Aminooxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, its preparation method and application

Abstract

The present invention discloses an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material and its preparation method and application, belonging to the technical field of inorganic nanomaterial synthesis. A substrate is placed in an electrolyte solution containing soluble nitrate and ferrous sulfate, with a saturated calomel electrode as the reference electrode and a Pt as the counter electrode. The hydrotalcite nanosheet array is directly grown on the surface of the cleaned conductive substrate by the potentiostatic method. Based on this, cyclic voltammetry is used for activation modification, and further organic combination is carried out on this basis to finally synthesize an organic-inorganic-organic hybrid electrode material. Subsequently, an electrode is prepared by assembling with amidoximated polyacrylonitrile. The present invention provides a new method for electro-synthesizing a nanosheet array by a one-step method. By regulating the potentiostatic time and voltage magnitude, the oxygen exposure degree in the target compound can be adjusted, enabling the product to have a large surface area and dispersion stability, and having a good synergistic adsorption effect on heavy metal ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic nanomaterial synthesis, and particularly relates to an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] In the prior art, the preparation of nanomaterials mostly uses the liquid-phase hydrothermal method. The structure and morphology of the materials obtained by this preparation method are relatively controllable, so it is widely favored by scientific researchers or enterprises. However, the hydrothermal method generally requires high temperature and high pressure, which leads to serious energy consumption and strict requirements for equipment during the production process. Electrochemical synthesis is a new, convenient and feasible method for rapidly preparing nanomaterials on a conductive substrate. By regulating the composition, pH, temperature, synthesis voltage, etc. of the electrolyte solution, it is expected to obtain a method for rapidly preparing new nanomaterials at a low voltage.

[0003] Layered double metal hydroxides (LDHs, also known as hydrotalcites) are a kind of inorganic layered materials with low cost, non-toxicity, high thermal stability and environmental friendliness, and are widely used. Due to the types, ratios and distributions of divalent and trivalent metal ions in the main layer board and the guest in the interlayer can be artificially regulated, and the diversity of their design, synthesis and assembly, the characteristics such as the exchangeability of interlayer anions and the variable valence states of metal ions in the layer board, the composition or structure of LDHs can be regulated or modified according to different requirements such as uses and properties to obtain LDHs materials that meet different needs. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and use of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, providing a new method for synthesizing nanosheet arrays by one-step electrosynthesis. By regulating the potentiostatic time and voltage magnitude, the oxygen exposure degree in the target compound can be adjusted, so that the product has a large surface area and dispersion stability, and has a good synergistic adsorption effect on heavy metal ions.

[0005] To achieve the above purpose, the present invention provides a preparation method of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, including the following steps:

[0006] S1. Construction of an LDHs structured electrode: Prepare a mixed solution of soluble metal nitrates and sulfates as an electrolyte solution, use a saturated calomel electrode as a reference electrode, a Pt as a counter electrode, select a cleaned conductive substrate for potentiostatic deposition, and directly grow an LDHs nanosheet array on the conductive substrate to obtain an LDHs structured electrode. The LDHs structured electrode is dried at 60 °C for 6 h and then stored;

[0007] S2. Construction of LDH-O electrode: Using cyclic voltammetry, in a KOH solution, the LDHs structured electrode was electrochemically activated by cyclic voltammetry to obtain the LDH-O electrode;

[0008] S3. Construction of LDH-O@PA two-dimensional nanosheet array electrode material: Mix PAN and DMF at a mass ratio of 1:30 and stir for 10 - 15 h, soak the LDH-O electrode in it, and dry it suspended at 70 °C; Prepare a 25 mL solution containing hydroxylamine hydrochloride and Na2CO3 with deionized water, soak the dried LDH-O electrode in it, carry out a water bath at 70 °C for 90 min, wash it with deionized water and then air-dry it in an oven at 80 °C to obtain the LDH-O@PA two-dimensional nanosheet array electrode material.

[0009] Preferably, in step S1, the conductive substrate is selected from any one of nickel foam, ITO, FTO, nickel sheet, titanium sheet, copper mesh, carbon fiber cloth, and transparent conductive cloth.

[0010] Preferably, the cleaning treatment method of the conductive substrate is: ultrasonically treat the conductive substrate with absolute ethanol, acetone, and deionized water for 10 - 20 min each to remove surface impurities, and then soak it in a potassium permanganate standard solution for 10 h.

[0011] Preferably, the soluble metal nitrate is selected from any one of Mg(NO3)2, Co(NO3)2, Ni(NO3)2, Ca(NO3)2, Cu(NO3)2, Fe(NO3)2, Mn(NO3)2, LiNO3; the sulfate is FeSO4·7H2O, the molar ratio of the soluble metal nitrate to the sulfate in the mixed solution is (2:1) - (1:2), the concentration of the soluble metal nitrate is 0.1 - 1.5 mg / mL, and the concentration of the divalent iron sulfate is 0.1 - 1.5 mg / mL.

[0012] Preferably, in step S1, the SCE potential of the conductive substrate is -2 to -0.5 V, the time of the constant potential deposition is 50 - 400 s, and the temperature of the constant potential deposition is 10 - 50 °C.

[0013] Preferably, in step S2, the concentration of the KOH solution is 0.1 M, and the cyclic voltammetry potential is 1 - 4 V vs SCE.

[0014] Preferably, in step S3, the soaking time of the LDH-O electrode is 30 - 90 min.

[0015] Preferably, in step S3, in the mixed solution of hydroxylamine hydrochloride and Na2CO3, the concentrations of hydroxylamine hydrochloride and Na2CO3 are 80 mg / mL and 60 mg / mL respectively.

[0016] The present invention also provides an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, which is prepared from the above-mentioned amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material.

[0017] The amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material provided by the present invention is applied in the fields of uranium extraction from seawater and nuclear sewage treatment.

[0018] Therefore, the present invention adopts the above-mentioned amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material and its preparation method and application, and the beneficial effects are as follows:

[0019] (1) By regulating the electrosynthesis time, the present invention well regulates the size and density of the hydrotalcite nanosheets to achieve the best performance. The material prepared based on this method can not only largely maintain the excellent morphology of the LDHs precursor and realize the high utilization rate of the active sites of the electrode material, but also realize the dehydrogenation reconstruction on the surface of the LDHs through the potentiostatic oxidation process, exposing the active oxygen groups (LDH-O). By regulating the potentiostatic time and voltage magnitude, the oxygen exposure degree in the target compound can be adjusted, thereby realizing the fine regulation of the microstructure of the electrode material.

[0020] (2) The present invention for the first time uses a simple and rapid one-step electrosynthesis method to prepare LDH nanosheet arrays on a conductive substrate and modify them to have good hydrophilicity; it has a high surface area and rich binding sites, enabling the electron-rich groups (amine and imine) on the polymer chain to have electrostatic interaction with the LDHs, thereby preventing the stacking characteristics of the LDHs layers. The LDHs composite nanomaterials usually have a large surface area and dispersion stability, and have a good synergistic adsorption effect on heavy metal ions. The synthesized transition metal-based two-dimensional structured electrode material has a quite broad application prospect in the field of uranium extraction from seawater.

[0021] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0022] Figure 1 It is a preparation flow chart of the amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material of the present invention;

[0023] Figure 2 It is a scanning electron microscope image of the CoFe-LDH nanosheet array prepared in Example 1 of the present invention;

[0024] Figure 3 It is a scanning electron microscope image of the CoFe-O nanosheet array prepared in Example 1 of the present invention;

[0025] Figure 4 Scanning electron microscopy image of the LDH-O@PA nanosheet array prepared in Example 1 of the present invention;

[0026] Figure 5 Scanning electron microscopy image of the LDH-O@PA nanosheet array after adsorbing uranium, prepared in Example 1 of the present invention. Detailed implementation manners

[0027] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and examples.

[0028] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0029] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered by the protection scope of the present invention.

[0030] As shown in the flow chart Figure 1 The present invention provides a method for preparing an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, including the following steps:

[0031] S1. Construction of the LDHs structured electrode: Prepare a mixed solution of soluble metal nitrates and sulfates as the electrolyte solution, use a saturated calomel electrode as the reference electrode, a Pt as the counter electrode, select a cleaned conductive substrate for potentiostatic deposition, and directly grow an LDHs nanosheet array on the conductive substrate to obtain the LDHs structured electrode, and the LDHs structured electrode is dried at 60 °C for 6 h and then stored;

[0032] S2. Construction of the LDH-O electrode: Use cyclic voltammetry to electrochemically activate the LDHs structured electrode in a KOH solution to obtain the LDH-O electrode;

[0033] S3. Construction of the LDH-O@PA two-dimensional nanosheet array electrode material: Mix PAN and DMF at a mass ratio of 1:30 and stir for 10 - 15 h, soak the LDH-O electrode, and dry it suspended at 70 °C; Prepare a 25 mL solution containing hydroxylamine hydrochloride and Na2CO3 with deionized water, soak the dried LDH-O electrode, perform a water bath at 70 °C for 90 min, wash with deionized water, and air-dry in an oven at 80 °C to obtain the LDH-O@PA two-dimensional nanosheet array electrode material.

[0034] In step S1, the conductive substrate is selected from any one of nickel foam, ITO, FTO, nickel sheet, titanium sheet, copper mesh, carbon fiber cloth, and transparent conductive cloth.

[0035] The cleaning treatment method of the conductive substrate is as follows: The conductive substrate is ultrasonically treated with absolute ethanol, acetone, and deionized water for 10 - 20 min each to remove surface impurities, and then soaked in a potassium permanganate standard solution for 10 h.

[0036] The soluble metal nitrate is selected from any one of Mg(NO3)2, Co(NO3)2, Ni(NO3)2, Ca(NO3)2, Cu(NO3)2, Fe(NO3)2, Mn(NO3)2, and LiNO3; the sulfate is FeSO4·7H2O. The molar ratio of the soluble metal nitrate to the sulfate in the mixed solution is (2:1) - (1:2), the concentration of the soluble metal nitrate is 0.1 - 1.5 mg / mL, and the concentration of the divalent iron sulfate is 0.1 - 1.5 mg / mL.

[0037] In step S1, the SCE potential of the conductive substrate is -2 to -0.5 V, the time of potentiostatic deposition is 50 - 400 s, and the temperature of potentiostatic deposition is 10 - 50 °C.

[0038] In step S2, the concentration of the KOH solution is 0.1 M, and the cyclic voltammetry potential is 1 - 4 V vs SCE.

[0039] In step S3, the soaking time of the LDH-O electrode is 30 - 90 min.

[0040] In step S3, in the mixed solution of hydroxylamine hydrochloride and Na2CO3, the concentrations of hydroxylamine hydrochloride and Na2CO3 are 80 mg / mL and 60 mg / mL respectively.

[0041] The present invention also provides a amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, which is prepared from the above-mentioned amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material.

[0042] The amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material provided by the present invention is applied in the fields of uranium extraction from seawater, nuclear sewage treatment, hydrogen evolution reaction (HER) in electrolytic water, and oxygen evolution reaction (OER).

[0043]

Example 1

[0044] Synthesis of carbon cloth supported cobalt-iron layered double hydroxide nanosheet array:

[0045] a: Ultrasonically clean the carbon cloth conductive substrate with absolute ethanol, acetone, and deionized water for 10 minutes each to remove surface impurities, and then soak it in a potassium permanganate standard solution for 8 hours;

[0046] b: Prepare 50 mL of a mixed salt solution containing 0.15 mg / mL cobalt nitrate (Co(NO3)2) and 0.15 mg / mL ferrous sulfate (FeSO4) as the electrolyte solution;

[0047] c: In the electrolyte solution prepared in step b, using a saturated calomel electrode as the reference electrode and a platinum wire as the counter electrode, directly grow cobalt-iron layered double hydroxide (CoFe-LDH) nanosheet arrays on nickel foam by the potentiostatic method. The potential for electrochemical synthesis is set to -1 V, the synthesis time is 200 s, and the synthesis temperature is 25 °C. The scanning electron microscope image of the prepared sample is as Figure 2 shown, and the prepared CoFe-LDH exhibits an obvious sheet-like array structure.

[0048] d: Prepare a 0.1 mg / mL KOH solution. Using a saturated calomel electrode as the reference electrode and a Pt as the counter electrode, synthesize LDH-O nanosheet arrays on the CoFe-LDH synthesized in step c by cyclic voltammetry. The scanning electron microscope image of the sample is as Figure 3 shown, and the activated sample LDH-O maintains the original nanosheet array structure.

[0049] e: Prepare PAN and DMF in a ratio of 1:30. Immerse the synthesized LDH-O for 30 minutes, dry it, and then place it in a solution containing 80 mg / mL hydroxylamine hydrochloride and 60 mg / mL sodium carbonate at 70 °C for a water bath for 90 minutes. Rinse with deionized water and dry to synthesize the LDH-O@PA nanosheet array electrode. The scanning electron microscope image of the sample is as Figure 4 shown. After being coated with PAO, the LDH-O still maintains a sheet-like structure, indicating that PAO is uniformly loaded on the nanosheets.

[0050] Use the synthesized LDH-O@PA nanosheet array electrode for uranium extraction from seawater. In this reaction, the LDH-O@PA nanosheet array electrodes are arranged in parallel, fixed 5 - 20 cm below the liquid surface, and a flow electrolytic cell or floating platform device layout is adopted. Adjust the distance between the electrode sheet and the counter electrode (platinum wire electrode) to 1 - 2 cm to optimize the electrolysis effect. Too large a distance will increase the resistance and energy consumption, while too small a distance may lead to short circuits or electrode damage. The electrolysis equipment can be paired with a solar circuit board to achieve self-powered operation.

[0051] The scanning electron microscope image of the electrode material after adsorption is as Figure 5 shown. Obvious uranium product deposits can be clearly seen on the surface of the LDH-O@PA after adsorption.

[0052]

Example 2

[0053] Synthesis of nickel-iron layered double hydroxide nanosheet arrays supported on nickel foam:

[0054] a: Ultrasonically treat the conductive substrate nickel foam with absolute ethanol, acetone, and deionized water for 10 min each to remove surface impurities;

[0055] b: Prepare 50 mL of a mixed salt solution containing 1 mg / mL nickel nitrate (Ni(NO3)2) and 0.5 mg / mL ferrous sulfate (FeSO4) as the electrolyte solution;

[0056] c: In the electrolyte solution prepared in step a, using a saturated calomel electrode as the reference electrode and a platinum wire as the counter electrode, directly grow nickel-iron layered double hydroxide nanosheet arrays on the nickel foam by the potentiostatic method. Set the potential for electrochemical synthesis to -0.9 V, the synthesis time to 200 s, and the synthesis temperature to 25 °C.

[0057] d: Prepare 0.1 mg / mL KOH solution, using a saturated calomel electrode as the reference electrode and Pt as the counter electrode, and synthesize LDH-O on the NiFe-LDH synthesized in step 2) by cyclic voltammetry.

[0058] e: Prepare PAN and DMF in a ratio of 1:30. Immerse the synthesized LDH-O for 30 min, dry it, and then perform a water bath at 70 °C for 90 min in a solution containing 80 mg / mL hydroxylamine hydrochloride and 60 mg / mL sodium carbonate. Rinse with deionized water and dry to synthesize LDH-O@PA.

[0059]

Example 3

[0060] Synthesis of lithium-iron layered double hydroxide nanosheet arrays:

[0061] a: Ultrasonically treat the conductive substrate nickel foam with absolute ethanol, acetone, and deionized water for 10 min each to remove surface impurities;

[0062] b: Prepare 50 mL of a mixed salt solution containing 0.5 mg / mL lithium nitrate (LiNO3) and 0.25 mg / mL ferrous sulfate (FeSO4) as the electrolyte solution;

[0063] c: In the electrolyte solution prepared in step a, using a saturated calomel electrode as the reference electrode and a platinum wire as the counter electrode, directly grow lithium-iron layered double hydroxide nanosheet arrays on the nickel foam by the potentiostatic method. Set the potential for electrochemical synthesis to -1.1 V, the synthesis time to 300 s, and the synthesis temperature to 25 °C.

[0064] d: Prepare 0.1 mg / mL KOH solution, using a saturated calomel electrode as the reference electrode and Pt as the counter electrode, and synthesize LDH-O on the LiFe-LDH synthesized in step 2) by cyclic voltammetry

[0065] e: Prepare PAN and DMF in a ratio of 1:30, soak the synthesized LDH-O for 30 min, dry it, and then perform a water bath at 70 °C for 90 min in a solution containing 80 mg / mL of hydroxylamine hydrochloride and 60 mg / mL of sodium carbonate. Rinse with deionized water and dry to synthesize LDH-O@PAN.

[0066] Therefore, the preparation method and use of a hydroxylamine-oxime modified LDH-O@PA two-dimensional nanosheet array electrode material provided by the present invention provide a new method for synthesizing nanosheet arrays by one-step electrosynthesis. By regulating the potentiostatic time and voltage magnitude, the oxygen exposure degree in the target compound can be adjusted, enabling the product to have a large surface area and dispersion stability, and having a good synergistic adsorption effect on heavy metal ions.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements do not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material, characterized in that It includes the following steps: S1. Construction of LDHs structured electrode: Prepare a mixed solution of soluble metal nitrate and sulfate as the electrolyte solution, use a saturated calomel electrode as the reference electrode, Pt as the counter electrode, select a cleaned conductive substrate for potentiostatic deposition, directly grow LDHs nanosheet arrays on the conductive substrate to obtain the LDHs structured electrode, and store the LDHs structured electrode after drying at 60 °C for 6 h; the soluble metal nitrate is selected from any one of Mg(NO3)2, Co(NO3)2, Ni(NO3)2, Ca(NO3)2, Cu(NO3)2, Fe(NO3)2, Mn(NO3)2, LiNO3; the sulfate is FeSO4·7H2O, and the molar ratio of the soluble metal nitrate to the sulfate in the mixed solution is (2:1)-(1:2), the concentration of the soluble metal nitrate is 0.1-1.5 mg / mL, and the concentration of the sulfate is 0.1-1.5 mg / mL; S2. Construction of LDH-O electrode: Using cyclic voltammetry, electrochemically activate the LDHs structured electrode in KOH solution to obtain the LDH-O electrode; S3. Construction of LDH-O@PA two-dimensional nanosheet array electrode material: Mix PAN and DMF at a mass ratio of 1:30 and stir for 10-15 h, immerse the LDH-O electrode, and dry it suspended at 70 °C; Prepare 25 mL of a solution containing hydroxylamine hydrochloride and Na2CO3 with deionized water, immerse the dried LDH-O electrode, bath at 70 °C for 90 min, wash with deionized water and air-dry at 80 °C in a drying oven to obtain the LDH-O@PA two-dimensional nanosheet array electrode material; In step S1, the SCE potential of the conductive substrate is -2~-0.5 V, the time of the potentiostatic deposition is 50-400 s, and the temperature of the potentiostatic deposition is 10-50 °C; In step S2, the concentration of the KOH solution is 0.1-2 M, and the cyclic voltammetry potential is 1-4 V vs SCE; In step S3, the immersion time of the LDH-O electrode is 30-90 min.

2. The preparation method of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material according to claim 1, wherein, In step S1, the conductive substrate is selected from any one of nickel foam, ITO, FTO, nickel sheet, titanium sheet, copper mesh, carbon fiber cloth and transparent conductive cloth.

3. The preparation method of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material according to claim 1, characterized in that, The cleaning treatment method of the conductive substrate is: ultrasonically clean the conductive substrate with anhydrous ethanol, acetone and deionized water for 10-20 min each to remove surface impurities, and then soak it in a potassium permanganate standard solution for 10 h.

4. The preparation method of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material according to claim 1, characterized in that, In step S3, in the mixed solution of hydroxylamine hydrochloride and Na2CO3, the concentrations of hydroxylamine hydrochloride and Na2CO3 are 80 mg / mL and 60 mg / mL respectively.

5. A hydroxylamine-oxime modified LDH-O@PA two-dimensional nanosheet array electrode material, characterized in that, The amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material is prepared by the preparation method of an amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material according to any one of claims 1-4.

6. The amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material according to claim 5, wherein, The amidoxime-modified LDH-O@PA two-dimensional nanosheet array electrode material is applied in the fields of uranium extraction from seawater or nuclear sewage treatment.

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