JP6630457B2 - Cathode, membrane electrode assembly and battery - Google Patents

Description

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

  Currently, platinum catalysts are used as electrode catalysts for fuel cells. However, there are many problems to be solved, such as the limited amount of platinum reserve, and the use of platinum in a polymer electrolyte fuel cell (PEFC) increases the cost. Particularly, in the cathode of the PEFC, there is a problem that a large amount of a platinum catalyst is required to obtain sufficient power generation performance and durability. In addition, the platinum catalyst has a problem that it is easily poisoned by adsorbing gases such as carbon monoxide, sulfur dioxide, nitrogen monoxide, and 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 has been promoted.

  For example, Patent Literature 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. It describes a cathode electrode structure for a fuel cell, wherein 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 disposed on one side in the thickness direction of the electrolyte layer and supplied with fuel, and a fuel-side electrode disposed on the other side in the thickness direction of the electrolyte layer are supplied with oxygen. A fuel cell includes an oxygen-side electrode, and a fuel decomposition layer disposed between the electrolyte layer and the oxygen-side electrode and decomposing fuel that has passed through the electrolyte layer.

JP-A-2016-015283 JP-A-2006-207575

  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 has as its object 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-described problem is a cathode of a battery including an electrolyte membrane, and includes a carbon catalyst having 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, exhibits a weight loss rate of 12.0% by weight or less from 200 ° C. to 1200 ° C. measured by thermogravimetric analysis under a nitrogen atmosphere, and shows an X-ray absorption at the K absorption edge of the iron. In the microstructure analysis, the following (a) and / or (b): (a) the ratio of the normalized absorbance of 7130 eV to the normalized absorbance of 7110 eV is 7.0 or more; (b) 7135 eV of the normalized absorbance of 7110 eV Is a normalized absorbance ratio of 7.0 or more;

The ratio of the mesopore volume to the total pore volume of the carbon catalyst may be 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 carbon catalyst may exhibit a ratio of a nitrogen atom content to a carbon atom content of 1.1% or more as measured by elemental analysis by a combustion method. The carbon catalyst may include iron and a metal other than iron. The carbon catalyst may have a specific surface area measured by a BET method of 800 m ² / g or more.

  The first layer may include 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 may be 0.30 or more. Good. The second layer contains 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 content of the platinum in the second layer to the content of the carbon catalyst in the first layer may be 20.00% by weight 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.

  A membrane electrode assembly according to one embodiment of the present invention for solving the above problems 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 one 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.

BRIEF DESCRIPTION OF THE DRAWINGS 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. FIG. 4 is an explanatory diagram showing an example of a result of measuring a weight loss rate of a carbon catalyst by thermogravimetric analysis in an example according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing an example of a result of performing an X-ray absorption fine structure analysis of a K absorption edge of iron in an example according to an embodiment of the present invention. FIG. 4 is an explanatory diagram showing an example of a result of evaluating a carbon catalyst in an example according to an embodiment of the present invention. It is an explanatory view showing another example of the result of having evaluated a carbon catalyst in an example concerning one embodiment of the present invention. FIG. 7 is an explanatory diagram showing an example of a result of evaluating durability in an example according to an embodiment of the present invention.

  Hereinafter, a cathode, a membrane electrode assembly, and a battery according to an embodiment of the present invention will be described. Note that 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, and includes a first layer including a carbon catalyst of 0.3 mg / cm ² or more and 9.0 mg / cm ² or less; 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 embodiment includes the cathode according to the embodiment, an anode, and an electrolyte membrane disposed between the cathode and the anode. The battery according to the embodiment includes the cathode according to the embodiment or the MEA according to the embodiment.

  The inventors of the present invention have intensively studied technical means for realizing a cathode, an MEA and a battery having excellent durability, and as a result, it has been found that 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 containing platinum in an amount within a specific range, disposed between the MEA or the electrolyte membrane of the battery. Has uniquely found that sexuality is achieved.

  FIG. 1 shows a cross section of an MEA 1 according to an example of the present embodiment. In the present specification, the present embodiment will be described mainly with reference to the example shown in FIG. 1. However, FIG. 1 merely conceptually shows the structure of the MEA 1. However, the present invention is not limited to the specific mode such as the size, shape, and positional relationship of the MEA1 shown in FIG.

  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 of the gas diffusion layers 30, The cathode 10 includes 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.

  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. 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 the CC layer 11 and the Pt layer 12.

  In the cathode 10, the CC layer 11 and the Pt layer 12 are stacked, but another layer may be included between the CC layer 11 and the Pt layer 12, as described later. 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 located 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 contains a carbon catalyst having an activity of 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 determined by 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 11 b of the CC layer 11 facing the surface 30 a of the layer 30.

The carbon catalyst content of the CC layer 11 is not particularly limited as long as it is in the 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 more. / Cm ² or less, 0.5 mg / cm ² or more and 9.0 mg / cm ² or less, or 0.5 mg / cm ² or more and 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 gas diffusion efficiency in the CC layer 11.

  Although the CC layer 11 may include another catalyst, the catalyst included in the CC layer 11 is preferably mainly composed of a carbon catalyst. Carbon catalyst content relative to the catalyst content in CC layer 11 (in the case where CC layer 11 contains another catalyst in addition to the carbon catalyst, the sum of the content of the carbon catalyst and the content of the other catalyst) Is not particularly limited as long as the effects of the present invention can be 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 particularly preferably at least 95% by weight.

  In addition, the content of the specific catalyst in the cathode 10 is determined, for example, such that the specific catalyst 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. If so, it is the content of the catalyst component.

  Other catalysts contained in the CC layer 11 are not particularly limited as long as the effects of the present invention can be obtained. Examples thereof include 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. , 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 include platinum. The CC layer 11 may not include gold. The CC layer 11 may not include ruthenium. The CC layer 11 may not contain rhodium. The CC layer 11 may not include palladium. The CC layer 11 may not include iridium. The CC layer 11 may not include manganese. The CC layer 11 may not include cerium. The CC layer 11 may not include a catalyst other than the carbon catalyst.

  The CC layer 11 may include 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, and for example, is preferably one or more selected from the group consisting of an ionomer and an ionic liquid. The ionomer is preferably, for example, one or more selected from the group consisting of a perfluorocarbon material and a hydrocarbon material. The perfluorocarbon material is preferably, for example, a perfluorocarbon sulfonic acid-based polymer. The perfluorocarbon sulfonic acid-based 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-based polymer. The hydrocarbon sulfonic acid-based 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), AQUISION (registered trademark), ACIPLEX (registered trademark), and FLEMION (registered trademark) are preferably used.

  The EW value of the electrolyte material contained in 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, 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, 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 included 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 (= the weight of the electrolyte material included in the CC layer 11 / (the weight of the CC layer 11) Weight-the weight of the electrolyte material contained 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 effects of the present invention can be obtained. That is all. 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.

  In addition, for example, when the CC layer 11 is composed of a carbon catalyst and an electrolyte material, since the remaining weight of the CC layer 11 is the weight of the carbon catalyst, the electrolyte material ratio of the CC layer 11 is: It is a ratio of the weight of the electrolyte material to the weight of the carbon catalyst. Further, 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. (That is, the sum of the weights of the components other than the electrolyte material), the electrolyte material ratio of the CC layer 11 is determined by the weight of the electrolyte material with respect to the sum of the weight of the carbon catalyst and the weight of the other components. Ratio.

  The upper limit of the electrolyte material ratio of the CC layer 11 is not particularly limited as long as the effects of the present invention can be obtained, but the electrolyte material ratio may be, for example, 1.70 or less, or 1.60 or less. It is preferably, and more preferably 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 limits and each of the above-described upper limits. 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 more preferably 0.50 or more. , 1.50 or less, more preferably 0.60 or more and 1.50 or less.

  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 gas diffusion efficiency in the CC layer 11.

  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 weight of the other components) The total ratio of the weight of the carbon catalyst and the weight of the electrolyte material contained in the CC layer 11 to the total weight of the CC layer 11 is not particularly limited as long as the effects of the present invention can be 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 include another conductive material other than 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 It is preferably at least one selected from the group consisting of tin oxide, and particularly preferably a conductive carbon material. 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. One or more types may be used. The conductive ceramic is not particularly limited as long as it is a ceramic having conductivity. For example, it is preferably at least one 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 effects of the present invention can be obtained, but is preferably silica, for example. The CC layer 11 may not include a conductive material other than the carbon catalyst. Further, the CC layer 11 may not include a 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) Is the sum of the weight of the carbon catalyst, the weight of the other conductive material, and the weight of the water retention material), the ratio of the weight of the carbon catalyst contained in the CC layer 11 to the effect of the present invention. Is not particularly limited as long as it is within the range in which is obtained, for example, it may be 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and more preferably 80% by weight. % 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 more preferably 5 μm or more and 60 μm or less. It is particularly preferred that:

  The Pt layer 12 contains a platinum-containing catalyst. The platinum-containing catalyst is not particularly limited as long as it contains 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 carrier and platinum particles and / or platinum alloy particles supported on the carrier.

  In this case, the carrier is not particularly limited as long as the effects of the present invention can be obtained. For example, a carbon material, ceramics (for example, one or more selected from the group consisting of alumina, silica, and cordierite), titanium oxide, oxide 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 effects 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 a carrier-free platinum particle and / or platinum alloy particle.

  The platinum alloy is not particularly limited as long as it is an alloy of platinum and another metal, and is, for example, 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 catalyst including a core made of a metal other than platinum and a platinum alloy, and a shell made of platinum and / or a platinum alloy covering the core. The platinum-containing catalyst is a nanostructured thin film (NSTF) type catalyst including a substrate (for example, whisker) composed of a metal other than platinum and a platinum alloy, and platinum and / or a platinum alloy laminated on the substrate. 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 determined by the weight (mg) of platinum contained in the Pt layer 12 and the area of the Pt layer 12 (in the example shown in FIG. Of the surface 12a of the Pt layer 12 facing the surface 20b of the electrolyte membrane 20 facing the surface of the Pt layer 12 (cm ² ). The weight of platinum contained in the Pt layer 12 is, for example, when the platinum-containing catalyst of the Pt layer 12 includes a carrier and platinum supported on the carrier, the weight of the platinum is used. 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 range, for example, excellent catalytic activity and durability can be achieved without making the catalytic activity of the cathode 10 largely dependent on the platinum-containing catalyst of the Pt layer 12. can do.

  The Pt layer 12 may include another catalyst, but the catalyst included in the Pt layer 12 is preferably mainly composed of platinum. The catalyst content of the Pt layer 12 (in the case where the Pt layer 12 contains another catalyst in addition to the platinum-containing catalyst composed of a carrier and platinum supported on the carrier, the platinum content of the platinum-containing catalyst Of the platinum content of the Pt layer 12 with respect to the total content of the Pt layer 12 and the content of the other catalyst is not particularly limited as long as the effects of the present invention can be obtained. It may be present, preferably at least 50% by weight, more preferably at least 75% by weight, particularly preferably at least 90% by weight.

  Other catalysts contained in the Pt layer 12 are not particularly limited as long as the effects of the present invention can be 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 something.

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

  The Pt layer 12 may include 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, and for example, is preferably one or more selected from the group consisting of an ionomer and an ionic liquid. The ionomer is preferably, for example, one or more selected from the group consisting of a perfluorocarbon material and a hydrocarbon material. The perfluorocarbon material is preferably, for example, a perfluorocarbon sulfonic acid-based polymer. The hydrocarbon material is preferably, for example, a hydrocarbon sulfonic acid-based polymer.

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

  The EW value of the electrolyte material contained in the Pt layer 12 is not particularly limited as long as the effects of the present invention can be 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, particularly preferably 500 or more and 1100 or less.

  The 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 / (weight 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 effects of the present invention can be obtained. It may be. 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 a carrier, In the case of being composed of supported platinum, the weight of the carrier and the weight of the platinum) is the sum of the weight of the carrier and the weight of the platinum. It is the ratio of the weight of the materials. Further, 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. (Ie, the sum of the weights of the components other than the electrolyte material), the electrolyte material ratio of the Pt layer 12 depends on the weight of the platinum-containing catalyst and the weight of the other catalyst. It is the ratio of the weight of the catalyst.

  The upper limit of the electrolyte material ratio of the Pt layer 12 is not particularly limited as long as the effects of the present invention can be obtained, but the electrolyte material ratio may be, for example, 1.40 or less, or 1.30 or less. It is preferably, more 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 limits and each of the above-described upper limits. 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 gas diffusion efficiency in the Pt layer 12.

  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 and the weight of the electrolyte material contained in the Pt layer 12 to the total weight of the Pt layer 12 is not particularly limited as long as the effects of the present invention can be 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 another conductive material other than 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 It is preferably at least one selected from the group consisting of tin oxide, and particularly preferably a conductive carbon material. 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. One or more types may be used. The conductive ceramic is not particularly limited as long as it is a ceramic having conductivity. For example, it is preferably at least one 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 effects of the present invention can be obtained, but is preferably silica, for example. The Pt layer 12 may not include a 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 include 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) Is the sum of the weight of the platinum-containing catalyst, the weight of the other conductive material, and the weight of the water-retentive material) in the Pt layer 12. There is no particular limitation 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.

  The thickness of the Pt layer 12 is not particularly limited as long as the effects of the present invention can be obtained, but may be, for example, 0.1 μm or more and 50 μm or less, preferably 0.5 μm or more and 20 μm or less, It is particularly preferable that the thickness be 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 more than any of the above lower limits (mg / cm ² ), the carbon catalyst content of the Pt layer 12 may be less than the lower limit. When the Pt layer 12 contains platinum in an amount equal to or more than any of the above lower limits (mg / cm ² ), the platinum content of the CC layer 11 may be lower than the lower limit.

  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 more than any of the lower limits (% by weight) described above, the Pt layer 12 May be less than the lower limit. When the ratio of the platinum content of the Pt layer 12 to the catalyst content of the Pt layer 12 is equal to or more than any of the lower limits (% by weight) described above, the CC layer 11 The platinum content ratio 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) ), The total ratio 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 more preferably 90% by weight or more. It is particularly preferred that there is.

  It is preferable that the carbon catalyst of the cathode 10 be mainly composed of the carbon catalyst of the CC layer 11. That is, the carbon catalyst content of the cathode 10 (for example, when the CC layer 11 and the Pt layer 12 both contain 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 to the CC layer 11 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 mainly composed of the 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 include platinum, the total of the platinum content of the CC layer 11 and the platinum content of the Pt layer 12). , Pt layer 12 may have a platinum content of, for example, 10% by weight or more, preferably 30% by weight or more, and particularly preferably 50% by weight or more.

  It is preferable that the oxygen reduction activity of the cathode 10 is mainly exerted by the carbon catalyst contained in the CC layer 11. That is, it is preferable that the platinum content of the cathode 10 be suppressed to such an extent that the oxygen reduction activity of the cathode 10 does not largely 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 largely depends on the platinum-containing catalyst, the performance of the battery is rapidly lowered 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 largely depend on the platinum-containing catalyst, even if the platinum-containing catalyst is poisoned, a sharp decrease in the performance of the battery 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 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 the content is not more than 2.80% by weight.

  The lower limit of the Pt / CC ratio of the cathode 10 is not particularly limited as long as the effects 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 at least 15% by weight.

  The Pt / CC ratio can be defined by arbitrarily combining each of the above-described lower limits and each of the above-described upper limits. Specifically, the Pt / CC ratio of the cathode 10 may be, for example, 0.10% by weight or more and 20.00% by weight or less, and is 0.15% by weight or more and 7.00% by weight or less. 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 0.15% by weight or less. More preferably, it is at most 2.80% by weight.

  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 direction of the Pt layer 12) and the direction of the gas diffusion layer 30 of the CC layer 11. The distance between the Pt layer 12 and the surface 12a of the Pt layer 12 facing the electrolyte membrane 20 and the direction of the gas diffusion layer 30 of the Pt layer 12 (that is, the direction of the CC layer 11). ) To the surface 12b.

  The Pt layer 12 covers part or all of the surface 11a of the CC layer 11 facing the electrolyte membrane 20. 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, preferably 70% or more, and more preferably 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, between the CC layer 11 and the Pt layer 12, between the CC layer 11 and the gas diffusion layer 30, Further, 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 another layer, 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 the Pt layer 12 and the thickness of the other layer may be, for example, 50% or more, or 70% or more. Is preferable, and 90% or more is particularly preferable.

When the CC layer 11 contains the carbon catalyst in an amount (mg / cm ² ) within the above-described specific range, the cathode 10 is provided between the CC layer 11 and the Pt layer 12 and between the CC layer 11 and the gas diffusion layer 30. And at least one layer selected from the group consisting of the Pt layer 12 and the electrolyte membrane 12 having a carbon catalyst content outside the specific range. It may not be.

When the Pt layer 12 contains platinum in an amount (mg / cm ² ) within the above-described specific range, the cathode 10 is disposed between the CC layer 11 and the Pt layer 12 and between the CC layer 11 and the gas diffusion layer 30. , And between the Pt layer 12 and the electrolyte membrane 12, not including another layer having a platinum content outside the specific range, which is disposed at one or more positions selected from the group consisting of: It may be.

  The cathode 10 has at least one position selected from the group consisting of between the CC layer 11 and the Pt layer 12, between the CC layer 11 and the gas diffusion layer 30, and between the Pt layer 12 and the electrolyte membrane 12. May be excluded from other layers containing a catalyst (for example, other layers containing a catalyst and an electrolyte material).

  The cathode 10 has at least one position selected from the group consisting of between the CC layer 11 and the Pt layer 12, between the CC layer 11 and the gas diffusion layer 30, and between the Pt layer 12 and the electrolyte membrane 12. May not include another layer that does not include a catalyst (for example, another layer that includes an electrolyte material and does not include a catalyst).

  The cathode 10 has at least one position selected from the group consisting of between the CC layer 11 and the Pt layer 12, between the CC layer 11 and the gas diffusion layer 30, and between the Pt layer 12 and the electrolyte membrane 12. , May not include another layer (for example, another layer including an electrolyte material). 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 to 12b) may be, for example, 20 μm or less, preferably 10 μm or less, and particularly preferably 5 μm or less.

  It is preferable that the CC layer 11 and the Pt layer 12 are 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.

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

  The substrate is not particularly limited as long as it enables the manufacture of the MEA 1 or the battery including the cathode 10, but is preferably, for example, the electrolyte membrane 20, the gas diffusion layer 30, or the transfer substrate.

  Specifically, the cathode 10 disposed on the gas diffusion layer 30 may include the CC layer 11 and the Pt layer 12 disposed on the opposite side of the gas diffusion layer 30 with respect to the CC layer 11. Good. In addition, the cathode 10 disposed on the electrolyte membrane 20 may include the CC layer 11 and the Pt layer 12 disposed between the CC layer 11 and the electrolyte membrane 20. Further, the cathode 10 disposed on the transfer base material is provided between the CC layer 11 and the CC layer 11 and the transfer base material or on the opposite side of the CC layer 11 from the transfer base material. May be included.

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

  Cathode 10 is manufactured by a method including forming CC layer 11 and 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 composition containing a platinum-containing catalyst and having fluidity (hereinafter, referred to as “Pt layer composition”).

  That is, for example, first, a CC layer composition is applied on a base material (for example, the gas diffusion layer 30 or the transfer base material) and dried to form the CC layer 11, and then the Pt layer composition is formed on the CC layer 11. An object is applied and dried to form a Pt layer 12. Further, for example, first, a Pt layer composition is applied on a base material (for example, the electrolyte membrane 20 or a transfer base material) and dried to form a 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. Further, for example, first, the CC layer composition is applied on a first base material (for example, the gas diffusion layer 30 or the transfer base material) and dried to form the CC layer 11, while the second base material ( 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 so that the Pt layer 12 is laminated. You may crimp a 1st base material and the said 2nd base material.

  Note that the CC layer 11 may be formed by applying the CC layer composition only once, or may be formed by applying the CC layer composition a plurality of times (that is, by applying multiple layers). You may. The carbon catalyst content of the CC layer composition and / or the amount and / or the number of times of applying the CC layer composition are determined so that the finally formed CC layer 11 has a carbon content within the above-described specific range. It is adjusted to include a 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 the number of times of applying the Pt layer composition are determined so that the finally formed Pt layer 12 contains platinum in an amount within the above-described specific range. Adjusted to include.

  When the cathode 10 includes another layer in addition to the CC layer 11 and the Pt layer 12, the method for manufacturing the cathode 10 further includes forming the other layer. The other layer is formed, for example, by applying and drying a fluid composition containing components corresponding to the composition of the other layer, similarly to 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 steps. 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 applying the CC layer composition last is The surface 11a of the CC layer 11 faces the electrolyte membrane 20.

  In addition, for example, when the Pt layer 12 is first formed, and then the CC layer composition is applied once or plural 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 applying the CC layer composition first after the formation of the layer 12 facing the Pt layer 12 is the surface 11a of the CC layer 11 facing 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, the electrolyte membrane 20 disposed between the pair of gas diffusion layers 30, 50, one of the gas diffusion layers 30, The cathode 10 includes a cathode 10 disposed between the electrolyte membrane 20, the other gas diffusion layer 50, and an anode 40 disposed between the electrolyte membrane 20. , 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 they are porous bodies capable of supplying a gas such as air to the cathode 10 and supplying a 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 water management or 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 cell 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 for a battery such as a fuel cell, but is preferably an ionomer membrane. The ionomer is preferably, for example, one or more selected from the group consisting of a perfluorocarbon material and a hydrocarbon material. The perfluorocarbon material is preferably, for example, a perfluorocarbon sulfonic acid-based polymer. The hydrocarbon material is preferably, for example, a hydrocarbon sulfonic acid-based polymer.

  Specifically, as the electrolyte membrane 20, for example, one or more membranes selected from the group consisting of NAFION (registered trademark), AQUISION (registered trademark), ACIPLEX (registered trademark), and FLEMION (registered trademark) are preferably used. You. 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 effects of the present invention can be obtained, but may be, for example, 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 or less. It is particularly preferred that:

  The anode 40 is not particularly limited as long as it contains 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, a hydrocarbon compound (for example, methane and / or ethane), an alcohol (for example, methanol and / or ethanol), and a carboxylic acid compound (for example, formic acid and / or acetic acid). , Sugars (eg, glucose), nitrogen-containing compounds (eg, ammonia and / or hydrazine), and other organic substances (eg, organic substances contained in sludge or industrial wastewater). Is also good.

  The catalyst of the anode 40 is, for example, at least one 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. Is preferred. The microorganism of the anode 40 is not particularly limited as long as it has a fuel oxidation ability.

The catalyst content of the anode 40 may be, for example, not less than 0.001 mg / cm ^{2 and not} more than 0.5 mg / cm ^{2, and not} less than 0.005 mg / cm ^{2 and not} more than 0.3 mg / cm ^2. Is preferred.

  The content of the catalyst in the anode 40 is determined, for example, by the fact 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) carried on the carrier. When constituted, it is the content of the catalyst component.

  The anode 40 may include an electrolyte material. As the electrolyte material, the same electrolyte material as that contained in the cathode 10 described above is preferably used. The type of the 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 the 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.

  In addition, the battery includes, for example, a pair of separators and an MEA 1 disposed between the pair of separators. In this case, the battery may include a single cell, and the single cell may include the pair of separators and the MEA 1 disposed between the pair of separators. A 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 unit cells.

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

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

  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 11 b of the CC layer 11 facing the gas diffusion layer 30 and the direction of the electrolyte membrane 20 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. That is, it is preferable that the surface 11b of the CC layer 11 facing the gas diffusion layer 30 is in contact with the surface 30a of the gas diffusion layer 30 facing the electrolyte membrane 20.

  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 of the Pt layer 12 facing the electrolyte membrane 20 and the surface 12a of the electrolyte membrane 20 facing the Pt layer 12). 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 carbon catalyst contains iron, and the weight loss rate from 200 ° C. to 1200 ° C. measured by thermogravimetric analysis under a nitrogen atmosphere. In the X-ray absorption fine structure analysis of the K absorption edge of the iron, the ratio of the normalized absorbance of 7130 eV to the normalized absorbance of 7110 eV is shown in the following (a) and / or (b): Is not less than 7.0; and (b) the ratio of the normalized absorbance at 7135 eV to the normalized absorbance at 7110 eV is 7.0 or more; . Note that the normalized absorbance in the XAFS analysis is an absorbance 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 conducted intensive studies on technical means of obtaining a carbon catalyst for realizing a cathode, MEA, and battery having excellent durability, and as a result, it has been found that iron containing iron and a weight loss by thermogravimetric analysis are obtained. A carbon catalyst having a specific rate of not more than a specific threshold value and having a carbon structure containing a large amount of iron in a specific state in the X-ray absorption fine structure analysis of the K absorption edge of the iron has the above-mentioned excellent durability. Has uniquely found that it contributes to

  This carbon catalyst contains iron derived from a raw material for carbonization during its production, as described later. That is, the carbon catalyst contains the iron in the carbonization raw material due to the fact that the raw material contained the iron. For this reason, even when the carbon catalyst is manufactured through the metal removal treatment described below, a trace amount of iron derived from the raw material remains inside 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 loss of 12.0% by weight or less from 200 ° C. to 1200 ° C. measured by thermogravimetric analysis (hereinafter referred to as “TG”) under a nitrogen atmosphere. The carbon catalyst preferably has the above-mentioned weight loss rate by TG of 11.0% by weight or less, more preferably 10.0% by weight or less, still more preferably 9.0% by weight or less, It is particularly preferred to show 8.0% by weight or less.

  The fact that the carbon catalyst exhibits the above-mentioned weight loss rate equal to or less than the above-mentioned 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. It is considered that the fact that the carbon catalyst is thermally stable is due to, for example, a large bond energy between atoms constituting the carbon structure of the carbon catalyst. Therefore, a thermally stable carbon catalyst is also electrochemically stable. In addition, the electrochemically stable carbon catalyst has high durability in applications such as fuel cells. Therefore, a carbon catalyst having a small weight loss rate in TG under a nitrogen atmosphere exhibits excellent durability. The lower limit of the weight reduction rate of the carbon catalyst is not particularly limited, but the weight reduction rate may be 1.0% by weight or more.

  Further, in the XAFS analysis of the K absorption edge of iron, the carbon structure of the carbon catalyst shows (a) a ratio of 7130/7110 or more, 7.0 (b) a ratio of 7135/7110 or more, or (a) 7130/7110 ratio 7.0 or more and (b) 7135/7110 ratio 7.0 or more. The 7130/7110 ratio and / or the 7135/7110 ratio of the carbon structure of the carbon catalyst are preferably 8.0 or more, more preferably 9.0 or more, and preferably 10.0 or more. Even more preferably, it is particularly preferably 11.0 or more. The upper limits 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.

  The fact that the carbon structure of the carbon catalyst shows a 7130/7110 ratio and / or 7135/7110 ratio in the XAFS analysis that is equal to or higher than the specific threshold value contributes to the excellent catalytic activity of the carbon catalyst. That is, in the XAFS analysis of the K absorption edge of iron, the energy of the peak after the K absorption edge indicates the energy at which the electron in the 1s orbit of the iron atom transits to the antibonding orbit of the σ bond, It reflects the binding energy. On the other hand, the peak before the K absorption edge indicates that the electron in the 1s orbit of the iron atom has transitioned to the d orbit, which indicates that the iron atom has an asymmetric structure. I have.

  Therefore, the fact that the normalized absorbance of 7130 eV and 7135 eV is high indicates that the iron atom has two kinds of specific bonds showing energies corresponding to the 7130 eV and 7135 eV, and that the normalized absorbance of 7110 eV is high. Indicates that the iron atom has an asymmetric structure. Then, in the carbon catalyst, it is considered that the above-mentioned iron atom having the two kinds of nonmetallic bonds functions 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 that is equal to or higher than the specific threshold in the XAFS analysis of the K absorption edge of iron is an iron having the two specific nonmetallic bonds. By having a relatively large number of atoms, it has excellent catalytic activity.

  In the case where the carbon structure of the carbon catalyst shows a 7130/7110 ratio and / or 7135/7110 ratio within the range of not less than the above-mentioned specific threshold value and not more than 30.0 in the XAFS analysis of iron, in the carbon catalyst, The two specific nonmetallic 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 excellent catalytic activity by including the above two specific nonmetallic bonds and the iron atom having the asymmetric structure.

  The carbon catalyst contains iron, has a weight loss rate of not more than the specific threshold, and has a carbon structure having a 7130/7110 ratio and / or 7135/7110 ratio of not less than the specific threshold. It has activity and excellent durability.

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

  Specifically, the carbon catalyst includes, for example, a carbon structure exhibiting the above 7130/7110 ratio and / or the above 7135/7110 ratio of 8.0 or more, and showing the above weight loss 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 shows the above weight loss rate of 10.0% by weight or less. It is even more preferable that the carbon structure having the above 7130/7110 ratio and / or the 7135/7110 ratio is included, and the weight loss ratio is not more than 9.0% by weight, and more preferably 11.0 or more. It is particularly preferable to include a carbon structure exhibiting the 7110 ratio and / or the 7135/7110 ratio and exhibit the weight loss rate of 8.0% by weight or less.

  In the carbon catalyst, the ratio of the mesopore volume to the total pore volume (hereinafter, “mesopore ratio”) may be 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 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 determined by arbitrarily combining the above lower limits and the upper limits. 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 total volume of the mesopores. The micropore is a pore having a diameter of less than 2 nm, and the micropore volume (cm ³ / g) is the total volume of the micropore. The macropores are pores having a diameter of more than 50 nm, and the macropore volume (cm ³ / g) is the total volume of the macropores. 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.

  The iron content of the carbon catalyst by ICP-MS is calculated as a ratio (weight%) of the weight of iron atoms to the total weight of the carbon catalyst. The upper limit of the iron content of the carbon catalyst is not particularly limited, but the iron content may be 10.00% by weight or less.

  The carbon catalyst may exhibit a nitrogen atom content of 1.0% by weight or more measured by elemental analysis by a combustion method. In this case, the carbon catalyst preferably has a nitrogen atom content of 1.1% by weight or more, particularly preferably 1.2% by weight or more, as determined by elemental analysis.

  The fact that the carbon catalyst shows the 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. Although the upper limit of the nitrogen atom content of the carbon catalyst by elemental analysis is not particularly limited, 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 has a nitrogen atom content of 1.0 atm measured by elemental analysis by a combustion method. % By weight or more.

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

  The fact that the carbon catalyst shows the nitrogen atom concentration by XPS above the specific threshold and the nitrogen atom content by elemental analysis above the specific threshold indicates that the carbon catalyst has a surface layer portion (a few nm from the surface). As well as its interior (the interior deeper than the surface layer) contains the same amount of nitrogen atoms as the surface layer, that is, a relatively homogeneous carbon from the surface to the interior. It reflects the fact 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 if the active points of the surface layer portion are lost, the inner portion is deeper than the surface layer portion. By the function of the active point, the decrease in the catalytic activity of the carbon catalyst is effectively suppressed.

  The nitrogen atom concentration of the carbon catalyst by XPS 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 concentration by the elemental analysis is 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, more preferably 1.4% or more, and more preferably 1% or more. It is particularly preferable to show 0.5% or more.

  The fact that the carbon catalyst shows the N / C ratio by the elemental analysis that is equal to or higher than the above-described specific threshold value 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.

  In addition, the carbon catalyst shows a ratio of nitrogen atom concentration to carbon atom concentration (hereinafter referred to as “N / C ratio by XPS”) of 1.1% or more as measured by XPS, and is analyzed by elemental analysis using a combustion method. The measured N / C ratio may be 1.1% or more.

  In this case, the carbon catalyst preferably shows an N / C ratio of 1.2% or more by XPS, and preferably shows an N / C ratio of 1.2% or more by elemental analysis, and an N / C ratio of 1.3% by XPS. More preferably, the N / C ratio by elemental analysis is 1.3% or more, and the N / C ratio by XPS is 1.4% or more, and the N / C ratio by elemental analysis is 1.4%. It is still more preferable to show the above, and it is particularly preferable to show the N / C ratio of 1.5% or more by XPS and to show the N / C ratio of 1.5% or more by elemental analysis.

  The fact that the carbon catalyst shows the above-mentioned specific threshold as the N / C ratio by XPS and the above-mentioned specific threshold as the N / C ratio by elemental analysis means that the carbon catalyst has its surface layer portion (a few nm from the surface). Not only the portion up to the depth of the surface layer), but also the inside thereof (the interior deeper than the surface layer portion) reflects the same amount of nitrogen atoms as 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 if the active points of the surface layer portion are lost, the inner portion is deeper than the surface layer portion. By the function of the active point, the decrease in the catalytic activity of the carbon catalyst is effectively suppressed.

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

  The carbon catalyst may include 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 characteristics of the carbon catalyst described above can be obtained, but is preferably a transition metal.

  In this 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 3 to Group 12 of the periodic table in the fourth period. Specifically, non-ferrous metals contained in the carbon catalyst include, 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 the group consisting of actinides, 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.

  Further, the carbon catalyst preferably contains Fe and at least one non-ferrous metal selected from the group consisting of Ti, Cr, Zn, Nd, Sm and Gd, and comprises 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 the carbon catalyst contains the specific transition metal as a non-ferrous metal, the carbon catalyst may further contain another transition metal. That is, for example, when the carbon catalyst contains Fe and one or more first non-iron transition metals selected from the group consisting of Ti, Cr, Zn, Nd, Sm, and Gd, Sc, Ti, V, Cr, A group consisting of 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 an actinoid; 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); At least one selected from the group consisting of actinoids and may further include a second non-ferrous transition metal different from the first non-ferrous transition metal.

  Further, 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). The above may not be included.

  When the carbon catalyst contains, in addition to iron, a non-ferrous metal derived from a raw material for carbonization described below, the carbon catalyst contains the iron and the non-ferrous metal in the raw material for carbonization. It contains the iron and the non-ferrous metal. That is, even when the carbon catalyst is manufactured through the metal removal treatment described below, a small amount of the iron and non-ferrous metal remains inside the carbon catalyst.

  Specifically, for example, when the carbon catalyst containing an iron and a non-ferrous metal is in the form of particles, when the particles constituting the carbon catalyst are cut, the iron and the non-ferrous metal 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.

The carbon catalyst may have a specific surface area measured by the BET method of 800 m ² / g or more. In this case, the specific surface area of the carbon catalyst obtained by the BET method using nitrogen gas is preferably at least 1000 m ² / g, particularly preferably at least 1200 m ² / g.

When the specific surface area of the carbon catalyst is equal to or larger than the specific threshold, it contributes to the efficiency of the chemical reaction by the carbon catalyst and contributes to excellent catalytic 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.

  The carbon catalyst is a carbon material that has catalytic activity (eg, oxygen reduction activity) by itself. This carbon material is a carbonized material obtained by carbonizing a raw material containing an organic substance and iron. That is, the carbon catalyst is a raw material carbonized material containing an organic substance and iron. Further, when the carbon catalyst is a carbonized material obtained by carbonizing 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 considered that the non-ferrous metal is mainly due to iron and the active sites contained in the carbon structure itself.

  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 containing 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 it is a method capable of obtaining a carbon catalyst having the above-described properties, but in the present embodiment, a method including carbonizing a raw material containing an organic substance and iron under pressure. Will be described.

  The organic matter 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 are used. In addition, biomass may be used 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 contains an organic compound containing a nitrogen atom in its molecule. When the carbon catalyst is a carbonized material containing a nitrogen-containing organic substance, the carbon structure of the carbon catalyst contains a nitrogen atom.

  Specifically, as the organic substance, for example, polyacrylonitrile, polyacrylonitrile-polyacrylic acid copolymer, polyacrylonitrile-polymethyl acrylate copolymer, polyacrylonitrile-polymethacrylic acid copolymer, polyacrylonitrile-polymethacrylic acid -Polymethallyl sulfonic 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, at least one 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, wool, polyamid Acid, nucleic acid, DNA, RNA, hydrazine, hydrazide, urea, salen, polycarbazole, polybismaleimide, triazine, polyacrylic acid, polyacrylate, polymethacrylate, polymethacrylic acid, polyurethane, polyamideamine 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, the content may be 5% by mass or more and 90% by mass or less, preferably 10% by mass or more and 80% by mass or less. % Or less.

  As the iron contained in the raw material for carbonization, a simple substance of the iron and / or a compound of the iron is used. As the iron compound, for example, at least one 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 iron content in the raw material is not particularly limited as long as the carbon catalyst can be obtained, but may be, for example, 0.001% by mass or more and 90% by mass or less, and 0.002% by mass or more. It is preferably at most 80% by mass.

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

  In this 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 3 to Group 12 of the periodic table in the fourth period. Specifically, the non-ferrous metals contained in the raw materials include, 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 the group consisting of actinides, 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.

  Further, the raw material preferably contains Fe and one or more non-ferrous metals selected from the group consisting of Ti, Cr, Zn, Nd, Sm and Gd, and more preferably from the group consisting of Fe, Cr, Zn and Gd. More preferably, it comprises one or more selected non-ferrous metals. In this case, the raw material may include Fe and Zn.

  When the raw material contains the above-mentioned 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 contains 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 consisting 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 at least one selected from the group consisting of actinides and a second non-ferrous transition metal different from the first non-ferrous transition metal.

  The raw material may not contain platinum (Pt). In this case, the raw material is at least one selected from the group consisting of platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), gold (Au), and osmium (Os). May not be included.

  As the non-ferrous metal contained in the raw material, a simple substance of the non-ferrous metal and / or a compound of the non-ferrous metal is used. Examples of the non-ferrous metal compound include a non-ferrous metal salt, a non-ferrous metal oxide, a non-ferrous metal hydroxide, a non-ferrous metal nitride, a non-ferrous metal sulfide, a non-ferrous metal carbide, and a non-ferrous metal complex. One or more selected from the group may be used.

  The content of the non-ferrous metal in the raw material (when two or more non-ferrous metals are used, 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 maintaining the raw material 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 an organic substance is carbonized at a temperature of 300 ° C. or more under pressure.

  Further, the carbonization temperature may be, for example, 700 ° C. or higher, preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, and particularly preferably 1100 ° C. or higher. Although the upper limit of the carbonization temperature is not particularly limited, the carbonization temperature is, for example, 3000 ° C. or less.

  The heating rate up 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. The carbonization is preferably performed in an inert gas atmosphere such as a nitrogen atmosphere. That is, 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 it is higher than the atmospheric pressure. For example, the pressure is 0.05 MPa or more as a gauge pressure. That is, in this case, the raw material containing the organic substance is carbonized under a gauge pressure of 0.05 MPa or more.

  Further, the pressure of the atmosphere for carbonization 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 performing a further treatment on the carbonized material obtained by the carbonization. That is, for example, a 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 performing a metal removal treatment on a carbonized material obtained by the carbonization. The metal removal treatment is a treatment for reducing the amount of metal derived from the raw material contained in the carbonized material. The metal removal treatment is, for example, a cleaning treatment with an acid and / or an electrolytic treatment.

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

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

  Dilute hydrochloric acid was added to the carbonized material obtained by carbonization, followed by stirring. 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. Thus, a metal removal treatment by acid cleaning was performed.

  The carbonized material after the metal removal treatment was pulverized by a fine 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 in 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 infusible, to prepare a mixture further comprising chromium chloride hexahydrate _{0.018g (CrCl 3 · 6H 2 O} ), the mixture except for 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]
Before infusibilization, a mixture further containing 0.06 g of boric acid (B (HO) ₃ ) was prepared, and in the same manner as in the above catalyst preparation example 1 except that the mixture was made infusible, catalyst preparation example 4 Was obtained.

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

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

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

  Dilute hydrochloric acid was added to the carbonized material obtained by carbonization, followed by stirring. 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. Thus, a metal removal treatment by acid cleaning was performed.

  The carbonized material after the metal removal treatment was pulverized by a fine pulverizer until the median particle diameter became 1 μm or less. Thus, the pulverized carbonized material 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 in 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 in 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 added and dissolved in a flask containing 280 mL of toluene, and 0.75 parts 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 that a white precipitate was generated, the reaction was completed. Tetrahydrofuran was added to the reaction product, the mixture was filtered, and the residue was washed with tetrahydrofuran, filtered and dried to obtain polyacrylonitrile particles.

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

[Thermogravimetric analysis]
Using a differential thermal balance (TG-DTA2020SA, manufactured by Bruker AXS Corporation), the weight loss rate of the carbon catalyst was measured by TG under a nitrogen atmosphere. That is, an alumina container containing 10 mg of the carbon catalyst was placed in the apparatus, and then the apparatus was held for 1 hour at room temperature while flowing nitrogen (200 mL / min). Thereafter, the carbon catalyst was heated from normal temperature to 1200 ° C. at a temperature rising rate of 10 ° C./min, and the weight loss rate from 200 ° C. to 1200 ° C. was measured. To remove the influence of water and the like 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 loss rate (% by weight) of the carbon catalyst was obtained.

  Here, FIG. 2 shows the measurement results of the weight loss rate by TG of the carbon catalysts obtained in Catalyst Preparation Example 1 and Comparative Preparation Examples 2 and 4. In FIG. 2, the horizontal axis indicates temperature (° C.), and the vertical axis indicates 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, using the beamline BL5S1 of the Aichi Synchrotron Light Center (Aichi, Japan), XAFS analysis by hard X-ray was performed (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 carbon catalyst adjusted in an amount such that an edge jump (difference in absorbance before and after the absorption edge) was 1 was packed in a cylinder, and a sample prepared by compression was measured by a transmission method. However, when the absorbance after the absorption edge (energy for exciting electrons bound to the orbit of an atom to the lowest unoccupied state (absorption edge energy)) when the edge jump becomes 1, exceeds 4, The amount of the carbon catalyst was adjusted so that the edge jump was maximized in a range where the absorbance after the absorption edge did not exceed 4. When the amount at which the edge jump was 1 was too small to be suitable for measurement, the mixture obtained by adding boron nitride (BN) to the 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 Iffit 1.2.12 copyright 2008 Matt Newville, Univ of Chicago).

The normalization was performed by inputting the following numerical values in the “Normalization and background removal parameters” field in the “Main window” of the analysis software “Athena”. E ₀ : energy when the first derivative of the absorbance is maximum. Normalization order: 3. Pre-edge range: -150 to -30. Normalization range: 150 to 1000. Flatten normalized data: On. However, the conditions were 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 catalysts obtained in Catalyst Preparation Example 1, Comparative Preparation Examples 1, 2 and 4, and powdery α-iron (iron powder, Japanese powder) having an average particle diameter of 150 μm for comparison. 2 shows an XAFS spectrum of K.K. In FIG. 3, the horizontal axis indicates energy (eV), and the vertical axis indicates normalized absorbance.

[BET specific surface area, micro pore volume, meso pore volume, macro pore 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 the carbon catalyst was held at 100 ° C. and 6.7 × 10 ⁻² Pa for 3 hours to remove water 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 a change in the amount of nitrogen adsorbed on the carbon material with a change in the pressure of the nitrogen gas at a temperature of 77K.

On the other hand, the macropore volume and the mesopore volume (cm ³ / g) were obtained from the nitrogen adsorption isotherm at a temperature of 77 K by the BJH method. Further, the point of P / P ₀ = 0.98 of the nitrogen adsorption isotherm at a temperature of 77 K (P indicates the pressure at equilibrium, and P ₀ indicates the saturated vapor pressure (1.01 × 10 ⁵ Pa for nitrogen at 77 K) ) Indicates the total pore volume (cm ³ / g). 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. Then, the value obtained by dividing the mesopore volume (cm ³ / g) by the total pore volume (cm ³ / g) was multiplied by 100 to calculate the mesopore ratio (%).

  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, non-metal components in the carbon catalyst were removed by heating and holding 25 mg of the carbon catalyst at 800 ° C. for 3 hours in an air atmosphere. Thereafter, the metal contained in the carbon catalyst was dissolved by immersing the carbon catalyst in 5 mL of concentrated hydrochloric acid. Thereafter, distilled water was added to dilute the mixture to a total weight of 25 g to obtain a metal solution. Then, the iron atom concentration of the obtained metal solution was measured using a sequential plasma emission spectrometer (ICP-8100, manufactured by Shimadzu Corporation).

  Then, the value obtained by multiplying the iron atom concentration (mg / g) of the metal solution by the weight (25 g) of the metal solution is divided by the weight (25 mg) of the carbon catalyst, and 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), the photoelectron spectrum from the core level of carbon, nitrogen and oxygen atoms on the surface of the carbon catalyst was measured. AlKα radiation (10 mA, 15 kV, Pass energy 40 eV) was 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 orbital 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. 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 of carbon catalyst by combustion method 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 the 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 value obtained by dividing the weight of the nitrogen atoms contained in the carbon catalyst by the total weight of the carbon catalyst was multiplied by 100 to calculate the nitrogen atom content (% by weight) of the carbon catalyst.

  Similarly, the value obtained by dividing the weight of the 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). Furthermore, 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 were evaluated. That is, first, a three-electrode rotating ring disk electrode device having a working electrode containing a carbon catalyst was manufactured. Specifically, 5 mg of carbon catalyst, 50 μL of 5% Nafion (registered trademark) (Nafion perfluorinated ion exchange resin, manufactured by Sigma-Aldrich Co., Ltd., 5% solution (arrangement number: 510211)), 400 μL of water, and 100 μL of isopropyl alcohol Was mixed to prepare a slurry. Next, this slurry was subjected to an ultrasonic treatment for 10 minutes, and then subjected to a homogenizer treatment for 2 minutes. The working slurry (ring disk electrode for RRDE-3A, platinum ring-gold disk electrode, disk diameter 4 mm, BAS) was applied to the obtained slurry so that the coating amount of the carbon catalyst was 0.1 mg / cm ^2. Co., Ltd.) and dried to produce a working electrode containing the carbon catalyst.

  A platinum electrode (Pt counter electrode 23 cm, manufactured by BS Co., Ltd.) was used as a counter electrode, and a reversible hydrogen electrode (RHE) (reservoir type reversible hydrogen electrode, manufactured by EC Frontier Co., Ltd.) was used as a 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. Further, a 0.1 M aqueous solution of perchloric acid was used as the electrolytic solution.

Then, the catalytic activity using the rotating ring disk electrode device was measured. That is, linear sweep voltammetry (N ₂ -LSV) under nitrogen atmosphere and linear sweep voltammetry (O ₂ ) under oxygen atmosphere using a three-electrode rotating ring disk electrode device having a working electrode containing a carbon catalyst. _2- LSV) was performed.

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 rotation 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 the case of O ₂ -LSV, oxygen bubbling was further performed for 10 minutes, and the inside of the electrolytic solution was filled with saturated oxygen. Thereafter, the electrode was rotated at a rotation 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 addition, in the obtained oxygen reduction voltammograms, numerals were assigned such that the reduction current was a negative value and the oxidation current was a positive value.

From the oxygen reduction voltammogram thus obtained, as one of the indexes 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) when a voltage of 0.7 V (vs. NHE) was applied) mA / cm ² ) was recorded.

[Example 1]
A CC layer containing a carbon catalyst was produced. That is, first, 0.25 g of the carbon catalyst prepared in Catalyst Preparation Example 1, 3.5 g of a 5% by weight solution of an ionomer having an EW value of 700, and 25 g of a ball were put into a pot, and ball milled at 200 rpm for 50 minutes. To obtain a slurry-like CC layer composition containing the carbon catalyst uniformly dispersed.

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

  Further, a Pt layer containing platinum was produced. That is, platinum-supported carbon (hereinafter, referred to as “Pt / C”) containing a carbon carrier and platinum particles supported on the carbon carrier as a platinum-containing catalyst (UNPC40-II, manufactured by Ishifuku Metal Industries) 0 .25 g, 3.5 g of a 5% by weight solution of an ionomer having an EW value of 700, 2.5 g of distilled water, and 25 g of a ball are put into a pot, and mixed with a ball mill at 200 rpm for 50 minutes to be uniformly mixed. 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 coated on a 5 cm ² area of a solid polymer electrolyte membrane (NAFION (registered trademark) 211, manufactured by Dupont) (2.3 cm × 2.3 cm) with a platinum content. The Pt layer containing platinum and having an electrolyte material ratio of 0.7 was formed on the solid polymer electrolyte membrane by coating and drying so that the amount became 0.050 mg / cm ² .

The Pt / C used was such that the ratio of the weight of platinum contained in the Pt / C to the weight of the Pt / C was 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. Both the area of the CC layer and the area of the Pt layer were 5 cm ^2. Therefore, the area of the catalyst layer of the cathode 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 a 5% by weight NAFION (registered trademark) solution (manufactured by Aldrich), 2 g of distilled water, and 25 g of a ball are put into a pot, and mixed with a ball mill at 200 rpm for 50 minutes. Thereby, a slurry-like anode composition was prepared. The slurry-type anode composition is applied onto a region having an area of 5 cm ² of the gas diffusion layer so that the Pt / C content becomes 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 thereon.

  And, 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 And an anode disposed between the other gas diffusion layer and the solid polymer electrolyte membrane, and a single cell including the MEA.

  That is, 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 surface of the solid polymer electrolyte membrane on which the Pt layer is not formed. By pressing the solid polymer membrane between a pair of gas diffusion layers at 150 ° C. and 1 MPa so that the anode formed on the other gas diffusion layer is in contact with the anode, the MEA is pressed. Produced. Next, a single cell of a fuel cell was manufactured by attaching a pair of gaskets to the MEA so as to sandwich the MEA and further sandwiching the pair of gaskets with the pair of separators so as to sandwich the pair of gaskets.

Thereafter, the unit cell prepared as described above was installed in a fuel cell automatic evaluation system (manufactured by Toyo Technica Co., Ltd.), and a power generation test was performed. In the power generation test, air (oxygen) having a relative humidity of 50% was supplied to the cathode at a back pressure of 20 kPa at a rate of 2.0 L / min, and hydrogen of a relative humidity of 50% was supplied to the anode at a rate of 0.2 L / min. The supply was performed, the cell temperature was set to 55 ° C., and the open circuit voltage was measured for 5 minutes. Then, while changing the cell current density 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, a potential (mV) observed at a current density of 0.2 A / cm ² was recorded as an initial potential BOL (Beginning Of Life) as one of the indexes indicating the catalyst activity at the start of the durability test. .

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

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

Further, immediately after the end of the durability test for 100 hours, a 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 changed to the catalyst after the end of the durability test. It was recorded as a potential EOL (End Of Life) which is one of the indices indicating the activity.

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

[Example 2]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the content of platinum in the Pt layer was changed to 0.020 mg / cm ² , and a power generation test, a poisoning test, and a durability test were performed.

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

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

[Example 5]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the content of the carbon catalyst in the CC layer was changed to 1.0 mg / cm ² , and a power generation test, a poisoning test, and a 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 content of the carbon catalyst in the CC layer was 1.0 mg / cm ² and the content of platinum 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 prepared in the same manner as in Example 1 except that the content of the carbon catalyst in the CC layer was 1.0 mg / cm ² and the content of platinum 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
A cathode, an MEA and a single cell were prepared in the same manner as in Example 1 except that the content of the carbon catalyst in the CC layer was 6.0 mg / cm ² , and a power generation test, a poisoning test, and a durability test were performed. .

[Example 9]
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 set to 0.9, and a power generation test, a poisoning test, and a 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 , and a power generation test was performed. A poisoning test and a durability test were performed.

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

[Example 12]
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 set to 0.5 and the platinum content in the Pt layer was set to 0.020 mg / cm ² , and a power generation test was performed. A poisoning test and a durability test were performed.

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

[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 set to 0.2 and the platinum content in the Pt layer was set to 0.020 mg / cm ² , and a power generation test was performed. A poisoning test and a durability test were performed.

[Example 15]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Catalyst Preparation Example 2 was used as the carbon catalyst, and a power generation test, a poisoning test, and a durability test were performed. .

[Example 16]
A cathode, an MEA and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Catalyst Preparation Example 3 was used as the carbon catalyst, and a power generation test, a poisoning test, and a durability test were performed. .

[Example 17]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Catalyst Preparation Example 4 was used as the carbon catalyst, and a power generation test, a poisoning test, and a durability test were performed. .

[Example 18]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Catalyst Preparation Example 5 was used as a carbon catalyst, and a power generation test, a poisoning test, and a durability test were performed. .

[Example 19]
A cathode, an MEA and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Catalyst Preparation Example 6 was used as the carbon catalyst, and a power generation test, a poisoning test, and a durability test were performed. .

[Example 20]
Examples of Pt / C were as follows except that the ratio of the weight of platinum contained in the Pt / C to the weight of the Pt / C was 20% by weight (UNPC20-II, manufactured by Ishifuku Metal Industries). Similarly to 1, a cathode, an MEA, and a single cell were prepared, and a power generation test, a poisoning test, and a durability test were performed.

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

[Example 22]
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 set to 0.1, and a power generation test, a poisoning test, and a durability test were performed.

[Example 23]
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 set to 0.5, and a power generation test, a poisoning test, and a durability test were performed.

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

[Comparative Example 2]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the content of platinum in the Pt layer was changed to 0.001 mg / cm ² , 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 prepared (the cathode did not contain the Pt layer), a cathode, an MEA and a single cell were prepared and a power generation test, a poisoning test, and a durability test were performed in the same manner as in Example 1. .

[Comparative Example 5]
A cathode, an MEA and a single cell were produced in the same manner as in Example 1 except that the Pt layer was not produced (the cathode did not contain the Pt layer) and the content of the carbon catalyst in the CC layer was changed to 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 prepared in the same manner as in Example 1 except that the CC layer was not prepared (the cathode did not include 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.

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

[Comparative Example 8]
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 0.020 mg / cm ^2. , A power generation test, a poisoning test, and a durability test.

[Comparative Example 9]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the content of the carbon catalyst in the CC layer was 10.0 mg / cm ² , and a power generation test, a poisoning test, and a 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 content of the carbon catalyst in the CC layer was 10.0 mg / cm ² and the content of the platinum 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]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the content of the carbon catalyst in the CC layer was changed to 0.2 mg / cm ² , and a power generation test, a poisoning test, and a durability test were performed. .

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

[Comparative Example 14]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Comparative Preparation Example 2 was used, and a power generation test, a poisoning test, and a durability test were performed. .

[Comparative Example 15]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Comparative Preparation Example 3 was used as the carbon catalyst, and a power generation test, a poisoning test, and a durability test were performed. .

[Comparative Example 16]
A cathode, an MEA, and a single cell were prepared in the same manner as in Example 1 except that the carbon catalyst prepared in Comparative Preparation Example 4 was used as the carbon catalyst, and a power generation test, a poisoning test, and a 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 (“Comparation 1” to “Comparative 4” in the figure). For the carbon catalyst, the weight loss rate (% by weight) by TG, the normalized absorbance at 7110 eV, 7130 eV and 7135 eV by XAFS, the 7130/7110 ratio and the 7135/7110 ratio, and the current density i _{0. 7} (mA / cm ² ) indicates the result of evaluation.

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

As shown in FIG. 4A, the weight reduction rate by TG of the carbon catalysts of Comparative Preparation Examples 2, 3, and 4 was 12.5% by weight or more. The XAFS 7130/7110 ratio and 7135/7110 ratio 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 , but that of the carbon catalysts 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 was 7.3% by weight or less, and the 7130/7110 ratio and 7135/7110 ratio by XAFS were all 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 Was.

  The iron content of the carbon catalysts of Catalyst Preparation Examples 1 to 6 by ICP-MS was 0.21% by weight to 0.30% by weight. The carbon atom concentration by XPS of the carbon catalysts of Catalyst Preparation Examples 1 to 6 was 84.75 atm% to 90.74 atm%, the oxygen atom concentration was 7.24 atm% to 13.65 atm%, and the nitrogen atom concentration was 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 higher than that of the carbon catalysts of Comparative Preparation Examples 1 to 4 (3.01 atm% to 5.85 atm%).

  The nitrogen content of the carbon catalysts of Catalyst Preparation Examples 1 to 6 by elemental analysis was 87.30% to 98.62% by weight, and the hydrogen atom content was 0.43% to 1.74% by weight. , 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, for the cathodes manufactured in Examples 1 to 23 and Comparative Examples 1 to 16, the conditions relating to the carbon catalyst contained in the CC layer, the conditions relating to the platinum contained in the Pt layer, and the cell containing the cathode. The results of a power generation test and a durability test are shown.

Specifically, regarding the carbon catalyst, which of catalyst preparation examples 1 to 6 and comparative preparation examples 1 to 4 was used (in the figure, “Example 1” to “Example 6” are catalyst preparation examples 1 to 6). the indicated "Comparative example 1" to "Comparative 4" indicates the Comparative preparation examples 1-4.), the amount contained in the CC layer (in Figure "catalyst content (mg / cm ^2)"), and CC layer In the case of platinum, the ratio of the weight of the platinum contained in the Pt / C to the weight of Pt / C (“Pt / carrier” in the figure) (“Pt / (Pt / Carrier)) (% by weight), the content in the Pt layer (“catalyst content (mg-Pt / cm ² )” in the figure), and the electrolyte material ratio in the Pt layer. , BOL (mV), EOL (mV) and the amount of potential decrease (“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, which is a Pt layer, an initial potential (BOL) of 700.2 mV to 760.6 mV was achieved in the power generation test, and the durability including the subsequent poisoning test was achieved. The amount of potential decrease (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, remarkably excellent 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 containing 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 The initial potential (BOL) of the power generation test was obtained for Comparative Examples 11 and 12 in which 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. Was 446.8 mV to 716.4 mV, and the amount of potential decrease (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.

It was confirmed that the cathode, the MEA, and the battery according to the present invention had excellent durability. In addition, as described above, the durability test was performed following the poisoning test, and thus it was confirmed that the cathode, the MEA, and the battery according to the present invention also had excellent poisoning resistance. Furthermore, from the results of the power generation test, it was confirmed that the cathode, the MEA, and the battery according to the present invention also had excellent power generation performance.

Claims (14)

A cathode of a battery including an electrolyte membrane,
A first layer containing 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,
Only including,
The carbon catalyst includes iron,
Shows a weight loss rate of 12.0% by weight or less from 200 ° C. to 1200 ° C. measured by thermogravimetric analysis under a nitrogen atmosphere,
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 is 7.0 or more;
(B) the ratio of the normalized absorbance of 7135 eV to the normalized absorbance of 7110 eV is 7.0 or more;
A cathode comprising a carbon structure that exhibits: The cathode according to claim 1, wherein the ratio of the mesopore volume to the total pore volume of the carbon catalyst is 20% or more. 3. The cathode according to claim 1, wherein the carbon catalyst has an iron content of 0.01% by weight or more as measured by inductively coupled plasma mass spectrometry. 4. The cathode according to any one of claims 1 to 3 , wherein the carbon catalyst has a nitrogen atom content of 1.0% by weight or more as measured by elemental analysis by a combustion method. The cathode according to any one of claims 1 to 4 , wherein the carbon catalyst exhibits a ratio of a nitrogen atom content to a 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 5 , wherein the carbon catalyst includes iron and a metal other than iron. The cathode according to any one of claims 1 to 6 , 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 7 , 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 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 second layer is 0.05 or more. The cathode according to any one of claims 1 to 9 , wherein a ratio of a content of the platinum in the second layer to a content of the carbon catalyst in the first layer is 20.00% by weight or less. The cathode according to any one of claims 1 to 10 , 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 11 ; an anode; and an electrolyte membrane disposed between the cathode and the anode. A battery comprising the cathode according to any one of claims 1 to 11 or the membrane electrode assembly according to claim 12 . 14. The battery according to claim 13 , which is a fuel cell.

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