Preparation method of three-dimensional structure egg membrane / cobalt-nickel composite electrode material

Abstract

The application discloses a preparation method of a three-dimensional structure eggshell membrane / cobalt-nickel / graphene composite electrode material. The method comprises the following steps: taking an eggshell membrane as a template substance, preparing nickel and cobalt through a hydrothermal method, and then reacting the three substances at high temperature to prepare a precursor, and finally preparing the composite material through sintering. The three substances, i.e. the skeleton matrix of the carbonized eggshell membrane, cobalt and nickel and graphene, are synergistically used, which not only reduces the disadvantage that metal particles are prone to agglomeration in the preparation process, but also optimizes the electronic configuration and reaction path of the unique three-dimensional skeleton matrix, greatly improving the electrochemical performance. The preparation method of the above material is simple and controllable, has low preparation temperature, is environment-friendly and pollution-free, has low cost, and is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano materials technology and relates to a method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material. Background Technology

[0002] The development of fuel cells has pointed the way to solving the problem of sustainable energy and environmental development for humanity. In practical fuel cells, although the oxygen reduction reaction (ORR) occurs at the cathode, its rate is extremely low. To address this issue, a catalyst needs to be added to the cathode to increase the ORR rate. Currently, the catalysts used in fuel cell technology are primarily platinum-carbon (Pt / C) catalysts because they can effectively increase the ORR rate. However, the scarcity and high cost of platinum significantly limit its large-scale application in fuel cells. Therefore, replacing precious metal catalysts with non-precious metal catalysts is necessary.

[0003] Non-precious metal catalysts have made rapid progress in terms of activity and performance. Among them, non-precious metal catalysts containing Fe, Co, and Ni exhibit catalytic activity almost approaching that of Pt / C catalysts. Meanwhile, carbon doping and the design of three-dimensional templates have also enabled composite electrodes to possess high conductivity and good electrochemical catalytic performance. Due to the strong adsorption capacity of cobalt-nickel alloys for OH*, extensive experimental research has been conducted on their use as oxygen reduction catalysts. However, during the preparation process, cobalt-nickel alloys suffer from poor electrochemical performance due to easy agglomeration, low exposure of active sites, and poor stability, hindering their application.

[0004] Therefore, it is necessary to find a catalyst that is low in cost, has good stability, and good electrochemical performance to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention aims to provide a method for preparing a three-dimensional egg membrane / cobalt-nickel / graphene composite electrode material. By carbonizing the egg membrane and using it as a three-dimensional framework substrate, it not only has a large specific surface area, exposing a large number of active sites, which is beneficial for electron mass transfer, but also plays an anchoring role for the cobalt-nickel alloy. Graphene is a two-dimensional carbon material with the advantages of large specific surface area and good conductivity. The composite of cobalt-nickel alloy particles can optimize the electronic configuration and reaction pathway of the carbon framework, improve the conductivity of the catalyst. The synergistic effect of the egg membrane, cobalt-nickel, and graphene not only reduces the disadvantage of easy agglomeration of metal particles during the preparation process, but also optimizes the electronic configuration and reaction pathway of the unique three-dimensional framework substrate, greatly improving the electrochemical performance. The preparation method of the above material is simple and controllable, with low preparation temperature, environmentally friendly and pollution-free, low cost, and suitable for industrial production.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material comprises the following steps in sequence:

[0008] S1. Mix cobalt nitrate solution, nickel nitrate solution, urea solution, and hydrazine hydrate solution with a mass concentration of 80%. After sealing, carry out the water bath reaction in a water bath at 40-90°C, stir and heat for 2 hours to obtain A.

[0009] S2. Cool A to room temperature, remove the cobalt and nickel from the solution, and wash it several times with alcohol and deionized water to obtain B;

[0010] S3. Place B in deionized water and ultrasonically disperse for 0.5 h, add graphene oxide solution and wet egg membrane, and react in a 120℃ reactor for 8-12 h to obtain a black cobalt-nickel / graphene composite material suspension, thus obtaining C.

[0011] S4. Wash C three times with deionized water, then dry it at 60℃ to obtain D;

[0012] S5. D is placed inside the quartz tube of a tube-type resistance furnace and heated. After sintering under a nitrogen atmosphere, a black egg membrane / cobalt-nickel / graphene composite material is obtained.

[0013] As a first limitation of the present invention, in step S1, the molar ratio of the cobalt nitrate solution, nickel nitrate solution, urea solution and hydrazine hydrate solution is 1:1:2.3:4.6.

[0014] In this invention, the ratio of cobalt nitrate solution, nickel nitrate solution, and urea solution affects the size of the synthesized cobalt-nickel particles, and thus affects the composite structure and properties of the composite material.

[0015] As a second limitation of the present invention, in step S3, the mass ratio of B, graphene oxide and wet egg membrane is 4:30:4.

[0016] In this step, B, the graphene oxide solution, and the wet egg membrane undergo self-assembly, and the ratio of the three affects the structure of the composite material.

[0017] As a third limitation of the present invention, in step S5, the sintering temperature is 600℃~750℃, and the holding time is 1~2h.

[0018] In step S5, the sintering process involves the carbonization of the egg membrane. The sintering temperature and holding time affect the decomposition of the internal biological material. When the sintering temperature is greater than 750°C, the internal three-dimensional structure will collapse. When the sintering temperature is less than 600°C, the biological material will not decompose completely. When the holding time is greater than 2 hours, the three-dimensional template will collapse after carbonization. When the holding time is less than 1 hour, the biological material will decompose incompletely.

[0019] As a fourth limitation of the present invention, in step S5, the size of the cobalt-nickel alloy in the egg membrane / cobalt-nickel / graphene composite material is approximately 1 μm.

[0020] As a fifth limitation of the present invention, in step S5, the egg membrane / cobalt-nickel / graphene composite material has a three-dimensional network structure.

[0021] This invention also has a limitation: the egg membrane / cobalt-nickel / graphene composite material obtained in step S5 is prepared into an electrode material according to the following steps:

[0022] (1) Clean the glassy carbon working electrode to eliminate the influence of residual samples from the previous experiment on the results of this experiment;

[0023] (2) Weigh 10 mg of egg membrane / cobalt nickel / graphene composite material, place it in a small sample tube, add 1 mL of ethanol solution, and then place it in an ultrasonic cleaner and sonicate for 1 h to obtain the sample solution.

[0024] (3) Use a micro-volume extractor to take 5 μL of sample solution, then dry it in an electric heating drying oven at 60°C. After drying, use a micro-volume extractor to take 2 μL of professional glue to coat it, and let it air dry naturally to obtain the final electrode material.

[0025] The above-mentioned technical solution of the present invention is as a whole, and the various steps are interconnected and all jointly affect the morphology, structure and properties of the final material.

[0026] The beneficial effects achieved by the present invention after adopting the above technical solution are as follows:

[0027] (1) In this invention, biological egg membrane is used as a template. After carbonization, it has a good three-dimensional network structure and forms a good interface with the active material, which can effectively improve the electrochemical performance of the product.

[0028] (2) The cobalt-nickel / graphene composite electrode material prepared by the method of the present invention has a large specific surface area, better conductivity and mechanical properties, and can exhibit better comprehensive performance and practicality when used as a cathode electrode material for fuel cells.

[0029] (3) Compared with the prior art, the preparation process of the present invention is simple, easy to implement and controllable, with low preparation temperature and low cost, and is suitable for industrial production.

[0030] This invention is applicable to the preparation of egg membrane / cobalt-nickel / graphene composite materials, which can be further used as electrode materials.

[0031] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0032] Instruction manual illustrations

[0033] Figure 1 The image shows the XRD pattern of the composite material prepared in Example 1 of this invention.

[0034] Figure 2 Here is a SEM image of the composite material prepared in Example 1 of this invention;

[0035] Figure 3 The LSV diagram shows the composite material prepared in Example 1 of this invention and the composite material without added graphene oxide.

[0036] Figure 4 The graphs show the polarization curves of the composite material electrode prepared in Example 1 of this invention at different rotational rates.

[0037] Figure 5 The composite material electrode prepared in Example 1 of this invention under different voltages I -1 Relative to ω -1 / 2 The curve graph. Detailed Implementation

[0038] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents, and all experimental and detection methods used in the following embodiments are existing experimental and detection methods.

[0039] Example 1

[0040] This embodiment prepares a three-dimensional composite electrode material. The preparation method of the three-dimensional egg membrane / cobalt-nickel composite electrode material is carried out in the following order:

[0041] S1. Prepare 30 mL of cobalt nitrate solution (concentration 32 g / L), and add nickel nitrate solution (concentration 32 g / L, volume 30 mL), urea solution (concentration 2.4 g / L, volume 20 mL), 10 mL, and 80 wt% hydrazine hydrate solution in sequence. That is, the molar ratio of cobalt nitrate, nickel nitrate, urea, and hydrazine hydrate solution is 1:1:2.3:4.6. After sealing, carry out water bath reaction in a 70℃ water bath, stir and heat for 2 hours to obtain a cobalt-nickel suspension solution.

[0042] S2. Cool the solution containing suspended cobalt and nickel obtained in S1 to room temperature, remove the cobalt and nickel, and wash it several times with alcohol and deionized water respectively.

[0043] S3. Place the cobalt and nickel washed in S2 into 100 mL of deionized water and ultrasonically disperse for 0.5 h. Add 1 g / L of graphene oxide solution and 2 g of wet egg membrane according to the mass ratio of cobalt and nickel, graphene and wet egg membrane of 4:30:4. Then put it into a reaction vessel at 120℃ and react for 12 h to obtain a black suspension of cobalt and nickel / graphene composite material.

[0044] S4. The suspension of the black egg membrane / cobalt-nickel / graphene composite material obtained in S3 was washed three times with deionized water and then dried at 60°C.

[0045] S5. The product obtained in step S3 is placed in a tube furnace and heated to 600°C for 1 hour under a nitrogen atmosphere to obtain a black composite material of egg membrane / cobalt nickel / graphene.

[0046] The composite material was prepared into an electrode material according to the following steps:

[0047] (1) Clean the glassy carbon working electrode to eliminate the influence of residual samples from the previous experiment on the results of this experiment;

[0048] (2) Weigh 10 mg of egg membrane / cobalt nickel / graphene composite material, place it in a small sample tube, add 1 mL of ethanol solution, and then place it in an ultrasonic cleaner and sonicate for 1 h to obtain the sample solution.

[0049] (3) Use a micro-volume extractor to take 5 μL of sample solution, then dry it in an electric heating drying oven at 60°C. After drying, use a micro-volume extractor to take 2 μL of professional glue to coat it, and let it air dry naturally to obtain the final electrode material.

[0050] The prepared composite material (denoted as CoNi / ESM / rGO) and electrode material were subjected to a series of performance measurements, and the specific results are as follows.

[0051] Figure 1 The image shows the XRD pattern of the composite material prepared in this embodiment. It can be seen from the image that the main diffraction peak is graphene, and the weaker diffraction peak is the position of the diffraction peak of cobalt-nickel alloy. This fully demonstrates that the present invention has successfully synthesized cobalt-nickel alloy composite material.

[0052] Figure 2 The image shows a SEM image of the composite material prepared in this embodiment. It can be seen from the image that the material has a three-dimensional network structure, with nickel-cobalt metal composited on the surface of the three-dimensional network carbon skeleton structure. The particle size of the nickel-cobalt alloy in the composite material is about 1 μm.

[0053] Figure 3 The LSV comparison graphs show the composite material and the material without graphene oxide. The specific tests were conducted in a three-electrode testing system: the composite material was used as the working electrode, a platinum-carbon electrode as the control electrode, and Ag / AgCl as the reference electrode in a 0.1M potassium hydroxide solution. Cyclic voltammetry was performed at a scan rate of 20 mV·s. -1 The test was conducted under O2 immersion and at a rotation speed of 1600 rpm. The results show that the current density of the electrode after composite graphene oxide was combined with the composite material was higher than that of the uncomposite electrode.

[0054] Figure 4 The graph shows the polarization curves of the composite electrode at different rotation speeds. The test was conducted at rotating disk speeds of (900 r / min, 1225 r / min, 1600 r / min, and 2025 r / min). It can be seen from the graph that the current density increases with the increase of the rotating disk speed.

[0055] Figure 5 Composite electrode under different voltages I -1 Relative to ω -1 / 2 The curve is based on the KL formula and polarization curves. Figure 4 Calculations can yield I for each electrode under a fixed voltage. -1 Relative to ω -1 / 2 The slope of the electrode represents the number of electrons transferred at that electrode. Calculations show that the number of electrons transferred at this electrode is 3.3, meaning its catalytic reduction process occurs between 2 and 4 electrons.

[0056] Examples 2-4

[0057] In Examples 2-4, a three-dimensional composite electrode material was prepared. The preparation method of the three-dimensional egg membrane / cobalt-nickel composite electrode material was similar to that in Example 1, except that the parameters in the preparation process were different.

[0058]

[0059] Comparative Example

[0060] The following groups were prepared with composite electrode materials. The preparation process was similar to that in the examples, except that the process or parameters were different, as detailed below.

[0061] Group A: No wet egg membrane is added in step S3, and the rest of the preparation process is the same as in Example 1.

[0062] Group B: Steps S1 and S2 do not occur, that is, nickel-cobalt particles are not introduced, and step S3 occurs directly. Graphene oxide and wet egg membrane are directly reacted at high temperature and then sintered. These two steps are the same as in Example 1.

[0063] Group C: No graphene oxide solution was added in step S3; the rest of the preparation process was the same as in Example 1. The product was denoted as CoNi / ESM, and the specific performance test results are shown in the figure. Figure 3 As shown in the figure, the current density of this electrode is lower than that of the composite with added graphene oxide.

[0064] Group D: Instead of using wet egg membrane as the carrier, carbon black is used. The rest of the preparation process is the same as in Example 1.

[0065] Group E: In step S1, the sodium citrate reduction method is used instead of the hydrazine hydrate reduction method to prepare cobalt-nickel particles, and the rest of the preparation process is the same as in Example 1.

[0066] The materials prepared by the above AE group were used to prepare electrode materials and assembled into batteries. A series of electrochemical performance tests were conducted. The test process was the same as in Example 1. The specific test results are shown in the table below.

[0067]

[0068] As can be seen from the above tests, the three-dimensional composite electrode material of this invention exhibits excellent electrochemical performance. This is mainly due to the synergistic effect of the three-dimensional framework substrate after egg membrane carbonization, nickel-cobalt particles, and graphene oxide. The strong coupling between the carbon framework and graphene in the in-situ composite three-phase compound is beneficial for improving electron transport, thereby favoring the reaction kinetics of oxygen reduction. The three-phase composite structure allows the high specific surface area and conductivity of the carbon framework and graphene, along with the catalytic effect of the cobalt-nickel bimetallic compound, to work synergistically. Therefore, the prepared composite catalyst exhibits high electrocatalytic activity in alkaline solutions.

[0069] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a three-dimensional structured egg membrane / cobalt-nickel composite electrode material, characterized by, Follow these steps in sequence: S1. Mix cobalt nitrate solution, nickel nitrate solution, urea solution, and hydrazine hydrate solution with a mass concentration of 80%. After sealing, carry out the water bath reaction in a water bath at 40~90 ℃, stir and heat for 2 h to obtain A; S2. Cool A to room temperature, remove the cobalt and nickel from the solution, and wash it several times with alcohol and deionized water to obtain B; S3. Place B in deionized water and ultrasonically disperse for 0.5 h, add graphene oxide solution and wet egg membrane, and react in a 120℃ reactor for 8~12 h to obtain a black cobalt-nickel / graphene composite material suspension, which is C. S4. Wash C three times with deionized water, then dry it at 60 ℃ to obtain D; S5. Place D inside the quartz tube of a tubular resistance furnace and heat it. After sintering under a nitrogen atmosphere, a black egg membrane / cobalt-nickel / graphene composite material is obtained. The sintering temperature is 600 ℃~750 ℃, and the temperature is held for 1~2 h.

2. The method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material according to claim 1, characterized in that, In step S1, the molar ratio of the cobalt nitrate solution, nickel nitrate solution, urea solution, and hydrazine hydrate solution is 1:1:2.3:4.

6.

3. The method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material according to claim 1, characterized in that, In step S3, the mass ratio of B, graphene oxide, and wet egg membrane is 4:30:

4.

4. The method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material according to claim 1, characterized in that, In step S5, the size of the cobalt-nickel alloy in the egg membrane / cobalt-nickel / graphene composite material is 1 mm.

5. The method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material according to claim 1, characterized in that, In step S5, the egg membrane / cobalt-nickel / graphene composite material has a three-dimensional network structure.

6. A method for preparing a three-dimensional egg membrane / cobalt-nickel composite electrode material according to any one of claims 1-5, characterized in that, The egg membrane / cobalt-nickel / graphene composite material obtained in step S5 is then used to prepare an electrode material according to the following steps: (1) Clean the glassy carbon working electrode to eliminate the influence of residual samples from the previous experiment on the results of this experiment; (2) Weigh 10 mg of egg membrane / cobalt nickel / graphene composite material, place it in a small sample tube, add 1 mL of ethanol solution, and then place it in an ultrasonic cleaner and sonicate for 1 h to obtain the sample solution. (3) Use a micro-volume extractor to take 5 μL of sample solution, and then use an electric heating drying oven at 60 ℃ to dry it. After drying, use a micro-volume extractor to take 2 μL of professional glue to coat it, and let it air dry naturally to obtain the final electrode material.

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