KR100420068B1 - Method of manufacturing diffusion layer by RuO2 for proton exchange membrane fuel cell - Google Patents

Abstract

The present invention relates to a method for producing a polymer electrolyte fuel cell using ruthenium metal oxide. In particular, the formation of ruthenium metal oxide between the support layer and the catalyst layer when forming the electrode electrolyte junction structure increases the diffusion efficiency of fuels (hydrogen or methanol as fuel and oxygen or air as reducing fuel) and reaction products (carbon dioxide, water), compared to the support layer. The present invention relates to a technique for preventing the loss of a catalyst by forming a dense layer, and improving the performance of a battery using the storage capacity of ruthenium metal oxide and oxygen reduction power.

According to the present invention, a ruthenium metal oxide (RuO2) is mixed with a polytetrafluoroethylene (PTFE) solution mixed with a predetermined amount of a water-soluble alcohol solvent and sufficiently stirred, and then a predetermined amount of carbon paper or carbon cloth is used as a support layer of the catalyst. Forming a diffusion layer having a thickness; After heat-treating the diffusion layer, forming a catalyst layer using a cathode and an anode catalyst; A method of manufacturing a polymer electrolyte fuel cell is provided, comprising forming an electrode electrolyte junction structure through thermocompression bonding together with the polymer electrolyte pretreated in the resultant product.

Description

Method for manufacturing polymer electrolyte fuel cell using ruthenium metal oxide {Method of manufacturing diffusion layer by RuO2 for proton exchange membrane fuel cell}

The present invention relates to a method for producing a polymer electrolyte fuel cell using ruthenium metal oxide. In particular, the formation of ruthenium metal oxide between the support layer and the catalyst layer when forming the electrode electrolyte junction structure increases the diffusion efficiency of fuels (hydrogen or methanol as fuel and oxygen or air as reducing fuel) and reaction products (carbon dioxide and water), The present invention relates to a technique for preventing the loss of a catalyst due to the formation of a dense layer and improving the performance of a battery using the storage capacity of ruthenium metal oxide and oxygen reducing power.

The polymer electrolyte fuel cell is a pollution-free energy source that can be operated at a low temperature of 130 ° C. or lower, and is applied to a wide variety of fields such as a power source of a pollution-free vehicle, a local power generation and a mobile power source. However, since the fuel cell operates at a low temperature, its efficiency is relatively low compared to other fuel cells, and various methods for improving performance have been tried.

Therefore, in order to solve this problem, by forming a diffusion layer using ruthenium metal oxide between the support layer and the catalyst layer of the catalyst, it is possible to improve the diffusion characteristics of the fuel and the reaction product and to prevent the loss of the catalyst. In addition, research is being conducted to complement the performance of the battery using the storage capacity and the oxygen reduction power of the ruthenium oxide.

In this regard, the carbon powder (Vulcan XC-72R or acetylene black, etc.) conventionally used to form a diffusion layer for a polymer electrolyte fuel cell is formed through the same method as the method of manufacturing a diffusion layer, but the performance improvement of the battery is constant. There is a limit.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide smooth diffusion of fuel and reaction products, respectively, compared to conventional diffusion layers through large porosity and low electrical resistance when forming ruthenium metal oxide as a diffusion layer. It is to construct an electrode electrolyte junction structure showing low ohmic overvoltage.

As a technical idea for achieving the above object of the present invention, the present invention is used as a support layer of the catalyst after mixing the ruthenium metal oxide in a polytetrafluoroethylene (PTFE) solution mixed with an appropriate amount of a water-soluble alcohol solvent A diffusion layer is formed to a suitable thickness on carbon paper or carbon cloth to implement a high performance polymer electrolyte fuel cell through a highly efficient electrode electrolyte junction structure.

1A and 1B are flowcharts illustrating a schematic diagram of an electrode electrolyte junction structure, a ruthenium metal oxide diffusion layer, and a process of forming an electrode electrolyte junction structure according to the present invention.

Figure 2 is a chart showing the results of measuring the material properties of the carbon powder and ruthenium metal oxide used as carbon paper and the conventional diffusion layer forming material according to the present invention.

3A to 3D are graphs illustrating the results of evaluation of unit cell performance when ruthenium metal oxide is not provided with a diffusion layer and when a diffusion layer is formed on both a cathode or an anode, or both an anode and an anode according to the present invention.

4A and 4B show a comparison result of unit cell performance evaluation when there is no diffusion layer according to the present invention, when the diffusion layer is formed of carbon powder, which is an existing diffusion layer forming material, and when the diffusion layer is formed using ruthenium metal oxide. Is a graph.

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the embodiment of the present invention will be described in detail.

1A and 1B are flowcharts illustrating a schematic diagram of an electrode electrolyte junction structure, a ruthenium metal oxide diffusion layer, and a process of forming an electrode electrolyte junction structure according to the present invention.

The electrode electrolyte bonding structure shown in FIG. 1A includes carbon paper 10a for the cathode on the left side of the electrolyte 40; Diffusion layer 20a; A catalyst layer (PtRu black; 30a) is formed, and on the right side, a catalyst layer (Pt black; 30b) for the anode; Diffusion layer 20b; Carbon paper 10b is formed sequentially.

Referring to Figure 1b, 0.533 g of polytetrafluoroethylene (PTFE) is added to 20 ml of isopropyl alcohol (IPA) and dissolved by stirring for at least 10 minutes at a speed of 800 rpm at room temperature. With continued stirring at this rate, 0.8 g of ruthenium metal oxide (RuO 2) is added to alternate stirring and ultrasonic grinding for at least 3 hours to ensure complete mixing.

At this time, polytetrafluoroethylene (PTFE), which is used as a binder and has a hydrophobic property, is mixed with isopropylalcohol (IPA), ethyl alcohol, or butyl acetate, which is a water-soluble alcohol solvent. After sufficient stirring, ruthenium metal oxide powder may be added to the solution, followed by further stirring to prepare a mixed solution for forming a diffusion layer.

The mixed solution may be prepared so that the mass ratio of polytetrafluoroethylene: ruthenium metal oxide is 10-50: 90-50, and in the case of a water-soluble alcohol solvent, the mass of polytetrafluoroethylene so that the mixed solution maintains an appropriate viscosity Compared to 5 to 100 times the water-soluble alcohol solvent may be added (step S100).

Subsequently, the suspension is formed on the carbon paper 10a, 10b as a support using a brushing method to form the diffusion layers 20a, 20b with a thickness of 10 to 100 µm (step S110).

The carbon papers 10a and 10b on which the diffusion layers 20a and 20b are formed are heat-treated under an air atmosphere at 100 to 400 ° C. for 30 minutes to 2 hours (step S120), and the cathode and anode catalysts are brushed thereon using a brush method. To form 5 mg of catalyst layers 30a and 30b per unit area (cm2).

At this time, ruthenium metal using a brush method or a paste method which is commonly used as a method for forming the diffusion layers 20a and 20b in the step S110 or the catalyst layers 30a and 30b in the step S130. The oxide diffusion layer can be formed to a uniform thickness of 10 to 80 micrometers (µm).

Since the diffusion layers 20a and 20b thus prepared have an average pore size of 155 nanometers (nm), they are used in a polymer electrolyte fuel cell as compared to a diffusion layer using a carbon powder. As a reducing fuel, it can improve the diffusion characteristics of oxygen and air) and reaction products (carbon dioxide and water), and show low ohmic polarization due to the low electrical resistance of ruthenium metal oxide. Implementation is possible.

Figure 2 shows the results of measuring the material properties of carbon paper and carbon powder (Vulcan XC-72R or acetylene black) and ruthenium metal oxide used as a conventional diffusion layer forming material.

In addition, as a dense layer is formed below the catalyst layers 30a and 30b as compared with the carbon papers 10a and 10b, the amount of catalyst loss participating in the electrode reaction due to the penetration of the catalyst into the carbon papers 10a and 10b is greatly reduced. You can.

In the present invention, the cathode catalyst 30a used in the catalyst layers 30a and 30b in step S120 is, for example, PtRu black of Johnson Matthey co., And the solution used for forming the catalyst layer is a catalyst. A solution formulated so that the mass ratio of Nafion is 85:15 is used. In addition, the anode catalyst 30b used uses, for example, Pt black of Johnson Matthey Co., at which time the Nafion content is adjusted to 7 percent.

Thereafter, the carbon papers 10a and 10b for the cathode and the anode in which the catalyst layers 30a and 30b and the diffusion layers 20a and 20b are formed are thermally compressed 110 together with the Nafion polymer electrolytes (Nafion 112, 115, 117) and 40 which have been pretreated. It is made to the electrode electrolyte bonding structure through 3 minutes) (step S140).

The pretreatment of Nafion 112,115,117 used as a polymer electrolyte was performed in four stages.

First, the hydrogen peroxide (H2O2) solution mixed with tertiary distilled water at a mass ratio of 3 percent was treated for 1 hour while heating to 80 ° C, and then washed again in tertiary distilled water for 1 hour at the same temperature. Subsequently, the mixture was continuously treated for 1 hour in 0.5 mol of sulfuric acid solution while maintaining the temperature, and then washed again in third distilled water for 1 hour.

The fabricated electrode electrolyte junction structure was fixed by using carbon plate (2cm) of electrode area used as current collector and then fixed by brass plate on the outside. The results of the operation are shown in FIGS. 3A and 3B and 3C and 3D.

The results shown in FIGS. 3A to 3D show the case where the diffusion layer is not used, the diffusion layer is formed only on the cathode, the diffusion layer is formed only on the anode, and the diffusion layer is formed on both the cathode and the anode. .

At this time, the cathode fuel used was 2 mol of methanol, which was flowed at a rate of 1 cc per minute, and the anode fuel was used at ultra high purity oxygen or ultra high purity air and flowed at 500 cc per minute. 3A and 3B show oxygen and air as anode fuel at 70 ° C., respectively. FIGS. 3C and 3D show oxygen and air as anode fuel at 30 ° C., respectively.

In the case where the diffusion layer is formed only on the cathode, the large average pore size of the ruthenium metal oxide diffusion layer facilitates the diffusion of methanol, which is a cathode fuel, in the current region in which concentration polarization occurs, thereby clearly showing an increase in performance. In the case where the diffusion layer was formed only at the anode, due to the hydrophobic nature of the diffusion layer, the performance was greatly increased in the entire current region due to the smooth discharge of water generated by the reaction.

At this time, the low electrical resistance characteristics of the ruthenium metal oxide diffusion layer resulted in a noticeable performance improvement of the battery, particularly in the ohmic region. In addition, it was confirmed in FIG. 3C and FIG. 3D that the performance of the battery when ruthenium metal oxide was used as the diffusion layer could cause a greater increase in performance at low temperatures.

Using the same method, an electrode electrolyte junction structure was fabricated using carbon powder (Vulcan XC-72R or acetylene black), which was used as a diffusion layer preparation material, and was tested under the same conditions, and performed with ruthenium metal oxide. The comparison result with the battery in which the diffusion layer was formed is shown in FIGS. 4A and 4D.

4A and 4B show 2 mol of methanol as the anode fuel and oxygen as the cathode fuel, and the battery performance evaluation results at 70 ° C. and 30 ° C., respectively. From this result, it can be seen that the unit cell using ruthenium metal oxide as the diffusion layer has higher output and higher efficiency than the diffusion layer using the carbon powder used as a conventional diffusion layer forming material.

As described above, according to the present invention, a diffusion layer using ruthenium metal oxide may be uniformly formed between the support and the catalyst layer at a thickness of 10 to 80 micrometers (µm). The high performance polymer electrolyte fuel cell may be implemented by forming a highly efficient electrode electrolyte junction structure.

Claims (6)

Ruthenium metal oxide (RuO2) is mixed in a polytetrafluoroethylene (PTFE) solution mixed with a predetermined amount of a water-soluble alcoholic solvent and sufficiently stirred to form a diffusion layer having a predetermined thickness on carbon paper or carbon cloth used as a support layer of the catalyst. Making a step; After heat-treating the diffusion layer, forming a catalyst layer using a cathode and an anode catalyst; And forming an electrode electrolyte junction structure through thermocompression bonding together with the polymer electrolyte pretreated in the resultant product. The method of claim 1, wherein when operating a fuel cell using the metal oxide as a diffusion layer, hydrogen or methanol is used as an anode fuel (oxidation fuel), and oxygen or air is used as an anode fuel (reduction fuel). Polymer electrolyte fuel cell manufacturing method. The method of claim 1 or 2, wherein the thickness of the diffusion layer using the metal oxide is 10 to 100 micrometers (µm). The method according to claim 1 or 2, wherein the mass content ratio of polytetrafluoroethylene in the preparation of the suspension for forming the diffusion layer of the metal oxide is 10 to 50 percent. The method of claim 4, wherein a water-soluble alcohol solvent such as isopropyl alcohol, ethyl alcohol or butyl acetate is used in the preparation of the suspension for forming the diffusion layer of the metal oxide, the mass content A method for producing a polymer electrolyte fuel cell, wherein the ratio is 5 to 100 times with respect to polytetrafluoroethylene. The method of manufacturing a polymer electrolyte fuel cell according to claim 1 or 2, wherein after forming the diffusion layer using the metal oxide, heat treatment is performed at 100 to 400 ° C. for 30 minutes to 2 hours.