KR20080048352A - Electrode for polymer electrolyte fuel cell with improved dispersibility, polymer electrolyte fuel cell comprising same and method for manufacturing same - Google Patents

Abstract

And a catalyst layer formed on the gas diffusion layer and the gas diffusion layer, wherein the catalyst layer includes an electrode catalyst and an electrode binder, and the electrode catalyst and the electrode binder are dispersed in a slurry by a surfactant in a slurry manufacturing step. To provide.

Description

Electrode for polymer electrolyte fuel cell with improved dispersibility, polymer electrolyte fuel cell comprising same and manufacturing method thereof {Electrode with Improved Dispersion for Polymer Electrolyte Fuel Cell, Polymer Electrolyte Fuel Cell comprising the Electrode, and Preparation method}

Figure 1 shows the performance of the membrane / electrode assembly prepared by Examples and Comparative Examples according to the present invention.

Figure 2 shows the surface microstructure of the electrode produced by the Example and Comparative Example according to the present invention.

3 is a general configuration diagram of a polymer electrolyte fuel cell.

The present invention relates to an electrode for a polymer electrolyte fuel cell, and more particularly, to a polymer electrolyte fuel cell electrode which improves electrochemical activity of an electrode by introducing a surfactant to improve the dispersibility of an electrode catalyst and a binder, and a polymer electrode including the same. A fuel cell and a method of manufacturing the same are provided.

Recently, as a variety of products have been developed due to the rapid development of information and communication technology, the rapid growth of technologies related to portable electronic devices such as mobile phones, notebook computers, personal digital assistants (PDAs), digital cameras, camcorders, and the like, has been made. The development of the technology related to the portable electronic device has emerged as a high functionalization of the portable electronic device to satisfy the preference of consumers who require more information. However, their high performance is constrained by long periods of continuous use due to a lot of energy consumption, and as a result, devices that supply energy have become a key technology element that determines the performance of electronic products. These technical demands are driving the active research and development of fuel cell technologies in many developed countries such as the United States and Japan.

A fuel cell is a device that converts chemical energy directly into electrical energy. The basic structure is composed of a catalyst-supported anode, an oxygen electrode, and a membrane / electrode assembly manufactured by placing an electrolyte membrane between two electrodes. In particular, the electrode that completes the electrochemical reaction through oxidation and reduction of fuel in the membrane / electrode assembly is one of the important components that greatly influence the performance of the fuel cell. Typically, the electrode for a polymer electrolyte fuel cell is prepared by applying a mixed slurry composed of a platinum catalyst, a hydrogen ion conductive electrolyte (electrode binder) and a solvent thereof to carbon fiber, which is an electrical conductor. Therefore, the technology of dispersing the nano-sized platinum catalyst and electrode binder in the manufacturing process will greatly influence the performance of the fuel cell. In other words, when the catalyst and the electrode binder are not satisfactorily dispersed, the aggregation is severe, making the three-phase interface in the catalyst layer difficult. This can greatly reduce not only the activity of the electrode but also the cell performance. As a result, in order to obtain improved cell performance, introduction of a new material for dispersing the electrode catalyst and the binder and a new electrode manufacturing method through the same are required.

On the other hand, there has been a study (US 6187467) in which a platinum catalyst and a perfluorinated hydrogen ion conductive polymer are dispersed in an alcohol solution as a related art. However, these studies did not lead to the alcohol solution inducing ideal dispersion of the platinum catalyst. In addition, when the perfluorinated polymer was introduced as the electrode binder, some dispersion was maintained by the alcohol solution, but when the electrode binder was introduced with a new polymer, for example, a hydrogen ion conductive hydrocarbon-based polymer electrolyte, the aggregation phenomenon in the electrode catalyst layer ( Aggregation occurs severely and it is difficult to induce an ideal dispersion state for maintaining the activity of the electrode. Therefore, in order to solve such a problem and to improve not only electrode activity but also cell performance, an electrode manufacturing method that can greatly improve the dispersing ability of the platinum catalyst and the electrode binder is urgently required.

The present invention has been made to solve the problems of the prior art as described above, the object of which is to improve the electrochemical activity of the electrode by improving the dispersibility of the electrode catalyst and binder, ultimately can improve the cell performance An electrode for a polymer electrolyte fuel cell is provided.

Another object of the present invention is to provide a membrane / electrode assembly for a polymer electrolyte fuel cell that can improve cell performance by improving the electrochemical activity of the electrode by improving the dispersibility of the electrode catalyst and the binder.

Another object of the present invention is to provide a polymer electrolyte fuel cell including a membrane / electrode assembly for a polymer fuel cell that can improve cell performance by improving the electrochemical activity of the electrode by improving the dispersibility of the electrode catalyst and the binder. Is in.

Another object of the present invention is to improve the electrochemical activity of the electrode by improving the dispersibility of the electrode catalyst and binder, to provide a method for producing an electrode for a polymer electrolyte fuel cell that can ultimately improve cell performance.

Another object of the present invention is to provide a method for preparing a membrane / electrode assembly for a polymer electrolyte fuel cell, which can improve cell performance by improving the electrochemical activity of the electrode by improving the dispersibility of the electrode catalyst and the binder.

The present invention includes a gas diffusion layer and a catalyst layer formed on the gas diffusion layer, wherein the catalyst layer includes an electrode catalyst and an electrode binder, and the electrode catalyst and the electrode binder are polymers having a state dispersed by a surfactant in a slurry preparation step. An electrode for an electrolyte fuel cell is provided.

In addition, the present invention is a polymer electrolyte membrane; A gas diffusion layer and a catalyst layer formed on the gas diffusion layer, wherein the catalyst layer comprises an electrode catalyst and an electrode binder, and the electrode catalyst and electrode binder include electrodes having a state dispersed by a surfactant in the step of preparing a slurry. A membrane / electrode assembly for a polymer electrolyte fuel cell is provided.

In addition, the present invention is a polymer electrolyte membrane; And a catalyst layer formed on the gas diffusion layer and the gas diffusion layer, wherein the catalyst layer includes an electrode catalyst and an electrode binder, and the electrode catalyst and the electrode binder are attached to electrodes having a state dispersed by a surfactant in a slurry manufacturing step. A polymer electrolyte fuel cell including an electrolyte membrane / electrode assembly is provided.

The present invention also provides a method of manufacturing a membrane / electrode assembly for a polymer electrolyte fuel cell by compressing an electrode having a catalyst layer having an electrode catalyst and an electrode binder dispersed by a surfactant on a gas diffusion layer on a polymer electrolyte membrane.

Hereinafter, the content of the present invention will be described in detail.

The electrode for a polymer electrolyte fuel cell according to the present invention improves the dispersion state of the catalyst and the binder in the electrode by introducing a surfactant into the slurry state in the manufacturing process. Such an ideal dispersed state of the electrode catalyst layer increases the electrochemically active surface area of the electrode and consequently greatly improves cell performance.

The surfactant that can be used in the present invention is not particularly limited as long as it is a material capable of improving the dispersibility of the material of the electrode catalyst and the electrode binder in the electrode slurry, for example, Ninate 411 (Ninate 411), Pluronic F68, Pluronic L64, Zonyl FSN100, Aerosol OT100%, Aerosol OT100%, Jerapon T-77, Biopont AS-40, Bio- Terge AS-40), Standapol ES-1, Benzalkonium chloride, Tetronic 1307, Surfynol 465, Sufinol 485, IGEPAL CA210272 Triton X-45, Triton X-100, Triton X-305, Silwet L7600, Rhodasurf ON-870, Cremophor EL , Tween 20, Tween 80, BRIJ 35, Kemal LA-9, Suspectant 10G, Sobitan monoleate, Sorbitan triol Sobitan trioleate, Propylene glycomonosteatate, Glycerol monostearate, Propylene glycol monolaurate, Sorbitan monostearate, Glyceryl monostearate Glyceryl monostearate, Polyoxyethylene-4-laurylether, Polyethylene glycol 400 monostearate, Polyethylene-4-sorbitan monostearate (Poly ethylene-4) -sobitan monostearate, Polyethylene-20-sobitan monospaliutate, polyethylene-40-stearate, sodium oleate, sodium lauryl sulfate, or the like. And mixtures of species or more. The amount of the surfactant introduced may be 0.001 to 100% by weight, preferably 0.01 to 50% by weight, and more preferably 0.1 to 10% by weight, based on the weight of the slurry.

The polymer which can be introduced into the electrode binder of the present invention may be a perfluorinated hydrogen ion conductive polymer or a sulfonated or acid-added hydrocarbon-based hydrogen ion conductive polymer.

Examples of the perfluorinated hydrogen ion conductive polymer include Nafion, Flemion, Asiplex, and the like. Examples of the hydrocarbon-based hydrogen ion conductive polymer include polysulfone, polyarylene ether sulfone, and polyether ether sulfone. , Polyether sulfone or polyimide, polyimidazole, polybenzimidazole, polyether benzimidazole, polyarylene ether ketone, polyether ether ketone, polyether ketone, polyether ketone ketone, polystyrene, and the like When used alone or a mixture of two or more kinds of sulfonated or a polymer material having excellent hydrogen ion conductivity doped with an acid to these polymers is not limited to the above examples. The amount of the polymer introduced may be 0.01 to 50.0% by weight based on the weight of the slurry.

Sulfonation of the polymer electrolyte membrane for fuel cells means introduction of sulfonic acid (sulfuric acid, -SO ₃ H) group in the polymer structure. These sulfonic acid groups play a role in facilitating proton transfer by forming clusters in the polymer structure by interaction between them. In particular, hydrogen peroxide-based polymers such as Nafion, Flemion, and Apsiplex have a structure that is easy to form clusters by introducing sulfonic acid groups at the end groups of the side chains. Fuming sulfuric acid) can be sulfonated (post sulfonation, post-sulfonation), or a polymer can be prepared by condensation reaction after introducing sulfonic acid group to monomer in fuming sulfuric acid (monomer sulfonation, monomer-sulfonation). All. The sulfonation in the present invention includes both post sulfonation and monomer sulfonation.

In the present invention, examples of the acid-doped polymer material include a case where the phosphoric acid is doped with polyimide, polybenzimidazole, polyimidazole, or the like in a high temperature polymer electrolyte fuel cell.

The metal which can be introduced into the electrode catalyst of the present invention is selected from the group consisting of Pt, Ru, W, Mo, P, Si, Co, Cs, V, and Ni, or a mixture of two or more thereof, or an alloy, and hydrogen In the case of a material having excellent oxidation and reducing properties such as methanol, ethanol and the like, the material is not limited to the above examples. The electrode catalyst may be applied on the gas diffusion layer in an amount of 0.01-5 mg / cm 2.

In addition, the preparation of the slurry of the present invention may further include an organic solvent. Specific examples of usable dispersion solvents include distilled water, isopropyl alcohol, methanol, ethanol, dimethylacetamide (DMAc), dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), tetrahydrofuran ( THF), glycerol, hexane, toluene, acetone, methyl ethyl ketone (MEK) and the like, or a mixture of two or more selected from the group of excellent dispersibility is not limited to the above examples. The dispersion solvent does not require any particular limitation, but preferably 1 to 99% by weight, more preferably 10 to 70% by weight, and most preferably 30 to 60% by weight, based on the weight of the electrode catalyst and electrode binder mixture. can do.

The gas diffusion layer used in the present invention should have electrical conductivity and can use carbon fiber having a smooth flow of fluid. Preferably, the carbon fiber bar is carbon cloth or carbon paper, and Toray Carbon Paper (Toray) is a representative product. The gas diffusion layer used in the present invention may be used by coating a hydrophobic layer such as polytetrafluoroethylene (PTFE) to facilitate fluid flow prior to use.

The electrode for a polymer electrolyte fuel cell according to the present invention is compressed to a polymer electrolyte membrane to form a membrane / electrode assembly. Electrolyte membranes that can be used in such membrane / electrode assemblies are sulfonated polysulfones, polyaryleneethersulfones, polyetherethersulfones, polyethersulfones, polyimides, polyimidazoles, polybenziimidazoles, polyetherbenziimidazoles And polyarylene ether ketones, polyether ether ketones, polyether ketones, polyether ketone ketones, polystyrenes and composite films selected solely or in combination of two or more selected from the group consisting of Nafion, Flemion and Asiplex. .

The polymer electrolyte membrane as described above is not particularly limited, and may be selected from, for example, a polymer electrolyte membrane having a number average molecular weight of 1,000 to 1,000,000 and a mass average molecular weight of 10,000 to 1,000,000.

In addition, the thickness of the polymer electrolyte membrane may be in the range of 10 ~ 300㎛.

The membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention may be prepared by thermally pressing a polymer electrolyte and an electrode according to the present invention under a pressure press of 500 to 2,000 psi and a temperature of 50 to 300 ° C. under a condition of 1 to 60 minutes.

The electrode prepared according to the present invention can be seen that the dispersion state of the catalyst is improved as shown in FIG.

The electrode for a polymer electrolyte fuel cell according to the present invention can be applied to a polymer electrolyte fuel cell, a general configuration of a polymer electrolyte fuel cell is known as shown in FIG. In addition to this, for example, the structure of the fuel cell described in US Patent US6187467 and the like, and a method of manufacturing the same (however, the electrode portion in the above configuration is replaced by the electrode according to the present invention) and the like are also cited for the present invention.

In order to facilitate a more clear understanding of the present invention, the contents of the present invention will be described in detail through preferred embodiments in which the manufacturing steps are more specific. However, these examples are only presented to understand the content of the present invention, and the scope of the present invention should not be construed as being limited to these embodiments.

<Example 1>

In order to sulfonate the polyether ether ketone, 50 ml of 98% concentrated sulfuric acid was added to a 100 ml round bottom flask, purged with nitrogen, and 2 g of vacuum-dried polyether ether ketone polymer was added at 100 ° C. for 24 hours, and the reactor temperature was 50 ° C. It was vigorously stirred at. The reactants reacted for 6, 9, 12, and 24 hours were precipitated in distilled water and recovered by filtration. The reaction was washed several times in the same manner to make the acidity neutral to 7 and the reaction was recovered through filtration. The recovered reactants were vacuum dried at 50 ° C. for 24 hours to obtain sulfonated polyetheretherketone polymer.

Table 1 shows the degree of sulfonation according to reaction time of polyetheretherketone, which is a sulfonated hydrocarbon-based polymer used as a matrix of the polymer electrolyte composite membrane.

<Table 1> Degree of sulfonation according to reaction time

Response time (hr) 6 9 12 24 Sulfonation degree (DS,%) 50 60 70 90

The sulfonated polyether ether ketone polymer prepared above was dissolved in 10% by weight of dimethylacetamide solvent and cast into a doctor blade on a glass plate. The resultant was dried for 72 hours in an oven at 50 ° C. and then impregnated with distilled water to obtain a sulfonated polyether ether ketone polymer membrane, which was then dried in a 50 ° C. vacuum oven for 24 hours to finally obtain a sulfonated polyether ether ketone polymer membrane.

<Example 2>

A binder solution was prepared by dissolving 0.05 g of sulfonated polyether ether ketone polymer in 0.95 g of dimethylacetamide. A binder mixture solution was prepared by introducing 0.01 g of Triton X-100 as a dispersant into 0.99 g of the binder solution. A catalyst slurry was prepared by introducing 0.105 g of the mixed solution prepared above into 0.1 g platinum catalyst and further introducing 0.1 g dimethylacetamide. The catalyst slurry prepared as described above was applied to carbon fibers to prepare a weight of the catalyst layer at 21.5 mg to complete the positive electrode.

<Example 3>

A positive electrode was prepared in the same manner using the same ingredients and compositions as in Example 2, except that sorbitan monoleate was introduced as a dispersant.

<Example 4>

Except for introducing sorbitan monostearate as a dispersant, the positive electrode was prepared in the same manner using the same ingredients and compositions as in Example 2 above.

Comparative Example 1

A positive electrode was prepared in the same manner using the same composition and composition as in Example 2 above except that no dispersant was introduced.

<Example 5>

A catalyst slurry was prepared by introducing 0.1 g deionized water, 0.353 g Nafion binder solution (5 wt%), and 0.1 g isopropyl alcohol (IPA) into a 0.1 g platinum catalyst. The catalyst slurry prepared as described above was applied to carbon fibers to prepare a weight of the catalyst layer at 23.5 mg to complete the negative electrode.

<Example 6>

The hydrogen ion conductive polymer electrolyte membrane prepared in Example 1 and the anode and cathode prepared in Examples 2 and 5 were thermally pressed at 130 ° C. to prepare a membrane / electrode assembly.

<Example 7>

A membrane / electrode assembly was prepared in the same manner as in Example 6, except that the positive electrode prepared in Example 3 was introduced.

<Example 8>

A membrane / electrode assembly was manufactured in the same manner as in Example 6, except that the positive electrode prepared in Example 4 was introduced.

Comparative Example 2

A membrane / electrode assembly was manufactured in the same manner as in Example 6, except that the positive electrode prepared in Comparative Example 1 was introduced.

<Test Example 1>

The performance of the membrane / electrode assembly prepared in Examples 6, 7, and 8 and Comparative Example 2 was 3 days after driving the unit cell by injecting 2M methanol solution into the cathode and supplying oxygen to the cathode at 200cc / min. The performance of the city was confirmed, and the results are shown in the graph of FIG. 1. As can be seen from the test results of FIG. 1, it can be seen that the unit cell manufactured with the Triton X-100-introduced electrode has the best performance.

<Test Example 2>

The active surface areas of the electrodes prepared in Examples 2, 3, and 4 and Comparative Example 1 were obtained at a scan speed of 10 mV / sec using cyclic voltametry, and the results are shown in Table 2. As can be seen from the test results in Table 2, the electrochemically active surface area of the electrode to which Triton X-100 is introduced is the widest.

TABLE 2

sample Electrochemically active surface area (m2 / g Pt) Example 2 79.2 Example 3 78.7 Example 4 75.1 Comparative Example 1 54.3

<Test Example 3>

The microstructures of the electrode surfaces prepared in Examples 2, 3, and 4 and Comparative Example 1 were confirmed by SEM, and the results are shown in FIG. 2. As can be seen from the results of FIG. 2, it can be seen that the electrode to which Triton X-100 is introduced is most advantageous for catalyst dispersion. It can be seen that such improved dispersion of the catalyst layer can increase the electrochemically active surface area and consequently improve the unit cell performance.

As described above, the electrode for the polymer electrolyte fuel cell of the present invention can improve the dispersion state of the catalyst and the binder in the electrode by introducing a surfactant. In addition, the ideal dispersed state of the electrode catalyst layer can increase the electrochemically active surface area of the electrode, and as a result can significantly improve cell performance.

Claims (17)

And a catalyst layer formed on the gas diffusion layer and the gas diffusion layer, wherein the catalyst layer comprises an electrode catalyst and an electrode binder, and the electrode catalyst and the electrode binder are dispersed in the manufacturing step of the slurry by a surfactant. electrode. The electrode of claim 1, wherein the electrode binder is a perfluorinated hydrogen ion conductive polymer or a sulfonated or acid-added hydrocarbon-based hydrogen ion conductive polymer. The electrode for a polymer electrolyte fuel cell according to claim 1, wherein the electrode catalyst is single or a mixture or alloys of two or more selected from the group consisting of Pt, Ru, W, Mo, P, Si, Co, Cs, V, and Ni. The electrode for a polymer electrolyte fuel cell according to claim 1, wherein the gas diffusion layer is carbon cloth or carbon paper. The electrode of claim 4, wherein the gas diffusion layer is coated with a hydrophobic layer. The electrode of claim 1, wherein the electrode catalyst is coated on the gas diffusion layer in an amount of 0.01 to 5 mg / cm ² . Polymer electrolyte membrane; A gas diffusion layer and a catalyst layer formed on the gas diffusion layer, wherein the catalyst layer comprises an electrode catalyst and an electrode binder, and the electrode catalyst and electrode binder include electrodes having a state dispersed by a surfactant in the step of preparing a slurry. Membrane / electrode assembly for polymer electrolyte fuel cell. 8. The polymer electrolyte membrane according to claim 7, wherein the polymer electrolyte membrane is sulfonated polysulfone, polyarylene ether sulfone, polyether ether sulfone, polyether sulfone, polyimide, polyimidazole, polybenzimidazole, polyetherbenzimidazole, polyaryl Membrane for polymer electrolyte fuel cell which is a single or a mixture of two or more kinds selected from the group consisting of ene ether ketone, polyether ether ketone, polyether ketone, polyether ketone ketone, polystyrene and nafion, plemion and asyplex Electrode assembly. 8. The membrane / electrode assembly of claim 7, wherein the polymer electrolyte membrane has a number average molecular weight of 1,000 to 1,000,000 and a mass average molecular weight of 10,000 to 1,000,000. The membrane / electrode assembly of claim 7, wherein the polymer electrolyte membrane has a thickness in a range of 10 to 300 μm. Polymer electrolyte membrane; And a catalyst layer formed on the gas diffusion layer and the gas diffusion layer, wherein the catalyst layer includes an electrode catalyst and an electrode binder, and the electrode catalyst and the electrode binder are attached to electrodes having a state dispersed by a surfactant in a slurry manufacturing step. A polymer electrolyte fuel cell comprising an electrolyte membrane / electrode assembly. A method for producing an electrode for a polymer electrolyte fuel cell, which is prepared by applying a slurry in which an electrode catalyst and an electrode binder are dispersed by a surfactant to a gas diffusion layer. The method of claim 12, wherein the amount of the surfactant added is 0.001 to 100% by weight based on the weight of the slurry. The method of claim 12, wherein the organic solvent for preparing the slurry is distilled water, isopropyl alcohol, methanol, ethanol, dimethylacetamide, dimethylformamide, 1-methyl-2-pyrrolidinone, tetrahydrofuran, glycerol, hexane, toluene A method for producing an electrode for a polymer electrolyte fuel cell which is a single or a mixture of two or more selected from the group consisting of acetone and methyl ethyl ketone. The method of claim 12, wherein the solvent is added in an amount of 1 to 99 wt% based on the weight of the electrode catalyst and the electrode binder mixture. A method of manufacturing a membrane / electrode assembly for a polymer electrolyte fuel cell by compressing an electrode having a catalyst layer having an electrode catalyst and an electrode binder dispersed by a surfactant on a gas diffusion layer on a polymer electrolyte membrane. The method of manufacturing a membrane / electrode assembly for a polymer electrolyte fuel cell according to claim 16, wherein the pressing is performed by thermal pressing at 500 to 2,000 psi and 50 to 300 ° C. under a condition of 1 to 60 minutes.

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