CuFeO2 / NiCo-LDH / NF heterojunction catalyst and preparation method and application thereof

Abstract

The invention discloses a CuFeO2 / NiCo-LDH / NF heterojunction catalyst as well as a preparation method and application thereof, and relates to the technical field of environmental pollutant detection. The specific preparation method comprises the following steps: dissolving sodium hydroxide and 2-methylimidazole in water, adding a cobalt nitrate solution, and reacting to prepare ZIF-67; dissolving ferric salt and copper salt in water to adjust the pH value, and then heating and calcining to obtain CuFeO2 nanoparticles; the method comprises the following steps: pretreating foamed nickel, and reacting the pretreated foamed nickel with nickel salt, ammonium salt and ZIF-67 to prepare NiCo-LDH / NF; finally, the CuFeO2 and the NiCo-LDH / NF are compounded, and the target heterojunction catalyst is obtained. The CuFeO2 / NiCo-LDH / NF heterojunction catalyst prepared by the invention can realize rapid trace detection of tetracycline, has high sensitivity, wide detection range and good stability, provides a reliable tool for rapid and accurate detection of trace tetracycline in a water body, and has a wide application prospect in the field of environmental monitoring.

Description

Technical Field

[0001] This invention relates to a CuFeO2 / NiCo-LDH / NF heterojunction catalyst, its preparation method and application, belonging to the field of environmental pollutant treatment technology. Background Technology

[0002] Tetracycline (TC) is widely used in the veterinary pharmaceutical industry due to its broad-spectrum antibacterial activity. However, in recent years, the overuse of tetracycline has led to serious pollution of aquatic environments. The accumulation of tetracycline in water bodies not only harms aquatic organisms but also promotes the emergence of drug-resistant bacteria and the spread of drug-resistant genes, posing a dual threat to ecosystems and human health. Currently, there are some highly sensitive methods for tetracycline detection, such as chromatography and liquid chromatography-mass spectrometry. Although these methods are effective, their widespread application in practical scenarios is limited by the high cost of the instruments and the complexity of operation.

[0003] Electrochemical technology, with its advantages of low cost, high sensitivity, good selectivity, rapid analysis, simple operation, and portability, shows great promise for the rapid and sensitive detection of tetracycline in water samples. The optimization of electrochemical detection performance is highly dependent on the design and selection of electrode materials. The electron transport efficiency, active site density, and surface chemical properties of the materials directly affect the sensitivity, selectivity, and stability of the detection system. Therefore, developing a rapid and sensitive tetracycline detection method based on electrochemical technology is urgently needed. By constructing a CuFeO2 / NiCo-LDH / NF heterojunction catalyst material, it is hoped that a high-performance tetracycline sensor can be developed.

[0004] Against this backdrop, the search for superior electrochemical sensing materials is crucial. This invention provides a CuFeO2 / NiCo-LDH / NF catalyst and its preparation method, enabling precise and efficient detection of tetracycline in the aquatic environment. This invention innovatively introduces layered double metal hydroxide (LDH) as a structure-regulating support: on the one hand, the unique two-dimensional layered topology of LDH can create a spatial confinement effect on CuFeO2 nanoparticles, effectively inhibiting particle aggregation through a physical barrier mechanism; on the other hand, by constructing a heterojunction system with n-type semiconductor NiCo-LDH and p-type CuFeO2, the formation of a built-in electric field at the interface can be induced. This electric field not only enhances the detection of OH- in the electrolyte but also... - directional adsorption promotes the redox cycle of Ni(OH)2 / NiOOH and Ni 3+ / Ni 2+ The efficient regeneration of the redox couple can significantly enhance the oxidation reaction of tetracycline molecules. Summary of the Invention

[0005] One of the objectives of this invention is to provide a CuFeO2 / NiCo-LDH / NF heterojunction catalyst, which is prepared by a hydrothermal method from NiCo-LDH / NF and CuFeO2 nanoparticles.

[0006] The second objective of this invention is to provide a method for preparing a CuFeO2 / NiCo-LDH / NF heterojunction catalyst, specifically including the following steps: (1) Dissolve NaOH and 2-methylimidazole in water to form a homogeneous solution. Add cobalt nitrate aqueous solution slowly to the homogeneous solution at a volume ratio of 5:1 to obtain a mixture containing solid product. Finally, separate the solid product and wash and dry it (preferably vacuum dry) to obtain ZIF-67.

[0007] (2) Disperse ferric chloride and copper chloride in water and sonicate them to form a mixture. Add NaOH aqueous solution to the mixture under stirring conditions, adjust the pH of the system and heat to obtain a solid product. Wash, dry and calcine the solid product at high temperature to obtain CuFeO2 nanoparticles.

[0008] (3) Cut the nickel foam into rectangular samples of a specific size, sonicate them first in acid solution, then sonicate them in organic solvent, and wash and dry them for later use; disperse cobalt nitrate hexahydrate (Ni(NO3)2·6H2O), ammonium fluoride (NH4F), and ZIF-67 in water and sonicate them to form a mixture. Mix the nickel foam and the mixture in a reaction vessel (preferably a polytetrafluoroethylene reactor) and heat them to react. Wash and dry the nickel foam after the reaction (preferably vacuum drying) to obtain NiCo-LDH / NF.

[0009] (4) Disperse CuFeO2 nanoparticles in water at a ratio of 8 g / L to form a dispersion, and add it to a reaction vessel (preferably a polytetrafluoroethylene reactor). Add NiCo-LDH / NF to the reaction vessel at a mass ratio of CuFeO2 nanoparticles to NiCo-LDH / NF of 10:1 and heat to react, and obtain a crude product. After washing and drying the crude product, obtain the CuFeO2 / NiCo-LDH / NF heterojunction catalyst.

[0010] Preferably, the molar concentration of NaOH in the homogeneous solution of step (1) is 2 mol / L; and the molar concentration of 2-methylimidazole is 3.36 mol / L.

[0011] Preferably, in step (1), the cobalt nitrate aqueous solution is prepared using cobalt nitrate hexahydrate with a molar concentration of 0.821 mol / L; the conditions for mixing the cobalt nitrate aqueous solution with the homogeneous solution are: mixing at 400 rpm for 3 h; and the resulting solid product is washed with methanol and ultrapure water.

[0012] Preferably, the ferric chloride used in step (2) is ferric chloride hexahydrate and the copper chloride is copper chloride dihydrate.

[0013] Preferably, the ultrasonic treatment time in step (2) is 10 min.

[0014] Preferably, the concentration of ferric chloride in the mixture of step (2) is 0.18 mol / L and the concentration of copper chloride is 0.15 mol / L.

[0015] Preferably, in step (2), the concentration of the NaOH aqueous solution is 2 mol / L; the pH value is adjusted by using NaOH aqueous solution to adjust the pH value of the system to 12-13; the heating conditions are: heating at 100℃ for 1 hour; and the obtained solid product is washed with ultrapure water and anhydrous ethanol.

[0016] Preferably, the conditions for high-temperature calcination in step (2) are: high-temperature calcination at 600°C for 6 hours.

[0017] Preferably, the size of the nickel foam in step (3) is 1×2cm. 2 .

[0018] Preferably, in step (3), the acid solution is a 3 mol / L aqueous solution of HCl; and the organic solvent is anhydrous ethanol.

[0019] Preferably, the conditions for ultrasonication in acid and in organic solvent in step (3) are: first acid washing and ultrasonication for 20 min, and then ultrasonication in organic solvent for 20 min.

[0020] Preferably, in step (3), nickel nitrate hexahydrate, ammonium fluoride, and ZIF-67 are dispersed in water and ultrasonically treated in a molar ratio of cobalt nitrate hexahydrate (Ni(NO3)2·6H2O), ammonium fluoride (NH4F), and ZIF-67 of 2.76:5.38:1; the ultrasonic treatment time is 30 min.

[0021] Preferably, the conditions for the heating reaction of the nickel foam and the mixture in step (3) are: heating at 80°C for 12 hours.

[0022] Preferably, the washing conditions in step (3) are: washing with water several times.

[0023] Preferably, the heating reaction conditions in step (4) are: heating at 80°C for 7 hours.

[0024] The third objective of this invention is to provide a CuFeO2 / NiCo-LDH / NF heterojunction catalyst as an electrochemical sensing material for the rapid and sensitive detection of tetracycline in water samples.

[0025] Mechanism of the invention: (1) Preparation of CuFeO2 / NiCo-LDH / NF heterojunction catalyst This study used ZIF-67 metal-organic frameworks as structural templates to construct NiCo-LDH with a unique nanocage structure in situ on a nickel foam substrate via a hydrothermal method, and further combined it with CuFeO2 to form a pn heterojunction system. This composite system exhibited significant synergistic effects: on the one hand, the ZIF-67-derived nanocage structure provided abundant active sites and mass transfer channels for the reaction, effectively promoting the diffusion and adsorption of tetracycline molecules; on the other hand, the pn heterojunction formed by NiCo-LDH and CuFeO2 achieved directional electron migration through the built-in electric field at the interface, significantly suppressing the recombination of photogenerated carriers. This synergistic optimization of structure and function enabled the composite material to exhibit excellent catalytic performance.

[0026] (2) Application of CuFeO2 / NiCo-LDH / NF heterojunction catalyst in the detection of tetracycline A three-electrode system was constructed using CuFeO2 / NiCo-LDH / NF catalyst as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl as the reference electrode. The current response of tetracycline was detected by differential pulse voltammetry in a phosphate buffer solution containing tetracycline. The tetracycline concentration was then obtained from the relationship curve between the oxidation peak current of tetracycline and the tetracycline concentration.

[0027] The beneficial effects of this invention are: This invention provides a CuFeO2 / NiCo-LDH / NF catalyst for tetracycline detection prepared via a hydrothermal method. In tetracycline detection applications, it exhibits a linear range of 0.00594-25.00 μM, a detection limit as low as 1.98 nM, high sensitivity, and strong anti-interference properties. Even in the presence of 50 times the concentration of interfering substances (such as sulfadiazine and bisphenol A), the effect on the tetracycline square wave pulse voltammetry (SWV) current response is minimal, and it demonstrates good reproducibility, repeatability, and stability. In actual water sample testing, the recovery rate is in the range of 92.0-109.0%, demonstrating accuracy and reliability. Attached Figure Description

[0028] Figure 1The CV curves (a) of the CuFeO2 / NiCo-LDH / NF electrode prepared in Example 1, the CuFeO2 / NF electrode prepared in Comparative Example 1, the NiCo-LDH / NF electrode prepared in Comparative Example 2, and the bare nickel foam (NF) electrode are shown, and the SWV curve (b) of 1 μM tetracycline is shown. Figure 2 The SWV curves (a) of the CuFeO2 / NiCo-LDH / NF electrode prepared in Example 1 for different concentrations of tetracycline; and the fitting curve (b) between the oxidation peak current and the concentration C. Figure 3 The SWV curves (a) of the CuFeO2 / NiCo-LDH / NF electrode for the detection of 1 μM tetracycline in phosphate-buffered saline (PBS) at different pH values; and the CV curves (b) of the CuFeO2 / NiCo-LDH / NF electrode with 1 μM tetracycline added at different scan rates in PBS buffer at pH 6.98. Figure 4 SEM images (a) of the precursor ZIF-67 used in Example 1, SEM images (b) and enlarged images (c) of NiCo-LDH / NF prepared in Comparative Example 2, SEM images (d) of CuFeO2 / NF prepared in Comparative Example 1, and SEM images (e, f) of CuFeO2 / NiCo-LDH / NF prepared in Example 1. Figure 5 TEM images (a) and (b) of CuFeO2 / NiCo-LDH / NF prepared in Example 1 at different magnifications; HRTEM image (c) of CuFeO2 / NiCo-LDH / NF prepared in Example 1; IFFT images (d) and (e) of CuFeO2 / NiCo-LDH / NF corresponding to regions 1 and 2 marked by white dashed boxes in (c). Figure 6 Elemental mapping diagram for CuFeO2 / NiCo-LDH / NF; Figure 7 XRD patterns of CuFeO2 / NiCo-LDH / NF materials and CuFeO2 / NiCo-LDH powder prepared in Example 1, and infrared spectra of CuFeO2, NiCo-LDH, and CuFeO2 / NiCo-LDH materials prepared in Comparative Example 1; (a) is the XRD pattern of nickel foam loading; (b) is the powder XRD pattern; (c) is the infrared spectrum. Figure 8The images show the Mott-Schottky and Tauc diagrams of the CuFeO2 and NiCo-LDH materials prepared in Comparative Examples 1 and 2, and a schematic diagram of the band structure of the CuFeO2 / NiCo-LDH heterojunction prepared in Example 1; (a) is the Mott-Schottky diagram of NiCo-LDH, (b) is the Mott-Schottky diagram of CuFeO2, (c) is the Tauc diagram of the CuFeO2 and NiCo-LDH materials, and (d) is a schematic diagram of the band structure of the CuFeO2 / NiCo-LDH heterojunction. Figure 9 The interference resistance (a), reproducibility (b) and (c) and long-term stability (d) of the CuFeO2 / NiCo-LDH / NF electrode prepared in Example 1 for detecting tetracycline were evaluated. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0030] All chemical reagents used in the chemical reagent experiments in the embodiments of this invention are commercially available and have not undergone further purification: Na2HPO4 (pure 99%), NaH2PO4 (pure 99%), methanol (CH3OH, pure 99%), anhydrous ethanol (CH3CH2OH, pure 99%), acetone (C3H6O, pure 99%), NaOH (pure 99%), Na2SO4 (pure 99%), Ni(NO3)2·6H2O (pure 99%), 2-methylimidazole (C4H6N2, pure 98%), NH4F (pure 99%), FeCl3·6H2O (pure 99%), CuCl2·2H2O (pure 99%), hydrochloric acid (HCl, pure 12.22%), Co(NO3)2·6H2O (pure 99%), tetracycline hydrochloride (TC, pure 97%), KCl (pure 99%), bisphenol A (BPA ... 15 H 16 O2 (pure 99%), 17α-ethynylestradiol (EE2, C 20 H 24 O2, 98% pure), sulfadiazine (SDZ, C 10 H 10 N4O2S, 99% pure), methylene blue (MB, C) 10 H 10 The following compounds were used: N4O2S (95% pure); CaCl2 (96% pure); MgCl2 (96% pure); Na2CO3 (96% pure); NaHCO3 (96% pure); and NaNO3 (96% pure). All water used in the experiment was deionized water. Commercially available nickel foam (1mm thick) was supplied by Suzhou Keshenghe Metal Materials.

[0031] Example 1 A method for preparing a CuFeO2 / NiCo-LDH / NF catalyst, specifically including the following steps: (1) Dissolve NaOH and 2-methylimidazole in deionized water to form a homogeneous solution containing 2 mol / L NaOH and 3.36 mol / L 2-methylimidazole. Add 0.821 mol / L cobalt nitrate aqueous solution to the homogeneous solution at a volume ratio of 5:1. Mix at 400 rpm for 3 h to obtain a mixture containing solid product. Finally, separate the solid product and wash it with methanol and deionized water and vacuum dry it to obtain ZIF-67.

[0032] (2) FeCl3·6H2O and CuCl2·2H2O were dispersed in deionized water and subjected to ultrasonic treatment for 10 min to form a mixed solution containing 0.18 mol / L of ferric chloride and 0.15 mol / L of copper chloride. Under magnetic stirring, 2 mol / L of NaOH aqueous solution was added to the mixed solution to adjust the pH of the system to 12-13. Then, the mixture was heated at 100℃ for 1 h to obtain a solid product. The solid product was washed with deionized water and anhydrous ethanol, dried, and calcined at 600℃ for 6 h to obtain CuFeO2 nanoparticles.

[0033] (3) Cut the nickel foam into 1×2cm pieces. 2 The rectangular sample was first sonicated in a 3 mol / L HCl aqueous solution for 20 min, then sonicated in anhydrous ethanol for 20 min, washed several times with deionized water and vacuum dried for later use. Ni(NO3)2·6H2O, NH4F and ZIF-67 were dispersed in deionized water in a molar ratio of 2.76:5.38:1 and sonicated for 30 min to ensure uniform mixing and form a mixture. The nickel foam and the mixture were mixed in a polytetrafluoroethylene reactor and heated at 80℃ for 12 h. The reacted nickel foam was washed several times with deionized water and dried to obtain NiCo-LDH / NF.

[0034] (4) Disperse CuFeO2 nanoparticles in deionized water at a ratio of 8 g / L to form a dispersion, and add it to a polytetrafluoroethylene reactor. Add NiCo-LDH / NF to the polytetrafluoroethylene reactor at a mass ratio of CuFeO2 nanoparticles to NiCo-LDH / NF of 10:1. Heat the reaction at 80°C for 7 h. After washing and drying the product, obtain CuFeO2 / NiCo-LDH / NF heterojunction catalyst.

[0035] Example of effect 1 A CHI 760E (Shanghai Chenhua Instrument Co., Ltd.) was used as the electrochemical detection platform. The working electrode was a CuFeO2 / NiCo-LDH / NF heterojunction catalyst electrode, Ag-AgCl was used as the reference electrode, and a platinum electrode was used as the auxiliary electrode. Cyclic voltammetry (CV) was used to study the electrochemical behavior of tetracycline; square wave pulse voltammetry (SWV) was used to determine the concentration of tetracycline. 0.1 mol / L PBS buffer solution was used as the electrolyte for SWV and CV tests.

[0036] The electrochemical performance of the electrodes was studied using a standard three-electrode system. 1 μmol / L tetracycline was added to 0.1 mol / L PBS buffer, and cyclic voltammetry (CV) was performed at 100 mV·s⁻¹. -1 The electrochemical performance of different electrodes was investigated. The results showed that ( Figure 1 a) Neither the NF nor the NiCo-LDH / NF electrode showed obvious redox peaks, indicating poor electrochemical performance. In the cyclic voltammetry curves of the CuFeO2 / NiCo-LDH / NF and CuFeO2 / NF electrodes, a pair of redox peaks appeared, and the reduction peak current of the CuFeO2 / NiCo-LDH / NF electrode was significantly higher than that of CuFeO2 / NF, indicating that the electrochemical performance of the CuFeO2 / NiCo-LDH / NF electrode (Example 1) was superior to that of the other electrodes (Comparative Examples 1 and 2). The combination of CuFeO2 and NiCo-LDH is beneficial for promoting electron transfer and enhancing electrocatalytic activity.

[0037] Example 2 A CuFeO2 / NiCo-LDH / NF electrode was used for the electrochemical detection of tetracycline (TC). In further research, the electrochemical response of different modified electrodes to 1 μmol / L tetracycline (TC) was investigated using square wave pulse voltammetry (SWV) in 0.1 mol / L PBS buffer. Figure 1 As can be seen from b, the NF electrode has almost no response to TC. The oxidation peak current of the SWV curves of NiCo-LDH / NF and CuFeO2 / NF is smaller than that of CuFeO2 / NiCo-LDH / NF, indicating that NiCo-LDH / NF and CuFeO2 / NF have poor response to tetracycline (TC); while CuFeO2 / NiCo-LDH / NF has a strong response to tetracycline (TC) and good detection effect.

[0038] Example 3 At a scan rate of 100 mV·s -1 Under certain conditions, different concentrations of tetracycline (TC) were added, and their SWV (Symptom Value) was analyzed. Figure 2a). The results show that with increasing TC concentration, the oxidation peak current of CuFeO2 / NiCo-LDH / NF gradually increases, with the peak potential appearing at around -0.04V. Figure 2 As shown in b, the oxidation peak response current (I) exhibits a good linear relationship with the concentration (C), with the linear equation: I = 95.2845C + 748.541 (0.00594 μmol / L – 1 μmol / L), R 2 =0.9965; I=2.1533C+843.114(1μmol / L–25μmol / L), R 2 =0.9902. Therefore, the detection range of this sensor for tetracycline (TC) is 0.00594 μmol / L–25 μmol / L. Based on a signal-to-noise ratio (S / N) of 3, the limit of detection is 1.98 nM, and the sensitivity is 95.2845 μA·μmol / L. -1 ·cm -2 (0.00594μmol / L–1μmol / L); 2.1534μA·μmol / L -1 ·cm -2 (1 μmol / L–25 μmol / L).

[0039] When I < 843, the relationship curve between the oxidation peak current I of the tetracycline and the tetracycline concentration C is 95.2845C + 748.541; when I ≥ 843, the relationship curve between the oxidation peak current I of the tetracycline and the tetracycline concentration C is I = 2.1533C + 843.114.

[0040] Example of effect 4 To evaluate the application capability of the CuFeO2 / NiCo-LDH / NF electrode in practical scenarios, tap water and effluent from the Kunming No. 6 Water Purification Plant were selected as actual samples. The standard addition method was used to add different concentrations of tetracycline (TC), and the TC recovery rate was measured. Table 1 shows the tetracycline content in the actual samples measured by the CuFeO2 / NiCo-LDH / NF electrode. When detecting different concentrations of TC, the recovery rate of the CuFeO2 / NiCo-LDH / NF electrode for tap water samples was 92-106% (RSD ≤ 4.5%), and the recovery rate for effluent from the wastewater treatment plant was 94-109% (RSD ≤ 2.6%). The recovery rates were all between 90% and 110% (some samples had recovery rates higher than 100% due to interfering ions), and the RSD was less than 5%. This indicates that the sensor has good detection performance for TC in actual water bodies and can be applied in practice.

[0041] Table 1 Optimized Implementation Examples Optimized Example 1: pH response of CuFeO2 / NiCo-LDH / NF electrode to TC: The response of the CuFeO2 / NiCo-LDH / NF electrode to TC under different pH conditions was studied using square wave pulse voltammetry (SWV). Figure 3 As shown in Figure a, in 0.1 mol / L PBS buffer, as the pH increased from 6.47 to 9.67, the oxidation peak current of the CuFeO2 / NiCo-LDH / NF electrode first increased and then decreased, reaching its maximum at pH 6.98. Furthermore, the oxidation peak current decreased sharply at pH 9.67, even showing no response to tetracycline. Therefore, the CuFeO2 / NiCo-LDH / NF electrode exhibits excellent TC detection performance at pH 6.98.

[0042] Optimized electrochemical test scan rate for CuFeO2 / NiCo-LDH / NF electrode in Example 1: The electrochemical behavior of TC on CuFeO2 / NiCo-LDH / NF at different scan rates was investigated using cyclic voltammetry (CV). Figure 3 b shows the cyclic voltammograms of the CuFeO2 / NiCo-LDH / NF electrode at different scan rates in 0.1 mol / L PBS buffer containing 1 μmol / L LTC. It can be seen that the oxidation peak current (Ipa) gradually increases with increasing scan rate. Considering economic feasibility, the CuFeO2 / NiCo-LDH / NF electrode was tested at a scan rate of 100 mV·s. -1 It exhibits excellent TC detection performance.

[0043] Comparative Example 1 A method for preparing a CuFeO2 / NF catalyst, specifically including the following steps: (1) Dissolve NaOH and 2-methylimidazole in deionized water to form a homogeneous solution containing 2 mol / L NaOH and 3.36 mol / L 2-methylimidazole. Add 0.821 mol / L cobalt nitrate aqueous solution to the mixture at a volume ratio of 5:1. Mix at 400 rpm for 3 h to obtain a mixture containing solid product. Finally, separate the solid product and wash it with methanol and deionized water and vacuum dry it to obtain ZIF-67.

[0044] (2) FeCl3·6H2O and CuCl2·2H2O were dispersed in deionized water and subjected to ultrasonic treatment for 10 min to form a mixed solution containing 0.18 mol / L of ferric chloride and 0.15 mol / L of copper chloride. Under magnetic stirring, 2 mol / L of NaOH aqueous solution was added to the mixed solution to adjust the pH of the system to 12-13. Then, the mixture was heated at 100℃ for 1 h to obtain a solid product. The solid product was washed with deionized water and anhydrous ethanol, dried, and calcined at 600℃ for 6 h to obtain CuFeO2 nanoparticles.

[0045] (3) Disperse CuFeO2 nanoparticles in deionized water at a ratio of 8 g / L to form a dispersion, and add it to the reaction vessel. Add NiCo-LDH / NF to the polytetrafluoroethylene reactor at a mass ratio of CuFeO2 nanoparticles to NiCo-LDH / NF of 10:1. Add NiCo-LDH / NF to the polytetrafluoroethylene reactor at a mass ratio of CuFeO2 to NiCo-LDH / NF of 10:1. Heat the reaction at 80°C for 7 h. After washing and drying the product, obtain CuFeO2 / NiCo-LDH / NF.

[0046] Comparative Example 2 A method for preparing a NiCo-LDH / NF catalyst specifically includes the following steps: (1) Dissolve NaOH and 2-methylimidazole in deionized water to form a homogeneous solution containing 2 mol / L NaOH and 3.36 mol / L 2-methylimidazole. Add 0.821 mol / L cobalt nitrate aqueous solution to the mixture at a volume ratio of 5:1. Mix at 400 rpm for 3 h to obtain a mixture containing solid product. Finally, separate the solid product and wash it with methanol and deionized water, and then vacuum dry it to obtain ZIF-67.

[0047] (2) FeCl3·6H2O and CuCl2·2H2O were dispersed in deionized water and subjected to ultrasonic treatment for 10 min to form a mixed solution containing 0.18 mol / L of ferric chloride and 0.15 mol / L of copper chloride. Under magnetic stirring, 2 mol / L of NaOH aqueous solution was added to the mixed solution to adjust the pH of the system to 12-13. Then, the mixture was heated at 100℃ for 1 h to obtain a solid product. The solid product was washed with deionized water and anhydrous ethanol, dried, and calcined at 600℃ for 6 h to obtain CuFeO2 nanoparticles.

[0048] (3) Cut the nickel foam into 1×2cm pieces. 2The rectangular sample was first sonicated in a 3 mol / L HCl aqueous solution for 20 min, then sonicated in anhydrous ethanol for 20 min, washed several times with deionized water and vacuum dried for later use. Ni(NO3)2·6H2O, NH4F and ZIF-67 were dispersed in deionized water in a molar ratio of 2.76:5.38:1 and sonicated for 30 min to ensure uniform mixing and form a mixture. The nickel foam and the mixture were mixed in a polytetrafluoroethylene reactor and heated at 80℃ for 12 h. The reacted nickel foam was washed several times with deionized water and dried to obtain NiCo-LDH / NF.

[0049] The microstructure of the material was systematically characterized using scanning electron microscopy (SEM). Figure 4 ).like Figure 4 As shown in figure a, the ZIF-67 precursor exhibits a typical rhombic dodecahedral morphology, with a smooth surface and clear geometric edges. Figure 4 As shown in b and c, the NiCo-LDH / NF material prepared in Comparative Example 2 was grown in situ, allowing NiCo-LDH to be uniformly coated on the surface of a nickel foam substrate, forming a three-dimensional nanocage structure with uniformly thick, wrinkled nanosheets vertically grown on its surface. Figure 4 As shown in d, in the CuFeO2 / NF material prepared in Comparative Example 1, CuFeO2 particles were successfully anchored on the surface of the nickel foam skeleton by a hydrothermal method. Figure 4 The ef data shows that CuFeO2 nanoparticles are incorporated into or attached to NiCo-LDH to form CuFeO2 / NiCo-LDH.

[0050] TEM images such as Figure 5 As shown, nanocage-like LDH was successfully composited with particulate CuFeO2 (as shown). Figure 5 ab). CuFeO2 particles and NiCo-LDH nanosheets are tightly bonded through a heterogeneous interface: CuFeO2 is doped in the LDH nanosheet array, while the wrinkled surface of NiCo-LDH provides a larger specific surface area for exposing active sites. TEM shows a clear heterogeneous interface ( Figure 5 c), HRTEM measurements showed that the NiCo-LDH(104) crystal plane (0.238 nm) and the CuFeO2(222) crystal plane (0.284 nm) coexisted. Figure 5 (de). Elemental mapping shows the uniform distribution of C, O, Ni, Co, Cu, and Fe as follows: Figure 6 As shown, the high specific surface area of ​​the nanocage structure provides an advantage for molecular diffusion and electron transfer.

[0051] XRD analysis confirmed the successful synthesis of the material. Figure 7a). Because the nickel foam substrate (strong peaks at 44.4°, 51.8°, and 76.3°) would mask the sample signal, powder samples were used for characterization. Figure 7 b). NiCo-LDH exhibits characteristic peaks at 11.8° (003), 23.7° (006), 33.4° (012), and 60.1° (110), completely replacing the characteristic peaks of ZIF-67. After composite CuFeO2, the (003) and (006) crystal plane peaks of NiCo-LDH are retained, and characteristic peaks of CuFeO2 appear at 31.3° (222), 35.7° (110), and 40.3° (112), confirming the formation of the composite material.

[0052] FT-IR analysis ( Figure 7 c) Display: All samples at 3450cm -1 An OH vibration peak exists at 565 cm⁻¹, and this peak is significantly enhanced in the composite material. CuFeO₂ exhibits this peak at 565 cm⁻¹. -1 (Cu-O), 435cm -1 (Fe-O) and 651cm -1 (O-Cu-O) exhibits characteristic vibrations. NiCo-LDH shows vibrations at 1059 cm⁻¹. -1 (Co-OH), 1495cm -1 (CO2 adsorption) and 647cm -1 Characteristic peaks exist at (Ni / Co-O), and these features are retained in the composite material, with a peak at 649 cm⁻¹. -1 The presence of superimposed peaks of metal-O bonds further verifies the formation of the heterostructure.

[0053] Mott-Schottky analysis showed that ( Figure 8 (ab) NiCo-LDH exhibits a positive slope in the potential range of -0.6 to 0.4 V (vs. Ag / AgCl) (n-type semiconductor, flat band potential -0.89 eV), while CuFeO2 shows a negative slope in the range of 0.3 to 0.9 V (p-type semiconductor, flat band potential 1.01 eV). The band matching characteristics of these two materials promote the formation of a pn heterojunction in the CuFeO2 / NiCo-LDH composite material. (Tauc diagram) Figure 8 c) Analysis was conducted to investigate the band gap energy (E) of CuFeO2 and layered double hydroxide (LDH). g Experimental results show that the E of CuFeO2 g It is 2.00 eV, while the E of LDH is 2.00 eV. gThe calculated flat band potentials of NiCo-LDH and CuFeO2 relative to the reversible hydrogen electrode are -0.28 eV and 1.62 eV, respectively. In n-type semiconductors, the flat band is near the bottom of the conduction band, while in p-type semiconductors, it is near the top of the valence band. Therefore, the conduction band potential E of NiCo-LDH can be obtained. CB = -0.28eV, while the valence band E of CuFeO2 VB =1.62 eV. Therefore, when CuFeO2 is in close contact with NiCo-LDH, a pn heterojunction is formed ( Figure 8 d).

[0054] The selectivity and anti-interference ability of the CuFeO2 / NiCo-LDH / NF electrode were evaluated using SWV. 50 μmol / L of interfering substances were added to a 0.1 mol / L PBS (pH=6.98) buffer containing 1 μmol / L LTC. These substances included contaminants such as bisphenol A (BPA), 17α-ethynylestradiol (EE2), sulfadiazine (SDZ), and methylene blue (MB); and common cations or anions found in water, such as Ca2+. 2+ Mg 2 + Cl - CO3 2- H2PO4 - HCO3 - NO3 - To examine the selectivity and anti-interference performance of the electrodes. For example... Figure 9 As can be seen, after adding 50 times the concentration of interfering substance TC, the SWV oxidation peak current changes very little. CuFeO2 / NiCo-LDH / NF has little or no response to these interfering substances, indicating that the sensor has good selectivity and anti-interference ability when detecting tetracycline (TC).

[0055] The reproducibility and stability of CuFeO2 / NiCo-LDH / NF were further evaluated. Three electrodes were synthesized under the same conditions, and 1 μmol / L TC was detected in 0.1 mol / L PBS (pH=6.98) buffer. The relative standard deviation (RSD) of the SWV oxidation peak current changes for the three electrodes was 2.6%. Figure 9 b). For the same electrode used to detect 1 μmol / L TC, the RSD of the change in the electrode SWV oxidation peak current was 1.8%. Figure 9 c). Figure 9 Figure d shows the current change of the CuFeO2 / NiCo-LDH / NF electrode detecting the same concentration of TC over 15 days. It can be concluded that on the 15th day, the SWV oxidation peak current is still 95% of the initial current value. The results indicate that the sensor has excellent reproducibility and stability.

[0056] This invention proposes a CuFeO2 / NiCo-LDH / NF heterojunction catalyst, its preparation method, and its application. A CuFeO2 / NiCo-LDH heterojunction is constructed on a nickel foam (NF) substrate via a ZIF-67 template-induced topological transformation method. This hierarchical heterostructure fully leverages the built-in electric field effect of the pn junction and the synergistic effect of the multi-metal redox centers, significantly improving the sensor's electron transport efficiency and catalytic activity. Experimental data show that the sensor exhibits a linear detection range for tetracycline spanning four orders of magnitude, while also possessing a low detection limit, making it applicable to the detection of tetracycline in real water bodies and demonstrating significant practical value. In contrast, the intrinsic conductivity defect of the comparative LDH restricts the electron transport kinetics at its electrode interface, a bottleneck that severely limits further improvement in its sensing performance. Furthermore, pure CuFeO2, due to its inherent high surface energy and low surface area, tends to aggregate, leading to a decrease in the number of active sites and catalytic efficiency. The material prepared by this invention can effectively overcome the performance limitations of single materials by constructing a heterogeneous composite structure. This composite strategy can not only make up for the lack of intrinsic conductivity of LDH, but also achieve a synergistic improvement in detection sensitivity and stability through the optimization of interfacial charge transport dynamics and the synergistic effect of multiple components.

[0057] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A CuFeO2 / NiCo-LDH / NF heterojunction catalyst, characterized in that: The catalyst was prepared by hydrothermal method from NiCo-LDH / NF and CuFeO2 nanoparticles.

2. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 1, characterized in that, Specifically, the following steps are included: (1) Dissolve NaOH and 2-methylimidazole in water to form a homogeneous solution. Add cobalt nitrate aqueous solution slowly to the homogeneous solution at a volume ratio of 5:1 to obtain a mixture containing solid product. Finally, separate the solid product and wash and dry it to obtain ZIF-67. (2) Disperse ferric chloride and copper chloride in water and sonicate them to form a mixture. Add NaOH aqueous solution to the mixture under stirring to adjust the pH value of the system. Then heat to obtain a solid product. Wash, dry and calcine the solid product at high temperature to obtain CuFeO2 nanoparticles. (3) Cut the nickel foam into rectangular samples of a specific size, sonicate them first in acid solution, then sonicate them in organic solvent, and wash and dry them for later use; disperse cobalt nitrate hexahydrate, ammonium fluoride, and ZIF-67 in water and sonicate them to form a mixture; mix the nickel foam and the mixture in a reaction vessel and heat them to react; wash and dry the nickel foam after the reaction to obtain NiCo-LDH / NF. (4) Disperse CuFeO2 nanoparticles in water at a ratio of 8 g / L to form a dispersion, and add it to the reaction vessel. Add NiCo-LDH / NF to the reaction vessel at a mass ratio of CuFeO2 nanoparticles to NiCo-LDH / NF of 10:1 and heat to react, and obtain crude product. After washing and drying the crude product, obtain CuFeO2 / NiCo-LDH / NF heterojunction catalyst.

3. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: In step (1), the molar concentration of NaOH in the homogeneous solution is 2 mol / L; the molar concentration of 2-methylimidazole is 3.36 mol / L.

4. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: In step (1), the cobalt nitrate aqueous solution was prepared using cobalt nitrate hexahydrate, and the molar concentration of the cobalt nitrate aqueous solution was 0.821 mol / L. The mixing conditions of the cobalt nitrate aqueous solution and the homogeneous solution were: mixing at 400 rpm for 3 h. The resulting solid product was washed with methanol and ultrapure water.

5. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: In step (2), the ferric chloride used was ferric chloride hexahydrate, and the copper chloride was copper chloride dihydrate; the ultrasonic treatment time was 10 min; the molar concentration of ferric chloride in the mixed solution was 0.18 mol / L, and the molar concentration of copper chloride was 0.15 mol / L; the concentration of NaOH aqueous solution was 2 mol / L; the pH value was adjusted by using NaOH aqueous solution to adjust the pH value of the system to 12-13; the heating conditions were: heating at 100℃ for 1 h; the obtained solid product was washed with ultrapure water and anhydrous ethanol; the high-temperature calcination conditions were: high-temperature calcination at 600℃ for 6 h.

6. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: In step (3), the size of the nickel foam is 1×2cm. 2 The acid solution is a 3 mol / L aqueous HCl solution; the organic solvent is anhydrous ethanol; the conditions for ultrasonication in the acid solution and in the organic solvent are: first acid washing and ultrasonication for 20 min, then ultrasonication in the organic solvent for 20 min.

7. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: In step (3), cobalt nitrate hexahydrate, ammonium fluoride, and ZIF-67 are dispersed in water and ultrasonically treated at a molar ratio of 2.76:5.38:1; the ultrasonic treatment time is 30 min.

8. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: In step (3), the conditions for the heating reaction of the nickel foam and the mixture are: heating at 80°C for 12 hours; the washing conditions are: washing with water several times.

9. The preparation method of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst according to claim 2, characterized in that: The conditions for the heating reaction in step (4) are: heating at 80°C for 7 hours.

10. The application of the CuFeO2 / NiCo-LDH / NF heterojunction catalyst of claim 1 as an electrochemical sensing material for detecting tetracycline in an aquatic environment.

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