KR20060095182A - Membrane electrode assemblies with porous electro catalytic layer, the method of this product and the electrochemical cell with membrane electrode assemblies with porous electro catalytic layer - Google Patents

Abstract

The present invention relates to an electrochemical cell membrane electrode assembly and a method for manufacturing the same, wherein an electrode catalyst layer forming electrodes on both surfaces of an ion exchange membrane has a porosity in which a plurality of pores are evenly distributed. The present invention has an effect of improving the efficiency by stabilizing the reaction efficiency as well as significantly reducing the production cost by reducing the amount of precious metal used by making the electrode catalyst layer porous.

Description

Membrane electrode assemblies with porous electro catalytic layer, the method of this product and the electrochemical cell with membrane electrode assemblies with porous electro catalytic layer}

1 is a conceptual diagram of a typical electrolysis cell which electrochemically decomposes water to produce hydrogen gas and oxygen gas,

2 is a photograph of a membrane electrode assembly prepared by a conventional adsorption reduction method,

3 is a conceptual diagram for explaining a current distribution in a membrane electrode assembly manufactured by a conventional adsorption reduction method,

Figure 4 is a block diagram showing the manufacturing process of the membrane electrode assembly having a porous electrode catalyst layer according to an embodiment of the present invention,

5 is a photograph of the electrode catalyst layer of the membrane electrode assembly prepared according to the present invention,

FIG. 6 is a graph showing pore distribution of the electrode catalyst layer shown in FIG. 5;

7 is a structural diagram of a unit electrochemical cell having a membrane electrode assembly prepared according to the present invention,

8 is a process diagram of an experimental system used to evaluate electrochemical cells having membrane electrode assemblies prepared according to the prior art and the present invention,

9 is a graph comparing the performance results of the comparative example and the invention example tested through the experimental system of FIG.

TECHNICAL FIELD The present invention relates to an electrochemical cell, and more particularly, to a membrane electrode assembly comprising a porous electrode catalyst layer on both surfaces of an ion exchange membrane constituting a membrane electrode assembly for an electrochemical cell, and a method of manufacturing the same. The present invention also relates to an electrochemical cell having a membrane electrode assembly having a porous electrode catalyst layer as described above.

Electrochemical cells are generally used in electrolysis cells that produce gas using raw materials such as water, and fuel cells that produce electricity using fuel. In other words, an electrochemical cell is an energy conversion device, and is classified into an electrolysis cell and a fuel cell. An electrolysis cell generates hydrogen and oxygen by electrochemically decomposing water, and a fuel cell is a device that obtains electricity by electrochemically reacting hydrogen and oxygen.

For example, a proton exchange membrane electrolysis cell serves to produce hydrogen gas and oxygen gas by electrochemically decomposing water. 1 is a conceptual diagram of a typical electrolysis cell that electrochemically decomposes water to produce hydrogen gas and oxygen gas.

As shown in FIG. 1, water H ₂ 0 is supplied to the anode 110 (oxygen electrode) and decomposed into oxygen gas O ₂ , electrons e ⁻ , and hydrogen ions H ⁺ protons. . At this time, a portion of the water H ₂ 0 flows out of the electrolysis cell 100 together with the oxygen gas O ₂ . The decomposed hydrogen ions (H ⁺ ) pass through the hydrogen ion exchange membrane 120 and move to the cathode 130 (hydrogen electrode), along the external circuit 140 connecting the anode 110 and the cathode 130. moving the electron (e ^-) is reacted with hydrogen gas (H _2). And the water (H ₂ 0) passing through the hydrogen ion exchange membrane 120 in conjunction with the hydrogen gas (H ₂ ) and hydrogen ions (H ⁺ ) is discharged to the outside of the electrolysis cell (100). In this case, the electrochemical reactions occurring in the anode 110 and the cathode 130, respectively, are represented by Schemes 1 and 2.

^{_{2H 2 O → 4H + + 4e}} - + O 2 ( positive electrode)

_{^{4H + + 4e - → 2H 2}} ( cathode)

The fuel cell reacts in reverse to the electrolysis mechanism of water as described above. In other words, in a fuel cell, hydrogen, methanol or another hydrogen fuel source and oxygen react to produce electricity. In this case, the general reaction occurring in the fuel cell is represented by the reaction equations 3 and 4.

_{^{2H 2 → 4H + + 4e -}} ( anode)

_{^{4H + + 4e - + O 2}} → 2H 2 O ( cathode)

If the electrochemical cell is used as an electrolysis cell that decomposes water, a current density of about 0.05 A / cm ² to 4.3 A / cm ² and a voltage of about 1.48 volts to 3.0 volts are applied. the voltage of the current density in ^{a / cm 2 ~ 10A / cm} 2 and about 0.4volts ~ 1volts is applied, it produces a gas or a fuel cell, respectively.

Such an electrochemical cell comprises a membrane electrode assembly having a positive electrode and a negative electrode (hereinafter referred to as 'MEA'), a frame, a separator, a MEA support, and a form arranged to supply and discharge electrons, reactants, and products. Gasket (packing) or the like. Such an electrochemical cell should have the conditions of excellent electrolytic performance, excellent durability, and low price.

In the case of hydrolysis, which electrolyzes water with respect to electrolytic performance, the theoretical decomposition voltage is 1.23V at a temperature of 25 ° C, but a voltage higher than this voltage is actually required. At this time, the difference between the actual voltage and the theoretical decomposition voltage is called an overvoltage, and the overvoltage is the sum of the overvoltages of the ion exchange membrane, the anode, and the cathode which constitute the electrolysis cell. Among these overvoltage components, the negative electrode overvoltage is an overvoltage generated when hydrogen is generated and is not large because the hydrogen generation reaction is reversible, whereas the positive electrode overvoltage has a relatively larger value than other overvoltages due to irreversible oxygen generation. Therefore, the improvement of the electrode for oxygen generation is very important.

Since the durability of the electrochemical cell is determined by the contact resistance and the bonding strength between the ion exchange membrane and the electrodes (anode and cathode), the durability of the electrochemical cell is greatly influenced by the manufacturing method of the MEA. At this time, the durability of the electrochemical cell is excellent to have a low contact resistance and high bonding strength between the ion exchange membrane and the electrode.

MEA manufacturing methods generally include a hot pressing method, an electrochemical method, an adsorption reduction method, and the like. The hot pressing method is a method in which a catalyst particle and a binder such as PTFE (Polytetrafluoroethylene) are thermocompressed and bonded to an ion exchange membrane. However, the membrane electrode assembly bonded by thermocompression bonding is a problem in durability because physically bonding different phases having different physical properties. In contrast, the adsorption reduction method reacts a metal salt aqueous solution with a reducing agent on the surface of the electrode, thereby increasing the adhesion strength of the electrode catalyst and almost eliminating the interfacial resistance between the electrode catalyst and the ion exchange membrane.

In 1993, Chen and Chou (J. Electroanalytical. Chem 360, 247-59) adsorbed lead and palladium on a cation exchange membrane Nafion (trade name). MEA was prepared by reducing these ions using sodium borohydride) and lithium hydroxide (Lithium Hydroxide). The MEA has been applied to electrochemically reduce benzaldehyde. In a similar way, in 1995, Millet (J. Appl. Electrochem, 25 227-32) and others produced a ruthenium anode and applied it to a faucet bath. Ruthenium anodes have a lower potential than platinum anodes but have corrosion problems. Therefore, afterwards, anodes having ruthenium and platinum were fabricated to improve the instability of ruthenium.

Although the adsorption reduction method has excellent durability, most of the electrode catalysts formed in the ion exchange membrane cannot be efficiently used, so that the electrolytic performance is lowered, and an excessive precious metal catalyst must be used.

Hereinafter, a process of manufacturing MEA using a conventional adsorption reduction method will be described in detail.

The ion exchange membrane is a perfluorosulfonic cation exchange membrane, using Nafion from DuPont. First, roughen both sides of the ion exchange membrane with sandpaper (Norton 600A), immerse it in ultrapure water for about 1 hour, and then take it out to a certain size. Cut. Then, electrode catalyst layers (anode and cathode) are formed on both surfaces of the ion exchange membrane as follows.

end. Cathode Catalyst Layer Formation

(1) pretreatment step

In order to remove organic matter present in the ion exchange membrane cut to a predetermined size, the ion exchange membrane is heated in an aqueous solution of H ₂ O ₂ (3%) for about 40 minutes and then washed with pure water. In addition, the ion exchange membrane was heated in a 1M H ₂ SO ₄ solution for about 30 minutes, washed with pure water, and then heated in ultrapure water for about 1 hour.

(2) adsorption step

Methanol containing 0.6 mM pt (NH ₃ ) ₄ Cl ₂ (tetra-amine platinum chloride hydrate, 98%) and water were mixed at a volume ratio of 1: 3 to form a mixed solution, which was then mixed into the mixed solution. The ion exchange membrane cleaned in the pretreatment step is introduced for about 40 minutes to allow platinum ions to diffuse and adsorb into the ion exchange membrane.

(3) reduction step

NaBH ₄ is mixed with a solution of pH 13 preheated to 50 ° C. to form a 1 mM reducing solution. An ion exchange membrane is added to the reducing solution to remove the platinum solution adsorbed in the adsorption step, and then 60 ml of reducing solution is filled instead. Then, after the reduction process of about 2 hours while stirring it, the ion exchange membrane is impregnated with 0.5M H ₂ SO ₄ for 2 hours, ultrapure water for 1 hour and then stored.

I. Anode Catalytic Layer Formation

(1) Pretreatment Step

After washing with pure water, it is heated in ultrapure water for about 1 hour.

(2) adsorption step

It is the same as the adsorption step of the cathode catalyst layer formation process.

(3) reduction step

It is the same as the reducing step of the cathode catalyst layer forming process.

Figure 2 is a photograph of a membrane electrode assembly prepared by the same method using a conventional adsorption reduction method. As can be seen from the photograph of FIG. 2, the MEA manufactured by the conventional adsorption reduction method covers the entire surface of the ion exchange membrane to form an electrode catalyst layer (platinum layer).

3 is a conceptual diagram illustrating a current distribution in a membrane electrode assembly manufactured by a conventional adsorption reduction method. As shown in FIG. 3, when a current is applied to the anode catalyst layer 310 and the cathode catalyst layer 330 positioned on both surfaces of the ion exchange membrane 320 to electrolyze water, an electrochemical reaction occurs. Here, the anode and cathode catalyst layers 310 and 330 serve as respective electrodes, and the anode catalyst layer 310 serves as an anode and the cathode catalyst layer 330 serves as a cathode.

That is, the supplied water H ₂ 0 passes through the inert catalyst layer B ′ of the anode catalyst layer 310 to the active catalyst layer A ′ and participates in Scheme 1. After the reaction, oxygen gas (O ₂ ) is again discharged through the active catalyst layer (A ') and inert catalyst layer (B'). At this time, the hydrogen ions generated by the reaction formula 1 passes through the ion exchange membrane 320 to the active catalyst layer (A) of the cathode catalyst layer 330 to become hydrogen gas (H ₂ ) by the reaction formula 2. The generated hydrogen gas (H ₂ ) is discharged to the outside through the active catalyst layer (A) and the inert catalyst layer (B). Arrows in FIG. 3 indicate the current distribution.

The distribution of electrochemical reactions in the MEA is about 95% or more between the sides of the MEA electrodes, i.e. between the A (cathode active catalyst layer) and A '(cathode active catalyst layer) portions, and B (cathode) The remaining 5% of the reaction takes place in the inert catalyst layer) and B '(anode inert catalyst layer). That is, most of the electrode catalyst layers in B (cathode inert catalyst layer) and B '(anode inert catalyst layer) of the MEA do not participate in the electrochemical reaction.

That is, in the MEA manufactured by the conventional adsorption reduction method, the entire surface of the ion exchange membrane is coated with a metal as shown in the photograph of FIG. 2, so that water (H ₂ 0) required for the electrochemical reaction is A (cathode active catalyst layer) and A '. It is difficult to move to the (cathode active catalyst layer), and it is difficult to discharge the produced hydrogen gas (H ₂ ) and oxygen gas (O ₂ ), and the reaction in the B (cathode inert catalyst layer) and B '(anode inert catalyst layer) portions Since there is a need to use a large amount of catalyst has a problem.

As such, the MEA produced by the conventional adsorption reduction method is excellent in durability, but due to excessive use of an unnecessary electrode catalyst that does not participate in the electrode reaction, and the reaction product does not diffuse into the reaction zone, the electrochemical reaction efficiency of the MEA decreases. There is a problem that the manufacturing cost rises.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, to provide a membrane electrode assembly having a porous electrode catalyst layer and a method for producing the same so that the reactants can easily diffuse into the active catalyst layer of the reaction zone The purpose is.

Another object of the present invention is to provide an electrochemical cell having a membrane electrode assembly having a porous electrode catalyst layer as described above.

According to the present invention for achieving the above object, in the electrochemical cell membrane electrode assembly (Membrane Electrode Assembly) each having an electrode catalyst layer for forming electrodes on both surfaces of the electrolyte membrane, the electrode catalyst layer is evenly distributed in a plurality of pores Characterized in that the porous electrode catalyst layer.

Further, according to the present invention, in the method of manufacturing a membrane electrode assembly for an electrochemical cell, each having an electrode catalyst layer forming electrodes on both surfaces of the electrolyte membrane, the pretreatment step of cleaning the electrolyte membrane, the pre-treated electrolyte membrane and the electrocatalyst ion An adsorption step of impregnating the ions into the surface and the inside of the electrolyte membrane by impregnation in a solution containing metal ions, which are easy to elute, and reducing the electrocatalyst ions fixed in the electrolyte membrane to the catalyst using a reducing agent. It is characterized in that it comprises a reduction and elution step of eluting easy metal ions to form a porous electrode catalyst layer, and a post-treatment step of cleaning the electrolyte membrane coated on both surfaces of the porous electrode catalyst layer.

In addition, according to the present invention, a packing, a separator and arranged on the basis of the membrane electrode assembly in a form capable of supplying and discharging the membrane electrode assembly, reactants and products each having an electrode catalyst layer forming electrodes on both surfaces of the electrolyte membrane; In the electrochemical cell comprising a frame, the electrode catalyst layer is characterized in that the porous electrode catalyst layer is a plurality of pores evenly distributed.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a membrane electrode assembly having a porous electrode catalyst layer according to the present invention, a method for producing the same and an electrochemical cell having the same will be described in detail.

Figure 4 is a block diagram showing the manufacturing process of the membrane electrode assembly having a porous electrode catalyst layer according to an embodiment of the present invention. The membrane electrode assembly according to the present invention has a porous electrode catalyst layer on both surfaces of an electrolyte membrane (eg, an ion exchange membrane), and the manufacturing process thereof will be described with reference to FIG. 4.

MEA production method of the present invention is classified into three stages by using the adsorption reduction method. First, the pretreatment step of the ion exchange membrane, and the second adsorption step of impregnating the ion exchange membrane into the surface and the inside of the ion exchange membrane by impregnating the ion exchange membrane in the solution containing the metal ions and the easily dissolved metal ions to create a porous structure The third step is to reduce and elute the metal ions fixed in the ion exchange membrane to the metal catalyst using a reducing agent and at the same time to elute the substance which is easy to elute.

As the ion exchange membrane suitable for the production of MEA according to the present invention, perfloonated sulfonic acid cation exchange membrane is most preferred.

The first step, the pretreatment step, is as follows.

First, the surface of the ion exchange membrane is roughened with sand blasting or sand paper to increase the reaction surface area. After roughening the surface of the ion exchange membrane as described above, the washing and washing steps are repeated to remove impurities and the like in the ion exchange membrane. In order to remove foreign substances on the surface of the ion exchange membrane, the cleaning solution is added to pure water or heated by using an auxiliary device such as an ultrasonic cleaner, and the washing step includes heating in an acid solution such as hydrochloric acid and sulfuric acid. At this time, the most preferable acid is hydrochloric acid. The pretreatment step includes a process of roughening the surface of the ion exchange membrane, a process of washing with pure water, a process of heating in an acid, and the like, and these components are preferably subjected to at least one iteration process.

The second step, the adsorption step, is as follows.

The adsorption step of the catalytic ion is to impregnate the metal ion and the metal by impregnating the ion exchange membrane at a certain temperature for a predetermined time in a solution containing a metal compound having an electrochemical catalytic function and a metal compound which can be eluted by post treatment. It diffuses and penetrates into this ion exchange membrane. At this time, temperature, impregnation time, stirring, and the like affect the physical properties of the ion exchange membrane.

At this time, as applicable electrochemical catalysts, any one or a mixture of ruthenium, iridium, manganese, cobalt, nickel, palladium, chromium, and platinum is known, and chloride or vaginal catalyst may be used to penetrate the metal catalyst into the ion exchange membrane. It is preferable to use compounds having a product RuCl ₃ , IrCl ₃ , Mn (NO ₃ ) ₂ , Co (NO ₃ ) ₂ , Ni (NO ₃ ) ₂ , SnCl ₃ , PdCl ₂ , CrCl ₃ , and the like. Preferred oxidation catalysts for the cathode include platinum, iridium, ruthenium, etc., which have a low oxygen generation overvoltage, and a single catalyst or a mixed catalyst thereof containing tin (Sn) having stability in a wide pH range. For example, platinum having a low hydrogen overvoltage is suitable.

The concentration of the anode catalyst reagent at the positive electrode is preferably 0.01 mmol ~ 5 mmol, and the concentration of the cathode catalyst reagent at the anode is preferably 0.01 mmol ~ 5 mmol. At this time, when the concentration is lower than 0.01 mmol, the catalyst ion component is less likely to penetrate into the ion exchange membrane, and at 5 mmol or more, an unreacted catalyst is present, which wastes expensive precious metals.

The suitable temperature in the adsorption step of the metal ions is 10 ~ 80 ℃, it is difficult to penetrate the catalyst ions in the ion exchange membrane below 10 ℃, it is difficult to operate due to severe deformation of the ion exchange membrane above 80 ℃, this time more preferred Temperature is 40-60 degreeC.

Considering the property that the metal ion to form the porous structure should be easily eluted in the reducing agent solution to be described later, it is preferable to use any one or one or more mixtures of aluminum, magnesium, zinc, wherein the compound is chloride, Nitrates are suitable. The concentration of the metal to be eluted is suitably 10% to 90% of the molar ratio with the anolyte catalyst. If it is lower than 10%, it is difficult for the porous ions to penetrate into the ion exchange membrane due to the interference of platinum ions, and also 90%. On the contrary, the performance of the MEA is deteriorated due to insufficient removal of the porous ions. At this time, the preferred concentration of the metal to be eluted is 30% to 70% is appropriate, the pore size is preferably having a size of 0.01㎛ ~ 0.1㎛.

The third step, reduction and elution, is as follows.

In the reduction and elution step, the metal catalyst ions penetrated and fixed in the ion exchange membrane are reduced to the metal catalyst using a reducing agent (for example, NaBH ₄ ) and a reducing accelerator (for example, NH ₄ OH and NaOH), and the elution ion is eluted. It is a process to make it. At this time, a reducing agent having a reducing and eluting function and a reducing accelerator (alkali component) for promoting the eluting function and reduction are introduced into a constant temperature bath at a constant temperature and the solution is stirred at a low speed. At this time, the preferred reduction temperature is 20 ~ 80 ℃, below 20 ℃, the reaction rate of the reducing agent and the elution function and the alkaline component to promote the reduction of the reduction efficiency is reduced, above 80 ℃ deformation of the ion exchange membrane like the adsorption step It is so severe that difficulties in operation occur. More preferred reduction temperature is 40 ~ 70 ℃. After the reduction and elution steps are completed, a post-treatment step of washing and storing with water or hydrochloric acid is performed.

In forming the electrode catalyst layers on both surfaces of the ion exchange membrane as described above, if the catalyst material of the anode and the cathode is the same, it is possible to form the electrode catalyst layer having a porosity in one step, but if the catalyst of the anode and the catalyst of the cathode is different Complete two different steps. In addition, the present invention may repeat the above adsorption step, reduction and elution step and after treatment step after the after treatment step to increase the amount of impregnation of the catalyst.

When the MEA is manufactured through the above process, electrode catalyst layers having porosity are formed on both surfaces of the ion exchange membrane as shown in FIG. 5. At this time, the pore distribution constituting the porous electrode catalyst layer is shown in FIG. 5 is a photograph of the electrode catalyst layer of the membrane electrode assembly prepared according to the present invention, Figure 6 is a graph showing the pore distribution of the electrode catalyst layer shown in FIG. As can be seen in Figure 6, the electrode catalyst layer is evenly distributed pores having a size of 0.01㎛ ~ 0.1㎛.

7 is a structural diagram of a unit electrochemical cell having a membrane electrode assembly prepared according to the present invention. As shown in FIG. 7, the unit electrochemical cell of the present invention includes a MEA configured to have a porous electrode catalyst layer on both surfaces of the ion exchange membrane as described above. Here, the MEA includes an anode 710 and a cathode 730 composed of an ion exchange membrane 720 and a porous electrode catalyst layer formed on both surfaces of the ion exchange membrane 720. In this case, the anode chamber 71 and the cathode chamber 73 formed by the anode 710 and the cathode 730 have a product and a reactant, and have a form facing each other.

The anode chamber 71 is formed to be cut off from the outside by the frame 711 and the separator 712, and has an anode 710 and an anode chamber MEA support 713. At this time, a gasket (packing) 714 is installed between the frame 711 and the separator 712 to prevent external leakage of reactants and products in the anode chamber 71.

And the cathode chamber 73 is formed to be cut off from the outside by the frame 731 and the separator 732, the anode 730, the cathode chamber MEA support 733, and the cathode chamber MEA support 733 and the separator plate And a pressure pad 734 positioned between 732. Here, the pressure pad 734 is made of a material suitable for the environment of the electrochemical cell, and functions to adjust the pressure in the unit electrochemical cell to be uniform, and does not always have to be installed. A gasket (packing) 735 is provided between the frame 731 and the separator 732 to prevent external leakage of reactants and products in the cathode chamber 73.

Among the components constituting the unit electrochemical cell, the frames 711 and 731, the separator plates 712 and 732, and the gaskets 714 and 735 are suitable holes to facilitate the inflow and outflow of reactants or products through the unit electrochemical cell. Has

Hereinafter, an example in which the performance of the MEA manufactured by the method of the related art and the MEA manufactured by the method according to an embodiment of the present invention will be described. However, the scope of the present invention is not limited to this example.

Invention Example 1 Porous Cathode Catalyst Layer (Pt) / Porous Cathode Catalyst Layer (Pt)

The ion exchange membrane is a perfluorosulfonic cation exchange membrane, using Nafion from DuPont, and roughly treated on both sides with sandpaper (Norton 600A), soaked in ultrapure water for about 1 hour, and cut out to a certain size. It was used.

end. Cathode Catalyst Layer Formation

(1) pretreatment step

In order to remove organic matter present in the ion exchange membrane cut to a predetermined size, the ion exchange membrane is heated in an aqueous solution of H ₂ O ₂ (3%) for about 40 minutes and then washed with pure water. In addition, the ion exchange membrane is heated in 1M H ₂ SO ₄ solution for about 30 minutes, washed with pure water, and then heated in ultrapure water for about 1 hour.

(2) adsorption step

Methanol containing 0.3 mM AlCl ₃ (aluminium chloride), 0.3 mM pt (NH ₃ ) ₄ Cl ₂ (tetra-amine platinum chloride hydrate, 98%) and water were mixed at a volume ratio of 1: 3. After the mixed solution is prepared, the ion exchange membrane cleaned in the pretreatment step is added to the mixed solution for about 40 minutes to allow the platinum ions to diffuse and adsorb into the ion exchange membrane.

(3) reduction step

NaBH ₄ is mixed with a solution of pH 13 preheated to 50 ° C. to form a 1 mM reducing solution. An ion exchange membrane is added to the reducing solution to remove the platinum solution adsorbed in the adsorption step, and then 60 ml of reducing solution is filled instead. Then, after the reduction process of about 2 hours while stirring it, the ion exchange membrane is impregnated with 0.5M H ₂ SO ₄ for 2 hours, ultrapure water for 1 hour and then stored.

I. Anode Catalytic Layer Formation

(1) Pretreatment Step

After washing with pure water, it is heated in ultrapure water for about 1 hour.

(2) adsorption step

It is the same as the adsorption step of the cathode catalyst layer formation process.

(3) reduction step

It is the same as the reducing step of the cathode catalyst layer forming process.

All. Evaluation of Unit Electrochemical Cells

The performance of the unit electrochemical cell equipped with the MEA prepared through the above steps was evaluated using the experimental system as shown in FIG. 8. The unit electrochemical cell used in the experiment of the present invention is configured as shown in FIG. 8 is a process diagram of an experimental system used to evaluate electrochemical cells having membrane electrode assemblies prepared according to the prior art and the present invention, respectively.

As shown in FIG. 8, DC current was supplied to the electrochemical cell 700 using the DC power supply 810, but distilled water of 1 Mega ohm cm or more was used as a raw material of water. At this time, the water is supplied to the anode chamber through the pump 820, oxygen and unreacted water generated in the anode chamber is separated in the water reservoir 830, the water level of the water reservoir 830 is sensed by the level sensor 831 The inflow of water was controlled via the on-off valve 832. Hydrogen generated in the cathode chamber was separated from the gas-liquid separator 840 of water and hydrogen and discharged. At this time, the water level of the gas-liquid separator 840 was sensed through the level sensor 841 and adjusted through the on-off valve 842. And the temperature of the electrolyte was set to be 80 ℃ by measuring the temperature of the electrochemical cell 700 with the sensor 850, controlled by the electric heater 870 through the controller 860, the voltage generated at this time ( CV, Cell Voltage, and Unit were measured.

la. result

The experimental results are represented by the data of Inventive Example 1 of FIG. 9.

9 is a graph comparing the performance results of the comparative example and the invention example tested through the experimental system of FIG.

Invention Example 2 Porous Cathode Catalyst Layer (Pt-Sn-Ir) / Porous Cathode Catalyst Layer (Pt)

The ion exchange membrane is the same as that of Inventive Example 1.

end. Cathode Catalyst Layer Formation

(1) pretreatment step

It is the same as the pretreatment step of the cathode catalyst layer forming process of Inventive Example 1.

(2) adsorption step

It is the same as the adsorption step of the cathode catalyst layer forming process of Inventive Example 1.

(3) reduction step

It is the same as the reducing step of the negative electrode catalyst layer forming process of Inventive Example 1.

I. Anode Catalytic Layer Formation

(1) Pretreatment Step

After washing with pure water, it is heated in ultrapure water for about 1 hour.

(2) adsorption step

0.3 mM AlCl ₃ (aluminium chloride), 0.1 mM pt (NH ₃ ) ₄ Cl ₂ (tetra-amine platinum chloride hydrate, 98%), 0.25 mM SnCl ₃ (Tin Chloride), and 0.1 mM Iridium Chloride (Iridium) Methanol containing chloride hydrate (98%) and water were mixed at a volume ratio of 1: 3 to form a mixed solution, and the ion exchange membrane washed in the pretreatment step was added to the mixed solution for about 40 minutes. Are allowed to diffuse and adsorb into the interior of the ion exchange membrane.

(3) reduction step

It is the same as the reducing step of the negative electrode catalyst layer forming process of Inventive Example 1.

All. Evaluation of Unit Electrochemical Cells

It is the same as the evaluation method of invention example 1.

la. result

The experimental results are represented by the data of Inventive Example 2 of FIG. 9.

Comparative Example 1

A cathode and a cathode catalyst layer were formed by the method mentioned in the prior art, evaluated in the same manner as in Inventive Example 1, and the experimental results are represented by the data of Comparative Example 1 of FIG.

Comparative Example 2 Electrode Catalyst Layer by Hot Pressing

The performance was evaluated by the evaluation method of Inventive Example 1 using an electrochemical cell having an electrode manufactured by a hot pressing method purchased from Ionic Power in the United States, and the experimental results are represented by the data of Comparative Example 2 of FIG. 9. .

As can be seen from FIG. 9 showing the experimental results of Inventive Examples 1 and 2 and Comparative Examples 1 and 2, Inventive Examples 1 and 2 corresponding to the present invention have a lower voltage regulation at the same current density than Comparative Examples 1 and 2 It can be seen that it has. This means that the present invention has improved performance over the prior art while using a small amount of precious metal (including platinum) to form the electrode catalyst layer.

As described in detail above, the present invention not only can significantly reduce the production cost (half of the conventional level) by reducing the amount of precious metals by porousizing the electrode catalyst layer, and also has an effect of improving the efficiency by stabilizing the reaction efficiency. have.

In the above description of the membrane electrode assembly having a porous electrode catalyst layer of the present invention, a method of manufacturing the same, and an electrochemical cell having the same, the accompanying drawings are described with reference to the accompanying drawings. It is not intended to limit the invention.

It is also apparent to those skilled in the art that various modifications and imitations can be made within the scope of the appended claims without departing from the scope of the technical idea of the present invention.

Claims (6)

In a membrane electrode assembly for an electrochemical cell, each having an electrode catalyst layer forming electrodes on both surfaces of the electrolyte membrane, The electrode catalyst layer is a membrane electrode assembly, characterized in that the porous electrode catalyst layer in which a plurality of pores evenly distributed. The membrane electrode assembly of claim 1, wherein the pores are distributed in a size of 0.01 μm to 0.1 μm to facilitate the inflow and outflow of reactants and products into the electrolyte membrane. In the manufacturing method of the membrane electrode assembly (Embrane Electrode Assembly) for each electrochemical cell having an electrode catalyst layer for forming electrodes on both surfaces of the electrolyte membrane, A pretreatment step of cleaning the electrolyte membrane, An adsorption step of impregnating the pre-treated electrolyte membrane in a solution containing electrode catalyst ions and metal ions which are easily eluted to infiltrate and immobilize the ions into and from the surface of the electrolyte membrane; A reduction and elution step of reducing the electrocatalyst ions fixed to the electrolyte membrane to a catalyst using a reducing agent and eluting metal ions which are easy to elute to form a porous electrode catalyst layer, and And a post-treatment step of washing the electrolyte membrane coated on both surfaces of the porous electrode catalyst layer. The method of claim 3, wherein in the adsorption step, the electrode catalyst is made of one or more mixtures of ruthenium, iridium, manganese, cobalt, nickel, palladium, chromium and platinum. . The method of claim 3 or 4, wherein in the adsorption step, any one or more mixtures of aluminum, magnesium, and zinc are used as the metal that is easily eluted. Membrane Electrode Assembly (Embrane Electrode Assembly) each having an electrode catalyst layer forming electrodes on both surfaces of the electrolyte membrane, the packing, the separator and the frame arranged based on the membrane electrode assembly in the form that can supply and discharge the reactants and products In the electrochemical cell comprising, The electrode catalyst layer is an electrochemical cell, characterized in that the porous electrode catalyst layer evenly distributed a plurality of pores.

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