JP2019212611A - Cathode, membrane electrode assembly, and battery - Google Patents

Abstract

To provide a cathode, a membrane electrode assembly and a battery, which have excellent durability.SOLUTION: A cathode (10) of a battery that includes an electrolyte membrane (20) includes: a first layer (11) including a carbon catalyst of 0.3 mg/cmor more and 9.0 mg/cmor less; and a second layer (12) disposed between the electrolyte membrane (20) and the first layer (11) in the battery, the second layer including platinum of 0.002 mg/cmor more and 0.190 mg/cmor less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cathode, a membrane electrode assembly, and a battery.

  At present, platinum catalysts are used as catalysts for fuel cell electrodes. However, there are many problems to be solved, such as the limited reserves of platinum and the high cost of the polymer electrolyte fuel cells (PEFC) due to the use of platinum. In particular, the PEFC cathode has a problem that a large amount of platinum catalyst is required to obtain sufficient power generation performance and durability. Further, the platinum catalyst has a problem that it is easily poisoned by adsorption of a gas such as carbon monoxide, sulfur dioxide, nitrogen monoxide, nitrogen dioxide. For this reason, the development of alternative technologies that do not use a platinum catalyst or reduce the amount of platinum catalyst used is being promoted.

  For example, Patent Document 1 discloses an electrode structure in which a layer A containing a catalyst and an ionomer and a layer B containing a catalyst and an ionomer are laminated, and the catalyst contained in the layer A contains 70% by weight or more of carbon. A cathode electrode structure for a fuel cell is described in which the catalyst contained in the layer B is 70% by weight or more of a platinum-supported carbon catalyst.

  Further, in Patent Document 2, an electrolyte layer, a fuel-side electrode that is disposed on one side in the thickness direction of the electrolyte layer and supplied with fuel, and a fuel-side electrode that is supplied on the other side in the thickness direction of the electrolyte layer are supplied with oxygen. A fuel cell comprising an oxygen side electrode and a fuel decomposition layer disposed between the electrolyte layer and the oxygen side electrode and decomposing the fuel that has passed through the electrolyte layer.

Japanese Patent Laid-Open No. 2006-015283 JP 2006-207575 A

  However, conventionally, the durability of the cathode of the fuel cell has not been sufficient.

  The present invention has been made in view of the above problems, and an object thereof is to provide a cathode, a membrane electrode assembly, and a battery having excellent durability.

A cathode according to an embodiment of the present invention for solving the above problems is a cathode of a battery including an electrolyte membrane, and includes a carbon catalyst of 0.3 mg / cm ² or more and 9.0 mg / cm ² or less. and one layer, the disposed between the electrolyte membrane and the first layer in the battery, 0.002 mg / cm ² or more, a second layer containing 0.190mg / cm ² or less of platinum, including. According to the present invention, a cathode having excellent durability is provided.

  The carbon catalyst contains iron and exhibits a weight loss rate of 12.0% by weight or less from 200 ° C. to 1200 ° C. as measured in a thermogravimetric analysis under a nitrogen atmosphere, and X-ray absorption at the K absorption edge of the iron In the microstructure analysis, the ratio of (a) and / or (b): (a) the normalized absorbance of 7130 eV to the normalized absorbance of 7110 eV is 7.0 or more; (b) 7135 eV relative to the normalized absorbance of 7110 eV It is good also as including the carbon structure which shows ratio of the normalization light absorbency of 7.0 or more.

The carbon catalyst may have a mesopore volume ratio with respect to the total pore volume of 20% or more. The carbon catalyst may have an iron content of 0.01% by weight or more as measured by inductively coupled plasma mass spectrometry. The carbon catalyst may have a nitrogen atom content of 1.0% by weight or more measured by elemental analysis by a combustion method. The said carbon catalyst is good also as showing 1.1% or more of the ratio of nitrogen atom content with respect to carbon atom content measured by the elemental analysis by a combustion method. The carbon catalyst may contain iron and a metal other than iron. The carbon catalyst may have a specific surface area measured by the BET method of 800 m ² / g or more.

  The first layer includes an electrolyte material, and the ratio of the weight of the electrolyte material to the remaining weight obtained by subtracting the weight of the electrolyte material from the weight of the first layer is 0.30 or more. Good. The second layer includes an electrolyte material, and the ratio of the weight of the electrolyte material to the remaining weight obtained by subtracting the weight of the electrolyte material from the weight of the second layer may be 0.05 or more. Good. The ratio of the platinum content in the second layer to the carbon catalyst content in the first layer may be 20.00 wt% or less. The first layer and / or the second layer may include an electrolyte material having an EW value of 300 or more and 1100 or less.

  In order to solve the above problems, a membrane electrode assembly according to an embodiment of the present invention includes any one of the cathodes, an anode, and an electrolyte membrane disposed between the cathode and the anode. According to the present invention, a membrane electrode assembly having excellent durability is provided.

  A battery according to an embodiment of the present invention for solving the above problems includes any one of the cathodes or the membrane electrode assembly. According to the present invention, a battery having excellent durability is provided. The battery may be a fuel cell.

  According to the present invention, a cathode, a membrane electrode assembly, and a battery having excellent durability are provided.

It is explanatory drawing which shows the cross section about the membrane electrode assembly which concerns on an example of one Embodiment of this invention. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having measured the weight reduction rate of the carbon catalyst by the thermogravimetric analysis. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having performed the X-ray absorption fine structure analysis of the K absorption edge of iron. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows an example of the result of having evaluated the carbon catalyst. In the Example which concerns on one Embodiment of this invention, it is explanatory drawing which shows the other example of the result of having evaluated the carbon catalyst. It is explanatory drawing which shows an example of the result of having evaluated durability in the Example which concerns on one Embodiment of this invention.

  Hereinafter, a cathode, a membrane electrode assembly, and a battery according to an embodiment of the present invention will be described. The present invention is not limited to the example shown in the present embodiment.

The cathode according to the present embodiment is a cathode of a battery including an electrolyte membrane, the first layer including a carbon catalyst of 0.3 mg / cm ² or more and 9.0 mg / cm ² or less, and the electrolyte in the battery. It is disposed between the membrane and the first layer, containing 0.002 mg / cm ² or more, a second layer containing 0.190mg / cm ² or less of platinum,.

  The membrane electrode assembly (hereinafter referred to as “MEA”) according to the present embodiment includes a cathode according to the present embodiment, an anode, and an electrolyte membrane disposed between the cathode and the anode. The battery according to the present embodiment includes the cathode according to the present embodiment or the MEA according to the present embodiment.

  The inventors of the present invention have intensively studied technical means for realizing a cathode, MEA, and battery having excellent durability. As a result, the cathode contains a carbon catalyst in an amount within a specific range. Excellent durability by including one layer, the first layer, and a second layer comprising platinum in an amount within a specified range, disposed between the MEA or the electrolyte membrane of the battery. I found out that sex was achieved.

  In FIG. 1, the cross section is shown about MEA1 which concerns on an example of this embodiment. In the present specification, the present embodiment will be described mainly with reference to the example shown in FIG. 1. However, FIG. 1 conceptually shows the structure of the MEA 1. The MEA 1 shown in FIG. 1 and the elements constituting the MEA 1 are not limited to specific aspects such as the size, shape, and positional relationship.

  As shown in FIG. 1, the MEA 1 includes a pair of gas diffusion layers 30, 50, an electrolyte membrane 20 disposed between the pair of gas diffusion layers 30, 50, one gas diffusion layer 30, The cathode 10 disposed between the electrolyte membrane 20, the other gas diffusion layer 50, and the anode 40 disposed between the electrolyte membrane 20 are included.

  That is, the cathode 10 is disposed between the electrolyte membrane 20 and the gas diffusion layer 30 in the MEA 1 or the battery. The cathode 10 includes a first layer (hereinafter referred to as “CC layer”) 11 containing a carbon catalyst and a second layer (hereinafter referred to as “Pt layer”) 12 containing platinum. That is, the cathode 10 includes a catalyst layer including a catalyst, and the catalyst layer includes a CC layer 11 and a Pt layer 12.

  In the cathode 10, the CC layer 11 and the Pt layer 12 are laminated. However, as described later, another layer may be included between the CC layer 11 and the Pt layer 12. The CC layer 11 is disposed between the gas diffusion layer 30 and the Pt layer 12 in the MEA 1 or the battery. That is, the cathode 10 includes the CC layer 11 at a position disposed between the gas diffusion layer 30 and the Pt layer 12 in the MEA 1 or the battery. The Pt layer 12 is disposed between the electrolyte membrane 20 and the CC layer 11 in the MEA 1 or the battery. That is, the cathode 10 includes the Pt layer 12 at a position disposed between the electrolyte membrane 20 and the CC layer 11 in the MEA 1 or the battery.

The CC layer 11 includes a carbon catalyst having an activity for catalyzing an oxygen reduction reaction (hereinafter referred to as “oxygen reduction activity”) in an amount within a specific range. That is, the CC layer 11 contains a carbon catalyst of 0.3 mg / cm ² or more and 9.0 mg / cm ² or less. The carbon catalyst content (mg / cm ² ) of the CC layer 11 is the weight (mg) of the carbon catalyst contained in the CC layer 11 per unit area (1 cm ² ) of the CC layer 11. Therefore, the carbon catalyst content (mg / cm ² ) of the CC layer 11 is the weight (mg) of the carbon catalyst contained in the CC layer 11 and the area of the CC layer 11 (in the example shown in FIG. It is obtained by dividing by the area) (cm ² ) of the surface 11b of the CC layer 11 facing the surface 30a of the layer 30.

The carbon catalyst content of the CC layer 11 is not particularly limited as long as it is within a range of 0.3 mg / cm ² or more and 9.0 mg / cm ² or less. For example, 0.4 mg / cm ² or more and 9.0 mg / Cm ² or less, 0.5 mg / cm ² or more, 9.0 mg / cm ² or less, or 0.5 mg / cm ² or more, 8.0 mg / cm ² or less. It may be 0.7 mg / cm ² or more and 8.0 mg / cm ² or less.

  When the carbon catalyst content of the CC layer 11 is within the above range, for example, excellent catalytic activity and durability can be achieved while maintaining the gas diffusion efficiency in the CC layer 11.

  The CC layer 11 may contain other catalysts, but the catalyst contained in the CC layer 11 is preferably mainly composed of a carbon catalyst. Carbon catalyst content with respect to catalyst content in CC layer 11 (when CC layer 11 contains other catalyst in addition to carbon catalyst, the total of the content of the carbon catalyst and the content of the other catalyst) The ratio is not particularly limited as long as the effect of the present invention is obtained, but may be, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. It is preferably 95% by weight or more.

  The specific catalyst content in the cathode 10 is, for example, that the specific catalyst is composed of a support (for example, a carbon support) and a catalyst component (for example, a metal catalyst such as platinum) supported on the support. If so, the content of the catalyst component.

  Other catalysts included in the CC layer 11 are not particularly limited as long as the effects of the present invention can be obtained. For example, a platinum-containing catalyst, a gold-containing catalyst, a ruthenium-containing catalyst, a rhodium-containing catalyst, a palladium-containing catalyst, and an iridium-containing catalyst. Or one or more selected from the group consisting of a manganese-containing catalyst and a cerium-containing catalyst. When the CC layer 11 includes a platinum-containing catalyst, the platinum-containing catalyst may be the same as or different from the platinum-containing catalyst included in the Pt layer 12.

  The CC layer 11 may not contain platinum. The CC layer 11 may not contain gold. The CC layer 11 may not contain ruthenium. The CC layer 11 may not contain rhodium. The CC layer 11 may not contain palladium. The CC layer 11 may not contain iridium. The CC layer 11 may not contain manganese. The CC layer 11 may not contain cerium. CC layer 11 is good also as not containing catalysts other than a carbon catalyst.

  The CC layer 11 may contain components other than the catalyst. That is, the CC layer 11 includes, for example, an electrolyte material. The electrolyte material is not particularly limited as long as it is a material having proton conductivity. For example, the electrolyte material is preferably one or more selected from the group consisting of an ionomer and an ionic liquid. The ionomer is preferably at least one selected from the group consisting of perfluorocarbon materials and hydrocarbon materials, for example. The perfluorocarbon material is preferably, for example, a perfluorocarbon sulfonic acid polymer. The perfluorocarbon sulfonic acid polymer is a perfluorocarbon material having a polytetrafluoroethylene skeleton and a sulfonic acid group. The hydrocarbon material is preferably, for example, a hydrocarbon sulfonic acid polymer. The hydrocarbon sulfonic acid polymer is a hydrocarbon material having a hydrocarbon skeleton and a sulfonic acid group.

  Specifically, as the electrolyte material, for example, one or more selected from the group consisting of NAFION (registered trademark), AQUIVION (registered trademark), ACIPLEX (registered trademark) and FREMION (registered trademark) is preferably used.

  The EW value of the electrolyte material included in the CC layer 11 is not particularly limited as long as the effect of the present invention can be obtained, but may be, for example, 300 or more and 1100 or less. In this case, the EW value of the electrolyte material is preferably 400 or more and 1100 or less, and particularly preferably 500 or more and 1100 or less. In addition, the EW value of the electrolyte material is equivalent weight (Equivalent Weight), and is the number of grams of the electrolyte material in a dry state per mole of the sulfonic acid group.

  The ratio of the weight of the electrolyte material contained in the CC layer 11 to the remaining weight obtained by subtracting the weight of the electrolyte material from the weight of the CC layer 11 (= weight of the electrolyte material contained in the CC layer 11 / (of the CC layer 11 Weight—weight of the electrolyte material included in the CC layer 11) (hereinafter referred to as “electrolyte material ratio” for the CC layer 11) is not particularly limited as long as the effect of the present invention is obtained. It is good also as being above. In this case, the electrolyte material ratio of the CC layer 11 is preferably 0.40 or more, more preferably 0.50 or more, and particularly preferably 0.60 or more.

  For example, when the CC layer 11 is composed of a carbon catalyst and an electrolyte material, the remaining weight of the CC layer 11 is the weight of the carbon catalyst, and thus the electrolyte material ratio of the CC layer 11 is It is the ratio of the weight of the electrolyte material to the weight of the carbon catalyst. For example, when the CC layer 11 is composed of a carbon catalyst, an electrolyte material, and other components, the remaining weight of the CC layer 11 is the sum of the weight of the carbon catalyst and the weight of the other components. (Ie, the total weight of the components other than the electrolyte material), the electrolyte material ratio of the CC layer 11 is the weight of the electrolyte material with respect to the total of the weight of the carbon catalyst and the weight of the other components. Is the ratio.

  The upper limit value of the electrolyte material ratio of the CC layer 11 is not particularly limited as long as the effect of the present invention is obtained, but the electrolyte material ratio may be 1.70 or less, for example, 1.60 or less. It is preferable that it is 1.50 or less.

  The electrolyte material ratio of the CC layer 11 may be specified by arbitrarily combining each of the above-described lower limit values and each of the above-described upper limit values. Specifically, the electrolyte material ratio of the CC layer 11 may be, for example, 0.30 or more and 1.70 or less, preferably 0.40 or more and 1.60 or less, and 0.50 or more. , 1.50 or less is more preferable, and 0.60 or more and 1.50 or less is particularly preferable.

  When the electrolyte material ratio of the CC layer 11 is within the above range, for example, excellent catalytic activity and durability can be achieved while maintaining the gas diffusion efficiency in the CC layer 11.

  The weight of the CC layer 11 (for example, when the CC layer 11 is composed of a carbon catalyst, an electrolyte material, and other components, the weight of the carbon catalyst, the weight of the electrolyte material, and the other components) The total ratio of the weight of the carbon catalyst contained in the CC layer 11 and the weight of the electrolyte material is not particularly limited as long as the effect of the present invention is obtained. It may be 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

  The CC layer 11 may contain other conductive materials besides the carbon catalyst. Other conductive materials are not particularly limited as long as the effects of the present invention can be obtained. For example, conductive carbon materials, conductive ceramics, titanium oxide, tin oxide, niobium-doped tin oxide, and antimony-doped One or more selected from the group consisting of tin oxide is preferable, and a conductive carbon material is particularly preferable. The conductive carbon material is not particularly limited as long as it is a carbon material having conductivity. For example, the conductive carbon material is selected from the group consisting of carbon black, graphite, carbon nanotube, carbon nanohorn, carbon fiber, carbon fibril, fullerene, and graphene. It is good also as being 1 or more types. The conductive ceramic is not particularly limited as long as it is a ceramic having conductivity. For example, the conductive ceramic is preferably one or more selected from the group consisting of alumina, silica, and cordierite.

  The CC layer 11 may include a water retention material. The water retention material is not particularly limited as long as the effect of the present invention can be obtained, but for example, silica is preferable. CC layer 11 is good also as not containing electroconductive materials other than a carbon catalyst. The CC layer 11 may not contain any carbon material other than the carbon catalyst. Further, the CC layer 11 may not include a water retention material.

  The remaining weight obtained by subtracting the weight of the electrolyte material from the weight of the CC layer 11 (for example, when the CC layer 11 is composed of a carbon catalyst, an electrolyte material, another conductive material, and a water retention material. The ratio of the weight of the carbon catalyst contained in the CC layer 11 to the weight of the carbon catalyst, the weight of the other conductive material, and the weight of the water retention material) is the effect of the present invention. Is not particularly limited, but may be, for example, 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and 80% by weight. % Or more is particularly preferable.

  The thickness of the CC layer 11 is not particularly limited as long as the effects of the present invention can be obtained, but may be, for example, 1 μm or more and 100 μm or less, preferably 3 μm or more and 80 μm or less, and preferably 5 μm or more and 60 μm. It is particularly preferred that

  The Pt layer 12 includes a platinum-containing catalyst. The platinum-containing catalyst is not particularly limited as long as it is a catalyst containing platinum and / or a platinum alloy. That is, the platinum-containing catalyst includes, for example, platinum particles and / or platinum alloy particles. The platinum-containing catalyst may include a support and platinum particles and / or platinum alloy particles supported on the support.

  In this case, the support is not particularly limited as long as the effect of the present invention is obtained. For example, the support is a carbon material, ceramics (for example, one or more selected from the group consisting of alumina, silica and cordierite), titanium oxide, oxidation It may be at least one selected from the group consisting of tin, niobium-doped tin oxide and antimony-doped tin oxide, and is preferably a carbon material.

  The carbon material is not particularly limited as long as the effect of the present invention can be obtained, but is preferably a conductive carbon material. Specifically, for example, carbon black (for example, ketjen black and / or vulcan), carbon It is preferably at least one selected from the group consisting of nanotubes, carbon fibers, graphite, graphite oxide, graphene and activated carbon. The platinum-containing catalyst may be platinum particles and / or platinum alloy particles that do not contain a support.

  The platinum alloy is not particularly limited as long as it is an alloy of platinum and another metal. For example, platinum is an alloy of platinum and one or more selected from the group consisting of nickel, cobalt, ruthenium, palladium, niobium, and iron. Preferably there is.

  The platinum-containing catalyst may be a core-shell type catalyst including a core composed of a metal other than platinum and a platinum alloy and a shell composed of platinum and / or a platinum alloy covering the core. The platinum-containing catalyst is a nanostructured thin film (NSTF) type catalyst including a base material (for example, whisker) composed of a metal other than platinum and a platinum alloy, and platinum and / or a platinum alloy laminated on the base material. There may be. The platinum-containing catalyst may be a catalyst including a nanoframe structure composed of platinum and / or a platinum alloy.

The Pt layer 12 contains platinum in an amount within a specific range. That, Pt layer 12, 0.002 mg / cm ² or more, including 0.190mg / cm ² or less platinum. The platinum content (mg / cm ² ) of the Pt layer 12 is the weight (mg) of platinum contained in the Pt layer 12 per unit area (1 cm ² ) of the Pt layer 12. Therefore, the platinum content (mg / cm ² ) of the Pt layer 12 is the same as the weight (mg) of platinum contained in the Pt layer 12, but the area of the Pt layer 12 (in the example shown in FIG. 1, the gas diffusion layer 30). It is obtained by dividing by the area of the surface 12a of the Pt layer 12 (cm ² ) facing the surface 20b of the electrolyte membrane 20 facing the surface. The weight of platinum contained in the Pt layer 12 is, for example, the weight of the platinum when the platinum-containing catalyst of the Pt layer 12 includes a carrier and platinum supported on the carrier. When the contained catalyst contains a platinum alloy, it is the weight of platinum contained in the platinum alloy.

Platinum content of Pt layer 12, 0.002 mg / cm ² or more, but not particularly limited as long as it is within a range of 0.190mg / cm ² or less, for example, 0.003 mg / cm ² or more, 0.190Mg / may be cm ² or less, 0.003 mg / cm ² or more, it may also be 0.170Mg / cm ² or less, 0.003 mg / cm ² or more, may be 0.150 mg / cm ² or less .

  When the platinum content of the Pt layer 12 is within the above-described range, for example, the catalytic activity of the cathode 10 is highly dependent on the platinum-containing catalyst of the Pt layer 12 and excellent catalytic activity and durability are achieved. can do.

  The Pt layer 12 may contain another catalyst, but the catalyst contained in the Pt layer 12 is preferably mainly composed of platinum. Catalyst content of the Pt layer 12 (in the case where the Pt layer 12 contains other catalyst in addition to the platinum-containing catalyst composed of the carrier and platinum supported on the carrier, platinum of the platinum-containing catalyst) The ratio of the platinum content of the Pt layer 12 to the total content of the other catalyst and the content of the other catalyst is not particularly limited as long as the effect of the present invention is obtained. The amount may be 50% by weight or more, more preferably 75% by weight or more, and particularly preferably 90% by weight or more.

  The other catalyst contained in the Pt layer 12 is not particularly limited as long as the effect of the present invention is obtained. For example, a carbon catalyst, a gold-containing catalyst, a ruthenium-containing catalyst, a rhodium-containing catalyst, a palladium-containing catalyst, an iridium-containing catalyst, It may be one or more selected from the group consisting of a manganese-containing catalyst and a cerium-containing catalyst. When the Pt layer 12 includes a carbon catalyst, the carbon catalyst is not particularly limited as long as it has oxygen reduction activity, and may be the same as or different from the carbon catalyst included in the CC layer 11. It may be a thing.

  The Pt layer 12 may not contain a carbon catalyst. The Pt layer 12 may not contain gold. The Pt layer 12 may not contain ruthenium. The Pt layer 12 may not contain rhodium. The Pt layer 12 may not contain palladium. The Pt layer 12 may not contain iridium. The Pt layer 12 may not contain manganese. The Pt layer 12 may not contain cerium. The Pt layer 12 may not contain any catalyst other than the platinum-containing catalyst.

  The Pt layer 12 may contain components other than the catalyst. That is, the Pt layer 12 includes, for example, an electrolyte material. The electrolyte material is not particularly limited as long as it is a material having proton conductivity. For example, the electrolyte material is preferably one or more selected from the group consisting of an ionomer and an ionic liquid. The ionomer is preferably at least one selected from the group consisting of perfluorocarbon materials and hydrocarbon materials, for example. The perfluorocarbon material is preferably, for example, a perfluorocarbon sulfonic acid polymer. The hydrocarbon material is preferably, for example, a hydrocarbon sulfonic acid polymer.

  Specifically, as the electrolyte material, for example, one or more selected from the group consisting of NAFION (registered trademark), AQUIVION (registered trademark), ACIPLEX (registered trademark) and FREMION (registered trademark) is preferably used.

  The EW value of the electrolyte material included in the Pt layer 12 is not particularly limited as long as the effect of the present invention is obtained, and may be, for example, 300 or more and 1100 or less. In this case, the EW value of the electrolyte material is preferably 400 or more and 1100 or less, and particularly preferably 500 or more and 1100 or less.

  Ratio of the weight of the electrolyte material contained in the Pt layer 12 to the remaining weight obtained by subtracting the weight of the electrolyte material from the weight of the Pt layer 12 (= weight of the electrolyte material contained in the Pt layer 12 / (of the Pt layer 12 Weight—weight of the electrolyte material contained in the Pt layer 12)) (hereinafter referred to as “electrolyte material ratio” for the Pt layer 12) is not particularly limited as long as the effect of the present invention is obtained. It may be there. In this case, the electrolyte material ratio of the Pt layer 12 is preferably 0.10 or more, and particularly preferably 0.15 or more.

  For example, when the Pt layer 12 is composed of a platinum-containing catalyst and an electrolyte material, the remaining weight of the Pt layer 12 is the weight of the platinum-containing catalyst (the platinum-containing catalyst is added to the carrier and the carrier). In the case of being composed of supported platinum, the ratio of the electrolyte material of the Pt layer 12 to the weight of the platinum-containing catalyst is the sum of the weight of the carrier and the weight of the platinum). It is the ratio of the weight of the material. For example, when the Pt layer 12 is composed of a platinum-containing catalyst, an electrolyte material, and other components, the remaining weight of the Pt layer 12 is the weight of the platinum-containing catalyst and the weight of the other components. Therefore, the ratio of the electrolyte material of the Pt layer 12 to the total of the weight of the platinum-containing catalyst and the weight of the other catalyst is It is the ratio of the weight of the catalyst.

  The upper limit value of the electrolyte material ratio of the Pt layer 12 is not particularly limited as long as the effect of the present invention can be obtained, but the electrolyte material ratio may be, for example, 1.40 or less, and 1.30 or less. Preferably, it is preferably 1.20 or less, particularly preferably 1.10 or less.

  The electrolyte material ratio of the Pt layer 12 may be specified by arbitrarily combining each of the above-described lower limit values and each of the above-described upper limit values. Specifically, the electrolyte material ratio of the Pt layer 12 may be, for example, 0.05 or more and 1.40 or less, preferably 0.05 or more and 1.30 or less, and 0.10 or more. 1.20 or less, more preferably 0.15 or more and 1.10 or less.

  When the electrolyte material ratio of the Pt layer 12 is within the above range, for example, excellent catalytic activity and durability can be achieved while maintaining the gas diffusion efficiency in the Pt layer 12.

  The weight of the Pt layer 12 (for example, when the Pt layer is composed of a platinum-containing catalyst, an electrolyte material, and other components, the weight of the platinum-containing catalyst, the weight of the electrolyte material, and the other components) The total ratio of the weight of the platinum-containing catalyst contained in the Pt layer 12 and the weight of the electrolyte material is not particularly limited as long as the effect of the present invention is obtained. % Or more, preferably 40% by weight or more, more preferably 60% by weight or more, and particularly preferably 80% by weight or more.

  The Pt layer 12 may include other conductive materials in addition to the platinum-containing catalyst. Other conductive materials are not particularly limited as long as the effects of the present invention can be obtained. For example, conductive carbon materials, conductive ceramics, titanium oxide, tin oxide, niobium-doped tin oxide, and antimony-doped One or more selected from the group consisting of tin oxide is preferable, and a conductive carbon material is particularly preferable. The conductive carbon material is not particularly limited as long as it is a carbon material having conductivity. For example, the conductive carbon material is selected from the group consisting of carbon black, graphite, carbon nanotube, carbon nanohorn, carbon fiber, carbon fibril, fullerene, and graphene. It is good also as being 1 or more types. The conductive ceramic is not particularly limited as long as it is a ceramic having conductivity. For example, the conductive ceramic is preferably one or more selected from the group consisting of alumina, silica, and cordierite.

  The Pt layer 12 may include a water retention material. The water retention material is not particularly limited as long as the effect of the present invention can be obtained, but for example, silica is preferable. The Pt layer 12 may not contain any carbon material other than the carbon catalyst. The Pt layer 12 may not include a conductive material other than the platinum-containing catalyst. Further, the Pt layer 12 may not contain a water retention material.

  The remaining weight obtained by subtracting the weight of the electrolyte material from the weight of the Pt layer 12 (for example, when the Pt layer 12 is composed of a platinum-containing catalyst, an electrolyte material, another conductive material, and a water retention material. The ratio of the weight of the platinum-containing catalyst contained in the Pt layer 12 to the total weight of the platinum-containing catalyst, the weight of the other conductive material, and the weight of the water retention material) is Although not particularly limited as long as the effects of the invention can be obtained, for example, it may be 20% by weight or more, preferably 40% by weight or more, and more preferably 60% by weight or more. 80% by weight or more is particularly preferable.

  The thickness of the Pt layer 12 is not particularly limited as long as the effects of the present invention can be obtained. For example, the thickness may be 0.1 μm or more and 50 μm or less, and preferably 0.5 μm or more and 20 μm or less. It is particularly preferably 1 μm or more and 10 μm or less.

In the cathode 10, the CC layer 11 and the Pt layer 12 have different catalyst compositions. That is, when the CC layer 11 contains the carbon catalyst in an amount equal to or higher than any one of the lower limit values (mg / cm ² ) described above, the carbon catalyst content of the Pt layer 12 may be less than the lower limit value. When the Pt layer 12 contains platinum in an amount equal to or higher than any one of the lower limit values (mg / cm ² ) described above, the platinum content of the CC layer 11 may be less than the lower limit value.

  When the ratio of the carbon catalyst content of the CC layer 11 to the catalyst content of the CC layer 11 is equal to or greater than any one of the lower limit values (% by weight) described above, the Pt layer 12 with respect to the catalyst content of the Pt layer 12 The proportion of the carbon catalyst content may be less than the lower limit. When the ratio of the platinum content of the Pt layer 12 with respect to the catalyst content of the Pt layer 12 is equal to or greater than any one of the lower limit values (% by weight) described above, the CC layer 11 with respect to the catalyst content of the CC layer 11 The ratio of the platinum content may be less than the lower limit.

  The catalyst of the cathode 10 is preferably mainly composed of a carbon catalyst and platinum. That is, the catalyst content of the cathode 10 (for example, when the cathode 10 is composed of the CC layer 11 and the Pt layer 12, the total of the catalyst content of the CC layer 11 and the catalyst content of the Pt layer 12) ) With respect to the total amount of the carbon catalyst content and the platinum content of the cathode 10 may be, for example, 50% by weight or more, preferably 80% by weight or more, and 90% by weight or more. It is particularly preferred.

  The carbon catalyst of the cathode 10 is preferably mainly composed of the carbon catalyst of the CC layer 11. That is, the carbon catalyst content of the cathode 10 (for example, when both the CC layer 11 and the Pt layer 12 include a carbon catalyst, the carbon catalyst content of the CC layer 11 and the carbon catalyst content of the Pt layer 12) The ratio of the carbon catalyst content of the CC layer 11 with respect to the total) may be, for example, 50% by weight or more, preferably 80% by weight or more, and particularly preferably 90% by weight or more. .

  The platinum of the cathode 10 is preferably composed mainly of platinum of the Pt layer 12. That is, with respect to the platinum content of the cathode 10 (for example, when both the CC layer 11 and the Pt layer 12 contain platinum, the total of the platinum content of the CC layer 11 and the platinum content of the Pt layer 12). The proportion of the platinum content in the Pt layer 12 may be, for example, 10% by weight or more, preferably 30% by weight or more, and particularly preferably 50% by weight or more.

  The oxygen reduction activity of the cathode 10 is preferably exerted mainly by the carbon catalyst contained in the CC layer 11. That is, the platinum content of the cathode 10 is preferably suppressed to such an extent that the oxygen reduction activity of the cathode 10 does not greatly depend on the platinum-containing catalyst of the cathode 10. Since platinum is more easily poisoned than a carbon catalyst, when the oxygen reduction activity of the cathode 10 is highly dependent on the platinum-containing catalyst, the performance of the battery is drastically reduced due to the poisoning of the platinum-containing catalyst. . On the other hand, when the oxygen reduction activity of the cathode 10 is mainly exerted by the carbon catalyst and does not depend greatly on the platinum-containing catalyst, even if the platinum-containing catalyst is poisoned, a sudden decrease in battery performance is avoided. Is done.

In this regard, the ratio of the platinum content (mg / cm ² ) in the Pt layer 12 to the carbon catalyst content (mg / cm ² ) in the CC layer 11 (hereinafter referred to as “Pt / CC ratio”) is as follows. For example, it may be 20.00% by weight or less.

  In this case, the Pt / CC ratio of the cathode 10 is preferably 7.00% by weight or less, more preferably 4.80% by weight or less, and even more preferably 3.80% by weight or less. It is particularly preferred that it is 2.80% by weight or less.

  The lower limit value of the Pt / CC ratio of the cathode 10 is not particularly limited as long as the effect of the present invention can be obtained, but the Pt / CC ratio may be, for example, 0.10% by weight or more. It is preferably 15% by weight or more.

  The Pt / CC ratio can be defined by arbitrarily combining each of the above-described lower limit values and each of the above-described upper limit values. Specifically, the Pt / CC ratio of the cathode 10 may be, for example, 0.10 wt% or more and 20.00 wt% or less, and is 0.15 wt% or more and 7.00 wt% or less. It is preferably 0.15% by weight or more and 4.80% by weight or less, more preferably 0.15% by weight or more and 3.80% by weight or less, and further preferably 0.15% by weight or less. The content is particularly preferably 2.80% by weight or less.

  In the cathode 10, the thickness of the Pt layer 12 may be smaller than the thickness of the CC layer 11. That is, the ratio of the thickness (μm) of the Pt layer 12 to the thickness (μm) of the CC layer 11 may be, for example, 1% or more and 99% or less, and 2% or more and 75% or less. Is preferably 2% or more and 50% or less.

  In the example of FIG. 1, the thickness of the CC layer 11 is such that the surface 11 a of the CC layer 11 facing the electrolyte membrane 20 direction (that is, the Pt layer 12 direction) and the gas diffusion layer 30 direction of the CC layer 11. The thickness of the Pt layer 12 is the distance between the Pt layer 12 and the gas diffusion layer 30 direction of the Pt layer 12 (ie, the CC layer 11 direction). ) Is the distance from the surface 12b facing.

  The Pt layer 12 covers part or all of the surface 11a of the CC layer 11 facing the electrolyte membrane 20 direction. In this regard, the Pt layer 12 may cover 30% or more of the area of the surface 11a of the CC layer 11 facing the electrolyte membrane 20, and preferably covers 70% or more, 90% or more. It is particularly preferable to cover

  The cathode 10 includes a CC layer 11 and a Pt layer 12 laminated on the CC layer 11, but between the CC layer 11 and the Pt layer 12, between the CC layer 11 and the gas diffusion layer 30, In addition, another layer disposed at one or more positions selected from the group consisting of the Pt layer 12 and the electrolyte membrane 12 may be further included. However, the catalyst layer of the cathode 10 is preferably mainly composed of the CC layer 11 and the Pt layer 12.

  The thickness of the catalyst layer of the cathode 10 (for example, when the catalyst layer of the cathode 10 is composed of the CC layer 11, the Pt layer 12, and other layers, the thickness of the CC layer 11 and the Pt layer) The total ratio of the thickness of the CC layer 11 and the thickness of the Pt layer 12 to the total thickness of 12 and the thickness of the other layer may be, for example, 50% or more, and 70% or more. It is preferable that it is 90% or more.

When the CC layer 11 includes the carbon catalyst in an amount (mg / cm ² ) within the specific range described above, the cathode 10 is between the CC layer 11 and the Pt layer 12 and between the CC layer 11 and the gas diffusion layer 30. And other layers having a carbon catalyst content outside the specific range, which are disposed at one or more positions selected from the group consisting of the Pt layer 12 and the electrolyte membrane 12. It's okay to not.

When the Pt layer 12 contains platinum in an amount (mg / cm ² ) within the specific range described above, the cathode 10 is between the CC layer 11 and the Pt layer 12, the CC layer 11, the gas diffusion layer 30, and the like. And other layers having a platinum content outside the specific range are disposed at one or more positions selected from the group consisting of the Pt layer 12 and the electrolyte membrane 12. It is good.

  The cathode 10 is at least one position selected from the group consisting of the CC layer 11 and the Pt layer 12, the CC layer 11 and the gas diffusion layer 30, and the Pt layer 12 and the electrolyte membrane 12. It is good also as not including the other layer (For example, the other layer containing a catalyst and electrolyte material) arrange | positioned in (1).

  The cathode 10 is at least one position selected from the group consisting of the CC layer 11 and the Pt layer 12, the CC layer 11 and the gas diffusion layer 30, and the Pt layer 12 and the electrolyte membrane 12. It is good also as not including the other layer (For example, the other layer which contains electrolyte material and does not contain a catalyst) arrange | positioned in (4).

  The cathode 10 is at least one position selected from the group consisting of the CC layer 11 and the Pt layer 12, the CC layer 11 and the gas diffusion layer 30, and the Pt layer 12 and the electrolyte membrane 12. It is good also as not including the other layer (For example, the other layer containing electrolyte material) arrange | positioned in (1). That is, in this case, the catalyst layer of the cathode 10 includes the CC layer 11 and the Pt layer 12.

  In the cathode 10, the distance between the CC layer 11 and the Pt layer 12 is preferably small. That is, the distance between the CC layer 11 and the Pt layer 12 (for example, in the example shown in FIG. 1, the surface 11a of the CC layer 11 facing the electrolyte membrane 20 and the surface of the Pt layer 12 facing the gas diffusion layer 30) The distance from 12b may be, for example, 20 μm or less, preferably 10 μm or less, and particularly preferably 5 μm or less.

  The CC layer 11 and the Pt layer 12 are preferably in contact with each other. That is, the surface 11a of the CC layer 11 facing the electrolyte membrane 20 and the surface 12b of the Pt layer 12 facing the gas diffusion layer 30 are preferably in contact with each other.

  The cathode 10 may be disposed on a substrate. In this case, the cathode 10 disposed on the substrate is disposed between the CC layer 11 containing the carbon catalyst in an amount within any one of the specific ranges described above, and between the CC layer 11 and the substrate. And a Pt layer 12 containing platinum in an amount within any one of the specific ranges disposed on the opposite side of the substrate relative to the CC layer 11. That is, in this case, a cathode structure including the base material and the cathode 10 disposed on the base material is formed.

  The substrate is not particularly limited as long as the MEA 1 including the cathode 10 or a battery can be manufactured. For example, the electrolyte membrane 20, the gas diffusion layer 30, or the transfer substrate is preferable.

  Specifically, the cathode 10 disposed on the gas diffusion layer 30 may include a CC layer 11 and a Pt layer 12 disposed on the opposite side of the gas diffusion layer 30 with respect to the CC layer 11. Good. The cathode 10 disposed on the electrolyte membrane 20 may include a CC layer 11 and a Pt layer 12 disposed between the CC layer 11 and the electrolyte membrane 20. Further, the cathode 10 disposed on the transfer substrate is the CC layer 11, the CC layer 11 and the transfer substrate, or the opposite side of the transfer substrate with respect to the CC layer 11. It is good also as including the Pt layer 12 arrange | positioned.

  When the cathode 10 is disposed on the transfer substrate, for example, the cathode 10 is first formed on the transfer substrate, and then the cathode 10 is manufactured in manufacturing the MEA 1 or the battery including the cathode 10. Is transferred from the transfer substrate to the electrolyte membrane 20 or the gas diffusion layer 30 included in the MEA 1 or the battery. The transfer substrate is not particularly limited as long as it enables transfer of the cathode 10 described above, but is preferably a resin film or a metal film, for example.

  The cathode 10 is manufactured by a method including forming the CC layer 11 and the Pt layer 12. The CC layer 11 is formed by applying and drying a composition containing a carbon catalyst and having fluidity (hereinafter referred to as “CC layer composition”). The Pt layer 12 is formed by applying and drying a flowable composition containing a platinum-containing catalyst (hereinafter referred to as “Pt layer composition”).

  That is, for example, first, a CC layer composition is applied and dried on a substrate (for example, the gas diffusion layer 30 or a transfer substrate) to form the CC layer 11, and then the Pt layer composition is formed on the CC layer 11. The material is applied and dried to form the Pt layer 12. Also, for example, first, a Pt layer composition is applied and dried on a substrate (for example, the electrolyte membrane 20 or a transfer substrate) to form the Pt layer 12, and then the CC layer composition is formed on the Pt layer 12. Is applied and dried to form the CC layer 11. In addition, for example, the CC layer composition is first applied and dried on a first substrate (for example, the gas diffusion layer 30 or a transfer substrate) to form the CC layer 11, while the second substrate ( For example, the Pt layer composition is applied and dried on the electrolyte membrane 20 or the transfer substrate) to form the Pt layer 12, and then the CC layer 11 and the Pt layer 12 are laminated. The first base material and the second base material may be pressure-bonded.

  The CC layer 11 may be formed by applying the CC layer composition only once, or by applying the CC layer composition a plurality of times (that is, by overcoating). May be. The carbon catalyst content of the CC layer composition and / or the amount and / or the number of times of application of the CC layer composition are such that the CC layer 11 finally formed is carbon in an amount within the specific range described above. It is adjusted to contain the catalyst.

  Similarly, the Pt layer 12 may be formed by applying the Pt layer composition only once, or may be formed by applying the Pt layer composition a plurality of times. The platinum content of the Pt layer composition and / or the amount and / or number of times of application of the Pt layer composition are determined so that the Pt layer 12 finally formed contains platinum in an amount within the specific range described above. Adjusted to include.

  When the cathode 10 includes other layers in addition to the CC layer 11 and the Pt layer 12, the method for manufacturing the cathode 10 further includes forming the other layers. Other layers are formed, for example, by application and drying of a fluid composition containing components corresponding to the composition of the other layers, like the CC layer 11 and the Pt layer 12.

  The surfaces 11a and 11b of the CC layer 11 and the surfaces 12a and 12b of the Pt layer 12 may be specified by these forming processes. That is, for example, when the CC layer composition is applied to the surface 30a of the gas diffusion layer 30 one or more times to form the CC layer 11, the surface formed by finally applying the CC layer composition is: The surface 11a of the CC layer 11 faces the electrolyte membrane 20 direction.

  In addition, for example, when the Pt layer 12 is first formed, and then the CC layer composition is applied one or more times to the position of the Pt layer 12 in the direction of the gas diffusion layer 30, the Pt layer 12 is formed. The surface of the layer formed by first applying the CC layer composition after the formation of 12 faces toward the Pt layer 12 is a surface 11a of the CC layer 11 facing toward the electrolyte membrane 20.

  The MEA 1 includes a cathode 10, an anode 40, and an electrolyte membrane 20 disposed between the cathode 10 and the anode 40. More specifically, the MEA 1 includes, for example, a pair of gas diffusion layers 30, 50, an electrolyte membrane 20 disposed between the pair of gas diffusion layers 30, 50, one gas diffusion layer 30, The cathode 10 disposed between the electrolyte membrane 20, the other gas diffusion layer 50, and the anode 40 disposed between the electrolyte membrane 20, and the cathode 10 includes the CC layer 11 And a Pt layer 20 disposed between the CC layer 11 and the electrolyte membrane 20.

  The gas diffusion layers 30 and 50 are not particularly limited as long as the gas diffusion layers 30 and 50 are porous bodies that enable supply of gas such as air to the cathode 10 and supply of fuel such as hydrogen to the anode 40. It may be a known gas diffusion layer used. The gas diffusion layers 30 and 50 may include, for example, carbon paper and / or carbon cloth.

  The gas diffusion layers 30 and 50 may include a microporous layer disposed between the cathode 10 and / or the anode 40 for the purpose of water management and the like. The microporous layer is not particularly limited as long as the effects of the present invention can be obtained, and may be a known microporous layer used for a gas diffusion layer included in a battery such as a fuel cell.

  The electrolyte membrane 20 is not particularly limited as long as it is a polymer membrane having proton conductivity, and may be a known electrolyte membrane used in a battery such as a fuel cell, but is preferably an ionomer membrane. The ionomer is preferably at least one selected from the group consisting of perfluorocarbon materials and hydrocarbon materials, for example. The perfluorocarbon material is preferably, for example, a perfluorocarbon sulfonic acid polymer. The hydrocarbon material is preferably, for example, a hydrocarbon sulfonic acid polymer.

  Specifically, as the electrolyte membrane 20, for example, one or more membranes selected from the group consisting of NAFION (registered trademark), AQUIVION (registered trademark), ACIPLEX (registered trademark) and FREMION (registered trademark) are preferably used. The The electrolyte membrane 20 is preferably a solid polymer electrolyte membrane.

  The thickness of the electrolyte membrane 20 is not particularly limited as long as the effect of the present invention can be obtained. For example, the thickness may be 1 μm or more and 100 μm or less, preferably 5 μm or more and 50 μm or less, and more preferably 8 μm or more and 30 μm. It is particularly preferred that

  The anode 40 is not particularly limited as long as it includes a catalyst having a fuel oxidation reaction activity and / or a microorganism having a fuel oxidation ability. The fuel supplied to the anode 40 is, for example, hydrogen, hydrocarbon compounds (for example, methane and / or ethane), alcohols (for example, methanol and / or ethanol), carboxylic acid compounds (for example, formic acid and / or acetic acid). , One or more selected from the group consisting of saccharides (eg, glucose), nitrogen-containing compounds (eg, ammonia and / or hydrazine), and other organic substances (eg, organic substances contained in sludge or industrial wastewater) Also good.

  The catalyst of the anode 40 is, for example, one or more selected from the group consisting of a platinum-containing catalyst, a ruthenium-containing catalyst, a rhodium-containing catalyst, a palladium-containing catalyst, an iridium-containing catalyst, a nickel-containing catalyst, a cobalt-containing catalyst, and an iron-containing catalyst. It is preferable. The microorganism of the anode 40 is not particularly limited as long as it has an ability to oxidize fuel.

The catalyst content of the anode 40 may be, for example, 0.001 mg / cm ² or more and 0.5 mg / cm ² or less, or 0.005 mg / cm ² or more and 0.3 mg / cm ² or less. Is preferred.

  The catalyst content in the anode 40 is, for example, that the catalyst contained in the anode 40 is composed of a carrier (for example, a carbon carrier) and a catalyst component (for example, a metal catalyst such as platinum) supported on the carrier. When comprised, it is content of the said catalyst component.

  The anode 40 may include an electrolyte material. As the electrolyte material, an electrolyte material similar to that contained in the cathode 10 described above is preferably used. The type of electrolyte contained in the catalyst layer of the anode 40 may be the same as or different from the electrolyte contained in the catalyst layer of the cathode 10 (for example, the CC layer 11 and / or the Pt layer 12).

  The battery includes a cathode 10 or MEA1. That is, the battery includes, for example, the cathode 10 and the anode 40. Specifically, the battery may include the cathode 10, the anode 40, and the electrolyte membrane 20 disposed between the cathode 10 and the anode 40.

  The battery includes, for example, a pair of separators and MEA 1 disposed between the pair of separators. In this case, the battery may include a single cell, and the single cell may include a pair of separators and the MEA 1 disposed between the pair of separators. The battery may include one or more single cells. That is, the battery may include one single cell or may include a plurality of single cells. The battery may include a plurality of stacked single cells.

  The separator is not particularly limited as long as it has corrosion resistance and conductivity and the effects of the present invention can be obtained, and may be a known separator used for a battery such as a fuel cell. Specifically, as the separator, for example, a carbon separator having corrosion resistance and conductivity is preferably used.

  The battery is not particularly limited as long as the effects of the present invention can be obtained. For example, the battery may be a fuel cell (for example, a polymer electrolyte fuel cell), an air cell, a redox flow cell, or a halogen cell. A battery is preferred, and a polymer electrolyte fuel cell (PEFC) is particularly preferred.

  In the MEA 1 or the battery, the distance between the CC layer 11 of the cathode 10 and the gas diffusion layer 30 is preferably small. That is, the distance between the CC layer 11 and the gas diffusion layer 30 (for example, in the example shown in FIG. 1, the surface 11b facing the gas diffusion layer 30 direction of the CC layer 11 and the electrolyte membrane 20 direction of the gas diffusion layer 30) The distance to the surface 30a facing the surface) may be, for example, 20 μm or less, preferably 10 μm or less, and particularly preferably 5 μm or less.

  In the MEA 1 or the battery, the CC layer 11 of the cathode 10 and the gas diffusion layer 30 are preferably in contact with each other. That is, it is preferable that the surface 11b of the CC layer 11 facing the gas diffusion layer 30 and the surface 30a of the gas diffusion layer 30 facing the electrolyte membrane 20 are in contact with each other.

  In the MEA 1 or the battery, the distance between the Pt layer 12 of the cathode 10 and the electrolyte membrane 20 is preferably small. That is, the distance between the Pt layer 12 and the electrolyte membrane 20 (for example, in the example shown in FIG. 1, the surface 12a facing the electrolyte membrane 20 direction of the Pt layer 12 and the Pt layer 12 direction of the electrolyte membrane 20) The distance from the surface 20b) may be, for example, 20 μm or less, preferably 10 μm or less, and particularly preferably 5 μm or less.

  In the MEA 1 or the battery, the Pt layer 12 of the cathode 10 is preferably in contact with the electrolyte membrane 20. That is, the surface 12a of the Pt layer 12 facing the electrolyte membrane 20 may be in contact with the surface 20b of the electrolyte membrane 20 facing the gas diffusion layer 30.

  The carbon catalyst contained in the CC layer 11 is not particularly limited as long as the effects of the present invention can be obtained. However, the weight loss rate from 200 ° C. to 1200 ° C. measured in thermogravimetric analysis under a nitrogen atmosphere contains iron. 12.0 wt% or less, and in the X-ray absorption fine structure analysis of the K absorption edge of the iron, the following (a) and / or (b): (a) the ratio of the normalized absorbance of 7130 eV to the normalized absorbance of 7110 eV It is particularly preferable that the specific carbon catalyst includes a carbon structure showing that (b) the ratio of the normalized absorbance of 7135 eV to the normalized absorbance of 7110 eV is 7.0 or more; . Note that the normalized absorbance in the XAFS analysis is an absorbance that has been normalized so that the absorbance before the absorption edge converges to 0 and the absorbance after the absorption edge converges to 1.

  The inventors of the present invention have intensively studied a technical means for obtaining a carbon catalyst for realizing a cathode, an MEA, and a battery having excellent durability. As a result, the present inventors have reduced the weight by thermogravimetric analysis including iron. In the X-ray absorption fine structure analysis of the K absorption edge of the iron, the carbon catalyst having a carbon structure that contains a large amount of iron in a specific state has the above-mentioned excellent durability. I found that I contributed to

  As will be described later, this carbon catalyst contains iron derived from the raw material for carbonization at the time of production. That is, the carbon catalyst contains iron in the interior due to the fact that the carbonization raw material contains iron. For this reason, even if a carbon catalyst is manufactured through the metal removal process mentioned later, a trace amount iron derived from a raw material remains in the inside of the carbon catalyst.

  Specifically, for example, when the carbon catalyst is in the form of particles, when the particles constituting the carbon catalyst are cut, iron is detected in the cross section of the particles exposed by the cutting. Iron contained in the carbon catalyst can be detected by, for example, inductively coupled plasma (ICP) emission spectrophotometry.

  The carbon catalyst exhibits a weight reduction rate of 12.0% by weight or less from 200 ° C. to 1200 ° C. as measured by thermogravimetric analysis (hereinafter referred to as “TG”) under a nitrogen atmosphere. The carbon catalyst preferably has a weight reduction rate of 11.0% by weight or less due to TG, more preferably 10.0% by weight or less, and even more preferably 9.0% by weight or less, It is particularly preferable to show 8.0% by weight or less.

  The carbon catalyst exhibiting the weight reduction rate below the specific threshold value contributes to the excellent durability of the carbon catalyst. That is, a small weight reduction rate of the carbon catalyst in the TG under a nitrogen atmosphere indicates that the carbon catalyst is thermally stable. The thermal stability of the carbon catalyst is considered to be caused by, for example, a large bond energy between atoms constituting the carbon structure of the carbon catalyst. For this reason, the thermally stable carbon catalyst is also electrochemically stable. The electrochemically stable carbon catalyst has high durability in applications such as fuel cells. Therefore, a carbon catalyst having a small weight reduction rate in TG under a nitrogen atmosphere exhibits excellent durability. Although the lower limit of the weight reduction rate of the carbon catalyst is not particularly limited, the weight reduction rate may be 1.0% by weight or more.

  Further, the carbon structure of the carbon catalyst shows (a) 7130/7110 ratio of 7.0 or higher, (b) 7135/7110 ratio of 7.0 or higher, or (a) in the XAFS analysis of the iron K absorption edge, or (a) 7130/7110 ratio is 7.0 or more and (b) 7135/7110 ratio is 7.0 or more. The 7130/7110 ratio and / or the 7135/7110 ratio of the carbon structure of the carbon catalyst is preferably 8.0 or more, more preferably 9.0 or more, and more preferably 10.0 or more. Even more preferred is 11.0 or greater. The upper limit values of the 7130/7110 ratio and the 7135/7110 ratio of the carbon catalyst are not particularly limited, but the 7130/7110 ratio and the 7135/7110 ratio may be 30.0 or less.

  When the carbon structure of the carbon catalyst exhibits a 7130/7110 ratio and / or a 7135/7110 ratio that are equal to or higher than the specific threshold in the XAFS analysis, it contributes to the excellent catalytic activity of the carbon catalyst. That is, in the XAFS analysis of the K absorption edge of iron, the peak energy after the K absorption edge indicates the energy at which the 1s orbital electron of the iron atom transitions to the antibonding orbital of the σ bond. Reflects binding energy. On the other hand, the peak before the K absorption edge shows that the 1s orbital electron of the iron atom has transitioned to the d orbital, which indicates that the iron atom has an asymmetric structure. Yes.

  Therefore, the high normalized absorbance of 7130 eV and 7135 eV indicates that the iron atom has two specific bonds showing energy corresponding to the 7130 eV and 7135 eV, and the normalized absorbance of 7110 eV is high. Indicates that the iron atom has an asymmetric structure. And in a carbon catalyst, it is thought that the iron atom which has the said specific 2 types of nonmetallic bond is functioning as one of the active sites. Therefore, a carbon catalyst having a carbon structure exhibiting a 7130/7110 ratio and / or a 7135/7110 ratio equal to or higher than the specific threshold in the XAFS analysis of the iron K absorption edge is an iron having the two specific nonmetallic bonds. By containing a relatively large number of atoms, it has excellent catalytic activity.

  Further, when the carbon structure of the carbon catalyst shows a 7130/7110 ratio and / or a 7135/7110 ratio within the range of the above specific threshold and 30.0 or less in the XAFS analysis of iron, in the carbon catalyst, The two specific non-metallic bonds of the iron atom and the asymmetric structure exist in a specific balance corresponding to the range. In this case, the carbon catalyst has an excellent catalytic activity by including an iron atom having the two specific non-metallic bonds and the asymmetric structure.

  The carbon catalyst contains iron, exhibits a weight loss rate equal to or less than the above-mentioned specific threshold value, and includes a carbon structure exhibiting a 7130/7110 ratio and / or a 7135/7110 ratio that is equal to or greater than the above-mentioned specific threshold value. It has activity and excellent durability.

  The carbon catalyst can be defined by arbitrarily combining each of the above-described threshold values of the weight loss rate and each of the above-described 7130/7110 ratio and / or each of the above-mentioned 7135/7110 ratio threshold values.

  Specifically, the carbon catalyst includes, for example, the carbon structure exhibiting the 7130/7110 ratio and / or the 7135/7110 ratio of 8.0 or more and exhibits the weight reduction rate of 11.0% by weight or less. More preferably, it contains a carbon structure exhibiting the above 7130/7110 ratio and / or the above 7135/7110 ratio of 9.0 or more, and more preferably 10.0% by weight or less. It is even more preferable that the carbon composition has the above 7130/7110 ratio and / or the above 7135/7110 ratio and has a weight reduction rate of 9.0% by weight or less. It is particularly preferable to include a carbon structure exhibiting the 7110 ratio and / or the 7135/7110 ratio and exhibit the weight reduction rate of 8.0% by weight or less.

  The carbon catalyst may have a mesopore volume ratio to the total pore volume (hereinafter referred to as “mesopore ratio”) of 20% or more. In this case, the mesopore ratio of the carbon catalyst is preferably 25% or more, and particularly preferably 30% or more. The upper limit value of the mesopore ratio of the carbon catalyst is not particularly limited, but the mesopore ratio may be, for example, 70% or less, and preferably 65% or less.

  The mesopore ratio of the carbon catalyst can be defined by arbitrarily combining the lower limit values and the upper limit values. That is, the mesopore ratio of the carbon catalyst is, for example, preferably 20% or more and 70% or less, more preferably 25% or more and 65% or less, and particularly preferably 30% or more and 65% or less. preferable.

In the present embodiment, the mesopores are pores having a diameter of 2 nm or more and 50 nm or less, and the mesopore volume (cm ³ / g) is the sum of the volumes of the mesopores. The micropores are pores having a diameter of less than 2 nm, and the micropore volume (cm ³ / g) is the sum of the volumes of the micropores. The macropores are pores having a diameter of more than 50 nm, and the macropore volume (cm ³ / g) is the sum of the macropore volumes. The total pore volume (cm ³ / g) is the sum of the micropore volume, the mesopore volume, and the macropore volume.

  The carbon catalyst may have an iron content of 0.01% by weight or more as measured by inductively coupled plasma mass spectrometry (hereinafter referred to as “ICP-MS”). In this case, the iron content of the carbon catalyst is particularly preferably 0.05% by weight or more.

  In addition, the iron content by ICP-MS of a carbon catalyst is computed as a ratio (weight%) of the weight of the iron atom with respect to the total weight of a carbon catalyst. Although the upper limit of the iron content of the carbon catalyst is not particularly limited, the iron content may be 10.00% by weight or less.

  A carbon catalyst is good also as showing the nitrogen atom content of 1.0 weight% or more measured by the elemental analysis by a combustion method. In this case, the carbon catalyst preferably exhibits a nitrogen atom content of 1.1% by weight or more by elemental analysis, and particularly preferably 1.2% by weight or more.

  The carbon catalyst exhibiting a nitrogen atom content by the elemental analysis that is equal to or higher than the specific threshold value indicates that the carbon catalyst contains a relatively large amount of nitrogen atoms. The upper limit of the nitrogen atom content by the elemental analysis of the carbon catalyst is not particularly limited, but the nitrogen atom content by the elemental analysis may be 10.0% by weight or less.

  The carbon catalyst has a nitrogen atom concentration of 1.0 atm% or more measured by X-ray photoelectron spectroscopy (hereinafter referred to as “XPS”), and a nitrogen atom content of 1.0 measured by elemental analysis by a combustion method. It is good also as showing weight% or more.

  In this case, the carbon catalyst preferably exhibits a nitrogen atom concentration of 1.1 atm% or more by XPS and a nitrogen atom content of 1.1% by weight or more by elemental analysis, and a nitrogen atom concentration by XPS of 1.2 atm% or more. And a nitrogen atom content of 1.2 wt% or more by elemental analysis is particularly preferred.

  The carbon catalyst exhibits the above-mentioned specific threshold value or more as the nitrogen atom concentration by XPS and the above-mentioned specific threshold value or more as the nitrogen atom content by the elemental analysis indicates that the carbon catalyst has a surface layer portion (several nm from the surface). Not only to the depth of the surface layer) but also to the inside (inside deeper than the surface layer part) contains the same amount of nitrogen atoms as the surface layer part, that is, relatively homogeneous carbon from the surface layer part to the inside. It reflects that it has a structure.

  And, since the carbon catalyst has a relatively homogeneous carbon structure from the surface layer portion to the inside in this way, for example, even when the active site of the surface layer portion is lost, the inner portion deeper than the surface layer portion. The function of these active sites effectively suppresses the decrease in the catalytic activity of the carbon catalyst.

  The nitrogen atom concentration by XPS of the carbon catalyst and the upper limit of the nitrogen atom content by elemental analysis are not particularly limited, but the nitrogen atom concentration by XPS is 10.0 atm% or less, and the nitrogen atom by elemental analysis The content may be 10.0% by weight or less.

  The carbon catalyst may have a ratio of nitrogen atom content to carbon atom content (hereinafter referred to as “N / C ratio by elemental analysis”) of 1.1% or more as measured by elemental analysis by a combustion method. Good. In this case, the carbon catalyst preferably exhibits an N / C ratio of 1.2% or more by elemental analysis, more preferably 1.3% or more, and more preferably 1.4% or more. It is particularly preferable to show 5% or more.

  The carbon catalyst exhibiting a specific threshold value or higher as the N / C ratio by the elemental analysis indicates that the carbon catalyst contains a relatively large amount of nitrogen atoms. The upper limit of the N / C ratio by elemental analysis of the carbon catalyst is not particularly limited, but may be 15.0% or less.

  The carbon catalyst has a nitrogen atom concentration ratio (hereinafter referred to as “NPS ratio by XPS”) of 1.1% or more, as measured by XPS, and is an elemental analysis by a combustion method. It is good also as showing N / C ratio 1.1% or more measured.

  In this case, the carbon catalyst preferably exhibits an N / C ratio of 1.2% or more by XPS and preferably an N / C ratio of 1.2% or more by elemental analysis, and the N / C ratio by XPS is 1.3%. More preferably, the N / C ratio by elemental analysis is 1.3% or more, more preferably, the XPS N / C ratio is 1.4% or more, and the N / C ratio by elemental analysis is 1.4%. More preferably, the N / C ratio by XPS is 1.5% or more, and the N / C ratio by elemental analysis is particularly preferably 1.5% or more.

  The carbon catalyst exhibits the above-mentioned specific threshold or more as the N / C ratio by XPS and the above-mentioned specific threshold or more as the N / C ratio by elemental analysis indicates that the carbon catalyst has its surface layer portion (several nm from the surface). It is reflected that nitrogen atoms in the same amount as that of the surface layer portion are included not only in the portion of the surface layer portion but also in the inside (inner portion deeper than the surface layer portion).

  And, since the carbon catalyst has a relatively homogeneous carbon structure from the surface layer portion to the inside in this way, for example, even when the active site of the surface layer portion is lost, the inner portion deeper than the surface layer portion. The function of these active sites effectively suppresses the decrease in the catalytic activity of the carbon catalyst.

  The upper limit of the N / C ratio by XPS and the N / C ratio by elemental analysis of the carbon catalyst is not particularly limited, but the N / C ratio by XPS is 15.0% or less and by the elemental analysis. The N / C ratio may be 15.0% or less.

  The carbon catalyst may contain iron and a metal other than iron (hereinafter referred to as “non-ferrous metal”). In this case, the non-ferrous metal contained in the carbon catalyst is not particularly limited as long as the above-described characteristics of the carbon catalyst are obtained, but is preferably a transition metal.

  In the present embodiment, the non-ferrous metal is a metal belonging to Group 3 to Group 12 of the periodic table, and is preferably a transition metal belonging to Group 4 to Group 12 of the periodic table. Specifically, the non-ferrous metal contained in the carbon catalyst is, for example, scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), Copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), Lanthanoids (for example, one or more selected from the group consisting of neodymium (Nd), samarium (Sm) and gadolinium (Gd)) and actinoids, or Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, lanthanoids (for example, one or more selected from the group consisting of Nd, Sm and Gd) and actinoids It may be Ranaru at least one selected from the group.

  The carbon catalyst preferably contains Fe and one or more non-ferrous metals selected from the group consisting of Ti, Cr, Zn, Nd, Sm, and Gd, and consists of Fe, Cr, Zn, and Gd. More preferably, it contains one or more non-ferrous metals selected from the group. In this case, the carbon catalyst may include, for example, Fe and Zn.

  When a carbon catalyst contains the said specific transition metal as a nonferrous metal, a carbon catalyst is good also as including another transition metal further. That is, for example, when the carbon catalyst includes Fe and one or more first non-ferrous transition metals selected from the group consisting of Ti, Cr, Zn, Nd, Sm, and Gd, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, a lanthanoid (for example, one or more selected from the group consisting of Nd, Sm and Gd) and a group consisting of actinoids, Or Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, a lanthanoid (for example, one or more selected from the group consisting of Nd, Sm and Gd) and A second nonferrous transition metal that is one or more selected from the group consisting of actinoids and different from the first nonferrous transition metal may be further included.

  The carbon catalyst may not contain platinum (Pt). In this case, the carbon catalyst is one selected from the group consisting of platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), gold (Au), and osmium (Os). It is good also as not including the above.

  When the carbon catalyst contains a non-ferrous metal derived from a carbonization raw material to be described later in addition to iron, the carbon catalyst has its iron and non-ferrous metal contained in the carbonization raw material. The iron and the non-ferrous metal are contained inside. That is, even when the carbon catalyst is manufactured through a metal removal process described later, a trace amount of the iron and non-ferrous metal remains in the carbon catalyst.

  Specifically, for example, when the carbon catalyst containing iron and non-ferrous metal is in the form of particles, when the particles constituting the carbon catalyst are cut, the iron and non-ferrous metals are detected in the cross section of the particles exposed by the cutting. The iron and non-ferrous metals contained in the carbon catalyst can be detected by, for example, inductively coupled plasma (ICP) emission spectrophotometry.

A carbon catalyst is good also as a specific surface area measured by BET method being 800 m < ² > / g or more. In this case, the specific surface area of the carbon catalyst by BET method using nitrogen gas is preferably 1000 m ² / g or more, particularly preferably 1200 m ² / g or more.

That the specific surface area of a carbon catalyst is more than the said specific threshold value contributes to the efficiency improvement of the chemical reaction by a carbon catalyst, and contributes to the outstanding catalyst activity. Although the upper limit of the specific surface area of the carbon catalyst is not particularly limited, the specific surface area may be 3000 m ² / g or less.

  A carbon catalyst is a carbon material that itself has catalytic activity (for example, oxygen reduction activity). This carbon material is a carbonized material obtained by carbonization of a raw material containing an organic substance and iron. That is, the carbon catalyst is a raw material carbonization material containing an organic substance and iron. Further, when the carbon catalyst is a carbonized material obtained by carbonization of a raw material containing an organic substance, iron and a non-ferrous metal, the carbon structure of the carbon catalyst includes the non-ferrous metal, but the catalytic activity of the carbon catalyst is It is thought that this is mainly due to iron and active sites contained in the carbon structure itself, rather than the non-ferrous metal.

  The carbon catalyst may be substantially free of organic compounds. That is, the content of the organic compound in the carbon catalyst may be, for example, 5% by weight or less, or 1% by weight or less.

  When the CC layer 11 includes the specific carbon catalyst described above, the Pt layer 12 may not include the specific carbon catalyst. In this case, the Pt layer 12 may include a carbon catalyst other than the specific carbon catalyst described above.

  When the CC layer 11 includes the specific carbon catalyst described above, the cathode 10 may not include the layer including the specific carbon catalyst. In this case, the cathode 10 may include a layer including a carbon catalyst other than the specific carbon catalyst described above.

  The method for producing the carbon catalyst is not particularly limited as long as the carbon catalyst having the above-described characteristics can be obtained. In the present embodiment, the method includes carbonizing a raw material containing an organic substance and iron under pressure. Will be described.

  The organic substance contained in the raw material is not particularly limited as long as it can be carbonized. That is, as the organic substance, for example, a high molecular weight organic compound (for example, a resin such as a thermosetting resin and / or a thermoplastic resin) and / or a low molecular weight organic compound is used. Moreover, you may use biomass as an organic substance.

  As the organic substance, a nitrogen-containing organic substance is preferably used. The nitrogen-containing organic substance is not particularly limited as long as it is an organic substance containing an organic compound containing a nitrogen atom in its molecule. When the carbon catalyst is a carbonized material of a raw material containing a nitrogen-containing organic material, the carbon structure of the carbon catalyst contains a nitrogen atom.

  Specifically, examples of the organic substance include polyacrylonitrile, polyacrylonitrile-polyacrylic acid copolymer, polyacrylonitrile-polymethyl acrylate copolymer, polyacrylonitrile-polymethacrylic acid copolymer, polyacrylonitrile-polymethacrylic acid. -Polymethallylsulfonic acid copolymer, polyacrylonitrile-polymethyl methacrylate copolymer, phenol resin, polyfurfuryl alcohol, furan, furan resin, phenol formaldehyde resin, melamine, melamine resin, epoxy resin, nitrogen-containing chelate resin ( For example, one or more selected from the group consisting of polyamine type, iminodiacetic acid type, aminophosphoric acid type and aminomethylphosphonic acid type), polyamideimide resin, pyrrole, polypyrrole, polyvinylpyrrole, 3 Methylpolypyrrole, acrylonitrile, polyvinylidene chloride, thiophene, oxazole, thiazole, pyrazole, vinylpyridine, polyvinylpyridine, pyridazine, pyrimidine, piperazine, pyran, morpholine, imidazole, 1-methylimidazole, 2-methylimidazole, quinoxaline, aniline, polyaniline , Succinic dihydrazide, adipic dihydrazide, polysulfone, polyaminobismaleimide, polyimide, polyvinyl alcohol, polyvinyl butyral, benzimidazole, polybenzimidazole, polyamide, polyester, polylactic acid, polyether, polyetheretherketone, cellulose, carboxymethylcellulose , Lignin, chitin, chitosan, pitch, lignite, silk, hair, polyami Acid, nucleic acid, DNA, RNA, hydrazine, hydrazide, urea, salen, polycarbazole, polybismaleimide, triazine, polyacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, polymethacrylic acid, polyurethane, polyamidoamine and polycarbodiimide One or more selected from the group consisting of:

  The content of the organic substance in the raw material is not particularly limited as long as the carbon catalyst can be obtained. For example, it may be 5% by mass or more and 90% by mass or less, and preferably 10% by mass or more and 80% by mass. % Or less.

  As iron contained in the carbonization raw material, the iron simple substance and / or the iron compound is used. Examples of the iron compound include one or more selected from the group consisting of iron salts, iron oxides, iron hydroxides, iron nitrides, iron sulfides, iron carbides, and iron complexes. It may be used.

  The content of iron in the raw material is not particularly limited as long as the carbon catalyst can be obtained. For example, the content of iron may be 0.001% by mass or more and 90% by mass or less, 0.002% by mass or more, It is preferable that it is 80 mass% or less.

  The raw material for carbonization may further include a non-ferrous metal. In this case, the raw material containing organic matter, iron and non-ferrous metal is carbonized under pressure. When a carbon catalyst is a carbonization material obtained by carbonization of the raw material containing organic substance, iron, and a nonferrous metal, a carbon catalyst contains the said iron and nonferrous metal. The non-ferrous metal contained in the raw material is not particularly limited as long as the characteristics of the carbon catalyst described above can be obtained, but is preferably a transition metal.

  In the present embodiment, the non-ferrous metal is a metal belonging to Group 3 to Group 12 of the periodic table, and is preferably a transition metal belonging to Group 4 to Group 12 of the periodic table. Specifically, the non-ferrous metal contained in the raw material is, for example, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, lanthanoid ( For example, one or more selected from the group consisting of Nd, Sm and Gd) and a group of actinoids, or Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo , Ag, lanthanoid (for example, one or more selected from the group consisting of Nd, Sm, and Gd) and one or more selected from the group consisting of actinoids.

  The raw material preferably contains Fe and at least one non-ferrous metal selected from the group consisting of Ti, Cr, Zn, Nd, Sm, and Gd. From the group consisting of Fe, Cr, Zn, and Gd It is more preferable to include one or more selected non-ferrous metals. In this case, the raw material may contain Fe and Zn.

  When the raw material contains the specific transition metal as a non-ferrous metal in addition to iron, the raw material may further contain another transition metal. That is, for example, when the raw material includes Fe and one or more first non-ferrous transition metals selected from the group consisting of Ti, Cr, Zn, Nd, Sm, and Gd, Sc, Ti, V, Cr, Mn , Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, a lanthanoid (for example, one or more selected from the group consisting of Nd, Sm, and Gd) and a group of actinoids Or Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, lanthanoid (for example, one or more selected from the group consisting of Nd, Sm and Gd) And a second non-ferrous transition metal that is one or more selected from the group consisting of actinides and different from the first non-ferrous transition metal.

  The raw material may not contain platinum (Pt). In this case, the raw material is one or more selected from the group consisting of platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), gold (Au), and osmium (Os). It is good also as not including.

  As the nonferrous metal contained in the raw material, a simple substance of the nonferrous metal and / or a compound of the nonferrous metal are used. Examples of non-ferrous metal compounds include non-ferrous metal salts, non-ferrous metal oxides, non-ferrous metal hydroxides, non-ferrous metal nitrides, non-ferrous metal sulfides, non-ferrous metal carbides, and non-ferrous metal complexes. It is good also as using 1 or more types selected from a group.

  The content of non-ferrous metals in the raw material (when using two or more non-ferrous metals, the total content of the two or more non-ferrous metals) is not particularly limited as long as the carbon catalyst can be obtained. For example, it may be 1% by mass or more and 90% by mass or less, and preferably 2% by mass or more and 80% by mass or less.

  Carbonization is performed by heating a raw material under pressure and holding at a temperature at which the raw material is carbonized (hereinafter referred to as “carbonization temperature”). The carbonization temperature is not particularly limited as long as the raw material is carbonized, and is, for example, 300 ° C. or higher. That is, in this case, the raw material containing the organic substance is carbonized at a temperature of 300 ° C. or higher under pressure.

  Moreover, carbonization temperature is good also as being 700 degreeC or more, for example, it is preferable that it is 900 degreeC or more, it is more preferable that it is 1000 degreeC or more, and it is especially preferable that it is 1100 degreeC or more. The upper limit value of the carbonization temperature is not particularly limited, but the carbonization temperature is, for example, 3000 ° C. or less.

  The rate of temperature rise to the carbonization temperature is, for example, 0.5 ° C./min or more and 300 ° C./min or less. The time for holding the raw material at the carbonization temperature is, for example, 1 second or more and 24 hours or less, and preferably 5 minutes or more and 24 hours or less. Carbonization is preferably performed in an inert gas atmosphere such as a nitrogen atmosphere. That is, the carbonization is preferably performed, for example, under the flow of an inert gas such as nitrogen gas.

  The pressure of the atmosphere in which carbonization is performed is not particularly limited as long as the pressure is higher than the atmospheric pressure. For example, the gauge pressure is 0.05 MPa or more. That is, in this case, the raw material containing the organic substance is carbonized under a pressure of a gauge pressure of 0.05 MPa or more.

  Furthermore, the pressure of the atmosphere in which carbonization is performed may be a gauge pressure of 0.10 MPa or more, 0.15 MPa or more, or 0.20 MPa or more.

  The method for producing a carbon catalyst may further include further processing the carbonized material obtained by the carbonization. That is, for example, metal removal treatment may be performed on the carbonized material. In this case, the method for producing a carbon catalyst includes carbonizing a raw material containing an organic substance under pressure, and then subjecting the carbonized material obtained by the carbonization to a metal removal treatment. A metal removal process is a process which reduces the quantity of the metal derived from the raw material contained in a carbonization material. The metal removal process is, for example, an acid cleaning process and / or an electrolytic process.

  Next, specific examples according to the present embodiment will be described.

[Catalyst Preparation Example 1]
1.0 g polyacrylonitrile (PAN), 1.0 g 2-methylimidazole, 6.0 g zinc chloride (ZnCl ₂ ), 0.18 g iron (III) chloride hexahydrate (FeCl _3. 6H ₂ O) and 30 g of dimethylformamide were mixed. The solvent was removed from the resulting mixture by drying. The dried mixture was heated in the atmosphere and infusibilized at 250 ° C. The mixture after infusibilization was carbonized by heating and maintaining at 1300 ° C. under a gauge pressure of 0.90 MPa in a nitrogen atmosphere.

  Dilute hydrochloric acid was added to the carbonized material obtained by carbonization and stirred. Thereafter, the suspension containing the carbonized material was filtered using a filtration membrane, and the carbonized material was washed with distilled water until the filtrate became neutral. In this way, the metal removal process by acid washing was performed.

  The carbonized material after the metal removal treatment was pulverized with a pulverizer until the median particle diameter became 1 μm or less. Thus, the pulverized carbonized material was obtained as the carbon catalyst of Catalyst Preparation Example 1.

[Catalyst Preparation Example 2]
A carbon catalyst of Catalyst Preparation Example 2 was obtained in the same manner as Catalyst Preparation Example 1 except that carbonization was performed under a gauge pressure of 0.20 MPa instead of 0.90 MPa.

[Catalyst Preparation Example 3]
Before infusibilization, a mixture containing 0.018 g of chromium chloride hexahydrate (CrCl ₃ · 6H ₂ O) was prepared, and the mixture was infusibilized in the same manner as in Catalyst Preparation Example 1 above. Thus, a carbon catalyst of Catalyst Preparation Example 3 was obtained.

[Catalyst Preparation Example 4]
A catalyst preparation example 4 was prepared in the same manner as catalyst preparation example 1 except that a mixture further containing 0.06 g of boric acid (B (HO) ₃ ) was prepared before infusibilization, and the mixture was infusible. Of carbon catalyst was obtained.

[Catalyst Preparation Example 5]
A carbon catalyst of Catalyst Preparation Example 5 was obtained in the same manner as Catalyst Preparation Example 1 except that 2.0 g of 2-methylimidazole was used instead of 1.0 g.

[Catalyst Preparation Example 6]
Catalyst preparation example 1 described above except that a mixture further containing 0.075 g of gadolinium nitrate hexahydrate (Gd (NO ₃ ) ₃ .6H ₂ O) was prepared before infusibilization, and the mixture was infusible. In the same manner as described above, a carbon catalyst of Catalyst Preparation Example 6 was obtained.

[Comparative Preparation Example 1]
1.0 g polyacrylonitrile (PAN), 1.0 g 2-methylimidazole, 6.0 g zinc chloride (ZnCl ₂ ), 0.18 g iron (III) chloride hexahydrate (FeCl _3. 6H ₂ O) and 30 g of dimethylformamide were mixed. The solvent was removed from the resulting mixture by drying. The dried mixture was heated in the atmosphere and infusibilized at 250 ° C. Carbonization was performed by heating and maintaining the infusible mixture at 1300 ° C. under normal pressure in a nitrogen atmosphere.

  Dilute hydrochloric acid was added to the carbonized material obtained by carbonization and stirred. Thereafter, the suspension containing the carbonized material was filtered using a filtration membrane, and the carbonized material was washed with distilled water until the filtrate became neutral. In this way, the metal removal process by acid washing was performed.

  The carbonized material after the metal removal treatment was pulverized with a pulverizer until the median particle diameter became 1 μm or less. Thus, the carbonized material after pulverization was obtained as the carbon catalyst of Comparative Preparation Example 1.

[Comparative Preparation Example 2]
A carbon catalyst of Comparative Preparation Example 2 was obtained in the same manner as Comparative Preparation Example 1 except that carbonization was performed at 1000 ° C. instead of 1300 ° C.

[Comparative Preparation Example 3]
A carbon catalyst of Comparative Preparation Example 3 was obtained in the same manner as Comparative Preparation Example 1 except that carbonization was performed at 800 ° C. instead of 1300 ° C.

[Comparative Preparation Example 4]
Under a nitrogen stream, 56.35 parts by mass of acrylonitrile was dissolved in a flask containing 280 mL of toluene, and then 0.75 part by mass of 2,2′-azobisisobutyronitrile was added. The mixture was heated to 60 ° C. and stirred and reacted for 3.5 hours. After confirming the occurrence of white precipitate, the reaction was terminated. Tetrahydrofuran was added to the reaction product and filtered, and the filtrate was washed with tetrahydrofuran and filtered and dried to obtain polyacrylonitrile particles.

  The obtained polyacrylonitrile particles were gradually heated from 190 ° C. and heat-treated in air at 230 ° C. for 1 hour to obtain an infusible polyacrylonitrile particle. The resulting infusibilized material is loaded with iron (II) chloride tetrahydrate so that the composition of iron atoms is 0.3% by mass, and the resulting polyacrylonitrile infusible material-iron (II) chloride is obtained. The tetrahydrate composition was heat-treated at 600 ° C. for 5 hours under a nitrogen stream, and then subjected to a dispersion treatment by a ball mill. Next, a particulate carbon catalyst (carbon catalyst of Comparative Preparation Example 4) was obtained by performing heat treatment (activation treatment) under an ammonia stream at 800 ° C. for 1 hour and at 1000 ° C. under an ammonia stream for 1 hour.

[Thermogravimetric analysis]
Using a differential thermal balance (TG-DTA2020SA, Bruker AXS Co., Ltd.), the weight reduction rate of the carbon catalyst was measured by TG in a nitrogen atmosphere. That is, an alumina container containing 10 mg of carbon catalyst was placed in the apparatus, and then the apparatus was held for 1 hour in a state where nitrogen (200 mL / min) was allowed to flow at room temperature. Thereafter, the carbon catalyst was heated from room temperature to 1200 ° C. at a rate of temperature increase of 10 ° C./min, and the weight loss rate from 200 ° C. to 1200 ° C. was measured. In order to remove the influence of water adsorbed on the carbon catalyst, the difference obtained by subtracting the weight of the carbon catalyst at 1200 ° C. from the weight of the carbon catalyst at 200 ° C. was divided by the weight of the carbon catalyst at 200 ° C. By multiplying the value by 100, the weight reduction rate (% by weight) of the carbon catalyst was obtained.

  Here, in FIG. 2, the measurement result of the weight reduction rate by TG of the carbon catalyst obtained in the catalyst preparation example 1 and the comparative preparation examples 2 and 4 is shown. In FIG. 2, the horizontal axis represents temperature (° C.), and the vertical axis represents TG weight reduction rate (%).

[X-ray absorption fine structure analysis]
XAFS analysis of the K absorption edge of iron contained in the carbon catalyst was performed. That is, XAFS analysis by hard X-ray was performed using the beam line BL5S1 of Aichi Synchrotron Light Center (Aichi Prefecture, Japan) (Ring: 1.2 GeV / 300.0 mA to 300.3 mA, Monochromator: Si ( 111), beam size: 0.50 mm × 0.30 mm, number of photons: 10 ¹⁰ @ 7000 eV, resolution (E / ΔE): 7000 @ 12 keV).

  Specifically, a sample prepared by packing and compressing a carbon catalyst, the amount of which was adjusted so that the edge jump (absorbance difference before and after the absorption edge) was 1, was measured by a permeation method. However, when the absorbance after the absorption edge (energy for exciting the electrons bound to the atomic orbitals to the lowest unoccupied state (absorption edge energy)) exceeds 4 when the edge jump is 1, The amount of the carbon catalyst was adjusted so that the edge jump was maximized in the range where the absorbance after the absorption edge did not exceed 4. If the amount of edge jump is 1 and the volume is too small to be suitable for measurement, a mixture obtained by adding boron nitride (BN) to a carbon catalyst was packed in a cylinder. The measurement range was 6813 eV to 8213 eV, the step width was 0.32 eV, and the measurement time was 0.06 seconds / point.

  In the analysis, “Athena” which is one of general XAFS analysis software was used. (Athena Demeter 0.9.24, copyright 2006-2015 Bruce Rave using Effect 1.2.12 copylight 2008 Matt Newville, Univ of Chicago).

The standardization was performed by inputting the following numerical values in the “Normalization and background removal parameters” column of “Main window” of the analysis software “Athena”. E ₀ : Energy when the first-order derivative of absorbance is maximized. Normalization order: 3. Pre-edge range: -150 to -30. Normalization range: 150 to 1000. Flatten normalized data: On. However, the condition was not changed from the default. The normalization is not particularly limited as long as the background before the absorption edge and the background after the absorption edge are drawn so as to pass through the center of the measurement data in each region.

  Here, FIG. 3 shows the carbon catalyst obtained in Catalyst Preparation Example 1 and Comparative Preparation Examples 1, 2, and 4 and powdered α-iron (iron powder, Japanese powder having an average particle diameter of 150 μm for comparison). The XAFS spectrum of an optical pure medicine industry company make) is shown. In FIG. 3, the horizontal axis indicates energy (eV), and the vertical axis indicates normalized absorbance.

[BET specific surface area, micropore volume, mesopore volume, macropore volume]
The specific surface area, micropore volume, mesopore volume, and macropore volume of the carbon catalyst were measured using a specific surface area / pore distribution measuring device (Tristar 3000, manufactured by Shimadzu Corporation).

That is, first, 0.1 g of a carbon catalyst was held at 100 ° C. and 6.7 × 10 ⁻² Pa for 3 hours to remove moisture adsorbed on the carbon catalyst. Next, the specific surface area (m ² / g) of the carbon catalyst was obtained from the nitrogen adsorption isotherm at 77 K by the BET method. The nitrogen adsorption isotherm at 77K was obtained by measuring the change in the amount of nitrogen adsorbed on the carbon material accompanying the change in the pressure of nitrogen gas at a temperature of 77K.

On the other hand, a macropore volume and a mesopore volume (cm ³ / g) were obtained from the nitrogen adsorption isotherm at a temperature of 77 K by the BJH method. Further, a point of P / P ₀ = 0.98 of the nitrogen adsorption isotherm at a temperature of 77K (P indicates a pressure at equilibrium, and P ₀ indicates a saturated vapor pressure (1.01 × 10 ⁵ Pa for 77K nitrogen). The total pore volume (cm ³ / g) was obtained by the amount of adsorption in (1). Furthermore, the micropore volume (cm ³ / g) was calculated by subtracting the sum of the macropore volume and the mesopore volume from the total pore volume. The mesopore ratio (%) was calculated by multiplying the value obtained by dividing the mesopore volume (cm ³ / g) by the total pore volume (cm ³ / g) by 100.

  The BJH method is a typical method for obtaining the distribution of mesopores proposed by Barrett, Joyner and Halenda (EP Barrett, LG Joyner and PP Halenda, J Am Chem Soc, 73, 373, (1951)). .

[Inductively coupled plasma mass spectrometry]
The iron content of the carbon catalyst was measured by ICP-MS. That is, 25 mg of the carbon catalyst was heated and held at 800 ° C. for 3 hours in an air atmosphere to remove non-metallic components in the carbon catalyst. Thereafter, the metal contained in the carbon catalyst was dissolved by immersing the carbon catalyst in 5 mL of concentrated hydrochloric acid. Then, distilled water was added and diluted so that the total weight might be 25g, and the metal solution was obtained. And the iron atom density | concentration of the obtained metal solution was measured using the sequential type plasma emission analyzer (ICP-8100, Shimadzu Corporation make).

  The value obtained by multiplying the iron atom concentration (mg / g) of the metal solution by the weight of the metal solution (25 g) and dividing the value by the weight of the carbon catalyst (25 mg) is multiplied by 100. Thus, the iron content (% by weight) of the carbon catalyst was calculated.

[X-ray photoelectron spectroscopy]
The carbon catalyst was analyzed by XPS. That is, using an X-ray photoelectron spectrometer (AXIS NOVA, manufactured by KRATOS), photoelectron spectra from the inner core levels of carbon atoms, nitrogen atoms and oxygen atoms on the surface of the carbon catalyst were measured. AlKα rays (10 mA, 15 kV, Pass energy 40 eV) were used as the X-ray source. In the obtained photoelectron spectrum, the binding energy was corrected so that the peak top of the C1s peak derived from the 1s orbit of the carbon atom was located at 284.5 eV.

  From the obtained photoelectron spectrum, a nitrogen atom concentration (atm%), a carbon atom concentration (atm%), and an oxygen atom concentration (atm%) were obtained. Further, the N / C ratio (%) by XPS was calculated by multiplying the value obtained by dividing the nitrogen atom concentration (atm%) by the carbon atom concentration (atm%) by 100.

[Elemental analysis]
Elemental analysis by combustion method of carbon catalyst was performed. That is, the nitrogen content of the carbon catalyst was measured by a combustion method using an organic trace element analyzer (2400II, Perkin Elmer Co., Ltd.). Using helium as a carrier gas, 2 mg of carbon catalyst was analyzed under the conditions of a combustion tube temperature of 980 ° C. and a reduction tube temperature of 640 ° C. Then, the nitrogen atom content (% by weight) of the carbon catalyst was calculated by multiplying the value obtained by dividing the weight of the nitrogen atom contained in the carbon catalyst by the total weight of the carbon catalyst by 100.

  Similarly, the value obtained by dividing the weight of carbon atom and the weight of hydrogen contained in the carbon catalyst by the total weight of the carbon catalyst is multiplied by 100 to obtain the carbon atom content (% by weight) and the hydrogen atom content ( % By weight) was calculated. Further, the value obtained by dividing the nitrogen atom content (% by weight) by the carbon atom content (% by weight) was multiplied by 100 to calculate the N / C ratio (%) by elemental analysis.

[Catalytic activity]
The catalytic activity of the carbon catalyst was measured using a rotating ring disk electrode device (RRDE-3A rotating ring disk electrode device ver. 1.2, manufactured by BAS Co., Ltd.) and a dual electrochemical analyzer (CHI700C, manufactured by ALS Co., Ltd.). ) And evaluated. That is, first, a tripolar rotating ring disk electrode device having a working electrode containing a carbon catalyst was produced. Specifically, 5 mg of a carbon catalyst, 50% of 5% Nafion (registered trademark) (manufactured by Sigma Aldrich, Nafion perfluorinated ion exchange resin, 5% solution (reference number: 510211)), 400 μL of water, and 100 μL of isopropyl alcohol Were mixed to prepare a slurry. Next, this slurry was subjected to ultrasonic treatment for 10 minutes, and then subjected to homogenizer treatment for 2 minutes. Then, the obtained slurry was mixed with a working electrode (ring disk electrode for RRDE-3A, platinum ring-gold disk electrode, disk diameter: 4 mm, BAS, so that the amount of carbon catalyst applied was 0.1 mg / cm ^2. The working electrode containing the said carbon catalyst was produced by apply | coating and drying.

  In addition, a platinum electrode (Pt counter electrode 23 cm, manufactured by BAS Co., Ltd.) is used as the counter electrode, and a reversible hydrogen electrode (RHE) (recumbent reversible hydrogen electrode, manufactured by EC Frontier Co., Ltd.) is used as the reference electrode. Using. Thus, a rotating ring disk electrode device having a working electrode containing a carbon catalyst, a platinum electrode as a counter electrode, and a reversible hydrogen electrode (RHE) as a reference electrode was obtained. Moreover, 0.1M perchloric acid aqueous solution was used as electrolyte solution.

And the catalyst activity using the said rotating ring disk electrode apparatus was measured. That is, linear sweep voltammetry (N ₂ -LSV) in a nitrogen atmosphere and linear sweep voltammetry (O ₂ ) in an oxygen atmosphere using a three-pole rotating ring disk electrode device having a working electrode containing a carbon catalyst. _2- LSV).

In N ₂ -LSV, nitrogen bubbling was first performed for 10 minutes to remove oxygen in the electrolytic solution. Thereafter, the electrode was rotated at a rotational speed of 1600 rpm, and the current density when the potential was swept at a sweep speed of 20 mV / sec was recorded as a function of the potential.

In O ₂ -LSV, oxygen bubbling was further performed for 10 minutes, and the electrolyte solution was filled with saturated oxygen. Thereafter, the electrode was rotated at a rotational speed of 1600 rpm, and the current density when the potential was swept at a sweep speed of 20 mV / sec was recorded as a function of the potential (O ₂ -LSV). Then, N ₂ -LSV was subtracted from O ₂ -LSV to obtain an oxygen reduction voltammogram. In the obtained oxygen reduction voltammogram, the numerical values were labeled so that the reduction current had a negative value and the oxidation current had a positive value.

From the oxygen reduction voltammogram obtained in this way, as one of the indices indicating the catalytic activity at the start of the durability test of the carbon catalyst, the current density i _0.7 ( _0.7 V (vs. NHE) applied) is applied. mA / cm ² ) was recorded.

[Example 1]
A CC layer containing a carbon catalyst was prepared. That is, first, 0.25 g of the carbon catalyst prepared in Catalyst Preparation Example 1, 3.5 g of a 5 wt% solution of ionomer having an EW value of 700, and 25 g of balls were put into a pot, and the ball mill was performed at 200 rpm for 50 minutes. The slurry CC layer composition containing the said carbon catalyst uniformly disperse | distributed was obtained by mixing by.

The obtained slurry-like CC layer composition was used in a gas diffusion layer (“29BC”, manufactured by SGL Carbon) (2.3 cm × 2.3 cm) having a carbon catalyst content of 2 on an area of 5 cm ² area. A CC layer containing a carbon catalyst and having an electrolyte material ratio of 0.7 was formed on the gas diffusion layer by applying and drying to 0.5 mg / cm ² .

  Further, a Pt layer containing platinum was produced. That is, platinum-supported carbon (hereinafter referred to as “Pt / C”) including a carbon support and platinum particles supported on the carbon support as a platinum-containing catalyst (UNPC40-II, manufactured by Ishifuku Metal Industry Co., Ltd.) 0 .25 g, 3.5 g of 5% by weight ionomer solution having an EW value of 700, 2.5 g of distilled water, and 25 g of balls are placed in a pot and mixed in a ball mill at 200 rpm for 50 minutes to uniformly A slurry-like Pt layer composition containing the dispersed Pt / C and having an electrolyte material ratio of 0.7 was obtained.

The obtained slurry-like Pt layer composition was placed on a solid polymer electrolyte membrane (NAFION (registered trademark) 211, manufactured by Dupont) (2.3 cm × 2.3 cm) in an area of 5 cm ² in area of platinum. A Pt layer containing platinum and having an electrolyte material ratio of 0.7 was formed on the solid polymer electrolyte membrane by applying and drying so that the amount was 0.050 mg / cm ² .

In addition, as Pt / C, the ratio of the weight of platinum contained in the Pt / C to the weight of the Pt / C is 40% by weight. The platinum content in the Pt layer was calculated by dividing the weight of platinum contained in Pt / C in the Pt layer by the area of the Pt layer. The area of the CC layer and the area of the Pt layer were both 5 cm ² , and therefore the area of the cathode catalyst layer composed of the CC layer and the Pt layer was also 5 cm ² .

On the other hand, an anode was produced. That is, 0.5 g of Pt / C, 10 g of 5 wt% NAFION (registered trademark) solution (manufactured by Aldrich), 2 g of distilled water, and 25 g of balls are put in a pot and mixed in a ball mill at 200 rpm for 50 minutes. Thus, a slurry-like anode composition was prepared. The slurry-like anode composition is applied onto a region having an area of 5 cm ² of the gas diffusion layer so that the content of Pt / C is 0.3 mg / cm ² and dried, whereby the gas diffusion layer is formed. An anode composed of a catalyst layer containing Pt / C was formed on the top.

  A pair of gas diffusion layers; a solid polymer electrolyte membrane disposed between the pair of gas diffusion layers; and a cathode disposed between one of the gas diffusion layers and the solid polymer electrolyte membrane. A MEA including the other gas diffusion layer and the anode disposed between the solid polymer electrolyte membrane and a single cell including the MEA were produced.

  That is, the surface where the CC layer formed on one gas diffusion layer is in contact with the Pt layer formed on the solid polymer electrolyte membrane and the Pt layer of the solid polymer electrolyte membrane is not formed And the anode formed on the other gas diffusion layer are in contact with each other at 150 ° C. and 1 MPa by pressing the solid polymer film between the pair of gas diffusion layers for 3 minutes, Produced. Next, a pair of gaskets was affixed to the MEA so as to sandwich the MEA, and the pair of gaskets were sandwiched by a pair of separators so that a single cell of a fuel cell was produced.

Then, the single cell produced as mentioned above was installed in the fuel cell automatic evaluation system (made by Toyo Corporation), and the power generation test was done. In the power generation test, first, with a back pressure of 20 kPa, air with 50% relative humidity (oxygen) is supplied to the cathode at 2.0 L / min and the anode is supplied with 50% relative humidity at 0.2 L / min. The cell temperature was set at 55 ° C. and the open circuit voltage was measured for 5 minutes. Thereafter, while the cell current density was changed from 1.5 A / cm ² to 0 A / cm ² , each current density was held for 3 minutes, and the cell voltage at each current density was measured. In this power generation test, the potential (mV) observed at a current density of 0.2 A / cm ² was recorded as the initial potential BOL (Beginning Of Life) as one of the indices indicating the catalytic activity at the start of the durability test. .

Next, a poisoning test was conducted. That is, first, for a single cell, a back pressure of 20 kPa and a relative humidity of 50% air (oxygen) are supplied to the cathode at 2.0 L / min, and a relative humidity of 50% hydrogen is supplied to the anode at 0.2 L / min. The cell temperature was set to 55 ° C. and a current density of 0.3 A / cm ² was maintained for 30 minutes. Thereafter, dry air (oxygen) containing 10 ppm of sulfur dioxide is supplied to the cathode at a back pressure of 20 kPa at 0.2 L / min, 50% relative humidity hydrogen is supplied to the anode at 0.2 L / min, and the cell temperature is set to 55. The temperature was set to 0 ° C. and a current density of 0.3 A / cm ² was maintained for 90 minutes. Furthermore, with a back pressure of 20 kPa, 50% relative humidity air (oxygen) is supplied to the cathode at 2.0 L / min, and 50% relative humidity hydrogen is supplied to the anode at 0.2 L / min, and the cell temperature is set to 55 ° C. Then, the current density of 0.3 A / cm ² was held for 30 minutes.

Thereafter, a current holding test (durability test) was performed. That is, for a single cell, saturated humidified air (oxygen) was supplied to the cathode at a back pressure of 70 kPa at 2.0 L / min, saturated humidified hydrogen was supplied to the anode at 0.5 L / min, and the cell temperature was 75 ° C. The current density was kept constant at 0.5 A / cm ² and this state was maintained for 100 hours.

Furthermore, immediately after the end of the 100-hour durability test, the power generation test was performed again, and the potential (mV) observed at a current density of 0.2 A / cm ² in the power generation test was determined as the catalyst after the end of the durability test. It recorded as electric potential EOL (End Of Life) which is one of the indexes showing activity.

Then, from the potential BOL (mV) observed at a current density of 0.2 A / cm ² in the power generation test at the start of the durability test, it was observed at a current density of 0.2 A / cm ² in the power generation test after the durability test. Further, a value obtained by reducing the EOL potential (mV) was obtained as a potential decrease amount (BOL-EOL) (mV) by the durability test for 100 hours.

[Example 2]
Except that the platinum content in the Pt layer was 0.020 mg / cm ² , cathodes, MEAs and single cells were produced in the same manner as in Example 1, and power generation tests, poisoning tests, and durability tests were performed.

[Example 3]
Except that the platinum content in the Pt layer was 0.005 mg / cm ² , a cathode, an MEA and a single cell were prepared in the same manner as in Example 1, and a power generation test, a poisoning test, and a durability test were performed.

[Example 4]
Except that the platinum content in the Pt layer was 0.100 mg / cm ² , a cathode, an MEA and a single cell were prepared in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed.

[Example 5]
Except that the content of the carbon catalyst in the CC layer was 1.0 mg / cm ² , the cathode, MEA and single cell were produced in the same manner as in Example 1, and the power generation test, poisoning test, and durability test were performed. .

[Example 6]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst content in the CC layer was 1.0 mg / cm ² and the platinum content in the Pt layer was 0.020 mg / cm ^2. Then, a power generation test, a poisoning test, and a durability test were performed.

[Example 7]
A cathode, an MEA and a single cell were produced in the same manner as in Example 1 except that the carbon catalyst content in the CC layer was 1.0 mg / cm ² and the platinum content in the Pt layer was 0.005 mg / cm ^2. Then, a power generation test, a poisoning test, and a durability test were performed.

[Example 8]
Except that the content of the carbon catalyst in the CC layer was 6.0 mg / cm ² , the cathode, the MEA and the single cell were produced in the same manner as in Example 1, and the power generation test, the poisoning test, and the durability test were performed. .

[Example 9]
Except that the electrolyte material ratio of the CC layer was 0.9, the cathode, MEA and single cell were produced in the same manner as in Example 1, and the power generation test, poisoning test, and durability test were performed.

[Example 10]
A cathode, an MEA and a single cell were prepared in the same manner as in Example 1 except that the electrolyte material ratio of the CC layer was 0.9 and the platinum content in the Pt layer was 0.020 mg / cm ² , A poisoning test and a durability test were conducted.

[Example 11]
Except that the electrolyte material ratio of the Pt layer was set to 0.5, the cathode, the MEA, and the single cell were produced in the same manner as in Example 1, and the power generation test, the poisoning test, and the durability test were performed.

[Example 12]
A cathode, an MEA, and a single cell were produced in the same manner as in Example 1 except that the electrolyte material ratio of the Pt layer was 0.5 and the platinum content in the Pt layer was 0.020 mg / cm ² . A poisoning test and a durability test were conducted.

[Example 13]
Except that the electrolyte material ratio of the Pt layer was set to 0.2, a cathode, MEA, and a single cell were produced in the same manner as in Example 1, and a power generation test, a poisoning test, and a durability test were performed.

[Example 14]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the electrolyte material ratio of the Pt layer was 0.2, and the platinum content in the Pt layer was 0.020 mg / cm ² . A poisoning test and a durability test were conducted.

[Example 15]
Except for using the carbon catalyst produced in Catalyst Preparation Example 2 as the carbon catalyst, a cathode, MEA, and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Example 16]
Except for using the carbon catalyst produced in Catalyst Preparation Example 3 as the carbon catalyst, a cathode, MEA and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Example 17]
Except for using the carbon catalyst produced in Catalyst Preparation Example 4 as the carbon catalyst, a cathode, MEA and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Example 18]
Except for using the carbon catalyst produced in Catalyst Preparation Example 5 as the carbon catalyst, a cathode, MEA, and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Example 19]
Except for using the carbon catalyst prepared in Catalyst Preparation Example 6 as the carbon catalyst, a cathode, MEA, and single cell were prepared in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Example 20]
Example of using Pt / C except that the weight ratio of platinum contained in the Pt / C to the weight of the Pt / C is 20% by weight (UNPC20-II, manufactured by Ishifuku Metal Industry Co., Ltd.) In the same manner as in Example 1, a cathode, MEA, and single cell were produced, and a power generation test, poisoning test, and durability test were performed.

[Example 21]
Except that the electrolyte material ratio of the Pt layer was 1.2, a cathode, an MEA and a single cell were produced in the same manner as in Example 1, and a power generation test, a poisoning test, and a durability test were performed.

[Example 22]
Except that the electrolyte material ratio of the Pt layer was set to 0.1, a cathode, MEA, and a single cell were produced in the same manner as in Example 1, and a power generation test, a poisoning test, and a durability test were performed.

[Example 23]
Except that the electrolyte material ratio of the CC layer was set to 0.5, the cathode, MEA, and single cell were produced in the same manner as in Example 1, and the power generation test, poisoning test, and durability test were performed.

[Comparative Example 1]
Except that the platinum content in the Pt layer was 0.200 mg / cm ² , a cathode, an MEA and a single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed.

[Comparative Example 2]
Except that the platinum content in the Pt layer was 0.001 mg / cm ² , a cathode, an MEA and a single cell were produced in the same manner as in Example 1, and a power generation test, a poisoning test, and a durability test were performed.

[Comparative Example 3]
A cathode, an MEA and a single cell were produced in the same manner as in Example 1 except that the platinum content in the Pt layer was 0.001 mg / cm ² and the carbon catalyst content in the CC layer was 1.0 mg / cm ^2. Then, a power generation test, a poisoning test, and a durability test were performed.

[Comparative Example 4]
Except that the Pt layer was not produced (the cathode did not contain the Pt layer), the cathode, MEA, and single cell were produced in the same manner as in Example 1, and the power generation test, poisoning test, and durability test were performed. .

[Comparative Example 5]
A cathode, MEA and single cell were prepared in the same manner as in Example 1 except that the Pt layer was not prepared (the cathode did not include the Pt layer) and the carbon catalyst content in the CC layer was 1.0 mg / cm ^2. Then, a power generation test, a poisoning test, and a durability test were performed.

[Comparative Example 6]
A cathode, an MEA and a single cell were produced in the same manner as in Example 1 except that the CC layer was not produced (the cathode did not contain the CC layer), and the platinum content in the Pt layer was 0.100 mg / cm ^2. A power generation test, a poisoning test, and a durability test were conducted.

[Comparative Example 7]
Except that the CC layer was not produced (the cathode did not contain the CC layer), the cathode, MEA, and single cell were produced in the same manner as in Example 1, and the power generation test, poisoning test, and durability test were performed. .

[Comparative Example 8]
A cathode, MEA, and single cell were prepared in the same manner as in Example 1 except that the CC layer was not prepared (the cathode does not include the CC layer) and the platinum content in the Pt layer was 0.020 mg / cm ^2. A power generation test, a poisoning test, and a durability test were conducted.

[Comparative Example 9]
Except that the content of the carbon catalyst in the CC layer was 10.0 mg / cm ² , a cathode, an MEA and a single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Comparative Example 10]
A cathode, an MEA and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst content in the CC layer was 10.0 mg / cm ² and the platinum content in the Pt layer was 0.020 mg / cm ^2. Then, a power generation test, a poisoning test, and a durability test were performed.

[Comparative Example 11]
Except that the content of the carbon catalyst in the CC layer was 0.2 mg / cm ² , the cathode, MEA and single cell were produced in the same manner as in Example 1, and the power generation test, poisoning test, and durability test were performed. .

[Comparative Example 12]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst content in the CC layer was 0.2 mg / cm ² and the platinum content in the Pt layer was 0.020 mg / cm ^2. Then, a power generation test, a poisoning test, and a durability test were performed.

[Comparative Example 13]
Except for using the carbon catalyst produced in Comparative Preparation Example 1 as the carbon catalyst, a cathode, MEA, and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Comparative Example 14]
Except for using the carbon catalyst produced in Comparative Preparation Example 2 as the carbon catalyst, a cathode, MEA, and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Comparative Example 15]
Except for using the carbon catalyst produced in Comparative Preparation Example 3 as the carbon catalyst, a cathode, MEA, and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[Comparative Example 16]
Except for using the carbon catalyst produced in Comparative Preparation Example 4 as the carbon catalyst, a cathode, MEA and single cell were produced in the same manner as in Example 1, and a power generation test, poisoning test, and durability test were performed. .

[result]
FIG. 4A shows catalyst preparation examples 1 to 6 (“Example 1” to “Example 6” in the figure) and Comparative Preparation Examples 1 to 4 (“Comparison 1” to “Comparison 4” in the figure). Regarding the carbon catalyst, the weight reduction rate (wt%) by TG, the normalized absorbance of 7110 eV, 7130 eV and 7135 eV, 7130/7110 ratio and 7135/7110 ratio by XAFS, and the current density i _{0. 7} (mA / cm ² ) is evaluated.

FIG. 4B shows the BET specific surface area (m ² / g), micropore volume (cm ³ / g), mesopores for the carbon catalysts obtained in Catalyst Preparation Examples 1-6 and Comparative Preparation Examples 1-4. Volume (cm ³ / g), Macropore volume (cm ³ / g), Mesopore ratio (%), Iron content (% by weight) by ICP-MS, Carbon atom concentration by XPS (atm%) , Oxygen atom concentration (atm%), nitrogen atom concentration (atm%) and N / C ratio (%), carbon atom content (% by weight) by elemental analysis (combustion method), hydrogen atom content (% by weight) The results of evaluating the nitrogen atom content (% by weight) and the N / C ratio (%) are shown.

As shown in FIG. 4A, the weight loss rate by TG of the carbon catalysts of Comparative Preparation Examples 2, 3, and 4 was 12.5% by weight or more. Moreover, 7130/7110 ratio and 7135/7110 ratio by XAFS of the carbon catalyst of Comparative Preparation Example 1 were 6.4 or less. The current density i _0.7 indicating the oxygen reduction activity of the carbon catalyst of Comparative Preparation Example 2 was −2.0 mA / cm ² , while that of the carbon catalyst of Comparative Preparation Examples 1, 3, and 4 was − was only ^{0.1mA / cm 2 ~-0.9mA /} cm 2.

On the other hand, in the carbon catalysts of Catalyst Preparation Examples 1 to 6, the weight reduction rate by TG is 7.3% by weight or less, and the 7130/7110 ratio and 7135/7110 ratio by XAFS are both 13.8 or more. Met. Then, the current density _{i 0.7} showing the oxygen reduction activity of the carbon catalyst of Catalyst Preparation Example 1-6 ^was reached -1.2mA / cm 2 ~-1.4mA / cm 2.

As shown in FIG. 4B, BET specific surface area of the carbon catalyst of Catalyst Preparation Example 1-6 is a 1440m ² / g or more, the micropore volume was 0.40cm ³ /g~0.52cm ³ / g, mesopore volume was 0.26cm ³ /g~0.50cm ³ / g, the macropore volume was 0.01cm ³ /g~0.02cm ³ / g, mesopores ratio, a 36% or more It was.

  The iron content of the carbon catalysts of Catalyst Preparation Examples 1 to 6 by ICP-MS was 0.21 wt% to 0.30 wt%. The carbon atom concentration by XPS of the carbon catalysts of Catalyst Preparation Examples 1 to 6 is 84.75 atm% to 90.74 atm%, the oxygen atom concentration is 7.24 atm% to 13.65 atm%, and the nitrogen atom concentration is 1. It was 42 atm% to 1.91 atm%, and the N / C ratio was 1.60% to 2.14%. In particular, the oxygen atom concentration by XPS of the carbon catalysts of Catalyst Preparation Examples 1 to 6 was larger than that of the carbon catalysts of Comparative Preparation Examples 1 to 4 (3.01 atm% to 5.85 atm%).

  The nitrogen atom content of the carbon catalysts of Catalyst Preparation Examples 1 to 6 by elemental analysis is 87.30 wt% to 98.62 wt%, and the hydrogen atom content is 0.43 wt% to 1.74 wt%. The nitrogen atom content was 1.47% by weight to 1.98% by weight, and the N / C ratio was 1.58% to 2.18%.

  FIG. 5 shows the conditions relating to the carbon catalyst contained in the CC layer, the conditions relating to platinum contained in the Pt layer, and the battery including the cathode for the cathodes manufactured in Examples 1 to 23 and Comparative Examples 1 to 16. The result of a power generation test and a durability test is shown.

Specifically, as for the carbon catalyst, it was prepared in any one of Catalyst Preparation Examples 1 to 6 and Comparative Preparation Examples 1 to 4 (in the figure, “Example 1” to “Example 6” are catalyst preparation examples 1 to 6). “Comparative Example 1” to “Comparative 4” represent Comparative Preparation Examples 1 to 4, and the content in the CC layer (“catalyst content (mg / cm ² )” in the figure), and the CC layer The ratio of the weight of platinum contained in the Pt / C to the weight of Pt / C (“Pt / carrier” in the figure) (“Pt / (Pt / Support)) (% by weight), content in the Pt layer (“catalyst content (mg-Pt / cm ² )” in the figure), and electrolyte material ratio in the Pt layer are shown. , BOL (mV), EOL (mV), and potential decrease amount ("BOL-EOL" in the figure) (mV ).

As shown in FIG. 5, the CC layer the content of the carbon catalyst is ^{1.0mg / cm 2 ~6.0mg / cm 2} , the content of platinum 0.005mg ^/ cm ² ~0.100mg ^/ cm 2 In Examples 1 to 23 using a cathode composed of a Pt layer, an initial potential (BOL) of 700.2 mV to 760.6 mV was achieved in a power generation test, and durability including a subsequent poisoning test The potential drop (BOL-EOL) in the test was suppressed to 27.4 mV to 58.0 mV. That is, in Examples 1 to 23, in addition to achieving a high initial potential, remarkable durability was achieved.

In contrast, Comparative Example platinum content of Pt layer was 0.200 mg / cm ² 1, comparative platinum content of Pt layer was 0.001 mg / cm ² Examples 2 and 3, includes a Pt layer Comparative Examples 4 and 5 using no cathode, Comparative Examples 6 to 8 using a cathode not including the CC layer, Comparative Examples 9 and 10 in which the carbon catalyst content of the CC layer was 10.0 mg / cm ² , CC For Comparative Examples 11 and 12 where the carbon catalyst content of the layer was 0.2 mg / cm ² and Comparative Examples 13 to 16 using the carbon catalysts of Comparative Preparation Examples 1 to 4, the initial potential (BOL) of the power generation test Was 446.8 mV to 716.4 mV, and the potential drop (BOL-EOL) in the durability test was 66.9 mV to 251.5 mV. That is, the durability shown in Comparative Examples 1 to 16 was lower than that of Examples 1 to 23, and a high initial potential was not necessarily achieved.

The cathode, MEA, and battery according to the present invention were confirmed to have excellent durability. Further, as described above, since the durability test was performed following the poisoning test, it was confirmed that the cathode, MEA, and battery according to the present invention also have excellent poisoning resistance. Furthermore, from the results of the power generation test, it was confirmed that the cathode, MEA and battery according to the present invention also have excellent power generation performance.

Claims (15)

A cathode of a battery including an electrolyte membrane,
A first layer comprising a carbon catalyst of 0.3 mg / cm ² or more and 9.0 mg / cm ² or less;
Wherein disposed between the electrolyte membrane and the first layer in the battery, 0.002 mg / cm ² or more, a second layer containing 0.190mg / cm ² or less of platinum,
Including cathode. The carbon catalyst includes iron,
The weight loss rate from 200 ° C. to 1200 ° C. measured in thermogravimetric analysis under a nitrogen atmosphere is 12.0% by weight or less,
In the X-ray absorption fine structure analysis of the iron K absorption edge, the following (a) and / or (b):
(A) the ratio of the normalized absorbance at 7130 eV to the normalized absorbance at 7110 eV is 7.0 or greater;
(B) the ratio of the normalized absorbance at 7135 eV to the normalized absorbance at 7110 eV is 7.0 or greater;
The cathode of claim 1, comprising a carbon structure exhibiting   The cathode according to claim 1 or 2, wherein the carbon catalyst has a ratio of mesopore volume to total pore volume of 20% or more.   The cathode according to any one of claims 1 to 3, wherein the carbon catalyst has an iron content measured by inductively coupled plasma mass spectrometry of 0.01 wt% or more.   The cathode according to any one of claims 1 to 4, wherein the carbon catalyst exhibits a nitrogen atom content of 1.0 wt% or more as measured by elemental analysis by a combustion method.   The cathode according to any one of claims 1 to 5, wherein the carbon catalyst exhibits a ratio of nitrogen atom content to carbon atom content of 1.1% or more as measured by elemental analysis by a combustion method.   The cathode according to any one of claims 1 to 6, wherein the carbon catalyst contains iron and a metal other than iron. The cathode according to any one of claims 1 to 7, wherein the carbon catalyst has a specific surface area measured by a BET method of 800 m ² / g or more. The first layer includes an electrolyte material;
The cathode according to any one of claims 1 to 8, wherein a ratio of a weight of the electrolyte material to a remaining weight obtained by subtracting a weight of the electrolyte material from a weight of the first layer is 0.30 or more. The second layer includes an electrolyte material;
The cathode according to any one of claims 1 to 9, wherein a ratio of a weight of the electrolyte material to a remaining weight obtained by subtracting a weight of the electrolyte material from a weight of the second layer is 0.05 or more.   The cathode according to any one of claims 1 to 10, wherein a ratio of the platinum content in the second layer to the carbon catalyst content in the first layer is 20.00 wt% or less.   The cathode according to any one of claims 1 to 11, wherein the first layer and / or the second layer includes an electrolyte material having an EW value of 300 or more and 1100 or less.   A membrane electrode assembly comprising the cathode according to any one of claims 1 to 12, an anode, and an electrolyte membrane disposed between the cathode and the anode.   A battery comprising the cathode according to claim 1 or the membrane electrode assembly according to claim 13. The battery according to claim 14, which is a fuel cell.

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