Bifacial membrane catalytic electrode, preparation method thereof and system for catalytically degrading pollutants in water

Abstract

The invention provides a double-sided film catalytic electrode, a preparation method thereof and a system for catalytically degrading pollutants in water. The double-sided film catalytic electrode comprises a carbon skeleton fiber, the carbon skeleton fiber is provided with a first surface and a second surface which are oppositely arranged, the first surface loads a first transition metal monatomic, and the second surface loads a second transition metal monatomic. One of the first transition metal monatomic and the second transition metal monatomic is used for inducing the production of oxidizing active species, and the other one is used for inducing the production of reducing active species. Oxidation-reduction synergy can be realized, so that the energy barrier of the reaction is reduced, and the reaction efficiency is improved; the two different metal single atoms have space partitions, so that the quenching reaction between active species is effectively reduced, and the reaction efficiency is improved; the reaction sequence of pollutants in the two surfaces of the double-surface membrane catalytic electrode can be adjusted by changing the flow direction of the sewage, and adjustable oxidation reduction is realized, so that new pollutants in the sewage are efficiently removed.

Description

Technical Field

[0001] The present invention relates to the technical field of materials, and specifically, to a double-membrane catalytic electrode, a preparation method thereof, an application thereof, and a system for catalytically degrading pollutants in water. Background Art

[0002] Emerging pollutants refer to those toxic and harmful chemical substances with characteristics such as biological toxicity, environmental persistence, and bioaccumulation. Emerging pollutants mainly include persistent organic pollutants, endocrine disruptors, antibiotics, etc. controlled by international conventions. The discharge of emerging pollutants in sewage further exacerbates the water crisis and poses potential hazards to human health. Electrochemical advanced oxidation and reduction is a promising advanced sewage treatment technology, with advantages such as high reaction activity, environmental friendliness, and modular device. However, it is difficult to efficiently remove organic compounds containing electron-withdrawing groups by oxidation alone, and it is difficult to mineralize organic compounds by reduction alone. Existing technologies are difficult to adapt to the efficient removal of various emerging pollutants. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, an object of the present invention is to provide a double-membrane catalytic electrode, which can effectively reduce the quenching reaction between active species, realize in-situ oxidation-reduction synergy, and thus effectively remove various types of emerging pollutants in sewage.

[0004] In one aspect of the present invention, the present invention provides a double-membrane catalytic electrode. According to an embodiment of the present invention, the double-membrane catalytic electrode includes carbon framework fibers, the carbon framework fibers having a first surface and a second surface disposed opposite to each other, the first surface being loaded with first transition metal single atoms, and the second surface being loaded with second transition metal single atoms, wherein one of the first transition metal single atoms and the second transition metal single atoms is used to induce the generation of oxidative active species, and the other is used to induce the generation of reductive active species. Thus, the first transition metal single atoms and the second transition metal single atoms in the double-membrane catalytic electrode can respectively induce the generation of oxidative active species and reductive active species, enabling redox synergy, thereby reducing the energy barrier of the reaction and improving the reaction efficiency; moreover, the first transition metal single atoms and the second transition metal single atoms are respectively located on two surfaces of the double-membrane catalytic electrode, and the two different metal single atoms have a certain distance, that is, there is spatial partitioning, which can further effectively reduce the quenching reaction between the active species, and thus contribute to further improving the reaction efficiency. Therefore, applying the above double-membrane catalytic electrode to the sewage treatment containing new pollutants can effectively remove various types of new pollutants in the sewage; moreover, since the first transition metal single atoms and the second transition metal single atoms can respectively induce the generation of oxidative active species and reductive active species, according to different types of new pollutants, the reaction sequence of the pollutants on the two surfaces of the double-membrane catalytic electrode can be adjusted by changing the sewage flow direction to achieve adjustable redox, thereby efficiently removing the new pollutants in the sewage.

[0005] According to an embodiment of the present invention, the transition metal single atoms include at least one of iron, nickel, copper, cobalt, zinc, and manganese, the coordination atoms coordinated with the transition metal include at least one of nitrogen, phosphorus, sulfur, and oxygen, and the number of the coordination atoms coordinated with one transition metal single atom is 1 to 6.

[0006] According to an embodiment of the present invention, the oxidative active species include one or more of hydroxyl radicals, sulfate radicals, or singlet oxygen, and the reductive active species include one or two of atomic hydrogen and hydrated electrons.

[0007] In another aspect of the present invention, the present invention provides a method for preparing the double-membrane catalytic electrode described above. According to an embodiment of the present invention, the method for preparing the double-membrane catalytic electrode includes: uniformly mixing a first polymer, a first transition metal single-atom precursor, and a first organic solvent to obtain a first spinning solution; uniformly mixing a second polymer, a second transition metal single-atom precursor, and a second organic solvent to obtain a second spinning solution; first performing first electrospinning with the first spinning solution for a period of time, and then replacing the second spinning solution to continue performing second electrospinning to obtain a double-membrane intermediate; performing pre-oxidation treatment on the double-membrane intermediate to obtain a pre-oxidized double membrane; and performing carbonization treatment on the pre-oxidized double membrane to obtain a double-membrane catalytic electrode. Thus, in the double-membrane catalytic electrode prepared by the above method, the first transition metal single-atom and the second transition metal single-atom can respectively induce the generation of oxidation active species and reduction active species, and oxidation-reduction synergy can be achieved, thereby reducing the energy barrier of the reaction and improving the reaction efficiency; moreover, the first transition metal single-atom and the second transition metal single-atom are respectively located on two surfaces of the double-membrane catalytic electrode, and the two different transition metal single-atoms have a certain distance, which can effectively reduce the quenching reaction between the active species, and further contribute to further improving the reaction efficiency. Therefore, applying the above double-membrane catalytic electrode to the sewage treatment containing new pollutants can effectively remove various types of new pollutants in the sewage; moreover, since the first transition metal single-atom and the second transition metal single-atom can respectively induce the generation of oxidation active species and reduction active species, the flow direction of the sewage to the two surfaces of the double-membrane catalytic electrode can be adjusted according to different types of new pollutants, and in-situ oxidation-reduction synergy can be more optimally achieved, thereby efficiently removing new pollutants in the sewage.

[0008] According to an embodiment of the present invention, the first transition metal single-atom precursor includes at least one of a metal-organic framework compound containing the first transition metal, a phthalocyanine salt containing the first transition metal, and a mixture of a transition metal salt containing the first transition metal and a first organic substance, and the second transition metal single-atom precursor includes at least one of a metal-organic framework compound containing the second transition metal, a phthalocyanine salt containing the second transition metal, or a mixture of a transition metal salt containing the second transition metal and a second organic substance.

[0009] According to an embodiment of the present invention, the mass ratio of the first polymer to the first transition metal single-atom precursor is 1:0.01 to 1:3; the mass ratio of the second polymer to the second transition metal single-atom precursor is 1:0.01 to 1:3.

[0010] According to an embodiment of the present invention, the first spinning solution is prepared by the following method A, method B or method C: Method A: Dissolve zinc nitrate and a first transition metal salt in a solvent, and then add a 2-methylimidazole solution to the mixture to obtain a mixed solution. After stirring, separating and drying the mixed solution, a metal-organic framework compound containing the first transition metal is obtained; uniformly mix the metal-organic framework compound containing the first transition metal, the first polymer and the first organic solvent to obtain the first spinning solution; Method B: Uniformly mix a phthalocyanine salt containing the first transition metal, the first polymer and the first organic solvent to obtain the first spinning solution; Method C: Uniformly mix the first transition metal salt, the first organic substance, the first polymer and the first organic solvent to obtain the first spinning solution, wherein the first organic substance includes at least one of phenanthroline and dopamine,

[0011] The second spinning solution is prepared by the following method D, method E or method F: Method D: Dissolve zinc nitrate and a second transition metal salt in a solvent, and then add a 2-methylimidazole solution to the mixture. After stirring, separating and drying, a metal-organic framework compound containing the second transition metal is obtained; uniformly mix the metal-organic framework compound containing the second transition metal, the second polymer and the second organic solvent to obtain the second spinning solution; Method E: Uniformly mix a phthalocyanine salt containing the second transition metal, the second polymer and the second organic solvent to obtain the second spinning solution; Method F: Uniformly mix the second transition metal salt, the second organic substance, the second polymer and the second organic solvent to obtain the second spinning solution, wherein the second organic substance includes at least one of phenanthroline and dopamine.

[0012] According to an embodiment of the present invention, at least one of the following conditions is satisfied in the method A: the first transition metal salt includes at least one of nitrate and acetylacetonate; the dosage ratio of the first transition metal salt to the solvent is (0.05-5) mmol: 100 mL; in the first spinning solution, the addition amount of the metal-organic framework compound is 0.08-0.12 g / mL of the first organic solvent, and the addition amount of the first polymer is 0.08-0.12 g / mL of the first organic solvent;

[0013] At least one of the following conditions is satisfied in the method B: in the first spinning solution, the addition amount of the phthalocyanine salt is 0.01-0.2 mmol / mL of the first organic solvent, and the addition amount of the first polymer is 0.08-0.12 g / mL of the first organic solvent;

[0014] In the method C, at least one of the following conditions is satisfied: the first transition metal salt includes at least one of nitrate and acetylacetonate; in the first spinning solution, the addition amount of the first transition metal salt is 0.01 to 0.1 mmol / mL of the first organic solvent, the molar ratio of the first organic matter to the first transition metal salt is 4:1 to 8:1, and the addition amount of the first polymer is 0.08 to 0.12 g / mL of the first organic solvent;

[0015] In the method D, at least one of the following conditions is satisfied: the second transition metal salt includes at least one of nitrate and acetylacetonate; the dosage ratio of the second transition metal salt to the solvent is (0.05 to 5) mmol: 100 mL; in the second spinning solution, the addition amount of the metal-organic framework compound is 0.08 to 0.12 g / mL of the second organic solvent, and the addition amount of the second polymer is 0.08 to 0.12 g / mL of the second organic solvent;

[0016] In the method E, at least one of the following conditions is satisfied: in the second spinning solution, the addition amount of the phthalocyanine salt is 0.01 to 0.2 mmol / mL of the second organic solvent, and the addition amount of the second polymer is 0.08 to 0.12 g / mL of the second organic solvent;

[0017] In the method F, at least one of the following conditions is satisfied: the second transition metal salt includes at least one of nitrate and acetylacetonate; in the second spinning solution, the addition amount of the second transition metal salt is 0.01 to 0.1 mmol / mL of the second organic solvent, the molar ratio of the second organic matter to the second transition metal salt is 4:1 to 8:1, and the addition amount of the second polymer is 0.08 to 0.12 g / mL of the second organic solvent.

[0018] According to the embodiments of the present invention, the conditions of the pre-oxidation treatment include: the temperature is 240 to 300 °C, and the time is 0.5 to 3 h; the conditions of the carbonization treatment include: the temperature is 600 to 1400 °C, and the time is 0.5 to 3 h.

[0019] In another aspect of the present invention, the present invention provides an application of the double-membrane catalytic electrode described above in degrading pollutants. Thus, applying the above double-membrane catalytic electrode to the sewage treatment containing new pollutants can effectively remove various types of new pollutants in the sewage; since the first transition metal single atom and the second transition metal single atom can respectively induce the generation of oxidation active species and reduction active species, the flow direction of the sewage to the two surfaces of the double-membrane catalytic electrode can be adjusted according to different types of new pollutants, and in-situ oxidation-reduction synergy can be better realized, so as to efficiently remove the new pollutants in the sewage.

[0020] In another aspect of the present invention, the present invention provides a system for catalytic degradation of pollutants in water. According to an embodiment of the present invention, the system for catalytic degradation of pollutants includes: an anode; and a cathode, where the cathode is the double-membrane catalytic electrode described above, or the double-membrane catalytic electrode prepared by the method described above. Thus, this system can effectively remove various emerging pollutants in sewage.

[0021] According to an embodiment of the present invention, when degrading the pollutants, at normal temperature and pressure, the voltage between the anode and the cathode is 0.5 - 5V, and the membrane flux of the sewage is 50 - 2000L m -2 h -1 。

[0022] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0024] Figure 1 is a graph showing the test results of the catalytic degradation of propranolol (PRO) in wastewater by the catalytic degradation of pollutants system in Examples 1-1, 1-2, and 1-3;

[0025] Figure 2 is a graph showing the test results of the catalytic degradation of propranolol (PRO) in wastewater by the catalytic degradation of pollutants system in Examples 1-1, 1-4, and 1-5;

[0026] Figure 3 is a schematic diagram of the double-membrane catalytic electrode after degrading wastewater in Example 1-4;

[0027] Figure 4 is a graph showing the test results of the catalytic degradation of propranolol (PRO) in wastewater by the catalytic degradation of pollutants system in Examples 2-1, 2-2, 2-3, and Comparative Example 2-1;

[0028] Figure 5 is the tensile stress-strain curve of the double-membrane catalytic electrode in Example 3-1;

[0029] Figure 6a is the electron micrograph of the double-membrane catalytic electrode in Example 3-1;

[0030] Figure 6b is the scanning electron micrograph of the iron-containing metal-organic framework compound powder and the nickel-containing metal-organic framework compound powder;

[0031] Figure 7 are the X-ray near-edge absorption structure spectrum, X-ray absorption fine structure spectrum, and fitting curve of the iron-containing side in the double-membrane catalytic electrode in Example 3-1;

[0032] Figure 8 are the X-ray near-edge absorption structure spectrum, X-ray absorption fine structure spectrum, and fitting curve of the nickel-containing side in the double-membrane catalytic electrode in Example 3-1;

[0033] Figure 9 is the test result curve graph of the catalytic degradation of propranolol (PRO) in wastewater by the catalytic degradation pollutant system in Example 3-1, Comparative Example 3-1, Comparative Example 3-2, and Comparative Example 3-3;

[0034] Figure 10 is the test result curve graph of the catalytic degradation of propranolol (PRO) in wastewater by the catalytic degradation pollutant system in Example 3-1, Example 3-2, Example 3-3, and Example 3-4;

[0035] Figure 11 is the test result curve graph of the catalytic degradation of propranolol (PRO) in wastewater by the catalytic degradation pollutant system in Example 3-1, Example 3-5, and Example 3-6;

[0036] Figure 12 is the Raman spectrum of the double-membrane catalytic electrode in Example 3-1, Example 3-5, and Example 3-6;

[0037] Figure 13 are the test curves of the catalytic degradation of different pollutants by the catalytic degradation pollutant systems in Example 3-1 and Comparative Example 3-4 respectively;

[0038] Figure 14 is the test curve of the catalytic degradation of different pollutants by the catalytic degradation pollutant system in Example 3-1;

[0039] Figure 15 are the electron paramagnetic resonance spectra of the double-membrane catalytic electrode in Example 3-1, the membrane catalytic electrode in Comparative Example 3-1, the membrane catalytic electrode in Comparative Example 3-2, and the membrane catalytic electrode with mixed loading of iron and nickel single atoms in Comparative Example 3-4;

[0040] Figure 16 is the in-situ Raman spectrum of the double-membrane catalytic electrode in Example 3-1;

[0041] Figure 17 is the quantitative test graph of the steady-state concentration of reactive species and the concentration of hydrogen peroxide of the double-membrane catalytic electrode in Example 3-1;

[0042] Figure 18It is the free energy change curve diagram during the degradation of chloramphenicol by the double-membrane catalytic electrode in Example 3-1;

[0043] Figure 19 It is the periodic degradation test diagram of the propranolol pollutant by the double-membrane catalytic electrode in Example 3-1;

[0044] Figure 20 It is the effect diagram of the double-membrane catalytic electrode in Example 3-1 for treating the secondary effluent of pharmaceutical wastewater;

[0045] Figure 21 It is the three-dimensional fluorescence spectrogram of the wastewater after the double-membrane catalytic electrode in Example 3-1 treats the secondary effluent of pharmaceutical wastewater. Detailed implementation manners

[0046] The following will explain the solution of the present invention in combination with the embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchases.

[0047] The following describes the present invention with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0048] In one aspect of the present invention, the present invention provides a double-membrane catalytic electrode. According to an embodiment of the present invention, the double-membrane catalytic electrode includes carbon framework fibers having a first surface and a second surface disposed opposite to each other. The first surface is loaded with first transition metal single atoms, and the second surface is loaded with second transition metal single atoms. Among them, one of the first transition metal single atoms and the second transition metal single atoms is used to induce the generation of oxidative active species, and the other is used to induce the generation of reductive active species. Thus, the catalytic active component transition metal exists in the form of single atoms, which can effectively improve the catalytic activity and efficiency of the double-membrane catalytic electrode and enhance the catalytic uniformity; the first transition metal single atoms and the second transition metal single atoms in the double-membrane catalytic electrode can respectively induce the generation of oxidative active species and reductive active species, realizing redox synergy, thereby reducing the energy barrier of the reaction and improving the reaction efficiency; moreover, the first transition metal single atoms and the second transition metal single atoms are respectively located on the two surfaces of the double-membrane catalytic electrode, and the two different transition metal single atoms have a certain distance, that is, there is spatial partitioning, which can effectively reduce the quenching reaction between the active species and further contribute to improving the reaction efficiency. Therefore, applying the above double-membrane catalytic electrode to the sewage treatment containing new pollutants can effectively remove various types of new pollutants in the sewage; moreover, since the first transition metal single atoms and the second transition metal single atoms can respectively induce the generation of oxidative active species and reductive active species, according to different types of new pollutants, the reaction sequence of pollutants on the two surfaces of the double-membrane catalytic electrode can be adjusted by changing the sewage flow direction, realizing adjustable redox, and thus efficiently removing the new pollutants in the sewage.

[0049] It should be noted that the above-mentioned transition metal single atoms refer to that the transition metal is loaded on the surface of the carbon framework fibers in the form of single dispersed atoms, and there is no interaction of any form between the metals, that is, there is no chemical bond. However, the above single atoms do not refer to the atomic state of the metal in its elemental form, but there is a chemical bond between the above-mentioned transition metal single atoms and non-metals. For example, the above-mentioned transition metal single atoms are coordinated with nitrogen atoms through chemical bonds.

[0050] Furthermore, the above "the reaction sequence of pollutants on the two surfaces of the double-membrane catalytic electrode can be adjusted by changing the sewage flow direction" means adjusting the flow direction of the sewage from the first surface to the second surface or from the second surface to the first surface.

[0051] According to some embodiments of the present invention, the transition metal single atoms include at least one of iron, nickel, copper, cobalt, zinc, and manganese. Thus, transition metal single atoms capable of inducing different active species can be respectively loaded on the two surfaces of the double-membrane catalytic electrode. In some specific embodiments, iron single atoms and nickel single atoms can be respectively loaded on the two surfaces of the double-membrane catalytic electrode. The iron single atom sites can induce the generation of the oxidative active species hydroxyl radical (·OH), and the nickel single atom sites can induce the generation of the reductive active species atomic hydrogen (H*).

[0052] According to some embodiments of the present invention, the ratio of the first transition metal single atoms and the second transition metal single atoms respectively loaded on the two surfaces of the double-membrane catalytic electrode can be set according to the specific types of metals loaded. In some embodiments, the loading molar ratio of nickel single atoms to iron single atoms can be 1 / 20 to 1 / 5, such as 1 / 20, 1 / 15, 1 / 10, 3 / 20, 1 / 5, etc.

[0053] In some embodiments, the coordination atoms coordinated with the transition metal include at least one of nitrogen, phosphorus, sulfur, and oxygen, and the number of coordination atoms coordinated with one transition metal single atom is 1 to 6. In some specific embodiments, in the iron single atom catalyst, the number of nitrogen atoms coordinated with iron is 6, and its main active site is the Fe-N6 configuration; in the nickel single atom catalyst, the number of nitrogen atoms coordinated with nickel is 4, and its main active site is the Ni-N4 configuration.

[0054] According to some embodiments of the present invention, the oxidative active species include one or more of hydroxyl radical, sulfate radical, or singlet oxygen, and the reductive active species include one or two of atomic hydrogen and hydrated electron. Thus, it is beneficial for the deep degradation of new pollutants such as Propranolol (PRO), Chloramphenicol (CAP), Carbamazepine (CBZ), Crotamiton (CRO), Antipyrine (ATP), p-chlorophenol (pCP), Diclofenac (DCF), Ciprofloxacin (CIP), etc., and organic wastewater that is difficult to degrade (such as pharmaceutical wastewater, medical wastewater, landfill leachate, coal chemical wastewater, paper-making wastewater, printing and dyeing wastewater, etc.).

[0055] In another aspect of the present invention, the present invention provides a method for preparing the double-membrane catalytic electrode described above. According to the embodiments of the present invention, the method for preparing the double-membrane catalytic electrode includes:

[0056] S100: Uniformly mix a first polymer, a first transition metal single-atom precursor, and a first organic solvent to obtain a first spinning solution.

[0057] S200: Uniformly mix a second polymer, a second transition metal single-atom precursor, and a second organic solvent to obtain a second spinning solution.

[0058] According to some embodiments of the present invention, the first polymer and the second polymer can be high polymers such as polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, polyester, polyamide, etc. Among them, there are no special requirements for the molecular weights of different polymers. Those skilled in the art can, in some specific embodiments, the polymer is polyacrylonitrile with a molecular weight Mw = 150000.

[0059] According to some embodiments of the present invention, the first organic solvent and the second organic solvent can be one or more of N,N-dimethylformamide, N,N-dimethylacetamide, methanol, ethanol, or acetone.

[0060] According to some embodiments of the present invention, the first transition metal single-atom precursor includes at least one of a metal-organic framework compound (MOFs) containing the first transition metal, a phthalocyanine salt containing the first transition metal, and a mixture of a transition metal salt containing the first transition metal and a first organic compound. According to some embodiments of the present invention, the second transition metal single-atom precursor includes at least one of a metal-organic framework compound (MOFs) containing the second transition metal, a phthalocyanine salt containing the second transition metal, or a mixture of a transition metal salt containing the second transition metal and a second organic compound.

[0061] In some specific embodiments of the present invention, the above-mentioned metal-organic framework compound (MOFs) can be ZIF8 (zeolitic imidazolate framework material); the phthalocyanine salt can be iron phthalocyanine, nickel phthalocyanine, copper phthalocyanine, cobalt phthalocyanine, zinc phthalocyanine, manganese phthalocyanine, etc.; the transition metal salt can be iron acetylacetonate, nickel acetylacetonate, copper acetylacetonate, cobalt acetylacetonate, zinc acetylacetonate, manganese acetylacetonate, etc.; the first organic compound and the second organic compound can be organic compounds such as phenanthroline (such as 1,10-phenanthroline), dopamine, etc. Among them, when using the metal-organic framework compound as a precursor, the prepared double-layer membrane catalytic electrode has more excellent mechanical strength. After using it for degradation, the membrane is not easily broken and has a longer service life.

[0062] According to some embodiments of the present invention, the mass ratio of the first polymer to the first transition metal single-atom precursor is 1:0.01 to 1:3, such as 1:0.01, 1:0.05, 1:0.1, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.3, 1:2.5, 1:2.8, 1:3, etc.; according to some embodiments of the present invention, the mass ratio of the second polymer to the second transition metal single-atom precursor is 1:0.01 to 1:3, such as 1:0.01, 1:0.05, 1:0.1, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.3, 1:2.5, 1:2.8, 1:3, etc. Thus, it is beneficial to load an appropriate amount of transition metal single atoms.

[0063] According to some embodiments of the present invention, the first spinning solution is prepared by the following method A, method B or method C:

[0064] The method for preparing the first spinning solution by method A includes: dissolving zinc nitrate and the first transition metal salt in a solvent, then adding a 2-methylimidazole solution to the mixed solution to obtain a mixed solution, and after stirring, separating and drying the mixed solution, a metal-organic framework compound containing the first transition metal is obtained; uniformly mixing the metal-organic framework compound containing the first transition metal, the first polymer and the first organic solvent to obtain the first spinning solution.

[0065] In some embodiments, in the above method A, the first transition metal salt includes at least one of nitrate and acetylacetonate, such as transition metal salts such as nickel nitrate, iron nitrate, nickel acetylacetonate, iron acetylacetonate, etc. Among them, in some embodiments, the solvent can be an organic solvent such as methanol or ethanol.

[0066] In some other embodiments, the dosage ratio of the first transition metal salt to the solvent is (0.05 - 5) mmol: 100 mL, such as the dosage ratio of the first transition metal salt to the solvent is 0.05 mmol: 100 mL, 0.1 mmol: 100 mL, 0.5 mmol: 100 mL, 0.75 mmol: 100 mL, 1 mmol: 100 mL, 1.5 mmol: 100 mL, 2.5 mmol: 100 mL, 3.5 mmol: 100 mL, 4.5 mmol: 100 mL, 5 mmol: 100 mL, etc. Furthermore, it is beneficial to load an appropriate amount of transition metal single atoms in the double-membrane catalytic electrode.

[0067] In still other embodiments, in the first spinning solution, the addition amount of the metal-organic framework compound is 0.08 to 0.12 g / mL of the first organic solvent, that is, for 1 mL of the first organic solvent, 0.08 to 0.12 g of the metal-organic framework compound is added correspondingly; the addition amount of the first polymer is 0.08 to 0.12 g / mL of the first organic solvent, that is, for 1 mL of the first organic solvent, 0.08 to 0.12 g of the first polymer is added correspondingly. Thus, it is beneficial to load an appropriate amount of the first transition metal single atoms in the double-membrane catalytic electrode, and further helps to improve the catalytic activity of the double-membrane catalytic electrode.

[0068] In some specific embodiments, taking the first transition metal as iron as an example, the preparation method of the first spinning solution includes: dissolving 10 mmol of zinc nitrate hexahydrate and 1 to 10 mmol (in some embodiments, preferably 4 to 6 mmol of iron acetylacetonate) of iron acetylacetonate in 100 mL of methanol, then adding 100 mL of methanol containing 80 mmol of 2-methylimidazole, and after stirring, standing, centrifugal separation, washing, and drying, an iron-containing metal-organic framework compound powder (which can be abbreviated as Fe@ZIF8) is obtained; then 1 g of the metal-organic framework compound containing the first transition metal prepared above, 1 g of polyacrylonitrile (Mw = 150000), and 10 mL of N,N-dimethylformamide are uniformly mixed to obtain the first spinning solution.

[0069] The method for preparing the first spinning solution by Method B includes: uniformly mixing a phthalocyanine salt containing a first transition metal, a first polymer, and a first organic solvent to obtain the first spinning solution.

[0070] In some embodiments, in the above Method B, in the first spinning solution, the addition amount of the phthalocyanine salt is 0.01 to 0.2 mmol / mL (such as 0.01 mmol / mL, 0.02 mmol / mL, 0.03 mmol / mL, 0.04 mmol / mL, 0.05 mmol / mL, 0.06 mmol / mL, 0.07 mmol / mL, 0.08 mmol / mL, 0.09 mmol / mL, 0.1 mmol / mL, 0.12 mmol / mL, 0.15 mmol / mL, 0.18 mmol / mL, 0.2 mmol / mL, etc.) of the first organic solvent, that is, for 1 mL of the first organic solvent, 0.01 to 0.2 mmol of the phthalocyanine salt is added correspondingly; the addition amount of the first polymer is 0.08 to 0.12 g / mL of the first organic solvent, that is, for 1 mL of the first organic solvent, 0.08 to 0.12 g of the first polymer is added correspondingly. Thus, it is beneficial to load an appropriate amount of the first transition metal single atoms in the double-membrane catalytic electrode, and further helps to improve the catalytic activity of the double-membrane catalytic electrode.

[0071] In some specific embodiments, taking the first transition metal as iron as an example, the preparation method of the first spinning solution includes: mixing 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150,000), and 0.1 to 2 mmol of iron phthalocyanine to obtain the first spinning solution.

[0072] The method for preparing the first spinning solution by Method C includes: uniformly mixing a first transition metal salt, a first organic substance, a first polymer, and a first organic solvent to obtain the first spinning solution, wherein the first organic substance includes at least one of phenanthroline and dopamine.

[0073] In some embodiments, in the above Method C, the first transition metal salt includes at least one of a nitrate and an acetylacetonate.

[0074] In some embodiments, in the first spinning solution, the addition amount of the first transition metal salt is 0.01 to 0.1 mmol / mL (such as 0.01 mmol / mL, 0.02 mmol / mL, 0.03 mmol / mL, 0.04 mmol / mL, 0.05 mmol / mL, 0.06 mmol / mL, 0.07 mmol / mL, 0.08 mmol / mL, 0.09 mmol / mL, 0.1 mmol / mL, etc.) of the first organic solvent, that is, for 1 mL of the first organic solvent, 0.01 to 0.1 mmol of the first transition metal salt is added correspondingly; the molar ratio of the first organic substance to the first transition metal salt is 4:1 to 8:1, such as 4:1, 5:1, 6:1, 7:1, 8:1, etc.; the addition amount of the first polymer is 0.08 to 0.12 g / mL of the first organic solvent, that is, for 1 mL of the first organic solvent, 0.08 to 0.12 g of the first polymer is added correspondingly. Thus, it is beneficial to load an appropriate amount of the first transition metal single atoms in the double-membrane catalytic electrode, and further helps to improve the catalytic activity of the double-membrane catalytic electrode.

[0075] In some specific embodiments, taking the first transition metal as iron as an example, the preparation method of the first spinning solution includes: uniformly mixing 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150,000), 0.1 to 1 mmol of iron acetylacetonate, and 1,10-phenanthroline to obtain the first spinning solution.

[0076] According to some embodiments of the present invention, the second spinning solution is prepared by the following Method D, Method E, or Method F:

[0077] The method for preparing the second spinning solution by Method D includes: dissolving zinc nitrate and a second transition metal salt in a solvent, and then adding a 2-methylimidazole solution to the mixture. After stirring, separating, and drying, the metal-organic framework compound containing the second transition metal is obtained; the metal-organic framework compound containing the second transition metal, the second polymer, and the second organic solvent are uniformly mixed to obtain the second spinning solution.

[0078] In some embodiments, in the above Method D, the second transition metal salt includes at least one of nitrates and acetylacetonates, such as transition metal salts like nickel nitrate, iron nitrate, nickel acetylacetonate, iron acetylacetonate, etc. Among them, in some embodiments, the solvent can be an organic solvent such as methanol or ethanol.

[0079] In other embodiments, the dosage ratio of the second transition metal salt to the solvent is (0.05 - 5) mmol: 100 mL. For example, the dosage ratio of the first transition metal salt to the solvent is 0.05 mmol: 100 mL, 0.1 mmol: 100 mL, 0.5 mmol: 100 mL, 0.75 mmol: 100 mL, 1 mmol: 100 mL, 1.5 mmol: 100 mL, 2.5 mmol: 100 mL, 3.5 mmol: 100 mL, 4.5 mmol: 100 mL, 5 mmol: 100 mL, etc. Furthermore, it is beneficial to load an appropriate amount of transition metal single atoms in the double-membrane catalytic electrode.

[0080] In still other embodiments, in the second spinning solution, the addition amount of the metal-organic framework compound is 0.08 - 0.12 g / mL of the second organic solvent, that is, for 1 mL of the second organic solvent, 0.08 - 0.12 g of the metal-organic framework compound is added; the addition amount of the second polymer is 0.08 - 0.12 g / mL of the second organic solvent, that is, for 1 mL of the second organic solvent, 0.08 - 0.12 g of the second polymer is added. In this way, it is beneficial to load an appropriate amount of the first transition metal single atoms in the double-membrane catalytic electrode, and further helps to improve the catalytic activity of the double-membrane catalytic electrode.

[0081] In some specific embodiments, taking the second transition metal as nickel as an example, the preparation method of the first spinning solution includes: dissolving 10 mmol of zinc nitrate hexahydrate and 0.1 - 2 mmol (in some embodiments, preferably 0.5 - 0.75 mmol of iron acetylacetonate) of nickel nitrate hexahydrate in 100 mL of methanol, then adding 100 mL of methanol containing 80 mmol of 2-methylimidazole, and after stirring, standing, centrifugal separation, washing, and drying, a metal-organic framework compound powder containing nickel (which can be abbreviated as Ni@ZIF8) is obtained; then 1 g of the metal-organic framework compound containing the second transition metal prepared above, 1 g of polyacrylonitrile (Mw = 150,000), and 10 mL of N,N-dimethylformamide are uniformly mixed to obtain the second spinning solution.

[0082] The method for preparing the second spinning solution by Method E includes: uniformly mixing the phthalocyanine salt containing the second transition metal, the second polymer, and the second organic solvent to obtain the second spinning solution.

[0083] In some embodiments, in the above Method E, in the second spinning solution, the addition amount of the phthalocyanine salt is 0.01 - 0.2 mmol / mL (such as 0.01 mmol / mL, 0.02 mmol / mL, 0.03 mmol / mL, 0.04 mmol / mL, 0.05 mmol / mL, 0.06 mmol / mL, 0.07 mmol / mL, 0.08 mmol / mL, 0.09 mmol / mL, 0.1 mmol / mL, 0.12 mmol / mL, 0.15 mmol / mL, 0.18 mmol / mL, 0.2 mmol / mL, etc.) of the second organic solvent, that is, for 1 mL of the second organic solvent, 0.01 - 0.2 mmol of the phthalocyanine salt is added correspondingly; the addition amount of the second polymer is 0.08 - 0.12 g / mL of the second organic solvent, that is, for 1 mL of the second organic solvent, 0.08 - 0.12 g of the second polymer is added correspondingly. In this way, it is beneficial to load an appropriate amount of the second transition metal single atoms in the double-membrane catalytic electrode, and thus helps to improve the catalytic activity of the double-membrane catalytic electrode.

[0084] In some specific embodiments, taking the second transition metal as nickel as an example, the preparation method of the second spinning solution includes: mixing 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150,000), and 0.1 - 2 mmol of nickel phthalocyanine to obtain the second spinning solution.

[0085] The method for preparing the second spinning solution by Method F includes: uniformly mixing the second transition metal salt, the second organic substance, the second polymer, and the second organic solvent to obtain the second spinning solution, wherein the second organic substance includes at least one of phenanthroline and dopamine.

[0086] In some embodiments, in the above method C, the second transition metal salt includes at least one of nitrates and acetylacetonates.

[0087] In some embodiments, in the second spinning solution, the addition amount of the second transition metal salt is 0.01 - 0.1 mmol / mL (such as 0.01 mmol / mL, 0.02 mmol / mL, 0.03 mmol / mL, 0.04 mmol / mL, 0.05 mmol / mL, 0.06 mmol / mL, 0.07 mmol / mL, 0.08 mmol / mL, 0.09 mmol / mL, 0.1 mmol / mL, etc.) of the second organic solvent, that is, for 1 mL of the second organic solvent, 0.01 - 0.1 mmol of the second transition metal salt is correspondingly added; the molar ratio of the second organic matter to the second transition metal salt is 4:1 - 8:1, such as 4:1, 5:1, 6:1, 7:1, 8:1, etc.; the addition amount of the second polymer is 0.08 - 0.12 g / mL of the second organic solvent, that is, for 1 mL of the second organic solvent, 0.08 - 0.12 g of the second polymer is correspondingly added. Thus, it is beneficial to load an appropriate amount of the second transition metal single atoms in the double - membrane catalytic electrode, and further helps to improve the catalytic activity of the double - membrane catalytic electrode.

[0088] In some specific embodiments, taking the second transition metal as nickel as an example, the preparation method of the second spinning solution includes: uniformly mixing 10 mL of N,N - dimethylformamide, 1 g of polyacrylonitrile (Mw = 150000), 0.1 - 1 mmol of nickel acetylacetonate, and 1,10 - phenanthroline to obtain the second spinning solution.

[0089] According to some embodiments of the present invention, the preparation methods of the first spinning solution and the second spinning solution are basically the same, and three different transition metal single - atom precursors can be selected. Among them, the first spinning solution and the second spinning solution can use the same transition metal single - atom precursor, or different transition metal single - atom precursors, and those skilled in the art can make flexible selections according to actual needs. For example, if the first spinning solution is prepared by method A, then the second spinning solution can be prepared by method D, method E or method F. That is to say, there is no specific corresponding relationship between the preparation methods used for the first spinning solution and the second spinning solution, and they can be prepared independently of each other.

[0090] S300: First, perform the first electrospinning with the first spinning solution for a period of time, and then replace it with the second spinning solution to continue the second electrospinning to obtain a double - membrane intermediate.

[0091] In some embodiments of the present invention, the spinning voltage in the first electrospinning and the second electrospinning is 15 - 25 kV, and the nozzle distance is 10 - 18 cm. This is beneficial for obtaining spun fibers with a finer diameter, which is conducive to increasing the loading area of transition metal single atoms and improving the catalytic activity.

[0092] S400: Pre-oxidize the double-membrane intermediate to obtain a pre-oxidized double membrane.

[0093] According to some embodiments of the present invention, the conditions for the pre-oxidation treatment include: the temperature is 240 - 300 °C, and the time is 0.5 - 3 h. Thus, through the pre-oxidation process, the first polymer and the second polymer will undergo reactions such as cyclization, dehydrogenation, oxidation, and crosslinking, so that the fibers will not melt and burn during the subsequent carbonization process at a higher temperature, and the carbonization temperature that can be applied is increased. In some specific embodiments, the temperature of the pre-oxidation treatment can be 260 - 280 °C, and the time is 2 h. Further, this pre-oxidation treatment can be carried out in a muffle furnace.

[0094] S500: Carbonize the pre-oxidized double membrane to obtain a double-membrane catalytic electrode.

[0095] According to some embodiments of the present invention, the conditions for the carbonization treatment include: the temperature is 600 - 1400 °C, and the time is 0.5 - 3 h. Thus, the carbonization of the polymer can be effectively achieved to obtain carbon skeleton fibers, and the transition metal loaded on them is converted into metal single atoms. In some specific embodiments, the temperature of the carbonization treatment is 900 - 1100 °C, and the time is 1 h.

[0096] According to the embodiments of the present invention, in the double-membrane catalytic electrode prepared by the above method, the first transition metal single atom and the second transition metal single atom can respectively induce the generation of oxidation active species and reduction active species, and oxidation-reduction synergy can be achieved, thereby reducing the energy barrier of the reaction and improving the reaction efficiency; moreover, the first transition metal single atom and the second transition metal single atom are respectively located on the two surfaces of the double-membrane catalytic electrode, and the two different transition metal single atoms have a certain distance, which can effectively reduce the quenching reaction between the active species, and further contribute to improving the reaction efficiency. Therefore, applying the above double-membrane catalytic electrode to the sewage treatment containing new pollutants can effectively remove various types of new pollutants in the sewage; moreover, since the first transition metal single atom and the second transition metal single atom can respectively induce the generation of oxidation active species and reduction active species, the flow direction of the sewage to the two surfaces of the double-membrane catalytic electrode can be adjusted according to different types of new pollutants, and in-situ oxidation-reduction synergy can be better achieved, thereby efficiently removing the new pollutants in the sewage.

[0097] In yet another aspect of the present invention, the present invention provides an application of the aforementioned dual-membrane catalytic electrode in degrading pollutants. Thus, applying the above dual-membrane catalytic electrode to the treatment of sewage containing new pollutants can effectively remove various types of new pollutants in the sewage; since the first transition metal single atom and the second transition metal single atom can respectively induce the generation of oxidation active species and reduction active species, the flow direction of the sewage to the two surfaces of the dual-membrane catalytic electrode can be adjusted according to different types of new pollutants, so as to better achieve in-situ oxidation-reduction synergy, thereby efficiently removing new pollutants in the sewage.

[0098] According to some embodiments of the present invention, the pollutants may be new pollutants such as Propranolol (PRO), Chloramphenicol (CAP), Carbamazepine (CBZ), Crotamiton (CRO), Antipyrine (ATP), p-chlorophenol (pCP), Diclofenac (DCF), Ciprofloxacin (CIP), etc., as well as organic wastewater that is difficult to degrade (such as pharmaceutical wastewater, medical wastewater, landfill leachate, coal chemical wastewater, papermaking wastewater, printing and dyeing wastewater, etc.).

[0099] In yet another aspect of the present invention, the present invention provides a catalytic degradation pollutant system. According to an embodiment of the present invention, the system for catalytically degrading pollutants includes: an anode; and a cathode, where the cathode is the aforementioned dual-membrane catalytic electrode or the dual-membrane catalytic electrode prepared by the aforementioned method. Thus, this system can effectively remove various new pollutants in water.

[0100] According to some embodiments of the present invention, the anode can be an inert titanium mesh.

[0101] According to some embodiments of the present invention, the catalytic degradation pollutant system may further include a current collecting layer. Further, a stainless steel mesh can be used as the current collecting layer. In some embodiments, in the catalytic degradation pollutant system, it is connected to a power source through a circular titanium sheet, and the cathode and the anode are separated by a plastic partition to prevent short circuit.

[0102] In some specific embodiments, the catalytic degradation pollutant system includes an inlet chamber, a dual-membrane catalytic electrode (i.e., the cathode), a current collecting layer, a plastic partition, an anode, and an outlet chamber arranged in sequence.

[0103] In some embodiments, in the catalytic degradation pollutant system, there is no special requirement for the effective filtration area of the cathode and the anode, and those skilled in the art can flexibly design according to actual usage requirements.

[0104] According to some embodiments of the present invention, when degrading pollutants, at normal temperature and pressure, the voltage between the anode and the cathode is 0.5 - 5V, and the membrane flux of the sewage is 50 - 2000L m -2 h -1 。

[0105] Example

[0106] Example 1-1

[0107] The method for preparing the double-membrane catalytic electrode includes:

[0108] Prepare the first spinning solution: uniformly mix 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150000), 0.5 mmol of iron acetylacetonate, and 3 mmol of 1,10-phenanthroline (the molar ratio of 1,10-phenanthroline to iron acetylacetonate is 6:1) to obtain the first spinning solution;

[0109] Prepare the second spinning solution: uniformly mix 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150000), 0.5 mmol of nickel acetylacetonate, and 3 mmol of 1,10-phenanthroline (the molar ratio of 1,10-phenanthroline to nickel acetylacetonate is 6:1) to obtain the second spinning solution;

[0110] First, perform the first electrospinning with the first spinning solution for a period of time, and then replace it with the second spinning solution to continue the second electrospinning to obtain a double-membrane intermediate. Among them, the electrospinning voltage is 21 kV, and the nozzle distance is 15 cm;

[0111] Perform pre-oxidation treatment on the double-membrane intermediate at 280 °C for 1 h to obtain a pre-oxidized double membrane;

[0112] Perform carbonization treatment on the pre-oxidized double membrane at 1000 °C for 1 h to obtain a double-membrane catalytic electrode (Janus Fe-Ni SA@CF) loaded with iron and nickel single atoms respectively, Figure 1 the corresponding test curve Janus Fe-Ni SA@CF(0.5 mmol) in Figure 2 the corresponding test curve Janus Fe-Ni SA@CF(280 °C) in

[0113] In the catalytic degradation of pollutants system, use an inert titanium mesh as the anode, and the above-prepared double-membrane catalytic electrode Janus Fe-Ni SA@CF as the cathode. The effective filtration areas of the anode and the cathode are both 7 cm 2 , use a stainless steel mesh as the current collector layer, connect it to the power supply through a circular titanium sheet, and separate the anode and the cathode by a plastic spacer with a thickness of 0.5 mm to avoid short circuit.

[0114] Example 1-2

[0115] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 1-1, except that: in the preparation of the first spinning solution, the dosage of iron acetylacetonate is 0.4 mmol; in the preparation of the second spinning solution, the dosage of nickel acetylacetonate is 0.4 mmol( Figure 1 The corresponding test curve is Janus Fe-Ni SA@CF (0.4 mmol)).

[0116] Example 1-3

[0117] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 1-1, except that: in the preparation of the first spinning solution, the dosage of iron acetylacetonate is 0.3 mmol; in the preparation of the second spinning solution, the dosage of nickel acetylacetonate is 0.3 mmol( Figure 1 The corresponding test curve is Janus Fe-Ni SA@CF (0.3 mmol)).

[0118] Example 1-4

[0119] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 1-1, except that: the temperature of the pre-oxidation treatment is 250 °C( Figure 2 The corresponding test curve is Janus Fe-Ni SA@CF (250 °C)).

[0120] Example 1-5

[0121] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 1-1, except that: the temperature of the pre-oxidation treatment is 240 °C( Figure 2 The corresponding test curve is Janus Fe-Ni SA@CF (240 °C)).

[0122] The catalytic degradation pollutant systems in Examples 1-1, 1-2, 1-3, 1-4 and 1-5 were respectively used to degrade propranolol (PRO) in wastewater. The test results can be respectively seen in Figure 1 and Figure 2 , in which, the initial concentration of propranolol in the wastewater before degradation is 5 mg / L, and the wastewater volume is 50 mL. During the 20-minute degradation process, the wastewater circulates in and out. Under normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1, the wastewater flows from the surface loaded with single-atom iron to the surface loaded with single-atom nickel.

[0123] From Figure 1 It can be seen that when the dosages of acetylacetonate salts in the first spinning solution and the second spinning solution are both 0.5 mmol, the removal rate of propranolol can reach 86% within 20 minutes. However, after the degradation ends, the mechanical properties of the double-membrane catalytic electrode decrease significantly, and fragmentation often occurs.

[0124] From Figure 2 It can be seen that when the pre-oxidation temperature is reduced from 280 °C to 250 °C, only a few cracks appear in the negative electrode membrane ( Figure 3 ), indicating that reducing the pre-oxidation temperature can improve the mechanical strength of the membrane; but when the temperature of the pre-oxidation treatment is reduced, the degradation effect on propranolol decreases rapidly ( Figure 2 ), which is mainly because at a lower pre-oxidation temperature (250 °C and below), the pre-oxidation cannot proceed sufficiently to complete the amorphous transformation and aromatization recombination of carbon.

[0125] Example 2-1

[0126] The method for preparing the double-membrane catalytic electrode includes:

[0127] Preparing the first spinning solution: uniformly mixing 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150000), and 0.5 mmol of iron phthalocyanine to obtain the first spinning solution;

[0128] Preparing the second spinning solution: uniformly mixing 10 mL of N,N-dimethylformamide, 1 g of polyacrylonitrile (Mw = 150000), and 0.5 mmol of iron phthalocyanine to obtain the second spinning solution;

[0129] First, perform the first electrospinning with the first spinning solution for a period of time, and then replace it with the second spinning solution to continue the second electrospinning to obtain a double-membrane intermediate, where the electrospinning voltage is 21 kV and the nozzle distance is 15 cm;

[0130] Perform pre-oxidation treatment on the double-membrane intermediate at 280 °C for 1 h to obtain a pre-oxidized double membrane;

[0131] Perform carbonization treatment on the pre-oxidized double membrane at 1000 °C for 1 h to obtain a double-membrane catalytic electrode (Janus Fe-Ni SA@CF, Figure 4 corresponding to the test curve Janus Fe-Ni SA@CF(0.5 mmol) in it).

[0132] The setting requirements of the catalytic degradation pollutant system are the same as those in Example 1-1.

[0133] Example 2-2

[0134] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation of pollutants system in Example 2-1, except that: in the preparation of the first spinning solution, the dosage of iron phthalocyanine is 0.75 mmol; in the preparation of the second spinning solution, the dosage of nickel phthalocyanine is 0.75 mmol( Figure 4 The corresponding test curve in it is Janus Fe-Ni SA@CF(0.75 mmol).

[0135] Example 2-3

[0136] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation of pollutants system in Example 2-1, except that: in the preparation of the first spinning solution, the dosage of iron phthalocyanine is 1 mmol; in the preparation of the second spinning solution, the dosage of nickel phthalocyanine is 1 mmol( Figure 4 The corresponding test curve in it is Janus Fe-Ni SA@CF(1 mmol).

[0137] Comparative Example 2-1

[0138] It is basically the same as the method for preparing the dual-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation of pollutants system in Example 2-1, except that: in the preparation of the first spinning solution, iron phthalocyanine is changed to iron acetylacetonate; in the preparation of the second spinning solution, nickel phthalocyanine is changed to nickel acetylacetonate( Figure 4 The corresponding test curve in it is Janus Fe-Ni@CF(0.5 mmol).

[0139] The catalytic degradation of pollutants systems in Examples 2-1, 2-2, 2-3 and Comparative Example 2-1 were respectively used to degrade propranolol (PRO) in wastewater, and the test results can be seen respectively in Figure 4 , where the initial concentration of propranolol in the wastewater before degradation is 5 mg / L, and the wastewater volume is 50 mL. During the 20-minute degradation process, the wastewater circulates in and out, and at normal temperature and pressure, the voltage between the anode and cathode is 3, and the membrane flux is 680 L m -2 h -1 , and the wastewater flow direction is from the surface loaded with single-atom iron to the surface loaded with single-atom nickel.

[0140] From Figure 4It can be seen that the effect of the Janus Fe-Ni SA@CF cathode membrane in degrading propranolol rapidly decreases with the increase in the doping amount of phthalocyanine salt. Through observation, its mechanical properties also decrease accordingly. Moreover, compared with the non-single-atom catalytic electrode membrane (Janus Fe-Ni@CF) with the same metal doping amount, the catalytic performance of the double-membrane catalytic electrode with single-atom loading in the examples is significantly more superior, and its removal rate of propranolol within 20 minutes is 79%.

[0141] Example 3-1

[0142] The method for preparing the double-membrane catalytic electrode includes:

[0143] Preparing the first spinning solution: Dissolve 10 mmol of zinc nitrate hexahydrate and 5 mmol of iron acetylacetonate in 100 mL of methanol, then add 100 mL of methanol containing 80 mmol of 2-methylimidazole. After stirring, standing, centrifugal separation, washing, and drying, obtain a metal-organic framework compound powder containing iron (which can be abbreviated as Fe@ZIF8); then uniformly mix 1 g of the metal-organic framework compound containing the first transition metal prepared above, 1 g of polyacrylonitrile (Mw = 150000), and 10 mL of N,N-dimethylformamide to obtain the first spinning solution;

[0144] Preparing the second spinning solution: Dissolve 10 mmol of zinc nitrate hexahydrate and 0.5 mmol of nickel nitrate hexahydrate in 100 mL of methanol, then add 100 mL of methanol containing 80 mmol of 2-methylimidazole. After stirring, standing, centrifugal separation, washing, and drying, obtain a metal-organic framework compound powder containing nickel (which can be abbreviated as Ni@ZIF8); then uniformly mix 1 g of the metal-organic framework compound containing the second transition metal prepared above, 1 g of polyacrylonitrile (Mw = 150000), and 10 mL of N,N-dimethylformamide to obtain the second spinning solution;

[0145] First, perform the first electrospinning with the first spinning solution for a period of time, and then replace it with the second spinning solution to continue the second electrospinning to obtain a double-membrane intermediate, where the spinning voltage is 21 kV and the nozzle distance is 15 cm;

[0146] Perform pre-oxidation treatment on the double-membrane intermediate at 280 °C for 2 h to obtain a pre-oxidized double membrane;

[0147] Perform carbonization treatment on the pre-oxidized double membrane at 1000 °C for 1 h to obtain a double-membrane catalytic electrode (Janus Fe-Ni SA@CF) respectively loaded with iron and nickel single atoms, where the molar ratio of the loaded nickel and iron single atoms is 1 / 10 (in Figure 10 the curve corresponding to the test result is Janus Fe-Ni 1 / 10 SA@CF).

[0148] The setting requirements of the catalytic degradation pollutant system are consistent with those in Example 1-1.

[0149] The double-sided film catalytic electrode (Janus Fe-Ni SA@CF) obtained in this example was subjected to a tensile stress test. The test results are shown in FIG. Figure 5 As shown, the maximum tensile stress of the double-sided film catalytic electrode (Janus Fe-Ni SA@CF) is 4.60 MPa, which is 4.3 times that of pure carbon fiber CF. This shows that the double-sided film catalytic electrode of the present invention has excellent mechanical properties.

[0150] The two sides of the double-sided film catalytic electrode (Janus Fe-Ni SA@CF) obtained in this example were respectively subjected to electron microscope scanning tests. Figure 6a As shown ( Figure 6a The middle left, middle, and right are scanning electron microscopy, transmission electron microscopy, and high-angle annular dark field scanning transmission electron microscopy images, respectively. The iron-containing metal organic framework compound powder (referred to as Fe@ZIF8) and the nickel-containing metal organic framework compound powder (referred to as Ni@ZIF8) obtained in the above preparation process were scanned by transmission electron microscopy, as shown in FIG. Figure 6b ( Figure 6b The left picture in the middle is a scanning electron micrograph of a metal organic framework compound powder containing iron, and the right picture is a scanning electron micrograph of a metal organic framework compound powder containing nickel). Figure 6a and 6b It can be seen that the metal organic framework compounds containing iron and nickel all present a regular dodecahedron shape, and still maintain the regular dodecahedron shape after being added to both sides of the carbon fiber membrane and pyrolysis, and the carbon fiber is continuous and uniform; from the transmission electron microscopy image and the high-angle annular dark field scanning transmission electron microscopy image, it can be seen that carbon, nitrogen, oxygen, iron / nickel elements are evenly distributed, without obvious nanoparticles, and the high-angle annular dark field scanning transmission electron microscopy image shows that iron and nickel are dispersed in the carbon fiber membrane in the form of single atoms.

[0151] The iron-containing side and the nickel-containing side of the double-sided film catalytic electrode (Janus Fe-Ni SA@CF) obtained in this example were respectively subjected to X-ray near-edge absorption structure spectra (such as Figure 7 (a) and Figure 8 (a) in the figure), X-ray absorption fine structure spectrum (such as Figure 7 (b) and Figure 8 (b)) and fitting curve test (such as Figure 7 (c) and Figure 8 (c) in ). By Figure 7 and Figure 8It can be seen that the valence states of Fe and Ni are both close to +2. The X-ray absorption fine structure spectra show that only the peaks of Fe-N and Ni-N are observed in the single-atom catalysts of iron and nickel, further proving that iron and nickel are in an atomically dispersed state. Through further fitting curve analysis, it is found that in the iron single-atom catalyst, the number of nitrogen atoms coordinated with iron is 6, so its main active site is the Fe-N6 configuration; in the nickel single-atom catalyst, the number of nitrogen atoms coordinated with nickel is 4, so its main active site is the Ni-N4 configuration.

[0152] Comparative Example 3-1

[0153] The method for preparing the double-membrane catalytic electrode includes:

[0154] Prepare the first spinning solution: Dissolve 10 mmol of zinc nitrate hexahydrate and 5 mmol of iron acetylacetonate in 100 mL of methanol, then add 100 mL of methanol containing 80 mmol of 2-methylimidazole. After stirring, standing, centrifugal separation, washing, and drying, a metal-organic framework compound powder containing iron (abbreviated as Fe@ZIF8) is obtained; then, 1 g of the metal-organic framework compound containing the first transition metal prepared above, 1 g of polyacrylonitrile (Mw = 150000), and 10 mL of N,N-dimethylformamide are uniformly mixed to obtain the first spinning solution;

[0155] Perform electrospinning with the first spinning solution for a period of time to obtain a catalytic membrane intermediate, where the spinning voltage is 21 kV and the nozzle distance is 15 cm;

[0156] Perform pre-oxidation treatment on the catalytic membrane intermediate at 280 °C for 2 h to obtain a pre-oxidized membrane;

[0157] Perform carbonization treatment on the pre-oxidized membrane at 1000 °C for 1 h to obtain a membrane catalytic electrode only loaded with iron single atoms (FeSA@CF).

[0158] The setting requirements of the catalytic degradation pollutant system are the same as those in Example 3-1.

[0159] Comparative Example 3-2

[0160] The method for preparing the double-membrane catalytic electrode includes:

[0161] Preparation of the second spinning solution: Dissolve 10 mmol of zinc nitrate hexahydrate and 0.5 mmol of nickel nitrate hexahydrate in 100 mL of methanol, then add 100 mL of methanol containing 80 mmol of 2-methylimidazole. After stirring, standing, centrifugal separation, washing, and drying, a nickel-containing metal-organic framework compound powder (abbreviated as Ni@ZIF8) is obtained; then 1 g of the metal-organic framework compound containing the second transition metal prepared above, 1 g of polyacrylonitrile (Mw = 150000), and 10 mL of N,N-dimethylformamide are uniformly mixed to obtain the second spinning solution;

[0162] Continue electrospinning using the second spinning solution to obtain a catalytic membrane intermediate, where the spinning voltage is 21 kV and the nozzle distance is 15 cm;

[0163] Perform pre-oxidation treatment on the catalytic membrane intermediate at 280 °C for 2 h to obtain a pre-oxidized membrane;

[0164] Perform carbonization treatment on the pre-oxidized membrane at 1000 °C for 1 h to obtain a membrane catalytic electrode (NiSA@CF) loaded only with nickel single atoms.

[0165] The setup requirements for the catalytic degradation of pollutants system are the same as those in Example 3-1.

[0166] Comparative Example 3-3

[0167] The setup requirements for the catalytic degradation of pollutants system are the same as those in Example 3-1, where a pure carbon fiber membrane CF is used as the cathode of the system.

[0168] Use the catalytic degradation of pollutants systems in Example 3-1 and Comparative Examples 3-1, 3-2, and 3-3 to degrade propranolol (PRO) in wastewater respectively. The test results can be seen in Figure 9 , where the initial concentration of propranolol in the wastewater before degradation is 5 mg / L and the wastewater volume is 50 mL. During the 20-minute degradation process, the wastewater circulates in and out. Under normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1 , and in Example 3-1, the wastewater flow direction is from the surface loaded with iron single atoms to the surface loaded with nickel single atoms.

[0169] From Figure 9 It can be seen that the Janus Fe-Ni SA@CF membrane cathode has more excellent electrochemical catalytic properties, achieving complete removal of propranolol within 15 minutes. Its first-order reaction kinetic constant (k = 0.315 min -1 ) is 1.7 to 6.3 times that of the other three membrane electrodes ( Figure 9), indicating that the Janus Fe-Ni SA@CF membrane cathode can efficiently remove propranolol.

[0170] Example 3-2

[0171] It is basically the same as the method for preparing the double-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 3-1, except that: in the preparation of the second spinning solution, the amount of nickel nitrate hexahydrate used is 0.25 mmol. In the prepared double-membrane catalytic electrode (Janus Fe-Ni SA@CF), the molar ratio of loaded nickel and iron single atoms is 1 / 20 (in Figure 10 the curve corresponding to the test result is Janus Fe-Ni 1 / 20 SA@CF).

[0172] Example 3-3

[0173] It is basically the same as the method for preparing the double-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 3-1, except that: in the preparation of the second spinning solution, the amount of nickel nitrate hexahydrate used is 0.75 mmol. In the prepared double-membrane catalytic electrode (Janus Fe-Ni SA@CF), the molar ratio of loaded nickel and iron single atoms is 3 / 20 (in Figure 10 the curve corresponding to the test result is Janus Fe-Ni 3 / 20 SA@CF).

[0174] Example 3-4

[0175] It is basically the same as the method for preparing the double-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 3-1, except that: in the preparation of the second spinning solution, the amount of nickel nitrate hexahydrate used is 1 mmol. In the prepared double-membrane catalytic electrode (Janus Fe-Ni SA@CF), the molar ratio of loaded nickel and iron single atoms is 1 / 5 (in Figure 10 the curve corresponding to the test result is Janus Fe-Ni 1 / 5 SA@CF).

[0176] The catalytic degradation pollutant systems in Example 3-1, Example 3-2, Example 3-3 and Example 3-4 were respectively used to degrade propranolol (PRO) in wastewater. The test results can be seen in Figure 10 , where the initial concentration of propranolol in the wastewater before degradation is 5 mg / L, and the amount of wastewater is 50 mL. During the 20-minute degradation process, the wastewater circulates in and out. Under normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1, the wastewater flow direction is from the surface loaded with single-atom iron to the surface loaded with single-atom nickel.

[0177] The results show that the degradation effect first increases and then decreases with the increase of nickel doping amount, and reaches the maximum when the molar ratio of nickel to iron is 1 / 10 (refer to Figure 10 ), which is mainly because too high nickel doping amount leads to the aggregation of single-atom nickel into nanoparticles, thus reducing the catalytic efficiency.

[0178] Examples 3-5

[0179] It is basically the same as the method for preparing the double-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 3-1, except that: the carbonization temperature is 900 °C.

[0180] Example 3-6

[0181] It is basically the same as the method for preparing the double-membrane catalytic electrode Janus Fe-Ni SA@CF and the catalytic degradation pollutant system in Example 3-1, except that: the carbonization temperature is 1100 °C.

[0182] The catalytic degradation pollutant systems in Example 3-1, Example 3-5 and Example 3-6 were respectively used to degrade propranolol (PRO) in wastewater. The test results can be respectively referred to Figure 11 , where the initial concentration of propranolol in the wastewater before degradation is 5 mg / L, and the wastewater volume is 50 mL. During the 20-minute degradation process, the wastewater circulates in and out. Under normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1 , the wastewater flow direction is from the surface loaded with single-atom iron to the surface loaded with single-atom nickel.

[0183] From Figure 11 the test results, it can be seen that the degradation effect increases with the increase of carbonization temperature. When the carbonization temperature increases from 900 °C to 1000 °C, the k value increases by 81%, while it only increases by 5% when increasing from 1000 °C to 1100 °C.

[0184] Raman tests were respectively carried out on the double-membrane catalytic electrodes in Example 3-1, Example 3-5 and Example 3-6. The test results are referred to Figure 12 . The Raman spectrogram shows that the graphitization degree of carbon fiber is the highest when the carbonization temperature is 1000 °C, which is beneficial to the occurrence of catalytic reactions. Although the conductivity increases monotonically with the carbonization temperature, when the conductivity is relatively high, its increase becomes weak for the improvement of the electrocatalytic effect. Generally speaking, the carbonization temperature of 1000 °C is the best choice.

[0185] Comparative Example 3-4

[0186] The method for preparing the mixed - membrane catalytic electrode includes:

[0187] Prepare Fe@ZIF8: Dissolve 10 mmol of zinc nitrate hexahydrate and 5 mmol of iron acetylacetonate in 100 mL of methanol, then add 100 mL of methanol containing 80 mmol of 2 - methylimidazole. After stirring, standing, centrifugal separation, washing, and drying, obtain a metal - organic framework compound powder containing iron (abbreviated as Fe@ZIF8 for short); Prepare Ni@ZIF8: Dissolve 10 mmol of zinc nitrate hexahydrate and 0.5 mmol of nickel nitrate hexahydrate in 100 mL of methanol, then add 100 mL of methanol containing 80 mmol of 2 - methylimidazole. After stirring, standing, centrifugal separation, washing, and drying, obtain a metal - organic framework compound powder containing nickel (abbreviated as Ni@ZIF8 for short);

[0188] Uniformly mix 1 g of the metal - organic framework compound containing iron, 1 g of the metal - organic framework compound containing nickel, 2 g of polyacrylonitrile (Mw = 150000), and 20 mL of N,N - dimethylformamide to obtain a mixed spinning solution;

[0189] Use the mixed spinning solution to continue electrospinning to obtain a mixed - membrane intermediate, where the spinning voltage is 21 kV and the nozzle distance is 15 cm;

[0190] Perform pre - oxidation treatment on the mixed - membrane intermediate at 280 °C for 2 h to obtain a pre - oxidized mixed membrane;

[0191] Perform carbonization treatment on the pre - oxidized mixed membrane at 1000 °C for 1 h to obtain a membrane catalytic electrode (Mixed Fe - Ni SA@CF) with iron and nickel single atoms loaded;

[0192] The setting requirements of the catalytic degradation pollutant system are the same as those in Example 3 - 1.

[0193] Use the catalytic degradation pollutant systems in Example 3 - 1 and Comparative Example 3 - 4 respectively to degrade the first wastewater and the second wastewater. The pollutant in the first wastewater is propranolol (PRO), and the pollutant in the second wastewater is chloramphenicol. The test results can be seen respectively in Figure 13 where the initial concentrations of propranolol and chloramphenicol in the wastewater before degradation are both 5 mg / L, and the wastewater volume is 50 mL. During the 20 - minute degradation process, the wastewater circulates in and out. Under normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1 where, for the double - membrane catalytic electrode in Example 3 - 1, two groups of tests are carried out. One group of tests is: the wastewater flow direction is from the surface loaded with iron single atoms to the surface loaded with nickel single atoms, that is, the iron - containing side faces the water inlet end (correspondingFigure 13 In the Janus Fe-Ni SA@CF curve); the other group of tests is that the wastewater flows from the surface loaded with single-atom nickel to the surface loaded with single-atom iron, that is, the nickel-containing side faces the water inlet end (corresponding to Figure 13 the Janus Ni-Fe SA@CF curve in

[0194] From Figure 13 From the test results, in the degradation tests of propranolol and chloramphenicol, the degradation effect of the Janus Fe-Ni SA@CF membrane cathode exceeded that of the Mixed Fe-Ni SA@CF membrane cathode. In the degradation of propranolol, when the iron-containing side of the Janus Fe-Ni SA@CF membrane cathode faces the water inlet end (k = 0.340 min -1 ), the degradation effect is better than that when the nickel-containing side faces the water inlet end (Janus Ni-Fe SA@CF, k = 0.267 min -1 ). In the degradation of chloramphenicol (CAP), on the contrary, when the nickel-containing side faces the water inlet end (k = 0.355 min -1 ), the degradation effect is better than that when the iron-containing side faces the water inlet end (k = 0.133 min -1 ).

[0195] Using the catalytic degradation pollutant system in Example 3-1 to degrade wastewater containing different pollutants respectively, the test results can be seen in Figure 14 respectively. Among them, the initial concentration of pollutants in the wastewater before degradation is 5 mg / L, and the wastewater volume is 50 mL. During the 20-minute degradation process, the wastewater circulates in and out, at normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1 . And for each pollutant, the double-membrane catalytic electrode in Example 3-1 is tested in two groups. One group of tests is: the wastewater flows from the surface loaded with single-atom iron to the surface loaded with single-atom nickel, that is, the iron-containing side faces the water inlet end (corresponding to Figure 14 the Janus Fe-Ni SA@CF curve in Figure 14 ); the other group of tests is that the wastewater flows from the surface loaded with single-atom nickel to the surface loaded with single-atom iron, that is, the nickel-containing side faces the water inlet end (corresponding to

[0196] From Figure 14As shown by the test results, for amide organic compounds such as propranolol, carbamazepine (CBZ), crotamiton (CRO), and antipyrine (ATP), the removal is faster when the iron-containing side faces the water inlet end, and their k values are 1.5 - 2.5 times that when the nickel-containing side faces the water inlet end; for halogenated organic compounds such as chloramphenicol, p-chlorophenol (pCP), diclofenac (DCF), and ciprofloxacin (CIP), the k values are larger (1.1 - 4.9 times) when the nickel-containing side faces the water inlet end. Thus, it can be seen that different inlet and outlet water directions are applicable to different categories of emerging pollutants, and the dominant order is related to their characteristic chemical groups. In addition, under the corresponding dominant order, the removal of the eight model pollutants all reached over 80% within 20 minutes, fully demonstrating the excellent electrocatalytic characteristics and wide adaptability of the Janus Fe-Ni SA@CF membrane cathode of the present invention.

[0197] Electron paramagnetic resonance analysis was respectively performed on the double surfaces of the double-membrane catalytic electrode (Janus Fe-Ni SA@CF) in Example 3-1, the membrane catalytic electrode (Fe SA@CF) in Comparative Example 3-1, the membrane catalytic electrode (Ni SA@CF) in Comparative Example 3-2, and the membrane catalytic electrode (Mixed Fe-Ni SA@CF) with mixed loading of iron and nickel single atoms in Comparative Example 3-4, as Figure 15 shown. It can be seen that hydroxyl radicals (·OH) and atomic hydrogen (H*) are the main active species in the double-membrane catalytic electrode (Janus Fe-Ni SA@CF) system, and the iron single-atom sites mainly generate ·OH, while the nickel single-atom sites mainly generate H*. The signals of both species in the Mixed Fe-Ni SA@CF membrane cathode are very weak, mainly because the distances between the iron and nickel single-atom sites are too close, resulting in mutual reaction and quenching consumption between the two species.

[0198] In-situ Raman tests were respectively performed on the double surfaces of the double-membrane catalytic electrode (Janus Fe-Ni SA@CF) in Example 3-1, as Figure 16 shown. Thus, it can be seen that the generation process of ·OH and H* is as follows: oxygen first undergoes one-electron reduction at the iron single-atom sites to become *OO - , and then forms the key intermediate *OOH in the hydrogen peroxide generation process; while water forms hydrated nickel at the nickel single-atom sites, further proving that the nickel single-atom sites can generate *H.

[0199] Furthermore, for the double surfaces of the double-membrane catalytic electrode (Janus Fe-Ni SA@CF) in Example 3-1, quantitative tests on its active species were carried out through probe experiments, asFigure 17 As shown. The steady-state concentration of ·OH generated by the mixed Fe-Ni SA@CF membrane cathode (5.7×10 -14 mol L -1 ) is only 1 / 5 to 1 / 3 of that of the Janus Fe-Ni SA@CF membrane cathode, further proving the mutual quenching of reactive species caused by the too-close active sites. When the iron-containing side faces the water inlet end, the steady-state concentration of ·OH is 1.7 times that when the nickel-containing side faces the water inlet end, while the hydrogen peroxide concentration is lower. This is because when the iron-containing side faces the water inlet end, the hydrogen peroxide generated on the iron-containing side can migrate with the water flow to the nickel-containing side and react with H*, and more is activated to generate ·OH.

[0200] Synergistic mechanism of ·OH and H* during pollutant degradation: The direct reaction between propranolol and H* is relatively weak. Its better degradation effect when the iron-containing side faces the water inlet end is attributed to the higher ·OH concentration. Chloramphenicol can undergo dechlorination reaction under the action of H*. When the nickel-containing side faces the water inlet end, the reaction sequence of dechlorination first and then hydroxylation is more thermodynamically advantageous than hydroxylation first and then dechlorination (as Figure 18 shown), so chloramphenicol has a better degradation effect in the descending order when the nickel-containing side faces the water inlet end. Therefore, the internal mechanism of the sequential strategy at the water inlet end of this application is that when the iron-containing side faces the water inlet end, more ·OH can be generated, which is beneficial to the degradation of amide pollutants; while when the nickel-containing side faces the water inlet end, the reaction sequence of dehalogenation first and then hydroxylation of halogenated pollutants has a thermodynamic advantage, so the degradation is faster.

[0201] Using the dual-membrane catalytic electrode Janus Fe-Ni SA@CF in Example 3-1, a periodic degradation test was carried out on propranolol pollutants. Each cycle was 20 min. The test results can be seen in Figure 19 . In 10 cycles, the Janus Fe-Ni SA@CF membrane cathode can achieve a degradation rate of more than 90% of propranolol within 20 minutes, and the contents of iron and nickel ions in the solution are both less than 70 μg L -1 , indicating that the dual-membrane catalytic electrode of the present invention has good stability and a low risk of secondary pollution caused by metal ion leakage.

[0202] Using the dual-membrane catalytic electrode Janus Fe-Ni SA@CF in Example 3-1 to treat the secondary effluent of pharmaceutical wastewater. Among them, the wastewater treatment volume is 50 mL. During the degradation process, the wastewater circulates in and out. Under normal temperature and pressure, the voltage between the anode and cathode is 3 V, and the membrane flux is 680 L m -2 h -1 , and the wastewater flow direction is from the surface loaded with single-atom iron to the surface loaded with single-atom nickel. The treatment effect is as Figure 20As shown. It can be seen that the Janus Fe-Ni SA@CF membrane cathode can reduce the Chemical Oxygen Demand (COD) from 120 mg / L -1 to 50 mg / L -1 or less within 1 hour, and the absorbance values at UV254 and UV280 are reduced by more than 78%. This shows that the dual-membrane catalytic electrode of the present invention can rapidly remove organic substances containing unsaturated bonds.

[0203] Furthermore, three-dimensional fluorescence spectroscopy analysis (which can be used to analyze dissolved organic matter in water) was performed on the above-mentioned degraded pharmaceutical wastewater. As Figure 21 (a) in shows, the main fluorescence intensity of the pharmaceutical wastewater before treatment is distributed in region V, indicating a large content of humic-like organic matter, and the biodegradability of this type of organic matter is poor. In addition, there are also a small amount of fulvic acid-like substances (region III) and soluble microbial products (region IV); after being treated with Janus Fe-Ni SA@CF for 30 minutes and 60 minutes, as shown in Figure 21 (b) and (c) in respectively, the fluorescence intensity in each region decreases significantly, indicating that a large amount of dissolved organic matter, including the recalcitrant humic substances, has been effectively removed. This proves that the Janus Fe-Ni SA@CF membrane cathode can rapidly degrade a large amount of dissolved organic matter, including the recalcitrant humic substances. These results show that the Janus Fe-Ni SA@CF membrane cathode has a significant effect in removing recalcitrant organic matter in sewage and has practical application prospects.

[0204] The terms "first" and "second" in the text are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0205] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0206] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A double-sided film catalytic electrode, characterized in that: It includes a carbon skeleton fiber, which has a first surface and a second surface arranged opposite to each other, the first surface is loaded with a first transition metal single atom, and the second surface is loaded with a second transition metal single atom, wherein one of the first transition metal single atom and the second transition metal single atom is used to induce the generation of oxidative active species, and the other is used to induce the generation of reductive active species.

2. The double-sided film catalytic electrode according to claim 1, characterized in that: The transition metal single atom includes at least one of iron, nickel, copper, cobalt, zinc and manganese, The coordinating atoms coordinated with the transition metal include at least one of nitrogen, phosphorus, sulfur and oxygen, and the number of the coordinating atoms coordinated with one transition metal atom is 1 to 6.

3. The double-sided film catalytic electrode according to claim 1 or 2, characterized in that: The oxidative active species include one or more of hydroxyl radicals, sulfate radicals or singlet oxygen, and the reductive active species include one or both of atomic hydrogen and hydrated electrons.

4. A method for preparing a double-sided film catalytic electrode according to any one of claims 1 to 3, characterized in that: include: Uniformly mixing a first polymer, a first transition metal single atom precursor, and a first organic solvent to obtain a first spinning solution; uniformly mixing a second polymer, a second transition metal single atom precursor, and a second organic solvent to obtain a second spinning solution; After performing a first electrostatic spinning process using the first spinning solution for a period of time, the second spinning solution is replaced to continue a second electrostatic spinning process to obtain a double-sided film intermediate; Performing a pre-oxidation treatment on the double-sided film intermediate to obtain a pre-oxidized double-sided film; The pre-oxidized double-sided film is subjected to carbonization treatment to obtain a double-sided film catalytic electrode.

5. The method according to claim 4, characterized in that The first transition metal single atom precursor includes at least one of a metal organic framework compound containing the first transition metal, a phthalocyanine salt containing the first transition metal, and a mixture of a transition metal salt containing the first transition metal and a first organic matter. The second transition metal single atom precursor includes at least one of a metal organic framework compound containing the second transition metal, a phthalocyanine salt containing the second transition metal, or a mixture of a transition metal salt containing the second transition metal and a second organic matter.

6. The method according to claim 5, characterized in that The mass ratio of the first polymer to the first transition metal single atom precursor is 1:0.01 to 1:3; the mass ratio of the second polymer to the second transition metal single atom precursor is 1:0.01 to 1:

3.

7. The method according to claim 5 or 6, characterized in that: The first spinning solution is prepared by the following method A, method B or method C: Method A: dissolving zinc nitrate and a first transition metal salt in a solvent, then adding a 2-methylimidazole solution to the mixed solution to obtain a mixed solution, stirring, separating, and drying the mixed solution to obtain the metal organic framework compound containing the first transition metal; uniformly mixing the metal organic framework compound containing the first transition metal, the first polymer, and the first organic solvent to obtain the first spinning solution; Method B: uniformly mixing the phthalocyanine salt containing the first transition metal, the first polymer and the first organic solvent to obtain the first spinning solution; Method C: uniformly mixing the first transition metal salt, the first organic matter, the first polymer and the first organic solvent to obtain the first spinning solution, wherein the first organic matter comprises at least one of phenanthroline and dopamine, The second spinning solution is prepared by the following method D, method E or method F: Method D: dissolving zinc nitrate and a second transition metal salt in the solvent, then adding a 2-methylimidazole solution to the mixture, stirring, separating, and drying to obtain the metal organic framework compound containing the second transition metal; uniformly mixing the metal organic framework compound containing the second transition metal, the second polymer, and the second organic solvent to obtain the second spinning solution; Method E: uniformly mixing the phthalocyanine salt containing the second transition metal, the second polymer and the second organic solvent to obtain the second spinning solution; Method F: uniformly mixing the second transition metal salt, the second organic matter, the second polymer and the second organic solvent to obtain the second spinning solution, wherein the second organic matter comprises at least one of phenanthroline and dopamine.

8. The method according to claim 7, characterized in that In the method A, at least one of the following conditions is met: The first transition metal salt includes at least one of nitrate and acetylacetonate; The usage ratio of the first transition metal salt to the solvent is (0.05-5) mmol:100 mL; In the first spinning solution, the metal organic framework compound is added in an amount of 0.08 to 0.12 g / mL of the first organic solvent, and the first polymer is added in an amount of 0.08 to 0.12 g / mL of the first organic solvent; In the method B, at least one of the following conditions is met: In the first spinning solution, the amount of the phthalocyanine salt added is 0.01 to 0.2 mmol / mL of the first organic solvent, and the amount of the first polymer added is 0.08 to 0.12 g / mL of the first organic solvent; In the method C, at least one of the following conditions is met: The first transition metal salt includes at least one of nitrate and acetylacetonate; In the first spinning solution, the addition amount of the first transition metal salt is 0.01 to 0.1 mmol / mL of the first organic solvent, the molar ratio of the first organic matter to the first transition metal salt is 4:1 to 8:1, and the addition amount of the first polymer is 0.08 to 0.12 g / mL of the first organic solvent; In the method D, at least one of the following conditions is met: The second transition metal salt includes at least one of nitrate and acetylacetonate; The dosage ratio of the second transition metal salt to the solvent is (0.05-5) mmol:100 mL; In the second spinning solution, the metal organic framework compound is added in an amount of 0.08 to 0.12 g / mL of the second organic solvent, and the second polymer is added in an amount of 0.08 to 0.12 g / mL of the second organic solvent; In the method E, at least one of the following conditions is met: In the second spinning solution, the added amount of the phthalocyanine salt is 0.01 to 0.2 mmol / mL of the second organic solvent, and the added amount of the second polymer is 0.08 to 0.12 g / mL of the second organic solvent; In the method F, at least one of the following conditions is met: The second transition metal salt includes at least one of nitrate and acetylacetonate; In the second spinning solution, the addition amount of the second transition metal salt is 0.01-0.1 mmol / mL of the second organic solvent, the molar ratio of the second organic matter to the second transition metal salt is 4:1-8:1, and the addition amount of the second polymer is 0.08-0.12 g / mL of the second organic solvent.

9. The method according to claim 4, characterized in that The pre-oxidation treatment conditions include: temperature of 240-300°C and time of 0.5-3h; The carbonization treatment conditions include: a temperature of 600 to 1400° C. and a time of 0.5 to 3 hours.

10. Use of the double-sided film catalytic electrode according to any one of claims 1 to 3 in degrading pollutants.

11. A system for catalytic degradation of pollutants in water, characterized in that: include: anode; A cathode, wherein the cathode is the double-sided film catalytic electrode according to any one of claims 1 to 3, or the double-sided film catalytic electrode prepared by the method according to any one of claims 4 to 9.

12. The catalytic degradation system for pollutants in water according to claim 11, characterized in that: When degrading the pollutants, at normal temperature and pressure, the voltage between the anode and the cathode is 0.5-5V, and the membrane flux of the sewage is 50-2000Lm -2 h -1 .

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