in Comparative Example 1 by changing the covalent organic framework precursor to linear polymer polyaniline with reference to Example 1. Detailed implementation manners

[0028] To make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific implementation manners.

[0029] Example 1 A preparation method of a covalent organic framework-derived low-loading Pt / C catalyst includes the following steps: S1: Take 50 mg of covalent organic framework and 100 μL (100 mg / mL) of chloroplatinic acid solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tubular furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat to 900 °C at a heating rate of 5 °C / min, and the pyrolysis time is 3 h. After cooling to room temperature, a covalent organic framework-derived low-loading Pt / C catalyst is obtained, named Pt / C-N-900.

[0030] In this example, the preparation method of the covalent organic framework is specifically as follows: Select pyrene tetrakis(4-formylphenyl) (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat to 90 °C and react for three days to obtain the covalent organic framework.

[0031] In this example, the volume ratio of argon to ammonia is 10:1.

[0032] Example 2 A preparation method of a covalent organic framework-derived low-loading Pt / C catalyst includes the following steps: S1: Take 50 mg of covalent organic framework and 100 μL (100 mg / mL) of chloroplatinic acid solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat it to 950 °C at a heating rate of 5 °C / min for 3 h of pyrolysis time. After cooling to room temperature, a covalent organic framework-derived low-loading Pt / C catalyst is obtained, named Pt / C-N-950.

[0033] In this example, the preparation method of the covalent organic framework is specifically as follows: Select pyrene tetrakis(4-formylphenyl) (PY, 15.00 mg, 0.024 mmol) and 1,4-phenyl diacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat it to 90 °C and react for three days to obtain the covalent organic framework.

[0034] In this example, the volume ratio of argon to ammonia is 10:1.

[0035] Example 3 A preparation method of a covalent organic framework-derived low-loading Pt / C catalyst includes the following steps: S1: Take 50 mg of covalent organic framework and 100 μL (100 mg / mL) of chloroplatinic acid solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat it to 1000 °C at a heating rate of 5 °C / min for 3 h of pyrolysis time. After cooling to room temperature, a covalent organic framework-derived low-loading Pt / C catalyst is obtained, named Pt / C-N-1000.

[0036] In this example, the preparation method of the covalent organic framework is specifically as follows: Select pyrene tetrakis(4-formylphenyl) (PY, 15.00 mg, 0.024 mmol) and 1,4-phenyl diacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat it to 90 °C and react for three days to obtain the covalent organic framework.

[0037] In this example, the volume ratio of argon to ammonia is 10:1.

[0038] Example 4 A preparation method of a covalent organic framework-derived low-loading Pt / C catalyst includes the following steps: S1: Take 50 mg of covalent organic framework and 200 μL (100 mg / mL) of chloroplatinic acid solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat it to 900 °C at a heating rate of 2 °C / min, and the pyrolysis time is 2 h. After cooling to room temperature, a low-loading Pt / C catalyst derived from the covalent organic framework is obtained, named Pt / C-N-900.

[0039] In this example, the preparation method of the covalent organic framework is as follows: Select tetrakis(4-formylphenyl)pyrene (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat it to 90 °C and react for three days to obtain the covalent organic framework.

[0040] In this example, the volume ratio of argon to ammonia is 10:1.

[0041] Example 5 A preparation method of a low-loading Pt / C catalyst derived from a covalent organic framework includes the following steps: S1: Take 50 mg of covalent organic framework and 300 μL (100 mg / mL) of chloroplatinic acid solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat it to 900 °C at a heating rate of 3 °C / min, and the pyrolysis time is 4 h. After cooling to room temperature, a low-loading Pt / C catalyst derived from the covalent organic framework is obtained, named Pt / C-N-900.

[0042] In this example, the preparation method of the covalent organic framework is as follows: Select tetrakis(4-formylphenyl)pyrene (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat it to 90 °C and react for three days to obtain the covalent organic framework.

[0043] In this embodiment, the volume ratio of argon to ammonia is 10:1.

[0044] Example 6 A preparation method of a covalently organic framework-derived low-loading Pt / C catalyst includes the following steps: S1: Take 50 mg of covalently organic framework and 400 μL (100 mg / mL) of chloroplatinic acid solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalently organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalently organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat to 900 °C at a heating rate of 3 °C / min, and the pyrolysis time is 2 h. After cooling to room temperature, a covalently organic framework-derived low-loading Pt / C catalyst is obtained, named Pt / C-N-900.

[0045] In this embodiment, the preparation method of the covalently organic framework is specifically as follows: Select tetrakis(4-formylphenyl)pyrene (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat to 90 °C and react for three days to obtain the covalently organic framework.

[0046] In this embodiment, the volume ratio of argon to ammonia is 10:1.

[0047] Example 7 A preparation method of a covalently organic framework-derived low-loading Pt / C catalyst includes the following steps: S1: Take 50 mg of covalently organic framework and 100 μL (100 mg / mL) of sodium chloroplatinate solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalently organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalently organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat to 900 °C at a heating rate of 5 °C / min, and the pyrolysis time is 3 h. After cooling to room temperature, a covalently organic framework-derived low-loading Pt / C catalyst is obtained.

[0048] In this example, the preparation method of the covalent organic framework is specifically as follows: Tetrakis(4-formylphenyl)pyrene (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) are selected as reaction monomers, and they are added to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). After heating to 90 °C and reacting for three days, a covalent organic framework is obtained.

[0049] In this example, the volume ratio of argon to ammonia is 10:1.

[0050] Example 8 A preparation method of a low-loading Pt / C catalyst derived from a covalent organic framework includes the following steps: S1: Take 50 mg of the covalent organic framework and 200 μL (100 mg / mL) of potassium chloroplatinate solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat to 950 °C at a heating rate of 3 °C / min, and the pyrolysis time is 4 h. After cooling to room temperature, a low-loading Pt / C catalyst derived from the covalent organic framework is obtained.

[0051] In this example, the preparation method of the covalent organic framework is specifically as follows: Tetrakis(4-formylphenyl)pyrene (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) are selected as reaction monomers, and they are added to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). After heating to 90 °C and reacting for three days, a covalent organic framework is obtained.

[0052] In this example, the volume ratio of argon to ammonia is 10:1.

[0053] Example 9 A preparation method of a low-loading Pt / C catalyst derived from a covalent organic framework includes the following steps: S1: Take 50 mg of the covalent organic framework and 300 μL (100 mg / mL) of sodium chloroplatinate solution and add them to 100 mL of ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat it to 1000 °C at a heating rate of 5 °C / min for a pyrolysis time of 2 h. After cooling to room temperature, a low-loading Pt / C catalyst derived from the covalent organic framework is obtained.

[0054] In this example, the preparation method of the covalent organic framework is as follows: Select pyrene tetrakis(4-formylphenyl) (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat it to 90 °C and react for three days to obtain the covalent organic framework.

[0055] In this example, the volume ratio of argon to ammonia is 10:1.

[0056] Example 10 A preparation method of a low-loading Pt / C catalyst derived from a covalent organic framework includes the following steps: S1: Take 50 mg of the covalent organic framework and 200 μL (100 mg / mL) of potassium chloroplatinate solution and add them to 100 mL of an ethanol solution. After sufficient reflux condensation, use a rotary evaporator to extract the covalent organic framework coordinated with platinum metal ions; S2: Transfer the obtained covalent organic framework coordinated with platinum metal ions to a tube furnace for pyrolysis. The gas atmosphere is an argon / ammonia atmosphere. Heat it to 900 °C at a heating rate of 2 °C / min for a pyrolysis time of 4 h. After cooling to room temperature, a low-loading Pt / C catalyst derived from the covalent organic framework is obtained.

[0057] In this example, the preparation method of the covalent organic framework is as follows: Select pyrene tetrakis(4-formylphenyl) (PY, 15.00 mg, 0.024 mmol) and 1,4-phenylenediacetonitrile (PA, 7.58 mg, 0.048 mmol) as reaction monomers, and add them to a sealed glass tube containing a mixed solution of mesitylene / 1,4-dioxane (1 ml, 1 / 5 volume) and NaOH (0.1 mL, 4 M). Heat it to 90 °C and react for three days to obtain the covalent organic framework.

[0058] In this example, the volume ratio of argon to ammonia is 10:1.

[0059] For the detailed structure diagram of the covalent organic framework precursor used in the present invention, see Figure 1 . The present invention uses a typical representative sp 2 covalent organic framework structure with a periodic structure.

[0060] Comparative Example 1 Commercial Pt / C catalyst with a platinum mass fraction of 20%.

[0061] Comparative Example 2 The difference from Example 1 is that: the gas atmosphere in step S2 is argon.

[0062] Comparative Example 3 The difference from Example 1 is that: the gas atmosphere in step S2 is hydrogen / argon, and their volumes are 10:1.

[0063] Comparative Example 4 The difference from Example 1 is that: chloroplatinic acid in S1 is replaced with platinum acetylacetonate.

[0064] Comparative Example 5 The difference from Example 1 is that: sp 2 Covalent organic framework is replaced with a linear polymer.

[0065] Test Example 1 Test groups: Examples 1 - 3.

[0066] Test method: (1) The products prepared in Examples 1 - 3 were characterized by transmission electron microscopy; (2) The products prepared in Examples 1 - 3 were characterized by X-ray diffraction; (3) The platinum content of the products prepared in Examples 1 - 3 was detected.

[0067] Test results: (1) Figure 2 are the transmission electron microscopy images of Pt / C-N-900, Pt / C-N-950, and Pt / C-N-1000. It can be seen from the figure that the size of the metallic Pt nanoparticles is about 4 - 6 nm, and they are evenly distributed on the surface of the carbon substrate.

[0068] (2) Figure 3 are the X-ray diffraction patterns of Pt / C-N-x (x = 900, 950, 1000). The phase information of them can be obtained from their diffraction peaks, which is face-centered cubic Pt metal.

[0069] (3) Figure 4 is the comparison chart of the platinum content in the samples of Pt / C-N-900, Pt / C-N-950, and Pt / C-N-1000. It can be seen from the figure that the platinum content in the products prepared by the present invention is between 8% and 12%.

[0070] Test Example 2 Test groups: Examples 1 - 3 and Comparative Example 1.

[0071] Test method: (1)Half-wave potential: In an oxygen-saturated 0.1 M KOH solution, the polarization curves of Pt / C-N-900, Pt / C-N-950, Pt / C-N-1000, and commercial Pt / C were measured using a rotating disk electrode device at a rotation rate of 1600 rpm / min; (2)Degree of attenuation: The attenuation was observed after 10,000 cycles using cyclic voltammetry.

[0072] Test results: (1)Referring to Figure 5 , it can be found that Pt / C-N-900, Pt / C-N-950, and Pt / C-N-1000 have a larger half-wave potential than commercial Pt / C (the half-wave potential can qualitatively analyze the electrocatalytic oxygen reduction activity of materials, and the larger the half-wave potential, the better the catalytic activity of the material). The specific results are shown in Table 1. In particular, the half-wave potential of Pt / C-N-900 is 0.90 V, which is much larger than that of commercial Pt / C, indicating that these catalysts have higher activity than commercial Pt / C. This may be because at this temperature, the carbon substrate has better conductivity, thus greatly improving their redox catalytic activity.

[0073] (2) Figure 6 The stability data of Pt / C-N-900, Pt / C-N-950, Pt / C-N-1000, and commercial Pt / C are shown. It can be found that the Pt / C-N-900 nanomaterial prepared in Example 1 exhibits excellent stability and shows a weak attenuation phenomenon only after 10,000 cycles using cyclic voltammetry, while for commercial Pt / C, obvious attenuation has occurred after 10,000 cycles. The specific stability results are shown in Table 1.

[0074] Table 1 Half-wave potential results of the Pt / C nanocatalysts obtained in Examples 1-3 and commercial Pt / C nanomaterial Pt / C-N-900 Pt / C-N-950 Pt / C-N-1000 commercial Pt / C Half-wave potential (V) 0.90 V 0.88 V 0.87 V 0.82 V <![CDATA[Degree of attenuation (△E 1 / 2 / mV)]]> 3 mV 22 mV 28 mV 55 mV

[0075] Test Example 3 Test groups: Example 1 and Comparative Example 1.

[0076] Test method: Power density test.

[0077] Test results: As Figure 7 shows the power density curves measured for the products of Example 1 and Comparative Example 1 placed in an H2-O2 fuel cell. Compared with commercial Pt / C, Pt / C-N-900 exhibits a larger maximum power density.

[0078] Test Example 4

[0079] Test group: Comparative Example 2-3.

[0080] Test method: The samples of Comparative Examples 2-3 were subjected to TEM analysis.

[0081] Test results: Figure 8 As shown, Figure 8 a is the TEM image of the sample of comparative example 2, Figure 8 b is the TEM image of the sample in comparative example 3. When the gas atmosphere is changed to argon, the particle size is larger and the distribution is uneven; when it is a hydrogen / argon mixed gas atmosphere, the Pt nanoparticle size is larger and the distribution is uneven, indicating that the rich nitrogen source of ammonia is crucial for regulating the size and distribution of Pt nanoparticles.

[0082] Test Example 5 Test group: Comparative Example 4.

[0083] Test method: The sample of Comparative Example 4 was subjected to TEM analysis.

[0084] Test results: Figure 9 As shown, Pt nanoparticles are unevenly distributed on the surface of the carbon substrate. When the electrocatalytic ORR performance is tested, it is found to be worse than that of commercial Pt / C, indicating that chloroplatinic acid as a platinum source can better coordinate with the nitrogen source in the covalent organic framework, and plays a vital role in the formation of uniformly distributed Pt nanoparticles in this system.

[0085] Test Example 6 Test group: Comparative Example 5.

[0086] Test method: The sample of Comparative Example 5 was subjected to TEM.

[0087] Test results: Figure 10 As shown in the figure, the platinum nanoparticles on the carbon substrate are large in size and unevenly distributed. In addition, when the electrocatalytic ORR performance is tested, it shows worse ORR activity than commercial Pt / C. The main reason for this may be that the ordered porous structure of the covalent organic framework is conducive to confining and regulating the size and distribution of Pt nanoparticles, avoiding the aggregation of Pt nanoparticles.

[0088] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0089] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Preparation method of covalently organic framework-derived low-loading Pt / C catalyst, characterized in that It includes the following steps: S1: Add a platinum metal salt and a covalent organic framework into an ethanol solution. After sufficient reflux condensation, a covalent organic framework coordinated with platinum metal ions is obtained. S2: Pyrolyze the covalent organic framework coordinated with platinum metal ions obtained in step S1 under the atmosphere of a mixed gas of argon and ammonia. After cooling, a derived low-loading Pt / C catalyst is obtained.

2. The preparation method of the covalently organic framework-derived low-loading Pt / C catalyst according to claim 1, characterized in that The specific preparation method of the covalent organic framework in step S1 is as follows: Select 15.00 mg (0.024 mmol) of tetrakis(4-formylphenyl)pyrene and 7.58 mg (0.048 mmol) of 1,4-phenyldiacetonitrile as reaction monomers. Add them into a sealed glass tube containing a mixed solution of 1 ml of 1 / 5 volume of mesitylene / 1,4-dioxane and 0.1 mL of 4 M NaOH. Heat to 90 °C and react for 3 days to obtain a covalent organic framework.

3. The preparation method of the covalently organic framework-derived low-loading Pt / C catalyst according to claim 1, characterized in that, The covalent organic framework is sp 2 covalent organic framework.

4. The preparation method of the covalently organic framework-derived low-loading Pt / C catalyst according to claim 1, wherein, The mass ratio of the platinum metal salt to the covalent organic framework in step S1 is 0.1 - 0.

4.

5. The preparation method of the covalently organic framework-derived low-loading Pt / C catalyst according to claim 4, wherein, The platinum metal salt is chloroplatinic acid, sodium chloroplatinate, or potassium chloroplatinate.

6. The preparation method of the covalently organic framework-derived low-loading Pt / C catalyst according to claim 1, wherein The pyrolysis treatment conditions in step S2 are: pyrolysis for 2 - 4 h, the temperature is 900 - 1000 °C, and the heating rate is 2 - 5 °C / min.

7. The preparation method of the covalent organic framework-derived low-loading Pt / C catalyst according to claim 1, characterized in that, The volume ratio of argon to ammonia in step S2 is 10:

1.

8. The low-loading Pt / C catalyst prepared by the method according to any one of claims 1-7, characterized in that, The mass fraction of platinum in the low-loading Pt / C catalyst is 8% - 12%.

9. Application of the low-loading Pt / C catalyst according to claim 8 in a cathode material, a fuel cell, or a fuel cell-driven device.

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