Oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film as well as preparation method and application thereof

Abstract

The invention discloses an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film and a preparation method and application thereof. The atomic ratio of nitrogen atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is 11: (6-15). The catalytic performance of the electrocatalytic oxidation film can be improved by controlling the atomic ratio of nitrogen atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film, and then the catalytic efficiency of the electrocatalytic oxidation film is improved.

Description

Technical Field

[0001] This application belongs to the field of electrocatalysis technology, specifically, it relates to an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, its preparation method and application. Background Technology

[0002] Electrocatalytic oxidation is one of the rapidly developing advanced oxidation technologies in recent years. Due to its high efficiency, strong controllability, no or very little secondary pollution, mild conditions, simple reactor and operating equipment, and ease of integration with other processes, this emerging advanced oxidation technology has attracted great interest from researchers in the application of purifying pollutants in water.

[0003] Among these applications, electrocatalytic oxidation membranes have attracted widespread attention in wastewater treatment. Wastewater can come into full contact with the electrocatalytic oxidation membrane, undergoing electrocatalytic oxidation or reduction reactions upon contact, thereby oxidizing and decomposing pollutants in the water and effectively removing pollutants such as organic matter and heavy metal ions from wastewater. However, the catalytic capacity of electrocatalytic oxidation membranes is limited, which restricts their wastewater treatment efficiency. Summary of the Invention

[0004] The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, its preparation method, and its application provided by the embodiments of this application can solve or partially solve the above-mentioned deficiencies or other deficiencies in the prior art.

[0005] The first aspect of this application provides an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane, wherein the atomic ratio of nitrogen atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is 11:(6~15), preferably 11:(8~10).

[0006] This application improves the catalytic performance of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane by controlling the atomic ratio of nitrogen to oxygen atoms within the above-mentioned range, thereby increasing its catalytic efficiency.

[0007] In some embodiments, the atomic ratio of carbon atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film is (75~85):(5~15), preferably (79~81):(8~11). By controlling the atomic ratio of carbon atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film within the above range, the catalytic performance of the electrocatalytic oxide film can be improved, thereby increasing its catalytic efficiency.

[0008] In some embodiments, the total number of nitrogen, oxygen, and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film is used as a basis, with the nitrogen atom percentage being 2% to 20%, preferably 9% to 11%. This helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency.

[0009] In some embodiments, based on the total number of nitrogen, oxygen, and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, the proportion of oxygen atoms is 6% to 15%, preferably 8% to 10%. This helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency.

[0010] In some embodiments, based on the total number of nitrogen, oxygen, and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, the proportion of carbon atoms is 74% to 83%, preferably 79% to 81%. This helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency.

[0011] In some embodiments, the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film includes COC bonds. This helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency.

[0012] In some embodiments, the pore size of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is 0.5 μm to 1.5 μm, preferably 0.8 μm to 1.2 μm.

[0013] In some embodiments, the porosity of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is 50% to 80%, preferably 60% to 75%.

[0014] In some embodiments, the electrocatalytic efficiency η of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film satisfies: η≥95%, preferably η≥99%.

[0015] In some embodiments, the mechanical strength R of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film satisfies: R≥5Gpa, preferably R≥8Gpa.

[0016] The second aspect of this application provides a method for preparing an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film according to the first aspect of this application. The method includes: mixing polyacrylonitrile, oxalic acid and an organic solvent to obtain a spinning solution; electrospinning the spinning solution to obtain a precursor carbon nanofiber film; and pre-oxidizing and carbonizing the precursor carbon nanofiber film to obtain an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film. The mass ratio of polyacrylonitrile to oxalic acid is (8~12):(0.1~0.3), preferably (8~10):0.1.

[0017] This application involves electrospinning a spinning solution comprising polyacrylonitrile and oxalic acid, then pre-oxidizing and carbonizing the resulting precursor carbon nanofiber membrane, and controlling the mass ratio of polyacrylonitrile to oxalic acid within the aforementioned range, thereby controlling the atomic ratio of nitrogen atoms to oxygen atoms in the final electrocatalytic oxidation membrane to be 11:(6~15), thus obtaining an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane with excellent catalytic performance.

[0018] In some embodiments, the mass ratio of polyacrylonitrile to organic solvent is (8~12):(85~95), preferably (8~10):(89~91). By controlling the mass ratio of polyacrylonitrile to organic solvent within the above range, the viscosity of the spinning solution can be adjusted, which is beneficial for obtaining precursor carbon nanofiber membranes.

[0019] In some embodiments, the weight-average molecular weight of polyacrylonitrile is 100,000 g / mol to 180,000 g / mol, preferably 130,000 g / mol to 160,000 g / mol. By controlling the weight-average molecular weight of polyacrylonitrile within the above range, the catalytic performance of the prepared oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film can be further improved.

[0020] In some embodiments, pre-oxidation is carried out in an air atmosphere at a temperature of 230°C to 280°C for a duration of 2 to 2.5 hours. By controlling the pre-oxidation process to meet the above conditions, the catalytic performance of the prepared oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film can be further improved.

[0021] In some embodiments, carbonization is carried out in an inert atmosphere at a temperature of 900°C to 1000°C for a time of 1 to 3 hours. By controlling the carbonization process to meet the above conditions, the catalytic performance of the prepared oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film can be further improved.

[0022] The third aspect of this application provides an application of an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane in wastewater treatment, wherein the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane includes the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane provided in the first aspect of this application and / or the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane prepared by the method of the second aspect of this application.

[0023] In some embodiments, oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide films are used in electrocatalytic systems as anodes and / or cathodes.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0025] The accompanying drawings, as part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application, but do not constitute an undue limitation of this application. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of the method for preparing oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide films according to this application; Figure 2 This is a process flow diagram for preparing the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film of this application; Figure 3 This is a schematic diagram illustrating the preparation principle of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film in Example 1 of this application; Figure 4 This is a schematic diagram illustrating the preparation principle of the carbon fiber membrane in Comparative Example 1 of this application; Figure 5 This is a schematic diagram of the through-type electrocatalytic system assembled from the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film of Example 1 in this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application are described clearly and completely below with reference to some embodiments. Those skilled in the art will understand that the following embodiments are only used to explain the technical principles of this application and are not intended to limit the scope of protection of this application.

[0027] my country faces a severe water shortage and uneven distribution problem, coupled with serious water pollution. Water treatment technology plays a crucial role in addressing this issue. Traditional wastewater treatment typically employs membrane technology, which mainly includes microfiltration, ultrafiltration, nanofiltration, electrodialysis, and reverse osmosis. Among these, microfiltration, ultrafiltration, and nanofiltration have been widely adopted in wastewater treatment due to their high filtration precision and stable effluent quality. However, issues such as high energy consumption, membrane flux decay, and the difficulty of membrane cleaning limit the widespread adoption of membrane technologies.

[0028] Electrocatalytic oxidation is one of the rapidly developing advanced oxidation technologies in recent years. Due to its high efficiency, strong controllability, minimal or no secondary pollution, mild conditions, simple reactor and operating equipment, and ease of integration with other processes, this emerging advanced oxidation technology has attracted great interest from researchers in the purification of pollutants in water. Among these, the application of electrocatalytic oxidation membranes in wastewater treatment has received widespread attention. Wastewater can fully contact the electrocatalytic oxidation membrane, undergoing electrocatalytic oxidation or reduction reactions to oxidize and decompose pollutants in the water, effectively removing organic matter, heavy metal ions, and other pollutants from wastewater. However, the limited catalytic capacity of electrocatalytic oxidation membranes restricts their wastewater treatment efficiency.

[0029] In view of this, the first aspect of this application provides an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane, wherein the atomic ratio of nitrogen atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane can be 11:(6~15), for example, 11:15, 11:14.2, 11:13.41, 11:12.36, 11:12.1, 11:11, 11:10, 11:9.9, 11:9, 11:8.25, 11:8, 11:7, 11:6, etc., or any range between two of the above values. In some other embodiments of this application, the atomic ratio of nitrogen atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane can be 11:(8~10).

[0030] This application improves the catalytic performance of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane by controlling the atomic ratio of nitrogen to oxygen atoms within the above-mentioned range, thereby increasing the catalytic efficiency of the membrane.

[0031] In some embodiments of this application, the carbon-to-oxygen ratio in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film can be (75~85):(5~15), for example, 75:15, 75:12.13, 76:11.6, 75:11, 76:11, 78:11, 79:11, 76:10, 78:10, 79:10, 80:10, 80:9, 81:9, 82:9, 83:9, 80:7, 80:6, 76:5, 80:5, 85:5, etc., or any range between any two of the above values. By controlling the atomic ratio of carbon atoms to oxygen atoms in the electrocatalytic oxide film within the aforementioned range, the catalytic activity of the electrocatalytic oxide film can be improved. Furthermore, the amount of oxygen doping in the electrocatalytic oxide film can be controlled to retain some defects, thereby increasing the disorder of the electrocatalytic oxide film and improving its catalytic performance, ultimately enhancing its catalytic efficiency. In some other embodiments of this application, the carbon atom to oxygen atom ratio in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film can be (79~81):(8~11).

[0032] In some embodiments of this application, based on the total number of nitrogen, oxygen, and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, the atomic percentage of nitrogen atoms can be 2% to 20%, for example, 2%, 5%, 9%, 10%, 11%, 15%, 18%, 20%, or any range between two of these values. By controlling the atomic percentage of nitrogen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, this application helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency. In other embodiments of this application, the atomic percentage of nitrogen atoms can be 9% to 11%.

[0033] In some embodiments of this application, based on the total number of nitrogen, oxygen, and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, the atomic percentage of oxygen atoms is 6% to 15%, for example, it can be 6%, 8%, 9%, 10%, 13%, 15%, or any range between two of the above values. By controlling the atomic percentage of oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, this application helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency. In other embodiments of this application, the atomic percentage of oxygen atoms can be 8% to 10%.

[0034] In some embodiments of this application, based on the total number of nitrogen, oxygen, and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, the atomic percentage of carbon atoms is 74% to 83%, for example, it can be 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, or any range between two of the above values. This application, by controlling the atomic percentage of carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film, helps to improve the catalytic performance of the electrocatalytic oxide film, thereby increasing its catalytic efficiency. In other embodiments of this application, the atomic percentage of carbon atoms can be 79% to 81%.

[0035] It should be noted that the number of atoms in the entire electrocatalytic oxidation film can be determined using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS), allowing for the calculation of the atomic ratio or atomic percentage. For example, the following testing methods can be referenced: (1) Sample preparation: The electrocatalytic oxidation film was cut into 5×5mm samples, ultrasonically cleaned with anhydrous ethanol for 5min to remove dust, and then vacuum dried and adhered to conductive carbon adhesive. (2) Test conditions: 1) Instruments: FESEM (such as FEI Nova NanoSEM 450) with EDS (such as Bruker XFlash 6160); 2) Accelerating voltage: 15 kV (to ensure the excitation of characteristic X-rays of C Kα, NKα, and OKα); 3) Scanning area: Randomly select three 200×200μm areas, avoiding edge effects; (3) Data analysis: 1) Use the standardless quantitative method (ZAF correction) to collect the atomic percentage (Atomic %). 2) Calculate the atomic ratio: Take the average of 3 measurements (allow ±0.5% deviation); It can be based on the standard: ISO 22309:2011 (Microbeam analysis - Guide to quantitative analysis of EDS).

[0036] In some embodiments of this application, the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film includes COC bonds. Theoretically, oxygen doping in this application would increase the crystallinity of the electrocatalytic oxide film and reduce its flexibility. However, due to the inclusion of COC bonds, which have large bond angles and low rotational steric hindrance of CO single bonds, the molecular chains are more flexible, thus increasing their flexibility and overall flexibility. Furthermore, the oxygen atoms in the COC bonds form hydrogen bonds with water, enhancing the adsorption capacity of the electrocatalytic oxide film surface for polar molecules, promoting reactions such as hydrolysis and oxidation, and contributing to improved catalytic performance and efficiency.

[0037] It should be noted that COC bonds in electrocatalytic oxidation films can be determined using X-ray absorption near-edge structure spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS). For example, the following testing methods can be referenced: (1) XPS test: 1) Sample preparation: The sample was etched with argon ions for 30 s (1 kV) to remove surface contaminants; 2) Test conditions: ① Instrument: Thermo Scientific K-Alpha X-ray photoelectron spectroscopy (XPS); ②X-ray source: monochromatic Al Kα (1486.6 eV), beam spot 400 μm; ③Step size: 1.0 eV for full spectrum, 0.05 eV for high resolution C1s spectrum.

[0038] 3) Bonded state analysis: C1s spectrum peak fitting (software: Avantage): CC / C=C (284.6 eV), COC (286.5±0.2 eV), OC=O (289.0 eV); COC determination criteria: A fitted peak exists at 286.5 eV and its area accounts for ≥8%.

[0039] (2) XANES test: 1) Synchrotron radiation conditions: Shanghai Synchrotron Radiation Facility BL08U beamline, carbon K side (280-320 eV). 2) Characteristic peak identification: The COC bond corresponds to the π peak at 287.2 eV. Resonance peak (distinct from 290.5 eV for C=O).

[0040] It should be noted that XPS can quantitatively test the content of COC, while XANES can verify the consistency of the chemical environment of the sample. The two can be used together to improve the accuracy of the test.

[0041] In some embodiments of this application, the pore size of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane can be 0.5 μm to 1.5 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or any range between two of the above values. When the pore size of the electrocatalytic oxidation membrane in this application meets the above range, it not only maintains good mechanical strength but also helps to increase the contact area between wastewater and the electrocatalytic oxidation membrane, thereby improving the electrocatalytic efficiency of the electrocatalytic oxidation membrane. In other embodiments of this application, the pore size of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane can be 0.8 μm to 1.2 μm.

[0042] In some embodiments, the porosity of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane can be 50% to 80%, for example, 50%, 55%, 60%, 68%, 75%, 80%, or any range between two of these values. When the porosity of the electrocatalytic oxidation membrane in this application meets the above range, it not only maintains good mechanical strength but also helps to increase the contact area between wastewater and the electrocatalytic oxidation membrane, thereby improving the electrocatalytic efficiency of the membrane. In other embodiments of this application, the porosity of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane can be 60% to 75%.

[0043] It should be noted that the pore size and porosity of electrocatalytic oxidation films can be tested using a surface area (BET) and porosity analyzer. For example, the following BET testing method can be referenced: (1) Pretreatment: The sample was degassed under vacuum at 300℃ for 8 h to remove adsorbed substances; (2) Test apparatus: Micromeritics ASAP 2460 physical adsorption instrument, using nitrogen adsorption (77 K). (3) Pore size distribution: The BJH model (Barrett-Joyner-Halenda method) was used to analyze the adsorption isotherm, with a focus on the peak value in the 0.5~1.5 μm range.

[0044] In some embodiments of this application, the mechanical strength R of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film satisfies: R ≥ 5 GPa, for example, it can be 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, 11 GPa, or any range between two of the above values. This application fills at least some of the vacancies in the molecular structure of the electrocatalytic oxide film by oxygen doping the oxide film and controlling the atomic ratio of nitrogen to oxygen atoms, thereby improving the crystallinity of the electrocatalytic oxide film and thus its mechanical strength. In other embodiments of this application, the mechanical strength R of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film can satisfy R ≥ 8 GPa.

[0045] It should be noted that the mechanical strength of the electrocatalytic oxide film can be tested using tensile stress-strain curves. For example, the following test methods can be referenced: (1) Sample preparation: Cut the sample into strips of 150×15 mm (ASTM D882), and measure the thickness at 5 points with a micrometer and take the average value. (2) Equipment setup: 1) Universal testing machine (Instron 5967), pneumatic clamps with anti-slip design; 2) Initial gauge length: 100 mm, stretching rate: 10 mm / min; (3) Mechanical strength calculation: Tensile strength = maximum load (N) / cross-sectional area (mm²), reported as the average of three fracture strengths, in GPa.

[0046] In some embodiments of this application, the electrocatalytic efficiency η of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film satisfies: η ≥ 95%, for example, it can be 95%, 96%, 97%, 98%, 99%, 99.9%, etc., or any range between two of the above values. In other embodiments of this application, the electrocatalytic efficiency η of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film can satisfy η ≥ 99%.

[0047] It should be noted that the electrocatalytic efficiency of an electrocatalytic oxidation film can be comprehensively assessed by measuring conductivity using electrochemical impedance spectroscopy (EIS), electrochemical active area (ECSA) using cyclic voltammetry (CV), and the concentration of generated free radicals and the degree of pollutant degradation using electron spin resonance (ESR). For example, the following testing methods can be referenced: (1) EIS test for conductivity: 1) Three-electrode system (working electrode: oxide film; reference electrode: Ag / AgCl; counter electrode: Pt sheet), 0.1 M Na2SO4 electrolyte.

[0048] 2) Frequency range: 100 kHz to 0.1 Hz, amplitude 10 mV; 3) Data output: Nyquist plot, series resistance Rs is obtained through the high-frequency intercept (the smaller the value, the better the conductivity).

[0049] (2) CV test ECSA: 1) Scan rate: 20~100 mV / s (multi-speed scan), voltage window: 0~0.2 V (vs RHE); 2) Calculate the double-layer capacitance Cdl: Fit the sweep rate-capacitive current slope: ECSA= C dl / C s ( C s Standard capacitance value, taken as 40μF / cm 2 ).

[0050] (3) ESR test for free radical concentration: 1) On-site capture: Add 50 mM DMPO capture agent to the reaction system, and after reacting for 10 min, take liquid nitrogen to quick-freeze the sample; 2) Instrument: Bruker EMXmicro ESR; Parameters: Microwave frequency 9.85 GHz, power 20 mW; 3) Free radical recognition: OH (quartet, intensity ratio 1:2:2:1), (Triple peak); The concentration of free radicals is proportional to the integral value of the peak area.

[0051] (4) Comprehensive reflection of the electrocatalytic efficiency of the electrocatalytic oxidation film: 1) Electrochemical performance indicators: ① Electrical conductivity and charge transfer characteristics: Evaluate the electron / ion transport capability of the material through EIS or electrical conductivity testing; ②ECSA and reactive active sites: Using methods such as CV and double-layer capacitance, the number of available active sites on the electrode surface is reflected; 2) Reactant conversion and product formation capabilities: ① Free radical / reactive species generation capacity: Quantitatively assess ·OH and · using ESR. The formation of reactive intermediates; ② Pollutant degradation effect: The actual catalytic application effect is reflected by the change in the concentration of organic pollutants (such as the degradation rate of target molecules).

[0052] The aforementioned electrochemical performance indicators, reactant conversion and product formation capabilities reflect the material's performance. When certain indicators are very good, they can be used to judge that the product has a high ability to electrocatalytically degrade pollutants. Then, based on the pollutant degradation situation, the electrocatalytic efficiency can be calculated.

[0053] The second aspect of this application provides a method for preparing the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film of the first aspect of this application. Figure 1 This paper presents a flowchart illustrating the steps involved in preparing the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film according to this application. Figure 2 A process flow diagram for preparing the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film of this application is shown.

[0054] refer to Figure 1 The method includes: S100: Polyacrylonitrile, oxalic acid and organic solvent are mixed to obtain a spinning solution; It should be noted that polyacrylonitrile is an electrospinning polymer raw material with good fiber-forming properties, capable of forming continuous nanofibers during electrospinning. These nanofibers possess high specific surface area, good mechanical properties, and chemical stability. Oxalic acid, as a dicarboxylic acid containing only two carbon atoms, exhibits less steric hindrance during oxygen doping, facilitating cross-linking with polyacrylonitrile molecules to achieve oxygen doping.

[0055] The reaction process of polyacrylonitrile and oxalic acid is shown in equation (1): (1); As shown in equation (1), the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film includes COC bonds. Theoretically, oxygen doping in this application would increase the crystallinity of the electrocatalytic oxide film and decrease its flexibility. However, due to the presence of COC bonds in the electrocatalytic oxide film, the bond angle is relatively large, and the rotational steric hindrance of the CO single bond is small, making the molecular chains easier to bend. This would actually increase the flexibility of the molecular chains, thereby improving the flexibility of the electrocatalytic oxide film. Furthermore, the oxygen atoms in the COC bonds form hydrogen bonds with water, which can enhance the adsorption capacity of the electrocatalytic oxide film surface for polar molecules, promoting reactions such as hydrolysis and oxidation, thus helping to improve the catalytic performance of the electrocatalytic oxide film and further increasing its catalytic efficiency.

[0056] In some embodiments of this application, the mass ratio of polyacrylonitrile to oxalic acid can be (8~12):(0.1~0.3), for example, 8:0.3, 9:0.2, 10:0.2, 8:0.1, 9:0.1, 10:0.1, 12:0.1, or any range between two of the above values. This application adds oxalic acid to polyacrylonitrile to induce organic oxygen doping, and controls the atomic ratio of nitrogen and oxygen atoms in the final electrocatalytic oxidation film by adjusting the mass ratio of polyacrylonitrile to oxalic acid. This allows the electrocatalytic oxidation film to retain some defects, increasing the disorder of the film and improving its catalytic performance, thereby further enhancing its catalytic efficiency. In other embodiments of this application, the mass ratio of polyacrylonitrile to oxalic acid can be (8~10):0.1.

[0057] In some embodiments of this application, the mass ratio of polyacrylonitrile to organic solvent can be (8~12):(85~95), for example, 8:95, 9:90, 10:89.9, 12:85, or any range between two of the above values. By controlling the mass ratio of polyacrylonitrile to organic solvent within the above range, the viscosity of the spinning solution can be adjusted, which is beneficial for electrospinning and obtaining precursor carbon nanofiber membranes. In other embodiments of this application, the mass ratio of polyacrylonitrile to organic solvent can be (8~10):(89~91).

[0058] In some embodiments of this application, the weight-average molecular weight of polyacrylonitrile can be from 100,000 g / mol to 180,000 g / mol, for example, 100,000 g / mol, 110,000 g / mol, 120,000 g / mol, 130,000 g / mol, 140,000 g / mol, 150,000 g / mol, 160,000 g / mol, 170,000 g / mol, 180,000 g / mol, or any range between any two of the above values. By controlling the weight-average molecular weight of polyacrylonitrile within the above range, this application can slow down the chain motion of polyacrylonitrile, which helps it maintain a longer effective contact time with oxalic acid, thus facilitating the completion of the reaction in formula (1). In other embodiments of this application, the weight-average molecular weight of polyacrylonitrile can be from 130,000 g / mol to 160,000 g / mol.

[0059] In some embodiments of this application, the organic solvent includes one or a combination of several of N,N-dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, and N-vinylpyrrolidone. These organic solvents enable good dissolution and mixing of polyacrylonitrile and oxalic acid, which is beneficial for subsequent electrospinning.

[0060] S200: Electrospinning the spinning solution to obtain a precursor carbon nanofiber membrane; In some embodiments of this application, electrospinning uses an electrospinning injector. The inner diameter of the needle of the electrospinning injector can be 0.4mm to 0.6mm, for example, 0.4mm, 0.5mm, 0.6mm, or any two of the above values.

[0061] In some embodiments of this application, the propulsion speed of the spinning solution can be 1.1 mL / h. -1 ~1.5mL h -1 For example, it can be 1.1 mL h -1 1.2 mL h -1 1.3 mL h -1 1.4 mL h -1 1.5 mL h -1 etc., or the range between any two of the above values.

[0062] In some embodiments of this application, the spinning distance of electrospinning can be 13cm to 17cm, for example, 13cm, 14cm, 15cm, 16cm, 17cm, or any range between two of the above values. It should be noted that the spinning distance refers to the distance between the needle of the electrospinning injector and the fiber receiving device.

[0063] In some embodiments of this application, the spinning pressure of electrospinning can be 21kV~25kV, for example, 21kV, 22kV, 23kV, 24kV, 25kV, or any range between two of the above values.

[0064] In some embodiments of this application, the spinning humidity of electrospinning can be 30% to 50%, for example, 30%, 40%, 50%, or any range between two of the above values.

[0065] In some embodiments of this application, the electrospinning temperature can be 25°C to 35°C, for example, 25°C, 27°C, 29°C, 32°C, 35°C, or any range between two of the above values.

[0066] In some embodiments of this application, the voltage of the fiber receiving device in electrospinning can be -2.0kV to -0.7kV, for example, -2.0kV, -1.5kV, -1.0kV, -0.7kV, or any range between two of the above values.

[0067] In some embodiments of this application, the rotational speed of the fiber receiving device in electrospinning can be 800 rpm to 1200 rpm, for example, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, or any range between two of the above values.

[0068] In this application, by controlling the conditions of electrospinning, such as controlling one or more of the following: the inner diameter of the electrospinning injector needle, the propulsion speed of the spinning solution, the spinning distance, the spinning pressure, the spinning humidity, the spinning temperature, the voltage of the fiber receiving device, and the rotation speed of the fiber receiving device, it is helpful to electrospin and obtain a precursor carbon nanofiber membrane.

[0069] S300: The precursor carbon nanofiber membrane is pre-oxidized and carbonized to obtain an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane.

[0070] Figure 3 The reaction process from a to b involves mixing polyacrylonitrile and oxalic acid, followed by electrospinning, pre-oxidation, and carbonization to form an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film. Specifically, the precursor carbon nanofiber film formed by electrospinning the mixture of polyacrylonitrile and oxalic acid forms an oxygen-containing structure after pre-oxidation. However, during carbonization, oxygen atoms in this oxygen-containing structure, as well as nitrogen atoms contained in the polyacrylonitrile itself, escape in gaseous form. At least some nitrogen atoms escape to form vacancies, which can be filled by oxygen doping in the oxalic acid. Since the amount of oxalic acid used is relatively small, only some vacancies are doped with oxygen, and some vacancies are still retained in the final electrocatalytic oxidation film.

[0071] In some embodiments of this application, pre-oxidation is carried out in an air atmosphere.

[0072] In some embodiments of this application, the pre-oxidation temperature can be 230°C to 280°C, for example, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, or any range between two of the above values.

[0073] In some embodiments of this application, the pre-oxidation time can be 2h to 2.5h, for example, 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, or any range between two of the above values.

[0074] In this application, by pre-oxidizing the precursor carbon nanofiber membrane in air and controlling the pre-oxidation conditions, an oxide layer with an oxygen-containing structure can be formed on the surface of the electrocatalytic oxidation membrane. This oxide layer can play a protective role, improving the stability of the electrocatalytic oxidation membrane at high temperatures and preventing excessive reaction or structural damage during further heating. Simultaneously, these oxygen-containing structures can be embedded in the fibers, transforming the linear chains of polyacrylonitrile into heat-resistant ladder-like structures, thus maintaining the fiber state during high-temperature carbonization.

[0075] In some embodiments of this application, carbonization is carried out in an inert atmosphere.

[0076] In some embodiments of this application, the carbonization temperature can be 900℃~1000℃, for example, 900℃, 930℃, 960℃, 1000℃, or any range between two of the above values.

[0077] In some embodiments of this application, the carbonization time can be 1h to 3h, for example, 1h, 1.5h, 2h, 3h, or any range between two of the above values.

[0078] In this application, by controlling the carbonization conditions, it is beneficial to remove non-carbon atoms. Under an inert atmosphere, non-carbon atoms such as hydrogen, oxygen, and nitrogen in the fiber escape in gaseous form, which improves the carbon purity and transforms the pre-oxidized carbon fiber into a random layered graphite structure dominated by carbon atoms, thus realizing the transformation of the material from an organic to an inorganic carbon structure.

[0079] This application involves electrospinning a spinning solution comprising polyacrylonitrile and oxalic acid, then pre-oxidizing and carbonizing the resulting precursor carbon nanofiber membrane, and controlling the mass ratio of polyacrylonitrile to oxalic acid within the aforementioned range, thereby controlling the atomic ratio of nitrogen atoms to oxygen atoms in the final electrocatalytic oxidation membrane to be 11:(6~15), thus obtaining an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane with excellent catalytic performance.

[0080] The third aspect of this application provides an application of an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane in wastewater treatment, wherein the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane includes the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane provided in the first aspect of this application and / or the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane prepared by the method of the second aspect of this application.

[0081] In some embodiments of this application, oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide films are used as anodes and / or cathodes in electrocatalytic systems. For example, the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film can be used alone as an anode, or alone as a cathode. More optionally, the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film can be used as both an anode and a cathode.

[0082] In this application, when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is used as the anode, pollutants in water can be oxidized and decomposed through a direct electron transfer process; when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is used as the cathode, dissolved oxygen in water can be activated into singlet oxygen through an oxygen activation reaction. 1 O2), which then oxidizes and removes pollutants from the water.

[0083] It should be noted that when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide film is used as the anode or cathode, other suitable electrodes, such as lithium metal sheets, graphite electrodes, platinum electrodes, nickel-based electrodes, and titanium-based coated electrodes, can be selected according to actual needs.

[0084] In some embodiments of this application, when oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membranes are used as anodes and / or cathodes in electrocatalytic systems to treat wastewater, they can effectively remove pollutants such as sulfamethoxazole (SMX), carbamazepine (CBZ), bisphenol A (BPA), atrazine (ATZ), tetrachlorobiphenyl (TCH), and ciprofloxacin (CIP) from wastewater.

[0085] In some embodiments of this application, an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane is used as the anode, and a nickel-based electrode is used as the cathode, assembled into an electrocatalytic system for removing SMX from wastewater. Specifically, when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane is used as the anode, SMX is oxidized and decomposed through a direct electron transfer process.

[0086] In some embodiments of this application, an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is used as the cathode, and a graphite electrode is used as the anode, assembled into an electrocatalytic system for removing SMX from wastewater. Specifically, when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is used as the cathode, dissolved oxygen in the water is activated into singlet oxygen through an oxygen activation reaction, thereby oxidizing and removing SMX.

[0087] In some embodiments of this application, oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membranes are used as both the anode and cathode, respectively, to assemble an electrocatalytic system for removing SMX from wastewater. Specifically: the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane used as the anode oxidizes and decomposes SMX through a direct electron transfer process; and the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane used as the cathode activates dissolved oxygen in the water into singlet oxygen through an oxygen activation reaction, thereby oxidizing and removing SMX.

[0088] In some embodiments of this application, such as Figure 5 As shown, oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membranes are used as the anode and cathode, respectively, to assemble a permeable electrocatalytic system for wastewater treatment. Figure 5 As shown, wastewater is pumped into the electrocatalytic system using negative pressure, such as a water pump. The wastewater comes into contact with the electrode formed by the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film and penetrates the micropores of the electrode. Within the micropores, the wastewater is in full contact with the electrode surface, and pollutants in the water are removed through electrocatalytic oxidation or reduction reactions, resulting in purified water. This process improves mass transfer efficiency, enhances the efficiency and selectivity of the electrocatalytic reaction, and improves wastewater treatment efficiency.

[0089] In this application, only one material, namely an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane, needs to be prepared. It can be used as both an anode and a cathode. Direct oxidation at the anode and indirect oxidation at the cathode can remove pollutants from the water. When the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is used as the anode and cathode respectively, it not only eliminates the need to find other suitable counter electrodes, but also increases the contact area and contact time between the wastewater and the electrode formed by the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane when both the anode and cathode are made of oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane, thereby effectively improving the wastewater treatment efficiency.

[0090] In some embodiments, when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane is used as an anode and / or cathode in an electrocatalytic system for wastewater treatment, the pore size of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane can be 0.5 μm to 1.5 μm, and the porosity can be 50% to 80%. When the pore size and porosity of the electrocatalytic oxide membrane in this application meet the above ranges, it can not only maintain good mechanical strength, but also help to increase the contact area between wastewater and the electrocatalytic oxide membrane, thereby improving the electrocatalytic efficiency of the electrocatalytic oxide membrane.

[0091] In some embodiments, when the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane is used as an anode and / or cathode in an electrocatalytic system for wastewater treatment, the thickness of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane can be, for example, 0.05 mm, 0.08 mm, 0.1 mm, 0.12 mm, 0.15 mm, or any range between two of the above values, as long as it meets the requirements for wastewater treatment.

[0092] Example 1

[0093] 1. Method for preparing oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation films: (1) Polyacrylonitrile, oxalic acid and N,N-dimethylformamide are mixed to obtain a spinning solution, wherein the mass ratio of polyacrylonitrile to oxalic acid is 10:0.1, the mass ratio of polyacrylonitrile to N,N-dimethylformamide is 10:89.9, and the molecular weight of polyacrylonitrile is 150000. (2) The spinning solution was electrospun to obtain a precursor carbon nanofiber membrane. The electrospinning parameters were set as follows: the needle inner diameter of the syringe was 0.5 mm and the propulsion speed of the spinning solution was 1.5 mL / h. -1 The spinning distance is 15cm, the spinning pressure is 18kV, the spinning humidity is 40%±10%, the spinning temperature is 30℃±5℃, the voltage of the fiber receiving device is -1.0kV, and the rotation speed of the fiber receiving device is 1000rpm. (3) After electrospinning, the precursor carbon nanofiber membrane is pre-oxidized and carbonized. First, it is pre-oxidized in air at 280°C for 2 hours to stabilize the molecular structure. Then, it is calcined in argon at 900°C for 1 hour to achieve pyrolysis. After cooling to room temperature, oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane is obtained.

[0094] 2. Applications of oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation films: like Figure 5 As shown, the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane prepared in Example 1 was used as both the anode and cathode, and assembled into a permeable electrocatalytic system for wastewater treatment. The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide membrane had a pore size of 1 μm, a porosity of 68%, and a thickness of 0.1 mm. The wastewater contained pollutants including SMX, CBZ, BPA, ATZ, TCH, and CIP, and the removal rates of each pollutant are shown in Table 1.

[0095] Table 1

[0096] The methods for preparing oxygen-doped carbon nanofiber bifunctional electrocatalytic oxide films in Examples 2-21 and Comparative Examples 1-4 are basically the same as those in Example 1, with the differences shown in Table 2: Table 2

[0097] As can be seen from Table 2, the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membranes prepared in Examples 1 to 21 according to the method of this application have a nitrogen-to-oxygen ratio within the protection range of this application, which can improve the catalytic performance of the electrocatalytic oxidation membrane and thus improve its catalytic efficiency; and the prepared electrocatalytic oxidation membrane also includes COC bonds, which is beneficial to improving the flexibility of the electrocatalytic oxidation membrane.

[0098] In Example 12, the weight-average molecular weight of polyacrylonitrile is significantly lower than that of Example 1. When the weight-average molecular weight of polyacrylonitrile is small, the chain movement of polyacrylonitrile is faster, which is not conducive to its effective contact with oxalic acid and the completion of the reaction of formula (1). The amount of oxygen atom doping is small, and the atomic ratio of oxygen atoms in the final electrocatalytic oxidation film is too low. The atomic ratio of nitrogen atoms to oxygen atoms is large, which leads to the catalytic performance of the electrocatalytic oxidation film in Example 12 being inferior to that in Example 1.

[0099] like Figure 3 The diagram shown illustrates the preparation principle of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film in Example 1. Figure 3 The reaction process from a to b involves mixing polyacrylonitrile and oxalic acid, followed by electrospinning, pre-oxidation, and carbonization to form an oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film. Specifically, the precursor carbon nanofiber film formed by electrospinning the mixture of polyacrylonitrile and oxalic acid forms an oxygen-containing structure after pre-oxidation. However, during carbonization, oxygen atoms in this oxygen-containing structure, as well as nitrogen atoms contained in the polyacrylonitrile itself, escape in gaseous form. At least some nitrogen atoms escape to form vacancies, which can be filled by oxygen doping in the oxalic acid. Since the amount of oxalic acid used is relatively small, only some vacancies are doped with oxygen, and some vacancies are still retained in the final electrocatalytic oxidation film.

[0100] like Figure 4 The diagram shown illustrates the preparation principle of the carbon fiber membrane in Comparative Example 1. Figure 4The reaction process from c to d in Comparative Example 1 involves the formation of a carbon fiber membrane from polyacrylonitrile through electrospinning, pre-oxidation, and carbonization. It should be noted that the conditions for electrospinning, pre-oxidation, and carbonization in Comparative Example 1 and Example 1 are the same. Specifically, although the polyacrylonitrile membrane formed by electrospinning forms an oxygen-containing structure after pre-oxidation, during carbonization, oxygen atoms in this structure, as well as nitrogen atoms present in the polyacrylonitrile itself, escape in gaseous form, with at least some nitrogen atoms escaping to form vacancies. Since the oxygen atoms in the oxygen-containing structure formed during pre-oxidation are inorganic dopants and mostly located on the membrane surface, they are easily removed during carbonization. Therefore, the final carbon fiber membrane has a low oxygen atom ratio, a large nitrogen-to-oxygen ratio, and many vacancies, resulting in poor catalytic performance.

[0101] In Example 1, the oxygen atoms doped with oxalic acid are more difficult to remove during carbonization compared to the oxygen atoms in the oxygen-containing structure formed by pre-oxidation. Therefore, the proportion of oxygen atoms in the final electrocatalytic oxide film formed in Example 1 is higher than that in Comparative Example 1. A small amount of the oxygen atoms doped with oxalic acid also escapes during carbonization, carrying away some carbon atoms. Therefore, the proportion of carbon atoms in the final electrocatalytic oxide film formed in Example 1 is lower than that in Comparative Example 1.

[0102] In Comparative Example 2, the amount of oxalic acid added was significantly higher than that in Example 1. When the amount of oxalic acid added was too high, there was too much oxygen atom doping, the atomic ratio of nitrogen atoms to oxygen atoms was too low, and oxygen atoms would replace all defects, increasing the material's orderliness but reducing its catalytic performance.

[0103] Citric acid in Comparative Example 3 is a tribasic acid, tannic acid in Comparative Example 4 is a macromolecular polybasic acid, and oxalic acid in Example 1 is a dibasic acid with only two carbon atoms. Comparatively, oxalic acid has a simpler molecular structure, exhibits less steric hindrance during oxygen doping, and is more readily cross-linked with polyacrylonitrile molecules to achieve oxygen doping. Furthermore, when using citric acid and tannic acid, excessive oxygen doping leads to an excessively high proportion of oxygen atoms in the electrocatalytic oxidation film and an excessively low ratio of nitrogen to oxygen atoms. Oxygen atoms then replace all defects, increasing the material's order and conductivity, but reducing its catalytic performance.

[0104] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has disclosed the preferred embodiment as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of this application.

Claims

1. An oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film, characterized in that, An atomic ratio of nitrogen atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is 11:(6-15), preferably 11:(8-10).

2. The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film according to claim 1, characterized in that, An atomic ratio of carbon atoms to oxygen atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is (75-85):(5-15), preferably (79-81):(8-11).

3. The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film according to claim 1, characterized in that, Based on a total number of atoms of nitrogen atoms, oxygen atoms and carbon atoms in the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film, at least one of the following is satisfied: The atomic percentage of the nitrogen atoms is 2%-20%, preferably 9%-11%; The atomic percentage of the oxygen atoms is 6%-15%, preferably 8%-10%; The atomic percentage of the carbon atoms is 74%-83%, preferably 79%-81%.

4. The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film according to claim 1, characterized in that, The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film comprises a C-O-C bond.

5. The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film according to any one of claims 1-4, characterized in that, At least one of the following is satisfied: A pore size of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is 0.5-1.5 microns, preferably 0.8-1.2 microns; A porosity of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is 50%-80%, preferably 60%-75%; An electrocatalytic efficiency η of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film satisfies: η≥95%, preferably η≥99%; A mechanical strength R of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film satisfies: R≥5 Gpa, preferably R≥8 Gpa.

6. A method for preparing the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film according to any one of claims 1 to 5, characterized by, The method comprises: Mixing polyacrylonitrile, oxalic acid and an organic solvent to obtain a spinning solution; Electrospinning the spinning solution to obtain a precursor carbon nanofiber film; Performing pre-oxidation and carbonization treatment on the precursor carbon nanofiber film to obtain the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film; The mass ratio of the polyacrylonitrile to the oxalic acid is (8-12):(0.1-0.3), preferably (8-10):0.

1.

7. The method of claim 6, wherein, The mass ratio of the polyacrylonitrile to the organic solvent is (8-12):(85-95), preferably (8-10):(89-91).

8. The method of claim 6, wherein, The weight average molecular weight of the polyacrylonitrile is 100000-180000 g / mol, preferably 130000-160000 g / mol.

9. The method of claim 6, wherein, At least one of the following is satisfied: The pre-oxidation is performed in an air atmosphere; The temperature of the pre-oxidation is 230-280 degrees Celsius; The time of the pre-oxidation is 2-2.5 hours; and The carbonization is performed in an inert atmosphere; The temperature of the carbonization is 900-1000 degrees Celsius; The time of the carbonization is 1-3 hours. The oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation film is applied to an electrocatalytic system as an anode and / or a cathode.

10. Use of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane according to any one of claims 1 to 5 and / or of the oxygen-doped carbon nanofiber bifunctional electrocatalytic oxidation membrane prepared by the method according to any one of claims 6 to 9 for treating wastewater, characterized in that, ​

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