Eluent for membrane electrode in waste fuel cell, preparation method and application method
By effectively separating the catalyst layer and proton exchange membrane in spent fuel cells using a composite solvent system, the problems of low separation efficiency and membrane damage in existing technologies are solved, achieving efficient separation and protection of the proton exchange membrane.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU LONGPAN HYDROGEN ENERGY TECH CO LTD
- Filing Date
- 2026-01-28
- Publication Date
- 2026-05-05
AI Technical Summary
Existing technologies struggle to efficiently separate the catalyst layer from the proton exchange membrane in spent fuel cells, and the proton exchange membrane is easily damaged.
A composite solvent system is adopted, including solvent A composed of mixed alcohol and water, and solvent B composed of one or more of dichloromethane, trichloromethane, and hexane. Combined with reducing agents such as potassium bromide, potassium iodide, and sodium bromide, and decomposing agents such as acetone, ethyl acetate, and toluene, a new eluent is formed to separate the catalyst layer from the proton exchange membrane.
It achieves efficient separation of the catalyst layer from the proton exchange membrane with an elution rate of over 99.5%, while protecting the proton exchange membrane from damage and ensuring its reuse.
Smart Images
Figure CN121983607A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst separation and recovery in battery MEAs, and particularly relates to an eluent, preparation method and application method for membrane electrodes in spent fuel cells. Background Technology
[0002] The membrane electrode assembly (MEA) in a proton exchange membrane fuel cell (PEMFC) typically consists of seven layers hot-pressed together: an anode diffusion layer, an anode porous carbon layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, a cathode porous carbon layer, and a cathode diffusion layer. The catalyst layer is composed of a platinum-carbon catalyst (or one with added iridium oxide) and a solid polymer electrolyte. After operating within the fuel cell for a certain period, the MEA may become unusable due to external contamination or catalyst buildup. However, the physicochemical properties of precious metals such as platinum and iridium in the catalyst layer of the spent fuel cell remain unchanged; only the catalytic activity decreases. Therefore, the catalyst and proton exchange membrane can be separated to recover the precious metals from both.
[0003] To achieve better separation of the membrane and catalyst layer, the applicant first studied an eluent for separating the PTFE layer and catalyst of spent fuel cells. This eluent is a mixed system composed of a solvent, a reducing agent, and a decomposing agent. The solvent is a mixed solution of anhydrous ethanol and ethylene glycol. In preparation, anhydrous ethanol and ethylene glycol are first mixed to obtain the solvent; then, a reducing agent (e.g., potassium bromide) and a decomposing agent (e.g., toluene) are added to the solvent to obtain the eluent. In application, the spent fuel cell PTFE layer (with a platinum content of 0.6%) needs to be pre-crushed before being added to the eluent. The mixture is stirred and eluted. After elution, the mixture is filtered through a sieve to obtain a slurry containing platinum-carbon catalyst and the eluted spent fuel cell PTFE layer. The eluted PTFE layer is white and has virtually no platinum-carbon residue. The eluted PTFE layer also shows no damage or corrosion, indicating good elution performance. The measured elution rate is 99.7%.
[0004] However, in the above-mentioned scheme, the eluent targets a single layer of PTFE, and the catalyst is directly coated onto the PTFE, which is a well-known semi-finished membrane electrode in the art. Furthermore, PTFE itself has strong resistance to acids, alkalis, and corrosion, so the eluent itself has little impact on it.
[0005] For membrane electrodes, which are finished membranes composed of proton exchange membranes, catalyst layers, carbon paper, and adhesives, firstly, their structure is complex and uses a variety of materials, making it difficult to achieve high-efficiency elution with previously developed eluents; secondly, the membrane electrodes use proton exchange membranes, the main material of which is perfluorosulfonic acid membranes. These membranes have weak resistance to acids, alkalis, and corrosion, and are prone to damage during elution, thus causing membrane damage. Therefore, it is necessary to pay attention to protecting these membranes during the elution process.
[0006] Based on this, a new type of eluent was designed, which not only achieves the separation and elution of the catalyst layer, carbon paper and proton exchange membrane on the finished membrane electrode with more complex composition, but also protects the proton exchange membrane itself and prevents unnecessary damage during the elution process. Summary of the Invention
[0007] Purpose of the invention: The present invention provides an eluent, its preparation method, and its application method that can effectively elute and separate the catalyst layer and the proton exchange membrane in the membrane electrode while avoiding damage to the proton exchange membrane itself.
[0008] Technical solution: The present invention is used as an eluent for membrane electrode in spent fuel cells. The eluent comprises a reducing agent, a decomposing agent, and a dissolving agent in a volume ratio of (1-4):2:(6-70).
[0009] The solvent comprises solvent A and solvent B in a volume ratio of (5-9):(1-4); wherein solvent A comprises a mixture of alcohol and water in a volume ratio of 1:(1-5), and solvent B is one or more of dichloromethane, trichloromethane, and hexane;
[0010] The reducing agent is one or more of potassium bromide, potassium iodide, sodium bromide, or sodium borohydride;
[0011] The decomposing agent is one or more of acetone, ethyl acetate, toluene, and N,N-dimethylformamide.
[0012] Furthermore, the eluent may be a mixture of two or more of ethanol, methanol, isopropanol, glycerol, or ethylene glycol. Preferably, the mixture may be ethanol and ethylene glycol in a volume ratio of (2-6):1. More preferably, the mixture may be ethanol and ethylene glycol in a volume ratio of (2.5-3):1.
[0013] Preferably, the solvent B used in the eluent can be dichloromethane and hexane in a volume ratio of (2-3):(1-6).
[0014] The method for preparing the above-mentioned eluent according to the present invention includes the following steps:
[0015] (1) Add solvent B to solvent A by volume ratio, stir and mix evenly to obtain a mixture;
[0016] (2) Add the reducing agent and the decomposing agent to the mixture in step (1) according to the volume ratio, and stir to mix evenly to obtain the eluent.
[0017] The application method of the above-mentioned eluent of the present invention includes the following steps: adding the membrane electrode of the waste fuel cell to the eluent at a mass ratio of 1:(5-15), eluting at 30-60℃ for 4-6 hours, and separating by filtration to obtain catalyst slurry and proton exchange membrane respectively.
[0018] Furthermore, after obtaining the above-mentioned catalyst slurry, the slurry can be concentrated at 90-100℃ to a solid content >90%, and then calcined at 800-900℃ for 6-8 hours to recover the catalyst metal material.
[0019] Beneficial effects: Compared with the prior art, the significant advantages of this invention are as follows: This eluent, based on the existing eluent composed of a decomposer, a reducing agent, and a solvent, uses a composite solvent, namely, solvent A composed of a mixed alcohol and water, and solvent B selected from one or more of dichloromethane, trichloromethane, and hexane, as both decomposers and reducing agents to form a new eluent system. When this system eludes and separates the membrane electrode assembly (MEA) in spent fuel cells, it can not only completely separate the carbon paper, catalyst layer, proton exchange membrane, and other materials from each other, achieving an elution rate of over 99.5%, but also ensure that the proton exchange membrane can still be used after washing and low-temperature drying, avoiding damage to the membrane caused by the eluent itself, and achieving effective washing while protecting the membrane. Attached Figure Description
[0020] Figure 1 This is a physical image of the fuel cell MEA in Embodiment 1 of the present invention;
[0021] Figure 2 This is a photograph of the fuel cell MEA after elution in Example 1 of the present invention;
[0022] Figure 3 This is a photograph of the fuel cell MEA after elution in Comparative Example 1-1 of the present invention;
[0023] Figure 4 These are actual images of the fuel cell MEA after elution in Comparative Examples 1-2 of this invention;
[0024] Figure 5 This is a physical image of the fuel cell MEA in Embodiment 2 of the present invention;
[0025] Figure 6 This is a photograph of the fuel cell MEA after elution in Example 2 of the present invention;
[0026] Figure 7 This is a physical diagram of the fuel cell MEA in Comparative Example 2-1 of the present invention;
[0027] Figure 8 This is a photograph of the fuel cell MEA after elution in Comparative Example 2-2 of the present invention. Detailed Implementation
[0028] The technical solution of the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.
[0029] It should be noted that in the waste fuel cell MEA targeted in the following embodiments and comparative examples of the present invention, the proton exchange membrane material is a perfluorosulfonic acid membrane (a known membrane), and the catalyst is a platinum-carbon catalyst (a known catalyst).
[0030] Furthermore, the eluent prepared in the embodiments and comparative examples of the present invention can be increased in the same proportion to meet the quality requirements of the MEA of the spent fuel cell during elution.
[0031] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available, as detailed in Table 1 below.
[0032] Table 1 Raw Material Information Table
[0033]
[0034] Example 1
[0035] The eluent in Example 1 comprises sodium borohydride (a reducing agent), acetone (a decomposing agent), and a solvent in a volume ratio of 4:2:6. The solvent comprises solvent A and solvent B in a volume ratio of 5:1.
[0036] Solvent A consists of a 1:1 volume ratio of mixed alcohol and water. The mixed alcohol is composed of anhydrous ethanol and ethylene glycol in a 4:1 volume ratio. Solvent B is composed of a 1:3 volume ratio of dichloromethane and hexane.
[0037] The preparation method of the eluent in Example 1 includes the following steps:
[0038] (1) Mix 800ml of anhydrous ethanol and 200ml of ethylene glycol, and then mix with 1000ml of water to form a mixed alcohol solution A;
[0039] (2) Mix 100ml of dichloromethane and 300ml of hexane to form solvent B;
[0040] (3) Add solvent B to solvent A according to the volume ratio and mix evenly to obtain the solvent;
[0041] (4) Mix 150ml sodium borohydride and 75ml acetone by volume, add to the solvent, and stir until homogeneous to obtain the eluent.
[0042] The application method of the eluent in Example 1 includes the following steps: 1.5 kg of waste fuel cell MEA is added to 15 kg of eluent, and the mixture is stirred at 40°C for 4 hours at a stirring rate of 100 rpm to obtain a slurry containing platinum carbon catalyst and a proton exchange membrane after elution.
[0043] Subsequently, the platinum-containing carbon catalyst slurry can be concentrated at 90°C to a solid content greater than 95%, and then subjected to pyrolysis at 800°C for 6 hours to extract the precious metal, ultimately obtaining the recovered platinum. The proton exchange membrane can be recycled after washing with ultrapure water and drying at low temperature.
[0044] In Example 1, the elution rate was measured to be over 99.8%. The elution rate was tested by measuring the percentage of the area washed off the membrane electrode after elution relative to the total area. In this scheme, the Fengyun ScanKing software was used to calculate the residual area of the membrane electrode on the image.
[0045] The spent fuel cell MEA used in Example 1 is as follows: Figure 1 As shown, the adhesive is the DB712H adhesive series from Huizhou Duko New Materials Co., Ltd. The proton exchange membrane after elution is transparent, as shown... Figure 2 As shown, there is virtually no platinum carbon residue, and the proton exchange membrane after elution shows no damage or corrosion.
[0046] Comparative Example 1-1
[0047] Comparative Example 1-1 is basically the same as Example 1, except that the solvent in the eluent is only solvent A.
[0048] The eluent was used to elute the MEA of a spent fuel cell. After eluent, the proton exchange membrane appeared as follows: Figure 3 As shown, no catalyst layer or carbon paper was observed to have detached from the surface of the MEA membrane of the spent fuel cell.
[0049] Comparative Examples 1-2
[0050] Comparative Examples 1-2 are basically the same as Example 1, except that 1,4-butyrolactone is used to replace solvent B in the eluent, which is YH-GBL995 purchased from Shanghai Yuhua Industrial Co., Ltd.
[0051] The eluent was used to elute the MEA of a spent fuel cell. After eluent, the proton exchange membrane appeared as follows: Figure 4 As shown, a small amount of catalyst and carbon paper have fallen off the surface of the spent fuel cell MEA membrane, and the membrane is broken, making it unusable.
[0052] Example 2
[0053] The eluent in Example 2 comprises potassium bromide (a reducing agent), toluene (a decomposing agent), and a solvent in a volume ratio of 2:2:10. The solvent comprises solvent A and solvent B in a volume ratio of 5:1.
[0054] Solvent A consists of a 1:1 volume ratio of mixed alcohol and water. The mixed alcohol is a 3:1 volume ratio of ethanol and ethylene glycol. Solvent B is a 3:1 volume ratio of trichloromethane and hexane.
[0055] The preparation method of the eluent in Example 2 includes the following steps:
[0056] (1) Mix 750ml of anhydrous ethanol and 250ml of ethylene glycol, and then mix with 1000ml of water to form a mixed alcohol solution A;
[0057] (2) Mix 300ml of chloroform and 100ml of hexane to form solvent B;
[0058] (3) Add solvent B to solvent A according to the volume ratio and mix evenly to obtain the solvent;
[0059] (4) Mix 150 ml of potassium bromide and 150 ml of toluene by volume, add them to the solvent, and stir until homogeneous to obtain the eluent.
[0060] The application method of the eluent in Example 2 includes the following steps: 5 kg of waste fuel cell MEA is added to 50 kg of eluent, and the mixture is stirred at 30°C for 4 hours to obtain a slurry containing platinum carbon catalyst and a proton exchange membrane after elution.
[0061] Subsequently, the platinum-containing carbon catalyst slurry can be concentrated at 90°C to a solid content greater than 95%, and then subjected to pyrolysis at 800°C for 6 hours to extract the precious metal, ultimately obtaining the recovered platinum. The proton exchange membrane can be recycled after washing with ultrapure water and drying at low temperature.
[0062] Example 2 uses a spent fuel cell MEA as follows: Figure 5 As shown, the adhesive is 3M P460 series from 3M China Co., Ltd. It should be noted that the MEA of the spent fuel cell in Example 2 is a cut membrane electrode material without a membrane frame. To prevent the catalyst and carbon paper from falling off, a frame of the same material as the proton exchange membrane is pressed around the catalyst and carbon paper. Figure 6 The black border in the image is not unwashed residue. The eluted proton exchange membrane is transparent, as shown in the image. Figure 6 As shown, there is virtually no platinum carbon residue, and the proton exchange membrane after elution shows no damage or corrosion.
[0063] Comparative Example 2-1
[0064] Comparative Example 2-1 is basically the same as Example 2, except that the solvent in the eluent is only solvent A.
[0065] The eluent was used to elute the MEA of the spent fuel cell. After elution, the following results were obtained: Figure 7 As shown, the proton exchange membrane was not fully eluted in this comparative example.
[0066] Comparative Example 2-2
[0067] Comparative Example 2-2 is basically the same as Example 2, except that 1,4-butyrolactone is used to replace solvent B in the eluent, which is YH-GBL995 purchased from Shanghai Yuhua Industrial Co., Ltd.
[0068] The eluent was used to elute the MEA of a spent fuel cell. In this comparative example, the membrane electrode was an intact membrane electrode material. The eluented proton exchange membrane was as follows: Figure 8 As shown, a small amount of catalyst and carbon paper have fallen off the surface of the spent fuel cell MEA membrane, and the membrane is broken in many places, making it unusable.
[0069] Based on the elution test results of Examples 1-2, i.e. Figure 2 and 6 It is known that the eluent system composed of the specific solvent, reducing agent and decomposing agent of this invention can achieve almost no carbon paper and catalyst residue on the proton exchange membrane after elution for 4 hours, and the membrane is intact and undamaged. This verifies that the eluent can not only promote the separation of the catalyst layer, carbon paper and proton exchange membrane from each other, but also promote the separation with high efficiency.
[0070] Furthermore, the adhesives used in Example 1 and Comparative Examples 1-1 and 1-2 are macromolecular resin adhesives, suitable for high-power batteries. The adhesives used in Example 2 and Comparative Examples 2-1 and 2-2 are low-molecular-weight epoxy structural adhesives, suitable for low-power batteries. The elution experiments of Examples 1 and 2 show that, regardless of the type of adhesive used to bond the membrane electrode, the eluent of this invention can increase the elution rate to over 99%, achieving thorough elution and separation without affecting the quality of the proton exchange membrane, allowing the proton exchange membrane to be recycled after elution.
[0071] Comparative Examples 1-1 and 2-1, which do not contain solvent B, represent the applicant's prior application scheme. When using the prior application scheme, the eluent cannot effectively remove the carbon paper and adhesive components from the finished waste fuel cell MEA. Figure 3 and 7As shown. Regardless of whether the spent fuel cell MEA is formed by macromolecular or small molecule adhesives, after elution, under the same time and stirring rate, it still fails to be fully eluted. In Comparative Examples 1-2 and 2-2, 1,4-butyrolactone, which has a polarity close to that of solvent B, was used as solvent B. This eluent was used to elute spent fuel cell MEAs with different adhesives. After elution, as shown... Figure 4 and 8 As shown, only a small amount of carbon paper and catalyst were eluted, and the proton exchange membrane suffered multiple damages, rendering it unusable. This demonstrates that the composite system composed of the reducing agent, solvent, and decomposing agent of this invention not only effectively elutes and separates the materials but also protects the membrane material itself.
[0072] Example 3
[0073] The eluent in Example 3 comprises potassium iodide (a reducing agent), ethyl acetate (a decomposing agent), and a solvent in a volume ratio of 3:2:40. The solvent comprises solvent A and solvent B in a volume ratio of 6:4.
[0074] Solvent A consists of a mixture of alcohol and water in a volume ratio of 1:3. The mixed alcohol is composed of anhydrous ethanol, ethylene glycol, and isopropanol in a volume ratio of 5:2:3. Solvent B is composed of a mixture of dichloromethane and hexane in a volume ratio of 1:3.
[0075] The preparation method of the eluent in Example 3 includes the following steps:
[0076] (1) Mix 500ml of anhydrous ethanol, 200ml of ethylene glycol, and 300ml of isopropanol with 1000ml of water to form a mixed alcohol solution A;
[0077] (2) Mix 100ml of dichloromethane and 300ml of hexane to form solvent B;
[0078] (3) Add solvent B to solvent A according to the volume ratio and mix evenly to obtain the solvent;
[0079] (4) Mix 150ml sodium borohydride and 100ml acetone by volume, then add the solvent (step (3) can be scaled up proportionally) and stir until homogeneous to obtain the eluent.
[0080] The application method of the eluent in Example 3 includes the following steps: 1.5 kg of waste fuel cell MEA is transferred to 15 kg of eluent, and the mixture is stirred at 40°C for 4 h at a stirring rate of 100 rpm to obtain a slurry containing platinum carbon catalyst and a proton exchange membrane after elution.
[0081] The proton exchange membrane after elution of the membrane electrode in Example 3 is transparent with virtually no platinum carbon residue, and the eluted proton exchange membrane shows no damage or corrosion.
[0082] Example 4
[0083] The eluent in Example 4 comprises potassium bromide (a reducing agent), toluene (a decomposing agent), and a solvent in a volume ratio of 1:2:60. The solvent comprises solvent A and solvent B in a volume ratio of 9:3.
[0084] Solvent A consists of a mixture of alcohol and water in a volume ratio of 1:5. The mixed alcohol is composed of methanol, glycerol, and isopropanol in a volume ratio of 4:3:3. Solvent B is composed of chloroform and hexane in a volume ratio of 3:5.
[0085] The preparation method of the eluent in Example 4 includes the following steps:
[0086] (1) Mix 400ml of anhydrous ethanol, 300ml of ethylene glycol, and 300ml of isopropanol with 1000ml of water to form a mixed alcohol solution A;
[0087] (2) Mix 300ml of chloroform and 500ml of hexane to form solvent B;
[0088] (3) Add solvent B to solvent A according to the volume ratio and mix evenly to obtain the solvent;
[0089] (4) Mix 150ml potassium bromide and 300ml toluene by volume, then add to the solvent (step (3) can be scaled up proportionally), and stir until uniform to obtain the eluent.
[0090] The application method of the eluent in Example 4 includes the following steps:
[0091] (1) 5 kg of waste fuel cell MEA was transferred to 50 kg of eluent and stirred at 30 °C for 4 h to obtain a slurry containing platinum carbon catalyst and a proton exchange membrane after elution.
[0092] (2) The slurry containing platinum carbon catalyst is concentrated at 90°C until the solid content is greater than 95%, and then the precious metal is extracted by fire treatment at 800°C for 6 hours. Finally, the recovered precious metal platinum is obtained. The proton exchange membrane is washed with ultrapure water and dried at low temperature for recycling.
[0093] The proton exchange membrane after elution of the membrane electrode in Example 4 is transparent with virtually no platinum carbon residue, and the eluted proton exchange membrane shows no damage or corrosion.
[0094] In addition to the above embodiments, it should be noted that the reducing agent used in the eluent of the present invention may also be one or more of potassium bromide, potassium iodide, sodium bromide, or sodium borohydride. The decomposing agent may also be one or more of acetone, ethyl acetate, toluene, and N,N dimethylformamide. The mixed alcohol may also be a mixture of two or more of ethanol, methanol, isopropanol, glycerol, or ethylene glycol. The volume ratio of the reducing agent, decomposing agent, and solvent may be (1-4):2:(6-70), preferably (1-4):2:(6-10). In the method of using the eluent of the present invention, the mass ratio of MEA of the spent fuel cell to the eluent may be 1:(5-15). During the elution process, the eluent may be added in batches according to the mass of the added material, ensuring that the MEA of the spent fuel cell is in uniform contact with the eluent. The elution temperature is controlled at 30-60℃. Elution at higher temperatures can easily cause the eluent to volatilize, affecting the elution effect. The elution time and amount of eluent are determined based on the quality of the spent fuel cell MEA. That is, the technical effects claimed by this invention can be achieved by using the eluent and the parameter range defined by its usage method; therefore, no further examples will be provided to support this claim.
Claims
1. An eluent for used fuel cell membrane electrodes, characterized in that, The eluent comprises a reducing agent, a decomposing agent, and a dissolving agent in a volume ratio of (1-4):2:(6-70); The solvent comprises solvent A and solvent B in a volume ratio of (5-9):(1-4); wherein solvent A comprises a mixture of alcohol and water in a volume ratio of 1:(1-5), and solvent B is one or more of dichloromethane, trichloromethane, and hexane; The reducing agent is one or more of potassium bromide, potassium iodide, sodium bromide, or sodium borohydride; The decomposing agent is one or more of acetone, ethyl acetate, toluene, and N,N-dimethylformamide.
2. The eluent according to claim 1, characterized in that, The mixed alcohol is a mixture of two or more of ethanol, methanol, isopropanol, glycerol or ethylene glycol.
3. The eluent according to claim 2, characterized in that, The mixed alcohol is ethanol and ethylene glycol in a volume ratio of (2-6):
1.
4. The eluent according to claim 3, characterized in that, The mixed alcohol is ethanol and ethylene glycol in a volume ratio of (2.5-3):
1.
5. The eluent according to claim 1, characterized in that, The solvent B is dichloromethane and hexane in a volume ratio of (2-3):(1-6).
6. A method for preparing the eluent according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Add solvent B to solvent A by volume ratio, stir and mix evenly to obtain solvent; (2) Add the reducing agent and the decomposing agent to the solvent in step (1) according to the volume ratio, and stir to mix evenly to obtain the eluent.
7. A method of applying the eluent according to any one of claims 1-5, characterized in that, The process includes the following steps: adding the membrane electrode assembly of the spent fuel cell to the eluent at a mass ratio of 1:(5-15), eluting at 30-60℃ for 4-6 hours, and separating by filtration to obtain the catalyst slurry and proton exchange membrane, respectively.