JP2016195027A - Method for removing solid electrolyte membrane from membrane-electrode assembly of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method for removing a solid electrolyte membrane from a membrane-electrode assembly of a polymer electrolyte fuel cell.SOLUTION: A method according to the present invention is a method for removing a solid electrolyte membrane from a membrane-electrode assembly of a polymer electrolyte fuel cell, the membrane-electrode assembly comprising a catalyst layer and a solid electrolyte membrane joined therein. The method includes the step of irradiating the catalyst layer with a laser beam to weaken the joint between the catalyst layer and the solid electrolyte membrane.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for removing a solid electrolyte membrane from a membrane-electrode assembly (MEA) of a fuel cell, and a method for analyzing the removed solid electrolyte membrane.

  A single cell, which is the basic structure of a polymer electrolyte fuel cell (PEMFC), is composed of a pair of separators and a membrane-electrode assembly (MEA) disposed between the separators.

  Since materials constituting the MEA include relatively expensive materials, they may be recycled. For example, Patent Document 1 discloses an MEA material recycling method for recovering electrode agent particles composed of carbon particles carrying a platinum catalyst adhering to an electrolyte membrane and an electrolyte membrane from MEA, in an organic solvent that is an immersion medium. A method using a milder 25% or less aqueous ethanol solution is described. In the method of Patent Document 1, stirring is performed when the diffusion layer is peeled from the electrolyte membrane, and ultrasonic irradiation is performed when the electrode agent particles are peeled from the electrolyte membrane.

  In Patent Document 2, in a method of recovering a catalyst material from a used MEA, a soluble adhesive tape is attached to the catalyst layer, and then the soluble adhesive tape is peeled off to separate the catalyst material from the polymer electrolyte membrane. A method comprising the steps of:

JP 2010-114031 (released on May 20, 2010) JP 2005-235511 (published September 2, 2005)

  However, the method described in Patent Document 1 has a problem that the electrolyte membrane constituting the MEA, in particular, the surface side is dissolved by the aqueous ethanol solution.

  The method described in Patent Document 2 has a problem that the surface of the polymer electrolyte membrane is destroyed because a soluble adhesive tape is stuck and the catalyst material is mechanically peeled off from the polymer electrolyte membrane.

  Dissolution and mechanical destruction of the electrolyte membrane may be permitted for the purpose of recycling the material (monomer molecules) constituting the electrolyte membrane. However, the methods for giving non-negligible damage to the electrolyte membrane as described in Patent Documents 1 and 2 are not suitable for the purpose of analyzing the state of the collected electrolyte membrane, for example.

  The present invention has been made to solve the above-described problems, and relates to a method for removing an electrolyte membrane from an MEA while suppressing damage to the electrolyte membrane.

In order to solve the above problems, the present invention provides any of the following.
(1) A method of removing a solid electrolyte membrane from a membrane-electrode assembly of a polymer electrolyte fuel cell in which a catalyst layer and a solid electrolyte membrane are joined, wherein the catalyst layer is irradiated with a laser, A method comprising the step of weakening the bonding between the catalyst layer and the solid electrolyte membrane.
(2) The method according to (1), wherein the laser is irradiated so as to penetrate the catalyst layer and the solid electrolyte.
(3) The method according to (1) or (2), wherein the laser exhibits absorption in the catalyst layer.
(4) The method according to any one of (1) to (3), wherein the laser irradiation is performed in an inert gas.
(5) The method according to (4), wherein the inert gas contains helium.
(6) The method according to any one of (1) to (5), wherein the catalyst layer includes a catalyst and carbon particles.
(7) The method according to any one of (1) to (6), including a step of removing the solid electrolyte membrane and recovering the catalyst layer.
(8) A method for analyzing a solid electrolyte membrane of a polymer electrolyte fuel cell, wherein the membrane-electrode assembly of the polymer electrolyte fuel cell is analyzed by the method according to any one of (1) to (7) A method comprising: recovering the detached solid electrolyte membrane; and analyzing the recovered solid electrolyte membrane.
(9) The method according to (8), wherein the membrane-electrode assembly is a membrane-electrode assembly of a used polymer electrolyte fuel cell.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that it becomes possible to remove a solid electrolyte membrane from the MEA of a polymer electrolyte fuel cell, suppressing the damage. Thereby, for example, the removed solid electrolyte membrane can be used for performance evaluation or quality control of the fuel cell.

It is a figure which represents typically the method of removing the solid electrolyte membrane which concerns on one Embodiment of this invention. It is the schematic which decomposes | disassembles and shows one structural example of the single cell which comprises a polymer electrolyte fuel cell regarding one Embodiment of this invention. It is a figure which shows the result of the SEM observation before and behind the process which removes a solid electrolyte membrane from a membrane-electrode assembly regarding one Example of this invention.

[1. How to remove the solid electrolyte membrane
A method according to an embodiment of the present invention is a method of removing a solid electrolyte membrane from a membrane-electrode assembly (MEA) of a polymer electrolyte fuel cell, wherein the MEA catalyst layer is irradiated with a laser, A step of weakening the bonding between the catalyst layer and the solid electrolyte membrane is included. Hereinafter, this method will be described more specifically.

(1) Polymer electrolyte fuel cell (PEMFC)
FIG. 2 is an exploded schematic view showing the structure of a single cell constituting the polymer electrolyte fuel cell. The single cell 10 includes a pair of separators 1 and 1 and one membrane-electrode assembly (MEA) 4 arranged so as to be sandwiched between the separators 1 and 1. The membrane-electrode assembly 4 is a laminated body in which the catalyst layer 2 and the gas diffusion layer 11 are laminated and joined to each surface of the solid electrolyte membrane 3 in this order. The combination of the catalyst layer 2 and the gas diffusion layer 11 constitutes an anode and a cathode (electrode). In the example shown in FIG. 2, each of the solid electrolyte membrane 3, the catalyst layer 2, and the gas diffusion layer 11 is a flat plate having a rectangular upper surface and lower surface.

  Hydrogen or methanol is supplied to the anode side (between the separator 1 and the gas diffusion layer 11), oxygen or air is supplied to the cathode side (between the other separator 1 and the gas diffusion layer 11), and between the anode and the cathode. By connecting an external load circuit to the single cell 10, the single cell 10 operates as a battery. Protons generated by the catalytic reaction at the anode pass through the solid electrolyte membrane 3 and move to the cathode, and react with oxygen to generate water.

  The type of the gas diffusion layer 11 is not limited as long as it can be used for the polymer electrolyte fuel cell, and examples thereof include a porous carbon material.

  The type of the solid electrolyte membrane 3 is not limited as long as it can be used for a polymer electrolyte fuel cell. For example, various proton conductive polymer membranes can be used. Specific examples of the proton conductive polymer membrane include ion exchange type polymer membranes having a sulfonic acid group. Among them, materials excellent in proton conductivity, strength, and chemical stability, for example, A fluoropolymer having a sulfonic acid group such as a perfluorosulfonic acid polymer is used. Specific examples of the fluorine-based polymer having a sulfonic acid group include Nafion (trademark), Flemion (trademark), and Aciplex (trademark). Specific examples of non-fluorine polymers include aromatic rings in aromatic polymers selected from, for example, polyarylene ethers such as polystyrene and polyetheretherketone, aromatic polyimides, polyphosphazenes, and polybenzimidazoles. Are sulfonated, and these may be constituted as a copolymer with an olefin.

  As the catalyst layer 2, for example, a metal catalyst (preferably a noble metal catalyst) or a nonmetal catalyst supported on a carrier having electrical conductivity is used, and preferably a noble metal catalyst. The carrier is preferably carbon material particles (carbon particles) such as carbon black. The noble metal catalyst is preferably metal particles containing a platinum group metal (PGM) such as a platinum catalyst, a ruthenium catalyst, and a ruthenium-platinum alloy catalyst on the anode side, and a metal such as a platinum catalyst on the cathode side. Particles are preferred. In the catalyst layer 2, the carrier and the catalyst are covered with the same polymer material as the components constituting the solid electrolyte membrane 3, and this polymer material is a binder that joins the catalyst layer 2 and the solid electrolyte membrane 3. It is functioning as well.

(2) Method for Removing Solid Electrolyte Membrane FIG. 1 is a schematic view showing an example of steps of a method for disassembling a polymer electrolyte fuel cell according to the present embodiment.

First step:
The separator 1 and the gas diffusion layer 11 are removed from the single cell 10 shown in FIG. 2, and the membrane-electrode assembly 4 in a state where the catalyst layer 2 is bonded to each surface of the solid electrolyte membrane 3 is recovered. The first step can be easily performed by, for example, a method of peeling the gas diffusion layer 11 and the catalyst layer 2 using a tool such as a cutter knife as necessary.

Second step:
The catalyst layer 2 constituting the membrane-electrode assembly 4 obtained in the first step is irradiated with the laser 5a, and compared with the state before the laser 5a irradiation, the catalyst layer 2 and the solid electrolyte membrane 3 are joined. Weaken. The second step can be performed using, for example, a chamber 6 including a sample stage 7 and a laser light source (laser irradiation unit) 5. In a state where the membrane-electrode assembly 4 is disposed on the sample stage 7, a laser 5 a is irradiated from the laser light source 5 to the membrane-electrode assembly 4. In some cases, it is particularly preferable that the bonding between the catalyst layer 2 and the solid electrolyte membrane 3 is weakened to the extent that both of them naturally peel off by irradiation with the laser 5a.

  The chamber 6 may be in a vacuum state, filled with gas, or filled with liquid, but is preferably filled with gas. The gas filling the chamber 6 is not particularly limited and may be air or the like, but is preferably an inert gas such as nitrogen gas, argon gas, helium gas, or a mixed gas thereof. Among inert gases, a helium-containing gas (or helium gas alone) is excellent in thermal diffusivity, so that the influence that the solid electrolyte film 3 can receive due to heat that can be generated by irradiation with the laser 5a can be suppressed to a minimum. .

  Although the kind of laser light source 5 is not specifically limited, For example, solid lasers, such as a YAG laser and a YVO4 laser; Semiconductor lasers, such as a gallium arsenide laser; Gas lasers, such as an excimer laser; The type of the laser light source 5 and the laser irradiation conditions (wavelength, irradiation time, power, etc.) indicate that the irradiated laser shows absorption in the catalyst layer 2 out of the materials constituting the membrane-electrode assembly 4, and the solid electrolyte What is necessary is just to select suitably so that the characteristic which permeate | transmits the film | membrane 3 may be shown. In addition, it is more preferable that the laser 5a shows absorption in the catalyst layer 2 if the laser 5a shows absorption in at least one of the carrier and the catalyst contained in the catalyst layer. Such irradiation conditions of the laser 5a can be appropriately set according to the types of the carrier and the catalyst. In the present embodiment, that the laser 5a is absorbed by the catalyst layer 2 means that at least a part of the laser 5a is absorbed, that is, a part of the laser 5a may pass through the catalyst layer 2. . Similarly, the fact that the laser 5a passes through the solid electrolyte membrane 3 does not exclude that a part of the laser 5a is absorbed by the solid electrolyte membrane 3. However, when the catalyst layer 2 and the solid electrolyte membrane 3 are compared, the laser 5 a is strongly absorbed by the catalyst layer 2.

  In a preferred embodiment, the laser 5a has 90% or more transmitted through the solid electrolyte membrane 3, but when a laser in which 10% or more is absorbed by the solid electrolyte membrane 3 is used, the solid electrolyte membrane 3 is used. This can be implemented by irradiating the laser 5a with a power not exceeding the processing threshold. In a preferred embodiment, the laser power is preferably in the range of 0.1 W to 10 W, more preferably in the range of 0.1 W to 1.0 W. The frequency of the laser is preferably in the range of 1 Hz to 100 kHz, more preferably in the range of 1 kHz to 50 kHz. The wavelength of the laser is preferably in the range of 193 nm to 10600 nm, more preferably in the range of 193 nm to 1064 nm.

  The laser 5a may be irradiated to the catalyst layer 2a (2). Preferably, a part of the laser 5a passes through the catalyst layer 2a and the solid electrolyte membrane 3, and the opposite catalyst layer 2b (2). ). Thereby, joining of catalyst layer 2a and solid electrolyte membrane 3, and joining of catalyst layer 2b and solid electrolyte membrane 3 can be weakened simultaneously. Although the reason why the bonding between the catalyst layer 2 and the solid electrolyte membrane 3 is weakened by the laser irradiation is not necessarily clear, it is possible that heat is generated in the catalyst layer 2 due to the laser 5a being absorbed by the catalyst layer 2. It is thought to be the cause.

  The laser 5a may be irradiated to a partial region of the catalyst layer 2, but it is preferable to irradiate substantially the entire surface of the catalyst layer 2. By weakening the bonding over the entire joint between the catalyst layer 2 and the solid electrolyte membrane 3, the solid electrolyte membrane 3 can be removed more easily.

Third step:
The solid electrolyte membrane 3 is removed from the membrane-electrode assembly 4 that has undergone laser irradiation through the second step. Since the bonding between the catalyst layer 2 and the solid electrolyte membrane 3 is weakened by receiving the laser irradiation, the solid electrolyte membrane 3 can be easily obtained by, for example, a mechanical peeling method or a peeling method that gives physical stimulation. Can be removed (peeled). In a particularly preferred embodiment, the bonding between the catalyst layer 2 and the solid electrolyte membrane 3 is weakened to such an extent that they both peel off naturally. Moreover, since the removed solid electrolyte membrane 3 is not directly affected by the laser irradiation, the damage is suppressed or substantially non-destructive.

  Since the removed solid electrolyte membrane 3 well reflects the state when it was in the polymer electrolyte fuel cell (breakage is suppressed), for example, the performance evaluation of the polymer electrolyte fuel cell Used for analysis. Alternatively, the raw material may be recovered from the solid electrolyte membrane 3 and reused. Similarly, a carrier, a catalyst, a polymer material (binder), and the like can be recovered from the separated catalyst layer 2. Alternatively, the removed solid electrolyte membrane 3 is used for analysis for quality evaluation of the polymer electrolyte fuel cell.

[2. Analysis method of solid electrolyte membrane]
A method according to an embodiment of the present invention is a method for analyzing a solid electrolyte membrane of a polymer electrolyte fuel cell. From the membrane-electrode assembly of the polymer electrolyte fuel cell, [1. The method includes a step of recovering the solid electrolyte membrane removed by the method described in the section [Method for removing solid electrolyte membrane] and a step of analyzing the recovered solid electrolyte membrane.

  The type of analysis performed in the step of analyzing the solid electrolyte membrane is not particularly limited. One example is microscopic observation. Another example is the evaluation of mechanical properties, such as a tensile strength test. Yet another example is chemical property evaluation, for example elemental analysis. More specifically, the types of analysis include, for example, measurement of tensile breaking stress and tensile modulus according to JIS K7127 (Plastics-Test method for tensile properties-Part 3: Test conditions for films and sheets). Can do.

  As described above, since the removed solid electrolyte membrane 3 well reflects the state when it is in the polymer electrolyte fuel cell (breakage is suppressed), for example, the polymer electrolyte fuel cell It is suitable for analysis for performance evaluation. In particular, the solid electrolyte membrane recovered from the membrane-electrode assembly of the used polymer electrolyte fuel cell is suitable for analysis for performance evaluation of the polymer electrolyte fuel cell. Alternatively, the removed solid electrolyte membrane 3 is used for analysis for quality evaluation of the polymer electrolyte fuel cell.

[3. Other aspects]
Another embodiment of the present invention is regarded as a method of isolating at least one of a catalyst layer and a solid electrolyte membrane by irradiating a membrane-electrode assembly (MEA) constituting a polymer electrolyte fuel cell with a laser. You can also.

Another embodiment of the present invention can be regarded as a method for recovering a solid electrolyte membrane in a non-destructive manner.
Another embodiment of the present invention can be regarded as a method of separately collecting the anode-side catalyst layer and the cathode-side catalyst layer from the membrane-electrode assembly.
According to another embodiment of the present invention, an intermediate solid electrolyte membrane can be isolated non-destructively by using a laser among the layers constituting the polymer electrolyte fuel cell, and the catalyst layer can be efficiently peeled off. it can. Furthermore, the catalyst layer can be efficiently peeled regardless of the joined state of the catalyst layer. Further, by collecting the solid electrolyte membrane in a non-destructive manner, it becomes possible to perform characteristics evaluation, component analysis, and the like of the solid electrolyte membrane.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

(Method for recovering electrolyte membrane according to the method of the present invention)
A commercially available polymer electrolyte fuel cell (Hydrogen Air MEA-5 layer 9 cm * 9 cm, fuel cell dot jp) was purchased. The fuel cell has a five-layer structure as shown in FIG. 2 (in order from the top: GDL, cathode electrode, Nafion 212, anode electrode, and GDL (gas diffusion layer 11, catalyst layer 2a, solid electrolyte membrane 3 in FIG. 2 respectively). Corresponding to the catalyst layer 2b and the gas diffusion layer 11). The specifications of the fuel cell are shown in the following table.

  The GDL on both sides was peeled off from the fuel cell to prepare a MEA-only layer structure excluding the GDL. In order to confirm the effectiveness of the laser irradiation treatment described later, the MEA at this point was scanned with a scanning electron microscope (FE-SEM: S-4800 (Hitachi High-Technologies)), and the cathode electrode, Nafion 212 and anode electrode were The condition was observed.

Next, the laser irradiation process for the MEA that has been observed will be described with reference to FIG. As shown in FIG. 1, the MEA excluding GDL is left on the sample stage 7 horizontally. Laser was irradiated on the entire surface of the MEA from the laser light source 5 toward the cathode electrode (catalyst layer 2a). A YVO 4 laser was used as the laser light source 5. The laser irradiation conditions are as follows.
Atmospheric gas (helium) flow rate = 1 L / min Laser output = 0.3 W
Frequency = 20kHz
Laser wavelength = 532 nm
Through the above laser irradiation treatment, the Nafion 212 layer (solid electrolyte membrane 3) was taken out from the MEA (the bond was weakened to such an extent that it naturally peeled) and collected. This layer is called a layer of this embodiment.

(Conventional method for collecting electrolyte membrane)
The electrolyte membrane was recovered according to a conventional method. First, MEA was prepared as described above, and observed using a scanning electron microscope (S-4800). A 50% v / v aqueous ethanol solution (water: ethanol = 1: 1) was immersed in the wipe. The cathode and anode electrodes were removed by rubbing the cathode and anode electrodes using this wipe. The resulting product was dried to obtain a layered product (referred to as a comparative layer).

(Observation result by scanning electron microscope (SEM))
The untreated MEA, the layer of this example and the comparative layer were observed using a scanning electron microscope (S-4800). These results will be described below with reference to FIG. FIG. 3 is a diagram showing an image (a) of an MEA before processing and an image (b) of a residue after laser irradiation using a scanning electron microscope.

  As shown in FIG. 3A, the untreated MEA had a catalyst layer of about 10 μm as the upper layer of the solid electrolyte membrane. As shown in FIG. 3B, only the catalyst layer that was on the solid electrolyte membrane by laser irradiation was removed while maintaining the shape of the surface of the solid electrolyte membrane.

  In contrast to the above results, warpage and undulation of the solid electrolyte membrane were observed in the comparative layer that was treated with the aqueous ethanol solution. Furthermore, when the surface of the comparative layer was measured with a level difference measuring instrument (P-16 + (KLA Tencor)), a thickness decrease of about 10 to 20 μm was recognized in the solid electrolyte membrane in the comparative layer. This indicates dissolution of the solid electrolyte membrane by ethanol.

  From the above, it was found that the electrolyte membrane can be taken out from the MEA without damaging the solid electrolyte membrane according to this example. The reason for this is that the laser irradiation conditions are controlled within a range in which the catalyst layer is ablated and the influence on the solid electrolyte membrane is minimized. As a result of the control of the laser irradiation conditions, the upper catalyst layer that has received the laser irradiation is ablated by the laser beam and peeled off from the solid electrolyte membrane. Further, the laser beam that has passed through the solid electrolyte is incident on the lower catalyst layer and ablate the catalyst layer. In this way, the lower catalyst layer is peeled off from the solid electrolyte membrane in the same manner as the upper catalyst layer.

  According to the present invention, a solid electrolyte membrane can be recovered nondestructively from a membrane-electrode assembly of a polymer electrolyte fuel cell using a laser. This enables an accurate analysis of the physical properties of the solid electrolyte membrane, contributing to an accurate evaluation of the performance of the fuel cell and an improvement in the performance of the fuel cell.

DESCRIPTION OF SYMBOLS 1 Separator 2 * 2a * 2b Catalyst layer 3 Solid electrolyte membrane 4 Membrane-electrode assembly (MEA)
5 Laser light source 5a Laser 6 Gas chamber 7 Sample stage 10 Single cell 11 Gas diffusion layer

Claims (9)

A method of removing a solid electrolyte membrane from a membrane-electrode assembly of a polymer electrolyte fuel cell in which a catalyst layer and a solid electrolyte membrane are joined,
A method comprising the step of irradiating the catalyst layer with a laser to weaken the bonding between the catalyst layer and the solid electrolyte membrane.   The method of claim 1, wherein the laser is irradiated through the catalyst layer and the solid electrolyte.   The method according to claim 1, wherein the laser exhibits absorption in the catalyst layer.   The method according to claim 1, wherein the laser irradiation is performed in an inert gas.   The method of claim 4, wherein the inert gas comprises helium.   The method according to any one of claims 1 to 5, wherein the catalyst layer comprises a catalyst and carbon particles.   The method according to any one of claims 1 to 6, comprising a step of removing the solid electrolyte membrane and recovering the catalyst layer. A method for analyzing a solid electrolyte membrane of a polymer electrolyte fuel cell, comprising:
Recovering the solid electrolyte membrane removed by the method according to any one of claims 1 to 7 from the membrane-electrode assembly of a polymer electrolyte fuel cell;
Analyzing the recovered solid electrolyte membrane.   The method according to claim 8, wherein the membrane-electrode assembly is a membrane-electrode assembly of a used polymer electrolyte fuel cell.

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