fuel cell

Abstract

To provide a fuel cell that can efficiently suppress the degradation of the electrolyte membrane. [Solution] A fuel cell comprising a separator having a flow path and an electrolyte membrane, wherein the surface of the flow path near the hydrogen outlet of the separator is coated with cerium.

Description

[Technical Field]

[0001] This disclosure relates to fuel cell cells. [Background technology]

[0002] Patent Document 1 discloses a fuel cell separator in which a corrosion-resistant coating is formed on a portion of the surface. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2001-068129 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Stainless steel is sometimes used as a separator, and iron can leach into the water generated during power generation. As a result, water containing iron ions tends to accumulate at the hydrogen outlet after power generation, and when this water moves to the electrolyte membrane, radicals are easily generated. These radicals accelerate the degradation of the electrolyte membrane.

[0005] In view of the above issues, this disclosure aims to provide a fuel cell that can efficiently suppress the degradation of the electrolyte membrane. [Means for solving the problem]

[0006] This application discloses a fuel cell comprising a separator having a flow channel and an electrolyte membrane, wherein the surface of the flow channel near the hydrogen outlet of the separator is coated with cerium.

[0007] This application discloses a fuel cell cell comprising a separator having a flow path and an electrolyte membrane, wherein in the separator, cerium is coated only on the surface of the flow path between the electrolyte membrane and the hydrogen outlet. [Effects of the Invention]

[0008] According to the present disclosure, radicals generated by iron ions can be inactivated by cerium, and deterioration of the electrolyte membrane can be suppressed.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is an exploded perspective view of a fuel cell 10. [Figure 2] FIG. 2 is a plan view of the fuel cell 10. [Figure 3] FIG. 3 is a conceptual diagram for explaining the layer structure in the power generation unit 11 of the fuel cell 10.

Modes for Carrying Out the Invention

[0010] 1. Basic Structure of Fuel Cell FIGS. 1 to 3 show diagrams for explaining the basic structure of a fuel cell 10 according to one embodiment. The fuel cell 10 is a unit element for generating power by supplying hydrogen and oxygen (air), and a plurality of such fuel cells 10 are stacked to form a fuel cell. FIG. 1 is an exploded perspective view of the fuel cell 10, and FIG. 2 is a plan view of the fuel cell 10 (in FIG. 2, the hydrogen flow path formed in the anode separator 18 is shown by a dotted line). Further, FIG. 3 is a diagram for explaining the layer structure in the power generation unit 11 of the fuel cell 10.

[0011] 1.1. Power Generation Unit The power generation unit 11 is a part that contributes to power generation, and as shown in FIG. 3 representing the layer structure (a part of the A-A cross section) in the power generation unit 11, a plurality of layers are stacked. In the power generation section 11 of the fuel cell 10, one side is the cathode (oxygen supply side) and the other side is the anode (hydrogen supply side) with the electrolyte membrane 12 interposed therebetween. On the cathode side, the cathode catalyst layer 13, the cathode diffusion layer 14, and the cathode separator 15 are laminated in this order from the electrolyte membrane 12 side. On the other hand, the anode includes the anode catalyst layer 16, the anode diffusion layer 17, and the anode separator 18 in this order from the electrolyte membrane 12 side. Note that the laminate of the electrolyte membrane 12, the cathode catalyst layer 13, the cathode diffusion layer 14, the anode catalyst layer 16, and the anode diffusion layer 17 may be referred to as a membrane electrode assembly. The thickness of the membrane electrode assembly is typically about 0.4 mm, and the thickness of the fuel cell 10 in the power generation section 11 is typically about 1.3 mm. Each layer can be configured as known, for example, as follows.

[0012] 1.1a. Electrolyte membrane The electrolyte membrane 12 is a solid polymer thin film that exhibits good proton conductivity in a wet state. For example, it is composed of a fluorine-based ion exchange membrane. For example, a carbon-fluorine-based polymer can be used, and specifically, perfluoroalkylsulfonic acid-based polymers (Nafion (registered trademark)) and the like can be mentioned. The thickness of the electrolyte membrane 12 is not particularly limited, but it is 100 μm or less, preferably 50 μm or less, and more preferably 10 μm or less.

[0013] 1.1b. Cathode catalyst layer The cathode catalyst layer 13 is a layer containing a catalyst metal in a form where the catalyst metal is supported on a carrier. For example, examples of the catalyst metal include Pt, Pd, Rh, or an alloy containing these. Examples of the carrier include carbon carriers, and more specifically, carbon particles composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite.

[0014] 1.1c. Anode catalyst layer The anode catalyst layer 16, like the cathode catalyst layer 13, is a layer containing a catalyst metal in the form of the catalyst metal supported on a support. For example, the catalyst metal can be Pt, Pd, Rh, or alloys containing these. The support can be a carbon support, more specifically carbon particles consisting of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite.

[0015] 1.1d. Cathode Diffusion Layer The cathode diffusion layer 14 can be made of, for example, a conductive porous material. More specific examples include carbon porous materials (carbon paper, carbon cloth, glassy carbon, etc.) and metal porous materials (metal mesh, foamed metal). A microporous layer (MPL) may be provided in the cathode diffusion layer as needed. The MPL is a thin film coating applied to the cathode catalyst layer 13 side of the cathode diffusion layer 14. The MPL has the function of regulating moisture by being water-repellent or hydrophilic as needed. Typical MPLs consist mainly of a water-repellent resin such as polytetrafluoroethylene (PTFE) and a conductive material such as carbon black.

[0016] 1.1e. Anode Diffusion Layer The anode diffusion layer 17 can be made of, for example, a conductive porous material. More specific examples include carbon porous materials (carbon paper, carbon cloth, glassy carbon, etc.) and metal porous materials (metal mesh, foamed metal).

[0017] 1.1f. Cathode Separator The cathode separator 15 is a component that supplies reaction gas (air in this embodiment) to the cathode diffusion layer 14. It has a plurality of grooves 15a on the surface facing the cathode diffusion layer 14, and these grooves function as reaction gas channels. The shape of the grooves is not particularly limited as long as the reaction gas can be properly supplied to the cathode diffusion layer 14. Examples include a plate-shaped component formed in a corrugated shape, as in this embodiment. In that case, the plate thickness is typically 0.1 mm to 0.2 mm, and the height of the irregularities is typically around 0.5 mm. In the case of a wavy shape, a groove 15b is formed on the opposite side of the cathode separator 15 between adjacent grooves 15a, and this functions as a cooling water channel.

[0018] The material constituting the cathode separator 15 may be any material that can be used as a separator in a fuel cell cell, and may be a gas-impermeable conductive material. Examples of such materials include metal sheets such as press-formed stainless steel.

[0019] 1.1g. Anode separator The anode separator 18 is a component that supplies reaction gas (hydrogen) to the anode diffusion layer 17. It has a plurality of grooves 18a on the surface facing the anode diffusion layer 17, and these grooves function as reaction gas channels. The shape of the grooves is not particularly limited as long as the reaction gas can be properly supplied to the anode diffusion layer 17. Examples include a plate-shaped component formed in a corrugated shape, as in this embodiment. In that case, the plate thickness is typically 0.1 mm to 0.2 mm, and the height of the irregularities is typically around 0.4 mm. In the case of a wavy shape, in this embodiment, a groove 18b is formed on the opposite side of the adjacent groove 18a, with an anode separator 18 in between, and this functions as a cooling water channel.

[0020] The material constituting the anode separator 18 may be any material that can be used as a separator in a fuel cell cell, and may be a gas-impermeable conductive material. Examples of such materials include metal sheets such as press-formed stainless steel.

[0021] 1.1h. Power generation by the power generation unit As is well known, the power generation unit 11 of the fuel cell cell 10 described above generates electricity as follows. When hydrogen is supplied from the groove 18a of the anode separator 18, the hydrogen passes through the anode diffusion layer 17 and is converted into protons (H) in the anode catalyst layer 16. + ) and electrons (e -The protons are broken down into electrons and electrons, and the protons pass through the electrolyte membrane 12, while the electrons pass through conductive wires leading to the outside, each reaching the cathode catalyst layer 13. Here, oxygen (air) is supplied to the cathode catalyst layer 13 from the groove 15a of the cathode separator 15 via the cathode diffusion layer 14, and water (H2O) is generated in the cathode catalyst layer 13 by the protons, electrons, and oxygen. The generated water passes through the cathode diffusion layer 14 and reaches the groove 15a of the cathode separator 15, where it is discharged. In other words, the fuel cell cell 10 utilizes the flow of electrons through conductive wires connecting the anode catalyst layer 16 to the outside as electric current.

[0022] 1.2. Outer perimeter The outer periphery 20 is located outside the power generation unit 11 and is the outer periphery of the fuel cell cell 10. It does not contribute to power generation, but it is responsible for supplying various fluids to the power generation unit 11, collecting and discharging fluids from the power generation unit, and sealing.

[0023] 1.2a. Seal In the outer periphery 20, a resin sheet 23 (see Figure 1) is placed between the cathode separator 15 and the anode separator 18. The resin sheet 23 seals the inside of the fuel cell cell 10 and separates the anode side from the cathode side in the outer periphery 20. As can be seen from Figure 1, the resin sheet 23 is positioned to surround the membrane electrode assembly. That is, the resin sheet 23 is sandwiched between the cathode separator 15 and the anode separator 18 at the outer periphery 20 of the fuel cell cell 10, sealing the inside. The resin sheet 23 comprises a base material, an adhesive layer positioned on one side of the base material (the cathode separator side), and an adhesive layer positioned on the other side of the base material (the anode separator side). The adhesive layers are bonded to the cathode separator 15 and the anode separator 18, respectively, sealing the inside of the power generation unit 11 and separating the cathode side and the anode side at the outer periphery 20.

[0024] 1.2b.Inlet / outlet As can be seen from FIGS. 1 and 2, in the outer peripheral portion 20, on one end side sandwiching the power generation unit 11 (the left side in FIG. 2), there are an air inlet hole A in , a cooling water inlet hole W in , a hydrogen outlet hole H out provided, and on the other end side, there are an air outlet hole A out , a cooling water outlet hole W out , a hydrogen inlet hole H in provided. Note that the groove 15a of the cathode separator 15 communicates with the air inlet hole A in , the air outlet hole A out through the resin sheet 23, and the groove 15b is configured to communicate with the cooling water inlet hole W in , the cooling water outlet hole W out . On the other hand, the groove 18a of the anode separator 18 communicates with the hydrogen inlet hole H in , the hydrogen outlet hole H out through the resin sheet 23, and the groove 18b is configured to communicate with the cooling water inlet hole W in , the cooling water outlet hole W out .

[0025] 1.2c. Inflow channel portion The cathode separator 15 has an inflow channel portion in which a channel is formed that passes through the air inlet hole A in and the groove 15a of the power generation unit 11, and the anode separator 18 is provided with an inflow channel portion 21 that passes through the hydrogen inlet hole H in and the groove 18a of the power generation unit 11. FIG. 2 shows the inflow channel portion 21 of the anode separator 18. In the inflow channel portion, as can be seen from FIG. 2, the channel is provided so as to spread from the inlet hole (the hydrogen inlet hole H in FIG. 2 in ) toward the power generation unit 11, and fluid (hydrogen in FIG. 2) is supplied to the power generation unit 11.

[0026] 1.2d. Outflow channel portion The cathode separator 15 has an outflow channel portion in which a channel is formed that passes through the air outlet hole A out and the groove 15a of the power generation unit 11, and the anode separator 18 is provided with an outflow channel portion that passes through the hydrogen outlet hole H outAn outflow channel section 22 is provided that passes through the groove 18a of the power generation section 11. Figure 2 shows the outflow channel section 22 of the anode separator 18. In the outflow channel section, as can be seen in Figure 2, the power generation section 11 leads to the outlet hole (hydrogen outlet hole H in Figure 2). out A flow path is provided to collect fluid (hydrogen and water in Figure 2) from the power generation unit 11, and the fluid is discharged towards it.

[0027] 2. Cerium coating In this disclosure, at least on the side of the anode separator 18 facing the cathode separator 15, the hydrogen outlet hole H out The vicinity of the hydrogen outlet hole H is coated with cerium. More specifically, the hydrogen outlet hole H on the surface in question out This is the surface between the anode separator 18 and the power generation unit 11. For example, one embodiment is one in which the flow channel surface of the outflow channel section 22 of the anode separator 18 is coated with cerium. Preferably, the hydrogen outlet hole H is located on the side of the cathode separator 15 facing the anode separator 18. out The vicinity of the hydrogen outlet hole H on that surface is also coated with cerium. out This is the surface between the power generation unit 11. Furthermore, the cathode separator 15 and the anode separator 18 have the hydrogen outlet holes H described above. out It is preferable that cerium is coated only in the vicinity of the part.

[0028] The method for forming the cerium coating is not particularly limited, but it can be done by applying a cerium ion solution to the area to be coated, and then fixing it by sintering and solidifying.

[0029] The leaching of Fe components due to the use of separators made of stainless steel, etc., can accelerate the reaction in which hydrogen peroxide becomes radical (Fenton reaction) when these Fe components are mixed into the electrolyte membrane, leading to deterioration of the electrolyte membrane. As a countermeasure, cerium can be added to the electrolyte membrane to inactivate it, but the inclusion of cerium in the electrolyte membrane tends to worsen the proton conductivity due to the substitution of H in sulfonic acid groups in the electrolyte membrane with cerium, thereby reducing fuel cell performance.

[0030] On the other hand, degradation of such electrolyte membranes occurs at the hydrogen outlet pore H out This is particularly noticeable in the electrolyte membrane on the side closer to the hydrogen outlet hole H. Therefore, as disclosed herein, out By placing cerium in the nearby separator, the cerium in that area dissolves during power generation and is incorporated into the nearby electrolyte membrane, exhibiting an inactivating effect. Thus, this disclosure enables efficient supply of cerium to parts that are prone to degradation, thereby suppressing the decline in fuel cell performance. [Explanation of Symbols]

[0031] 10...Fuel cell, 11...Power generation section, 15...Cathode separator, 18...Anode separator, 20...Outer periphery, 21...Inflow channel section, 22...Outflow channel section, 23...Resin sheet

Claims

1. A fuel cell comprising a separator having a flow path and an electrolyte membrane, The surface of the flow path near the hydrogen outlet of the separator is coated with cerium. Fuel cell.

2. A fuel cell comprising a separator having a flow path and an electrolyte membrane, In the separator, cerium is coated only on the surface of the flow path between the electrolyte membrane and the hydrogen outlet. Fuel cell.

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