Self-limited feco-nc / nanowire graphite felt composite electrode and preparation and application thereof
By constructing nanowells on the surface of graphite felt fibers and self-confining and anchoring FeCo-PBA catalysts, the problems of complex preparation and secondary pollution of traditional confined electrodes were solved, achieving efficient and stable heterogeneous electro-Fenton reaction and improving the degradation efficiency of recalcitrant organic pollutants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING UNIV OF TECH
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-05
AI Technical Summary
In existing heterogeneous electro-Fenton technology, traditional supported cathode catalysts are prone to detachment, have high metal ion leaching rates, poor stability, short ROS lifetime, and low mass transfer efficiency, resulting in low reaction efficiency. Furthermore, current finite-domain electrode preparation methods are complex and pose a risk of secondary pollution.
Using inexpensive graphite felt as the substrate and FeCo-PBA as the etchant and catalyst precursor, a nano-trap is constructed on the surface of the graphite felt fiber through an in-situ etching-self-confined strategy. The FeCo-PBA-derived catalyst particles are self-confined and anchored in the nano-trap, avoiding the use of template agents and highly corrosive reagents, thus forming a self-confined FeCo-NC/nano-trap graphite felt composite electrode.
It significantly improves the stability and reaction efficiency of the catalyst, reduces metal ion leaching, enhances the degradation ability of pollutants, increases the reaction frequency of ROS with pollutants, and improves catalytic performance, especially in the degradation efficiency of recalcitrant organic pollutants in heterogeneous electro-Fenton systems.
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Figure CN122144860A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical oxidation water treatment, specifically relating to a method for preparing and applying a self-confined FeCo-NC / nano-trap graphite felt composite electrode. Background Technology
[0002] Recalcitrant organic pollutants in industrial wastewater pose a persistent threat to aquatic environmental safety, making the development of efficient and stable wastewater treatment technologies urgent. Heterogeneous electro-Fenton technology, capable of generating hydrogen peroxide (H₂O₂) in situ without the need for additional oxidants (such as H₂O₂, persulfate, peracetic acid, etc.), is considered a promising advanced oxidation process. The key to this technology lies in the cathode material's ability to efficiently activate H₂O₂ to generate highly reactive oxygen species (ROS). However, traditional supported cathodes suffer from inherent problems such as easy detachment of nanocatalytic particles, high metal ion leaching, and poor stability. More critically, the in-situ generated ROS has an extremely short lifetime and low mass transfer efficiency, resulting in a low probability of effective collision with target pollutants, thus limiting the overall reaction efficiency.
[0003] Nanoconfined catalysis, by confining active centers within a nanoscale space, leverages physical confinement effects and interfacial electronic effects with the confined environment to significantly enhance catalytic reaction efficiency. The key to translating the advantages of nanoconfined catalysis into tangible performance improvements lies in designing catalytic materials with specific confinement structures. Currently, composite electrical confinement methods often rely on template methods (such as anodic alumina and mesoporous silica), strong acid-base etching for pore creation, core-shell embedding (e.g., Applied Catalysis B: Environment and Energy, 2025, 374, 125372, which provides a Fe / Mn-in-CNT confined electrode), and carbon nanotube confinement (e.g., Applied Catalysis B: Environmental, 2023, 328, 122538, which provides a CoNi...). SA (OCF / CF core-shell confinement electrode, etc.)
[0004] However, existing methods have limitations such as complex and demanding template introduction and removal processes, secondary pollution caused by highly corrosive reagents such as concentrated acids and alkalis, and the high cost of carbon nanotubes. Furthermore, current finite-domain electrodes also suffer from low catalytic activity. Summary of the Invention
[0005] (a) Purpose of the invention The purpose of this invention is to address the problems of complex template removal processes and / or secondary pollution and high costs in existing finite-domain composite electrode preparation methods, and to provide a self-confined FeCo-NC / nano-trap graphite felt composite electrode, its preparation method and application.
[0006] (II) Technical Solution To address the above problems, this invention provides a method for preparing a self-confined FeCo-NC / nano-trap graphite felt composite electrode, comprising the following steps: Step 1: Clean and activate the graphite felt to obtain pretreated graphite felt; Step 2: Anodize the pretreated graphite felt; Step 3: Mix solution a and solution b to form FeCo-PBA precursor solution, and impregnate the graphite felt obtained by anodizing in step 2 into the FeCo-PBA precursor solution to obtain graphite felt loaded with FeCo-PBA precursor, wherein solution a is an aqueous solution containing iron source, cobalt source and polyvinylpyrrolidone, and solution b is an aqueous solution containing potassium cobalt cyanide. Step 4: The graphite felt loaded with FeCo-PBA precursor is calcined in two steps at different temperatures and atmospheres to make the graphite felt covered with nano-trap with a diameter of 20-40 nm, exhibiting a honeycomb structure, and the FeCo-PBA-derived catalyst particles are anchored in the nano-trap, thus obtaining a self-confined FeCo-NC / nano-trap graphite felt composite electrode.
[0007] This invention uses inexpensive graphite felt as a matrix and iron-cobalt Prussian blue analogue (FeCo-PBA) as an etchant and catalyst precursor. An in-situ etching-self-confining strategy is employed, involving calcination in air and nitrogen atmospheres respectively. The etching effect of FeCo-PBA on carbon fibers is used to prepare uniformly distributed nanowells with a diameter of 20-40 nm on the surface of the graphite felt fibers. FeCo-PBA-derived catalyst particles are self-confined and anchored within these nanowells. FeCo-PBA acts as both an etchant and a catalyst precursor, achieving in-situ nanowell construction and catalyst self-confining anchoring, while effectively avoiding the introduction of template agents, acids, alkalis, and binders, thus preventing the removal of template agents and secondary pollution. Furthermore, the nanowells not only provide stable anchoring points and physical protection for the catalyst particles, improving the stability of the composite electrode, but also significantly reduce metal ion leaching. The resulting confined microenvironment acts like a microreactor, enabling more efficient enrichment of pollutants, H2O2, and ROS. This increases the reaction frequency between ROS and pollutants, thereby enhancing the catalytic performance of the composite electrode. The reaction rate constant is 1.5 times higher than that of the existing Fe / Mn-in-CNT confined electrode and higher than that of CoNi. SA The reaction rate constant of the / OCF / CF core-shell confined electrode was increased by 2.7 times.
[0008] Specifically, the washing solvent used in step 1 is ethanol; Cleaning time: 30-60 minutes.
[0009] Preferably, the specific activation conditions described in step 1 include: Calcination at 300-500 ℃ for 2-4 h. The preferred heating rate is 5-10 ℃ / min. Preferably, step 2, which involves anodizing the pretreated graphite felt, specifically includes: The pretreated graphite felt was anoly oxidized in an electrolytic cell using ammonium salt solution as electrolyte; The concentration of the ammonium salt solution is 0.05-0.15 M, and the anodic oxidation current density is 4-6 mA / cm². 2 The anodizing time is 15-25 min; The ammonium salt in the ammonium salt solution is selected from at least one of ammonium dihydrogen phosphate, ammonium persulfate, and ammonium sulfate.
[0010] Preferably, the preparation method of solution a and solution b in step 3 includes: Solution a is prepared by dissolving the iron source, cobalt source, and polyvinylpyrrolidone in ultrapure water. The molar ratio of the iron source to the cobalt source is 3:1-4. The total metal concentration of the iron source and cobalt source in solution a is 1.5-15 mM, the polyvinylpyrrolidone content is 6-60 g / L, and the average molecular weight of polyvinylpyrrolidone is preferably 8000-24000 g / mol. Solution b is a potassium cobalt cyanide solution with a concentration of 1-10 mM. The molar ratio of the potassium cobalt cyanide to the iron source is 1:1-1.5.
[0011] Preferably, the molar ratio of the iron source to the cobalt source is 3:2-3, the total metal concentration of the iron and cobalt sources in solution a is 1.5-6.25 mM, the polyvinylpyrrolidone content is 10-30 g / L, and the average molecular weight of polyvinylpyrrolidone is preferably 8000-24000 g / mol; solution b is a potassium cobalt cyanide solution with a concentration of 2-5 mM. Under these conditions, the composite electrode prepared as the cathode and the platinum sheet as the anode, in a heterogeneous electro-Fenton oxidation system, achieves a ciprofloxacin removal rate of over 90% after 60-90 min of reaction.
[0012] Preferably, the specific conditions for the two-step calcination in step 4 include: The first step, calcination, is an in-situ etching process: Under air atmosphere, the calcination temperature is 350-450 ℃, the calcination time is 30-60 min, and the heating rate is preferably 5-10 ℃ / min. An in-situ etching-self-confining strategy is employed, using FeCo-PBA as the etchant and catalyst precursor. During calcination, FeCo-PBA reacts with the carbon fibers to etch and oxidize the surface carbon into CO2, thereby constructing uniformly distributed nanowells with a diameter of 20-40 nm on the surface of the graphite felt fibers. FeCo-PBA is self-confined and anchored within these nanowells. The preferred calcination temperature under air atmosphere is 400-450 ℃.
[0013] The second step, calcination, is a catalyst derivatization and self-confined anchoring process: Under a nitrogen atmosphere, the calcination temperature is 600-700 ℃, the calcination time is 60-120 min, and the heating rate is preferably 5-10 ℃ / min. Using FeCo-PBA as a catalyst precursor, FeCo-PBA anchored in the nanotrap is derived into a FeCo bimetallic catalyst (FeCo-NC), realizing the in-situ construction of nanotrap and catalyst self-confinement.
[0014] In a specific embodiment of the present invention, a method for preparing a self-confined FeCo-NC / nanowell graphite felt composite electrode includes the following steps: Step 1: Soak the graphite felt in an ethanol solution and ultrasonically clean it for 30-60 minutes to remove oil and impurities from the surface of the graphite felt fibers. Then ultrasonically wash it several times with deionized water to remove residual ethanol. After drying, the cleaned graphite felt is activated at 300-500 ℃ in a high-temperature atmosphere furnace for 2-4 hours. Step 2: Using high-temperature treated graphite felt as the anode, a platinum sheet as the cathode, and ammonium dihydrogen phosphate as the electrolyte, the graphite felt is anodized. The anodized graphite felt is then washed with deionized water to remove residual ammonium dihydrogen phosphate. The concentration of ammonium dihydrogen phosphate is 0.05-0.15 M, and the anodizing current density is 4-6 mA / cm². 2 The anodizing time is 15-25 minutes. Step 3: Dissolve ferrous chloride, cobalt chloride, and polyvinylpyrrolidone in 20 mL of ultrapure water to obtain solution a, wherein the molar ratio of iron to cobalt is 3:1-4, the total metal concentration of iron and cobalt in solution a is 1.5-15 mM, and the polyvinylpyrrolidone content is 6-60 g / L; solution b is 20 mL of potassium cobalt cyanide solution with a concentration of 1-10 mM; add solution b to solution a and stir for 5-15 min, then immerse the anodized graphite felt in the mixed solution for 18-24 h, and finally remove the graphite felt matrix loaded with FeCo-PBA precursor, wash with deionized water and dry.
[0015] Step 4: The graphite felt loaded with FeCo-PBA precursor was calcined at high temperatures and under different atmospheres. The first calcination step was an in-situ etching process: under an air atmosphere, the calcination temperature was 350-450 ℃, the heating rate was 5-10 ℃ / min, and the calcination time was 30-60 min. During the calcination process, FeCo-PBA played a dual role as an etchant and catalyst precursor. FeCo-PBA reacted with carbon fibers to etch and oxidize the surface carbon into CO2, thereby constructing uniformly distributed nanowells with a diameter of 20-40 nm on the surface of the graphite felt fibers. FeCo-PBA was self-confined and anchored in the nanowells. The second calcination step was a catalyst derivation and self-confined anchoring process: under a nitrogen atmosphere, the calcination temperature was 600-700 ℃, the heating rate was 5-10 ℃ / min, and the calcination time was 60-120 min. Using FeCo-PBA as a catalyst precursor, FeCo-PBA anchored in nanowells was derived into a FeCo bimetallic catalyst. In-situ nanowell construction and catalyst self-confinement were achieved, ultimately yielding a self-confined FeCo-NC / nanowell graphite felt composite electrode. Compared to traditional surface-supported electrodes, the self-confined FeCo-NC / nanowell graphite felt composite electrode possesses abundant mesoporous nanowell structures, promoting the enrichment of pollutants and reactive oxygen species within the nanowells. Furthermore, the nanowell-confined microenvironment optimizes the catalyst's electronic structure and improves electron transfer performance; its spatial confinement also enhances catalyst stability and reduces metal ion leaching.
[0016] The composite electrode can be used as a cathode material in heterogeneous electro-Fenton advanced oxidation systems, and can efficiently generate activated H2O2 in situ, and efficiently degrade recalcitrant organic pollutant wastewater containing ciprofloxacin in a pH range of 3-11.
[0017] In a preferred embodiment, the molar ratio of the iron source to the cobalt source is 3:2-3; the total metal concentration of the iron and cobalt sources in solution a is 2.5-3.5 mM; the polyvinylpyrrolidone content is 11-12 g / L; and the average molecular weight of the polyvinylpyrrolidone is preferably 8000-10000 g / mol. Solution b is a potassium cobalt cyanide solution with a concentration of 1.5-2 mM. The calcination temperature is 400-450 °C under air atmosphere. The composite electrode prepared under these conditions serves as the cathode, and the platinum sheet serves as the anode in a heterogeneous electro-Fenton oxidation system, achieving a 100% removal rate of ciprofloxacin within 60 min.
[0018] In another aspect, the present invention provides a self-confined FeCo-NC / nanowell graphite felt composite electrode prepared by the method described in any of the above-mentioned claims.
[0019] In another aspect, the present invention provides the application of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared by the method described in any of the above-mentioned methods in the degradation of organic pollutants in a heterogeneous electro-Fenton system, wherein the organic pollutants include at least one of ciprofloxacin, phenol, catechol, bisphenol A, sulfadiazine, and atenolol.
[0020] Specifically, the self-confined FeCo-NC / nano-trap graphite felt composite electrode serves as the cathode, a platinum sheet as the anode, a pH value of 3-11, and a current density of 0.5-2 mA / cm². 2 The aeration rate is 0.3-0.8 L / min, and the sodium sulfate concentration is 50-100 mM.
[0021] Preferably, the composite electrode is a cathode, with a pH value of 5-7 and a current density of 0.5-1.5 mA / cm². 2 The aeration rate is 0.5-0.6 L / min, which can achieve 100% removal of ciprofloxacin from wastewater within 60 min.
[0022] Specifically, a heterogeneous electro-Fenton oxidation system was constructed using the self-confined FeCo-NC / nano-trap graphite felt composite electrode as the cathode and a platinum sheet as the anode; a constant current mode was adopted, with a current density of 1-6 mA / cm² based on the effective cathode area. 2 Air was used as the aeration gas, with an aeration rate of 0.2-0.8 L / min, an initial pH of 3-11, a 50-100 mM sodium sulfate aqueous solution as the electrolyte, a pollutant concentration of 5-20 mg / L, and a total solution volume of 100-500 mL.
[0023] Compared with the prior art, the present invention has the following superior effects: This invention uses low-cost, highly conductive, and chemically stable graphite felt as a substrate, and FeCo-PBA as an etchant and catalyst precursor. An in-situ etching-self-confining strategy is employed to create pores and self-confine the catalyst in air and nitrogen atmospheres, respectively. The etching effect of FeCo-PBA on carbon fibers is used to prepare uniformly distributed nanowells with diameters of 20-40 nm on the surface of the graphite felt fibers. Simultaneously, FeCo-PBA-derived catalyst particles are self-confined and anchored within the nanowells. FeCo-PBA acts as both an etchant and a catalyst precursor, achieving in-situ nanowell construction and catalyst self-confining anchoring, effectively avoiding the introduction of templates, acids, alkalis, and binders, thus simplifying the fabrication conditions of the confined composite electrode.
[0024] This composite electrode fully leverages the advantages of confined catalysis, significantly enhancing electrode stability, reducing metal ion leaching, and improving resistance to interference from coexisting components such as anions and cations. Furthermore, the nano-trap confinement promotes the redistribution of charges at the carbon substrate interface with CoFe2O4 and CoO, optimizes the electronic structure of active sites, accelerates electron transfer, and improves the adsorption performance of intermediates, creating a favorable nano-microenvironment for pollutant enrichment, H2O2 activation, and ROS-pollutant reactions. This composite electrode achieves highly efficient degradation of ciprofloxacin across a wide pH range in a heterogeneous electro-Fenton system, while also exhibiting excellent applicability to the degradation of organic pollutants such as phenol, catechol, bisphenol A, sulfadiazine, and atenolol, demonstrating broad-spectrum, efficient, and stable pollutant degradation performance. Attached Figure Description
[0025] Figure 1 The images shown are scanning electron microscope (SEM) images of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of this invention, where the magnification of a is 8000x and the magnification of b is 30000x. Figure 2 The scanning electron microscope images of the unconfined FeCo-NC / graphite felt composite electrode prepared in Comparative Example 1 are shown, where a is magnified by 8000x and b is magnified by 30000x. Figure 3 Transmission electron microscope image of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of the present invention; Figure 4 Transmission electron microscope image of the unconfined FeCo-NC / graphite felt composite electrode prepared for Comparative Example 1; Figure 5 The X-ray photoelectron spectrum of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of the present invention is shown, where a is the C 1s spectrum, b is the O 1s spectrum, and c is the N 1s spectrum. Figure 6 X-ray diffraction patterns of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of the present invention and the unconfined FeCo-NC / graphite felt composite electrode prepared in Comparative Example 1. Figure 7 Electrochemical impedance spectroscopy of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of the present invention and the unconfined FeCo-NC / graphite felt composite electrode prepared in Comparative Example 1. Figure 8 The graphs show the degradation effects of ciprofloxacin on wastewater in Examples 1, 1, and 2 of the present invention. Figure 9 The graphs show the degradation effects of ciprofloxacin wastewater under different iron-cobalt metal ratios in Examples 2-5 of the present invention. Figure 10 The graphs show the degradation effects of ciprofloxacin on wastewater under different total metal concentrations in Examples 6-9 of the present invention. Figure 11 The graph shows the degradation effect of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of this invention on ciprofloxacin wastewater under different pH conditions. Figure 12 The graph shows the degradation effect of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of this invention on different recalcitrant organic pollutants. Figure 13 The graphs show the degradation effects of the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of this invention and the unconfined FeCo-NC / graphite felt composite electrode prepared in Comparative Example 1 on ciprofloxacin under different interference from coexisting components. Figure 14 The metal ion leaching concentration diagrams are for the self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared in Example 1 of the present invention and the unconfined FeCo-NC / graphite felt composite electrode prepared in Comparative Example 1. Figure 15 Cyclic stability diagrams of the self-confined FeCo-NC / nanowell graphite felt composite electrode prepared in Example 1 of the present invention and the unconfined FeCo-NC / graphite felt composite electrode prepared in Comparative Example 1. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.
[0027] The raw materials and reagents used in the embodiments and comparative examples of this invention are all conventional commercially available products; The graphite felt was purchased from Hebei Jingtan Technology Co., Ltd. Polyvinylpyrrolidone (PVP) with a molecular weight of 10,000 g / mol was purchased from Shanghai Yuanye Biotechnology Co., Ltd.
[0028] The wastewater mentioned in each embodiment of the present invention is simulated wastewater prepared by mixing the target pollutant with ultrapure water; The heterogeneous electro-Fenton oxidation treatment of wastewater was carried out in a constant current mode in an electrolytic cell at room temperature (25 °C). The pH value of the wastewater was adjusted by 0.1 M sulfuric acid and 0.1 M sodium hydroxide.
[0029] Example 1 (1) Soak the graphite felt in an ethanol solution and ultrasonically clean it for 30 min to remove oil and impurities from the surface of the graphite felt fibers. Then, ultrasonically wash it several times with deionized water to remove residual ethanol. After drying, the cleaned graphite felt is activated at 400 °C for 2 h in a high-temperature atmosphere furnace. (2) The graphite felt (5×2×0.5 cm) treated at high temperature was used as the anode, and a platinum sheet (5×2×0.02 cm) was used as the cathode. 0.1 M ammonium dihydrogen phosphate was used as the electrolyte to perform anodic oxidation of the graphite felt in constant current mode. Subsequently, the anodicized graphite felt was washed with deionized water to remove residual ammonium dihydrogen phosphate. The distance between the anode and cathode was 3 cm, and the anodic oxidation current density was 5 mA / cm. 2 The anodizing time is 20 min. (3) Dissolve 0.036 mmol ferrous chloride, 0.024 mmol cobalt chloride and 0.24 g polyvinylpyrrolidone in 20 mL of deionized water to obtain solution a. The molar ratio of iron to cobalt is 3:2. The total metal concentration of iron and cobalt in solution a is 3 mM and the polyvinylpyrrolidone content is 12 g / L. Solution b is 20 mL of potassium cobalt cyanide solution with a concentration of 2 mM. Add solution b to solution a and stir for 10 min to obtain a mixed solution. Then, immerse the anodized graphite felt in the mixed solution for 24 h. Finally, take out the graphite felt matrix loaded with FeCo-PBA precursor, wash it with deionized water and dry it in a vacuum oven at 80 °C.
[0030] (4) The graphite felt loaded with FeCo-PBA precursor was calcined in air at a temperature of 450 °C, a heating rate of 5 °C / min, and a calcination time of 30 min. Then, under nitrogen atmosphere protection, the temperature was further increased to 650 °C at a heating rate of 5 °C / min and a calcination time of 120 min. Finally, the self-confined FeCo-NC / nanowell graphite felt composite electrode was obtained.
[0031] The obtained composite electrode was characterized, and the results are as follows: Figure 1 ab、 Figure 3 , Figure 5 ac and Figure 6 As shown. By Figure 1 ab and Figure 3 As shown, the fiber surface of the self-confined FeCo-NC / nanowell graphite felt composite electrode exhibits abundant honeycomb-like nanowell confinement structures, with nanowell sizes ranging from 20-40 nm. The FeCo-PBA calcination-derived catalyst particles (FeCo-NC) are anchored within these nanowells. Figure 5 As shown in Figure ac, the FeCo-NC catalyst has an elemental composition of C, O, N, Fe, and Co, and contains abundant pyridine nitrogen, pyrrole nitrogen, and oxygen-containing functional groups. For example... Figure 6As shown, the catalyst composition is CoFe2O4 and CoO. The confined nanowell structure and catalyst distribution are uniform, with no aggregation, and the active sites are highly dispersed. The confinement effect of the nanowells not only provides a confined microenvironment for the catalyst but also provides a protective barrier, which is beneficial to improving the catalyst's stability and catalytic activity.
[0032] Examples 2-5 The preparation process of the composite electrode in Examples 2-5 is basically the same as that in Example 1, except that: in step (3), the concentration of polyvinylpyrrolidone is 30 g / L, the concentration of potassium cobalt cyanide is 5 mM, and the total metal concentration of ferrous chloride and cobalt chloride is 7.5 mM, wherein the metal molar ratio of ferrous chloride to cobalt chloride is 3:1, 3:2, 3:3, 3:4, respectively, and the air calcination temperature in step (4) is 400 ℃.
[0033] The electrodes prepared in Examples 2-5 were used to degrade ciprofloxacin wastewater in a heterogeneous electro-Fenton system, specifically including: Heterogeneous electro-Fenton oxidation systems were constructed using the electrodes prepared in Examples 2-5 as cathodes and platinum sheets as anodes, respectively, employing a constant current mode with a current density of 3 mA / cm². 2 The aeration rate was 0.3 L / min, the pH was 6.4, the electrolyte was 50 mM sodium sulfate aqueous solution, the ciprofloxacin concentration was 10 mg / L, and the total solution volume was 200 mL. A heterogeneous electro-Fenton oxidation reaction was carried out at room temperature (25 ℃), and the results are as follows: Figure 9 As shown.
[0034] Examples 6-9 The preparation process of the composite electrodes in Examples 6-9 is basically the same as that in Example 1, except that: in step (3), the concentrations of ferrous chloride in solution a are 0.9 mM, 1.8 mM, 4.5 mM, and 9 mM, the concentrations of cobalt chloride are 0.6 mM, 1.2 mM, 3 mM, and 6 mM, the concentrations of polyvinylpyrrolidone are 6 mg / L, 12 mg / L, 30 mg / L, and 60 mg / L, the concentrations of potassium cobalt cyanide in solution b are 1 mM, 2 mM, 5 mM, and 10 mM, and the total metal concentrations in the PBA precursor mixed solution are 1.25 mM, 2.5 mM, 6.25 mM, and 12.5 mM, respectively.
[0035] The electrodes prepared in Examples 6-9 were used to degrade ciprofloxacin wastewater in a heterogeneous electro-Fenton system, with experimental conditions similar to those in Examples 2-5, except that the electrodes prepared in Examples 6-9 were used as cathodes. The results are as follows: Figure 10 As shown.
[0036] Comparative Example 1 The preparation process of the composite electrode in Comparative Example 1 is similar to that in Example 1, except that the calcination process in step (4) is a one-step calcination, that is, the temperature is directly raised to 650 ℃ under nitrogen atmosphere protection, the heating rate is 5 ℃ / min, and the calcination time is 120 min, so as to obtain the unconfined FeCo-NC / graphite felt composite electrode.
[0037] The obtained composite electrode was characterized, and the results are as follows: Figure 2 , Figure 4 and Figure 6 As shown. By Figure 2 and Figure 4 As shown, the unconfined FeCo-NC / graphite felt composite electrode has a smooth fiber surface without forming nanotrap structures, and FeCo-PBA derivatives are uniformly loaded on the graphite felt fiber surface. Figure 6 As shown, the catalyst composition of the unconfined FeCo-NC / graphite felt composite electrode is CoFe2O4 and CoO, and the phase composition is the same as that of the self-confined FeCo-NC / nano-trap graphite felt composite electrode.
[0038] Comparative Example 2 The electrodes provided in this comparative example are the original graphite felt after being cleaned with ethanol and deionized water.
[0039] Performance tests were conducted on the embodiments and comparative examples: Electrochemical impedance spectroscopy was used to analyze the electron transfer performance of the composite electrodes provided in Example 1 and Comparative Example 1: The electrolyte was 50 mM sodium sulfate aqueous solution, the reference electrode was saturated calomel electrode, the counter electrode was platinum sheet, and the working electrode was a composite electrode. The test voltage was the open circuit potential, the frequency range was 100 mHz-1 MHz, and the perturbation amplitude was 5 mV.
[0040] The results are as follows Figure 7 As shown, the unconfined FeCo-NC / graphite felt composite electrode provided in Comparative Example 1 has a higher charge transfer resistance, while the self-confined FeCo-NC / nano-trap graphite felt composite electrode provided in Example 1 has a lower charge transfer resistance. Its electron transfer performance is significantly improved, thereby enhancing its electrocatalytic activity.
[0041] The electrodes provided in Example 1 and the comparative example were used as cathodes in the heterogeneous electro-Fenton system, respectively, to test the pollutant removal performance. Test 1: The electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2 were used to degrade ciprofloxacin wastewater in a heterogeneous electro-Fenton system, specifically including: Heterogeneous electro-Fenton oxidation systems were constructed using electrodes prepared in Example 1, Comparative Example 1, or Comparative Example 2 as cathodes and platinum sheets as anodes, respectively, employing a constant current mode with a current density of 1 mA / cm².2 The aeration rate was 0.6 L / min, the pH was 6.4, the electrolyte was 50 mM sodium sulfate aqueous solution, the ciprofloxacin concentration was 10 mg / L, and the total solution volume was 200 mL. A heterogeneous electro-Fenton oxidation reaction was carried out at room temperature (25 ℃). Figure 8 As shown, the composite electrode provided in Example 1 achieved 100% removal of ciprofloxacin in 60 min, while the original graphite felt and the unconfined FeCo-NC / graphite felt composite electrode only achieved removal rates of 49.3% and 64.9% of ciprofloxacin in 60 min.
[0042] Test 2: The results were basically the same as those in Test 1, except that the self-confined FeCo-NC / nano-trap graphite felt composite electrode provided in Example 1 was used as the cathode, and the initial pH of the ciprofloxacin wastewater was adjusted to 3.0, 5.0, 6.4, 9.0, and 11.0, respectively.
[0043] The results are as follows Figure 11 As shown, within 60 min, the self-confined FeCo-NC / nano-trap graphite felt composite electrode provided in Example 1 maintained a removal rate of ciprofloxacin above 93.7% in a wide pH range of 3-11, and the removal rate was close to 100% after 90 min, indicating that the composite electrode has good practicality in a wide pH range.
[0044] Test 3: The heterogeneous electro-Fenton system with the self-confined FeCo-NC / nano-trap graphite felt composite electrode provided in Example 1 as the cathode is basically the same as that in Test 1, except that the target pollutants are phenol, catechol, bisphenol A, sulfadiazine and atenolol.
[0045] The results are as follows Figure 12 As shown, within 60 min, the composite electrode provided in Example 1 achieved a 100% removal rate for phenol, ciprofloxacin, and bisphenol A, and a removal rate for catechol, sulfadiazine, and atenolol all exceeded 95%, indicating that the composite electrode has good removal performance for a variety of different types of pollutants.
[0046] Test 4: The results were essentially the same as in Test 1, except that 50 mM sodium carbonate, 50 mM sodium chloride, 50 mM sodium nitrate, 50 mM sodium phosphate, 50 mM calcium sulfate, 50 mM magnesium sulfate, and 10 mg / L humic acid were added to the composite electrodes provided in Example 1 and Comparative Example 1 to analyze their anti-interference ability against different coexisting components.
[0047] The results are as follows Figure 13As shown, the composite electrode provided in Example 1 is used in CO3... 2- Cl - NO3 - PO4 3- Ca 2+ Ma 2+ Even in the presence of coexisting components such as humic acid, the removal rate of ciprofloxacin remained above 93.3% within 60 min, indicating that the composite electrode exhibits excellent resistance to complex anions, cations, and humic acids, and can adapt to various complex water bodies. Compared with the self-confined FeCo-NC / nano-trap graphite felt composite cathode provided in Example 1, the unconfined FeCo-NC / graphite felt composite electrode provided in Comparative Example 1 showed better performance in CO3 removal. 2- and Mg 2+ In its presence, its catalytic activity is significantly reduced, with removal rates of ciprofloxacin at only 55.6% and 46.1%, respectively. This difference indicates that nano-trap confinement not only enhances the stability of FeCo-NC active sites but also strengthens the effective utilization of reactive oxygen species in the confined microenvironment through local spatial constraint, reducing the ineffective consumption caused by free diffusion and non-selective quenching of reactive oxygen species, thereby significantly improving the anti-interference ability of the heterogeneous electro-Fenton system against coexisting components.
[0048] Test 5: The degradation process of ciprofloxacin by the heterogeneous electro-Fenton system with the composite electrode as the cathode is basically the same as that in Test 1. The difference is that the leaching concentration of metal ions from the composite electrode after the reaction was analyzed.
[0049] The results are as follows Figure 14 As shown, the unconfined FeCo-NC / graphite felt composite electrode provided in Comparative Example 1 exhibits higher metal ion leaching, with Co and Fe ion leaching concentrations of 0.49 mg / L and 0.19 mg / L, respectively. In contrast, the self-confined FeCo-NC / nano-trap graphite felt composite electrode showed Co and Fe ion leaching concentrations of only 0.13 mg / L and 0.02 mg / L, respectively, after the reaction. Confined modification significantly reduced metal ion leaching of the composite electrode and improved its stability and catalytic activity.
[0050] Test 6: The process of ciprofloxacin degradation in the heterogeneous electro-Fenton system with composite electrodes as cathodes is basically the same as in Test 1. The difference is that this test conducted seven cycles of experiments on the two composite cathodes provided in Example 1 and Comparative Example 1 to analyze their stability.
[0051] The results are as follows Figure 15As shown, the unconfined FeCo-NC / graphite felt composite electrode provided in Comparative Example 1 only achieved a ciprofloxacin removal rate of 43.0% after 7 cycles, while the composite cathode provided in Example 1 still achieved a ciprofloxacin removal rate of 90.5% after 7 cycles. Confined modification significantly improved the stability of the composite electrode.
[0052] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.
Claims
1. A method for preparing a self-confined FeCo-NC / nano-trap graphite felt composite electrode, characterized in that, Includes the following steps: Step 1: Clean and activate the graphite felt to obtain pretreated graphite felt; Step 2: Anodize the pretreated graphite felt; Step 3: Mix solution a and solution b to form FeCo-PBA precursor solution, and impregnate the graphite felt obtained by anodizing in step 2 into the FeCo-PBA precursor solution to obtain graphite felt loaded with FeCo-PBA precursor, wherein solution a is an aqueous solution containing iron source, cobalt source and polyvinylpyrrolidone, and solution b is an aqueous solution containing potassium cobalt cyanide. Step 4: The graphite felt loaded with FeCo-PBA precursor is calcined in two steps at different temperatures and atmospheres to make the graphite felt covered with nano-trap with a diameter of 20-40 nm, exhibiting a honeycomb structure, and the FeCo-PBA-derived catalyst particles are anchored in the nano-trap, thus obtaining a self-confined FeCo-NC / nano-trap graphite felt composite electrode.
2. The preparation method according to claim 1, characterized in that, The specific activation conditions described in step 1 include: Calcination at 300-500 ℃ for 2-4 h.
3. The preparation method according to claim 1, characterized in that, Step 2, which involves anodizing the pretreated graphite felt, specifically includes: The pretreated graphite felt was anoly oxidized in an electrolytic cell using ammonium salt solution as electrolyte; The concentration of the ammonium salt solution is 0.05-0.15 M, and the anodic oxidation current density is 4-6 mA / cm². 2 The anodizing time is 15-25 min; The ammonium salt in the ammonium salt solution is selected from at least one of ammonium dihydrogen phosphate, ammonium persulfate, and ammonium sulfate.
4. The preparation method according to claim 1, characterized in that; The iron source mentioned in step 3 is selected from at least one of ferrous chloride, ferrous sulfate, and ferrous nitrate; The cobalt source mentioned in step 3 is selected from at least one of cobalt chloride, cobalt sulfate, and cobalt nitrate; The average molecular weight of the polyvinylpyrrolidone mentioned in step 3 is 8000-24000 g / mol.
5. The preparation method according to claim 4, characterized in that: In terms of the molar amount of metal ions, the molar ratio of the iron source and the cobalt source in step 3 is 3:1-4; The total metal concentration of iron and cobalt sources in solution a is 1.5-15 mM, and the polyvinylpyrrolidone content is 6-60 g / L. Solution b is a potassium cobalt cyanide solution with a concentration of 1.0-10 mM; The molar ratio of potassium cobalt cyanide to the iron source is 1:1-1.
5.
6. The preparation method according to claim 1, characterized in that, The specific conditions for the two-step calcination described in step 4 include: Under air atmosphere, the calcination temperature is 350-450 ℃ and the calcination time is 30-60 min; Under a nitrogen atmosphere, the calcination temperature is 600-700 ℃ and the calcination time is 60-120 min.
7. The preparation method according to claim 6, characterized in that, The heating rate is 5-10 ℃ / min.
8. The self-confined FeCo-NC / nano-trap graphite felt composite electrode prepared by the method according to any one of claims 1-7.
9. The application of the composite electrode prepared by the method according to any one of claims 1-7 in the degradation of organic pollutants in a heterogeneous electro-Fenton system, characterized in that, The organic pollutants include at least one of ciprofloxacin, phenol, catechol, bisphenol A, sulfadiazine, and atenolol.
10. The application according to claim 9, characterized in that, A heterogeneous electro-Fenton oxidation system was constructed using the self-confined FeCo-NC / nano-trap graphite felt composite electrode as the cathode and a platinum sheet as the anode; a constant current mode was employed, with a current density of 1-6 mA / cm² based on the effective cathode area. 2 Air was used as the aeration gas, with an aeration rate of 0.2-0.8 L / min, an initial pH of 3-11, a 50-100 mM sodium sulfate aqueous solution as the electrolyte, a pollutant concentration of 5-20 mg / L, and a total solution volume of 100-500 mL.