Anti-start-stop membrane electrode assembly and preparation method thereof

Abstract

The present invention relates to the field of fuel cell technology, and in particular to a start-stop resistant membrane electrode assembly and a preparation method thereof. The start-stop resistant membrane electrode assembly comprises: a proton exchange membrane, an anode catalyst layer and a cathode catalyst layer; the anode catalyst layer and the cathode catalyst layer are respectively arranged on both sides of the proton exchange membrane; the anode catalyst layer contains an antioxidant; the antioxidant is at least one of polyphenols, butylated hydroxyanisole, dibutylhydroxytoluene, tert-butylated diphenol, and vitamin C; the weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1 to 2:1. The membrane electrode of the present invention has an "anti-start-stop" protection function, which can significantly reduce the damage to the fuel cell membrane electrode during the start-stop process. Moreover, the present invention adopts a material science solution, which can effectively alleviate the design pressure of the fuel cell system control strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a start-stop resistant membrane electrode assembly and a preparation method thereof. Background Art

[0002] A hydrogen fuel cell is a device that directly converts the chemical energy in hydrogen into electrical energy, boasting high energy conversion efficiency and zero pollution. The membrane electrode (MEA) is the "heart" of a hydrogen fuel cell, where the electrochemical reactions occur. The MEA typically consists of an anode catalyst layer, a cathode catalyst layer, a proton exchange membrane (PEM), an anode gas diffusion layer (GDL), and a cathode GDL. The anode catalyst layer undergoes the hydrogen oxidation reaction (HOR) and is typically composed of a Pt / C catalyst and a proton-conducting resin. The cathode catalyst layer also undergoes the oxygen reduction reaction (ORR) and is typically composed of a Pt / C catalyst and a GDL. The PEM is typically composed of a perfluorosulfonic acid resin and primarily functions as a proton conductor while isolating electrons and gases. The anode and cathode GDLs typically consist of carbon paper or carbon cloth with a microporous layer on each side, respectively, for transporting air and hydrogen to the anode and cathode catalyst layers and for removing excess water.

[0003] During the start-up and shutdown process of the fuel cell, a certain amount of air is easily mixed into the anode catalyst layer, thus forming a hydrogen-air interface. Figure 1 As shown. Under the catalytic action of the Pt / C catalyst, the air region of the anode catalyst layer can undergo an oxygen reduction reaction, thereby raising the potential of the local position of the cathode catalyst layer. The local (IV) potential of the cathode catalyst layer can even reach 2.0V, forcing the water in this area to undergo an oxygen evolution reaction (OER) and the carbon support to undergo a carbon oxidation reaction (COR). The carbon support acts as a catalyst, support, and skeleton of the catalyst layer. Oxidation of the carbon support will lead to a large amount of Pt loss and even cause the catalyst layer skeleton to collapse, seriously damaging the battery performance.

[0004] In the prior art, CN201180061661.X discloses an improved membrane electrode assembly for a PEM fuel cell, which has two electrode layers (EL1 and / or EL2), at least one of which contains a first electrocatalyst (EC1) comprising a combination of an iridium oxide component and at least one other inorganic oxide component; and a second electrocatalyst (EC2 / EC2') that does not contain iridium. Preferably, an iridium oxide / titanium dioxide catalyst is used as EC1. These membrane electrodes have shown good performance, especially under various harsh operating conditions such as fuel starvation and start / stop cycles. However, this design uses iridium oxide to accelerate the water electrolysis reaction to inhibit the corrosion of the cathode carbon material and prevent the degradation of battery performance. This cannot fundamentally eliminate the degradation mechanism during the start-stop process, and its protective effect is limited. Moreover, the design of the double-layer cation and cation catalytic layer is complex in structure, difficult in process, and not easy to mass produce. Summary of the Invention

[0005] In view of this, the present invention provides a membrane electrode assembly, comprising: a proton exchange membrane, an anode catalyst layer and a cathode catalyst layer;

[0006] The anode catalyst layer and the cathode catalyst layer are respectively arranged on both sides of the proton exchange membrane;

[0007] The anode catalyst layer contains an antioxidant;

[0008] The antioxidant is at least one of polyphenols, butylated hydroxyanisole, butylated hydroxytoluene, tert-butylated diphenol, and vitamin C;

[0009] The weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1 to 2:1.

[0010] As a preferred embodiment of the present invention, the anode catalyst layer further comprises: perfluorosulfonic acid resin;

[0011] Preferably, the weight percentage of the perfluorosulfonic acid resin in the anode catalyst layer is 8% to 40%.

[0012] As a preferred embodiment of the present invention, the catalyst in the anode catalyst layer is at least one of Pt / C, PtRu / C, PtIr / C, PtCo / C, PtCoMn / C, PtNi / C, Ir / C, Ru / C, and IrRu / C hydrogen oxidation reaction catalysts.

[0013] As a preferred embodiment of the present invention, the weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1 to 0.5:1.

[0014] Furthermore, the present invention also provides a method for preparing the membrane electrode assembly, comprising:

[0015] (1) dispersing the material of the anode catalyst layer in a solvent to prepare an anode slurry;

[0016] Dispersing the material of the cathode catalyst layer in a solvent to prepare a cathode slurry;

[0017] (2) The anode slurry and the cathode slurry are respectively coated on both sides of a proton exchange membrane to prepare the membrane electrode assembly.

[0018] As a preferred embodiment of the present invention, the solvent comprises an alcohol solution.

[0019] As a preferred embodiment of the present invention, the solvent is an aqueous solution of alcohol, and the alcohol is preferably n-propanol, isopropanol, ethanol and ethylene glycol, and the weight ratio of water to alcohol is 1:4 to 4:1.

[0020] As a preferred embodiment of the present invention, the coating method includes direct coating and indirect coating;

[0021] The direct coating is spraying or slot extrusion;

[0022] The indirect coating specifically includes: coating the anode slurry or cathode slurry onto a PTFE substrate respectively, and then transferring the anode slurry onto a proton exchange membrane.

[0023] Furthermore, the present invention provides a membrane electrode assembly prepared by any of the above embodiments.

[0024] Furthermore, the present invention provides a membrane electrode comprising the membrane electrode assembly according to any one of the above embodiments.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The membrane electrode assembly (MEA) of the present invention incorporates an antioxidant in the anode catalyst layer, which effectively reduces the oxygen content in the anode catalyst layer during the start-stop process. This effectively interrupts the electrical circuit generated by the "reverse current mechanism" at the anode hydrogen-air interface during the start-stop process, thereby effectively inhibiting oxidation of the cathode carbon material. This provides the MEA with "anti-start-stop" protection, significantly reducing damage to the fuel cell MEA during the start-stop process. Furthermore, the present invention utilizes a materials science solution that effectively alleviates the design pressure of the fuel cell system control strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic diagram of the "reverse current mechanism" of the membrane electrode in the prior art.

[0029] Figure 2 This is a schematic diagram of the design principle of the membrane electrode assembly with "anti-start and stop" protection function of the present invention. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0031] As an embodiment of the present invention, this embodiment provides a membrane electrode assembly, comprising: a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer;

[0032] The anode catalyst layer and the cathode catalyst layer are respectively arranged on both sides of the proton exchange membrane;

[0033] The anode catalyst layer contains an antioxidant;

[0034] The antioxidant is at least one of polyphenols, butylated hydroxyanisole, butylated hydroxytoluene, tert-butylated diphenol, and vitamin C;

[0035] The weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1 to 2:1.

[0036] The present invention has found that the membrane electrode used in the prior art will undergo the following Figure 1 The “reverse current mechanism” shown in FIG5 is that, specifically, a higher local high potential (>2.0 V) is formed in the cathode catalyst layer, which accelerates the oxidation reaction of the carbon support and causes the loss and collapse of the cathode catalyst layer Pt.

[0037] While existing technologies exist for improving the start-stop durability of membrane electrode materials, the principles underlying these solutions differ significantly from those of the present application. For example, CN201180061661.X employs a double-layer cathode catalyst layer, one of which is composed of iridium oxide. The technical principle is that iridium oxide accelerates the water electrolysis reaction, inhibiting corrosion of the cathode carbon material and preventing battery performance degradation.

[0038] The present invention targets the above mechanism discovered by the inventors. By adding a certain amount of antioxidant to the anode catalyst layer, the oxygen content in the anode catalyst layer can be reduced during the start-stop process, cutting off the electrical circuit generated by the "reverse current mechanism" of the anode hydrogen-air interface during the start-stop process, inhibiting the oxidation of the cathode carbon material, and thus preventing the battery performance from declining. The schematic diagram of the design principle of the membrane electrode assembly with "anti-start-stop" protection function of the present invention is shown in the figure. Figure 2 shown.

[0039] As a preferred embodiment of the present invention, the anode catalyst layer further comprises: perfluorosulfonic acid resin;

[0040] Preferably, the weight percentage of the perfluorosulfonic acid resin in the anode catalyst layer is 8% to 40%.

[0041] As a preferred embodiment of the present invention, the catalyst in the anode catalyst layer is at least one of Pt / C, PtRu / C, PtIr / C, PtCo / C, PtCoMn / C, PtNi / C, Ir / C, Ru / C, and IrRu / C hydrogen oxidation reaction catalysts.

[0042] The present invention finds that when a non-Pt catalyst is used to catalyze the hydrogen oxidation reaction, the non-Pt catalyst can work together with an antioxidant to further reduce the damage to the fuel cell membrane electrode during the start-stop process.

[0043] As an embodiment of the present invention, the weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1-0.5:1.

[0044] As an embodiment of the present invention, this embodiment provides a method for preparing a membrane electrode assembly, comprising:

[0045] (1) dispersing the material of the anode catalyst layer in a solvent to prepare an anode slurry;

[0046] Dispersing the material of the cathode catalyst layer in a solvent to prepare a cathode slurry;

[0047] (2) The anode slurry and the cathode slurry are respectively coated on both sides of a proton exchange membrane to prepare the membrane electrode assembly.

[0048] The above-mentioned preparation method of the present invention is similar to the preparation process of the traditional membrane electrode, is easy to mass produce, and is simple and convenient to operate.

[0049] As a preferred embodiment of the present invention, the solvent includes an alcohol solution.

[0050] As a preferred embodiment of the present invention, the solvent is an aqueous solution of alcohol, and the alcohol is preferably n-propanol, isopropanol, ethanol and ethylene glycol, and the weight ratio of water to alcohol is 1:4 to 4:1.

[0051] As a preferred embodiment of the present invention, the coating method includes direct coating and indirect coating;

[0052] The direct coating is spraying or slot extrusion;

[0053] The indirect coating specifically includes: coating the anode slurry or cathode slurry onto a PTFE substrate respectively, and then transferring the anode slurry onto a proton exchange membrane.

[0054] As a more preferred embodiment of the present invention, the preparation method comprises the following steps:

[0055] (1) A catalyst, an antioxidant, a perfluorosulfonic acid resin, and a solvent are mixed, ultrasonically dispersed, and stirred at a speed of more than 8000 rpm to prepare an anode slurry; the antioxidant is at least one of polyphenols, butylated hydroxyanisole, butylated hydroxytoluene, tert-butylated p-diphenol, and vitamin C; the solvent is an aqueous solution of alcohol, and the alcohol is preferably n-propanol, isopropanol, ethanol, and ethylene glycol, and the weight ratio of water to alcohol is 1:4 to 4:1;

[0056] (2) mixing the catalyst, the perfluorosulfonic acid resin, and the solvent, and stirring at a speed of 8000 rpm or more after ultrasonic dispersion to prepare a cathode slurry;

[0057] (3) The anode slurry and the cathode slurry are respectively coated on both sides of a proton exchange membrane to prepare the membrane electrode assembly.

[0058] As an embodiment of the present invention, this embodiment provides a membrane electrode assembly prepared by any of the above embodiments.

[0059] As an embodiment of the present invention, this embodiment provides a membrane electrode comprising the membrane electrode assembly of any of the above embodiments.

[0060] As a preferred embodiment of the present invention, the prepared membrane electrode assembly is placed between two gas diffusion layers to prepare a membrane electrode.

[0061] Since the membrane electrode of the present invention contains the above-mentioned membrane electrode assembly with the "anti-start-stop" function, the membrane electrode in the above-mentioned embodiment also has the "anti-start-stop" function, which can significantly reduce the damage to the fuel cell membrane electrode during the start-stop process and extend the service life of the membrane electrode.

[0062] The technical solutions and beneficial effects of the present invention are explained below with reference to more specific embodiments.

[0063] In the following examples, unless specific techniques or conditions are specified, all methods were performed according to conventional methods, techniques or conditions described in literature in the field, or according to product specifications. Reagents and instruments used, unless the manufacturer is specified, are conventional products available through regular channels.

[0064] Example 1

[0065] This embodiment provides a membrane electrode assembly, and the preparation method thereof is as follows:

[0066] (1) 1 g of catalyst Pt / C (50 wt.% Pt), 0.2 g of antioxidant tert-butyl-p-diphenol, and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of a solvent, wherein the solvent was a mixture of water and n-propanol in a weight ratio of 1:1. After ultrasonic dispersion for 5 min, the mixture was stirred at a speed of 8000 rpm to prepare an anode slurry.

[0067] (2) 1 g of Pt / C catalyst and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of the above solvent, ultrasonically dispersed for 5 min, and stirred at 8000 rpm to prepare a cathode slurry;

[0068] (3) The anode slurry and cathode slurry are sprayed on both sides of the proton exchange membrane to prepare a membrane electrode assembly.

[0069] Furthermore, the membrane electrode assembly is placed between two gas diffusion layers to obtain a membrane electrode.

[0070] Example 2

[0071] This embodiment provides a membrane electrode assembly, and the preparation method thereof is as follows:

[0072] (1) 1 g of catalyst Pt / C (50 wt.% Pt), 2 g of antioxidant butylated hydroxyanisole, and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of a solvent, wherein the solvent was a solution of water and n-propanol mixed in a weight ratio of 1:1, and ultrasonically dispersed for 5 min and stirred at a speed of 8000 rpm to prepare an anode slurry;

[0073] (2) 1 g of Pt / C catalyst and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of the above solvent, ultrasonically dispersed for 5 min, and stirred at 8000 rpm to prepare a cathode slurry;

[0074] (3) The anode slurry and cathode slurry are sprayed on both sides of the proton exchange membrane to prepare a membrane electrode assembly.

[0075] Furthermore, the membrane electrode assembly is placed between two gas diffusion layers to obtain a membrane electrode.

[0076] Example 3

[0077] This embodiment provides a membrane electrode assembly, and the preparation method thereof is as follows:

[0078] (1) 1 g of catalyst Pt / C (50 wt.% Pt), 0.2 g of antioxidant butylated hydroxyanisole, and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of a solvent, wherein the solvent was a solution of water and n-propanol mixed in a weight ratio of 1:1, and ultrasonically dispersed for 5 min and stirred at a speed of 8000 rpm to prepare an anode slurry;

[0079] (2) 1 g of Pt / C catalyst and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of the above solvent, ultrasonically dispersed for 5 min, and stirred at 8000 rpm to prepare a cathode slurry;

[0080] (3) The anode slurry and cathode slurry are sprayed on both sides of the proton exchange membrane to prepare a membrane electrode assembly.

[0081] Furthermore, the membrane electrode assembly is placed between two gas diffusion layers to obtain a membrane electrode.

[0082] Example 4

[0083] (1) 1 g of Ru / C catalyst (50 wt.% Ru), 0.2 g of antioxidant tert-butyl-p-diphenol, and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of a solvent, wherein the solvent was a mixture of water and n-propanol in a weight ratio of 1:1. After ultrasonic dispersion for 5 min, the mixture was stirred at 8000 rpm to prepare an anode slurry.

[0084] (2) 1 g of Pt / C catalyst (50 wt.% Pt) and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of the above solvent, ultrasonically dispersed for 5 min, and stirred at 8000 rpm to prepare a cathode slurry;

[0085] (3) The anode slurry and cathode slurry are sprayed on both sides of the proton exchange membrane to prepare a membrane electrode assembly.

[0086] Furthermore, the membrane electrode assembly is placed between two gas diffusion layers to obtain a membrane electrode.

[0087] Example 5

[0088] (1) 1 g of catalyst Ir / C (50 wt.% Ir), 0.2 g of antioxidant tert-butyl-p-diphenol, and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of a solvent, wherein the solvent was a mixture of water and n-propanol in a weight ratio of 1:1. After ultrasonic dispersion for 5 min, the mixture was stirred at a speed of 8000 rpm to prepare an anode slurry.

[0089] (2) 1 g of Pt / C catalyst (50 wt.% Pt) and 20 g of perfluorosulfonic acid resin solution (5 wt.%) were dispersed in 20 g of the above solvent, ultrasonically dispersed for 5 min, and stirred at 8000 rpm to prepare a cathode slurry;

[0090] (3) The anode slurry and cathode slurry are sprayed on both sides of the proton exchange membrane to prepare a membrane electrode assembly.

[0091] Furthermore, the membrane electrode assembly is placed between two gas diffusion layers to obtain a membrane electrode.

[0092] Comparative Example

[0093] This comparative example provides a membrane electrode assembly, the preparation method of which is different from that of Example 1 only in that no antioxidant is added.

[0094] Furthermore, the membrane electrode assembly is placed between two gas diffusion layers to obtain a membrane electrode.

[0095] Test example

[0096] The start-stop resistance of the membrane electrodes prepared in the examples and comparative examples was tested. Specifically:

[0097] The test method is as follows:

[0098] The active area is 25 cm 2 After the membrane electrode prepared in the embodiment and comparative example is assembled into a battery, it is fully activated. Activation conditions: 80°C, anode hydrogen excess coefficient 1.5, cathode air excess coefficient 2.0, current density less than 400mA / cm 2 When 400mA / cm 2 Current density flow rate supply, 100% / 100% relative humidity, 100kPa / 100kPa back pressure. After activation, the polarization curve of the single cell was measured. The polarization curve was the same as the activation conditions.

[0099] After completing the above experiments, the start-stop acceleration test was started. The acceleration test refers to the DOE test method, and the experimental conditions are: 35°C, atmospheric pressure. The entire acceleration test is 5000 cycles. The steps in each cycle are shown in Table 1. The air flow rate is fixed during the entire experiment (excess coefficient 2.0, 1.0A / cm 2 After the start-stop acceleration experiment is completed, the polarization curve of the single battery is tested.

[0100] Table 1 Start-stop test method

[0101]

[0102] The test results are shown in Table 2.

[0103] Table 2 Comparison of anti-start and stop capabilities of the embodiment and the comparative example

[0104]

[0105]

[0106] It can be seen from Table 2 that the membrane electrode of the present invention can effectively inhibit the oxidation of the cathode carbon material and has an "anti-start-stop" protection function.

[0107] Finally, 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A membrane electrode assembly, characterized in that: include: Proton exchange membrane, anode catalyst layer and cathode catalyst layer; The anode catalyst layer and the cathode catalyst layer are respectively arranged on both sides of the proton exchange membrane; The anode catalyst layer contains an antioxidant; The antioxidant is tert-butyl-p-diphenol; The weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1 to 2:1; The catalyst in the anode catalyst layer is Ir / C or Ru / C.

2. The membrane electrode assembly according to claim 1, wherein: The anode catalyst layer also includes: perfluorosulfonic acid resin.

3. The membrane electrode assembly according to claim 2, characterized in that The weight percentage of the perfluorosulfonic acid resin in the anode catalyst layer is 8% to 40%.

4. The membrane electrode assembly according to any one of claims 1 to 3, characterized in that The weight ratio of the antioxidant to the catalyst in the anode catalyst layer is 0.1-0.5:

1.

5. The method for preparing a membrane electrode assembly according to any one of claims 1 to 4, characterized in that: include: (1) Dispersing the material of the anode catalyst layer in a solvent to prepare an anode slurry; Dispersing the material of the cathode catalyst layer in a solvent to prepare a cathode slurry; (2) The anode slurry and the cathode slurry are respectively coated on both sides of a proton exchange membrane to prepare the membrane electrode assembly.

6. The method for preparing a membrane electrode assembly according to claim 5, wherein: The solvent includes an alcohol solution.

7. The method for preparing a membrane electrode assembly according to claim 5, wherein: The solvent is an aqueous solution of alcohol, and the weight ratio of water to alcohol is 1:4 to 4:

1.

8. The method for preparing a membrane electrode assembly according to claim 7, wherein: The alcohol is n-propanol, isopropanol, ethanol or ethylene glycol.

9. The method for preparing a membrane electrode assembly according to any one of claims 5 to 8, characterized in that: The coating method includes direct coating and indirect coating; The direct coating is spraying or slot extrusion; The indirect coating specifically includes: coating the anode slurry or cathode slurry onto a PTFE substrate respectively, and then transferring the anode slurry onto a proton exchange membrane.

10. A membrane electrode, characterized in that: It contains the membrane electrode assembly according to any one of claims 1 to 4.

Images