JP2020173905A - Evaluation method of catalyst layer - Google Patents

Abstract

To restrain deterioration of yield due to transfer failure.SOLUTION: An evaluation method of catalytic layer for use in a fuel cell having polymer electrolyte includes a step of executing surface interfacial cutting test by SAICAS method for a catalytic layer formed on a backing material, in a state before being transferred to the polymer electrolyte, a step of identifying the quotient by dividing the value of perpendicular force obtained when a cutting blade for cutting the catalytic layer reaches the boundary surface of the catalytic layer and the backing material, by the value of horizontal force obtained after the cutting blade reaches the boundary surface, in the surface interfacial cutting test, and a step of determining that transfer failure does not occur when the quotient is equal to or more than a predetermined threshold level, and that transfer failure occurs when the quotient is less than the threshold level.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for evaluating a catalyst layer used in a fuel cell.

Conventionally, a membrane electrode assembly of a fuel cell may be manufactured including a step of transferring a catalyst layer formed on a base material to an electrolyte membrane. In Patent Document 1, it is determined that a transfer defect has occurred when a residue of a predetermined amount or more of the catalyst layer is detected on the substrate after the catalyst layer is transferred.

Japanese Unexamined Patent Publication No. 2014-201053

In Patent Document 1, since the determination is made using the base material after the catalyst layer has been transferred, material loss such as the catalyst layer and the base material may occur when a transfer failure occurs, and the yield may decrease. Therefore, there has been a demand for a technique capable of suppressing a decrease in yield due to poor transcription.

The present invention can be realized as the following forms.

According to one embodiment of the present invention, a method for evaluating a catalyst layer is provided. This method for evaluating the catalyst layer is a method for evaluating the catalyst layer used in a fuel cell having an electrolyte membrane, and is used on the catalyst layer formed on the substrate in a state before being transferred to the electrolyte membrane. On the other hand, in the step of performing the surface interface cutting test by the SAICAS method and the surface interface cutting test, the value of the vertical force when the cutting blade for cutting the catalyst layer reaches the interface between the catalyst layer and the base material. The step of specifying the quotient obtained by dividing the quotient by the value of the horizontal force after the cutting blade reaches the interface, and determining that transfer failure does not occur when the quotient is equal to or higher than a predetermined threshold, and the above-mentioned A step of determining that the transfer defect occurs when the quotient is less than the threshold value is provided. According to the evaluation method of the catalyst layer of this form, the cutting edge determines the value of the vertical force when the cutting blade for cutting the catalyst layer reaches the interface between the catalyst layer and the base material in the surface interface cutting test by the SAICAS method. Since the determination is made based on the quotient divided by the value of the horizontal force after reaching, the transferability can be determined at the stage before the catalyst layer is transferred to the electrolyte membrane. Therefore, since the catalyst layer determined to "do not cause transfer failure" can be transferred to the electrolyte membrane to form a membrane electrode assembly, the occurrence of transfer failure can be suppressed, and the material such as the catalyst layer and the base material can be used. It is possible to suppress the occurrence of loss. Therefore, it is possible to suppress a decrease in yield due to poor transcription.

The present invention can also be realized in various forms. For example, a method for manufacturing a membrane electrode assembly and a method for manufacturing a fuel cell including the above evaluation method as a part of a process, a computer program for realizing these methods, a storage medium for storing the computer program, and the like. can do.

It is a flowchart which shows the evaluation method of the catalyst layer as one Embodiment of this invention. It is sectional drawing which shows typically the catalyst layer formed on the base material. It is explanatory drawing which shows typically the outline of the surface interface cutting test by the SAICAS method. It is a graph which shows an example of the relationship between the peel strength and the transfer residue ratio measured in the surface interface cutting test by the SAICAS method. It is a table which shows the estimation requirement for transcription establishment. It is a graph which shows an example of the relationship between a quotient and a transcription residue ratio. It is explanatory drawing which shows typically the outline of the evaluation method of the catalyst layer in the comparative example. It is a graph which shows an example of the relationship between the tape peeling strength and the transfer residue ratio.

A. Embodiment:
FIG. 1 is a flowchart showing a method for evaluating a catalyst layer as an embodiment of the present invention. This evaluation method targets the catalyst layer of a membrane electrode assembly (MEA) used in polymer electrolyte fuel cells.

First, the configuration and manufacturing method of the membrane electrode assembly and the fuel cell including the membrane electrode assembly will be briefly described. The fuel cell has a stack structure in which a plurality of single cells are laminated, and each single cell is composed of a membrane electrode assembly and a gas diffusion layer, and a pair of separators sandwiching the membrane electrode assembly and the gas diffusion layer. To. The membrane electrode assembly has a structure in which catalyst layers are arranged on both sides of an electrolyte membrane containing an electrolyte resin as a main component, which exhibits good proton conductivity in a wet state. One of the catalyst layers functions as an anode electrode and the other functions as a cathode electrode.

Each catalyst layer is formed mainly of catalyst-supported carbon supporting catalyst particles and an electrolyte resin. As the catalyst particles, for example, platinum or the like may be used. As the electrolyte resin, for example, a fluorine-based resin such as Nafion (registered trademark) may be used. At least one of the two catalyst layers is formed by applying a catalyst ink containing a catalyst-supporting carbon, an electrolyte resin, and a solvent to a base material and drying the base material, and is transferred from the base material to the electrolyte membrane. As the base material, for example, a sheet such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polytetrafluoroethylene (PTFE) may be used.

FIG. 2 is a cross-sectional view schematically showing the catalyst layer 30 formed on the base material 20. The catalyst layer 30 formed on the base material 20 is transferred to an electrolyte membrane (not shown) by being peeled off at the interface with the base material 20.

In the evaluation method of the catalyst layer 30 shown in FIG. 1, the catalyst ink is applied onto the base material 20 to form the catalyst layer 30 by the above method, and a continuous trial production of the catalyst layer 30 prior to the continuous production of the catalyst layer 30 is performed. Executed before doing.

A surface interface cutting test by the SAICAS method is performed on the catalyst layer 30 formed on the base material 20 in a state before being transferred to the electrolyte membrane (step P110).

FIG. 3 is an explanatory diagram schematically showing an outline of a surface interface cutting test by the SAICAS method. FIG. 3 shows how the cutting blade 90 moves along the time-series TA indicated by the white arrow. Generally, a surface interface cutting test by the SAICAS (Surface And Interfacial Cutting Analysis System) method (hereinafter, simply referred to as "surface interface cutting test") is performed by cutting a sample from the surface to the interface with a cutting blade 90 of a test device. Will be implemented. As a result, the material strength and the adhesion of the material at the interface are analyzed. In the surface interface cutting test, the cutting depth (vertical displacement amount d) and the cutting force (horizontal force FH and vertical force FV) are recorded. The horizontal force FH means the force that the cutting blade 90 receives from the sample in the horizontal direction. The horizontal direction means the direction along the interface of the sample, and corresponds to the direction along the mounting surface of the test apparatus. The normal force FV means the force that the cutting blade 90 receives from the sample in the vertical direction. The vertical direction means a direction perpendicular to the horizontal direction and corresponds to a vertical direction.

FIG. 3A shows a state before the catalyst layer 30 is cut by the cutting blade 90. FIG. 3B shows a state in which the catalyst layer 30 is cut by the cutting blade 90. The horizontal force FH and the normal force FV recorded in this state increase as the vertical displacement amount d increases, that is, as the cutting depth increases. FIG. 3C shows a state in which the cutting blade 90 reaches the interface between the catalyst layer 30 and the base material 20 and the catalyst layer 30 begins to be peeled off from the base material 20. The horizontal force FH and the normal force FV recorded in the state (c) of FIG. 3 are maximum on the time axis of the surface interface cutting test. After the state (c) of FIG. 3, the cutting blade 90 moves horizontally, so that the catalyst layer 30 and the base material 20 are interfacially separated. The horizontal force FH recorded at the time of interfacial peeling changes at a substantially constant value, and the normal force FV recorded at the time of interfacial peeling changes at a value of almost zero.

The surface interface cutting test can be performed using, for example, a DN-100S type SAICAS manufactured by Daipla Wintes Co., Ltd. as a test apparatus. In this embodiment, a Borazon cutting blade having a blade width of 1 mm, a rake angle of 20 °, and a clearance angle of 10 ° is used as the cutting blade 90. Further, in the present embodiment, in the measurement mode of the constant speed mode, cutting is performed under the conditions of a vertical speed of 0.1 μm / sec and a horizontal speed of 10 μm / sec, and the horizontal force FH and the normal force FV are recorded.

In the evaluation method shown in FIG. 1, in the surface interface cutting test, the value A of the vertical force FV when the cutting blade 90 for cutting the catalyst layer 30 reaches the interface between the catalyst layer 30 and the base material 20 is set to the cutting blade 90. The quotient X divided by the value B of the horizontal force FH after reaching the interface is specified (step P120).

The value A of the normal force FV when the cutting blade 90 reaches the interface between the catalyst layer 30 and the base material 20 correlates with the strength of the catalyst layer 30. More specifically, it correlates with the shear strength of the catalyst layer 30. The value A of the normal force FV when the cutting blade 90 reaches the interface between the catalyst layer 30 and the base material 20 is the normal force FV (kN) recorded at the timing of the state (c) in FIG. Corresponds to the peak value of the normal force FV with respect to the time axis.

The value B of the horizontal force FH after the cutting blade 90 reaches the interface correlates with the peel strength P between the catalyst layer 30 and the base material 20. The peel strength P is calculated using the following formula (1). In the formula (1), w means the blade width. The peel strength P between the catalyst layer 30 and the base material 20 can be rephrased as the adhesive strength between the catalyst layer 30 and the base material 20.
P [kN / m] = FV [kN] / w [m] ... (1)

The value B of the horizontal force FH after the cutting blade 90 reaches the interface is such that the cutting blade 90 moves horizontally after the state of (c) in FIG. 3 and the catalyst layer 30 and the base material 20 are separated from each other at the interface. Corresponds to the horizontal force FH (kN) recorded in the state. The horizontal force FH in the state where the catalyst layer 30 and the base material 20 are interfacially separated is substantially constant with respect to the time axis. In the present embodiment, the average value of the substantially constant horizontal force FH within a predetermined time is used as the value B, but the value B is not limited to the average value and is recorded at a certain timing. May be used as.

As shown in FIG. 1, it is specified whether or not the quotient X is equal to or higher than a predetermined threshold value α (step P130). When it is specified that the quotient X is equal to or higher than the threshold value α (step P130: YES), it is determined that no transfer defect occurs (step P140). On the other hand, when it is specified that the quotient X is not equal to or more than the threshold value α, that is, when the quotient X is specified to be less than the threshold value α (step P130: NO), it is determined that a transfer defect occurs (step P150). The reason for making such a determination will be described below.

The inventor of the present application has a better transferability when the catalyst layer 30 formed on the base material 20 is transferred to the electrolyte film, as the adhesive strength between the base material 20 and the catalyst layer 30, that is, the peel strength P is lower. It was assumed that transferability could be obtained. Based on this assumption, the inventor of the present application carries out a surface interface cutting test by the SAICAS method on a plurality of samples, and transfers the catalyst layer 30 formed on the base material 20 to an electrolyte membrane to peel it off. The relationship between the intensity P and the transfer residual rate was determined.

FIG. 4 is a graph showing an example of the relationship between the peel strength P and the transfer residual ratio measured in the surface interface cutting test by the SAICAS method. In FIG. 4, the horizontal axis represents the peel strength P (kN / m) between the base material 20 and the catalyst layer 30 under the above test conditions, and the vertical axis represents the transfer residual ratio (%). In the present embodiment, the “transfer residue rate” means that the catalyst layer 30 having a length of 0.5 mm or more remains on the plane of the base material 20 after the catalyst layer 30 is transferred to the electrolyte membrane. It means the value obtained by dividing the number of samples by the total number of samples. According to FIG. 4, it can be seen that there is no correlation between the peel strength P between the base material 20 and the catalyst layer 30 and the transfer residue rate.

FIG. 5 is a table showing the estimation requirements for the establishment of transcription. Based on the results of FIG. 4, the inventor of the present application considers that the strength of the catalyst layer 30 itself is lower than the peel strength P even when the peel strength P between the base material 20 and the catalyst layer 30 is relatively low. It was presumed that the catalyst layer 30 was destroyed during the transfer and a transfer residue was generated. That is, when the strength of the catalyst layer 30 itself is high and the peel strength P between the base material 20 and the catalyst layer 30 is small, the base material 20 and the catalyst layer 30 are held together while the destruction of the catalyst layer 30 is suppressed during transfer. It was presumed that the transferability to the electrolyte film would be improved because the adhesion at the interface would be broken. According to this estimation, it is considered that the balance of the strength ratio between the peel strength P between the base material 20 and the catalyst layer 30 and the strength of the catalyst layer 30 itself is important.

Based on this estimation, the inventor of the present application carries out a surface interface cutting test using the SAICAS method under the above-mentioned test conditions, and sets a value A that correlates with the strength of the catalyst layer 30 itself between the base material 20 and the catalyst layer 30. The quotient X divided by the value B, which correlates with the peeling strength with, is obtained, and the catalyst layer 30 formed on the base material 20 is transferred to the electrolyte membrane to obtain the relationship between the quotient X and the transfer residual ratio. It was.

FIG. 6 is a graph showing an example of the relationship between the quotient X and the transfer residual rate. In FIG. 6, the horizontal axis represents the quotient X, and the vertical axis represents the transcription residue rate (%). According to FIG. 6, it can be seen that there is a correlation between the quotient X and the transcription residual rate. More specifically, when the value of the quotient X is larger than a certain value, the transfer residue rate is zero, and when the value of the quotient X is smaller than a certain value, the smaller the value of the quotient X is, the more the transfer residue is. The rate is rising.

In the present embodiment, by setting a certain value as the threshold value α, it is specified in the step P130 shown in FIG. 1 whether or not the quotient X is equal to or higher than the predetermined threshold value α. In the present embodiment, the threshold value α is set to, for example, 4.3 as a value at which the transcription residue ratio becomes zero. As described above, the threshold value α is predetermined by an experiment.

As described above, when it is specified that the quotient X is equal to or higher than the threshold value α (step P130: YES), it is determined that no transfer failure occurs (step P140). Therefore, after the step P140, the catalyst layer 30 A continuous trial production of the above may be carried out.

Further, when the quotient X is specified not to be equal to or higher than the threshold value α, that is, when the quotient X is specified to be less than the threshold value α (step P130: NO), it is determined that a transfer defect occurs (step P150). Therefore, after the step P150, the catalyst layer 30 may be recreated by recreating the catalyst ink and applying it on the base material 20.

When the catalyst layer 30 determined not to cause transfer defects by the above evaluation is transferred to the electrolyte membrane, the occurrence of transfer defects can be suppressed. On the other hand, when the catalyst layer 30 determined to cause transfer failure is transferred to the electrolyte membrane, transfer failure occurs. Therefore, by transferring the catalyst layer 30 determined to "do not cause transfer failure" to the electrolyte membrane as described above to form a membrane electrode assembly, the material such as the catalyst layer 30 and the base material 20 can be formed. It is possible to suppress the occurrence of loss. Therefore, it is possible to suppress a decrease in the yield of the catalyst layer 30 and the membrane electrode assembly due to poor transfer.

According to the evaluation method of the catalyst layer 30 in the present embodiment described above, when the cutting blade 90 for cutting the catalyst layer 30 reaches the interface between the catalyst layer 30 and the base material 20 in the surface interface cutting test by the SAICAS method. The quotient X obtained by dividing the value A of the vertical force FV of the above by the value B of the horizontal force FH after the cutting blade 90 reaches the interface is specified, and when the quotient X is equal to or more than a predetermined threshold value α, transfer failure Is determined not to occur, and it is determined that transfer failure occurs when the quotient X is less than the threshold value α. Therefore, the transferability can be determined at the stage before the catalyst layer 30 is transferred to the electrolyte membrane. Therefore, the catalyst layer 30 determined to "do not cause transfer defects" can be transferred to the electrolyte membrane to form a membrane electrode assembly, so that the occurrence of transfer defects can be suppressed, and the catalyst layer 30, the base material 20, and the like can be suppressed. It is possible to suppress the occurrence of material loss. Therefore, it is possible to suppress a decrease in the yield of the catalyst layer 30 and the membrane electrode assembly due to poor transfer. Further, since the determination is performed using the value of the quotient X that correlates with the transfer residual rate, it is possible to suppress a decrease in determination accuracy and suppress the occurrence of transcription defects. Further, since the occurrence of transfer defects can be suppressed, the deterioration of reliability in the membrane electrode assembly and the fuel cell can be suppressed.

Further, the quotient X is obtained by using the value A of the normal force FV and the value B of the horizontal force FH continuously recorded in the surface interface cutting test by the SAICAS method. Therefore, the quotient X can be obtained quickly, and the time required for the evaluation of the catalyst layer 30 can be shortened.

Further, since the value at which the transfer residual rate becomes zero is set as the threshold value α, it is possible to prevent the catalyst layer 30 from remaining on the base material 20 in the state after the catalyst layer 30 is transferred, and the base material 20 can be regenerated. Since it can be used, it leads to resource saving.

B. Comparative example:
FIG. 7 is an explanatory diagram schematically showing an outline of the evaluation method of the catalyst layer 30 in the comparative example. In the evaluation method of the catalyst layer 30 in the comparative example, the tape peel strength P1 is measured by using the tape peeling test, and the catalyst layer 30 formed on the base material 20 is transferred to the electrolyte membrane to transfer the tape peel strength P1. And the transfer residual rate are being sought. In the tape peeling test, for example, a tape 95 having a width of 10 mm manufactured by Nichiban Co., Ltd. is attached to the surface of the catalyst layer 30, and then a tensile tester is used to perform a tape peeling test of 30 mm / min. It can be carried out by pulling the tape 95 vertically upward at the pulling speed of.

FIG. 8 is a graph showing an example of the relationship between the tape peeling strength P1 and the transfer residual ratio. In FIG. 8, the horizontal axis represents the tape peeling strength P1 (kN / m) between the base material 20 and the catalyst layer 30 measured in the tape peeling test under the above conditions, and the vertical axis represents the transfer residual ratio (transfer residue ratio). %) Is shown. According to FIG. 8, it can be seen that there is no correlation between the tape peeling strength P1 between the base material 20 and the catalyst layer 30 and the transfer residual ratio. The reason for this is that the tape peeling test combines three strengths: the adhesive strength between the tape 95 and the catalyst layer 30, the strength of the catalyst layer 30 itself, and the adhesive strength between the base material 20 and the catalyst layer 30. This is probably because it is an evaluation method. Therefore, according to the evaluation method of the catalyst layer 30 in the comparative example, since there is no correlation between the tape peeling strength P1 and the transfer residual ratio, accurate evaluation cannot be performed.

On the other hand, according to the evaluation method of the catalyst layer 30 in the present embodiment, the determination is performed using the value of the quotient X that correlates with the transfer residual rate, so that the determination accuracy as to whether or not a transfer defect occurs is high. It is possible to suppress the decrease and suppress the occurrence of transcription defects.

C. Other embodiments:
(1) In the above embodiment, the threshold value α is predetermined as a value at which the transcription residue rate becomes zero, but is not limited to a value at which the transcription residue rate becomes zero, for example, the transcription residue rate becomes less than 1%. It may be predetermined to an arbitrary value such as a value that can realize a desired small transfer residual ratio. Even with such a configuration, the same effect as that of the above-described embodiment can be obtained.

(2) In the above embodiment, the evaluation of the catalyst layer 30 is performed before the continuous trial production of the catalyst layer 30 prior to the continuous production of the catalyst layer 30, but before the continuous production of the catalyst layer 30, for example. It may be executed. Further, the test conditions of the surface interface cutting test may be arbitrarily determined. Even with such a configuration, the same effect as that of the above-described embodiment can be obtained.

The present invention is not limited to the above-described embodiment, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments corresponding to the technical features in each form described in the column of the outline of the invention may be used to solve some or all of the above-mentioned problems, or one of the above-mentioned effects. It is possible to replace or combine as appropriate to achieve part or all. Further, if the technical feature is not described as essential in the present specification, it can be appropriately deleted.

20 ... base material, 30 ... catalyst layer, 90 ... cutting blade, 95 ... tape, A ... value, B ... value, FH ... horizontal force, FV ... vertical force, P ... peel strength, P1 ... tape peel strength, TA ... Time series, X ... quotient, d ... vertical displacement, α ... threshold

Claims (1)

A method for evaluating a catalyst layer used in a fuel cell having an electrolyte membrane.
A step of performing a surface interface cutting test by the SAICAS method on the catalyst layer formed on the base material in a state before being transferred to the electrolyte membrane, and
In the surface interface cutting test, the value of the vertical force when the cutting blade for cutting the catalyst layer reaches the interface between the catalyst layer and the base material is the horizontal force after the cutting blade reaches the interface. The process of identifying the quotient divided by the value of
A step of determining that a transfer defect does not occur when the quotient is equal to or more than a predetermined threshold value, and determining that a transfer defect occurs when the quotient is less than the threshold value.
A method for evaluating a catalyst layer.

Images