KR102957230B1 - Composition for fuel cell electrode and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a composition for forming a fuel cell electrode comprising a catalyst including a carrier and metal particles supported on the carrier, a dispersant, and an ionomer, wherein the dispersant comprises an amine compound, and a method for manufacturing the same.

Description

Composition for forming a fuel cell electrode and method of manufacturing the same

The present invention relates to a composition for forming a fuel cell electrode and a method for manufacturing the same. More specifically, the invention relates to a composition for forming a fuel cell electrode and a method for manufacturing the same, which can improve the performance and durability of a fuel cell electrode by introducing a volatile dispersant that can be easily removed during the electrode manufacturing process without a separate additional process, while simultaneously improving the dispersibility of a catalyst included in the composition for forming the electrode.

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained within hydrocarbon-based substances, such as methanol, ethanol, and natural gas, into electrical energy. A representative example of such a fuel cell is the Polymer Electrolyte Membrane Fuel Cell (PEMFC). PEMFCs are gaining attention as a next-generation energy source, and active research for commercialization is underway, particularly in the automotive sector, due to advantages such as their eco-friendly image.

In the above fuel cell system, the membrane electrode assembly (MEA) that substantially generates electricity has a structure in which an anode electrode (also known as the fuel electrode or oxidation electrode) and a cathode electrode (also known as the air electrode or reduction electrode) are positioned with a polymer electrolyte membrane containing a hydrogen ion-conducting polymer in between. Each electrode is composed of a catalyst, an ionomer, a solvent, and additives, and among these components, the catalyst is a major factor determining the activity and durability of the fuel cell.

Pt/C catalysts, which support platinum nanoparticles on a carbon support with a large specific surface area and excellent electrical conductivity, are the most widely used catalysts for oxidation and reduction electrodes. However, Pt/C catalysts are manufactured using pure platinum, an expensive metal, which is a major cause of the increase in catalyst costs. Furthermore, the overpotential generated by the formation of platinum oxides through the adsorption of oxygen on the platinum surface due to the oxygen reduction reaction at the reduction electrode causes an energy loss of approximately 30%, which is a major cause of delaying commercialization.

In addition, as the need for increased durability is required in conjunction with the recent requirements for transportation fuel cells, the above catalyst utilizes highly crystalline carbon such as graphitized carbon, carbon nanotubes, and graphene as a support to enhance durability. However, even in this case, the aggregation of the catalyst particles or their detachment from the support becomes a problem when the fuel cell is operated. This is fundamentally caused by the thermodynamic characteristics of the catalyst, such as platinum, dissolving via oxygen species, and is caused by the aggregation of platinum particles and the corrosion of the carbon support.

The objective of the present invention is to provide a composition for forming a fuel cell electrode that can improve the performance and durability of a fuel cell electrode and a fuel cell including the same by improving the dispersion of the catalyst within the electrode.

Another objective of the present invention is to provide a method for manufacturing the composition for forming the fuel cell electrode.

One embodiment of the present invention provides a composition for forming a fuel cell electrode comprising a catalyst including a carrier and metal particles supported on the carrier, a dispersant, and an ionomer, wherein the dispersant comprises an amine compound.

The above amine compound may have a boiling point of 150°C or lower.

The above amine compound may be any one selected from the group consisting of linear amine compounds, branched amine compounds, cyclic amine compounds, and combinations thereof.

The above amine compound may be propylamine, butylamine, triethylamine, tetramethylethylenediamine, pyrrolidine, piperidine, pyrrole, pyridine, pyrimidine, or a combination thereof.

The above amine compound may be a cyclic amine compound.

The mass ratio of the catalyst and the dispersant in the above electrode-forming composition may be 1:0.1 to 1:10.

The above carrier may be any one selected from the group consisting of graphite, Denka black, Ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs, activated carbon, and combinations thereof.

The metal particles may be any one selected from the group consisting of platinum, ruthenium, osmium, platinum-M alloy (wherein M is any one transition metal selected from the group consisting of Pd, Ir, Os, Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru and alloys thereof) and mixtures thereof.

The above ionomer may be any one selected from the group consisting of fluorinated polymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyphenylene sulfide polymers, polysulfone polymers, polyethersulfone polymers, polyetherketone polymers, polyether-etherketone polymers, polyphenylquinoxaline polymers, and combinations thereof.

The above composition for forming a fuel cell electrode further comprises a solvent, and the solvent may be any one selected from the group consisting of water, methanol, ethanol, butanol, n-propanol, isopropanol, n-butyl acetate, ethylene glycol, dipropylene glycol, glycerol, and combinations thereof.

Another embodiment of the present invention provides a method for manufacturing an electrode for a fuel cell, comprising the steps of: preparing a catalyst by supporting metal particles on a carrier; preparing a composition for forming an electrode by adding the catalyst, a dispersant, and an ionomer to a solvent; and manufacturing an electrode by applying the composition for forming an electrode, wherein the dispersant comprises an amine compound.

The step of manufacturing the electrode may further include the step of drying the coated electrode-forming composition at a temperature of 60 to 100°C and then heat-treating it at 110 to 200°C.

The step of preparing the above electrode-forming composition may further include the step of preparing a mixture by adding the catalyst, dispersant, and ionomer to a solvent, and dispersing the prepared mixture by selecting from the group consisting of an ultrasonic grinder, a homomixer, a 3-roll mill, a resonant acoustic mixer, a paste mixer, a stirrer, a high-shear disperser, and combinations thereof. However, the technical concept of the present invention is not limited thereto, and various dispersion methods may be used.

According to the present invention, the catalytic dispersibility within a composition for forming a fuel cell electrode can be improved by introducing a volatile dispersant with a low molecular weight and boiling point, and the dispersant has a relatively small molecular size and low intrinsic resistance, which is advantageous for forming an ion conduction network within the fuel cell electrode.

In addition, since the dispersant included in the composition can be easily removed during the drying and heat treatment processes when forming an electrode using the above-mentioned fuel cell electrode forming composition, the performance and durability of the fuel cell electrode and fuel cell manufactured thereby can be improved.

FIG. 1 is a schematic cross-sectional view of a membrane-electrode assembly according to one embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating the overall configuration of a fuel cell according to one embodiment of the present invention.
Figure 3 is a photograph showing the results of the dispersibility evaluation of the electrode forming composition according to Experimental Evaluation Example 1.
Figure 4 is an optical microscope image of the surface of an electrode prepared using the compositions of Comparative Example and Examples 1 to 4 according to Experimental Evaluation Example 2.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

In the drawings, thicknesses have been enlarged to clearly represent various layers and regions, and the same reference numerals have been used for similar parts throughout the specification. When a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between. Conversely, when a part is described as being "immediately on" another part, it means that there is no other part in between.

A composition for forming a fuel cell electrode according to one embodiment is described below.

The present invention relates to a composition for forming a fuel cell electrode that can improve the performance and durability of a fuel cell electrode and a fuel cell including the same by improving the dispersion of catalyst within the electrode.

Specifically, a composition for forming a fuel cell electrode according to one embodiment comprises a catalyst comprising a carrier and metal particles supported on the carrier, a dispersant, and an ionomer, and in particular, the dispersant comprises an amine compound.

Typically, in the process of manufacturing fuel cell electrodes, a catalyst is supported on a carbon material carrier and dispersed. At this time, the method of dispersing the carbon material carrier supported with the catalyst can be broadly classified into a physical dispersion method using various dispersion equipment, such as ultrasonic dispersion devices, by applying strong energy, and a chemical dispersion method using a separate dispersant to induce chemical bonding with the carrier.

However, although the above chemical dispersion method using a dispersant can ensure high dispersibility and dispersion stability of the catalyst-supported carrier compared to the physical dispersion method, in most cases, the molecular weight of the dispersant is high, making it difficult to remove, and as the contact resistance between carbon materials increases due to the inherent resistance of the dispersant, it acts as a defect in the ion conduction network of the fuel cell, which can ultimately degrade the performance of the fuel cell.

In this regard, the composition for forming a fuel cell electrode according to the present invention has the advantage of improving the dispersibility of the catalyst within the composition and facilitating the formation of an ion conduction network within the fuel cell electrode by introducing an amine compound as a volatile dispersant with a low molecular weight and boiling point, while dispersing a carbon material carrier supported with a catalyst using a chemical dispersion method during the process of forming a fuel cell electrode. Furthermore, since the dispersant included in the composition can be easily removed during the electrode drying and heat treatment processes after coating the electrode using the composition for forming a fuel cell electrode, the performance and durability of the fuel cell electrode and fuel cell manufactured thereby can be improved.

According to one embodiment, the amine compound may have a boiling point of 150°C or lower, preferably 130°C or lower. Since the amine compound is used as a volatile dispersant, it is desirable that it be liquid at room temperature and easy to remove. Therefore, it is desirable to use an amine compound with an upper limit of the boiling point of the aforementioned value, for example, 150°C. If the boiling point exceeds 150°C, it is difficult to remove, which may be detrimental to the performance and durability of the fuel cell due to increased resistance to mass transfer and charge transfer.

In one embodiment, the amine compound may be any one selected from the group consisting of linear, branched, cyclic, and combinations thereof, and specifically, the linear or branched amine compound may be an aliphatic amine compound, and the cyclic amine compound may be an alicyclic amine compound or an aromatic amine compound.

Specifically, the linear amine compound may refer to a structure in which a linear alkyl group is connected to a nitrogen atom included in the amine compound, and, for example, may be an alkyl amine in which a linear alkyl group having 1 to 30 carbon atoms is connected. The linear amine compound may include primary amine compounds, secondary amine compounds, and tertiary amine compounds depending on the number of linear alkyl groups connected to the nitrogen atom of the amine compound.

The above branched amine compound refers to a structure in which a branched alkyl group is connected to the nitrogen atom of the amine compound, and, for example, may be an alkyl amine connected to a branched alkyl group having 1 to 30 carbon atoms. The above branched amine compound may also include all primary to tertiary amine compounds, just like the above straight-chain amine compound.

The above-mentioned cyclic amine compound may mean that a straight-chain or branched-chain substituent included in the amine compound is bonded to a nitrogen atom to form a ring shape, and may include, for example, a straight-chain or branched-chain alkyl group having 1 to 30 carbon atoms connected to a nitrogen atom of the amine compound to form a ring shape.

The above amine compound may include two or more nitrogen atoms in its molecular structure, a structure in which the two or more nitrogen atoms are directly connected by a single bond, or a structure in which they are connected by an alkylene group having 1 to 10 carbon atoms.

In addition, the above amine compound may include atoms such as oxygen and phosphorus in addition to nitrogen atoms included in the molecular structure.

In one embodiment, the amine compound may include propylamine (boiling point 87°C), butylamine (boiling point 78°C), triethylamine (boiling point 89°C), tetramethylethylenediamine (boiling point 121°C), pyrrolidine (boiling point 89°C), piperidine (boiling point 106°C), pyrrole (boiling point 129°C), pyridine (boiling point 115°C), pyrimidine (boiling point 123°C), or a combination thereof. According to one embodiment, pyridine, butylamine, triethylamine, tetramethylethylenediamine, or a combination thereof may be used as the amine compound, considering the process of forming a fuel cell ion conduction network, which can be easily volatilized through drying and heat treatment processes.

In one embodiment, the amine compound is preferably a cyclic amine compound, particularly a heterocyclic compound having 5 to 10 atoms containing 1 or 2 nitrogen atoms as heteroatoms, such as pyrrole, pyridine, pyrimidine, etc. Here, the heterocyclic compound may not be substituted with other substituents. By using the heterocyclic compound as a dispersant, excellent effects can be exhibited in pore characteristics such as the pore distribution and porosity of the electrode, or in fuel cell performance.

In one embodiment, the amine compound may be a cyclic amine compound having a boiling point of 150°C or lower.

In one embodiment, the mass ratio of the catalyst to the dispersant in the fuel cell electrode forming composition may be 1:0.1 to 1:10, preferably 1:0.3 to 1:5, and more preferably 1:0.5 to 1:3. If the mass ratio of the catalyst to the dispersant is less than 1:0.1, the dispersibility of the catalyst is not sufficiently ensured during the electrode forming process, which may lead to a decrease in the performance of the electrode; and if the mass ratio exceeds 1:10, the residual dispersant remaining after the drying and heat treatment steps may be adsorbed to the ionomer functional groups, which may significantly reduce electrical conductivity. Therefore, it is necessary to appropriately adjust the content within the above range.

In one embodiment, the carrier may be a carbon-based material comprising graphite, Denka black, Ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs, activated carbon, and combinations thereof. More specifically, the carbon-based carrier is most preferably selected from the group consisting of hollow carbon capsules (HCC), multimodal porous carbon (MPC), carbon nanotubes (CNT), carbon nanofibers (CNF), mesoporous carbon, graphene, high surface area high conductivity carbon black, and combinations thereof.

Any metal particle capable of participating in the reaction of a fuel cell and serving as a catalyst can be used, and specifically, a platinum-based catalyst can be used.

As the platinum-based catalyst, any metal particle selected from the group consisting of platinum, ruthenium, osmium, platinum-M alloy (wherein M is any one transition metal selected from the group consisting of Pd, Ir, Os, Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru and alloys thereof) and mixtures thereof may be used.

The anode electrode and the cathode electrode of the fuel cell may use the same material as a catalyst, but more specific examples of the platinum-based catalyst may be any one selected from the group consisting of Pt, Pt/Ru, Pt/W, Pt/Ni, Pt/Sn, Pt/Mo, Pt/Pd, Pt/Fe, Pt/Cr, Pt/Co, Pt/Ru/W, Pt/Ru/Mo, Pt/Ru/V, Pt/Fe/Co, Pt/Ru/Rh/Ni, and Pt/Ru/Sn/W.

At this time, the metal particles may be located on the surface of the carrier, or they may penetrate into the carrier while filling the internal pores of the carrier.

Any polymer resin having a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphate groups, phosphonic acid groups, and derivatives thereof in a side chain can be used as the above ionomer.

In one embodiment, the ionomer may comprise one or more hydrogen ion-conducting polymers selected from fluorinated polymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyphenylene sulfide polymers, polysulfone polymers, polyethersulfone polymers, polyetherketone polymers, polyether-etherketone polymers, and polyphenylquinoxaline polymers; more specifically, the ionomer may comprise one or more hydrogen ion-conducting polymers selected from poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, sulfated polyetherketones, aryl ketones, poly(2,2'-m-phenylene)-5,5'-bibenzimidazole, and poly(2,5-benzimidazole). there is.

The above-described polymer resin having hydrogen ion conductivity may substitute H with Na, K, Li, Cs, or tetrabutylammonium at the cation exchange group at the end of the side chain. When substituting H with Na at the ion exchange group at the end of the side chain, NaOH is used during the preparation of the catalyst composition; when substituting with tetrabutylammonium, tetrabutylammonium hydroxide is used for substitution; K, Li, or Cs may also be substituted using appropriate compounds. Since the above substitution method is widely known in the art, a detailed description thereof is omitted in this specification.

The above ionomer may be included in an amount of 20 to 50 parts by weight based on 100 parts by weight of solid content in a composition for forming a fuel cell electrode, for example, in an amount of 25 to 40 parts by weight. If the content of the above ionomer is less than 20 parts by weight, problems may occur in the formation of an ion conduction network of the fuel cell electrode, which may lead to a decrease in performance, and if it exceeds 50 parts by weight, a decrease in pores within the electrode and a decrease in water drainage ability may lead to an increase in resistance, which may result in a decrease in performance.

The above ionomer can be used in the form of a single substance or a mixture, and may also be optionally used in combination with a non-conductive compound to further enhance adhesion to the polymer electrolyte membrane. It is preferable to adjust the amount used to suit the intended purpose.

One or more of the above-mentioned non-conductive compounds may be used, selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene/tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol.

In one embodiment, the composition for forming a fuel cell electrode may further include a solvent. The solvent may be any one selected from the group consisting of water, methanol, ethanol, butanol, n-propanol, isopropanol, n-butyl acetate, ethylene glycol, dipropylene glycol, glycerol, and combinations thereof, and is not limited to any type as long as it is included in the composition for forming a fuel cell electrode and can effectively disperse the catalyst.

The above solvent may be included in an amount of 50 to 95 parts by weight based on 100 parts by weight of the composition for forming a fuel cell electrode, for example, in an amount of 80 to 90 parts by weight. If the content of the solvent is 50 parts by weight or more, it prevents the viscosity of the catalyst composition from becoming too high, thereby preventing a decrease in the dispersion of catalyst particles and uneven formation of the catalyst layer. If the content of the solvent is 95 parts by weight or less, it prevents the viscosity of the catalyst composition from becoming too low, thereby preventing the problem of the catalyst layer being thin and requiring repeated coating.

Another embodiment of the present invention provides a method for manufacturing an electrode for a fuel cell, comprising the steps of: preparing a catalyst by supporting metal particles on a carrier; preparing a composition for forming an electrode by adding the catalyst, a dispersant, and an ionomer to a solvent; and manufacturing an electrode by applying the composition for forming an electrode, wherein the dispersant comprises an amine compound.

In the step of preparing the catalyst, the catalyst may be prepared by any one reduction method selected from the group consisting of polyol reduction, electron beam reduction, sodium borohydride ( _NaBH4 ) reduction, and urea-assisted homogeneous reduction.

In the step of preparing the electrode-forming composition, the prepared catalyst is added to a solvent together with a dispersant and an ionomer, mixed, and dispersed to prepare the electrode-forming composition. The mixing and dispersion step may be performed by selecting from the group consisting of an ultrasonic grinder, a homomixer, a 3-roll mill, a resonant acoustic mixer, a paste mixer, a stirrer, a high-shear disperser, and combinations thereof.

Any method capable of uniformly dispersing the above catalyst, dispersant, and ionomer may be used without limitation.

The description of the metal particles and carrier included in the catalyst, and the ionomer and dispersant, is as described above.

As described above, since a composition for forming a fuel cell electrode is prepared by mixing a catalyst supported with metal particles and an ionomer together with a dispersant containing an amine compound, the catalyst can be uniformly distributed on the electrode.

Finally, the electrode is manufactured by applying the above electrode-forming composition.

Depending on the viscosity of the electrode forming composition, the coating process described above may utilize a screen printing method, a spray coating method, a coating method using a doctor blade, a spray coating method, etc., but the present invention is not limited thereto.

In addition, the electrode may be applied with a thickness of 1 to 100 μm. If the thickness is less than 1 μm, the reaction area may be small and activity may decrease, and if it exceeds 100 μm, the travel distance of ions and electrons may increase and resistance may increase.

Meanwhile, after applying the electrode-forming composition, the electrode-forming composition may be dried to evaporate the solvent, and then heat-treated to remove the dispersant. The drying process may be performed at 60 to 100°C for 8 hours or more. This is not limited to the above conditions and may vary depending on the solvent composition in the electrode-forming composition. If the drying temperature is below 60°C, the evaporation of the solvent is not smooth, so a sufficiently dried electrode may not be formed; if it exceeds 100°C, there may be a risk of catalyst ignition and cracking of the electrode may occur. It is preferable to select the drying time under conditions where the solvent in the electrode layer can evaporate sufficiently. In addition, the heat treatment may be performed at 110 to 200°C for 1 to 4 hours. At this time, it should be noted that if the heat treatment is below 110°C, residual dispersant may be adsorbed to the functional groups of the ionomer, causing a decrease in conductivity, and if it exceeds 200°C, the functional groups of the ionomer may be damaged, and that the temperature and time conditions that can affect the functional groups may vary depending on the type of ionomer used.

According to another embodiment of the present invention, a membrane-electrode assembly for a fuel cell is provided, comprising an electrode prepared from the composition for forming the fuel cell electrode.

FIG. 1 is a cross-sectional view schematically illustrating the membrane-electrode assembly. Hereinafter, the membrane-electrode assembly will be described with reference to FIG. 1.

The above membrane-electrode assembly (150) comprises an anode electrode (110) and a cathode electrode (110) positioned opposite each other; and a polymer electrolyte membrane (130) positioned between the anode electrode (110) and the cathode electrode (110). In the above membrane-electrode assembly (150), the electrode disposed on one side of the polymer electrolyte membrane (130) and causing an oxidation reaction that generates hydrogen ions and electrons from fuel is called the anode electrode (110), and the electrode causing a reduction reaction that generates water from hydrogen ions supplied through the polymer electrolyte membrane (130) and the oxidizing agent of the electrode is called the cathode electrode (110).

At least one of the anode electrode (110) and the cathode electrode (110) is used as the electrode for the fuel cell of the present invention as described above.

The polymer electrolyte membrane (130) is a solid polymer electrolyte with a thickness of 10 to 200 μm and has the function of ion exchange for moving hydrogen ions generated at the anode electrode (110) to the cathode electrode (110).

The above polymer electrolyte membrane (130) may be a hydrocarbon-based polymer electrolyte membrane, a fluorine-based polymer electrolyte membrane, and a mixture or copolymer of one or more of these.

The above hydrocarbon-based polymer electrolyte membrane may include a hydrocarbon-based polymer, and the polymer may be selected from styrene, imide, sulfone, phosphazene, ether-ether ketone, ethylene oxide, polyphenylene sulfide, or homopolymers or copolymers of aromatic groups and derivatives thereof, and these polymers may be used alone or in combination. Manufacturing an electrolyte membrane using a hydrocarbon-based polymer is cheaper and easier to manufacture than using a fluorine-based polymer, and exhibits high ionic conductivity.

More preferably, one or more selected from the group consisting of sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherketone, sulfonated polyetheretherketone, sulfonated polyaryrene ether ether ketone, sulfonated polyaryrene ether ether ketone, sulfonated polyaryrene ether sulfone, sulfonated polyaryrene ether benzimidazole, and a membrane into which an ion conductor has been introduced may be used as the suitable hydrocarbon membrane.

The above-mentioned fluorine-based polymer electrolyte membrane can be used without special limitations as long as it is a material having sufficient mechanical strength and high electrochemical stability to form a film as an ion-conducting membrane. Specific examples of fluorine-based polymer electrolyte membranes include perfluorosulfonic acid resin and copolymers of tetrafluoroethylene and fluorovinyl ether. The fluorovinyl ether moiety has the function of conducting hydrogen ions. The above-mentioned copolymer is commercially available as it is sold by DuPont under the trade name Nafion.

Meanwhile, the membrane-electrode assembly (150) may further include an interfacial adhesive layer (not shown) located between the polymer electrolyte membrane (130) and the electrode (110).

The above interface adhesive layer enables the membrane-electrode assembly (150) to have low hydrogen permeability without a decrease in hydrogen ion conductivity, improves the interfacial bonding between the electrode (110) and the polymer electrolyte membrane (130), thereby improving the durability of the membrane-electrode assembly (150) and improving the performance and durability of the membrane-electrode assembly (150) under high temperature/low humidity conditions. The above interface adhesive layer may be located on only one side of the polymer electrolyte membrane (130).

According to another embodiment of the present invention, a fuel cell comprising the membrane-electrode assembly is provided. FIG. 2 is a schematic diagram illustrating the overall configuration of the fuel cell.

Referring to FIG. 2 above, the fuel cell (200) includes a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reforming unit (220) that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack (230) that generates electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizing agent supply unit (240) that supplies an oxidizing agent to the reforming unit (220) and the stack (230).

The stack (230) comprises a plurality of unit cells that generate electrical energy by inducing an oxidation/reduction reaction between a reforming gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizing agent supplied from the oxidizing agent supply unit (240).

Each unit cell refers to a unit cell that generates electricity and includes a membrane-electrode assembly that oxidizes/reduces oxygen in an oxidant and a reforming gas containing hydrogen gas, and a separator (also called a bipolar plate, hereinafter referred to as a 'separator') for supplying the reforming gas containing hydrogen gas and the oxidant to the membrane-electrode assembly. The separator is positioned on both sides of the membrane-electrode assembly with the membrane-electrode assembly at the center. At this time, the separator located at the outermost side of the stack is specifically referred to as an end plate.

Among the above separator plates, the end plate is provided with a pipe-shaped first supply pipe (231) for injecting a reforming gas containing hydrogen gas supplied from the reforming unit (220) and a pipe-shaped second supply pipe (232) for injecting oxygen gas, and the other end plate is provided with a first discharge pipe (233) for discharging to the outside a reforming gas containing hydrogen gas that is finally unreacted and remaining in a plurality of unit cells, and a second discharge pipe (234) for discharging to the outside an oxidizing agent that is finally unreacted and remaining in the above unit cells.

Specific embodiments of the present invention are presented below. However, the embodiments described below are merely for the purpose of specifically illustrating or explaining the present invention and do not limit the present invention. Furthermore, details not described herein can be sufficiently technically inferred by a person skilled in the art, so their description is omitted.

[Preparation Example: Preparation of a composition for forming a fuel cell electrode]

Example 1

5 g of Pt/CB (Tanaka, TEC10E50E) as a catalyst, 10 g of Nafion D2021 (Dupont), a perfluorosulfonic acid polymer, as an ionomer, and 3 g of pyridine (boiling point 115°C) as a dispersant were mixed with 30 g of a solvent prepared by mixing dipropylene glycol and distilled water in a 1:1 ratio, and the catalyst, ionomer, and dispersant were mixed sufficiently for 1 hour using a 3-roll mill (EXAKT 50) so that they could be uniformly dispersed to prepare a composition for forming a fuel cell electrode.

Example 2

A composition for forming a fuel cell electrode was prepared in the same manner as in Example 1, except that 3 g of butylamine (boiling point 78°C) was used instead of pyridine in Example 1.

Example 3

A composition for forming a fuel cell electrode was prepared in the same manner as in Example 1, except that 3 g of triethylamine (boiling point 89°C) was used instead of pyridine in Example 1.

Example 4

A composition for forming a fuel cell electrode was prepared in the same manner as in Example 1, except that 3 g of tetramethylethylenediamine (boiling point 121°C) was used instead of pyridine in Example 1.

Comparative Example 1

A composition for forming a fuel cell electrode was prepared in the same manner as in Example 1, except that no dispersant was added in Example 1.

[Preparation of Membrane-Electrode Assembly Example]

The compositions for forming fuel cell electrodes prepared in Examples 1 to 4 and Comparative Example 1 were bar-coated onto a fluorinated ethylene propylene release film under conditions of a coating speed of 10 mm/s and a coating thickness of 100 μm, then dried at 60°C for 8 hours, and then heat-treated at 150°C for 2 hours to produce electrodes.

The above dried electrode was cut to the required size, aligned so that the electrode surface and the electrolyte membrane were in contact on both sides of a polymer electrolyte membrane (DuPont product; Nafion 212 Membrane), and then transferred by hot pressing under heat and pressure conditions of 140°C and 1 MPa for 5 minutes, followed by maintaining at room temperature for 1 minute, and the release film was peeled off to manufacture a membrane-electrode assembly.

[Experimental Evaluation Example: Performance Evaluation of Membrane-Electrode Assembly]

Experimental Evaluation Example 1 : Comparison of variance stability

0.1g of catalyst, 2g of water, 0.2g of ionomer (Nafion D2021), and 0.2g of dispersant were mixed, dispersed by ultrasound for 5 minutes, and then left at room temperature for 24 hours. Afterward, the dispersibility of each composition was observed visually, and the results are shown in Fig. 3. From Fig. 3, it can be confirmed that in the compositions of Examples 1 to 4, in which the dispersant was added, the aggregation of the carbon-based catalyst was significantly reduced and the dispersibility was well maintained. In contrast, in Comparative Example 1, the catalyst precipitated to form a transparent supernatant.

Experimental Evaluation Example 2 : Comparison of the coating surface condition of the electrode layer

Electrodes were prepared in the same manner as in the preparation example using the compositions of Comparative Example and Examples 1 to 4, and the surface of the electrode layer coated on the release film was analyzed using an optical microscope (VHX-600) (x500x). Optical microscope images of the surface of each electrode are shown in Fig. 4. From Fig. 4, it can be confirmed that the surface is smooth when the composition of the example according to the present invention is used.

Experimental Evaluation Example 3 : Comparison of electrode pore diameter and porosity

The pore diameter and porosity of electrodes prepared using the compositions prepared in Comparative Example and Examples 1 to 4 were compared via Mercury Porosity Measurement (MIP). Specifically, using an Autopore 9605 system, electrode layer samples of 1 x 5 cm ^{and 2} x 10 EA were introduced to analyze and measure the average pore diameter and porosity. Only data with a pore diameter of 5 μm or less were used. The results are shown in Table 1 below.

Average pore diameter (nm) Porosity (%) Comparative Example 1 41.11 37.84 Example 1 52.42 41.67 Example 2 49.85 39.92 Example 3 49.25 39.36 Example 4 46.47 38.58

From Table 1 above, it can be seen that the average pore diameter and porosity of the electrode layer increased when the dispersant according to the present invention was added. In particular, the best average pore diameter and porosity were observed in Example 1, which used pyridine, a cyclic amine compound, rather than in Example 2, which used butylamine, the dispersant with the lowest boiling point among the examples.

Experimental Evaluation Example 4 : Comparison of fuel cell performance, electrochemical active area, and charge transfer resistance

The output performance of the membrane-electrode assembly prepared in the preparation example was evaluated through I-V measurement. Specifically, to verify the output performance under actual fuel cell operating conditions, hydrogen (100 %RH) and air (100 %RH) were supplied to the anode and cathode, respectively, at amounts corresponding to Stoichiometry 1.2/2.0 under conditions of 65°C using a fuel cell unit cell evaluation device (Scribner 850 fuel cell test system). The current density was measured at a voltage of 0.6V, and a higher result value indicates superior output performance.

An electrochemical analyzer (Biologic SP-200) was used to verify the electrochemical active area and charge transfer resistance. The charge transfer resistance was tested at a frequency range of 0.1 Hz to 10 kHz and a current density of 600 mA/ ^cm² under the same temperature and fuel supply conditions as the output performance evaluation. For the measurement of the electrochemical active area (ECSA), a CV experiment was performed at a scan rate of 50 mV/s under conditions of 65°C, with hydrogen (100 %RH) and nitrogen (100 %RH) supplied to the anode and cathode, respectively, in amounts corresponding to Stoichiometry 1.2/2.0, and the Pt desorption area was calculated.

The results of the above experiment are shown in Table 2 below.

Battery Performance Evaluation (A/ ^cm² ) Catalytic active area ( ^m² /g _pt ) Charge transfer resistance Comparative Example 1 1.35 38.1 0.0471 Example 1 1.55 43.7 0.0428 Example 2 1.51 42.6 0.0439 Example 3 1.48 41.8 0.0445 Example 4 1.41 39.8 0.0458

From Table 2 above, it was confirmed that when the dispersant according to the present invention was added, the battery performance and catalytic active area increased, and the charge transfer resistance decreased. Similar to the porosity results mentioned earlier, the best performance was confirmed in Example 1, which used pyridine, a cyclic amine compound, rather than Example 2, which used butylamine, the dispersant with the lowest boiling point among the examples.

Although preferred embodiments of the present invention have been described in detail above, the above-described embodiments are presented as specific examples of the present invention and are not intended to limit the present invention. Furthermore, various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the claims set forth below also fall within the scope of the present invention.

110: Anode electrode and cathode electrode
130: Polymer electrolyte membrane
150: Membrane-electrode assembly
200: Fuel cell
210: Fuel supply unit 220: Reforming unit
230: Stack 231: First Supply Pipe
232: Second supply pipe 233: First discharge pipe
234: Second discharge pipe 240: Oxidizer supply unit

Claims (13)

A composition for forming fuel cell electrodes,
A catalyst comprising a carrier and metal particles supported on the carrier,
Dispersant, and
Includes ionomer,
The above dispersant includes an amine compound, and
The above amine compound includes pyridine, and
The above dispersant is one in which the mass ratio of the catalyst to the dispersant in the fuel cell electrode forming composition is 1:0.1 to 1:10.
Composition for forming fuel cell electrodes. In paragraph 1,
The above amine compound is one having a boiling point of 150°C or lower,
Composition for forming fuel cell electrodes. delete In paragraph 1,
The above amine compound further comprises propylamine, butylamine, triethylamine, tetramethylethylenediamine, pyrrolidine, piperidine, pyrrole, pyrimidine, or a combination thereof,
Composition for forming fuel cell electrodes. delete delete In paragraph 1,
The above carrier is any one selected from the group consisting of graphite, Denka black, Ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs, activated carbon, and combinations thereof.
Composition for forming fuel cell electrodes. In paragraph 1,
The metal particles are any one selected from the group consisting of platinum, ruthenium, osmium, platinum-M alloy (wherein M is any one transition metal selected from the group consisting of Pd, Ir, Os, Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru and alloys thereof), and mixtures thereof.
Composition for forming fuel cell electrodes. In paragraph 1,
The above ionomer is any one selected from the group consisting of fluorinated polymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyphenylene sulfide polymers, polysulfone polymers, polyethersulfone polymers, polyetherketone polymers, polyether-etherketone polymers, polyphenylquinoxaline polymers, and combinations thereof.
Composition for forming fuel cell electrodes. In paragraph 1,
The solvent further comprises a solvent, wherein the solvent is any one selected from the group consisting of water, methanol, ethanol, butanol, n-propanol, isopropanol, n-butyl acetate, ethylene glycol, dipropylene glycol, glycerol, and combinations thereof.
Composition for forming fuel cell electrodes. A step of preparing a catalyst by supporting metal particles on a support;
A step of preparing an electrode-forming composition by adding the above catalyst, dispersant, and ionomer to a solvent; and
The method includes the step of manufacturing an electrode by applying the above electrode-forming composition, and
The above dispersant includes an amine compound, and
The above amine compound includes pyridine, and
The above dispersant is one in which the mass ratio of the catalyst to the dispersant in the electrode-forming composition is 1:0.1 to 1:10,
Method for manufacturing an electrode for a fuel cell. In Paragraph 11,
The step of manufacturing the above electrode is,
The method further comprises the step of drying the above-described coated electrode-forming composition at a temperature of 60 to 100°C and heat-treating it at 110 to 200°C.
Method for manufacturing an electrode for a fuel cell. In Paragraph 11,
The step of preparing the above electrode-forming composition is:
The method further comprises the step of preparing a solution by adding the catalyst, dispersant, and ionomer to a solvent, and mixing the prepared solution using any one selected from the group consisting of an ultrasonic grinder, a homomixer, a 3-roll mill, a resonant acoustic mixer, a paste mixer, a stirrer, a high-shear disperser, and combinations thereof.
Method for manufacturing an electrode for a fuel cell.