JP2020140869A - Manufacturing method of fuel cell catalyst layer - Google Patents

Abstract

To provide a manufacturing method of a fuel cell catalyst layer that can enhance the catalytic performance.SOLUTION: A manufacturing method of a fuel cell catalyst layer includes at least a coating step S1 of applying a catalyst ink containing a high boiling point solvent DAA, an ionomer, and a catalyst carrier to a transfer substrate 61 to form a catalyst layer 62, and a drying step S2 of drying the catalyst layer 62. In the drying step S2, ultrasonic oscillating air is blown onto the surface of the catalyst layer 62 to dry the catalyst layer 62 with the surface temperature of the catalyst layer 62 equal to or below the boiling point of the high boiling point solvent DAA.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for manufacturing a catalyst layer for a fuel cell.

Conventionally, as a technique in such a field, for example, there is one described in Patent Document 1 below. In the method for producing a catalyst layer for a fuel cell described in Patent Document 1, a catalyst ink containing a solvent and an electrolyte resin is applied to a transfer substrate to form a catalyst layer, and then the catalyst layer is formed at a temperature equal to or higher than the boiling point of the solvent. Is further dried, and further dried at a temperature equal to or higher than the glass transition temperature of the electrolyte resin. By doing so, it is possible to suppress the occurrence of cracks and irregularities on the surface of the catalyst layer after drying.

Japanese Unexamined Patent Publication No. 2015-201254

However, in the method for producing a catalyst layer for a fuel cell described above, there is room for improvement in the catalytic performance of the produced catalyst layer.

The present invention has been made to solve such a technical problem, and an object of the present invention is to provide a method for manufacturing a catalyst layer for a fuel cell, which can enhance the catalyst performance.

The method for producing a catalyst layer for a fuel cell according to the present invention includes a coating step of applying a catalyst ink containing a solvent, an ionomer, and a catalyst carrier to a transfer substrate to form a catalyst layer, and drying the catalyst layer. A method for producing a catalyst layer for a fuel cell, which comprises at least a drying step. In the drying step, ultrasonic vibration air is applied to the surface of the catalyst layer in a state where the surface temperature of the catalyst layer is equal to or lower than the boiling point of the solvent. It is characterized in that the catalyst layer is dried by spraying.

According to the method for producing a catalyst layer for a fuel cell according to the present invention, in the drying step, the surface temperature of the catalyst layer is kept below the boiling point of the solvent, and ultrasonic vibration air is blown onto the surface of the catalyst layer to form the catalyst layer. Since it is dried, the drying time of the catalyst layer can be shortened at a temperature equal to or lower than the boiling point of the solvent, and the ionomers can be unevenly distributed on the surface side of the catalyst layer. As a result, the resistance of the catalyst layer can be reduced and the catalyst performance can be improved. Then, when the catalyst layer thus formed is transferred to, for example, an electrolyte membrane for a fuel cell, if the ionomer unevenly distributed on the surface side of the catalyst layer is transferred so as to be in contact with the electrolyte membrane, the electrolyte membrane and the catalyst layer can be connected. The impedance between can be reduced. Therefore, the high-temperature power generation performance of the fuel cell and the sub-zero starting durability performance can be improved.

According to the present invention, the catalytic performance can be improved.

It is a schematic cross-sectional view which shows the main part of the fuel cell provided with the catalyst layer for a fuel cell. It is a schematic block diagram which shows the manufacturing apparatus which concerns on the manufacturing method of the catalyst layer for a fuel cell. It is a schematic block diagram which shows the other manufacturing apparatus which concerns on the manufacturing method of the catalyst layer for a fuel cell. It is a figure which shows the thickness and variation of the electrode catalyst layer with respect to Example 1, 2 and Comparative Example 1. It is a figure which shows the relationship between the temperature and TG about Examples 3-5 and Comparative Example 2. It is a figure which shows the impedance characteristic about Example 3-5 and Comparative Example 2. It is a figure which shows the relationship between the thickness of the electrode catalyst layer and the fluorescence intensity of an ionomer in a cross-sectional direction regarding Examples 3 to 5 and Comparative Example 2. It is a figure which shows the thickness and variation of the electrode catalyst layer with respect to Examples 6-8 and Comparative Example 3.

Hereinafter, embodiments of the method for manufacturing a fuel cell catalyst layer according to the present invention will be described with reference to the drawings, but before that, a structure of a fuel cell provided with a fuel cell catalyst layer will be briefly described based on FIG. explain.

[About fuel cells equipped with a catalyst layer for fuel cells]
FIG. 1 is a schematic cross-sectional view showing a main part of a fuel cell provided with a catalyst layer for a fuel cell. As shown in FIG. 1, a plurality of fuel cell cells 1, which are basic units, are stacked on the fuel cell 10. The fuel cell 1 is a solid polymer fuel cell that generates an electromotive force by an electrochemical reaction between an oxidant gas (for example, air) and a fuel gas (for example, hydrogen gas). The fuel cell 1 includes MEGA (Membrane Electrode & Gas Diffusion Layer Assembly) 2 and a pair of separators 3 and 3 that sandwich MEGA 2.

MEGA2 is a combination of MEA (Membrane Electrode Assembly) 4 and gas diffusion layers 7 and 7 arranged on both sides of MEA4. The MEA4 is composed of an electrolyte membrane 5 and a pair of electrode catalyst layers 6 and 6 bonded so as to sandwich the electrolyte membrane 5. The electrolyte membrane 5 is made of a proton-conducting ion exchange membrane made of a solid polymer material. The electrode catalyst layer 6 corresponds to the "catalyst layer for a fuel cell" described in the claims, and is formed of, for example, a porous carbon material carrying a catalyst such as platinum. The electrode catalyst layer 6 arranged on one side of the electrolyte film 5 serves as the anode electrode catalyst layer, and the electrode catalyst layer 6 on the other side serves as the cathode electrode catalyst layer. The gas diffusion layer 7 has a structure for uniformly supplying the oxidant gas or the fuel gas to the electrode catalyst layer 6.

The MEGA 2 constitutes a power generation unit of the fuel cell 10, and the separator 3 is arranged so as to be in contact with the gas diffusion layer 7 of the MEGA 2. The separator 3 is formed into a corrugated shape by alternately repeating the concave portion 3a and the convex portion 3b. The bottom of the recess 3a has a flat surface and is in surface contact with the gas diffusion layer 7 of MEGA2. On the other hand, the top of the convex portion 3b is also flat, and is in surface contact with the top of the convex portion 3b in the adjacent separator 3.

As shown in FIG. 1, one of the pair of gas diffusion layers 7 and 7 has a groove-shaped fuel gas flow path 11 through which fuel gas flows, together with a convex portion 3b of a separator 3 adjacent thereto. It is drawing. The other gas diffusion layer 7 defines a groove-shaped oxidant gas flow path 12 through which the oxidant gas flows, together with the convex portion 3b of the separator 3 adjacent thereto.

The fuel cell 1s are laminated so that the anode electrode catalyst layer 6 of a certain fuel cell 1 and the cathode electrode catalyst layer 6 of another fuel cell 1 adjacent thereto face each other. As a result, a space 13 is formed between the groove-shaped recesses 3a in the adjacent separators 3. This space 13 becomes a refrigerant flow path through which the refrigerant flows.

[Manufacturing method of catalyst layer for fuel cell]
Hereinafter, a manufacturing method for manufacturing the electrode catalyst layer 6 using the manufacturing apparatus shown in FIG. 2 will be described. FIG. 2 is a schematic configuration diagram showing a manufacturing apparatus according to a method for manufacturing a catalyst layer for a fuel cell. The manufacturing apparatus 20 includes an upstream transfer roller 21 and a downstream transfer roller 22 for transporting the strip-shaped transfer substrate 61, a die head 23 for applying catalyst ink to the transfer substrate 61 to be transported, and an upstream side. It is provided with an ultrasonic nozzle 24 arranged between the transfer roller 21 and the downstream transfer roller 22.

The upstream transfer roller 21 and the downstream transfer roller 22 are arranged apart from each other at a predetermined distance, and the transfer substrate 61 is conveyed in a state where a constant tension is applied to the transfer substrate 61. The die head 23 is arranged in the vicinity of the upstream transfer roller 21, and a predetermined amount of catalyst ink is applied to the transfer base material 61 passing through the upstream transfer roller 21. The ultrasonic nozzle 24 is arranged on the downstream side of the die head 23, and blows ultrasonic vibration air onto the surface of the catalyst layer 62 formed on the transfer base material 61 by applying the catalyst ink to dry the catalyst layer 62. .. The ultrasonic nozzle 24 is connected to a heater 25, which will be described later, and injects ultrasonic vibration toward the catalyst layer 62 in a state where ultrasonic vibration is applied to the warm air heated and supplied by the heater 25.

Further, the manufacturing apparatus 20 further includes a pressure blower 26 for introducing air, a vacuum blower 29 for sucking air, and a heater 25 which is connected to the pressure blower 26 and warms the air sent from the pressure blower 26. A motor 27 for rotating a fan attached to the pressure blower 26, and a control panel 28 for controlling the operation of the heater 25 and the motor 27 are provided.

The method for producing the catalyst layer for a fuel cell according to the present embodiment is mainly formed in a coating step S1 in which the catalyst ink is applied to the transfer substrate 61 to form the catalyst layer 62, and a coating step S1. It includes a drying step S2 for drying the catalyst layer 62.

Specifically, in the coating step S1, the catalyst ink is applied to the transfer base material 61 passing through the upstream transfer roller 21 using the die head 23, and the catalyst layer 62 is formed on the transfer base material 61. The catalyst layer 62 here is the electrode catalyst layer 6 before drying, in other words, when the catalyst layer 62 is dried (that is, the catalyst layer 62 after drying), it becomes the electrode catalyst layer 6.

The catalyst ink contains a solvent, an ionomer, and a catalyst carrier. As the solvent, for example, diacetone alcohol having a high boiling point (hereinafter, referred to as a high boiling point solvent DAA) is used. The ionomer is an ionic electrolyte resin, and in the present embodiment, for example, a perfluorocarbon sulfonic acid resin is used as the ionomer. The catalyst carrier is a carrier on which a catalyst is supported. In this embodiment, platinum or an alloy of platinum is used as the catalyst, and carbon powder is used as the carrier.

The composition of the catalyst ink is a solid content concentration of 9.1%, a weight ratio of ionomer to carbon of 0.75 to 0.85, a water content of 60%, and a high boiling point solvent DAA ratio of 20%. Regarding the particle size distribution of the catalyst ink, D50 is 1 μm or less and D90 is 3 μm or less. Further, the shear viscosity of the catalyst ink is 35 to 110 mPa · s (562s ^-1 ).

In the drying step S2, the surface temperature of the catalyst layer 62 formed in the coating step S1 is kept below the boiling point of the high boiling point solvent DAA, and ultrasonic vibration air is blown onto the surface of the catalyst layer 62 to dry the catalyst layer 62. .. Since the boiling point of the high boiling point solvent DAA is 168 ° C., the surface temperature of the catalyst layer 62 is set to, for example, 100 ° C. here. Then, in order to maintain the surface temperature of the catalyst layer 62 at 100 ° C., for example, the distance between the ultrasonic nozzle 24 and the surface of the catalyst layer 62, the internal pressure of the ultrasonic nozzle 24, and the injection of the ultrasonic nozzle 24 per unit time. The heating temperature by the heater 25 is adjusted based on the amount and the like.

Here, it is preferable that the internal pressure of the ultrasonic nozzle 24 is 13 kPa or more. Further, when the ultrasonic vibration air is blown onto the surface of the catalyst layer 62 by the ultrasonic nozzle 24, the blowing is performed so that the catalyst layer 62 is not cracked or blown off.

Then, when the catalyst layer 62 is dried by spraying the ultrasonic nozzle 24, the above-mentioned electrode catalyst layer 6 is manufactured. The electrode catalyst layer 6 produced in this way is carried to the next step, and transfer to the electrolyte membrane 5 is carried out.

In the method for producing a catalyst layer for a fuel cell according to the present embodiment, in the drying step S2, ultrasonic vibration air is applied to the surface of the catalyst layer 62 in a state where the surface temperature of the catalyst layer 62 is equal to or lower than the boiling point of the high boiling point catalyst DAA. The catalyst layer 62 is dried by spraying. The ultrasonic oscillating air can destroy the volatile matter retention layer existing on the surface of the catalyst layer 62, prevent the retention of solvent and water due to the volatile retention layer, and shorten the drying time of the catalyst layer 62. ..

Moreover, by doing so, it is possible to reduce the variation in the thickness of the manufactured electrode catalyst layer 6, and as an example, for example, the variation in the thickness is within ± 10% with respect to a predetermined reference value. Can be. Further, since the drying time can be shortened in a state where the surface temperature of the catalyst layer 62 is equal to or lower than the boiling point of the high boiling point solvent DAA, it is possible to suppress an increase in cost due to heating.

In addition, in this way, the ionomers can be unevenly distributed on the surface side of the catalyst layer. Therefore, the resistance of the manufactured electrode catalyst layer 6 can be reduced, and the catalyst performance can be improved. For example, when the electrode catalyst layer 6 produced in this way is transferred to the electrolyte membrane 5, if the ionomer unevenly distributed on the surface side is transferred so as to be in contact with the electrolyte membrane 5, the space between the electrolyte membrane 5 and the electrode catalyst layer 6 can be obtained. The impedance of the can be reduced. This makes it possible to improve the high-temperature power generation performance and the sub-zero starting durability performance of the fuel cell 10 having the electrolyte membrane 5 and the electrode catalyst layer 6.

The method for manufacturing the catalyst layer for a fuel cell according to the present embodiment may be carried out using the manufacturing apparatus 20A shown in FIG. FIG. 3 is a schematic configuration diagram showing another manufacturing apparatus according to a method for manufacturing a catalyst layer for a fuel cell. The manufacturing apparatus 20A shown in FIG. 3 is different from the manufacturing apparatus 20 described above in the arrangement position of the ultrasonic nozzle 24, but other configurations are the same as those of the manufacturing apparatus 20 described above.

In the manufacturing apparatus 20A, the ultrasonic nozzle 24 is arranged in the vicinity of the downstream transfer roller 22, and ultrasonic vibration air is injected toward the catalyst layer 62 passing through the downstream transfer roller 22. By doing so, the following effects can be expected as compared with the case where the above-mentioned manufacturing apparatus 20 is used.

That is, even if the transfer base material 61 is thin and a certain tension is applied when it is transferred to the upstream transfer roller 21 and the downstream transfer roller 22, there is no support from below, so that it is for transfer. The base material 61 and the catalyst layer 62 formed on the transfer base material 61 may become unstable. In the manufacturing apparatus 20 shown in FIG. 2, since ultrasonic oscillating air is blown onto the catalyst layer 62 in such an unsupported state, the thickness of the manufactured electrode catalyst layer 6 may vary.

On the other hand, in the manufacturing apparatus 20A shown in FIG. 3, the ultrasonic nozzle 24 blows ultrasonic oscillating air toward the catalyst layer 62 passing through the downstream transfer roller 22. Therefore, since the ultrasonic vibration air is blown to the transfer base material 61 and the catalyst layer 62 while being supported by the downstream transfer roller 22, the catalyst layer 62 can be stabilized. As a result, it is possible to reduce variations in the thickness of the manufactured electrode catalyst layer 6.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the scope of the Examples.

[Examples 1 and 2]
In Examples 1 and 2, electrode catalyst layers were prepared under various conditions shown in Table 1 by using the above-mentioned manufacturing apparatus 20 and the method for manufacturing a catalyst layer for a fuel cell, and the drying rate of the solvent was measured. The composition of the catalyst ink used in Examples 1 and 2 was the same as that described in the above-described embodiment. Further, although the internal pressure of the ultrasonic nozzle was different from that of Example 1 and Example 2, other conditions were the same.

[Comparative Example 1]
Further, for comparison, after forming the catalyst layer using the catalyst ink having the same composition as in Examples 1 and 2, the catalyst layer was dried in the current hot air drying furnace to prepare an electrode catalyst layer (Comparative Example). 1). With respect to the prepared electrode catalyst layer, the solvent drying rate was measured in the same manner as in Examples 1 and 2.

Table 1 shows the measurement results of the solvent drying rate in Example 1, Example 2, and Comparative Example 1. From Table 1, it was found that in Examples 1 and 2, the drying rate of the solvent was significantly faster than that in Comparative Example 1. As a result, it was shown that the drying time of the catalyst layer can be shortened by blowing ultrasonic oscillating air in the present invention. Further, from the results of Examples 1 and 2, it was found that the drying speed of the solvent increases as the internal pressure of the ultrasonic nozzle increases. The ultrasonic nozzle distance shown in Table 1 refers to the distance from the ultrasonic nozzle to the surface of the catalyst layer.

FIG. 4 is a diagram showing the thickness and variation of the electrode catalyst layer with respect to Examples 1, 2 and Comparative Example 1. From FIG. 4, it was found that in Examples 1 and 2, the variation in the thickness of the electrode catalyst layer was smaller than that in Comparative Example 1.

[Examples 3 to 5]
In Examples 3 to 5, electrode catalyst layers were prepared under the conditions shown in Table 2 by using the manufacturing apparatus 20 and the method for manufacturing the catalyst layer for a fuel cell described above, and the prepared electrode catalyst layers were subjected to 260 ° C. TG-DTA analysis was performed by heating to, and the weight loss rate was measured. The composition of the catalyst inks used in Examples 3 to 5 is the same as that described in the above-described embodiment except for the concentration of the high boiling point solvent DAA. Then, Example 3, Example 4, and Example 5 differ only in the concentration of the high boiling point solvent DAA.

[Comparative Example 2]
Further, for comparison, after forming the catalyst layer using the catalyst ink having the same composition as in Examples 3 to 5, the catalyst layer was dried in the current hot air drying furnace to prepare an electrode catalyst layer (Comparative Example). 2). The weight loss rate of the produced electrode catalyst layer was measured in the same manner as in Examples 3 to 5.

Table 2 shows the results of the weight loss rates in Examples 3 to 5 and Comparative Example 2. From Table 2, it was found that the weight loss rate of Examples 3 to 5 was smaller than that of Comparative Example 2, and the catalyst layer was dried faster and better. Further, when Examples 3 to 5 were compared, it was found that the weight loss rate did not change so much even if the concentration of the high boiling point solvent DAA was changed.

FIG. 5 is a diagram showing the relationship between the temperature and TG with respect to Examples 3 to 5 and Comparative Example 2. In FIG. 5, the horizontal axis is the temperature and the vertical axis is the TG (wt%) at the time of reference to 80 ° C. From FIG. 5, it was found that when dried at a temperature lower than the high boiling point solvent DAA (here, 100 ° C.), almost no water was present. Further, as described above, it was found that the degree of drying was almost the same (that is, the weight loss rate did not change much) even if the concentration of the high boiling point solvent DAA was changed.

Further, the electrode catalyst layer produced in Examples 3 to 5 and Comparative Example 2 is transferred to one side of the electrolyte membrane to serve as a cathode, and the electrode catalyst layer is also transferred to the other side of the electrolyte membrane to serve as an anode. A junction (MEA) was made. At the time of transfer, the ionomers unevenly distributed on the surface side of the electrode catalyst layer were brought into contact with the electrolyte membrane. Subsequently, each membrane electrode assembly prepared was sandwiched between gas diffusion layers to prepare each membrane electrode gas diffusion layer assembly (MEGA). Next, each of the prepared membrane electrode gas diffusion layer joints was set in an evaluation cell, and the catalyst layer resistance was measured using an AC impedance meter in an atmosphere of 90 ° C. and 33% humidity. The measurement results are shown in Table 3.

From Table 3, it was found that the impedances of Examples 3 to 5 were smaller than those of Comparative Example 2. Further, when Examples 3 to 5 were compared, it was found that the impedance decreased as the concentration of the high boiling point solvent DAA increased.

FIG. 6 is a diagram showing impedance characteristics according to Examples 3 to 5 and Comparative Example 2. FIG. 6 shows the conditions that the temperature of the fuel cell is 90 °, the humidity is 33%, the anode gas H ₂ is 500 sccm, the cathode gas N ₂ is 1000 sccm, the voltage range is 0.5 V to 10 mV, and the frequency is 10 kHz to 0.1 Hz. It is a plot of the results obtained in.

As shown in FIG. 6, it is already known that the slope of the high frequency region plot (see the part surrounded by an ellipse) depends on the distribution of resistance in the thickness direction of the electrode catalyst layer, and if the ionomer is uniform, that is the case. When the inclination becomes 45 ° and the ionomer is biased (that is, the ionomer is unevenly distributed) and the resistance increases from the electrolyte membrane toward the gas diffusion layer, the inclination becomes larger than 45 °. From FIG. 6, it was found that the slope of the high frequency region plot was as large as 55 ° only in Example 5. Therefore, it is presumed that the ionomer bias is large in the electrode catalyst layer of Example 5.

In addition, the cathode side of each membrane electrode assembly was stained with an ionomer with a fluorescent substance, and the relationship between the brightness of the image obtained by fluorescence microscope observation and the thickness direction of the electrode catalyst layer was determined. The result is shown in FIG. FIG. 7 is a diagram showing the relationship between the thickness of the electrode catalyst layer and the fluorescence intensity of the ionomer in the cross-sectional direction with respect to Examples 3 to 5 and Comparative Example 2, and FIGS. The result of Comparative Example 2 is shown. Further, the fluorescence intensity in FIG. 7 indicates the amount of ionomer, and the larger the value, the larger the amount of ionomer. Further, the arrows shown in each figure of FIG. 7 indicate the direction from the cathode electrode catalyst layer side to the electrolyte membrane side. Therefore, the left side of the horizontal axis of each figure of FIG. 7 is the cathode electrode catalyst layer side and the horizontal axis. The right side of is shown on the electrolyte membrane side.

From FIG. 7, it was found that in the case of Example 5, the bias of the ionomer toward the electrolyte membrane was the most remarkable. Therefore, it was found that when the concentration of the high boiling point solvent DAA is high and the drying rate is high, an electrode catalyst layer having a large ionomer bias can be obtained. The bias of the ionomer toward the electrolyte membrane can improve the high-temperature power generation performance of the fuel cell and the sub-zero starting durability performance.

[Examples 6 to 8]
In Examples 6 to 8, electrode catalyst layers were prepared under various conditions shown in Table 4 by using the above-mentioned production apparatus 20A and the method for producing a catalyst layer for a fuel cell, and the drying rate of the solvent was measured. The composition of the catalyst ink used in Examples 6 to 8 is the same as that described in the above-described embodiment. Examples 6 to 8 differed in the catalyst layer surface temperature, the ultrasonic nozzle distance, and the line speed (that is, the speed of transportation by the upstream transfer roller and the downstream transfer roller), but other conditions were the same.

[Comparative Example 3]
Further, for comparison, after forming the catalyst layer under various conditions shown in Table 4, the catalyst layer was dried in the current hot air drying furnace to prepare an electrode catalyst layer (Comparative Example 3). With respect to the prepared electrode catalyst layer, the solvent drying rate was measured in the same manner as in Examples 6 to 8.

Table 4 shows the measurement results of the solvent drying rate in Examples 6 to 8 and Comparative Example 3. From Table 4, it was found that in Examples 6 to 8, the drying rate of the solvent was faster than that in Comparative Example 3. As a result, it was shown that the drying time of the catalyst layer can be shortened by blowing ultrasonic oscillating air in the present invention.

FIG. 8 is a diagram showing the thickness and variation of the electrode catalyst layer according to Examples 6 to 8 and Comparative Example 3. From FIG. 8, it was found that in Examples 6 to 8, the variation in the thickness of the electrode catalyst layer was smaller than that in Comparative Example 3.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs are designed without departing from the spirit of the present invention described in the claims. It is something that can be changed.

1 fuel cell 2 MEGA
3 Separator 4 MEA
5 Electrolyte membrane 6 Electrode catalyst layer (catalyst layer for fuel cell)
7 Gas diffusion layer 10 Fuel cell 20, 20A Manufacturing equipment 21 Upstream transfer roller 22 Downstream transfer roller 23 Die head 24 Ultrasonic nozzle 25 Heater 26 Pressure blower 27 Motor 28 Control panel 29 Vacuum blower 61 Transfer base material 62 Catalyst layer

Claims (1)

A method for producing a catalyst layer for a fuel cell, which comprises at least a coating step of applying a catalyst ink containing a solvent, an ionomer, and a catalyst carrier to a transfer substrate to form a catalyst layer, and a drying step of drying the catalyst layer. And
In the drying step, a catalyst for a fuel cell is characterized in that the surface temperature of the catalyst layer is set to be equal to or lower than the boiling point of the solvent, and ultrasonic vibration air is blown onto the surface of the catalyst layer to dry the catalyst layer. How to make the layer.

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