KR20210109226A - Membrane electrode assembly for water electrolysis and manufacturing method thereof and electrochemical cell having the same - Google Patents

Abstract

According to a method for manufacturing a membrane electrode assembly for water electrolysis of the present invention, gas diffusion layers are integrated with each other by being pressed under a constant pressure at a constant temperature in a state that the gas diffusion layers combined with both positive electrode and negative electrode catalyst layers are placed on both sides of a polymer electrolyte membrane, and the gas diffusion layers combined with the positive electrode catalyst layer are manufactured by a dip coating method in which the gas diffusion layers are immersed in catalyst ink. The present invention reduces the amount of catalysts used through the effective use of both catalysts by coating the positive electrode catalysts on the gas diffusion layers in a dip coating method and bonding the same to the electrolyte polymer membrane, and can reduce manufacturing costs and manufacturing time through the simplification of processes.

Description

Membrane electrode assembly for water electrolysis, manufacturing method thereof, and electrochemical cell having the same

The present invention relates to a membrane electrode assembly for water electrolysis and a method for producing the same, and more particularly, by coating a catalyst on a gas diffusion layer in a dip coating method and bonding it to an electrolyte polymer membrane, thereby reducing the amount of catalyst used through effective use of the catalyst and to a membrane electrode assembly for water electrolysis capable of reducing manufacturing cost and manufacturing time through simplification of the process, a manufacturing method thereof, and an electrochemical cell having the same.

Water electrolysis technology is a technology that can use hydrogen as fuel by electrolyzing water to separate it into oxygen and hydrogen. are receiving

The components of the water electrolysis cell are largely composed of an electrode (hydrogen electrode, oxygen electrode) where an electrochemical reaction occurs, and a membrane, which is a polymer electrolyte membrane, which transfers hydrogen ions generated by the reaction.

The principle of water electrolysis is that water (H ₂ O) is supplied to the anode and decomposed into oxygen gas, electrons, and hydrogen ions.

The electrochemical cell is generally used in an electrolysis cell that uses water as an electrolyte and a raw material to produce gas, and a fuel cell that uses fuel to produce electricity.

As shown in FIG. 1 , water is supplied to the anode and decomposed into oxygen gas, electrons, and hydrogen ions. At this time, a part of the water moves to the cathode together with the oxygen gas and reacts with the electrons moving along the external circuit connecting the anode and the cathode to become hydrogen gas. Then, water passing through the hydrogen ion exchange membrane along with hydrogen gas and hydrogen ions flows out of the electrolysis cell. At this time, the electrochemical reactions occurring at the anode and the cathode, respectively, are expressed as Schemes 1 and 2.

[Scheme 1]

2H ₂ O → 4H ⁺ + 4e ^- + O ₂

[Scheme 2]

4H ⁺ + 4e ^- → 2H ₂

The electrochemical cell is a membrane electrode assembly (hereinafter referred to as "MEA") having an anode and a cathode, a frame arranged in a form capable of supplying and discharging electrons, reactants and products, a separator, a MEA support and a gasket ( packing), etc. Such an electrochemical cell must have excellent electrolytic performance, excellent durability, and low price.

However, in the conventional membrane electrode assembly, anode catalyst ink production → ink spray → electrolyte polymer membrane transfer → gas diffusion layer bonding was prepared in the order of the membrane electrode assembly. That is, the conventional membrane electrode assembly used a spray method. Therefore, the conventional method has problems in that the manufacturing process is complicated and the manufacturing period is long, and the use of unnecessary catalysts generated during the anode catalyst ink spraying process increases.

Therefore, this invention was developed to solve the problems of the prior art as described above, and by coating the catalyst on the gas diffusion layer in a dip coating method and bonding it to the electrolyte polymer membrane, the amount of catalyst used through effective use of the catalyst is reduced. An object of the present invention is to provide a membrane electrode assembly for water electrolysis, a method for manufacturing the same, and an electrochemical cell having the same, which can reduce manufacturing cost and manufacturing time through simplification of the process.

The method for manufacturing a membrane electrode assembly for water electrolysis of the present invention for achieving the above object is integrated with each other by pressing under a constant pressure at a constant temperature in a state in which gas diffusion layers for both anode and cathode are placed on both sides of a polymer electrolyte membrane. However, the gas diffusion layer combined with the catalyst layer of the anode is characterized in that it is manufactured by a dip coating method in which the gas diffusion layer is immersed in the catalyst ink.

In addition, according to the present invention, the catalyst layer of the anode is formed of anode catalyst ink, and the cathode catalyst ink is a water electrolysis nanocatalyst containing an oxide component of Ir, Ru, Pt, Co, Ce, Sn, Sb, or Ti. The particles were quantified so that the catalyst loading amount was 4 mg/cm ² and the content of Nafion ionomer (20 wt% solution) was 10 to 50 wt% compared to the catalyst, and Titanium (IV) isopropoxide (TPT) And it is characterized in that it is added with HCl and ultrasonically dispersed for at least 1 hour.

In addition, according to this invention, the gas diffusion layer combined with the catalyst layer of the positive electrode has a catalyst loading of 4 mg by repeatedly performing the process of coating the gas diffusion layer by the dip coating method and sintering at 400° C. for 10 minutes.

In addition, according to this invention, the constant temperature is 110 ~ 140 ℃, the constant pressure is characterized in that 1 ~ 4Mpa.

In addition, the membrane electrode assembly for water electrolysis of the present invention for achieving the above object is characterized in that it was manufactured by the manufacturing method of the membrane electrode assembly for water electrolysis as described above.

In addition, the electrochemical cell of the present invention for achieving the above object is characterized in that it includes the membrane electrode assembly as described above.

In this invention, the catalyst is coated on the gas diffusion layer in a dip coating method and bonded to the electrolyte polymer membrane. There is this.

1 is a cross-sectional view of the basic structure of a hydrogen and oxygen generating MEA,
2 is a flowchart of a method for manufacturing an MEA according to an embodiment of the present invention;
3 is a graph comparing the performance according to the ratio of the anode catalyst ink according to the present invention,
4 is a graph comparing the performance according to the ratio of the pretreatment solution of the gas diffusion layer according to the present invention,
5 is a graph of the electrolytic voltage performance of the MEA according to the present invention.

Hereinafter, a preferred embodiment of a membrane electrode assembly for water electrolysis, a method for manufacturing the same, and an electrochemical cell having the same according to the present invention will be described in detail with reference to the accompanying drawings. This invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete and to completely convey the scope of the invention to those of ordinary skill in the art. It is provided to inform you.

2 is a flowchart illustrating a method for manufacturing an MEA according to an embodiment of the present invention. As shown in FIG. 2, the MEA manufacturing method according to this embodiment consists of catalyst ink preparation → gas diffusion layer coating → electrolyte polymer membrane bonding method, thereby simplifying the process and reducing manufacturing cost and manufacturing time. In addition, in coating the catalyst layer on the gas diffusion layer, by adopting a dip coating method in which the gas diffusion layer is immersed in the catalyst ink, the amount of catalyst used is reduced through effective use of the catalyst. In addition, it is possible to manufacture a large-area gas diffusion electrode by adopting the dip coating method, thereby making it possible to manufacture large-capacity MEA and electrochemical cells.

[Example] Formation of catalyst layer on gas diffusion layer and preparation of membrane electrode assembly

1. Anode Catalyst Ink Fabrication

Water electrolysis nanocatalyst particles containing oxide components such as Ir, Ru, Pt, Co, Ce, Sn, Sb, and Ti, that is, catalyst particles with a particle diameter of about 3 to 10 nm, have a catalyst loading of 4 mg/cm ² compared to the catalyst. Quantify so that the content of Nafion ionomer (20wt% solution) of 10 to 50wt% is added to IPA and pure solvent along with Titanium(IV) isopropoxide(TPT) and HCl and ultrasonically dispersed for over 1 hour. A catalyst ink was prepared. Here, TPT and HCl play a role in helping the dispersion of the catalyst particles and the smooth coating of the gas diffusion layer. 3 is a graph comparing the performance according to the ratio of the anode catalyst ink according to the present invention.

IPA : DI Water TPT [wt%] HCl [wt%] Example 1 1:1 0.5 0.1 Example 2 3:1 0.7 0.5 Example 3 1:3 1.3 1.7 Example 4 2:3 5 2 Example 5 3:2 7 5

2. Pretreatment of Ti gas diffusion layer and preparation of gas diffusion electrode

In order to properly coat the catalyst particles on the gas diffusion layer, a _{solution such as H 2} O ₂ , H ₂ SO ₄ is prepared in a predetermined ratio, and then the Ti gas diffusion layer is immersed in the solution to be etched and pretreated. , showed the same performance as in FIG. 4 when pre-treated under the conditions of Table 2 below. 4 is a graph comparing the performance according to the ratio of the pretreatment solution of the gas diffusion layer according to the present invention.

H ₂ O _{2 :} H ₂ SO ₄ Time Example 1 1:1 30 min Example 2 1:3 60 min Example 3 3:1 30 min Example 4 2:3 120 min Example 5 3:2 180 min

Then, the gas diffusion layer is coated using a dip coating method in which the gas diffusion layer is immersed in the anode catalyst ink prepared above, and then sintered at 400° C. for 10 minutes. This method was repeated three times to prepare a gas diffusion electrode having a catalyst loading of 4 mg.

3. Fabrication of the cathode electrode

As a cathode catalyst, a commercial Pt-supported carbon catalyst was applied and sprayed so that ^{the catalyst loading amount was 2 mg/cm 2 .} Meanwhile, as the cathode gas diffusion layer, carbon paper in which the microporous layer was previously formed was used.

4. Fabrication of membrane electrode assembly

When the gas diffusion layers for both the anode and the cathode are prepared as described above, the polymer electrolyte membrane is also prepared. Here, as the gas diffusion layer for the catalyst layer of the anode, those prepared under the conditions of Tables 1 and 2 were used. On the other hand, the polymer electrolyte membrane was prepared with pores of 150 to 180 μm, which were pre-treated by immersion in sulfuric acid and pure water at 80° C. or higher for about 1 hour. Then, a membrane electrode assembly was prepared by pressing at a pressure of 1 to 4 Mpa and a temperature of 110 to 140 ° C. for about 2 minutes or more while placing the gas diffusion layers (combining the catalyst layer) of the anode and the cathode on both sides of the polymer electrolyte membrane.

5. Water Electrolysis Voltage Performance of Membrane Electrode Assemblies

In order to confirm the electrolytic voltage performance of the membrane electrode assembly prepared as described above, an experiment was conducted using a cell having a flow path through which water, hydrogen, and oxygen can be supplied and discharged to a current feeder made of titanium. . At this time, when fastening the membrane electrode assembly to the cell, it was tightened by adjusting ^{it to 10 ~ 100 kgf.cm 2 .} On the current plate of the cell where the connection is completed, connect the negative terminal to the negative terminal and the positive terminal to the positive terminal from the rectifier, and supply pure water (resistance 18MΩ or more) maintained at 80°C to the positive electrode at a flow rate between 100 and 1,000 per minute. The voltage was measured while varying the 5 is a graph of the electrolysis voltage performance of the MEA according to the present invention, and as can be seen in FIG. 5 , it was confirmed that the water electrolysis voltage performance of the membrane electrode assembly according to the present invention was excellent.

In the above, the description of the membrane electrode assembly for water electrolysis of the present invention, the method for manufacturing the same, and the electrochemical cell having the same have been described along with the accompanying drawings, but this is an exemplary description of the best embodiment of the present invention. Therefore, the present invention is not limited to the above-described embodiments, and it is apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Examples or modifications will also fall within the scope of the claims of this invention.

Claims (6)

In a state where the gas diffusion layer for both the anode and the cathode is placed on both sides of the polymer electrolyte membrane, it is pressed under a certain pressure at a certain temperature to integrate it with each other,
The method of manufacturing a membrane electrode assembly for water electrolysis, characterized in that the gas diffusion layer for the catalyst layer of the anode is prepared by a dip coating method in which the gas diffusion layer is immersed in the catalyst ink. The method according to claim 1,
The catalyst layer of the anode is formed of anode catalyst ink,
The cathode catalyst ink contains aqueous electrolytic nanocatalyst particles containing an oxide component of Ir, Ru, Pt, Co, Ce, Sn, Sb, or Ti with a catalyst loading of 4 mg/cm ² and 10 to 50 wt% of Nafion compared to the catalyst. The faucet, characterized in that it is quantified so that the content of Nafion ionomer (20wt% solution) becomes, and is added to IPA and pure solvent along with Titanium(IV) isopropoxide(TPT) and HCl, followed by ultrasonic dispersion for at least 1 hour. A method for manufacturing a dissolving membrane electrode assembly. The method according to claim 1,
Method for producing a membrane electrode assembly for water electrolysis, characterized in that the gas diffusion layer combined with the catalyst layer of the anode has a catalyst loading of 4 mg by repeating the process of coating the gas diffusion layer by the dip coating method and sintering at 400° C. for 10 minutes . The method according to claim 1,
The constant temperature is 110 ~ 140 ℃, the method of manufacturing a membrane electrode assembly for water electrolysis, characterized in that the constant pressure is 1 ~ 4Mpa. A membrane electrode assembly, characterized in that it is manufactured by the method for manufacturing a membrane electrode assembly for water electrolysis according to any one of claims 1 to 4. An electrochemical cell comprising the membrane electrode assembly according to claim 5 .

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