A polypyrrole-coated multi-walled carbon nanotube electrocatalyst, a preparation method and application thereof
Patent Information
- Application Number
- CN202310570829.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-19
- Publication Date
- 2026-09-29
- Estimated Expiration
- 2043-05-19
AI Technical Summary
其次，由于金属原子容易聚集，催化剂表面的多金属活性中心的密度很难达到足够高的水平
[0021]1.本发明的聚吡咯包覆多壁碳纳米管电催化剂相较于单或多金属催化剂具有更持久的催化性能，在催化材料的合理利用和绿色能源等方面均展现出来巨大的潜力。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to a polypyrrole-coated multi-walled carbon nanotube electrocatalyst, its preparation method, and its application. Background Technology
[0002] Hydrogen peroxide (H2O2) is a very important chemical substance with wide applications in a range of industrial and healthcare fields, including disinfection, bleaching, and water treatment. The demand for H2O2 disinfectants has increased significantly, especially given the pandemic. Currently, industrial production of H2O2 mainly uses the traditional anthraquinone oxidation process (AOP), which is energy-intensive and causes significant pollution. Furthermore, to reduce transportation costs, the produced H2O2 is often in a high concentration, which inevitably introduces additional safety risks.
[0003] Therefore, developing a miniaturized, distributed, and energy-efficient H2O2 production process is of great and urgent significance for the sustainable development of H2O2-related industries. Electrocatalytic two-electron oxygen reduction reaction (2e... - -ORR (Optical Orbit Reduction) is considered a promising alternative to traditional AOP due to its energy-saving and environmentally friendly characteristics. In 2e - The ORR plays a crucial role in the production of H2O2, fundamentally determining the selectivity, yield, and stability of the entire process. Therefore, exploring advanced methods with these characteristics has become an important topic in this field.
[0004] Multi-site catalysts not only increase the number of active sites but also allow for broad tuning of the electronic structure of the material surface, effectively optimizing the adsorption of various reactants and intermediates, making them a subject of considerable interest. However, for 2e... - The research on ORR (Organic-Organic Catalysts) mainly focuses on the construction of active centers with multi-metal atom coordination, including homonuclear and heteronuclear metal atoms. However, the inherent problems of these metal-based multi-site catalysts may pose a significant obstacle to further improving their catalytic activity.
[0005] First, similar to metal-based catalysts, multi-site catalysts are also easily passivated in electrocatalytic reactions, especially by various oxygen-containing substances. Second, due to the tendency of metal atoms to aggregate, the density of multi-metal active sites on the catalyst surface is difficult to achieve a sufficiently high level. Therefore, although these metal-based multi-site catalysts typically exhibit high activity (2e... - While catalysts with high overpotential and high selectivity (such as those with negative overpotential and positive overpotential) often fail to achieve satisfactory hydrogen peroxide yields and electrocatalytic durability, constructing multi-site catalysts based on non-metallic active centers may be a feasible approach to address these issues. Summary of the Invention
[0006] The purpose of this invention is to address the technical deficiencies in the prior art by providing a polypyrrole-coated multi-walled carbon nanotube electrocatalyst.
[0007] Another object of the present invention is to provide a method for preparing a polypyrrole-coated multi-walled carbon nanotube electrocatalyst.
[0008] Another objective of this invention is to provide an application of a polypyrrole-coated multi-walled carbon nanotube electrocatalyst in the electrocatalytic oxygen reduction to prepare hydrogen peroxide.
[0009] The technical solution adopted to achieve the purpose of this invention is:
[0010] A method for preparing a polypyrrole-coated multi-walled carbon nanotube electrocatalyst includes the following steps: dispersing multi-walled carbon nanotubes in deionized water and stirring to obtain a multi-walled carbon nanotube dispersion; sequentially adding pyrrole monomer, hydrogen peroxide, and ammonium persulfate aqueous solution to the multi-walled carbon nanotube dispersion and continuously stirring to obtain a dispersion; centrifuging and washing the dispersion; and freeze-drying the obtained product to obtain the polypyrrole-coated multi-walled carbon nanotube electrocatalyst.
[0011] In the above technical solution, the mass ratio of the multi-walled carbon nanotubes to the pyrrole monomer is 1:(0-2), and the mass of the pyrrole monomer is not 0.
[0012] In the above technical solution, the hydrogen peroxide is an aqueous solution with a mass fraction of 30%, and the mass ratio of pyrrole monomer to hydrogen peroxide is 1:(10-20).
[0013] In the above technical solution, the mass ratio of the pyrrole monomer to the ammonium persulfate aqueous solution is 1:(2-5).
[0014] In the above technical solution, the continuous stirring of the dispersion is carried out in an ice-water bath at 0 degrees Celsius for 3-12 hours.
[0015] In the above technical solution, the dispersion is washed by centrifugation using deionized water, methanol, and acetone, respectively.
[0016] In the above technical solution, the freeze-drying of the product is performed by vacuum freezing.
[0017] Another aspect of the present invention includes a polypyrrole-coated multi-walled carbon nanotube electrocatalyst obtained using the preparation method described above.
[0018] Another aspect of the present invention includes the application of the polypyrrole-coated multi-walled carbon nanotube electrocatalyst in the preparation of hydrogen peroxide. The polypyrrole-coated multi-walled carbon nanotube electrocatalyst is uniformly dispersed in a mixed solution containing nafion, isopropanol and water to obtain a slurry with a concentration of 2-10 mg / mL. The slurry is drop-coated onto a glassy carbon electrode on a rotating disk electrode and dried at room temperature to obtain a glassy carbon electrode loaded with a graphene mesoporous electrocatalyst containing multiple pyrrole nitrogen atoms. Using an aqueous solution of KOH as the electrolyte, the glassy carbon electrode containing the polypyrrole-coated multi-walled carbon nanotube electrocatalyst is used as the working electrode to electrocatalyze the reduction of oxygen to prepare hydrogen peroxide.
[0019] In the above technical solution, the volume ratio of nafion, isopropanol and water is (3-5):20:(75-77).
[0020] Compared with the prior art, the beneficial effects of the present invention are:
[0021] 1. The polypyrrole-coated multi-walled carbon nanotube electrocatalyst of the present invention has more durable catalytic performance compared with single or multi-metal catalysts, and shows great potential in the rational utilization of catalytic materials and green energy.
[0022] 2. Compared with metal atom catalysts, the polypyrrole-coated multi-walled carbon nanotube electrocatalyst of the present invention has a large number of oxygen-containing functional groups introduced into the surface of polypyrrole due to the chemical oxidation method used in the polymerization process. Together with the large number of nitrogen atoms regularly arranged in the polypyrrole structure, they form a large number of highly active sites. By directly introducing the polypyrrole active sites containing oxygen and regularly arranged nitrogen into the multi-walled carbon nanotube framework, a P-CNTs-X catalytic material with a large number of oxygen and nitrogen synergistic effects is obtained. The material has a rich and ordered polymer structure and can be used for economical, efficient and small-scale preparation of hydrogen peroxide.
[0023] 3. In the polypyrrole-coated multi-walled carbon nanotube electrocatalyst of the present invention, the synergistic effect of the regularly arranged pyrrole nitrogen and oxygen atoms effectively activates the surrounding carbon atoms, giving them good activity and conductivity. This enables them to exhibit excellent reactivity, yield, selectivity and stability in the electrocatalytic two-electron oxygen reduction to prepare hydrogen peroxide.
[0024] 4. This invention utilizes a chemical oxidation method to obtain an electrocatalyst with polypyrrole encapsulated on multi-walled carbon nanotubes, using hydrogen peroxide as the oxidant and ammonium persulfate as the initiator. The preparation method of this invention is simple, with low equipment and material costs, and meets the needs of actual production. Attached Figure Description
[0025] Figure 1 A schematic diagram of oxygen-doped polypyrrole.
[0026] Figure 2This is a surface SEM image of the P-CNTs-100 composite material prepared in Example 1.
[0027] Figure 3 This is a TEM image of the surface of the P-CNTs-100 composite material prepared in Example 1.
[0028] Figure 4 This is a TEM magnified image of the P-CNTs-100 composite material prepared in Example 1.
[0029] Figure 5 This is the infrared spectrum of the P-CNTs-X composite material prepared in Example 1.
[0030] Figure 6 This is the Raman spectrum of the P-CNTs-X composite material prepared in Example 1.
[0031] Figure 7 The TEM surface distribution scan of the P-CNTs-100 material prepared in Example 1 is shown below.
[0032] Figure 8 The XPS full spectrum of the P-CNTs-X composite material prepared in Example 1 is shown below.
[0033] Figure 9 XPS nitrogen fine spectrum of the P-CNTs-X composite material prepared in Example 1
[0034] Figure 10 XPS oxygen fine spectrum of the P-CNTs-X composite material prepared in Example 1
[0035] Figure 11 The P-CNTs-X composite material prepared in Example 1 was used as a catalyst at a scan rate of 5 mV / s. -1 Linear scan voltage (LSV) curves for the electrocatalytic oxygen reduction to prepare hydrogen peroxide in saturated electrolytes of Ar and O2.
[0036] Figure 12 The P-CNTs-X composite material prepared in Example 1 was used as a catalyst at a scan rate of 5 mV / s. -1 Linear scan voltage (LSV) curves of hydrogen peroxide prepared by electrocatalytic oxygen reduction in O2 saturated electrolyte (rotating disk electrode).
[0037] Figure 13 The curves show the selectivity and electron transfer number of the P-CNTs-X composite material prepared in Example 1 as a catalyst for the preparation of hydrogen peroxide.
[0038] Figure 14The hydrogen peroxide yield and Faraday efficiency (FE) of the P-CNTs-100 composite material prepared in Example 1 as a catalyst are shown.
[0039] Figure 15 The figures show the amperometric curve and hydrogen peroxide concentration change of the P-CNTs-100 composite material prepared in Example 1 as a catalyst over 24 hours. Detailed Implementation
[0040] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0041] Example 1
[0042] A polypyrrole-coated multi-walled carbon nanotube electrocatalyst is prepared by the following steps:
[0043] Step 1: Disperse 0.3g of multi-walled carbon nanotubes in 50mL of deionized water and stir continuously with magnetic force for 10 minutes to obtain a multi-walled carbon nanotube dispersion.
[0044] Step 2: Slowly add 0.3g of pyrrole monomer to the multi-walled carbon nanotube dispersion prepared in Step 1, and continuously stir the dispersion magnetically for 10min.
[0045] Step 3: Add 5.1g of hydrogen peroxide (mass fraction 30%) to the dispersion prepared in Step 2, and continuously stir magnetically during this process;
[0046] Step 4: Dissolve 0.8g of ammonium persulfate in 10mL of deionized water, and add the ammonium persulfate solution to the dispersion prepared in Step 3. During this process, the mixture is continuously stirred magnetically.
[0047] Step 5: The dispersion obtained in step 4 is magnetically stirred in an ice-water bath at 0 degrees Celsius for 6 hours.
[0048] Step 6: Wash the dispersion obtained in step 5 by centrifugation with deionized water, methanol and acetone respectively.
[0049] Step 7: The product obtained in step 6 is freeze-dried in a vacuum freeze dryer to finally obtain a polypyrrole-coated multi-walled carbon nanotube catalyst, denoted as P-CNTs-100 composite material.
[0050] Using the same method, except that the mass of pyrrole monomer in step 2 was modified to 0.15 g and 0.6 g, P-CNTs-50 composite material and P-CNTs-200 composite material were obtained. The 50 and 200 in P-CNTs-50 and P-CNTs-200 refer to the mass percentage ratio of the pyrrole monomer in step 2 to the mass of multi-walled carbon nanotubes in step 1 during the preparation process. The polypyrrole content in CNTs, P-CNTs-50, P-CNTs-100 and P-CNTs-200 composite materials gradually increases.
[0051] like Figure 1 As shown, during the reaction, multi-walled carbon nanotubes and pyrrole molecules are thoroughly mixed and undergo chemical oxidative polymerization under the action of the oxidant hydrogen peroxide and the initiator ammonium persulfate. Individual pyrrole molecules polymerize into chain-like polypyrrole molecules, and at the same time, under the action of the oxidant, a large number of oxygen atoms are introduced into the chain structure, forming an oxygen-doped polypyrrole structure that coats the multi-walled carbon nanotubes.
[0052] The surface morphology of the prepared P-CNTs-100 catalytic material was observed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Figure 2 As shown, a tubular material of uniform thickness was observed. Figure 3-4 As shown, P-CNTs-100 exhibit a significantly larger diameter compared to CNTs. For example... Figure 5 As shown, the specific surface area of the material, measured by the low-temperature nitrogen adsorption method, reaches 529 m². 2 g -1 Surface functional groups and defect structures are characterized using infrared spectroscopy and Raman spectroscopy. For example... Figure 5 As shown, P-CNTs-X exhibits more pyrrole nitrogen functional groups with increasing pyrrole monomer content. Figure 6 As shown, P-CNTs-X exhibits a defect level closer to that of pure polypyrrole with increasing pyrrole monomer content.
[0053] Example 2
[0054] The catalytic performance of the P-CNTs-100 composite material prepared in Example 1 was tested. Specifically, a 0.1M KOH aqueous solution was used as the electrolyte for the catalytic performance test. The P-CNTs-100 composite material was uniformly dispersed in a mixed solution of nafion, isopropanol, and water at a volume ratio of 3:35:62, resulting in a slurry with a concentration of 1 mg / mL. This slurry was then drop-coated onto a commercial hydrophobic carbon paper electrode and dried at room temperature to obtain a hydrophobic carbon paper electrode loaded with the P-CNTs-100 composite material. The slurry was also drop-coated onto a glassy carbon portion of a rotating disk electrode and dried at room temperature to obtain a glassy carbon electrode loaded with the P-CNTs-100 composite material. Using the glassy carbon electrode loaded with the P-CNTs-100 composite material as the working electrode, a carbon rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode, its selectivity, bilayer capacitance, and activity for the electrocatalytic oxygen reduction to hydrogen peroxide production were tested. Using the hydrophobic carbon paper loaded with P-CNTs-100 composite material as the working electrode, Pt as the counter electrode, and Ag / AgCl electrode as the reference electrode, the yield and stability of its electrocatalytic oxygen reduction to hydrogen peroxide were tested.
[0055] like Figure 11 As shown, in an O2-saturated electrolyte, the P-CNTs-100 composite material exhibits a significant ORR current at an initial reaction potential of 0.50 V vs. RHE, while this current is absent in an Ar-saturated electrolyte, indicating that P-CNTs-100 possesses good ORR activity. P-CNTs-50 and P-CNTs-200 show lower activity than P-CNTs-100, but still exhibit higher current densities, demonstrating that the P-CNTs-X (X = 50-200) series materials all possess good ORR activity.
[0056] like Figure 12-13 As shown, the 2e of P-CNTs-100 on a rotating disk electrode - ORR performance evaluation revealed that the P-CNTs-100 composite material exhibited higher ring current and lower disk current, while also demonstrating higher H2O2 activity and selectivity (90%). P-CNTs-50 and P-CNTs-200 showed slightly lower selectivity (65% and 75%) and electron transfer numbers (2.7 and 2.5, respectively), but were still more inclined towards two-electron oxygen reduction reactions.
[0057] like Figure 14 The hydrogen peroxide yield of P-CNTs-100 was tested at different current densities, with a yield of 80 mA / cm⁻¹. -1 It exhibits a Faraday efficiency of over 90% at the following current densities, along with extremely high yield. At 200 mA / cm²... -1The current density has 55 molg. -1 h -1 Extremely high yield.
[0058] like Figure 15 As shown, in order to evaluate the effect of P-CNTs-100 on the electrocatalysis of 2e - -ORR stability was assessed by measuring the cumulative concentration of H2O2 in the electrolyte every 1 hour. The average rate of increase in H2O2 concentration after the test was 559 mg / L. -1 h -1 After 24 hours, the cumulative H2O2 concentration reached 13 g / L. -1 This indicates that the material also has excellent stability.
[0059] By adjusting the process parameters according to the content of this invention, the polypyrrole-coated multi-walled carbon nanotube electrocatalyst of this invention can be prepared and exhibits performance that is basically the same as that of Example 1.
[0060] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a polypyrrole-coated multi-walled carbon nanotube electrocatalyst, characterized in that, The process includes the following steps: dispersing multi-walled carbon nanotubes in deionized water and stirring to obtain a multi-walled carbon nanotube dispersion; sequentially adding pyrrole monomer, hydrogen peroxide, and ammonium persulfate aqueous solution to the multi-walled carbon nanotube dispersion and stirring continuously to obtain a dispersion; centrifuging and washing the dispersion; and freeze-drying the obtained product to obtain a polypyrrole-coated multi-walled carbon nanotube electrocatalyst. The mass ratio of the multi-walled carbon nanotubes to the pyrrole monomer is 1:(0-2), and the mass of the pyrrole monomer is not 0. The mass ratio of pyrrole monomer to hydrogen peroxide is 1:(10-20); The mass ratio of pyrrole monomer to ammonium persulfate is 1:(2-5); The dispersion was continuously stirred in an ice-water bath at 0 degrees Celsius for 3-12 hours.
2. The preparation method of the polypyrrole-coated multi-walled carbon nanotube electrocatalyst as described in claim 1, characterized in that, The hydrogen peroxide is a 30% (w / w) aqueous solution.
3. The preparation method of the polypyrrole-coated multi-walled carbon nanotube electrocatalyst as described in claim 1, characterized in that, The dispersion was washed by centrifugation with deionized water, methanol, and acetone, respectively.
4. The preparation method of the polypyrrole-coated multi-walled carbon nanotube electrocatalyst as described in claim 1, characterized in that, The product is freeze-dried under vacuum.
5. The polypyrrole-coated multi-walled carbon nanotube electrocatalyst prepared by the preparation method according to any one of claims 1-4.
6. The application of the polypyrrole-coated multi-walled carbon nanotube electrocatalyst according to claim 5 in the preparation of hydrogen peroxide, characterized in that, The polypyrrole-coated multi-walled carbon nanotube electrocatalyst was uniformly dispersed in a mixed solution containing nafion, isopropanol, and water to obtain a slurry with a concentration of 2-10 mg / mL. The slurry was then drop-coated onto a glassy carbon electrode on a rotating disk electrode and dried at room temperature to obtain a glassy carbon electrode loaded with the polypyrrole-coated multi-walled carbon nanotube electrocatalyst. Using an aqueous solution of KOH as the electrolyte and the glassy carbon electrode loaded with the polypyrrole-coated multi-walled carbon nanotube electrocatalyst as the working electrode, hydrogen peroxide was prepared by electrocatalytic oxygen reduction.
7. The application of the polypyrrole-coated multi-walled carbon nanotube electrocatalyst as described in claim 6 in the preparation of hydrogen peroxide, characterized in that, The volume ratio of nafion, isopropanol and water is (3-5):20:(75-77).