Fuel cell separator
The fuel cell separator addresses water accumulation issues by using projections with thin films and grooves to discharge water efficiently, improving gas distribution and reducing resistance for enhanced power generation.
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- TOYOTA BOSHOKU KK
- Filing Date
- 2019-05-24
- Publication Date
- 2026-05-13
Smart Images
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Abstract
Description
Background 1. Area
[0001] The following description concerns a fuel cell separator. 2. Description of the state of the art
[0002] Japanese patent no. JP 6 199 266 B2 discloses a fuel cell comprising a membrane electrode assembly (MEA) and two separators that hold the MEA between them in the thickness direction. The membrane electrode assembly comprises an electrolyte film, an anode electrode layer, and a cathode electrode layer. The cathode electrode layer is bonded to one of the opposite faces of the electrolyte film in the thickness direction. The anode electrode layer is bonded to the other of the opposite faces of the electrolyte film in the thickness direction. In a fuel cell, separators divide the membrane electrode assemblies and arrange them between them in the thickness direction as described above.
[0003] As in Fig. As shown schematically in Figure 5, typical separators 51 each comprise a separator body 53, recesses 54, and projections 55. The separator body 53 is arranged between membrane electrode units 52 (electrolyte film 61, anode electrode layer 57, and cathode electrode layer 58) and is conductive. The recesses 54 and the projections 55 are configured in the separator body 53 such that the recesses 54 and projections 55 are arranged alternately parallel to each other. The surface of each projection 55 comprises a thin film 56 with a higher conductivity than the separator body 53. The projections 55 are each in contact with the anode electrode layer 57 or the cathode electrode layer 58 of the membrane electrode unit 52 with the intervening thin films 56.
[0004] The separator body 53 includes a passage 59 formed in the inner side of each recess 54 located between the projections 55 facing the anode electrode layer 57 of the membrane electrode assembly 52. The passage 59 is configured to supply fuel gas, such as hydrogen, to the anode electrode layer 57. The separator body 53 also includes a passage 60 formed in the inner side of each recess 54 located between the projections 55 facing the cathode electrode layer 58 of the membrane electrode assembly 52. The passage 60 is configured to supply oxidation gas, such as air, to the cathode electrode layer 58.
[0005] In the fuel cell, when fuel gas is supplied to the anode electrode layer 57 and oxidation gas is supplied to the cathode electrode layer 58, the fuel gas reacts with the oxidation gas in the membrane electrode assembly 52, thereby generating power. The reaction also produces water in the cathode electrode layer 58. The water produced in this way is discharged from the fuel cell using the flow of oxidation gas in the passage 60.
[0006] The reaction of fuel gas with oxidation gas in the membrane electrode assembly 52 is influenced by an electrical resistance between the membrane electrode assembly 52 and the separator body 53. To reduce the increase in electrical resistance, a thin film 56 is formed on the surface of each projection 55 in the separator body 53.
[0007] In separator 51, the ones on one side (bottom side in) Fig. 5) The projections 55 of the separator body 53, located in the thickness direction, are in contact with the cathode electrode layer 58 of the membrane electrode assembly 52 and the thin films 56 located between them. Thus, when power generation produces water in the cathode electrode layer 58, the water is easily retained between the cathode electrode layer 58 and the thin films 56. Consequently, the water produced in the cathode electrode layer 58 cannot be completely discharged from the fuel cell by the flow of oxidation gas. This can cause water to accumulate near the cathode electrode layer 58. The accumulation of water near the cathode electrode layer 58 limits the contact of oxidation gas with the cathode electrode layer 58. As a result, oxidation gas is not completely distributed throughout the membrane electrode assembly 52, thus impairing the reaction of fuel gas with oxidation gas.
[0008] The separator 51 contains the projections 55, which are located on the other side (upper side in Fig. 5) of the separator body 53, located in the thickness direction, are in contact with the anode electrode layer 57 of the membrane electrode assembly 52 and the intervening thin films 6. If a certain amount of moisture is contained in the thin films 56 of the separator 51, the increase in the electrical resistance of the thin films 56 is slightly reduced. Thus, if the membrane electrode assembly 52 is made thinner, water generated in the cathode electrode layer 58 can migrate through the electrolyte film 61 and move towards the anode electrode layer 58. In this case, if water is contained in the thin films 56 that are in contact with the anode electrode layer 57 of the membrane electrode assembly 52 in the separator 51, the increase in the electrical resistance in the thin films 56 can be slightly reduced.However, if the water between the thin films 56 and the anode electrode layer 57 is retained in greater quantities than necessary, causing excessive accumulation of water near the anode electrode layer 57, the contact of fuel gas with the anode electrode layer 57 is reduced. This can impair the reaction of fuel gas with oxidation gas in the membrane electrode assembly 52.
[0009] Furthermore, a fuel cell separator according to the preamble of claim 1 is known from EP 1 887 643 A1. Other fuel cell separators are known from JP 6 199 266 B2, DE 10 2012 205 692 A1 and US 2018 / 0069248 A1. Summary
[0010] The purpose of the present disclosure is to provide a fuel cell separator that reduces the accumulation of water between an electrode layer of a membrane electrode assembly and a thin film formed on the surface of a projection of a separator body.
[0011] This problem is solved with a fuel cell separator having the features of claim 1. Further embodiments are set out in the dependent claims.
[0012] Other features and aspects will become apparent from the following detailed description, drawings, and claims. Brief description of the drawings Fig. Figure 1 is a cross-sectional view showing a fuel cell separator. Fig. Figure 2 is a perspective view showing the separator from a section in contact with a cathode electrode layer. Fig. Figure 3 is a perspective view showing the separator from a section in contact with an anode electrode layer. Fig. Figure 4 is a perspective view showing another example of the grooves. Fig. Figure 5 is a cross-sectional view showing a typical fuel cell separator. Detailed description
[0013] This description provides a comprehensive understanding of the described procedures, devices, and / or systems. Variations and equivalents of the described procedures, devices, and / or systems are apparent to those skilled in the art. Work processes are exemplary and may be modified as would be apparent to those skilled in the art, with the exception of operations that necessarily occur in a specific sequence. Descriptions of functions and designs that are known to those skilled in the art may be omitted.
[0014] Exemplary embodiments can take various forms and are not limited to the examples described. However, the examples described are comprehensive and complete, conveying the full scope of the disclosure to those skilled in the art.
[0015] A fuel cell separator according to one embodiment is now described with reference to Fig. 1 to 3 described.
[0016] In a Fig. In the fuel cell shown, membrane electrode assemblies 1 are each located between two separators 2 in one thickness direction (vertical direction in Fig. 1) held. In other words, the membrane electrode assemblies 1 in the fuel cell are separated from each other by the separators 2. Each membrane electrode assembly of the fuel cell comprises an electrolyte film 3, an anode electrode layer 4, and a cathode electrode layer 5. The cathode electrode layer 5 is joined to the upper surface of the electrolyte film 3 with opposite surfaces in the thickness direction. The anode electrode layer 4 is joined to the lower surface of the electrolyte film 3 with opposite surfaces in the thickness direction. One membrane electrode assembly 1 and two separators 2, which hold the membrane electrode assembly 1 in the thickness direction, form a cell. The fuel cell comprises a cell stack formed by layers of cells in the thickness direction.
[0017] The separator 2 comprises a plate-shaped separator body 6, recesses 7, and projections 8. The separator body 6 is located between the membrane electrode assemblies 1. The recesses 7 and the projections 8 are configured in the separator body 6 such that they are arranged alternately parallel to each other. The separator body 6 is made of a conductive material such as titanium and stainless steel. The recesses 7 and the projections 8 are located on one side (lower side) and the other side. Fig. 1) as well as the other side (top side in Fig. 1) of the separator body 6 in the thickness direction.
[0018] As in Fig. As shown in Figure 1, the separator body 6, which is located on the upper side of the membrane electrode assembly 1, has projections 8 on one side (underside in Fig. 1) The thin films 9 are located on the surfaces of the projections 8 of the separator body 6, in the thickness direction, and are in contact with the cathode electrode layer 5 of the membrane electrode assembly 1, with thin films 9 located between them. The thin films 9 are arranged on the surfaces of the projections 8. The thin film 9 is made of a material with a higher conductivity than that of the separator body 6, such as carbon, gold, or platinum. The thin film 9 is formed by inkjet printing with a thickness of, for example, 10 nm to 900 µm. The thin film 9 has a higher hydrophilicity than the separator body 6. Passages 10 are formed in the inner surfaces of the recesses 7 of the separator body 6, which extend in the projection direction (lower side in the Fig. 1) The projections 8 with the thin films 9 on the surfaces of the projections 8 open. Oxide gas (e.g., air) is supplied through the passages 10 of the cathode electrode layer 5 of the membrane electrode assembly 1. That is, if those projections 8 of the separator body 6 that face the cathode electrode layer 5 of the membrane electrode assembly 1 are referred to as the first projections, the thin film 9 is arranged on the surface of each of the first projections. The first projections are in contact with the cathode electrode layer 5 of the membrane electrode assembly 1 via the thin films 9 located between them.Furthermore, if those of the depressions 7 of the first separator body 6 which open in the direction of the first projections are referred to as first depressions, the passages 10, through which oxidation gas (e.g. air) is supplied to the cathode electrode layer 5 of the membrane electrode unit 1, are formed in the inner sides of the first depressions.
[0019] In Fig. In Figure 1, the cell formed by the membrane electrode assembly 1 shown by the solid line and the two separators 2 shown by the solid lines, which arrange the membrane electrode assembly 1 between them in the thickness direction, is referred to as a first cell. As in Fig. As shown in Figure 1, the separator body 6 of a second cell is located on the upper side of the upper separator body 6 of the membrane electrode assembly 1 in the first cell. The separator body 6 of a second cell is located on the upper side of the first cell. The facing projections 8 in the separator bodies 6 are in contact with each other by means of intervening layers 15. That is, if those projections 8 of separator body 6 that face another separator body 6 are referred to as second projections, the facing second projections in the separator bodies 6 are in contact with each other by means of the intervening layers 15. The projections 8 (second projections) that face each other in this way are parallel to each other in the lateral direction. Fig. 1. Passages 16 are arranged through the openings of the recesses 7 on the opposite sides of the facing projections 8 in the lateral direction. A cooling fluid (for example, a coolant) flows through the passages 16. That is, if those of the recesses 7 of the separator body 6 that open in the projection direction of the second projections are referred to as second recesses, then the passages 16, through which a cooling fluid (for example, a coolant) flows, are formed through the openings of the second recesses of the separator body 6.
[0020] As in Fig. As shown in Figure 1, in the separator body 6, which is located on the lower side of the membrane electrode assembly 1, the projections 8, which are located on the upper side of the separator body 6 in the thickness direction, are in contact with the anode electrode layer 4 of the membrane electrode assembly 1 with interposed thin films 11. The thin films 11 are arranged on the surfaces of the projections 8. The thin film 11 is made of a material with a higher conductivity than that of the separator body 6, such as carbon, gold, or platinum. The thin film 11 is formed by inkjet printing with a thickness of, for example, 10 nm to 900 µm. The thin film 11 has a higher hydrophilicity than the separator body 6. Passages 12 are formed in the inner surfaces of the recesses 7 of the separator body 6, which extend in the projection direction (upper side in the Fig. 1) The projections 8 open, which have thin films 11 on their surfaces. Fuel gas (e.g., hydrogen) is supplied to the anode electrode layer 4 of the membrane electrode assembly 1 through the passages 12. That is, if those projections 8 of the separator body 6 facing the anode electrode layer 4 of the membrane electrode assembly 1 are called first projections, the thin film 11 is arranged on the surface of each of the first projections. The first projections are in contact with the anode electrode layer 4 of the membrane electrode assembly 1 via the thin films 11 located between them.Furthermore, if those of the recesses 7 of the separator body 6 which open in the direction of the projections of the first projections are referred to as first recesses, the passages 12, through which fuel gas (for example hydrogen) is supplied to the anode electrode layer 4 of the membrane electrode unit 1, are formed in the inner sides of the first recesses.
[0021] As described above, in Fig. 1 The cell formed by the membrane electrode assembly 1 shown by the solid line and the two separators 2 shown by the solid lines, which arrange the membrane electrode assembly 1 between them in the thickness direction, is referred to as the first cell. As in Fig. As shown in Figure 1, the separator body 6 of a third cell is located on the lower side of the lower separator body 6 of the membrane electrode assembly 1 in the first cell. The separator body 6 of a third cell is located on the lower side of the first cell. The mutually facing projections 8 (second projections) in the separator body 6 are in contact with each other through the intervening layers 15. The projections 8 (second projections), which are thus facing each other, are parallel to each other in the lateral direction. Fig. 1. Passages 16 are arranged through the openings of the recesses 7 (secondary recesses) on the opposite sides of the facing projections 8 (secondary projections) in the lateral direction. Coolant flows through the passages 16.
[0022] In the fuel cell, hydrogen (fuel gas) is supplied to the anode electrode layer 4 of the membrane electrode assembly 1 through ports 12, and air (oxidation gas) is supplied to the cathode electrode layer 5 of the membrane electrode assembly 1 through ports 10. The hydrogen reacts with the air in the membrane electrode assembly 1, generating power. The reaction also produces water in the cathode electrode layer 5.
[0023] More precisely, when hydrogen is supplied to the anode electrode layer 4 of the membrane electrode assembly 1, an electron is removed from a hydrogen atom and transferred to the anode electrode layer 4. The electron then flows through the conductor of an external circuit (not shown) from the anode electrode layer 4 to the cathode electrode layer 5. When the electron is absorbed in the anode electrode layer 4, a hydrogen ion (proton) becomes positively charged. This ion passes through the electrolyte film 3 of the membrane electrode assembly 1 to move towards the cathode electrode layer 5. In the cathode electrode layer 5 of the membrane electrode assembly 1, where air is supplied, the electron, which flowed as described above, is absorbed by an oxygen molecule to become an oxygen ion.Furthermore, the hydrogen ion, which has passed from the anode electrode layer 4 through the electrolyte film 3 to move towards the cathode electrode layer 5, binds to the oxygen ion, thereby producing water in the cathode electrode layer 5. The water produced in this way is released from the fuel cell by the airflow in passage 10.
[0024] The thin film (thin film 9 or thin film 11) is arranged on the surface of each of the projections 8 (first projections) of the separator body 6, which is oriented to face the electrode layer (anode electrode layer 4 or cathode electrode layer 5). This is because the thin film (thin film 9 or thin film 11) reduces the increase in electrical resistance between the membrane electrode assembly 1 and the separator body 6, so that the increase in electrical resistance does not prevent the reaction of hydrogen with air in the membrane electrode assembly 1.
[0025] Thin films 9 and 11 will now be described in detail.
[0026] As in Fig. As shown in section 2, the section (lower surface in Fig. 2) of the thin film 9, which is in contact with the cathode electrode layer 5 of the membrane electrode assembly 1, grooves 13. The grooves 13 extend in a direction that intersects the recesses 7 and the projections 8 to connect with the passage 10. The grooves 13 are spaced apart from each other in the direction in which the projections 8 extend. One end of each groove 13 in the longitudinal direction is connected to the passage 10. More precisely, the grooves 13 that are adjacent to each other in the direction in which the projections 8 extend are connected to different passages 10 located on opposite sides of the corresponding projection 8 (first projection)., one of the adjacent grooves 13 in the direction in which the projections 8 extend is connected to one of the opposite passages 10 that arrange the corresponding projection 8 (first projection) between them, and the other of the adjacent grooves 13 is connected to the other of the opposite passages 10 that arrange the corresponding projection 8 (first projection) between them.
[0027] As in Fig. As shown in section 3, the upper surface in Fig. 3) of the thin film 11, which is in contact with the anode electrode layer 4 of the membrane electrode assembly 1, grooves 14. The grooves 14 extend in the direction that intersects the recesses 7 and the projections 8 to be connected to the passage 12. The grooves 14 are spaced apart from each other in the direction in which the projections 8 extend. One end of each groove 14 in the longitudinal direction is connected to the passage 12. More precisely, the grooves 14 that are adjacent to each other in the direction in which the projections 8 extend are connected to different passages 12 located on opposite sides of the corresponding projection 8 (first projection). That is to say, one of the adjacent grooves 14 in the direction in which the projections 8 extend is connected to one of the opposite passages 12 which arrange the corresponding projection 8 (first projection) between them, and the other of the adjacent grooves 14 is connected to the other of the opposite passages 12 which arrange the corresponding projection 8 (first projection) between them.
[0028] The operation of separator 2 in the present embodiment will now be described.
[0029] When power generation in the fuel cell produces water in the cathode electrode layer 5 of the membrane electrode assembly 1, the water is retained between the cathode electrode layer 5 and the thin films 9. As a result, the water generated in the cathode electrode layer 5 is not completely discharged from the fuel cell by the airflow in passage 10. Thus, the water can accumulate near the cathode electrode layer 5. This accumulation of water near the cathode electrode layer 5 limits the contact between air and the cathode electrode layer 5. Consequently, oxidation gas is not completely distributed throughout the membrane electrode assembly 1, thus impairing the reaction of fuel gas with oxidation gas.
[0030] In the separator 2 of the present embodiment, however, the grooves 13 in the thin film 9 limit situations in which the water generated in the cathode electrode layer 5 of the membrane electrode assembly 1 due to power generation in the fuel cell is retained between the cathode electrode layer 5 and the thin film 9. That is, the water between the cathode electrode layer 5 and the thin film 9 is discharged from the passage 10, through which air flows, via the grooves 13 in the thin film 9. Furthermore, the airflow in the passage 10 causes the water to be discharged from the fuel cell.
[0031] If a certain amount of moisture is contained in the thin films 9 and 11, the thin films 9 and 11 slightly reduce the increase in electrical resistance. Thus, if the membrane electrode assembly 1 is made thinner, the water generated in the cathode electrode layer 5 can migrate through the electrolyte film 3 and move towards the anode electrode layer 4. In this case, if water is contained in the thin films 11, which are in contact with the anode electrode layer 4 of the membrane electrode assembly 1 in the separator 2, the increase in electrical resistance in the thin films 11 is slightly reduced. If more water than necessary is retained between the thin films 11 and the anode electrode layer 4, causing excessive water accumulation near the anode electrode layer 4, contact of fuel gas (hydrogen) at the anode electrode layer 4 is limited.This can worsen the reaction of fuel gas with oxidation gas in the membrane electrode assembly 1.
[0032] In the separator 2 of the present embodiment, however, grooves 14 are formed in the thin films 11, which are in contact with the anode electrode layer 4. Thus, the grooves 14 of the thin films 11 limit the amount of water retained between the anode electrode layer 4 and the thin films 11. This means that excess water between the anode electrode layer 4 and the thin film 11 is discharged from the passage 12, through which the fuel gas (hydrogen) flows, via the grooves 4 in the thin film 11. Furthermore, the fuel gas flow in the passage 12 discharges the water from the fuel cell.
[0033] The present embodiment has the following advantages. (1) In the cathode electrode layer 5 of the membrane electrode assembly 1, the generation of power produces water. The accumulation of this water between the cathode electrode layer 5 and the thin films 9 arranged on the surfaces of the projections 8 (first projections) of the separator body 6 is limited. (2) One end of each longitudinal groove 13 is connected to the passage 10. This causes a slight release of water from the passage 10 through the grooves 13 between the thin film 9 and the cathode electrode layer 5 of the membrane electrode assembly 1. One of the opposite ends of each longitudinal groove 13 is connected to the passage 10, and the other of the opposite ends is not connected to the passage 10. As a result, the pressure in the groove 13 increases slightly, thereby accelerating the release of water from between the thin film 9 and the cathode electrode layer 5. (3) If the hydrophilicity of the thin film 9 is low, water in the groove 13 is easily repelled from the inner surfaces of the groove 13. This limits the movement of water in the groove 13 and thus limits the movement of water in the direction in which it is discharged to the passage 10. However, the thin film 9 has a higher hydrophilicity than the separator body 6. Thus, water in the grooves 13 is easily spread across the inner surfaces of the thin film 9. This facilitates the movement of water in the direction in which it is discharged from the grooves 13 to the passage 10. (4) Even if water generated in the cathode electrode layer 5 of the membrane electrode assembly 1 moves towards the anode electrode layer 4, the grooves 14 of the thin films 11 limit the amount of water retained between the anode electrode layer 4 and the thin films 11, which are arranged on the surfaces of the projections 8 (first projections) of the separator body 6, to prevent the accumulation of excess water between the anode electrode layer 4 of the membrane electrode assembly 1 and the thin films 11, which are arranged on the surfaces of the projections 8 (first projections) of the separator body 6. (5) One end of each groove 14 in the longitudinal direction is connected to the passage 12. This causes the water between the thin film 11 and the anode electrode layer 4 of the membrane electrode assembly 1 to be easily released from the passage 12 via the grooves 14 for the same reason as for the advantage described above (2). (6) The thin film 11 has a higher hydrophilicity than the separator body 6. Thus, for the same reason as in the advantage described above (3), water moves easily in the grooves 14 in the direction in which the water is discharged to the passage 12.
[0034] The embodiment described above can be modified as described below.
[0035] Separator body 6 is made of titanium or stainless steel. Alternatively, separator body 6 can be made of other types of conductive materials such as carbon.
[0036] The grooves 13, which are adjacent to each other in the direction in which the projections 8 extend, can be connected to the same of the opposite passages 10, which arrange the corresponding projection 8 (first projection) between them. In the same way, the grooves 14, which are adjacent to each other in the direction in which the projections 8 extend, can be connected to the same of the opposite passages 12, which arrange the corresponding projection 8 (first projection) between them.
[0037] As in Fig.As shown in Figure 4, each groove 13 can be arranged such that one of the opposite ends of the groove 13 is connected longitudinally to one of the opposite passages 10, which arrange the corresponding projection 8 (first projection) between them, and the other of the opposite ends of the groove 13 is connected longitudinally to the other of the opposite passages 10, which arrange the corresponding projection 8 (first projection) between them.In the same way, each groove 14 can be arranged such that one of the opposite ends of the groove 14 is connected longitudinally to one of the opposite passages 12, which arrange the corresponding projection 8 (first projection) between them, and the other of the opposite ends of the groove 14 is connected longitudinally to the other of the opposite passages 12, which arrange the corresponding projection 8 (first projection) between them.
[0038] The thin films 9 and 11, each encompassing grooves 13 and 14, are formed by inkjet printing. Therefore, pattern adaptation of an inkjet print can be used to modify the shapes of grooves 13 and 14 in the thin films 9 and 11.
[0039] The grooves 13 of the thin film 9 or the grooves 14 of the thin film 11 can be omitted.
[0040] The thin films 9 and 11 do not necessarily have to have a higher hydrophilicity than the separator body 6.
[0041] Various modifications in form and details may be made to the examples above without altering the spirit and scope of the claims and their equivalents. The examples serve only for description and not for limitation. Descriptions of features in each example are to be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if processes are carried out in a different order and / or if components in a described system, architecture, device, or circuit are combined differently and / or replaced or supplemented by other components or their equivalents. The scope of disclosure is not defined by the detailed description but by the claims and their equivalents. All modifications within the scope of the claims and their equivalents are included in the disclosure.
[0042] A fuel cell separator comprises a separator body designed to be positioned between membrane electrode assemblies and includes recesses and projections formed in the separator body. The projections include first projections oriented towards an electrode layer of the membrane electrode assembly. A thin film is arranged on one face of each of the first projections. The recesses include first depressions that open in a projection direction of the first projections. Each of the first depressions is designed to form a passage through which oxidizer gas or fuel gas is supplied to the electrode layer.A section of each of the thin films that is in contact with the electrode layer of the membrane electrode assembly comprises a groove, the groove being connected to at least one of the passages located on opposite sides of one of the first projections encompassing the thin film.
Claims
Fuel cell separator comprising: a plate-shaped conductive separator body (6) designed to be arranged between membrane electrode assemblies (1) in a fuel cell; and recesses (7) and projections (8) formed in the separator body (6) such that the recesses (7) and the projections (8) are arranged alternately parallel to each other, characterized in that the projections (8) comprise first projections (8) which are arranged to face an electrode layer (4, 5) of the membrane electrode assembly (1), a thin film (9, 11) is arranged on a surface of each of the first projections (8), the thin film (9, 11) having a higher conductivity than the separator body (6), the first projections (8) are arranged to be in contact with the electrode layer (4, 5) of the membrane electrode assembly (1) with the thin films (9, 11) located between them, the recesses (7) comprise first recesses (7),which open in a projection direction of the first projections (8), each of the first depressions (7) is configured to form a passage (10, 12) through which oxidation gas or fuel gas is supplied to the electrode layer (4, 5) of the membrane electrode assembly (1), the passage (10, 12) being located on an inner side of each of the first depressions (7), and a section of each of the thin films (9, 11) in contact with the electrode layer (4, 5) of the membrane electrode assembly (1) comprising a groove (13, 14), the groove (13, 14) extending in a direction that intersects the depressions (7) and the projections (8), and being connected to at least one of the passages (10, 12) located on opposite sides of one of the first projections (8) comprising the thin film (9, 11). Fuel cell separator according to claim 1, characterized in that the groove (13, 14) has an end in a longitudinal direction of the groove (13, 14), wherein the end is connected to the passage (10, 12). Fuel cell separator according to claim 2, characterized in that the groove (13, 14) is one of a plurality of grooves (13, 14) which are spaced apart from one another in a direction in which the projections (8) extend, and those of the grooves (13, 14) which are adjacent to one another in the direction in which the projections (8) extend are connected to different passages (10, 12) which are located on opposite sides of the corresponding first projection (8). Fuel cell separator according to claim 1, characterized in that the groove (13, 14) has opposite ends in a longitudinal direction of the groove (13, 14), wherein one of the opposite ends is connected to one of the passages (10, 12) located on opposite sides of the corresponding first projection (8), and the other of the opposite ends is connected to the other of the passages (10, 12) located on opposite sides of the corresponding first projection (8). Fuel cell separator according to one of claims 1 to 4, characterized in that the thin film (9, 11) has a higher hydrophilicity than the separator body (6).