JP2007258008A - Separator for fuel cell, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator achieving fuel cells with which stable operation can be performed easily and well by surely preventing shortcut and flooding of reactant gas and supplying it evenly all over an MEA. <P>SOLUTION: The separator has a secondary surface (inner wall face) 20b, a gas passage 22 including a partial passage 22a crossing over the direction of gravity, and a rib part which consists of a primary surface which separates the partial passage on a surface being contact with an anode or a cathode. Hydrophilicity 200 of the primary surface is made higher than that of the secondary surface. And in lower side 201 in the gravity direction of the primary surface and in upper side in the gravity direction of the primary part where the secondary surface stands next to the primary surface, hydrophilicity of at least one of the secondary parts where the secondary surface stands next to the primary surface is made higher than that of the secondary surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell separator and a fuel cell.

  A polymer electrolyte fuel cell generates electricity and heat simultaneously by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as air with a gas diffusion electrode. FIG. 8 is a schematic cross-sectional view showing a configuration of a conventional polymer electrolyte fuel cell. This polymer electrolyte fuel cell 111 basically includes a polymer electrolyte membrane 101 that selectively transports cations (hydrogen ions), and a pair of electrodes (anode or cathode) disposed on both sides of the polymer electrolyte membrane 101. ) 104. The electrode 104 includes a catalyst layer 102 mainly composed of carbon powder supporting an electrode catalyst (for example, platinum metal) and a gas diffusion layer 103 formed on the outer surface of the catalyst layer 102 and having both air permeability and conductivity. .

  On the outside of a membrane electrode assembly (MEA) 110 composed of the polymer electrolyte membrane 101 and the electrode 104, the MEA is mechanically fixed, and adjacent MEAs 110 are electrically connected in series to each other, and further the electrodes Plate-like separators 120 and 130 having gas flow paths 122 and 132 for supplying fuel gas or oxidant gas (reactive gas) to 104 and carrying away the gas generated by the reaction or surplus gas are arranged. . Further, a gas seal material 106 is disposed around the electrode 104 with the polymer electrolyte membrane 101 interposed therebetween so that fuel gas and oxidant gas do not leak out of the battery or mix with each other. O-rings 124 and 125 are also arranged to prevent leakage from the battery.

  The gas flow paths 122 and 132 through which the fuel gas and the oxidant gas flow can be provided separately from the separators 120 and 130. However, as shown in FIG. The method of 122 is general. The other surfaces of the separators 120 and 130 are provided with cooling water passages 123 and 133 for circulating cooling water for keeping the battery temperature constant. By circulating the cooling water, the heat energy generated by the reaction can be used in the form of hot water or the like.

  The separators 120 and 130 are required to have high conductivity, high gas tightness against the fuel gas, and high corrosion resistance against the oxidation-reduction reaction of the fuel gas and the oxidant gas. For these reasons, the conventional separators 120 and 130 are generally composed of a carbon material such as glassy carbon or expanded graphite. In addition, the gas flow paths 122 and 132 and the cooling water flow paths 123 and 133 have been used by cutting the surfaces of the separators 120 and 130 or forming them with a mold when the separators 120 and 130 are molded.

  In the conventional fuel cell 111 as described above, water generated by the cell reaction tends to stay in the gas flow paths 122 and 132 of the separator plates 120 and 130, and water generated in the catalyst layer 102 or condensed water (generation When the amount of water) is excessive, the gas flow paths 122 and 132 are completely blocked. This is called a flooding phenomenon. The flooding phenomenon can occur not only due to generated water but also when the feed gas is excessively humidified. Once the flooding phenomenon occurs, there is a possibility that the gas will not flow in that portion, and the battery performance will be abruptly deteriorated so that it does not function as a battery.

  Further, for example, a shortcut occurs in which the fuel gas does not pass through the gas flow path 122 but passes over the rib portion separating the gas flow path 122 and flows to the adjacent gas flow path 122, and the fuel gas is sufficiently utilized by the shortcut. However, there is also a problem that the battery performance deteriorates. This shortcut is also a problem that occurs in the gas flow path 132 through which the oxidant gas flows. This shortcut will be described in more detail with the anode side as a representative while referring to the drawings.

  FIG. 9 is a front view of the anode-side separator 120 in FIG. 8 as viewed from the gas flow path 122 side. As shown in FIG. 9, when the gas flow path 122 has a serpentine shape including, for example, a straight part 122 p and a turn part 122 q that connects the adjacent straight part 122 p, the gas flow path 122 passes through the gas flow path 122 as indicated by an arrow P. The fuel gas flows from the upstream side to the downstream side, but there is a difference in pressure between the adjacent gas flow paths 122. Therefore, if the fuel gas is not sufficiently sealed, as shown by an arrow Q, the gas flow path 122 adjacent to the fuel flow path beyond the rib portion (not shown) separating the straight portions 122p of the gas flow path 122 is used. The amount of fuel gas supplied to the turn part 122q is reduced. Therefore, the fuel gas cannot be uniformly supplied to the entire surface of the electrode 104 of the MEA 110, and the battery performance is deteriorated.

  The separator 120 shown in FIG. 9 has a fuel gas supply manifold hole 120p and a fuel gas discharge manifold hole 120q, and further includes an oxidant gas supply manifold hole 130p, an oxidant gas discharge manifold hole 130q, and a cooling device. It has a water supply manifold hole 133p and a cooling water discharge manifold hole 133q.

  On the other hand, Patent Document 1 proposes a method of applying a hydrophilic treatment to a part of the separator surface with the intention of suppressing the retention of water in the reaction gas channel. Specifically, as shown in FIG. 10, by performing hydrophilic treatment on a part of the surface 126 of the separator 122 in contact with the gas diffusion layer and the inner surface of the gas flow path 122 to provide a hydrophilic treatment portion 120 a, the generated water is It has been proposed to discharge without passing through the gas diffusion layer and without staying in the gas flow path 122 through the hydrophilic treatment region. FIG. 10 is a schematic sectional view showing a sectional structure of a conventional separator.

Furthermore, in Patent Document 2, in order to prevent the above-described shortcut of the reaction gas, the gas diffusion layer is deformed when the separator and the MEA are assembled, and the part of the gas diffusion layer where the reaction gas is desired to be sealed It has been proposed to reduce the porosity of the.
JP 2005-116179 A JP 2004-87491 A

  However, even the technique proposed in Patent Document 1 cannot sufficiently solve the problem of flooding and shortcuts, and there is still room for improvement. Further, when reducing the porosity of the gas diffusion layer as proposed in Patent Document 2, if there are irregularities due to scratches or construction tolerances on the surface of the gas diffusion layer, it is sufficient after deformation due to assembly. Gas seal performance may not be obtained.

  Accordingly, the present invention has been made in view of the above viewpoints, and can more reliably suppress the shortcut and flooding of the reaction gas in the gas flow path, and reliably and uniformly supply the reaction gas to the entire MEA. An object of the present invention is to provide a fuel cell separator capable of realizing a fuel cell that can be stably and easily operated. Another object of the present invention is to provide a fuel cell in which the reaction gas can be reliably and uniformly supplied to the entire MEA and can be stably and easily operated.

In order to solve the above problems, the present invention provides:
A separator used in a fuel cell, comprising a polymer electrolyte membrane having hydrogen ion conductivity, a membrane electrode assembly including an anode and a cathode sandwiching the polymer electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly. ,
The separator has a gas flow path including a plurality of partial flow paths that intersect with the direction of gravity, provided on a surface that contacts the anode or the cathode, and a rib portion that separates the partial flow paths,
The rib portion has a first surface that contacts the anode or the cathode;
The partial flow path has a second surface constituting the inner wall surface of the partial flow path,
The hydrophilicity (A ₁ ) of the first surface is higher than the hydrophilicity (B) of the second surface, and the second surface is adjacent to the first surface below the first surface in the direction of gravity. The hydrophilicity (A ₂ ) of at least one of the first portion and the second portion adjacent to the first surface on the upper side in the gravity direction of the first surface is the hydrophilicity of the second surface. Higher than sex (B),
A separator is provided.

  According to such a configuration, by providing a part having a different hydrophilicity on the surface of the separator and intentionally retaining the generated water in the part where the reactive gas is shortcut, the gas sealing property can be more reliably exhibited. . That is, by utilizing the property that the generated water moves from a low hydrophilic part to a high part, the generated water is intentionally present in the part where the reactive gas is shortcut, and the shortcut can be more reliably suppressed. it can.

  More specifically, when the hydrophilicity of the surface of the separator before the treatment is low, even if the hydrophilic treatment is applied to the first surface formed of the rib portion of the separator in contact with the anode or the cathode, If the hydrophilicity of all of the second surfaces consisting of the inner wall surfaces is substantially uniform, some of the water passing through the gas flow channel stays and cannot be reliably discharged out of the gas flow channel tube. Therefore, in the present embodiment, of the second surface consisting of the inner wall surface of the gas flow path, the portion adjacent to the first surface in contact with the anode or the cathode (that is, the first surface on the lower side in the gravity direction of the first surface). A region having high hydrophilicity up to a first portion in which the second surface is adjacent to the first surface and a second portion in which the second surface is adjacent to the first surface on the upper side in the gravity direction of the first surface By spreading the water, the water flowing in the gas channel becomes a liquid film at a highly hydrophilic portion, and the water can enter the contact surface between the anode or the cathode and the separator. In this way, the water that has entered between the separator and the anode or cathode is not easily discharged due to the effect of capillary action.

  In addition, if the highly hydrophilic region as described above exists on all the inner wall surfaces of the gas flow path, flooding may be caused when the amount of water passing through the gas flow path increases. In addition, by providing both a low hydrophilic area for preventing water clogging and a high hydrophilic area for feeding water to the target area in the gas flow path, the flooding can be more reliably performed. Can be suppressed.

  Therefore, when the separator of the present invention having the above-described configuration is used in a fuel cell, flooding can be more reliably suppressed, and water can be actively retained in a portion of the separator that contacts the anode or cathode. Thus, the water that stays in this way can more reliably seal the reaction gas that shortcuts between adjacent gas flow paths. That is, according to the present invention, the shortcut and flooding of the reaction gas in the gas flow path can be more reliably suppressed, the reaction gas can be reliably and uniformly supplied to the entire MEA, and stable operation can be easily and sufficiently performed. A fuel cell separator capable of realizing a fuel cell can be provided.

The present invention also provides:
A polymer electrolyte membrane having hydrogen ion conductivity, a membrane electrode assembly including an anode and a cathode sandwiching the polymer electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly,
At least one of the pair of separators is the separator of the present invention,
A fuel cell is provided.

In the fuel cell according to the present invention, since the separator described above is used, it becomes possible to stably supply the reaction gas to the entire catalyst layer of the anode or cathode of the MEA, and more reliably suppress flooding. be able to. In particular, it is possible to more reliably prevent water from blocking the gas flow path by limiting the highly hydrophilic portion of the separator surface. That is, according to the present invention, it is possible to provide a fuel cell in which the reaction gas can be reliably and uniformly supplied to the entire MEA, and stable operation can be easily and sufficiently performed.
In the present specification, the reaction gas includes a fuel gas and an oxidant gas.

  As described above, according to the present invention, reactive gas shortcuts and flooding in the gas flow path can be more reliably suppressed, and the reactive gas can be reliably and uniformly supplied to the entire MEA, enabling stable operation. A fuel cell separator capable of realizing a fuel cell can be provided. In addition, according to the present invention, it is possible to provide a fuel cell that can reliably and uniformly supply the reaction gas to the entire MEA and can perform stable operation easily and sufficiently.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted.

[First embodiment]
FIG. 1 is a schematic cross-sectional view showing the basic configuration of the first embodiment of the fuel cell of the present invention. First, the configuration of the fuel cell 100 of the present embodiment will be described. A fuel cell 100 shown in FIG. 1 basically includes a polymer electrolyte membrane 1 that selectively transports cations (hydrogen ions), and a pair of electrodes (anode and cathode) disposed on both sides of the polymer electrolyte membrane 1. ) 4. The electrode 4 includes a catalyst layer 2 mainly composed of carbon powder carrying an electrode catalyst (for example, platinum metal) and a gas diffusion layer 3 formed on the outer surface of the catalyst layer 2 and having both air permeability and conductivity. .

  On the outside of the membrane electrode assembly (MEA) 10 composed of the polymer electrolyte membrane 1 and the electrode 4, the MEA is mechanically fixed, and adjacent MEAs 10 are electrically connected to each other in series. Further, a configuration is provided in which plate-like separators 20 and 30 having gas flow paths for supplying a fuel gas or an oxidant gas (reactive gas) to the electrode 4 and carrying away a gas generated by the reaction or surplus gas are arranged. have.

  Further, a gas seal material 6 is disposed around the electrode 4 with the polymer electrolyte membrane 1 interposed therebetween so that fuel gas and oxidant gas do not leak out of the battery or mix with each other. Is configured such that O-rings 24 and 25 are arranged so as not to leak outside the battery. A cell stack of the fuel cell 100 is configured by alternately stacking a plurality of MEAs 10 configured as described above via separator plates.

  The material constituting the gas diffusion layer 3 is not particularly limited, and those known in the art can be used. For example, a conductive porous substrate such as carbon cloth or carbon paper can be used. The catalyst layer 2 includes conductive carbon particles supporting an electrode catalyst made of a noble metal and a polymer electrolyte having cation (hydrogen ion) conductivity.

  As described above, the fuel cell of the present invention is mainly characterized by the gas flow paths 22 and 32 of the separators 20 and 30. Gas channels 22 and 32 are formed by providing grooves on the surfaces of the gas channels 22 and 32. Further, on the other surface of the separators 20 and 30, cooling water flow paths 23 and 33 for circulating cooling water for keeping the battery temperature constant are provided. By circulating the cooling water here, the heat energy generated by the reaction can be utilized in the form of hot water or the like.

  The separator in the fuel cell 100 of the present invention includes an anode side separator 20 and a cathode side separator 30, and a cooling water flow path is formed between them. The anode separator 20 has a gas flow path 22 for supplying fuel gas to the anode on the surface facing the anode, and a cooling water flow path 23 on the opposite surface. The cathode-side separator 30 has a gas flow path 32 for an oxidant gas for supplying an oxidant gas to the cathode on the face facing the cathode, and a flow path 33 for cooling water on the opposite face.

  Between the anode-side separator 20 and the cathode-side separator 30 of the adjacent unit cell, a set of cooling water channels formed by the channels 23 and 33 is formed. A groove is formed in the anode side separator 20 so as to surround the cooling water flow path 23, and by inserting an O-ring 25 therein, the cooling water leaks from between the separators 20 and 30 to the outside. To prevent. In FIG. 1, a cooling water flow path is formed between the single cells, but a cooling water flow path may be arranged for every two to three single cells. When a cooling water flow path is not formed between single cells, a fuel gas flow path is provided on one side, and an oxidant gas flow path is provided on the other side. A single separator can also be used.

Moreover, as a material of a separator, there exist metal, carbon, the material which mixed graphite and resin, etc., and it can be used widely. For example, a separator obtained by injection-molding a mixture of carbon powder and a binder, or a titanium or stainless steel separator whose surface is plated with gold can be used.
Here, in the fuel cell 100 of the present embodiment, as shown in FIG. 1, the MEA 10 is in the normal direction of the ground plane (the surface indicated by X in FIG. 1) of the fuel cell 100 via the separators 20 and 30. A plurality of layers are stacked in a direction substantially perpendicular to the vertical direction, and the vertical direction indicated by the Y axis in FIG.

  In the following, a separator (one embodiment of the separator of the present invention) mounted on the fuel cell 100 will be described in more detail with reference to the drawings, represented by the anode-side separator 20. In the present embodiment, the cathode side separator 30 has the same configuration as the anode side separator 20.

  FIG. 2 is an enlarged cross-sectional view of a main part of the anode-side separator 20 of the fuel cell 100 shown in FIG. That is, FIG. 2 is an enlarged view of a portion X of the fuel cell 100 shown in FIG. 1, and an enlarged view of the main portion when the main portion of the anode separator 20 is cut along a direction substantially perpendicular to the ground plane X. It is sectional drawing. Therefore, the gas flow path 22 shown in FIG. 2 is a flow path portion 22a that intersects the direction of gravity. The gas flow path 22 for the fuel gas of the anode separator 20 is constituted by a groove provided so as to open on the surface of the anode separator 20. When this groove is covered with the gas diffusion layer 3, it becomes a channel portion having a substantially rectangular cross section.

FIG. 3 is a front view of the anode-side separator 20 in FIG. 1 as viewed from the gas flow path 22 side. As shown in FIG. 3, the gas flow path 22 has a straight part 22p, which is a substantially straight main flow path part for making the gas travel substantially straight, and a turn part 22q connecting the adjacent straight part 22p. As shown by an arrow P, the fuel gas flows in the gas flow path 22 from the upstream side to the downstream side. And the linear part 22p contains said partial flow path 22a.
3 has a fuel gas supply manifold hole 20p and a fuel gas discharge manifold hole 20q, and further includes an oxidant gas supply manifold hole 30p and an oxidant gas discharge manifold hole 30q. And a cooling water supply manifold hole 33p and a cooling water discharge manifold hole 33q. These communicate with the gas flow path or the cooling water flow path by a conventionally known method.

  In the fuel cell 100 of the present embodiment, as shown in FIG. 2, the anode-side separator 20 includes a gas flow path 22 including a partial flow path 22 a that intersects the gravitational direction and is provided on a surface that contacts the anode. A rib portion (not shown) that separates the flow path 22a, and the rib portion has a first surface 20a that contacts the anode. Moreover, the partial flow path 22a has the 2nd surface 20b which comprises the inner wall face of the partial flow path 22a. Moreover, the area | region shown with the dashed-dotted line R is an area | region corresponding to the anode which has a substantially rectangular shape.

The anode-side separator 20 includes a hydrophilic treatment portion 200 formed on the first surface 20a, and a second surface 20b adjacent to the first surface 20a on the lower side in the gravity direction of the first surface 20a. The hydrophilic treatment portion 201 formed on the portion 20c ₁ (that is, the portion of the second surface 20b that is in contact with the first surface 20a across the corner located on the lower side in the gravitational direction of the rib portion); The second surface 20b is located on the upper side of the first surface 20a in the gravity direction, and the second portion 20c ₂ adjacent to the first surface 20a (that is, the second surface 20b is located on the upper side of the rib portion in the gravity direction). The hydrophilic processing part 202 formed in the part which contact | connects the 1st surface 20a on both sides of a corner | angular part is provided.

By such hydrophilic treatment parts 200, 201, and 202, the hydrophilicity (A ₁ ) of the first surface 20a is higher than the hydrophilicity (B) of the second surface 20b, and the gravity of the first surface 20a. continuous second surface 20b in the direction of gravity above the first portion 20c ₁ and the first surface 20a of the second surface 20b are in contact in succession in the first surface 20a in the direction lower side on the first surface 20a Thus, the hydrophilicity (A ₂ ) of the second portion 20c _{2 in} contact with the second portion 20c ₂ is set higher than the hydrophilicity (B) of the second surface 20b.

With such a configuration, first, the generated water is discharged from the gas diffusion layer of the anode to the gas flow path 22 in a substantially normal direction of the main surface of the anode separator 20 (direction indicated by an arrow S in the figure). Since the gas diffusion layer usually has a certain level of water repellency, the discharged generated water does not return to the gas diffusion layer side. In the flow path portion 22a of the gas flow path 22, the hydrophilicity (A ₂ ) of the second portion 20c ₂ in which the hydrophilic treatment portion 202 is formed is more than the hydrophilicity (B) of the second surface 20b. Since it is high, the generated water falls more toward the lower part of the flow path part 20a in the direction of gravity (that is, in the direction substantially parallel to the direction of the arrow T in the figure) compared to the case where it receives only the action of gravity. easily generated water is liable to dwell move preferentially to the second portion c _2. As the generated water stays in the second portion c ₂ in this way, the fuel gas flows into the gas diffusion layer in contact with the gas flow path 22 side of the anode separator 20 and the adjacent gas flow path 22 (flow path portion 22a). ) Can be suppressed.

Further, in the flow channel portion 22a of the gas flow channel 22, the hydrophilicity (A ₂ ) of the first portion 20c ₁ in which the hydrophilic treatment portion 201 is formed is more than the hydrophilicity (B) of the second surface 20b. Since it is high, the generated water also moves and stays in the first portion c ₁ easily. As the generated water stays in the first part c ₁ in this way, the fuel gas flows into the gas diffusion layer in contact with the gas flow path 22 side of the anode separator 20, and the adjacent gas flow path 22 (flow path part). The shortcut to 22a) can be suppressed.
In addition to the above, since the hydrophilicity (A ₁ ) of the first surface 20a is also higher than the hydrophilicity (B) of the second surface 20b, water tends to stay in the portion of the first surface 20a. Thus, it is possible to block a shortcut for the reaction gas to move to the adjacent gas flow path beyond the rib portion.

The second portion c ₂ of the hydrophilic (A ₂₎ is higher than the hydrophilicity of the second surface 20b which constitutes the inner wall surface of the flow path portion 22a (B), produced water becomes liquid film The space that allows gas to flow is easily secured on the upper side of the flow path portion 22a. Therefore, the generated water is substantially in the normal direction of the cross section of the flow path portion 22a in FIG. Along the flow path portion 22a and smoothly discharged. That is, water can be smoothly discharged from the gas diffusion layer, and at least the upper side of the flow path portion 22a can be opened without being blocked, and the gas flow path 22 can be prevented from being blocked by flooding.

  Thus, in the fuel cell 100, water is smoothly discharged from the gas diffusion layer. Regardless of the presence or absence of generated water, surplus water that has become droplets in other parts of the gas flow path 22 also spreads as a liquid film in this region and does not block the gas flow path 22.

Incidentally, the first surface 20a, second surface 20b and the extent of the first portion c ₁ and a second hydrophilic portion c ₂ can be confirmed by measuring the contact angle with water. The contact angle of water with respect to the hydrophilic treatment portions 201, 202, and 203 is smaller than the contact angle of water with respect to other portions. For example, when the anode side separator 20 and the cathode side separator 30 are made of carbon or resin, the contact angle of water with respect to these is 90 ° to 130 °. a hydrophilic moiety c ₁ and a second portion c _2, can be set higher than the hydrophilicity of the second surface 20b.

Design conditions of the fuel cell 100, arrangement condition, the operating conditions and the like, the first surface 20a, the optimum value of the second surface 20b and the contact angle of water with respect to the first portion c ₁ and the second portion c ₂ is Kazuyoshi However, if the contact angle of water with respect to the second surface 20b is approximately 60 ° to 180 °, a sufficient effect can be obtained. Further, the first surface 20a and the contact angle of water with respect to the first portion c ₁ and a second portion c ₂ generally may be a 0 ° to 50 °.
The contact angle of water can be measured using, for example, FACE X-150 manufactured by Kyowa Interface Chemical Co., Ltd. Moreover, it can also measure using, for example, the Wilhelmi method.

Next, a manufacturing method of the fuel cell 100 of the present embodiment will be described.
The fuel cell 100 of the present embodiment can be manufactured by a conventionally known method. For example, the catalyst layer 2 is known in the art using a catalyst layer forming ink containing the electrode catalyst and a dispersion medium. It can be formed by a method. Furthermore, the MEA 10 can also be produced from the polymer electrolyte membrane 1, the catalyst layer 2, and the gas diffusion layer 3 as described above by a technique known in the art.

Anode separator 20 and cathode separator 30 in this embodiment, can be manufactured by a conventionally known method, among others a first surface 20a and the first portion c ₁ and second the portion c ₂ Hydrophilic There are no particular limitations on the method of providing the hydrophilic treatment parts 200, 201, and 202 by performing the treatment as long as the effects of the present invention described above can be obtained. For example, (1) plasma treatment, (2) aluminum oxide Blasting to control the surface roughness by spraying fine powder such as (3) coating by metal plating such as gold or coating by vapor deposition, (4) applying a highly hydrophilic material such as titanium oxide, Treatment for immobilization, (5) ultraviolet treatment, (6) imparting a hydrophilic functional group, and the like can be used.

These types of treatment methods can be properly used depending on the material of the separator plate. For example, the plasma treatment can be suitably used for a carbon separator, and the blast treatment can be suitably used for a carbon separator and a metal separator.
In the method by plasma treatment, it may be performed under reduced pressure or under atmospheric pressure. Moreover, in the method by a blast process, the surface roughness (Ra) of the surface of a separator is changed by a blast process, and the contact angle of water is made small as a result. Since it varies depending on the material of the separator used, etc., it cannot be uniquely defined. However, in the case of a carbon separator plate, the contact angle of water can be reduced by increasing Ra.
On the other hand, the ultraviolet irradiation process which irradiates ultraviolet light in ozone atmosphere may be sufficient.

Here, a method for producing the anode-side separator 20 in the present embodiment will be described.
FIG. 4 is a view for explaining a method of performing a hydrophilic treatment in the production of the anode-side separator 20 of the present embodiment. As shown in FIG. 4A, first, glass powder 36 is spread for the mask in the flow path portion 22a of the gas flow path 22 of the anode separator 20, and then oxygen plasma is supplied to the surface. Apply hydrophilic treatment. Thereby, as shown to (b) of FIG. 4, the hydrophilic process part 203 can be formed. The hydrophilic processing unit 203 has a configuration in which the hydrophilic processing units 200, 201, and 202 in FIG. 2 are integrated.

  In addition, after performing the said plasma processing, as shown to (a) of FIG. 5, the 1st surface (namely, anode side separator) is further used using the mask 38 which has the opening part 38a corresponding to the flow-path part 22a. By additionally performing the plasma treatment only on the surface in contact with the anode, the hydrophilicity of the first surface can be further improved (FIG. 5B). Thus, by further improving the hydrophilicity of the first surface, the retained water is likely to be present in the region having the strongest hydrophilicity, and flooding can be more reliably suppressed.

  As described above, according to the present embodiment, the reactive gas shortcut and flooding in the gas flow path can be more reliably suppressed, the reactive gas can be reliably and uniformly supplied to the entire MEA, and stable operation is possible. A fuel cell separator capable of realizing a simple fuel cell can be provided. In addition, according to the present invention, it is possible to provide a fuel cell that can reliably and uniformly supply the reaction gas to the entire MEA and can perform stable operation easily and sufficiently.

[Second Embodiment]
Next, a second embodiment of the fuel cell of the present invention will be described. The fuel cell (not shown) of the second embodiment is obtained by replacing the anode-side separator 20 and the cathode-side separator 30 in the fuel cell 100 of the first embodiment shown in FIG. The configuration is the same as that of the fuel cell 100 of the first embodiment.
Hereinafter, the separator provided in the fuel cell according to the second embodiment (second embodiment of the separator plate of the present invention) will be described as an anode side separator.

FIG. 6 is an enlarged cross-sectional view of a main part of an anode separator provided in the fuel cell according to the second embodiment. That is, FIG. 6 is an enlarged cross-sectional view of a main part when a main part of the separator of the fuel cell according to the second embodiment is cut along a direction substantially perpendicular to the ground plane P shown in FIG. As shown in FIG. 6, the anode-side separator 20 of the present embodiment is the same as the anode-side separator 20 of the first embodiment, but the second surface 20b is the first surface 20a above the first surface 20a in the direction of gravity. The second embodiment is the same as the first embodiment except that there is no hydrophilic treatment portion 202 formed in the second portion 20c ₂ continuously in contact with the first portion.

In the anode separator 20 of the present embodiment, the hydrophilic treatment portion 200 formed on the first surface 20a and the second surface 20b are continuous with the first surface 20a on the lower side in the gravity direction of the first surface 20a. And a hydrophilic treatment portion 201 formed on the first portion 20c ₁ that is in contact with each other. By such hydrophilic processing parts 200 and 201, the hydrophilicity (A ₁ ) of the first surface 20a is higher than the hydrophilicity (B) of the second surface 20b and the first surface 20a is below the direction of gravity. The hydrophilicity (A ₂ ) of the first portion 20c ₁ where the second surface 20b continuously contacts the first surface 20a on the side is set higher than the hydrophilicity (B) of the second surface 20b. Yes.

  With such a configuration, first, the generated water is discharged from the gas diffusion layer of the anode to the gas flow path 22 in a substantially normal direction of the main surface of the anode separator 20 (direction indicated by an arrow S in the figure). Since the gas diffusion layer usually has a certain level of water repellency, the discharged generated water does not return to the gas diffusion layer side. Then, in the flow path portion 22a of the gas flow path 22, the generated water falls toward a lower portion in the direction of gravity (that is, in a direction substantially parallel to the direction of the arrow T in the figure), and the hydrophilic treatment section 200 below. It becomes easy to move and stay. As the generated water stays in the hydrophilic treatment section 200 in this way, the fuel gas flows into the gas diffusion layer in contact with the gas flow path 22 side of the anode separator 20 and enters the adjacent gas flow path 22 (flow path portion 22a). It is possible to suppress shortcuts.

Further, in the flow channel portion 22a of the gas flow channel 22, the hydrophilicity (A ₂ ) of the first portion 20c ₁ in which the hydrophilic treatment portion 201 is formed is more than the hydrophilicity (B) of the second surface 20b. Since it is high, the generated water also moves and stays in the first portion c ₁ easily. As the generated water stays in the first part c ₁ in this way, the fuel gas flows into the gas diffusion layer in contact with the gas flow path 22 side of the anode separator 20, and the adjacent gas flow path 22 (flow path part). The shortcut to 22a) can be suppressed.

  Thus, in the fuel cell 100, water is smoothly discharged from the gas diffusion layer. Regardless of the presence or absence of generated water, surplus water that has become droplets in other parts of the gas flow path 22 also spreads as a liquid film in this region and does not block the gas flow path 22.

Here, a method for producing the anode-side separator 20 in the present embodiment will be described.
FIG. 7 is a diagram for explaining a method of performing a hydrophilic treatment in the production of the anode-side separator 20 of the present embodiment. As shown in FIG. 7A, first, the main surface of the anode-side separator 20 is set at an angle θ with respect to the traveling direction of the plasma supplied with the anode-side separator 20 (the direction indicated by the arrow α in the figure). In an inclined state, glass powder is spread for the mask in the gas flow path 22 of the anode-side separator 20, and then oxygen plasma is supplied to the surface to perform a hydrophilic treatment. Thereby, as shown to (b) of FIG. 7, the hydrophilic process part 205 can be formed. The hydrophilic processing unit 205 has a configuration in which the hydrophilic processing units 200 and 201 in FIG. 6 are integrated. Note that the angle θ may be appropriately selected according to the desired shape of the hydrophilic treatment unit 205.

  As described above, according to the present embodiment, the reactive gas shortcut and flooding in the gas flow path can be more reliably suppressed, the reactive gas can be reliably and uniformly supplied to the entire MEA, and stable operation is possible. A fuel cell separator capable of realizing a simple fuel cell can be provided. In addition, according to the present invention, it is possible to provide a fuel cell that can reliably and uniformly supply the reaction gas to the entire MEA and can perform stable operation easily and sufficiently.

  As mentioned above, although embodiment of this invention was described, this invention is not limited only to these, For example, in the said embodiment, the gas flow path 22 for fuel gas of the anode side separator 20 is anode side. A case has been described in which the groove is provided so as to open on the surface of the separator 20, and when the groove is covered with the gas diffusion layer 3, the flow path portion has a substantially rectangular cross section. However, the cross section of the groove is not limited to a substantially rectangular shape, and may be a semicircular shape, for example.

  Moreover, in the said embodiment, only the method of providing a hydrophilic treatment part was demonstrated as a method of forming a part with high hydrophilicity and a part with low hydrophilicity. However, contrary to the above, By subjecting a predetermined portion (for example, only the second surface) to water repellency, a portion having high hydrophilicity and a portion having low hydrophilicity can be provided as a result. In this case, a fluororesin dispersion such as polyethylene terephthalate (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) may be applied to portions other than the bottom surface side, and dried to impart water repellency. . Of course, the hydrophilic treatment and the magazine water repellent treatment may be performed as described above. The water repellent treatment method is not limited to this.

Further, in addition to the above, water repellent treatment may be performed on the gas diffusion layer side facing the gas flow path. Although the gas diffusion layer inherently has a certain degree of water repellency, the effect of the present invention can be more reliably obtained by performing the water repellency treatment on the gas diffusion layer side facing the gas flow path 22. It becomes like this.
As a method for performing water repellency treatment on the gas diffusion layer, it is sufficient to perform water repellency treatment at least in the same shape as the shape of the gas flow path 22 at the portion facing the gas flow path of the gas diffusion layer. Therefore, it is preferable that the entire gas diffusion layer is subjected to water repellent treatment. A water-repellent treatment can be performed by immersing the conductive porous substrate such as carbon paper or carbon cloth described above in a fluororesin dispersion containing PTFE or FEP, and drying to remove the dispersion medium.

In the first embodiment, the second surface is adjacent to the first surface on the lower side in the gravitational direction of the first surface and the second surface on the upper side in the gravitational direction of the first surface. Is described in the case where the hydrophilicity (A ₂ ) of both of the second portions adjacent to the first surface is higher than the hydrophilicity (B) of the second surface. In the second embodiment, The second surface is adjacent to the first surface on the lower side of the first surface in the direction of gravity and the second surface is adjacent to the first surface on the upper side of the first surface in the direction of gravity. The case where the hydrophilicity (A ₂ ) of the first portion of the portion is higher than the hydrophilicity (B) of the second surface has been described. Of the first portion and the second portion, Only the hydrophilicity of the second part may be set higher than the hydrophilicity (B) of the second surface.

However, from the viewpoint of obtaining the effect of the present invention more reliably, as described in the second embodiment, the hydrophilicity of at least the first portion of the first portion and the second portion is at least. (A ₂ ) is preferably set to be higher than the hydrophilicity of the second surface. From the viewpoint of obtaining the effect of the present invention more reliably, as described in the first embodiment, The hydrophilicity (A ₂ ) of both the first part and the second part is preferably set higher than the hydrophilicity of the second surface.

In the first embodiment and the second embodiment, the hydrophilicity (A ₁ ) of the first surface, the hydrophilicity (A ₂ ) of both the first portion and the second portion, In addition, the hydrophilicity (B) of the second surface has been described on the premise that it is substantially uniform. However, from the viewpoint of more reliably retaining water near the rib portion and suppressing the shortcut, the rib portion, It is preferable that the hydrophilicity at the center of the first surface is set to be the highest. For example, the hydrophilicity (A ₁ ) of the first surface is inclined so as to decrease from the center of the rib portion in the direction of gravity toward the gas flow path side (that is, from the center of the rib portion in the direction of gravity Preferably, the hydrophilicity (A ₂ ) of the first portion and the second portion is set to be lower than that of the first portion and the second portion.

  A fuel cell (particularly a polymer electrolyte fuel cell) using the separator of the present invention can be suitably used for a stationary fuel cell cogeneration system. Further, the fuel cell using the separator of the present invention can be applied to a driving force mounted on a moving / transporting machine such as an automobile and a motorcycle.

It is a schematic sectional drawing which shows the basic composition of 1st embodiment of the fuel cell of this invention. FIG. 2 is an enlarged cross-sectional view of a main part of an anode separator 20 of the fuel cell 100 shown in FIG. It is the front view seen from the gas flow path 22 side of the separator 20 of the anode side in FIG. It is a figure for demonstrating the method to perform a hydrophilic process in preparation of the anode side separator 20 of 1st embodiment. It is another figure for demonstrating the method to perform a hydrophilic process in preparation of the anode side separator 20 of 1st embodiment. It is a principal part expanded sectional view of the anode side separator with which the fuel cell of 2nd embodiment is equipped. It is a figure for demonstrating the method to perform a hydrophilic process in preparation of the anode side separator 20 of 2nd embodiment. It is a schematic sectional drawing which shows the structure of the conventional polymer electrolyte fuel cell. FIG. 9 is a front view of the anode-side separator 120 in FIG. 8 as viewed from the gas flow path 122 side. It is a schematic sectional drawing which shows the cross-section of the conventional separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 ... Polymer electrolyte membrane, 2, 102 ... Catalyst layer, 3, 103 ... Gas diffusion layer, 4, 104 ... Electrode, 6, 106 ... Gas seal material, 20, 120 ... Anode separator, 20a ... first surface, 20b ... second surface, 20c ₁ ... first portion, 20c ₂ ... second portion, 22, 32, 122, 132 ... gas flow path, 22a ... flow path portion, 22p, 122p ... straight line part, 22q, 122q ... turn part, 24, 25, 124, 125 ... O-ring, 30 , 130... Cathode side separator, 33, 133... Cooling water flow path, 20p, 120p... Manifold hole for fuel gas supply, 20q, 120q... Manifold hole for fuel gas discharge, 30p, 130p ... Oxidant gas supply manifold holes , 30q, 120q ... oxidant gas discharge manifold hole, 33p, 133p ... cooling water supply manifold hole, 33q, 123q ... cooling water discharge manifold hole, 36 ... glass powder, 200, 201, 202, 203, 204, 205... Hydrophilic treatment section.

Claims (5)

A separator used in a fuel cell, comprising a polymer electrolyte membrane having hydrogen ion conductivity, a membrane electrode assembly including an anode and a cathode sandwiching the polymer electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly There,
The separator has a gas flow path including a plurality of partial flow paths that intersect with the direction of gravity provided on a surface that contacts the anode or the cathode, and a rib portion that separates the partial flow paths,
The rib portion has a first surface that contacts the anode or the cathode;
The partial flow path has a second surface constituting the inner wall surface of the partial flow path,
The hydrophilicity (A ₁ ) of the _first surface is higher than the hydrophilicity (B) of the second surface, and the second surface is below the first surface in the direction of gravity. Hydrophilicity (A ₂ ) of at least one of the first portion adjacent to the first surface and the second portion adjacent to the first surface above the first surface in the gravitational direction. Is higher than the hydrophilicity (B) of the second surface,
A separator characterized by. The hydrophilicity (A ₁ ) of the _first surface is higher than the hydrophilicity (B) of the second surface, and the second surface is below the first surface in the direction of gravity. The hydrophilicity (A ₂ ) of the first portion adjacent to the first surface and the second portion adjacent to the first surface above the first surface in the direction of gravity of the first surface is the second portion. Higher than the hydrophilicity (B) of the surface of
The separator according to claim 1. The gas flow path has a serpentine structure having a substantially straight main flow path section that makes gas substantially straight and a turn section that turns the gas that moves substantially straight through the main flow path section,
The main flow path portion includes the partial flow path;
The separator according to claim 1 or 2. The hydrophilicity of the first surface is inclined so as to decrease from the center of the rib portion in the direction of gravity toward the gas flow path side;
The separator according to any one of claims 1 to 3. A polymer electrolyte membrane having hydrogen ion conductivity, a membrane electrode assembly including an anode and a cathode sandwiching the polymer electrolyte membrane, and a pair of separators sandwiching the membrane electrode assembly,
At least one of the pair of separators is the separator according to any one of claims 1 to 4,
A fuel cell.

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