CN112599792B - A kind of preparation method of fuel cell membrane electrode catalytic layer - Google Patents

Abstract

The invention belongs to the field of fuel cell membrane electrode preparation, in particular to a fuel cell membrane electrode catalyst layer coating uniformity control method, which comprises the preparation of catalyst slurry and the setting of a coating process, wherein the catalyst slurry comprises solid catalyst particles, a binder, a dispersant and a stabilizer; the method comprises the following steps: mixing solid catalyst particles and a dispersing agent, and adding Na⁺The formed binder is dispersed by ultrasonic oscillation and high-speed stirring to prepare catalyst slurry; in the coating process, a catalyst layer is prepared by controlling coating thickness, coating speed, coating pressure, coating die head retreat, drying tunnel temperature and other coating processes, and the thickness and uniformity of the catalyst layer are controlled; the catalyst layer prepared by the method disclosed by the invention is excellent in electrochemical performance, thin and uniform, the usage amount of the catalyst is reduced, the cost is saved, and the yield is improved.

Description

A kind of preparation method of fuel cell membrane electrode catalytic layer

technical field

The invention relates to a method for controlling the coating uniformity of a fuel cell membrane electrode catalyst layer, which belongs to the field of fuel cell membrane electrode preparation.

Background technique

A fuel cell is a power generation device that can directly convert chemical energy contained in hydrogen fuel and oxidant into electrical energy and reaction products. The proton exchange membrane fuel cell has attracted much attention because of its high stability, no pollution, low noise and high energy conversion rate.

The electrode part, the key component of proton exchange membrane fuel cell, is where the chemical reaction takes place inside the cell. The preparation method and structure of the electrode have been the research hotspots in recent years. In the electrode preparation process, whether the catalytic layer is directly prepared on the gas diffusion layer to form a gas diffusion electrode; or the catalytic layer is directly prepared on the proton exchange membrane to form a proton exchange membrane electrode; the uniformity and microstructure of the electrode are directly Affect the use of fuel cells. In the current electrode preparation process, the spraying method is a relatively common preparation method. The prepared catalytic layer is uniform and dense, but the efficiency is slow, and a large amount of catalyst is wasted due to the spraying airflow. The coating method can effectively solve the shortcoming of slow electrode production efficiency. However, the electrodes prepared by this method often cause irreversible damages such as leakage, cracks, and peeling of the catalytic layer due to the slurry and process.

In the preparation process of the catalyst layer, the preparation and dispersion degree of the catalyst slurry directly affect the uniformity and electrochemical performance of the catalyst layer. People usually use complicated processing methods to prepare the catalyst slurry, such as adding anti-precipitation agents, A series of additives such as thickeners, the addition of such additives will not only make the dispersion process of the catalyst slurry more difficult, but also be left in the catalyst layer during the preparation of the catalyst layer, which will not only affect its electrochemical performance, but also affect the battery. The resistance increases, the transmission efficiency decreases, and the catalytic layer will appear uneven, perforated, cracks, etc., and may even have an adverse effect on the proton exchange membrane and affect the mechanical strength of the membrane.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing a catalyst layer for a membrane electrode of a fuel cell, which can control the uniformity of the catalyst layer from the two aspects of catalyst slurry preparation and continuous coating.

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

The present invention provides a method for preparing a membrane electrode catalytic layer of a fuel cell, which is characterized by comprising the following steps:

(1) mixing the solid catalyst particles and dispersing agent, ultrasonically vibrating and dispersing for 10-30min to form a uniform mixed solution; then adding a stabilizer, and forming a uniform mixed solution via ultrasonic vibration and dispersion for 10-30min and high-speed stirring and dispersing for 30-60min;

(2) Add 1 mol/L NaOH solution to the binder, the molar ratio of NaOH to the molar ratio of sulfonate in the binder is 0.1-2:1, and the binder is Na ⁺ typed to make it Convert from H ⁺ type to Na ⁺ type;

(3) adding the Na ⁺ type-treated binder in step (2) into the mixed solution of (1), ultrasonically oscillating and stirring and dispersing at a high speed for 60-100min to prepare a catalyst slurry;

The mass ratio of the solid catalyst particles, the binder, the dispersant and the stabilizer is 1-3:7-11:30-50:20-35;

(4) Coating the catalyst slurry of step (3) on the proton exchange membrane to obtain the catalyst layer.

In the above technical scheme, further, the coating described in the step (4) comprises the following steps:

(A) feeding the catalyst slurry prepared in step (1) into the coating die head in the continuous coating equipment, and tensioning the proton exchange membrane web into the conveying mechanism in the continuous coating equipment ;

(B) the coating die head coats the proton exchange membrane coil material in transmission, and the coating die head stops feeding every time the coating is completed, and then retreats along the vertical direction of the proton exchange membrane coil material;

(C) the coating die head of completing step B is vertically advanced to the place close to the proton exchange membrane coil, and then the coating die head is fed to realize the next coating of the proton exchange membrane;

(D) repeating steps C-D to realize intermittent coating of the proton exchange membrane to form a proton exchange membrane electrode with a catalyst layer;

(E) The proton exchange membrane electrode that has completed step D is dried.

In the above technical solution, further, the solid catalyst particles are carbon-supported Pt catalysts or carbon-supported Pt alloy catalysts, wherein the Pt content in the carbon-supported Pt catalysts or carbon-supported Pt alloy catalysts is 20-80wt%.

In the above technical solution, further, the binder is selected from the perfluorosulfonic acid resin liquid with a content of 5-20wt%, the sulfonated polyetheretherketone resin liquid with a content of 1-20wt%, and the sulfonic acid with a content of 1-20wt% One or more combinations of trifluorostyrene resin liquid and 1wt%-20wt% polymethylphenylsulfonic acid siloxane resin liquid.

In the above technical scheme, further, the dispersing agent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, butanol; the stabilizer is selected from propylene glycol, glycerol, ethylene glycol, One or more of n-butyl acetate, propylene glycol ether and 2-ethoxyethanol.

In the above technical solution, further, the viscosity of the catalyst slurry is 100-1000mPa﹒ s, the solid content of the catalyst slurry is 5-20 wt%.

In the above technical solution, further, the catalyst slurry in the step (3) is tested for uniformity, and the uniformity test method is as follows: drop the catalyst slurry on a smooth and clean glass surface to level it naturally and then observe it with the naked eye. After the catalyst slurry is dried, it is observed that there is light transmission and cracks, which proves that the dispersion is not uniform. The catalyst slurry is ultrasonically oscillated again and stirred at a high speed for 30-60min.

In the above technical solution, further, the retreat distance of the coating die in step S2 (B) is 100-1000 μm; the coating speed is 1-10 m/min, the coating thickness is 50-400 μm, and the coating pressure is 0.01-2bar.

In the above technical solution, further, in step E, the drying adopts a four-stage oven to realize the gradient drying of the proton exchange membrane electrode, and the temperature of the four-stage oven is respectively set to The temperature is 30-70°C, the temperature of the third stage is 40-80°C, and the temperature of the fourth stage is 60-120°C.

Compared with the prior art, the beneficial effects of the present invention:

1. In the preparation process of the catalyst slurry of the present invention, the catalyst slurry is dispersed more uniformly through the change of the binder and the addition of the stabilizer; first of all, the Na ⁺ type of the sulfonic acid group of the binder makes the When the catalyst slurry is coated on the surface of the proton exchange membrane, the thermal stability is greatly increased, which is conducive to the volatilization of the stabilizer. On the other hand, the gas permeability of the prepared catalytic layer will also increase, which reduces the gas mass transfer resistance and improves the electrical chemical properties; secondly, the addition of the stabilizer makes the catalyst slurry have a larger viscosity, and its stability is greatly improved, avoiding the sedimentation and stratification of the catalyst slurry; finally, ultrasonic vibration and high-speed stirring are selected in the dispersion process of the catalyst slurry. , which not only shortens the dispersion time, but also removes the bubbles in the catalyst slurry by ultrasonic waves;

2. In the process of coating the catalytic layer with the catalyst slurry of the present invention, the die head retreat process steps are designed to solve the defects of uneven coating head and tail in the intermittent coating process. , the die head did not retreat during the coating process, resulting in tailing at the end of the coating and because the coating ended early, the coating in the trailing part was thinner; the stable coating pressure ensures continuous coating and inter-section coating process. The thickness of the coating layer is uniform, the catalyst slurry prepared by the present invention has good dispersion and excellent stability due to the change of the binder and the addition of the stabilizer, and the catalyst slurry and the proton exchange membrane have better adhesion. The uniformity of the catalytic layer is better. In addition, the optimization and improvement of the coating method, such as the retreat control of the coating die, can avoid the catalyst slurry with strong adhesion during coating. Serious tailing phenomenon further ensures the uniformity of the catalyst layer obtained by coating; finally, the drying of the catalyst slurry layer selects a gradient drying drying tunnel, on the one hand, to avoid cracks and shedding of the catalyst slurry layer due to excessive temperature at the beginning of drying. On the other hand, the catalyst slurry layer volatilizes the dispersant at low temperature, gradually increases the temperature, evaporates the stabilizer with a higher boiling point, increases the natural leveling of the coating during the drying process, and ensures the stability and uniformity of the catalytic layer;

3. The catalytic layer prepared by the present invention has excellent electrochemical performance, and the catalytic layer is thin and uniform, which not only reduces the usage amount of the catalyst, saves the cost, but also improves the yield.

Detailed ways

The present invention is further described below in conjunction with specific embodiments, but does not limit the present invention in any way.

Example 1

The preparation of the catalyst layer of the membrane electrode of the fuel cell includes the following steps:

(1) take by weighing the Pt/C catalyst of 10g 20wt% and mix with 300g isopropanol, ultrasonic vibration 10min; Then add 200g n-butyl acetate, continue to use ultrasonic vibration 10min;

(2) Weigh 70g of 5wt% perfluorosulfonic acid resin solution and put it into a glass container, add 10mL of 1mol/L NaOH aqueous solution, and stir at 25°C for 4h to obtain Na ^- typed perfluorosulfonic acid resin solution;

(3) Add the Na ⁺ type perfluorosulfonic acid resin solution in (2) into (1), ultrasonically vibrate for 30 minutes, stir and disperse at a high speed for 60 minutes to obtain a catalyst slurry, and detect the presence of the catalyst slurry through the smooth glass surface. Uniformity, that is, drop the catalyst slurry on a smooth and clean glass surface and level it naturally, and observe after drying. If there is no light transmission, no cracks, no graininess, and no flocculation, it will be dispersed evenly. Otherwise, the catalyst slurry will be ultrasonically oscillated again. Stir and disperse at high speed for 30-60min;

(4) Select the coating speed of (3) 1 m/min, the coating thickness 50 μm, the die head retreats to the distance of 100 μm from the surface of the proton exchange membrane at the end of coating, and the feeding pressure is 0.01 bar. It is clothed on the proton exchange membrane and passed through the drying tunnel with the temperatures of 20°C, 30°C, 40°C and 60°C, respectively, to obtain a uniform catalytic layer.

Example 2:

The preparation of the catalyst layer of the membrane electrode of the fuel cell includes the following steps:

(1) take by weighing the Pt/C catalyst of 20g 80wt% and mix with 333g ethanol, ultrasonic vibration 30min; Then add 233g propylene glycol, continue to use ultrasonic vibration 30min;

(2) weigh 73g of 5wt% perfluorosulfonic acid resin solution and put it into a glass container, add 12mL of 1mol/L NaOH aqueous solution, and stir at 25°C for 4h to obtain Na ^- typed perfluorosulfonic acid resin solution;

(3) Add the Na ⁺ type perfluorosulfonic acid resin solution in (2) into (1), ultrasonically vibrate for 60 minutes, stir and disperse at a high speed for 100 minutes to obtain a catalyst slurry, and detect the presence of the catalyst slurry through the smooth glass surface. uniformity;

(4) Select the catalyst slurry of (3) with a coating speed of 10 m/min, a coating thickness of 100 μm, the die head retreating to a distance of 200 μm from the surface of the proton exchange membrane at the end of coating, and a feed pressure of 2 bar. Process intermittent coating On the proton exchange membrane, a uniform catalytic layer was obtained by drying in a drying tunnel at temperatures of 60 °C, 70 °C, 80 °C and 120 °C, respectively.

Example 3:

The preparation of the catalyst layer of the membrane electrode of the fuel cell includes the following steps:

(1) take by weighing the Pt/C catalyst of 15g 40wt% and mix with 400g ethanol, ultrasonic vibration 20min; Then add 187g glycerol, continue to use ultrasonic vibration 20min;

(2) Weigh 60g of 5wt% perfluorosulfonic acid resin solution and put it into a glass container, add 8mL of 1mol/L NaOH aqueous solution, and stir at 25°C for 4h to obtain Na ^- typed perfluorosulfonic acid resin solution;

(3) Add the Na ⁺ type perfluorosulfonic acid resin solution in (2) into (1), ultrasonically vibrate for 60 minutes, stir and disperse at a high speed for 100 minutes to obtain a catalyst slurry, and detect the presence of the catalyst slurry through the smooth glass surface. uniformity;

(4) Select the catalyst slurry of (3) with a coating speed of 10 m/min, a coating thickness of 100 μm, the die head retreating to a distance of 200 μm from the surface of the proton exchange membrane at the end of coating, and a feed pressure of 2 bar. Process intermittent coating On the proton exchange membrane, a uniform catalytic layer was obtained through drying tunnels with temperatures of 50 °C, 60 °C, 80 °C and 100 °C, respectively.

Comparative Example 1:

(1) mix by weighing 10g 20wt% Pt/C catalyst and 300g isopropanol, ultrasonically vibrate for 10min; add 70g5wt% perfluorosulfonic acid resin liquid, ultrasonically vibrate for 30min, stir and disperse at high speed for 60min to obtain catalyst slurry;

(2) The catalyst slurry of (1) was intermittently coated on the proton exchange membrane with a coating speed of 1 m/min and a coating thickness of 50 μm, and passed through a drying tunnel with a temperature of 60° C. respectively to obtain a catalyst layer.

Comparative Example 2:

(1) take by weighing the Pt/C catalyst of 20g 80wt% and mix with 333g ethanol, ultrasonic vibration 30min; Then add 233g propylene glycol, continue to use ultrasonic vibration 30min; Add the perfluorosulfonic acid resin liquid of 73g 5wt%, ultrasonic vibration 60min, high speed Stir and disperse for 100min to obtain catalyst slurry;

(2) The catalyst slurry of (1) was intermittently coated on the proton exchange membrane with a selected coating speed of 10 m/min, a coating thickness of 100 μm and a pressure of 2 bar, and was dried through a drying tunnel at a temperature of 120° C. to obtain a catalyst Floor.

Through the examples and comparative examples, it is found that in the preparation process of the catalyst slurry, the stability of the catalyst slurry is greatly improved after adding the stabilizer, ^and the catalyst viscosity can be controlled within a suitable range; , During the drying process of the catalyst layer slurry layer, the ion binding force is stronger, so there will be no defects such as cracks, and the prepared catalyst layer is more uniform; and after the Na ⁺ type treatment, the gas transmission of the catalyst layer is reduced. resistance, the battery performance is excellent. In the intermittent coating process, the die head retreat is increased and the gradient drying tunnel is adopted, and the thickness of the coating head and tail is uniform.

The stability of the catalyst slurry prepared by the present invention is tested by the following method: placing the catalyst slurry in a glass container for 48 hours, dividing it into upper, middle and lower layers according to the scale line on the glass container, and testing the viscosity of the three-layer slurry respectively , and analyze whether the slurry settles by viscosity change. Tested by an electronic digital viscometer, the results are shown in Table 1. The viscosity of the catalyst slurry prepared by the present invention is still stable after as long as 48 hours, and the phenomenon of sedimentation and delamination does not appear. And no sediments and agglomerates appear.

The test results are shown in Table 1:

Example 1 2 3 Contrast 1 Contrast 2 Upper layer viscosity/cp 168 179 171 112 132 Middle viscosity/cp 170 184 181 150 186 Lower viscosity/cp 180 192 188 187 221

The porosity of the catalyst layer prepared in the present invention is tested by mercury intrusion method. The mercury intrusion instrument model is PoremasterGT60 (Quantachrome), the pressure range is 1.38×10 ³ -4.13×10 ⁷ Pa (0.2-0.4×10 ⁴ psi), and the mercury The contact angle is 140°. The obtained porosity is shown in Table 2. It can be seen from the table that the porosity of the catalyst layer prepared by the present invention is significantly higher than that of the catalyst layer without the binder treatment.

The catalyst slurry prepared by the present invention is used to prepare a film-forming electrode and assemble a battery, and then evaluate its battery performance under the condition of hydrogen and oxygen. Test conditions: battery operating temperature: 60°C, H2/O2 100RH%, flow rate 40/100mL/min, and air inlets are at normal pressure. The test results are shown in Table 2. It can be seen from the battery test results that the power generation performance of the battery is obviously excellent by adopting the preparation method of the catalyst slurry and the preparation and treatment process of the catalyst layer of the present invention.

The test results are shown in Table 2:

Example Porosity/% 0.6V 0.7V 0.8V 1 82 0.79 0.65 0.42 2 79 0.82 0.68 0.44 3 81 0.78 0.59 0.47 Contrast 1 63 0.63 0.41 0.21 Contrast 2 71 0.61 0.39 0.19

For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical content disclosed above, or modified into equivalents of equivalent changes Example. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention should still fall within the protection scope of the technical solutions of the present invention.

Claims (6)

1. a preparation method of a fuel cell membrane electrode catalytic layer, is characterized in that, comprises the steps: (1) Mix the solid catalyst particles and dispersant, and disperse by ultrasonic vibration for 10-30 minutes to form a uniform mixture; then add a stabilizer, and disperse by ultrasonic vibration for 10-30 minutes and high-speed stirring for 30-60 minutes to form a uniform mixture; (2) Add 1 mol/L NaOH solution to the binder, the ratio of the molar amount of sodium hydroxide to the molar amount of sulfonate in the binder is 0.1-2:1, and the binder is Na ⁺ type treatment , so that it is converted from H ⁺ type to Na ⁺ type; (3) adding the Na ⁺ type-treated binder in step (2) into the mixed solution of (1), ultrasonically oscillating and stirring and dispersing at high speed for 60-100min to prepare a catalyst slurry; The mass ratio of the solid catalyst particles, the binder, the dispersant and the stabilizer is 1-3:7-11:30-50:20-35; (4) coating the catalyst slurry of step (3) on the proton exchange membrane to obtain the catalyst layer; The coating described in the step (4) includes the following steps: (A) feeding the catalyst slurry prepared in step (1) into the coating die head in the continuous coating equipment, and tensioning the proton exchange membrane web in the conveying mechanism of the continuous coating equipment ; (B) the coating die head coats the proton exchange membrane web material being conveyed, and the coating die head stops feeding every time the coating is completed, and then retreats along the vertical direction of the proton exchange membrane web material; (C) The coating die head that has completed step B is vertically advanced to the position close to the proton exchange membrane coil, and then the coating die head is supplied with material to realize the next coating of the proton exchange membrane; (D) Steps B-C are repeated to realize intermittent coating of the proton exchange membrane to form a proton exchange membrane electrode with a catalyst layer; (E) drying the proton exchange membrane electrode after completing step D; In step (B), the retreat distance of the coating die is 100-1000 μm; the coating speed is 1-10 m/min, the coating thickness is 50-400 μm, and the coating pressure is 0.01-2 bar; In step (E), a four-stage oven is used to realize the gradient drying of the proton exchange membrane electrode. The temperature of the four-stage oven is respectively set as: the temperature of the first stage is 20-60°C, and the temperature of the second stage is 30-70°C. , the temperature of the third section is 40-80 °C, and the temperature of the fourth section is 60-120 °C. 2. The preparation method according to claim 1, wherein the solid catalyst particle is a carbon-supported Pt catalyst or a carbon-supported Pt alloy catalyst, wherein the Pt content in the carbon-supported Pt catalyst or the carbon-supported Pt alloy catalyst is 20- 80wt%. 3. The preparation method according to claim 1, wherein the binder is selected from the group consisting of 5-20wt% perfluorosulfonic acid resin solution and 1-20wt% sulfonated polyetheretherketone resin solution One or more combinations of 1wt%-20wt% of sulfonated trifluorostyrene resin liquid and 1wt%-20wt% of polymethylphenylsulfonic acid siloxane resin liquid. 4. preparation method according to claim 1, is characterized in that: described dispersant is selected from one or more in methanol, ethanol, n-propanol, isopropanol, butanol; Described stabilizer is selected from One or more of propylene glycol, glycerol, ethylene glycol, n-butyl acetate, propylene glycol ethyl ether and 2-ethoxyethanol. 5. The preparation method according to claim 1, characterized in that: the viscosity of the catalyst slurry is 100-1000mPa﹒ s, the solid content of the catalyst slurry is 5-20 wt%. 6 . The preparation method according to claim 1 , wherein the catalyst slurry in step (3) is subjected to uniformity detection, and the uniformity detection method is: dropping the catalyst slurry on a smooth and clean glass surface. 7 . After natural leveling, observe with the naked eye. After drying, the catalyst slurry is observed to have light transmission and cracks. Then, ultrasonically vibrate the catalyst slurry again and stir and disperse it at a high speed for 30-60min.