Direct methanol fuel cell membrane electrode complex and preparation method thereof

Abstract

The invention relates to the technical field of fuel cells, and particularly discloses a direct methanol fuel cell membrane electrode complex and a preparation method thereof.The preparation method comprises the steps that 4, 4 '-(9-fluorenyl) diphenylamine, terephthalic acid, 2, 5-diaminobenzene sulfonic acid and anhydrous L iCl are dissolved in N-methyl pyrrolidone, pyridine and triphenyl phosphite, heating and stirring are conducted in the argon atmosphere, and the membrane electrode complex is obtained; precipitating, washing and drying to obtain polyamide, preparing a proton exchange membrane, and respectively coating two sides of the proton exchange membrane with an anode catalyst and a cathode catalyst to obtain a proton exchange membrane loaded with the catalyst; the anode diffusion layer, the proton exchange membrane loaded with the catalyst and the cathode diffusion layer are subjected to hot-pressing compounding to obtain a membrane electrode complex, and the cell membrane electrode complex is obtained by stacking the anode diffusion layer and the cathode diffusion layer, so that the membrane electrode complex of the direct methanol fuel cell prepared by the method has low methanol permeability, and can be used for preparing the fuel cell. And meanwhile, the preparation process is simple, and the time cost of the test is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and in particular relates to a direct methanol fuel cell membrane electrode complex and a preparation method thereof. Background Art

[0002] A fuel cell is an electrochemical power generation device that converts the chemical energy of fuel and oxidant directly into electrical energy through an electrochemical reaction without going through a thermal engine process and is not restricted by the Carnot cycle. Therefore, it has a very high energy conversion efficiency. Secondly, the product is usually water, which causes little pollution to the environment. This makes direct methanol fuel cells likely to become the mainstream application of portable electronic products in the future. At the same time, it has broad application prospects in transportation, military, aerospace and other fields. This will inevitably make fuel cells play an important role in my country's process of achieving the "carbon neutrality" goal.

[0003] Proton exchange membrane fuel cells are the most promising fuel cells. The main clean energy sources used are hydrogen, methanol, ethanol, etc. However, due to the huge investment in the construction of hydrogen supply facilities and the relatively backward hydrogen transportation, storage and on-site hydrogen production technologies, it is easier to handle liquid fuels such as methanol than hydrogen. It is a commonly used energy source for fuel cells. The proton exchange membrane is the core component of the fuel cell. It not only conducts protons, but also separates fuels and determines the power output of the fuel cell.

[0004] The existing direct methanol fuel cell includes a fuel tank, a membrane electrode complex, a current collector and a plate. Among them, the membrane electrode complex includes: an anode diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode diffusion layer placed in sequence. The preparation method is as follows: the anode catalyst layer and the cathode catalyst layer are coated on the anode diffusion layer and the cathode diffusion layer respectively, the proton exchange membrane is placed between the anode diffusion layer and the cathode diffusion layer, and they are pressed together by a hot pressing method to obtain a membrane electrode complex. The working process of the existing direct methanol fuel cell is as follows: the fuel is transferred to the anode current collector and the anode diffusion layer by diffusion to reach the anode catalyst layer. In the anode catalyst layer, the fuel methanol is oxidized to generate protons, electrons, carbon dioxide and heat. This reaction is called methanol oxidation reaction (MOR). The electrons and protons generated in the methanol oxidation reaction pass through the external circuit and the proton exchange membrane respectively to reach the cathode catalyst layer. Oxygen passes through the cathode current collector and the cathode diffusion layer to reach the cathode catalyst layer, where oxygen combines with protons and electrons to generate water and release heat.

[0005] Although direct methanol fuel cells have many advantages, they also have certain defects, the main one being severe methanol permeation. Methanol permeation mainly produces a mixed potential, leading to battery voltage loss, poisoning the cathode catalyst, and aggravating cathode water injection, resulting in decreased battery performance, decreased fuel efficiency, and damage to the proton exchange membrane.

[0006] In order to solve the serious methanol permeation problem of direct methanol fuel cells, the prior art also provides a variety of methods, mainly for designing a new proton exchange membrane to replace the perfluorosulfonic acid proton exchange membrane. For example, Chinese patent application number CN116666712A discloses a method for preparing an organic proton exchange membrane for a direct methanol fuel cell, which can effectively solve the problem caused by methanol permeation.

[0007] For example, Chinese patent application number CN111477922A discloses a method for preparing a proton exchange membrane and a membrane electrode thereof, in which graphene oxide is sprayed on the surface of a Nafion117 proton exchange membrane. The graphene oxide coating can effectively block methanol, but it also causes the proton conductivity of the proton exchange membrane to decrease.

[0008] Based on the above analysis, this patent proposes a direct methanol fuel cell membrane electrode complex and its preparation method to solve the current problems of poor proton conductivity and high methanol permeability of proton exchange membranes. Summary of the invention

[0009] The object of the present invention is to provide a direct methanol fuel cell membrane electrode assembly and a preparation method thereof to solve the problems raised in the above background technology.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A method for preparing a direct methanol fuel cell membrane electrode complex comprises the following steps:

[0012] (1) 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid, 2,5-diaminobenzenesulfonic acid and anhydrous LiCl are dissolved in N-methylpyrrolidone, pyridine and triphenyl phosphite, and heated and stirred under an argon atmosphere for reaction. After the reaction is completed, the mixture is precipitated in ice methanol, washed with methanol and deionized water for several times, and then placed in a forced air drying oven for drying and then placed in a vacuum drying oven for drying to obtain polyamide;

[0013] (2) The proton exchange membrane is prepared by solution casting. A certain mass of the synthesized polyamide is weighed and dissolved in DMSO. The solution is heated and stirred until it is completely dissolved to obtain a transparent solution. The solution is then filtered into a culture dish using an organic filter head and placed in an oven to remove the solvent. The solution is then placed in a vacuum drying oven to dry and remove the remaining residual solvent. The membrane is peeled off from the culture dish and then activated with an HCl solution at room temperature. The activated membrane is then washed with deionized water until it is neutral to obtain a proton exchange membrane.

[0014] (3) coating an anode catalyst and a cathode catalyst on both sides of the proton exchange membrane to obtain a catalyst-loaded proton exchange membrane;

[0015] (4) The anode diffusion layer, the proton exchange membrane loaded with the catalyst, and the cathode diffusion layer are composited by hot pressing to obtain a membrane electrode composite.

[0016] Preferably, in step (1), the molar ratio of 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid and 2,5-diaminobenzenesulfonic acid is 1:3:2, the volume ratio of N-methylpyrrolidone, pyridine and triphenyl phosphite is 3:1:1, the heating temperature is 100°C, the reaction time is 24h, the drying temperature is 80°C, and the drying time is 12h and 24h.

[0017] Preferably, in step (2), the polyamide is 0.4 g, the DMSO is 20 mL, the drying temperature is 80° C., and the HCl solution is 1 mol / L.

[0018] Preferably, in step (3), the anode catalyst layer is a PtRu / C electrocatalyst.

[0019] Preferably, the cathode catalyst layer is a Pt / C electrocatalyst.

[0020] Preferably, the coating comprises spraying or brushing.

[0021] Preferably, the anode catalyst layer and the cathode catalyst layer are carbon paper and carbon cloth.

[0022] A direct methanol fuel cell membrane electrode complex, the membrane electrode complex comprises an anode diffusion layer, a catalyst-carrying proton exchange membrane, and a cathode diffusion layer, the catalyst-carrying proton exchange membrane comprises a proton exchange membrane, an anode catalyst, and a cathode catalyst, the proton exchange membrane is stacked at the bottom end of the anode diffusion layer, the cathode diffusion layer is stacked at the bottom end of the catalyst-carrying proton exchange membrane, and the anode catalyst and the cathode catalyst are coated on both sides of the proton exchange membrane, respectively.

[0023] A direct methanol fuel cell of a direct methanol fuel cell membrane electrode complex, the fuel cell comprising an anode support plate, an anode current collector, an anode plate, an anode sealing sheet, an anode diffusion layer, a proton exchange membrane carrying a catalyst, a cathode diffusion layer, a cathode sealing sheet, a cathode plate, a cathode current collector and a cathode support plate which are sequentially bonded.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention prepares a proton exchange membrane, and coats an anode catalyst and a cathode catalyst on both sides of the proton exchange membrane respectively to obtain a proton exchange membrane loaded with a catalyst, and then obtains a battery membrane electrode complex by stacking an anode diffusion layer and a cathode diffusion layer. The membrane electrode complex of the direct methanol fuel cell prepared by this method has a low methanol permeability, can adapt to a higher concentration of methanol, and thus shows a high energy density in the fuel cell test. At the same time, the production process is simple, which reduces the time cost of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of a membrane electrode assembly of a direct methanol fuel cell according to the present invention;

[0027] Figure 2 A schematic diagram of the exploded structure of a direct methanol fuel cell of the present invention;

[0028] Figure 3 A schematic diagram of the assembly structure of a direct methanol fuel cell of the present invention;

[0029] Figure 4 This is a schematic diagram of a polarization curve of a direct methanol fuel cell of the present invention.

[0030] In the figure: 1. anode diffusion layer; 2. proton exchange membrane carrying catalyst; 3. cathode diffusion layer; 21. proton exchange membrane; 22. anode catalyst; 23. cathode catalyst; 4. cathode sealing sheet; 5. cathode plate; 6. cathode current collector; 7. cathode support plate; 8. anode support plate; 9. anode current collector; 10. anode plate. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1:

[0033] See also Figures 1 to 4 As shown, a direct methanol fuel cell and its membrane electrode assembly and preparation method include the following steps:

[0034] Dissolve 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid, 2,5-diaminobenzenesulfonic acid and anhydrous LiCl in N-methylpyrrolidone, pyridine and triphenyl phosphite, and heat and stir to react under an argon atmosphere. After the reaction is completed, precipitate the mixture in ice methanol, wash it with methanol and deionized water several times, and then dry it in a forced air drying oven and then dry it in a vacuum drying oven to obtain polyamide;

[0035] The proton exchange membrane was prepared by solution casting, a certain mass of the synthesized polyamide was weighed and dissolved in DMSO, heated and stirred until completely dissolved to obtain a transparent solution, then the solution was filtered into a culture dish with an organic filter head, and placed in an oven to remove the solvent, and then placed in a vacuum drying oven to dry and remove the remaining residual solvent, the membrane was peeled off from the culture dish, and then activated with HCl solution at room temperature, and then the activated membrane was washed with deionized water to neutrality to obtain a proton exchange membrane.

[0036] An anode catalyst and a cathode catalyst are coated on both sides of the proton exchange membrane respectively to obtain a catalyst-loaded proton exchange membrane;

[0037] The anode diffusion layer, the proton exchange membrane loaded with the catalyst and the cathode diffusion layer are composited by hot pressing to obtain a membrane electrode composite.

[0038] The molar ratio of 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid and 2,5-diaminobenzenesulfonic acid is 1:3:2, the volume ratio of N-methylpyrrolidone, pyridine and triphenyl phosphite is 3:1:1, the heating temperature is 100°C, the reaction time is 24h, the drying temperature is 80°C, and the drying time is 12h and 24h.

[0039] The amount of polyamide is 0.4 g, the amount of DMSO is 20 mL, the drying temperature is 80° C., and the amount of HCl solution is 1 mol / L.

[0040] The proton exchange membrane used in this embodiment is a proton exchange membrane prepared by dissolving a polyamide synthesized from 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid, and 2,5-diaminobenzenesulfonic acid in a molar ratio of 1:3:2 in a solvent, and has a thickness of 0.102 mm;

[0041] The anode diffusion layer and the cathode diffusion layer are both carbon papers provided by Shengernuo Technology Co., Ltd., and the thickness is 0.23 mm.

[0042] The anode catalyst and cathode catalyst are both electrocatalysts provided by MacLean, with PtRu / C on the anode side and Pt / C on the cathode side, with a loading of 2 mg / cm 2 .

[0043] The specific operations are as follows:

[0044] 1. Spray the anode catalyst and cathode catalyst uniformly on the anode diffusion layer and cathode diffusion layer respectively. The thickness of the anode catalyst layer and the cathode catalyst layer are both 200 Å, to obtain an anode and a cathode with a size of 2 cm×2 cm.

[0045] 2. The anode diffusion layer and the cathode diffusion layer are sandwiched on both sides of the proton exchange membrane loaded with the catalyst and hot-pressed to obtain a membrane electrode assembly. During the hot-pressing process, the hot-pressing temperature is set to 120° C., the pressure is set to 8 MPa, and the hot-pressing time is set to 1.5 min.

[0046] 3. The corresponding positions on both sides of the membrane electrode assembly electrode prepared in step 2 are respectively pressed against the anode plate and the cathode plate. The outermost layer is the supporting plate. The anode current collector, anode plate anode sealing sheet, membrane electrode assembly, cathode sealing sheet, cathode plate, and cathode current collector are fixed on the fuel tank in sequence and fixed with insulating bolts to make a self-breathing passive direct methanol fuel cell.

[0047] The performance of the membrane electrode of the above embodiment was tested. The performance of the proton exchange membrane is shown in Table 1, and the performance of the electrode is shown in Table 2. Figure 4 shown.

[0048] The membrane performance test conditions are as follows:

[0049] 1. Tensile strength: The proton exchange membrane was cut into rectangular strips of 1×7 cm and tested on an electronic tensile machine at a tensile speed of 50 mm / min.

[0050] 2. Methanol permeability:

[0051] The methanol permeability of the proton exchange membrane was tested by an "H" type membrane diffusion test device, which consists of two compartments, one side is 20mL of methanol solution with a concentration of 1M, and the other side is added with the same volume of deionized water, and the membrane is sandwiched between the two compartments. The change in methanol concentration is measured at room temperature using a gas chromatograph. The methanol permeability is calculated as follows:

[0052]

[0053] 3. Proton conductivity: The proton conductivity of the membrane was tested using the electrochemical workstation (CH I, 604e) of Shanghai Chenhua Instrument Co., Ltd. using the AC impedance method. The prepared membrane was cut into a 1 cm × 3 cm rectangle and activated by soaking in 1M HCl solution for 12 hours. The proton conductivity of the membrane was tested at 20 to 80°C under a relative humidity of 100%. The calculation formula is as follows:

[0054]

[0055] 4. Selectivity: Selectivity is used to evaluate the comprehensive performance of proton exchange membranes and is defined as the ratio of proton conductivity to methanol permeability. The calculation formula is as follows:

[0056]

[0057] Table 1 Performance of proton exchange membrane

[0058]

[0059] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0060] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a direct methanol fuel cell membrane electrode assembly, characterized in that: The following steps are involved: (1. Dissolve 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid, 2,5-diaminobenzenesulfonic acid and anhydrous LiCl in N-methylpyrrolidone, pyridine and triphenyl phosphite, and heat and stir to react under an argon atmosphere. After the reaction, precipitate the mixture in ice methanol, wash it with methanol and deionized water several times, and then dry it in a forced air drying oven and then dry it in a vacuum drying oven to obtain polyamide; (2) A proton exchange membrane was prepared by a solution casting method. 0.4 g of the synthesized polyamide was weighed and dissolved in DMSO. The solution was heated and stirred until it was completely dissolved to obtain a transparent solution. The solution was then filtered into a culture dish using an organic filter head and placed in an oven to remove the solvent. The solution was then placed in a vacuum drying oven to dry and remove the remaining residual solvent. The membrane was peeled off from the culture dish and then activated with an HCl solution at room temperature. The activated membrane was then washed with deionized water until it was neutral to obtain a proton exchange membrane. (3. Coating an anode catalyst and a cathode catalyst on both sides of the proton exchange membrane to obtain a catalyst-loaded proton exchange membrane; (4. The anode diffusion layer, the proton exchange membrane loaded with the catalyst, and the cathode diffusion layer are composited by hot pressing to obtain a membrane electrode composite.

2. The method for preparing a direct methanol fuel cell membrane electrode assembly according to claim 1, characterized in that: In step (1), the molar ratio of the 4,4'-(9-fluorenyl)diphenylamine, terephthalic acid and 2,5-diaminobenzenesulfonic acid is 1:3:2, the volume ratio of the N-methylpyrrolidone, pyridine and triphenyl phosphite is 3:1:1, the heating temperature is 100°C, the reaction time is 24h, the drying temperature is 80°C, and the drying time is 12h and 24h.

3. The method for preparing a direct methanol fuel cell membrane electrode assembly according to claim 1, characterized in that: In step (2), the polyamide is 0.4 g, the DMSO is 20 mL, the drying temperature is 80° C., and the HCl solution is 1 mol / L.

4. The method for preparing a direct methanol fuel cell membrane electrode assembly according to claim 1, characterized in that: In step (3), the anode catalyst layer is a PtRu / C electrocatalyst.

5. The method for preparing a direct methanol fuel cell membrane electrode assembly according to claim 1, characterized in that: The cathode catalyst layer is a Pt / C electrocatalyst.

6. The method for preparing a direct methanol fuel cell membrane electrode assembly according to claim 1, characterized in that: The coating includes spraying or brushing.

7. The method for preparing a direct methanol fuel cell membrane electrode assembly according to claim 1, characterized in that: The anode catalyst layer and the cathode catalyst layer are carbon paper and carbon cloth.

8. A direct methanol fuel cell membrane electrode assembly, characterized in that: The membrane electrode complex comprises an anode diffusion layer (1), a catalyst-carrying proton exchange membrane (2), and a cathode diffusion layer (3); the catalyst-carrying proton exchange membrane (2) comprises a proton exchange membrane (21), an anode catalyst (22), and a cathode catalyst (23); the proton exchange membrane (2) is stacked at the bottom end of the anode diffusion layer (1); the cathode diffusion layer (3) is stacked at the bottom end of the catalyst-carrying proton exchange membrane (2); and the anode catalyst (22) and the cathode catalyst (23) are coated on both sides of the proton exchange membrane (21), respectively.

9. The direct methanol fuel cell of the direct methanol fuel cell membrane electrode assembly according to claim 8, characterized in that: The fuel cell comprises an anode support plate (8), an anode current collector (9), an anode plate (10), an anode sealing sheet (11), an anode diffusion layer (1), a proton exchange membrane (2) carrying a catalyst, a cathode diffusion layer (3), a cathode sealing sheet (4), a cathode plate (5), a cathode current collector (6) and a cathode support plate (7) which are sequentially bonded.

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