Porous carbon and catalyst for cathode of polymer electrolyte fuel cell

Abstract

To provide a porous carbon having mesopores formed therein that can support platinum or platinum alloy nanoparticles, which has a structure suitable for high-speed transport of substances, such as by making it easy for water vapor generated by the battery reaction at the cathode to escape from the electrode, while ensuring high utilization efficiency of the platinum or platinum alloy nanoparticles in the battery reaction at the cathode.SOLUTION: A porous carbon has a three-dimensional network structure, and the average diameter of the skeleton is 20.0 to 45.0 nm, the total volume of pores A VP2.9-8.3 is 0.060 to 0.100 cm3 / g, the total volume of pores B VP10.0-62.0 is 0.100 to 0.400 cm3 / g, and the density of pores having a diameter of 3.0 nm or more and 10.0 nm or less formed in the skeleton in an SEM image is 30.0 to 120.0 pores / 104nm2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a porous carbon having mesopores and a catalyst for a cathode of a polymer electrolyte fuel cell in which platinum or platinum alloy nanoparticles are supported on the mesopores.

Background Art

[0002] In recent years, as research and development for realizing a carbon-neutral society, in the field of automobiles, automobiles equipped with engines using fossil fuels are being developed to be replaced by electric vehicles using secondary batteries such as lithium-ion secondary batteries as energy devices, and fuel cell vehicles using fuel cells as energy devices.

[0003] As a result of the rapid spread of passenger cars in recent years due to the improvement of the charging capacity and the reduction of the price of lithium-ion secondary batteries, the replacement with electric vehicles has been promoted. On the other hand, trucks and buses have a longer driving distance per trip than passenger cars. Therefore, it is not possible to cover the required driving distance with a single charge of a secondary battery such as a lithium-ion secondary battery, and it is not practical to increase the battery loading amount due to the battery weight and its cost. Therefore, trucks and buses are considered to be promising candidates for replacement with fuel cell vehicles.

[0004] As the fuel cell of a fuel cell vehicle, a polymer electrolyte fuel cell (PEFC) composed of an anode catalyst layer, a polymer electrolyte membrane, and a cathode catalyst layer is used. And, as a catalyst for the cathode which is the air electrode of the fuel cell, a catalyst in which platinum or a platinum alloy is supported on a carbon carrier is used.

[0005] Since platinum has a small global reserve and is expensive, it is necessary to reduce the amount of platinum used. Therefore, in order to reduce the amount of platinum used as a cathode catalyst of a fuel cell, attempts have been made to reduce the particle size of platinum and support it on a carbon carrier.

[0006] However, when the platinum particles that have been made into small particles are repeatedly used as a catalyst for the battery reaction, they tend to aggregate and sinter to form large particles. If they become large particles, the performance as a catalyst for the battery reaction deteriorates. Therefore, simply supporting small platinum particles will result in a large rate of performance degradation of the fuel cell.

[0007] Therefore, by supporting platinum nanoparticles in the mesopores of a carbon support in which mesopores are formed, it has been possible to prevent the platinum nanoparticles from aggregating and sintering during repeated use in the battery reaction. Patent Document 1 discloses a platinum-supported metal catalyst in which a platinum catalyst is supported on mesoporous carbon nanodendrite (MCND).

[0008] However, in the platinum-supported metal catalyst described in Patent Document 1, homogeneous mesopores are not formed in the support, and platinum particles supported deep in the mesopores that are too deep cannot contribute to the catalytic reaction, resulting in a problem of low utilization efficiency of the platinum catalyst.

[0009] Therefore, in order to improve the utilization efficiency of the platinum catalyst supported on the carbon support, Patent Document 2 discloses a support that is an aggregate of conductive particles and active metal particles dispersed and supported on the conductive particles. The conductive particles include a plurality of pores, the average inlet pore diameter of the pores is 1 to 20 nm, the standard deviation of the average inlet pore diameter is 50% or less of the average inlet pore diameter, and the number fraction of the active metal particles supported in the surface layer region of the conductive particles is 50% or more. The surface layer region is a region on the surface of the conductive particles or a region within the pores within 15 nm from the surface. A supported metal catalyst is disclosed.

[0010] In addition, in the supported metal catalyst of Patent Document 2, the skeleton part of the carbon support on which the metal particles are supported has a three-dimensional network structure in which spherical carbon nanoparticles are connected in three-dimensional directions. Such a three-dimensional network structure contributes to the high-speed transport of products and reactants, such as making it easier for water vapor generated by the battery reaction at the cathode to escape from the electrode.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] For the carbon support used in the cathode catalyst of a fuel cell, as described in Patent Document 2, a structure that facilitates the escape of water vapor generated by the battery reaction at the cathode from the electrode is required.

[0013] However, according to the carbon support of Patent Document 2, although the utilization efficiency of platinum nanoparticles can be increased to a certain extent compared to the support of the platinum - supported metal catalyst of Patent Document 1, within the carbon - spherical nanoparticles that form the skeleton part of the carbon support, mesopores that are difficult to contribute to the catalytic reaction and platinum nanoparticles still remain. Therefore, further improvement in the utilization efficiency of platinum nanoparticles is required.

[0014] Therefore, an object of the present invention is to provide a porous carbon in which mesopores capable of supporting platinum or platinum - alloy nanoparticles are formed, having high utilization efficiency of platinum or platinum - alloy nanoparticles in the battery reaction at the cathode, and having a structure suitable for high - speed transport of substances such as easy escape of water vapor generated in the battery reaction at the cathode from the electrode. Another object of the present invention is to provide a porous carbon having a novel structure and pore characteristics.

Means for Solving the Problems

[0015] The above problems are solved by the following present invention. That is, the present invention is (i) It has a three-dimensional network structure in which the skeletal part branches and connects in three-dimensional directions, the average diameter of the skeletal part is 20.0 nm or more and 45.0 nm or less, the total volume V of pore A with a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less, the total volume V of pore B with a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement P10.0-62.0 is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less, in scanning electron microscope observation, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less formed in the skeletal part is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less, characterized by the porous carbon. (ii) It includes a porous carbon carrier and platinum or platinum alloy nanoparticles supported in the pores of the porous carbon carrier, the porous carbon carrier has a three-dimensional network structure in which the skeletal part branches and connects in three-dimensional directions, the average diameter of the skeletal part is 20.0 nm or more and 45.0 nm or less, and the total volume V of pore A with a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less, the total volume V of pore B with a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement P10.0-62.0 is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less, and in scanning electron microscope observation, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less formed in the skeletal part is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2The following A catalyst for the cathode of a polymer electrolyte fuel cell, characterized by is provided.

Effect of the Invention

[0016] According to the present invention, a porous carbon having mesopores capable of supporting platinum or platinum alloy nanoparticles is provided. The porous carbon has a structure suitable for high-speed transport of substances such as high utilization efficiency of platinum or platinum alloy nanoparticles in the battery reaction at the cathode and easy escape of water vapor generated in the battery reaction at the cathode from the electrode. Further, according to the present invention, a porous carbon having a novel structure and pore characteristics can be provided.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. The following detailed description of the present invention is an example of the embodiments, and the present invention is not construed as being limited to the present embodiments.

[0019] The porous carbon of the present invention has a three-dimensional network structure in which the skeleton portions are branched and connected in three-dimensional directions, the average diameter of the skeleton portions is 20.0 nm or more and 45.0 nm or less, the total volume V of pores A having a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement P2.9-8.3 is 0.060 cm 30.100 cm / g or more 3 is 0.100 cm / g or less, the total pore volume V of pore B where the pore diameter in nitrogen adsorption measurement is 10.0 nm or more and 62.0 nm or less P10.0-62.0 is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less, in scanning electron microscope observation, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less formed in the skeleton part is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less, and is characterized by the above.

[0020] In the present invention, pore A refers to pores where the pore diameter in nitrogen adsorption measurement is 2.9 nm or more and 8.3 nm or less. In the present invention, pores suitable for supporting platinum or platinum alloy nanoparticles with a particle size of 2.0 nm or more and 7.0 nm or less are "pores formed in the skeleton part of the porous carbon of the present invention and having a pore diameter of 3.0 nm or more and 10.0 nm or less in scanning electron microscope observation". And in the present invention, pores having a pore diameter of 3.0 nm or more and 10.0 nm or less in scanning electron microscope observation are defined as corresponding to pores having a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement. That is, as an index of the pore volume of "pores formed in the skeleton part of the porous carbon of the present invention and having a pore diameter of 3.0 nm or more and 10.0 nm or less in scanning electron microscope observation", the total volume V of pore A having a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement is defined. Note that having a pore diameter of 3.0 nm or more and 10.0 nm or less in scanning electron microscope observation can be rephrased as having a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image. Note that since mesopores generally refer to pores with a diameter of 2 nm or more and 50 nm or less, it can be said that pore A is a kind of mesopore. P2.9-8.3

[0021] ​In the present invention, pore B refers to pores having a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement. Further, in the present invention, since pore B is presumed to correspond to the gap between the skeleton portions when observed in the SEM image, in the present invention, as an index of the volume of the gap between the skeleton portions when observed in the SEM image, the total volume V of pore B having a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement P10.0-62.0 is defined.

[0022] The porous carbon of the present invention will be described with reference to FIG. 2. FIG. 2 is a diagram schematically showing pores having a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image and the gap between the skeleton portions when observed in the SEM image, after performing image processing on a scanning electron micrograph (SEM image) of an embodiment of the porous carbon of the present invention to clearly show the contour of the skeleton portion of the porous carbon. In FIG. 2, the porous carbon 1 has a three-dimensional network structure in which the skeleton portions 2 are branched and connected in the three-dimensional direction, pores 3 having a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed in the skeleton portions, and a gap 4 between the skeleton portions 2 formed between the skeleton portions 2.

[0023] The porous carbon of the present invention has a three-dimensional network structure in which the skeleton portions in which pores having a pore diameter of 3.0 nm or more and 10.0 nm or less are formed in the SEM image are branched and connected in the three-dimensional direction. That is, the porous carbon of the present invention is constructed with a skeleton having a three-dimensional network structure branched and connected in the three-dimensional direction. In other words, the porous carbon of the present invention is composed of at least a skeleton portion branched and connected three-dimensionally and a gap formed between the skeleton portions.

[0024] The shape of the skeleton portion of the porous carbon according to the present invention is a shape in which particles are connected, a shape in which no constriction with a smaller diameter than the surroundings is clearly observed at the connecting portion of the particles, or a fibrous shape. That is, in the porous carbon of the present invention, when observing one skeleton portion, there is little difference in diameter due to the difference in position in the skeleton portion.

[0025] The average diameter of the framework part of the porous carbon of the present invention is 20.0 nm or more and 45.0 nm or less. When the average diameter of the framework part is 20.0 nm or more and 45.0 nm or less, the number of pores suitable for supporting platinum or platinum alloy nanoparticles formed inside the framework part decreases, and pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image can be concentrated near the outer surface of the framework part. For example, when the porous carbon of the present invention is used as a carrier for a catalyst for the air electrode of a fuel cell supporting platinum or platinum alloy nanoparticles, since the average diameter of the framework part is 20.0 nm or more and 45.0 nm or less, platinum or platinum alloy nanoparticles can be concentrated and supported near the outer surface of the framework part, which is easily used in the battery reaction. Therefore, the amount of platinum or platinum alloy nanoparticles not used in the battery reaction can be reduced, so that the utilization efficiency of platinum or platinum alloy nanoparticles can be increased, and thereby the catalytic activity per loading amount can be increased. In the porous carbon of the present invention, from the viewpoint of increasing the effective Pt mass ratio, the average diameter of the framework part is preferably 20.0 nm or more and 40.0 nm or less, and more preferably 20.0 nm or more and 35.0 nm or less. On the other hand, when the average diameter of the framework part is less than 20.0 nm, the curvature of the particle surface constituting the framework part of the porous carbon becomes large, so that it becomes difficult to form pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image on the surface. Further, when it exceeds 45.0 nm, the formation depth of pores suitable for supporting platinum or platinum alloy nanoparticles becomes deep. In the present invention, the measurement method of the average diameter of the framework part is as follows. First, the porous carbon of the present invention is observed with a scanning electron microscope (SEM: SU9000 (manufactured by Hitachi High-Technologies Corporation)) to obtain an SEM image. Next, 100 circles circumscribed on the framework image of the obtained SEM image are arranged, and the average value of their diameters is taken as the average diameter of the framework part.

[0026] The BET specific surface area of the porous carbon of the present invention is preferably 200 m 2 / g or more and 800 m 2 / g or less. For example, when the porous carbon of the present invention is used as a carrier for a catalyst for the air electrode of a fuel cell supporting platinum or platinum alloy nanoparticles, when the BET specific surface area of the porous carbon is 200 m2 800 m / g or more 2 By being 800 m / g or less, it is possible to prevent an excessive presence of mesopores containing pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image in the skeleton part, and to reduce micropores. Note that micropores refer to all pores with a pore diameter of less than 2 nm, excluding those with a pore diameter of 0 nm. Micropores are pores that do not contribute to the loading of platinum or platinum alloy nanoparticles and become a resistance component from the viewpoint of conductivity. Therefore, it is preferable that the number of micropores is small. The BET specific surface area of the porous carbon of the present invention is 250 m 2 / g or more and 750 m 2 / g or less, preferably 300 m 2 / g or more and 700 m 2 / g or less, more preferably 400 m 2 / g or more and 700 m 2 / g or less, more preferably.

[0027] The statistical thickness specific surface area (STSA) of the porous carbon of the present invention is 120 m 2 / g or more and 300 m 2 / g or less, preferably. STSA is a value measured under the condition that the relative pressure P / P0 is 0.5 or less, and in the porous carbon of the present invention, it is presumed to be the specific surface area excluding micropores among the specific surface areas of the skeleton part. For example, when the porous carbon of the present invention is used as a carrier for a catalyst for an air electrode of a fuel cell on which platinum or platinum alloy nanoparticles are supported, if the STSA of the porous carbon is 120 m 2 / g or more and 300 m 2 / g or less, it is possible to prevent the aggregation and sintering of platinum or platinum alloy nanoparticles and to increase the utilization efficiency of platinum or platinum alloy nanoparticles. The STSA of the porous carbon of the present invention is 150 m 2 / g or more and 300 m 2 / g or less, more preferably 150 m 2 / g or more and 250 m 2It is more preferable that it is below / g. The STSA of the present invention means a value measured according to "Carbon black for rubber - Basic characteristics - Part 7, Rubber compound - Method for determining multi - point nitrogen specific surface area (N2SA) and statistical thickness specific surface area (STSA)" specified in JIS K 6217 - 7.

[0028] The density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the skeletal part of the porous carbon of the present invention, that is, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image, is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less. That the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less indicates that pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image are regularly formed in the skeletal part. For example, when the porous carbon of the present invention is used as a carrier for a catalyst for an air electrode of a fuel cell supporting platinum or platinum alloy nanoparticles, since the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less, pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image are regularly formed in the skeletal part, so the loading amount of platinum or platinum alloy nanoparticles with a diameter of 2.0 nm or more and 7.0 nm or less supported near the outer surface of the skeletal part can be increased, and thus the catalytic activity can be enhanced. In the porous carbon of the present invention, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image is 50.0 pieces / 10 4 nm 2 or more and 110.0 pieces / 10 4 nm2 It is preferably the following, 70.0 pieces / 10 4 nm 2 or more and 100.0 pieces / 10 4 nm 2 More preferably, it is the following.

[0029] In the present invention, in the scanning electron microscope observation, the density of pores formed in the skeleton part of the porous carbon and having a pore diameter of 3.0 nm or more and 10.0 nm or less is a value measured by the following procedure. First, the measurement target is observed with a scanning electron microscope. Next, in the obtained SEM image, the number of pores formed in the skeleton part of the observation region and having a pore diameter of 3.0 nm or more and 10.0 nm or less when observed on the SEM image is counted, and the area of the skeleton part of the observation region is measured. Next, the number of pores counted is divided by the area of the skeleton part to calculate the density of pores of 3.0 nm or more and 10.0 nm or less. Note that for the measurement of the number of pores and the measurement of the area, the out-of-focus parts in the SEM image are removed, and the measurement is performed only in the region where pores of 3.0 nm or more and 10.0 nm or less formed in the skeleton part can be confirmed. Also, for the measurement of the number of pores of 3.0 nm or more and 10.0 nm or less and the measurement of the area, the measurement is performed when the area of the skeleton part is 10×10 4 nm 2 or more.

[0030] In the porous carbon of the present invention, the total volume V of pores A having a pore diameter of 2.9 nm or more and 8.3 nm or less in the nitrogen adsorption measurement P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less. The total volume V of pores A P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less, which indicates that there are many pores A formed near the outer surface of the skeleton part. The pores A formed near the outer surface of the skeleton part are suitable for supporting platinum or platinum alloy nanoparticles. For example, when the porous carbon of the present invention is used as a carrier for a catalyst for an air electrode of a fuel cell supporting platinum or platinum alloy nanoparticles, the total volume V P2.9-8.3 is 0.060 cm 30.100 cm / g or more 3 By being 2.0 nm or more and 7.0 nm or less, the amount of platinum or platinum alloy nanoparticles supported near the outer surface of the skeletal part can be increased, so the utilization efficiency of platinum or platinum alloy nanoparticles can be increased, and thereby, the catalytic activity per supported amount can be increased. In the porous carbon of the present invention, the total volume V P2.9-8.3 is preferably 0.070 cm 3 / g or more and 0.100 cm 3 / g or less from the viewpoint of preventing aggregation and sintering of platinum or platinum alloy nanoparticles and supporting a large amount, and more preferably 0.075 cm 3 / g or more and 0.100 cm 3 / g or less.

[0031] In the porous carbon of the present invention, since the total volume V P2.9-8.3 of the pores A is the total volume of the pores suitable for supporting platinum or platinum alloy nanoparticles, the value of the total volume V P2.9-8.3 is used for calculating the effective Pt mass ratio.

[0032] In the porous carbon of the present invention, the total volume V P10.0-62.0 of the pores B having a pore diameter of 10.0 nm or more and 62.0 nm or less in the nitrogen adsorption measurement is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less. The pores B are not pores suitable for supporting platinum or platinum alloy nanoparticles, but contribute to the high-speed transport of products and reactants. For example, the pores B are suitable for the water vapor generated in the battery reaction at the air electrode to escape. When the porous carbon of the present invention is used as a carrier for a catalyst for the air electrode of a fuel cell on which platinum or platinum alloy nanoparticles are supported, the total volume V P10.0-62.0 being 0.100 cm 3 / g or more and 0.400 cm 3 / g or less can make it easy for the water vapor generated in the battery reaction at the air electrode to escape while maintaining the high utilization efficiency of platinum or platinum alloy nanoparticles.

[0033] Incidentally, the total volume V P10.0-62.0is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less, while maintaining the three-dimensional network structure that facilitates the escape of water vapor generated in the battery reaction at the air electrode, the network-like three-dimensional network structure of the porous carbon can be made dense. As the three-dimensional network structure becomes denser, the conductive paths in the porous carbon develop and the conductivity improves. In the porous carbon of the present invention, the total volume V P10.0-62.0 is preferably 0.160 cm 3 / g or more and 0.400 cm 3 / g or less, more preferably 0.180 cm 3 / g or more and 0.400 cm 3 / g or less, and even more preferably 0.180 cm 3 / g or more and 0.350 cm 3 / g or less from the viewpoint of improving the diffusibility of water vapor while improving the conductivity.

[0034] In the porous carbon of the present invention, the total volume V P2.9-5.2 of pores having a pore diameter of 2.9 nm or more and 5.2 nm or less in nitrogen adsorption measurement is preferably 0.033 cm 3 / g or more and 0.050 cm 3 / g or less, more preferably 0.036 cm 3 / g or more and 0.048 cm 3 / g or less.

[0035] In the porous carbon of the present invention, the total pore volume V Total is preferably 0.550 cm 3 / g or more and 1.200 cm 3 / g or less, more preferably 0.600 cm 3 / g or more and 1.000 cm 3 / g or less, still more preferably 0.650 cm 3 / g or more and 0.900 cm 3 / g or less. The total pore volume is the sum of the volumes of all pores, and in the present invention, it refers to the adsorption volume of nitrogen gas per sample mass when the relative pressure P / P0 is 0.9860. The value of the total pore volume V Total is 0.550 cm3 1.200 cm or more per g 3 By being 1.200 cm or less per g, while maintaining the three-dimensional network structure that facilitates the escape of water vapor generated in the battery reaction at the air electrode, the network-like three-dimensional network structure of the porous carbon can be made dense.

[0036] In the porous carbon of the present invention, the total pore volume V of the micropores micro is preferably as small as possible. However, in one embodiment of the present invention, for example, 0.050 cm 3 / g or more and 0.200 cm 3 / g or less. Micropores refer to all pores with a pore diameter exceeding 0 nm and less than 2 nm in nitrogen adsorption measurement.

[0037] In the porous carbon of the present invention, the ratio of the total pore volume (total volume V micro + total volume V P2.0-62.0 ) of pores with a pore diameter of 62.0 nm or less in nitrogen adsorption measurement to the total volume V P2.9-8.3 ((total volume V P2.9-8.3 / (total volume V micro + total volume V P2.0-62.0 )) × 100) is preferably 10.0% or more and 19.0% or less, more preferably 12.0% or more and 18.0% or less. Also, in the porous carbon of the present invention, the ratio of the total pore volume (total volume V micro + total volume V P2.0-62.0 ) of pores with a pore diameter of 62.0 nm or less in nitrogen adsorption measurement to the total volume V P10.0-62.0 ((total volume V P10.0-62.0 / (total volume V micro + total volume V P2.0-62.0 )) × 100) is preferably 20.0% or more and 70.0% or less, more preferably 30.0% or more and 60.0% or less. Also, in the porous carbon of the present invention, the ratio of the total volume V Total to the total pore volume V P10.0-62.0 ((total volume V P10.0-62.0 / V Total ) × 100) is preferably 18.0% or more and 45.0% or less, more preferably 20.0% or more and 35.0% or less.

[0038] In the present invention, the measurement of the total volume of pores A is a value measured by the following procedure. First, the measurement target is subjected to nitrogen adsorption measurement using a measuring device under the conditions of an adsorption temperature of 77 K and a relative pressure of 0.01 to 0.99, and the nitrogen adsorption amount is determined from the adsorption isotherm. Next, using analysis software, the pore size distribution and pore volume are determined by the Barrett-Joyner-Halenda method (BJH method). Then, the total volume of pores with a pore diameter of 2.9 nm or more and 8.3 nm or less is calculated. Examples of the measuring device include BELSORP-max manufactured by MicrotracBEL Corporation, and examples of the analysis software include BELMaster 7.3.1.0. However, the measuring device and analysis software that can obtain similar results are not particularly limited. Note that the BJH method is based on the Kelvin equation: r k =-2γV m / RTln(P / P0) (where P / P0 is the relative pressure in the nitrogen adsorption measurement, V m is the molar volume of the condensed layer at that time (= adsorption amount), and γ is the surface tension of the adsorption layer.) Based on this, the pore diameter D is calculated by the following equation: D=2(r k +t) (where t is the thickness of the adsorption layer.) This is a method of calculation and is a method recommended by IUPAC. And from the above equation, the nitrogen adsorption amount corresponding to each BJH pore diameter D can be known, and the total volume of pores within the specified pore range can be calculated.

[0039] In the present invention, the measurement of the total volume of pores B is the value measured by the following procedure. First, the measurement target is subjected to nitrogen adsorption measurement using a measuring device under the conditions of an adsorption temperature of 77 K and a relative pressure of 0.01 to 0.99, and the nitrogen adsorption amount is determined from the adsorption isotherm. Next, using analysis software, the pore size distribution and pore volume are determined by the Barrett-Joyner-Halenda method (BJH method). Next, the total volume of pores with a pore diameter of 10.0 nm or more and 62.0 nm or less is calculated. Examples of the measuring device include BELSORP-max manufactured by MicrotracBEL Corporation, and examples of the analysis software include BELMaster 7.3.1.0. However, the measuring device and analysis software that can obtain the same results are not particularly limited.

[0040] In the present invention, the total volume of other pores is also measured according to the above procedure. Specifically, after determining the pore size distribution and pore volume by the BJH method, the total volume of pores in each pore diameter range may be calculated.

[0041] In the porous carbon of the present invention, the conductivity is not particularly limited. For example, in one embodiment of the present invention, when the compression density of the porous carbon is 0.2 g / cm 3 it is 100 S / m or more and 400 S / m or less, in a more preferred embodiment it is 130 S / m or more and 400 S / m or less, and in a more preferred embodiment it is 150 S / m or more and 400 S / m or less. In the present invention, the compression density refers to the bulk density after compression, and is the density obtained by dividing the mass of the powder by the volume after compression by pushing the powder in the uniaxial direction for compression. In the present invention, the pressure during compression is not particularly limited as long as the compression density of the porous carbon becomes 0.2 g / cm 3 but is, for example, 0.1 MPa or more and 30.0 MPa or less, and in one embodiment of the present invention, it is 2.0 MPa or more and 20.0 MPa or less.

[0042] In the present invention, the conductivity measurement is a value measured by the following procedure. First, a sample of porous carbon is put into a non-conductive cylinder made of ceramics in an amount of 0.1 g to 0.3 g, and a compression test is carried out by applying a load with a metal cylindrical indenter having a diameter of 8 mm using a small bench tester EZGraph manufactured by Shimadzu Corporation. Simultaneously with the compression test, a constant current of 0.5 A is applied to the sample of porous carbon using a constant current generator, and the DC voltage is measured. The conductivity can be calculated from the obtained DC voltage and the dimensions of the sample of porous carbon.

[0043] The use of the porous carbon of the present invention is not particularly limited, and examples thereof include a carrier for platinum or platinum alloy nanoparticles in a cathode catalyst of a polymer electrolyte fuel cell, a carrier for an ammonia synthesis catalyst, a conductive auxiliary agent, and the like.

[0044] The method for producing the porous carbon of the present invention is not particularly limited, and it may be obtained by any production method. The porous carbon of the present invention is preferably produced by the method for producing the porous carbon of the present invention described below.

[0045] The method for producing the porous carbon of the present invention uses a phenol compound and formaldehyde as reaction raw materials, and these raw materials are reacted using an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, and then heat treatment is performed to obtain a sol. Next, the obtained sol is gelled and dried to obtain a porous phenolic resin, and a carbonization step of carbonizing the obtained porous phenol to obtain porous carbon. In the porous phenolic resin production step, the reaction temperature of the raw materials and the heating temperature for subsequent sol formation are selected, and in the carbonization step, the firing temperature conditions are selected.

[0046] Examples of the porous phenolic resin production step include the porous phenolic resin production steps of the first to third forms shown below.

[0047] The porous phenolic resin production step of the first form is A first step of heating a mixture of a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water at 73°C or higher and lower than 78°C to obtain a first treated product; A second step of mixing water with the first treated product and heating the resulting mixture at 67°C or higher and 72°C or lower to obtain a sol solution; A gelation step of mixing water with the sol solution and heating the resulting mixture under pressure at 120°C or higher and 140°C or lower to obtain a wet gel; A drying step of drying the wet gel to obtain a porous phenolic resin; It has.

[0048] Also, the manufacturing process of the porous phenolic resin of the second form is as follows: A first step of heating a mixture of a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water at 50°C or higher and lower than 58°C to obtain a first treated product; A second step of mixing water with the first treated product and heating the resulting mixture at 73°C or higher and 78°C or lower to obtain a sol solution; A gelation step of mixing water with the sol solution and heating the resulting mixture under pressure at 120°C or higher and 140°C or lower to obtain a wet gel; A drying step of drying the wet gel to obtain a porous phenolic resin; It has.

[0049] Also, the manufacturing process of the porous phenolic resin of the third form is as follows: A first step of heating a mixture of a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water at 50°C or higher and lower than 90°C to obtain a first treated product; A second step of mixing water with the first treated product and heating the resulting mixture at 55°C or higher and 92°C or lower to obtain a sol solution; A multi-liquid mixing step of mixing the sol solution with a plurality of sol solutions adjusted under different temperature conditions to obtain a mixed sol solution; Water is mixed with the mixed sol solution, and the resulting mixture is heated under pressure at 120 °C or higher and 140 °C or lower to obtain a wet gel in a gelation step. The wet gel is dried to obtain a porous phenolic resin in a drying step. It has.

[0050] Although the heating conditions and the like in the first step and the second step are different in the production processes of the porous phenolic resins of the first to third forms, there are also similar parts. Therefore, for the different parts, they will be described respectively, and for the similar parts, the production processes of the porous phenolic resins of the first to third forms will be collectively referred to as the production process of the porous phenolic resin and described.

[0051] The first step in the production process of the porous phenolic resin is a step of heating a mixture of a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water to obtain a first treated product.

[0052] The phenolic compound used in the first step in the production process of the porous phenolic resin is not particularly limited as long as it is a compound having a phenolic skeleton, and examples include phenol (C6H5OH), a substituted phenol in which one or more aromatic rings are substituted with alkyl groups, specifically C6H4(OH)CH3 (any one or a combination of two or more of 2-methylphenol, 3-methylphenol, and 4-methylphenol), C6H3(OH)(CH3)2 (any one or a combination of two or more of 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, and 3,5-dimethylphenol), resorcinol (C6H4(OH)2), pyrocatechol (C6H4(OH)2), and the like. Among these, phenol (C6H5OH) is preferred as the phenolic compound.

[0053] The formaldehyde used in the first step of the process for producing the porous phenolic resin is usually added to the water for preparing the mixture as an aqueous formaldehyde solution. The concentration of the aqueous formaldehyde solution is not particularly limited and is usually 10.0% by mass or more and 40.0% by mass or less.

[0054] The alkali metal hydroxide used in the first step of the process for producing the porous phenolic resin is not particularly limited, but sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferred, and sodium hydroxide is particularly preferred in terms of preferentially promoting the addition reaction of phenol.

[0055] In the first step of the process for producing the porous phenolic resin, instead of the alkali metal hydroxide, ammonia, organic amines such as ethanolamine, and quaternary organic ammonium salts such as tetramethylammonium hydroxide can be used. By using an alkali metal hydroxide or ammonia or an organic amine or a quaternary ammonium salt in the first step of the present invention, a production reaction of a resol resin under basic conditions can be caused.

[0056] Examples of the organic amine used in the first step include ethanolamine, propanolamine, alkylamine, and cyclic amine. Examples of ethanolamine include monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, aminoethoxyethanol, etc. Examples of propanolamine include 1-amino-2-propanol, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, etc. Examples of alkylamine include monomethylamine, dimethylamine, trimethylamine, ethylenediamine, ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenetetramine, tetraethylenepentamine, etc. Examples of cyclic amine include choline, morpholine, etc.

[0057] Examples of the quaternary organic ammonium salt used in the first step include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, N,N,N-triethyl-N-(2-hydroxyethyl)ammonium hydroxide, N,N-diethyl-N,N-di(2-hydroxyethyl)ammonium hydroxide, and the like.

[0058] As the organic amine or quaternary organic ammonium salt used in the first step, those having strong basicity are preferred, and quaternary ammonium salts are particularly preferred, and tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc. are particularly preferred.

[0059] Examples of the nonionic surfactant used in the first step related to the porous phenolic resin production process include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, etc. More specifically, copolymers of polyethylene oxide (PEO) and polypropylene oxide (PPO) are included, and among them, those having a molar mass of PPO of 3000 or more and 4000 or less and a ratio of PEO in the molecule of 30% or more and 90% or less are included.

[0060] The water used in the first step related to the porous phenolic resin production process is not particularly limited, and examples include distilled water, ion-exchanged water, industrial water, etc. The water used in the first step related to the porous phenolic resin of the present invention is preferably less in impurities in terms of suppressing the inhibition of the addition polymerization reaction by impurities.

[0061] In the mixture used in the first step of the process for producing the porous phenolic resin, the molar ratio of formaldehyde to the phenolic compound (formaldehyde / phenolic compound) is 2.6 or more and 5.0 or less, the molar ratio of alkali metal hydroxide to the phenolic compound (alkali metal hydroxide / phenolic compound) is 0.24 or more and 0.48 or less, the molar ratio of ammonia to the phenolic compound (ammonia / phenolic compound) is 0.24 or more and 0.96 or less, the molar ratio of organic amine to the phenolic compound (organic amine / phenolic compound) is 0.24 or more and 0.96 or less, and the molar ratio of quaternary organic ammonium salt to the phenolic compound (quaternary organic ammonium salt / phenolic compound) is 0.24 or more and 0.48 or less.

[0062] In the first step of the process for producing the porous phenolic resin, the mixing amount of the nonionic surfactant is an amount such that the mass ratio of the nonionic surfactant to the phenolic compound in the first treated product (nonionic surfactant / phenolic compound) is 1.5 or more and 2.3 or less.

[0063] In the first step of the process for producing the porous phenolic resin, the amount of water to be mixed is an amount such that the concentration of the nonionic surfactant with respect to the total amount of the first treated product is 21 mg / mL or more and 45 mg / mL or less.

[0064] The method for preparing the mixture used in the first step of the process for producing the porous phenolic resin of the present invention is not particularly limited, and examples include a method of adding a predetermined amount of a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, and a nonionic surfactant to a predetermined amount of water and mixing them. Formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt may be added in an aqueous solution state.

[0065] And in the first step of the production process of the porous phenolic resin of the first form, a mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water is heated at a temperature of 73°C or higher and lower than 78°C to obtain a first treated product. In the first step of the production process of the porous phenolic resin of the first form, when heating the mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water, the heating time is 1 hour or longer and 6 hours or shorter.

[0066] Also, in the first step of the production process of the porous phenolic resin of the second form, a mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water is heated at a temperature of 50°C or higher and 58°C or lower to obtain a first treated product. In the first step of the production process of the porous phenolic resin of the second form, when heating the mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide or ammonia or an organic amine or a quaternary organic ammonium salt, a nonionic surfactant, and water, the heating time is 1 hour or longer and 6 hours or shorter.

[0067] In the first step of the manufacturing process of the third form of porous phenolic resin, a mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide, ammonia, an organic amine, or a quaternary organic ammonium salt, a nonionic surfactant, and water is heated at 50°C or higher and 90°C or lower to obtain a first treated product. In the first step of the manufacturing process of the third form of porous phenolic resin, when heating the mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide, ammonia, an organic amine, or a quaternary organic ammonium salt, a nonionic surfactant, and water, the heating time is 1 hour or more and 6 hours or less. And in the first step of the manufacturing process of the third form of porous phenolic resin, the first step is carried out under a plurality of different temperature conditions to obtain a plurality of first treated products. That is, at least, the first step (1) is carried out under a temperature condition of 50°C or higher and 90°C or lower to obtain a first treated product (1), and the first step (2) is carried out under a temperature condition different from the temperature condition of the first step (1) to obtain a first treated product (2). Further, if necessary, one or two or more first steps (3, 4 ··· n) can be carried out under temperature conditions different from these to obtain first treated products (3, 4 ··· n).

[0068] In the first step of the manufacturing process of the third form of porous phenolic resin, a mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide, ammonia, an organic amine, or a quaternary organic ammonium salt, a nonionic surfactant, and water is heated at 50°C or higher and 90°C or lower, preferably 50°C or higher and 70°C or lower, to carry out the first step (1A) to obtain a first treated product (1A). Also, it is more preferable to heat a mixture obtained by mixing a phenolic compound, formaldehyde, an alkali metal hydroxide, ammonia, an organic amine, or a quaternary organic ammonium salt, a nonionic surfactant, and water at 50°C or higher and 90°C or lower, preferably 65°C or higher and 75°C or lower, to carry out the first step (2B) to obtain a first treated product (2B).

[0069] The second step of the manufacturing process of the porous phenolic resin is a step of mixing water with the first treated product obtained by carrying out the first step and heating the resulting mixture to obtain a sol solution.

[0070] The water used in the second step of the process for producing the porous phenolic resin is not particularly limited, and examples include distilled water, ion-exchanged water, industrial water, and the like. The water used in the second step of the process for producing the porous phenolic resin is preferably less in impurities in terms of suppressing the inhibition of the addition polymerization reaction by impurities.

[0071] In the second step of the process for producing the porous phenolic resin, the mixing amount of water when mixing water with the first treated product is an amount such that the concentration of the nonionic surfactant in the mixture obtained after mixing water with the first treated product is 9 mg / mL or more and 20 mg / mL or less.

[0072] In the second step of the process for producing the porous phenolic resin, the method of mixing water with the first treated product is not particularly limited, and examples include a method of adding a predetermined amount of water to a predetermined amount of the first treated product and mixing them.

[0073] Then, in the second step of the process for producing the porous phenolic resin of the first form, the mixture obtained by mixing water with the first treated product is heated at 67°C or higher and 72°C or lower to obtain a sol solution. In the second step of the process for producing the porous phenolic resin of the first form, the heating time when heating the mixture obtained by mixing water with the first treated product is 12 hours or more and 24 hours or less.

[0074] Also, in the second step of the process for producing the porous phenolic resin of the second form, the mixture obtained by mixing water with the first treated product is heated at 73°C or higher and 78°C or lower to obtain a sol solution. In the second step of the process for producing the porous phenolic resin of the second form, the heating time when heating the mixture obtained by mixing water with the first treated product is 12 hours or more and 24 hours or less.

[0075] Also, in the second step of the manufacturing process of the third-form porous phenolic resin, a mixture obtained by mixing water with the first treated product is heated at 55°C or higher and 92°C or lower to obtain a sol solution. In the second step of the manufacturing process of the third-form porous phenolic resin, when heating the mixture obtained by mixing water with the first treated product, the heating time is 12 hours or more and 24 hours or less. And, in the second step of the manufacturing process of the third-form porous phenolic resin, using a plurality of first treated products prepared under different temperature conditions in the first step, for each of them, the second step is performed to obtain a plurality of sol solutions. That is, at least, the second step (1) is performed using the first treated product (1) obtained by performing the first step (1) to obtain the sol solution (1), and the second step (2) is performed using the first treated product (2) obtained by performing the first step (2) to obtain the sol solution (2). Also, if necessary, when one or more first steps (3, 4 ··· n) are performed under further different temperature conditions to obtain the first treated products (3, 4 ··· n), the second steps (3, 4 ··· n) can be performed using these first treated products (3, 4 ··· n) respectively to obtain the sol solutions (3, 4 ··· n).

[0076] In the second step of the manufacturing process of the third-form porous phenolic resin, it is more preferable to heat the first treated product (1A) to obtain the sol solution (1A) and heat the first treated product (2B) to obtain the sol solution (2B).

[0077] In the second step of the manufacturing process of the third-form porous phenolic resin, as the conditions for obtaining the sol solution (1A), when the heating temperature in the first step is 50°C or higher and less than 73°C, the heating temperature in the second step is preferably 70°C or higher and 80°C or lower. Also, as the conditions for obtaining the sol solution (1A), when the heating temperature in the first step is 73°C or higher and 90°C or lower, the heating temperature in the second step is 80°C or lower, and it is preferably set so that the sum of the values of the heating temperature in the first step and the heating temperature in the second step is 145 or more.

[0078] In the second step of the manufacturing process of the third form of the porous phenolic resin, as the conditions for obtaining the sol solution (2B), when the heating temperature in the first step is 50°C or higher and lower than 73°C, the heating temperature in the second step is preferably 55°C or higher and lower than 70°C. Further, as the conditions for obtaining the sol solution (2B), when the heating temperature in the first step is 73°C or higher and 90°C or lower, the heating temperature in the second step is lower than 70°C, and it is preferable to set the sum of the values of the heating temperature in the first step and the heating temperature in the second step to be less than 145.

[0079] The multi-liquid mixing step in the manufacturing process of the third form of the porous phenolic resin is a step of mixing two or more types of sol solutions, and is a step of mixing a plurality of sol solutions prepared under different temperature conditions, that is, at least sol solution (1) and sol solution (2) to obtain a mixed sol solution. Further, when sol solutions (3, 4 ··· n) are obtained as necessary, in the multi-liquid mixing step, sol solution (1), sol solution (2), and sol solutions (3, 4 ··· n) are mixed to obtain a mixed sol solution.

[0080] In the multi-liquid mixing step, the method of mixing a plurality of sol solutions prepared under different temperature conditions is not particularly limited, and examples include a method of putting the plurality of sol solutions into one container and stirring. The sol solutions to be mixed in the multi-liquid mixing step may be two or more types, and three or more types or four or more types of sol solutions may be mixed. In the multi-liquid mixing step, it is more preferable to mix the sol solution (1A) obtained in the second step of the manufacturing process of the third form of the porous phenolic resin and the sol solution (2B). Further, in the multi-liquid mixing step, it is preferable to mix the sol solution (1A) and the sol solution (2B) at a ratio of 2.0:1.0 to 1.0:2.0, more preferably at a ratio of 1.0:0.9 to 1.0:1.1, and even more preferably at a ratio of 1:1.

[0081] In the production process of the porous phenolic resin in the first form and the second form, the sol solution obtained by performing the second step may be directly used as the sol solution in the gelation step. Alternatively, in the production process of the porous phenolic resin in the first form and the second form, after performing the second step and before performing the gelation step, the sol solution may be filtered, and the obtained filtrate may be used as the sol solution in the gelation step. In the production process of the porous phenolic resin in the third form, the sol solution obtained by performing the second step may be directly used as the sol solution in the multi-liquid mixing step. Alternatively, in the production process of the porous phenolic resin in the third form, after performing the second step and before performing the multi-liquid mixing step, the sol solution may be filtered, and the obtained filtrate may be used as the sol solution in the multi-liquid mixing step. In the production process of the porous phenolic resin in the third form, the mixed sol solution obtained by performing the multi-liquid mixing step may be directly used as the mixed sol solution in the gelation step. Alternatively, in the production process of the porous phenolic resin in the third form, after performing the multi-liquid mixing step and before performing the gelation step, the mixed sol solution may be filtered, and the obtained filtrate may be used as the sol solution in the gelation step.

[0082] The gelation step in the production process of the porous phenolic resin is, in the case of the production process of the porous phenolic resin in the first form or the second form, water is mixed with the sol solution obtained by performing the second step, and in the case of the production process of the porous phenolic resin in the third form, water is mixed with the mixed sol solution obtained by performing the multi-liquid mixing step, and the obtained mixture is heated under pressure to obtain a wet gel.

[0083] The water used in the gelation step in the production process of the porous phenolic resin is not particularly limited, and examples include distilled water, ion-exchanged water, industrial water, etc. The water used in the gelation step in the production process of the porous phenolic resin is preferably less in impurities in terms of suppressing the inhibition of the addition polymerization reaction by impurities.

[0084] In the gelation step in the production process of the porous phenolic resin, the mixing amount of water when mixing water with the sol solution is an amount that is 1.5 times or more and 6.0 times or less with respect to the mass of the first processed product.

[0085] In the gelation step of the process for producing a porous phenolic resin, the method of mixing water into the sol solution is not particularly limited, and examples include a method of adding a predetermined amount of water to a predetermined amount of the sol solution and mixing them.

[0086] Then, in the gelation step of the process for producing a porous phenolic resin, the mixture obtained by mixing water into the sol solution is heated at 120°C or higher and 140°C or lower under pressure to obtain a wet gel. In the gelation step of the process for producing a porous phenolic resin, the pressure (absolute pressure) when heating the mixture obtained by mixing water into the sol solution is 0.34 MPa or higher and 0.51 MPa or lower. In the gelation step of the process for producing a porous phenolic resin, the heating time when heating the mixture obtained by mixing water into the sol solution is 6 hours or longer and 48 hours or shorter.

[0087] The wet gel obtained by performing the gelation step of the process for producing a porous phenolic resin may be directly dried in the drying step. Alternatively, after performing the gelation step of the process for producing a porous phenolic resin and before performing the drying step, the wet gel obtained by performing the gelation step may be washed one or more times, and the obtained wet gel may be dried in the drying step.

[0088] The drying step of the process for producing a porous phenolic resin is a step of drying the wet gel obtained by performing the gelation step to obtain a porous phenolic resin.

[0089] In the drying step of the process for producing a porous phenolic resin, the method of drying the wet gel is not particularly limited, and includes: (a) a method of adding the wet gel to water, dispersing it in water, spraying the resulting dispersion of the wet gel into liquid nitrogen using a spray freeze granulator to perform freeze granulation, and then drying the obtained freeze granulated product under vacuum to dry the wet gel; (b) a method of adding the wet gel to water, dispersing it in water, spraying the resulting dispersion of the wet gel into hot air using a spray dryer to perform heat drying; and (c) a method of performing heat drying by treating with microwaves.

[0090] Then, a drying process related to the porous phenol resin manufacturing process is performed to obtain a porous phenol resin.

[0091] Examples of the carbonization process include the first to second forms of carbonization processes shown below.

[0092] The carbonization process of the first form is to heat-treat the porous phenol resin obtained in the porous phenol resin manufacturing process of the first, second, or third form of the present invention at 300°C or higher and 450°C or lower in an inert gas atmosphere, bake the obtained heat-treated product at 450°C or higher and 800°C or lower in an inert gas atmosphere, and then carbonize the obtained baked product at 800°C or higher and 2000°C or lower in an inert gas atmosphere to obtain porous carbon.

[0093] In the carbonization process of the first form, the heat treatment temperature when heat-treating the porous phenol resin is 300°C or higher and 450°C or lower. By heat-treating the porous phenol resin at 300°C or higher and 450°C or lower in the carbonization process of the first form, the nonionic surfactant remaining in the porous phenol resin can be removed, and it becomes possible to maintain a pore structure suitable for supporting platinum or platinum alloy nanoparticles. In the carbonization process of the first form, the heat treatment time when heat-treating the porous phenol resin is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the first form, the heat treatment atmosphere when heat-treating the porous phenol resin is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0094] In the carbonization process of the first form, the baking temperature when baking the heat-treated product of the porous phenol resin is 450°C or higher and 800°C or lower. In the carbonization process of the first form, the baking time when baking the heat-treated product of the porous phenol resin is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the first form, the baking atmosphere when baking the heat-treated product of the porous phenol resin is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0095] In the carbonization process of the first form, the carbonization temperature when carbonizing the fired product of the porous phenolic resin is 800 °C or higher and 2000 °C or lower. In the carbonization process of the first form, the carbonization time when carbonizing the fired product of the porous phenolic resin is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the first form, the firing atmosphere when carbonizing the fired product of the porous phenolic resin is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0096] The carbonization process of the second form is a process of obtaining porous carbon by subjecting the porous phenolic resin obtained in the porous phenolic resin production process of the first form, second form, or third form of the present invention to a first heat treatment at 200 °C or higher and 360 °C in an inert gas atmosphere, once cooling to 100 °C or lower, then subjecting the obtained first heat-treated product to a second heat treatment at 300 °C or higher and 450 °C or lower in an inert gas atmosphere, then firing the obtained second heat-treated product at 450 °C or higher and 800 °C or lower in an inert gas atmosphere, and then carbonizing the obtained fired product at 800 °C or higher and 2000 °C or lower in an inert gas atmosphere.

[0097] In the carbonization process of the second form, the heat treatment temperature when performing the first heat treatment on the porous phenolic resin is 200 °C or higher and 360 °C or lower. By performing the first heat treatment on the porous phenolic resin at 200 °C or higher and 360 °C or lower in the carbonization process of the second form, it is possible to remove the nonionic surfactant remaining in the porous phenolic resin and maintain a pore structure suitable for supporting platinum or platinum alloy nanoparticles. In the carbonization process of the second form, the heat treatment time when performing the first heat treatment on the porous phenolic resin is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the second form, the heat treatment atmosphere when performing the first heat treatment on the porous phenolic resin is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0098] In the carbonization process of the second form, after performing the first heat treatment, the cooling temperature when cooling the first heat-treated product once is 100 °C or lower, preferably 0 °C or higher and 100 °C or lower. By performing cooling once after performing the first heat treatment, the total volume VP2.9-8.3 is improved.

[0099] In the carbonization process of the second form, when the first heat-treated product of the porous phenolic resin is second heat-treated, the heat treatment temperature is 300°C or higher and 450°C or lower. In the carbonization process of the second form, by heat-treating the first heat-treated product of the porous phenolic resin at 300°C or higher and 450°C or lower, only the nonionic surfactant can be decomposed and removed while maintaining the pore structure suitable for supporting platinum or platinum alloy nanoparticles. In the carbonization process of the second form, the heat treatment time when the first heat-treated product of the porous phenolic resin is second heat-treated is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the second form, the heat treatment atmosphere when the first heat-treated product of the porous phenolic resin is second heat-treated is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0100] In the carbonization process of the second form, the firing temperature when the second heat-treated product is fired is 450°C or higher and 800°C or lower. In the carbonization process of the second form, the firing time when the second heat-treated product is fired is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the second form, the firing atmosphere when the second heat-treated product is fired is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0101] In the carbonization process of the second form, the carbonization temperature when the fired product of the porous phenolic resin is carbonized is 800°C or higher and 2000°C or lower. In the carbonization process of the second form, the carbonization time when the fired product of the porous phenolic resin is carbonized is 30 minutes or longer and 6 hours or shorter. In the carbonization process of the second form, the firing atmosphere when the fired product of the porous phenolic resin is carbonized is an inert gas atmosphere such as nitrogen gas, helium gas, or argon gas.

[0102] And, by performing the carbonization process of the first form or the second form of the present invention, the porous carbon of the present invention can be obtained.

[0103] The cathode catalyst for the solid polymer fuel cell of the present invention is It includes a porous carbon carrier and platinum or platinum alloy nanoparticles supported in the pores of the porous carbon carrier. The porous carbon carrier has a three-dimensional network structure in which the skeleton part branches and connects in three-dimensional directions. The average diameter of the skeleton part is 20.0 nm or more and 45.0 nm or less, and the total volume V of pores A with a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less, and the total volume V of pores B with a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement P10.0-62.0 is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less. In scanning electron microscope observation, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less formed in the skeleton part is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less. It is characterized by the above.

[0104] The cathode catalyst for a polymer electrolyte fuel cell of the present invention includes a porous carbon carrier and platinum or platinum alloy nanoparticles supported in the pores of the porous carbon carrier. That is, the cathode catalyst for a polymer electrolyte fuel cell of the present invention is one in which platinum or platinum alloy nanoparticles are supported in pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed in the skeleton part of the porous carbon of the present invention.

[0105] In the cathode catalyst for a polymer electrolyte fuel cell of the present invention, the porous carbon carrier serving as the carrier of platinum or platinum alloy nanoparticles is the porous carbon of the present invention. Therefore, the description of the porous carbon carrier related to the cathode catalyst for a polymer electrolyte fuel cell of the present invention is the same as the description of the porous carbon of the present invention.

[0106] The platinum alloy for the cathode catalyst of the polymer electrolyte fuel cell of the present invention is an alloy of platinum and one or more metals selected from known metal elements such as cobalt, nickel, ruthenium, palladium, gold, scandium, yttrium, and lanthanum.

[0107] The particle size of the platinum or platinum alloy nanoparticles for the cathode catalyst of the polymer electrolyte fuel cell of the present invention is 2.0 nm or more and 7.0 nm or less, preferably 3.0 nm or more and 5.0 nm or less.

[0108] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the effective Pt mass ratio of the platinum or platinum alloy nanoparticles is preferably 20.0 mass% or more and 40.0 mass% or less, more preferably 23.0 mass% or more and 40.0 mass% or less. In the present invention, the effective Pt mass ratio means that assuming that the carbon carrier supports the platinum or platinum alloy nanoparticles at the theoretically maximum amount, it represents the value in mass% of how much platinum or platinum alloy nanoparticles that function effectively as a catalyst exist with respect to the total mass of the platinum or platinum alloy nanoparticles and the carbon carrier supported at the maximum amount. It is a value calculated by a calculation based on the structure of the porous carbon and depends on the value of the pore volume of the diameter and the total volume V P2.9-8.3 of the skeleton part.

[0109] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the supported amount of the platinum or platinum alloy nanoparticles is preferably 12.0 mass% or more and 40.0 mass% or less, more preferably 18.0 mass% or more and 40.0 mass% or less. In the present invention, the supported amount of the platinum or platinum alloy nanoparticles means the value in mass% of how much platinum or platinum alloy nanoparticles (including platinum or platinum alloy nanoparticles that do not function effectively as a catalyst) are supported with respect to the total mass of the platinum or platinum alloy nanoparticles and the carbon carrier. Note that in the present invention, the supported amount of the platinum or platinum alloy nanoparticles is the actual supported amount and is distinguished from the effective Pt mass ratio which represents the amount of the effective catalyst when supporting the theoretically maximum amount.

[0110] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the porous carbon of the present invention used as a carrier has an average diameter of the skeleton portion of 20.0 nm or more and 45.0 nm or less, preferably 20.0 nm or more and 40.0 nm or less, more preferably 20.0 nm or more and 35.0 nm or less. Therefore, pores suitable for supporting platinum or platinum alloy nanoparticles in the skeleton portion are not formed deep into the skeleton portion. Therefore, in the cathode catalyst of the polymer electrolyte fuel cell of the present invention, platinum or platinum alloy nanoparticles are concentrated and supported near the surface of the skeleton portion, so the utilization efficiency of platinum or platinum alloy nanoparticles in the battery reaction is very high.

[0111] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the porous carbon of the present invention used as a carrier preferably has a BET specific surface area of 200 m 2 / g or more and 800 m 2 / g or less, more preferably 250 m 2 / g or more and 750 m 2 / g or less, more preferably 300 m 2 / g or more and 700 m 2 / g or less, more preferably 400 m 2 / g or more and 700 m 2 / g or less. Therefore, while there are few micropores, pores having a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image on which platinum or platinum alloy nanoparticles are supported are sufficiently present. Therefore, in the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the utilization efficiency of platinum or platinum alloy nanoparticles is very high.

[0112] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the density of pores having a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed in the skeleton portion of the porous carbon of the present invention used as a carrier is 30.0 pieces / 10 4 nm 2 or more and 120.0 pieces / 10 4 nm 2 or less, preferably 50.0 pieces / 10 4 nm 2 or more and 110.0 pieces / 10 4 nm 2Hereinafter, more preferably 70.0 pieces / 10 4 nm 2 or more and 100.0 pieces / 10 4 nm 2 Since it is as follows, pores having a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image are regularly formed in the skeleton portion, so that the loading amount of platinum or platinum alloy nanoparticles of 2.0 nm or more and 7.0 nm or less supported near the outer surface of the skeleton portion is large and the catalytic activity is high.

[0113] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the porous carbon of the present invention used as a carrier has a total volume V of pores A having a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less, preferably 0.070 cm 3 / g or more and 0.100 cm 3 / g or less, more preferably 0.075 cm 3 / g or more and 0.100 cm 3 / g or less. Since it is as follows, the loading amount of platinum or platinum alloy nanoparticles of 2.0 nm or more and 7.0 nm or less supported near the outer surface of the skeleton portion is large and the catalytic activity is high.

[0114] In the cathode catalyst of the polymer electrolyte fuel cell of the present invention, the porous carbon of the present invention used as a carrier has a total volume V of pores B having a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement P10.0-62.0 is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less, preferably 0.160 cm 3 / g or more and 0.400 cm 3 / g or less, more preferably 0.180 cm 3 / g or more and 0.350 cm 3 / g or less. Since it is as follows, while maintaining a three-dimensional network structure that facilitates the escape of water vapor generated in the battery reaction at the cathode, the conductive path in the porous carbon is developed and the conductivity is high.

[0115] The method for producing the catalyst for the cathode of the polymer electrolyte fuel cell of the present invention is not particularly limited. For example, the porous carbon of the present invention is used to support platinum or platinum alloy nanoparticles on the skeleton portion of the porous carbon of the present invention by the reverse micelle method or the protective colloid method described in Patent Document 2, etc., to produce a catalyst for the cathode of a polymer electrolyte fuel cell.

[0116] The present invention will be described using the following examples. However, the following examples are merely examples of the present invention and are not limited thereto.

Examples

[0117] (Example 1) (1) First step An aqueous solution prepared by dissolving 3.84 g of a nonionic surfactant (a copolymer of polyethylene oxide (PEO) and polypropylene oxide (PPO) (trade name Pluronic (registered trademark) F127, structural formula: PEO m -PPO n -PEO m , m = 106, n = 70)) in 60 g of pure water was placed in a flask together with 2.42 g of phenol, 8.40 g of formaldehyde solution (formaldehyde concentration: 35% by mass), and 60.65 g of 0.1 mol / L aqueous sodium hydroxide solution, and stirred with a stirrer at a speed of 200 rpm at an internal temperature (heating temperature) of 75 °C for 120 minutes to obtain a first treated product.

[0118] (2) Second step Next, 200 g of pure water was added to the first treated product obtained in (1), the internal temperature (heating temperature) was adjusted to 70 °C, and the mixture was stirred for 20 hours to obtain a sol solution.

[0119] (3) Gelation step The sol solution prepared in (2) was filtered through a 5 μm membrane filter, and the filtrate was collected. 700 g of pure water was added to 280 g of this filtrate (the total amount of the sol solution considering the evaporation component was 300 mL), placed in a stainless steel sealed container, and subjected to hydrothermal treatment at 130 °C for 20 hours to obtain a wet gel. It was filtered through a 5 μm membrane filter to collect the wet gel.

[0120] (4) Drying process The total amount of the wet gel obtained in (3) was put into 160 g of pure water, stirred at 2,000 rpm for 5 minutes with a high-speed stirrer, and further treated in an ultrasonic cleaner with an output of 70 W for 5 to 10 minutes to prepare a dispersion. This dispersion was spray-frozen granulated by spraying it into liquid nitrogen with a spray-freeze granulator, and then put into a dedicated glass container cooled with liquid nitrogen, attached to a vacuum dryer, and vacuum-dried at about -40°C for 60 hours to obtain granulated dry gel (porous phenolic resin).

[0121] (5) Carbonization process The dry gel obtained in (4) was put into a firing furnace, heated from room temperature to 330°C to 360°C at a heating rate of 1°C / min under a nitrogen gas flow, maintained for a total of 4 hours, and then cooled to room temperature. Next, it was heated to 350°C at a heating rate of 1°C / min under a nitrogen gas flow, maintained for 2 hours, then heated to 600°C at a heating rate of 1°C / min again, and maintained for 2 hours. Then, it was put into a carbonization furnace, heated to 1,000°C at a heating rate of 1°C / min under a pressurized nitrogen gas atmosphere, maintained for 2 hours, and then cooled to room temperature to obtain porous carbon as a carbonized product.

[0122] Scanning electron microscope observation (SEM) was performed on the obtained porous carbon to confirm the structure of the porous carbon. The results are shown in Figure 1. Also, from the obtained SEM images, the average diameter of the skeleton part was measured. Also, scanning electron microscope observation (SEM) was performed on the obtained porous carbon, and from the obtained SEM images, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less observed on the SEM image formed in the skeleton part was determined. Also, the BET specific surface area and pore volume of the obtained porous carbon were measured. Also, when platinum nanoparticles were supported on the pores of the skeleton part in the obtained porous carbon, the mass ratio of platinum (effective Pt mass ratio) that was presumed to function effectively was calculated. The results are shown in Table 1.

[0123] <Confirmation of the structure of porous carbon and measurement of the average diameter of the skeleton part> The porous carbon was observed with a scanning transmission electron microscope (SEM: SU9000 manufactured by Hitachi High-Tech Corporation) to observe the pore structure. Next, regarding the diameter of the skeleton part, 100 circles circumscribed on the skeleton image of the obtained SEM image were arranged, and the average value of their diameters was taken as the diameter of the skeleton part. · Measuring device: SU9000 manufactured by Hitachi High-Tech Corporation · Measuring conditions: 50×10 4 times, 15 kV

[0124] <Measurement of the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed on the skeleton part of the porous carbon> The measurement object was observed with a scanning electron microscope. Next, in the obtained SEM image, the number of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed on the skeleton part of the observation region was counted, and the area of the skeleton part of the observation region was measured. Next, the number of pores counted was divided by the area of the skeleton part to calculate the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image. In addition, regarding the measurement of the number of pores and the measurement of the area, the out-of-focus parts in the SEM image were removed, and the measurement was performed only in the region where pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed on the skeleton part could be confirmed. Also, regarding the measurement of the number of pores and the measurement of the area, the measurement was performed when the area of the skeleton part was 10×10 4 nm 2 or more. · Measuring device: SU9000 manufactured by Hitachi High-Tech Corporation · Measuring conditions: Measuring conditions: 50×10 4 times, 15 kV

[0125] <Measurement of the BET specific surface area of the porous carbon> In accordance with JIS Z 8830, the specific surface area was analyzed by the BET method. · Measuring device: BELSORP-max manufactured by MicrotracBEL Corporation

[0126] <Measurement of the pore volume of the porous carbon> The measurement target was subjected to nitrogen adsorption measurement using a measuring device under the conditions of an adsorption temperature of 77 K and a relative pressure of 0.01 to 0.99, and the nitrogen adsorption amount was determined from the adsorption isotherm. Subsequently, using analysis software, the pore size distribution and pore volume were determined by the Barrett-Joyner-Halenda method (BJH method). Subsequently, in addition to the total pore volume V Total , the total volume V micro , the total volume V P2.9-5.2 , the total volume V P2.9-8.3 , the total volume V P10.0-62.0 , the total volume V of pores with a pore diameter of 2.0 nm or more and 62.0 nm or less in the nitrogen adsorption measurement P2.0-62.0 was calculated. · Measuring device: BELSORP-max manufactured by MicrotracBEL Corporation · Analysis software: BELMaster7.3.1.0

[0127] <Calculation of effective Pt mass ratio> First, the value of the particle volume V (nm 3 ) of the porous carbon is calculated by the following formula. Hereinafter, in the formula, d refers to the diameter d (nm) of the skeleton part of the porous carbon. V = (4π(d / 2) 3 ) / 3 Next, when platinum nanoparticles are supported on the mesopores of the skeleton part in the particle volume V of the porous carbon, the volume V ac (nm 3 ) at which the catalyst functions effectively is calculated by the following formula. V ac = V - (4π((d - 20) / 2) 3 ) / 3 Next, the value of the platinum mass A (g) that can be supported in pore A, which is a mesopore where the catalyst functions effectively, that is, pore A existing within 10.0 nm from the surface of the porous carbon, is calculated by the following formula. Hereinafter, in the formula, V P2.9-8.3 refers to the total volume (cm 3 / g) of pore A with a pore diameter of 2.9 nm or more and 8.3 nm or less. A = (V P2.9-8.3 × 10 21 × (V ac / V)) × 3.03 × 10 -19 / 50.26 Next, calculate the effective Pt mass ratio using the following formula. Effective Pt mass ratio (mass %) = (A / (A + 1)) × 100 Note that the calculation of the effective Pt mass ratio was performed based on the following assumptions. · The porous carbon with volume V is spherical with a radius of d. · Among the Pt particles supported on the mesopores, those that can effectively function in the battery reaction are the Pt particles supported in pore A within 10.0 nm from the surface of the porous carbon serving as the carrier. · The particle diameter of the Pt particles is 3.0 nm and uniform. · The mesopores on which Pt particles with a diameter of 3.0 nm are supported are cylindrical with a diameter of 4.0 nm. · The density of the platinum particles is 21.45 g / cm 3 Let it be.

[0128] (Example 2) (1) First step Into 60 g of pure water, an aqueous solution in which 3.84 g of a nonionic surfactant (a copolymer of polyethylene oxide (PEO) and polypropylene oxide (PPO) (trade name Pluronic (registered trademark) F127, structural formula: PEOm - PPOn - PEOm, m = 106, n = 70)) was dissolved was placed in a flask together with 2.42 g of phenol, 8.40 g of formaldehyde solution (formaldehyde concentration: 35 mass %), and 60.65 g of a 0.1 mol / L aqueous sodium hydroxide solution, and stirred with a stirrer at a speed of 200 rpm for 120 minutes at an internal temperature (heating temperature) of 50 °C to obtain a first processed product (1A). Also, an aqueous solution prepared by dissolving 3.84 g of a nonionic surfactant (a copolymer of polyethylene oxide (PEO) and polypropylene oxide (PPO) (trade name Pluronic (registered trademark) F127, structural formula: PEOm-PPOn-PEOm, m = 106, n = 70)) in 60 g of pure water was placed in a flask together with 2.42 g of phenol, 8.40 g of formaldehyde solution (formaldehyde concentration: 35% by mass), and 60.65 g of 0.1 mol / L aqueous sodium hydroxide solution, and stirred with a stirrer at a speed of 200 rpm at an internal temperature (heating temperature) of 68 °C for 120 minutes to obtain a first treated product (2B).

[0129] (2) Second step Next, 200 g of pure water was added to the first treated product (1A) obtained in (1) in the flask, the internal temperature (heating temperature) was adjusted to 75 °C, and stirred for 20 hours to obtain a sol solution (1A). Also, 200 g of pure water was added to the first treated product (2B) obtained in (1) in the flask, the internal temperature (heating temperature) was adjusted to 68 °C, and stirred for 20 hours to obtain a sol solution (2B). (2’) Multiple liquid mixing step The sol solution (1A) and sol solution (2B) prepared in (2) were put into one container in a ratio of 1:1 and mixed by stirring to obtain a mixed sol solution. (3) Gelation step The mixed sol solution prepared in (2’) was filtered through a 5 μm membrane filter, and the filtrate was collected. 700 g of pure water was added to 280 g of this filtrate (the total amount of the sol solution considering the evaporation component was 300 mL), placed in a stainless steel sealed container, and subjected to hydrothermal treatment at 130 °C for 48 hours to obtain a wet gel. It was filtered through a 5 μm membrane filter to collect the wet gel.

[0130] (4) Drying step The total amount of the wet gel obtained in (3) was put into 160 g of pure water, stirred with a high-speed stirrer at 2,000 rpm for 5 minutes, and further treated in an ultrasonic cleaner with an output of 70 W for 5 to 10 minutes to prepare a dispersion. This dispersion was spray-frozen granulated by spraying it into liquid nitrogen with a spray freeze granulator, and then put into a dedicated glass container cooled with liquid nitrogen, attached to a vacuum dryer, and vacuum-dried at about -40 °C for 60 hours to obtain granulated dry gel (porous phenolic resin).

[0131] (5) Carbonization step The dry gel obtained in (4) was put into a firing furnace, heated from room temperature to 330 °C to 360 °C at a heating rate of 1 °C / min under a nitrogen gas flow, maintained for a total of 4 hours, and then cooled to room temperature. Next, it was heated to 350 °C at a heating rate of 1 °C / min under a nitrogen gas flow, maintained for 2 hours, then heated to 600 °C at a heating rate of 1 °C / min again, and maintained for 2 hours. Then, it was put into a carbonization furnace, heated to 1000 °C at a heating rate of 1 °C / min under a pressurized nitrogen gas atmosphere, maintained for 2 hours, and then cooled to room temperature to obtain porous carbon as a carbonized product.

[0132] (Example 3) It was carried out in the same manner as in Example 2 except that the temperature conditions and the hydrothermal treatment time were as described in Table 1.

[0133] (Example 4) It was carried out in the same manner as in Example 1 except that the temperature conditions and the hydrothermal treatment time were as described in Table 1.

[0134] (Example 5) The temperature conditions and the hydrothermal treatment time were as described in Table 1, and the amount of phenol added in the step of obtaining the first processed product (2B) in the first step was 1.85 g, and the amount of formaldehyde solution was 6.41 g. Also, the conditions of the carbonization step were as described below. Otherwise, it was carried out in the same manner as in Example 2. (5) Carbonization step (Example 5) The dried gel obtained in (4) was placed in a firing furnace, heated from room temperature to 330 °C to 360 °C at a heating rate of 1 °C / min under a nitrogen gas flow, maintained for a total of 4 hours, and then cooled to room temperature. Next, it was heated from room temperature to 350 °C at a heating rate of 1 °C / min under a nitrogen gas flow, maintained for 2 hours, then heated from room temperature to 600 °C at a heating rate of 1 °C / min and maintained for 2 hours. Next, it was placed in a carbonization furnace, heated from room temperature to 1000 °C at a heating rate of 1 °C / min under a pressurized nitrogen gas atmosphere, maintained for 2 hours, then heated from room temperature to 1400 °C at a heating rate of 1 °C / min and maintained for 2 hours. Then, it was cooled to room temperature to obtain porous carbon as the carbide.

[0135] (Example 6) The temperature conditions and hydrothermal treatment time were as described in Table 1, and the amount of phenol added in the step of obtaining the first treated product (2B) in the first step was 1.85 g, and the amount of formaldehyde solution was 6.41 g. Otherwise, it was carried out in the same manner as in Example 2.

[0136] (Comparative Example 1) It was carried out in the same manner as in Example 1, except that the temperature conditions and hydrothermal treatment time were as described in Table 1.

[0137] (Comparative Example 2) The physical properties of Ketjenblack EC300J of Lion Specialty Chemicals Co., Ltd. were evaluated and used as a comparative example.

[0138] [Table 1]

[0139] In Table 1, the first step refers to the heating temperature of the first step, and the second step refers to the heating temperature of the second step. The hydrothermal treatment temperature refers to the hydrothermal treatment temperature of the gelation step, and the hydrothermal treatment time refers to the hydrothermal treatment time of the gelation step. The average skeletal diameter refers to the average diameter of the skeletal part of the porous carbon measured and calculated from the SEM image. The pore density is the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less in the SEM image formed in the skeletal part. Also, the total volume V micro 、total volume V P2.9-5.2, total volume V P2.9-8.3 , total volume V P10.0-62.0 is respectively the total volume of micropores, the total volume of pores with a pore diameter of 2.9 nm or more and 5.2 nm or less in nitrogen adsorption measurement, the total volume of pore A with a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement, and the total volume of pore B with a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement. Further, the pore A ratio is the ratio of the total volume of pores with a pore diameter of 62.0 nm or less in nitrogen adsorption measurement (total volume V micro + total volume V P2.0-62.0 ) to the total volume V P2.9-8.3 ((total volume V P2.9-8.3 / (total volume V micro + total volume V P2.0-62.0 )) × 100). The pore B ratio (1) is the ratio of the total volume of pores with a pore diameter of 62.0 nm or less in nitrogen adsorption measurement (total volume V micro + total volume V P2.0-62.0 ) to the total volume V P10.0-62.0 ((total volume V P10.0-62.0 / (total volume V micro + total volume V P2.0-62.0 )) × 100). The pore B ratio (2) is the ratio of the total volume V Total to the total pore volume V P10.0-62.0 ((total volume V P10.0-62.0 / V Total ) × 100).

[0140] Since the porous carbon of Example 1 was obtained under the conditions that the heating temperature in the first step was 73 °C or more and less than 78 °C, and the heating temperature in the second step was 67 °C or more and 72 °C or less, the average diameter of the skeleton part is 20.0 nm or more and 45.0 nm or less, the total volume V P2.9-8.3 is 0.060 cm 3 / g or more and 0.100 cm 3 / g or less, and the total volume V P10.0-62.0 is 0.100 cm 3 / g or more and 0.400 cm 3 / g or less. From this, it can be seen that the porous carbon obtained in Example 1 has a three-dimensional network structure through which water vapor generated in the battery reaction of the air electrode easily escapes, and has many pores suitable for supporting platinum or platinum alloy nanoparticles. Also, since the porous carbon of Example 4 was obtained under the conditions that the heating temperature in the first step was 50°C or higher and 58°C or lower, and the heating temperature in the second step was 73°C or higher and 78°C or lower, the obtained porous carbon has a three-dimensional network structure through which water vapor generated in the battery reaction of the air electrode easily escapes, and has many pores suitable for supporting platinum or platinum alloy nanoparticles. The porous carbons of Examples 2 to 3 and Examples 5 to 6 were obtained through the step of mixing the sol solution (1A) and the sol solution (2B) where the heating temperature in the first step was 50°C or higher and 90°C or lower, and the heating temperature in the second step was 55°C or higher and 92°C or lower. Therefore, the obtained porous carbon has a three-dimensional network structure through which water vapor generated in the battery reaction of the air electrode easily escapes, and has many pores suitable for supporting platinum or platinum alloy nanoparticles. On the other hand, since the porous carbon of Comparative Example 1 was obtained under the conditions that the heating temperature in the first step was 73°C or higher and less than 78°C, and the heating temperature in the second step was less than 67°C, the average diameter of the skeleton part exceeds 45.0 nm, and V P2.9-8.3 is 0.060 cm 3 / g or less, and the total volume V P10.0-62.0 is 0.100 cm 3 / g or less. From this, it can be seen that the porous carbon obtained in Comparative Example 1 does not have sufficient pores suitable for supporting platinum or platinum alloy nanoparticles. Also, for the Ketjen black of Comparative Example 2, although the total volume V P2.9-8.3 is more than 0.100 cm 3 / g, the pore density is extremely low at 5.8 pores / 10 4 nm 2 . Therefore, there are almost no pores suitable for supporting platinum or platinum alloy nanoparticles on the outer surface of the skeleton part where the catalyst functions effectively, and it can be seen that most of the pores suitable for supporting platinum or platinum alloy nanoparticles exist inside the skeleton part. Moreover, the Ketjen black of Comparative Example 2 has an STSA of 300 cm 3Since it exceeds / g, it is suggested that the pores inside the skeleton part may be connected. When platinum or platinum alloy nanoparticles are supported, there is a risk that the platinum or platinum alloy nanoparticles will easily aggregate and sinter. Therefore, it can be said that the Ketjen black of Comparative Example 2 does not have sufficient pores suitable for supporting platinum or platinum alloy nanoparticles.

[0141] <Measurement of Conductivity> Regarding the porous carbon obtained in Example 5, Example 6, and Comparative Example 1, and the Ketjen black EC300J of Comparative Example 2, compression was performed under a load of up to 20.0 MPa, and the conductivity was measured. The conductivity when the compression density of the porous carbon sample was 0.2 g / cm 3 is shown in Table 2.

[0142]

Table 2

[0143] The porous carbon obtained in Example 5 and Example 6 has a total volume V P10.0-62.0 of 0.100 cm 3 / g or more and 0.400 cm 3 / g or less, and has a dense three-dimensional network structure. Therefore, the conductive path is well developed and shows a high conductivity of 100 S / m or more. When manufacturing a cell of a polymer electrolyte fuel cell, by using porous carbon with high conductivity as the carbon carrier of the cathode catalyst, an effect of reducing the resistance of the electrodes constituting the cell can be expected. On the other hand, the porous carbon obtained in Comparative Example 1 has a developed three-dimensional network structure that forms a good conductive path, but the total volume V P10.0-62.0 is less than 0.100 cm 3 / g, and the gaps between the skeleton parts are not dense, so the conductivity is less than 100 S / m. Note that in Comparative Example 2, the total volume V P10.0-62.0 is 0.400 cm 3Since it exceeded / g, the gaps between the framework parts have a dense structure, but they do not form a developed three-dimensional network structure that serves as a good conductive path, so the conductivity was less than 10 S / m. When Example 5 and Example 6 were compared, the porous carbon obtained in Example 5 showed a higher conductivity. This is considered to be because the heat treatment at 1400 °C in the carbonization process improved the crystallinity of the porous carbon and reduced the micropores that become resistance components.

[0144] <Production of Catalyst for Cathode of Polymer Electrolyte Fuel Cell> 37 g of ultrapure water, 0.83 g of an aqueous solution of hexachloroplatinic(IV) acid (200 g / L in terms of platinum), and 1.96 g of sodium bisulfite were mixed in a flat-bottomed beaker. Next, after adding 150 g of ultrapure water, while dropping 15 mL of 30% hydrogen peroxide solution, a 5% aqueous sodium hydroxide solution was added using an automatic titrator to adjust the final pH of the mixed solution to 5 to obtain a colloidal solution. At this time, the dropping amount of the 5% aqueous sodium hydroxide solution when the pH was adjusted to 5 was 11.38 mL. 350 mL of ultrapure water was added to 9.7 mg of the porous carbon obtained in Example 1 and Comparative Example 1, and it was treated with a defoaming stirrer for 10 minutes and then with a homogenizer for 3 minutes. Then, it was boiled for 1.5 hours and cooled to room temperature while stirring. Next, 4.87 ml of the colloidal solution was added, heated to 50 °C over 20 minutes, held for 3 hours, and then cooled to room temperature. The obtained suspension was filtered, washed, and vacuum dried at 50 °C for 12 hours. The obtained powder was reduced at 300 °C under a hydrogen flow and cooled to room temperature to obtain a catalyst powder (catalyst for the cathode of a polymer electrolyte fuel cell).

[0145] <Measurement of Platinum Loading Amount of Catalyst for Cathode of Polymer Electrolyte Fuel Cell> The catalyst for the cathode of the polymer electrolyte fuel cell to be evaluated was burned in air to remove the porous carbon, and the platinum loading amount of the catalyst was calculated from the remaining platinum. The results are shown in Table 3. The platinum loading amount corresponds to the loading amount of platinum or platinum alloy nanoparticles, preferably 12.0 mass% or more and 40.0 mass% or less, more preferably 18.0 mass% or more and 40.0 mass% or less.

[0146] <Evaluation of Catalytic Activity> Using the cathode catalyst of the solid polymer fuel cell to be evaluated, the catalytic activity of the prepared catalyst was measured by the rotating electrode method. The catalyst powder was ultrasonically dispersed in an ethanol solution with a small amount of ultrapure water to prepare a catalyst ink. The catalyst ink was dropped onto a graphite disk with a diameter of 10 mm and dried in an ethanol vapor atmosphere. The dropping and drying of the ink were repeated several times so that the Pt loading became 5.0 μg / cm 2 (representative value). Next, a 5 wt% Nafion solution was dropped so that the Nafion film thickness after drying became 0.05 μm, dried at room temperature, and then put into an electric furnace maintained at 130 °C and solidified for 3 hours. The graphite disk coated with the catalyst fixed to a stainless steel rod was used as the working electrode and attached to a rotating electrode device. Then, the working electrode was immersed in a three-electrode cell made of Pyrex (registered trademark) filled with a 0.1 M perchloric acid electrolyte. After purging the electrolyte with nitrogen for 30 minutes, sweeping was repeated at a rate of 500 mV / s between 0.05 V and 1.0 V until the waveform change disappeared. Next, sweeping was performed at a rate of 50 mV / s between 0.05 V and 1.0 V to obtain a cyclic voltammogram, and the electrochemically active surface area (ECA) was determined from the area of the hydrogen adsorption wave. Next, the electrolyte was purged with oxygen for 30 minutes, and a convection voltammogram was obtained by sweeping at 5 mV / s between 0.25 V and 1.0 V. The mass activity (catalytic activity) was calculated from the Koutecky-Levich plot using the current values at 0.70 V, 0.75 V, 0.85 V, and 0.90 V of the obtained convection voltammogram. The results are shown in Table 3.

[0147]

Table 3

[0148] As shown in Table 3, the catalytic activity of the cathode catalyst of the solid polymer fuel cell obtained in Example 1 is higher than that of the cathode catalyst of the solid polymer fuel cell obtained in Comparative Example 1. That is, the porous carbon obtained in Example 1 can be more suitably used as a carrier for the cathode catalyst of the solid polymer fuel cell.

[0149] Incidentally, it is considered that the catalytic activity of the catalyst for the cathode of a polymer electrolyte fuel cell is related to the effective Pt mass ratio of the porous carbon. Although there is no significant difference in the actual platinum loading between Example 1 and Comparative Example 1, there is a difference in the values of the catalytic activity. Therefore, when the values of the respective catalytic activities were divided by the values of the effective Pt mass ratio, Example 1 and Comparative Example 1 showed almost the same values (Table 3 Catalytic activity / Effective Pt mass ratio). This result suggests the possibility that the catalytic activity of the catalyst for the cathode of a polymer electrolyte fuel cell is proportional to the effective Pt mass ratio of the porous carbon. A high effective Pt mass ratio means that mesopores are concentrated on the surface of the skeleton part of the porous carbon. Therefore, when the actual loading amount of platinum or platinum alloy nanoparticles is the same, it is considered that the catalytic activity of the catalyst for the cathode of a polymer electrolyte fuel cell is higher when using porous carbon with a high effective Pt mass ratio.

Explanation of Signs

[0150] 1 Porous carbon 2 Skeleton part 3 Pores in the SEM image formed in the skeleton part with a pore diameter of 3.0 nm or more and 10.0 nm or less 4 Gap between skeleton parts formed between two skeleton parts

Claims

**Claim 1** It has a three-dimensional network structure in which the skeletal part branches and connects in three-dimensional directions, the average diameter of the skeletal part is 20.0 nm or more and 45.0 nm or less, The total volume V of pore A with a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement Ｐ２．９－８．３ is 0.060 cm ３ / g or more and 0.100 cm ３ / g or less, and The total volume V of pore B with a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement Ｐ１０．０－６２．０ is 0.100 cm ３ / g or more and 0.400 cm ３ / g or less, and In the observation with a scanning electron microscope, the density of pores formed in the skeleton part, having a pore diameter of 3.0 nm or more and 10.0 nm or less, is 30.0 pieces / 10 ４ nm ２ or more and 120.0 pieces / 10 ４ nm ２ or less, and is a porous carbon characterized by this. **Claim 2** It contains a porous carbon carrier and platinum or platinum alloy nanoparticles supported in the pores of the porous carbon carrier, The porous carbon carrier has a three-dimensional network structure in which the skeleton part branches and connects in three-dimensional directions, the average diameter of the skeleton part is 20.0 nm or more and 45.0 nm or less, and the total volume V of pores A with a pore diameter of 2.9 nm or more and 8.3 nm or less in nitrogen adsorption measurement Ｐ２．９－８．３ is 0.060 cm ３ / g or more and 0.100 cm ３ / g or less, and the total volume V of pores B with a pore diameter of 10.0 nm or more and 62.0 nm or less in nitrogen adsorption measurement Ｐ１０．０－６２．０ is 0.100 cm ３ / g or more and 0.400 cm ３ / g or less, and in scanning electron microscope observation, the density of pores with a pore diameter of 3.0 nm or more and 10.0 nm or less formed in the skeleton part is 30.0 pieces / 10 ４ nm ２ or more and 120.0 pieces / 10 ４ nm ２ or less, and is a catalyst for the cathode of a polymer electrolyte fuel cell characterized by this.

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