Fuel cell unit

Abstract

The present invention addresses the problem of providing a fuel cell capable of effectively suppressing deterioration of an electrolyte membrane. A fuel cell is provided with a separator having a flow path and an electrolyte membrane, and the surface of the flow path in the vicinity of a hydrogen outlet of the separator is covered with cerium.

Description

TECHNICAL FIELD

[0001] The present application relates to a fuel cell unit. BACKGROUND

[0002] A separator for a fuel cell having a corrosion-resistant film formed on a part of a surface is disclosed in Patent Document 1.

[0003] Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2001-068129 SUMMARY

[0004] As the separator, stainless steel is sometimes used, and iron is sometimes eluted in water generated during power generation. Therefore, generated water containing iron ions is easily accumulated at a hydrogen outlet after power generation, and if it moves to an electrolyte membrane, free radicals are easily generated. The free radicals promote deterioration of the electrolyte membrane.

[0005] In view of the above problems, an object of the present application is to provide a fuel cell unit capable of effectively suppressing deterioration of an electrolyte membrane.

[0006] The present application discloses a fuel cell unit provided with a separator having a flow path and an electrolyte membrane, and cerium is covered on a surface of the flow path in the vicinity of a hydrogen outlet of the separator.

[0007] The present application discloses a fuel cell unit provided with a separator having a flow path and an electrolyte membrane, and in the separator, cerium is covered only on a surface of the flow path between the electrolyte membrane and a hydrogen outlet.

[0008] EFFECT OF THE INVENTION

[0009] According to the present application, free radicals generated from iron ions can be deactivated by cerium, and thus deterioration of an electrolyte membrane can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is an exploded perspective view of a fuel cell unit 10.

[0011] Figure 2 is a view when the fuel cell unit 10 is viewed from above.

[0012] Figure 3 is a conceptual view illustrating a layer structure in a power generation section 11 of the fuel cell unit 10. DETAILED DESCRIPTION

[0013] 1. Basic structure of fuel cell unit

[0014] In Figures 1-3A diagram illustrating the basic structure of a fuel cell unit 10 according to one embodiment is shown in FIG. 1. The fuel cell unit 10 is a basic unit for generating electricity by supplying hydrogen and oxygen (air), and a plurality of such fuel cell units 10 are stacked to constitute a fuel cell.

[0015] Figure 1 FIG. 2 is an exploded perspective view of the fuel cell unit 10, Figure 2 FIG. 3 is a diagram as viewed from above of the fuel cell unit 10 (in Figure 2 In FIG. 4, the hydrogen flow path formed in the anode separator 18 is indicated by a broken line. Also, Figure 3 FIG. 5 is a diagram illustrating the layer structure in the power generation section 11 in the fuel cell unit 10.

[0016] 1.1. Power generation section

[0017] The power generation section 11 is a portion that contributes to electricity generation, and as shown in FIG. 5, the layer structure in the power generation section 11 (a portion of the A-A cross section) is formed by stacking a plurality of layers. Figure 3

[0018] In the power generation section 11 of the fuel cell unit 10, the electrolyte membrane 12 is interposed, and one side is a cathode (oxygen supply side), and the other side is an anode (hydrogen supply side). The cathode has, in order from the electrolyte membrane 12 side, a cathode catalyst layer 13, a cathode diffusion layer 14, and a cathode separator 15. On the other hand, the anode has, in order from the electrolyte membrane 12 side, an anode catalyst layer 16, an anode diffusion layer 17, and an anode separator 18. In addition, the stack 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 is sometimes 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 unit 10 in the power generation section 11 is typically about 1.3 mm.

[0019] Each layer can be configured as known, for example, as follows.

[0020] 1.1a. Electrolyte membrane

[0021] The electrolyte membrane 12 is a solid polymer film that exhibits good proton conductivity in a wet state. For example, it is configured from a fluorine-based ion exchange membrane, and for example, a carbon-fluorine-based polymer can be used, and specifically, a perfluoroalkyl sulfonic acid-based polymer (Nafion (registered trademark)), and the like can be mentioned.

[0022] The thickness of the electrolyte membrane 12 is not particularly limited, and the thickness is 100 μm or less, preferably 50 μm or less, and more preferably 10 μm or less.

[0023] 1.1b. Cathode catalyst layer

[0024] ​The cathode catalyst layer 13 is a layer containing a catalyst metal in a state where the catalyst metal is supported on a carrier. As the catalyst metal, for example, Pt, Pd, Rh, or an alloy containing these can be given. As the carrier, for example, a carbon carrier, more specifically, a carbon particle composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, and the like can be given.

[0025] 1.1c. Anode catalyst layer

[0026] The anode catalyst layer 16 is also, like the cathode catalyst layer 13, a layer containing a catalyst metal in a state where the catalyst metal is supported on a carrier. As the catalyst metal, for example, Pt, Pd, Rh, or an alloy containing these can be given. As the carrier, for example, a carbon carrier, more specifically, a carbon particle composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, and the like can be given.

[0027] 1.1d. Cathode diffusion layer

[0028] The cathode diffusion layer 14 can be composed of, for example, a porous body having electrical conductivity. As a more specific example, a carbon porous body (carbon paper, carbon cloth, glassy carbon, and the like), a metal porous body (metal mesh, foamed metal), and the like can be given.

[0029] If necessary, an MPL (microporous layer) can be provided in the cathode diffusion layer. The MPL is a covering-like thin film coated on the cathode catalyst layer 13 side in the cathode diffusion layer 14. The MPL has a function of adjusting moisture, having hydrophobicity or hydrophilicity as necessary. As the MPL, typically, an MPL in which a hydrophobic resin such as polytetrafluoroethylene (PTFE) and an electrically conductive material such as carbon black are main components is given.

[0030] 1.1e. Anode diffusion layer

[0031] The anode diffusion layer 17 can be composed of, for example, a porous body having electrical conductivity. As a more specific example, a carbon porous body (carbon paper, carbon cloth, glassy carbon, and the like), a metal porous body (metal mesh, foamed metal), and the like can be given.

[0032] 1.1f. Cathode separator

[0033] The cathode separator 15 is a member that supplies a reaction gas (in the present mode, air) to the cathode diffusion layer 14, and has a plurality of grooves 15a on a surface opposed to the cathode diffusion layer 14, the grooves functioning as a reaction gas flow path. As for the shape of the grooves, as long as the reaction gas can be appropriately supplied to the cathode diffusion layer 14, there is no particular limitation, and a type in which a plate-like member is formed in a wavy shape as in the present mode can be given. At this time, the plate thickness is typically 0.1 mm to 0.2 mm, and the height of the concave-convex is typically about 0.5 mm.

[0034] In the case of the corrugated shape, grooves 15b are formed on the opposite side of the cathode separator 15 between the adjacent grooves 15a, and function as cooling water flow paths.

[0035] The material constituting the cathode separator 15 can be any material that can be used as a separator of a fuel cell unit, and can be a gas-impermeable conductive material. As such a material, for example, a metal plate such as a stainless steel formed by press molding can be given.

[0036] 1.1g. Anode separator

[0037] The anode separator 18 is a member that supplies a reaction gas (hydrogen) to the anode diffusion layer 17, and has a plurality of grooves 18a on the surface facing the anode diffusion layer 17, which function as reaction gas flow paths. As for the shape of the grooves, there is no particular limitation as long as the reaction gas can be supplied to the anode diffusion layer 17 appropriately, and a type in which a plate-shaped member is formed in a corrugated shape as in the present embodiment can be given. At this time, the plate thickness is typically 0.1 to 0.2 mm, and the height of the concave-convex is typically about 0.4 mm.

[0038] In the case of the corrugated shape, grooves 18b are formed on the opposite side of the anode separator 18 between the adjacent grooves 18a in the present embodiment, and function as cooling water flow paths.

[0039] The material constituting the anode separator 18 can be any material that can be used as a separator of a fuel cell unit, and can be a gas-impermeable conductive material. As such a material, for example, a metal plate such as a stainless steel formed by press molding can be given.

[0040] 1.1h. Power generation based on power generation portion

[0041] As is well known, power generation is performed by the power generation portion 11 of the fuel cell unit 10 described above as follows.

[0042] If hydrogen is supplied from the grooves 18a of the anode separator 18, the hydrogen passes through the anode diffusion layer 17 and is decomposed into protons (H+) and electrons (e-) in the anode catalyst layer 16, the protons pass through the electrolyte membrane 12, and the electrons pass through the conductive wire connected to the outside, and reach the cathode catalyst layer 13, respectively. At this time, oxygen (air) is supplied from the grooves 15a of the cathode separator 15 to the cathode catalyst layer 13 via the cathode diffusion layer 14, and water (H2O) is generated in the cathode catalyst layer 13 from the protons, the electrons, and the oxygen. The generated water reaches the grooves 15a of the cathode separator 15 via the cathode diffusion layer 14 and is discharged.

[0043] That is, in the fuel cell unit 10, the flow of the electrons through the conductive wire connected to the outside from the anode catalyst layer 16 is utilized as an electric current.

[0044] 1.2. Outer peripheral portion

[0045] The outer peripheral portion 20 is located outside the power generation portion 11 and is the outer peripheral portion of the fuel cell unit 10. Although it does not participate in power generation, it is the part that supplies various fluids to the power generation portion 11, collects and discharges fluids from the power generation portion, or seals them.

[0046] 1.2a. Sealing

[0047] In the outer peripheral portion 20, a resin sheet 23 is disposed between the cathode separator 15 and the anode separator 18 (see reference). Figure 1 The interior of the fuel cell unit 10 is sealed by the resin sheet 23, and the anode side and cathode side are separated in the outer peripheral portion 20.

[0048] from Figure 1 It is understood that the resin sheet 23 is configured to surround the membrane electrode assembly. That is, the resin sheet 23 is sandwiched between the cathode separator 15 and the anode separator 18 in the outer periphery 20 of the fuel cell unit 10 to seal its inner side.

[0049] The resin sheet 23 has a substrate, an adhesive layer disposed on one side of the substrate (the side facing the cathode separator), and an adhesive layer disposed on the other side of the substrate (the side facing the anode separator). The adhesive layers are bonded to the cathode separator 15 and the anode separator 18 respectively to seal the inside of the power generation section 11, and to separate the cathode side and the anode side in the outer peripheral portion 20.

[0050] 1.2b. Inlet / Outlet

[0051] from Figure 1 , Figure 2 It can be seen that in the outer peripheral part 20, separated from the power generation part 11, on one end side ( Figure 2 On the left side, there is an air inlet port Ain, a cooling water inlet port Win, and a hydrogen outlet port Hout. On the other side, there is an air outlet port Aout, a cooling water outlet port Wout, and a hydrogen inlet port Hin.

[0052] Furthermore, the groove 15a of the cathode separator 15 is configured to communicate with the air inlet hole Ain and the air outlet hole Aout via the resin sheet 23, and the groove 15b is configured to communicate with the cooling water inlet hole Win and the cooling water outlet hole Wout. On the other hand, the groove 18a of the anode separator 18 is configured to communicate with the hydrogen inlet hole Hin and the hydrogen outlet hole Hout via the resin sheet 23, and the groove 18b is configured to communicate with the cooling water inlet hole Win and the cooling water outlet hole Wout.

[0053] 1.2c. Inflow channel part

[0054] An inflow flow path portion is formed in the cathode separator 15 through the flow path of the air inlet hole Ain and the groove 15a of the power generation portion 11, and an inflow flow path portion 21 is provided in the anode separator 18 through the hydrogen inlet hole Hin and the groove 18a of the power generation portion 11. In Figure 2 The inflow flow path portion 21 of the anode separator 18 is shown in FIG. 12B.

[0055] As is apparent from Figure 2 in the inflow flow path portion, the flow path is set to expand from the inlet hole (in this case, the hydrogen inlet hole Hin) toward the power generation portion 11, and to supply fluid (in this case, hydrogen) to the power generation portion 11. Figure 2 Figure 2

[0056] 1.2d. Outflow flow path portion

[0057] An outflow flow path portion is formed in the cathode separator 15 through the flow path of the air outlet hole Aout and the groove 15a of the power generation portion 11, and an outflow flow path portion 22 is provided in the anode separator 18 through the hydrogen outlet hole Hout and the groove 18a of the power generation portion 11. In Figure 2 The outflow flow path portion 22 of the anode separator 18 is shown in FIG. 13B.

[0058] As is apparent from Figure 2 in the outflow flow path portion, the flow path is set to gather from the power generation portion 11 toward the outlet hole (in this case, the hydrogen outlet hole Hout), and to discharge fluid (in this case, hydrogen and water) from the power generation portion 11. Figure 2 ​

[0059] 2. Cerium-based coverage

[0060] In the present application, cerium is covered near the hydrogen outlet hole Hout on the side of the face of at least the anode separator 18 that opposes the cathode separator 15. More specifically, the face between the hydrogen outlet hole Hout and the power generation portion 11 in the face. For example, a mode in which cerium is covered on the flow path face of the outflow flow path portion 22 of the anode separator 18 can be cited.

[0061] It is preferable that cerium is also covered near the hydrogen outlet hole Hout on the side of the face of the cathode separator 15 that opposes the anode separator 18. For example, the face between the hydrogen outlet hole Hout and the power generation portion 11 in the face.

[0062] Furthermore, in the cathode separator 15 and the anode separator 18, it is preferable that cerium is covered only near the above-mentioned hydrogen outlet hole Hout.

[0063] The method of forming the cerium-based coverage is not particularly limited, and can be performed by applying a cerium ion solution to the portion where coverage is to be formed, and then sintering and solidifying it to fix it.

[0064] ​​​​By using separators made of stainless steel or the like, elution of Fe components occurs, and if the Fe components are mixed into the electrolyte membrane, a reaction in which hydrogen peroxide becomes a free radical (Fenton reaction) is promoted, thereby causing degradation of the electrolyte membrane. As a countermeasure, cerium can also be contained in the electrolyte membrane to deactivate it, but the cerium content in the electrolyte membrane deteriorates the proton conductivity by substitution of H of the sulfonic acid group in the electrolyte membrane with cerium, thereby tending to degrade the performance of the fuel cell.

[0065] On the other hand, such degradation of the electrolyte membrane is significant in the electrolyte membrane on the side close to the hydrogen outlet hole Hout. Therefore, as in the present application, by disposing cerium in the separator near the hydrogen outlet hole Hout, cerium dissolves at this site during power generation, and cerium is absorbed by the electrolyte membrane in the vicinity to exert a deactivating action.

[0066] Thus, in the present application, cerium can be effectively supplied to a site that is easily degraded, thereby enabling degradation of the performance of the fuel cell to be suppressed.

[0067] Explanation of Symbols

[0068] 10 - fuel cell unit, 11 - power generation section, 15 - cathode separator, 18 - anode separator, 20 - outer peripheral section, 21 - inflow flow path section, 22 - outflow flow path section, 23 - resin sheet.

Claims

1. A fuel cell unit, characterized in that, It has a separator with a flow path and an electrolyte membrane. The surface of the flow path near the hydrogen outlet of the partition is covered with cerium.

2. A fuel cell unit, characterized in that, It has a separator with a flow path and an electrolyte membrane. In the partition, cerium is only coated on the surface of the flow path between the electrolyte membrane and the hydrogen outlet.

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