Gas diffusion bed, separator, and electrochemical reaction device

Abstract

A gas supply diffusion layer (42A) for a fuel cell, having a sheet-shaped porous body layer (40) capable of gas permeability and diffusion and also having conductivity, and a plurality of gas flow path grooves formed on one side of the porous body layer (40), each extending from the gas inlet side to the gas outlet side. In the gas supply diffusion layer (42A) for a fuel cell, the plurality of gas flow path grooves include a plurality of gas inlet side grooves (53a, 53b) formed on the gas inlet side and a plurality of gas outlet side grooves (54a, 54b) formed on the gas outlet side, and the plurality of gas inlet side grooves (53a, 53b) include two or more types of gas inlet side grooves (53a, 53b) having different lengths. According to the present invention, a gas supply diffusion layer (42A) for a fuel cell capable of increasing reaction efficiency (power generation efficiency) compared to conventional methods can be provided.

Description

Technology Field

[0001] The present invention relates to a gas diffusion layer, a separator, and an electrochemical reaction device. Background Technology

[0002] In the technical field of solid polymer fuel cells (PEFC: Polymer Electrolyte Fuel Cell), a fuel cell stack capable of uniformly supplying and diffusing fuel cell gases (anode gas, cathode gas) is known (see, for example, Patent Document 1). FIG. 32 is a front view schematically showing a conventional fuel cell stack (920). FIG. 33 and FIG. 34 are plan views of a separator (921) of type CA in a conventional fuel cell stack (920). FIG. 33 is a plan view seen from the side of the fuel cell gas supply diffusion layer (cathode gas supply diffusion layer) (942), and FIG. 34 is a plan view seen from the side of the fuel cell gas supply diffusion layer (anode gas supply diffusion layer) (941). FIG. 35 is a cross-sectional view along line AA of FIG. 33.

[0003] A conventional fuel cell cell stack (920) has a structure in which a plurality of separators (a separator of type CA (921), a separator of type A (922), a separator of type C (923), and a separator of type AW (924)) are stacked, with a gas supply diffusion layer for a fuel cell formed by a porous body layer provided on at least one side of a metal plate (30), as shown in FIGS. 32 to 35. Additionally, in the separator (921) of type CA, the separator (922) of type A, and the separator (924) of type AW, “A” represents a gas supply diffusion layer (anode gas supply diffusion layer) (941) for a fuel cell, and “C” in the separator (921) of type CA and the separator (923) of type C represents a gas supply diffusion layer (cathode gas supply diffusion layer) (942) for a fuel cell, and “W” in the separator (924) of type AW represents a cooling water supply diffusion layer. According to the conventional fuel cell cell stack (920), the gas supply diffusion layer (941, 942) for a fuel cell, which includes a porous body layer, is formed in the separator itself, so that the gas for the fuel cell can be uniformly diffused over the entire surface of the gas supply diffusion layer for the fuel cell. As a result, the fuel cell gas can be supplied uniformly across the entire surface of the membrane electrode assembly (MEA) (81), thereby increasing the power generation efficiency of the fuel cell compared to conventional methods.

[0004] Furthermore, in the field of electrochemistry, power generation using chemical reactions of gases and electrolysis are inextricably linked. It is believed that the gas supply diffusion layer, separator, and fuel cell stack for fuel cells described above can be adapted almost entirely with their original configurations, and that using water instead of gas makes it possible to utilize them exclusively for electrolysis (generation of cathode and anode gases). Additionally, it is believed that the gas supply diffusion layer, separator, and fuel cell stack for fuel cells described above can be adapted almost entirely with their original configurations for methanol fuel cells (methanol aqueous solution anode, air cathode), lithium-ion / air batteries (air cathode), and redox flow batteries (anode / cathode supplied with vanadium ion water solution), which use a liquid that is a fluid similar to gas instead of gas. For this reason, in this specification, the term "gas diffusion layer" is used as an expression including "gas supply diffusion layer for a fuel cell" (an expression that does not distinguish between fuel cells and electrolysis), and the term "electrochemical reaction device" is used as an expression including "fuel cell cell stack." Furthermore, "gas diffusion layer" has the meaning of "a layer intended primarily for the diffusion of gas," and substances other than gas (especially liquids such as water) may be diffused or circulated within the layer. Prior art literature

[0005] International Publication No. 2015 / 072584 The problem to be solved

[0006] However, in the field of electrochemical technology, there is a demand for technology capable of increasing reaction efficiency (or power generation efficiency in the case of fuel cells) compared to conventional methods. Therefore, the present invention aims to provide a gas diffusion layer, a separator, and an electrochemical reaction apparatus capable of increasing reaction efficiency compared to conventional methods. means of solving the problem

[0007] A gas diffusion layer according to one embodiment of the present invention is a gas diffusion layer having a sheet-shaped porous body layer capable of gas permeability and diffusion and also having conductivity, and a plurality of gas flow path grooves formed on one side of the porous body layer, each extending from the gas inlet side to the gas outlet side, wherein the plurality of gas flow path grooves include a plurality of gas inlet side grooves formed on the gas inlet side and a plurality of gas outlet side grooves formed on the gas outlet side, and the plurality of gas inlet side grooves include two or more types of gas inlet side grooves having different lengths.

[0008] A separator according to one embodiment of the present invention is a separator comprising a gas shielding plate and a gas diffusion layer disposed on at least one side of the gas shielding plate, wherein the gas diffusion layer is the gas diffusion layer of the present invention, and wherein a plurality of grooves for gas flow paths are disposed relative to the gas shielding plate such that they are located on the side of the gas shielding plate, and the gas flow path is formed by the grooves for gas flow paths and the gas shielding plate.

[0009] An electrochemical reaction device according to one embodiment of the present invention is an electrochemical reaction device formed by stacking a separator and a membrane electrode assembly, wherein the separator is the separator of the present invention, and the separator and the membrane electrode assembly are stacked in a positional relationship such that the membrane electrode assembly is located on the side of the gas diffusion layer where the plurality of gas flow path grooves are not formed. Effects of the invention

[0010] According to the present invention, a gas diffusion layer, a separator, and an electrochemical reaction device capable of increasing reaction efficiency compared to conventional methods can be provided. Brief explanation of the drawing

[0011] FIG. 1 is a front view schematically showing a fuel cell stack (20) according to embodiment 1. FIG. 2 is a side view schematically showing a fuel cell stack (20) according to embodiment 1. Figure 3 is a drawing illustrating a membrane electrode assembly (MEA) (81). FIG. 4 is a plan view of a fuel cell separator (23A) according to embodiment 1. FIG. 5 is a cross-sectional view of a fuel cell separator (23A) according to embodiment 1. FIG. 6 is a drawing illustrating the gas inlet side grooves (53a, 53b) and gas outlet side grooves (54a, 54b) in the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1. FIG. 7 is a drawing illustrating relay grooves (55a to 55d) and communication grooves (56a, 56b) in a gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1. FIG. 8 is a cross-sectional view of a separator (fuel cell separator (21, 22, 24, 25)) other than the fuel cell separator (23A) according to Embodiment 1. FIG. 9 is a plan view of a fuel cell separator (23B) according to embodiment 2. FIG. 10 is a drawing illustrating the gas inlet side grooves (53c to 53f) and gas outlet side grooves (54c to 54f) in the gas supply diffusion layer (42B) for a fuel cell according to embodiment 2. FIG. 11 is a drawing illustrating the relay groove (55e) and the communication groove (56c) in the gas supply diffusion layer (42B) for a fuel cell according to embodiment 2. FIG. 12 is a plan view of a fuel cell separator (23C) according to embodiment 3. FIG. 13 is a drawing illustrating the gas inlet side grooves (53g to 53j) and gas outlet side grooves (54g to 54j) in the gas supply diffusion layer (42C) for a fuel cell according to Embodiment 3. FIG. 14 is a drawing illustrating relay grooves (55d to 55j) and communication grooves (56d, 56e) in a gas supply diffusion layer (42C) for a fuel cell according to Embodiment 3. FIG. 15 is a plan view of a fuel cell separator (23D) according to embodiment 4. FIG. 16 is a drawing illustrating the gas inlet side grooves (53k to 53n) and gas outlet side grooves (54k, 54l) in the gas supply diffusion layer (42D) for a fuel cell according to embodiment 4. FIG. 17 is a drawing illustrating relay grooves (55k to 55p) in a gas supply diffusion layer (42D) for a fuel cell according to embodiment 4. FIG. 18 is a plan view of a fuel cell separator (23E) according to embodiment 5. FIG. 19 is a plan view of a fuel cell separator (23F) according to embodiment 6. FIG. 20 is a plan view of a fuel cell separator (23G) according to embodiment 7. FIG. 21 is a plan view of a fuel cell separator (23H) according to embodiment 8. FIG. 22 is a plan view of a fuel cell separator (23I) in a comparative example. FIG. 23 is a plan view of a fuel cell separator (22A) for anode gas used in a test example. Figure 24 is a diagram illustrating the division of regions when measuring the current density distribution in Test Example 3. Figure 25 is a graph showing the results of Test Example 1 (relationship between the pattern of the groove for the gas flow path and the power generation characteristics). Figure 26 is a graph showing the results of Test Example 2 (relationship between the pattern of the groove for the gas flow path and the pressure loss in the gas supply diffusion layer for the fuel cell). Figure 27 is a graph showing the results of Test Example 3 (relationship between the pattern of the groove for the gas flow path and the current density distribution in the gas supply diffusion layer for the fuel cell). FIG. 28 is a plan view of a fuel cell separator (23J) according to Variant Example 1. FIG. 29 is a plan view of a fuel cell separator (23K) according to variant example 2. FIG. 30 is a plan view of a fuel cell separator (23L) according to Variant Example 3. FIG. 31 is a plan view of a fuel cell separator (23M) according to variant 4. FIG. 32 is a front view schematically showing a conventional fuel cell cell stack (920). FIG. 33 is a plan view of a separator (921) for a fuel cell of type CA in a conventional fuel cell cell stack (920). FIG. 34 is a plan view of a separator (921) for a fuel cell of type CA in a conventional fuel cell cell stack (920). FIG. 35 is a cross-sectional view along line AA of FIG. 33. Specific details for implementing the invention

[0012] Hereinafter, the gas diffusion layer, separator, and electrochemical reaction apparatus of the present invention will be described in detail using the embodiments shown in the drawings.

[0013] [Embodiment 1]

[0014] FIG. 1 is a front view schematically showing a fuel cell stack (20) (electrochemical reaction device) according to embodiment 1. FIG. 2 is a side view schematically showing a fuel cell stack (20) according to embodiment 1.

[0015] The fuel cell stack (20) (electrochemical reaction device) according to Embodiment 1 is a fuel cell stack formed by stacking a separator (21, 22, 23A, 24) (separator) for a fuel cell and a membrane electrode assembly (81). More specifically, the fuel cell stack (20) is a solid polymer fuel cell (PEFC: Polymer Electrolyte Fuel Cell). The fuel cell stack (20) has a plurality of single cells. Each cell of the fuel cell stack (20) has a membrane electrode assembly (81) and an element constituting the cathode side and an element constituting the anode side with the membrane electrode assembly (81) in between.

[0016] A fuel cell separator (21) has a cathode gas supply diffusion layer C formed on one side of a metal plate (30) (gas shielding plate) and an anode gas supply diffusion layer A formed on the other side (Type CA separator). A fuel cell separator (22) has an anode gas supply diffusion layer A formed on one side of a metal plate (30) (Type A separator). A fuel cell separator (23A) has a cathode gas supply diffusion layer C formed on one side of a metal plate (30) (Type C separator). A fuel cell separator (24) has a cathode gas supply diffusion layer C formed on one side of a metal plate (30) and a cooling water supply diffusion layer W formed on the other side (Type CW separator).

[0017] Each cell is arranged so that the cathode side and the anode side alternate. The cathode gas supply diffusion layer C and the anode gas supply diffusion layer A are arranged facing each other with a membrane electrode assembly (MEA) (81) in between. In an embodiment, a cooling water supply diffusion layer W is provided to supply cooling water whenever two single cells are arranged. Additionally, the cooling water supply diffusion layer W may be arranged every other single cell, every three or more cells. Fuel cell separators (21, 22, 23A, 24) are combined and stacked so that a metal plate (30) (preferably a metal plate (30) in a type A or type C separator) faces the cooling water supply diffusion layer W.

[0018] Additionally, although not illustrated in FIG. 1 and FIG. 2, the fuel cell cell stack may be provided with an anode gas supply diffusion layer A formed on one side of a metal plate (30) and a cooling water supply diffusion layer W formed on the other side (Type AW separator). Additionally, it may be provided with a separator (Type W separator) in which a cooling water supply diffusion layer W is formed on one side of a metal plate (30). Additionally, it may be provided with a separator in which a cooling water supply diffusion layer W is formed on both sides of a metal plate. Details regarding the configuration of each separator will be described later.

[0019] Current collector plates (27A, 27B) are disposed at both ends of the stacked cells. Additionally, end plates (75, 76) are disposed on the outer side of the current collector plates (27A, 27B) through an insulating sheet (28A, 28B). The fuel cell separators (21, 22, 23A, 24) are pressed from both sides by the end plates (75, 76). For the separators located at both ends of the fuel cell cell stack (20) and in contact with the current collector plates (27A, 27B), it is preferable that the metal plate (30) (corrosion-resistant layer) faces outward.

[0020] In FIGS. 1 and 2, the fuel cell separator (21, 22, 23A, 24), membrane electrode assembly (81), current collector plate (27A, 27B), insulating sheet (28A, 28B), and end plate (75, 76) are drawn spaced apart for ease of understanding, but they are closely joined to each other in the order of the illustrated arrangement. The method of joining is not particularly limited. For example, they may be joined only by pressing each member from both sides with the end plate (75, 76), or joined by pressing each member from both sides with the end plate (75, 76) after attaching a suitable position of each member with an adhesive, or joined by other methods. Each fuel cell separator (21, 22, 23A, 24), membrane electrode assembly (81), current collector plate (27A, 27B), insulating sheet (28A, 28B), etc., has a thickness of, for example, about 100 μm to about 10 mm. In each embodiment of this specification, each drawing is drawn with an exaggerated thickness.

[0021] At one end of the end plate (75) on the anode side, an anode gas supply port (71in), a cathode gas discharge port (72out), and a cooling water discharge port (73out) are respectively provided. Meanwhile, at one end of the end plate (76) on the cathode side (opposite to the end of the end plate (75)), an anode gas discharge port (71out), a cathode gas supply port (72in), and a cooling water supply port (73in) (in FIG. 2, these are integrated and shown as dashed lines) are provided. A supply pipe and a discharge pipe for a corresponding fluid are connected to each of these supply ports and each of these discharge ports.

[0022] Each fuel cell separator (21, 22, 23A, 24) is provided with an anode gas inlet (61in) communicating with an anode gas supply port (71in), a cathode gas (and generated water) outlet (62out) communicating with a cathode gas outlet (72out), and a cooling water outlet (63out) communicating with a cooling water outlet (73out). Additionally, each fuel cell separator (21, 22, 23A, 24) is provided with an anode gas outlet (61out) communicating with an anode gas outlet (71out), a cathode gas inlet (62in) communicating with a cathode gas supply port (72in), and a cooling water inlet (63in) communicating with a cooling water supply port (73in).

[0023] Cathode gas, anode gas, and cooling water are supplied through the anode gas supply port (71in), cathode gas supply port (72in), and cooling water supply port (73in). In Embodiment 1, hydrogen gas is used as the anode gas and air is used as the cathode gas.

[0024] Next, the membrane electrode assembly (81) will be described.

[0025] FIG. 3 is a drawing illustrating a membrane electrode assembly (MEA) (81). FIG. 3 (a) is a top view of the membrane electrode assembly (81), FIG. 3 (b) is a front view of the membrane electrode assembly (81), and FIG. 3 (c) is a side view of the membrane electrode assembly.

[0026] As shown in FIG. 3, the membrane electrode assembly (81) has an electrolyte membrane (PEM) (82), catalyst layers (CL) (85) disposed on each side of the electrolyte membrane (82), and a microporous layer (MPL) (83) disposed on the outer side of each catalyst layer (85). In this specification, a structure composed of an electrolyte membrane (82) and catalyst layers (85) disposed on both sides thereof is referred to as a Catalyst Coated Membrane (CCM). The microporous layer (83) has pores (fine diameters) that are finer than those of the porous layer (40). Additionally, the microporous layer (83) may be omitted. In addition, as described in Variant Example 7 below, if the direct application of the microporous layer (83) to the catalyst layer (85) is omitted, the microporous layer (83) may be applied to the surface of the fuel cell gas supply diffusion layer (41, 42A) in contact with the catalyst layer (85).

[0027] Next, the gas supply diffusion layer (42A) (gas supply diffusion layer) for a fuel cell is described using a separator (23A) for a fuel cell as an example. FIG. 4 is a plan view of a separator (23A) for a fuel cell.

[0028] FIG. 4 is a plan view of a separator (23A) for a Type C fuel cell viewed from the side of a metal plate (30), but the metal plate (30) is omitted to make it easier to understand the arrangement of multiple gas flow grooves in the separator (23A) for the fuel cell. In addition, in the plan view of the separator including FIG. 4, to avoid making the display of symbols complicated, regarding the gas flow grooves (gas inlet side groove, gas outlet side groove and relay groove), even if there are multiple grooves of the same shape, in principle, only one groove is marked with a symbol.

[0029] FIG. 5 is a cross-sectional view of a fuel cell separator (23A) according to Embodiment 1. FIG. 5 (a) is a cross-sectional view along line A1-A1 of FIG. 4, FIG. 5 (b) is a cross-sectional view along line A2-A2 of FIG. 4, and FIG. 5 (c) is a cross-sectional view along line A3-A3 of FIG. 4. FIG. 5 shows a fuel cell separator (23A) in a state where the membrane electrode assembly (81) is joined, in order to show the positional relationship between the fuel cell separator (23A) and the membrane electrode assembly (81). Also, the illustration of the cross-sectional structure of the membrane electrode assembly (81) is omitted. FIG. 6 is a drawing shown to explain the gas inlet side grooves (53a, 53b) and gas outlet side grooves (54a, 54b) in the fuel cell separator (23A) according to Embodiment 1. FIG. 7 is a drawing illustrating relay grooves (55a to 55d) and communication grooves (56a, 56b) in a fuel cell separator (23A) according to Embodiment 1. In order to make the arrangement of the grooves easier to understand, the illustration of relay grooves (55a to 55d) and communication grooves (56a, 56b) in FIG. 6 is omitted, and the illustration of gas inlet side grooves (53a, 53b) and gas outlet side grooves (54a, 54b) in FIG. 7 is omitted.

[0030] As shown in FIGS. 4 and 5, the separator (23A) for a fuel cell is a separator comprising a metal plate (30) which is a gas shielding plate and a gas supply diffusion layer (42A) for a fuel cell disposed on at least one side of the metal plate (30). In FIGS. 5, the metal plate (30) has a hatching indicating that it is a cross-section. The metal plate (30) is preferably a metal containing one or more of Inconel, nickel, gold, silver, and platinum, or a metal plate or clad material made of an austenitic stainless steel plate. Corrosion resistance can be improved by using these metals.

[0031] In the fuel cell separator (23A), a cathode gas inlet (62in), a cooling water inlet (63in), and an anode gas outlet (61out) are provided in the order of right, center, and left of Fig. 4 at one end (lower part of Fig. 4) in the vertical direction of the metal plate (30). Additionally, a cathode gas outlet (62out), a cooling water outlet (63out), and an anode gas inlet (61in) are provided in the order of left, center, and right of Fig. 4 at the other end (upper part of Fig. 4).

[0032] Each inlet (61in, 62in, 63in), each outlet (61out, 62out, 63out), and each formation area of ​​the gas supply diffusion layer (42A) for the fuel cell are surrounded by a dense frame (32) that is electronically conductive or non-electronically conductive. The dense frame (32) prevents leakage of anode gas, cathode gas, and coolant. On the outer surface of the dense frame (32), a groove is formed along the dense frame (32) to surround each inlet (61in, 62in, 63in), each outlet (61out, 62out, 63out), and the formation area of ​​the gas supply diffusion layer (42A) for the fuel cell (not shown). A gasket (a sealing material such as a packing or O-ring) (33) is disposed within this groove.

[0033] On both sides of the metal plate (30), an electromagnetically conductive corrosion-resistant layer (not shown in FIG. 5) is formed on the entire surface, except for the portions where each of the inlets (61in, 62in, 63in) and each of the outlets (61out, 62out, 63out) described above are provided. A corrosion-resistant layer may also be formed on the inner circumference of each of the inlets (61in, 62in, 63in) and each of the outlets (61out, 62out, 63out). A corrosion-resistant layer may also be formed on the side and end surfaces of the metal plate (30). The corrosion-resistant layer is preferably a dense layer having the same composition as the dense frame (32) and has the function of inhibiting corrosion of the metal plate (30). In the step of forming a fuel cell stack (20) as shown in FIG. 1 or FIG. 2 by combining separators, the gasket (33) is in close contact with other separators, membrane electrode assembly (81), or current collector plates (27A, 27B) to be joined, thereby suppressing fluid leakage.

[0034] The fuel cell separator (23A) is a type C separator, and as shown in FIGS. 4 to 7, a fuel cell gas supply diffusion layer (42A) for supplying and diffusing cathode gas is formed in the central part of one side of a rectangular metal plate (30) that serves as a substrate. That is, the fuel cell gas supply diffusion layer (42A) is a fuel cell gas supply diffusion layer for cathode gas. The fuel cell gas supply diffusion layer (42A) has a sheet-shaped porous body layer (40) that allows gas permeability and diffusion and is also conductive, and a plurality of gas flow path grooves formed on one side of the porous body layer (40), each extending from the inlet side of the gas (cathode gas in the fuel cell separator (23A)) toward the outlet side. A plurality of gas flow grooves are arranged relative to the metal plate (30) (gas shielding plate) so as to be located on the side of the metal plate (30) (gas shielding plate), and the gas flow path is formed by the gas flow grooves and the metal plate (30) (gas shielding plate). In addition, the fuel cell separator (23A) and the membrane electrode assembly (81) are stacked in a positional relationship such that the membrane electrode assembly (81) is located on the side of the fuel cell gas supply diffusion layer (42A) where a plurality of gas flow grooves are not formed (see FIG. 5). Furthermore, the "gas flow grooves" and "gas flow paths" are not exclusively for gas, and can also be used to circulate substances other than gas (especially liquids such as water).

[0035] In this specification, "from the gas inlet side toward the gas outlet side" means "approximately along the direction of gas flow," and the direction "from the gas inlet side toward the gas outlet side" is the direction of gas flow within the porous body layer (40) when viewed as a whole of the porous body layer (40). In this case, as with the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, when the cathode gas inlet (62in) and the cathode gas outlet (62out) are positioned on the diagonal of the metal plate (30), the gas flow path does not need to be formed along the diagonal mentioned above. In the case where the direction "from the gas inlet side to the gas outlet side" as in Embodiment 1 is "when the direction of gas flow within the porous body layer (40) as viewed from the entire porous body layer (40) is in the vertical direction from below to above the ground of FIG. 4," a plurality of grooves for the gas flow path may be formed along the vertical direction from below to above the ground of FIG. 4 as in FIG. 4, and may also be formed along other directions.

[0036] A plurality of gas flow path grooves include a plurality of gas inlet grooves (53a, 53b) formed on the gas inlet side (lower side of FIG. 4 and 6) and a plurality of gas outlet grooves (54a, 54b) formed on the gas outlet side (upper side of FIG. 4 and 6). The plurality of gas inlet grooves (53a, 53b) include two or more types (in this case, two types) of gas inlet grooves (53a, 53b) having different lengths.

[0037] In the gas supply diffusion layer (42A) for a fuel cell, two adjacent gas inlet grooves (53a, 53b) have different lengths (see FIG. 6). In other words, the end of the outlet side of two adjacent gas inlet grooves (53a, 53b) is located at a position spaced apart along the "y-direction" along the "x-direction" which is perpendicular to the "y-direction" from the gas inlet side to the outlet side. Furthermore, in the gas supply diffusion layer (42A) for a fuel cell, at least one of three adjacent gas inlet grooves has a different length from the other gas inlet grooves, and at least one of four adjacent gas inlet grooves has a different length from the other gas inlet grooves.

[0038] In addition, in this specification, the phrases “at least one of the three adjacent gas inlet grooves has a different length from the other gas inlet grooves” and “at least one of the four adjacent gas inlet grooves has a different length from the other gas inlet grooves” mean “when the three adjacent gas inlet grooves are defined as a set of gas inlet groove groups, looking at any of the multiple sets of gas inlet groove groups included in the gas diffusion layer, at least one of the three gas inlet grooves has a different length from the other gas inlet grooves” and “when the four adjacent gas inlet grooves are defined as a set of gas inlet groove groups, looking at any of the multiple sets of gas inlet groove groups included in the gas diffusion layer, at least one of the four gas inlet grooves has a different length from the other gas inlet grooves.” The same applies to the gas outlet grooves described later.

[0039] In the gas supply diffusion layer (42A) for a fuel cell, the plurality of gas outlet side grooves (54a, 54b) include two or more types (in this case, two types) of gas outlet side grooves (54a, 54b) having different lengths. Two adjacent gas outlet side grooves (54a, 54b) have different lengths (see FIG. 6). In other words, the starting end of the inlet side of two adjacent gas outlet side grooves (54A, 54B) along the "x-direction" exists at a position spaced apart along the "y-direction". Furthermore, in the gas supply diffusion layer (42A) for a fuel cell, at least one of three adjacent gas outlet side grooves has a different length from the other gas outlet side grooves, and at least one of four adjacent gas outlet side grooves has a different length from the other gas outlet side grooves.

[0040] In the gas supply diffusion layer (42A) for a fuel cell, the gas inlet groove (53a) having the shortest length among the plurality of gas inlet grooves (53a, 53b) has a length of less than 30% of the length along the gas inlet side to the outlet side of the porous body layer (40), and the gas inlet groove (53b) having the longest length among the plurality of gas inlet grooves (53a, 53b) has a length of 40% or more of the length along the gas inlet side to the outlet side of the porous body layer (40).

[0041] In the gas supply diffusion layer (42A) for a fuel cell, the gas inlet groove (53a) having the shortest length among the plurality of gas inlet grooves (53a, 53b) has a length of less than 30% of the length along the gas inlet side to the outlet side of the porous body layer (40). In addition, the gas outlet groove (54b) having the longest length among the plurality of gas outlet grooves (54a, 54b) has a length of 30% or more of the length along the gas inlet side to the outlet side of the porous body layer (40).

[0042] Additionally, the plurality of gas flow grooves include, in addition to the plurality of gas inlet grooves (53a, 53b) and the plurality of gas outlet grooves (54a, 54b), a plurality of relay grooves (55a to 55d) formed between the gas inlet grooves (53a, 53b) and the gas outlet grooves (54a, 54b). The plurality of relay grooves (55a to 55d) are connected along a direction (x-direction) perpendicular to the direction from the gas inlet side to the gas outlet side. Specifically, the relay grooves (55a, 55b) are connected by a connecting groove (56a), and the relay grooves (55c, 55d) are connected by a connecting groove (56b) (see FIG. 7). Since the relay grooves (55a, 55b) and the relay grooves (55c, 55d) are independent, it may be said that in the gas supply diffusion layer (42A) for the fuel cell, a plurality of relay grooves (55a to 55d) are formed in two stages. In addition, in the gas flow path grooves that are identical to the communication portion between the relay grooves and the communication grooves, appropriate chamfering or rounding treatment may be performed on the portions where angles or corners are formed.

[0043] A plurality of gas inlet grooves (53a, 53b), a plurality of gas outlet grooves (54a, 54b), and a plurality of relay grooves (55a to 55d) are formed to interpenetrate each other (see FIG. 4 and FIG. 5). Additionally, when the gas supply diffusion layer (42A) for the fuel cell is viewed in a planar view, the ratio of the area of ​​the gas flow path groove formation area to the total area of ​​the porous body layer (40) is within the range of 30% to 80%. It is preferable that the ratio of the said area be within the range of 40% to 70%.

[0044] Air (oxygen gas and nitrogen gas) as the cathode gas diffuses within the porous body layer (40) (gas diffusion layer (43)). The porous body layer (40) comprises a mixture of a conductive material (preferably a carbon-based conductive material) and a polymer resin. By mixing the carbon-based conductive material with the polymer resin, high conductivity can be imparted to the polymer resin, and the moldability of the carbon material can also be improved through the binding properties of the polymer resin. The fluid resistance of the porous body layer (40) depends on the porosity of the porous body layer and the surface area through which the fluid flows. As the porosity increases, the fluid resistance decreases. As the surface area through which the fluid flows increases, the fluid resistance decreases. As a rough standard, in the gas supply diffusion layer (42A) for a fuel cell (for cathode gas), the porosity of the porous body layer (40) is approximately 50 to 85%. In addition, in the gas supply diffusion layer (41) for a fuel cell (for anode gas), the porosity of the porous body layer (40) is about 30 to 85%.

[0045] In this case, since the porosity of the porous body layer (40) is configured as described above, the flow of cathode gas, water vapor, and condensed water between the gas flow groove and the porous body layer (40) is properly carried out through the inner surface of the plurality of gas flow grooves, so that a large amount of gas can be uniformly supplied to the membrane electrode assembly, and also, cathode gas that is not used during power generation or water vapor and condensed water generated during power generation can be efficiently discharged out of the gas flow groove. As a result, there is no need to form a gas permeable filter, such as one having a plurality of fine gas flow holes in a gas impermeable layer containing metal, ceramics, resin, etc., on the inner surface of the gas flow groove.

[0046] By adjusting the content of the carbon-based conductive material, the porosity of the gas supply diffusion layer (42A) for the fuel cell can be adjusted, and furthermore, the movement resistance of the gas supply diffusion layer (42A) for the fuel cell can be adjusted. In particular, if the content of the carbon-based conductive material is increased, the movement resistance decreases (the porosity increases). Conversely, if the content of the carbon-based conductive material is decreased, the movement resistance increases (the porosity decreases). The corrosion-resistant layer and the dense frame (32) are also a mixture of the carbon-based conductive material and the polymer resin, and it is preferable that they are densified while ensuring conductivity through an appropriate content of the carbon-based conductive material.

[0047] Carbon-based conductive materials are not particularly limited, but examples include graphite, carbon black, diamond-coated carbon black, silicon carbide, titanium carbide, carbon fiber, carbon nanotubes, etc. As polymer resins, both thermosetting resins and thermoplastic resins can be used. Examples of polymer resins include phenolic resin, epoxy resin, melamine resin, rubber-based resin, furan resin, vinylidene fluoride resin, etc.

[0048] An inlet passage (57) is formed between the cathode gas inlet (62in) and the region where the porous body layer (40) is formed (see FIG. 4). An outlet passage (58) is formed between the cathode gas outlet (62out) and the region where the porous body layer (40) is formed. These inlet passages (57) and outlet passages (58) are intended to support the membrane electrode assembly (81) or its frame (81A). Therefore, the structure must be capable of allowing the cathode gas to flow smoothly and also supporting the membrane electrode assembly (81). For example, it may be a porous layer with a very high porosity, or a structure in which a number of supports are arranged. In the region facing the inlet passage (57) in the porous body layer (40), a thin, long gas inlet side step (51) is formed along the width direction of the metal plate (30). Additionally, a thin, long gas outflow side step (52) is formed along the width direction of the metal plate (30) in the area facing the outflow passage (58) in the porous body layer (40). However, the gas inflow side step (51) and the gas outflow side step (52) may be omitted.

[0049] The porous body layer (40), the inlet passage (57), and the outlet passage (58) are formed with the same height (thickness) as the dense frame (32). On the side facing the metal plate (30) in the gas supply diffusion layer (42A) for the fuel cell, a plurality of gas flow path grooves containing voids are provided, and a plurality of gas flow paths are formed in the gap between these plurality of gas flow path grooves and the metal plate (30). A plurality of gas inlet side grooves (53a, 53b) communicate with the inlet passage (57) through the gas inlet side step (51), and a plurality of gas outlet side grooves (54a, 54b) communicate with the outlet passage (58) through the gas outlet side step (52). The number and structure of the gas flow path grooves are not limited to those shown.

[0050] When the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 is used in a fuel cell for a transport device, the width of the porous body layer (40) varies depending on the type and size of the transport device, for example, about 30 mm to 300 mm. The width of the groove for the gas flow path is for example, about 0.3 mm to 2 mm. The thickness of the porous body layer (40) is for example, about 150 to 400 μm, the depth of the groove for the gas flow path is for example, about 100 to 300 μm, and the distance (ceiling thickness) between the bottom of the groove for the gas flow path and the other side of the porous body layer (40) is for example, about 100 to 300 μm. When the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 is used for a fuel cell or an electrolysis device for a purpose other than a transport device (e.g., stationary), it is not limited to the size described above, and a suitable size can be used depending on the required performance, etc.

[0051] The gas supply diffusion layer (41) for a fuel cell in the separator (22) for a Type A fuel cell also basically has the same configuration as the gas supply diffusion layer (42A) for a fuel cell. However, since the gas supplied to the gas supply diffusion layer is hydrogen gas, the porosity is lower and the thickness is thinner than that of the gas supply diffusion layer (42A) for a fuel cell (see Figure 8 (b) described later).

[0052] In the separator (21) for a fuel cell of type CA, a gas supply diffusion layer (41) for a fuel cell and a gas supply diffusion layer (42A) for a fuel cell are used as gas diffusion layers (see FIG. 8(a) described later). In the separator (24) for a fuel cell of type CW, a cooling water supply diffusion layer is formed on the surface where the gas supply diffusion layer (42A) for a fuel cell of type C is not formed (see FIG. 8(c) described later). In the separator (25) for a fuel cell of type AW, a cooling water supply diffusion layer is formed on the surface where the gas supply diffusion layer (41) for a fuel cell of type A is not formed (see FIG. 8(d) described later).

[0053] When the fuel cell stack (20) according to Embodiment 1 is operated, protons (H+) are generated at the fuel electrode where the anode gas (hydrogen gas) is introduced. The protons diffuse through the membrane electrode assembly (81) and move toward the oxygen electrode side, where they react with oxygen to produce water. The generated water is discharged from the oxygen electrode side. At this time, in a fuel cell separator (23A) having a fuel cell gas supply diffusion layer (42A) having the structure as described above, air introduced from the cathode gas inlet (62in) is introduced into the gas inlet side grooves (53a, 53b) through the inlet passage (57) and the gas inlet side step (51). A portion of the air introduced into the gas inlet side step (51) enters the groove for the gas flow path and enters the porous body layer (40) (gas diffusion layer (43)) from the groove for the gas flow path, and another portion enters the porous body layer (40) (gas diffusion layer (43)) directly from the end surface of the porous body layer (40) (gas diffusion layer (43)) and diffuses within the porous body layer (40) (gas diffusion layer (43)).

[0054] Air diffuses in the planar direction within the porous body layer (40) (gas diffusion layer (43)) and in the thickness direction, and is supplied to a membrane electrode assembly (81) provided in contact with the porous body layer (40) (gas diffusion layer (43)) to contribute to the power generation reaction. Gases not used for power generation (unused oxygen gas and nitrogen gas) and water generated during power generation (water vapor or condensate) are discharged into the discharge passage (58) through the porous body layer (40) (gas diffusion layer (43)), the groove for the gas flow path, and the gas discharge side step (52). The oxygen gas, nitrogen gas, and water discharged into the discharge passage (58) are finally discharged from the discharge passage (58) through the cathode gas outlet (62out) and the cathode gas discharge port (72out). At this time, due to the structure of the gas supply diffusion layer (42A) for the fuel cell, not all water is discharged, and some remains in the porous body layer (40) (gas diffusion layer (43)).

[0055] The gas supply diffusion layer (42A) for a fuel cell according to embodiment 1 has the above-mentioned characteristics, so that water (steam or condensate) generated in the membrane electrode assembly (81) during power generation can be efficiently discharged out of the gas flow path through the porous body layer (40) and the gas flow path groove.

[0056] [Effect of Embodiment 1]

[0057] According to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, a plurality of gas flow grooves (gas inlet side grooves (53a, 53b), gas outlet side grooves (54a, 54b) and relay grooves (55a to 55d)) are formed on one side of the porous body layer (40), so the resistance to gas movement is reduced compared to the conventional method, and a larger amount of gas can be supplied to the membrane electrode assembly compared to the conventional method.

[0058] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to embodiment 1, since a plurality of gas flow path grooves are formed on one side of the porous body layer (40), the supply of gas to the membrane electrode assembly (81) disposed on the other side of the porous body layer (40) is necessarily carried out through the porous body layer (40), so the gas can be supplied uniformly to the membrane electrode assembly (81) more than in the case where a plurality of gas flow paths are open from one side of the porous body layer (40) to the other side.

[0059] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, since a plurality of gas flow path grooves are formed on one side of the porous body layer (40), gas not used for power generation (in this case, cathode gas for the fuel cell (oxygen gas, nitrogen gas)) can be efficiently discharged out of the gas flow path grooves through the porous body layer (40) and the gas flow path grooves. Also, since gas not used for power generation can be efficiently discharged out of the gas flow path grooves in a form that is extruded as a double-flow gas flow in a double-flow region formed between a plurality of gas inlet side grooves (53a, 53b) and a plurality of gas outlet side grooves (54a, 54b), it is possible to maintain a lower resistance to gas movement than in the conventional method, and furthermore, to maintain a higher concentration of reaction gas, thereby making it possible to increase the reaction efficiency (in the case of Embodiment 1, the power generation efficiency of the fuel cell) than in the conventional method.

[0060] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, since a plurality of gas flow path grooves are formed on one side of the porous body layer (40), moisture (water vapor or condensate) generated in the membrane electrode assembly (81) during power generation can be efficiently discharged out of the gas flow path grooves through the porous body layer (40) and the gas flow path grooves. Also, in the double flow region, moisture (water vapor or condensate) can be efficiently discharged out of the gas flow path grooves in a form that is extruded as a double flow gas flow, so it becomes a gas diffusion layer with better drainage than conventional ones.

[0061] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to embodiment 1, a plurality of gas flow path grooves include a plurality of gas inlet side grooves (53a, 53b) and a plurality of gas outlet side grooves (54a, 54b), and among these, the plurality of gas inlet side grooves (53a, 53b) include two or more types of gas inlet side grooves (53a, 53b) having different lengths. In this case, due to the action of the gas inlet side groove (53a) (outlet side end portion) having a relatively short length among the plurality of gas inlet side grooves, the porous body layer (40) in the inlet side region, which is originally easy to dry, becomes difficult to dry, thereby suppressing the decrease in reaction efficiency caused by the porous body layer (40) becoming too dry. In addition, due to the action of the gas inlet groove (53b) having a relatively longer length among the plurality of gas inlet grooves (53a, 53b), moisture (water vapor or condensate) that is prone to naturally accumulating is efficiently discharged through the gas inlet groove (53b), thereby increasing drainage performance. Furthermore, even in the area separated from the inlet area where the gas pressure is prone to naturally decreasing, the gas pressure becomes difficult to decrease, thereby suppressing the decrease in reaction efficiency caused by the decrease in gas pressure. By these factors, the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 can increase the reaction efficiency (in the case of Embodiment 1, the power generation efficiency of the fuel cell) compared to conventional methods, and furthermore, becomes a gas diffusion layer with superior drainage performance compared to conventional methods.

[0062] In addition, the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 has two adjacent gas inlet grooves (53a, 53b) having different lengths, that is, the position of the outlet end portion (dead end portion) in the two adjacent gas inlet grooves (53a, 53b) along the x-direction is located at a position spaced apart along the y-direction, thereby further dispersing the outlet end portion. As a result, the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 can further increase reaction efficiency and, furthermore, becomes a gas diffusion layer with even better drainage properties.

[0063] In addition, in the present invention, at least one of the four or three adjacent gas inlet grooves may have a different length from the other gas inlet grooves. Even in this case, the gas supply diffusion layer for the fuel cell has the same effect as when two adjacent gas inlet grooves have different lengths.

[0064] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, the gas inlet groove (53a), which has the shortest length among the plurality of gas inlet grooves (53a, 53b), has a length of less than 30% of the length along the gas inlet side to the outlet side of the porous body layer (40), thereby further suppressing the decrease in reaction efficiency caused by the porous body layer (40) becoming too dry. In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, the gas inlet groove (53b), which has the longest length among the plurality of gas inlet grooves (53a, 53b), has a length of 40% or more of the length along the gas inlet side to the outlet side of the porous body layer (40), thereby further increasing drainage and further suppressing the decrease in reaction efficiency caused by the decrease in gas pressure.

[0065] In addition, the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 includes two or more types of gas outflow side grooves (54a, 54b) having different lengths. Accordingly, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, in the case of the multiple gas outflow side grooves (54a, 54b), the discharge efficiency of moisture (water vapor / condensed water) that is originally prone to retention is increased by the action of the relatively long gas outflow side groove (54b) among the multiple gas outflow side grooves (54a, 54b), gas diffusion is promoted, and reaction efficiency (in the case of Embodiment 1, power generation efficiency) is increased. Meanwhile, by the action of the relatively short gas outlet side groove (54a) among the multiple gas outlet side grooves (54a, 54b), a predetermined reaction (power generation in the case of Embodiment 1) is carried out by the reverse flow of gas from the upstream gas diffusion groove even in the gas outlet side area, thereby increasing the overall reaction efficiency (power generation efficiency in the case of Embodiment 1).

[0066] In addition, the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 is arranged such that the two adjacent gas outlet-side grooves (54a, 54b) have different lengths, and the long grooves and short grooves are dispersed. As a result, the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1 can further increase reaction efficiency and, furthermore, becomes a gas diffusion layer with even better drainage properties.

[0067] In addition, in the present invention, at least one of the four or three adjacent gas outlet-side grooves may have a different length from the other gas outlet-side grooves. Even in this case, the gas supply diffusion layer for the fuel cell has the same effect as when two adjacent gas outlet-side grooves have different lengths.

[0068] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, the gas inlet groove (53a), which has the shortest length among the plurality of gas inlet grooves (53a, 53b), has a length of less than 30% of the length along the gas inlet side to the outlet side of the porous body layer (40), so it is possible to make it particularly difficult to dry the porous body layer (40) on the inlet side, which is prone to drying, and thus it is possible to further increase the reaction efficiency. In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, the gas outlet side groove (54b), which has the longest length among the plurality of gas outlet side grooves (54a, 54b), has a length of 30% or more of the length along the gas outlet side from the gas inlet side of the porous body layer (40), so that moisture (water vapor / condensed water) that tends to stay is efficiently discharged through the gas outlet side groove (54b), thereby promoting gas diffusion, and in this respect, the reaction efficiency can be further increased.

[0069] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, since the plurality of gas flow path grooves include a plurality of relay grooves (55a to 55d), it is possible to increase the number of outlet-side end portions (dead end portions), thereby increasing the amount of gas passing through the double-flow region and further increasing the reaction efficiency. In addition, it is possible to optimize the balance between preventing drying of the porous body layer (40) and improving the discharge efficiency of moisture (water vapor / condensed water).

[0070] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, since the plurality of relay grooves (55a to 55d) are connected along a direction (x-direction) perpendicular to the direction from the gas inlet side to the gas outlet side, it is possible to equalize the gas pressure along the connected direction.

[0071] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, since the plurality of gas inlet grooves (53a, 53b), the plurality of gas outlet grooves (54a, 54b), and the plurality of relay grooves (55a to 55d) are formed to penetrate each other, it is possible to equalize the gas pressure or increase the flow rate.

[0072] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to embodiment 1, when the gas supply diffusion layer (42A) for a fuel cell is viewed in a planar view, the ratio of the area of ​​the groove forming area for the gas flow path to the total area of ​​the porous body layer (40) is within the range of 30% to 80%, so it is possible to achieve both sufficient gas supply capacity and sufficient mechanical strength.

[0073] In addition, according to the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, since the gas supply diffusion layer (42A) for a fuel cell is a gas supply diffusion layer for a cathode gas, the performance of the fuel cell cell stack can be improved.

[0074] The fuel cell separator (23A) according to embodiment 1 is a separator having a metal plate (30) which is a gas shielding plate and a fuel cell gas supply diffusion layer (42A) disposed on at least one side of the metal plate (30). The fuel cell gas supply diffusion layer (42A) is the fuel cell gas supply diffusion layer (42A) according to embodiment 1, and a plurality of gas flow path grooves (gas inlet side grooves (53a, 53b), gas outlet side grooves (54a, 54b), and relay grooves (55a to 55d)) are disposed on the metal plate (30) so as to be located on the side of the metal plate (30). In that the gas flow path is composed of the gas flow path grooves and the metal plate (30), it is a separator that can increase reaction efficiency more than conventional separators.

[0075] The fuel cell stack (20) according to embodiment 1 is a fuel cell stack formed by stacking a separator and a membrane electrode assembly (81), the separator is a fuel cell separator (23A) according to embodiment 1, and the fuel cell separator (23A) and the membrane electrode assembly (81) are stacked in a positional relationship such that the membrane electrode assembly (81) is located on the side where a plurality of gas flow path grooves (gas inlet side grooves (53a, 53b), gas outlet side grooves (54a, 54b) and relay grooves (55a to 55d)) of the fuel cell gas supply diffusion layer (42A) are not formed, thereby making it a fuel cell stack that can increase reaction efficiency more than conventional ones.

[0076] In addition, according to the fuel cell stack (20) of embodiment 1, the fuel cell stack (20) is a fuel cell stack that can increase the power generation efficiency of the fuel cell compared to conventional fuel cells.

[0077] [Method for manufacturing a separator (23A) for a fuel cell]

[0078] For example, the corrosion-resistant layer, the dense frame (32), the gas supply diffusion layer (42A) for the fuel cell, etc., can be formed by isotropic pressure using a paste-like material in which a thermosetting resin (or thermoplastic resin), carbon-based conductive material powder (and carbon fiber depending on the situation), resin powder, and a volatile solvent are mixed. The specific shape of each member and part can be formed, for example, by printing, stamping, pressing, etc. Additionally, each member may be arranged or formed by hot pressing or a roll press (hot press).

[0079] In addition, the above-described manufacturing method can also be applied when manufacturing separators other than the fuel cell separator (23A) (fuel cell separators (21, 22, 24, 25)).

[0080] [Separator other than the fuel cell separator (23A)]

[0081] FIG. 8 is a cross-sectional view of separators other than the fuel cell separator (23A) (fuel cell separators (21, 22, 24, 25)). FIG. 8 (a) is a cross-sectional view of a fuel cell separator (21) of type CA, FIG. 8 (b) is a cross-sectional view of a fuel cell separator (22) of type A, FIG. 8 (c) is a cross-sectional view of a fuel cell separator (24) of type CW, and FIG. 8 (d) is a cross-sectional view of a fuel cell separator (25) of type AW. FIG. 8 is a cross-sectional view of the A1-A1 section (see FIG. 5 (a)) of the fuel cell separator (23A). In FIG. 8, since it would be difficult to understand the drawing if symbols were assigned to all multiple gas flow grooves, the symbol “53” is assigned to only one gas flow groove to indicate that it is a gas flow groove (whichever is a gas inlet groove, a gas outlet groove, or a relay groove).

[0082] The gas diffusion layer of the present invention can be applied to the gas supply diffusion layer (42A) for the fuel cell (for cathode gas) and / or the gas supply diffusion layer (41) for the fuel cell (for anode gas) of the fuel cell separator (21) (see FIG. 8(a)). Additionally, the gas diffusion layer of the present invention can be applied to the gas supply diffusion layer (41) for the fuel cell (for anode gas) of the fuel cell separator (22) (see FIG. 8(b)). Additionally, the gas diffusion layer of the present invention can be applied to the gas supply diffusion layer (42A) for the fuel cell (for cathode gas) of the fuel cell separator (24) (see FIG. 8(c)). Additionally, the gas diffusion layer of the present invention can be applied to the gas supply diffusion layer (41) for the fuel cell (for anode gas) of the fuel cell separator (25) (see FIG. 8(d)).

[0083] Even when the gas diffusion layer of the present invention is applied to the gas supply diffusion layer of the fuel cell separator (21, 22, 24, 25) as described above, it becomes a gas diffusion layer that can increase reaction efficiency (or power generation efficiency in the case of a fuel cell) compared to conventional methods.

[0084] [Embodiment 2]

[0085] FIG. 9 is a plan view of a separator (23B) for a fuel cell according to Embodiment 2. However, as with FIG. 4, the drawing of the metal plate (30) is omitted to make it easier to understand the flow path pattern of the gas supply diffusion layer (42B) for the fuel cell. The same applies to FIG. 10 to 23 and FIG. 29 to 31. FIG. 10 is a drawing to explain the gas inlet side grooves (53c to 53f) and gas outlet side grooves (54c to 54f) in the gas supply diffusion layer (42B) for the fuel cell according to Embodiment 2. FIG. 11 is a drawing to explain the relay groove (55e) and communication groove (56c) in the gas supply diffusion layer (42B) for the fuel cell according to Embodiment 2.

[0086] The gas supply diffusion layer (42B) for a fuel cell in the separator (23B) for a fuel cell according to Embodiment 2 basically has the same configuration as the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, but the configuration of the grooves for the gas flow paths is different from that of the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1. In the gas supply diffusion layer (42B) for a fuel cell according to Embodiment 2, as shown in FIGS. 9 to 11, two or more types (in this case, four types) of gas inlet grooves (53c to 53f) and gas outlet grooves (54c to 54f) with different lengths are formed. Additionally, a relay groove (55e) is formed to enter the gas inlet grooves (53c to 53f) and the gas outlet grooves (54c to 54f). Multiple relay grooves (55e) are formed, and each relay groove (55e) is connected by a connecting groove (56c).

[0087] The gas supply diffusion layer (42B) and fuel cell separator (23B) for the fuel cell according to Embodiment 2 are gas diffusion layers and separators capable of increasing reaction efficiency compared to conventional ones, just like the gas supply diffusion layer (42A) and fuel cell separator (23A) for the fuel cell according to Embodiment 1. In addition, according to the gas supply diffusion layer (42B) and fuel cell separator (23B) for the fuel cell according to Embodiment 2, common effects are also obtained due to features common to the gas supply diffusion layer (42A) and fuel cell separator (23A) for the fuel cell according to Embodiment 1.

[0088] [Embodiment 3]

[0089] FIG. 12 is a plan view of a separator (23C) for a fuel cell according to Embodiment 3. FIG. 13 is a drawing illustrating the gas inlet side grooves (53g to 53j) and gas outlet side grooves (54g to 54j) in the gas supply diffusion layer (42C) for a fuel cell according to Embodiment 3. FIG. 14 is a drawing illustrating the relay grooves (55d to 55j) and communication grooves (56d, 56e) in the gas supply diffusion layer (42C) for a fuel cell according to Embodiment 3.

[0090] The gas supply diffusion layer (42C) for a fuel cell in the separator (23C) according to Embodiment 3 basically has the same configuration as the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, but the configuration of the grooves for the gas flow paths is different from that of the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1. In the gas supply diffusion layer (42C) for a fuel cell according to Embodiment 3, as shown in FIGS. 12 to 14, two or more types (in this case, four types) of gas inlet grooves (53g to 53j) and gas outlet grooves (54g to 54j) with different lengths are formed. Additionally, relay grooves (55f to 55j) are formed to enter the gas inlet grooves (53g to 53j) and gas outlet grooves (54g to 54j). Among these, the gas inlet grooves (53i, 53j) and the relay grooves (55i, j) have branching points from one groove to two grooves. Additionally, the relay groove (55f) and the relay groove (55g) are connected by a connecting groove (56d), and the relay grooves (55f, 55g) and the relay groove (55h) are connected by a connecting groove (56d). That is, the gas supply diffusion layer (42C) for a fuel cell includes a plurality of relay grooves, wherein a pair of relay grooves formed so that two adjacent relay grooves are connected is formed along a direction perpendicular to the direction from the gas inlet side to the gas outlet side.

[0091] The gas supply diffusion layer (42C) and the fuel cell separator (23C) according to Embodiment 3 are gas diffusion layers and separators capable of increasing reaction efficiency compared to conventional ones, just like the gas supply diffusion layer (42A) and the fuel cell separator (23A) according to Embodiment 1. Furthermore, according to the gas supply diffusion layer (42C) for the fuel cell according to Embodiment 3, since it includes a plurality of relay grooves (55f to 55h) formed such that two adjacent relay grooves are connected, and the pair of relay grooves is formed along a direction perpendicular to the direction from the gas inlet side to the gas outlet side, it is possible to lower the pressure loss, and the gas and water vapor or condensed water flowing downstream can be easily introduced to the downstream side, making it possible to diffuse the gas more uniformly, and at the same time, it is possible to discharge water vapor or condensed water more efficiently out of the gas supply diffusion layer (42C) for the fuel cell. In addition, according to the gas supply diffusion layer (42C) for a fuel cell according to Embodiment 3, since some of the grooves for multiple gas flow paths have "branching points from one groove to two grooves," it is possible to equalize the gas pressure in a limited area. In addition, it is possible to increase the number of outlet-side end sections (dead end sections) and increase the amount of gas passing through the double-flow region, thereby further increasing the reaction efficiency. Furthermore, according to the gas supply diffusion layer (42C) for a fuel cell and the separator (23C) for a fuel cell according to Embodiment 3, a common effect is also obtained due to features common to the gas supply diffusion layer (42A) for a fuel cell and the separator (23A) for a fuel cell according to Embodiment 1.

[0092] [Embodiment 4]

[0093] FIG. 15 is a plan view of a separator (23D) for a fuel cell according to embodiment 4. FIG. 16 is a drawing illustrating the gas inlet side grooves (53k to 53n) and gas outlet side grooves (54k, 54l) in the gas supply diffusion layer (42D) for a fuel cell according to embodiment 4. FIG. 17 is a drawing illustrating the relay grooves (55k to 55p) in the gas supply diffusion layer (42D) for a fuel cell according to embodiment 4.

[0094] The gas supply diffusion layer (42D) for a fuel cell in the separator (23D) according to Embodiment 4 basically has the same configuration as the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1, but the configuration of the grooves for the gas flow paths is different from that of the gas supply diffusion layer (42A) for a fuel cell according to Embodiment 1. In the gas supply diffusion layer (42D) for a fuel cell according to Embodiment 4, as shown in FIGS. 15 to 17, two or more types (in this case, four types) of gas inlet grooves (53k to 53n) and gas outlet grooves (54k, 54l) with different lengths are formed. Additionally, relay grooves (55k to 55p) are formed to enter the gas inlet grooves (53k to 53n) and gas outlet grooves (54k, 54l). Among these, the relay grooves (55k to 55n) have a joining point from two grooves to one groove. Additionally, as a variation of Embodiment 4, a form is also considered in which the gas inlet side grooves (53k to 53n) and the gas outlet side grooves (54k, 54l) are swapped, and the relay grooves (55k to 55n) are arranged and shaped to correspond to the swap.

[0095] The gas supply diffusion layer (42D) and fuel cell separator (23D) according to Embodiment 4 are gas diffusion layers and separators capable of increasing reaction efficiency compared to conventional ones, just like the gas supply diffusion layer (42A) and fuel cell separator (23A) according to Embodiment 1. Furthermore, according to the gas supply diffusion layer (42D) for the fuel cell according to Embodiment 4, since some of the grooves for multiple gas flow paths have a "junction point where two grooves merge into one groove," it is possible to equalize gas pressure in a limited area. In addition, according to the gas supply diffusion layer (42D) and fuel cell separator (23D) for the fuel cell according to Embodiment 4, common effects are also obtained due to features common to the gas supply diffusion layer (42A) and fuel cell separator (23A) for the fuel cell according to Embodiment 1.

[0096] [Embodiments 5 to 8]

[0097] FIG. 18 is a plan view of a fuel cell separator (23E) according to embodiment 5. FIG. 19 is a plan view of a fuel cell separator (23F) according to embodiment 6. FIG. 20 is a plan view of a fuel cell separator (23G) according to embodiment 7. FIG. 21 is a plan view of a fuel cell separator (23H) according to embodiment 8.

[0098] The fuel cell separator (23E to 23H) and the fuel cell gas supply diffusion layer (42E to 42H) according to embodiments 5 to 8 basically have the same configuration as the fuel cell separator (23A to 23D) and the fuel cell gas supply diffusion layer (42A to 42D) according to embodiments 1 to 4, but the aspect ratio of the fuel cell gas supply diffusion layer is different from that of the fuel cell separator (23A to 23D) and the fuel cell gas supply diffusion layer (42A to 42D) according to embodiments 1 to 4. In addition, in the fuel cell gas supply diffusion layer (42E to 42H) according to embodiments 5 to 8, the width of each groove constituting the groove for the gas flow path is also different from that of the fuel cell separator (23A to 23D) according to embodiments 1 to 4. However, regarding the pattern of the groove for the gas flow path, the gas supply diffusion layer (42E) for the fuel cell according to Embodiment 5 is the same as the gas supply diffusion layer (42A) for the fuel cell according to Embodiment 1, the gas supply diffusion layer (42F) for the fuel cell according to Embodiment 6 is the same as the gas supply diffusion layer (42B) for the fuel cell according to Embodiment 2, the gas supply diffusion layer (42G) for the fuel cell according to Embodiment 7 is the same as the gas supply diffusion layer (42C) for the fuel cell according to Embodiment 3, and the gas supply diffusion layer (42H) for the fuel cell according to Embodiment 8 is the same as the gas supply diffusion layer (42D) for the fuel cell according to Embodiment 4, respectively (see FIGS. 18 to 21).

[0099] The gas supply diffusion layer (42E to 42H) for a fuel cell and the fuel cell separator (23E to 23H) according to embodiments 5 to 8 are gas supply diffusion layer (42A) for a fuel cell and the fuel cell separator (23A) for a fuel cell according to embodiment 1, and are gas supply diffusion layer and fuel cell separator that can increase reaction efficiency compared to conventional ones. In addition, according to the fuel cell separator (23E to 23H) and the fuel cell gas supply diffusion layer (42E to 42H) according to embodiments 5 to 8, the same effect as the corresponding fuel cell gas supply diffusion layer (42A to 42D) and fuel cell separator (23A to 23D) is obtained.

[0100] [Test Example]

[0101] Next, the gas diffusion layer and separator according to the present invention were actually manufactured to form a single cell, which is the minimum unit of a fuel cell, and the results of testing how the difference in the pattern of the groove for the gas flow path affects the characteristics will be explained. The test examples were performed by measuring the "relationship between current density and voltage" (Test Example 1), measuring the "relationship between current density and cathode gas pressure" (Test Example 2), and measuring the "current density distribution" (Test Example 3) for the Example 1, Example 2, and Comparative Example described below. Since these tests compare the test results for Example 1, Example 2, and Comparative Example, they may also be referred to as "comparative tests."

[0102] First, the single cells manufactured in the test examples will be described. As single cells, three types were manufactured and tested: the single cell according to Example 1 (hereinafter simply referred to as "Example 1"), the single cell according to Example 2 (hereinafter simply referred to as "Example 2"), and the single cell according to the comparative example (hereinafter simply referred to as "Comparative Example"). As single cells, a membrane electrode assembly was inserted into a fuel cell separator for cathode gas (Type C separator) and a fuel cell separator for anode gas (Type A separator) (not shown). In the gas supply diffusion layer for the fuel cell for cathode gas of Example 1, the shape of the groove for the gas flow path was made as shown in Example 5 (see FIG. 18). In the gas supply diffusion layer for the fuel cell for cathode gas of Example 2, the shape of the groove for the gas flow path was made as shown in Example 8 (see FIG. 21). In the gas supply diffusion layer for a fuel cell for a cathode gas of a comparative example, the shape of the groove for the gas flow path is shown in FIG. 22.

[0103] FIG. 22 is a plan view of a fuel cell separator (23I) in a comparative example. FIG. 22 (a) is a drawing showing all the grooves for the gas flow path, and FIG. 22 (b) is a drawing showing only the gas inlet side groove (53o) and the gas outlet side groove (54m) among the grooves for the gas flow path (a drawing not showing the relay grooves (55q to 55t) and the connecting grooves (56f, 56g). In the gas supply diffusion layer for the fuel cell for the cathode gas of the comparative example, the shape of the grooves for the gas flow path is formed in the gas supply diffusion layer (42I) for the fuel cell separator (23I) (see FIG. 22). In the gas supply diffusion layer (42I) for the fuel cell, grooves of the same length are used for the gas inlet side groove (53o) and the gas outlet side groove (54m), respectively. In the case of the first half of the year, the second half of the year, the third half of the year, the third half of the year, the fourth half of the year, the fourth half of the year, the fourth half of the year, the fifth

[0104] FIG. 23 is a plan view of a fuel cell separator (22A) for anode gas used in test examples (Example 1, Example 2 and Comparative Example). In Example 1, Example 2 and Comparative Example, the fuel cell gas supply diffusion layer for anode gas used was the fuel cell gas supply diffusion layer (41A) described in the fuel cell separator (22A) shown in FIG. 23. The shape of the groove for the gas flow path in the fuel cell gas supply diffusion layer (41A) is basically the same as the shape of the groove for the gas flow path in the fuel cell gas supply diffusion layer (42I) in Comparative Example, and a gas inlet side groove (53o), a gas outlet side groove (54m), and a relay groove (55q to 55s) are formed. However, since the anode gas and cathode gas flow directions are reversed in a single cell, the upstream and downstream of the gas flow path grooves are reversed in the gas supply diffusion layer (41A) for the fuel cell. Also, in the test example, the only thing affecting the test result is the difference in the pattern of the gas flow path grooves (since components other than the gas flow path grooves are common in Example 1, Example 2 and Comparative Example), so the explanation regarding the gas flow path groove pattern and other aspects is omitted.

[0105] In each test example (Test Examples 1 to 3), "dry condition, no back pressure (Power Generation Condition 1)," "dry condition, with back pressure (Power Generation Condition 2)," and "wet condition, no back pressure (Power Generation Condition 3)" were adopted as power generation conditions, considering the operating conditions of the fuel cell. The temperature of the single cell during the test was set to 80°C. Air was used as the cathode gas, and hydrogen gas was used as the anode gas. The cathode gas utilization rate was set to 40%, and the anode gas utilization rate was set to 70%. A platinum catalyst (TEC10E50E manufactured by Tanaka Kikinzoku High School) was used as the catalyst, and the loading amount was set to approximately 0.3 mg / cm² for both anodes. As the polymer membrane, a 25 μm thick one containing Merck’s NAFION (registered trademark) NR211 was used. The effective area was set to 29.16 cm² (3 cm × 9.72 cm). Under "dry conditions," the humidity of the cathode gas and anode gas was set to 30% RH, and under "wet conditions," the humidity of the cathode gas and anode gas was set to 80% RH. Under "no back pressure," the back pressure was set to 0 kPaG, i.e., atmospheric pressure. Under "back pressure," the back pressure was set to 150 kPaG, i.e., atmospheric pressure plus 150 kPa.

[0106] In Test Examples 1 to 3, a fuel cell single-cell evaluation device manufactured by Panasonic Production Engineering Co., Ltd. was used. Furthermore, the measurement of the "relationship between current density and voltage" in Test Example 1 and the measurement of the "relationship between current density and cathode gas pressure" in Test Example 2 were performed by measuring the voltage and the pressure at the inlet side of the cathode gas while gradually increasing the current density by changing the current value of the electronic load device. In addition, during the measurement, the gas utilization rate was kept constant by adjusting the supply amount of reaction gas (anode gas and cathode gas) according to the current value.

[0107] In Test Example 3, the Current scan lin, a current density distribution sensor manufactured by S++, was used in combination. Furthermore, the measurement of the "current density distribution" in Test Example 3 was performed by dividing the area where power generation occurs in the single cell into 20 rows and 6 columns and measuring the current density for each division. The measurement was performed under conditions where the average current density remained constant. FIG. 24 is a diagram illustrating the division of areas when measuring the current density distribution in Test Example 3. Separator S shown in FIG. 24 represents a configuration common to Type C separators used in the single cell (with the grooves for the gas flow path omitted). The number shown in the third column from the right on the gas supply diffusion layer (42) in FIG. 24 is an area number assigned to the divided area from the gas inlet side to the gas outlet side. The number of the area number corresponds to the number on the horizontal axis (area number) of the graph in FIG. 27, which will be described later.

[0108] Next, the results of the test will be described. FIG. 25 is a graph showing the results of Test Example 1 (relationship between the pattern of the grooves for the gas flow path and power generation characteristics), and directly, a graph showing the relationship between current density and voltage (so-called IV performance) in Example 1, Example 2 and Comparative Example. FIG. 26 is a graph showing the results of Test Example 2 (relationship between the pattern of the grooves for the gas flow path and pressure loss in the gas supply diffusion layer for the fuel cell), and directly, a graph showing the relationship between current density and cathode gas pressure in Example 1, Example 2 and Comparative Example. FIG. 27 is a graph showing the results of Test Example 3 (relationship between the pattern of the grooves for the gas flow path and the current density distribution in the gas supply diffusion layer for the fuel cell), and directly, a graph showing the current density distribution in Example 1, Example 2 and Comparative Example. FIGS. 25(a), FIGS. 26(a), and FIGS. 27(a) are graphs for power generation condition 1, FIGS. 25(b), FIGS. 26(b), and FIGS. 27(b) are graphs for power generation condition 2, and FIGS. 25(c), FIGS. 26(c), and FIGS. 27(c) are graphs for power generation condition (3). In addition, in FIGS. 27(a), FIGS. 27(b), and FIGS. 27(c), the value of “output voltage obtained when a current of average current density is flowed” is indicated after the letters Example 1, Example 2, and Comparative Example. In addition, in each graph, the result of Example 1 is indicated by a dashed line, the result of Example 2 by a dotted line, and the result of Comparative Example by a solid line.

[0109] In addition, in generation condition 1, since the voltage obtained decreased rapidly when the current density was increased and no meaningful results were obtained, the measurement of the relationship between current density and voltage was stopped at 0.6 to 0.8 A / cm² as shown in FIGS. 25 and 26. In addition, as a result, in FIG. 27, the measurement of the current density distribution was performed only in the case of generation condition 1, under the condition where the set average current density was 0.6 A / cm².

[0110] 1. Results of Test Example 1

[0111] As a result of Test Example 1, it was found that for any power generation condition and at any current density comparison, the voltage obtained in Examples 1 and 2 was higher than that of the Comparative Example, indicating that the power generation efficiency was higher (see FIG. 25).

[0112] 2. Results of Test Example 2

[0113] As a result of Test Example 2, it was found that the pressure loss in the gas supply diffusion layer for the fuel cell of the cathode gas, which occurs when the same current density is obtained under any power generation conditions, was lower in Test Examples 1 and 2 than in the Comparative Example (see FIG. 26).

[0114] These results indicate that in the case of Example 1 and Example 2, the power generation efficiency can be higher than in the case of the comparative example.

[0115] 3. Results of Test Example 3

[0116] First, the average current density (Jm) is the value obtained by dividing the sum of the individual current densities (Ji) obtained in each section (i) including regions 1 to 20 of FIG. 24 by the total area of ​​the section. Within these sections, the smaller the activation overpotential (Ea) determined by the effective utilization rate of the catalyst, the gas diffusion overpotential (Ed) determined by the gas supply / exhaust capacity within the gas supply diffusion layer for the fuel cell, and the resistance overpotential (Er) determined by the conductivity of electrons and ions within the electrode, the larger the current density value obtained. The relationship between the voltage (Ei) obtained involving a particular section and the theoretically possible cell voltage (Et) is obtained by the formula “Ei = Et - Ea - Ed - Er”.

[0117] Since the catalyst layer and the gas supply diffusion layer for the fuel cell are electronically conductive, the voltage (Ei) obtained through the involvement of individual compartments has the same value as the potential (E, which substantially matches the voltage (V) shown in FIG. 25) measured across the entire electrode. Therefore, if the supply / discharge capability of the reaction gas can be improved by applying the pattern of the grooves for the gas flow path in the gas supply diffusion layer for the fuel cell of the present invention, the activation overpotential (Ea) and the gas diffusion overpotential (Ed) are reduced, and if the discharge of reaction products at local areas and the even distribution within the electrode can be achieved, the resistance overpotential (Er) is reduced, and as a result, the voltage (Ei) obtained through the involvement of individual compartments and the potential (E) measured across the entire electrode will increase.

[0118] First, regarding the "dry condition, no back pressure" of power generation condition 1 (see FIG. 27 (a)), the cell output at 0.6 A / cm² was 0.522 × 0.6 W / cm² in Example 1 and 0.551 × 0.6 W / cm² in Example 2, which is clearly higher compared to 0.452 × 0.6 W / cm² in the comparative example. Nevertheless, it was found that in the gas inlet side (regions numbered 1 to 7), only a current density of a similarly low degree was obtained in either case. This is thought to be due to the porous body layer (particularly the porous body layer in the gas inlet side region) becoming too dry because the gas was used under dry conditions. However, in Examples 1 and 2, the reaction product water effectively humidifies the intermediate region (regions numbered 7 to 16), resulting in a higher current density compared to the comparative example and the high cell output described above. It is determined that the reason for this is that the activation overpotential (Ea) and gas diffusion overpotential (Ed) were reduced because the ability to supply / discharge reaction gas was improved by the pattern of the groove for the gas flow path in the present invention, and as a result of the discharge of reaction product water and even distribution within the electrode, the resistance overpotential (Er) was reduced, leading to an increase in the voltage (Ei) obtained by the involvement of individual sections and the potential (E) measured throughout the electrode.

[0119] Next, in the “dry condition, back pressure present” of power generation condition 2 (see FIG. 27 (b)), the cell output at 2.0 A / cm² was 0.519 × 2 W / cm² in Example 1 and 0.554 × 2 W / cm² in Example 2, which was higher than the 0.436 × 2 W / cm² of the comparative example. In power generation condition 2, it was possible to achieve a higher cell output than any result in power generation condition 1. This is because, as the amount of power generated itself increases due to the effect of applying back pressure, the amount of moisture produced by power generation increases, which suppresses the drying of the porous body layer and thus increases the cell output. In addition, the current density distribution of Examples 1 and 2 under power generation condition 2 is clearly shifted to the gas inlet side (region numbers 1 to 10) compared to the current density distribution of the comparative example under power generation condition 2 and the current density distribution of Examples 1, 2 and the comparative example under power generation condition 1. In the case of Examples 1 and 2, it is believed that the moisture generated during power generation in the gas inlet side region is increased due to the action of the gas inlet side groove having a relatively short length, and the drying of the porous body layer in this region is further suppressed, and a higher cell output is obtained throughout the electrode due to the reduction of the activation overpotential (Ea) and gas diffusion overpotential (Ed).

[0120] Next, regarding the "wet condition, no back pressure" of the power generation condition (3) (see (c) of FIG. 27), it was found that in any of the cases of Example 1, Example 2 and Comparative Example, the cell output could be increased more than in the case of Power Generation Condition 1. It was found that this result was due to the effect of adopting the wet condition, which suppressed the drying of the porous body layer on the gas inlet side (region numbers 1 to 10), and increased the current density in these regions, thereby increasing the cell output. Compared to the Comparative Example, in Example 1 and Example 2, the effect of gas supply and humidification to the entire surface of the electrode was expanded by the pattern of the grooves for the gas flow path, so the potential (Ei) of each section was improved, and thus the electrode potential (E) was also improved, resulting in an improvement in cell output.

[0121] [Variations 1 to 4]

[0122] The pattern of the plurality of grooves for gas flow paths in the present invention is not limited to that described in each of the above embodiments. FIG. 28 is a plan view of a fuel cell separator (23J) according to Variant Example 1. FIG. 29 is a plan view of a fuel cell separator (23K) according to Variant Example 2. FIG. 30 is a plan view of a fuel cell separator (23L) according to Variant Example 3. FIG. 31 is a plan view of a fuel cell separator (23M) according to Variant Example 4.

[0123] In the gas supply diffusion layer (42J) for a fuel cell separator (23J) according to Variant Example 1, two or more types of gas inlet grooves (53p, 53q) having different lengths (in this case, two types) are formed, and two of the longer gas inlet grooves (53q) are connected to a connecting groove (56f) formed along the entire x-direction of the gas supply diffusion layer (42J) for a fuel cell (see FIG. 28). The connecting groove (56f) is connected to additional grooves (53r, 53s) formed along the direction of gas flow. In addition, in the gas supply diffusion layer (42J) for a fuel cell according to Variant Example 1, the gas outlet grooves (54m) are all of the same length, but the present invention is not limited to this and may have gas outlet grooves with a different length from the gas outlet grooves (54m).

[0124] In the gas supply diffusion layer (42K) for a fuel cell separator (23K) according to Variant Example 2, two or more types of gas inlet grooves (53t, 53u) having different lengths (in this case, two types) are formed, and the two longer gas inlet grooves (53u) among them are configured to divide the gas supply diffusion layer (42K) for a fuel cell into three regions (see FIG. 29). The relay grooves, such as the relay groove (55u), are connected to the communication grooves (56g to 56i), such as the communication grooves, which are each formed in the regions separated by the gas inlet grooves (53u). Additionally, in the gas supply diffusion layer (42K) for a fuel cell according to Variant Example 2, the gas outlet grooves (54n) are all of the same length, but there may be gas outlet grooves with a different length from the gas outlet grooves (54n).

[0125] In the gas supply diffusion layer (42L) of the fuel cell separator (23L) according to Variation Example 3, not only are grooves of different lengths formed, but grooves that branch or merge in multiple stages, such as the gas inlet side groove (53v), the gas outlet side groove (54o), and the relay groove (55v), are also formed (see FIG. 30). In FIG. 30, as an example of branching or merging in multiple stages, the location where the gas inlet side groove (53v) branches is highlighted by surrounding it with a dashed line labeled V.

[0126] In the gas supply diffusion layer (42M) for a fuel cell of the fuel cell separator (23M) according to Variant Example 4, the basic pattern of the plurality of gas flow path grooves is basically the same as the gas supply diffusion layer (42A) for a fuel cell of the fuel cell separator (23A) according to Embodiment 1. However, in Variant Example 4, the gas inlet grooves (53w, 53x), gas outlet grooves (54q, 54r), and relay grooves (55x to 55z) are each formed in a zigzag shape. Furthermore, in the present invention, the gas flow path grooves may be formed in a wave shape or an arc shape. Also, in the present invention, the gas flow path grooves may have a shape in which the width varies. That is, in the present invention, the gas flow path grooves may be formed in a shape other than a straight line shape. As such, the pattern of the plurality of grooves for gas flow paths in the present invention can be formed in any shape according to individual circumstances, provided that it is not a shape that impairs the effects of the present invention.

[0127] [Variation Example 5]

[0128] In each of the above embodiments, a membrane electrode assembly (81) having a catalyst layer (85) with an area approximately equal to that of a gas supply diffusion layer for a fuel cell was used as the membrane electrode assembly, but the present invention is not limited thereto. As the membrane electrode assembly, a membrane electrode assembly having a catalyst layer (85) with an area smaller than that of a gas supply diffusion layer for a fuel cell may also be used.

[0129] [Variation Example 6]

[0130] In each of the above embodiments, as a gas flow path groove, a gas flow path groove having a rectangular cross-section and a width of the gas flow path groove on the surface of the porous body layer (40) (or gas flow path groove) and a width of the gas flow path groove at the bottom of the gas flow path groove are equal (see FIG. 5 and FIG. 8), but the present invention is not limited thereto. It may be a gas flow path groove with a triangular cross-section where the bottom of the groove is narrower than the surface, a gas flow path groove with a semicircular cross-section where the bottom of the groove is narrower than the surface, or a gas flow path groove of other shapes.

[0131] [Variation Example 7]

[0132] In each of the above embodiments, a gas supply diffusion layer for a fuel cell having a porous body layer (40) having a groove for a gas flow path formed on one side was used as the gas diffusion layer (see FIG. 4), but the present invention is not limited thereto. For example, a gas supply diffusion layer for a fuel cell having a porous body layer (40) having a groove for a gas flow path formed on one side and a microporous layer disposed on the other side of the porous body layer (40) may also be used. In such a configuration, a separator can be constructed using a membrane electrode assembly that does not have a microporous layer.

[0133] [Variation Example 8]

[0134] In each of the above embodiments, a metal plate (30) was used as a gas shielding plate, but the present invention is not limited thereto. A plate containing a material having gas shielding properties other than the metal plate (30) may also be used (for example, a conductive composite material plate containing conductive fine particles and resin, or a ceramic plate or resin plate combined with a current collection sheet).

[0135] In addition, the features described in each variant are applicable to the gas diffusion layer, separator, and electrochemical reaction device of the present invention. For example, the features described in each variant are applicable to a separator (21) for a fuel cell of type CA, a separator (24) for a fuel cell of type CW, a separator (22) for a fuel cell of type A, a separator (25) for a fuel cell of type AW, a separator for a fuel cell having a gas supply diffusion layer for these fuel cells, and a fuel cell cell stack.

[0136] [Variation Example 9]

[0137] The gas diffusion layer, separator, and electrochemical reaction device of the present invention may also be used for electrolysis.

[0138] Although the gas diffusion layer, separator, and electrochemical reaction apparatus of the present invention have been described above based on illustrated embodiments, the present invention is not limited to each of the above-mentioned embodiments, and various modifications can be made within the scope of not departing from the gist of the present invention. Explanation of the symbols

[0139] 20: Fuel cell cell stack 21, 22, 22A, 23A to 23L, 24, 25: Separators for fuel cells 27A, 27B: Collector's plate 28A, 28B: Insulation sheets 30: Metal plate 32: Intricate Frame 33: Gasket 40: Porous body layer 41, 41A, 42, 42A to 42L: Gas supply diffusion layer for fuel cell 43: Gas diffusion layer 51: Step on the gas inlet side 52: Step on the gas outlet side 53: Home for gas flow 53a to 53q, 53t to 53x: Gas inlet side grooves 53r, 53s: Additional Home 54a to 54q: Gas outlet side groove 55a to 55z: Relay grooves 56a to 56i: Chimney groove 57: Inflow channel 58: Outflow Channel 61in: Anode gas inlet 61out: Anode gas outlet 62in: Cathode gas inlet 62out: Cathode gas outlet 63in: Coolant inlet 63out: Coolant outlet 71in: Anode gas supply port 71out: Anode gas outlet 72in: Cathode gas supply port 72out: Cathode gas outlet 73in: Coolant supply port 73out: Coolant drain 75, 76: End plates 81: Membrane electrode assembly 81A: Frame 82: Electrolyte membrane 83: Microporous layer 85: Catalyst layer

Claims

Claim 1 A gas diffusion layer comprising a sheet-shaped porous body layer capable of gas permeability and diffusion and also having conductivity, and a plurality of gas flow path grooves formed on one side of the porous body layer from the gas inlet side to the gas outlet side, wherein the plurality of gas flow path grooves include a plurality of gas inlet side grooves formed on the gas inlet side and a plurality of gas outlet side grooves formed on the gas outlet side, wherein the plurality of gas inlet side grooves include two or more types of gas inlet side grooves having different lengths, and wherein the plurality of gas flow path grooves include, in addition to the plurality of gas inlet side grooves and the plurality of gas outlet side grooves, a plurality of relay grooves that increase the number of outlet side end portions formed between the gas inlet side grooves and the gas outlet side grooves. Claim 2 A gas diffusion layer according to claim 1, characterized in that at least one of the four adjacent gas inlet grooves has a different length from the other gas inlet grooves. Claim 3 A gas diffusion layer according to paragraph 2, characterized in that the two adjacent gas inlet grooves have different lengths. Claim 4 A gas diffusion layer according to claim 1, wherein the gas inlet groove having the shortest length among the plurality of gas inlet grooves has a length of less than 30% of the length along the gas inlet side to the gas outlet side of the porous body layer, and the gas inlet groove having the longest length among the plurality of gas inlet grooves has a length of 40% or more of the length along the gas inlet side to the gas outlet side of the porous body layer. Claim 5 A gas diffusion layer according to claim 1, wherein the plurality of gas outlet-side grooves comprises two or more types of gas outlet-side grooves having different lengths. Claim 6 A gas diffusion layer according to claim 5, characterized in that at least one of the four adjacent gas outlet-side grooves has a different length from the other gas outlet-side grooves. Claim 7 A gas diffusion layer according to claim 6, characterized in that the two adjacent gas outlet-side grooves have different lengths. Claim 8 A gas diffusion layer according to claim 1, wherein the gas inlet groove having the shortest length among the plurality of gas inlet grooves has a length of less than 30% of the length along the gas inlet side to the gas outlet side of the porous body layer, and the gas outlet groove having the longest length among the plurality of gas outlet grooves has a length of 30% or more of the length along the gas inlet side to the gas outlet side of the porous body layer. Claim 9 A gas diffusion layer according to claim 1, wherein the plurality of relay grooves are connected along a direction perpendicular to the direction from the inlet side to the outlet side of the gas. Claim 10 A gas diffusion layer according to claim 1, characterized in that the plurality of relay grooves comprises a plurality of relay grooves formed such that two adjacent relay grooves are connected, and the pair of relay grooves is formed along a direction perpendicular to the direction from the inlet side to the outlet side of the gas. Claim 11 A gas diffusion layer according to claim 1, characterized in that the plurality of gas inlet grooves, the plurality of gas outlet grooves, and the plurality of relay grooves are formed to penetrate each other. Claim 12 A gas diffusion layer according to claim 1, characterized in that all or part of the plurality of grooves for gas flow paths have a “branching point from one groove to two grooves” or a “joining point from two grooves to one groove.” Claim 13 A gas diffusion layer according to claim 1, characterized in that, when the gas diffusion layer is viewed in a planar view, the ratio of the area of ​​the groove-forming region for the gas flow path to the total area of ​​the porous body layer is within the range of 30% to 80%. Claim 14 A gas diffusion layer characterized as being a gas supply diffusion layer for a fuel cell in claim 1. Claim 15 A gas diffusion layer characterized by being a gas supply diffusion layer for a fuel cell for cathode gas in claim 14. Claim 16 A gas diffusion layer comprising a sheet-shaped porous body layer capable of gas permeability and diffusion and also having conductivity, and a plurality of gas flow path grooves formed on one side of the porous body layer from the gas inlet side to the gas outlet side, wherein the plurality of gas flow path grooves include a plurality of gas inlet side grooves formed on the gas inlet side and a plurality of gas outlet side grooves formed on the gas outlet side, wherein the plurality of gas inlet side grooves include two or more types of gas inlet side grooves having different lengths, and wherein all or part of the plurality of gas flow path grooves have a “branching point from one groove to two grooves” or a “merging point from two grooves to one groove.” Claim 17 A gas diffusion layer comprising a sheet-shaped porous body layer capable of gas permeability and diffusion and also having conductivity, and a plurality of gas flow path grooves formed on one side of the porous body layer from the gas inlet side to the gas outlet side, wherein the plurality of gas flow path grooves include a plurality of gas inlet side grooves formed on the gas inlet side and a plurality of gas outlet side grooves formed on the gas outlet side, wherein the plurality of gas inlet side grooves include two or more types of gas inlet side grooves having different lengths, and wherein, when the gas diffusion layer is viewed in a planar view, the ratio of the area of ​​the gas flow path groove formation region to the total area of ​​the porous body layer is within the range of 30% to 80%. Claim 18 A separator comprising a gas shielding plate and a gas diffusion layer disposed on at least one side of the gas shielding plate, wherein the gas diffusion layer is a gas diffusion layer described in any one of claims 1 to 17, and wherein a plurality of grooves for gas flow paths are disposed relative to the gas shielding plate such that they are located on the side of the gas shielding plate, and wherein a gas flow path is formed by the grooves for gas flow paths and the gas shielding plate. Claim 19 An electrochemical reaction device comprising a separator and a membrane electrode assembly stacked thereon, wherein the separator is the separator described in claim 18, and the separator and the membrane electrode assembly are stacked in a positional relationship such that the membrane electrode assembly is located on the side of the gas diffusion layer where the plurality of gas flow path grooves are not formed. Claim 20 An electrochemical reaction device characterized as being a fuel cell cell stack in claim 19.

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