JP2007128803A - Separator and manufacturing method therefor, as well as fuel cell using separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell separator which can contribute to suppressing destruction of natural environment by reducing wastes, even though it may be small, by utilizing biodegradable plastics for fuel cell separators, when fuel cells are unfortunately illegally dumped, provide its manufacturing method, and to provide the fuel cell that uses the separator. <P>SOLUTION: By means that the wastes are reduced by utilizing the biodegradable plastics for the separators, when the fuel cells are illegally dumped, this separator can contribute to suppressing destruction of the natural environment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a separator comprising a biodegradable plastic and a conductive pin, a method for producing the separator, and a fuel cell using the separator.

Fuel cells are used in various applications such as electric vehicle power supplies and mobile phone power supplies, and their usage is increasing.

A fuel cell has an MEA (solid polymer electrolyte membrane electrode assembly) in which a catalyst layer is provided on the front and back surfaces of an electrolyte membrane, and a gas diffusion material is provided on the surface opposite to the electrolyte membrane of the catalyst membrane, and a separator. A plurality of layers are stacked.

As the separator of the fuel cell, a molded one of a conductive carbon material or a molded metal is used. (See Patent Document 1)

JP 2003-249237 A

However, such separators remain permanently after using the fuel cell, and if the fuel cell is unfortunately dumped illegally, the natural environment is destroyed.

The object of the present invention is to use biodegradable plastic for the fuel cell separator, so that when the fuel cell is unfortunately dumped illegally, even if it is a little, the waste is reduced and the destruction of the natural environment is suppressed. The present invention provides a fuel cell separator and a method for manufacturing the same, and a fuel cell using the separator.

The invention according to claim 1 is a biodegradable plastic separator characterized in that the surface on which the reaction gas flow channel is formed is electrically connected to the surface opposite to the surface by the conductive pin. .
By using biodegradable plastic for the separator, when the fuel cell is illegally dumped, it can contribute to reducing waste and suppressing destruction of the natural environment.

The invention according to claim 2 is the biodegradable plastic separator according to claim 1, wherein the conductive pin is made of carbon, gold, silver, copper, or iron.
Since biodegradable plastics are not electrically conductive, the use of carbon, gold, silver, copper, and iron conductive pins makes it possible to provide a surface on which the reaction gas flow channel of the separator is formed, and the reaction gas flow channel. Conduction is conducted between the surface opposite to the formed surface.

The invention according to claim 3 is the biodegradable plastic separator according to claim 1 or 2, wherein the biodegradable plastic is made of polylactic acid resin and layered silicate.
The operating temperature of the PAFC (phosphoric acid type) fuel cell is about 90 ° C., and the operating temperature of the PEFC (solid polymer type) fuel cell is about 120 ° C.
The heat resistance of a biodegradable plastic made of polylactic acid resin that is generally used is about 60 ° C., whereas the heat resistance of a biodegradable plastic made of polylactic acid resin and layered silicate is about 140 ° C. .
Heat resistance and mechanical strength can be imparted by adding layered silicate to the polylactic acid resin.
A biodegradable plastic made of polylactic acid resin and layered silicate is used so that the separator can withstand the operating temperature of the fuel cell.

According to a fourth aspect of the present invention, there is provided a method for producing a biodegradable plastic separator, wherein a conductive pin is disposed in an injection mold and the biodegradable plastic is injected and integrally molded.
In a manufacturing method in which a hole is drilled in a biodegradable plastic and a conductive pin is inserted into the hole, a gap is formed between the biodegradable plastic and the conductive pin, and the reaction gas passes to the electrode through the gap. It flows in and causes oxidation of the electrode, and as a result, the fuel cell cannot generate electricity.
In order to cope with this, a conductive pin is arranged in an injection mold, and then a biodegradable plastic is injected and integrally molded to manufacture a separator.

In the invention according to claim 5, a catalyst layer is provided on the front and back surfaces of the solid polymer electrolyte membrane, a gas diffusion material is provided on the surface of the catalyst layer opposite to the solid polymer electrolyte membrane, and the gas diffusion is provided. A fuel cell using the biodegradable plastic separator according to any one of claims 1 to 3 as a separator on a surface of the material opposite to the catalyst layer.

The invention according to claim 6 is the fuel cell according to claim 5, wherein the solid polymer electrolyte membrane is a sulfone group-containing perfluorocarbon or a carboxyl group-containing perfluorocarbon.

The invention according to claim 7 is the fuel cell according to claim 5 or 6, wherein the catalyst layer is made of a proton conductive material, an electron conductive material, and a catalyst.

The invention according to claim 8 is characterized in that the proton conductive material is perfluorocarbon sulfonic acid, polyether sulfone, sulfonated polyether ether ketone, or sulfonated polyimide. It is a fuel cell.

The invention according to claim 9 is the fuel cell according to claim 7 or claim 8, wherein the electron conductive material is silicon dioxide or carbon.

The invention according to claim 10 is characterized in that the catalyst is made of one or more metals selected from gold, platinum, palladium, rhodium, ruthenium, osmium and iridium. 10. The fuel cell according to any one of items 9.

The invention according to claim 11 is the fuel cell according to any one of claims 7 to 10, wherein an average particle diameter of the catalyst is 1 nm or more and 5 nm or less.
When the minimum particle size of gold, platinum, palladium, rhodium, ruthenium, and iridium serving as a catalyst is 1 nm or more and the average particle size of the catalyst exceeds 5 nm, the surface area per unit weight of the catalyst is very small. The activity is also small, and the output characteristics of the fuel cell are poor.

The invention according to claim 12 is the fuel cell according to any one of claims 7 to 11, wherein a supporting rate of the catalyst of the electron conductive material is 1% to 80%. It is.
When the catalyst loading is less than 1%, the output characteristics of the fuel cell are poor, and when the catalyst loading exceeds 80%, the battery output does not change and the catalyst is wasted.

The invention according to claim 13 is the fuel cell according to any one of claims 5 to 12, wherein the gas diffusion material is a conductive porous substrate.

The invention according to claim 14 is the fuel cell according to claim 13, wherein the conductive porous substrate is carbon paper or carbon cloth.

In the present invention, by using a biodegradable plastic for the fuel cell separator, when the fuel cell is unfortunately dumped illegally, even if it is a little, the waste is reduced and the destruction of the natural environment is suppressed. It is possible to provide a fuel cell separator that can contribute, a manufacturing method thereof, and a fuel cell using the separator.

An example of a method for forming a fuel cell according to the present invention will be described with reference to FIG.

First, the catalyst layer 2 or the catalyst layer 4 is formed on the gas diffusion material 1 or the gas diffusion material 5. (Fig. 1 (a))

As a material of the gas diffusion material 1 or the gas diffusion material 5, carbon paper or carbon cloth can be used.

Examples of the material of the catalyst layer 2 and the catalyst layer 4 include perfluorocarbon sulfonic acid, polyether sulfone, sulfonated polyether ether ketone, sulfonated polyimide, etc., which are proton conductive materials, and silicon dioxide, which is an electron conductive material, Carbon and the like, and catalysts such as gold, platinum, palladium, rhodium, ruthenium, osmium and iridium can be used.

The catalyst layer 2 and the catalyst layer 4 are produced by dissolving a catalyst-supported electron conductive material and proton conductive material in alcohol such as IPA and NPA and water to produce a catalyst ink, A method of bar coating, spraying, or screen printing on the gas diffusion material 1 or 5 can be used.

The weight ratio of the electron conductive material carrying the catalyst and the proton conductive material is preferably in the range of 1: 1 to 50: 1.

Next, with the catalyst layer 2 and the catalyst layer 4 facing each other, the solid polymer electrolyte membrane 3 is sandwiched to produce a solid polymer electrolyte membrane electrode assembly 6 (hereinafter referred to as MEA). (Fig. 1 (c))

As a material for the solid polymer electrolyte membrane 3, a sulfone group-containing perfluorocarbon or a carboxyl group-containing perfluorocarbon can be used.

As a method for producing the MEA 6, a method in which the solid polymer electrolyte membrane 3 is sandwiched with the catalyst layer 4 (fuel electrode side) and the catalyst layer 2 (air electrode side) facing each other and thermocompression bonded can be used.
As the heating temperature, a temperature exceeding the softening temperature of the resin of the catalyst layer 2, the catalyst layer 4, and the solid polymer electrolyte membrane 3 or the glass transition temperature can be used.
When the resin of catalyst layer 2, catalyst layer 4 and solid polymer electrolyte membrane 3 is perfluorocarbon sulfonic acid, thermocompression bonding conditions of temperature = 100 ° C. to 300 ° C., pressure = 1 MPa to 15 MPa, time = 5 seconds to 400 seconds Can be used.

Next, the separator 9 (fuel electrode side) and the separator 12 (air electrode side) are molded. (Figure 2)

The material of the separator 9 or the separator 12 includes biodegradable plastic 7 or biodegradable plastic 10 made of polylactic acid resin and layered silicate, and conductive pins 8 made of carbon, gold, silver, copper, and iron. Alternatively, the conductive pin 11 can be used.

As a manufacturing method of the separator 9 (fuel electrode side) and the separator 12 (air electrode side), a conventional molding method such as injection molding or hot press molding can be used.

In the case of injection molding, the polylactic acid resin and the layered silicate are melt-kneaded, the conductive pin 8 or the conductive pin 11 is set in the mold, and injection molding is performed, whereby the separator 9 (fuel electrode side) and the separator 12 (air electrode side) can be manufactured.

As the mold, a mold having an uneven portion for forming a gas flow path on one side of the separator 9 (fuel electrode side) and the separator 12 (air electrode side) can be used.

The blend of the polylactic acid resin and the layered silicate is preferably 0.1 to 50 parts by mass of the layered silicate with respect to 100 parts by mass of the polylactic acid resin.

The melting temperature of the mixture of the polylactic acid resin and the layered silicate can be 170 ° C. to 190 ° C., and the residence time can be 3 to 5 minutes.

Next, the MEA 6 is sandwiched with the gas flow path forming surfaces of the separator 9 (fuel electrode side) and the separator 12 (air electrode side) facing each other, thereby producing a battery cell. (Fig. 3 (b))

Next, a current collector plate (fuel electrode side) 13 and a current collector plate (air electrode side) 14 are laminated on both surfaces of the battery cell to obtain a fuel cell. (Fig. 3 (c))

As a lamination method of the solid polymer electrolyte membrane 3, the separator 9 (fuel electrode side), the separator 12 (air electrode side), the current collector plate (fuel electrode side) 13, and the current collector plate (air electrode side) 14, A method of fixing with a fastening rod can be used.

As materials for the current collector plate (fuel electrode side) 13 and the current collector plate (air electrode side) 14, stainless steel and copper can be used.

First, an electron conductive material carrying platinum having an average particle diameter of 3 nm (platinum: electron conductive material = 1: 1 (weight ratio)) and a proton conductive material were dissolved in a solvent so as to have the following composition. A catalyst ink was prepared.
-Carbon carrying platinum (electron-conducting substance) 7.5% by weight
・ Perfluorocarbon sulfonic acid (proton conductive material) 2.5% by weight
・ Water 30.0% by weight
・ IPA 30.0% by weight
・ NPA 30.0% by weight

Next, this catalyst ink was applied onto carbon paper having a thickness of 190 μm cut into a size of 200 mm × 200 mm using a bar coater.

Next, after heat treatment at 120 ° C. for 1 hour in a nitrogen atmosphere, the mixture was allowed to cool for 30 minutes to produce a fuel cell catalyst electrode.

Next, the catalyst layers of the two fuel cell catalyst electrodes produced by the above method are face to face, and a sulfone group-containing perfluorocarbon having a thickness of 50 μm is sandwiched between 130 ° C., 30 minutes, and 3 MPa. MEA was produced by heat molding.

Next, 20 cylindrical conductive pins having a diameter of 0.5 mm and a height of 6 mm were arranged in parallel in the area of 11 cm × 11 cm in the center of the surface, with the height direction of the conductive pins and the separator thickness direction being parallel. After setting in a male-female mold with grooves (width: 2 mm, length: 10 cm, depth: 3 mm, groove spacing: 2 mm), 25 parts by mass of layered silicate with respect to 100 parts by mass of polylactic acid resin A biodegradable plastic obtained by melting and kneading the compound at a melting temperature of 180 ° C. under a residence time of 4 minutes is injected into a mold under the conditions of 130 ° C., 30 minutes, and 3 MPa to produce a separator having a thickness of 3 mm. did.

Finally, the gas flow path forming surfaces of the two separators face each other, the MEA is sandwiched between them, SUS-made current collector plates with a thickness of 0.3 mm are arranged on both sides, and fastened with rods. A battery was obtained.

Next, the output of the fuel cell is measured by a fuel cell using an electrochemical interface (Solaron SI-1287), a frequency response analyzer (Solartron SI-1260), and an electronic loader (Scribner 890CL). Using system GFT-SG1 (manufactured by Toyo Corporation), the measurement was performed as follows.

First, after mounting the fuel cell on a power generation cell made of graphite, it was stored for 1 hour under the conditions of 40 ° C. and relative humidity of 100%.
During this time, a direct current of 1 A / cm ² was continuously supplied to the fuel cell in the power generation mode in order to sufficiently wet the sulfone group-containing perfluorocarbon membrane having a thickness of 50 μm.

Next, the cell temperature is 80 ° C., the anode humidifier temperature is 80 ° C., the cathode humidifier temperature is 80 ° C., the piping temperature is 120 ° C., the anode hydrogen gas flow rate is 0.3 liter / min, and the cathode oxygen gas flow rate is The output of the fuel cell was measured under the condition of 1.0 liter / min.
The output of the fuel cell was 1.0 W / cm ² , indicating good power generation characteristics.

<Comparative example>
First, an electron conductive material carrying platinum having an average particle diameter of 3 nm (platinum: electron conductive material = 1: 1 (weight ratio)) and a proton conductive material were dissolved in a solvent so as to have the following composition. A catalyst ink was prepared.
-Carbon carrying platinum (electron-conducting substance) 7.5% by weight
・ Perfluorocarbon sulfonic acid (proton conductive material) 2.5% by weight
・ Water 30.0% by weight
・ IPA 30.0% by weight
・ NPA 30.0% by weight

Next, this catalyst ink was applied onto carbon paper having a thickness of 190 μm cut into a size of 200 mm × 200 mm using a bar coater.

Next, after heat treatment at 120 ° C. for 1 hour in a nitrogen atmosphere, the mixture was allowed to cool for 30 minutes to produce a fuel cell catalyst electrode.

Next, the catalyst layers of the two fuel cell catalyst electrodes produced by the above method are face to face, and a sulfone group-containing perfluorocarbon having a thickness of 50 μm is sandwiched between 130 ° C., 30 minutes, and 3 MPa. A plate-like MEA was produced by thermocompression bonding.

Finally, a 3 mm thick copper separator with 20 parallel grooves (width: 2 mm, length: 10 cm, depth: 3 mm, groove spacing: 2 mm) in an 11 cm × 11 cm region in the center of the surface Two sets are prepared, the gas flow path forming surfaces of the two separators face each other, the MEA is sandwiched, SUS current collector plates with a thickness of 0.3 mm are arranged on both sides, and fastened with rods A fuel cell was obtained.

Next, the output of the fuel cell is measured by a fuel cell using an electrochemical interface (Solartron SI-1287), a frequency response analyzer (Solartron SI-1260), and an electronic loader (Scribner 890CL). Using system GFT-SG1 (manufactured by Toyo Corporation), the measurement was performed as follows.

First, after mounting the fuel cell on a power generation cell made of graphite, it was stored for 1 hour under the conditions of 40 ° C. and relative humidity of 100%.
During this time, a direct current of 1 A / cm ² was continuously supplied to the fuel cell in the power generation mode in order to sufficiently wet the sulfone group-containing perfluorocarbon membrane having a thickness of 50 μm.

Next, the cell temperature is 80 ° C., the anode humidifier temperature is 80 ° C., the cathode humidifier temperature is 80 ° C., the piping temperature is 120 ° C., the anode hydrogen gas flow rate is 0.3 liter / min, and the cathode oxygen gas flow rate is The output of the fuel cell was measured under the condition of 1.0 liter / min.
The output of the polymer electrolyte fuel cell was 1.0 W / cm ² .

It has been confirmed that the fuel cell using the separator of the present invention has output characteristics equivalent to those of a fuel cell using a copper separator that has been conventionally used.

The separator of the present invention, the manufacturing method thereof, and the fuel cell using the separator can be used for a power source for electric vehicles, a power source for mobile phones, and the like.

It is sectional drawing for demonstrating MEA (solid polymer electrolyte membrane electrode assembly) of the fuel cell of this invention. It is sectional drawing for demonstrating the separator of the fuel cell of this invention. It is sectional drawing for demonstrating the fuel cell of this invention.

Explanation of symbols

1. Gas diffusion material (air electrode side)
2 .... Catalyst layer (Air electrode side)
3 ... Solid polymer electrolyte membrane 4 ... Catalyst layer (fuel electrode side)
5. Gas diffusion material (fuel electrode side)
6 ... MEA (Solid polymer electrolyte membrane electrode assembly)
7 ··· Biodegradable plastic part of separator (fuel electrode side)
8 ... Conductive pin (fuel electrode side)
9 ... Separator (fuel electrode side)
10 ... Biodegradable plastic part of separator (air electrode side)
11 ... Conductive pin (air electrode side)
12 ... Separator (Air electrode side)
13 ... collector plate (fuel electrode side)
14 ... collector plate (air electrode side)

Claims (14)

A biodegradable plastic separator, characterized in that a conductive pin is connected between a surface on which a reaction gas flow channel is formed and a surface facing the surface. The biodegradable plastic separator according to claim 1, wherein the conductive pin is made of carbon, gold, silver, copper, or iron. The biodegradable plastic separator according to claim 1 or 2, wherein the biodegradable plastic comprises a polylactic acid resin and a layered silicate. A method for producing a biodegradable plastic separator, wherein a conductive pin is disposed in an injection mold and the biodegradable plastic is injected and integrally molded. A catalyst layer is provided on the front and back surfaces of the solid polymer electrolyte membrane, a gas diffusion material is provided on the surface of the catalyst layer opposite to the solid polymer electrolyte membrane, and the gas diffusion material on the side opposite to the catalyst layer is provided. A fuel cell using the biodegradable plastic separator according to any one of claims 1 to 3 on the surface as a separator. 6. The fuel cell according to claim 5, wherein the solid polymer electrolyte membrane is a sulfone group-containing perfluorocarbon or a carboxyl group-containing perfluorocarbon. The fuel cell according to claim 5, wherein the catalyst layer is made of a proton conductive material, an electron conductive material, and a catalyst. 8. The fuel cell according to claim 7, wherein the proton conductive material is perfluorocarbon sulfonic acid, polyether sulfone, sulfonated polyether ether ketone, or sulfonated polyimide. The fuel cell according to claim 7 or 8, wherein the electron conductive material is silicon dioxide or carbon. 10. The catalyst according to claim 7, wherein the catalyst is made of one or more metals selected from gold, platinum, palladium, rhodium, ruthenium, osmium and iridium. Fuel cell. The fuel cell according to any one of claims 7 to 10, wherein the catalyst has an average particle diameter of 1 nm or more and 5 nm or less. The fuel cell according to any one of claims 7 to 11, wherein a loading ratio of the catalyst of the electron conductive material is 1% to 80%. The fuel cell according to any one of claims 5 to 12, wherein the gas diffusion material is a conductive porous substrate. The fuel cell according to claim 13, wherein the conductive porous substrate is carbon paper or carbon cloth.