KR20230174373A - Electrode manufacturing method for increasing durability of MEA support of hydrogen fuel cell - Google Patents

Abstract

In the present invention, an electrode slurry is prepared by mixing a first electrode composition in which platinum-fibrous carbon is attached to the surface of a spherical catalyst with a mixed solution of a solvent and an ionomer, and an electrode is manufactured from this electrode slurry. The platinum-fibrous carbon contained in the electrode maintains the electrode structure well even during long-term fuel cell operation. As a result, it is possible to prevent the MEA support from being damaged when the electrode structure collapses and the spherical catalysts clump together, thereby improving the durability of the MEA support.

Description

Electrode manufacturing method for increasing durability of MEA support of hydrogen fuel cell}

The present invention relates to an electrode manufacturing method for increasing the durability of a hydrogen fuel cell MEA support.

A fuel cell is a device that converts chemical energy into electrical energy using a fuel such as hydrogen.

Depending on the type of electrolyte used, fuel cells include molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), phosphoric acid fuel cell (PAFC), It can be classified into polymer electrolyte membrane fuel cell (PEMFC), direct methanol fuel cell (DMFC), etc.

Each fuel cell has fundamentally the same operating principle. However, each fuel cell can be classified differently depending on various conditions such as the type of fuel used, operating temperature, catalyst, and electrolyte.

Among them, polymer electrolyte membrane fuel cells have the advantages of having higher power density and efficiency compared to other fuel cells, operating at low operating temperatures, and having fast start-up and response characteristics. For this reason, polymer electrolyte membrane fuel cells can be used in various ways as transportation power sources for automobiles, distributed power sources for residential environments, and mobile power sources for various portable devices.

The innermost part of a polymer electrolyte membrane fuel cell is the main component, the membrane-electrode assembly (hereinafter referred to as 'MEA'). This MEA consists of electrodes, that is, an anode and a cathode. It consists of poles located on both sides of the electrolyte membrane.

Conventionally, an electrode slurry containing a solvent, an ionomer, and a spherical catalyst was coated on an electrolyte membrane and then dried to manufacture an electrode. The spherical catalyst mixed at this time is manufactured by carrying active metal particles on a spherical carbon support (MEA support). Platinum (Pt) is widely used as an active metal.

In hydrogen fuel cells that use hydrogen as fuel, as the cumulative power generation time increases, the agglomeration of spherical catalysts becomes more severe, and the structure of the MEA support quickly collapses. If the structure of the MEA support collapses, MEA performance quickly decreases. Therefore, there is a need to improve the durability of the MEA support from the time of electrode manufacturing.

Korean registered patent (10-0831659)

The purpose of the present invention is to provide an electrode manufacturing method for increasing the durability of a hydrogen fuel cell MEA support that can solve the above-mentioned problems.

The electrode manufacturing method for increasing the durability of the hydrogen fuel cell MEA support to achieve the above purpose is,

A first step of producing a spherical catalyst by supporting active metal particles on a spherical carbon support;

A second step of producing platinum_fibrous carbon by supporting platinum particles on fibrous carbon;

A third step of manufacturing a first electrode composition by attaching the platinum fibrous carbon to the surface of the spherical catalyst;

A fourth step of preparing an electrode slurry by mixing the first electrode composition with a mixed solution of a solvent and an ionomer; and

It is characterized by comprising a fifth step of manufacturing an electrode using the electrode slurry.

In addition, the above purpose is to

A first step of producing a spherical catalyst by supporting active metal particles on a spherical carbon support;

A second step of producing platinum_fibrous carbon by supporting platinum particles on fibrous carbon;

A third step of mixing the platinum fibrous carbon and fibrous carbon at a set ratio and attaching the platinum fibrous carbon to the surface of the spherical catalyst to prepare a second electrode composition;

A fourth step of preparing an electrode slurry by mixing the second electrode composition with a mixed solution of a solvent and an ionomer; and

This is achieved by an electrode manufacturing method for increasing the durability of a hydrogen fuel cell MEA support, which includes a fifth step of manufacturing an electrode using the electrode slurry.

In the present invention, an electrode slurry is prepared by mixing a first electrode composition in which platinum-fibrous carbon is attached to the surface of a spherical catalyst with a mixed solution of a solvent and an ionomer, and an electrode is manufactured from this electrode slurry. The platinum-fibrous carbon contained in the electrode maintains the electrode structure well even during long-term fuel cell operation. As a result, it is possible to prevent the MEA support from being damaged when the electrode structure collapses and the spherical catalysts clump together, thereby improving the durability of the MEA support.

In addition, platinum particles surround the fibrous carbon, preventing the fibrous carbon from acting as a resistor, which not only stabilizes the electrode condition but also improves MEA performance.

In addition, since the first electrode composition is manufactured using a ball miller, platinum fibrous carbon can be firmly attached to the surface of the spherical catalyst. Additionally, by controlling the amounts of spherical catalyst and platinum-fibrous carbon introduced into the ball miller, the ratio of spherical catalyst and platinum-fibrous carbon in the first electrode composition can be easily adjusted.

In the present invention, platinum fibrous carbon and fibrous carbon are mixed at a set ratio and then attached to the surface of a spherical catalyst to prepare a second electrode composition. This second electrode composition is mixed with a mixed solution of a solvent and an ionomer to form an electrode. A slurry is prepared, and an electrode is manufactured from this electrode slurry. The platinum-fibrous carbon and fibrous carbon contained in the electrode maintain the electrode structure well even during long-term fuel cell operation. As a result, it is possible to prevent the MEA support from being damaged when the electrode structure collapses and the spherical catalysts clump together, thereby improving the durability of the MEA support. In addition, the amount of expensive platinum used can be reduced compared to the case where only platinum fibrous carbon is used.

Figure 1 is a flowchart showing an electrode manufacturing method for increasing durability of a hydrogen fuel cell MEA support according to the first embodiment of the present invention.
Figure 2 is a schematic diagram showing (a) a spherical catalyst and (b) platinum_fibrous carbon manufactured by an electrode manufacturing method for increasing the durability of a hydrogen fuel cell MEA support according to the first embodiment of the present invention.
Figure 3 is a schematic diagram showing a first electrode composition manufactured by an electrode manufacturing method for increasing durability of a hydrogen fuel cell MEA support according to the first embodiment of the present invention.
Figure 4 is a schematic diagram showing the production of a first electrode composition by attaching platinum particles to the surface of a spherical catalyst and fibrous carbon by ball milling.
Figure 5 is a schematic diagram showing manufacturing a first electrode composition by ball milling balls with different diameters.
Figure 6 is a schematic diagram showing filtering the first electrode composition prepared by ball milling.
Figure 7 is a graph showing the voltage drop according to the current density of the electrode before (fresh) and after (after AST) an accelerated stress test (AST). Figure 7(a) is a graph showing the voltage drop according to the current density of the electrode with platinum particles supported. A graph showing the case in which no carbon nanotubes were added, Figure 7(b) showing the case in which 10% of carbon nanotubes carrying platinum particles were added, and Figure 7(c) showing the case in which 20% of carbon nanotubes carrying platinum particles were added. am.
Figure 8 is a flowchart showing an electrode manufacturing method for stabilizing the state of a hydrogen fuel cell electrode according to a second embodiment of the present invention.
Figure 9 is a schematic diagram showing a second electrode composition manufactured by an electrode manufacturing method for increasing durability of a hydrogen fuel cell MEA support according to a second embodiment of the present invention.

Hereinafter, a method for manufacturing an electrode for increasing durability of a hydrogen fuel cell MEA support according to the first embodiment of the present invention will be described in detail.

As shown in Figure 1, the electrode manufacturing method for increasing the durability of the hydrogen fuel cell MEA support according to the first embodiment of the present invention is,

A first step (S11) of producing a spherical catalyst by supporting active metal particles on a spherical carbon support;

A second step (S12) of producing platinum_fibrous carbon by supporting platinum particles on fibrous carbon;

A third step (S13) of manufacturing a first electrode composition by attaching the platinum fibrous carbon to the surface of the spherical catalyst;

A fourth step (S14) of preparing an electrode slurry by mixing the first electrode composition with a mixed solution of a solvent and an ionomer; and

It consists of a fifth step (S15) of manufacturing an electrode using the electrode slurry.

Hereinafter, the first step (S11) will be described.

The spherical catalyst 10 is manufactured by supporting active metal particles 12 on a spherical carbon support 11. The spherical catalyst 10 can be divided into three types: a catalyst using a high specific surface area carrier (BET 600-700 or more), a catalyst that has undergone a heat treatment process, and an alloy catalyst.

The spherical carbon support 11 is made of carbon black particles, and in order to create numerous pores in the spherical carbon black particles, the carbon black particles are revived with water vapor.

Types of carbon black particles include thermal black particles, acetylene black particles, and ketjen black particles.

The active metal particles 12 are made of a metal selected from the transition metal group such as platinum (Pt), nickel (Ni), palladium (Pd), rhodium (Rh), titanium (Ti), and zirconium (Zr). Or, it may be an alloy particle made of one or more metals selected from among these.

In the case of single metal particles, platinum particles 14 are preferably used.

If the active metal is alloyed with another metal rather than a single platinum metal, less oxide film is formed. This is because when alloyed, the electrons of platinum are drawn away, making the platinum surface less oxidized. At this time, melting of the alloy itself can be a problem. However, it can be adjusted to the optimal ratio so that the alloy does not melt easily. In addition, the alloy melts in advance everything that will be melted through acid treatment. Therefore, when alloy particles are used, costs are reduced compared to when expensive platinum is used alone, and not only performance but also durability is improved.

When the spherical carbon support 11, platinum particles 12, solvent, and ionomer are mixed and reacted at the hydrogen ion concentration (PH) and temperature, the platinum particles 12 are supported in the pores formed in the spherical carbon support 11. When this is filtered, dried, and heat treated, a spherical catalyst 10 as shown in FIG. 2(a) is manufactured.

The solvent may be selected from the group consisting of ethanol, isopropyl alcohol, propanol, butanol, amyl alcohol, and distilled water.

Ionomers include polysulfone-based resins, polyether ketone-based resins, polyether-based resins, polyester-based resins, polybenzimidazole-based resins, polyimide-based resins, polyphenylene sulfide-based resins, polyphenylene oxide-based resins, and It may be selected from the group consisting of nepion.

Hereinafter, the second step (S12) will be described.

As shown in FIG. 2(b), platinum particles 12 are supported on fibrous carbon 13.

The fibrous carbon 13 is preferably either carbon nanotubes (carbon nano tubes, CNTs) or carbon nanofibers (CNFs), or a mixture of the two.

Supporting the platinum particles 12 on the surface of carbon nanotubes or carbon nanofibers can be performed using known techniques such as a wet electrochemical process, a dry thin film deposition process, or a supercritical carbon dioxide fluid loading process.

Carbon nanotubes have a structure in which hexagonal carbon planes are arranged parallel to the fiber axis, and have a tube-shaped space inside of them of 0.4 nm or more. As carbon nanotubes, single wall carbon nanotubes (SWCNT), double wall carbon nanotubes (DWCNT), and multi wall carbon nanotubes (MWCNT) can be applied.

Carbon nanofibers have a structure in which the hexagonal carbon planes are arranged at right angles to the fiber axis (column structure or platelet structure) and a structure with a constant inclination to the fiber axis (feather structure or herringbone structure). It does not show the space of a tube like a carbon nanotube inside the fiber.

Hereinafter, the third step (S13) will be described.

A ball miller is used to manufacture the first electrode composition 30 by attaching platinum fibrous carbon 20 to the surface of the spherical catalyst 10 as shown in FIG. 3.

As shown in FIG. 4, the ball miller 100 includes a barrel 101, two rollers 102 and 103 on which the barrel 101 is placed, a drive unit (not shown) that rotates the two rollers 102 and 103, and a barrel. It consists of balls (104) placed inside (101). There is an entrance through which the spherical catalyst (10), platinum fibrous carbon (20), and ball (104) can be placed and taken out of the barrel (101), but this is not shown. Additionally, since the configuration of the driving unit can be implemented using known technologies such as motors, detailed description will be omitted.

[1st ball milling method]

The first ball milling method manufactures the first electrode composition 30 by applying physical force to the spherical catalyst 10 and the platinum fibrous carbon 20 using balls 104 having the same diameter.

For this purpose, balls 104 having the same diameter as the spherical catalyst 10 and platinum fibrous carbon 20 are placed in the barrel 101. The barrel 101 is placed on the two rollers 102 and 103. The two rollers 102 and 103 rotate to rotate the barrel 101. While the barrel 101 rotates, the balls 104 move randomly and pressurize the spherical catalyst 10 and the platinum fibrous carbon 20. Combine.

[Second ball milling method]

See Figure 5.

The second ball milling method manufactures the first electrode composition (30) by applying physical force to the spherical catalyst (10) and the platinum-fibrous carbon (20) using balls (104, 105) having different diameters.

For this purpose, balls 104 and 105 of different sizes are placed into the barrel 101. The barrel 101 is placed on the two rollers 102 and 103. Two rollers 102 and 103 rotate the barrel 101. While the barrel 101 rotates, the balls 104 and 105 of different sizes move randomly and pressurize the spherical catalyst 10 and the platinum fibrous carbon 20. Combine (20).

At this time, the balls 104 with a relatively large diameter (10 mm) roughly combine the spherical catalyst 10 and the platinum fibrous carbon 20, and the balls 105 with a relatively small diameter (3 mm) combine the spherical catalyst 10 and the platinum fibrous carbon 20. (10) and platinum-fibrous carbon (20) go into the area where they are not bonded and bond the spherical catalyst (10) and platinum-fibrous carbon (20) in detail. Therefore, by using the second ball milling method, the first electrode composition 30 can be manufactured with better bonding strength between the spherical catalyst 10 and the platinum fibrous carbon 20 than by the first ball milling method.

[Filtering Method]

See Figure 6.

The filtering method is to filter the first electrode composition 30 prepared by the first method or the second method through the filter 132, and remove the spherical catalyst 10 or the spherical catalyst buried in the first electrode composition 30 in an unbound state. Platinum_fibrous carbon (20) is dropped below the filter (132), and only the first electrode composition (30) is left on the filter (132). For this purpose, as shown in FIG. 6, a filter unit 130 consisting of a container 131, a filter 132, and a vibrator 133 is used. The vibrator 133 vibrates the container 131, causing the spherical catalyst 10 or platinum fibrous carbon 20 to fall easily below the filter 132.

Hereinafter, the fourth step (S14) will be described.

An electrode slurry is prepared by mixing the first electrode composition 30 with a mixed solvent containing a solvent and an ionomer. The solvent and ionomer are the same as those described in the first step (S11).

In this way, when platinum-fibrous carbon (20) is added together with the spherical catalyst (10) to the electrode slurry, the platinum-fibrous carbon (20) holds the structure within the electrode slurry and prevents the spherical catalysts (10) from clumping together. , platinum particles 12 surround the surface of the fibrous carbon 13, preventing the fibrous carbon 13 from acting as a resistor.

In addition, since platinum fibrous carbon 20 is added to the surface of the spherical catalyst 10, the platinum fibrous carbon 20 can be distributed evenly and more firmly on the surface of the spherical catalyst 10, and the spherical catalyst 10 can be distributed evenly and more firmly. It becomes easy to control the ratio of (10) and fibrous carbon (13).

Hereinafter, the fifth step (S15) will be described.

An electrode is manufactured using the electrode slurry prepared as described above.

The electrode is formed by coating the electrode slurry on a release film and drying it. Two release films with electrodes are transferred to the upper and lower surfaces of the electrolyte membrane and the electrodes are attached to the electrolyte membrane.

Alternatively, an electrode can be formed by directly coating the electrode slurry on the electrolyte membrane.

The method of forming electrodes on the electrolyte membrane is not limited to this, and can be performed in various ways using known technologies.

[MEA support durability evaluation]

To evaluate the durability of the MEA support for the electrode manufactured in this way, an accelerated stress test (AST) is performed. Figure 7 is a graph showing the voltage drop according to the current density of the electrode before (fresh) and after (after AST) the accelerated stress test.

The accelerated stress test to evaluate the durability of the MEA support is performed by repeating the process of applying a voltage of 1.0 V to the anode and cathode and maintaining it for 30 seconds, and applying a voltage of 1.4 V to the anode and cathode and maintaining it for 30 seconds, repeating 500 times. .

Looking at FIG. 7(a), it can be seen that when the carbon nanotubes carrying platinum particles are not inserted into the spherical catalyst 10, the voltage drop according to the voltage density is large after the accelerated stress test.

In addition, looking at Figure 7(b) and Figure 7(c), the voltage density after the accelerated stress test when 10% of the carbon nanotubes supported with platinum particles were inserted and when 20% of the carbon nanotubes supported with platinum particles were inserted. It can be seen that the voltage drop gradually decreases.

When 20% of carbon nanotubes loaded with platinum particles are added, the performance reduction rate is about 10 times better than when carbon nanotubes loaded with platinum particles are not added. This shows that as the amount of carbon nanotubes loaded with platinum particles increases, the electrode structure is better maintained and the durability of the MEA support improves.

Hereinafter, the electrode manufacturing method for increasing the durability of the hydrogen fuel cell MEA support according to the second embodiment of the present invention will be described in detail. Basically refer to FIGS. 1 to 7.

As shown in Figure 8, the electrode manufacturing method for increasing the durability of the hydrogen fuel cell MEA support according to the second embodiment of the present invention is,

A first step (S21) of producing a spherical catalyst by supporting active metal particles on a spherical carbon support;

A second step (S22) of producing platinum_fibrous carbon by supporting platinum particles on fibrous carbon;

A third step (S23) of mixing the platinum fibrous carbon and fibrous carbon at a set ratio and attaching them to the surface of the spherical catalyst to prepare a second electrode composition (S23);

A fourth step (S24) of preparing an electrode slurry by mixing the second electrode composition with a mixed solution of a solvent and an ionomer; and

It consists of a fifth step (S25) of manufacturing an electrode using the electrode slurry.

The first step (S21), the second step (S22), the fourth step (S24), and the fifth step (S25) of the second embodiment are the first step (S11), the second step (S12), and the first step (S12) of the first embodiment. Since they are the same as the fourth step (S14) and the fifth step (S15), detailed descriptions will be omitted and only the distinct third step (S23) will be described.

Hereinafter, the third step (S23) will be described.

As shown in FIG. 9, the second electrode composition 40 is manufactured by attaching platinum fibrous carbon 20 and fibrous carbon 13 mixed at a set ratio to the surface of the spherical catalyst 10.

The fibrous carbon 13 is preferably either carbon nanotubes (carbon nano tubes, CNTs) or carbon nanofibers (CNFs), or a mixture of the two.

To manufacture the second electrode composition 40, a ball miller is used as in the first embodiment. Since it is the same as the first embodiment except that platinum_fibrous carbon (20) and fibrous carbon (13) are added in a set ratio instead of platinum_fibrous carbon (20), detailed description will be omitted.

In this way, when platinum_fibrous carbon (20) and fibrous carbon (13) are mixed at a set ratio, the effect of increasing the durability of the MEA support can be maintained while reducing the amount of expensive platinum used.

10: Spherical catalyst 11: Spherical carbon support 12: Active metal particles 13: Fibrous carbon
14: Platinum particles 20: Platinum_fibrous carbon
30: first electrode composition 40: second electrode composition
100: Ball Miller 101: Tong
102,103: roller 104, 105: ball
130: filter unit 131: container
132: filter 133: exciter

Claims (3)

A first step of producing a spherical catalyst by supporting active metal particles on a spherical carbon support;
A second step of producing platinum_fibrous carbon by supporting platinum particles on fibrous carbon;
A third step of manufacturing a first electrode composition by attaching the platinum fibrous carbon to the surface of the spherical catalyst;
A fourth step of preparing an electrode slurry by mixing the first electrode composition with a mixed solution of a solvent and an ionomer; and
An electrode manufacturing method for increasing durability of a hydrogen fuel cell MEA support, comprising a fifth step of manufacturing an electrode using the electrode slurry. A first step of producing a spherical catalyst by supporting active metal particles on a spherical carbon support;
A second step of producing platinum_fibrous carbon by supporting platinum particles on fibrous carbon;
A third step of mixing the platinum fibrous carbon and fibrous carbon at a set ratio and attaching the platinum fibrous carbon to the surface of the spherical catalyst to prepare a second electrode composition;
A fourth step of preparing an electrode slurry by mixing the second electrode composition with a mixed solution of a solvent and an ionomer; and
An electrode manufacturing method for increasing durability of a hydrogen fuel cell MEA support, comprising a fifth step of manufacturing an electrode using the electrode slurry. According to claim 1 or 2,
The fibrous carbon is a method of manufacturing an electrode for increasing durability of a hydrogen fuel cell MEA support, characterized in that one of carbon nanotubes (CNT), carbon nanofiber (CNF), or a mixture of the two. .