Preparation method of silk-derived self-supported catalytic electrode

Abstract

The invention provides a preparation method of a silk-derived self-supported catalytic electrode, and belongs to the technical field of electrodes. The preparation method comprises the following steps: by taking silk cloth as a carrier, soaking the silk cloth in a cobalt nitrate solution, then adding a dimethylimidazole solution to complete growth loading of ZIF-67, cleaning and drying, putting the silk cloth at a downstream position of a tubular furnace, simultaneously filling a phosphating agent at the downstream position of the tubular furnace, heating to 500-800 DEG C in an inert atmosphere, and carrying out calcination phosphating, so as to obtain the ZIF-67 composite material. The phosphorizing agent is any one of sodium phosphite, monopotassium phosphate and sodium dihydrogen phosphate, and the silk-derived self-supported catalytic electrode with the three-dimensional network structure is obtained. The obtained electrode is used for electrolyzed water catalysis and has good catalytic activity.

Description

Technical Field

[0001] The present application relates to a method for preparing a silk-derived self-supporting catalytic electrode, belonging to the field of electrode technology. Background Art

[0002] Silk material can be transformed into nitrogen-doped carbon material through high-temperature heat treatment. This carbon material has good flexibility and conductivity and is widely used in the development and application of flexible wearable electronic devices. However, it is rarely used in catalytic electrodes and further research and development is still needed.

[0003] Since silk-derived carbon materials have good flexibility, they can be developed into self-supporting electrodes, such as those used in water electrolysis catalysis, eliminating the tedious preparation process of granular catalyst electrodes and the influence of nafilon solution on catalyst materials during electrode preparation. However, there is a problem: silk-derived carbon materials have low activity in oxygen evolution in water electrolysis, so their catalytic efficiency needs to be improved if they are used directly as electrode materials. Summary of the invention

[0004] In view of this, the present application provides a method for preparing a silk-derived self-supporting catalytic electrode, wherein the prepared electrode is loaded with catalytically active substances and has good catalytic activity.

[0005] Specifically, the present application is implemented through the following scheme: A method for preparing a silk-derived self-supporting catalytic electrode comprises the following steps: taking silk cloth as a carrier, immersing the silk cloth in a cobalt nitrate solution, adding a dimethyl imidazole solution to complete the growth loading of ZIF-67, washing and drying the silk cloth, placing the silk cloth at a downstream position of a tubular furnace, and simultaneously adding a phosphating agent at the downstream position of the tubular furnace. The silk cloth is heated to 500-800° C. in an inert atmosphere for calcination and phosphating for 4-6 hours to obtain a silk-derived self-supporting catalytic electrode with a three-dimensional network structure, wherein the phosphating agent is any one of sodium phosphite, potassium dihydrogen phosphate and sodium dihydrogen phosphate, and the mass ratio of the phosphating agent to the silk cloth in the tubular furnace is 3-10:1.

[0006] The above preparation method is simple to operate, controllable, low-cost, and has good economic benefits; at the same time, the prepared self-supporting water electrolysis catalytic electrode achieves a significant improvement in catalytic performance. The electrode membrane has a three-dimensional network structure and has great application potential in water electrolysis, battery electrodes, etc.

[0007] Further, as a preference: The concentration of the cobalt acetate solution is 0.1-1 mol / L.

[0008] Using any one of methanol, ethanol and water or a mixture of more than one of them as a solvent, dissolving cobalt nitrate hexahydrate in the solvent to obtain a cobalt acetate solution.

[0009] The concentration of the dimethylimidazole solution is 0.4-4 mol / L.

[0010] The dimethylimidazole solution uses methanol, ethanol and water or a mixture of more than one of them as solvent.

[0011] The inert atmosphere is nitrogen or argon.

[0012] The mass ratio of the phosphating agent to the silk cloth is 5-8:1, and 5:1 is the best.

[0013] The silk cloth is silk non-woven cloth, silk knitted cloth or silk woven cloth.

[0014] The silk-derived self-supported catalytic electrode is used for water electrolysis catalysis.

[0015] Compared with the prior art, the preparation method of the present application has the following advantages: First, the silk-derived electrode prepared by the present invention is a self-supporting flexible electrode and can be directly used for water electrolysis catalysis.

[0016] Second, the silk fabrics used in the present invention are common non-woven fabrics, knitted fabrics and woven fabrics in the market, which will be conducive to the high-value recycling of waste silk fabrics.

[0017] Third, the present invention utilizes the three-dimensional network structure of the fabric to impart corresponding properties to the product, thereby facilitating the desorption of product gas from the electrode during the catalytic process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a scanning electron microscope image of the flexible self-supporting electrode material CoP@NC@CF obtained in Example 1.

[0020] Figure 2 This is a scanning electron microscope image of the silk non-woven fabric-derived carbon material CF obtained in Comparative Example 1.

[0021] Figure 3 This is a comparison chart of the LSV test results of the catalytic oxygen evolution performance of water electrolysis of CoP@NC@CF of Example 1 and CF of Comparative Example 1.

[0022] Figure 4This is a comparison chart of the LSV test results of the catalytic hydrogen evolution performance of CoP@NC@CF in Example 1 and CF in Comparative Example 1. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below in conjunction with the drawings in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0024] Example 1

[0025] The method for preparing the silk-derived self-supporting water electrolysis catalytic electrode in this embodiment is as follows: Weigh 2.18 g (7.5 mmol) of cobalt nitrate hexahydrate (Co(NO3)2⋅6H2O) and add it to 75 mL of methanol until it is completely dissolved to obtain a cobalt nitrate solution with a concentration of 0.1 mol / L. Immerse the silk non-woven fabric in the cobalt nitrate solution and let it stand for 12 hours. Weigh 2.46 g (30 mmol) of 2-methylimidazole (2-MIM) and add it to 75 mL of methanol until it is completely dissolved to obtain a 0.4 mol / L 2-methylimidazole solution. Add the 2-methylimidazole solution to the solution of step (1) to carry out the growth loading of the metal organic framework material ZIF-67 for about 6 hours; (3) After cleaning and drying the silk cloth loaded with ZIF-67 particles, 1 g of the silk cloth was placed in the downstream position of the tube furnace, and 5 g of potassium dihydrogen phosphate was placed in the upstream position. In a nitrogen atmosphere, the temperature was increased to 800 °C at a heating rate of 5 °C / min and kept at this temperature for 4 h to obtain a flexible self-supporting electrode material CoP@NC@CF.

[0026] Example 2

[0027] The method for preparing the silk-derived self-supporting water electrolysis catalytic electrode in this embodiment is as follows: Weigh 2.18 g (7.5 mmol) of cobalt nitrate hexahydrate (Co(NO3)2⋅6H2O) and add it to 75 mL of methanol until it is completely dissolved to obtain a cobalt nitrate solution with a concentration of 0.1 mol / L. Immerse the silk non-woven fabric in the cobalt nitrate solution and let it stand for 12 hours. Weigh 2.46 g (30 mmol) of 2-methylimidazole (2-MIM) and add it to 75 mL of methanol until it is completely dissolved to obtain a 0.4 mol / L 2-methylimidazole solution. Add the 2-methylimidazole solution to the solution in step (1) to carry out the growth loading of ZIF-67 for about 6 hours. After the silk cloth loaded with ZIF-67 particles was cleaned and dried, 1 g of the silk cloth was placed in the downstream position of the tube furnace, and 5 g of sodium dihydrogen phosphate was placed in the upstream position; in a nitrogen atmosphere, the temperature was increased to 600 °C at a heating rate of 5 °C / min and kept for 4 hours to obtain a flexible self-supporting electrode material CoP@NC@CF.

[0028] Comparative Example 1

[0029] The preparation process of this comparative example product comprises the following steps: The silk nonwoven fabric was immersed in the methanol solution and allowed to stand for 12 h; (2) After 1 g of silk cloth soaked in methanol solution was washed and dried, it was placed in the downstream position of a tubular furnace, and 5 g of potassium dihydrogen phosphate was placed in the upstream position; in a nitrogen atmosphere, the temperature was increased to 800 °C at a heating rate of 5 °C / min and kept at this temperature for 4 h, and then a silk non-woven fabric-derived carbon material CF was obtained.

[0030] Figure 1 Scanning electron microscope image of the silk-derived self-supporting electrolytic water catalytic electrode prepared in Example 1: A large number of particles are loaded on the surface of the fiber. This shows that the scheme is conducive to the growth of ZIF-67 particles on the surface of silk fibers, and high-temperature carbonization and phosphating are carried out simultaneously, and they do not fall off during this process.

[0031] Figure 2 Scanning electron microscopy image of the silk-derived carbon material CF prepared in Comparative Example 1: Although there are a small amount of CoP@NC particles on the fabric surface, the number is significantly less than Figure 1 The particle loading in the solution is relatively large and the distribution is obviously uneven, indicating that immersion in cobalt nitrate solution is of great significance for the loading of ZIF-67 on the surface of silk fibers.

[0032] The electrode obtained in Example 2 was tested. The phosphating agent and phosphating conditions used were different from those in Example 1, but ZIF-67 particles were also successfully loaded and grown. The grown ZIF-67 did not fall off due to the influence of high-temperature phosphating, and the catalytic performance was consistent with that in Example 1.

[0033] The products obtained in Example 1 and Comparative Example 1 were tested for oxygen evolution and hydrogen evolution performance by electrolysis of water. The test process is as follows: The electrochemical performance tests were all completed at room temperature using a standard three-electrode system. In the three-electrode system, a graphite rod was used as the counter electrode, Hg / HgO was used as the reference electrode, and an electrode clip was used as the working electrode. The test electrolyte was 1.0 M KOH solution. The catalytic oxygen and hydrogen evolution performance of the samples was obtained by LSV polarization curves with a scan rate of 5 mVs -1 The performance of oxygen and hydrogen evolution is measured by overpotential, and the smaller the overpotential, the higher the electrocatalytic activity.

[0034] The test results of oxygen evolution performance of electrolyzed water are as follows: Figure 3 As shown in Figure 1, there are significant differences in the electrolysis and oxygen evolution performance of the silk-derived carbon materials prepared in Example 1 and Comparative Example 1. The overpotential of CoP@NC@CF in Example 1 is 250 mV ( Figure 3 10 mA / cm for the middle blue line 2 The corresponding horizontal axis is 1.48V, and the converted overpotential is: 1.48-1.23=0.25V, i.e. 250mV). The CF overpotential of comparative example 1 is 380 mV ( Figure 3 10 mA / cm for the middle green line 2 The corresponding horizontal axis is 1.61V, and the converted overpotential is: 1.61-1.23=0.38V, or 380mV).

[0035] The test results of hydrogen evolution performance of water electrolysis are as follows Figure 4 As shown: the overpotentials of the CoP@NC@CF prepared in Example 1 and the CF material prepared in Comparative Example 1 in the LSV test of hydrogen evolution by electrolysis of water are 220 mV ( Figure 4 10 mA / cm for the middle blue line 2 The corresponding horizontal axis is 0.22V, that is, 220mV) and 300mV ( Figure 4 10 mA / cm for the middle green line 2 The corresponding horizontal axis is 0.3V, i.e. 300mV).

[0036] In summary, the hydrogen and oxygen evolution performances of the flexible self-supporting electrode material CoP@NC@CF prepared in Example 1 are better than those of the pure silk-derived carbon material CF prepared in Comparative Example 1. This indicates that the ZIF-67-derived CoPCoP@NC is a catalytically active substance. In addition, the silk and the ZIF-67 supported and grown thereon cooperate with each other, giving the silk-derived material obtained in Example 1 a three-dimensional network structure, which is conducive to the catalytic process and the timely desorption of the product gas.

[0037] The above-mentioned embodiments only express several feasible implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention, and the embodiments are not used to limit the scope of protection in the claims of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and all equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A method for preparing a silk-derived self-supporting catalytic electrode, characterized in that: Silk cloth is used as a carrier, immersed in a cobalt nitrate solution, and then a dimethylimidazole solution is added to complete the growth load of ZIF-67, and then it is washed and dried, and arranged at the downstream position of a tubular furnace. At the same time, a phosphating agent is loaded at the downstream position of the tubular furnace, and the temperature is raised to 500-800°C in an inert atmosphere for calcination and phosphating for 4-6 hours to obtain a silk-derived self-supporting catalytic electrode with a three-dimensional network structure. The phosphating agent is any one of sodium phosphite, potassium dihydrogen phosphate, and sodium dihydrogen phosphate. The mass ratio of the phosphating agent to the silk cloth in the tubular furnace is 3-10:

1.

2. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: The concentration of the cobalt acetate solution is 0.1-1 mol / L.

3. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: Using any one of methanol, ethanol and water or a mixture of more than one of them as a solvent, dissolving cobalt nitrate hexahydrate in the solvent to obtain a cobalt acetate solution.

4. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: The concentration of the dimethylimidazole solution is 0.4-4 mol / L.

5. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: The dimethylimidazole solution uses methanol, ethanol and water or a mixture of more than one of them as solvent.

6. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: The inert atmosphere is nitrogen or argon.

7. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: The mass ratio of phosphating agent to silk cloth is 5~8:

1.

8. The method for preparing a silk-derived self-supporting catalytic electrode according to claim 1, characterized in that: The silk cloth is silk non-woven cloth, silk knitted cloth or silk woven cloth.

9. A method for preparing a silk-derived self-supporting catalytic electrode according to any one of claims 1 to 8, characterized in that: The silk-derived self-supporting catalytic electrode is used for water electrolysis catalysis.

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