Preparation of high-entropy hydrotalcite / graphene / foam nickel composite electrode and its application in degradation of tetracycline

Abstract

The application discloses a kind of preparation of high-entropy hydrotalcite / graphene / foam nickel composite electrode and the application of degrading tetracycline, belong to environmental functional materials and electrocatalytic oxidation technical field.The high-entropy hydrotalcite / reduced graphene oxide / foam nickel composite electrode material is synthesized by optimized aqueous coprecipitation-hydrothermal strategy, and its characteristics are that high-entropy hydrotalcite nanosheet size is 50-90 nm, thickness is 10-15 nm, and vertical staggered growth on the surface of reduced graphene oxide / foam nickel substrate.In the application of electrocatalytic degradation of tetracycline antibiotics, the electrode has the advantages of high degradation efficiency, low energy consumption, good stability, environmental friendliness, etc., especially for high-concentration tetracycline wastewater, it shows excellent treatment effect, the degradation rate is 99.32% under the concentration of 500 mg / L tetracycline solution for two hours, and the energy consumption can be as low as 0.0395 kWh / kg TC, with good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and electrocatalytic oxidation technology, and in particular provides a high-entropy hydrotalcite / graphene / nickel foam composite electrode and its preparation method. This electrode material can be effectively used for the electrocatalytic degradation of tetracycline antibiotics. Background Technology

[0002] Tetracycline antibiotics are widely used in human medicine, livestock farming, and aquaculture due to their broad-spectrum antibacterial activity and low price. However, these drugs have low metabolic rates in organisms, with most entering the environment through excretion as unchanged or active metabolites. Because tetracycline molecules are stable and difficult to degrade naturally, they can persist in water and soil for extended periods, inducing the growth of drug-resistant bacteria, leading to ecosystem damage and risks to human health. Studies have shown that tetracycline detection rates are high in water and soil in many parts of my country, and it has already induced antibiotic resistance genes, seriously threatening public health.

[0003] Currently, methods for treating tetracycline wastewater mainly include adsorption, photocatalytic oxidation, Fenton oxidation, and electrocatalytic oxidation. Among these, while commonly used adsorbents such as activated carbon and molecular sieves can remove some tetracycline, they require regeneration or treatment after saturation, easily leading to secondary pollution. Photocatalytic methods, such as those using TiO2 and g-C3N4 catalysts, are often limited by low light energy utilization and easy catalyst deactivation. Fenton oxidation has stringent pH requirements and is prone to iron sludge pollution. Conversely, electrocatalytic oxidation has attracted widespread attention due to its advantages such as strong oxidation capacity, high removal efficiency, good controllability, mild reaction conditions, and environmental friendliness.

[0004] The core of electrocatalytic oxidation lies in the design and fabrication of electrode materials. Traditional two-dimensional electrodes, such as platinum sheets and graphite electrodes, suffer from severe oxygen evolution side reactions and low current efficiency. In recent years, layered double hydroxides (LDHs) have been widely studied due to their unique layered structure, tunable metal composition, high atomic-level dispersion of metal elements, and excellent electrochemical performance. However, due to strong interparticle interactions, single layered double hydroxide nanosheets are prone to aggregation. Hybridizing LDH with graphene, which has high specific surface area, good conductivity, and high chemical and thermal stability, and loading it onto a three-dimensional porous nickel foam substrate can effectively improve the electron transport rate and the dispersion of active LDH nanosheets, promoting the exposure of active sites. However, traditional LDH electrode materials have limited metal types and insufficient catalytic active sites, resulting in limited catalytic efficiency under complex reaction conditions, especially for treating high-concentration tetracycline wastewater; moreover, the electrode materials lack stability and are prone to metal ion dissolution and catalytic activity decay during long-term use.

[0005] High-entropy layered double hydroxides (HE-LDHs) are a novel class of layered high-entropy materials developed in recent years. Their layers contain five or more metal cations in equimolar or near-equimolar ratios, endowing the material with unique structure and catalytic properties through the cocktail effect and entropy stabilization effect. Applying them to the catalytic oxidative degradation of tetracycline antibiotics holds promise for enhancing the catalytic degradation performance by promoting the generation of hydroxyl radicals through the synergistic effect of multiple variable-valence metals. However, the differences in solubility products and coordination abilities of the various metals make the preparation of well-crystallized HE-LDHs and their effective composite with conductive substrate materials a challenge, and no reports have been found to date. Summary of the Invention

[0006] This invention aims to provide a method for preparing a high-entropy hydrotalcite / graphene / nickel foam composite electrode and its application in tetracycline degradation. The synthesis process is simple and environmentally friendly, avoiding high-temperature and high-pressure operating conditions and the use of organic reagents. The resulting electrode material exhibits excellent catalytic oxidation degradation performance of tetracycline, with advantages such as high efficiency, low energy consumption, and good stability, thus solving the problems of low degradation efficiency, high energy consumption, and difficulty in treating high-concentration tetracycline antibiotic wastewater in existing technologies.

[0007] This invention first employs organic acid-assisted hydrothermal treatment to obtain a nickel foam framework uniformly coated with graphene oxide. Then, a high-entropy layered double hydroxide (HE-LDH) / reduced graphene oxide (rGO) / nickel foam composite electrode material (HE-LDH / rGO / NF) is synthesized via an optimized aqueous co-precipitation-hydrothermal strategy. The HE-LDH nanosheets are characterized by a size of 50–90 nm and a thickness of 10–15 nm, vertically interleaved on the surface of the rGO / NF substrate, forming a multi-level nanosheet array structure. This high-entropy composite electrode not only exhibits a multi-metal synergistic effect, significantly promoting the generation of hydroxyl radicals, but also possesses an entropy stabilizing effect, resulting in excellent structural stability. Furthermore, thanks to the three-dimensional nanosheet array structure of the composite electrode and the strategy of direct growth on the NF substrate, charge transfer resistance is significantly reduced, and electrocatalytic activity and current efficiency are improved.

[0008] The preparation method of the high-entropy hydrotalcite / graphene / nickel foam composite electrode of the present invention specifically includes the following steps: (1) Pretreatment of nickel foam: The nickel foam was ultrasonically cleaned for 15 minutes each with acetone, 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol to remove surface oil and oxides, and then vacuum dried at 80 °C for 3 hours. (2) Graphene oxide coating: Graphene oxide is dispersed in deionized water and ultrasonically dispersed for 25 minutes. The graphene oxide suspension is peeled off and a uniform graphene oxide suspension is formed. Citric acid is added and ultrasonic treatment is continued for 5-10 minutes to obtain a uniform and stable citric acid modified graphene oxide suspension. The suspension is then transferred to a high-pressure reactor lined with polytetrafluoroethylene. The concentration range of the graphene oxide suspension is 1-5 mg / mL. The mass ratio of graphene oxide to citric acid is 1:1-3:1 and the ultrasonic power is 300W. The pretreated nickel foam from step (1) is immersed in the above suspension and hydrothermally reacted at 80-140 °C for 4-8 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The product is taken out and washed repeatedly with deionized water. After freeze-drying for 6 hours, a graphene oxide-coated nickel foam skeleton GO / NF is obtained. (3) Growth of high-entropy hydrotalcite: Prepare a mixed salt solution containing five or more metal ions and a mixed alkali solution containing NaOH and Na2CO3; place the graphene oxide-coated nickel foam substrate obtained in step (2) into a four-necked flask containing 100 mL of deionized water, add 10-60 mg of citric acid, stir for 5-10 minutes, then adjust the pH to 8.5 ± 0.1 ~ 10.5 ± 0.1 with the mixed alkali solution; after stabilizing for 5-10 minutes, add the mixed salt solution and mixed alkali solution simultaneously by double drop method while continuously stirring, and keep the pH value of the solution stable at 8.5 ± 0.1 ~ 10.5 ± 0.1; after the mixed salt solution is added, transfer the reaction system to a high-pressure reactor and heat at 70-150 °C. The product was crystallized and grown at ℃ for 6-10 hours. After the reaction was completed, it was naturally cooled to room temperature. The product was repeatedly washed with deionized water and freeze-dried for 6 hours to obtain the high-entropy hydrotalcite / reduced graphene oxide / nickel foam composite electrode material HE-LDH / rGO / NF.

[0009] (4) Electrocatalytic degradation of tetracycline antibiotics: The composite electrode obtained in step (3) was used for electrocatalytic degradation of tetracycline antibiotics. Electrochemical tests were performed using a three-electrode system. The composite electrode obtained in step (3) was used as the working electrode, the platinum sheet as the counter electrode, and the calomel electrode as the reference electrode. Degradation was carried out under constant current or constant voltage conditions.

[0010] (5) The mixed salt mentioned in step (3) includes divalent and trivalent metal salts, which exist in the form of one or a mixture of nitrates or chlorides, and the divalent metal M in the metal salts is... 2+ Cu 2+ Ni 2+ Co 2+ Mn 2+ Mg 2+ and Zn 2+ Three or four of them, trivalent metal ions M 3+For V 3+ Fe 3+ Ti 3+ Cr 3+ And Al 3+ Two or three of the metals are added in equal molar proportions, with the total amount of metal salts added ranging from 5 to 30 mmol.

[0011] (6) The tetracycline antibiotics mentioned in step (4) include at least one of tetracycline, oxytetracycline, chlortetracycline and doxycycline, with an initial concentration of 50 to 500 mg / L.

[0012] Compared with the prior art, the present invention has the following advantages and features: (1) High catalytic degradation activity for high concentrations of tetracycline antibiotics: Through the design of high-entropy hydrotalcite, Cu 2+ / Cu + Ni 3+ / Ni 2+ Mn 4+ / Mn 3+ / Mn 2+ Fe 3+ / Fe 2+ V 5+ / V 4+ / V 3+ The synergistic effect of multiple variable-valence metals significantly promotes the generation of hydroxyl radicals, thereby rapidly degrading tetracycline molecules. Experiments show that the degradation rate can reach over 96% in a 50 mg / L tetracycline solution; at a high concentration of 500 mg / L, the degradation rate is as high as 99.32%. The obtained electrode material is not only suitable for the degradation of low-concentration tetracycline, but also can efficiently degrade high-concentration tetracycline antibiotics, which is significantly superior to existing technologies.

[0013] (2) Low energy consumption in the catalytic degradation of tetracycline: The unique nanosheet-like array structure and the introduction of reduced graphene oxide improve the conductivity of the electrode and the utilization rate of active sites. At the same time, the high oxygen evolution potential effectively suppresses the oxygen evolution side reaction, resulting in a significant increase in current efficiency. When degrading a high concentration of tetracycline solution of 500 mg / L, the energy consumption is as low as 0.0395 kWh / kg TC, which has obvious advantages.

[0014] (3) Environmentally friendly: The use of toxic binders is avoided in the preparation of composite electrodes, and the degradation products are small molecules such as phenylacetone as analyzed by LC-MS. According to MSDS, they are non-toxic and harmless, and there is no risk of secondary pollution. Attached Figure Description

[0015] Figure 1 X-ray diffraction pattern of the CuNiMnFeV-LDH / rGO / NF composite electrode prepared in Example 1 Figure 2 Scanning electron microscope image of the CuNiMnFeV-LDH / rGO / NF composite electrode prepared in Example 1. Figure 3 The graph shows the degradation rate and energy consumption of the CuNiMnFeV-LDH / rGO / NF composite electrode prepared in Example 1 in low-concentration and high-concentration tetracycline solutions. Detailed Implementation The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0016] Example 1 (1) Two pieces of nickel foam with a size of 4 cm × 4 cm were ultrasonically cleaned for 15 minutes each with acetone, 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol to remove surface oil and oxides, and then vacuum dried at 80 ℃ for 3 hours. (2) 120 mg of graphene oxide gel was dispersed in 60 mL of deionized water and ultrasonically dispersed for 25 minutes to obtain a completely exfoliated graphene oxide suspension. Then, 120 mg of citric acid was added and ultrasonically dispersed for 5 minutes to obtain a uniform and stable citric acid-modified graphene oxide suspension. The suspension was then transferred to a high-pressure reactor lined with polytetrafluoroethylene. The pretreated nickel foam obtained in step (1) was then completely immersed in the citric acid-modified graphene oxide suspension and hydrothermally reacted at 100 °C for 6 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was removed and repeatedly washed with deionized water. After freeze-drying, the graphene oxide-coated nickel foam skeleton GO / NF was obtained. (3) Dissolve 4 mmol of Cu(NO3)2·3H2O (0.8044 g), Ni(NO3)2·6H2O (0.9683 g), 50% Mn(NO3)2 (0.9691 g), Fe(NO3)3·9H2O (0.9906 g), and VCl3 (0.6292 g) in 100 mL of deionized water, and sonicate for 5 minutes to obtain a mixed salt solution; the mixed alkali solution is prepared according to [OH-]. - ] / [CO3 2- ] = 3.2 and [CO3 2- ] / [M 3+ To prepare a mixed alkaline solution, 24 mmol Na2CO3 (2.5440 g) and 76.8 mmol NaOH (3.0720 g) were dissolved in 150 mL of deionized water and sonicated for 5 minutes. (4) Place the GO / NF substrate obtained in step (2) into a four-necked flask containing 100 mL of deionized water, add 10 mg of citric acid, stir for 5 minutes, and then adjust the pH of the solution to 9.5 ± 0.1 with a mixed alkali solution. After stabilizing for 5 minutes, add the mixed salt solution and the mixed alkali solution simultaneously by double drop method while stirring continuously, and keep the pH of the solution stable at 9.5 ± 0.1. After the mixed salt solution is added, transfer the reaction system to a high-pressure reactor and crystallize and grow at 100 °C for 8 hours. After the reaction is completed, cool naturally to room temperature, wash the obtained product repeatedly with deionized water, freeze dry, and then obtain the high-entropy hydrotalcite / reduced graphene oxide / nickel foam CuNiMnFeV-LDH / rGO / NF composite electrode.

[0017] The X-ray diffraction pattern of the composite electrode CuNiMnFeV-LDH / rGO / NF is shown below. Figure 1 As shown in Figure a, three sharp characteristic peaks are observed at approximately 45.1° (111), 52.6° (200), and 76.7° (220), belonging to the metallic nickel species (standard card number 04-0850), corresponding to the nickel foam substrate. The X-ray diffraction pattern of the composite electrode CuNiMnFeV-LDH / rGO / NF surface-active material powder was obtained by scraping it off. Figure 1 b) The diffraction peaks appearing around 12.0° (003), 35.0° (012), and 60.3° (110) correspond to copper-aluminum hydrotalcite Cu6Al2(CO3)(OH). 16 · 4H2O (Standard Card No. 37-0630).

[0018] Scanning electron microscope image of the composite electrode CuNiMnFeV-LDH / rGO / NF is shown below. Figure 2 (A: low magnification, B: high magnification) As shown. The electrode material consists of CuNiMnFeV-LDH nanosheets with a size of ~67 nm × 10 nm grown vertically and alternately on the surface of rGO / NF substrate, exhibiting a nanosheet-like array morphology.

[0019] The obtained CuNiMnFeV-LDH / rGO / NF composite electrode was used to test the electrocatalytic oxidation degradation of tetracycline.

[0020] A three-electrode system was employed, using the prepared CuNiMnFeV-LDH / rGO / NF composite electrode as the working electrode, a platinum sheet electrode as the counter electrode, and a calomel electrode as the reference electrode. The electrolyte consisted of low-concentration (50 mg / L) and high-concentration (500 mg / L) tetracycline solutions (containing 0.1 mol / L Na₂SO₄ as the supporting electrolyte). A constant current of 10 mA / cm² was used. 2Under the given conditions, an electric current was applied for 7200 s, and samples were taken at regular intervals. The absorbance at 359 nm was measured using a UV spectrophotometer to calculate the degradation rate. Energy consumption was calculated using the formula E = UIt / (m·C0·α), where U is the average voltage, I is the current, t is the time, m is the molar mass of tetracycline, C0 is the initial concentration, and α is the degradation rate. The CuNiMnFeV-LDH / rGO / NF composite electrode exhibited excellent electrocatalytic degradation performance of tetracycline. Its degradation rate and energy consumption in low-concentration and high-concentration tetracycline solutions are shown in the figure. Figure 3 In a 50 mg / L tetracycline solution, the CuNiMnFeV-LDH / rGO / NF electrode exhibited a degradation rate of 96.22% with an energy consumption of 0.1646 kWh / kg TC. At a high concentration of 500 mg / L, the degradation rate reached 99.32%, with an energy consumption of only 0.0395 kWh / kg TC. The CuNiMnFeV-LDH / rGO / NF composite electrode was continuously cycled 10 times in a 50 mg / L tetracycline solution, with each cycle lasting 120 min. After 10 cycles, the degradation rate remained above 90%, indicating good reusability of the electrode.

[0021] Example 2 This embodiment is the same as Example 1 except for the following features: 60 mg of graphene oxide gel is dispersed in 60 mL of deionized water and ultrasonically dispersed for 25 minutes to obtain a completely exfoliated graphene oxide suspension. Then, 30 mg of citric acid is added and ultrasonically dispersed for another 5 minutes to obtain a uniform and stable citric acid-modified graphene oxide suspension. This suspension is then transferred to a high-pressure reactor lined with polytetrafluoroethylene. The pretreated nickel foam obtained in step (1) is then completely immersed in the citric acid-modified graphene oxide suspension and hydrothermally reacted at 90 °C for 5 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The product is then removed and repeatedly washed with deionized water. After freeze-drying, a graphene oxide-coated nickel foam skeleton GO / NF is obtained. The subsequent steps are the same as in Example 1 to obtain the CuNiMnFeV-LDH / rGO / NF-1 composite electrode.

[0022] Example 3 This embodiment is the same as Example 1 except for the following features: 300 mg of graphene oxide gel is dispersed in 60 mL of deionized water and ultrasonically dispersed for 25 minutes to obtain a completely exfoliated graphene oxide suspension. Then, 100 mg of citric acid is added and ultrasonically dispersed for another 10 minutes to obtain a uniform and stable citric acid-modified graphene oxide suspension. This suspension is then transferred to a high-pressure reactor lined with polytetrafluoroethylene. The pretreated nickel foam obtained in step (1) is then completely immersed in the citric acid-modified graphene oxide suspension and hydrothermally reacted at 140 °C for 8 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The product is then removed, washed repeatedly with deionized water, and freeze-dried to obtain a graphene oxide-coated nickel foam skeleton GO / NF. The subsequent steps are the same as in Example 1 to obtain a CuNiMnFeV-LDH / rGO / NF-2 composite electrode.

[0023] Example 4 This embodiment is the same as that in Embodiment 1 except for the following features: The GO / NF substrate obtained in step (2) is placed in a four-necked flask containing 100 mL of deionized water, 30 mg of citric acid is added, and the mixture is stirred for 5 minutes. Then, the pH of the solution is adjusted to 8.5 ± 0.1 with a mixed alkali solution. After stabilizing for 5 minutes, the mixed salt solution and the mixed alkali solution are added simultaneously by double drop method under continuous stirring, and the pH of the solution is kept stable at 8.5 ± 0.1. After the mixed salt solution is added, the reaction system is transferred to a high-pressure reactor and crystallized at 70 °C for 10 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The obtained product is repeatedly washed with deionized water and freeze-dried to obtain the composite electrode CuNiMnFeV-LDH / rGO / NF-3.

[0024] Example 5 This embodiment is the same as that in Embodiment 1 except for the following features: The GO / NF substrate obtained in step (2) is placed in a four-necked flask containing 100 mL of deionized water, 60 mg of citric acid is added, and the mixture is stirred for 10 minutes. Then, the pH of the solution is adjusted to 10.5 ± 0.1 with a mixed alkali solution. After stabilizing for 10 minutes, the mixed salt solution and the mixed alkali solution are added simultaneously by double drop method under continuous stirring, and the pH of the solution is kept stable at 10.5 ± 0.1. After the mixed salt solution is added, the reaction system is transferred to a high-pressure reactor and crystallized at 150 °C for 6 hours. After the reaction is completed, the mixture is naturally cooled to room temperature. The obtained product is repeatedly washed with deionized water and freeze-dried to obtain the composite electrode CuNiMnFeV-LDH / rGO / NF-4.

[0025] Example 6 This embodiment is the same as Example 1 except for the following features: Equimolar amounts of 1 mmol of Cu(NO3)2·3H2O (0.2011 g), Co(NO3)2·6H2O (0.2431 g), 50% Mn(NO3)2 (0.2423 g), Fe(NO3)3·9H2O (0.2476 g), and VCl3 (0.1573 g) were dissolved in 100 mL of deionized water and sonicated for 5 minutes to obtain a mixed salt solution; the mixed alkali solution was prepared according to [OH... - ] / [CO3 2- ] = 3.2 and [CO3 2- ] / [M 3+ The solution was prepared in a ratio of 2: 6 mmol Na2CO3 (0.6360 g) and 19.2 mmol NaOH (0.7680 g) were dissolved in 150 mL of deionized water and sonicated for 5 minutes to obtain a mixed alkaline solution. The subsequent steps were the same as in Example 1 to obtain the CuCoMnFeV-LDH / rGO / NF composite electrode.

[0026] Example 7 This embodiment is the same as Example 1 except for the following features: Equimolar amounts of 6 mmol of Cu(NO3)2·3H2O (1.2066 g), Ni(NO3)2·6H2O (1.4524 g), Co(NO3)2·6H2O (1.4586 g), VCl3 (0.9438 g), and Al(NO3)3·9H2O (0.7179 g) were dissolved in 100 mL of deionized water and sonicated for 5 minutes to obtain a mixed salt solution; the mixed alkali solution was prepared according to [OH... - ] / [CO3 2- ] = 3.2 and [CO3 2- ] / [M 3+ The solution was prepared in a ratio of 2: 36 mmol Na2CO3 (3.8160 g) and 115.2 mmol NaOH (4.6080 g) were dissolved in 150 mL of deionized water and sonicated for 5 minutes to obtain a mixed alkaline solution. The subsequent steps were the same as in Example 1 to obtain the CuNiCoVAl-LDH / rGO / NF composite electrode.

[0027] Example 8 This embodiment is the same as Example 1 except for the following features: Equimolar amounts of 3 mmol of Cu(NO3)2·3H2O (0.6033 g), Ni(NO3)2·6H2O (0.7262 g), Co(NO3)2·6H2O (0.7293 g), 50% Mn(NO3)2 (0.7269 g), VCl3 (0.4719 g), and Al(NO3)3·9H2O (0.3589 g) are dissolved in 100 mL of deionized water and sonicated for 5 minutes to obtain a mixed salt solution; the mixed alkali solution is prepared according to [OH... - ] / [CO3 2- ] = 3.2 and [CO3 2- ] / [M 3+ The solution was prepared in a ratio of 1:2. 18 mmol Na2CO3 (1.9080 g) and 57.6 mmol NaOH (2.3040 g) were dissolved in 150 mL of deionized water and sonicated for 5 minutes to obtain a mixed alkaline solution. The subsequent steps were the same as in Example 1 to obtain the CuNiCoMnVAl-LDH / rGO / NF composite electrode.

[0028] Example 9 This embodiment is the same as Example 1 except for the following features: Equimolar amounts of 3 mmol of Cu(NO3)2·3H2O (0.6033 g), Ni(NO3)2·6H2O (0.7262 g), Co(NO3)2·6H2O (0.7293 g), TiCl3 (0.4627 g), VCl3 (0.4719 g), and Al(NO3)3·9H2O (0.3589 g) were dissolved in 100 mL of deionized water and sonicated for 5 minutes to obtain a mixed salt solution; the mixed alkali solution was prepared according to [OH-]. - ] / [CO3 2- ] = 3.2 and [CO3 2- ] / [M 3+ The solution was prepared in a ratio of 2: 27 mmol Na2CO3 (2.8620 g) and 86.4 mmol NaOH (3.4560 g) were dissolved in 150 mL of deionized water and sonicated for 5 minutes to obtain a mixed alkaline solution. The subsequent steps were the same as in Example 1 to obtain the CuNiCoTiVAl-LDH / rGO / NF composite electrode.

[0029] Example 10 This embodiment is the same as Example 1 except for the following features: Equimolar amounts of 3 mmol of Cu(NO3)2·3H2O (0.6033 g), Ni(NO3)2·6H2O (0.7262 g), Co(NO3)2·6H2O (0.7293 g), Cr(NO3)3·9H2O (1.200 g), VCl3 (0.4719 g), and Al(NO3)3·9H2O (0.3589 g) are dissolved in 100 mL of deionized water and sonicated for 5 minutes to obtain a mixed salt solution; the mixed alkali solution is prepared according to [OH... - ] / [CO3 2- ] = 3.2 and [CO3 2- ] / [M 3+ The solution was prepared in a ratio of 2: 27 mmol Na2CO3 (2.8620 g) and 86.4 mmol NaOH (3.4560 g) were dissolved in 150 mL of deionized water and sonicated for 5 minutes to obtain a mixed alkaline solution. The subsequent steps were the same as in Example 1 to obtain the CuNiCoCrVAl-LDH / rGO / NF composite electrode.

Claims

1. A high-entropy hydrotalcite / graphene / nickel foam composite electrode, characterized in that: In the high-entropy hydrotalcite / graphene / nickel foam composite electrode, the hydrotalcite nanosheets, with a size of 50-90 nm and a thickness of 10-15 nm, are vertically and alternately grown on the surface of rGO / NF substrate, forming a multi-level nanosheet array structure. The current high-entropy composite electrode not only exhibits a multi-metal synergistic effect, which can significantly promote the generation of hydroxyl radicals, but also has an entropy stabilizing effect, giving it excellent structural stability. At the same time, thanks to the three-dimensional nanosheet array structure of the composite electrode and the strategy of direct growth on the NF substrate, the charge transfer resistance is significantly reduced, and the electrocatalytic activity and current efficiency are improved.

2. The preparation and application of the high-entropy hydrotalcite / graphene / nickel foam composite electrode according to claim 1 in degrading tetracycline, characterized in that, Includes the following steps: (1) Disperse graphite oxide in deionized water, sonicate for 25 minutes, peel off to form a uniform graphene oxide suspension, add citric acid and continue sonication for 5-10 minutes to obtain a uniform and stable citric acid modified graphite oxide suspension, and transfer it to a polytetrafluoroethylene-lined high-pressure reactor, wherein the concentration range of the graphite oxide suspension is 1-5 mg / mL; the mass ratio of graphite oxide to citric acid is 1:1-3:1; immerse the pretreated clean nickel foam into the above suspension, and hydrothermally react at 80-140 °C for 4-8 hours. After the reaction is completed, cool naturally to room temperature, take out the product and wash it repeatedly with deionized water, freeze dry for 6 hours to obtain graphene oxide-coated nickel foam skeleton GO / NF; (2) Prepare a mixed salt solution containing five or more metal ions and a mixed alkali solution containing NaOH and Na2CO3 respectively; place the GO / NF substrate obtained in step (1) into a four-necked flask containing 100 mL of deionized water, add 10~60 mg of citric acid, stir for 5~10 minutes, then adjust the pH to 8.5 ± 0.1 ~ 10.5 ± 0.1 with the mixed alkali solution; after stabilizing for 5~10 minutes, add the mixed salt solution and mixed alkali solution simultaneously by double drop method while stirring continuously, and keep the pH value of the solution stable at 8.5 ± 0.1 ~ 10.5 ± 0.1; after the mixed salt solution is added, transfer the reaction system to a high-pressure reactor and heat at 70~150 °C. The product was crystallized and grown at ℃ for 6-10 hours. After the reaction was completed, it was naturally cooled to room temperature. The product was repeatedly washed with deionized water and freeze-dried for 6 hours to obtain the high-entropy hydrotalcite / reduced graphene oxide / nickel foam composite electrode material HE-LDH / rGO / NF.

3. The preparation method according to claim 2, characterized in that: The mixed salt mentioned in step (2) includes divalent and trivalent metal salts, which exist in the form of one or a mixture of nitrates or chlorides, wherein the divalent metal M in the metal salt is... 2+ Cu 2+ Ni 2+ Co 2+ Mn 2+ Mg 2+ and Zn 2+ Three or four of them, trivalent metal ions M 3+ For V 3+ Fe 3+ Ti 3 + Cr 3+ And Al 3+ Two or three of the metals are added in equal molar proportions, with the total amount of metal salts added ranging from 5 to 30 mmol.

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