CN100388539C - Composite catalyst layer proton exchange membrane fuel cell electrode and manufacturing method thereof - Google Patents

Abstract

A composite catalyst layer proton exchange membrane fuel cell electrode and its manufacturing method, preparing more than one catalyst layer containing hydrophobic substance (such as PTFE) and carbon-supported platinum (Pt/C) catalyst on the leveling layer side surface of gas diffusion layer which is previously leveled by hydrophobic and carbon powder, baking under the protection of inert gas at 320-380 ℃, spraying a certain amount of solid polymer electrolyte, and then preparing more than one layer of slurry composed of solid polymer electrolyte, electrode catalyst and solvent in different proportions on the catalyst layer. Drying or roasting at 100-380 deg.c under the protection of inert gas to obtain the fuel cell electrode comprising composite catalyst layers with different hydrophilicity and hydrophobicity. The composite catalyst layer fuel cell electrode has sufficient electron conductivity and proton conductivity, and has good gas and water transfer or diffusion capacity, the three-phase interface area of the electrode reaction is expanded, and the power density of the fuel cell is greatly improved.

Description

Composite catalytic layer proton exchange membrane fuel cell electrode and manufacturing method thereof

Field of invention:

The invention relates to a solid polymer proton exchange membrane fuel cell electrode and a manufacturing method thereof, in particular to a composite electrode catalytic layer having two or more layers with different affinity and hydrophobicity, capable of obtaining a high output power density composite catalyst Layer-structured gas diffusion electrode and method for producing the same.

technical background:

A fuel cell is a power generation device that directly converts the chemical energy stored in fuel and oxidant into electrical energy. The fuel cell has the advantages of high power generation efficiency, environmental friendliness, and energy diversification. Fuel cells can be divided into proton exchange membrane fuel cells (PEMFC), alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (MCFC), etc. according to different electrolytes. Proton exchange membrane fuel cell with gas as fuel and air as oxidant, due to its advantages of high current density, low operating temperature, and miniaturization, is regarded as the power source of automobiles and other vehicles, small and medium-sized distributed power stations, household use Combined heat and power system and so on have received widespread attention, and have broad application prospects and huge potential markets.

Proton exchange membrane fuel cells are usually composed of proton exchange membranes, both sides of the membrane are connected with a catalytic layer containing catalytically active components, and the outer side of the catalytic layer is a gas diffusion layer with carbon paper or carbon cloth as the main component. The outer side of the gas diffusion layer is equipped with a bipolar plate with gas flow channels and good conductivity. When fuel and oxidant are supplied, the gas diffusion layer with current collection performance conducts the current to the external circuit.

When the anode uses hydrogen (H ₂ ) as fuel and the cathode uses oxygen as the oxidant, under the action of the electrode catalyst, the following electrode reactions occur respectively.

Anode: 2H ₂ —— 4H ⁺ +4e ^-

Cathode: O ₂ +4H ⁺ +4e ^- ——H ₂ O

It can be seen from the above formula that in PEMFC, the necessary condition for the electrochemical reaction is not only the reaction substance, but also the supply, conduction and acceptance of protons and electrons. That is, the electrochemical reaction is carried out on the three-phase interface of the reactant gas, protons, and electrons. The electrode catalyst particles not only play a catalytic role, but also play the role of conducting electrons (electron channel), and the polymer electrolyte plays the role of conducting protons (proton channel). The fine pores in the electrodes act as channels for passing reactants (H ₂ , O ₂ ) and products (H ₂ O). In order to obtain a three-phase interface in the anode and cathode, the electrode usually adopts a gas diffusion electrode composed of a gas diffusion layer and a catalytic layer.

The catalytic layer and the conductive porous body acting as a collector form a gas diffusion electrode, which is used as an anode and a cathode on both sides of the proton exchange membrane to form a three-in-one membrane electrode. The catalytic layer is a mixture of carbon-supported catalytic active components, solid polymer electrolytes, PTFE and other hydrophobic agents, and is a place for electrode reactions. To obtain fuel cell electrodes with high output power density, high proton conductivity, electron conductivity and gas diffusivity are necessary. Therefore, it is necessary to form three kinds of channels in communication within the electrode.

In the fuel cell, in order to make the electrochemical reaction proceed, the catalytic layer needs to have continuous gas channels, proton channels and electron channels. However, when the humidified gas is supplied and water is generated due to the cathode reaction, when the fuel cell operates at a high density, water is stored on the surface of the catalytic layer and in the pores, gas diffusion is hindered, and the performance of the battery is significantly reduced.

Usually, PTFE is mixed into the catalyst layer to impart hydrophobicity so that water does not remain. In order to prevent water in the electrode during high-density operation, it is necessary to increase the amount of PTFE added to improve hydrophobicity. Although PTFE has strong hydrophobicity, the particle itself is very large. After increasing the mixing amount of PTFE to improve hydrophobicity, the proton conduction channel, electron conduction channel and gas diffusion layer channel are blocked, thereby reducing the performance of the fuel cell.

Contents of the invention

The purpose of the present invention is to provide a high gas conductivity, electrochemical three-phase The gas diffusion electrode with large reaction interface area, high electrocatalyst utilization rate and high output power density and its manufacturing method are provided. The fuel cell electrode, in the gas diffusion electrode, does not hinder the proton conduction conductor channel, the electron channel and the gas diffusion channel, and has strong hydrophobicity and high output power density.

In order to achieve the above object, the technical solution of the present invention is to provide a kind of composite catalytic layer proton exchange membrane fuel cell electrode, all joins with catalytic layer on both sides of proton exchange membrane, the outside of catalytic layer is gas diffusion layer, gas diffusion layer The outer side is the bipolar plate. When the fuel and oxidant are supplied, the gas diffusion layer conducts the current to the external circuit. The catalytic layer is a composite catalytic layer. The composite catalytic layer is composed of one or more catalytic layers with different hydrophobicities. Composed of more than one catalytic layer with different hydrophilicity, the side connected to the proton exchange membrane is a hydrophilic catalytic layer, and the side connected to the gas diffusion layer is a hydrophobic catalytic layer; the gas diffusion layer and composite catalytic layer The layers make up the electrodes.

In the proton exchange membrane fuel cell electrode, the total thickness of the composite catalytic layer is 5-40 μm, wherein the thickness of the hydrophobic catalytic layer is 3-25 μm, and the thickness of the hydrophilic catalytic layer is 2-15 μm.

In the electrode of the proton exchange membrane fuel cell, the electrode catalyst used in the composite catalytic layer is platinum black or the carbon-supported catalytic active component is Pt, Au, Ru, Rh, Pd, Ag, Ir, Co, Fe, Ni, One or more catalysts in Mn; the loading amount of catalytically active components on the carbon carrier is 20-80 wt%.

In the proton exchange membrane fuel cell electrode, in the carbon-supported catalytic active components, the usage amount of the anode or cathode catalytic active components is 0.01-0.7 mg/cm ² .

As for the proton exchange membrane fuel cell electrode, the gas diffusion layer is made of carbon paper or carbon cloth, and the carbon paper or carbon cloth is treated with water-repellent treatment.

In the proton exchange membrane fuel cell electrode, the weight ratio of the catalytically active component to the hydrophobic agent in the hydrophobic catalytic layer is 1:0.05-1.8; the weight ratio of the catalytically active component to the solid polymer electrolyte in the hydrophilic catalytic layer is The ratio is 1:0.1-5.

In the proton exchange membrane fuel cell electrode, the total thickness of the composite catalytic layer is 7-25 μm, the thickness of the hydrophobic catalytic layer is 4-15 μm, and the thickness of the hydrophilic catalytic layer is 3-10 μm.

In the proton exchange membrane fuel cell electrode, the loading amount of the catalytically active component on the carbon carrier is 30-70wt%.

In the electrode of the proton exchange membrane fuel cell, the usage amount of the catalytically active component of the anode or cathode is 0.05-0.5 mg/cm ² .

The manufacturing method of described proton exchange membrane fuel cell electrode, it comprises the steps:

a) Use carbon powder or carbon powder and organic hydrophobic compound slurry on the surface of one or both sides of the gas diffusion layer to perform pretreatment of leveling, drying and roasting;

b) Prepare catalyst layer slurries with different hydrophobic ratios on one side of the gas diffusion layer in batches, and then bake them at a temperature of 320-380° C. under the protection of an inert gas;

c) Then, spray a certain amount of solid polymer electrolyte solution on the surface of the hydrophobic catalytic layer, after drying, prepare in batches the semi-hydrophobic catalyst layer slurry that has been sprayed with the solid polymer electrolyte solution in the above-mentioned spray-coated solid polymer electrolyte solution. surface of the catalytic layer;

d) Calcining at a temperature of 100-360° C. under the protection of an inert gas to obtain a proton exchange membrane fuel cell electrode.

The manufacturing method of the proton exchange membrane fuel cell electrode, when making more than one layer of hydrophobic catalytic layer, repeat step b) times according to the required number of more than one layer, and then carry out steps c), d); when making one layer For the above hydrophilic catalytic layer, repeat step c) several times according to the number of layers required, and then proceed to step d).

The manufacturing method of the proton exchange membrane fuel cell electrode, one of the steps of making the three-in-one membrane electrode is: after step a) and b);

c) spraying a solid polymer electrolyte solution on the surface of the hydrophobic catalytic layer, and drying;

d) prepare the catalytic layer slurry with different hydrophilic proportions, spray the slurry evenly on the surface of the PTFE membrane in batches, after drying, hot press the two hydrophilic catalytic layers prepared on the PTFE membrane together Stretch both sides of the proton exchange membrane, so that the hydrophilic catalytic layer is transferred to both sides of the proton exchange membrane;

e) Put the two three-dimensionally treated hydrophobic electrodes obtained in step c) respectively on the hydrophilic catalytic layer obtained in step d), and hot press to obtain a three-in-one membrane electrode.

The present invention adopts two or more hydrophobic and hydrophilic composite catalytic layer electrodes, the side combined with the proton exchange membrane is a catalytic layer with strong hydrophilicity, and the side close to the gas diffusion layer is a hydrophobic The electrode structure of the composite catalytic layer not only has good electron conduction and proton conduction capacity, but also has good gas conduction and water transfer capacity, which effectively expands the three-phase interface area of the catalytic layer and improves the fuel efficiency. Battery output power density.

Description of drawings

Fig. 1 is a schematic diagram of the electrode microstructure of a proton exchange membrane fuel cell of the present invention;

Fig. 2 is a schematic diagram of a composite electrode with a multilayer catalytic layer of the present invention; a gas diffusion electrode structure on one side with a composite hydrophilic/hydrophobic gradient catalytic layer.

Fig. 3 shows the comparison of the V-I curve and the P-I curve of the single cell formed by the three-in-one membrane electrode (MEA) prepared in Example 1 and Comparative Example.

Fig. 4 shows the comparison of the V-I curve and the P-I curve of the single cell formed by the three-in-one membrane electrode (MEA) prepared in Example 2 and Comparative Example.

Fig. 5 is a comparison of the V-I curve and the P-I curve of the single cell formed by the three-in-one membrane electrode (MEA) prepared in Example 3 and Comparative Example.

Detailed ways

As shown in FIG. 2 , it is a schematic diagram of an electrode of a proton exchange membrane fuel cell provided by the present invention. On one side of a proton exchange membrane 1 , the electrode is composed of a gas diffusion layer 2 and a composite catalytic layer 3 . The electrode is characterized in that the existing catalytic layer is changed into a composite catalytic layer 3, and the composite catalytic layer 3 is composed of one or more catalytic layers 31 with stronger hydrophilicity and one or more catalytic layers with different hydrophobicity. Layers 32 and 33 are formed. The side in contact with the proton exchange membrane 1 is a hydrophilic catalytic layer 31 , and the side in contact with the gas diffusion layer 2 is a hydrophobic catalytic layer 32 . The composite catalytic layer 3 on the side in contact with the proton exchange membrane 1 is hydrophilic, and the closer it is to the gas diffusion layer 2, the stronger the hydrophobicity of the composite catalytic layer 3 is.

The total thickness of the composite catalytic layer 3 is 5-40 μm, preferably 7-25 μm, wherein the thickness of the hydrophobic catalytic layer 32 is 3-25 μm, preferably 4-15 μm, and the thickness of the hydrophilic catalytic layer 31 is 2-15 μm. It is preferably 3-10 μm. The thickness of the intermediate transition catalytic layer 33 should be less than 2 μm.

The electrode catalyst used in the composite catalytic layer 3 is platinum black or carbon-supported platinum or carbon-supported alloy catalyst, and the catalyst active component is one or one of Pt, Au, Ru, Pd, Ir, Ag, Co, Fe, Ni, Mn A metal or alloy catalyst composed of more than one substance.

The gas diffusion layer 2 used in the present invention adopts carbon paper or carbon cloth through hydrophobization treatment, and carries out flattening, drying with carbon powder or carbon powder and organic hydrophobic compound (such as PTFC) slurry on its one or both sides surface , Roasting pretreatment.

The homogeneously mixed hydrophobic catalytic layer 32 slurry is prepared by well-known methods, such as (but not limited to) spraying, scraping or screen printing. On the side of the gas diffusion layer 2 that has been leveled, the hydrophobic catalytic layer The weight ratio of the catalyst active component to the hydrophobic agent in 32 is 1:0.05-1.8; then, after roasting at 320-380°C under the protection of an inert gas, spray an appropriate amount of solid polymer electrolyte solution on the surface of the hydrophobic catalytic layer 32, Such as Nafion solution. After drying, the hydrophilic catalytic layer 31 slurry is prepared on the surface of the above-mentioned hydrophobic catalytic layer 32, and the weight ratio of the catalytically active component in the hydrophilic catalytic layer 31 to the solid polymer electrolyte is 1: 0.1-5; Dry at 100-380° C. under gas protection to obtain a gas diffusion electrode with composite catalytic layer 3 .

Example 1:

a) According to the catalyst consumption of 0.25mgPt/cm ² , weigh the Pt/C catalyst with a Pt load of 40wt% and put it into a beaker, add a small amount of deionized water to make the catalyst soak, and use 50ml of absolute ethanol per gram of catalyst After weighing, ethanol was added into the catalyst beaker, mixed and stirred evenly, and the material was slurry. Then according to the ratio of Pt/C: PTFE = 1: 1.5, weigh PTFE and add it to the feed liquid, mix evenly, and mature.

Scrape-coat the above-mentioned cured slurry on one side of the gas diffusion layer leveling layer that has been hydrophobized and leveled on one side, dry at 160°C for 30 minutes under the protection of nitrogen, and then heat up to 250°C and bake for 30 minutes, then raise the temperature To 360°C, bake for 30 minutes. After cooling, weigh 5wt% Nafion solution in an amount of 1 mg polymer electrolyte per square centimeter; add appropriate isopropanol, mix evenly, and spray evenly on the surface of the hydrophobic catalytic layer to make the catalytic layer three-dimensional.

b) Weigh the Pt/C catalyst with a Pt load of 40wt% according to the catalyst usage of 0.25mg Pt/ ^cm2 , put it into a beaker, add a small amount of deionized water to soak it, and add an appropriate amount of Dehydrated alcohol, after uniform mixing and stirring, weigh 5wt% Nafion solution according to the ratio of Pt/C catalyst and solid polymer electrolyte resin amount of 1:3, add it to the above liquid material, continue to mix and stir evenly, and obtain hydrophilic Squeeze-coat the slurry on the aforementioned hydrophobic catalytic layer by the scraper coating method, and dry it at 150° C. for 30 minutes under the protection of nitrogen to obtain a composite-layer hydrophilic-hydrophobic gradient electrode. Put two composite layers of hydrophilic-hydrophobic gradient electrodes on both sides of a pre-treated Nafion112 membrane, and hot press to obtain a three-in-one membrane electrode.

Comparative example 1

Weigh the Pt/C catalyst with a Pt load of 40wt% according to the catalyst usage of 0.60mgPt/ ^cm2 and put it into a beaker, add a small amount of deionization to soak the catalyst, and weigh 50ml of absolute ethanol per gram of catalyst. Finally, after adding the catalyst to the beaker, mix and stir evenly to obtain a slurry liquid material. Then according to the ratio of Pt/C:PTFE=1:1.5, weigh 20wt% PTFE emulsion and add it into the liquid material, and then continue to mix and stir evenly and mature.

Scrape-coat the above-mentioned cured slurry on one side of the leveling layer of the gas diffusion layer after hydrophobization and single-side leveling, dry at 160°C for 30 minutes under the protection of nitrogen, and then heat up to 250°C for 30 minutes. Afterwards, the temperature was raised to 360° C. and baked for 30 minutes to obtain a hydrophobic catalytic layer electrode. After cooling, weigh 5wt% Nafion solution in an amount of 1 mg polymer electrolyte per square centimeter, add appropriate isopropanol, mix, and evenly spray onto the surface of the hydrophobic catalytic layer to make the catalytic layer three-dimensional.

Put two three-dimensional hydrophobic electrodes on both sides of a pre-treated Nafion112 membrane, and hot press to obtain a three-in-one membrane electrode.

Example 2

a) The hydrophobic catalyst slurry was prepared according to the method in a) of Example 1, and the hydrophobic catalytic layer was prepared on the gas diffusion layer according to the method of Example 1, and the hydrophobic catalytic layer was three-dimensionalized.

b) prepare hydrophilic catalytic layer slurry by the b) method of embodiment 1, this slurry is sprayed on the surface of PTFE film equably, the usage amount of hydrophilic catalytic layer Pt is by 0.25mg/cm ^Regulate . After drying, put two pieces of hydrophilic catalytic layers prepared on PTFE membranes on both sides of a pre-treated Nafion112 membrane, heat press to transfer the hydrophilic catalytic layers to both sides of the proton exchange membrane, and then put the two pieces of the above The three-dimensionally treated hydrophobic electrodes are respectively placed on the above-mentioned hydrophilic catalytic layer, and hot-pressed to obtain a three-in-one membrane electrode.

Example 3

The electrode manufactured in Example 1 was used as a cathode, and the electrode manufactured in Comparative Example was used as an anode, which were hot-pressed with Nafion 1035 membrane to obtain a three-in-one membrane electrode.

The three-in-one membrane electrodes prepared in the above-mentioned Example 1, Example 2, Example 3 and Comparative Example were respectively assembled into single cells and evaluated on a fuel cell evaluation system. The evaluation results are shown in the curves in Fig. 3, Fig. 4 and Fig. 5. The specific operating parameters of the fuel cell are as follows. The working temperature of the fuel cell is 80°C, the temperature of the humidifier is 78-80°C, the working pressure of the fuel cell is 0.2MPa, and the hydrogen and air volumes are strictly controlled. The hydrogen stoichiometric ratio is 1.17 and the air stoichiometric ratio is 2.5.

Claims (12)

1. A kind of composite catalytic layer proton exchange membrane fuel cell electrode, all joins with catalytic layer at both sides of proton exchange membrane, the outside of catalytic layer is gas diffusion layer, and the outer side of gas diffusion layer is bipolar plate again, when supplying fuel and oxidant, the gas diffusion layer conducts the current to the external circuit, which is characterized in that: the catalytic layer is a composite catalytic layer, and the composite catalytic layer is composed of one or more catalytic layers with different hydrophobicity and one or more hydrophilic The catalytic layer is composed of different water properties. The side connected to the proton exchange membrane is a hydrophilic catalytic layer, and the side connected to the gas diffusion layer is a hydrophobic catalytic layer; the gas diffusion layer and the composite catalytic layer form an electrode. 2. The proton exchange membrane fuel cell electrode according to claim 1, characterized in that: the total thickness of the composite catalytic layer is 5-40 μm, wherein the thickness of the hydrophobic catalytic layer is 3-25 μm, and the hydrophilic catalytic layer The thickness is 2-15μm. 3. The proton exchange membrane fuel cell electrode according to claim 1, characterized in that: the electrode catalyst used in the composite catalytic layer is platinum black or the carbon-supported catalytic active component is Pt, Au, Ru, Rh, Pd, Ag , Ir, Co, Fe, Ni, Mn one or more catalysts; the loading of catalytically active components on the carbon carrier is 20-80wt%. 4. The proton exchange membrane fuel cell electrode according to claim 3, characterized in that: among the carbon-supported catalytically active components, the usage amounts of the catalytically active components of the anode or cathode are respectively 0.01 to 0.7 mg/cm ² . 5 . The proton exchange membrane fuel cell electrode according to claim 1 , characterized in that: the gas diffusion layer is made of carbon paper or carbon cloth, and the carbon paper or carbon cloth has been subjected to hydrophobic treatment. 6 . 6. The proton exchange membrane fuel cell electrode according to claim 1 or 2, characterized in that: in the hydrophobic catalytic layer, the weight ratio of the catalytically active component to the hydrophobic agent is 1: 0.05-1.8; The weight ratio of the catalytically active component to the solid polymer electrolyte is 1:0.1-5. 7. The proton exchange membrane fuel cell electrode according to claim 2, characterized in that: the total thickness of the composite catalytic layer is 7 to 25 μm, the thickness of the hydrophobic catalytic layer is 4 to 15 μm, and the thickness of the hydrophilic catalytic layer is The thickness is 3-10 μm. 8. The proton exchange membrane fuel cell electrode according to claim 3, characterized in that: the loading amount of the catalytically active component on the carbon carrier is 30-70 wt%. 9 . The proton exchange membrane fuel cell electrode according to claim 4 , characterized in that: the usage amount of the catalytically active component of the anode or cathode is 0.05-0.5 mg/cm ² . 10. The method for manufacturing a proton exchange membrane fuel cell electrode according to claim 1, characterized in that: comprising the steps of: a) Use carbon powder or carbon powder and organic hydrophobic compound slurry on the surface of one or both sides of the gas diffusion layer to perform pretreatment of leveling, drying and roasting; b) Prepare catalyst layer slurries with different hydrophobic ratios on one side of the gas diffusion layer in batches, and then bake them at a temperature of 320-380° C. under the protection of an inert gas; c) Then, spray a certain amount of solid polymer electrolyte solution on the surface of the hydrophobic catalytic layer, after drying, prepare in batches the semi-hydrophobic catalyst layer slurry that has been sprayed with the solid polymer electrolyte solution in the above-mentioned spray-coated solid polymer electrolyte solution. surface of the catalytic layer; d) Calcining at a temperature of 100-360° C. under the protection of an inert gas to obtain a proton exchange membrane fuel cell electrode. 11. The manufacturing method of proton exchange membrane fuel cell electrode according to claim 10, is characterized in that: make more than one layer of hydrophobic catalytic layer, repeat step b) times according to the required number of layers above, and then carry out step c) , d); make more than one layer of hydrophilic catalytic layer, repeat step c) times according to the required number of more than one layer, and then proceed to step d). 12. A method for manufacturing an electrode of a proton exchange membrane fuel cell, characterized in that: a step of making a three-in-one membrane electrode is: a) Use carbon powder or carbon powder and organic hydrophobic compound slurry on the surface of one or both sides of the gas diffusion layer to perform pretreatment of leveling, drying and roasting; b) Prepare catalyst layer slurries with different hydrophobic ratios on one side of the gas diffusion layer in batches, and then bake them at a temperature of 320-380° C. under the protection of an inert gas; c) spraying a solid polymer electrolyte solution on the surface of the hydrophobic catalytic layer, and drying; d) prepare the catalytic layer slurry with different hydrophilic proportions, spray the slurry evenly on the surface of the PTFE membrane in batches, after drying, hot press the two hydrophilic catalytic layers prepared on the PTFE membrane together Stretch both sides of the proton exchange membrane, so that the hydrophilic catalytic layer is transferred to both sides of the proton exchange membrane; e) Put the two three-dimensionally treated hydrophobic electrodes obtained in step c) respectively on the hydrophilic catalytic layer obtained in step d), and hot press to obtain a three-in-one membrane electrode.

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