Iron-based bimetallic phosphide electro-fenton electrode material and preparation method and application thereof

Abstract

The application discloses an iron-based bimetallic phosphide electro-Fenton electrode material and a preparation method and application thereof, the electrode material is an iron-vanadium bimetallic phosphide, presents a nano-flower-shaped structure, and is obtained by phosphorization of iron-vanadium bimetallic hydroxide; the preparation method comprises the following steps: (1) dissolving iron salt and vanadium salt and urea in an organic solvent, uniformly mixing, performing a solvothermal synthesis reaction, filtering, washing and drying after the reaction is completed to obtain iron-vanadium bimetallic hydroxide; (2) high-temperature phosphorization is performed on the iron-vanadium bimetallic hydroxide to obtain the iron-based bimetallic phosphide electro-Fenton electrode material. The electrode material utilizes the electronic interaction between vanadium ions and iron ions, cooperatively optimizes the electronic structure, has excellent ORR performance, realizes efficient catalytic reaction and stronger ·OH generation capacity, and exhibits good degradation efficiency in degradation of nitenpyram by the electro-Fenton technology.

Description

Technical Field

[0001] This invention relates to an electrode material, its preparation method and application, and particularly to an iron-based bimetallic phosphide electro-Fenton electrode material, its preparation method and application. Background Technology

[0002] my country is a major agricultural country, and the use of pesticides and herbicides to increase crop yields is widespread in agricultural production. However, large-scale and frequent application of pesticides poses potential risks to human health and the environment. Neonicotinoid pesticides have high water solubility and a long half-life. Therefore, once they enter aquatic environments, they can remain there for extended periods. Their accumulation in the environment not only affects the survival of non-target organisms but also causes chronic harm to human health. Therefore, there is an urgent need to develop effective wastewater remediation methods to address pesticide pollution.

[0003] In recent years, electro-Fenton technology, as a promising electrochemical advanced oxidation process, has attracted increasing attention due to its rapid reaction kinetics, high oxidizing power, and environmental friendliness. •OH is produced by the reaction of H₂O₂ and Fe. 2+ The large amount of oxidizing agents generated by these interactions indicates its strong oxidizing capacity, enabling it to rapidly degrade various organic pollutants. EF technology emphasizes the role of 2e⁻ on the cathode. - In-situ synthesis of H2O2 via oxygen reduction eliminates the potential explosion risks during H2O2 transportation and handling. Furthermore, in the electrocatalytic process, cathode reduction enhances Fe... 2+ The regeneration of Fe greatly reduces the Fe 2+ The amount of catalyst used. However, the low efficiency of H2O2 production is attributed to 4e. - Competition for pathways, and relatively poor electron transfer between the Fe(III) / Fe(II) cycles, led to the accumulation of •OH and Fe. 3+ The issue of precipitation. Therefore, improving the yield and activation efficiency of H2O2 is of great practical significance for the development and application of electro-Fenton technology.

[0004] Noble metal-based catalysts exhibit excellent ORR catalytic activity and high H2O2 selectivity, but their high cost and scarcity limit their large-scale application in wastewater treatment. In Fe... 2+ In terms of regeneration, the addition of organic reducing agents such as organic acids and metal sulfides has become a way to promote Fe regeneration. 3+Reduction is an effective strategy. However, secondary pollution and higher costs will follow. In this context, heterogeneous electro-Fenton electrodes are receiving increasing attention. To date, first-row transition metal (Fe, Co, Mn, Ni, Cu, etc.) based oxides have the advantages of various nanostructures and high corrosion resistance, making them suitable for various catalytic processes. Among them, single metal electrodes, such as iron phosphide, as catalysts alone, have weak catalytic activity and low reaction efficiency. Summary of the Invention

[0005] Objectives of the Invention: The first objective of this invention is to provide an iron-based bimetallic phosphide electro-Fenton electrode material with improved catalytic activity; the second objective of this invention is to provide a method for preparing the iron-based bimetallic phosphide electro-Fenton electrode material; and the third objective of this invention is to provide the application of the iron-based bimetallic phosphide electro-Fenton electrode material in the degradation of organic pollutants in three-dimensional electro-Fenton.

[0006] Technical solution: The iron-based bimetallic phosphide electro-Fenton electrode material of the present invention is an iron-vanadium bimetallic phosphide, which exhibits a nanoflower-shaped structure and is obtained by phosphating iron-vanadium bimetallic hydroxide.

[0007] Preferably, the molar ratio of iron to vanadium is 1:1 to 1:5.

[0008] More preferably, the molar ratio of iron to vanadium is 1:1 to 1:3.

[0009] The preparation method of the iron-based bimetallic phosphide electro-Fenton electrode material of the present invention includes the following steps:

[0010] (1) Iron salts and vanadium salts are dissolved in an organic solvent with urea and mixed evenly; a solvothermal synthesis reaction is carried out, and after the reaction is completed, the mixture is filtered, washed and dried to obtain iron-vanadium bimetallic hydroxide;

[0011] (2) The iron-vanadium bimetallic hydroxide is subjected to high-temperature phosphating to obtain the iron-based bimetallic phosphide electro-Fenton electrode material.

[0012] Preferably, in step (1), the temperature of the solvothermal reaction is 100~120 ℃.

[0013] Preferably, in step (1), the organic solvent is ethanol.

[0014] Preferably, in step (1), the iron salt is ferric nitrate nonahydrate and the vanadium salt is vanadium chloride (vanadium is trivalent vanadium).

[0015] Preferably, the phosphating agent for high-temperature phosphating is sodium hypophosphite, the high-temperature phosphating temperature is 350~400℃, and the phosphating time is 1.5~2 h.

[0016] The application of the iron-based bimetallic phosphide electro-Fenton electrode material described in this invention in the degradation of organic pollutants in three-dimensional electro-Fenton.

[0017] Preferably, the organic pollutant is a neonicotinoid insecticide.

[0018] Preferably, the neonicotinoid insecticide is acetamiprid.

[0019] Invention Mechanism: To improve the mass transfer efficiency of the electro-Fenton reaction, this invention proposes a vanadium-doped iron phosphide bimetallic phosphide electrode material, designated V-FeP. Because V... 3+ and Fe 3+ The electronic interactions between cations synergistically optimize the electronic structure, resulting in excellent ORR performance. On the other hand, phosphating the vanadium-iron bimetallic oxide allows it to form a unique metallic structure. The graphene-like network formed by phosphating provides abundant electron transport channels, which promotes electron transport. V, Fe, and P together accelerate the valence cycle of the metal, thereby achieving rapid regeneration of active sites. Therefore, it achieves highly efficient catalytic reactions and stronger •OH generation capacity, further enabling the efficient removal of neonicotinoid insecticides.

[0020] The principle of this invention is to add a transition metal catalyst as a particle electrode to the traditional electro-Fenton system. The particle electrode participates in the reaction, expanding the reaction area and enhancing the generation of •OH, thereby improving mass transfer efficiency and electrochemical active surface area. This makes the three-dimensional electro-Fenton system suitable for the degradation of complex pollutants and large-volume water treatment. A key design concept of this invention is that the traditional electro-Fenton reaction is confined to the vicinity of the electrode, resulting in low mass transfer efficiency, a limited reaction area, and difficulty in covering the entire system. To address these issues, this invention proposes using a transition metal catalyst as a particle electrode to achieve greater •OH generation. Under the influence of current, the particle electrode is dispersed around the pollutant, allowing for large-area contact and enabling Fe... 3+ / Fe 2+ High-efficiency cycling was achieved by preparing a bimetallic phosphide electrode material, vanadium-doped iron phosphide, labeled V-FeP.

[0021] In this invention, a V-FeP electrode is introduced into the traditional electro-pesticide system, using a carbon felt as the cathode and a titanium plate as the anode. This particle electrode is polarized into an independent microelectrode under the action of current. The particle electrode participates in the reaction, expanding the reaction area, improving mass transfer efficiency and electrochemical active surface area, and achieving efficient degradation of pesticides.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The iron-based bimetallic phosphide electro-Fenton electrode material of the present invention utilizes the electronic interaction between vanadium ions and iron ions to synergistically optimize the electronic structure, has excellent ORR performance, and achieves efficient catalytic reaction and stronger •OH generation ability; (2) The preparation method is simple and easy to industrialize; (3) The catalyst of the present invention shows good degradation efficiency in the degradation of acetamiprid in three-dimensional electro-Fenton. Attached Figure Description

[0023] Figure 1 TEM images of the V-FeP bimetallic phosphide electrode prepared in Example 1 at magnifications of 100 nm and 200 nm;

[0024] Figure 2 TEM images of V, Fe, and P elements in V-FeP prepared in Example 1;

[0025] Figure 3 XPS image of V-FeP prepared in Example 1;

[0026] Figure 4 The comparison of the degradation effects of V-FeP electrode materials prepared in Examples 1-4 and FeP electrode materials prepared in Comparative Example 1 on acetamiprid in water.

[0027] Figure 5 Comparison of the degradation effects of V-FeP bimetallic phosphide electrode material prepared in Example 1 on acetamiprid in water under different currents;

[0028] Figure 6 Comparison of the degradation effect of V-FeP bimetallic phosphide electrode material prepared in Example 1 on acetamiprid in water under different pollutant concentrations;

[0029] Figure 7 Comparison of the degradation effect of V-FeP bimetallic phosphide electrode material prepared in Example 1 on acetamiprid in water under different dosages;

[0030] Figure 8 The cycling performance diagram shows the V-FeP bimetallic phosphide electrode material prepared in Example 1.

[0031] Figure 9 The image shows the CV curve of the V-FeP bimetallic phosphide electrode material prepared in Example 1. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the embodiments.

[0033] Example 1

[0034] The iron-based bimetallic phosphide electro-Fenton electrode material of the present invention is prepared by the following steps:

[0035] (1) 0.4848 g (1.2 mmol) of ferric nitrate nonahydrate, 0.189 g (1.2 mmol) of vanadium chloride and 1.0000 g of urea in a molar ratio of 1:1 were mixed in 60 mL of anhydrous ethanol. After stirring continuously for 20 min, the mixture was sonicated to obtain a transparent yellow-green solution. The solution was placed in an autoclave and subjected to hydrothermal treatment at 120 °C for 6 h. The obtained product was centrifuged, washed multiple times with ultrapure water and dried in a vacuum oven to obtain iron-vanadium bimetallic hydroxide.

[0036] (2) The obtained iron-vanadium bimetallic hydroxide was phosphated in a tube furnace under N2 atmosphere. 0.8g sodium hypophosphite was used as the phosphating agent. Sodium hypophosphite was placed in a porcelain boat as a prerequisite. The boat containing the bimetallic hydroxide was placed upstream and heated to 400℃ at a rate of 5℃ / min. After calcination for 2 h, V-FeP electrode material was obtained.

[0037] Example 2

[0038] Based on Example 1, the molar ratio of ferric nitrate nonahydrate and vanadium chloride was changed to 1:2, while the other conditions remained unchanged.

[0039] Example 3

[0040] Based on Example 1, the molar ratio of ferric nitrate nonahydrate and vanadium chloride was changed to 1:3, while the other conditions remained unchanged.

[0041] Example 4

[0042] Based on Example 1, the molar ratio of ferric nitrate nonahydrate and vanadium chloride was changed to 1:5, while the other conditions remained unchanged.

[0043] Comparative Example 1

[0044] Based on Example 1, without adding vanadium chloride, and with all other conditions unchanged, iron phosphide was obtained.

[0045] Structural characterization

[0046] The structure of the V-FeP electrode material prepared in Example 1 was characterized, and the results are as follows: Figures 1-3 As shown.

[0047] Figure 1 The TEM image of this electrode material shows that V-FeP exhibits a nanoflower shape.

[0048] Figure 2 The TEM images of V, Fe, and P, in order, demonstrate the successful incorporation of vanadium.

[0049] Figure 3 The XPS plot of this electrode material clearly shows the peak value of vanadium.

[0050] Performance testing

[0051] 1. Performance testing of V-FeP electrode materials with different vanadium introduction amounts for degrading acetamiprid

[0052] Electro-Fenton degradation of acetamiprid: A two-electrode reaction system was used, with a titanium electrode as the anode and a carbon felt material as the cathode. The electrode spacing was 4 cm. The electrode materials were connected to a DC power supply via electrode clips and wires. A constant current of 50 mA was used during the degradation process. The NIT (acetamiprid) solution concentration was 10 mg / L, and the volume was 100 mL. 0.05 M Na2SO4 was used as the electrolyte. A magnetic stirrer was used at a speed of 700 r / min to enhance the mass transfer effect. After adding 0.01 g of the particle electrodes prepared in Examples 1-4 and Comparative Example 1, respectively, and allowing them to stand for 20 min to reach adsorption saturation, the reaction was started and timed at 50 mA. The reaction time was 50 min, and 1 mL samples were taken at fixed time intervals (10 min) for analysis by HPLC.

[0053] The concentration of acetamiprid was analyzed by high performance liquid chromatography (HPLC). The chromatographic column was a Zorbax SB-C18 (4.6 × 150 mm, 5 μm), the mobile phase was 70% A (water) and 30% B (methanol), the detection wavelength was 270 nm, and the retention time was 8 min. The test results are as follows: Figure 4 As shown.

[0054] Depend on Figure 4 The degradation efficiencies of the materials in Examples 1-4 and Comparative Example 1 at 50 min were 99.3%, 91%, 79.2%, 75.6%, and 69%, respectively. This demonstrates that the V-FeP electrode materials prepared in Examples 1-4 exhibit superior catalytic performance compared to undoped vanadium iron phosphide. When the vanadium-iron ion molar ratio is 1:1, the synergistic effect between iron and vanadium is strongest, accelerating the redox cycle and resulting in the best degradation performance of V-FeP for NIT, reaching a rapid rate of 99%.

[0055] 2. Performance testing of acetamiprid degradation at different current values

[0056] Based on the above testing methods, the V-FeP electrode material prepared in Example 1 was selected as the particle electrode, and the current for the electro-Fenton degradation of acetamiprid was changed to 10 mA, 30 mA, 50 mA, and 70 mA. The test results are as follows. Figure 5 As shown.

[0057] like Figure 5 As shown, when the current intensity increased from 10 mA to 70 mA, the degradation efficiencies at 50 min were 55.1%, 82.5%, 99.3%, and 87%, respectively. The overall removal efficiency of NIT improved, which is attributed to the easier generation of ROS and accelerated Fenton reaction when the current density increased. Current is a key factor driving O2 reduction and can promote the generation of H2O2 in the cathode region. With the increase of current density, the yield of H2O2 also increases, while Fe... 2+ Increased regeneration enhances the efficiency of the electro-Fenton reaction. At a current density of 50 mA, a peak NIT removal efficiency of 99.3% was achieved within 50 min. However, further increases in current lead to decreased degradation efficiency. It is speculated that at higher currents, excess H₂O₂ captures •OH, generating •O₂H with a weaker oxidation potential, which is detrimental to the removal of organic pollutants.

[0058] 3. Degradation performance test at different initial concentrations of acetamiprid

[0059] Based on the above test methods, the V-FeP electrode material prepared in Example 1 was selected as the particle electrode, and the initial concentrations of acetamiprid were changed to 5 mg / L, 10 mg / L, 20 mg / L, and 30 mg / L. The test results are as follows. Figure 6 As shown.

[0060] Depend on Figure 6 It was found that 5 mg / L NIT was completely removed within 50 min. However, when the initial NIT concentration was increased to 10 mg / L, 20 mg / L, and 30 mg / L, the degradation efficiencies at 50 min were 89.0%, 70.0%, and 67.0%, respectively. The limited number of metal active sites restricts the production of ·OH. As the pollutant concentration increases, more free radicals are required for decomposition, leading to a decrease in the reaction rate. With further increases in pollutant concentration, NIT and intermediates should occupy more electrocatalytic active sites on the electrode and consume more free radicals, resulting in a continuous decrease in degradation efficiency.

[0061] 4. Performance test of different catalyst addition amounts on the degradation of acetamiprid

[0062] Based on the above testing methods, the V-FeP electrode material prepared in Example 1 was selected as the particle electrode, and the amount of V-FeP electrode material added was changed to 5 mg / L, 10 mg / L, 20 mg / L, and 30 mg / L. The test results are as follows. Figure 7 As shown.

[0063] Depend on Figure 7It was found that when the catalyst dosage increased from 5 mg to 10 mg, the catalytic efficiencies of the heterogeneous EF reaction within 50 min were 77% and 99.3%, respectively. The removal rate of NIT significantly increased (75-99%) with increasing catalyst dosage. This is likely due to the increase in catalytic active sites during the heterogeneous EF process, promoting the generation of •OH. However, when the dosage was further increased to 30 mg, the removal rate of NIT after 50 min of heterogeneous EF reaction did not increase but rather decreased. This is because when other operating parameters (such as applied current, aeration rate, and effective electrode area) are fixed, the amount of hydrogen peroxide generated during the heterogeneous EF process can be considered constant. Therefore, adding excess catalyst in this process does not improve its catalytic degradation performance of NIT. Furthermore, the generated •OH may also react with excess catalyst such as ferrous iron.

[0064] 5. Cyclic stability test of electrodes

[0065] Based on the above testing methods, the V-FeP electrode material prepared in Example 1 was used for four-cycle experiments. The V-FeP that had completed one degradation cycle was rinsed, dried, and then used in the second degradation experiment, thus performing four consecutive cycles. The test results are as follows: Figure 8 As shown.

[0066] Depend on Figure 8 It can be seen that the removal rates of NIT within 90 min were 99.3%, 92.7%, 90.1%, and 92.1% in the 1st, 2nd, 3rd, and 4th cycles, respectively. These four cycles demonstrate that V-FeP exhibits good stability during the three-dimensional electro-Fenton process.

[0067] 6. Compare the changes in CV curves of vanadium-doped phosphide electrode materials at different scan rates.

[0068] The test method involved preparing 40 ml of 0.1 M Na₂SO₄ solution, coating the prepared catalyst material onto a graphite sheet, attaching an electrode clamp, and inserting the sheet into a container containing the reaction solution. CV (chromatic spectroscopy) tests were performed at scan rates of 10 mV, 20 mV, 40 mV, 60 mV, and 100 mV. The test results are as follows: Figure 9 As shown.

[0069] Depend on Figure 9 As can be seen, the area of ​​the CV curve increases linearly with the increase of the scan rate, indicating that the electrode material has good electrochemical performance.

Claims

1. The application of an iron-based bimetallic phosphide electro-Fenton electrode material in the degradation of organic pollutants in three-dimensional electro-Fenton, characterized in that, The electrode material is an iron-vanadium bimetallic phosphide with a nanoflower-shaped structure, obtained by phosphating an iron-vanadium bimetallic hydroxide; the molar ratio of iron to vanadium is 1:1 to 1:5; the iron-vanadium bimetallic phosphide is used as a particle electrode.

2. The application according to claim 1, characterized in that, The molar ratio of iron to vanadium in the iron-based bimetallic phosphide electro-Fenton electrode material is 1:1 to 1:

2.

3. The application according to claim 1 or 2, characterized in that, The preparation method of the iron-based bimetallic phosphide electro-Fenton electrode material includes the following steps: (1) Iron salts and vanadium salts are dissolved in an organic solvent with urea and mixed evenly; a solvothermal synthesis reaction is carried out, and after the reaction is completed, the mixture is filtered, washed and dried to obtain iron-vanadium bimetallic hydroxide; (2) The iron-vanadium bimetallic hydroxide is subjected to high-temperature phosphating to obtain the iron-based bimetallic phosphide electro-Fenton electrode material.

4. The application according to claim 3, characterized in that, In step (1), the temperature of the solvothermal reaction is 100~120 ℃.

5. The application according to claim 3, characterized in that, The phosphating agent for high-temperature phosphating is sodium hypophosphite, and the temperature for high-temperature phosphating is 350~400℃.

6. The application according to claim 3, characterized in that, In step (1), the organic solvent is ethanol.

7. The application according to claim 1, characterized in that, The organic pollutant is a neonicotinoid insecticide.

8. The application according to claim 7, characterized in that, The neonicotinoid insecticide mentioned is acetamiprid.

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