A method for carbon dioxide and plastic waste utilization coupled electrolysis for membrane electrode assemblies

Abstract

The application discloses a carbon dioxide and plastic waste utilization coupling electrolysis method for a membrane electrode stack and belongs to the technical field of electrocatalytic materials and devices. The application synthesizes a nickel unit point / silver nanoparticle composite material by using a calcination method, loads the catalyst on a gas diffusion electrode, and uses the catalyst and a self-supporting iron hydroxide / manganese carbonate electrode for carbon dioxide reduction and plastic hydrolysate oxidation respectively, so that a carbon dioxide and plastic waste utilization coupling electrolysis system is constructed, and preparation of an industrial-grade current density of carbon monoxide and formic acid is realized. 2 In the membrane electrode device, the coupling system can realize an industrial-grade current density of 800 mA / cm 2 at a tank voltage of 2.4 V, and the faradic efficiencies of carbon monoxide and formic acid at the anode and the cathode are both kept above 95%. The electrode area is further enlarged to 10*10 cm 2 , and the membrane electrode stack is assembled into a membrane electrode stack which can be assembled into five electrodes, so that preparation of an ampere-grade current of carbon monoxide and formic acid is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of electrocatalytic materials and devices, and relates to a coupled electrolytic method for utilizing carbon dioxide and plastic waste in a membrane electrode stack. Specifically, it involves the oxidation of plastic hydrolysate to formic acid at the anode, the reduction of carbon dioxide to carbon monoxide at the cathode, and the assembly of the membrane electrode. Background Technology

[0002] Plastics, as a crucial industrial material, have become an essential component of modern life, with a global annual production exceeding 380 million tons. Polyethylene terephthalate (PET), a common polyester plastic, is widely used in food / beverage packaging, medical supplies, electronics, and polyester fibers. However, its natural decomposition rate is relatively slow, leading to severe environmental pollution. Therefore, effective strategies for degrading and recycling waste plastics are needed. Currently, technologies for recycling PET plastics include mechanical, biological, and chemical methods. Among these, the chemical route shows greater potential in upgrading the recycling of PET plastic waste. PET plastics can be effectively hydrolyzed into terephthalic acid and ethylene glycol monomers under alkaline conditions, and ethylene glycol can be further synthesized into desired chemicals through chemical oxidation. Furthermore, carbon dioxide, as one of the main greenhouse gases, can disrupt the ecological balance and cause a series of environmental problems if emitted excessively. As an abundant small carbon molecule, carbon dioxide can be further converted into higher-value chemicals through electrochemical processes. Therefore, a fully electrolytic system coupling carbon dioxide reduction and PET hydrolysate oxidation can realize the utilization of plastics and greenhouse gases / flue gas waste.

[0003] For the construction of co-electrolysis systems for the utilization of carbon dioxide and plastic waste, highly efficient anode and cathode electrocatalysts are essential. Single-site catalysts and single-atom catalysts are widely used in the catalysis field due to their high atom utilization and excellent catalytic performance. However, the tendency of single-metal-site catalysts to aggregate during long-term catalytic reactions, leading to decreased stability, is a major factor restricting their development. Furthermore, in the carbon dioxide reduction reaction, the excessive adsorption of carbon dioxide molecules by single-metal-site catalysts makes product desorption difficult, necessitating further catalyst regulation to balance adsorption and desorption. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention couples carbon dioxide reduction with PET hydrolysate oxidation, thereby achieving the utilization of carbon dioxide and plastic waste. For the cathode carbon dioxide reduction reaction, a composite material of nickel unit point / silver nanoparticles was synthesized via calcination. The charge structure was adjusted by regulating the amount of silver incorporated, and the synergistic effect of nickel and silver promoted carbon monoxide generation. For the anode, a water oxidation electrode (iron hydroxide / manganese carbonate self-supporting electrode) was used for the PET hydrolysate oxidation reaction, and the synergistic effect of iron and manganese promoted formic acid generation. A full-cell electrolysis system was formed by combining a gas diffusion electrode loaded with nickel unit point / silver nanoparticles and the iron hydroxide / manganese carbonate self-supporting electrode, achieving the synthesis of carbon monoxide and formic acid at industrial-grade current densities.

[0005] The purpose of this invention is to provide a coupled electrolysis method for the utilization of carbon dioxide and plastic waste in membrane electrode stacks, which mainly solves the problems of low catalytic activity, low current density, and poor stability in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a coupled electrolysis method for utilizing carbon dioxide and plastic waste in a membrane electrode stack, wherein a membrane electrode assembly is assembled using a nickel unit point / silver nanoparticle electrode as the cathode and an iron hydroxide / manganese carbonate self-supporting electrode as the anode, and electrolysis is performed; carbon dioxide is introduced into the cathode channel at a flow rate of 20~40 ml / min, and polyethylene terephthalate hydrolysate is introduced into the anode channel at a flow rate of 10~30 ml / min; an anion exchange membrane is provided between the cathode and the anode.

[0007] The preparation method of the nickel unit point / silver nanoparticle electrode includes the following steps:

[0008] S1. Place nickel nitrate, silver nitrate, and dicyandiamide in a test tube, add anhydrous ethanol, and ultrasonically disperse until uniform to obtain a mixture; the ratio of nickel nitrate: silver nitrate: dicyandiamide: anhydrous ethanol is (0.5-1.5) g: (0.2-0.6) g: (2-3) g: (1-3) mL;

[0009] S2. Pour the mixture into a quartz boat and place it in a tube furnace for calcination under an argon atmosphere; the argon flow rate is 10~30 ml / min; the tube furnace heating rate is 2~5 ℃ / min, the maximum temperature is 900~1100 ℃, and the holding time is 2~4 hours.

[0010] S3. After calcination, remove the powder and place it in a dilute sulfuric acid solution for acid washing;

[0011] S4. After acid washing, centrifuge with deionized water and anhydrous ethanol respectively;

[0012] S5. After centrifugation, the material obtained above is placed in a vacuum drying oven and dried overnight to obtain a nickel unit point / silver nanoparticle composite material.

[0013] S6. Weigh the above nickel unit point / silver nanoparticle composite material, ultrasonically disperse it in a mixture of Nafion and anhydrous ethanol, spray the suspension onto a gas diffusion electrode, and vacuum dry it to obtain a nickel unit point / silver nanoparticle electrode.

[0014] Furthermore, the concentration of the dilute sulfuric acid is 0.1~1 mol / L, the pickling time is 5~10 hours, and the pickling temperature is 50~100 ℃.

[0015] Furthermore, the particles in the nickel unit point / silver nanoparticle electrode exist in the morphology of hollow nanotubes.

[0016] Furthermore, the preparation method of the iron hydroxide / manganese carbonate self-supporting electrode (refer to the preparation method in CN112342563A):

[0017] S1. The nickel foam substrate was ultrasonically washed with dilute hydrochloric acid, anhydrous ethanol and ultrapure water respectively to obtain the ultrasonically washed nickel foam substrate.

[0018] S2. A mixed solution of manganese chloride and urea is added to a hydrothermal reactor with a polytetrafluoroethylene liner. The ultrasonically cleaned nickel foam substrate is immersed in the above solution and hydrothermally reacted at 120°C for 8-15 hours to obtain a nickel foam electrode loaded with manganese carbonate. The concentration of urea in the mixed solution is 0.1-0.2 mol / L and the concentration of manganese chloride solution is 0.01-0.05 mol / L.

[0019] S3. The nickel foam electrode loaded with manganese carbonate is electrodeposited in ferric nitrate solution using a three-electrode system to obtain a self-supporting electrode of ferric hydroxide / manganese carbonate-nickel foam. The deposition potential is -0.8V-1.5V and the deposition time is 100-600s.

[0020] The concentration of the ferric nitrate solution is 0.005-0.02 mol / L;

[0021] S4. Wash with ultrapure water to remove residual ions on the surface, and then air dry to obtain a self-supporting electrode of iron hydroxide / manganese carbonate-nickel foam.

[0022] Furthermore, a membrane electrode stack is assembled from multiple sets of the above-mentioned membrane electrode components.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention synthesizes a nickel-based single-point / silver nanoparticle composite material using a calcination method for research on the electrocatalytic reduction of carbon dioxide to carbon monoxide. A gas diffusion electrode loaded with nickel-based single-point / silver nanoparticles and a self-supporting iron hydroxide / manganese carbonate electrode form a dual-electrode configuration for constructing a carbon dioxide reduction-coupled PET hydrolysate oxidation full electrolytic cell. In the membrane electrode device, at a cell voltage of 2.4 V, this coupling system can achieve 800 mA / cm². 2 The industrial-grade current density and the Faraday efficiency of carbon monoxide and formic acid at both the anode and cathode remain above 95%. This excellent catalytic performance and stability are mainly attributed to the synergistic effect of nickel-silver at the cathode and the synergistic effect of iron-manganese at the anode.

[0025] (1) The nickel single-point / silver nanoparticle catalyst prepared in this invention has better catalytic activity and stability than the nickel single-point catalyst.

[0026] (2) The strategy of replacing water oxidation with anode PET hydrolysate oxidation in this invention reduces the tank pressure of the system and realizes the co-production of anode and cathode chemicals.

[0027] (3) The present invention uses a carbon dioxide reduction coupled with PET hydrolysate oxidation system for the assembly of large-area membrane electrode stacks, realizing the synthesis of carbon monoxide and formic acid with industrial-grade current density. Attached Figure Description

[0028] Figure 1 Linear voltammetry, impedance diagram, electrochemical active surface area diagram, and Tafel slope diagram for bismuth / bismuth oxide heterojunction electrodes.

[0029] Figure 2 Stability test results are shown when the cathode is a nickel unit point or nickel unit point / silver nanoparticle 2 gas diffusion electrode and the anode is an iron hydroxide / manganese carbonate self-supporting electrode.

[0030] Figure 3 The cyclic voltammetry curves of various catalysts at the cathode with different scan rates at non-Radida potentials of -0.1 to 0 V are shown.

[0031] Figure 4 The impedance fitting diagrams for each catalyst at the cathode are shown.

[0032] Figure 5 The images show the X-ray diffraction patterns of the various catalysts at the cathode.

[0033] Figure 6 Aberration-corrected electron microscopy images of nickel unit points and nickel unit points / silver nanoparticles 2.

[0034] Figure 7 Scanning electron microscope (SEM) images of nickel unit dots and nickel unit dots / silver nanoparticles 2.

[0035] Figure 8 The X-ray photoelectron spectra of each catalyst element are shown.

[0036] Figure 9 The specific surface area of ​​each catalyst was measured.

[0037] Figure 10 Raman spectral characterization of each catalyst.

[0038] Figure 11 This is a test of the adsorption of hydroxide ions by various catalysts.

[0039] Figure 12 Carbon dioxide adsorption-desorption tests were performed on each catalyst.

[0040] Figure 13 Carbon monoxide adsorption-desorption tests were performed on various catalysts.

[0041] Figure 14 10*10 cm 2 Gas diffusion electrode assembly and test diagram.

[0042] Figure 15 Five 10*10 cm pieces 2 A membrane electrode stack consisting of gas diffusion electrodes and a test diagram. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0044] A coupled electrolysis method for utilizing carbon dioxide and plastic waste in a membrane electrode stack includes the following steps:

[0045] S1. Place nickel nitrate, silver nitrate, and dicyandiamide in a test tube, add anhydrous ethanol dropwise, and disperse evenly by ultrasonication; the amount of nickel nitrate added is 0~1 g, the amount of silver nitrate added is 0~0.6 g, the amount of dicyandiamide added is 2~3 g, and the amount of anhydrous ethanol added is 1~3 ml.

[0046] S2. Pour the mixture obtained in (S1) into a quartz boat and place it in a tube furnace for calcination under an argon atmosphere; the argon flow rate is 10~30 ml / min; the heating rate of the tube furnace is 2~5 ℃ / min, the maximum temperature is 900~1100℃, and the holding time is 2~4 hours.

[0047] S3. After calcination, the powder is removed and placed in a dilute sulfuric acid solution for acid washing; the concentration of the dilute sulfuric acid is 0.1~1 mol / L, the acid washing time is 5~10 hours, and the acid washing temperature is 50~100 ℃.

[0048] S4. After acid washing, centrifuge and wash with deionized water and anhydrous ethanol respectively.

[0049] S5. After centrifugation, the material obtained above is placed in a vacuum drying oven and dried overnight to obtain a nickel unit point / silver nanoparticle composite material.

[0050] S6. Weigh the above nickel unit point / silver nanoparticle composite material, ultrasonically disperse it in a mixture of Nafion and anhydrous ethanol, spray the suspension onto the gas diffusion electrode, and vacuum dry it to obtain the nickel unit point / silver nanoparticle gas diffusion electrode.

[0051] A nickel unit point / silver nanoparticle gas diffusion electrode and an iron hydroxide / manganese carbonate self-supporting electrode were used as the anode and cathode to form a dual electrode system. Carbon dioxide was introduced into the cathode at a flow rate of 20-40 ml / min, and PET hydrolysate was introduced into the anode at a flow rate of 10-30 ml / min. The anode and cathode were separated by an anion exchange membrane, and the tests were conducted on an electrochemical workstation and a DC power supply.

[0052] The specific implementation method is as follows:

[0053] Examples 1-4

[0054] The specific steps for preparing the nickel unit point / silver nanoparticle composite material are as follows: 1 g of nickel nitrate, 0-0.4 g of silver nitrate, and 2.9 g of dicyandiamide are placed in a test tube, and 2 ml of anhydrous ethanol is added dropwise. The mixture is then ultrasonically dispersed until homogeneous. The mixture is then poured into a quartz boat and placed in a tube furnace for calcination under an argon atmosphere at a flow rate of 20 ml / min. The heating rate of the tube furnace is 3 °C / min, reaching a maximum temperature of 100 °C, and holding for 3.5 hours. After calcination, the powder is removed and acid-washed in a dilute sulfuric acid solution with a concentration of 0.5 mol / L for 8 hours at a temperature of 80 °C. After acid washing, the powder is centrifuged and washed three times with deionized water and anhydrous ethanol. Finally, the powder is placed in a vacuum drying oven and dried overnight at 60 °C. The amount of silver nitrate added was 0, 0.2, 0.3, and 0.4 g, and the resulting catalyst materials were nickel unit dots (Example 1), nickel unit dots / silver nanoparticles 1 (Example 2), nickel unit dots / silver nanoparticles 2 (Example 3), and nickel unit dots / silver nanoparticles 3 (Example 4), respectively. The catalysts were characterized using a series of instruments including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy.

[0055] Weigh 25 mg of the above catalyst and ultrasonically disperse it in 2.25 ml of anhydrous ethanol and 0.25 ml of 5% Nafion solution. Take a measured amount of the catalyst dispersion and spray it onto a gas diffusion electrode with a loading of 0.5 mg / cm². 2 .

[0056] Preparation method of ferric hydroxide / manganese carbonate self-supporting electrode (Publication No.: CN112342563A): A nickel foam substrate was ultrasonically washed for 20 minutes each with dilute hydrochloric acid, anhydrous ethanol, and ultrapure water to remove residual oxides and organic impurities. Then, 40 ml of a mixed aqueous solution of manganese chloride and urea was added to a stainless steel hydrothermal reactor, where the concentration of manganese chloride solution was 0.025 mol / L and the concentration of urea solution was 0.125 mol / L. The nickel foam was immersed in the solution for a hydrothermal reaction at 120℃ for 11 h. Then, electrodeposition was performed in a 0.01 mol / L ferric nitrate solution using a three-electrode system at a deposition potential of -1 V (vs Ag / AgCl electrode) for 300 s. The resulting ferric hydroxide / manganese carbonate-nickel foam self-supporting electrode was obtained.

[0057] A membrane electrode assembly was constructed using a nickel unit point / silver nanoparticle electrode as the cathode and an iron hydroxide / manganese carbonate self-supporting electrode as the anode. Both the cathode and anode areas were 2*2 cm². 2 Carbon dioxide was introduced into the cathode at a flow rate of 30 ml / min, and PET hydrolysate was introduced into the anode at a flow rate of 20 ml / min. The anode and cathode were separated by an anion exchange membrane, and the test was conducted on an electrochemical workstation and a DC power supply.

[0058] like Figure 1 As shown in Figure ab, the membrane electrode assembly underwent linear voltammetry testing in the voltage range of 0–3 V. It can be seen that the nickel unit point / silver nanoparticle 2 gas diffusion electrode exhibits optimal catalytic performance as the cathode. Figure 1 In the figure, c and 1e represent the potentiostatic electrolysis diagrams of nickel unit point and nickel unit point / silver nanoparticle 2 within the range of 1.9~2.4 V, respectively, and quantitative analysis and calculations were performed on the anode and cathode products, such as... Figure 1 Figures d and 1f show the Faradaic efficiencies of the cathode and anode products when the cathode is a single nickel point and when the cathode is composed of two nickel-unit points and two silver nanoparticles, respectively. The Faradaic efficiency of carbon monoxide (CMOS) for the nickel-unit point / silver nanoparticle 2 cathode is above 95%, reaching a maximum of 98% at 2.2 V. At 2.4 V, the CMOS current density reaches 800 mA / cm². 2 The above demonstrates excellent selectivity and industrial-grade current density. In contrast, the highest Faradaic efficiency for carbon monoxide produced by the nickel-based catalyst is only 83% within the 1.9–2.4 V voltage range. The Faradaic efficiency for formic acid produced by the ferric hydroxide / manganese carbonate self-supported electrode remains above 95% within the 1.9–2.4 V voltage range. This superior catalytic activity is primarily attributed to the synergistic effects of nickel and silver, and iron and manganese.

[0059] When the cathode is a nickel unit point / silver nanoparticle gas diffusion electrode, the current density remains stable for over 100 hours at 2.2 V, and the Faradaic efficiencies of carbon monoxide and formic acid at both the anode and cathode do not decrease. At the same voltage, when the cathode is a nickel unit point gas diffusion electrode, the Faradaic efficiency of carbon monoxide at the cathode decreases significantly after more than 20 hours. This demonstrates that the introduction of silver nanoparticles can improve the stability of the catalyst.

[0060] Figure 3 The cyclic voltammetry curves of various catalysts at different scan rates within the non-Radida potential range of -0.1 to 0 V are shown for calculating the double-layer capacitance. Figure 3 In the figure, e represents the bilayer capacitance value of each catalyst, with nickel per unit point / silver nanoparticle 2 exhibiting the highest bilayer capacitance value of 9.2 mF / cm². -2 A higher bilayer capacitance value indicates that it has a higher electrochemical active area.

[0061] Figure 4 The impedance fitting plots for each catalyst at the cathode show that the nickel unit point / silver nanoparticle 2 has the smallest semicircular diameter, indicating that it has the fastest charge transport rate.

[0062] Figure 5 The images show the X-ray diffraction patterns of the various catalysts in the cathode. The nickel unit point mainly represents the diffraction peaks of metallic nickel, while the nickel unit point / silver nanoparticle mainly represents the diffraction peaks of metallic silver.

[0063] Figure 6 The aberration-corrected electron micrographs of nickel unit sites and nickel unit sites / silver nanoparticles 2 show uniformly distributed single metal sites. Combined with the fact that no nickel diffraction peaks were observed in the X-ray diffraction pattern of nickel unit sites / silver nanoparticles, it is proven that metallic nickel is distributed in unit sites.

[0064] Figure 7 The images show scanning electron microscope (SEM) images of nickel unit dots and nickel unit dots / silver nanoparticles 2. It is observed that the nickel unit dots have a nanotube morphology, while the nickel unit dots / silver nanoparticles 2 have a nanotube and nanoparticle morphology.

[0065] Figure 8 The X-ray photoelectron spectra of each catalyst element are shown below. Figure 8 In the spectrum where b represents nitrogen, peaks of pyridine nitrogen, metal-nitrogen, pyrrole nitrogen, and graphitic nitrogen were observed, which also confirms that the existence state of the nickel unit point is nickel-nitrogen-carbon coordination. Figure 8 In the spectrum of nickel (c), it can be observed that after silver doping, the characteristic peaks of nickel shift to areas with lower binding energies, indicating that nickel in the nickel unit point / silver nanoparticle 2 is in a charge-enriched state, confirming the synergistic effect of nickel and silver.

[0066] Figure 9For the specific surface area test of each catalyst, the nickel unit point / silver nanoparticle 2 has the largest specific surface area of ​​169.2.

[0067] Figure 10 For Raman spectral characterization of each catalyst, the adsorption bands (I0) were compared by integration. D ) and graphite belt (I G The ratio of nickel unit points to silver nanoparticles 2 has the largest I. D / I G The value indicates that it has larger carbon defects inside. Carbon defects are conducive to more stable anchoring of single-atom sites.

[0068] Figure 11 To test the adsorption of hydroxide ions by various catalysts, the adsorption capacity for carbon dioxide reduction intermediates was evaluated by simulating hydroxide adsorption. As shown in the figure, nickel unit point / silver nanoparticle 2 has a more negative hydroxide adsorption potential, thus suggesting that it has a better adsorption capacity for carbon dioxide reduction intermediates.

[0069] Figure 12 For the carbon dioxide adsorption and desorption tests of various catalysts, the highest desorption temperature of nickel unit point / silver nanoparticle 2 indicates that it has the strongest carbon dioxide adsorption capacity, and at the same time proves that the combination of nickel and silver improves the catalyst's adsorption capacity for carbon dioxide.

[0070] Figure 13 For the carbon monoxide adsorption and desorption tests of various catalysts, the strongest desorption temperature and peak intensity per unit point for nickel indicate that its desorption capacity for carbon monoxide is the weakest. This is combined with the previous stability tests per unit point for nickel. Figure 2 (a) It is speculated that the reduced activity of nickel single-site catalysts may be due to deactivation caused by carbon monoxide poisoning. Silver nanoparticles and nickel single-sites, on the other hand, are beneficial for enhancing carbon monoxide desorption, improving catalyst stability, and preventing carbon monoxide poisoning.

[0071] Example 5

[0072] The gas diffusion electrode was enlarged to 10*10 cm. 2 The iron hydroxide / manganese carbonate self-supporting electrode was also enlarged to 10*10 cm. 2 Used in membrane electrode devices. Figure 14 10*10 cm 2 The gas diffusion electrode assembly and test diagram were used to compare the currents of carbon dioxide reduction coupled with water oxidation and plastic hydrolysate oxidation by applying different voltages. Figure 14 As can be seen in Figure c, the carbon dioxide reduction coupled plastic hydrolysate oxidation exhibits a higher current. At a voltage of 3.8 V, the current of the carbon dioxide reduction coupled plastic hydrolysate oxide film electrode assembly reaches 51.9 A, while the carbon monoxide and formic acid Faradaic efficiencies remain above 80%.

[0073] Example 6

[0074] Five 10*10 cm pieces 2 A gas diffusion electrode and a self-supporting iron hydroxide / manganese carbonate electrode are assembled into a membrane electrode stack. Figure 15 Five 10*10 cm pieces 2 The membrane electrode stack, composed of gas diffusion electrodes, and its test diagram show that at a total voltage of 11V, the average voltage per electrode is 2.2V, the total current of the stack reaches approximately 30A, and it can remain stable for over 30 hours. The carbon monoxide Faraday efficiency at the cathode remains around 80%, and the formic acid Faraday efficiency at the anode remains around 90%.

[0075] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any changes made based on the design principles of the present invention, or any non-creative modifications made thereon, shall fall within the scope of protection of the present invention.

Claims

1. A coupled electrolysis method for utilizing carbon dioxide and plastic waste in a membrane electrode stack, characterized in that, A membrane electrode assembly was assembled using a nickel unit point / silver nanoparticle electrode as the cathode and an iron hydroxide / manganese carbonate self-supporting electrode as the anode, and then electrolyzed. Carbon dioxide was introduced into the cathode channel at a flow rate of 20-40 ml / min, and polyethylene terephthalate hydrolysate was introduced into the anode channel at a flow rate of 10-30 ml / min. An anion exchange membrane was placed between the cathode and the anode. The preparation method of the nickel unit point / silver nanoparticle electrode includes the following steps: S1. Place nickel nitrate, silver nitrate, and dicyandiamide in a test tube, add anhydrous ethanol, and ultrasonically disperse until uniform to obtain a mixture; the ratio of nickel nitrate: silver nitrate: dicyandiamide: anhydrous ethanol is (0.5-1.5) g: (0.2-0.6) g: (2-3) g: (1-3) mL; S2. Pour the mixture into a quartz boat and place it in a tube furnace for calcination under an argon atmosphere; the argon flow rate is 10~30 ml / min; the tube furnace heating rate is 2~5 ℃ / min, the maximum temperature is 900~1100 ℃, and the holding time is 2~4 hours. S3. After calcination, remove the powder and place it in a dilute sulfuric acid solution for acid washing; S4. After acid washing, add deionized water and anhydrous ethanol respectively and centrifuge to wash. S5. After centrifugation, the material obtained above is placed in a vacuum drying oven and dried overnight to obtain a nickel unit point / silver nanoparticle composite material. S6. The above nickel unit point / silver nanoparticle composite material is ultrasonically dispersed in a mixture of Nafion and anhydrous ethanol. The suspension is sprayed onto a gas diffusion electrode and vacuum dried to obtain a nickel unit point / silver nanoparticle electrode.

2. The method for coupled electrolysis of carbon dioxide and plastic waste for membrane electrode stacks according to claim 1, characterized in that: The concentration of the dilute sulfuric acid solution is 0.1~1 mol / L, the pickling time is 5~10 hours, and the pickling temperature is 50~100 ℃.

3. The method for coupled electrolysis of carbon dioxide and plastic waste for membrane electrode stacks according to claim 1, characterized in that: The nickel unit point / silver nanoparticle electrode contains particles that exist in the morphology of hollow nanotubes.

4. The method for coupled electrolysis of carbon dioxide and plastic waste for membrane electrode stacks according to claim 1, characterized in that, The method for preparing the iron hydroxide / manganese carbonate self-supporting electrode: S1. The nickel foam substrate was ultrasonically washed with dilute hydrochloric acid, anhydrous ethanol and ultrapure water respectively to obtain the ultrasonically washed nickel foam substrate. S2. A mixed solution of manganese chloride and urea is added to a hydrothermal reactor with a polytetrafluoroethylene liner. The ultrasonically cleaned nickel foam substrate is immersed in the above solution and hydrothermally reacted at 120°C for 8-15 hours to obtain a nickel foam electrode loaded with manganese carbonate. The concentration of urea in the mixed solution is 0.1-0.2 mol / L and the concentration of manganese chloride solution is 0.01-0.05 mol / L. S3. Electrodeposition of the manganese carbonate-loaded nickel foam electrode in ferric nitrate solution using a three-electrode system yields a self-supporting ferric hydroxide / manganese carbonate-nickel foam electrode with a deposition potential of -0.8V to 1.5V and a deposition time of 100 to 600s. The concentration of the ferric nitrate solution is 0.005-0.02 mol / L; S4. Wash with ultrapure water to remove residual ions on the surface, and then air dry to obtain a self-supporting electrode of iron hydroxide / manganese carbonate-nickel foam.

5. A membrane electrode stack, characterized in that: It is assembled using multiple membrane electrode assemblies as described in claim 1.

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