KR101916529B1 - Accelerated Electrochemical and Mechanical Stress Test for GDL in PEM Fuel Cells - Google Patents

Abstract

The present invention relates to an apparatus and a method for stress acceleration testing of a gas diffusion layer for a fuel cell, which can easily confirm corrosion and deterioration phenomena of a gas diffusion layer through electrochemical and mechanical stress acceleration tests of a gas diffusion layer for a fuel cell.
That is, one surface of the gas diffusion layer is brought into contact with the electrolyte solution to provide electrochemical stress to the gas diffusion layer by reaction with the electrolyte solution, while the other surface of the gas diffusion layer is brought into contact with the gas flow, The present invention provides an apparatus and method for accelerating stress in a gas diffusion layer for a fuel cell, which is capable of confirming degradation and erosion of a gas diffusion layer due to electrochemical stress and mechanical stress in a short time by providing a mechanical stress by a flow.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of accelerating stress acceleration of a gas diffusion layer for a fuel cell,

The present invention relates to an apparatus and method for accelerating stress in a gas diffusion layer for a fuel cell, and more particularly, to an apparatus and method for accelerating stress in a gas diffusion layer for a fuel cell, And more particularly, to an apparatus and method for stress acceleration testing of a gas diffusion layer for a fuel cell.

The unit cell of the fuel cell includes a polymer electrolyte membrane and a cathode and an anode which are electrode catalyst layers coated on both sides of the electrolyte membrane so that hydrogen and oxygen can react with each other, A gas diffusion layer (GDL), and a separator plate stacked on the outside of the gas diffusion layer to supply fuel and discharge water generated by the reaction.

Particularly, the gas diffusion layer is made of a carbon-based material and a microporous layer to support an air electrode and a fuel electrode which are catalyst layers, to disperse the reactive gas uniformly in the catalyst layer, to collect electrons generated in the catalyst layer, And discharging moisture generated by the electrochemical reaction.

Such a gas diffusion layer may degrade its life with carbon corrosion due to electrochemical and mechanical deterioration over time, and a method of predicting the deterioration of the gas diffusion layer and predicting the service life thereof is proceeding.

A conventional test method for observing deterioration of the gas diffusion layer is proceeded in two ways.

The first method comprises: forming an electrode by applying a catalyst layer (air electrode and fuel electrode) to a polymer electrolyte membrane; forming a unit cell cell by stacking a gas diffusion layer (GDL) to be observed on a catalyst layer; The performance of the unit cell cell is being measured while applying a voltage of 1.0 V or more for a predetermined time so that the inert gas is humidified and flowed and the carbon corrosion is greatly caused.

However, in the case of the first method, when a voltage of 1.0 V is applied to the unit cell, the carbon material contained in the gas diffusion layer as well as the air electrode and the carbon material (the carbon support or the support for catalyst of the air electrode and the anode) included in the fuel electrode (GDL) due to corrosion is limited because both the carbon of the electrodes (the air electrode and the catalyst layer as the anode) and the carbon substrate of the constituent material of the gas diffusion layer are exposed to the same voltage, .

The second method comprises: immersing the gas diffusion layer in an electrolyte solution such as an aqueous solution of sulfuric acid; injecting nitrogen into the gas diffusion layer contained in the electrolyte solution and simultaneously applying a voltage of 1.0 V or more to electrochemically deteriorate the gas diffusion layer; The gas diffusion layer is taken out from the solution, dried, and then connected to the unit cell. Then, the performance of the unit cell is measured.

However, in the case of the second method, since only the gas diffusion layer is tested in the electrolyte solution alone, corrosion of only the gas diffusion layer is possible and corrosion phenomenon of only the gas diffusion layer can be observed. However, due to the characteristics of the experiment in the electrolyte solution, There is a disadvantage in that the deterioration of the gas diffusion layer and the corrosion test can not be accurately performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a gas diffusion layer which is in contact with an electrolyte solution to provide electrochemical stress by reaction with an electrolyte solution, An apparatus and a method for accelerating stress of a gas diffusion layer for a fuel cell in which a gas diffusion layer is brought into contact with a gas to provide a mechanical stress to the gas diffusion layer so that deterioration and corrosion phenomena of the gas diffusion layer due to electrochemical stress and mechanical stress can be confirmed in a short time. The purpose is to provide.

According to an aspect of the present invention, there is provided an apparatus for providing a mechanical stress comprising a gas flow path formed therein; An electrochemical stress providing block in which a first filling space filled with the electrolyte solution and a second filling space communicating with the first filling space are formed; And a gas diffusion layer disposed between the mechanical stress providing block and the electrochemical stress providing block, the gas diffusion layer being coated with a predetermined amount of platinum; Wherein one surface of the gas diffusion layer is brought into contact with a gas flowing in the gas flow passage and at the same time the other surface of the gas diffusion layer is brought into contact with the electrolyte solution in the first filling space, Lt; / RTI >

Preferably, the gas flow passage comprises: a gas inlet formed in a lower portion of the mechanical stress providing block; A gas outlet formed on an upper portion of the mechanical stress providing block; A gas contact space formed between the gas inlet and the gas outlet; And the gas in the gas contact space is in contact with one surface of the gas diffusion layer.

In particular, the electrochemical stress providing block may further include a voltage applying unit for applying electrochemical stress to the gas diffusion layer.

Preferably, the voltage application means comprises: a working electrode mounted on the upper end of the block for providing electrochemical stress and in electroconductive contact with the gas diffusion layer; A counter electrode mounted in the first filling space; A standard electrode mounted in the second filling space; .

In addition, the gas discharge port of the mechanical stress providing block is further provided with a blocking plate which is opened and closed by an actuator.

According to another aspect of the present invention, there is provided a method of manufacturing a gas diffusion layer, comprising the steps of: i) applying a predetermined amount of platinum without a support to a gas diffusion layer; Ii) arranging the gas diffusion layer between the mechanical stress providing block formed with the gas flow path and the electrochemical stress providing block filled with the electrolyte solution so that one surface of the gas diffusion layer is brought into contact with the gas flowing through the gas flow path Contacting the other surface of the gas diffusion layer with the electrolyte solution; Iii) providing the gas diffusion layer with one of mechanical stress due to gas flow, mechanical stress due to gas flow, and electrochemical stress due to voltage application to measure the degree of deterioration and corrosion of the gas diffusion layer; The stress accelerating test method for a gas diffusion layer for a fuel cell is provided.

In step (iii), an inert gas acting as a mechanical stress is caused to flow through the gas flow path so that the inert gas diffuses through the gas diffusion layer toward the electrolyte solution, and simultaneously the voltage is applied to the gas diffusion layer through the working electrode And the electrochemically active area of the gas diffusion layer of platinum is observed by using the circulation transfer method.

The step (iii) may include: flowing oxygen (air) acting as mechanical stress to the gas flow path so that oxygen diffuses through the gas diffusion layer toward the electrolyte solution, and simultaneously applying voltage to the gas diffusion layer through the working electrode And then proceeding by observing the oxygen reduction polarization of the gas diffusion layer coated with platinum by using the polarization method.

The step (iii) may include: flowing oxygen (air) acting as mechanical stress to the gas flow path so that oxygen diffuses through the gas diffusion layer toward the electrolyte solution, and simultaneously applying voltage to the gas diffusion layer through the working electrode And then the impedance of the gas diffusion layer is measured using the AC impedance method.

Through the above-mentioned means for solving the problems, the present invention provides the following effects.

First, the electrochemical stress and the mechanical stress can be arbitrarily given to the gas diffusion layer (GDL) used in the polymer electrolyte fuel cell, whereby the progressive corrosion phenomenon and deterioration phenomenon of the gas diffusion layer can be confirmed for a short time.

Second, in order to reproduce the carbon corrosion phenomenon and the mechanical deterioration phenomenon of the gas diffusion layer, a voltage of 1.0 V or more is applied over time while flowing an inert gas, 1) measurement of carbon corrosion current, 2) 3) measurement of the oxygen reduction polarization curve using the polarization method, and 4) measurement of the impedance using the AC impedance method. In this way, corrosion and deterioration of the gas diffusion layer can be observed in real time.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a configuration diagram showing a device for stress acceleration testing of a gas diffusion layer for a fuel cell according to the present invention;
2 is a schematic view showing a kind of a gas diffusion layer applicable to a stress acceleration test of a gas diffusion layer for a fuel cell according to the present invention,
3 is an image obtained by microscopically photographing a gas diffusion layer before and after a carbon corrosion potential is applied as a test result according to Example 1 of the present invention,
4 is a graph showing carbon corrosion current of a gas diffusion layer after carbon corrosion potential application as a test result according to Example 1 of the present invention,
FIG. 5 is a graph showing a carbon corrosion current of a gas diffusion layer after carbon corrosion potential application as a test result according to Example 2 of the present invention. FIG.

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The present invention is based on the point that it is possible to measure the performance of the gas diffusion layer alone without separately assembling the gas diffusion layer into the fuel cell by allowing electrochemical stress and mechanical stress to be added to the gas diffusion layer.

To this end, a predetermined amount of platinum (Pt Black), which does not have a support, is applied to the surface of the gas diffusion layer of the test object to form a gas diffusion electrode. This is because the corrosion effect of carbon used in the catalyst layers (anode and cathode) So that only the corrosion of the gas diffusion layer can be accurately determined.

Referring to FIG. 2 (a), the gas diffusion layer 10 to be tested may be composed of a carbon fiber layer and a microporous layer (MPL). MPL may be a combination of carbon black and a hydrophobic binder For example, PTFE (Polytetrafluoroethylene)).

Referring to FIG. 2 (b), the gas diffusion layer 10 to be tested may be composed of a MPL (microporous layer) sheet excluding a carbon fiber layer. As described above, Carbon black and a hydrophobic component (e.g., PTFE (Polytetrafluoroethylene)) are slurried and dried.

Referring to FIG. 2 (c), the gas diffusion layer 10 to be tested can be formed by simply bonding an MPL (microporous layer) sheet to a carbon fiber layer.

As described above, the gas diffusion layer to be tested is selected to contain a carbon component and is made by coating a predetermined amount of platinum with no supporting material for the purpose of conducting.

Hereinafter, the configuration for the accelerated deterioration test of the gas diffusion layer constructed as above will be described.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram showing an apparatus for stress acceleration testing of a gas diffusion layer for a fuel cell according to the present invention; FIG.

As shown in FIG. 1, the gas diffusion layer 10 is disposed between the mechanical stress providing block 20 and the electrochemical stress providing block 30.

The mechanical stress providing block 20 is provided with a structure in which a gas flow passage 21 is formed in a vertical direction.

At this time, the gas flow passage 21 includes a gas inlet 22 formed at the bottom of the mechanical stress providing block 20, a gas outlet 24 formed at the top of the mechanical stress providing block 20, And a gas contact space 23 formed between the substrate 22 and the gas outlet 24. One wall surface of the gas contact space 23 is opened for contact with the gas diffusion layer 10. [

The gas discharge port 24 of the mechanical stress providing block 20 is further provided with a shutoff plate 25 which is opened and closed by an actuator (not shown) so that the gas discharge amount from the gas contact space 23 And to control.

The electrochemical stress providing block 30 has a structure in which a first filling space 31 and a second filling space 32 in which the electrolyte solution is filled are formed in the first filling space 31 and the first filling space 31, The reason why the second filling space 32 is divided is that the counter electrode 34 and the standard electrode 35 are mounted in separate filling spaces.

At this time, one wall surface of the first filling space 31 is opened for contact with the gas diffusion layer 10.

Therefore, after the gas diffusion layer 10 is disposed between the mechanical stress providing block 20 and the electrochemical stress providing block 30, the mechanical stress providing block 20 and the electrochemical stress providing block 30 Is filled with the electrolyte solution in the first filling space 31 and the second filling space 32 by using a conventional clamping means (not shown) The other surface of the gas diffusion layer 10 comes into contact with the electrolyte solution in the first filling space 31. At this time,

On the other hand, the electrochemical stress providing block 30 is further equipped with a voltage applying means for applying electrochemical stress to the gas diffusion layer 10.

Preferably, the voltage application means comprises a working electrode 33 mounted on the upper end of the electrochemical stress providing block 30 and in conductive contact with the gas diffusion layer 10, And a standard electrode 35 mounted in the second filling space 32. The counter electrode 34 is connected to the counter electrode 34 and the standard electrode 35,

Hereinafter, the gas diffusion layer stress acceleration test method of the present invention based on the above configuration will be described.

The stress accelerating test method according to the present invention measures the performance of the initial gas diffusion layer and then measures the performance of the degraded gas diffusion layer by simultaneously providing electrochemical stress and mechanical stress to the gas diffusion layer, The present invention has been made in view of the fact that, after applying a sustained stress, the gradual erosion phenomenon and deterioration phenomenon of the gas diffusion layer can be accurately confirmed.

First, a gas diffusion layer 10 in which a predetermined amount of platinum without a support is applied is fabricated.

That is, as described above with reference to FIG. 2, the gas diffusion layer 10 to be tested is selected to contain a carbon component, and is plated with a predetermined amount of platinum, which does not have a carrier for conductivity.

By providing the gas diffusion layer 10 between the mechanical stress providing block 20 in which the gas flow passage 21 is formed and the electrochemical stress providing block 30 filled with the electrolyte solution and clamping the gas diffusion layer 10, The one surface of the gas diffusion layer 10 comes into contact with the gas flowing in the gas flow passage 21 and the other surface of the gas diffusion layer 10 comes into contact with the electrolyte solution filled in the first filling space 31 .

Subsequently, when the gas is injected through the gas inlet 22 of the mechanical stress providing block 20, the gas passes through the gas contact space 23 and is discharged through the gas outlet 24. [

Since the gas in the gas contact space 23 is in contact with the gas diffusion layer 10, it diffuses into the electrolyte solution in the first filling space 31 through the gas diffusion layer 10 Such a flow of gas has a flow similar to the operation in which the reaction gas is introduced into the front end of the electrode (anode or cathode) where reaction occurs as a normal fuel cell operating condition and the reaction gas is discharged to the downstream end.

Therefore, as the gas permeates through the gas diffusion layer, it causes mechanical stress (physical fatigue) in the gas diffusion layer.

The reason for providing a predetermined amount of gas (inert gas or oxygen) to the gas diffusion layer 10 and diffusing it to the electrolyte solution through the gas diffusion layer 10 is not only to reduce the mechanical stress on the gas diffusion layer, It is also possible to remove the oxygen on the electrolyte solution which may be present around the counter electrode 34 and the standard electrode 35 within the electrolyte solution.

At the same time, a voltage exceeding a certain level (1.0 V or more near the open circuit voltage of the fuel cell as a potential causing carbon corrosion) is applied to the gas diffusion layer through the working electrode 33 and the counter electrode 34, For a certain period of time.

By providing the gas diffusion layer with the electrochemical stress along with the mechanical stress, it is possible to simulate the electrochemical deterioration phenomenon due to the carbon corrosion of the gas diffusion layer and the mechanical deterioration phenomenon caused by the gas, It is possible to accurately measure the degree of deterioration and corrosion of the gas diffusion layer due to the electrochemical stress due to the voltage application. As a result, a robust gas diffusion layer and a microporous layer sheet can be developed.

On the other hand, as a method of measuring the degree of deterioration and corrosion of the gas diffusion layer, an inert gas acting as mechanical stress is caused to flow in the gas flow passage 21 as described above, so that the inert gas diffuses through the gas diffusion layer 10 toward the electrolyte solution And at the same time a voltage is applied to the gas diffusion layer 10 through the working electrode 33 for a predetermined period of time and then the electrochemical active area of the gas diffusion layer with respect to the platinum is observed using a normal circulation transfer method .

Alternatively, as a method of measuring the degree of deterioration and corrosion of the gas diffusion layer, oxygen (air) acting as a mechanical stress is caused to flow through the gas flow passage 21 so that oxygen diffuses through the gas diffusion layer 10 toward the electrolyte solution , And simultaneously a voltage is applied to the gas diffusion layer 10 through the working electrode 33 for a predetermined period of time and then the oxygen reduction polarization of the gas diffusion layer coated with platinum is observed using a normal polarization method.

Alternatively, as a method of measuring the degree of deterioration and corrosion of the gas diffusion layer, oxygen (air) acting as a mechanical stress is caused to flow through the gas flow passage 21 so that oxygen diffuses through the gas diffusion layer 10 toward the electrolyte solution A method may be used in which a voltage is applied to the gas diffusion layer 10 through the working electrode 33 for a predetermined period of time and then the impedance of the gas diffusion layer is measured using a normal AC impedance method.

Hereinafter, the present invention will be described in more detail with reference to Examples and Test Examples.

Example  One

First, as a gas diffusion layer to be tested, a gas diffusion layer composed of a carbon fiber layer and an MPL (Microporous Layer), or an MPL sheet (carbon black as a carbon component and a bonding agent such as PTFE (Polytetrafluoroethylene) ), And the selected gas diffusion layer is fabricated as a platinum (Pt) powder coated electrode (gas diffusion electrode) so that a fuel cell reaction can take place.

At this time, the MPL sheet is prepared by mixing carbon black, PTFE (Polytetrafluoroethylene, Teflon) with a small amount of water or ethanol, and then solidifying the volatilized solid dough into a thin sheet having a thickness of 50-200 μm .

Subsequently, as described above, the gas diffusion layer 10 is clamped between the mechanical stress providing block 20 in which the gas flow passage 21 is formed and the electrochemical stress providing block 30 filled with the electrolyte solution, One surface of the gas diffusion layer 10 is in contact with the gas flowing in the gas flow passage 21 and the other surface of the gas diffusion layer 10 is in contact with the electrolyte solution filled in the first filling space 31 .

Next, a gas is flowed through the gas flow passage 21 to diffuse the gas toward the electrolyte solution through the gas diffusion layer 10, thereby providing mechanical stress to the gas diffusion layer, and at the same time, 10 to provide a gas diffusion layer with electrochemical stress.

At this time, the amount of gas (for example, inert gas or oxygen) supplied to the gas diffusion layer was 129 sccm, which is a corresponding amount of 1. 2A / cm 2, and a voltage of 1.45 V was applied.

Preferably, when a voltage is applied to the gas diffusion layer, 1.4 V or more is required as the theoretical potential for causing erosion of the carbon component contained in the gas diffusion layer, so that 1.45 V is applied to the gas diffusion layer.

In this way, mechanical stress was applied to the gas diffusion layer, and electrochemical stress was provided. Then, the carbon corrosion current of the gas diffusion layer generated at this time was measured. The results are shown in FIGS. 3 and 4.

3, the corrosion current and the mechanical deterioration due to the injected gas in the gas diffusion layer (MPL) after the application of the carbohydrate corrosion potential (after 50 hours) as compared to before the carbon corrosion potential application (Gas diffusion layer) damage was observed (black region in FIG. 3 (b)), and platinum was lost due to carbon corrosion.

In addition, as shown in FIG. 4, it can be seen that the structure of the gas diffusion layer is unstably increased with time after the carbon corrosion current as a generated current due to the cumulative exposure of the carbon corrosion potential.

Example  2

The MPL sheet used in Example 1 was prepared by putting multi-walled carbon nanotubes in place of carbon black, and then evaluated in the same manner as in Example 1, and the results are shown in FIG.

As shown in FIG. 5, the MPL sheet composed of the carbon nanotubes was found to have less carbon corrosion even when the carbon corrosion voltage and the gas injection were the same as in Example 1. The MPL sheet used as the gas diffusion layer, It is evidence that it is advantageous in terms of corrosion when it is made with tubes.

As described above, since the electrochemical stress and the mechanical stress can be arbitrarily provided simultaneously to the gas diffusion layer used in the polymer electrolyte fuel cell, the gradual erosion phenomenon and the deterioration phenomenon of the gas diffusion layer can be checked and evaluated for a short time, Accordingly, the method / structure / structure of the gas diffusion layer can be evaluated in various ways, which can contribute to the production of a stress-resistant gas diffusion layer.

10: gas diffusion layer
20: Block for providing mechanical stress
21: gas flow passage
22: gas inlet
23: Gas contact space
24: gas outlet
25:
30: Block for providing electrochemical stress
31: First filling space
32: second filling space
33: working electrode
34: Counter electrode
35: Standard electrode

Claims (17)

A mechanical stress providing block having a gas flow passage formed therein;
An electrochemical stress providing block in which a first filling space filled with the electrolyte solution and a second filling space communicating with the first filling space are formed;
A gas diffusion layer disposed between the mechanical stress providing block and the electrochemical stress providing block and having a predetermined amount of platinum applied thereto;
/ RTI >
One surface of the gas diffusion layer is brought into contact with the gas flowing in the gas flow path, and the other surface of the gas diffusion layer is brought into contact with the electrolyte solution in the first filling space,
The gas flow passage comprises:
A gas inlet formed at the bottom of the mechanical stress providing block;
A gas outlet formed on an upper portion of the mechanical stress providing block;
A gas contact space formed between the gas inlet and the gas outlet;
So that the gas in the gas contact space is in contact with one surface of the gas diffusion layer,
Wherein the gas discharge port of the mechanical stress providing block is further provided with a blocking plate which is opened and closed by an actuator.
delete The method according to claim 1,
Wherein the electrochemical stress providing block further comprises voltage applying means for applying electrochemical stress to the gas diffusion layer.
The method of claim 3,
The voltage application means comprises:
A working electrode mounted on an upper end of the electrochemical stress providing block and in conductive contact with the gas diffusion layer;
A counter electrode mounted in the first filling space;
A standard electrode mounted in the second filling space;
And the stress concentration of the gas diffusion layer of the fuel cell.
delete I) applying a predetermined amount of platinum to the gas diffusion layer;
Ii) a mechanical stress providing block formed with a gas flow path including a gas inlet, a gas outlet, and a gas contact space formed between the gas inlet and the gas outlet,
Between a first filling space filled with the electrolyte solution and a second filling space communicated with the first filling space is formed between the electrochemical stress providing block
Arranging the gas diffusion layer so that one surface of the gas diffusion layer is brought into contact with the gas flowing in the gas flow passage and the other surface of the gas diffusion layer is brought into contact with the electrolyte solution in the first filling space;
Iii) measuring the deterioration and corrosion degree of the gas diffusion layer by providing the gas diffusion layer with the mechanical stress caused by the gas flow flowing through the gas inlet, the gas contact space, and the gas outlet, and the electrochemical stress due to the voltage application;
Lt; / RTI >
Wherein the gas discharge port of the mechanical stress providing block is further provided with a shielding plate which is opened and closed by an actuator so as to control the gas discharge amount from the gas contact space.
The method of claim 6,
Wherein step iii) comprises:
An inert gas acting as a mechanical stress is caused to flow in the gas flow passage so that the inert gas diffuses through the gas diffusion layer toward the electrolyte solution and simultaneously the voltage is applied to the gas diffusion layer through the working electrode for a predetermined time, Wherein the electrochemically active area of the gas diffusion layer is measured by observing the electrochemically active area of the gas diffusion layer with respect to platinum.
The method of claim 6,
Wherein step iii) comprises:
Oxygen (air) acting as a mechanical stress is caused to flow in the gas flow path so that oxygen diffuses through the gas diffusion layer toward the electrolyte solution and simultaneously a voltage is applied to the gas diffusion layer through the working electrode for a predetermined time, And the oxygen diffusion polarization of the gas diffusion layer coated with platinum is observed.
The method of claim 6,
Wherein step iii) comprises:
Oxygen (air) acting as a mechanical stress is caused to flow through the gas flow path so that oxygen diffuses through the gas diffusion layer toward the electrolyte solution and simultaneously a voltage is applied to the gas diffusion layer through the working electrode for a predetermined time, Wherein the step of measuring the impedance of the gas diffusion layer for the fuel cell comprises the step of measuring the impedance of the gas diffusion layer. delete delete delete delete delete delete delete delete

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