A Fe-NC bifunctional catalyst and its preparation method and application

Abstract

The present invention discloses a Fe-N-C bifunctional catalyst and a preparation method and application thereof. The present invention adopts a synthesis strategy of calcination after a one-pot hydrothermal method, so that dianhydride and diamine are copolymerized with iron compounds while being connected and cyclized by hydrogen bonds, and the electrocatalytic performance and stability of the Fe-N-C oxygen reduction / oxygen evolution reaction bifunctional catalyst are improved by regulating hydrogen bonds. The bifunctional catalyst of the present invention shows excellent oxygen reduction / oxygen evolution reaction electrocatalytic performance under alkaline conditions, and has the advantages of simple preparation method, rich source of raw materials, easy industrial production, low cost, more uniform dispersion of iron elements, etc. Therefore, it has a wide range of application prospects in energy conversion devices such as fuel cells and metal-air batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a Fe-NC bifunctional catalyst and a preparation method and application thereof. Background Art

[0002] Energy conversion devices, such as fuel cells and metal-air batteries, can directly convert chemical energy into electrical energy. They have the advantages of clean fuel and large reserves, and can effectively improve the problems of energy loss and environmental pollution. Oxygen reduction reaction and oxygen evolution reaction, as a pair of reverse reactions, usually occur at the cathode of these energy conversion devices. However, their reaction rates are slow, so a large amount of catalysts are required to accelerate the reaction rate to improve battery performance. At present, the most commonly used catalysts are Pt / C and RuO2 catalysts, but due to the disadvantages of high cost and low reserves of precious metals, cheap Fe-NC catalysts have received more attention.

[0003] The reaction kinetics of oxygen reduction reaction (ORR) is mainly limited by the key problem of linear relationship between OOH* and OH* reaction intermediates. Because this linear relationship not only increases the difficulty of catalysts to show the best adsorption energy for intermediates, but also brings about a minimum theoretical overpotential of about 300-400 mV, which limits the improvement of catalytic activity. According to the adsorption evolution mechanism (AEM), OOH* and OH* mainly come from two reaction pathways of ORR - 4-electron reaction pathway (O2→OOH*→O*→OH*→H2O, * represents adsorption state) and 2-electron reaction pathway (O2→OOH*→H2O2). Since the 4-electron reaction pathway can provide a stronger driving force, it is the negative electrode reaction expected by energy conversion technologies such as metal-air batteries or fuel cells. According to the reaction path, whether it is the 4-electron reaction pathway or the 2-electron reaction pathway, the first step is O2→OOH*. When the OOH* adsorption strength is strong, it is conducive to the occurrence of the 4-electron reaction pathway, while when the OOH* adsorption is weak, ORR mainly proceeds through the 2-electron reaction pathway. This means that the adsorption strength of OOH* determines the selectivity of the reaction pathway. As a key intermediate in the 4-electron reaction pathway, reducing the adsorption energy of OH* is the key to improving catalytic activity. However, the linear relationship between the adsorption energies of OOH* and OH* means that while enhancing the adsorption energy of OOH*, the adsorption energy of OH* is also increased, which is not conducive to the catalyst surface showing the optimal adsorption energy for the key intermediate. On the other hand, this linear relationship also brings a minimum theoretical overpotential of 300-400 mV, which theoretically limits the room for improving the electrochemical performance of ORR. Therefore, regulating the linear relationship between the adsorption energies of OOH* and OH* is of great significance for improving the ORR reaction kinetics.

[0004] It can be seen that the current regulation and The main measure to achieve a linear relationship between them is to adopt a series of covalent interaction component regulation methods (including selecting metal center types, heteroatom doping, defect modification, electrode potential regulation, building axial coordination, regulating ligand effect, etc.) to adjust the electronic structure and improve the adsorption energy of OOH* and OH*, thereby modifying and The linear relationship between them.

[0005] However, non-covalent interactions are often overlooked. Hydrogen bonds are widely present in O- and H-containing environments, and in the ORR reaction under alkaline conditions, reaction intermediates such as O*, OH*, and OOH* easily form hydrogen bonds with the coordinating atoms in the catalyst. Therefore, ignoring the important influence of hydrogen bonding interactions in electrocatalytic ORR has led to a relatively blank study on the mechanism of regulating the characteristic structure of hydrogen bonds to modify the linear relationship.

[0006] Therefore, it is still necessary to study how to regulate the characteristic structure of hydrogen bonds to improve the electrocatalytic performance and stability of the catalyst in oxygen reduction / oxygen evolution reactions.

[0007] The information in the background technology is only for illustrating the general background of the present invention and should not be regarded as admitting or suggesting in any form that such information constitutes the prior art known to a person skilled in the art. Summary of the invention

[0008] In order to solve at least some of the technical problems in the above-mentioned prior art, the present invention calcines dianhydride, diamine, iron compound and cyclization promoter after a one-pot hydrothermal reaction, so that dianhydride and diamine are copolymerized with iron compound while being connected by hydrogen bonds and forming a ring, thereby obtaining Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst with more uniform iron element doping and larger doping amount. At the same time, by adjusting the number and strength of hydrogen bonds, the oxygen reduction / oxygen evolution reaction electrocatalytic performance and stability of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst are improved. Specifically, the present invention includes the following contents.

[0009] The first aspect of the present invention provides a method for preparing a hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, which comprises the following steps:

[0010] (1) introducing an inert gas into an organic solvent until the solvent is saturated, adding a dianhydride, a diamine, an iron compound and a cyclization promoter into the organic solvent, and stirring to obtain a mixed solution;

[0011] (2) subjecting the mixed solution to a hydrothermal reaction, and performing centrifugation and drying to obtain a solid;

[0012] (3) calcining the solid to obtain the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0013] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, the organic solvent comprises at least one of N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, acetone, tetrahydrofuran, benzene, toluene, xylene, mesitylene or diethyl ether.

[0014] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, the organic solvent is N-methylpyrrolidone and mesitylene.

[0015] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, the volume ratio of the N-methylpyrrolidone to the mesitylene is (0.5-10):1.

[0016] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, the inert gas comprises at least one of nitrogen, argon or helium.

[0017] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, the molar ratio of the dianhydride, the diamine and the iron compound is (5-9):(7-11):(0.5-1.8), and the volume ratio of the cyclization promoter and the organic solvent is (1-5):(10-50).

[0018] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, the dianhydride includes at least one of pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, perylene 3,4,9,10-tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride or 1,2,3,4-cyclobutanetetracarboxylic dianhydride; the diamine includes at least one of melamine, phenylenediamine, benzimidazole diamine, 4,4'-diaminodiphenylmethane or 2,2-bis[4-(4-aminophenoxy)phenyl]propane; the iron compound includes at least one of ferric chloride, ferric nitrate, ferric sulfate, ferric oxide or ferroferric oxide; and the cyclization promoter includes quinoline or a quinoline derivative.

[0019] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, wherein in step (2), the temperature of the hydrothermal reaction is 100-220° C. and the time is 1-100 h.

[0020] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, wherein in step (3), the calcination temperature is 300-1200° C., the calcination time is 2-10 h, and the heating rate is 2-10° C. / min.

[0021] In certain embodiments, according to the method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention, wherein, in step (3), the calcination is carried out under a protective atmosphere, and the protective atmosphere comprises at least one of nitrogen, argon or a hydrogen-argon mixture.

[0022] The second aspect of the present invention provides a Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, which is prepared by the preparation method of the present invention.

[0023] The third aspect of the present invention provides use of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst according to the present invention in an energy conversion device.

[0024] The Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention adopts a synthesis strategy of one-pot hydrothermal method and post-calcination, so that the dianhydride and diamine are copolymerized with the iron compound while being connected and ring-formed by hydrogen bonds, wherein the hydrogen bonds can cause changes in the local chemical and electronic environment of the relevant protons and atomic nuclei, effectively activate the proton activity, and increase the oxygen reduction or oxygen evolution reaction intermediate absorption-desorption rate. In addition, the electrostatic potential generated by the hydrogen bonds has different adsorption capacities for Fe, resulting in different Fe doping amounts of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst. Therefore, the present invention ultimately improves the electrocatalytic performance (e.g., lower overpotential, higher current density, etc.) and stability of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst by regulating the number and strength of hydrogen bonds. The Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention also shows excellent oxygen reduction / oxygen evolution reaction electrocatalytic performance under alkaline conditions. In addition, the catalyst of the present invention has the advantages of simple preparation method, abundant raw material sources, easy industrial production, low cost, and more uniform dispersion of iron elements. Therefore, it has broad application prospects in energy conversion devices such as fuel cells and metal-air batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a SEM image of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Comparative Example 1 of the present invention.

[0026] Figure 2 This is a SEM image of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Example 1 of the present invention.

[0027] Figure 3 This is a TEM image of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Example 2 of the present invention.

[0028] Figure 4 Electrochemical performance diagram of oxygen reduction reaction of Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalysts prepared in Examples 1, 2 and 3 of the present invention and Comparative Examples 1, 2 and 3.

[0029] Figure 5 Electrochemical performance diagram of oxygen evolution reaction of Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Examples 1, 2 and 3 of the present invention. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that the upper and lower limits of the scope and each intermediate value therebetween are specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0032] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the invention belongs. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0033] Preparation method

[0034] One aspect of the present invention provides a method for preparing a hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, which comprises steps (1)-(3). Steps (1)-(3) are described in detail below.

[0035] The step (1) of the present invention is to introduce an inert gas into an organic solvent until it is saturated, add dianhydride, diamine, iron compound and cyclization promoter into the organic solvent, and stir to obtain a mixed solution.

[0036] In the present invention, the organic solvent includes at least one of N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, acetone, tetrahydrofuran, benzene, toluene, xylene, mesitylene or ether. In a preferred embodiment, the organic solvent is N-methylpyrrolidone and mesitylene, and the volume ratio of N-methylpyrrolidone to mesitylene is (0.5-10):1, preferably (1-8):1, such as 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] The inert gas in step (1) of the present invention is not particularly limited, and examples thereof include, but are not limited to, nitrogen, argon, helium, etc., or a combination thereof.

[0038] In a preferred embodiment, the time for passing the inert gas is 20-40 min, preferably 25-35 min, for example 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In order to improve the doping of iron elements, the dispersion performance of iron elements, regulate the number and strength of hydrogen bonds, and improve the electrocatalytic performance (such as lower overpotential, higher current density, etc.) and stability of Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalysts, the ratio of dianhydride, diamine and iron compound and the addition amount of cyclization promoter should not be too high or too low. In a preferred embodiment, the molar ratio of the dianhydride, the diamine and the iron compound is (5-9):(7-11):(0.5-1.8), preferably (6-9):(8-11):(0.5-1.5), for example 6:8:0.5, 7:8:0.5, 8:8:0.5, 9:8:0.5, 6:9:0.5, 7:9:0.5, 8:9:0.5, 9:9:0.5, 6:10:0.5, 7:10:0.5, 8:10:0.5, 9:10:0.5, 6:11:0.5, 7:11:0.5, 8:11:0.5, 9:11:0.5, 6:8:1, 7:8:1, 8:8:1, 9:8:1, 6:9:1 , 7:9:1, 8:9:1, 9:9:1, 6:10:1, 7:10:1, 8:10:1, 9:10:1, 6:11:1, 7:11:1, 8:11:1, 9:11:1, 6:8:1.5, 7:8:1.5, 8:8:1.5, 9:8:1.5, 6:9:1.5, 7:9:1.5, 8:9:1.5, 9:9:1.5, 6:10:1.5, 7:10:1.5, 8:10:1.5, 9:10:1.5, 6:11:1.5, 7:11:1.5, 8:11:1.5, 9:11:1, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] In a preferred embodiment, the volume ratio of the cyclization promoter to the organic solvent is (1-5): (10-50), preferably (1-4): (20-40), and the cyclization promoter within this range promotes the cyclization reaction while reducing the number of hydrogen bonds, thereby controlling the number and strength of hydrogen bonds within a suitable range. The volume ratio of the cyclization promoter to the organic solvent can be, for example, 1:20, 1:25, 1:30, 2:35, 3:20, 3:40, 3:50, 4:75, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0041] In the present invention, the dianhydride includes at least one of pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, perylene 3,4,9,10-tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride or 1,2,3,4-cyclobutanetetracarboxylic dianhydride. In a preferred embodiment, the dianhydride is pyromellitic dianhydride.

[0042] In the present invention, the diamine includes at least one of melamine, phenylenediamine, benzimidazole diamine, 4,4'-diaminodiphenylmethane or 2,2-bis[4-(4-aminophenoxy)phenyl]propane. In a preferred embodiment, the diamine is melamine.

[0043] In the present invention, the iron compound includes at least one of ferric chloride, ferric nitrate, ferric sulfate, ferric oxide or ferrosoferric oxide. In a preferred embodiment, the iron compound is ferric nitrate.

[0044] In the present invention, the cyclization accelerator includes quinoline or a quinoline derivative. In a preferred embodiment, the cyclization accelerator is isoquinoline.

[0045] In a preferred embodiment of step (1) of the present invention, the stirring time is 20-40 min, preferably 25-35 min, for example 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Step (2) of the present invention is to subject the mixed solution to a hydrothermal reaction, and to centrifuge and dry the mixed solution to obtain a solid.

[0047] In order to obtain Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst with excellent electrocatalytic performance and stability for oxygen reduction / oxygen evolution reaction, it is necessary to control the hydrothermal temperature and hydrothermal time within an appropriate range. In a preferred embodiment, the temperature of the hydrothermal reaction is 100-220°C, preferably 120-220°C, also preferably 140-220°C, more preferably 160-220°C, such as 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, etc., and the time of the hydrothermal reaction is 1-100 h, preferably 10-90 h, also preferably 20-80 h, such as 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80 h, etc., but are not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. In a preferred embodiment, the temperature of the hydrothermal reaction is 210°C and the time of the hydrothermal reaction is 72 h. In another preferred embodiment, the temperature of the hydrothermal reaction is 210°C and the time of the hydrothermal reaction is 24 h.

[0048] In a preferred embodiment of step (2) of the present invention, the centrifugation comprises centrifuging at a speed of 5000-10000 r / min, preferably 6000-9000 r / min, and further preferably 7000-8500 r / min, for example, 7000, 7100, 7200, 7300, 7400, 7500, 7600, 7700, 7800, 7900, 8000, 8100, 8200, 8300, 8400, 8500 r / min for 1-20 min, preferably 1-15 min, and further preferably 1-10 min, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 min, in the presence of a washing solution, and the number of centrifugations is not particularly limited, for example, 1, 2, 3, 4, 5, 6 times, wherein the washing solution is not particularly limited, and examples thereof include, but are not limited to, N-methylpyrrolidone, anhydrous ethanol, distilled water, and the like. In certain embodiments, the centrifugation comprises using N-methylpyrrolidone, anhydrous ethanol and distilled water as washing solutions, respectively, centrifuging at a speed of 8000 r / min for 5 min, and repeating each washing solution 3 times.

[0049] Step (3) of the present invention is a step of calcining the solid to obtain the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0050] In order to obtain Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalysts with excellent electrocatalytic performance and stability for oxygen reduction / oxygen evolution reaction, it is necessary to control appropriate calcination conditions. In a preferred embodiment, the calcination is preferably a two-stage calcination, the first stage calcination temperature is 300-700°C, preferably 350-650°C, and also preferably 400-600°C, such as 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, the first stage calcination time is 2-10h, such as 2, 3, 4, 5, 6, 7, 8, 9, 10 h, and a heating rate of 2-10°C / min, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10°C / min; the second stage calcination temperature is 700-1100°C, preferably 750-1050°C, and further preferably 800-1000°C, for example, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, the second stage calcination time is 2-10h, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10 h, and the heating rate is 2-10°C / min, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10°C / min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. In a preferred embodiment, the calcination comprises calcining at 500° C. for 3 h and then calcining at 900° C. for 3 h, wherein the heating rate is 5° C. / min.

[0051] In a preferred embodiment, the calcination is carried out under a protective atmosphere, and the protective atmosphere is not particularly limited, and examples thereof include but are not limited to nitrogen, argon, a hydrogen-argon mixed gas, etc. In a preferred embodiment, the protective atmosphere is nitrogen.

[0052] The present invention also provides a Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, which is prepared by the preparation method of the present invention.

[0053] application

[0054] One aspect of the present invention provides the use of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst in an energy conversion device.

[0055] In the present invention, the energy conversion device includes a battery, wherein the battery is not particularly limited, and examples thereof include but are not limited to a fuel cell, a metal-air battery, and the like.

[0056] The hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention also has high oxygen reduction / oxygen evolution reaction electrocatalytic performance and stability under alkaline conditions, and can effectively improve the power generation performance of batteries such as fuel cells and metal-air batteries.

[0057] Example 1

[0058] The following shows the preparation method and performance test results of the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0059] 1. Preparation

[0060] Step 1: 20 mL of N-methylpyrrolidone (NMP) and 20 mL of mesitylene were mixed in equal proportions in a hydrothermal autoclave and an inert gas was introduced for 30 min until saturation to obtain an organic solution;

[0061] Step 2: 9 mmol of pyromellitic anhydride, 11 mmol of melamine, 0.5 mmol of Fe(NO3)3·9H2O and 2 mL of isoquinoline were added to the organic solution and stirred until it turned into a brick red solution;

[0062] Step 3: subjecting the brick-red solution to a hydrothermal reaction at 210° C. for 72 h, using N-methylpyrrolidone, anhydrous ethanol and distilled water as washing solutions, respectively, and centrifuging at a speed of 8000 r / min for 5 min, repeating each washing solution for 3 times, and then freeze-drying to obtain a brown solid;

[0063] Step 4: The brown solid was calcined at 500°C for 3 h and then at 900°C for 3 h under a N2 atmosphere at a heating rate of 5°C / min to obtain a PI-COF / Fe-202 oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0064] 2. Performance Testing

[0065] Step I: 4 mg of the PI-COF / Fe-202 oxygen reduction / oxygen evolution reaction bifunctional catalyst was added to 1000 μL of a dispersion prepared by 250 μL of ethanol and 750 μL of distilled water, and after ultrasonication for 20 min, 20 μL of nafion was added and ultrasonication was continued for another 20 min to form an ink-like slurry;

[0066] Step II: Measure 20 μL of the ink-like slurry and drop it onto the surface of the rotating disk electrode and wait for it to completely dry;

[0067] Step III: Another 20 μL of the ink-like slurry was measured and dropped onto the nickel foam (1 cm×1 cm), and then allowed to dry completely;

[0068] Step IV: Using platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the completely dried rotating disk electrode described in step II as the working electrode, the electrocatalytic performance of the oxygen reduction reaction of the sample was tested in a 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 4 As shown, the half-wave potential is 0.751 V vs. RHE;

[0069] Step V: Using high-purity graphite carbon rod as counter electrode, Ag / AgCl as reference electrode, and the completely dried nickel foam described in step III as working electrode, the electrocatalytic performance of the sample for oxygen evolution reaction was tested in 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 5 As shown, the overpotential is 509.6 mV vs. RHE.

[0070] Example 2

[0071] The following shows the preparation method and performance test results of the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0072] 1. Preparation

[0073] Step 1: Mix 20 mL of N-methylpyrrolidone and 20 mL of mesitylene in equal proportions in a hydrothermal autoclave and introduce inert gas for 30 min until saturated to obtain an organic solution;

[0074] Step 2: 9 mmol of pyromellitic anhydride, 11 mmol of melamine, 1.5 mmol of Fe(NO3)3·9H2O and 2 mL of isoquinoline were added to the organic solution and stirred until it turned into a brick red solution;

[0075] Step 3: The brick-red solution was hydrothermaled at 210° C. for 72 h, and N-methylpyrrolidone, anhydrous ethanol and distilled water were used as washing solutions, respectively, and centrifuged at a speed of 8000 r / min for 5 min, and each washing solution was repeated 3 times, and then freeze-dried to obtain a brown solid;

[0076] Step 4: The brown solid was calcined at 500°C for 3 h and then at 900°C for 3 h under N2 atmosphere at a heating rate of 5°C / min to obtain a PI-COF / Fe-606 oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0077] 2. Performance Testing

[0078] Step I: 4 mg of the PI-COF / Fe-606 oxygen reduction / oxygen evolution reaction bifunctional catalyst was added to 1000 μL of a dispersion prepared by 250 μL of ethanol and 750 μL of distilled water, and after ultrasonication for 20 min, 20 μL of nafion was added and ultrasonication was continued for another 20 min to form an ink-like slurry;

[0079] Step II: Measure 20 μL of the ink-like slurry and drop it onto the surface of the rotating disk electrode and wait for it to completely dry;

[0080] Step III: Another 20 μL of the ink-like slurry was measured and dropped onto the nickel foam (1 cm×1 cm), and then allowed to dry completely;

[0081] Step IV: Using platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the completely dried rotating disk electrode described in step II as the working electrode, the electrocatalytic performance of the oxygen reduction reaction of the sample was tested in a 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 4 As shown, the half-wave potential is 0.809 V vs. RHE;

[0082] Step V: Using high-purity graphite carbon rod as counter electrode, Ag / AgCl as reference electrode, and the completely dried nickel foam described in step III as working electrode, the electrocatalytic performance of the sample for oxygen evolution reaction was tested in 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 5 As shown, the overpotential is 455.6 mV vs. RHE.

[0083] Example 3

[0084] The following shows the preparation method and performance test results of the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0085] 1. Preparation

[0086] Step 1: Mix 20 mL of N-methylpyrrolidone and 20 mL of mesitylene in equal proportions in a hydrothermal autoclave and introduce inert gas for 30 min until saturated to obtain an organic solution;

[0087] Step 2: 9 mmol of pyromellitic anhydride, 11 mmol of melamine, 1.5 mmol of Fe(NO3)3·9H2O and 2 mL of isoquinoline were added to the organic solution and stirred until it turned into a brick red solution;

[0088] Step 3: The brick-red solution was hydroheated at 210° C. for 24 h, and N-methylpyrrolidone, anhydrous ethanol and distilled water were used as washing solutions, respectively, and centrifuged at a speed of 8000 r / min for 5 min, and each washing solution was repeated 3 times, and then freeze-dried to obtain a brown solid;

[0089] Step 4: The brown solid was calcined at 500°C for 3 h and then at 900°C for 3 h under N2 atmosphere at a heating rate of 5°C / min to obtain a PI-COF / Fe--24 h oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0090] 2. Performance Testing

[0091] Step I: 4 mg of the PI-COF / Fe--24 h oxygen reduction / oxygen evolution reaction bifunctional catalyst was added to 1000 μL of a dispersion prepared by 250 μL of ethanol and 750 μL of distilled water, and after ultrasonication for 20 min, 20 μL of nafion was added and ultrasonication was continued for another 20 min to form an ink-like slurry;

[0092] Step II: Measure 20 μL of the ink-like slurry and drop it onto the surface of the rotating disk electrode and wait for it to completely dry;

[0093] Step III: Another 20 μL of the ink-like slurry was measured and dropped onto the nickel foam (1 cm×1 cm), and then allowed to dry completely;

[0094] Step IV: Using platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the completely dried rotating disk electrode described in step II as the working electrode, the electrocatalytic performance of the oxygen reduction reaction of the sample was tested in a 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 4 As shown, the half-wave potential is 0.828 V vs. RHE;

[0095] Step V: Using high-purity graphite carbon rod as counter electrode, Ag / AgCl as reference electrode, and the completely dried nickel foam described in step III as working electrode, the electrocatalytic performance of the sample for oxygen evolution reaction was tested in 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 5 As shown, the overpotential is 441.6 mV vs. RHE.

[0096] Comparative Example 1

[0097] The following shows the preparation method and performance test results of the PI-COF oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0098] 1. Preparation

[0099] Step 1: Mix 20 mL of N-methylpyrrolidone and 20 mL of mesitylene in equal proportions in a hydrothermal autoclave and introduce inert gas for 30 min until saturated to obtain an organic solution;

[0100] Step 2: Add 9 mmol of pyromellitic anhydride, 11 mmol of melamine and 2 mL of isoquinoline to the organic solution and stir until the solution turns into a light yellow solution;

[0101] Step 3: The light yellow solution was hydroheated at 210°C for 72 h, and N-methylpyrrolidone, anhydrous ethanol and distilled water were used as washing liquids, respectively, and centrifuged at a speed of 8000 r / min for 5 min. Each washing liquid was repeated 3 times, and then freeze-dried to obtain a brown solid, i.e., the PI-COF oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0102] 2. Performance Testing

[0103] Step I: 4 mg of the PI-COF oxygen reduction / oxygen evolution reaction bifunctional catalyst was added to 1000 μL of a dispersion prepared by 250 μL of ethanol and 750 μL of distilled water, and after ultrasonication for 20 min, 20 μL of nafion was added and ultrasonication was continued for another 20 min to form an ink-like slurry;

[0104] Step II: Measure 20 μL of the ink-like slurry and drop it onto the surface of the rotating disk electrode and wait for it to completely dry;

[0105] Step III: Using platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the completely dried rotating disk electrode described in step II as the working electrode, the electrocatalytic performance of the oxygen reduction reaction of the sample was tested in a 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 4 As shown, the half-wave potential is 0.612 V vs . RHE.

[0106] Comparative Example 2

[0107] The following shows the preparation method and performance test results of the PI-COF / Fe-NPY oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0108] 1. Preparation

[0109] Step 1: Mix 20 mL of N-methylpyrrolidone and 20 mL of mesitylene in equal proportions in a hydrothermal autoclave and introduce inert gas for 30 min until saturated to obtain an organic solution;

[0110] Step 2: 9 mmol of pyromellitic anhydride, 11 mmol of melamine, 1.5 mmol of Fe(NO3)3·9H2O and 2 mL of isoquinoline were added to the organic solution and stirred until it turned into a brick red solution;

[0111] Step 3: The brick-red solution was subjected to hydrothermal reaction at 210°C for 72 h, and N-methylpyrrolidone, anhydrous ethanol and distilled water were used as washing solutions, respectively, and centrifuged at a speed of 8000 r / min for 5 min. Each washing solution was repeated 3 times, and then freeze-dried to obtain a brown solid, namely the PI-COF / Fe-NPY oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0112] 2. Performance Testing

[0113] Step I: 4 mg of the PI-COF / Fe-NPY oxygen reduction / oxygen evolution reaction bifunctional catalyst was added to 1000 μL of a dispersion prepared by 250 μL of ethanol and 750 μL of distilled water, and after ultrasonication for 20 min, 20 μL of nafion was added and ultrasonication was continued for another 20 min to form an ink-like slurry;

[0114] Step II: Measure 20 μL of the ink-like slurry and drop it onto the surface of the rotating disk electrode and wait for it to completely dry;

[0115] Step III: Using platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the completely dried rotating disk electrode described in step II as the working electrode, the electrocatalytic performance of the oxygen reduction reaction of the sample was tested in a 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 4 As shown, the half-wave potential is 0.586 V vs. RHE.

[0116] Comparative Example 3

[0117] The following shows the preparation method and performance test results of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0118] 1. Preparation

[0119] Step 1: 20 mL of N-methylpyrrolidone (NMP) and 20 mL of mesitylene were mixed in equal proportions in a hydrothermal autoclave and an inert gas was introduced for 30 min until saturation to obtain an organic solution;

[0120] Step 2: adding 9 mmol of pyromellitic anhydride, 11 mmol of melamine and 0.5 mmol of Fe(NO3)3·9H2O to the organic solution and stirring until the solution turns into a brick red color;

[0121] Step 3: subjecting the brick-red solution to a hydrothermal reaction at 210° C. for 72 h, using N-methylpyrrolidone, anhydrous ethanol and distilled water as washing solutions, respectively, and centrifuging at a speed of 8000 r / min for 5 min, repeating each washing solution for 3 times, and then freeze-drying to obtain a brown solid;

[0122] Step 4: The brown solid was calcined at 500°C for 3 h and then at 900°C for 3 h under N2 atmosphere at a heating rate of 5°C / min to obtain a PI-COF / Fe-202(N) oxygen reduction / oxygen evolution reaction bifunctional catalyst.

[0123] 2. Performance Testing

[0124] Step I: 4 mg of the PI-COF / Fe-202(N) oxygen reduction / oxygen evolution reaction bifunctional catalyst was added to 1000 μL of a dispersion prepared by 250 μL of ethanol and 750 μL of distilled water, and after ultrasonication for 20 min, 20 μL of nafion was added and ultrasonication was continued for another 20 min to form an ink-like slurry;

[0125] Step II: Measure 20 μL of the ink-like slurry and drop it onto the surface of the rotating disk electrode and wait for it to completely dry;

[0126] Step III: Using platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the completely dried rotating disk electrode described in step II as the working electrode, the electrocatalytic performance of the oxygen reduction reaction of the sample was tested in a 0.1 mol / L KOH aqueous solution. The test results are as follows: Figure 4 As shown, the half-wave potential is 0.596 V vs. RHE.

[0127] 3. Results and Discussion

[0128] Figure 1 This is a scanning electron microscope image of the PI-COF oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Comparative Example 1. It can be clearly seen from the image that PI-COF is composed of multiple two-dimensional sheets stacked into a block structure. Figure 2 This is a scanning electron microscope image of the PI-COF / Fe-202 oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Example 1 of the present invention. From the image, it can be seen that the doping of iron elements thickens the layered structure, the outermost layer forms a scale-like network structure, and a plurality of small particles are formed. Figure 3 This is a scanning electron microscope image of the PI-COF / Fe-606 oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared in Example 2 of the present invention. From the image, it can be clearly seen that the iron element is dispersed in the layered PI-COF structure in the form of small particles with a high degree of dispersion.

[0129] Figure 4It is a schematic diagram of the ORR electrochemical performance of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention. It can be seen from the figure that the half-wave potentials of the oxygen reduction / oxygen evolution reaction bifunctional catalysts prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, Example 1, Example 2 and Example 3 are 0.612 V, 0.586 V, 0.596 V, 0.751 V, 0.809 V and 0.828 V, respectively. The results show that the doping of iron elements can greatly improve the performance of PI-COF electrocatalytic oxygen reduction, and with the increase of the amount of iron element doping, the oxygen reduction electrochemical performance of the prepared Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst is further enhanced. Secondly, the hydrothermal time is also one of the important factors affecting the oxygen reduction electrochemical performance of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst. In particular, when the Fe doping amount is 1.5 mmol, the oxygen reduction electrochemical performance of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst obtained by hydrothermal treatment at 210°C for 24 h is the best.

[0130] Figure 5 Schematic diagram of the electrochemical performance of the oxygen evolution reaction (OER) of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst of the present invention. It can be seen that the overpotentials of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalysts prepared in Example 1, Example 2 and Example 3 are 509.6 mV, 455.6 mV and 441.6 mV, respectively. The results show that with the increase of the amount of iron doping, the electrochemical performance of the oxygen evolution reaction of the prepared Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst is further enhanced. Secondly, the hydrothermal time is also one of the important factors affecting the electrochemical performance of the oxygen evolution reaction of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst. In particular, when the Fe doping amount is 1.5 mmol, the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst obtained by hydrothermal treatment at 210°C for 24 h has the best electrochemical performance of oxygen evolution reaction.

[0131] In summary, the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst prepared by the present invention shows excellent oxygen reduction electrochemical performance, oxygen evolution reaction electrochemical performance and stability. In addition, the preparation method of the present invention has the advantages of easy availability of raw materials, low equipment cost, simple operation, short time consumption, and suitability for industrial production and promotion.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, characterized in that: The following steps are involved: (1) introducing an inert gas into an organic solvent until saturated, adding a dianhydride, a diamine, an iron compound and a cyclization promoter into the organic solvent, and stirring to obtain a mixed solution, wherein the molar ratio of the dianhydride, the diamine and the iron compound is (5-9):(7-11):(0.5-1.8), the volume ratio of the cyclization promoter to the organic solvent is (1-5):(10-50), and the cyclization promoter comprises quinoline or a quinoline derivative; (2) subjecting the mixed solution to a hydrothermal reaction, and centrifuging and drying to obtain a solid, wherein the hydrothermal reaction temperature is 100-220° C., and the time is 1-100 h; (3) calcining the solid to obtain the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, wherein the calcination temperature is 300-1200° C., the calcination time is 2-10 h, and the heating rate is 2-10° C. / min.

2. The method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst according to claim 1, characterized in that: The organic solvent includes at least one of N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, acetone, tetrahydrofuran, benzene, toluene, xylene, mesitylene or diethyl ether.

3. The method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst according to claim 1, characterized in that: The organic solvent is N-methylpyrrolidone and mesitylene, wherein the volume ratio of the N-methylpyrrolidone to the mesitylene is (0.5-10):

1.

4. The method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst according to claim 1, characterized in that: The dianhydride includes at least one of pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic anhydride, perylene 3,4,9,10-tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride or 1,2,3,4-cyclobutanetetracarboxylic dianhydride; the diamine includes at least one of melamine, phenylenediamine, benzimidazole diamine, 4,4'-diaminodiphenylmethane or 2,2-bis[4-(4-aminophenoxy)phenyl]propane; the iron compound includes at least one of ferric chloride, ferric nitrate, ferric sulfate, ferric oxide or ferroferric oxide.

5. The method for preparing the hydrogen bond enhanced Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst according to claim 1, characterized in that: In step (3), the calcination is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, argon or a hydrogen-argon mixture.

6. Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the Fe-NC oxygen reduction / oxygen evolution reaction bifunctional catalyst according to claim 6 in energy conversion devices.

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