Sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of preparation of electrochemical materials, in particular to a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material and a preparation method and application thereof. The preparation method comprises the following steps: jointly dissolving melamine, trithiocyanuric acid and soluble cobalt salt in water, carrying out a cross-linking reaction to generate a cobalt-doped melamine-trithiocyanuric acid supramolecular precursor, drying and crushing, and then carrying out pre-calcining treatment to obtain a sulfur-nitrogen-cobalt co-doped tubular material; and co-dissolving the sulfur-nitrogen-cobalt co-doped tubular material and asphaltene oxide in a solvent, performing drying treatment, and performing calcination treatment to obtain the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material. The adsorption capacity and electrochemical activity of the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material on heavy metal ions in a water body are improved by combining the advantages of heteroatom doping and tubular morphology through a step-by-step synthesis method, so that high-sensitivity detection on the heavy metal ions in the water body is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical material preparation, and in particular to a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of industry, heavy metal ion pollution in water bodies is becoming increasingly serious. Even at low doses, long-term ingestion of heavy metal ions such as lead, cadmium, and mercury can cause serious damage to human health, leading to lesions in the nervous system and kidneys. Therefore, accurate and rapid detection of heavy metal ions in water bodies is of great practical significance.

[0003] Currently, there are multiple methods for detecting heavy metal ions in water, such as atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. While these methods offer high accuracy, they suffer from expensive equipment, complex operation, and long detection cycles, making them difficult to meet the demands of rapid on-site detection. Electrochemical detection technology, with its advantages of high sensitivity, rapid response, low cost, and ease of miniaturization, has become a research hotspot for heavy metal ion detection in water. The key to electrochemical detection technology lies in the properties of the electrode materials. Developing electrode materials with high sensitivity, high selectivity, and stability is crucial for improving electrochemical detection performance.

[0004] Electrochemical electrode materials used for heavy metal ion detection in water mainly include precious metal electrode materials (such as gold and platinum) and carbon-based electrode materials. Although precious metal electrode materials have good electrochemical properties, their high cost limits their widespread application. Carbon-based electrode materials, such as graphene and carbon nanotubes, have high specific surface area and good conductivity, but their sensitivity and selectivity for heavy metal ion detection need to be improved. To improve the performance of carbon-based electrode materials, researchers generally use heteroatom doping (such as nitrogen or sulfur doping) to enhance the electrochemical activity and adsorption capacity of the materials for heavy metal ions. In addition, manipulating the material's morphology (such as tubular morphology) can increase the material's mass transfer rate and active sites, further improving detection performance. However, single heteroatom doping or simple morphology manipulation currently cannot meet the demand for high-sensitivity detection of low-concentration heavy metal ions in water. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, a preparation method thereof, and an application thereof. The present invention uses melamine, thiocyanuric acid, a soluble cobalt salt, and asphaltene oxide as raw materials. The melamine, thiocyanuric acid, and soluble cobalt salt are first dissolved in water, and the melamine and thiocyanuric acid undergo a cross-linking reaction. After drying and crushing, a cobalt-doped melamine-thiocyanuric acid supramolecular powder is obtained. Subsequently, the cobalt-doped melamine-thiocyanuric acid supramolecular powder is pre-calcined to form a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure, thereby obtaining a sulfur-nitrogen-cobalt co-doped tubular material. Finally, the sulfur-nitrogen-cobalt co-doped tubular material and asphaltene oxide are dissolved in a solvent, and the mixture is dried and calcined in sequence to form porous carbon, thereby obtaining a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material. The present invention uses a step-by-step synthesis method, combined with the advantages of heteroatom doping and tubular morphology, to improve the adsorption capacity and electrochemical activity of sulfur-nitrogen-cobalt co-doped porous carbon tube electrode materials for heavy metal ions in water, thereby achieving high-sensitivity detection of heavy metal ions in water.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: The first object of the present invention is to provide a method for preparing the above-mentioned sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, comprising the following steps: S1. Melamine, thiocyanuric acid, and a soluble cobalt salt are dissolved in water. Melamine and thiocyanuric acid undergo a cross-linking reaction to generate a melamine-thiocyanuric acid supramolecular precursor. Cobalt ions of the soluble cobalt salt are doped into the melamine-thiocyanuric acid supramolecular precursor. The precursor is dried and crushed to obtain a cobalt-doped melamine-thiocyanuric acid supramolecular powder.

[0007] S2. Pre-calcining the cobalt-doped melamine-thiocyanate supramolecular powder, during the heating process, a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure is formed, thereby obtaining a sulfur-nitrogen-cobalt co-doped tubular material; wherein, the formation of the hollow tubular structure is mainly attributed to the escape of N2O, CO2, CO, NO, NH3, SO, SO2, H2S and H2O generated during the calcination process; in the early stage of evaporation-induced drying during the pre-calcination treatment, the supramoleculars on the plane of the cobalt-doped melamine-thiocyanate supramolecular powder are rapidly crystallized, resulting in high-density defects in the center. Based on this, the pyrolysis or etching process starts from the center of the cobalt-doped melamine-thiocyanate supramolecular powder and gradually expands outward, thereby forming a tubular structure.

[0008] S3. Dissolve the sulfur-nitrogen-cobalt co-doped tubular material and asphaltene oxide in a solvent, and dry them at room temperature to obtain sulfur-nitrogen-cobalt co-doped tubes coated with asphaltene oxide; calcine the sulfur-nitrogen-cobalt co-doped tubes coated with asphaltene oxide. During the calcination process, the sulfur-nitrogen-cobalt co-doped tubes coated with asphaltene oxide are carbonized to form porous carbon, thereby obtaining a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material.

[0009] Preferably, the mass ratio of melamine, thiocyanuric acid and cobalt acetate tetrahydrate is 1:3:0.5-1.5.

[0010] Preferably, the mass ratio of the sulfur-nitrogen-cobalt co-doped tubular material to the oxidized asphaltene is 1:0.2-0.6.

[0011] Preferably, the conditions of the pre-calcination treatment are the same as those of the calcination treatment, that is, calcination at 550° C. to 650° C. for 2 h in an inert atmosphere.

[0012] Preferably, the cross-linking reaction is carried out under stirring at room temperature for 2 to 3 hours.

[0013] The second object of the present invention is to provide a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material prepared by the above preparation method.

[0014] Preferably, the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material has a porous tubular morphology, and sulfur, nitrogen, and cobalt elements are uniformly co-doped in the carbon-based skeleton.

[0015] The third object of the present invention is to provide the use of the above-mentioned sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material in electrochemical detection of heavy metal ions in water.

[0016] Preferably, the application method is: A sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material was coated on an electrode substrate to obtain a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode; a three-electrode system was composed of the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum wire as the counter electrode; and an electrochemical detection method was used to detect the concentration of heavy metal ions in water.

[0017] Preferably, the heavy metal ions are selected from cadmium ions or lead ions, and the minimum detection limits of cadmium ions and lead ions are both nmol / L.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, comprising dissolving melamine, thiocyanuric acid and a soluble cobalt salt in water, cross-linking melamine and thiocyanuric acid to generate a melamine-thiocyanuric acid supramolecular precursor, doping cobalt ions of the soluble cobalt salt into the melamine-thiocyanuric acid supramolecular precursor, and drying and crushing the precursor to obtain a cobalt-doped melamine-thiocyanuric acid supramolecular powder; pre-calcining the cobalt-doped melamine-thiocyanuric acid supramolecular powder, and heating the precursor. In the present invention, a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure is formed to obtain a sulfur-nitrogen-cobalt co-doped tubular material; the sulfur-nitrogen-cobalt co-doped tubular material and oxidized asphaltene are dissolved in a solvent, and dried to obtain an oxidized asphaltene-coated sulfur-nitrogen-cobalt co-doped tube; the oxidized asphaltene-coated sulfur-nitrogen-cobalt co-doped tube is then calcined, and during the calcination process, the oxidized asphaltene-coated sulfur-nitrogen-cobalt co-doped tube is carbonized to form porous carbon, thereby obtaining a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material. The present invention improves the adsorption capacity and electrochemical activity of the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material for heavy metal ions in water by a step-by-step synthesis method, combining the advantages of heteroatom doping and tubular morphology, thereby achieving high-sensitivity detection of heavy metal ions in water.

[0019] 2. The sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material of the present invention not only has high sensitivity, but also has good stability. Among them, the co-doping of heteroatoms (sulfur, nitrogen, cobalt) provides abundant active sites for the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, increasing the adsorption capacity and electrochemical activity for heavy metal ions; the porous tubular morphology has a large specific surface area, which is conducive to the enrichment of heavy metal ions and electron transport, thereby improving the detection sensitivity. The sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material of the present invention can achieve a detection limit of nmol / L for heavy metal ions in water, which can meet the detection requirements of low-concentration heavy metal ions. In addition, through pre-calcination and calcination treatments, the structure of the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material of the present invention is more stable. During long-term use and repeated detection, the electrode performance remains good, reducing detection errors.

[0020] 3. The preparation method of the present invention is simple and cost-effective. The raw materials used—melamine, thiocyanuric acid, cobalt acetate, and asphaltene oxide—are all relatively inexpensive and commonly available chemical reagents. The synthesis process is simple and suitable for large-scale production. Furthermore, the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material of the present invention eliminates the need for complex pretreatment steps during electrochemical detection, enabling rapid on-site detection and improving detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the SEM image of the sulfur-nitrogen-cobalt co-doped carbon tube of Example 1.

[0022] Figure 2 The sulfur-nitrogen-cobalt co-doped carbon tube of Example 1 is Cd 2+ and Pb 2+ Individual test result diagram, where (a) is Cd 2+ The stripping voltammetry curve of (b) is Cd 2+ The linear relationship curve between the current and concentration of Pb 2+ The stripping voltammetry curve of Pb 2+ The linear relationship curve between current and concentration.

[0023] Figure 3 The sulfur-nitrogen-cobalt co-doped carbon tube of Example 1 is Cd 2+ and Pb 2+ Simultaneous detection results, where (a) is the stripping voltammetry curve and (b) is the linear relationship curve between current and concentration.

[0024] Figure 4 The sulfur-nitrogen-cobalt co-doped carbon tube of Example 1 is Cd 2+ and Pb 2+ Reproducibility test results of the graph, where (a) is Cd 2+ , (b) is Pb 2+ . DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solution of the present invention in conjunction with the data in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0027] In the electrochemical electrode materials used for heavy metal ion detection in water bodies prepared by existing preparation methods, single heteroatom doping or simple morphology control cannot meet the demand for high-sensitivity detection of low-concentration heavy metal ions in water bodies.

[0028] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, comprising the following steps: dissolving melamine, thiocyanuric acid and a soluble cobalt salt in water, cross-linking melamine and thiocyanuric acid to generate a melamine-thiocyanuric acid supramolecular precursor, doping cobalt ions of the soluble cobalt salt into the melamine-thiocyanuric acid supramolecular precursor, drying and crushing the precursor to obtain a cobalt-doped melamine-thiocyanuric acid supramolecular powder; and subjecting the cobalt-doped melamine-thiocyanuric acid supramolecular powder to a slurry of molten salt. A pre-calcination treatment is performed, and during the heating process, a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure is formed to obtain a sulfur-nitrogen-cobalt co-doped tubular material; the sulfur-nitrogen-cobalt co-doped tubular material and asphaltene oxide are dissolved in a solvent, and after drying, an asphaltene oxide-coated sulfur-nitrogen-cobalt co-doped tube is obtained; the asphaltene oxide-coated sulfur-nitrogen-cobalt co-doped tube is then calcined, and during the calcination process, the asphaltene oxide-coated sulfur-nitrogen-cobalt co-doped tube is carbonized to form porous carbon, thereby obtaining a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material.

[0029] To address the problem of insufficient sensitivity of existing carbon-based electrode materials for heavy metal ion detection, the present invention introduces abundant active sites through sulfur-nitrogen-cobalt co-doping. The porous tubular morphology provides a high specific surface area, synergistically enhancing the adsorption and electrochemical response to heavy metal ions, and achieving a detection limit of nmol / L, thus solving this problem.

[0030] In order to solve the problem of high cost of existing precious metal electrodes, the present invention replaces precious metals with cheap raw materials, namely melamine, thiocyanuric acid and asphaltene oxide. The process is simple and suitable for large-scale production, thus solving the problem.

[0031] In order to solve the problem of complex operation of traditional detection methods, the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material prepared by the present invention can be directly used for electrochemical rapid detection without the need for complex sample pretreatment.

[0032] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments: Example 1 A method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material comprises the following steps: S1. Weigh 1g of melamine and 3g of thiocyanate, add 100mL of deionized water, stir for 2h to fully dissolve and mix, then add 0.5g of cobalt acetate tetrahydrate and continue stirring for 1h. After fully dissolving, place in an oven to dry. After drying, grind to obtain a rod-shaped precursor powder, recorded as STB-Co0.5.

[0033] S2. Place STB-Co0.5 in a muffle furnace and calcine it at 550°C for 2 hours to form a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure, and obtain a sulfur-nitrogen-cobalt co-doped tubular material, which is recorded as STB-Co0.5-C.

[0034] S3. STB-Co0.5-C and oxidized asphaltene were mixed in a mass ratio of 1:0.2 and dissolved in 20 mL of tetrahydrofuran. After drying at room temperature for 2 h, sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were obtained. Subsequently, the sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were placed in a muffle furnace and calcined at 550 °C for 2 h to obtain sulfur-nitrogen-cobalt co-doped porous carbon tube electrode materials, which were recorded as STB-Co0.5-C-ASP-C.

[0035] Example 2 A method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material is the same as the preparation steps in Example 1, except that the amount of cobalt acetate tetrahydrate in S1 is replaced from 0.5 g to 1 g. The method comprises the following steps: S1. Weigh 1g of melamine and 3g of thiocyanate, add 100mL of deionized water, stir for 2h to fully dissolve and mix, then add 1g of cobalt acetate tetrahydrate and continue stirring for 1h. After fully dissolving, place in an oven to dry. After drying, grind to obtain a rod-shaped precursor powder, recorded as STB-Co1.

[0036] S2. Place STB-Co1 in a muffle furnace and calcine at 550°C for 2 hours to form a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure, and obtain a sulfur-nitrogen-cobalt co-doped tubular material, which is recorded as STB-Co1-C.

[0037] S3. STB-Co1-C and oxidized asphaltene were mixed in a mass ratio of 1:0.2 and dissolved in 20 mL of tetrahydrofuran. After drying at room temperature for 2 h, sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were obtained. Subsequently, the sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were placed in a muffle furnace and calcined at 550 °C for 2 h to obtain sulfur-nitrogen-cobalt co-doped porous carbon tube electrode materials, which were recorded as STB-Co1-C-ASP-C.

[0038] Example 3 A method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material is the same as the preparation steps in Example 1, except that the amount of cobalt acetate tetrahydrate in S1 is replaced from 0.5 g to 1.5 g. The method comprises the following steps: S1. Weigh 1g of melamine and 3g of thiocyanate, add 100mL of deionized water, stir for 2h to fully dissolve and mix, then add 1.5g of cobalt acetate tetrahydrate and continue stirring for 1h. After fully dissolving, place in an oven to dry. After drying, grind to obtain a rod-shaped precursor powder, recorded as STB-Co1.5.

[0039] S2. Place STB-Co1.5 in a muffle furnace and calcine it at 550°C for 2 hours to form a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure, and obtain a sulfur-nitrogen-cobalt co-doped tubular material, which is recorded as STB-Co1.5-C.

[0040] S3. STB-Co1.5-C and oxidized asphaltene were mixed in a mass ratio of 1:0.2 and dissolved in 20 mL of tetrahydrofuran. After drying at room temperature for 2 h, sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were obtained. Subsequently, the sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were placed in a muffle furnace and calcined at 550 °C for 2 h to obtain sulfur-nitrogen-cobalt co-doped porous carbon tube electrode materials, which were recorded as STB-Co1.5-C-ASP-C.

[0041] Example 4 A method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material is the same as the preparation steps in Example 1, except that the mass ratio of STB-Co0.5-C to asphaltene oxide in S3 is replaced from 1:0.2 to 1:0.6. The method comprises the following steps: S1. Weigh 1g of melamine and 3g of thiocyanate, add 100mL of deionized water, stir for 2h to fully dissolve and mix, then add 0.5g of cobalt acetate tetrahydrate and continue stirring for 1h. After fully dissolving, place in an oven to dry. After drying, grind to obtain a rod-shaped precursor powder, recorded as STB-Co0.5.

[0042] S2. Place STB-Co0.5 in a muffle furnace and calcine it at 550°C for 2 hours to form a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure, and obtain a sulfur-nitrogen-cobalt co-doped tubular material, which is recorded as STB-Co0.5-C.

[0043] S3. STB-Co0.5-C and oxidized asphaltene were mixed in a mass ratio of 1:0.6 and dissolved in 20 mL of tetrahydrofuran. After drying at room temperature for 2 h, sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were obtained. Subsequently, the sulfur-nitrogen-cobalt co-doped tubes coated with oxidized asphaltene were placed in a muffle furnace and calcined at 550 °C for 2 h to obtain sulfur-nitrogen-cobalt co-doped porous carbon tube electrode materials.

[0044] Examples 1 to 4 of the present invention all produced sulfur-nitrogen-cobalt co-doped porous carbon tube electrode materials, and the effects were comparable. The following uses the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material of Example 1 as an example to study its application performance, as follows:

[0045] Table 1 Element distribution of sulfur-nitrogen-cobalt co-doped carbon tubes of Example 1 The results in Table 1 show that the sulfur-nitrogen-cobalt co-doped carbon tubes prepared in the present invention have higher nitrogen and sulfur contents, indicating the successful synthesis of the sulfur-nitrogen-cobalt co-doped carbon tubes.

[0046] observe Figure 1 It was found that the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material of the present invention had a hollow tube structure, indicating that the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material was successfully synthesized.

[0047] Table 2 Detection effect of sulfur-nitrogen-cobalt co-doped carbon tube on actual water samples Add 1μmol / L~3μmol / L of Cd into mineral water 2+ and Pb 2+ solution, sulfur-nitrogen-cobalt co-doped carbon nanotubes to Cd 2+ and Pb 2+ The recoveries of the spiked samples were 93.50%~97.20% and 100.00%~103.70% respectively; 1μmol / L~3μmol / L Cd was added to tap water. 2+ and Pb 2+ solution, sulfur-nitrogen-cobalt co-doped carbon nanotubes to Cd 2+ and Pb 2+ The spiked recoveries were 97.325% to 109.62% and 101.99% to 105.786%, respectively. The results in Table 2 show that the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material has good practical application capabilities.

[0048] The prepared sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material was coated onto an electrode substrate to prepare a working electrode. Electrochemical detection was performed using a three-electrode system (glassy carbon electrode, platinum wire electrode, and Ag / AgCl). The water to be tested was added to an electrolytic cell, and a specific potential sweep signal was applied to record the current signal during the electrochemical reaction. A calibration curve was established based on the relationship between the current signal and the heavy metal ion concentration, enabling quantitative detection of heavy metal ion concentrations in the water.

[0049] Depend on Figure 2 (a) and (c) in the above equation show that Cd 2+The concentration range of Pb is 0.0250μmol / L~6.0000μmol / L. 2+ The concentration range of Cd was 0.0250μmol / L~8.0000μmol / L. The results showed that the response current of the two heavy metal ions increased with the increase of Cd 2+ and Pb 2+ The concentration of Cd increases linearly. 2+ and Pb 2+ The response current value of Cd was linearly fitted with the corresponding concentration. 2+ and Pb 2+ The linear regression equation is shown in Figure 2 (b) and (d) in . Figure 2 Cd can be found in (b) and (d) 2+ and Pb 2+ The response current has a good linear relationship with the concentration, among which Cd 2+ The linear regression equation is y=13.0211x+0.7436, Pb 2+ The linear regression equation is y=26.3942x+1.3930. Therefore, the sulfur-nitrogen-cobalt co-doped carbon tube modified electrode has a significant effect on Cd 2 + and Pb 2+ The sensitivities of Cd were 13.0211μA / μmol and 26.3942μA / μmol, respectively. Based on the signal-to-noise ratio S / N=3, it was calculated that 2+ and Pb 2+ The detection limits of Cd and Cd were 6.45 nmol / L and 3.18 nmol / L, respectively, which are lower than the drinking water quality standards proposed by the World Health Organization ( 2+ : about 26.6nmol / L; Pb 2+ : about 48nmol / L).

[0050] Figure 3 The sulfur-nitrogen-cobalt co-doped porous carbon tube modified electrode is Cd 2+ and Pb 2+ Simultaneous detection. Figure 3 (a) shows that the response current signals of the two heavy metal ions increase with the increase of concentration, and Figure 3 (b) shows that Cd 2+ and Pb 2+ There is a good linear relationship between the current response signal and the concentration (R 2 =0.9902 and R 2 =0.9872). From the linear equation, it can be seen that the sulfur-nitrogen-cobalt co-doped carbon tube modified electrode has a significant effect on the Cd 2+ and Pb 2+The sensitivities of Cd were 7.9365μA / μmol and 28.8346μA / μmol, respectively. Based on the signal-to-noise ratio S / N=3, the Cd 2+ and Pb 2+ The detection limits were 10.58 nmol / L and 2.91 nmol / L, respectively.

[0051] observe Figure 4 It is concluded that sulfur-nitrogen-cobalt co-doped carbon nanotubes have a significant effect on Cd 2+ and Pb 2+ The detection of Cd has good repeatability. 2+ The relative standard deviation (RSD) of the detection was only 2.86%, which was not significant for Pb 2+ The relative standard deviation of the detection was also as low as 2.78%.

[0052] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art will be able to make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Claims

1. A method for preparing a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, characterized in that: The steps include: Melamine, thiocyanuric acid and a soluble cobalt salt are dissolved in water, melamine and thiocyanuric acid undergo a cross-linking reaction to generate a melamine-thiocyanuric acid supramolecular precursor, cobalt ions of the soluble cobalt salt are doped into the melamine-thiocyanuric acid supramolecular precursor, and the precursor is dried and crushed to obtain a cobalt-doped melamine-thiocyanuric acid supramolecular powder; The cobalt-doped melamine-thiocyanate supramolecular powder is pre-calcined to form a sulfur-nitrogen-cobalt co-doped carbon-based skeleton with a hollow tubular structure during the heating process, thereby obtaining a sulfur-nitrogen-cobalt co-doped tubular material. The sulfur-nitrogen-cobalt co-doped tubular material and asphaltene oxide are dissolved in a solvent, and dried to obtain an asphaltene oxide-coated sulfur-nitrogen-cobalt co-doped tube; The sulfur-nitrogen-cobalt co-doped tube coated with oxidized asphaltene is calcined. During the calcination process, the sulfur-nitrogen-cobalt co-doped tube coated with oxidized asphaltene is carbonized to form porous carbon, thereby obtaining a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material.

2. The method for preparing the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material according to claim 1, characterized in that: The mass ratio of melamine, thiocyanate and soluble cobalt salt is 1:3:0.5~1.

5.

3. The method for preparing the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material according to claim 1, characterized in that: The mass ratio of the sulfur-nitrogen-cobalt co-doped tubular material to oxidized asphaltene is 1:0.2~0.

6.

4. The method for preparing the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material according to claim 1, characterized in that: The conditions of the pre-calcination treatment are the same as those of the calcination treatment, that is, calcination at 550°C~650°C in an inert atmosphere for 2h.

5. The method for preparing the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material according to claim 1, characterized in that: The conditions for the cross-linking reaction are: stirring at room temperature for 2h~3h.

6. A sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material, characterized in that: The method is prepared according to any one of claims 1 to 5.

7. The sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material according to claim 6, characterized in that: The sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material presents a porous tubular morphology, and sulfur, nitrogen and cobalt elements are uniformly co-doped in the carbon-based skeleton.

8. Use of the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material according to claim 6 in electrochemical detection of heavy metal ions in water.

9. The use according to claim 8, characterized in that The application method is: The sulfur-nitrogen-cobalt co-doped porous carbon tube electrode material is coated on the electrode substrate to obtain the sulfur-nitrogen-cobalt co-doped porous carbon tube electrode; A three-electrode system was formed with a sulfur-nitrogen-cobalt co-doped porous carbon tube electrode as the working electrode, Ag / AgCl as the reference electrode, and a platinum wire as the counter electrode. The concentration of heavy metal ions in water was detected by electrochemical detection.

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