JP6814339B2 - Carbon material for catalyst carrier, 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 layer for a polymer electrolyte fuel cell, and a polymer electrolyte fuel cell.

A polymer electrolyte 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 gas diffusion layer on the anode side is introduced into the anode after diffusing the reducing gas. The anode includes a catalyst component, a catalyst carrier supporting the catalyst component, and an electrolyte material having proton conductivity. On the catalyst component, an oxidation reaction of the reducing gas occurs to generate protons and electrons. 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. After working in an external circuit, these electrons are introduced into the separator on the cathode side. 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 gas diffusion layer on the cathode side is introduced into the cathode after diffusing the oxidizing gas. The cathode includes a catalyst component, a catalyst carrier supporting the catalyst component, and an electrolyte material having proton conductivity. On the catalyst component, 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.
_{^{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.

Therefore, in the polymer electrolyte fuel cell, the gas diffusion path through which the reducing gas or the oxidizing gas can move from the gas flow path of each separator to the anode or the catalyst component inside the cathode is formed without interruption. is important. Furthermore, it is also important that the proton conduction path in which the protons generated on the catalyst component of the anode can move through the solid polymer electrolyte membrane to the catalyst component of the cathode is also formed without interruption. Furthermore, it is also important that the electron conduction path through which the electrons generated on the catalyst component of the anode can move to the catalyst component of the cathode through the external circuit is also formed without interruption. If these paths are disrupted, current cannot be efficiently extracted from the polymer electrolyte fuel cell.

Therefore, in the catalyst layer, it is important that the pores forming the gas diffusion path, the electrolyte material forming the proton conduction path, and the catalyst carrier forming the electron conduction path form a continuous network.

Patent No. 4799897 Patent No. 5358408 JP-A-2007-220414 Patent No. 5213499 Japanese Patent Publication No. 2008-501211 International Publication No. 2014/185498 International Publication No. 2010/047415 Patent No. 5650542 Japanese Unexamined Patent Publication No. 6-194174

By the way, a very expensive precious metal such as Pt is used as a catalyst component of a polymer electrolyte fuel cell. Therefore, various attempts have been made to increase the catalyst utilization rate. This is because if the catalyst utilization rate is increased, the amount of the catalyst component used can be reduced without deteriorating the performance of the polymer electrolyte fuel cell.

Specifically, conventionally, it exists at the contact portion (so-called three-phase interface) between the pore network constituting the gas diffusion path, the electrolyte material network forming the proton conduction path, and the catalyst carrier network forming the electron conduction path. It was thought that an electrode reaction (either the reduction reaction or the oxidation reaction) would occur on the catalyst component. Therefore, conventionally, it has been considered important to increase the contact area between the three-phase interface and the catalyst component as much as possible. Furthermore, it was considered important that these networks were formed as continuously as possible. This is because if these networks are divided, the three-phase interface will decrease.

Therefore, in order to increase the utilization rate of the catalyst component, it has been proposed to make the catalyst component into fine particles. By making the catalyst component into fine particles, the surface area of the catalyst component per unit mass increases. Therefore, the contact area between the three-phase interface and the catalyst component increases.

According to this method, the initial power generation performance is improved when a small amount of catalyst particles finely divided to about 1 to 3 nm is used. Therefore, it can be said that the utilization rate of the catalyst component is high in the initial stage of power generation. However, the finely divided catalyst particles repeatedly elute and precipitate due to potential fluctuations during fuel cell operation. As a result, the catalyst component may be enlarged or eluted outside the catalyst layer. As a result, the catalyst utilization rate decreases.

Therefore, in order for the catalyst component to withstand the potential fluctuation, the catalyst component needs to have a certain particle size. For example, when the catalyst component is platinum, the size of the catalyst component that can withstand potential fluctuations is considered to be about 3 to 7 nm. Therefore, conventionally, various attempts have been made to increase the utilization rate of the catalyst component having such a particle size.

For example, in the technique disclosed in Patent Document 1, a gas-diffused carbon material-aggregated phase formed by aggregating a gas-diffused carbon material that does not support a catalyst component as a main component is dispersed in a catalyst layer on the cathode side. According to this technique, a stomatal network can be continuously formed by the gas diffusion carbon material aggregated phase. Therefore, it can be expected that the catalyst utilization rate on the cathode side will be improved.

Further, in the technique disclosed in Patent Document 2, a particulate medium covered with an electrolyte material is added to the catalyst layer. In this technique, excessive coating of the catalyst carrier by the electrolyte material is suppressed, so that conduction between the catalyst carriers is ensured. That is, from the viewpoint of forming the three-phase interface, it is necessary to secure a contact area between the electrolyte material and the catalyst carrier to some extent, but if the contact area becomes excessively large, the contact area between the catalyst carriers is reduced. That is, the catalyst carrier network is disrupted. In the technique disclosed in Patent Document 2, excessive coating of the catalyst carrier by the electrolyte material is suppressed, so that the disruption of the catalyst carrier network is suppressed. Further, since the pores on the surface of the catalyst carrier are less likely to be blocked by the electrolyte material, the disruption of the pore network is suppressed. Therefore, improvement in catalyst utilization rate can be expected.

However, in the techniques disclosed in Patent Documents 1 and 2, it is necessary to include a special material such as a gas diffusion carbon material or a particulate medium in the catalyst layer. Therefore, there is a problem that the manufacturing cost of the polymer electrolyte fuel cell increases. Moreover, even with these techniques, the catalyst utilization rate could not be sufficiently increased.

Patent Documents 3 and 4 disclose a technique for increasing the catalyst utilization rate in a low humidification environment. That is, in order for the electrolyte material to stably conduct protons, the electrolyte material needs to be kept in a wet state to some extent. For this reason, a humidifier is often installed in a system including a polymer electrolyte fuel cell. The reducing gas and the oxidizing gas are humidified by this humidifier. Then, the humidified gas is introduced into the polymer electrolyte fuel cell. However, in low cost systems, the humidifier may be omitted. In this case, it is necessary to keep the inside of the catalyst layer wet. Therefore, in the techniques disclosed in Patent Documents 3 and 4, a catalyst carrier having fine pores formed on the surface is used. According to the techniques disclosed in these, since the micropores formed in the catalyst carrier can retain water, the wet state of the electrolyte material can be maintained. The water content here is, for example, the water content generated by the reduction reaction. As a result, the disruption of the electrolyte material network is suppressed, and an improvement in the catalyst utilization rate can be expected.

The techniques described in Patent Documents 3 and 4 can be expected to improve the catalyst utilization rate under the limited conditions of a low humidification environment. However, under high humidification conditions, the oxidizing gas contains not only the water from the humidifier but also the water generated by the reduction reaction. The water content in the oxidizing gas is particularly large on the downstream side in the flow direction of the oxidizing gas. As described above, the oxidizing gas contains a large amount of water. Therefore, the pores between the catalyst carriers may be blocked by water, and the pore network may be disrupted. Such a phenomenon is also called flooding. Further, the micropores may be completely blocked by water, and the catalyst component in the micropores may not be used for the electrode reaction. Therefore, the techniques disclosed in Patent Documents 3 and 4 have a problem that the catalyst utilization rate on the cathode side is significantly reduced, particularly in a highly humid environment.

In the technique disclosed in Patent Document 5, the electrolyte material is inserted into the nano-order pores from the viewpoint of increasing the contact area between the catalyst component and the three-phase interface as much as possible. By allowing the electrolyte material to enter the nano-order pores, the catalyst component existing in the nano-order pores becomes easy to come into contact with the electrolyte material. That is, the contact area between the catalyst component and the three-phase interface increases. However, even with this technology, the catalyst utilization rate did not increase so much. It is considered that the reason for this is that the catalyst component is covered with the electrolyte material, so that the contact area between the catalyst component and the gas becomes small. As a result, it is considered that the electrode reaction on the catalyst component is inhibited. In particular, the catalyst component on the cathode side is susceptible to this effect.

Patent Document 6 proposes a carbon material for a catalyst carrier made of a special mesoporous carbon having a crystallite diameter Lc on the 002 surface of 1.5 nm or less. By using this carbon material for a catalyst carrier, the catalyst utilization rate can be improved. However, this carbon material for a catalyst carrier is a special carbon material obtained by exploding silver acetylide or the like on a nanoscale, and has a problem that the production cost is very high. Further, the carbon material for the catalyst carrier has a problem that the durability is not sufficient because the crystallites are randomly arranged.

In Patent Document 7, the specific surface area of 1000 m ² / g or more and 4000 m ² / g or less as evaluated by BET, and the ratio S _micro / S of the micropore specific surface area S _micro and the total specific surface area S _catalyst of 2 nm or less by t-plot analysis _A carbon material for a catalyst carrier has been proposed, characterized in that the _total is 0.5 or more (synonymous with S _out / S _total is less than 0.5). Since such a carbon material for a catalyst carrier has a property of storing water, it has a feature of excellent power generation characteristics under low humidification conditions.

By the way, the single cell voltage of the polymer electrolyte fuel cell is about 1.0 V at the open circuit voltage. If the potential of the force sword is less than this value, the carbon material used as the carrier of the catalyst is electrochemically oxidized and consumed as carbon dioxide gas (deterioration of the carrier carbon material) can be substantially ignored. .. However, under actual operating conditions, for example, when the fuel cell is started or stopped, the cathode potential may rise to 1.0 V or higher. That is, when hydrogen and oxygen are mixed in the electrode of the anode, a hydrogen oxidation reaction in which hydrogen is oxidized and an oxygen reduction reaction in which oxygen is reduced occur in the electrode of the anode, and a local battery is formed. Since the potential of the part where the oxygen reduction reaction occurs in the electrode of the anode becomes the oxygen reduction potential (about 1V), the opposite electrode facing through the electrolyte, that is, the potential of the cathode further adds the battery voltage to the oxygen reduction potential in the anode. It will rise to the added potential, and it is observed that the potential of the force sword rises to 1.0 V or more, and in some cases to about 1.5 V. The mixing of hydrogen and oxygen in the electrode of the anode is caused by the oxygen of the electrode of the force sword permeating through the solid polymer electrolyte membrane and reaching the electrode of the anode. This phenomenon is unavoidable in principle, whether it is used for a stationary fuel cell or a fuel cell vehicle, as long as a fluorine-based film having high oxygen permeability is used.

When the potential of the cathode is 1.0 V or higher in this way, the high potential of the force sword causes oxidation of the carbon material for the catalyst carrier represented by the reaction formula of C + O ₂ → CO ₂ , and the carbon material for the catalyst carrier becomes Deteriorates and wears out. As a result, the catalyst metal particles fall off from the carrier, the amount of the catalyst that functions effectively decreases, and the power generation performance deteriorates. Alternatively, the catalyst layer is thinned due to the consumption of the carrier and the pores are crushed, resulting in a gas supply failure, which also reduces the power generation performance. In addition, deactivation of the catalyst metal due to high potential oxidation of platinum, which is the catalyst metal, may occur, and the power generation performance also deteriorates. Therefore, in an actual usage environment, start-stop is repeated, and the force sword is exposed to a voltage of 1.0 V or more each time, and when this is repeated for a long period of time, such potential fluctuations occur. Depending on the number of times, the power generation performance deteriorates due to the consumption of the carbon material for the catalyst carrier.

The carbon material proposed in Patent Document 7 has not been subjected to any treatment for suppressing such oxidative consumption. Therefore, the carbon material for the catalyst carrier of Patent Document 7 has a problem of low durability. Further, for the purpose of imparting durability to the carbon material for a catalyst carrier of Patent Document 7, a treatment for suppressing oxidative consumption, for example, a heat treatment at 1600 ° C. or higher in an inert atmosphere reduces the specific surface area. According to the investigation by the present inventors, the major factor of the decrease in the area is the decrease in the micropore specific surface area. That is, it is considered that the micropores were crushed by the high temperature heat treatment and the specific surface area was reduced. Therefore, when the catalyst carrier carbon material of Patent Document 7 is simply treated to suppress oxidative consumption, the characteristic of Patent Document 7, "Micropore specific surface area S _micro and total specific surface area S _total ratio S _micro / S _total, is obtained. It becomes difficult to maintain "0.5 or more". Further, since the specific surface area is also significantly reduced, the initial performance is not always satisfactory, and the catalyst utilization rate is particularly low. As a result, there is a problem that the characteristics of the excellent low load region possessed before the heat treatment are lost.

In response to the problems of Patent Document 7, Patent Document 8 and Patent Document 9 describe an activation treatment for increasing the specific surface area of a carbon material as a method for producing a carbon material for a catalyst carrier that improves the life characteristics of a fuel cell. , A method of combining high-temperature heat treatment for making carbon materials highly graphite has been proposed. In general, when graphene treatment is applied, graphene grows and develops, and graphene stacking order develops to improve oxidative consumption resistance. However, graphene treatment causes micropores to collapse, reducing the specific surface area, or It causes a decrease in the micropore specific surface area. A carbon material having a reduced specific surface area or a carbon material having a reduced micropore specific surface area has fewer graphene edge portions on which the catalyst component can be adsorbed when the catalyst component is supported. Therefore, when the catalyst component is supported at a high loading ratio, the catalyst is used. The components tend to aggregate, the particle size of the catalyst component becomes coarse, and the dispersibility of the catalyst component tends to decrease. In order to prevent this, a "activation treatment" is performed in advance to slightly oxidize and consume the carbon material to increase the specific surface area and the micropore specific surface area. Patent Document 8 and Patent Document 9 propose a method for producing a carbon material having a high specific surface area and oxidative wear resistance by combining such an activation treatment and a high graphitization treatment, and have a high specific surface area of 700 m. ^A method for producing a carbon material of less than ² / g is illustrated. When the carbon material produced by such a method is used as the carbon material for the catalyst carrier of the fuel cell, the initial performance is maintained and the durability is extremely high. However, the initial performance is not always satisfactory due to the influence of the specific surface area reduced by the high graphitization treatment, and there is a problem that the catalyst utilization rate is particularly low.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is that the catalyst utilization rate can be improved without using an expensive material, and the catalyst is used regardless of humidification conditions. To provide a new and improved carbon material for a catalyst carrier, a catalyst layer, and a polymer electrolyte fuel cell, which can improve the utilization rate, have high durability, and can be manufactured at low cost. It is in.

In order to solve the above problems, the present inventor has focused on a carbon material constituting a catalyst carrier on the cathode side, that is, a carbon material for a catalyst carrier on the cathode side. As described above, this is mainly because the catalyst utilization rate on the cathode side is low. As a result, the present inventor has obtained the following findings.

1) In order to increase the durability of the carbon material for the catalyst carrier, it is effective to make the carbon material highly graphitized. That is, a carbon material generally used as a catalyst carrier for a polymer electrolyte fuel cell has a structure in which a large number of a plurality of crystallites are arranged. Each crystallite has a structure in which a plurality of condensed polycyclic aromatic skeletons (hereinafter, also referred to as “graphene”) are laminated. Oxidative consumption of carbon material occurs when carbon at the end of graphene (hereinafter, also referred to as “edge carbon”) is oxidized to CO ₂ . Therefore, reducing edge carbon is directly linked to the suppression of oxidative consumption in carbon materials. Therefore, the carbon material is made highly graphite. Graphene grows and develops by the high graphitization treatment, and the graphene stacking order develops. That is, by increasing the graphite, the crystallites constituting the carbon material for the catalyst carrier can be greatly grown, so that the edge carbon can be reduced, and the durability of the carbon material for the catalyst carrier is enhanced. The graphitization treatment is performed, for example, by performing a heat treatment at 1600 ° C. or higher in an inert atmosphere. Further, the degree of graphitization of the carbon material can be evaluated by, for example, the half width of the G band measured by Raman spectroscopy.

2) As described above, when the contact between the electrolyte material and the catalyst component is increased, the catalyst utilization rate does not increase so much. The reason for this is considered to be that the catalyst component is covered with the electrolyte material. When the catalyst component is covered with the electrolyte material, the contact area between the catalyst component and the gas becomes small. As a result, the electrode reaction on the catalyst component is inhibited.

Therefore, the present inventor has considered supporting the catalyst component in the pores of the carbon material in order to avoid contact between the catalyst component and the electrolyte material as much as possible. Specifically, the present inventor activated the highly graphitized carbon material much stronger than before. As a result, the specific surface area of the carbon material should be extremely large (specifically, up to over 700 m ² / g), and in particular, the external specific surface area of the carbon material should be extremely large (specifically, up to over 300 m ² / g). succeeded in. Here, the external specific surface area corresponds to the external specific surface area obtained by t-plot analysis of the nitrogen adsorption isotherm, and is the ratio of the total specific surface area of the carbon material other than the specific surface area of micropores (pores having a diameter of 2 nm or less). The surface area.

The present inventor considered that the external specific surface area became extremely large because the carbon material became a hollow structure by the activation treatment. That is, in the initial stage of activation, the amorphous portion of the gap between the crystallites and the edge of graphene constituting the crystallites are preferentially scraped. As a result, pores are formed on the surface of the carbon material. After that, when the activation further progresses, the amorphous portion existing inside the carbon material is scraped off. As a result, a carbon material having a hollow structure is produced. The hollow portion of the carbon material and the outer surface are connected by pores. In the hollow carbon material, the "mass of the carbon material", which is the denominator of the specific surface area, becomes extremely small, so that the external specific surface area increases.

Then, when the catalyst component was supported on such a carbon material, the catalyst utilization rate was greatly improved. The present inventor considers this reason as follows. That is, when the catalyst component is supported on the carbon material having the hollow portion, the catalyst component is also supported on the pores and the wall surface of the hollow portion. Since the electrolyte material cannot penetrate into the pores and hollow portions, the number of catalyst components covered by the electrolyte material is reduced. Conventionally, it has been considered that only the catalytic component in contact with the electrolyte material is used in the reduction reaction. According to this idea, the catalyst component supported on the wall surface of the pores and the hollow portion should not be used in the reduction reaction because it is not in contact with the electrolyte material. Nevertheless, the catalyst utilization rate has improved. Therefore, the catalyst component supported on the wall surface of the pores and the hollow portion is also used in the reduction reaction.

Then, it is considered that the edge portion of graphene is exposed on the wall surface of the pores and the hollow portion. Then, a hydrophilic group is introduced into the carbon atom (hereinafter, such a carbon atom is also referred to as "edge carbon atom") constituting the edge portion of graphene by the activation treatment. Therefore, the present inventor considered that this hydrophilic group serves as an adsorption point for water. That is, the wall surfaces of the pores and the hollow portion have high hydrophilicity, and water is adsorbed on the wall surfaces of the pores and the hollow portion at a high density. Then, the catalyst component supported on the wall surface of the pores and the hollow portion is in contact with the water content. Then, the protons in the electrolyte material reach the catalyst component through the water adsorbed on the wall surfaces of the pores and the hollow portion. Then, a reduction reaction occurs on the catalyst component. As described above, the present inventor considered that the water adsorbed on the wall surface of the pores and the hollow portion becomes a proton conductor instead of the electrolyte material. That is, the present inventor considered that these waters serve as a proton conduction path. Further, since the hydrophilicity of the pores and the hollow portion is increased by the activation treatment, the electrolyte material can be maintained in a wet state even in a low humidification environment.

The order in which the activation treatment and the graphitization treatment are performed is not particularly limited, but it is preferable that the activation treatment is performed before the graphitization treatment. If the graphitization treatment is performed first, the crystallites grow large, so that the portion scraped by the activation treatment is reduced. Therefore, it may be difficult to activate the carbon material, and it may be difficult to obtain a desired external specific surface area. On the other hand, the carbon material can be easily activated by performing the activation treatment first. Therefore, a carbon material having a desired external specific surface area can be easily produced. In addition, the activation process can be easily controlled.

3) The hydrophilicity of the carbon material can be sufficiently increased only by the above activation treatment, but the hydrophilicity treatment may be further performed. This makes it possible to further increase the hydrophilicity of the surface of the carbon material.

4) From the viewpoint of suppressing flooding in a highly humid environment, the external specific surface area needs to be a certain ratio to the total specific surface area. If the external specific surface area is too small with respect to the total specific surface area, many pores that easily retain water will be formed on the surface of the carbon material. As a result, water tends to accumulate around the carbon material, which may lead to flooding.

As a method for evaluating the external specific surface area, t-plot analysis is known. However, in the conventional t-plot analysis, there is a possibility that the micropores of the carbon material that has been highly graphitized to the extent that it has the high durability required for a fuel cell cannot be accurately discriminated. In the t-plot analysis, it is necessary to use a carbon material having as few micropores as possible as a standard material. However, conventional standard materials sometimes have a higher proportion of micropores than highly graphitized carbon materials. For this reason, the conventional t-plot analysis has a problem that the micropores of the highly graphitized carbon material cannot be accurately discriminated. The present inventor has diligently studied a method capable of discriminating such micropores in a carbon material. As a result, the present inventor has come up with the idea of using the carbon material obtained by heat-treating the carbon material at 2600 ° C. or higher as a standard substance. There are almost no micropores on the surface of such a standard material. Therefore, by performing t-plot analysis using this standard substance, it is possible to accurately discriminate the micropores of the graphitized carbon material. The present inventor has come up with the present invention based on these findings.

According to a certain aspect of the present invention, it is a carbon material for a catalyst carrier capable of supporting a catalyst component for a solid polymer fuel cell, and the half-value width of the G band measured by Raman spectroscopy is 30 cm ^-1 more than 65 cm. less than ^-1, BET specific surface area _S BET to be evaluated by the BET method ^(m 2 / g) is less than 700 meters ² / g ultra 3000 m ² / g, a total specific surface area _{S total} is evaluated at t plot analysis the ratio _S out _{/ S total} of the external specific surface area _{S out} is at greater than 0.3, catalyst support, wherein the external specific surface area _{S out} which is evaluated at t plot analysis is 300 meters ² / g than Carbon material is provided.

Here, BET specific surface area _S BET to be evaluated by the BET method ^(m 2 / g) may be less than 700 meters ² / g Ultra 1300 m ² / g.

Also, t plot analysis at Rated micropore specific surface area _S micro ^(m 2 / g) it is, 250m ² / g may be less than ultra 700m ² / g.

Here, the t-plot analysis may be performed using a carbon material heat-treated at 2600 ° C. or higher as a standard substance.

Further, the external specific surface area S _out evaluated by the t-plot analysis may be more than 300 m ² / g.

According to another aspect of the present invention, there is provided a catalyst layer for a polymer electrolyte fuel cell, which comprises a catalyst component and the above-mentioned carbon material for a catalyst carrier that supports the catalyst component.

Here, the catalyst loading ratio may be 30% by mass or more and less than 80% by mass.

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

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

As described above, according to the present invention, the half-value width of the G band is 30 cm ^{-1 and} more than 65 cm ^-1 , so that the durability of the polymer electrolyte fuel cell can be improved. Further, since the BET specific surface area _S BET ^(m 2 / g) is 700 meters ² / g Ultra 3000m less than ² / g, a large number of pores are formed on the surface of the carbon material. Therefore, more catalyst components can be supported in the pores. Further, the external specific surface area S _out evaluated by the t-plot analysis is more than 300 m ² / g. Therefore, the catalyst component can be supported not only on the wall surface of the pores but also on the wall surface of the hollow portion. Since edge carbon atoms are exposed on the wall surfaces of the pores and the hollow portion, the hydrophilicity of these wall surfaces is high. Therefore, protons also reach these catalyst components. As a result, many catalytic components supported on the walls of the pores and hollow portions can be used in the reduction reaction. Furthermore, since these catalyst components are not easily covered by the electrolyte material, they can be used more reliably in the reduction reaction. Therefore, the utilization rate of the catalyst component is improved. Further, since the carbon material according to the present invention has high hydrophilicity, the electrolyte material can be maintained in a wet state even in a low humidification environment. Furthermore, the total specific surface area _{S total} and ratio _S out _{/ S total} of the external specific surface area _{S out} is because it is greater than 0.3, less likely flooding even under high humidification environment occurs. As described above, the carbon material according to the present invention can improve the catalyst utilization rate without using an expensive material, can improve the catalyst utilization rate regardless of the humidification conditions, and has high durability. Have. Further, since the carbon material of the present invention can be produced without a special process as in Patent Document 6, it can be produced at low cost.

(A) It is sectional drawing which shows typically the carbon material which is a starting material. (B) It is sectional drawing which shows typically the carbon material which hollow part was formed by the activation which concerns on this embodiment. It is sectional drawing which shows typically the state that the catalyst component was supported on the carbon material for a catalyst carrier which concerns on this embodiment. This is an example of a graph obtained by the t-plot analysis of the present embodiment. It is a schematic diagram which shows the schematic structure of the fuel cell which concerns on embodiment of this invention.

Preferred embodiments of the present invention will be described in detail below 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. Composition of carbon materials for catalyst carriers>
First, the composition of 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 is mainly used for the catalyst layer on the cathode side.

(1-1. Definition of terms)
The "pore" in this embodiment is any of a macropore, a mesopore, and a micropore. The classification of these holes shall be in accordance with the IUPAC classification.

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 basis weight of the catalyst components is the same and the characteristics of the fuel cell are high.

(1-2. Raman)
When the G band of the carbon material for the catalyst carrier is measured by Raman spectroscopy, the half width (ΔG) of the G band is more than 30 cm ^-1 and less than 65 m ^-1 . The full width at half maximum (ΔG) of the G band is preferably more than 50 cm ^-1 and less than 65 m ^-1 . Here, the G band is a band detected in the range of 1550 to 1650 cm ^{-1 in} the Raman spectroscopic spectrum.

When the half width of the G band is within this range, the degree of graphitization of the carbon material for the catalyst carrier is high. Therefore, the carbon material for the catalyst carrier is less likely to be oxidatively consumed even if the solid polymer type secondary battery is repeatedly started and stopped. That is, the durability of the carbon material for the catalyst carrier is improved.

On the other hand, when the half width of the G band is 30 cm ^-1 or less, the number of pores is reduced, so that the number of catalyst components supported in the pores is reduced. In addition, the number of edge carbon atoms decreases, and the possibility that micropores are crushed increases. Further, when the half width of the G band is 65 m ^-1 or more, durability cannot be expected.

As a method of adjusting the half price width of the G band of the carbon material for the catalyst carrier within the above range, for example, a treatment of graphitizing the carbon material which is a raw material of the carbon material for the catalyst carrier can be mentioned. Specifically, the carbon material is exposed to a high temperature environment of 1600 ° C. or higher. By graphitizing the carbon material, the crystallites 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. The heat treatment of the graphitization treatment is preferably 1800 to 2400 ° C. When the heating temperature is 1600 ° C. or lower, the growth of crystallites may be small and the amount of edge carbon may be large. As a result, the half width of the G band is often 65 cm ^-1 or more. On the other hand, when the half width of the G band exceeds 2400 ° C., the crystallites grow excessively, and the half width of the G band often becomes 30 cm ^-1 or less. Even if the half-value width of the G band is 30 cm ^-1 or less as a result of excessive graphitization treatment, the half-value width of the G band is within the above-mentioned range by the subsequent activation treatment. Can be adjusted to a value.

(1-3. BET specific surface area)
BET specific surface area _S BET to be evaluated by the BET method ^(m 2 / g) is 700 meters ² / g Ultra 3000m less than ² / g. Preferably, BET specific surface area _S BET ^(m 2 / g) is 700 meters ² / g Ultra 1300m less than ² / g. When the BET specific surface area S _BET is within this range, a large number of pores are formed on the surface of the carbon atom for the catalyst carrier, so that more catalyst components can be supported in the pores. When the BET specific surface area S _BET is 700 m ² / g or less, the carbon materials for the catalyst carrier are likely to aggregate with each other during the step of supporting the catalyst component on the carbon material for the catalyst carrier or during the operation of the polymer electrolyte fuel cell. .. In this case, the catalyst utilization rate tends to decrease. On the other hand, when _SBET (m ² / g) is 3000 m ² / g or more, the mechanical strength of the carbon material for the catalyst carrier decreases. As a result, the catalyst layer is easily crushed, and the gas is less likely to diffuse into the catalyst layer. Further, when _SBET (m ² / g) is 1300 m ² / g or more, it may be difficult to achieve both durability and durability. Specifically, when the _SBET (m ² / g) is 1300 m ² / g or more, it is difficult to control the half width of the G band measured by Raman spectroscopy to less than 30 cm ^{-1 and} 65 cm ^-1. There is a possibility of becoming.

(1-4. Ratio of external specific surface area)
The ratio S _out / S _total between the _total specific surface area S _total (m ² / g) and the external specific surface area S _out (m ² / g) evaluated by the t-plot analysis is more than 0.3. Here, the external specific surface area means the specific surface area of the outer surface, that is, the portion of the carbon material for the catalyst carrier facing the outside. When S _out / _Total is more than 0.3, flooding in a highly humid environment can be suppressed. On the other hand, when S _out / _Total is 0.3 or less, the number of pores (for example, micropores) in which water tends to accumulate increases. In this case, the pores are easily blocked by water. When the pores are blocked with water, the catalyst component supported in the pores is submerged. Then, when the pores are closed with water, the catalyst component supported in the pores is submerged. Then, if the catalyst component supported in the pores is submerged in water, the oxidizing gas cannot reach this catalyst component. In addition, since water tends to accumulate around the carbon material for the catalyst carrier, the pore network is easily divided by the water. As a result, the catalyst utilization rate decreases.

Here, t-plot analysis is a kind of analysis evaluation method of nitrogen adsorption isotherm obtained by measuring nitrogen adsorption at liquid nitrogen temperature of nitrogen gas. That is, the t-plot analysis analyzes the deviation of the nitrogen adsorption isotherm of the measurement sample from the linearity based on the nitrogen adsorption isotherm of the standard substance which is the same material as the measurement sample and has no micropores. This is a type of comparative plot (edited by the Chemical Society of Japan, Colloidal Chemistry I, Tokyo Chemical Co., Ltd., published in 1995).

The micropore specific surface area is obtained as the difference between the total specific surface area and the external specific surface area of the measurement sample in the t-plot analysis. Here, the external specific surface area means the specific surface area of the portion of the measurement sample facing the outside. In the t-plot analysis of the measurement sample having micropores, the following tendency is observed. That is, at a very low pressure, the nitrogen gas is adsorbed on the entire surface of the measurement sample including the surface of the micropores (that is, the surface of the micropores and the outer surface other than the micropores). Therefore, in the region where t (that is, the adsorption thickness) is small, the adsorption amount shifts upward with respect to the standard substance having no micropores. That is, the slope of the t-plot becomes larger than that of the standard substance. From this slope, the total specific surface area of the measurement sample is calculated.

Then, when the pore filling of the micropores is completed, the adsorption of nitrogen gas proceeds only to the outer surface other than the micropores. Therefore, the slope of the t-plot becomes small in the region where the adsorption thickness is large. From this slope, the external specific surface area of the measurement sample (the surface area of the outer surface excluding the micropores of the measurement sample) is calculated. Therefore, the t-plot of the measurement sample having micropores has an upwardly convex shape. On the other hand, when the measurement sample has no micropores, the t-plot is a straight line passing through the origin. An example is shown in FIG. The horizontal axis of FIG. 3 shows the adsorption thickness (nm) of nitrogen gas, and the vertical axis shows the adsorption amount of nitrogen gas (molg ^-1 or cm ³ (STP) g ^-1 etc.). The t-plot L has an upwardly convex shape, and is divided into a t-plot L1 having a large inclination and a t-plot L2 having a small inclination. The t-plot L1 is a graph that reflects the adsorption to the micropores. On the other hand, the t-plot L2 is a graph that reflects the adsorption of nitrogen gas on an external surface other than the micropores. Therefore, the external specific surface area of the measurement sample can be obtained from the slope of the t-plot L2, and the total specific surface area of the measurement sample can be obtained from the slope of the nitrogen adsorption isotherm L1. Then, the surface area of the micropores can be obtained from these differences. The volume of the micropores can also be obtained from the intercept (Y) of the t-plot L2.

By the way, in the process of proceeding with the study of the present invention by the present inventors, a measurement sample subjected to the above-mentioned graphitization treatment was prepared. Then, the present inventor tried t-plot analysis of the measurement sample using the nitrogen adsorption isotherm of the standard substance which is generally open to the public. As a result, there is a problem that the nitrogen adsorption isotherm of the measurement sample may have a downwardly convex shape. In this case, it cannot be determined whether or not the measurement sample satisfies the condition of the carbon material for the catalyst carrier of the present embodiment.

The present inventor presumes that the cause of this is that the publicly available standard material of carbon material has more fine micropores than the carbon material for catalyst carrier used in the present embodiment. did. Then, the present inventor prepares a carbon material having as few micropores as possible by heat-treating the measurement sample (or a sample of the same type as the measurement sample) at a temperature of 2600 ° C. or higher in an inert atmosphere, and uses this as a standard substance. And said. Here, the same type of sample means a material showing the same physical properties as the measurement sample. A similar sample is, for example, a carbon material if it is a carbon material, and more preferably, the same type of carbon material is used. That is, if it is carbon black, it is carbon black, and if it is activated carbon, it is activated carbon. More preferably, the brand and lot are the same. As a result, the present inventor has solved the above problem. That is, when the t-plot analysis of the above-mentioned measurement sample was performed using this standard substance, it was successful to obtain an upwardly convex nitrogen adsorption isotherm. Therefore, in the t-plot analysis for discriminating a carbon material that can be used as a carbon material for a catalyst carrier, first, a standard substance is prepared by heat-treating the measurement sample at a temperature of 2600 ° C. or higher in an inert atmosphere. Then, t-plot analysis may be performed using this standard substance. With such reference materials, the micropores are negligibly reduced. Therefore, the t-plot analysis can be performed correctly. The heat treatment time is not particularly limited. Since the number of micropores decreases as the heat treatment time becomes longer, the heat treatment may be performed until a desired nitrogen adsorption isotherm can be obtained.

(1-5. Size of micropore specific surface area)
It is preferable micropore specific surface area _{S micro} evaluated at t plot analysis is less than 250 meters ² / g Ultra 700m ² / g. When the micropore specific surface area _Micro is within this range, the supportability of the catalyst component is enhanced because there are many edge portions of graphene on which the catalyst component is easily adsorbed when the catalyst is supported. In addition, since hydrophilic groups are present at the edge of graphene, there is a large amount of adsorbed water that serves as a proton conduction path. That is, the catalyst utilization rate can be increased.

On the other hand, when the micropore specific surface area S _micro is 250 m ² / g or less, the graphene edge portion where the catalyst component is easily adsorbed when the catalyst is supported is reduced. Therefore, if the catalyst component is supported at a high loading rate, the catalyst component may aggregate, the particle size of the catalyst component may become coarse, or the dispersibility of the catalyst component may decrease. In addition, since the number of hydrophilic groups present at the edge portion of graphene is reduced, the amount of adsorbed water serving as a proton conduction path may be reduced. That is, the catalyst utilization rate may decrease. When the micropore specific surface area S _micro is 700 m ² / g or more, it may be difficult to achieve both durability. Specifically, when the micropore specific surface area S _micro is 700 m ² / g or more, it may be difficult to control the half width of the G band measured by Raman spectroscopy to less than 30 cm ^{-1 and} more than 65 cm ^-1. There is sex.

(1-6. Size of external specific surface area)
The external specific surface area S _out evaluated by t-plot analysis is more than 300 m ² / g. In this case, the carbon material for the catalyst carrier has a hollow portion. That is, since the carbon material for the catalyst carrier has a hollow structure, the "mass of the carbon material", which is the denominator of the specific surface area, becomes extremely small. Therefore, the external specific surface area S _out becomes more than 300 m ² / g. Further, among the pores formed on the surface of the carbon material for the catalyst carrier, some of the pores are connected to the hollow portion. Further, since the pores and the hollow portion are formed by the activation treatment, the surface of the pores and the hollow portion has high hydrophilicity. That is, the edge carbon atoms of graphene are exposed on the surfaces of the pores and the hollow portion, and hydrophilic groups are introduced into these edge carbon atoms by activation treatment. Therefore, the surfaces of the pores and hollow portions have high hydrophilicity. Therefore, water is adsorbed at high density on the surfaces of the pores and hollow portions. When the catalyst component is supported on such a carbon material for a catalyst carrier, the catalyst component is supported not only on the outer surface of the carbon material for the catalyst carrier but also on the surfaces of the pores and the hollow portion. Then, since protons are conducted to the catalyst components by the water adsorbed on the surfaces of the pores and the hollow portion, these catalyst components can be used in the reduction reaction. Furthermore, since these catalyst components are not easily covered by the electrolyte material, they can be used more reliably in the reduction reaction. Therefore, the utilization rate of the catalyst component is improved.

Further, since the surfaces of the pores and the hollow portion have high hydrophilicity, the carbon material for the catalyst carrier can keep the electrolyte material in a wet state even in a low humidification environment. Further, the catalyst component is less likely to aggregate in the catalyst layer.

On the other hand, when the external specific surface area S _out is 300 m ² / g or less, the pores and the hollow portion become small, so that the number of catalyst components supported on the surface of the hollow portion decreases. Furthermore, since the hydrophilicity of the pores and hollow portions is also reduced, the density of water adsorbed on these surfaces is also reduced. Therefore, the proton conduction resistance increases. As a result, the catalyst utilization rate decreases. Further, when the catalyst component is supported on the carbon material for the catalyst carrier at a high density, the catalyst component tends to aggregate. Therefore, when the polymer electrolyte fuel cell is operated for a long time, the catalyst utilization rate tends to decrease.

The preferable range of the external specific surface area S _out is more than 400 m ² / g. In this case, more catalyst components can be supported on the surfaces of the pores and hollow portions. In addition, the proton conduction resistance is significantly reduced. As a result, the catalyst utilization rate is significantly improved.

In Patent Document 6, the specific surface area (m ² / g) of the mesopores is analyzed by the DH (Dollimore-Heal) method. In the carbon material disclosed in Patent Document 6, the specific surface area of the mesopores evaluated by this method is 400 m ² / g or more. On the other hand, in the present embodiment, the external specific surface area is analyzed by the t-plot method. In the t-plot method, the external specific surface area is measured with the portion other than the micropores as the outer surface, so that the two are similar at first glance. This is because the portion other than the micropores also includes the mesopores. However, as a result of the examination by the present inventors, it was found that the catalyst utilization rate may be low even when the specific surface area of the mesopores is large by the DH method. Since the pore diameter calculated by the DH method is assumed to be a cylinder shape, it is presumed that the cause is that the actual carbon material structure cannot be reflected when slit-shaped pores or the like are included. On the other hand, in the t-plot analysis, since the external specific surface area is calculated by the difference from the adsorption behavior of the reference substance having no pores, a value reflected in the actual structure can be obtained regardless of the shape of the pores. In fact, as shown in the comparative example described later, in the carbon material disclosed in Patent Document 6, the specific surface area of the mesopores calculated by the DH method is certainly 400 m ² / g or more, but it is calculated by the t plot. The external specific surface area is much smaller than 300 m ² / g.

Examples of the method of setting the external specific surface area of the carbon material for the catalyst carrier to more than 300 m ² / g include a method of activating the carbon material as a starting material much stronger than before. The type of activation treatment is not particularly limited, and any treatment may be used as long as it causes defects in the molecular structure of the carbon material. Examples of the activation treatment include a treatment in which a carbon material is heated in an environment in which a gas such as oxygen, air, water vapor, or carbon dioxide, or an inert gas containing these gases is circulated. Thereby, a carbon material for a catalyst carrier having a hollow structure can be produced. Hereinafter, a state in which a hollow portion is formed in the carbon material by the activation treatment will be described with reference to FIG.

FIG. 1A is a cross-sectional view schematically showing a carbon material 110 as a starting material. A plurality of pores 110a are formed on the surface of the carbon material 110. When the carbon material 110 is subjected to the activation treatment, the amorphous portion of the gap between the crystallites and the edge of graphene constituting the crystallites are preferentially scraped at the initial stage of activation. Then, the bottom portion of the pore 110a advances toward the center side of the carbon material 110 while the entire surface of the carbon material 110 is thinned. After that, the bottom of the pore 110a reaches the amorphous portion existing inside the carbon material. Then, as the activation further progresses, this amorphous portion is preferentially scraped. As a result, the carbon material 110A for the catalyst carrier shown in FIG. 1B is produced. The carbon material 110A for the catalyst carrier has a hollow portion 110b, and the pores 110a connect the hollow portion 110b and the outer surface 110e. Further, the wall surface 110c of the pore 110a and the wall surface 110d of the hollow portion 110b have high hydrophilicity.

FIG. 2 shows a state in which the catalyst component 120 is supported on the carbon material 110A for the catalyst carrier. The catalyst component 120 is supported not only on the outer surface 110e of the carbon material 110A for the catalyst carrier, but also on the wall surface 110c of the pores 110a and the wall surface 110d of the hollow portion 110b. Note that FIG. 2 shows the catalyst component 120 supported on the wall surface 110d of the hollow portion 110b.

Although the hydrophilicity of the carbon material can be sufficiently increased only by the above activation treatment, the hydrophilicity treatment may be further performed. This makes it possible to further increase the hydrophilicity of the surface of the carbon material. The type of the hydrophilic treatment is not particularly limited, and any treatment may be used as long as it is a treatment for increasing the hydrophilicity of the carbon material. Examples of the hydrophilic treatment include a treatment in which a carbon material is immersed in a heated nitric acid aqueous solution.

(1-7. Types of carbon materials for catalyst carriers)
The type of carbon material for the catalyst carrier is preferably a chemically stable carbon material. A preferable example of the carbon material for a catalyst carrier is carbon black. The carbon material for the catalyst carrier 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 for the catalyst carrier may be a mixture of two or more of these.

<2. Method for manufacturing carbon material for catalyst carrier>
Next, a method for producing a carbon material for a catalyst carrier will be described. First, a carbon material as a starting material is prepared. Here, the carbon material is preferably a chemically stable carbon material. A preferable example of the carbon material is 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 carbon material is activated. The type of activation treatment is not particularly limited, and any treatment may be used as long as it causes defects in the molecular structure of the carbon material. Examples of the activation treatment include a treatment in which a carbon material is heated in an environment in which a gas such as oxygen, air, water vapor, or carbon dioxide, or an inert gas containing these gases is circulated. The activation treatment may be carried out until the external specific surface area exceeds 300 m ² / g.

Then, the carbon material is graphitized. Specifically, the carbon material is exposed to a high temperature environment of 1600 ° C. or higher. By graphitizing the carbon material, the crystallites 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. The heat treatment of the graphitization treatment is preferably 1800 to 2400 ° C. The graphitization treatment may be performed until the half width of the G band is more than 30 cm ^-1 and less than 65 m ^-1 .

Then, each of the above-mentioned parameters, that is, the half width of the G band, the BET specific surface area _SBET (m ² / g), and the _Out / _Total , and the external specific surface area S _out are measured. Then, a carbon material in which these parameters have values within the above-mentioned range is selected as the carbon material for the catalyst carrier. If it is desired to further enhance the hydrophilicity of the carbon material for the catalyst carrier (specifically, for example, if it is desired to further enhance the characteristics of the polymer electrolyte fuel cell), an additional hydrophilic treatment may be performed. The type of the hydrophilic treatment is not particularly limited, and any treatment may be used as long as it is a treatment for increasing the hydrophilicity of the carbon material. Examples of the hydrophilic treatment include a treatment in which a carbon material is immersed in a heated nitric acid aqueous solution. By the above steps, a carbon material for a catalyst carrier is produced.

<3. Composition of polymer electrolyte fuel cell>
The carbon material for a catalyst carrier according to the present 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 and 20, gas diffusion layers 30 and 40, catalyst layers 50 and 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 introduces an oxidizing gas such as oxygen gas or air 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. An example is a gas diffusion layer having a two-layer structure that serves as a micropore layer.

The catalyst layer 50 is a so-called anode. In the catalyst layer 50, an oxidation reaction of the reducing gas occurs to generate protons and electrons. 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.

The catalyst layer 60 preferably 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 30% by mass or more and less than 80% by mass. Here, the catalyst-supporting ratio is preferably the mass% of the catalyst component with respect to the total mass of the catalyst-supporting particles (particles in which the catalyst component is supported on the carbon material for the catalyst carrier). In this case, the catalyst utilization rate becomes even higher. When the catalyst loading ratio is less than 30% 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 is 80% by mass or more, catalyst aggregation is likely to occur. In addition, the catalyst layer 60 becomes too thin, which may cause flooding.

The mass ratio I / C of the mass I (g) of the electrolyte material and the mass C (g) of the carbon material for the catalyst carrier in the catalyst layer 60 is not particularly limited, but is preferably more than 0.5 and less than 5.0. .. In this case, the pore network and the electrolyte material network can be compatible with each other, and the catalyst utilization rate becomes high. On the other hand, when the mass ratio I / C is 0.5 or less, the electrolyte material network tends to be poor and the proton conduction resistance tends to be high. When the mass ratio I / C is 5.0 or more, the pore network may be disrupted by the electrolyte material. In either case, the catalyst utilization rate may decrease.

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 easily diffuses 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 in 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 suitable example is an electrolyte material used in a polymer electrolyte fuel cell, that is, an electrolyte resin. Examples of the electrolyte resin include polymers into which a phosphoric acid group, a sulfonic acid group and the like have been introduced, for example, a perfluorosulfonic acid polymer and a polymer into which a benzenesulfonic acid has been introduced. Of course, the electrolyte material according to this embodiment may be another kind of electrolyte material. Examples of such an electrolyte material include an inorganic material, an inorganic-organic hybrid type, and the like. The fuel cell 1 may be a fuel cell that operates in the range of room temperature to 150 ° C.

<4. Manufacturing method of polymer electrolyte fuel cell>
The manufacturing method of the polymer electrolyte fuel cell 1 is not particularly limited, and any manufacturing method similar to the conventional one 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 ＞
Three types of carbon materials are used as starting materials: MCND (S-Carbon manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), EC300 (Ketchen Black EC300 manufactured by Lion Corporation), and EC600JD (Ketchen Black EC600JD manufactured by Lion Corporation). Got ready.

<2. Parameter measurement method>
(2-1. Raman)
The Raman spectrum was measured using NRS-7100 type (manufactured by JASCO Corporation). The measurement conditions are excitation laser wavelength: 532 nm, laser power: 100 mW (sample irradiation power: 0.1 mW), microscopic arrangement: Backscattering, slit size: 100 μm × 100 μm, objective lens: × 100, spot diameter: 1 μm, exposure time: The number of observed waves was set to 30 sec, 3,000 to 750 cm ^-1 , and the number of integrations was set to 2. Then, the half width (ΔG) of the peak intensity in the range of 1550 to 1650 cm ^-1 called the G band was calculated.

(2-2. BET specific surface area)
The BET specific surface area was determined using BELSORPmini manufactured by Microtrac Bell. Specifically, a measurement sample vacuum-dried at 120 ° C. was placed in an automatic specific surface area measuring device, and an adsorption isotherm was created using nitrogen gas. Then, the BET specific surface area (S _BET ) was calculated using the attached software BELMaster.

(2-3. T plot analysis and DH (Dollimore-Heal) analysis)
As a standard substance, Ketjen Black EC600JD (manufactured by Lion) heat-treated at 2600 ° C. for 2 hours in an argon stream was prepared. Then, the nitrogen adsorption isotherm of this standard substance was measured using BELSORPmini manufactured by Microtrac Bell. This nitrogen adsorption isotherm was registered as reference data of the software BELMaster attached to BELSORPmini. The nitrogen adsorption isotherm of the substance to be measured was measured using BELSORPmini, and t-plot analysis and DH analysis were performed using the standard sample as reference data using BELMaster. In the t-plot analysis, the total specific surface area _Total (m ² / g), the micropore specific surface area S _micro , and the external specific surface area S _out (m ² / g) were calculated (that is, analyzed) by the t-plot method. In the DH analysis, the specific surface area (m ² / g) of the mesopores was calculated (that is, analyzed) by the DH method.

<3. Example 1>
(3-1. Carbon material)
EC300 was prepared as a carbon material as a starting material.

(3-2. Activation process)
It has been of H _{2 O} activation treatment to a carbon material. Specifically, 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 kept at 950 ° C. for 2 hours.

(3-3. Graphitization treatment)
The activated carbon material was held in an argon air stream for 2 hours at 1800 ° C. to perform graphitization treatment. Through the above steps, the carbon material for the catalyst carrier according to Example 1 was prepared.

(3-4. Platinum-supported treatment)
A carbon material for a catalyst carrier was dispersed in an aqueous solution of chloroplatinic acid. Then, the dispersion was kept warm at 50 ° C., and hydrogen peroxide solution was added while stirring the dispersion. Next, a catalyst precursor was obtained by adding an aqueous Na ₂ S ₂ O ₄ solution to the dispersion. The catalyst precursor is filtered, washed with water, 100% _{H 2} gas stream after drying for 3 hours at 300 ° C., was subjected to reduction treatment. Through the above steps, catalyst-supported particles in which platinum was supported in an amount of 50% by mass based on the total mass of the catalyst-supported particles were produced.

(3-5. Adjustment of applied ink)
The catalyst-supported particles were placed in a container, and a 5 mass% Nafion solution (DE521 manufactured by DuPont) was added thereto so that the ratio of Nafion to 1 part by mass of the carbon material for the catalyst carrier was 1.5 parts by mass. Then, the dispersion was lightly stirred. Then, the catalyst-supported particles were pulverized by ultrasonic waves. Then, the dispersion liquid was further stirred to obtain a coating ink.

(3-6. Preparation of catalyst layer)
The obtained coating ink was sprayed on a Teflon (registered trademark) sheet and then dried in argon at 80 ° C. for 10 minutes, and then dried in argon at 120 ° C. for 60 minutes to prepare a catalyst layer. The platinum basis weight of the catalyst layer was 0.10 mg / cm ² . Here, the platinum basis weight was measured in the following steps. First, the prepared Teflon sheet and catalyst layer were cut into 3 cm square squares, and the total mass of the Teflon sheet and catalyst layer was measured. Then, the mass of the Teflon sheet after the catalyst layer was scraped off with a scraper was measured. Then, the catalyst layer mass was calculated from the difference between the first mass and the second mass. Then, the basis weight of platinum was calculated from the ratio of platinum in the solid content in the catalyst ink.

(3-8. Preparation of MEA)
Next, MEA (membrane electrode composite) was prepared using the prepared catalyst layer. Specifically, the Nafion membrane (N112 manufactured by DuPont) was cut into a 6 cm square with a cutter knife, and the catalyst layer applied on the Teflon sheet was cut into a 2.5 cm square with a cutter knife. A laminate was prepared by sandwiching these catalyst layers as anodes and cathodes so that the central portion of the naphthion membrane was not displaced. Then, the laminate was pressed at 120 ° C. and 100 kg / cm ² for 10 minutes. After cooling the pressed laminate to room temperature, only the Teflon sheet was carefully peeled off for both the anode and cathode. As a result, the catalyst layers of the anode and the cathode were fixed to the Nafion film.

Next, a commercially available carbon cloth (LT1200W manufactured by E-TEC) was cut into a 2.5 cm square as a gas diffusion layer with a cutter knife. Then, the cut carbon cloth was laminated so that the anode and the cathode did not deviate from each other to prepare a laminated body. Then, the laminate was pressed at 120 ° C. and 50 kg / cm ² for 10 minutes to prepare MEA. The weight of the fixed catalyst layer was obtained from the difference between the weight of the Teflon sheet with the catalyst layer before pressing and the weight of the Teflon sheet peeled off after pressing, and the platinum coating amount was calculated from the mass ratio of the composition of the catalyst layer. It was confirmed that it was 0.10 mg / cm ² .

(3-9. Fuel cell power generation performance test)
Each of the produced 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.

First, the performance was evaluated under "highly humidified" conditions. Air was supplied to the cathode and pure hydrogen was supplied to the anode so that the gas utilization rates were 30% and 60%, respectively. The pressure of each gas was adjusted by a back pressure valve provided downstream of the cell and set to 0.1 MPa. The cell temperature was set to 80 ° C. Further, the air supplied to the fuel cell and pure hydrogen were each passed through distilled water kept at 80 ° C. (that is, bubbling) to humidify the fuel cell. Then, the humidified gas was supplied to the cell. After supplying gas to the cell under such conditions, the current density was gradually increased until the cell voltage reached 0.6 V, and the cell voltage was fixed at 0.6 V for 60 minutes. After that, the cell voltage was fixed at 0.85 V, and the current density after 60 minutes was recorded as the power generation performance.

The power generation performance result is based on the current density obtained in the power generation performance test of Comparative Example 1. If the current density is lower than the standard, it is ×, and if the current density is higher than the standard in the range of more than 0% and 20% or less, it is ○. If the current density is higher than the standard in the range of more than 20%, it is marked with ⊚.

Next, performance evaluation was performed under "low humidification" conditions. Air was supplied to the cathode and pure hydrogen was supplied to the anode so that the gas utilization rates were 30% and 60%, respectively. The pressure of each gas was adjusted by a back pressure valve provided downstream of the cell and set to 0.1 MPa. The cell temperature was set to 80 ° C. Further, the air supplied to the fuel cell and pure hydrogen were each passed through distilled water kept at 50 ° C. (that is, bubbling) to humidify the fuel cell. Then, the humidified gas was supplied to the cell. After supplying gas to the cell under such conditions, the current density was gradually increased until the cell voltage reached 0.6 V, and the cell voltage was fixed at 0.6 V for 60 minutes. After that, the cell voltage was fixed at 0.85 V, and the current density after 30 minutes was recorded as the power generation performance.

The power generation performance result is based on the current density obtained in the power generation performance test of Comparative Example 1. If the current density is lower than the standard, it is ×, and if the current density is higher than the standard in the range of more than 0% and 20% or less, it is ○. If the current density is higher than the standard in the range of more than 20%, it is marked with ⊚.

(3-10. Fuel cell durability performance test)
For cells whose power generation performance was evaluated as ○ or ◎, a durability performance test was conducted after the power generation performance test. The durability performance test was carried out in the following steps. That is, after the power generation performance test, the cathode gas was changed to Ar, and the gas was sufficiently replaced. Here, the argon gas was humidified by passing it through distilled water kept at 80 ° C. (that is, bubbling). Then, using a potentiostat, a process of holding the cathode at 0.6 V for 4 seconds and a process of holding the cathode at 1.3 V for 4 seconds with reference to the anode through which hydrogen gas flows were repeated 200 times. After that, the cathode gas was replaced with air, and a power generation performance test was conducted under the conditions of the fuel cell performance evaluation test. Here, the air was humidified by passing it through distilled water kept at 50 ° C. (that is, bubbling). Based on the current density before the potential fluctuation, when the current density after the potential fluctuation was more than 50%, the evaluation was evaluated as ◯, and when it was 50% or less, the evaluation was evaluated as x.

The carbon material for the catalyst carrier of Example 1 satisfied all the requirements of this embodiment. The result of the high humidification power generation performance test was ○, the result of the low humidification power generation performance test was ○, and the result of the fuel cell durability performance test was ○. The results are summarized in Table 1.

<4. Example 2>
The same treatment as in Example 1 was carried out except that the CO2 activation treatment was carried out as the activation treatment. Here, in Example 2, the following treatment was performed as the CO ₂ activation treatment. Specifically, 100% by volume of CO ₂ gas was brought into contact with a carbon material held at 1050 ° C. for 2 hours. The carbon material for the catalyst carrier of Example 2 satisfied all the requirements of this embodiment. In particular, the external specific surface area of Example 2 was more than 400 m ² / g. Therefore, the result of the high humidification power generation performance test was ⊚, the result of the low humidification power generation performance test was ◎, and the result of the fuel cell durability performance test was ◯. The results are summarized in Table 1.

<5. Example 3>
The same treatment as in Example 1 was carried out except that EC600JD was used as the starting material carbon material, the graphitization treatment was performed before the activation treatment, and the O ₂ activation treatment was performed as the activation treatment. .. Here, in Example 3, the following treatment was performed as the O ₂ activation treatment. Specifically, 1 vol% O ₂ gas diluted with argon gas, was contacted for 6 hours to the carbon material held in the 950 ° C.. The carbon material for the catalyst carrier of Example 3 satisfied all the requirements of this embodiment. The result of the high humidification power generation performance test was ○, the result of the low humidification power generation performance test was ○, and the result of the fuel cell durability performance test was ○. The results are summarized in Table 1.

<6. Example 4>
For the use of EC600JD as the carbon material serving as a starting material, it was subjected to graphitization treatment in the previous H _{2 O} activation treatment, except that went to hydrophilization treatment after the activation treatment, the same treatment as in Example 1 went. Here, in Example 4, the temperature of the H 2 _O activation treatment and 900 ° C., processing time was 6 hours. Further, as the hydrophilic treatment, the following treatment was performed. That is. The carbon material was immersed in concentrated nitric acid (specific gravity 1.38) and kept at 100 ° C. for 2 hours. Then, after diluting concentrated nitric acid with sufficient water, the dispersion liquid of the carbon material was filtered. Then, washing of the carbon material with distilled water was repeated until the pH of the filtrate became 5.5 or more. The obtained carbon material was vacuum dried at 110 ° C. Through the above steps, a carbon material for a catalyst carrier was obtained. The carbon material for the catalyst carrier of Example 4 satisfied all the requirements of this embodiment. In particular, the external specific surface area of Example 4 was more than 400 m ² / g. Therefore, the result of the high humidification power generation performance test was ○, the result of the low humidification power generation performance test was ⊚, and the result of the fuel cell durability performance test was ○. The results are summarized in Table 1.

<7. Example 5>
Except that EC600JD was used as the starting material carbon material, CO ₂ activation treatment was performed as activation treatment, the graphitization treatment temperature was set to 1900 ° C, and hydrophilic treatment was performed after graphitization treatment. , The same treatment as in Example 1 was performed. Here, in Example 5, the following treatment was performed as the CO ₂ activation treatment. Specifically, 100% by volume of CO ₂ gas was brought into contact with a carbon material held at 1050 ° C. for 2 hours. The hydrophilic treatment was the same as in Example 4. The carbon material for the catalyst carrier of Example 5 satisfied all the requirements of this embodiment. In particular, the external specific surface area of Example 5 was more than 400 m ² / g. Therefore, the result of the high humidification power generation performance test was ○, the result of the low humidification power generation performance test was ⊚, and the result of the fuel cell durability performance test was ○. The results are summarized in Table 1.

<8. Example 6>
The same treatment as in Example 1 was carried out except that EC600JD was used as the starting material carbon material, the graphitization treatment was performed before the activation treatment, and the CO ₂ activation treatment was performed as the activation treatment. .. Here, in Example 3, the following treatment was performed as the CO ₂ activation treatment. Specifically, 100% by volume of CO ₂ gas was brought into contact with a carbon material held at 1050 ° C. for 2 hours. The carbon material for the catalyst carrier of Example 6 satisfied all the requirements of this embodiment. In particular, the external specific surface area of Example 6 was more than 400 m ² / g. Therefore, the result of the high humidification power generation performance test was ⊚, the result of the low humidification power generation performance test was ◎, and the result of the fuel cell durability performance test was ◯. The results are summarized in Table 1.

<9. Comparative Example 1>
MCND (S Carbon manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) was used as the starting material carbon material. Then, the carbon material was subjected to the same graphitization treatment as in Example 1. The temperature of the graphitization treatment was 2000 ° C. The same evaluation as in Example 1 was performed using the carbon material for the catalyst carrier obtained as a result. In Comparative Example 1, the specific surface area of the mesopores evaluated by the DH method was certainly 400 m ² / g or more, but the external specific surface area S _out was much smaller than 300 m ² / g and S _out /. S _total has become much smaller than 0.3. Then, in Comparative Example 1, the results of the high humidification power generation performance test and the low humidification power generation performance test were good. Therefore, the current density obtained in Comparative Example 1 was used as the reference value for the fuel cell power generation performance test. However, despite the graphitization treatment of the carbon material at 2000 ° C., the current density decreased to 50% or less in the fuel cell durability performance test. That is, the result of the fuel cell durability performance test was x. It is considered that the reason for this is that the external specific surface area S _out is much smaller than 300 m ² / g and the S _out / _total is much smaller than 0.3. The results are summarized in Table 1.

<10. Comparative Example 2>
EC300 was used as the starting material carbon material. This carbon material was subjected to the same graphitization treatment as in Example 1. Then, the carbon material was subjected to the same hydrophilization treatment as in Example 4. The same evaluation as in Example 1 was performed using the carbon material for the catalyst carrier obtained as a result. In Comparative Example 2, the _SBET was 700 m ² / g or less, the external specific surface area S _out was 300 m ² / g or less, and the _Out / _Total was 0.3 or less. The result of the high humidification power generation performance test was ×, and the result of the low humidification power generation performance test was ×. In Comparative Example 2, it is estimated that the catalyst utilization rate was low because the _SBET was 700 m ² / g or less, the external specific surface area S _out was 300 m ² / g or less, and the S _out / _total was 0.3 or less. .. The results are summarized in Table 1.

<11. Comparative Example 3>
EC300 was used as the starting material carbon material. Similar H _{2 O} activation treatment as in Example 1 to the carbon material was carried out. The same evaluation as in Example 1 was performed using the carbon material for the catalyst carrier obtained as a result. In Comparative Example 3, the half width of the G band was 65 cm ^-1 or more. And then, the result of the high humidification power generation performance test was ×, and the result of the low humidification power generation performance test was ○. However, the result of the fuel cell durability performance test was x. In Comparative Example 3, since the half width of the G band was 65 cm ^-1 or more, it is presumed that the durability was insufficient. The results are summarized in Table 1.

<12. Comparative Example 4>
EC300 was used as the starting material carbon material. This carbon material was subjected to CO ₂ activation treatment. Here, in Comparative Example 4, the following treatment was performed as the CO ₂ activation treatment. Specifically, 100% by volume of CO ₂ gas was brought into contact with a carbon material held at 900 ° C. for 2 hours. The same evaluation as in Example 1 was performed using the carbon material for the catalyst carrier obtained as a result. In Comparative Example 4, the _SBET was 700 m ² / g or less, and the external specific surface area S _out was 300 m ² / g or less. The result of the high humidification power generation performance test was ×, and the result of the low humidification power generation performance test was ×. In Comparative Example 4, since the _SBET was 700 m ² / g or less and the external specific surface area S _out was 300 m ² / g or less, it is estimated that the catalyst utilization rate was low. The results are summarized in Table 1.

<13. Comparative Example 5>
EC600JD was used as the starting material carbon material. This carbon material was subjected to the same graphitization treatment as in Example 1. The same evaluation as in Example 1 was performed using the carbon material for the catalyst carrier obtained as a result. In Comparative Example 5, the _SBET was 700 m ² / g or less, and the external specific surface area S _out was 300 m ² / g or less. The result of the high humidification power generation performance test was ×, and the result of the low humidification power generation performance test was ×. In Comparative Example 5, since the _SBET was 700 m ² / g or less and the external specific surface area S _out was 300 m ² / g or less, it is estimated that the catalyst utilization rate was low. The results are summarized in Table 1.

<14. Comparative Example 6>
EC600JD was used as the starting material carbon material. After the same graphitization treatment as in Example 1 to the carbon material, it was performed of H 2 _O activation treatment. However, in Comparative Example 6, the temperature of the H 2 _O activation treatment with 850 ° C., was 3 hours treatment time. The same evaluation as in Example 1 was performed using the carbon material for the catalyst carrier obtained as a result. In Comparative Example 6, the _SBET was 700 m ² / g or less, and the external specific surface area S _out was less than 300 m ² / g. In Comparative Example 6, it is estimated that the _SBET and the external specific surface area S _out became the above values because the temperature of the activation treatment was low (that is, the activation treatment was weak). The result of the high humidification power generation performance test was ×, and the result of the low humidification power generation performance test was ×. In Comparative Example 6, since the _SBET was 700 m ² / g or less and the external specific surface area S _out was 300 m ² / g or less, it is considered that the catalyst utilization rate was lowered.

<15. Verification of catalyst loading rate>
By performing the same treatment as in Comparative Example 2, Comparative Example 5, Example 1, and Example 5 except that the catalyst loading ratio was changed in the range of 30 to 80% by mass in increments of 10% by mass, a plurality of types were used. Catalyst-supported particles were prepared. Then, the catalyst-supported particles were observed at a magnification of 500,000 using a transmission electron microscope to confirm the presence or absence of aggregation of the catalyst component (that is, platinum particles).

As a result, in the catalyst-supported particles of Comparative Example 2 and Comparative Example 5, aggregation of the catalyst component was not observed when the catalyst-supporting ratio was 30 to 50% by mass. However, when the catalyst loading ratio was 60% by mass, aggregation of the catalyst components was observed. On the other hand, in the catalyst-supporting particles of Examples 1 and 5, when the catalyst-supporting ratio was 30 to 70% by mass, aggregation of the catalyst components was not observed, but the catalyst-supporting ratio was 80% by mass. In the case, some aggregation was observed. As a result, it was found that the catalyst loading ratio is preferably 30% by mass or more and less than 80% by mass.

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 such examples. It is clear that a person having ordinary knowledge in the field of technology 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 (9)

A carbon material for a catalyst carrier capable of supporting a catalyst component for a polymer electrolyte fuel cell.
Half width of G band as measured by Raman spectroscopy is less than 30 cm ^-1 super 65cm ^-1,
BET specific surface area _S BET to be evaluated by the BET method ^(m 2 / g) is less than 700 meters ² / g Ultra 3000 m ² / g,
The ratio S _out / S _total between the _total specific surface area _Total and the external specific surface area S _out evaluated by the t-plot analysis is more than 0.3.
A carbon material for a catalyst carrier, characterized in that the external specific surface area S _out evaluated by t-plot analysis is more than 300 m ² / g. Wherein the BET specific surface area _S BET to be evaluated by the BET method ^(m 2 / g) is less than 700 meters ² / g Ultra 1300 m ² / g, a carbon material for a catalyst carrier of claim 1, wherein. t plot analysis at Rated micropore specific surface area _S micro ^(m 2 / g), characterized in that it is less than 250 meters ² / g Ultra 700 meters ² / g, for catalyst carrier according to claim 1 or 2 Carbon material. The carbon material for a catalyst carrier according to any one of claims 1 to 3, wherein the t-plot analysis is performed using a carbon material heat-treated at 2600 ° C. or higher as a standard substance. The carbon material for a catalyst carrier according to any one of claims 1 to 4, wherein the external specific surface area S _out evaluated by t-plot analysis is more than 400 m ² / g. With the catalyst component
A catalyst layer for a polymer electrolyte fuel cell, which comprises the carbon material for a catalyst carrier according to any one of claims 1 to 5, which carries the catalyst component. The catalyst layer for a polymer electrolyte fuel cell according to claim 6, wherein the catalyst loading ratio is 30% by mass or more and less than 80% by mass. A polymer electrolyte fuel cell comprising the catalyst layer according to claim 6 or 7. The polymer electrolyte fuel cell according to claim 8, wherein the polymer electrolyte fuel cell includes the catalyst layer as a catalyst layer on the cathode side.

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