KR100761525B1 - Integrated type gas diffusion layer, electrode comprising the same, membrane electrode assembly comprising the same, and fuel cell comprising the same - Google Patents

Abstract

A gas diffusion layer having a microporous layer(MPL) integrally formed with a substrate is provided to eliminate a bottle neck phenomenon occurring on the interface between a carbon substrate layer and an MPL, thereby ensuring improved contact between fuel and reaction gases and uniform electroconductivity. A gas diffusion layer includes no carbon substrate and comprises carbon powder and a microporous layer(3) containing a fluororesin that is not carbonized but molten at 250-450 deg.C to impart a binding force. The carbon powder comprises a mixture of: (a) 100 parts by weight of framework-maintaining carbon powder having a particle diameter of 0.1 micrometer or more and showing a self-supporting property; and (b) 20-80 pars by weight of electroconductive carbon powder having an electrical resistivity of 1 ohm.cm or less. The carbon powder and the fluororesin are used in a weight ratio of 60-95 wt% : 5-40 wt%.

Description

Integrated type gas diffusion layer, electrode comprising the same, membrane electrode assembly comprising the same, and fuel cell comprising the same {Integrated type gas diffusion layer, electrode comprising the same, membrane electrode assembly comprising the same, and fuel cell comprising the same}

1 is a schematic diagram showing a cross-sectional structure of a conventional gas diffusion layer (GDL).

2 is a flowchart showing a conventional GDL manufacturing process having the above structure.

3 is a schematic diagram showing a cross-sectional structure of a GDL according to an aspect of the present invention.

4 is a flowchart of a conventional method for producing a carbon slurry composition.

5-10 are micrographs (5 or 40 times) of GDL surfaces according to some examples and comparative examples.

11 is a voltage drop curve of a membrane electrode assembly MEA according to some embodiments and comparative examples.

The present invention relates to a gas diffusion layer, an electrode comprising the same, a membrane electrode assembly including the same, and a fuel cell including the same, and more particularly, sufficient mechanical strength, electrical conductivity, and mass transfer properties without a conventional carbon substrate. It relates to an integrated gas diffusion layer having a, a fuel cell electrode comprising the same, a fuel cell membrane electrode assembly comprising the same, and a fuel cell comprising the same.

A fuel cell is a device that produces electric energy by electrochemically reacting fuel and oxygen. Unlike thermal power generation, a fuel cell does not undergo a Carno cycle, and thus its theoretical power generation efficiency is very high. In addition, since NO _x and CO ₂ emissions and noise are lower than thermal power generation, the fuel cell is an environmentally friendly power generation device.

Fuel cells can be classified into polymer electrolyte type (PEM), phosphoric acid type, molten carbonate type, solid oxide type and alkaline aqueous solution type according to the type of electrolyte used. Depending on the operating temperature of the fuel cell and the material of the components. In addition, the fuel cell is an external reforming type for converting fuel into a hydrogen-enriched gas through a fuel reformer and supplying the anode to the anode and a direct oxidation type or an internal reforming type for supplying fuel directly to the anode according to the fuel supply method to the anode. It can be divided into. Natural fuels, methanol, and the like are generally used as fuels used in fuel cells, but other hydrocarbon fuels or derivatives thereof may be used.

Among the fuel cells, the polymer electrolyte fuel cell (abbreviated as "PEMFC") has a lower operating temperature, higher efficiency, higher current density, higher output density, shorter startup time, and lower load change than other fuel cells. The response is fast. In addition, since the polymer membrane is used as the electrolyte, there is no need for corrosion and electrolyte control, the design is simple, the manufacturing is easy, and the volume and weight are smaller than those of the phosphate fuel cell having the same operation principle. Compared with the secondary battery developed as a power source for electric vehicles, the specific energy density of PEMFC is higher than the secondary battery having a value of 200 Wh / kg or less, from 200 Wh / kg to thousands of Wh / kg or more. Have. In addition, in terms of charging time, a lithium battery requires about three hours of charging time, whereas fuel cells require only a few seconds to inject fuel. Therefore, PEMFC is actively researching and developing the world as transportation power source, mobile and emergency power source, and military power source that replace battery of electric vehicle.

An electrode that causes an electrochemical reaction in a fuel cell includes a gas diffusion layer (GDL) and a catalyst layer. GDL connects the electric current generated in the electrochemical reaction with the external electric circuit. GDLs are suitable materials that have pores and allow smooth access of fuel and reactor gas to the catalyst bed.

1 is a schematic diagram showing a cross-sectional structure of a conventional GDL. Referring to FIG. 1, the conventional GDL 100 is formed by stacking a microporous layer 3 (“MPL”) on a carbon substrate 1. Generally, this carbon substrate is in the form of carbon paper, carbon fiber woven fabrics, or carbon fiber non-woven fabrics.

2 is a flowchart showing a conventional GDL manufacturing process having the above structure. With reference to FIG. 2, the manufacturing process of the conventional GDL is demonstrated. First, a fiber obtained by spinning a polymer material such as PAN, rayon, pitch, etc. is made into a sheet by a weaving process or a nonwoven fabric manufacturing process. The sheet is thermally stabilized at a temperature of about 500 to about 800 ° C. The stabilized sheet is then further carbonized in an oxidizing atmosphere at about 2000 ° C. or higher to obtain a carbon substrate in the form of a carbon fiber fabric or a carbon fiber nonwoven fabric. If this is further compressed to a thin film, a carbon substrate in the form of carbon paper can be obtained.

Subsequently, a highly fluorinated polymer resin is coated on the carbon substrate to perform hydrophobic treatment, and then coated with MPL containing carbon and hydrophobic polymer, followed by drying and heat treatment to obtain a GDL having a cross-sectional structure shown in FIG. 1. .

However, since the conventional GDL having such a cross-sectional structure includes a carbon substrate, the following problems are exhibited.

i) First, the cost of the substrate is expensive because the process of producing the carbon substrate is very complicated and difficult. This leads to an increase in fuel cell manufacturing costs. That is, it is expensive because it requires a complicated process of manufacturing carbon fibers having a diameter of several micrometers and then forming a woven nonwoven fabric.

ii) It is preferable that the carbon substrate has a thickness of about 100 to 400 µm in order to exhibit the characteristics required by the fuel cell. However, it is difficult to make a carbon substrate into a thin film. In other words, the number of strands of carbon fibers must be reduced in order to make them thin because weaving carbon fibers into woven fabrics or irregularly laminating them into nonwoven fabrics. In this case, however, it is difficult to manufacture a thin film of the above thickness.

iii) Due to the low mechanical strength, the carbon fiber is stretched when the carbon fiber is pulled with a constant force to apply the MPL. Therefore, when MPL is applied on a carbon substrate, macro cracks are generated on the MPL surface due to the difference in mechanical strength and shrinkage ratio of the uncoated portion and the coated portion during drying. This macrocrack is one of the major causes of poor performance of the MEA.

iv) The thickness variation of the carbon substrate is large. That is, carbon fibers having a diameter of several micrometers constituting the carbon fiber nonwoven substrate are discharged through a large number of nozzles to form a precursor fiber, and then they are randomly stacked and converted into sheets. Therefore, the thickly laminated portion of the raw material precursor resin composition becomes a thick carbon substrate portion, and the thinly laminated portion becomes a thin carbon substrate portion, depending on the discharge conditions. Moreover, in the carbon base material which is rolled, the thickness variation with a direction is very large. This problem is difficult to overcome with current technology, and membrane electrode assemblies (MEA) using such carbon substrates are very difficult to obtain thickness and performance reproducibility. This situation is the same for carbon substrates in the form of carbon paper or carbon fiber nonwovens.

v) The porosity inside the carbon substrate is not uniform and the variation is large depending on the position. This causes a large voltage drop when transferring electrons of a fuel cell generated in a region where high current flows to an external circuit. Carbon fiber fabrics are in the form of woven carbon fibers and therefore have a greater porosity that can be observed with the naked eye when compared to carbon paper. Because of this, carbon fiber fabrics tend to be more voltage-strengthened.

In this way, the porosity of the carbon substrate varies greatly depending on the location, and when the catalyst is applied, MPL is coated on the carbon substrate to obtain a stable fuel cell because the performance decreases due to the penetration of hydrogen ions into the polymer substrate and the distance to the polymer membrane. To prepare the GDL. However, in this case, since the thickness variation of the carbon substrate is large, the change of the amount of loading of the composition for forming MPL is large according to the position of the carbon substrate. This means that different thicknesses of MPL are formed depending on the position of the carbon substrate, which results in a GDL having a large change in properties depending on the position of the carbon substrate.

vi) Rolling is particularly difficult because carbon paper has a low mechanical strength and high brittleness. That is, since carbon paper has a high rotation radius because of poor flexibility, the radius of the unwinding roll and the rewinding roll of the coater should be large, and also the guide roll. Since the distance between the should be large, causing the size of the coating apparatus. This makes the preparation of the microporous layer (MPL) and the catalyst layer very difficult.

vii) Although carbon fiber has excellent mechanical strength, the woven fabric made of carbon fiber is well stretched when rolled, so that the carbon substrate is difficult to apply to a roll-to-roll coating apparatus. In other words, even when the tension is applied when the carbon substrate is mounted on a roll, the carbon fiber is usually about 10 to 40% elongated and easily broken. In addition, after elongation, it has a structure different from the original.

As described above, the conventional GDL is manufactured by forming MPL including carbon particles (fibers) and a hydrophobic polymer on a porous carbon substrate.

For example, International Patent WO2003 / 054994 (Korean Patent Publication No. 2004-0071725) discloses an aqueous coating composition comprising carbon particles, at least one high fluorinated polymer, and at least one amine oxide based surfactant on a carbon substrate. A method of preparing GDL by coating is disclosed.

Korean Patent Application No. 2004-7009514 describes the preparation of a precomposition by combining carbon and one or more surfactants in an aqueous fluid, typically by high shear mixing, wherein one or more highly fluorinated polymers are added to the composition by low shear mixing. A method of making a GDL for an electrochemical cell, comprising the steps of preparing a coating composition, and coating the coating composition on an electrically conductive porous substrate, typically by a low shear coating method.

In addition, Korean Patent Application No. 2004-7009592 discloses a method of manufacturing GDL by compressing MPL coated on a carbon fiber plain fabric with a compression ratio of 25% or more.

As described above, the basic structure of the conventional GDL consists of a structure coated with MPL formed of carbon and a hydrophobic polymer on a carbon substrate. As described above, the conventional GDL having a two-layer structure in which MPL is formed on a carbon substrate having completely different physical properties such as porosity tends to exhibit the following problems.

i) MPL has different pore distribution and porosity depending on carbon type and structure, hydrophobic polymer content, MPL thickness, etc. In general, the pores contained in the carbon substrate have large porosities ranging from tens of micrometers to several millimeters, while MPLs have small porosities of several nanometers to several tens of micrometers. Therefore, the porosity of the carbon substrate is large, but because the porosity of the MPL stacked thereon is very small, bottlenecks occur at the interface, and the inflow and discharge of the material is not smooth. In particular, a large amount of fuel reacts in the high current region, and a large amount of carbon dioxide is generated in the anode and a large amount of water is generated in the cathode, but it is difficult to discharge them smoothly due to a bottleneck between the carbon substrate and the MPL.

ii) The current generated in the catalyst layer on the MPL is collected in the bipolar plate through the MPL and the carbon substrate and connected to the external circuit. Current loss occurs due to the contact resistance at the interface of each layer. In the case of using a carbon substrate, the number of interfaces increases, so that the current loss increases accordingly. In particular, the current loss is large in the contact between the carbon substrate and the bipolar plate.

iii) Commercial fuel cells have a structure in which MEAs are stacked in series to increase voltage. The fuel cell stacks stacked in the order of MEA / bipolar plate / MEA and the like are fastened externally for sealing. At this time, several hundreds of kgf / cm ² Because of the high degree of force applied, it is frequently the case that the carbon substrate is recessed into the channel of the bipolar plate or the substrate breaks. This is a problem caused by the presence of a carbon substrate with low mechanical strength and MPL separately.

iv) GDLs of this structure generally have irregular cracks on the surface of the MPL. Irregular cracks on the surface of the MPL cause irregular distribution of large pores in the GDL, which impedes the smooth and uniform supply of fuel and reaction gas, and deteriorates the efficiency of the catalyst by causing the catalyst of the catalyst layer coated on the GDL to sink into the GLD. Can be a major cause. This is also a problem caused by forming MPL on a carbon base material having completely different physical properties such as porosity.

v) Such a two layer GDL is very difficult to manufacture. Although the process of making a carbon substrate is also very difficult, in order to form a constant thickness MPL on the carbon substrate must be mounted on the coating apparatus to have a constant tension to coat a constant thickness MPL. However, when the carbon substrate is subjected to mechanical deformation primarily, and the carbon slurry for forming MPL formed of carbon + hydrophobic polymer + dispersant + solvent is coated on the carbon substrate and dried, the carbon substrate has a property of not shrinking. The MPL shrinks as the solvent of the slurry volatilizes, thereby causing cracks on the surface, and variations in thickness of the MPL occur due to the flowability of the slurry. In addition, a thickness variation occurs locally because the coating is performed on a carbon substrate having an irregular porous structure instead of coating a carbon slurry on a smooth surface. For this reason, GDL becomes a nonuniform pore distribution, and GDL which has a different structure for each position at the time of MEA manufacture is used.

Accordingly, an object of the present invention is to provide an integrated GDL in which a carbon substrate and MPL are integrated in order to solve the problems of the conventional GDL described above.

Another object of the present invention is to provide an electrode for a fuel cell comprising the integrated GDL described above.

Still another object of the present invention is to provide a fuel cell MEA including the integrated GDL.

Still another object of the present invention is to provide a fuel cell including the integrated GDL.

In order to achieve the above object, one aspect of the present invention is a fuel diffusion gas diffusion layer (GDL) consisting of only carbon powder, and MPL containing a fluorinated resin that is not carbonized in the temperature range of 250 to 400 ℃ fused to impart a binding force ), It provides a GDL characterized by not including a carbon substrate.

In one embodiment of the present invention, the carbon powder is activated carbon, carbon black, acetylene black, Ketjen black, denka black, carbon whisker, carbon fiber, activated carbon fiber, vapor growth carbon fiber, carbon aerosol, carbon nanotube, It may be at least one selected from the group consisting of carbon nanofibers, carbon nanohorn, and natural or synthetic graphite.

In another embodiment of the present invention, the fluorinated resin is polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoro It may be at least one selected from the group consisting of ethylene, tetrafluoroethylene-ethylene copolymer and polyfluorovinylidene (PVDF).

In another embodiment of the present invention, the carbon powder comprises a) a skeleton-maintaining carbon powder component having a self-supporting particle diameter of 1 µm or more, and b) an electrically conductive carbon having an electrical resistivity of 1 Ωcm or less. It may be a mixture comprising a powder component, 20 to 80 parts by weight of the electrically conductive carbon powder component of b) based on 100 parts by weight of the skeletal maintenance component of a).

In another embodiment of the present invention, the carbon powder may include a carbon powder having a particle diameter of 0.1 μm or more and an electrical resistivity of 1 Ωcm or less.

In another embodiment of the present invention, the thickness of the MPL is 50 ~ 1,000㎛, the carbon powder: the weight ratio of the fluorinated resin may be 60 to 95% by weight carbon powder: 5 to 40% by weight fluorinated resin have.

Another aspect of the invention is a GDL consisting of only carbon powder and MPL comprising a fluorinated resin that melts and imparts a binding force without carbonization in the temperature range of 250 to 400 ° C., which does not include a carbon substrate. Does not have GDL; And it provides an electrode comprising a catalyst layer laminated on the GDL.

Another aspect of the invention is a GDL comprising only carbon powder and MPL comprising a fluorinated resin that melts and imparts a binding force without carbonization in the temperature range of 250 to 400 ° C., which does not include a carbon substrate. A membrane electrode assembly (MEA) comprising a GDL, a catalyst layer stacked on the GDL, and a polymer electrolyte membrane (PEM) stacked on the catalyst layer.

Another aspect of the invention is a GDL comprising only carbon powder and MPL comprising a fluorinated resin that melts and imparts a binding force without carbonization in the temperature range of 250 to 400 ° C., which does not include a carbon substrate. GDL does not provide a fuel cell comprising a catalyst layer stacked on the GDL.

Still another aspect of the present invention provides a carbon powder, a dispersant, a polymer resin that can be carbonized in an air or oxygen atmosphere at a temperature of 250 to 400 ° C. and a fluorinated resin that is melted without carbonization in the above temperature range to impart a binding force. Preparing a carbon slurry composition comprising;

Coating the carbon slurry composition on a substrate and then drying to form a microporous precursor layer; And

After peeling off and removing the substrate, the microporous precursor layer is heat treated in an air or oxygen atmosphere at 250 to 400 ° C. to carbonize or decompose the dispersant and the polymer resin, thereby removing the carbon powder and the 250 to 400 ° C. It provides a method for producing a GDL comprising the step of obtaining a GDL consisting of only the MPL containing a fluorinated resin that is not carbonized in the temperature range and melted to impart a binding force.

The electrode and fuel cell employing the integrated gas diffusion layer in which the carbon substrate and the MPL are integrated according to the present invention can greatly reduce the manufacturing cost, and also do not include the carbon substrate, and thus occur at the interface between the carbon substrate and the MPL. Eliminate bottlenecks and contact resistance to mass transfer. As a result, the electrode and the fuel cell according to the present invention can ensure smooth access and uniform electronic conductivity of the fuel and the reactor body to the catalyst layer. In addition, since the macrocracks as well as the microcracks are formed smoothly on the surface of the MPL, the pores are regularly distributed and the utilization rate of the catalyst can be improved. Therefore, the electrode and the fuel cell employing the GDL according to the present invention can exhibit uniform electrical characteristics.

Hereinafter, the GDL, the electrode and the fuel cell according to the present invention will be described in more detail.

3 is a schematic diagram showing a cross-sectional structure of a GDL according to an aspect of the present invention. Referring to FIG. 3, the GDL of the present invention does not include a carbon substrate (1 in FIG. 1), and consists only of the MPL 3. The MPL 3 comprises a carbon powder and a fluorinated resin that is melted without carbonization in the temperature range of 250 to 400 ° C. to impart a binding force. The thickness of the MPL 3 is not particularly limited, but may be 50 to 1,000 μm, and preferably 150 to 500 μm. If the thickness of the layer is less than 50 μm, there may be a problem such as tearing during handling due to low mechanical strength. If the thickness is more than 1,000 μm, the material movement distance is increased and the resistance is increased. There may be a problem such as.

The gas diffusion layer of the present invention may typically have an electrical resistivity (in-plane and thru-plane resistance) of about 10 Ωcm or less, and more preferably about 5 Ωcm or less. And even more preferably, may have a resistance of about 1 Ωcm or less.

In MPL (3), the weight ratio of carbon powder to fluorinated resin is not particularly limited, but may be 60 to 95% by weight of carbon powder: 5 to 40% by weight of fluorinated resin, preferably 70 to 90 carbon powder. % By weight: 10-30% by weight of the fluorinated resin. If the content ratio of the carbon powder is less than 60% by weight, the electrode resistance may not be sufficient to increase the electrical conductivity. If the content is more than 95% by weight, the content of the fluorinated resin is small, so that the binding strength is lowered and the mechanical strength is not sufficient. have.

The carbon powder is porous and electrically conductive, and can be used in one or two or more various combination ratios, regardless of crystalline carbon, amorphous carbon or activated carbon. The carbon powder that can be used is not particularly limited, but specifically, activated carbon, carbon black, acetylene black, ketene black, carbon whisker, carbon fiber, activated carbon fiber, vapor grown carbon fiber (VGCF) carbon It may be at least one selected from the group consisting of aerosols, carbon nanotubes, carbon nanofibers, carbon nanohorn, and natural or synthetic graphite. There is no particular limitation on the average particle size, specific surface area, average pore size, etc. of the carbon powder. However, if the average particle size of the carbon powder is too small, smooth access of the fuel and the reactor gas to the catalyst layer may be prevented, and the ability to discharge carbon dioxide and water generated during the reaction may be reduced. On the other hand, if the average particle size of the carbon powder is too large, the macropores may be formed to reduce the fuel carrying capacity, the interface resistance between the electrons and the current collector generated during the reaction may be excessively increased. In view of this, the carbon powder used in the present invention is a) a skeleton-maintaining carbon powder component which allows MPL to have self-support even without a carbon substrate, and has a particle diameter of 0.1 mu m or more, for example, 0.1 to 100 mu m carbon. Powder and b) an electrically conductive carbon powder component having an electrical resistivity of 1 Ωcm or less, for example, 0.01 to 1 Ωcm. Specific examples of the a) skeletal-maintaining carbon powder component are compared with those of artificial graphite MCMB (Osaka Gas), natural graphite P15B-ZG (Japan carbon), GX-15P (carbonics), carbon fiber or ordinary carbon fiber. At least one selected from the group consisting of activated carbon fibers having a small surface area. B) The electrically conductive carbon powder component is activated carbon having an electrical resistivity of 1 Ωcm or less, such as carbon black, for example, Vulcan XC-72 (Cabot Corporation), Shawinigan Black of grade C55. (Cevron Phillips Chemical Company), or Ketjenblack EC300J (Akzo Nobel Chemicals Inc., Chicago, IL) may be used. Typically, when graphite particles are used, larger In this case, the mixture may include 20 to 80 parts by weight of the electrically conductive carbon powder component of b) based on 100 parts by weight of the skeletal maintenance component of a).

In the present invention, the carbon powder is used in the form of fiber, i.e., including carbon fiber. In the case of carbon fibers, the fiber length can be several hundred micrometers to several millimeters or centimeters.

If the specific surface area of the carbon powder is too small, not only the supporting capacity of the fuel may be lowered, but also the contact resistance with the catalyst may be increased. If the carbon powder is too large, the reaction product may not be smoothly discharged due to excessive microporosity. In view of this, the specific surface area of the carbon powder may be about 20 m 2 / g to about 2000 m 2 / g, more preferably, about 50 m 2 / g to about 1500 m 2 / g, Even more preferably, it may be about 80 m 2 / g to about 800 m 2 / g.

For example, the carbon powder may be a) a particle diameter of 0.1 µm or more, for example, 0.1 to 100 µm, a skeleton-supporting carbon powder component that is self-supporting, and b) an electrical resistivity of 1 Ωcm, eg For example, it may be a mixture containing an electrically conductive carbon powder component of 0.01 ~ 1Ωcm, 20 to 80 parts by weight of the electrically conductive carbon powder component of b) based on 100 parts by weight of the skeletal maintenance component of a). Alternatively, when the particle diameter of the carbon powder is 0.1 μm or more and the electrical resistivity is 1 Ωcm or less, the carbon powder may be used alone so that the MPL may have sufficient mechanical strength and electrical conductivity. It may be.

The fluorinated resin is melted without being carbonized in the temperature range of 250 to 400 ° C. to impart a binding force, thereby imparting a binding force to the MPL to help maintain mechanical strength. This fluorinated resin contains 40 weight% or more, normally 50 weight% or more, and more typically 60 weight% or more. Specific examples thereof include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE) And at least one selected from the group consisting of tetrafluoroethylene-ethylene copolymer (ETFE) and polyfluorovinylidene (PVDF).

As described above, the electrode and the fuel cell employing the integrated GDL in which the carbon substrate and the MPL are integrated according to the present invention can greatly reduce the manufacturing cost and above all, and do not include the carbon substrate. Eliminate bottlenecks and contact resistance to mass transfer at the interface As a result, the electrode and the fuel cell according to the present invention can ensure smooth access and uniform electron conductivity of the fuel and the reactor body to the catalyst layer. In addition, the surface of the MPL as well as macrocracks as well as microcracks are not formed at all, so that the pores are regularly distributed and can improve the utilization of the catalyst. Therefore, the electrode and the fuel cell employing the GDL according to the present invention can exhibit uniform electrical characteristics.

The technical effects that the integrated GDL of the present invention can exhibit will be described in more detail as follows.

i) In the structure of the fuel cell stack, the bipolar plate having the largest current loss and the surface of the carbon substrate are eliminated, and the GDL having the uniform surface is brought into contact with the bipolar plate, thereby minimizing the current loss.

ii) It has uniform structure and uniform pore distribution over the entire thickness of GDL. Therefore, it has a uniform thickness, pore structure, and electrical conductivity compared to the conventional GDL, which showed different characteristics for each position.

iii) Because of its high mechanical strength, it can be applied to the roll-to-roll method. Therefore, the electrode can be manufactured by using a general-purpose coating device, not a special coating device for GDL.

iv) Since it is coated on a substrate such as PET film, dried, removed, and heat treated after rewinding, it is difficult to generate cracks on the surface of the GDL, so that the surface is smooth and it is easy to obtain a uniform thickness of GDL. Since the coating method is a coating method that is already generalized in a method such as a secondary battery or a video tape, the manufacturing process is very simple and the production line operation speed can be increased.

v) It is easy to manufacture the carbon slurry composition for manufacturing GDL. Conventional systems for dispersing dozens of nanoscale activated carbon and PTFE resins such as Vulcan XC-72 in a solvent are difficult to prepare a slurry having a constant dispersion and viscosity, but in the present invention, carbon powders of various sizes and types are used. Therefore, it is easy to produce a carbon slurry composition having a uniform viscosity because it is easy to disperse.

vi) Significant savings in GDL manufacturing costs can be achieved by eliminating the need for carbon substrates, which account for 70-80% of GDL prices. In addition, the burden on raw material prices, which is the biggest problem in mass production of fuel cells, can be significantly lowered.

vii) GDLs of various compositions and structures can be obtained without limiting the type and structure of carbon. For example, various combinations such as spherical carbon powder of several tens of micrometers, carbon fibers, and activated carbon or combinations of carbon fibers and conductive materials can be used. In addition, when MPL is formed in multiple layers, the lower layer has a macropore structure using large carbon powder or carbon fiber, and the upper layer has a micropore structure using small carbon powder or carbon fiber. The porosity can be adjusted as desired.

viii) As a result of the integrated structure, the MEA performance can be increased by 200% or more compared with the existing GDL. This is because the interface resistance between the catalyst layer is dense and well adhered, so that the interface resistance therebetween is small, and the contact resistance with the bipolar plate is also greatly reduced.

ix) GDLs of tens of micrometers to several millimeters in thickness can be produced arbitrarily. MPL of the existing GDL has a very low mechanical strength, it is difficult to form a film alone without a substrate, in the case of the GDL of the present invention, because the mechanical strength of the MPL is large, it is possible to manufacture GDLs of various thicknesses alone.

4 is a flowchart showing a manufacturing process of the GDL of the present invention having the above structure. With reference to FIG. 4, the manufacturing process of GDL of this invention is demonstrated.

First, the carbon slurry composition used for manufacturing GDL which concerns on this invention is prepared. The composition comprises an appropriate amount of dispersant in addition to the above-described types and content ratios of carbon powder and fluorinated resin, and a polymer resin which can be carbonized in an air or oxygen atmosphere at a temperature of 250 to 400 ° C. That is, the carbon slurry composition may be further added to the carbon powder and the basic constituents of the fluorinated resin by adding an appropriate amount of a dispersant and a polymer resin which may be carbonized in an air or oxygen atmosphere at a temperature of 250 to 400 ° C. and uniformly dispersing the carbon slurry composition. Get

The dispersant for dispersing the carbon powder may include at least one of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant which is excellent in compatibility with the fluorinated resin and capable of dispersing the carbon powder. Can be. Specific examples include cationic surfactants such as alkyltrimethylammonium salts, alkyldimethylbenzylammonium salts and phosphate amine salts; Anionic surfactants such as polyoxyalkylene alkyl ethers, polyoxyethylene derivatives, alkylamine oxides and polyoxyalkylene glycols; Amphoteric surfactants such as alanine, imidazolium betaine, amidepropyl betaine and aminodipropionate; Nonionic surfactants, such as alkylaryl polyether alcohols, etc. can be used, It is not limited to the kind listed. Among the commercialized products, anionic surfactants may include Clariant's HOSTAPAL, EMULSOGEN, BYK's Dispersbyk, TEGO's Dispers, and the like. Triton X-100 may be used as the nonionic surfactant. The dispersant to be used may be any substance which can be thermally decomposed and removed at a temperature of 250 to 400 ° C.

The polymer resin, which may be carbonized in an air or oxygen atmosphere at a temperature of 250 to 400 ° C., provides a bonding force to the carbon slurry generated by connecting carbon and carbon of the carbon powder to affect the electrode reaction of the fuel cell. It is possible to improve the properties of the slurry without. The polymer resin may be removed by carbonization in an air or oxygen atmosphere at a temperature in the range of 250 to 400 ° C., and the remaining amount upon removal does not affect the reaction of the fuel cell (eg, dissolved in an aqueous solvent). In the form of a solution) can be used. For example, polyethers consisting of polyethylene oxide, polyethylene glycol, polyacetaldehyde, and the like, polysulfides, polyesters, polycarbonates, ethylene-propylene-elastomers (EPDM), polyethylene, polypropylene, PVC, and It may include one or more of polyvinyls made of polyvinyl fluoride and the like, cellulose, cellulose derivatives, and polysacaccharides made of starch series. The water-based polymer resin is a polymer resin that can be carbonized in an air or oxygen atmosphere at a temperature of 250 to 400 ℃ is added in a dissolved or dispersed form in a solvent such as water.

In the carbon slurry composition according to the present invention, 1 to 50 parts by weight of the dispersant and 5 to 50 parts by weight of the water-based polymer resin are usually mixed with the carbon powder and the fluorinated resin in the above content ratio. For example, 5 to 30 parts by weight of the dispersant and 10 to 30 parts by weight of the aqueous polymer resin may be mixed with respect to the carbon powder and the fluorinated resin 110 to 130 parts by weight in the above-described content ratio.

The content of the dispersant and the water-based polymer resin can vary greatly depending on the type, specific surface area and structure of the carbon used in the slurry. For example, in the case of carbon having a large specific surface area such as Vulcan XC-72, since a large amount of polymer resin may be impregnated in the micropores, a large amount of water-based polymer resin is required and a large amount of dispersant is difficult to disperse. need. However, the use of acetylene black with a small specific surface area requires a smaller amount of aqueous polymer resin and dispersant.

The carbon slurry composition according to the present invention may comprise two or more solvents. As a solvent, in addition to the basic solvents of water, n-propanol and isopropanol, some high boiling point solvents such as ethylene glycol, propylene glycol, DMSO, NMP, and butyl acetate can be mixed and used, and most preferably, It is to mix part of the point solvent.

In the dispersion preparation process, the solvent, the dispersant and the water-based polymer resin may be added at the same time or added sequentially. For details of the method for producing the carbon slurry composition, refer to Korean Patent Application No. 2006-10077 of the applicant.

The carbon slurry composition thus prepared is coated on a polymer substrate such as PET or a metal thin film such as a stainless steel plate. The coating method is not specifically limited. For example, general coating methods such as die, comma, bar, gravure, knife coating and the like can be used without limitation.

The coated result is then dried to form the microporous precursor layer. Subsequently, after the substrate is peeled off and removed, the microporous precursor carbon layer may be heat-treated to obtain a GDL according to the present invention consisting of only MPL. The heat treatment firing process is performed in an oxidizing atmosphere of 250 to 400 ° C. In this process, the dispersant, the aqueous polymer resin, and the solvent are all evaporated or decomposed to remove or carbonize, leaving only carbon powder and fluorinated resin. The GDL of the present invention obtained as described above may exhibit mechanical strength and flexibility enough to be rolled because the fluorinated resin melted during the heat treatment process uniformly binds the carbon powder even without a carbon substrate. The carbon slurry composition coating and drying process may be repeated two or more times to form a multi-layer MPL.

The electrode according to the invention comprises the GDL of the invention having the above characteristics. That is, the electrode of the present invention is a GDL consisting of only carbon powder, and MPL containing a fluorinated resin which is melted without imparting carbonization in the temperature range of 250 to 400 ° C. to impart a binding force, comprising: a GDL containing no carbon substrate; And a catalyst layer laminated on the GDL.

The electrode according to the present invention can be used as an electrode for fuel cells, for example, the fuel cell electrode refers to an anode electrode or a cathode electrode used in the fuel cell. Oxidation reaction of fuel occurs in the catalyst layer of the anode, and oxygen reduction reaction occurs in the catalyst layer of the cathode. For example, the catalyst layer of anode and cathode of PEMFC or direct methanol fuel cell (DMFC) is generally a catalyst capable of causing an oxidation reaction and a reduction reaction of oxygen, respectively, and the mechanical strength of the catalyst layer after fixing the catalyst It includes a hydrogen ion conductive binder resin to maintain.

The catalyst may be a metal catalyst or a supported catalyst. By metal catalyst is meant a catalytic metal powder itself which can cause oxidation of fuel or reduction of oxygen. The supported catalyst refers to a catalyst composed of a catalyst carrier having micropores and catalytic metal particles supported in the micropores of the catalyst carrier. As the catalyst metal particles, for example, platinum powder, Pt-Ru powder, or the like may be used, but is not limited thereto. As the catalyst carrier, for example, active carbon powder, carbon nanotube powder, carbon nanohorn powder, artificial or natural carbon black, or the like can be used.

As the hydrogen ion conductive binder resin, for example, a polymer having a cation exchange group such as a sulfonic acid group, a carboxyl group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, a hydroxy group, or the like can be used. Specific examples of the polymer having a cation exchange group include trifluoroethylene, tetrafluoroethylene, styrene-divinyl benzene, α, β, β-trifluorostyrene, styrene, imide, sulfone, phosphazene , Ether ether ketones, ethylene oxide, polyphenylene sulfide or homopolymers and copolymers of aromatic groups and derivatives thereof, and the like, and these polymers may be used alone or in combination. More preferably, the polymer having a cation exchange group is a high fluoropolymer in which the number of fluoro atoms is 90% or more in the total of the number of fluorine atoms and hydrogen atoms bonded to carbon atoms in the main and side chains thereof. (highly fluorinated polymer). In addition, the polymer having a cation exchange group has a sulfonate as a cation exchange group at the end of the side chain and is fluorine in the sum of the number of fluoro atoms and hydrogen atoms bonded to the carbon atoms of the main and side chains. Furnace may comprise a highly fluorinated polymer with sulfonate groups, wherein the number of atoms is greater than 90%.

The catalyst layer can be prepared, for example, in the following manner. That is, (i) homogeneously dispersing the catalyst and the hydrogen ion conductive binder resin in a solvent to prepare a catalyst ink, (ii) printing, spraying, rolling, brushing (for example, In a method such as brushing), an electrode including the catalyst layer and the GDL is prepared by uniformly coating the catalyst ink on the diffusion layer and (iii) drying the resultant to form the catalyst layer.

The membrane electrode assembly (MEA) of the present invention comprises the GDL of the present invention having the above characteristics. That is, the electrode assembly (MEA) of the present invention is a GDL composed of only carbon powder and MPL containing a fluorinated resin that is melted and imparts a binding force without carbonization at a temperature range of 250 to 400 ° C., and does not include a carbon substrate. GDL, a catalyst layer stacked on the GDL, and a polymer electrolyte membrane (PEM) stacked on the catalyst layer.

The fuel cell of the present invention includes the GDL of the present invention having the above characteristics. That is, the fuel cell of the present invention includes an anode electrode, a cathode electrode and a hydrogen ion conductive electrolyte membrane, wherein the anode, or the cathode, or the anode and the cathode comprises a GDL of the above-described structure and configuration according to the present invention. do.

The fuel cell of the present invention can be applied to, for example, PAFC, PEMFC, DMFC, or the like. The construction and manufacturing method of this kind of fuel cell are well known in the literature and will be readily apparent to those skilled in the art, and thus further detailed description thereof will be omitted.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the technical scope of the present invention is not limited to the following examples.

Example

Example  One

50 g of mesocarbon microbead (MCMB) (Osaka Gas, MCMB25-28), and 50 g of carbon fiber (Carbon Korea, product number: Carbonex), and 20 g of carbon black powder (Cabot Corporation, Vulcan XC-72) were added 1000 g of pure water. After mixing and mixing in a high speed mixer (2000 rpm), 10 g of the dispersant Triton X-100 was added and dispersed for 1 hour, followed by adding 30 g of carboxymethyl cellulose (Aldrich, 31069-7) and further dispersing for 1 hour. A composition was obtained. 20 g of PTFE (Dupont, 30J) was further added thereto, followed by stirring for 1 hour with a low speed mixer (200 rpm) to prepare a carbon slurry composition.

The carbon slurry was coated by a knife coating method and coated on a PET film, followed by drying in a drying oven at 80 ° C. for 1 hour to form an MPL precursor layer. Subsequently, after peeling and removing the PET film, only the microporous layer precursor layer was placed in an oven at about 350 ° C. and fired for 30 minutes to obtain a GDL including only MPL having a thickness of about 200 μm.

The composition of GDL thus obtained was synthesized in Table 1, and the general physical property values measured for this GDL were synthesized in Table 2.

Subsequently, in order to form a catalyst layer, Pt-Ru powder and Nafion were added to a mixed solvent (1: 1 weight ratio) of isopropyl alcohol and water, and then dispersed in an ultrasonic bath for about 10 minutes or more. The catalyst ink thus obtained was coated on the GDL by spray coating, followed by drying to complete the anode electrode. At this time, the Nafion content of the dried catalyst layer was about 10% by weight, and the amount of catalyst loading of the anode electrode was about 5 mg / cm 2.

Pt black powder and Nafion were added to a mixed solvent (1: 1 weight ratio) of isopropyl alcohol and water, and then dispersed in an ultrasonic bath for about 10 minutes or longer. The cathode ink thus obtained was coated on the GDL prepared in the above manner by spray coating and then dried. At this time, the Nafion content of the dried catalyst layer was about 10% by weight, and the amount of catalyst loading of the cathode was about 5 mg / cm 2.

The hydrogen-ion conductive polymer electrolyte membrane was prepared by treating Nafion 115 of Dupont with hydrogen peroxide and sulfuric acid to remove organic substances on the surface and to replace sodium ions in the Nafion functional group with hydrogen ions.

The prepared anode and cathode electrodes were cut to a size of 5 cm and 5 cm, and the prepared hydrogen ion conductive electrolyte membrane was cut to a size of 7 cm and 7 cm. The anode catalyst layer and the cathode catalyst layer were placed in contact with the hydrogen ion conductive electrolyte membrane, and then pressurized at 100 kg _f / cm 2 at a temperature of about 140 ° C. to prepare a MEA.

The prepared MEA was mounted on a unit cell test jig, and a 2M aqueous methanol solution was supplied to the anode at a rate of 1 ml / min using a pump, and oxygen was supplied to the cathode at a rate of 1 l / min. Under an operating condition of 50 ° C, an electronic load was connected to the unit cell to measure the voltage drop according to the current density. The results are shown in FIG.

Example  2

MEA was prepared in the same manner as in Example 1, except that GDL was prepared in the composition shown in Table 1.

Example  3

MEA was prepared in the same manner as in Example 1, except that GDL was prepared in the composition shown in Table 1.

Example  4

MEA was prepared in the same manner as in Example 1, except that GDL was prepared in the composition shown in Table 1.

Example  5

MEA was prepared in the same manner as in Example 1, except that GDL was prepared in the composition shown in Table 1. The voltage drop according to the current density was measured by the method described in Example 1 using the prepared MEA. The results are shown in FIG.

Example  6-10

MEA was prepared in the same manner as in Example 1, except that GDL was prepared in the composition shown in Table 1.

Comparative example  One

1000 g of ultrapure water was added to 100 g of Cabot Corporation's Vulcan XC-72, mixed in a high speed mixer (2000 rpm), 10 g of dispersant Triton X-100 was added and dispersed for 1 hour, and 20 g of PTFE (Dupont, 30J) was added thereto. The carbon slurry composition obtained by adding and stirring for 1 hour with a low speed mixer (200 rpm) was coated on carbon paper (manufacturer: NOK, product number: H2315) having a thickness of 200 µm. The MEA was produced in the same manner as in Example 1, except that the entire resultant was heat-treated together to form GDL. The voltage drop according to the current density was measured by the method described in Example 1 using the prepared MEA. The results are shown in FIG.

Comparative example  2

Example 1, except that GDL was formed using the composition shown in Comparative Example 1 on a carbon felt (manufacturer: SGL, product number: 10AA) having a thickness of 390 µm impregnated with 5% PTFE. MEA was prepared in the same manner as in.

Comparative example  3

In the same manner as in Example 1, except that GDL was formed using the composition shown in Comparative Example 1 on a 290 탆 thick carbon fabric impregnated with 5% PTFE (manufacturer: Ballard, product number: HCB1071). MEA was prepared.

Carbon combination ratio in GDL (total content ratio of carbon in carbon and PTFE is 80% by weight) PTFE content (% by weight) Carbon substrate Example 1 50% by weight of carbon fiber MCMB 50% by weight Vulcan XC-72 20% by weight - 20 wt% none Example 2 50% by weight of carbon fiber MCMB 50% by weight 10% by weight of Vulcan XC-72 Super-P 10% by weight 20 wt% none Example 3 50% by weight of carbon fiber MCMB 50% by weight 10% by weight of Vulcan XC-72 Super-P 20 wt% 20 wt% none Example 4 50% by weight of carbon fiber Vulcan XC-72 60% by weight VGCF 10% by weight - 20 wt% none Example 5 50% by weight of carbon fiber Super-P 40 wt% 10% by weight of Vulcan XC-72 - 20 wt% none Example 6 50% by weight of carbon fiber Super-P 40 wt% Denka Black 10% by weight - 20 wt% none Example 7 50% by weight of carbon fiber Super-P 70 wt% Ketjen Black 10% by weight - 20 wt% none Example 8 50% by weight of carbon fiber Super-P 70 wt% 10% by weight of Vulcan XC-72 - 20 wt% none Example 9 MCMB 50% by weight Super-P 40 wt% VGCF 10% by weight - 20 wt% none Example 10 MCMB 50% by weight Super-P 40 wt% Denka Black 10% by weight - 20 wt% none Comparative Example 1 Vulcan XC-72 100% by weight 20 wt% Carbon paper Comparative Example 2 Vulcan XC-72 100% by weight 20 wt% Carbon fiber nonwoven fabric Comparative Example 3 Vulcan XC-72 100% by weight 20 wt% Carbon fiber fabric

Table 2 summarizes the various physical property values obtained for the MEA obtained in Examples 1-10 and Comparative Examples 1-3.

In Table 2, various physical property values were measured as follows.

Thickness measurement

The thickness of the GDL and carbon substrate was measured by a universal testing machine at a pressure of 20 kPa using the conditions and methods specified in ASTM D645.

Penetration resistivity

Penetration resistivity was measured using a voltmeter and ammeter at a pressure of 600 kPa with a universal tester using the conditions and methods specified in ASTM C611.

Per unit area Carbon loading amount

This was made using a condition and the method specified in ASTM D646 and the specimen was made of 5cm in width and length and measured using a balance.

Average pore size

This was measured using a PMI capillary flow porometer using the conditions and methods specified in ASTM D737.

GDL thickness (㎛) Carbon loading amount per unit area (mg / ㎠) Through-plane Resistivity (mΩcm) Average pore size (㎛) Carbon substrate thickness (㎛) Example 1 200 12 11 6 - Example 2 200 13 13 8 - Example 3 200 15 11 5 - Example 4 200 6 9 10 - Example 5 200 10 12 12 - Example 6 200 10 11 11 - Example 7 200 12 8 5 - Example 8 200 12 9 6 - Example 9 200 14 10 8 - Example 10 200 13 12 7 - Comparative Example 1 240 2.5 20 3 190 Comparative Example 2 420 4.7 25 7 390 Comparative Example 3 360 4.5 28 10 290

In Table 2, GDL thickness of Comparative Examples 1-3 is a sum of carbon base material / MPL, and carbon loading amount per unit area is a value only MPL. Through-plane resistivity and average pore size are measured for GDL.

The thickness of the GDL of Examples 1 to 10 was prepared to evaluate to 200um, it can be manufactured in various thicknesses.

As the thickness of MPL increases, the carbon loading, such as carbon fiber and MCMB, increases and the carbon loading density increases. Referring to Table 2, since the GDL of Examples 1 to 10 is an integral structure without a carbon substrate, the penetration resistance of the electrode is very low, about 30 to 50% of Comparative Examples 1 to 3. In addition, since the pores were uniformly distributed in the cross-sectional direction of the GDL, the average pore size was similar to that of the carbon substrate.

5 to 7 are micrographs (magnification: 5x) of the surface of the GDL prepared for the anode electrode in Examples 1, 4, and 8, respectively. 8 to 10 show surface photographs of GDLs (magnification: 40 times) prepared for the anode electrodes in Comparative Examples 1, 2, and 3, respectively.

As shown in Figs. 5-7, the GDLs of Examples 1, 4, and 8 according to the present invention show a completely different surface of GDL according to various carbon combinations, but in any case, it has a smooth surface. have. As shown in Figs. 8-10, in Comparative Examples 1, 2, and 3, since the same slurry was coated on different carbon substrates, it can be seen that the skeleton of the substrate appeared partially and had an uneven surface.

FIG. 11 is a voltage drop curve of the membrane electrode assembly MEA according to Examples 1 and 5 and Comparative Example 1. FIG.

As shown in Figure 11, it can be seen that the degree of voltage drop with increasing current density in Examples 1 and 5 is gentler than that of Comparative Example 1. The gentle slope of the voltage drop curve means that the polymer electrolyte membrane fuel cell according to the present invention can respond to load variations more efficiently. In addition, it can be seen that the maximum current density in Examples 1 and 5 is larger than in Comparative Example 1. The improvement of the maximum current density is indicated by the improvement of the maximum value of the supply power.

As described above, in the case of the MEA manufactured by using the integrated GDL of the present invention, it can be seen that the performance of the fuel cell can be improved because the interface resistance is small, the electrical conductivity of the GDL is high, and the pore distribution is uniform.

As described above, the electrode and the fuel cell employing the integrated GDL in which the carbon substrate and the MPL are integrated according to the present invention can greatly reduce the manufacturing cost and above all, and do not include the carbon substrate. Eliminate bottlenecks and contact resistance to mass transfer at the interface As a result, the electrode and the fuel cell according to the present invention can ensure smooth access and uniform electron conductivity of the fuel and the reactor body to the catalyst layer. In addition, the surface of the MPL as well as macrocracks as well as microcracks are not formed at all, so that the pores are regularly distributed and can improve the utilization of the catalyst. Therefore, the electrode and the fuel cell employing the GDL according to the present invention can exhibit uniform electrical characteristics.

The carbon slurry composition of the present invention is not limited to the GDL of a polymer fuel cell, and by using the principles of the present invention, it is applied to various types of fuel cells using GDL such as a phosphoric acid fuel cell, a formic acid fuel cell, and a dimethyl ether fuel cell. This is possible.

Claims (11)

A gas diffusion layer comprising only a microporous layer that does not include a carbon substrate and contains a carbon powder and a fluororesin that is melted without carbonization in the temperature range of 250 to 400 ° C. to impart a binding force, The carbon powder comprises a) a skeleton-maintaining carbon powder component having a self-supporting particle diameter of 0.1 µm or more, and b) an electrically conductive carbon powder component having an electrical resistivity of 1 Ωcm or less. A mixture comprising 20 to 80 parts by weight of the electrically conductive carbon powder component of b) based on 100 parts by weight of the skeletal maintenance component; Or carbon powder having a particle diameter of 0.1 µm or more and an electrical resistivity of 1 Ωcm or less, The weight ratio of the carbon powder: fluorinated resin is 60 to 95% by weight carbon powder: 5 to 40% by weight of the fluorinated resin gas diffusion layer. delete The method of claim 1, wherein the carbon powder is activated carbon, carbon black, acetylene black, ketene black, carbon whisker, carbon fiber, activated carbon fiber, vapor growth carbon fiber, carbon aerosol, carbon nanotube, carbon nanofiber, carbon nano Gas diffusion layer, characterized in that at least one selected from the group consisting of carbon nanohorn, natural or synthetic graphite (graphite). The method of claim 1, wherein the fluorinated resin is polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), poly Gas diffusion layer, characterized in that at least one selected from the group consisting of chlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE) and polyfluorovinylidene (PVDF). delete delete The gas diffusion layer according to claim 1, wherein the microporous layer has a thickness of 50 to 1000 µm. An electrode comprising the gas diffusion layer of any one of claims 1, 3, 4 or 7 and a catalyst layer laminated on the gas diffusion layer. A membrane electrode assembly (MEA) comprising a gas diffusion layer of any one of claims 1, 3, 4 or 7, a catalyst layer stacked on the gas diffusion layer and a polymer electrolyte membrane (PEM) stacked on the catalyst layer. . A fuel cell comprising the gas diffusion layer of any one of claims 1, 3, 4 or 7 and a catalyst layer stacked on the gas diffusion layer. To prepare a carbon slurry composition comprising a carbon powder, a dispersant, a polymer resin that can be carbonized in an air or oxygen atmosphere at a temperature of 250 to 400 ℃ and a fluorinated resin that is not carbonized in the temperature range to give a binding force step; Coating the carbon slurry composition on a substrate and then drying to form a microporous precursor layer; After peeling off and removing the substrate, the microporous precursor layer is heat treated in an air or oxygen atmosphere at 250 to 400 ° C. to carbonize or decompose the dispersant and the polymer resin, thereby removing the carbon powder and the 250 to 400 ° C. Obtaining a gas diffusion layer consisting of only a microporous layer containing a fluorinated resin that is not carbonized in the temperature range and melts to impart a binding force,  The carbon powder comprises a) a skeleton-maintaining carbon powder component having a self-supporting particle diameter of 0.1 µm or more, and b) an electrically conductive carbon powder component having an electrical resistivity of 1 Ωcm or less. A mixture comprising 20 to 80 parts by weight of the electrically conductive carbon powder component of b) based on 100 parts by weight of the skeleton-maintaining carbon powder component; or A method for producing a gas diffusion layer, wherein the particle diameter is at least 0.1 μm and the electrical resistivity is at most 1 Ωcm.

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