Patent Publication Number: US-2023142786-A1

Title: Separator for fuel cell and fuel cell including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims under 35 U.S.C. § 119(a) the benefit of Korean Patent Application No. 10-2020-0036275, filed on Mar. 25, 2020, which is hereby incorporated by reference herein. 
     BACKGROUND 
     (a) Technical Field 
     Exemplary embodiments relate to a separator for a fuel cell and a fuel cell including the separator. 
     (b) Description of the Related Art 
     Fuel cells, which generate electricity from a reaction between a fuel (for example, hydrogen) and air, generally include: a membrane electrode assembly (MEA) including a membrane, a fuel electrode, and an air electrode; a gas diffusion layer in which the fuel and air diffuse; and a separator. Among the constituents described above, the separator is configured to face each of the fuel electrode and the air electrode and has roles in discharging, to the outside, water produced by a reaction inside a fuel cell while supplying fuel and air from the outside and in providing a path through which current generated by the reaction inside the fuel cell is able to flow 
     Here, in the separator, each of an air channel serving as a path through which the air flows and a fuel channel serving as a path through which the fuel flows is provided, and a manifold for supplying the outside fuel and air to the fuel channel and the air channel, respectively, is provided. 
     However, according to the related art, amounts of air supply between a region of the air channel relatively close to the manifold and a region of the air channel relatively far from the manifold are not uniform. In this case, the air is more smoothly supplied to the region of the air channel relatively close to the manifold that supplies the air, and thus, an electrochemical reaction of the MEA more actively occurs in that region than in other regions. Accordingly, degradation of the fuel cell occurs earlier in the region adjacent to the manifold that supplies the air. Particularly, this degradation occurs more severely in the region to which the air is most directly supplied from the manifold. For example, according to the related art, the degradation of the fuel cell heavily occurs in a region closest to the manifold in an inlet region of the air channel. 
     SUMMARY 
     Exemplary embodiments of the present disclosure is to supply a constant amount of air to a fuel cell irrespective of positions within an air channel to prevent degradation of the fuel cell. 
     A first aspect of the present disclosure provides a separator for a fuel cell, including: a separator body; and a porous structure which is stacked on one surface of the separator body and has a plurality of pores defined therein to provide a path through which a fluid flows, wherein the separator body includes: a fluid inlet part having a space into which the fluid is introduced; a reaction region configured to receive the fluid; and a diffusion part which is provided between the fluid inlet part and the reaction region and has a passage to provide a path through which the fluid within the fluid inlet part is supplied to the reaction region, wherein the porous structure is stacked on one surface of the reaction region, and the number of pores per unit volume of the porous structure in an inlet region (A 1 , hereinafter, referred to as a ‘closest inlet region (A 1 )’ or a first inlet region), which is closest to the fluid inlet part in an inlet region of the porous structure facing the diffusion part, is less than the number of pores per unit volume of the porous structure in a second inlet region except for the first/closest inlet region (A 1 ) in the inlet region of the porous structure facing the diffusion part. 
     The number of pores per unit volume of the porous structure in the inlet region of the porous structure may be less than the number of pores per unit volume of the porous structure in the other regions except for the inlet region in the porous structure. 
     The fluid may be air. 
     The reaction region may include a first reaction region and a second reaction region, and the porous structure may include: a first porous structure stacked on one surface of the first reaction region; and a second porous structure stacked on one surface of the second reaction region, wherein the first reaction region and the second reaction region are disposed so that a distance between the first reaction region and the fluid inlet part is less than a distance between the second reaction region and the fluid inlet part, and the number of pores per unit volume in the inlet region of the first porous structure is less than the number of pores per unit volume in the inlet region of the second porous structure. 
     The reaction region may further include a third reaction region, and the porous structure may further include a third porous structure stacked on one surface of the third reaction region, wherein the third reaction region is disposed so that a distance between the second reaction region and the fluid inlet part is less than a distance between the third reaction region and the fluid inlet part, and the number of pores per unit volume of the third porous structure is constant over all regions of the third porous structure. 
     In other regions except for the inlet regions of the first to third porous structures, the numbers of pores per unit volume of the first to third porous structures may be the same as each other. 
     A second aspect of the present disclosure provides a separator for a fuel cell, including: a separator body; and a porous structure which is stacked on one surface of the separator body and has a plurality of pores defined therein to provide a path through which a fluid flows, wherein the separator body includes: a fluid inlet part having a space into which the fluid is introduced; a reaction region configured to receive the fluid; and a diffusion part which is provided between the fluid inlet part and the reaction region and has a passage to provide a path through which the fluid within the fluid inlet part is supplied to the reaction region, wherein the porous structure is stacked on one surface of the reaction region, and an inlet region (F 1 , hereinafter, referred to as a ‘same height inlet region (F 1 )’ or a first inlet region), which is provided at the same height as the fluid inlet part in a height direction (h) in an inlet region of the porous structure facing the diffusion part, is provided closer to a central region of the porous structure than a second inlet region except for the first/same height inlet region (F 1 ) in the inlet region of the porous structure facing the diffusion part. 
     The inlet region of the porous structure may be closer to the central region of the porous structure as the inlet region is closer to the fluid inlet part in the height direction (h) of the fluid inlet part. 
     A boundary of outlet region of the porous structure provided on an opposite side of the inlet region of the porous structure may extend in a direction perpendicular to a direction in which the porous structure extends from the inlet region to the outlet region. 
     The reaction region may include a first reaction region and a second reaction region, and the porous structure may include: a first porous structure stacked on one surface of the first reaction region; and a second porous structure stacked on one surface of the second reaction region, wherein the first reaction region and the second reaction region are disposed so that a difference in height between the first reaction region and the fluid inlet part is less than a difference in height between the second reaction region and the fluid inlet part, and a distance between the inlet region of the first porous structure and the fluid inlet part is the same as a distance between the inlet region of the second porous structure and the fluid inlet part. 
     A third aspect of the present disclosure provides a separator for a fuel cell, including: a separator body; and a porous structure which is stacked on one surface of the separator body and has a plurality of pores defined therein to provide a path through which a fluid flows, wherein the separator body includes: a fluid inlet part having a space into which the fluid is introduced; a reaction region configured to receive the fluid; and a diffusion part which is provided between the fluid inlet part and the reaction region and has a passage to provide a path through which the fluid within the fluid inlet part is supplied to the reaction region, wherein the porous structure is stacked on one surface of the reaction region, and a passage formation region (D 1 ) facing a passage of the diffusion part is provided in an inlet region (A 1 , hereinafter, referred to as a ‘closest inlet region (A 1 )’ or first inlet region), which is closest to the fluid inlet part in an inlet region of the porous structure facing the diffusion part, and a pore formation region (D 2 ) having a porous pore structure is provided in a second inlet region except for the first/passage formation inlet region (D 1 ) in the porous structure. 
     The passage formation region (D 1 ) of the porous structure may have a shape protruding toward a central region of the porous structure as the passage formation region (D 1 ) is closer to the fluid inlet part in a height direction (h) of the fluid inlet part. 
     The reaction region may include a first reaction region and a second reaction region, and the porous structure may include: a first porous structure stacked on one surface of the first reaction region; and a second porous structure stacked on one surface of the second reaction region, wherein the first reaction region and the second reaction region are disposed so that a distance between the first reaction region and the fluid inlet part is less than a distance between the second reaction region and the fluid inlet part, and the passage formation region (D 1 ) provided in the inlet region of the first porous structure has a shape further protruding from the passage formation region (D 1 ) provided in the inlet region of the second porous structure toward a central region of the porous structure. 
     A fourth aspect of the present disclosure provides a fuel cell including: a membrane electrode assembly (MEA) including a membrane, a fuel electrode, and an air electrode; a gas diffusion layer stacked on one surface of the MEA; and a separator stacked on one surface of the gas diffusion layer, wherein the separator includes: a separator body; and a porous structure which is stacked on one surface of the separator body and has a plurality of pores defined therein to provide a path through which a fluid flows, wherein the separator body includes: a fluid inlet part having a space into which the fluid is introduced; a reaction region configured to receive the fluid; and a diffusion part which is provided between the fluid inlet part and the reaction region and has a passage to provide a path through which the fluid within the fluid inlet part is supplied to the reaction region, wherein the porous structure is stacked on one surface of the reaction region, and the number of pores per unit volume of the porous structure in an inlet region (A 1 , hereinafter, referred to as a ‘closest inlet region (A 1 )’ or first inlet region), which is closest to the fluid inlet part in an inlet region of the porous structure facing the diffusion part, is less than the number of pores per unit volume of the porous structure in a second inlet region except for the first/closest inlet region (A 1 ) in the inlet region of the porous structure facing the diffusion part. 
     A fifth aspect of the present disclosure provides a fuel cell including: a membrane electrode assembly (MEA) including a membrane, a fuel electrode, and an air electrode; a gas diffusion layer stacked on one surface of the MEA; and a separator stacked on one surface of the gas diffusion layer, wherein the separator includes: a separator body; and a porous structure which is stacked on one surface of the separator body and has a plurality of pores defined therein to provide a path through which a fluid flows, wherein the separator body includes: a fluid inlet part having a space into which the fluid is introduced; a reaction region configured to receive the fluid; and a diffusion part which is provided between the fluid inlet part and the reaction region and has a passage to provide a path through which the fluid within the fluid inlet part is supplied to the reaction region, wherein the porous structure is stacked on one surface of the reaction region, and an inlet region (F 1 , hereinafter, referred to as a ‘same height inlet region (F 1 )’ or first inlet region), which is provided at the same height as the fluid inlet part in an inlet region of the porous structure facing the diffusion part, is provided closer to a central region of the porous structure than a second inlet region except for the first/same height inlet region (F 1 ) in the inlet region of the porous structure facing the diffusion part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention. 
         FIG.  1    is a plan view illustrating a structure of a separator for a fuel cell according to a first exemplary embodiment of the present disclosure. 
         FIG.  2    is an enlarged perspective view of a porous structure and a configuration around the porous structure in a fuel cell equipped with the separator for a fuel cell according to the first exemplary embodiment of the present disclosure. 
         FIG.  3    is a plan view illustrating a structure of a separator for a fuel cell according to a second exemplary embodiment of the present disclosure. 
         FIG.  4    is a plan view illustrating a structure of a separator for a fuel cell according to a third exemplary embodiment of the present disclosure. 
         FIG.  5    is a cross-sectional view illustrating a stack structure of a fuel cell according to one example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term in “and/or” includes any and all combinations of one or more of the associated listed items. Throughout the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, the terms “unit”, “-er”, “-or”, and “module” described in the specification mean units for processing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof. 
     Further, the control logic of the present disclosure may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller or the like. Examples of computer readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
     Hereinafter, a separator for a fuel cell and a fuel cell including the separator according to the present disclosure will be described with reference to the accompanying drawings. 
       FIG.  1    is a plan view illustrating a structure of a separator for a fuel cell according to a first exemplary embodiment of the present disclosure, and  FIG.  2    is an enlarged perspective view of a porous structure and a configuration around the porous structure in a fuel cell equipped with the separator for a fuel cell according to the first exemplary embodiment of the present disclosure. 
     As illustrated in  FIG.  1   , a separator for a fuel cell (hereinafter, referred to as a separator  10 ) according to the present disclosure may include a separator body  100 . 
     The separator body  100  may include: a fluid inlet part  110  having a space into which a fluid is introduced; a reaction region  130  to receive the fluid from the fluid inlet part  110 ; and a diffusion part  120  which is provided between the fluid inlet part  110  and the reaction region  130  and has a passage to provide a path through which the fluid within the fluid inlet part  110  is supplied to the reaction region  130 . 
     As illustrated in  FIG.  2   , according to the present disclosure, a reaction surface  20  including an electrode is provided in a fuel cell, and the reaction surface  20  may have a structure stacked on one surface of the reaction region  130  of the separator  10 . The fluid supplied to the fluid inlet part  110  is supplied to the reaction region  130  via the diffusion part  120 , and then, the fluid supplied to the reaction region  130  is supplied again to the reaction surface  20  including the electrode. An electrochemical reaction may occur on the reaction surface  20  by the fluid supplied to the reaction surface  20 , thereby generating current in the fuel cell. 
     Here, the fluid may be air. Thus, the fluid introduced to the fluid inlet part  110  may also be air. Also, in addition to the air, a fuel (for example, hydrogen) may also be introduced to the separator  10 . Thus, the fuel cell according to the present disclosure may be configured to generate the current by a reaction between the hydrogen and the oxygen inside the air. 
     Here, as illustrated in  FIG.  2   , in the separator  10  according to the present disclosure, a porous structure  200  may be stacked on one surface of the separator body  100 . In particular, the porous structure  200  may be stacked on one surface of the reaction region  130 . 
     The porous structure  200  has a plurality of pores defined therein to provide a path through which the fluid supplied to the reaction region  130  flows, and also has a role in changing a passage of the fluid supplied to the reaction region  130  and supplying the fluid to the reaction surface  20 . 
     That is, the fluid introduced to the reaction region  130  flows through the pores provided in the porous structure  200 , and collides with a structure providing a body of the porous structure  200 . A movement direction of the fluid, colliding with the structure providing the body of the porous structure  200 , may be changed into a direction toward the reaction surface  20 . The fluid, of which the movement direction has changed, is supplied to the reaction surface  20 , and thus, the electrochemical reaction may occur on the reaction surface  20 . 
     Also, referring to  FIG.  1   , the reaction region  130  provided in the separator  10  may have a plurality of regions. For example, the reaction region  130  may include a first reaction region  130   a,  a second reaction region  130   b,  and a third reaction region  130   c.  Here,  FIG.  1    illustrates a state in which the first to third reaction regions  130   a,    130   b,  and  130   c  are partitioned separately from each other. However, unlike this configuration, the plurality of reaction regions including the first to third reaction regions  130   a,    130   b,  and  130   c  may be connected and integrated with each other. 
     Also, as described above, the porous structure  200  may be stacked on the one surface of the reaction region  130 , and the reaction region  130  may include the first to third reaction regions  130   a,    130   b,  and  130   c.  Thus, the porous structure  200  may include a first porous structure stacked on one surface of the first reaction region  130   a,  a second porous structure stacked on one surface of the second reaction region  130   b,  and a third porous structure stacked on one surface of the third reaction region  130   c.  The first to third porous structures may be partitioned separately from each other, but unlike this configuration, the first to third porous structures may be connected and integrated with each other. 
     Also, the first to third reaction regions  130   a,    130   b,  and  130   c  may be arranged in one direction on the basis of a distance from the fluid inlet part  110 . That is, as illustrated in  FIG.  1   , the first reaction region  130   a  and the second reaction region  130   b  may be disposed so that a distance between the first reaction region  130   a  and the fluid inlet part  110  is less than a distance between the second reaction region  130   b  and the fluid inlet part  110 . Also, the second reaction region  130   b  and the third reaction region  130   c  may be disposed so that a distance between the second reaction region  130   b  and the fluid inlet part  110  is less than a distance between the third reaction region  130   c  and the fluid inlet part  110 . 
     According to one aspect of the present disclosure, the density of pores defined in the porous structure  200  provided in the separator  10  may change depending on positions. That is, according to the first exemplary embodiment, when a region of the porous structure  200 , which faces the diffusion part  120 , is referred to as an ‘inlet region E 1 ’, and an inlet region A 1  of the inlet region E 1 , which is closest to the fluid inlet part  110 , is referred to as a ‘closest inlet region’, the number of pores per unit volume of the porous structure  200  in the closest inlet region A 1  may be less than the number of pores per unit volume of the porous structure  200  in an inlet region except for the closest inlet region A 1  in the inlet region E 1  of the porous structure  200 . The small number of pores per unit volume may be understood as an average size of the pores is large. 
     According to the related art, the closest inlet region A 1  of the porous structure  200  is closest to the fluid inlet part  110 , and thus, a large amount of the fluid discharged from the fluid inlet part  110  may supplied to the closest inlet region A 1  of the porous structure  200  and a region of the reaction region facing the closest inlet region A 1 . In this case, however, in the closest inlet region A 1 , a large amount of the fluid is supplied to the reaction surface due to the collision with the porous structure  200 , and thus, the electrochemical reaction heavily occurs on the reaction surface facing the closest inlet region A 1 , which causes the degradation. 
     According to the first exemplary embodiment of the present disclosure, the number of pores per unit volume of the porous structure  200  in the closest inlet region A 1  of the porous structure  200  is relatively small, and thus, as illustrated in  FIG.  2   , a structure providing the body of the porous structure  200  has a relatively low density in the closest inlet region A 1 . Thus, the frequency of collisions between the porous structure  200  and the fluid which, of the fluid (that is, the air) supplied to the reaction region  130 , passes through the closest inlet region A 1  of the porous structure  200  is reduced, and thus, an amount of the fluid supplied to the reaction surface  20  is also reduced. Thus, a relatively little electrochemical reaction occurs in the reaction surface  20  facing the closest inlet region A 1 . That is, according to the present disclosure, the degradation may be prevented from occurring on the reaction surface  20  facing the closest inlet region A 1  of the porous structure  200 . Here, in a case where each of the reaction region  130  and the porous structure  200  is partitioned into a plurality of regions as illustrated in  FIG.  1   , the closest inlet region A 1  of the porous structure  200  may be provided in a region facing the first reaction region  130   a.  On the other hand, in a case where each of the reaction region  130  and the porous structure  200  is integrated into one region, the closest inlet region A 1  of the porous structure  200  may be defined as a region of the inlet region E 1  horizontally facing the fluid inlet part  110 , which is an upper region of the inlet region E 1  with reference to  FIG.  1   . 
     Here, according to the first exemplary embodiment of the present disclosure, the number of pores per unit volume in the inlet region E 1  of the porous structure  200  may be less than the number of pores per unit volume of the porous structure  200  in other regions except for the inlet region E 1  in the porous structure  200 . 
     As described above, the degradation of the fuel cell including the reaction surface  20  may occur most frequently around the closest inlet region A 1  of the porous structure  200 , but the degradation may also occur relatively easily in the inlet region E 1  of the porous structure  200  directly receiving the fluid from the fluid inlet part  110 , compared to in the other regions of the porous structure  200 . Thus, according to the first exemplary embodiment of the present disclosure, as the number of pores per unit volume in the inlet region E 1  of the porous structure  200  is made relatively small, the degradation may be prevented from occurring on the reaction surface  20  facing the inlet region E 1  of the porous structure  200 . 
     Also, according to the first exemplary embodiment of the present disclosure, the numbers of pores per unit volume may be different from each other even within the inlet region E 1  of the porous structure  200 . For example, the number of pores per unit volume in the inlet region of the first porous structure provided to face the first reaction region  130   a  may be less than the number of pores per unit volume in the inlet region of the second porous structure provided to face the second reaction region  130   b.  On the other hand, the number of pores per unit volume of the third porous structure provided to face the third reaction region  130   c  may be constant over all regions of the third porous structure. As described above, the number of pores per unit volume is configured to change by regions of the porous structure  200  because the degradation may relatively easily occur on the reaction surface  20  which faces a region of the inlet region E 1  of the porous structure  200 , adjacent to the fluid inlet part  110 , but the degradation relatively little occurs on the reaction surface  20  which faces a region of the inlet region E 1  of the porous structure  200 , away from the fluid inlet part  110 . 
     Also, according to the first exemplary embodiment of the present disclosure, in other regions except for the inlet region E 1  of the porous structure  200 , the numbers of pores per unit volume of the porous structure  200  may be the same as each other. For example, referring to  FIG.  1   , in the other regions except for the inlet regions of the first to third porous structures, the numbers of pores per unit volume of the first to third porous structures may be the same as each other. 
       FIG.  3    is a plan view illustrating a structure of a separator for a fuel cell according to a second exemplary embodiment of the present disclosure. 
     Similar to the first exemplary embodiment of the present disclosure, a separator for a fuel cell (hereinafter, referred to as a separator  10 ) according to the second exemplary embodiment of the present disclosure may include a separator body  100 , as illustrated in  FIG.  3   . 
     Also, the separator body  100  may include: a fluid inlet part  110  having a space into which a fluid is introduced; a reaction region  130  to receive the fluid from the fluid inlet part  110 ; and a diffusion part  120  which is provided between the fluid inlet part  110  and the reaction region  130  and has a passage to provide a path through which the fluid within the fluid inlet part  110  is supplied to the reaction region  130 . 
     Also, in the separator  10  according to the second exemplary embodiment of the present disclosure, a porous structure  200  may be stacked on one surface of the separator body  100 . In particular, the porous structure  200  may be stacked on one surface of the reaction region  130 . Descriptions of both the content that fluid supplied to the fluid inlet part  110  is supplied to the reaction region  130  via the diffusion part  120  and the principle that the fluid supplied into the reaction region  130  is supplied to the reaction surface including the electrode will be replaced with the above descriptions of the separator according to the first exemplary embodiment of the present disclosure. 
     Also, even in the separator  10  according to the second exemplary embodiment of the present disclosure, the reaction region  130  provided in the separator  10  may have a plurality of regions as illustrated in  FIG.  3   . For example, the reaction region  130  may include a first reaction region  130   a,  a second reaction region  130   b,  and a third reaction region  130   c.  Here,  FIG.  3    illustrates a state in which the first to third reaction regions  130   a,    130   b,  and  130   c  are partitioned separately from each other. However, unlike this configuration, the plurality of reaction regions including the first to third reaction regions  130   a,    130   b,  and  130   c  may be connected and integrated with each other. 
     Also, as described above, the porous structure  200  may be stacked on the one surface of the reaction region  130 , and the reaction region  130  may include the first to third reaction regions  130   a,    130   b,  and  130   c.  Thus, the porous structure  200  may include a first porous structure stacked on one surface of the first reaction region  130   a,  a second porous structure stacked on one surface of the second reaction region  130   b,  and a third porous structure stacked on one surface of the third reaction region I  30   c.  The first to third porous structures may be partitioned separately from each other, but unlike this configuration, the first to third porous structures may be connected and integrated with each other. 
     Also, the first to third reaction regions  130   a,    130   b,  and  130   c  may be arranged in one direction on the basis of a distance from the fluid inlet part  110 . That is, as illustrated in  FIG.  3   , the first reaction region  130   a  and the second reaction region  130   b  may be disposed so that a distance between the first reaction region  130   a  and the fluid inlet part  110  is less than a distance between the second reaction region  130   b  and the fluid inlet part  110 . Also, the second reaction region  130   b  and the third reaction region  130   c  may be disposed so that a distance between the second reaction region  130   b  and the fluid inlet part  110  is less than a distance between the third reaction region  130   c  and the fluid inlet part  110 . 
     According to another aspect of the present disclosure, some regions of the porous structure  200  of the separator  10  have a shape curved in the opposite direction to a direction facing the fluid inlet part  110 , compared to the other regions. That is, according to the second exemplary embodiment of the present disclosure, when a region of the porous structure  200 , which faces the diffusion part  120 , is referred to as an ‘inlet region E 1 ’, and an inlet region of the inlet region E 1 , which is provided at the same height as the fluid inlet part  110  in a height direction h, is referred to as a ‘same height inlet region F 1 ’, the same height inlet region F 1  of the porous structure  200  may be provided closer to a central region E 3  of the porous structure  200  than a region except for the same height inlet region F 1  in the inlet region of the porous structure  200 . More preferably, the inlet region E 1  of the porous structure  200  may be closer to the central region E 3  of the porous structure  200  as the inlet region E 1  is closer to the fluid inlet part  110  in the height direction (h) of the fluid inlet part  110 . 
     According to the second exemplary embodiment of the present disclosure, the same height inlet region F 1  of the porous structure  200  has a shape closer to the central region E 3  of the porous structure  200 , a distance between the same height inlet region F 1  of the porous structure  200  and the fluid inlet part  110  become increased, compared to the related art. Thus, an amount of a fluid supplied to the same height inlet region F 1  of the porous structure  200  is reduced, and accordingly, the degradation on a reaction surface facing the same height inlet region F 1  may be prevented. Particularly, according to a further preferred exemplary embodiment, the inlet region E 1  of the porous structure  200  has a shape closer to the central region E 3  as the inlet region E 1  is closer to the fluid inlet part  110  in a height direction h of the fluid inlet part  110 , and thus, compared to the related art, the degradation on a reaction surface facing a region of the inlet region E 1  of the porous structure  200 , which is relatively close to the fluid inlet part  110 , may be prevented. 
     Also, according to the present disclosure as illustrated in  FIG.  3   , an outlet region E 2  through which the supplied fluid is discharged may be provided on an opposite side of the inlet region E 1  of the porous structure  200 . Here, according to the present disclosure, a boundary of the outlet region E 2  in the porous structure  200  may extend in a direction perpendicular to a direction in which the porous structure  200  extends from the inlet region E 1  to the outlet region E 2 . This may be understood as the boundary of the porous structure  200  in the outlet region E 2  does not have a curved shape or a recessed shape, but has a straight line shape. 
     Also, according to the second exemplary embodiment, a distance between the fluid inlet part  110  and the inlet region of the first porous structure provided to face the first reaction region  130   a  may be the same as a distance between the fluid inlet part  110  and the inlet region of the second porous structure. In this case, a movement distance of the fluid supplied from the fluid inlet part  110  to the first reaction region  130   a  and the first porous structure is the same as a movement distance of the fluid supplied from the fluid inlet part  110  to the second reaction region  130   b  and the second porous structure, and thus, the degradation on the reaction region facing the same height inlet region F 1  due to the fluid intensively supplied to the inlet region (that is, the same height inlet region F 1 ) closest to the fluid inlet part  110  may be prevented from occurring. 
       FIG.  4    is a plan view illustrating a structure of a separator for a fuel cell according to a third exemplary embodiment of the present disclosure. 
     Similar to the first exemplary embodiment and the second exemplary embodiment of the present disclosure, a separator for a fuel cell (hereinafter, referred to as a separator  10 ) according to the third exemplary embodiment of the present disclosure may include a separator body  100 , as illustrated in  FIG.  4   . 
     Also, the separator body  100  may include: a fluid inlet part  110  having a space into which a fluid is introduced; a reaction region  130  to receive the fluid from the fluid inlet part  110 ; and a diffusion part  120  which is provided between the fluid inlet part  110  and the reaction region  130  and has a passage to provide a path through which the fluid within the fluid inlet part  110  is supplied to the reaction region  130 . 
     Also, in the separator  10  according to the third exemplary embodiment of the present disclosure, a porous structure  200  may be stacked on one surface of the separator body  100 . In particular, the porous structure  200  may be stacked on one surface of the reaction region  130 . Descriptions of both the content that fluid supplied to the fluid inlet part  110  is supplied to the reaction region  130  via the diffusion part  120  and the principle that the fluid supplied into the reaction region  130  is supplied to the reaction surface including the electrode will be replaced with the above descriptions of the separator according to the first exemplary embodiment of the present disclosure. 
     Also, even in the separator  10  according to the third exemplary embodiment of the present disclosure, the reaction region  130  provided in the separator  10  may have a plurality of regions as illustrated in  FIG.  4   . For example, the reaction region  130  may include a first reaction region  130   a,  a second reaction region  130   b,  and a third reaction region  130   c.  Here,  FIG.  4    illustrates a state in which the first to third reaction regions  130   a,    130   b,  and  130   c  are partitioned separately from each other. However, unlike this configuration, the plurality of reaction regions including the first to third reaction regions  130   a,    130   b,  and  130   c  may be connected and integrated with each other. 
     Also, as described above, the porous structure  200  may be stacked on the one surface of the reaction region  130 , and the reaction region  130  may include the first to third reaction regions  130   a,    130   b,  and  130   c.  Thus, the porous structure  200  may include a first porous structure stacked on one surface of the first reaction region  130   a,  a second porous structure stacked on one surface of the second reaction region  130   b,  and a third porous structure stacked on one surface of the third reaction region  130   c.  The first to third porous structures may be partitioned separately from each other, but unlike this configuration, the first to third porous structures may be connected and integrated with each other. 
     Also, the first to third reaction regions  130   a,    130   b,  and  130   c  may be arranged in one direction on the basis of a distance from the fluid inlet part  110 . That is, as illustrated in  FIG.  4   , the first reaction region  130   a  and the second reaction region  130   b  may be disposed so that a distance between the first reaction region  130   a  and the fluid inlet part  110  is less than a distance between the second reaction region  130   b  and the fluid inlet part  110 . Also, the second reaction region  130   b  and the third reaction region  130   c  may be disposed so that a distance between the second reaction region  130   b  and the fluid inlet part  110  is less than a distance between the third reaction region  130   c  and the fluid inlet part  110 . 
     Here, according to the third exemplary embodiment of the present disclosure, the porous structure  200  of the separator  10  may include not only a pore formation region which has a plurality of pores but a passage formation region which is provided in a region facing a passage provided in the diffusion part  120  of the separator body  100 . 
     That is, according to the third exemplary embodiment, the porous structure  200  may be stacked on the one surface of the reaction region  130 . When a region of the porous structure  200 , which faces the diffusion part  120 , is referred to as an ‘inlet region E 1 ’, and an inlet region A 1  of the inlet region E 1 , which is closest to the fluid inlet part  110 , is referred to as a ‘closest inlet region’, a passage formation region D 1  provided to face the passage of the diffusion part  120  may be provided in the closest inlet region A 1  of the porous structure  200 , and a pore formation region D 2  having a porous pore structure may be provided in a region except for the passage formation region D 1  in the porous structure  200 .  FIG.  4    illustrates a state in which the passage formation region D 1  is provided in a portion of the closest inlet region A 1 . 
     Here, according to the third exemplary embodiment, the passage formation region D 1  of the porous structure  200  may have a shape protruding toward a central region of the porous structure  200  as the passage formation region D 1  is closer to the fluid inlet part  110  in a height direction h of the fluid inlet part  110 . This may be understood that the passage formation region D 1  of the porous structure  200  may have a shape curved toward the central region of the porous structure  200  as the passage formation region D 1  is closer to the fluid inlet part  110  in the height direction h of the fluid inlet part  110 . 
     As described above, according to the third exemplary embodiment, the passage formation region D 1  may be provided in the closest inlet region A 1  of the porous structure  200 , and more preferably, the passage formation region D 1  of the porous structure  200  may have a shape protruding toward the central region of the porous structure  200  as the passage formation region D 1  is closer to the fluid inlet part  110  in the height direction h of the fluid inlet part  110 . In this case, similar to the second exemplary embodiment, the degradation on the reaction region facing the closest inlet region A 1  due to the fluid intensively supplied to the inlet region (that is, the closest inlet region A 1 ) closest to the fluid inlet part  110  may be prevented from occurring. 
     Also, as described above, the reaction region  130  may include the first reaction region  130   a  and the second reaction region  130   b,  and the porous structure  200  may include the first porous structure stacked on the one surface of the first reaction region  130   a  and the second porous structure stacked on the one surface of the second reaction region  130   b . Here, according to the third exemplary embodiment, the passage formation region D 1  provided in the inlet region of the first porous structure may have a shape further protruding from the passage formation region D 1  provided in the inlet region of the second porous structure toward the central region of the porous structure  200 . Thus, according to the third exemplary embodiment, the pore formation region D 2  provided in the first porous structure may have a shape further curved from the pore formation region D 2  provided in the second porous structure toward the central region of the porous structure  200 . 
       FIG.  5    is a cross-sectional view illustrating a stack structure of a fuel cell according to one example of the present disclosure. 
     Referring to  FIG.  5   , a fuel cell according to the present disclosure may include: a membrane electrode assembly (MEA)  22  including a membrane, a fuel electrode, and an air electrode; a gas diffusion layer  24  stacked on one surface of the MEA  22 ; and a separator  10  stacked on one surface of the gas diffusion layer  24 . The gas diffusion layer  24  may include an air diffusion layer  24   a  stacked on one surface of the MEA  22  and a fuel diffusion layer  24   b  stacked on the other surface of the MEA  22 . 
     As described above, the separator  10  may include a separator body  100  and a porous structure  200  which is stacked on one surface of the separator body  100  and has a plurality of pores defined therein to provide a path through which a fluid flows. Also, as described above, the separator body  100  may include: a fluid inlet part  110  having a space into which the fluid is introduced; a reaction region  130  to receive the fluid; and a diffusion part  120  which is provided between the fluid inlet part  110  and the reaction region  130  and has a passage to provide a path through which the fluid within the fluid inlet part  110  is supplied to the reaction region  130  (see  FIGS.  1 ,  3 , and  4   ). Also, the reaction surface  20  (see  FIG.  2   ) may include the MEA  22  and the gas diffusion layer  24  of the fuel cell according to the present disclosure. 
     Here, the shapes of the fluid inlet part and the diffusion part described and illustrated in the present specification and drawings are merely illustrative, and the present disclosure may be applied regardless of the specific shapes of the fluid inlet part and the diffusion part. 
     According to the present disclosure, the constant amount of air is supplied to the fuel cell irrespective of the positions within the air channel, and thus, the degradation of the fuel cell may be prevented. 
     Although the present disclosure is described by specific embodiments and drawings as described above, the present disclosure is not limited thereto, and it is obvious that various changes and modifications may be made by a person skilled in the art to which the present disclosure pertains within the technical idea of the present disclosure and equivalent scope of the appended claims.