CN100486006C - Method for preparing membrane electrode of proton exchange membrane fuel cell - Google Patents

Abstract

The invention relates to a membrane electrode trinity for a proton exchange membrane fuel cell, in particular to a membrane electrode preparation method for the proton exchange membrane fuel cell, which takes an organic porous membrane as an electrode support body, the thickness of the porous membrane is 1-20 mu m, the porosity is 50-99 percent, and catalyst materials are directly adhered to the porous membrane to prepare an electrode catalyst layer; the catalyst layer and the electrolyte membrane are combined into a membrane electrode assembly by hot pressing. The MEA catalyst prepared by the method has high utilization rate, good activity and better strength, and is convenient for large-scale continuous production.

Description

A kind of membrane electrode preparation method of proton exchange membrane fuel cell

technical field

The invention relates to a three-in-one membrane electrode for a proton exchange membrane fuel cell, specifically a method for preparing a membrane electrode for a proton exchange membrane fuel cell, which uses a porous film as a support to prepare a mixture of an electrocatalyst and a proton conductor. The electrode active layer is formed on the membrane, and then it is combined with the electrolyte membrane to form a method of MEA.

Background technique

A fuel cell is a power generation device that directly converts chemical energy in fuel and oxidant into electrical energy through an electrocatalytic reaction on electrodes. It is not limited by the Carnot cycle and can efficiently convert chemical energy into electricity. So far, five types of fuel cells have been developed: alkaline, phosphoric acid, molten carbonate, high-temperature solid electrolyte and proton exchange membrane. Among them, the proton exchange membrane fuel cell (Proton Exchange Membrane Fuel Cell, referred to as PEMFC) has broad application prospects, it can start at low temperature, no electrolyte corrosion and leakage, simple structure, easy operation; has been recognized as electric vehicles, regional power stations, The preferred energy source for mobile power sources, submarines, spacecraft, etc. (Document 1: Yi Baolian. Fuel cells—an efficient and environmentally friendly power generation method. Beijing: Chemical Industry Press, 2000.).

Membrane electrode assembly (Membrane electrode assembly) is the core component of a proton exchange membrane fuel cell, and its performance directly affects the performance and stability of the battery.

US Patent (Document 2: US 5211984) describes a manufacturing method of a proton exchange membrane fuel cell. The battery has a thin catalytic layer between a solid electrolyte (SPE) and a porous bottom electrode. The thickness of the catalytic layer is less than 10 μm, and the load of the supported platinum catalyst is less than 0.35 mg/cm ² . The catalyst material is formulated into ink and sprayed on the membrane to be transferred, then cured, and the cured catalytic layer is transferred to the proton membrane and hot-pressed to form a membrane electrode. In addition, the catalytic layer can be directly made on the proton membrane by using Na ⁺ perfluorosulfonic acid ionomer, then dried at high temperature, and then converted into H ⁺ type. The catalytic layer has sufficient gas channels so that the battery performance does not decrease under the condition of low platinum loading.

European Patent (Document 3: EP 1318559 A2) describes a method of fabricating a membrane electrode assembly (MEA). The MEA consists of a polymer electrolyte membrane, a cathode (composed of a catalyst layer and a gas diffusion layer), and an anode (composed of a catalyst layer and a gas diffusion layer). A catalytic layer is interposed between the membrane and the gas diffusion layer. The cathode or anode catalyst layer comprises at least two sublayers. In this patent, at least one sublayer of the cathode or anode catalytic layer is applied directly to the membrane, and the remaining sublayers are applied to the corresponding gas diffusion layer. Finally, the membrane coated with the catalytic layer and the gas diffusion layer coated with the catalytic layer are assembled into an MEA. There is no description of performance in this patent.

U.S. Patent (Document 4: US 2003/0224233 A1) describes a manufacturing process of a proton exchange membrane fuel cell (PEMFC) MEA, to be precise, a lamination process of MEA, which is simple and fast. The MEA has a 5-layer structure, and the 5-layer MEA contains adhesive components and is pressed together by lamination. The anode gas diffusion layer, membrane electrode, and cathode gas diffusion layer are laminated together under low temperature and low pressure conditions. This simplifies MEA handling and stack assembly. Moreover, the phenomenon that the membrane electrode is damaged or perforated due to hot pressing is reduced, and the performance of the MEA is improved.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a membrane electrode of a proton exchange membrane fuel cell. It uses an organic porous membrane as an electrode support, and directly acts on the electrochemically active material on the support, so that the electrode active layer is an independent component , this structure is not only beneficial to the preparation of the electrode, but also conducive to the modification of the active layer to increase its function.

To achieve the above object, the technical solution adopted in the present invention is:

A method for preparing a membrane electrode for a proton exchange membrane fuel cell, characterized in that: an organic porous membrane is used as an electrode support, the thickness of the porous membrane is 1-20 μm, the porosity is 50%-99%, and the catalyst material is directly adhered to the Attached to the porous membrane to prepare the electrode catalytic layer; the catalytic layer and the electrolyte membrane are combined into a membrane electrode assembly by hot pressing and other means.

The organic porous membrane is polytetrafluoroethylene, vinylidene, polypropylene, polyethylene, polyimide or polysulfone porous membrane, etc.; the catalyst material is a mixture of electrocatalyst and proton-conducting resin, and the concentration of the catalyst can be 10% to 80% Pt/C or PtRu/C catalyst can also be Pt black or PtRu black catalyst, proton conductor solution (such as perfluorosulfonic acid resin), the mixing ratio is catalyst: resin solution is 10:1 ~ 1 : 1; electrocatalyst can be Pt/C, PtRu/C, Pt black or PtRu black catalyst of weight content 10～80%; Proton conductor is the material with proton conduction function with perfluorosulfonic acid resin class; Adhesion to the porous membrane means that the catalyst material can be prepared on the porous membrane by means of spraying, scraping or printing;

A pore-forming agent of 10-90% by weight can be added to the catalyst material, and the pore-forming agent is compatible with the catalyst material liquid, can be decomposed and volatilized at 100-300°C, and can be deposited in the catalytic layer. Materials that form a pore structure, such as ammonium oxalate, ammonium carbonate, pyrazolone, histamine, n-pentanamide, hexamethylenediamine, pyrrolidone, urea or lower alcohols, etc.; 1-50% of its weight can also be added in the catalyst material. Self-moisturizing agent (hygroscopic agent) with water absorption function, the prepared active layer has better moisturizing ability. If Pt catalyst is added, under the action of Pt catalyst, the reaction 2H ₂ +O ₂ → 2H ₂ O will occur, making MEA It has the function of self-humidification; the self-humidifying agent is silicon dioxide, titanium dioxide, water-absorbing resin or sulfonated organic matter; the self-humidifying agent added in the catalyst material can be used as a carrier for commonly used electrocatalysts for fuel cells, such as Pt, Electrochemically active electrocatalysts such as Ru and PtRu make MEA self-humidifying;

The catalyst material adheres to the porous membrane, and after the prepared porous membrane with the catalyst material is formed, it needs to undergo a treatment process at 120-320°C to obtain an electrode catalytic layer; the porous membrane can act as a catalyst support and form a gas channel function and enhance the multiple roles of membrane electrolytes.

Compared with the aforementioned background technology, the technical solution adopted in the present invention has the following characteristics:

1) Patent US5211984 A uses the transfer method to prepare electrodes, and the active layer is prepared on the membrane electrolyte. The process is complicated, the repeatability is poor, the membrane electrolyte is easy to be damaged, and the preparation cycle is long, which is not suitable for commercial production. In the electrode preparation method of the present invention, the catalyst material is easy to prepare, the process is simple, the preparation cycle is short, the production repeatability is good, the battery assembly is convenient, and the conditions for commercial production are met.

2) In patent US 2003/0224233 A1 and patent EP 1318559 A2, the catalytic layer is directly prepared on the membrane, and then the MEA is combined by an adhesive and a low-pressure combination method. The active layer cannot be prepared independently. In the present invention, the active layer is prepared as a separate component, while It is not directly on the membrane electrolyte, which avoids possible damage to the membrane electrolyte during operation. At the same time, the porous membrane supporting the active layer is closely combined with the electrolyte membrane, which not only improves the performance of the MEA, but also enhances the strength of the electrolyte.

The present invention has the following advantages:

1. The present invention uses the organic porous membrane as the electrode support, and the electrode active layer is an independent component. This structure is beneficial to the preparation of the electrode; in the separate preparation process of the active layer, components with various functions can be added to improve the MEA Performance, such as adding a water-absorbing agent can realize the self-humidification function, and adding an anti-impurity catalyst can improve the environmental adaptability of the MEA.

2. The porous membrane supporting the active layer (that is, the catalytic layer) can function to strengthen the MEA. The middle of the prepared electrode is an organic porous membrane, and the catalyst particles are distributed in the pores of the membrane, which is not only beneficial to the uniform distribution of the catalyst material, but also beneficial to the electrochemical reaction.

3. Compared with the catalyst directly on the electrode of the proton membrane, the organic porous membrane will not swell rapidly when encountering a solvent like the Nafion membrane, and has good dimensional stability and is easy to manufacture.

4. High catalyst utilization in MEA. In the traditional method, the catalyst layer is prepared on the gas diffusion layer, and the catalyst material will inevitably leak into the pores of the diffusion layer, which not only affects the pore structure in the diffusion layer, but also reduces the utilization rate of the catalyst. In the present invention, when preparing the electrode active layer, all the catalyst materials are prepared on the organic porous membrane, which avoids the disadvantages of the traditional method, reduces the catalyst loading, improves the performance and reduces the cost at the same time, and has the conditions for commercialization; through the present invention The inventive method prepares the MEA, so that the MEA has better catalyst utilization rate and better strength, and at the same time facilitates large-scale continuous production, which is beneficial to the enlarged production of the MEA.

In a word, the technology of the present invention has the advantages of simple process, convenient operation, strong repeatability, etc., and can be mass-produced.

Description of drawings

Fig. 1 is the structural representation of MEA among the present invention; Wherein: 1 is cathode diffusion layer, 2 is cathodic protection frame, 3 adhesive sublayers, 4 is anode diffusion layer, 5 is cathode catalytic layer, 6 is proton exchange membrane, 7 is the anode catalytic layer, and 8 is the anode protection frame;

Fig. 2 is the MEA voltammetry curve of embodiment 1 of the present invention;

Fig. 3 is the MEA voltammetry curve of embodiment 2 of the present invention;

Fig. 4 is the MEA voltammetry curve of Example 3 of the present invention.

Detailed ways

Example 1

1) Cut a 5 μm polytetrafluoroethylene porous membrane (the porosity of the membrane is 90%, and the thickness is 5 μm) into a suitable size, put it in an ethanol solvent, place it in an ultrasonic wave for half an hour, and repeat it again. Cleaning and processing spare;

2) The solution containing 5% perfluorosulfonic acid resin (such as Nafion) and the Pt/C catalyst of 70% WT are mixed according to the ratio of Nafion:catalyst=1:3. The amount of anode catalyst is calculated by 0.5mg/ ^cm2 , The amount of cathode catalyst is calculated according to 0.3 mg/cm ² , and a certain amount of isopropanol is added. In order to allow the catalyst material to disperse evenly in the solution, the proportion of isopropanol should be larger, and add according to the ratio of catalyst:isopropanol=1:100:

3) Mix the solution with ultrasonic waves, so that the catalyst material is evenly dispersed in the solution, and set aside;

4) Spray a thin layer of adhesive on both sides of the porous membrane, such as the mixture of Nafion and carbon powder;

5) spraying the catalyst material onto one side of the porous membrane electrode;

6) Repeat steps (2) to (4) on the other side of the membrane:

7) Dry the membrane electrode at 140°C for 4 hours;

8) Place the membrane electrode on both sides of the Nafion membrane, pre-press for 1min at 160°C and 0.35MPa, and hot-press for 1min to make a membrane-electrode assembly;

9) Place the diffusion layer and the protective frame on both sides of the membrane electrode, pre-press for 1 min and hot-press for 1 min under the conditions of 160° C. and 0.7 MPa to prepare the MEA.

The performance of this MEA is shown in Figure 1. It can be seen from Fig. 1 that under the condition of normal pressure, it reaches 0.65V@500mA/cm ² .

Example 2

1) repeat step 1) in embodiment one;

2) Mix the solution containing 5% perfluorosulfonic acid resin (such as Nafion) and the Pt/C catalyst of 70% WT by Nafion:catalyst=1:3 ratio, and the cathode catalyst consumption is calculated by 0.75mg/ ^cm2 , The amount of anode catalyst is calculated on the basis of 0.75 mg/cm ² , and isopropanol in the same proportion as in Example 1 is added.

3) Repeat steps (3) to (9) in Example 1.

The performance of the MEA in this embodiment is shown in FIG. 2 . It can be seen from FIG. 2 that the performance of the electrode under normal pressure conditions reaches 0.66V@500mA/cm ² , which is slightly better than that of Example 1.

Example 3

1) repeat step 1) in embodiment one;

2) According to step 2) of Example 1, the catalyst material was prepared, and at the same time, 10% of the total weight of the catalyst material was added to the self-humidifying agent silica, and the dispersion was uniform;

3) Repeat steps (3) to (9) in Example 1.

The performance of the MEA in this embodiment is shown in FIG. 3 . It can be seen from Figure 3 that after adding the self-humidifying agent, the performance of passing dry air is slightly better than that of humidified air. Therefore, the effect of self-humidification is played.

Example 4

1) Cut a 2 μm polyethylene porous membrane (the porosity of the membrane is 55%, and the thickness is 2 μm) into a suitable size, put it in an ethanol solvent, place it in an ultrasonic wave for half an hour, and repeat it again for cleaning processing spare;

2) The solution containing 5% perfluorosulfonic acid resin (such as Nafion) and the Pt/C catalyst of 10% WT are mixed by Nafion: catalyst = 1: 10 ratio, and 1% of the total weight of the material is added in the catalyst material. Wetting agent titanium dioxide, evenly dispersed; the amount of anode catalyst is calculated according to 0.5mg/ ^cm2 , the amount of cathode catalyst is calculated according to 0.3mg/ ^cm2 , and a certain amount of isopropanol is added. In order to disperse the catalyst material evenly in the solution, the proportion of isopropanol should be larger, and add according to the ratio of catalyst: isopropanol=1:100;

3) Mix the solution with ultrasonic waves, so that the catalyst material is evenly dispersed in the solution, and set aside;

1) Spray a thin layer of adhesive on both sides of the porous membrane, such as a mixture of Nafion and carbon powder;

5) Scrape-coating the catalyst material onto one side of the porous membrane electrode;

6) Repeat steps (2) to (4) on the other side of the membrane;

7) Dry the membrane electrode at 320°C for 4 hours;

8) Place the membrane electrode on both sides of the Nafion membrane, pre-press for 1min at 160°C and 0.35MPa, and hot-press for 1min to make a membrane-electrode assembly;

9) Place the diffusion layer and the protective frame on both sides of the membrane electrode, pre-press for 1 min and hot-press for 1 min under the conditions of 160° C. and 0.7 MPa to prepare the MEA.

Example 5

The difference from Example 4 is that

In step 1), the porous membrane is a polysulfone porous membrane, the porosity of the membrane is 70%, and the thickness is 18 μm;

In step 2), the solution of perfluorosulfonic acid resin (such as Nafion) and the Pt black catalyst are mixed by Nafion:catalyst=1:8 weight ratio; the self-moisturizing agent water-absorbing resin of 4% of the total weight of catalyst material is added in the catalyst material (such as silica colloid), evenly dispersed;

In step 7), the drying temperature of the membrane electrode is 260°C.

Example 6

The difference from Example 4 is that

In step 1), the porous membrane is a polyimide porous membrane, the porosity of the membrane is 60%, and the thickness is 12 μm;

Step 2) in, the solution of perfluorosulfonic acid resin (such as Nafion) and PtRu black catalyst are mixed by the weight ratio of Nafion: catalyst=1:5; Add the self-wetting agent sulfonation of catalyst material gross weight 4% in the catalyst material Organic matter (such as sulfonated polysulfone), evenly dispersed;

In step 7), the drying temperature of the membrane electrode is 180°C.

Claims (5)

1. A membrane electrode preparation method for a proton exchange membrane fuel cell, characterized in that: an organic porous membrane is used as an electrode support, the thickness of the porous membrane is 1 to 20 μm, and the porosity is 50% to 99%, and the catalyst material Adhere to the porous membrane directly to prepare the electrode catalytic layer; combine the catalytic layer and the electrolyte membrane by hot pressing to form a membrane electrode assembly; The organic porous membrane is polytetrafluoroethylene, polypropylene, polyethylene, polyimide or polysulfone porous membrane; The catalyst material is adhered to the porous membrane, and after the prepared porous membrane with the catalyst material is formed, it undergoes a treatment process at 120-320°C to obtain an electrode catalyst layer; 10-90% by weight of a pore-forming agent is added to the catalyst material, the pore-forming agent is compatible with the catalyst material liquid, can be decomposed and volatilized at 100-300°C, and forms a pore structure in the catalytic layer the substance; 1-50% by weight of a self-moistening agent with water absorption function is added to the catalyst material, and the self-moistening agent is silicon dioxide, titanium dioxide or sulfonated polysulfone. 2. according to claim 1, is used for the membrane electrode preparation method of proton exchange membrane fuel cell, it is characterized in that: described catalyst material is the mixture of electrocatalyst and proton conduction resin, and electrocatalyst is the Pt of weight content 10～80%. /C, PtRu/C, Pt black or PtRu black catalyst with a weight content of 10-80%, the weight mixing ratio of catalyst:resin is 10:1-1:4. 3. according to claim 1, be used for the membrane electrode preparation method of proton exchange membrane fuel cell, it is characterized in that: described catalyst material is directly adhered to on the porous membrane and is meant that catalyst material is prepared into porous film by spraying, scraping or printing. film. 4. according to the membrane electrode preparation method that is used for proton exchange membrane fuel cell according to claim 1, it is characterized in that: described pore-forming agent is ammonium oxalate, ammonium carbonate, pyrazolone, histamine, n-valeramide, hexamethylene diacetate Amines, pyrrolidone or urea. 5. according to claim 1, be used for the membrane electrode preparation method of proton exchange membrane fuel cell, it is characterized in that: the self-humidifying agent that adds in the described catalyst material is as the carrier of carrying the common electrocatalyst of fuel cell, makes membrane electrode It has the function of self-humidification; the electrocatalyst is Pt, Ru or PtRu.

Images