Method for preparing catalyst with high transition metal content through vacuum-assisted permeation method

Abstract

The invention provides a method for preparing a catalyst with high transition metal content through a vacuum-assisted permeation method, which comprises the following steps: preparing a phenanthroline-based porous organic polymer (POPs) through a solvothermal reaction, and modifying a transition metal (TM) and a small molecule ligand on the POPs through the vacuum-assisted permeation method. The obtained phenanthroline-based POPs catalyst has excellent oxygen reduction catalytic activity, has a half-wave potential of 0.79 V vs. RHE in an alkaline environment, and also has excellent 4-electron selectivity, the selectivity is higher than 90% in a potential range of 0.3-0.7 V vs. RHE, and the content of transition metal is increased to 4% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalyst preparation, and particularly relates to a method for preparing a catalyst with a high transition metal content through vacuum-assisted infiltration, and the application of the catalyst in the field of green energy storage and conversion devices represented by fuel cells and rechargeable metal-based batteries. Background Art

[0002] Catalysts containing transition metals (such as Fe, Co, Ni, Cu and their alloys) have important application values in the field of energy catalysis (such as hydrogen production by electrolysis of water, fuel cells, CO 2 reduction, etc.). Research shows that the activity of the catalyst is directly related to the loading amount, dispersion degree and carrier binding strength of the transition metal. Although traditional impregnation methods, deposition precipitation methods and ion exchange methods can load metal active components, they are prone to particle agglomeration under high metal content conditions, reducing the exposure rate of active sites. In addition, traditional methods may not penetrate enough in porous carriers, and the metal particles are unevenly distributed, affecting the catalytic efficiency.

[0003] Therefore, the present invention proposes a method for preparing a catalyst with a high transition metal content through vacuum-assisted infiltration, providing a new catalyst preparation method with a simple preparation process, low cost and high metal loading. The vacuum-assisted infiltration method can remove the gas inside the carrier through vacuum treatment, allowing the metal precursor solution to better penetrate into the pores of the carrier, improving the loading amount and dispersion. Summary of the Invention

[0004] In view of this, the present invention provides a preparation method of a phenanthroline-based organic porous material with a high transition metal content obtained through vacuum infiltration, and its preparation includes the following steps: S1. Preparation of POP: Dissolve 5,5'-dibromo-2,2'-bipyridine and 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline and the catalyst tetrakis(triphenylphosphine)palladium in a solvent, and keep it in an inert gas environment for a period of time, then add a certain amount of saturated Na 2 CO 3 solution. After heating and stirring the reaction to completion, filter, wash, collect the red solid, and after vacuum drying, obtain the bipyridine unit of POP; S2. Preparation of POP-TM-Ligand: Disperse the small molecule ligand in a solvent. After uniform dispersion, add a part of the solution to the mixed solution of POP and transition metal salt, ultrasonically disperse, then perform freeze-vacuum-thawing, add another part of the small molecule ligand solution, and perform freeze-vacuum-thawing again. After multiple cycles of the freeze-vacuum-thawing steps, seal and oscillate the reaction. After the reaction, the obtained product is washed and dried to obtain the target catalyst.

[0005] The molar ratio of 5,5'-dibromo-2,2'-bipyridine, 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline, and tetrakis(triphenylphosphine)palladium in S1 is 1:1~2:0.25~1.

[0006] The volume ratio of the saturated Na 2 CO 3 solution and N',N'-dimethylformamide (DMF) solvent added in S1 is 1:1~2.

[0007] Among them, the purpose of adding the saturated Na 2 CO 3 solution is for catalytic effect.

[0008] The heating temperature in S1 is 80~100 °C, and the heating reaction time is 36~48 h.

[0009] The solvent used in S1 is selected from any one of DMF, DMSO, and NMP.

[0010] During the washing process, water, ethanol, and tetrahydrofuran are used for washing in sequence.

[0011] The molar ratio of the bipyridine unit of POP, metal ions of transition metal salts, and small molecule ligands in S2 is 1:1~1.2:0.8~1.5.

[0012] The transition metal salts described in S2 are selected from any one or a combination of oxalates, acetates, halides, nitrates, or sulfates of cobalt, nickel, and iron.

[0013] In this step, to increase the transition metal loading on POP as much as possible, the transition metal salt should be in excess. The precipitate obtained after the reaction must be washed with a large amount of solvent to remove the residual excess metal salt on POP-TM-Ligand.

[0014] The types of the small molecule ligands include 4,7-dihydroxy-1,10-phenanthroline or 4,4'-dihydroxy-2,2'-bipyridine.

[0015] To avoid the "pulling off" of transition metal ions from the framework by small molecule ligands, the small molecule ligands should be slowly added dropwise to the ampoule in steps, and the molar ratio of the bipyridine unit in POP to the small molecule ligand is 1:1~1.5.

[0016] The dispersion of the small molecule ligand in N',N-dimethylformamide is 1~2 mg L -1 .

[0017] In step S2, it is carried out in an ampoule. The freeze-vacuum-thaw condition means using liquid nitrogen to freeze the ampoule until it becomes solid inside, then evacuating the vacuum for five minutes, and then thawing it with warm water until it becomes liquid inside the ampoule. The purpose of performing cyclic freeze-vacuum-thaw is to remove the gas inside the carrier through vacuum treatment, allowing the metal precursor solution to better penetrate into the pores of the carrier, and improving the loading amount and dispersion. For the above technical solution, the present invention also provides a fuel cell or rechargeable metal-based battery material, including the o-phenanthroline-based catalyst with a high transition metal content prepared by the method of vacuum-assisted infiltration described above.

[0018] Above, the o-phenanthroline-based POPs catalyst obtained by a simple method does not need to be carbonized under an inert atmosphere, but has excellent oxygen reduction catalytic activity, has a half-wave potential of 0.79 V vs. RHE in an alkaline environment, and also has excellent electron selectivity, with a selectivity higher than 90% in the potential range of 0.3 - 0.7 V vs. RHE. The transition metal content has a large increase, and the content is not less than 4%, and it can be used as a fuel cell or rechargeable metal-based battery material. Description of the Drawings

[0019] Figure 1 (a) ORR polarization curve measured for Example 1 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0020] Figure 2 SEM-EDS diagram of the sample prepared in Example 1.

[0021] Figure 3 (a) ORR polarization curve measured for Example 2 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0022] Figure 4 SEM-EDS diagram of the sample prepared in Example 2.

[0023] Figure 5 (a) ORR polarization curve measured for Example 3 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0024] Figure 6 SEM-EDS diagram of the sample prepared in Example 3.

[0025] Figure 7(a) ORR polarization curves measured for Example 4 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0026] Figure 8 SEM-EDS images of the sample prepared for Example 4.

[0027] Figure 9 (a) ORR polarization curves measured for Comparative Example 1 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0028] Figure 10 SEM-EDS images of the sample prepared for Comparative Example 1.

[0029] Figure 11 (a) ORR polarization curves measured for Comparative Example 2 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0030] Figure 12 SEM-EDS images of the sample prepared for Comparative Example 2.

[0031] Figure 13 (a) ORR polarization curves measured for Comparative Example 3 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0032] Figure 14 SEM-EDS images of the sample prepared for Comparative Example 3.

[0033] Figure 15 (a) ORR polarization curves measured for Comparative Example 4 in an oxygen-saturated 0.1 M KOH solution; (b) H 2 O 2 yield and number of transferred electrons.

[0034] Figure 16 SEM-EDS images of the sample prepared for Comparative Example 4.

[0035] Figure 17 Flowcharts for the preparation of Examples 1 and 2.

[0036] Figure 18 Flowcharts for the preparation of Comparative Examples 1 and 2. Detailed implementation manners

[0037] Characterization conditions: ORR test method in the examples and comparative examples of the present invention: Grind 3 mg of catalyst, 2.5 mg of carbon black and 2.5 mg of carbon nanotubes, and then disperse them in 760 μL of ethanol, 200 μL of water and 20 μL of 5 wt% Nafion. Mix the slurry thoroughly with ultrasound for 60 minutes. Then, load the catalyst slurry onto a rotating ring-disk electrode (RRDE, with an area of 0.1256 cm -2 ), and the catalyst loading is always maintained at 0.6 mg cm -2 . Then, use a reference electrode (mercuric oxide), a counter electrode (carbon rod), and a working electrode three-electrode system to perform tests in an oxygen-saturated 0.1 M KOH solution.

[0038] Calculation formula for hydrogen peroxide yield: , Calculation formula for the number of transferred electrons: , where N is the collection efficiency of the ring electrode, and its value is 0.4.

[0039] The SEM-EDS images were collected on a TESCAN MIRA LMS apparent scanning electron microscope with an accelerating voltage of 3 kV.

[0040] Example 1 Dissolve 5,5'-dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) in N',N'-dimethylformamide solvent (DMF) (15 mL), and place it in an argon environment for 15 min, then add saturated Na 2 CO 3 solution (7 mL). Finally, stir and heat in an oil bath for 48 h. After the reaction is completed, wash with deionized water, ethanol 3 times and tetrahydrofuran 1 time, collect the red solid, and vacuum dry it for 24 h to obtain the final POP.

[0041] Disperse 4,7-dihydroxy-1,10-phenanthroline (11 mg) in N',N'-dimethylformamide (9 mL). After uniform dispersion, add 1 / 3 of the ligand solution to the solution containing POP (20 mg) and Co(OAc) 2 ·4H 2Disperse it in an ampoule containing O (8 mg) by ultrasonic dispersion. Freeze-vacuum-thaw the ampoule, then add 1 / 3 of the ligand solution. Freeze-vacuum-thaw the ampoule again, add another 1 / 3 of the ligand solution, and then freeze-vacuum the ampoule. Finally, seal the ampoule by flame. React the sealed ampoule in a constant temperature shaker at 60 °C for 6 h. Wash the obtained product with N',N-dimethylformamide multiple times, collect the red solid, and then vacuum dry it for 24 h to obtain the target catalyst.

[0042] Figure 1 a-b shows the ORR catalytic performance of the sample in Example 2 in alkaline electrolyte, and its half-wave potential ( E 1 / 2 ) is 0.79 V. The number of electron transfers is greater than 3.9 in the potential range of 0.3 - 0.7 V, and the hydrogen peroxide yield is less than 5%. Figure 2 It shows that the cobalt content of the sample in Example 1 is 7.97%.

[0043] Example 2 Dissolve 5,5'-dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) in N',N'-dimethylformamide solvent (DMF) (15 mL). After keeping it in an argon environment for 15 min, add saturated Na 2 CO 3 solution (7 mL). Finally, heat and stir it in an oil bath for 48 h. After the reaction is completed, wash it with deionized water, ethanol three times and tetrahydrofuran once, collect the red solid, and vacuum dry it for 24 h to obtain the final POP. Disperse 4,7-dihydroxy-1,10-phenanthroline (11 mg) in N',N-dimethylformamide (9 mL). After uniform dispersion, add 1 / 3 of the ligand solution to an ampoule containing POP (20 mg) and Co(OAc) 2 ·4H 2 O (8 mg). Disperse it by ultrasonic dispersion. Freeze-vacuum-thaw the ampoule, then add 1 / 3 of the ligand solution. Freeze-vacuum-thaw the ampoule again, add another 1 / 3 of the ligand solution, and then freeze-vacuum the ampoule. Finally, seal the ampoule by flame. React the sealed ampoule in a constant temperature shaker at room temperature for 24 h. Wash the obtained product with N',N-dimethylformamide multiple times, collect the red solid, and then vacuum dry it for 24 h to obtain the target catalyst. Figure 3a-b shows the ORR catalytic performance of the sample of Example 4 in alkaline electrolyte, with its half-wave potential (E 1 / 2 ), which is 0.78 V, the number of electron transfers is greater than 3.8 in the potential range of 0.3 - 0.7 V, and the hydrogen peroxide yield is less than 10%. Figure 4 It shows that the cobalt content of the sample of Example 2 is 9.50%.

[0044] Example 3 Dissolve 5,5'-dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) in N',N'-dimethylformamide solvent (DMF) (15 mL), and after keeping it in an argon environment for 15 min, add saturated Na 2 CO 3 solution (7 mL). Finally, stir it with an oil bath for 48 h. After the reaction is completed, wash it 3 times with deionized water and ethanol and 1 time with tetrahydrofuran. Collect the red solid and vacuum dry it for 24 h to obtain the final POP. Disperse 4,4'-dihydroxy-2,2'-bipyridine (10 mg) in N',N'-dimethylformamide (9 mL). After uniform dispersion, add 1 / 3 of the ligand solution to an ampoule containing POP (20 mg) and Co(OAc) 2 ·4H 2 O (8 mg), and disperse it by ultrasonic wave. Freeze-vacuum-thaw the ampoule, then add 1 / 3 of the ligand solution, freeze-vacuum-thaw the ampoule again, add 1 / 3 of the ligand solution again, and then freeze-vacuum the ampoule. Finally, flame-seal the ampoule. Oscillate and react the sealed ampoule in a constant temperature shaker at 60 °C for 6 h. Wash the obtained product with N',N'-dimethylformamide for many times, collect the red solid, and then vacuum dry it for 24 h to obtain the target catalyst. Figure 5 a-b shows the ORR catalytic performance of the sample of Example 6 in alkaline electrolyte, with its half-wave potential (E 1 / 2 ), which is 0.78 V, the number of electron transfers is greater than 3.9 in the potential range of 0.3 - 0.7 V, and the hydrogen peroxide yield is less than 10%. Figure 6 It shows that the cobalt content of the sample of Example 3 is 6.33%.

[0045] Example 4 Dissolve 5,5'-dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) in N,N-dimethylformamide solvent (DMF) (15 mL). After keeping it under an argon atmosphere for 15 min, add saturated Na 2 CO 3 solution (7 mL). Finally, stir with heating in an oil bath for 48 h. After the reaction is completed, wash it 3 times with deionized water and ethanol and 1 time with tetrahydrofuran. Collect the red solid and vacuum dry it for 24 h to obtain the final POP; Disperse 4,4'-dihydroxy-2,2'-bipyridine (10 mg) in N,N-dimethylformamide (9 mL). After uniform dispersion, add 1 / 3 of the ligand solution to an ampoule containing POP (20 mg) and Co(OAc) 2 ·4H 2 O (8 mg), ultrasonically disperse it, subject the ampoule to freeze-vacuum-thaw, then add 1 / 3 of the ligand solution, subject the ampoule to freeze-vacuum-thaw again, then add 1 / 3 of the ligand solution, and then subject the ampoule to freeze-vacuum, and finally flame-seal the ampoule. Shake the sealed ampoule at room temperature in a constant-temperature shaker for 24 h. Wash the obtained product with N,N-dimethylformamide multiple times, collect the red solid, and then vacuum dry it for 24 h to obtain the target catalyst; Figure 7 a - b shows the ORR catalytic performance of the sample in Example 8 in an alkaline electrolyte. Its half-wave potential (E 1 / 2 ) is 0.77 V, the number of electron transfers is greater than 3.9 in the potential range of 0.3 - 0.7 V, and the hydrogen peroxide yield is less than 10%. Figure 8 It shows that the cobalt content of the sample in Example 4 is 4.53%.

[0046] Control Example 1 Dissolve 5,5'-dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) in N,N-dimethylformamide solvent (DMF) (15 mL). After keeping it under an argon atmosphere for 15 min, add saturated Na 2 CO 3Solution (7 mL), and finally heated and stirred in an oil bath for 48 h. After the reaction was completed, it was washed 3 times with deionized water and ethanol and 1 time with tetrahydrofuran. The red solid was collected and vacuum dried for 24 h to obtain the final POP; Disperse POP (20 mg) and Co(OAc) 2 ·4H 2 O (8 mg) in a round-bottom flask containing N',N'-dimethylformamide solvent (DMF) (15 mL), stir and react at 60 °C for 6 h. After the reaction, the obtained product was washed 3 times with N',N'-dimethylformamide solvent (DMF) and vacuum dried for 24 h to obtain POP-TM containing TM-N 2 precursor sites. Then, disperse POP-TM and 4,7-dihydroxy-1,10-phenanthroline (11 mg) in N',N'-dimethylformamide solvent (DMF) (15 mL), stir and react at 60 °C for 6 h. After the reaction, the obtained product was washed multiple times with N',N'-dimethylformamide solvent (DMF) and vacuum dried for 24 h to obtain the catalyst.

[0047] Figure 9 a-b shows the ORR catalytic performance of the sample in Example 1 in an alkaline electrolyte, and its half-wave potential (E 1 / 2 ) is 0.71 V, the number of electron transfers is greater than 3.0 in the potential range of 0.3 - 0.7 V, and the hydrogen peroxide yield is less than 50%. Figure 10 It shows that the cobalt content of the sample in Comparative Example 1 is 2.13%.

[0048] Comparative Example 2 Dissolve 5,5'-dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) in N',N'-dimethylformamide solvent (DMF) (15 mL), and place it in an argon environment for 15 min, then add saturated Na 2 CO 3 solution (7 mL). Finally, heat and stir in an oil bath for 48 h. After the reaction is completed, wash it 3 times with deionized water and ethanol and 1 time with tetrahydrofuran. Collect the red solid and vacuum dry it for 24 h to obtain the final POP; Disperse POP (20 mg) and Co(OAc) 2 ·4H 2O (8 mg) was dispersed in a round-bottom flask containing N',N'-dimethylformamide solvent (DMF) (15 mL), and the reaction was stirred at room temperature for 24 h. After the reaction, the obtained product was washed 3 times with N',N'-dimethylformamide solvent (DMF) and dried in vacuum for 24 h to obtain POP-TM containing TM-N 2 precursor sites. Then, POP-TM and 4,7-dihydroxy-1,10-phenanthroline (11 mg) were dispersed in N',N'-dimethylformamide solvent (DMF) (15 mL), and the reaction was stirred at room temperature for 24 h. After the reaction, the obtained product was washed multiple times with N',N'-dimethylformamide solvent (DMF) and dried in vacuum for 24 h to obtain the catalyst.

[0049] Figure 11 a-b shows the ORR catalytic performance of the sample in Example 3 in alkaline electrolyte, and its half-wave potential (E 1 / 2 ) is 0.69 V, the number of electron transfers is greater than 3.5 in the potential range of 0.3 - 0.7 V, and the yield of hydrogen peroxide is less than 20%. Figure 12 It shows that the cobalt content of the sample in Comparative Example 2 is 2.77%.

[0050] Comparative Example 3 5,5'-Dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) were dissolved in N',N'-dimethylformamide solvent (DMF) (15 mL), and after being in an argon environment for 15 min, saturated Na 2 CO 3 solution (7 mL) was added. Finally, it was heated and stirred in an oil bath for 48 h. After the reaction was completed, it was washed 3 times with deionized water and ethanol and 1 time with tetrahydrofuran, and the red solid was collected and dried in vacuum for 24 h to obtain the final POP; POP (20 mg) and Co(OAc) 2 ·4H 2 O (8 mg) was dispersed in a round-bottom flask containing N',N'-dimethylformamide solvent (DMF) (15 mL), and the reaction was stirred at 60 °C for 6 h. After the reaction, the obtained product was washed 3 times with N',N'-dimethylformamide solvent (DMF) and dried in vacuum for 24 h to obtain POP-TM containing TM-N 2The POP-TM of the precursor site, and then POP-TM and 4,4'-dihydroxy-2,2'-bipyridine (10 mg) were dispersed in N',N'-dimethylformamide solvent (DMF) (15 mL), and stirred at 60 °C for 6 h. After the reaction, the obtained product was washed with N',N'-dimethylformamide solvent (DMF) for several times and dried in vacuum for 24 h to obtain the catalyst.

[0051] Figure 13 a-b shows the ORR catalytic performance of the sample in Example 5 in the alkaline electrolyte, and its half-wave potential (E 1 / 2 ) is 0.70 V, the number of electron transfers is greater than 3.6 in the potential range of 0.3 - 0.7 V, and the yield of hydrogen peroxide is less than 20%. Figure 14 It shows that the cobalt content of the sample in Comparative Example 3 is 1.56%.

[0052] Comparative Example 4 5,5'-Dibromo-2,2'-bipyridine (150 mg), 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]aniline (200 mg), and the catalyst tetrakis(triphenylphosphine)palladium (30 mg) were dissolved in N',N'-dimethylformamide solvent (DMF) (15 mL), and after being in an argon environment for 15 min, saturated Na 2 CO 3 solution (7 mL) was added. Finally, it was heated and stirred in an oil bath for 48 h. After the reaction was completed, it was washed 3 times with deionized water and ethanol and 1 time with tetrahydrofuran. The red solid was collected and dried in vacuum for 24 h to obtain the final POP. POP (20 mg) and Co(OAc) 2 ·4H 2 O (8 mg) were dispersed in a round-bottom flask containing N',N'-dimethylformamide solvent (DMF) (15 mL), and stirred at room temperature for 24 h. After the reaction, the obtained product was washed 3 times with N',N'-dimethylformamide solvent (DMF) and dried in vacuum for 24 h to obtain POP-TM containing the TM-N 2 precursor site. Then POP-TM and 4,4'-dihydroxy-2,2'-bipyridine (10 mg) were dispersed in N',N'-dimethylformamide solvent (DMF) (15 mL), and stirred at room temperature for 24 h. After the reaction, the obtained product was washed with N',N'-dimethylformamide solvent (DMF) for several times and dried in vacuum for 24 h to obtain the catalyst.

[0053] Figure 15a-b shows the ORR catalytic performance of the sample of Example 7 in an alkaline electrolyte. Its half-wave potential (E 1 / 2 ) in the alkaline electrolyte is 0.69 V, the number of electron transfers is greater than 3.6 in the potential range of 0.3 - 0.7 V, and the hydrogen peroxide yield is lower than 20%. Figure 16 It shows that the cobalt content of the sample of Comparative Example 4 is 1.83%.

[0054] By comparing the examples and the comparative examples, it can be clearly found that compared with the method of stirring at atmospheric pressure (Comparative Example), the vacuum infiltration method adopted in the present invention shows significant advantages in preparing samples. In terms of metal content, for the samples prepared by the vacuum infiltration method, the internal metal content can be increased to 4at% - 10at%, and at the same time, the ORR performance has also been significantly improved. In terms of the preparation process, the atmospheric pressure stirring method requires chelating metal ions with POPs first, then washing and vacuum drying, and then chelating small molecule ligands again, followed by washing and vacuum drying. It should be noted that these two washing / vacuum drying operations cannot be combined because the unchelated metal ions must be removed first to prevent local enrichment of metal ions and the formation of precipitates. In contrast, in the vacuum infiltration method, the vacuum environment can assist the uniform penetration of ions and ligand molecules in the solvent. This characteristic enables the simultaneous addition of POPs, metal salts, and small molecule ligands in a "one-pot" during the preparation process, and the entire process only requires one step of washing / vacuum drying to complete (comparing Figure 17 and Figure 18 ). Therefore, it can be seen that compared with the atmospheric pressure two-step stirring method, the overall operation steps of the vacuum infiltration method are more concise.

Claims

1. A method for preparing a phenanthroline-based catalyst with a high transition metal content by vacuum-assisted infiltration, characterized in that: The method comprises the following preparation steps: S1. Preparation of POP: 5,5'-dibromo-2,2'-bipyridine, 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenylaniline and catalyst tetrakis(triphenylphosphine)palladium are dissolved in a solvent, and after being placed in an inert gas environment for a period of time, a certain amount of saturated Na2CO3 solution is added, and after the reaction is completed by heating and stirring, the red solid is filtered, washed, collected, and vacuum dried to obtain the bipyridine unit of POP; S2. Preparation of POP-TM-Ligand: small molecule ligands are dispersed in a solvent. After uniform dispersion, a portion of the solution is added to a mixed solution of POP and transition metal salts, and ultrasonic dispersion is performed. The mixture is then freeze-vacuum-thawed, and then a portion of the small molecule ligand solution is added. The mixture is freeze-vacuum-thawed again. The freeze-vacuum-thaw steps are repeated multiple times to seal and oscillate the reaction. The product obtained after the reaction is washed and dried to obtain the target catalyst.

2. The method for preparing a phenanthroline-based catalyst having a high transition metal content by vacuum-assisted infiltration according to claim 1, wherein: The molar ratio of 5,5'-dibromo-2,2'-bipyridine to 4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-N,N-bis-[4-(tetramethyl-1,3,2-dioxaborolan-2-yl)phenylaniline and tetrakis(triphenylphosphine)palladium described in S1 is 1:1~2:0.25~1.

3. The method for preparing a phenanthroline-based catalyst with a high transition metal content by vacuum-assisted infiltration according to claim 1, wherein: The volume ratio of the saturated Na2CO3 solution and N', N'-dimethylformamide (DMF) solvent added to S1 is 1:1~1.

4.

4. The method for preparing a phenanthroline-based catalyst with a high transition metal content by vacuum-assisted infiltration according to claim 1, wherein: In S1, the heating temperature is 80~100 ℃, and the heating reaction time is 36~48 h.

5. The method for preparing a phenanthroline-based catalyst with a high transition metal content by vacuum-assisted infiltration according to claim 1, characterized in that: The molar ratio of the bipyridine unit of POP to the metal ions and small molecule ligands of the transition metal salt in S2 is 1:1~1.2: 0.8~1.

5.

6. The method for preparing a phenanthroline-based catalyst having a high transition metal content by vacuum-assisted infiltration according to claim 5, characterized in that: The transition metal salt is selected from any one or more combinations of oxalates, acetates, halides, nitrates or sulfates of cobalt, nickel or iron.

7. The method for preparing a phenanthroline-based catalyst having a high transition metal content by vacuum-assisted infiltration according to claim 5, characterized in that: The types of small molecule ligands include 4,7-dihydroxy-1,10-phenanthroline or 4,4'-dihydroxy-2,2'-bipyridine.

8. The method for preparing a phenanthroline-based catalyst having a high transition metal content by vacuum-assisted infiltration according to claim 7, characterized in that: The dispersion of small molecule ligands in N',N'-dimethylformamide is 1~2 mg L -1 .

9. The method for preparing a phenanthroline-based catalyst having a high transition metal content by vacuum-assisted infiltration according to claim 7, wherein: Freeze-vacuum-thaw conditions involve freezing the ampoule with liquid nitrogen until the inside is solid, then evacuating the ampoule for five minutes, and then thawing it with warm water until the inside of the ampoule is liquid.

10. A fuel cell or rechargeable metal-based battery material, characterized in that: The invention relates to a phenanthroline-based catalyst with a high transition metal content prepared by a vacuum-assisted infiltration method, which is prepared by the method described in any one of claims 1 to 9.

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