JP7094075B2 - Carbon material for catalyst carrier, catalyst for polymer electrolyte fuel cell, catalyst layer for polymer electrolyte fuel cell, and polymer electrolyte fuel cell - Google Patents

Description

The present invention relates to a carbon material for a catalyst carrier, a catalyst for a polymer electrolyte fuel cell, a catalyst layer for a polymer electrolyte fuel cell, and a polymer electrolyte fuel cell.

A solid polymer fuel cell, which is a type of fuel cell, has a pair of catalyst layers arranged on both sides of a solid polymer electrolyte membrane, a gas diffusion layer arranged outside each catalyst layer, and each gas diffusion layer. It is provided with a separator arranged on the outside. Of the pair of catalyst layers, one catalyst layer serves as the anode of the polymer electrolyte fuel cell, and the other catalyst layer serves as the cathode of the polymer electrolyte fuel cell. In a normal polymer electrolyte fuel cell, a plurality of unit cells having the above components are stacked in order to obtain a desired output.

A reducing gas such as hydrogen is introduced into the separator on the anode side. The reducing gas is introduced into the anode via the gas diffusion layer on the anode side. The anode includes a catalyst component, a catalyst carrier supporting the catalyst component, and an electrolyte material (ionomer) having proton conductivity. The catalyst carrier is often composed of a porous carbon material. On the catalyst component, an oxidation reaction of the reducing gas occurs, and protons and electrons are generated. For example, when the reducing gas becomes hydrogen gas, the following oxidation reaction occurs.
H ₂ → 2H ⁺ + ^2e- (E ₀ = 0V)

The protons generated in this oxidation reaction are introduced into the cathode through the electrolyte material in the anode and the solid polymer electrolyte membrane. In addition, electrons are introduced into an external circuit through a catalyst carrier, a gas diffusion layer, and a separator. This electron is introduced into the separator on the cathode side after working in an external circuit. Then, these electrons are introduced into the cathode through the separator on the cathode side and the gas diffusion layer on the cathode side.

The polymer electrolyte membrane is composed of an electrolyte material having proton conductivity. In the solid polymer electrolyte membrane, the protons generated by the above oxidation reaction are introduced into the cathode.

Oxidizing gas such as oxygen gas or air is introduced into the separator on the cathode side. The oxidizing gas is introduced into the cathode via the gas diffusion layer on the cathode side. The cathode includes a catalyst component, a catalyst carrier supporting the catalyst component, and an electrolyte material (ionomer) having proton conductivity. The catalyst carrier is often composed of a porous carbon material. On the catalyst component, a reduction reaction of the oxidizing gas occurs and water is produced. For example, when the oxidizing gas becomes oxygen gas or air, the following reduction reaction occurs.
O ₂ + 4H ⁺ + ^4e- → 2H ₂ O (E ₀ = 1.23V)

The water generated in the reduction reaction is discharged to the outside of the fuel cell together with the unreacted oxidizing gas. As described above, in the polymer electrolyte fuel cell, power is generated by utilizing the energy difference (potential difference) between the oxidation reaction and the reduction reaction. In other words, the electrons generated by the oxidation reaction do the work in the external circuit.

By the way, in recent years, there has been a strong demand for further improvement in the utilization rate of catalyst components, that is, the utilization rate of catalysts. This is because the higher the catalyst utilization rate, the less the amount of catalyst components required for the polymer electrolyte fuel cell, and the lower the cost and higher performance of the polymer electrolyte fuel cell. be. Conventionally, as disclosed in Patent Document 1, for example, an attempt has been made to improve the catalyst utilization rate by focusing on the pore structure of the carbon material used as the catalyst carrier, that is, the carbon material for the catalyst carrier, and the polarity of the surface. ing.

International Publication No. 2014/1259597

However, although the pore structure and surface polarity of the carbon material for the catalyst carrier are one of the factors for increasing the catalyst utilization rate, they are not the factors that control the catalyst utilization rate. That is, even if these values are adjusted to values within a desired range, the catalyst utilization rate may vary.

By the way, a high catalyst utilization means that more catalyst components contribute to the electrode reaction (that is, the above-mentioned oxidation reaction and reduction reaction). In order for more catalyst components to contribute to the electrode reaction, the carbon material for the catalyst carrier that supports the catalyst components needs to be coated with the electrolyte material as uniformly as possible. This is because by uniformly coating the carbon material for the catalyst carrier with the electrolyte material, more catalyst components can be brought into contact with the electrolyte material. In order for the carbon material for the catalyst carrier to be uniformly coated with the carbon material for the catalyst carrier, it is necessary that the carbon material for the catalyst carrier has a high affinity for the electrolyte material.

For this reason, in recent years, attention has been paid to the affinity of carbon materials for catalyst carriers with respect to electrolyte materials as an element for controlling the catalyst utilization rate. However, the affinity for the electrolyte material often varies depending on the type of the electrolyte material. That is, even if the carbon material for a catalyst carrier shows a high affinity for a specific electrolyte material, the carbon material for a catalyst carrier does not necessarily show a high affinity for other electrolyte materials. ..

Therefore, there has been a strong demand for a technique for quantitatively evaluating the affinity for a plurality of types of electrolyte materials, that is, a technique for evaluating the affinity for an electrolyte material in a general-purpose and quantitative manner.

However, no such technique has been proposed. A technique for observing the coating state of the electrolyte material has been proposed. In this technique, the electrolyte material in the catalyst layer is dyed with Ru, and the catalyst layer is sliced by FIB (focused ion beam). Then, an element distribution map is created by analyzing the flaked catalyst layer with TEM-EDX. Then, in this map, it is evaluated that the electrolyte material exists in the region where Ru is concentrated. However, this technique only qualitatively evaluates the affinity for electrolyte materials.

Therefore, the present invention has been made in view of the above problems, and the object of the present invention is new and improved so that the affinity for the electrolyte material can be evaluated universally and quantitatively. It is an object of the present invention to provide a test method, and by extension, to provide a carbon material for a catalyst carrier capable of further improving the characteristics of a polymer electrolyte fuel cell.

In order to solve the above problems, the present inventor has diligently studied a technique for evaluating the affinity for an electrolyte material in a general-purpose and quantitative manner. As described above, the affinity of the carbon material for the catalyst carrier with respect to the electrolyte material often varies depending on the type of the electrolyte material. Therefore, the present inventor first diligently studied a model resin as a model for these electrolyte materials. As a result, the present inventor focused on polyethylene glycol. Polyethylene glycol, like the electrolyte material, has polar moieties in its structure. Furthermore, polyethylene glycol can be synthesized by controlling the size and distribution of the molecular weight. Therefore, it is presumed that by appropriately adjusting the molecular weight distribution of polyethylene glycol, the adsorption characteristics (specifically, the adsorption characteristics for the carbon material for the catalyst carrier) similar to those of various electrolyte materials are exhibited. Then, the present inventor conducted a resin adsorption amount evaluation test using polyethylene glycol, a so-called polyethylene glycol resin adsorption amount evaluation test.

In this resin adsorption amount evaluation test, first, a mixed solution containing a polyethylene glycol resin, a carbon material for a catalyst carrier, and water is stirred in the range of 95 to 100 ° C. for 1 to 10 hours (first step). Then, the carbon material for the catalyst carrier to which the polyethylene glycol resin is attached is separated from the mixture (second step). Then, the amount of resin adsorbed is measured by subtracting the mass of the carbon material for the catalyst carrier used in the first step from the mass of the carbon material for the catalyst carrier to which the polyethylene glycol resin is attached (third step). Then, the resin adsorption rate W, that is, the adsorption rate of polyethylene glycol is calculated based on the amount of resin adsorbed and the mass of the carbon material for the catalyst carrier used in the first step (fourth step).

Next, the present inventor diligently studied the parameters that affect the resin adsorption rate W. The mass average molecular weight of the electrolyte material is generally tens of thousands or more. When such an electrolyte material becomes temari-shaped, its diameter is 10 nm or more. On the other hand, pores having a diameter of less than 3 nm, that is, micropores may be formed on the surface of the carbon material particles for the catalyst carrier. However, the electrolyte material particles (temari-shaped particles) cannot enter into such fine pores. Therefore, the electrolyte material adheres to the outer surface of the carbon material particles for the catalyst carrier, that is, the surface of the portion excluding the micropores.

Therefore, the present inventor paid attention to the uneven shape of the outer surface of the carbon material particles for the catalyst carrier. This is because the more irregularities formed on the carbon material particles for the catalyst carrier, the larger the contact area with polyethylene glycol. Specifically, the present inventor focused on the specific volume V _3-10 (mL / g) of the mesopores having a diameter of 3 to 10 nm. The upper limit of the diameter is set to 10 nm because it is considered that the mesopores (and macropores) having a diameter of more than 10 nm do not affect the contact area with polyethylene glycol so much.

As a result, the present inventor found that there is a high positive correlation between the specific volume V _3-10 (mL / g) and the resin adsorption rate W. That is, it was found that the resin adsorption rate W can be adjusted to a desired value by adjusting the specific volume V _3-10 (mL / g) of the mesopores.

Furthermore, the present inventor has focused on activation treatment as a technique for adjusting the specific volume V _3-10 (mL / g). First, the present inventor applied an activation treatment generally applied to a carbon material for a catalyst carrier to the carbon material for a catalyst carrier, but the specific volume V _3-10 (mL / g) hardly changed. Therefore, the present inventor activated the carbon material for the catalyst carrier under more reactive activation conditions. As a result, the specific volume V _3-10 (mL / g) fluctuated. Therefore, the present inventor has found a highly reactive activation treatment as a technique for adjusting the specific volume V _3-10 (mL / g).

Then, the present inventor prepared a plurality of types of carbon materials for catalyst carriers having different resin adsorption rates W and specific volumes V _3-10 (mL / g). In addition, multiple types of electrolyte materials were prepared. Then, a polymer electrolyte fuel cell was produced using these, and the characteristics of the polymer electrolyte fuel cell were evaluated. As a result, when the resin adsorption rate W and the specific volume V _3-10 (mL / g) are within a certain range, the characteristics of the polymer electrolyte fuel cell (specifically) even if the type of electrolyte material changes. It was found that the power generation performance) was improved. Therefore, a carbon material for a catalyst carrier having a resin adsorption rate W and a specific volume V _3-10 (mL / g) within a certain range has high affinity for various types of electrolyte materials. Further, in the polymer electrolyte fuel cell using such a carbon material for a catalyst carrier, the catalyst utilization rate becomes high even if the type of the electrolyte material changes. That is, the characteristics of the polymer electrolyte fuel cell are improved.

That is, by conducting the polyethylene glycol resin adsorption amount evaluation test, the catalyst carrier having the resin adsorption rate W and the specific volume V _3-10 (mL / g) within the desired ranges (specific ranges will be described later). Carbon material can be specified. And, such a carbon material for a catalyst carrier has a high affinity for various electrolyte materials. Therefore, the resin adsorption rate W and the specific volume V _3-10 (mL / g) can be parameters that generally specify the affinity for the electrolyte material.

As described above, the present inventor has found a polyethylene glycol resin adsorption amount evaluation test as a general-purpose and quantitative test method for evaluating the affinity for an electrolyte material. Furthermore, the present inventor has set the resin adsorption rate W and the specific volume V _3-10 (mL / g) as parameters that generically specify the affinity for the electrolyte material (that is, parameters that can control the catalyst utilization rate). I found it.

Furthermore, the present inventor investigated other parameters that affect the resin adsorption rate W (in other words, the affinity for the electrolyte material). Electrolyte materials generally have a functional group that dissociates protons, and this functional group has polarity. The present inventor speculates that when the surface of the carbon material for a catalyst carrier has polarity, it is possible to enhance the affinity with the electrolyte material by controlling the degree of the polarity. Therefore, the present inventor further studied the polarity of the surface of the carbon material for the catalyst carrier. As a result, the present inventor has found that the oxygen content and the nitrogen content of the carbon material for the catalyst carrier affect the affinity for the electrolyte material. The oxygen content corresponds to the number of oxygen-containing functional groups contained in the carbon material for the catalyst carrier. The nitrogen content corresponds to the number of nitrogen-containing functional groups contained in the carbon material for the catalyst carrier. That is, the affinity for the electrolyte material is influenced by the number of oxygen-containing functional groups and nitrogen-containing functional groups of the carbon material for the catalyst carrier.

Further, the carbon material for the catalyst carrier needs to have a surface on which the catalyst component is supported to some extent. Further, the carbon material for the catalyst carrier is also required to have durability. The present inventor came up with the present invention based on these findings. That is, the present inventor focused on the BET specific surface area as an index representing the area required for supporting the catalyst, and found a suitable range thereof. In addition, the present inventor has focused on the half-value width of the G band ΔG by Raman spectroscopy in order to enhance durability, that is, oxidative wear resistance, and has found a suitable range thereof. The G band is the Raman effect due to the lattice vibration of the crystalline part of the carbon material, and its half width corresponds to the size of the crystallite. Since increasing the oxidative wear resistance corresponds to a large crystallite size, it is presumed that ΔG can adjust the oxidative wear resistance of the carbon material for the catalyst carrier.

According to a certain aspect of the present invention, the amount of polyethylene glycol resin adsorbed using a polyethylene glycol resin having a mass average molecular weight of 4000 , which is a carbon material for a catalyst carrier capable of supporting a catalyst component for a solid polymer fuel cell. The resin adsorption rate W calculated by the evaluation test is 30 to 100% by mass, and the specific volume V3 of the mesopores having a diameter of ₃ to 10 nm obtained by BJH (Barrett, Joiner, Hallender) analysis of the nitrogen adsorption isotherm. _-10 (mL / g) is 1.0 to 2.0 mL / g, and the BET specific surface area _SBET (m ² / g) evaluated by the BET method is 500 to 1500 m ² / g, and Raman spectroscopy. Provided is a carbon material for a catalyst carrier, characterized in that the half-value width ΔG of the G band measured by is 30 to 70 cm ^-1 .

Here, the oxygen content O _mass may be 0.2 to 1.0% by mass.

Further, the nitrogen content N _mass may be 0.25 to 1.5% by mass.

Further, the oxygen content O _mass may be 0.2 to 1.0% by mass, and the nitrogen content N _mass may be 0.25 to 1.5% by mass.

Further, the resin adsorption rate W may be 40 to 90% by mass.

According to another aspect of the present invention, there is provided a catalyst for a solid polymer fuel cell, which comprises the above-mentioned carbon material for a catalyst carrier and a catalyst component supported on the carbon material for a catalyst carrier. Will be done.

Here, the catalyst loading ratio may be 10 to 80% by mass.

According to another aspect of the present invention, there is provided a catalyst layer for a polymer electrolyte fuel cell, which comprises the above-mentioned catalyst for a polymer electrolyte fuel cell.

According to another aspect of the present invention, there is provided a polymer electrolyte fuel cell comprising the catalyst layer for the polymer electrolyte fuel cell described above.

Here, the polymer electrolyte fuel cell may include a catalyst layer for a polymer electrolyte fuel cell as a catalyst layer on the cathode side.

As described above, the evaluation test according to the present invention can evaluate the affinity for the electrolyte material in a general-purpose and quantitative manner. Further, the carbon material for a catalyst carrier according to the present invention can improve the characteristics of a polymer electrolyte fuel cell.

It is a schematic diagram which shows the schematic structure of the fuel cell which concerns on embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Polyethylene glycol resin adsorption amount evaluation test>
As described above, the present inventor has conducted a resin adsorption amount evaluation test using polyethylene glycol, a so-called polyethylene glycol resin adsorption, as an evaluation test for evaluating the affinity of a carbon material for a catalyst carrier with an electrolyte material in a general-purpose and quantitative manner. I came up with a quantity evaluation test. Therefore, first, the resin adsorption amount evaluation test will be described.

(1-1. First step)
The resin adsorption amount evaluation test according to the present embodiment is a test for evaluating the affinity of the carbon material for a catalyst carrier with polyethylene glycol, and is classified into the first to fourth steps. In the first step, the mixture containing the polyethylene glycol resin, the carbon material for the catalyst carrier, and water is stirred in the range of 95 to 100 ° C. for 1 to 10 hours. As described above, in the resin adsorption amount evaluation test according to the present embodiment, polyethylene glycol is used as a resin as a model for various electrolyte materials. This is because polyethylene glycol is presumed to exhibit adsorption properties similar to those of various electrolyte materials. However, when the present inventor examined polyethylene glycol in more detail, it was found that the mass average molecular weight of polyethylene glycol is very important. Specifically, the mass average molecular weight of polyethylene glycol is preferably 1000 to 20000. By setting the mass average molecular weight of polyethylene glycol to 1000 to 20000, the reliability of the evaluation result becomes higher. Specifically, in the present embodiment, a carbon material for a catalyst carrier having a resin adsorption rate W of 30 to 100% by mass is selected. When the mass average molecular weight of polyethylene glycol is 1000 to 20000, the selected carbon material for a catalyst carrier exhibits more stable and high characteristics (specifically, power generation performance). That is, the selected carbon material for the catalyst carrier has a stable and high affinity for various electrolyte materials.

In the first step, the mixed solution is heated to the boiling point of water or a temperature close to it (95 to 100 ° C.) and stirred. That is, in the first step, the resin adsorption rate W in an environment in which polyethylene glycol is difficult to be adsorbed on the carbon material for the catalyst carrier is calculated. By performing such processing, the reliability of the evaluation result becomes higher.

(1-2. Second step)
In the second step, the carbon material for the catalyst carrier to which the polyethylene glycol resin is attached is separated from the mixture. The method of separation is not particularly limited, but separation may be performed by, for example, filtration or the like.

(1-3. Third step)
In the third step, the amount of resin adsorbed is measured by subtracting the mass of the carbon material for the catalyst carrier used in the first step from the mass of the carbon material for the catalyst carrier to which the polyethylene glycol resin is attached. That is, in the resin adsorption amount evaluation test, the affinity of the carbon material for the catalyst carrier with respect to polyethylene glycol is evaluated based on the resin adsorption amount.

(1-4. Fourth step)
In the fourth step, the resin adsorption rate W, that is, the adsorption rate of polyethylene glycol is calculated based on the amount of resin adsorbed and the mass of the carbon material for the catalyst carrier used in the first step. Specifically, the resin adsorption rate W can be obtained by dividing the resin adsorption amount by the mass of the carbon material for the catalyst carrier used in the first step.

The resin adsorption rate W is one of the parameters for evaluating the affinity for the electrolyte material. In the present embodiment, a carbon material for a catalyst carrier having a resin adsorption rate W of 30 to 100% by mass is selected.

<2. Composition of carbon materials for catalyst carriers>
Next, the carbon material for the catalyst carrier according to the present embodiment will be described. The carbon material for a catalyst carrier according to this embodiment satisfies at least the following requirements (a) to (d).
(A) The resin adsorption rate W calculated by the resin adsorption amount evaluation test is 30 to 100% by mass.
(B) The specific volume V _3-10 (mL / g) of the mesopores having a diameter of 3 to 10 nm obtained by BJH analysis of the nitrogen adsorption isotherm is 1.0 to 2.0 mL / g.
(C) The BET specific surface area S _BET (m ² / g) evaluated by the BET method is 500 to 1500 m ² / g.
(D) The half-value width ΔG of the G band measured by Raman spectroscopy is 30 to 70 cm ^-1 .

(2-1. About requirement (a))
The requirement (a) is one of the requirements that defines the affinity of the carbon material for the catalyst carrier for the electrolyte material. When the resin adsorption rate W is less than 30% by mass, the affinity of the carbon material for the catalyst carrier with respect to the electrolyte material is too low, and the carbon material for the catalyst carrier is not sufficiently coated with the electrolyte material. Therefore, the number of catalyst components that do not contribute to the electrode reaction increases. That is, the catalyst utilization rate decreases. On the other hand, when the resin adsorption rate W exceeds 100% by mass, the affinity of the carbon material for the catalyst carrier with the electrolyte material is too high, and the carbon material for the catalyst carrier is excessively coated with the electrolyte material. In this case, the gas (specifically, a reducing gas and an oxidizing gas, particularly an oxidizing gas) becomes difficult to permeate through the layer of the electrolyte material. That is, it becomes difficult for the gas to reach the catalyst component in the electrolyte material. Therefore, in this case as well, the number of catalyst components that do not contribute to the electrode reaction increases. That is, the catalyst utilization rate decreases. The resin adsorption rate W is preferably 40 to 90% by mass. The "catalyst utilization rate" is the ratio of the total number of catalyst components in the catalyst layer to the number of catalyst components used in the electrode reaction. In the experiment, it can be said that the catalyst utilization rate is high when the weight of the catalyst components is the same and the characteristics of the fuel cell are high.

As described above, the resin adsorption rate W can be measured by the resin adsorption amount evaluation test. Further, the resin adsorption rate W has a high positive correlation with the specific volume V _3-10 (mL / g), which is the parameter of the requirement (b). Therefore, by adjusting the specific volume V _3-10 (mL / g), the resin adsorption rate W can be set to 30 to 100% by mass.

(2-2. About requirement (b))
The requirement (b) is also one of the requirements that defines the affinity of the carbon material for the catalyst carrier for the electrolyte material. When the specific volume V _3-10 (mL / g) is less than 1.0 mL / g, the affinity of the carbon material for the catalyst carrier with the electrolyte material is too low, and the carbon material for the catalyst carrier is sufficiently coated with the electrolyte material. do not do. Therefore, the number of catalyst components that do not contribute to the electrode reaction increases. That is, the catalyst utilization rate decreases. On the other hand, when the specific volume V _3-10 (mL / g) exceeds 2.0 mL / g, the affinity of the carbon material for the catalyst carrier with the electrolyte material is too high, and the electrolyte material is excessive in the carbon material for the catalyst carrier. Cover. In this case, it becomes difficult for the gas to permeate the layer of the electrolyte material. That is, it becomes difficult for the gas to reach the catalyst component in the electrolyte material. Therefore, in this case as well, the number of catalyst components that do not contribute to the electrode reaction increases. That is, the catalyst utilization rate decreases. The specific volume V _3-10 (mL / g) is preferably 1.35 to 1.95 (mL / g).

Here, the specific volume V _3-10 (mL / g) is obtained by BJH analysis of the nitrogen adsorption isotherm. The nitrogen adsorption isotherm is obtained by measuring nitrogen adsorption at the liquid nitrogen temperature of nitrogen gas. BJH analysis is a method of mesopore analysis. That is, there are various methods for mesopore analysis, but when the present inventor examined these methods, the specific volume V _3-10 (mL / g) obtained by BJH analysis correlates with the resin adsorption rate W. Was the highest.

Therefore, the resin adsorption rate W and the specific volume V _3-10 (mL / g) are parameters that contribute to the affinity for the electrolyte material. That is, when the resin adsorption rate W and the specific volume V _3-10 (mL / g) are within the above-mentioned ranges, the affinity of the carbon material for the catalyst carrier with the electrolyte material is generally high. Specifically, the polymer electrolyte fuel cell using the carbon material for the catalyst carrier has high characteristics (specifically, power generation performance) even if the type of the electrolyte material fluctuates.

Here, as a method for adjusting the specific volume V _3-10 (mL / g), for example, activation treatment can be mentioned. The type of activation treatment is not particularly limited, and any treatment may be used as long as it is a treatment that causes defects in the molecular structure of the carbon material. Examples of the activation treatment include a treatment in which the carbon material is heated in an environment in which a gas such as steam or carbon dioxide or an inert gas containing these gases is circulated.

However, even if the activation treatment generally applied to the carbon material for the catalyst carrier is applied to the carbon material for the catalyst carrier, the specific volume V _3-10 (mL / g) hardly changes. That is, in order to change the specific volume V _3-10 (mL / g), it is necessary to carry out a highly reactive activation treatment.

Specifically, in the activation treatment using steam, the temperature of steam needs to be 1050 ° C. or higher. The preferred range of temperature is about 1200 to 1500 ° C. The activation treatment time may be, for example, 0.1 to 1.0 hour. The specific volume V _3-10 (mL / g) can be adjusted by the temperature and time of the activation treatment. In the normal activation treatment, the temperature of steam is about 850 to 1000 ° C.

Further, in the activation treatment using carbon dioxide, the temperature of carbon dioxide needs to be 1150 ° C. or higher. The preferred range of temperature is about 1200 to 1500 ° C. The activation treatment time may be, for example, 0.1 to 1.0 hour. The specific volume V _3-10 (mL / g) can be adjusted by the temperature and time of the activation treatment. In the normal activation treatment, the temperature of carbon dioxide is about 900 to 1000 ° C.

Conventionally, the temperature of water vapor and carbon dioxide has not been raised to the above range in the activation treatment. The reason is that the usual activation treatment is mainly performed for the purpose of introducing micropores into the carbon material, and when the carbon material is treated at the above high temperature, the carbon consumption rate is high, so the cost increases. This is because it was not expected that the activation treatment would be performed at such a high temperature. In the present embodiment, even if the cost required for the activation treatment of the carbon material increases, the resulting carbon material for the catalyst carrier can greatly improve the catalyst utilization rate. Therefore, the cost of the polymer electrolyte fuel cell as a whole will be greatly reduced.

Further, by performing the highly reactive activation treatment as described above, a commercially available non-porous carbon material can also be a suitable carbon material for a catalyst carrier in the present embodiment. When such a non-porous carbon material is used as a starting material, it is preferable to first perform a normal activation treatment to introduce micropores into the carbon material, and then perform a highly reactive activation treatment.

(2-3. Requirements (c))
The requirement (c) is a requirement for securing a surface (specifically, a surface area) on which the catalyst component is supported. If the BET specific surface area is less than 500 m ² / g, the surface area for sufficiently supporting the catalyst component may be insufficient, and sufficient power generation performance may not be exhibited. On the other hand, when the BET specific surface area exceeds 1500 m ² / g, the number of defective portions of the carbon material for the catalyst carrier increases. Therefore, the strength of the carbon material itself for the catalyst carrier is lowered, and there is a possibility that the carbon material itself cannot be used as a catalyst for a fuel cell. The BET specific surface area is preferably 1100 to 1300 m ² / g.

(2-4. About requirement (d))
The requirement (d) is a requirement for ensuring the durability of the carbon material for the catalyst carrier. When the half-value width ΔG of the G band is smaller than 30 cm ^-1 , the crystallinity of the carbon material for the catalyst carrier becomes too high, and it may be difficult to support the catalyst metal in a highly dispersed manner in the step of supporting the catalyst component. On the other hand, when the half-value width ΔG of the G band exceeds 70 cm ^-1 , sufficient durability against repeated load fluctuations such as start / stop may not be obtained. The full width at half maximum ΔG of the G band is preferably 35 to 50 cm ^-1 .

As a method for setting the half-value width ΔG of the G band to a value within the above-mentioned range, for example, graphitization treatment can be mentioned. In the graphitization treatment, the carbon material for the catalyst carrier is exposed to a high temperature environment of 1600 ° C. or higher. By graphitizing the carbon material, the crystals constituting the carbon material grow significantly. As a result, the half width of the G band of the carbon material can be a value within the above range. When the heating temperature is less than 1600 ° C., the growth of crystallites may be reduced. As a result, the half-value width ΔG of the G band often exceeds 70 cm ^-1 .

Depending on the type of carbon material used as a raw material, graphitization may not proceed sufficiently at a heating temperature of about 1600 to 1800 ° C. Further, when the heating temperature exceeds 2200 ° C., the crystallites grow excessively, and the half width of the G band is often smaller than 30 cm ^-1 . Therefore, the heat treatment of the graphitization treatment is preferably 1900 to 2200 ° C.

The carbon material for the catalyst carrier preferably further satisfies at least one of the following requirements (e) and (f), and more preferably both. Both are parameters that contribute to the affinity of the carbon material for the catalyst carrier with the electrolyte material.
(E) Oxygen content O _mass is 0.2 to 1.0% by mass.
(F) The nitrogen content N _mass is 0.25 to 1.5% by mass.

The oxygen content O _mass is the mass% of the oxygen atom with respect to the total mass of the carbon material for the catalyst carrier, and corresponds to the number of oxygen-containing functional groups contained in the carbon material for the catalyst carrier. The nitrogen content N _mass is the mass% of the nitrogen atom with respect to the total mass of the carbon material for the catalyst carrier, and corresponds to the number of nitrogen-containing functional groups contained in the carbon material for the catalyst carrier. That is, the affinity for the electrolyte material is influenced by the number of oxygen-containing functional groups and nitrogen-containing functional groups of the carbon material for the catalyst carrier. When at least one of the requirements (e) and (f) is satisfied, the affinity of the carbon material for the catalyst carrier with the electrolyte material is further improved. Specifically, the characteristics of the polymer electrolyte fuel cell using the carbon material for the catalyst carrier are further improved. The oxygen content O _mass is preferably 0.23 to 0.86% by mass. The nitrogen content N _mass is preferably 0.30 to 1.45% by mass.

Here, as the treatment for adjusting the oxygen content O _mass (hereinafter, such treatment is also referred to as “oxygen introduction treatment”), the carbon material for the catalyst carrier is oxidized and then heat-treated in an inert atmosphere or in vacuum. Processing is mentioned. The oxidation treatment is not particularly limited as long as it is a method capable of introducing an oxygen-containing functional group into the carbon material for the catalyst carrier. Examples of the oxidation treatment include a method of treating a carbon material for a catalyst carrier with nitric acid, hydrogen peroxide, or the like. Other examples include the Brodie method in which the carbon material for the catalyst carrier is oxidized with fuming nitric acid and potassium chlorate (KClO ₃ ), and the carbon material for the catalyst carrier is concentrated sulfuric acid, concentrated nitric acid and potassium chlorate (KClO ₃ ) (or excess). Staudenmaier method to oxidize with potassium chlorate (KClO ₄ )), Hummers, Offeman method to oxidize carbon material for catalyst carrier with concentrated sulfuric acid, sodium nitrate (NaNO ₃ ) and potassium permanganate (KMnO ₄ ), HNO ₃ treatment, Examples thereof include HClO ₄ treatment, NaClO ₄ treatment, oxygen plasma treatment, ozone treatment and the like. As the inert atmosphere, nitrogen, argon, helium or the like is preferably used. The temperature and time of the heat treatment may be adjusted according to the degree of the strength of the oxidation treatment. The heat treatment temperature may be, for example, 700 to 1500 ° C., and the heat treatment time may be, for example, 0.5 to 10 hours. Oxygen-containing functional groups can be introduced into the carbon material for the catalyst carrier by the oxidation treatment, and unnecessary oxygen-containing functional groups can be removed by the heat treatment after the oxidation treatment. Therefore, the oxygen content O _mass can be adjusted by the strength of the oxidation treatment (for example, acid concentration, etc.), the temperature and time of the heat treatment.

Further, as a treatment for adjusting the nitrogen content N _mass (hereinafter, such treatment is also referred to as “nitrogen introduction treatment”), for example, a treatment in which a carbon material for a catalyst carrier is heat-treated together with a nitrogen-containing compound in a nitrogen gas atmosphere. Can be mentioned.
Here, the nitrogen-containing compound is not particularly limited as long as it is a compound capable of introducing a nitrogen-containing functional group into the carbon material for the catalyst carrier. Examples of the nitrogen-containing compound include nitrogen-containing heterocyclic compounds such as melamine and hexamethylenetetramine. Other examples of nitrogen-containing heterocyclic compounds include 5-membered cyclic compounds such as pyrrole, imidazole, pyrazole, oxazole, isooxazole, thiazole, pyrazoline and derivatives thereof, pyridine, pyrazine, pyrimidine, pyridazine, triazine, etc. 6-membered ring-type compounds such as tetrazine, uracil and their derivatives, and 5-membered + 6-membered ring-type compounds such as indol, isoindole, benzoimidazole, purine, xanthin, indazole, benzoxazole, benzothiazole and their derivatives. Examples thereof include 6-membered ring + 6-membered ring-type compounds such as quinoline, quinoxalin, quinazoline, cinnoline, pteridine and derivatives thereof, and further, tetraphenylporphyrin, phthalocyanine, phenazine, phenothiazine, acridin and taclin. , Polycyclic compounds such as melanin and the like. The heat treatment temperature may be, for example, 600 to 1200 ° C., and the heat treatment time may be, for example, 0.5 to 10 hours. The nitrogen content N _mass can be adjusted by the temperature and time of the heat treatment.

Another example of the nitrogen introduction treatment includes a treatment in which the carbon material for a catalyst carrier is heat-treated in ammonia gas and then heat-treated in an inert atmosphere or in vacuum. By heat-treating the carbon material for the catalyst carrier in ammonia gas, nitrogen-containing functional groups can be introduced into the carbon material for the catalyst carrier, and unnecessary nitrogen-containing functional groups can be removed by the subsequent heat treatment. The temperature of the heat treatment in the ammonia gas may be, for example, 500 to 1000 ° C., and the time of the heat treatment may be, for example, 0.5 to 10 hours. The temperature of the heat treatment performed in an inert atmosphere or vacuum may be, for example, 700 to 1100 ° C., and the time of the heat treatment may be, for example, 0.5 to 10 hours. As the inert atmosphere, nitrogen, argon, helium or the like is preferably used.

The nitrogen introduction treatment may be performed after the oxygen introduction treatment. Thereby, at least a part (or all) of the oxygen-containing functional group can be replaced with the nitrogen-containing functional group.

Further, the oxygen content O _mass and the nitrogen content N _mass can be measured by using, for example, an inert gas fusion heat conduction type analytical instrument.

<3. Manufacturing method of carbon material for catalyst carrier>
Next, a method for producing a carbon material for a catalyst carrier will be described. First, a starting material for a carbon material for a catalyst carrier is prepared. The starting material of the carbon material for the catalyst carrier is preferably a chemically stable carbon material. Preferred examples of carbon materials include carbon black. The carbon material may be another type of carbon material, for example, graphite, carbon fiber, activated carbon or the like, pulverized products thereof, carbon nanofibers, carbon nanotubes or the like, or the like. Further, the carbon material may be a mixture of two or more of these.

Then, the above-mentioned activation treatment, graphitization treatment, oxygen introduction treatment, and nitrogen introduction treatment are appropriately combined. Then, the resin adsorption rate W is measured by performing the above-mentioned resin adsorption amount evaluation test on the treated carbon material. Then, when the resin adsorption rate W is less than 30% by mass, the activation treatment is further performed. As a result, a carbon material for a catalyst carrier that satisfies the requirements (a) to (d), preferably (e) and (f) is produced.

<4. Polymer electrolyte fuel cell ＞
The carbon material for a catalyst carrier according to this embodiment can be applied to, for example, the polymer electrolyte fuel cell 1 shown in FIG. The polymer electrolyte fuel cell 1 includes separators 10, 20, gas diffusion layers 30, 40, catalyst layers 50, 60, and an electrolyte membrane 70.

The separator 10 is a separator on the anode side, and a reducing gas such as hydrogen is introduced into the gas diffusion layer 30. The separator 20 is a separator on the cathode side, and an oxidizing gas such as oxygen gas or air is introduced into the gas diffusion-aggregated phase. The types of the separators 10 and 20 are not particularly limited, and any separator used in a conventional fuel cell, for example, a polymer electrolyte fuel cell may be used.

The gas diffusion layer 30 is a gas diffusion layer on the anode side, and after diffusing the reducing gas supplied from the separator 10, it is supplied to the catalyst layer 50. The gas diffusion layer 40 is a gas diffusion layer on the cathode side, and after diffusing the oxidizing gas supplied from the separator 20, it is supplied to the catalyst layer 60. The types of the gas diffusion layers 30 and 40 are not particularly limited, and any gas diffusion layer used in a conventional fuel cell, for example, a polymer electrolyte fuel cell may be used. Examples of the gas diffusion layers 30 and 40 include porous carbon materials such as carbon cloth and carbon paper, and porous metal materials such as metal mesh and metal wool. As a preferable example of the gas diffusion layers 30 and 40, the layer on the separator side of the gas diffusion layer is a gas diffusion fiber layer containing a fibrous carbon material as a main component, and the layer on the catalyst layer side is mainly composed of carbon black. A gas diffusion layer having a two-layer structure as a micropore layer can be mentioned.

The catalyst layer 50 is a so-called anode. In the catalyst layer 50, an oxidation reaction of the reducing gas occurs, and protons and electrons are generated. For example, when the reducing gas becomes hydrogen gas, the following oxidation reaction occurs.
H ₂ → 2H ⁺ + ^2e- (E ₀ = 0V)

The protons generated by the oxidation reaction reach the catalyst layer 60 through the catalyst layer 50 and the electrolyte membrane 70. The electrons generated by the oxidation reaction reach the external circuit through the catalyst layer 50, the gas diffusion layer 30, and the separator 10. The electrons are introduced into the separator 20 after working in an external circuit. After that, the electrons reach the catalyst layer 60 through the separator 20 and the gas diffusion layer 40.

The configuration of the catalyst layer 50 serving as the anode is not particularly limited. That is, the structure of the catalyst layer 50 may be the same as that of the conventional anode, the same as that of the catalyst layer 60, or the structure having higher hydrophilicity than that of the catalyst layer 60. You may.

The catalyst layer 60 is a so-called cathode. In the catalyst layer 60, a reduction reaction of the oxidizing gas occurs to generate water. For example, when the oxidizing gas becomes oxygen gas or air, the following reduction reaction occurs. The water generated in the oxidation reaction is discharged to the outside of the fuel cell 1 together with the unreacted oxidizing gas.
O ₂ + 4H ⁺ + ^4e- → 2H ₂ O (E ₀ = 1.23V)

As described above, in the fuel cell 1, power is generated by utilizing the energy difference (potential difference) between the oxidation reaction and the reduction reaction. In other words, the electrons generated by the oxidation reaction do the work in the external circuit.

It is preferable that the catalyst layer 60 contains the carbon material for the catalyst carrier according to the present embodiment. That is, the catalyst layer 60 includes a carbon material for a catalyst carrier according to the present embodiment, an electrolyte material, and a catalyst component. As a result, the catalyst utilization rate in the catalyst layer 60 can be increased, and by extension, the catalyst utilization rate of the polymer electrolyte fuel cell 1 can be increased.

The catalyst loading ratio in the catalyst layer 60 is not particularly limited, but is preferably 10 to 80% by mass. Here, the catalyst loading ratio is the mass% of the catalyst component with respect to the total mass of the catalyst (that is, the particles in which the catalyst component is supported on the carbon material for the catalyst carrier). When the catalyst loading rate is within this range, the catalyst utilization rate is further increased. When the catalyst loading ratio is less than 10% by mass, it may be necessary to thicken the catalyst layer 60 in order to make the polymer electrolyte fuel cell 1 practically usable. On the other hand, when the catalyst loading ratio exceeds 80% by mass, catalyst aggregation is likely to occur. In addition, the catalyst layer 60 becomes too thin, which may cause flooding.

The thickness of the catalyst layer 60 is not particularly limited, but is preferably more than 5 μm and less than 20 μm. In this case, the oxidizing gas is likely to diffuse into the catalyst layer 60, and flooding is less likely to occur. When the thickness of the catalyst layer 60 is 5 μm or less, flooding is likely to occur. When the thickness of the catalyst layer 60 is 20 μm or more, the oxidizing gas is less likely to diffuse in the catalyst layer 60, and the catalyst component in the vicinity of the electrolyte membrane 70 is less likely to work. That is, the catalyst utilization rate may decrease.

The electrolyte membrane 70 is made of an electrolyte material having proton conductivity. The electrolyte membrane 70 introduces the protons generated by the oxidation reaction into the catalyst layer 60 which is a cathode. Here, the type of the electrolyte material is not particularly limited, and any electrolyte material used in a conventional fuel cell, for example, a polymer electrolyte fuel cell may be used. A preferred example is the electrolyte material used in the polymer electrolyte fuel cell, i.e., the electrolyte resin. Examples of the electrolyte resin include a polymer having a phosphoric acid group, a sulfonic acid group or the like introduced therein, for example, a perfluorosulfonic acid polymer or a polymer having a benzenesulfonic acid introduced therein. Of course, the electrolyte material according to this embodiment may be another type of electrolyte material. Examples of such an electrolyte material include an inorganic type, an inorganic-organic hybrid type, and the like electrolyte materials. The fuel cell 1 may be a fuel cell that operates in the range of room temperature to 150 ° C.

<5. Manufacturing method of polymer electrolyte fuel cell ＞
The manufacturing method of the polymer electrolyte fuel cell 1 is not particularly limited, and any conventional manufacturing method may be used. However, it is preferable to use the carbon material for the catalyst carrier according to the present embodiment as the catalyst carrier on the cathode side.

<1. Preparation of carbon material ＞
As a starting material for the carbon material for the catalyst carrier, Ketjen Black EC600JD manufactured by Lion Co., Ltd. (hereinafter abbreviated as "EJ") and Scarbon MCND manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd. (hereinafter abbreviated as "MC"). ) And Tokai Carbon Co., Ltd. Talker Black # 4500 (hereinafter abbreviated as "TC") were prepared.

<2. Parameter measurement>
(2-1. Measurement of resin adsorption rate W)
1.00 g of a carbon material for a catalyst carrier was added to 100 mL of distilled water in which 0.50 mass% of polyethylene glycol (polyethylene glycol 4000 manufactured by Kanto Chemical Co., Inc., mass average molecular weight 4000) was dissolved, and the mixture was sufficiently dispersed. Then, it was further dispersed for 5 minutes with an ultrasonic disperser (UH-50 manufactured by SMT). As a result, a mixed solution was prepared. Then, the mixture was stirred with a magnetic rotor for 5 hours while heating in an oil bath set at 100 ° C. (first step). Then, the dispersion was rapidly cooled to 60 ° C. Then, the dispersion liquid was filtered through a resin membrane filter to separate the carbon material for the catalyst carrier (second step). Then, the carbon material for the catalyst carrier was taken in a beaker, 500 mL of distilled water was added and dispersed, and the carbon material for the catalyst carrier was washed. After filtering the dispersion again, the carbon material for the catalyst carrier was vacuum dried at 90 ° C. for 5 hours. Then, the mass of the carbon material for the catalyst carrier (polyethylene glycol was attached to the carbon material for the catalyst carrier) was measured. Then, the amount of resin adsorbed was measured by subtracting the mass of 1.00 g of the carbon material for the catalyst carrier used in the first step from the measured value (third step). Then, the resin adsorption rate W was calculated by dividing the amount of resin adsorbed by the mass of the carbon material for the catalyst carrier used in the first step of 1.00 g. For example, if the measured value obtained in the third step is 1.54 g, the resin adsorption rate W is 54% by mass. Regarding the resin adsorption rate W of the carbon material "E30" for catalyst carriers (see Table 1), in addition to the above-mentioned polyethylene glycol 4000, the mass average molecular weight is 1000 (polyethylene glycol 1000 manufactured by Wako Pure Chemical Industries, Ltd.), 20000. The resin adsorption rate W was calculated using polyethylene glycol (polyethylene glycol 20000 manufactured by Wako Pure Chemical Industries, Ltd.).

(2-2. Measurement of specific volume V _3-10 )
A sample of about 50 mg of a carbon material for a catalyst carrier was weighed and vacuum dried at 90 ° C. for 2 hours. The obtained dried sample was set in an automatic gas adsorption measuring device (BELSORP-MAX manufactured by Microtrac Bell), and the adsorption isotherm of nitrogen gas at the liquid nitrogen temperature was measured. Then, the specific volume (mL / g) was calculated by BJH analysis of the attached analysis software.

(2-3. Measurement of BET specific surface area S _BET )
A sample of about 50 mg of a carbon material for a catalyst carrier was weighed and vacuum dried at 90 ° C. for 2 hours. The obtained dried sample was set in an automatic gas adsorption measuring device (BELSORP-MAX manufactured by Microtrac Bell), and the adsorption isotherm of nitrogen gas was measured at the liquid nitrogen temperature. Then, the BET specific surface area (m ² / g) was calculated by BET analysis of the attached analysis software.

(2-4. Measurement of half width of G band)
A sample of about 3 mg of a carbon material for a catalyst carrier was measured and set in a laser Raman spectrophotometer (NRS-7100 type manufactured by JASCO Corporation). Next, the excitation laser 532 nm, laser power 100 mW (sample irradiation power: 0.1 mW), microscopic arrangement: Backscattering, slit: 100 μm × 100 μm, objective lens: × 100, spot diameter: 1 μm, exposure time: 30 sec, observed wave number: 3200. The half-value width (cm ^-1 ) of the G band was measured under the measurement conditions of ~ 750 cm ^-1 and the number of integrations: 2 times.

(2-5. Measurement of oxygen content O _mass and nitrogen content N _mass )
Using the LECO RH402 type as an analyzer, the oxygen content O _mass and the nitrogen content N _mass (mass%) were measured by applying the usual inert gas fusion heat conduction method of C, H, O and N.

<3. Experimental Example 1>
(3-1. Preparation of carbon material for catalyst carrier)
In Experimental Example 1, a carbon material for a catalyst carrier was produced by performing any one or more of the following activation treatment, graphitization treatment, oxygen introduction treatment, and nitrogen introduction treatment in combination.

(3-1-1. Activation treatment using carbon dioxide (CO ₂ activation treatment))
The carbon material for the catalyst carrier was heated at a temperature of 900 to 1600 ° C. for 0.2 to 4 hours in a CO ₂ flow atmosphere. For example, when the EJ is subjected to CO ₂ activation treatment at 900 ° C. for 3 hours, the EJ after the CO ₂ activation treatment is referred to as "EJ-C09 / 30". When the EJ is subjected to CO ₂ activation treatment at 1400 ° C. for 0.2 hours, the EJ after the CO ₂ activation treatment is referred to as "EJ-C14 / 02".

Since TC is a non-porous carbon, when TC is used as a carbon material for a catalyst carrier, the above-mentioned CO ₂ activation treatment is performed after the usual CO ₂ activation treatment. Here, in the normal CO ₂ activation treatment, the carbon material for the catalyst carrier was heated at a temperature of 900 to 1100 ° C. for 4 hours in a CO ₂ flow atmosphere. For example, when the TC is subjected to CO ₂ activation treatment at 1000 ° C. for 2 hours and then CO ₂ activation treatment at 1300 ° C. for 0.3 hours, the TC after the CO ₂ activation treatment is referred to as “TC-C10 / 20-C13 / 03”. It is written as.

(3-1-2. Activation treatment using steam ( _H2O activation treatment))
Argon gas was passed through distilled water maintained at 90 ° C. Then, the obtained humidified argon gas was brought into contact with a carbon material for a catalyst carrier kept at 1200 to 1400 ° C. for 5 hours. For example, when the EJ is subjected to the _H2O activation treatment at 1200 ° C. for 5 hours, the EJ after the _H2O activation treatment is referred to as "EJ-H12 / 05".

(3-1-3. Graphitization treatment)
The carbon material for the catalyst carrier was set in a graphitization furnace (Tanman type graphitization furnace manufactured by Shinsei Electric Furnace Co., Ltd.) and heat-treated at a temperature of 1600 to 2300 ° C. for 1 hour under an argon gas flow. For example, when the EJ is graphitized at 1800 ° C., the EJ after the graphitization treatment is referred to as “EJ18”.

(3-1-4. Oxygen introduction treatment (nitric acid treatment))
1.0 g of a carbon material for a catalyst carrier was put into 200 mL of a 69 mass% nitric acid aqueous solution, and the mixture was sufficiently stirred. Then, the dispersion was heated in an oil bath at 90 ° C. for 2 hours. Oxidation treatment was performed by the above steps. Then, the dispersion was heat-treated in an argon gas atmosphere at a temperature of 600 to 1400 ° C. for 1 hour. In addition, only the oxidation treatment was performed on some carbon materials for catalyst carriers. For example, when the EJ18 is oxidized, the EJ18 after the oxidation treatment is referred to as "EJ18-NA". Further, when the EJ18 is oxidized and then heat-treated at 700 ° C., the heat-treated EJ18 is referred to as "EJ18-NA07".

(3-1-5. Nitrogen introduction treatment (melamine treatment))
4.0 g of melamine (general reagent manufactured by Kanto Chemical Co., Inc.) was put into a reaction vessel containing 1.0 g of a carbon material for a catalyst carrier, and these were mixed. The mixture was then heated at a rate of 3 ° C. per minute under nitrogen gas flow. The mixture was then heat treated at 600-1300 ° C. for 1 hour under nitrogen gas flow. Through the above steps, nitrogen introduction treatment was performed. For example, when nitrogen is introduced into EJ18 at 1000 ° C., the EJ18 after heat treatment is referred to as "EJ18-ML10".

As described above, in Experimental Example 1, a carbon material for a catalyst carrier was produced by performing any one or more of the above activation treatment, graphitization treatment, oxygen introduction treatment, and nitrogen introduction treatment in combination. .. The symbol indicating the carbon material for the catalyst carrier is expressed in the order in which each treatment is performed. For example, the carbon material for a catalyst carrier described as "EJ18-C12 / 02-NA09-ML11" is produced by the following steps. That is, first, EJ-18 is obtained by graphitizing the EJ at 1800 ° C. Then, EJ-18 is subjected to CO ₂ activation treatment at 1200 ° C. for 0.2 hours to obtain EJ18-C12 / 02. Then, EJ18-C12 / 02 is subjected to an oxidation treatment. Then, the oxidation-treated EJ18-C12 / 02 is heat-treated at 900 ° C. As a result, EJ18-C12 / 02-NA09 is obtained. Then, nitrogen introduction treatment is performed on EJ18-C12 / 02-NA09 at 1100 ° C. As a result, EJ18-C12 / 02-NA09-ML11 is obtained.

(3-2. Manufacture of polymer electrolyte fuel cell)
(3-2-1. Platinum-supported treatment)
Above 3-1. The carbon material for the catalyst carrier prepared in 1 was dispersed in distilled water. Then, formaldehyde was added to the dispersion, and the dispersion was set in a water bath set at 40 ° C. After the temperature of the dispersion became 40 ° C., which was the same as that of the water bath, the dinitrodiamine Pt complex nitric acid aqueous solution was slowly poured into the dispersion while stirring the dispersion. Then, stirring was continued for about 2 hours. Then, the dispersion was filtered and the obtained solid matter was washed. The solid thus obtained was vacuum dried at 90 ° C. and then pulverized in a mortar. Then, the pulverized product was heat-treated at 150 ° C. for 1 hour in a hydrogen atmosphere. Through the above steps, Pt particles were supported on the carbon material for the catalyst carrier. That is, a Pt catalyst (a carbon material for a catalyst carrier on which Pt particles are supported) was prepared. The catalyst loading ratio was 40% by mass. The catalyst coverage was confirmed by inductively coupled plasma emission spectroscopy (ICP-AES: Inductively Coupled Plasma-Atomic Emission Spectroscopy).

(3-2-2. Adjustment of coated ink)
Nafion DE2020 (registered trademark: Nafion; persulfonic acid-based ion exchange resin) manufactured by DuPont was prepared as an electrolyte material. Then, the Pt catalyst and Nafion DE2020 were mixed in an Ar atmosphere at a ratio where the mass of the solid content of Nafion DE2020 was 1.25 times the mass of the carbon material for the catalyst carrier. The mixture was then lightly stirred. Then, the Pt catalyst was crushed by ultrasonic waves. Then, ethanol was added to the mixture so that the total solid content concentration of the Pt catalyst and Nafion DE2020 was 1.1% by mass. A coating ink was produced by the above steps.

(3-2-3. Preparation of catalyst layer)
Ethanol was further added to the coated ink to prepare an ink for spraying having a platinum concentration of 0.5% by mass. Then, the spray conditions were adjusted so that the mass per unit area of the catalyst layer of platinum (hereinafter referred to as "platinum basis weight") was 0.2 mg / cm ² , and the spray ink was applied onto a Teflon (registered trademark) sheet. Then, the coating layer was dried in argon at 120 ° C. for 60 minutes. A catalyst layer was prepared by the above steps.

(3-2-4. Preparation of MEA)
A square electrolyte membrane having a side of 6 cm was cut out from a Nafion membrane (NR211 manufactured by DuPont). Further, two square catalyst layers having a side of 2.5 cm were cut out from the catalyst layer formed on the Teflon (registered trademark) sheet with a cutter knife. One catalyst layer is a catalyst layer for an anode, and the other catalyst layer is a catalyst layer for a cathode.

Then, between the anode and the catalyst layers for the cathode, each catalyst layer was in contact with each other with the central portion of the electrolyte membrane interposed therebetween, and the electrolyte membrane was sandwiched so as not to be displaced from each other. Then, the laminate was pressed at 120 ° C. and 100 kg / cm ² for 10 minutes. The laminate was then cooled to room temperature. Then, only the Teflon sheet was carefully peeled off from each catalyst layer of the laminate. Through the above steps, a catalyst layer-electrolyte membrane conjugate in which the catalyst layer serving as the anode and the cathode is fixed to the electrolyte membrane was produced.

Next, two square carbon papers having a side of 2.5 cm were cut out from carbon paper (35BC manufactured by SGL Carbon Co., Ltd.). These carbon paver was used as a gas diffusion layer. That is, the catalyst layer-electrolyte film junction was sandwiched between these square carbon papers so that there would be no deviation between the catalyst layers serving as the anode and the cathode and these square carbon papers. Then, the laminate was pressed at 120 ° C. and 50 kg / cm ² for 10 minutes. MEA was produced by the above steps.

The amount of the catalyst metal component, the carbon material for the catalyst carrier, and the electrolyte material in each of the produced MEAs was confirmed in the following steps. That is, the mass of the catalyst layer fixed on the Nafion membrane (electrolyte membrane) was measured from the difference between the mass of the Teflon sheet with the catalyst layer before pressing and the mass of the Teflon sheet peeled off after pressing. Then, the basis weight of each component was calculated based on the measured value and the mass ratio of each component in the catalyst layer.

(3-3. Fuel cell power generation performance test)
Each of the prepared MEAs was incorporated into a cell, and the performance of the fuel cell was evaluated using a fuel cell measuring device. Specifically, the following evaluations were made.

Air was supplied to the cathode and pure hydrogen was supplied to the anode so that the gas utilization rates were 40% and 70%, respectively. Each gas pressure was adjusted by a back pressure valve provided downstream of the cell and set to 0.2 MPa (outlet side pressure). The cell temperature was set to 80 ° C. Here, the air and pure hydrogen supplied to the fuel cell are supplied to the fuel cell after passing through the humidifier, respectively. Therefore, air and pure hydrogen are supplied to the fuel cell with saturated steam corresponding to the water temperature in the humidifier. By controlling the humidification state at this time with the temperature of the humidifier, the relative humidity of air and pure hydrogen was adjusted to 30%. Then, the power generation performance in such an environment was evaluated.

Specifically, while supplying air to the cathode and pure hydrogen to the anode, the load on the fuel cell was gradually increased, and the fuel cell was operated at 1000 mA / cm ² for 1 hour. Then, the current density was fixed at 50 mA / cm ² , and the fuel cell was operated for another hour. The voltage between the cell terminals after that was recorded as the output voltage. Based on this value, the power generation performance of the fuel cell was evaluated. Specifically, the power generation performance was evaluated based on the following criteria.

Less than 0.70V: × (Fail)
0.70V or more and less than 0.80V: ○ (pass)
0.80V or more and less than 0.90V: ◎ (good)
0.90V or higher: ◎◎ (excellent)

(3-4. Durability performance test)
The humidifier was controlled so that the humidified state of air and pure hydrogen became a saturated humidified state at a cell temperature of 80 ° C. Then, in the measurement mode in which the output voltage was constant, the voltage between the cell terminals was maintained at 1.0 V for 1.5 seconds. Next, the voltage between the cell terminals was increased to 1.35 V and held for 1.5 seconds. Then, the voltage between the cell terminals was returned to 1.0V. The above cycle was repeated 3000 times. After that, the power generation performance test described above was performed, and the output voltage was measured.

Then, the ratio of the output voltage after the endurance test to the output voltage before the endurance test was defined as the output retention rate. Then, the main maintenance rate was used as an evaluation index for durability. That is, the case where the output maintenance rate is 80% or more is regarded as a pass, and the case where the output maintenance rate is less than 80% is regarded as a failure.

Then, the power generation performance and the durability performance were comprehensively judged. That is, if the power generation performance or the durability performance is unacceptable, the comprehensive judgment is unacceptable (×), and if the durability performance is acceptable, the results of ○, ◎, ◎◎ of the power generation performance are taken as the comprehensive judgment result. .. The results are shown in Tables 1 to 3. The underlined values in Tables 1 to 3 are values that do not satisfy the requirements (a) to (f). For requirements (e) and (f), values beyond the range of requirements (e) and (f) are underlined.

<4. Experimental Example 2>
In Experimental Example 2, the carbon material for the catalyst carrier shown in Table 4 was used, and Nafion DE2021 manufactured by DuPont (registered trademark: Nafion; persulfonic acid-based ion exchange resin. DE2020 is a sulfonic acid group) was used for adjusting the coating ink. The same treatment as in Experimental Example 1 was carried out except that (concentrations differed) were used. The results are shown in Table 4. DE2021 and DE2020 are resins having the same monomer structure but different amounts of side chains containing sulfonic acid with respect to the main chain. That is, DE2021 and DE2020 are resins having different amounts of dissociated protons per unit mass of the polymer.

<5. Consideration>
The following points were confirmed by Experimental Examples 1 and 2. When the requirements (a) to (d) were satisfied, good determination results were obtained. Therefore, the carbon material for the catalyst carrier that satisfies the requirements (a) to (d) has a high affinity for the electrolyte material. That is, the polymer electrolyte fuel cell using such a carbon material for a catalyst carrier has a high catalyst utilization rate. Here, since the requirements (c) and (d) are considered to not contribute much to the affinity for the electrolyte material, the requirements (a) and (b) greatly contribute to the affinity for the electrolyte material. Further, according to Experimental Example 2, when the requirements (a) and (b) are satisfied, good judgment results are obtained even if the electrolyte material fluctuates. Therefore, the resin adsorption rate W and the specific volume V _3-10 (mL / g) can be parameters that generally specify the affinity for the electrolyte material.

Furthermore, there is a high positive correlation between the resin adsorption rate W and the specific volume V _3-10 (mL / g). Therefore, the resin adsorption rate W can be adjusted to a desired value by adjusting the specific volume V _3-10 (mL / g). Furthermore, the specific volume V _3-10 (mL / g) cannot be adjusted by a normal activation treatment, but can be adjusted only by a highly reactive activation treatment. Further, the resin adsorption rate W can be specified by the resin adsorption amount evaluation test. That is, by conducting the resin adsorption amount evaluation test, the resin adsorption rate W and the specific volume V _3-10 (mL / g) can be set to values within a desired range. Therefore, the resin adsorption amount evaluation test is a general-purpose and quantitative evaluation test for the affinity for the electrolyte material.

Further, in the carbon material "E30" for a catalyst carrier, the resin adsorption rate W was calculated by changing the mass average molecular weight of polyethylene glycol, but even if the mass average molecular weight fluctuates between 1000 and 20000, the resin adsorption rate W greatly fluctuates. There was no. Therefore, it can be said that the resin adsorption rate W and the specific volume V _3-10 (mL / g) show a high correlation when the mass average molecular weight is 1000 to 20000. That is, the reliability of the evaluation result becomes higher.

Further, when one of the requirements (e) and (f) is further satisfied, the determination result is further improved, and when both the requirements (e) and (f) are further satisfied, the determination result is further improved. Therefore, the oxygen content O _mass and the nitrogen content N _mass can also be parameters for universally specifying the affinity for the electrolyte material.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of the art to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Polymer electrolyte fuel cell 10, 20 Separator 30, 40 Gas diffusion layer 50, 60 Catalyst layer 70 Electrolyte membrane

Claims (10)

A carbon material for a catalyst carrier capable of supporting a catalyst component for a polymer electrolyte fuel cell.
The resin adsorption rate W calculated by the polyethylene glycol resin adsorption amount evaluation test using the polyethylene glycol resin having a mass average molecular weight of 4000 is 30 to 100% by mass.
The specific volume V _3-10 (mL / g) of the mesopores having a diameter of 3 to 10 nm obtained by BJH analysis of the nitrogen adsorption isotherm is 1.0 to 2.0 mL / g.
The BET specific surface area S _BET (m ² / g) evaluated by the BET method is 500 to 1500 m ² / g.
A carbon material for a catalyst carrier, characterized in that the half-value width ΔG of the G band measured by Raman spectroscopy is 30 to 70 cm ^-1 . The carbon material for a catalyst carrier according to claim 1, wherein the oxygen content O _mass is 0.2 to 1.0% by mass. The carbon material for a catalyst carrier according to claim 1 or 2, wherein the nitrogen content N _mass is 0.25 to 1.5% by mass. Any of claims 1 to 3, wherein the oxygen content O _mass is 0.2 to 1.0 mass% and the nitrogen content N _mass is 0.25 to 1.5 mass%. The carbon material for a catalyst carrier according to item 1. The carbon material for a catalyst carrier according to any one of claims 1 to 4, wherein the resin adsorption rate W is 40 to 90% by mass. The carbon material for a catalyst carrier according to any one of claims 1 to 5.
A catalyst for a polymer electrolyte fuel cell, which comprises a catalyst component supported on the carbon material for a catalyst carrier. The catalyst for a polymer electrolyte fuel cell according to claim 6, wherein the catalyst loading ratio is 10 to 80% by mass. A catalyst layer for a polymer electrolyte fuel cell, which comprises the catalyst for a polymer electrolyte fuel cell according to claim 6 or 7. The polymer electrolyte fuel cell according to claim 8, further comprising the catalyst layer for the polymer electrolyte fuel cell. The solid polymer fuel cell according to claim 9, wherein the polymer electrolyte fuel cell includes the catalyst layer for the polymer electrolyte fuel cell as a cathode-side catalyst layer.

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