A copper-doped ionic COF material Cu@TVPT-COF, a preparation method thereof and application thereof in electrochemical nitrate reduction

Abstract

The application relates to a copper-doped ionic COF material Cu@TVPT-COF, a preparation method thereof and application thereof in electrochemical nitrate reduction. N,N'-disubstituted-4,4'-bipyridine cation salt is mixed with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and after freeze-thaw-circulating degassing, reaction is carried out, and after washing and drying, TVPT-COF is obtained. Copper sulfate and TVPT-COF are dissolved in tetrahydrofuran, and reaction is carried out in a high-pressure reaction kettle. After centrifugal collection of the precipitate, washing and drying, Cu@TVPT-COF is obtained. The application obtains a COF material which is convenient to synthesize, stable in structure and good in catalytic performance. The material is prepared into a reduction electrode. The electrode is used for electrocatalytic nitrate reduction to produce ammonia, reaches 95.92% of the Faraday efficiency at-0.5V vs.RHE, reaches the highest ammonia nitrogen yield of 202.97mmol h ‑1 g ‑1 , and has excellent catalytic activity in nitrate reduction. The application has a wide application prospect in the field of catalysis.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrocatalysis, and relates to a copper-doped ionic COF material Cu@TVPT-COF, a preparation method thereof and application thereof in electrochemical nitrate reduction. BACKGROUND

[0002] With the increasing severity of global environmental problems, especially the intensification of water pollution, the treatment of nitrogen oxides (NO x ) and their derivatives has become an important research topic. Nitrate ions (NO3-) as a common water pollutant are usually derived from agricultural, industrial wastewater and urban sewage discharge. Traditional treatment methods such as biological degradation and chemical reduction often have the defects of low efficiency, high cost and secondary pollution to the environment. Therefore, developing efficient and green electrochemical methods to reduce nitrate ions has become one of the current research hotspots.

[0003] In recent years, metal-doped organic framework materials (COFs) have gradually attracted widespread attention due to their excellent structural stability, adjustable porosity and good electrical conductivity. COF materials have a highly ordered pore structure, which can provide a large number of reaction sites, thereby improving the efficiency of electrochemical reactions. Among the many metals, copper metal has become a research focus due to its good catalytic performance and relatively low cost.

[0004] The copper-doped ionic COF material can effectively promote the electrochemical reduction of nitrate ions. The presence of copper not only enhances the electrical conductivity of the material, but also promotes the reduction process of nitrate through its unique catalytic properties. In addition, the organic framework of the COF material can provide stable support to prevent the aggregation of metal particles, thereby maintaining good catalytic activity.

[0005] In order to further improve the performance of the electrode, researchers can also modify the material using other methods. For example, by doping other metal ions or introducing conductive materials (such as carbon nanotubes, graphene, etc.), the electrical conductivity and stability of the electrode can be improved. In addition, adjusting the synthesis conditions (such as reaction temperature, time, solvent, etc.) can also optimize the microstructure of the material, thereby improving its catalytic performance in electrochemical reactions.

[0006] In the application of electrochemical nitrate reduction, the copper-doped ionic COF material exhibits good catalytic activity and selectivity. Studies have shown that under appropriate potential, nitrate ions can be effectively reduced to harmless substances such as nitrogen or ammonia. This process not only reduces nitrogen pollution in water bodies, but also provides a new idea for the recycling of nitrogen resources.

[0007] In summary, the study of copper-doped ionic COF material electrodes has important theoretical significance and practical application value. By optimizing the preparation method and modification means of the material, its performance in electrochemical nitrate reduction can be further improved, providing an effective solution for water pollution control. Through in-depth study of the electrode, efficient removal of nitrate in water is expected to be achieved, making a positive contribution to environmental protection. SUMMARY

[0008] The purpose of the present application is to provide a preparation method of Cu@TVPT-COF electrode with stable structure, simple preparation method, high catalytic efficiency and good selectivity, and its application in electrocatalytic reduction of nitrate.

[0009] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a copper-doped ionic COF material Cu@TVPT-COF, taking Cu as the central metal atom and taking ionic COF material as the matrix to obtain Cu@TVPT-COF.

[0010] The preparation method of the above-mentioned copper-doped ionic COF material Cu@TVPT-COF is as follows:

[0011] 1) Mix N,N'-disubstituted-4,4'-bipyridine cation salt TVN with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine TAPT, dissolve in ethanol / water, and after three cycles of freeze-thaw-degassing, carry out the reaction, wash with ethanol and water for six times, filter, and dry to obtain ionic COF material TVPT-COF;

[0012] 2) Dissolve copper sulfate and TVPT-COF in tetrahydrofuran THF, mix and stir uniformly, transfer to a high-pressure reaction kettle for reaction, centrifuge to collect the precipitate, wash with ethanol for several times, and dry to obtain Cu@TVPT-COF.

[0013] In step 1) of the above-mentioned preparation method of copper-doped ionic COF material Cu@TVPT-COF, the molar ratio of TAPT to TVN is 5:3, and the volume ratio of ethanol to water is 4:1.

[0014] In step 1) of the above-mentioned preparation method of copper-doped ionic COF material Cu@TVPT-COF, the reaction is carried out at 120℃ for 72h.

[0015] In step 2) of the above-mentioned preparation method of copper-doped ionic COF material Cu@TVPT-COF, the mass ratio of copper sulfate to TVPT-COF is 2:1.

[0016] The reaction condition in step 2) of the preparation method of the copper-doped ionic COF material Cu@TVPT-COF is 120 DEG C for 36 h.

[0017] A Cu@TVPT-COF electrode containing the above Cu@TVPT-COF is prepared by the following method: the above Cu@TVPT-COF, acetylene black, naphthol film solution, isopropyl alcohol, ultrapure water, and carbon cloth are dropped and coated on the carbon cloth after ultrasonic treatment, and then dried to obtain the Cu@TVPT-COF electrode.

[0018] Application of the above Cu@TVPT-COF electrode in electrochemical nitrate reduction.

[0019] In the application, the above Cu@TVPT-COF electrode is used as a working electrode, a platinum sheet electrode is used as a counter electrode, an Ag / AgCl reference electrode is used as a reference electrode, and 0.1M KNO3 solution and 1M KOH solution are used as cathode electrolyte and anode electrolyte.

[0020] The application has the following beneficial effects:

[0021] 1. The Cu@TVPT-COF is synthesized by a simple, green and easily available raw material through a simple hydrothermal method, and is configured into a mixed ink and loaded on a carbon cloth, so that the material has stable structure and simple synthesis operation.

[0022] 2. The catalyst synthesized in the application is used for electrocatalytic nitrate reduction, and reaches a Faraday efficiency of 95.92% at-0.5V vs.RHE and a highest ammonia nitrogen yield of 202.97mmol h -1 g -1 .

[0023] 3. The raw material used in the application is simple and easily available, the operation steps are simple and feasible, the material shows excellent and stable electrocatalytic performance, and has a good application prospect in the field of electrocatalytic reduction of nitrate to produce ammonia. DETAILED DESCRIPTION

[0024] Figure 1 is the FT-IR spectrum of the TVPT-COF material prepared in Example 1 and two raw materials.

[0025] Figure 2 is the synthesis and molecular formula of the TVPT-COF material in Example 1.

[0026] Figure 3 is an electrochemical test experimental device diagram of the Cu@TVPT-COF as a working electrode in Example 2.

[0027] Figure 4is the UV-vis absorption spectrum of the electrolyte in Example 2 for the detection of faradic efficiency and ammonia nitrogen content by indophenol blue method.

[0028] Figure 5 is the ammonia nitrogen standard curve for the detection of ammonia nitrogen content and faradic efficiency of the electrolyte in Example 2 by indophenol blue method.

[0029] Figure 6 is the ammonia nitrogen yield and faradic efficiency graph of Cu@TVPT-COF electrode material in Example 2.

[0030] Figure 7 is the XRD spectrum of Cu@TVPT-COF and TVPT-COF materials prepared in Example 1 and two raw materials. DETAILED DESCRIPTION

[0031] Preparation of Cu@TVPT-COF material electrode in Example 1

[0032] (I) Preparation method as follows:

[0033] 1) Pretreatment of carbon cloth: cut the rectangular carbon cloth with a size of 1 cm x 2 cm into a rectangular shape, and then immerse it in acetone, ethanol, concentrated nitric acid, ethanol, and acetone in turn, each time for 30 min, and then wash it with ultrapure water for several times and dry it in a 60°C vacuum drying oven for 72 hours.

[0034] 2) Preparation method of Cu@TVPT-COF material: mix 35.441 mg of TAPT and 37.4 mg of TVN with Pyrex test tube, dissolve in 3 mL of ethanol / water (4:1), and after three cycles of freeze-thaw degassing, react at 120°C for 72 h, wash and filter with ethanol and water for six times, and dry to obtain ionic COF material TVPT-COF.

[0035] 3) Weigh 80 mg of copper sulfate and 40 mg of TVPT-COF material and dissolve in 20 ml of THF, stir uniformly, and then transfer to a polytetrafluoroethylene-lined stainless steel autoclave for reaction at 120°C for 36 h. After high-temperature reaction, cool to room temperature, centrifuge to collect the precipitate, wash with ethanol for three times, dry at 60°C for 48 hours, and grind into powder to obtain Cu@TVPT-COF material.

[0036] 4) Preparation method of Cu@TVPT-COF electrode: use 3 mg of Cu@TVPT-COF catalyst powder, 3 mg of acetylene black, 40 ul of naphthol film solution, 200 ul of isopropyl alcohol, 20 ul of ultrapure water, and ultrasonic for 60 min to disperse uniformly. Use a 1 mL syringe to drop the ink on the carbon cloth, the drop amount is 10-13 drops, and after drying, weigh it, and according to the mass difference of the carbon cloth before and after, calculate the loading amount of the catalyst.

[0037] (ii) detection results

[0038] Figure 1 is the powder FT-IR spectrum of the TVPT-COF material prepared in Example 1, from which Figure 1 It can be seen that the TVPT-COF material has no raw material peaks at 2200 cm -1 , 3800 cm -1 , and 3321.29 cm -1 , indicating that the material was successfully synthesized and the reaction proceeded as designed. Figure 2 is a reaction schematic diagram for preparing the TVPT-COF in Example 1, as well as the chemical structures of the raw materials and the product. Figure 7 is the XRD pattern of the Cu@TVPT-COF and TVPT-COF materials prepared in Example 1, as well as the two raw materials, from which Figure 7 It can be seen that the TVPT-COF material prepared in Example 1 has no characteristic peaks of the raw materials, proving that the reaction of TAPT and TVN proceeded as designed, and that, by comparing the TVPT-COF and Cu@TVPT-COF, copper sulfate was successfully incorporated into the TVPT-COF.

[0039] Application of the Cu@TVPT-COF material electrode in the electrocatalytic reduction of nitrate in Example 2

[0040] Test method: The prepared Cu@TVPT-COF electrode was used as the working electrode.

[0041] The electrolytic cell used in the experiment was an H-type electrolytic cell, Nafion 117 membrane was used as the proton exchange membrane, the Cu@TVPT-COF electrode prepared in Example 1 was used as the working electrode, an Ag / AgCl electrode was used as the reference electrode, and a platinum sheet electrode was used as the counter electrode. The cathode electrolyte and the anode electrolyte were both 35 ml of 0.1M KNO3 solution and 35 ml of 1M KOH solution. The experimental potential was set to -0.3 to -0.7V vs. RHE, the IT test time was 1h, and the indophenol blue method was used to detect the ammonia nitrogen content in the electrolyte to calculate the yield and Faraday efficiency.

[0042] Figure 3 is a diagram of the electrochemical test device, which uses an H-type electrolytic cell and a three-electrode system for testing.

[0043] Figure 4 , Figure 5 is the UV-vis absorption spectrum and standard curve of the indophenol blue method used in the experiment to detect the Faraday efficiency and ammonia nitrogen content in the electrolyte. As shown in the figure, five standard curve concentrations were set in the experiment, ranging from 0.0, 0.2, 0.4, 0.8, to 1.2 ug ml -1 , and the R 2The reliability is higher, and can be used as an external standard curve. Figure 6 For the determination results, the electrode is used for electrocatalytic nitrate to reach 95.92% of Faraday efficiency at-0.5V vs.RHE, and can reach the highest 202.97mmol h -1 g -1 The ammonia nitrogen yield.

[0044] In summary, the Cu@TVPT-COF electrode material has higher ammonia nitrogen yield and Faraday efficiency, and has good electrocatalytic stability, so the Cu@TVPT-COF material has a relatively ideal development and application prospect in the field of electrocatalytic nitrate reduction.

[0045] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the technical scheme of the present application still falls within the protection scope of the present application.

Claims

1. A copper-doped ionic COF material Cu@TVPT-COF, characterized in that, Cu as the central metal atom, and an ionic COF material as the matrix to obtain Cu@TVPT-COF; The preparation method of the copper-doped ionic COF material Cu@TVPT-COF is as follows: 1) TVN and TAPT are mixed, dissolved in ethanol / water, degassed by three freeze-thaw cycles, and then reacted, washed with ethanol and water six times, filtered, and dried to obtain the ionic COF material TVPT-COF; 2) copper sulfate and TVPT-COF are dissolved in THF, mixed, stirred, transferred to a high-pressure reaction kettle, reacted, centrifuged to collect the precipitate, washed with ethanol, and dried to obtain Cu@TVPT-COF.

2. The preparation method of the copper-doped ionic COF material Cu@TVPT-COF in claim 1, characterized in that, The preparation method is as follows: 1) TVN and TAPT are mixed, dissolved in ethanol / water, degassed by three freeze-thaw cycles, and then reacted, washed with ethanol and water six times, filtered, and dried to obtain the ionic COF material TVPT-COF; 2) copper sulfate and TVPT-COF are dissolved in THF, mixed, stirred, transferred to a high-pressure reaction kettle, reacted, centrifuged to collect the precipitate, washed with ethanol, and dried to obtain Cu@TVPT-COF.

3. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 1), the molar ratio of TAPT to TVN is 5:3, and the volume ratio of ethanol to water is 4:

1.

4. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 1), the reaction is carried out at 120°C for 72h.

5. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 2), the mass ratio of copper sulfate to TVPT-COF is 2:

1.

6. The method for preparing a copper-doped ionic COF material Cu@TVPT-COF according to claim 2, characterized in that: In step 2), the reaction is carried out at 120°C for 36h.

7. A Cu@TVPT-COF electrode comprising the Cu@TVPT-COF of claim 1. The preparation method is as follows: Cu@TVPT-COF, acetylene black, naphthol film solution, isopropyl alcohol, ultrapure water, and Cu@TVPT-COF electrode are prepared by the method of claim 1.

8. The application of the Cu@TVPT-COF electrode of claim 7 in electrochemical nitrate reduction.

9. Use according to claim 8, characterized in that, The Cu@TVPT-COF electrode of claim 7 is used as the working electrode, the counter electrode is a platinum sheet electrode, the reference electrode is an Ag / AgCl reference electrode, and both the cathode electrolyte and the anode electrolyte use 0.1 M KNO3 solution and 1 M KOH solution. The Cu@TVPT-COF electrode of claim 7 is used as the working electrode, the counter electrode is a platinum sheet electrode, the reference electrode is an Ag / AgCl reference electrode, and both the cathode electrolyte and the anode electrolyte use 0.1 M KNO3 solution and 1 M KOH solution.

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