Preparation method of bimetallic cathode and application of bimetallic cathode in reductive degradation of polyfluorinated compounds

Abstract

This invention provides a method for preparing a bimetallic cathode and its application in the reduction and degradation of polyfluorinated compounds, including the preparation of a hydrophilic carbon cloth electrode and an electrodeposition Cu source stock solution. The Pd source stock solution is prepared using ultrasonic-assisted dissolution. The hydrophilic carbon cloth electrode is used as the working electrode, a saturated silver chloride electrode as the reference electrode, and a platinum sheet electrode as the counter electrode, connected to an electrochemical workstation. Preparation... 5 mM Cu(NO3)2 and 0.5 M H2SO4 A mixed deposition solution was used to deposit Cu onto the surface of a hydrophilic carbon cloth electrode, resulting in a Cu-modified carbon cloth electrode. This was achieved through a substitution reaction. Pd0 Nanoparticles are loaded onto the surface of a Cu-modified carbon cloth electrode to obtain a bimetallic modified electrode. This invention allows for the direct in-situ synthesis of CuPd bimetals on a low-cost carbon substrate. The operation is simple, the bimetallic loading method consumes less energy, requires no additional chemical reagents, and achieves high degradation, defluorination, and dechlorination rates of chlorinated polyfluorinated compounds in the aquatic environment at relatively low voltage, thus achieving a good degradation effect.

Description

Technical Field

[0001] This invention relates to the fields of environmental protection and electrochemical technology, specifically to a method for preparing a bimetallic cathode and its application in the reduction and degradation of polyfluorinated compounds. Background Technology

[0002] Currently, the main technologies for removing PFAS from groundwater fall into three categories: physical removal, biodegradation, and chemical degradation. Physical removal primarily includes physical adsorption and membrane filtration. While these methods can achieve short-term enrichment, they merely transfer PFAS from the liquid phase to the solid phase without damaging the molecular structure, posing a risk of secondary pollution. Biodegradation offers mild conditions but is inefficient and time-consuming. Furthermore, the degradation of different types of PFAS depends on specific microbial communities, resulting in significant differences in degradation behavior and limiting its practical application. Chemical degradation mainly involves injecting remediation agents or introducing energy such as light, electricity, and heat to generate active substances, such as sulfate radicals and hydrated electrons, to redox PFAS. These active substances possess strong oxidizing or reducing properties, aiming to destroy the molecular structure of PFAS, transforming its high toxicity into low or even non-toxicity. Electrochemical technology offers advantages such as in-situ remediation, no need for additional reagents, and environmental friendliness. Because the fluorine atoms in PFAS molecules are strong electron-withdrawing groups with high electronegativity, they are more prone to reductive defluorination. Studies have found that the oxidation peak of PFAS appears at a potential of approximately +2.0 V, while the reduction peak appears at a potential of -1.0 V, proving that the reduction of PFAS is thermodynamically superior to oxidation.

[0003] Recent studies have demonstrated the feasibility of electroreductive defluorination. However, due to the high bond dissociation energy of the CF bonds in PFAS, common cathode materials (such as carbon and platinum) struggle to overcome this energy barrier. Increasing research focuses on modifying cathode materials to improve their defluorination performance. For example, introducing cations enhances the positive charge on the cathode surface, thereby promoting the enrichment of PFAS at the electrode interface and improving reductive defluorination performance. However, this system has limitations in defluorination. Research has concentrated on PFAS derivatives containing unsaturated structures such as C=C. For saturated PFAS, which are more common and persistent in the environment, the high bond energy of the CF bonds and the low electron cloud density of the carbon skeleton result in insufficient thermodynamic driving force for electroreductive defluorination, leading to low defluorination efficiency. Alternatively, the interaction between metals and fluorine can polarize and weaken the CF bonds to achieve defluorination. However, this technique relies on organic solvent systems and has a low defluorination rate. Furthermore, the intensification of the hydrogen evolution reaction (HER) in aqueous solutions further reduces the Faraday efficiency of defluorination.

[0004] In summary, there is a need for a cathode material that can be synthesized in situ using bimetallic materials. This material would enhance the activation of carbon-halogen bonds by utilizing the charge transfer characteristics between different metals, thereby achieving the reduction and degradation of chlorinated polyfluorinated compounds such as fluorochlorooctanoic acid (Cl4-PFOA) in an aquatic environment. Summary of the Invention

[0005] To overcome the problems existing in related technologies, the purpose of this invention is to provide a method for preparing a bimetallic cathode and its application in the reduction and degradation of polyfluorinated compounds. The cathode material prepared by the method can synthesize bimetals in situ, and enhance the activation of carbon-halogen bonds by utilizing the charge transfer characteristics between different metals, thereby achieving the reduction and degradation effect on chlorinated polyfluorinated compounds such as fluorochlorooctanoic acid (Cl4-PFOA) in an aqueous environment.

[0006] A method for preparing a bimetallic cathode, comprising: S1: Fabrication of hydrophilic carbon cloth electrode; S2: Prepare Cu source stock solution for electrodeposition by ultrasonic-assisted dissolution; S3: Pd source stock solution was prepared by ultrasonic-assisted dissolution; S4: Connect the hydrophilic carbon cloth electrode as the working electrode, the saturated silver chloride electrode as the reference electrode, and the platinum sheet electrode as the counter electrode to an electrochemical workstation. S5: Prepare a mixed deposition solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4, and deposit Cu on the surface of the hydrophilic carbon cloth electrode to obtain a Cu-modified carbon cloth electrode; S6: Pd 0 Nanoparticles are loaded onto the surface of the Cu-modified carbon cloth electrode via a displacement reaction to obtain a bimetallic modified electrode.

[0007] In a preferred embodiment of the present invention, the hydrophilic carbon cloth electrode is prepared in step S1 by cutting a rigid carbon cloth electrode into a rectangle of 1×1.5 cm, soaking the cut carbon cloth electrode in nitric acid for 12 h, taking it out, rinsing it with deionized water and anhydrous ethanol in sequence, and then air-drying it to obtain the hydrophilic carbon cloth electrode.

[0008] In a preferred embodiment of the present invention, the method for preparing the electrodeposition Cu source stock solution in step S2 is to weigh 1.208 g of copper nitrate trihydrate, make up to 10 mL in a volumetric flask, and dissolve it with ultrasonic assistance for 5 min to obtain 0.5 M Cu(NO3)2, and use Cu(NO3)2 as the Cu source stock solution.

[0009] In a preferred embodiment of the present invention, the method for preparing the Pd source stock solution in step S3 includes weighing 0.067 g of palladium nitrate dihydrate, making up to 50 mL in a brown volumetric flask, dissolving it with ultrasonic assistance for 5 min to prepare 5 mM Pd(NO3)2, and using Pd(NO3)2 as the Pd source stock solution.

[0010] In a preferred embodiment of the present invention, the method for preparing the mixed deposition solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4 in step S5 is to take 200 μL of 0.5 M Cu(NO3)2 stock solution and add the Cu(NO3)2 stock solution to 19.8 mL of deionized water containing 0.5 M H2SO4 to obtain the mixed deposition solution.

[0011] In a preferred embodiment of the present invention, the method for depositing Cu on the surface of the hydrophilic carbon cloth electrode in step S5 is to set the voltage of the working electrode to -1.8 V and deposit it for 300 s under a constant voltage.

[0012] In a preferred embodiment of the present invention, in step S6, Pd 0 Nanoparticles are loaded onto the surface of the Cu-modified carbon cloth electrode via a displacement reaction, comprising: The Cu-modified carbon cloth electrode was immersed in a Pd source stock solution; Under magnetic stirring conditions, Pd in ​​the solution is removed through a spontaneous displacement reaction. 2+ Restore to Pd 0 Nanoparticles are loaded onto the surface of a Cu-modified carbon cloth electrode.

[0013] In a preferred embodiment of the present invention, immersing the Cu-modified carbon cloth electrode in the Pd source stock solution includes: The Cu-modified carbon cloth electrode is held in place by an insulating clamp; The Cu-modified carbon cloth electrode was immersed in a 2 mM Pd(NO3)2 solution.

[0014] The application of bimetallic cathodes prepared by various methods in the reductive degradation of polyfluorinated compounds includes: An H-type two-chamber electrochemical reaction device was constructed, with the two chambers separated by a cation exchange membrane; Add 5 mg / L of chlorinated polyfluoride and 50 mM phosphate buffer to the cathode chamber, and add 50 mM PBS to the anode chamber; purge the cathode chamber with nitrogen gas for 40 min before the reaction begins. A bimetallic modified electrode was used as the working electrode, a silver chloride electrode as the reference electrode, and a platinum sheet electrode as the counter electrode. Connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation, start the electrochemical workstation, and degrade the chlorinated polyfluorinated compounds in the cathode chamber; place the reaction system in a 30°C constant temperature water bath, and keep the cathode chamber magnetically stirred at 300 rpm during the reaction time.

[0015] In a preferred embodiment of the present invention, the chlorinated polyfluorinated compound is Cl4-PFOA, and the cathode potential of the working electrode is set to -1.0 V, -1.2 V, -1.4 V or -1.6 V, respectively, and the degradation rate and defluorination rate of Cl4-PFOA are measured at different cathode potentials.

[0016] The beneficial effects of this invention are as follows: The method for preparing a bimetallic cathode provided by this invention includes preparing a hydrophilic carbon cloth electrode and preparing a Cu source stock solution for electrodeposition using ultrasonic-assisted dissolution. A Pd source stock solution is prepared using ultrasonic-assisted dissolution. The hydrophilic carbon cloth electrode is used as the working electrode, a saturated silver chloride electrode as the reference electrode, and a platinum sheet electrode as the counter electrode, connected to an electrochemical workstation. A mixed deposition solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4 is prepared, and Cu is deposited on the surface of the hydrophilic carbon cloth electrode to obtain a Cu-modified carbon cloth electrode. Pd... 0 Nanoparticles are loaded onto the surface of the Cu-modified carbon cloth electrode via a displacement reaction to obtain a bimetallic modified electrode. This invention allows for the direct in-situ synthesis of CuPd bimetals on a low-cost carbon substrate. The operation is simple, the bimetallic loading method consumes less energy, requires no additional chemical reagents, and achieves high degradation and defluorination rates of chlorinated polyfluorinated compounds in the aquatic environment at relatively low voltage, thus achieving a good degradation effect. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method for preparing the bimetallic cathode of the present invention; Figure 2 This is an enlarged view of the Cu-modified carbon cloth electrode of the present invention; Figure 3 This is an enlarged view of the bimetallic modified electrode prepared according to the present invention; Figure 4 This is a diagram showing the result of the simultaneous presence of Cu and Pd elements on the bimetallic modified electrode of this invention. Figure 5 This is a line graph showing the degradation rate and defluorination rate of Cl4-PFOA by different working electrodes of the present invention over time; Figure 6 This is a line graph showing the dechlorination rate of CC-CuPd on Cl4-PFOA over time when the voltage of the working electrode of this invention is -1.6 V; Figure 7The graph shows the degradation rate and defluorination rate of Cl4-PFOA under different degradation potentials according to the present invention. Detailed Implementation

[0018] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0019] Example 1: Preparation of bimetallic modified electrode like Figure 1 As shown, this embodiment provides a method for preparing a bimetallic cathode, including: S1: Fabrication of hydrophilic carbon cloth electrode; S2: Prepare Cu source stock solution for electrodeposition by ultrasonic-assisted dissolution; S3: Pd source stock solution was prepared by ultrasonic-assisted dissolution; S4: Connect the hydrophilic carbon cloth electrode as the working electrode, the saturated silver chloride electrode as the reference electrode, and the platinum sheet electrode as the counter electrode to an electrochemical workstation. S5: Prepare a mixed deposition solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4, and deposit Cu on the surface of the hydrophilic carbon cloth electrode to obtain a Cu-modified carbon cloth electrode; S6: Pd 0 Nanoparticles are loaded onto the surface of the Cu-modified carbon cloth electrode via a displacement reaction to obtain a bimetallic modified electrode.

[0020] First, the rigid carbon cloth electrode is cut into a 1×1.5 cm rectangle. In order to enhance the hydrophilicity of the carbon cloth surface and remove surface organic impurities, a hydrophilic treatment is performed by nitric acid oxidation. The specific operation is as follows: the cut carbon cloth is soaked in nitric acid for 12 h and then taken out. It is then rinsed repeatedly with a large amount of deionized water until neutral, and then rinsed three times with anhydrous ethanol to remove residual organic matter. Finally, it is air-dried to obtain a hydrophilic carbon cloth electrode (denoted as CC) for later use.

[0021] Weigh 1.208 g of copper nitrate trihydrate and dilute to 10 mL in a volumetric flask. Dissolve the solution using ultrasound for 5 min to prepare 0.5 M Cu(NO3)2 as a Cu electrodeposition source stock solution. Copper nitrate trihydrate has high solubility in water, and the key role of ultrasound-assisted dissolution is physical acceleration.

[0022] Weigh 0.067 g of palladium nitrate dihydrate and dilute to 50 mL in a brown volumetric flask. Dissolve the solution with ultrasonic assistance for 5 min to prepare 5 mM Pd(NO3)2 as a Pd source stock solution. Store the solution in a sealed container at 4°C for later use.

[0023] A three-electrode system was used for potentiostatic electrodeposition, with a hydrophilic carbon cloth electrode as the working electrode, fixed by a platinum electrode clamp to ensure good contact. A saturated silver chloride electrode was used as the reference electrode, and a platinum electrode (1×1 cm) was used as the counter electrode. All three electrodes were connected to an electrochemical workstation. 200 μL of 0.5 M Pd(NO3)2 stock solution was added to 19.8 mL of deionized water containing 0.5 M H2SO4 to prepare a mixed deposition solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4, which was then ultrasonically degassed for 10 min.

[0024] Subsequently, deposition was performed at a constant voltage of -1.8 V vs. Ag / AgCl for 300 s. During the deposition process, the carbon cloth surface gradually turned reddish-brown, indicating successful Cu deposition on the working electrode surface. The working electrode was removed, rinsed with deionized water, and air-dried to obtain a Cu-modified carbon cloth electrode (denoted as CC-Cu). The Cu-modified carbon cloth electrode after Cu deposition is shown below. Figure 2 As shown, Cu was successfully loaded onto carbon fiber.

[0025] The above electrode preparation scheme is applicable to a pollutant solution volume of 100 mL. The electrode size and the volume of the loaded solution can be modified as needed, while the concentration of the loaded solution remains unchanged.

[0026] A Cu-modified carbon cloth electrode (denoted as CC-Cu) was prepared by clamping it with insulating clips. The electrode was then completely immersed in a 2 mM Pd(NO3)2 solution (diluted from a stock solution) and magnetically stirred at 300 rpm for 20 minutes at 27 °C. The standard redox potential difference between copper (Cu) and palladium (Pd) is approximately 0.488 V to 0.493 V, with palladium having a more positive redox potential (+0.830 V) and copper a more negative redox potential (+0.337 V). Utilizing the redox potential difference between Cu and Pd, a spontaneous substitution reaction (Cu...) was conducted... 0 + Pd 2+ → Cu 2+ + Pd 0 ), to remove Pd from the solution 2+ Restore to Pd 0 Nanoparticles are loaded onto the surface of a CC-Cu electrode, Pd 0This represents zero-valent palladium. After the reaction is complete, the electrode is removed, rinsed with deionized water, and air-dried to obtain a bimetallic modified electrode (denoted as CC-CuPd). The bimetallic modified electrode is shown below. Figure 3 As shown, Cu-Pd substitution increases the electrode's specific surface area. Increasing the electrode's specific surface area has three main effects on the electrochemical degradation of chlorinated polyfluorinated compounds: improving degradation efficiency, enhancing reaction kinetics, and reducing energy consumption. Figure 4 As shown in the EDS energy spectrum, both Cu and Pd elements are present on the electrode surface, and the Pd element is evenly distributed, confirming that Pd was successfully loaded onto the electrode.

[0027] Example 2: Construction of an electrochemical reaction system An H-type two-chamber electrochemical reactor was constructed, with the two chambers separated by a cation exchange membrane (FKE-50) to prevent interference from anodic oxidation to the cathodic reduction reaction, while allowing proton migration to maintain charge balance. The effective volume of both the cathode and anode chambers was 100 mL. The cathode chamber contained 5 mg / L Cl₄-PFOA and 50 mM phosphate-buffered saline (PBS), while the anode chamber contained 50 mM PBS. Nitrogen gas was introduced into the cathode chamber for 40 min before the reaction began.

[0028] The bimetallic modified electrode CC-CuPd prepared in Example 1 was used as the working electrode (cathode), a platinum sheet electrode (1 cm × 1 cm) as the counter electrode (anode), and a silver chloride electrode as the reference electrode. The three electrodes were connected via an electrochemical workstation, ensuring that the cathode and anode surfaces were opposite each other and that the reference electrode was close to the cathode surface. The working electrode and the reference electrode formed a measurement circuit, through which no current flowed. The electrochemical workstation used this circuit to measure and control the potential of the working electrode relative to the reference electrode. The working electrode and the counter electrode formed a current circuit, achieving precise control of the electrochemical reaction by separating the paths of the measured potential and the conduction current.

[0029] Example 3: Degradation of Cl4-PFOA using a bimetallic modified electrode The electrochemical reaction system from Example 2 was placed in a 30°C constant temperature water bath. During the reaction time, the cathode chamber was magnetically stirred at 300 rpm to ensure uniform mass transfer and reduce concentration polarization. Potentially constant reduction degradation was performed at -1.6 V vs. Ag / AgCl to test its electroreductive degradation effect on Cl4-PFOA. At time points of 0, 1, 2, 4, 6, 8, 12, and 24 h after the start of the reaction, 2 mL of the reaction solution was transferred from the cathode chamber, filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane, and the concentration of Cl4-PFOA was detected using high-resolution liquid chromatography-tandem triple quadrupole mass spectrometry. The concentrations of fluoride and chloride ions generated during reductive dehalogenation were detected using ion chromatography.

[0030] Figure 5 This is a line graph showing the degradation rate and defluorination rate of Cl4-PFOA over time for different working electrodes at a voltage of -1.6 V. CC represents hydrophilic carbon paper without any modification; CC-Cu represents a modified carbon cloth electrode with only Cu electrodeposition; and CC-Pd represents a electrode simply suspended in Pd. 2+ The Pd-modified carbon cloth electrodes obtained by treating the solution for the corresponding time are all control groups; CC-CuPd is the bimetallic modified electrode prepared in this invention.

[0031] Depend on Figure 5 It was found that after 24 hours of reaction, the defluorination rate of Cl4-PFOA by the CC-CuPd bimetallic cathode reached 62.36%, which was twice that of the blank electrode (CC) at 31.28%. The defluorination effect of the metal-loaded cathode was not simply additive; the single-metal Cu loading (CC-Cu) may actually inhibit defluorination, resulting in the lowest defluorination rate of 26.04%. The defluorination rate of Pd-loaded cathode alone (CC-Pd) was 44.39%.

[0032] In the CuPd bimetallic compound, Pd has a higher electronegativity, and Cu will undergo interfacial electron transfer to Pd. Cu, as an electron donor metal, can form Cu... δ The + site is also the main adsorption site and active site center for carbon-halogen bond activation, and due to its weaker hydrogen evolution reaction reactivity, it may have higher defluorination selectivity. Pd has high electronegativity, acting as an electron acceptor metal, and is an excellent atomic hydrogen (H*) binding site, which may facilitate attack on the carbon-halogen bond to achieve reductive defluorination. The CuPd bimetallic design in this scheme can enhance the efficiency of hydrodefluorination while suppressing hydrogen evolution. δ The + sites primarily adsorb pollutants and lower the activation energy of carbon-halogen bonds, enabling electroreduction defluorination via direct electron transfer. Pd sites provide sufficient H*, increasing defluorination performance through indirect electron transfer. Through a CuPd bimetallic synergistic mechanism, both direct and indirect electron transfer are utilized to enhance electroreduction defluorination performance.

[0033] Cu exhibits significantly lower catalytic activity for the cracking of carbon-halogen bonds compared to noble metals, making it difficult to defluorinate via direct electron transfer. It is more prone to hydrogen evolution side reactions (poor hydrogen storage capacity). Furthermore, its negatively charged surface at the cathode potential creates electrostatic repulsion between Cu and negatively charged PFAS, hindering PFAS from approaching the electrode surface. The blank electrode CC, being an inert electrode, lacks strong hydrogen evolution reaction activity and possesses a large specific surface area, thus performing better than CC-Cu. Pd, a metal with strong hydrogen storage capacity, can stably provide H* for hydrodefluorination.

[0034] Figure 6The graph shows the dechlorination rate of CC-CuPd on Cl4-PFOA over time at a voltage of -1.6 V. The results indicate that the bimetallic cathode modified material described in this invention can achieve a dechlorination rate of nearly 90% after 24 h of electroreduction, demonstrating good reduction dechlorination performance.

[0035] To investigate the effect of cathode potential on the electrocatalytic reduction defluorination performance, electrocatalytic reduction defluorination experiments were conducted at different potentials following the same experimental procedure described above. The cathode potentials were set to -1.0 V, -1.2 V, -1.4 V, or -1.6 V (vs. Ag / AgCl), while other conditions remained constant. Results are referenced... Figure 7 It can be seen that as the degradation potential increases, i.e., the voltage difference between the working electrode and the reference electrode increases, the degradation rate and defluorination rate of Cl4-PFOA gradually increase. When the cathode potential, i.e. the degradation potential, is -1.6V, the degradation rate of Cl4-PFOA is close to 100%, and the defluorination rate is greater than 60%.

[0036] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0037] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made based on the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing a bimetallic cathode, characterized in that, include: S1: Fabrication of hydrophilic carbon cloth electrode; S2: Prepare Cu source stock solution for electrodeposition by ultrasonic-assisted dissolution; S3: Pd source stock solution was prepared by ultrasonic-assisted dissolution; S4: Connect the hydrophilic carbon cloth electrode as the working electrode, the saturated silver chloride electrode as the reference electrode, and the platinum sheet electrode as the counter electrode to an electrochemical workstation. S5: Prepare a mixed deposition solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4, and deposit Cu on the surface of the hydrophilic carbon cloth electrode to obtain a Cu-modified carbon cloth electrode; S6: Pd 0 Nanoparticles are loaded onto the surface of the Cu-modified carbon cloth electrode via a displacement reaction to obtain a bimetallic modified electrode.

2. The method for preparing a bimetallic cathode according to claim 1, characterized in that, In step S1, the hydrophilic carbon cloth electrode is prepared by cutting a rigid carbon cloth electrode into a rectangle of 1×1.5 cm, soaking the cut carbon cloth electrode in nitric acid for 12 h, taking it out, rinsing it with deionized water and anhydrous ethanol in sequence, and then air drying it naturally to obtain the hydrophilic carbon cloth electrode.

3. The method for preparing a bimetallic cathode according to claim 1, characterized in that, In step S2, the method for preparing the Cu source stock solution for electrodeposition is to weigh 1.208 g of copper nitrate trihydrate, make up to 10 mL in a volumetric flask, and dissolve it with ultrasonic assistance for 5 min to obtain 0.5 M Cu(NO3)2. The Cu(NO3)2 is used as the Cu source stock solution.

4. The method for preparing a bimetallic cathode according to claim 1, characterized in that, The method for preparing the Pd source stock solution in step S3 includes weighing 0.067 g of palladium nitrate dihydrate, making up to 50 mL in a brown volumetric flask, and dissolving it with ultrasonic assistance for 5 min to prepare 5 mM Pd(NO3)2, which is then used as the Pd source stock solution.

5. The method for preparing a bimetallic cathode according to claim 1, characterized in that, In step S5, the mixed sedimentation solution of 5 mM Cu(NO3)2 and 0.5 M H2SO4 is prepared by taking 200 μL of 0.5 M Cu(NO3)2 stock solution and adding it to 19.8 mL of deionized water containing 0.5 M H2SO4 to obtain the mixed sedimentation solution.

6. The method for preparing a bimetallic cathode according to claim 1, characterized in that, In step S5, Cu is deposited on the surface of the hydrophilic carbon cloth electrode by setting the voltage of the working electrode to -1.8 V and depositing for 300 s at a constant voltage.

7. The method for preparing a bimetallic cathode according to claim 1, characterized in that, In step S6, Pd 0 Nanoparticles are loaded onto the surface of the Cu-modified carbon cloth electrode via a displacement reaction, comprising: The Cu-modified carbon cloth electrode was immersed in the Pd source stock solution; Under magnetic stirring conditions, Pd in ​​the solution is removed through a spontaneous displacement reaction. 2+ Restore to Pd 0 Nanoparticles are loaded onto the surface of a Cu-modified carbon cloth electrode.

8. The method for preparing a bimetallic cathode according to claim 7, characterized in that, The step of immersing the Cu-modified carbon cloth electrode in the Pd source stock solution includes: The Cu-modified carbon cloth electrode is held in place by an insulating clamp; The Cu-modified carbon cloth electrode was immersed in a 2 mM Pd(NO3)2 solution.

9. The application of the bimetallic cathode prepared according to any one of claims 1-8 in the reductive degradation of polyfluorinated compounds, characterized in that, include: An H-type two-chamber electrochemical reaction device was constructed, with the two chambers separated by a cation exchange membrane; Add 5 mg / L of chlorinated polyfluoride and 50 mM phosphate buffer to the cathode chamber, and add 50 mM PBS to the anode chamber; purge the cathode chamber with nitrogen gas for 40 min before the reaction begins. A bimetallic modified electrode was used as the working electrode, a silver chloride electrode as the reference electrode, and a platinum sheet electrode as the counter electrode. Connect the working electrode, reference electrode, and counter electrode to the electrochemical workstation, start the electrochemical workstation, and degrade the chlorinated polyfluorinated compounds in the cathode chamber; place the reaction system in a 30°C constant temperature water bath, and keep the cathode chamber magnetically stirred at 300 rpm during the reaction time.

10. The application according to claim 9, characterized in that, The chlorinated polyfluorinated compound is Cl4-PFOA. The cathode potential of the working electrode is set to -1.0 V, -1.2 V, -1.4 V or -1.6 V, respectively, and the degradation rate and defluorination rate of Cl4-PFOA are measured at different cathode potentials.

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