Electro-Fenton electrode material of iron-based bimetallic phosphide as well as preparation method and application of electro-Fenton electrode material

Abstract

The invention discloses an electro-Fenton electrode material of an iron-based bimetallic phosphide and a preparation method and application of the electro-Fenton electrode material of the iron-based bimetallic phosphide, the electrode material is iron-vanadium bimetallic phosphide, is of a nanoflower-shaped structure and is obtained by phosphating iron-vanadium bimetallic hydroxide; the preparation method comprises the following steps: (1) dissolving ferric salt, vanadium salt and urea in an organic solvent, and uniformly mixing; carrying out solvothermal synthesis reaction, and after the reaction is finished, filtering, washing and drying to obtain ferrovanadium double-metal hydroxide; and (2) performing high-temperature phosphorization on the iron-vanadium double-metal hydroxide to obtain the electro-Fenton electrode material of the iron-based double-metal phosphide. According to the electrode material, the electron interaction between vanadium ions and iron ions is utilized, the electron structure is synergistically optimized, the electrode material has excellent ORR performance, efficient catalytic reaction and higher. OH generation capacity are achieved, and good degradation efficiency is shown in the process of degrading nitenpyram through the electro-Fenton technology.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrode material and a preparation method and application thereof, in particular to an iron-based bimetallic phosphide electro-Fenton electrode material and a preparation method and application thereof. BACKGROUND

[0002] China is a large agricultural country, and the use of pesticides or herbicides in agricultural production activities to improve crop yield is very common. However, large-scale and frequent application of pesticides can pose potential risks to human health and the environment. Neonicotinoid insecticides have high water solubility and long half-life. Therefore, once they enter the aquatic environment, they can stay for a long time, and their accumulation in the environment not only affects the survival of non-target organisms, but also causes chronic harm to human health. Therefore, it is urgent to develop effective wastewater remediation methods to solve the problem of pesticide pollution.

[0003] In recent years, electro-Fenton technology as a promising electrochemical advanced oxidation process has attracted more and more attention due to its fast reaction kinetics, high oxidation ability and environmental friendliness. ·OH is produced in large quantities by the interaction of H2O2 and Fe 2+ , which indicates that it has very strong oxidation ability and can quickly degrade various organic pollutants. EF technology emphasizes the in-situ synthesis of H2O2 by 2e - oxygen reduction reaction on the cathode, eliminating the potential explosion risk in H2O2 transportation and operation. In addition, in the process of electrocatalysis, cathodic reduction enhances the regeneration of Fe 2+ , thereby greatly reducing the dosage of Fe 2+ catalyst. However, the low production efficiency of H2O2 is attributed to the competition of the 4e- pathway, and the relatively poor electron transfer between Fe(III) / Fe(II) cycles leads to the problems of ·OH accumulation and Fe 3+ precipitation. Therefore, improving the yield and activation efficiency of H2O2 has great practical significance for the development and application of electro-Fenton technology.

[0004] Noble metal-based catalysts have excellent ORR catalytic activity and high H2O2 selectivity, but their high cost and scarcity limit their large-scale application in wastewater treatment. In terms of Fe 2+ regeneration, the addition of organic acids and metal sulfides and other organic reducing agents has become an effective strategy to promote the reduction of Fe 3+ . However, secondary pollution and higher cost will be accompanied. In this case, heterogeneous electro-Fenton has attracted more and more attention. So far, the first row transition metals (Fe, Co, Mn, Ni, Cu, etc.) based oxides have the advantages of multiple nanostructures and high corrosion resistance, which are suitable for various catalytic processes. Among them, single-metal electrodes such as iron phosphide alone as a catalyst have low catalytic activity and low reaction efficiency. SUMMARY

[0005] The first object of the present application is to provide an iron-based bimetallic phosphide electro-Fenton electrode material with improved catalytic activity; the second object of the present application is to provide a preparation method of the iron-based bimetallic phosphide electro-Fenton electrode material; and the third object of the present application is to provide an application of the iron-based bimetallic phosphide electro-Fenton electrode material in degrading organic pollutants in three-dimensional electro-Fenton.

[0006] Technical solution: The iron-based bimetallic phosphide electro-Fenton electrode material is an iron-vanadium bimetallic phosphide, which has a nanoflower structure and is obtained by phosphorization of iron-vanadium bimetallic hydroxide.

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

[0008] Further 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 comprises the following steps:

[0010] (1) Dissolve iron salt and vanadium salt in an organic solvent and mix uniformly; perform a solvothermal synthesis reaction, filter, wash and dry after the reaction to obtain iron-vanadium bimetallic hydroxide;

[0011] (2) Perform high-temperature phosphorization on the iron-vanadium bimetallic hydroxide 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 iron nitrate nonahydrate, and the vanadium salt is vanadium chloride (vanadium is trivalent vanadium).

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

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

[0017] Preferably, the organic pollutants are neonicotinoid insecticides.

[0018] Preferably, the neonicotinoid insecticide is nitenpyram.

[0019] Invention mechanism: In order to improve the mass transfer efficiency of the electro-Fenton reaction, a vanadium-doped iron phosphide bimetallic phosphide electrode material is proposed, marked as V-FeP, due to the electronic interaction between V 2+ and Fe 3+ Cations, synergistically optimize the electronic structure, so as to have excellent ORR performance. On the other hand, the phosphatization of vanadium-iron bimetallic oxide can form a unique metal-like structure, in which the graphene-like network formed by phosphatization can provide abundant electron transport channels, which is beneficial to promote electron transport, and V, Fe and P together accelerate the valence state cycle of the metal, so as to realize the rapid regeneration of active sites, thus realizing high-efficiency catalytic reaction and stronger ·OH generation capacity, and further realizing high-efficiency removal of neonicotinoid insecticides.

[0020] The principle of the present application is to add a transition metal catalyst as a particle electrode in the traditional electro-Fenton system, the particle electrode participates in the reaction to expand the reaction area, and also enhances the generation capacity of ·OH, improves the mass transfer efficiency and electrochemical active surface area, so that the three-dimensional electro-Fenton is suitable for complex pollutant degradation and large-volume water treatment. The important design idea of the present application is that the traditional electro-Fenton reaction is limited to the vicinity of the electrode, resulting in low mass transfer efficiency and limited reaction area, which is difficult to cover the entire system. In order to solve the above problems, an idea of using a transition metal catalyst as a particle electrode to realize more ·OH generation is proposed, the particle electrode is dispersed around the pollutants under the action of current, and a large area of contact can realize Fe 3+ / Fe 2+ Efficient cycle, that is, a vanadium-doped iron phosphide bimetallic phosphide electrode material is prepared, marked as V-FeP.

[0021] In the present application, carbon felt is used as the cathode and titanium plate is used as the anode in the traditional electro-F system, and V-FeP electrode is introduced. The particle electrode is polarized into an independent microelectrode under the action of current, the particle electrode participates in the reaction to expand the reaction area, improve the mass transfer efficiency and electrochemical active surface area, and realize high-efficiency degradation of pesticides.

[0022] Advantages: Compared with the prior art, the present application has the following obvious advantages: (1) the iron-based bimetallic phosphide electro-Fenton electrode material of the present application utilizes the electronic interaction between vanadium ions and iron ions, synergistically optimizes the electronic structure, has excellent ORR performance, realizes high-efficiency catalytic reaction and stronger ·OH generation capacity; (2) the preparation method is simple and easy to industrialize; (3) the catalyst of the present application shows good degradation efficiency in the degradation of nitenpyram in the three-dimensional electro-Fenton. BRIEF DESCRIPTION OF DRAWINGS

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

[0024] Figure 2 TEM images of V, Fe, P elements of V-FeP prepared for example 1;

[0025] Figure 3 XPS chart of V-FeP prepared for example 1;

[0026] Figure 4 Comparison of degradation effects of V-FeP prepared for examples 1-4 and FeP electrode material prepared for comparative example 1 on nitenpyram in water;

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

[0028] Figure 6 Comparison of degradation effects of V-FeP bimetallic phosphide electrode material prepared for example 1 on nitenpyram in water under different pollutant concentrations;

[0029] Figure 7 Comparison of degradation effects of V-FeP bimetallic phosphide electrode material prepared for example 1 on nitenpyram in water under different dosages;

[0030] Figure 8 Cycle effect chart of V-FeP bimetallic phosphide electrode material prepared for example 1;

[0031] Figure 9 CV chart of V-FeP bimetallic phosphide electrode material prepared for example 1. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be further described below in combination with examples.

[0033] Example 1

[0034] The preparation method of the iron-based bimetallic phosphide electro-Fenton electrode material described in the present application comprises the following steps:

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

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

[0037] Example 2

[0038] On the basis of Example 1, the molar ratio of iron nitrate nonahydrate and vanadium chloride was changed to 1:2, and the other conditions were unchanged.

[0039] Example 3

[0040] On the basis of Example 1, the molar ratio of iron nitrate nonahydrate and vanadium chloride was changed to 1:3, and the other conditions were unchanged.

[0041] Example 4

[0042] On the basis of Example 1, the molar ratio of iron nitrate nonahydrate and vanadium chloride was changed to 1:5, and the other conditions were unchanged.

[0043] Comparative Example 1

[0044] On the basis of Example 1, vanadium chloride was not added, and the other conditions were unchanged, to obtain phosphatized iron.

[0045] Structural characterization

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

[0047] Figure 1 The SEM image of the electrode material is shown, and it can be seen that the V-FeP presents a nanoflower shape.

[0048] Figure 2 The TEM images of the V, Fe and P elements are shown in sequence, which shows that vanadium is successfully doped.

[0049] Figure 3 The XPS image of the electrode material is shown, and from the image it can be clearly seen that the peak value of vanadium.

[0050] Performance test

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

[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 (current magnitude 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 NTP degradation performance of V-FeP, 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 10mA, 50mA, and 70mA, respectively. 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 50 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+ The regeneration of H2O2 was increased, which improved the efficiency of the E-Fenton reaction. The best removal efficiency of NIT was 99.3% within 50 min at a current density of 50 mA. Meanwhile, further increase of the current led to a decrease in the degradation efficiency. It was speculated that excessive H2O2 at a higher current would capture ·OH, producing ·O2H with a weaker oxidation potential, which was not conducive to the removal of organic pollutants.

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

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

[0060] As can be seen from Figure 6 , 5 mg / L of NIT was completely removed within 50 min, while when the initial concentration of NIT increased to 10 mg / L, 20 mg / L, and 30 mg / L, the degradation efficiency was 89.0%, 70.0%, and 67.0% at 50 min. Limited metal active sites limited the production of ·OH, and higher pollutant concentrations required more free radicals to participate in decomposition, resulting in a decrease in reaction rate. With further increase in the concentration of pollutants, 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 degradation of nitenpyram

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

[0063] As can be seen from Figure 7It can be seen that, with the increase of catalyst dosage from 5 mg to 10 mg, the catalytic efficiency of heterogeneous EF reaction within 50 min is 77% and 99.3%, respectively, and the removal rate of NIT is significantly improved (75-99%) with the increase of catalyst dosage. This may be due to the increase of catalytic active sites in the heterogeneous EF process, which promotes the generation of ·OH. However, when the dosage is further increased to 30 mg, the removal rate of NIT after 50 min of heterogeneous EF reaction does not increase but decreases, because when other operating parameters (such as applied current, aeration amount and effective electrode area, etc.) are fixed, the amount of hydrogen peroxide generated in the heterogeneous EF process can be considered constant, so adding excessive catalyst in the process will not improve its catalytic degradation performance for NIT. In addition, the generated ·OH may also react with excessive catalyst such as divalent iron.

[0064] 5. Cycle stability test of electrode

[0065] Based on the above test method, the V-FeP electrode material prepared in Example 1 was used to conduct four cycles of experiments. After completing the degradation of V-FeP, it was washed, dried and used for the second degradation experiment, and so on for four consecutive cycles. The test results are shown in Figure 8 .

[0066] As can be seen from Figure 8 , in the first, second, third and fourth cycles, the removal rate of NIT within 90 min is 99.3%, 92.7%, 90.1% and 92.1%, respectively. In the four cycles, it is shown that V-FeP exhibits good stability in the three-dimensional electro-Fenton process.

[0067] 6. Comparison of CV curve changes of vanadium-doped phosphide electrode material at different scan rates

[0068] The test method configures 40 ml of 0.1M Na2SO4 solution, the prepared catalyst material is coated on a graphite sheet, the electrode clamp is connected, and the CV test is conducted by inserting the graphite sheet into the container containing the reaction solution, with a scan rate of 10 mV, 20 mV, 40 mV, 60 mV and 100 mV. The test results are shown in Figure 9 .

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

Claims

1. An iron-based bimetallic phosphide electro-Fenton electrode material, characterized in that, The electrode material is iron-vanadium bimetallic phosphide, which has a nanoflower structure and is obtained by phosphorization of iron-vanadium bimetallic hydroxide.

2. The Fe-based bimetallic phosphide electro-Fenton electrode material of claim 1, wherein, The molar ratio of iron to vanadium is 1:1-1:

5.

3. The Fe-based bimetallic phosphide electro-Fenton electrode material of claim 1, wherein, The molar ratio of iron to vanadium is 1:1-1:

2.

4. A method for preparing the electro-Fenton electrode material of the iron-based double metal phosphide according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) dissolving iron salt and vanadium salt and urea in an organic solvent and mixing uniformly; performing a solvothermal synthesis reaction, filtering, washing and drying after the reaction to obtain iron-vanadium bimetallic hydroxide; (2) high-temperature phosphorization of the iron-vanadium bimetallic hydroxide to obtain the electro-Fenton electrode material of the iron-based bimetallic phosphide.

5. The method for preparing the iron-based bimetallic phosphide electro-Fenton electrode material according to claim 4, characterized in that, In step (1), the temperature of the solvothermal reaction is 100-120℃.

6. The method for preparing the iron-based bimetallic phosphide electro-Fenton electrode material according to claim 4, characterized in that, The phosphorization agent for the high-temperature phosphorization is sodium hypophosphite, and the temperature of the high-temperature phosphorization is 350-400℃.

7. The method of claim 6, wherein the method further comprises the step of: In step (1), the organic solvent is ethanol.

8. Application of the electro-Fenton electrode material of the iron-based bimetallic phosphide of claims 1-3 in degradation of organic pollutants in three-dimensional electro-Fenton.

9. Use according to claim 8, characterized in that, The organic pollutants are neonicotinoid insecticides.

10. Use according to claim 9, characterized in that, The neonicotinoid insecticide is nitenpyram.

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