Carbon catalyst, electrode and battery

Abstract

Provided are a carbon catalyst, an electrode, and a battery that exhibit high catalytic activity while effectively avoiding problems caused by iron. The carbon catalyst has an L / La ratio of an average carbon network plane size L to a crystallite size La of 12 or more, the average carbon network plane size L being obtained by a temperature programmed desorption analysis capable of raising the temperature to 1600 DEG C, the crystallite size La is obtained from a diffraction peak near a diffraction angle (2 [theta]) of 43 DEG in an X-ray diffraction pattern obtained by powder X-ray diffraction using a CuK [alpha] ray, and the carbon catalyst has an iron content of 3000 ppm or less.

Description

Technical Field

[0001] The present invention relates to a carbon catalyst, an electrode, and a battery. Background Art

[0002] In Patent Document 1, an oxygen reduction catalyst is described. The oxygen reduction catalyst includes composite particles having titanium compound particles dispersed in a carbon structure, and the composite particles contain titanium, iron, carbon, nitrogen, and oxygen as constituent elements.

[0003] Citation List

[0004] Patent Document

[0005] [PTL 1]JP 2016-123894 A Summary of the Invention

[0006] Technical problem

[0007] Meanwhile, it has not been fully elucidated what kind of carbon structure improves the catalytic activity of carbon materials. In addition, it has been found that when a catalyst containing iron is used for an electrode of a fuel cell, defects occur due to leakage of iron from the catalyst.

[0008] The present invention has been made in view of the above-mentioned problems, and one of the objects of the present invention is to provide a carbon catalyst, an electrode, and a battery that exhibit high catalytic activity and at the same time effectively avoid problems caused by iron.

[0009] Solution to the problem

[0010] [1]In order to achieve the above-mentioned object, according to one embodiment of the present invention, there is provided a carbon catalyst having an L / La ratio of an average carbon network plane size L to a crystallite size La of 12 or more, the average carbon network plane size L being obtained by temperature-programmed desorption analysis capable of heating up to 1600 °C, and the crystallite size La being obtained from a diffraction peak near a diffraction angle (2θ) of 43° in an X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα rays; the carbon catalyst has an iron content of 3000 ppm or less. According to the present invention, there is provided a carbon catalyst that exhibits high catalytic activity and at the same time effectively avoids problems caused by iron.

[0011] [2]In the carbon catalyst according to the above-mentioned item [1], the crystallite size La may be 10.00 nm or less. [3]In the carbon catalyst according to the above-mentioned item [1] or [2], the average carbon network plane size L may be 5 nm or more.

[0012] [4] The carbon catalyst according to any one of the above-mentioned items [1] to [3] may contain nitrogen atoms. [5] The carbon catalyst according to any one of the above-mentioned items [1] to [4] may have a ratio of the nitrogen atom concentration to the carbon atom concentration obtained by X-ray photoelectron spectroscopy of 0.0005 or more.

[0013] [6] The carbon catalyst according to any one of the above-mentioned items [1] to [5] may have a BET specific surface area of 100 m 2 / g or more. [7] The carbon catalyst according to any one of the above-mentioned items [1] to [6] may have a micropore volume of 0.05 cm 3 / g or more. [8] The carbon catalyst according to any one of the above-mentioned items [1] to [7] may have a micropore volume of 2.50 cm 3 / g or less. [9] The carbon catalyst according to any one of the above-mentioned items [1] to [8] may have a mesopore volume of 0.001 cm 3 / g or more.

[10] The carbon catalyst according to any one of the above-mentioned items [1] to [9] may contain a non-noble metal other than iron.

[0014]

[11] To achieve the above-mentioned object, according to an embodiment of the present invention, there is provided an electrode including the carbon catalyst according to any one of the above-mentioned items [1] to

[10] . According to an embodiment of the present invention, there is provided an electrode that exhibits high catalytic activity and effectively avoids problems caused by iron at the same time.

[0015]

[12] To achieve the above-mentioned object, according to an embodiment of the present invention, there is provided a battery including the electrode according to the above-mentioned item

[11] . According to an embodiment of the present invention, there is provided a battery including an electrode that exhibits high catalytic activity and effectively avoids problems caused by iron at the same time.

[0016] Advantageous effects of the present invention

[0017] According to the present invention, there are provided a carbon catalyst, an electrode, and a battery that exhibit high catalytic activity and effectively avoid problems caused by iron at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is an explanatory view of a coronene model regarding the average carbon network plane size L.

[0019] Figure 2It is an illustrative schematic diagram showing the evaluation results of the characteristics of the carbon catalyst in an embodiment according to an embodiment of the present invention. Detailed Description

[0020] One embodiment of the present invention will be described below. The present invention is not limited to the examples described in this embodiment.

[0021] The carbon catalyst according to an embodiment of the present invention (hereinafter referred to as "the catalyst of the present invention") is a carbon material exhibiting catalytic activity. The catalyst of the present invention mainly contains carbon. Specifically, the carbon content of the catalyst of the present invention can be, for example, 70% by weight or more, preferably 75% by weight or more, more preferably 80% by weight or more, and particularly preferably 85% by weight or more. The carbon content of the catalyst of the present invention can be, for example, 100% by weight or less, 95% by weight or less, or 90% by weight or less. The carbon content of the carbon catalyst can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above. The carbon content of the carbon catalyst is obtained by elemental analysis (combustion method).

[0022] The catalyst of the present invention itself exhibits catalytic activity alone. That is, the catalyst of the present invention exhibits catalytic activity without containing noble metals supported thereon. The catalytic activity exhibited by the catalyst of the present invention is, for example, reduction reaction catalytic activity and / or oxidation reaction catalytic activity, more specifically, oxygen reduction reaction catalytic activity and / or hydrogen oxidation reaction catalytic activity, and at least oxygen reduction reaction catalytic activity.

[0023] The iron content of the catalyst of the present invention can be, for example, 3000 ppm or less, preferably 2000 ppm or less, more preferably 1000 ppm or less, still more preferably 500 ppm or less, still more preferably 300 ppm or less, still more preferably 200 ppm or less, still more preferably 100 ppm or less, and particularly preferably 50 ppm or less. 1 ppm means 0.0001% by weight. The iron content is obtained by inductively coupled plasma (ICP) atomic emission spectrometry.

[0024] When the iron content of the catalyst of the present invention falls within the range mentioned above, for example, even when the catalyst of the present invention is used as an electrode catalyst for a fuel cell, defects caused by iron can be effectively avoided.

[0025] The inventors of the present invention have conducted in-depth research on technical means for improving the catalytic activity of the carbon catalyst while effectively avoiding problems caused by iron, and thus have uniquely found that a carbon catalyst having a carbon structure with an L / La ratio of the average carbon network plane size L to the crystallite size La falling within a predetermined range exhibits high catalytic activity. Therefore, the inventors have completed the present invention.

[0026] That is, the catalyst of the present invention has an L / La ratio of the average carbon network plane size L to the crystallite size La of 12 or greater, where the average carbon network plane size L is obtained by temperature-programmed desorption analysis capable of heating up to 1600 °C, and the crystallite size La is obtained from the diffraction peak near a diffraction angle (2θ) of 43° in the X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα radiation.

[0027] The L / La ratio of the catalyst of the present invention is preferably 13 or greater, particularly preferably 14 or greater. The upper limit value of the L / La ratio of the catalyst of the present invention is not particularly limited as long as the effects of the present invention are obtained. The upper limit value can be, for example, 12500 or less, 10000 or less, 5000 or less, 1000 or less, 700 or less, 500 or less, 300 or less, 200 or less, or 100 or less. The L / La ratio of the catalyst of the present invention can be specified by arbitrarily combining any one of the above-mentioned lower limit values with any one of the above-mentioned upper limit values.

[0028] The L / La ratio falling within the above-mentioned range contributes to improving the catalytic activity of the catalyst of the present invention. That is, for example, when the L / La ratio is equal to or higher than the above-mentioned lower limit value, the carbon structure of the catalyst of the present invention includes a structure having appropriate planarity. Therefore, the active structures included in the carbon structure are effectively increased. Therefore, the catalytic activity of the catalyst of the present invention is effectively improved. At the same time, for example, when the L / La ratio is equal to or lower than the above-mentioned upper limit value, an electron conduction path is effectively formed in the carbon structure, and thus the catalytic activity of the catalyst of the present invention is more effectively improved.

[0029] The crystallite size La of the carbon catalyst is obtained from the diffraction peak near a diffraction angle (2θ) of 43° in the X-ray diffraction pattern of the carbon catalyst obtained by powder X-ray diffraction using CuKα radiation. When the carbon catalyst has a structure in which carbon hexagonal network planes are connected and extended in the a-axis direction, in the crystallites forming the curved carbon network plane that contributes to its catalytic activity, a diffraction line (10) of carbon having a peak top near a diffraction angle (2θ) of 43° (for example, in the range of 35° to 60°) appears in the X-ray diffraction pattern using CuKα radiation (hereinafter referred to as "diffraction peak f 10 ").

[0030] Then, the crystallite size La is calculated by analyzing diffraction peak f 10 That is, by using diffraction peak f 10Substitute the Bragg angle and full width at half maximum into the following Scherrer formula (Scherrer's formula) to calculate the crystallite size La: La = Kλ / (βcosθ). In the Scherrer formula, K represents the Scherrer constant (0.94), λ represents the wavelength of the CuKα ray (0.15418 nm), β represents the full width at half maximum (in radians), and θ represents the Bragg angle (in radians).

[0031] The crystallite size La of the catalyst of the present invention is not particularly limited as long as the effects of the present invention are obtained. The crystallite size La can be, for example, 10.00 nm or less, preferably 5.00 nm or less, more preferably 3.00 nm or less, still more preferably 2.50 nm or less, still more preferably 2.40 nm or less, still more preferably 2.35 nm or less, still more preferably 2.30 nm or less, still more preferably 2.25 nm or less, still more preferably 2.20 nm or less, and particularly preferably 2.15 nm or less.

[0032] The crystallite size La of the catalyst of the present invention can be, for example, 0.40 nm or more, 0.70 mm or more, 1.00 nm or more, 1.10 nm or more, 1.15 nm or more, 1.20 nm or more, 1.23 nm or more, or 1.25 nm or more. The crystallite size La of the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above.

[0033] The crystallite size La falling within the range mentioned above contributes to improving the catalytic activity of the catalyst of the present invention. That is, when the crystallite size La is too large, the carbon structure extends excessively in the a-axis direction, and there may be a problem that the active structure included in the carbon structure is excessively reduced. In contrast, when the crystallite size La is equal to or less than the upper limit value mentioned above, the extension of the carbon structure in the a-axis direction is appropriately suppressed, so that the active structure included in the carbon structure effectively increases. Therefore, the catalytic activity of the catalyst of the present invention is effectively improved. At the same time, when the crystallite size La is too small, the crystallinity of the carbon structure in the a-axis direction is too low. Therefore, the carbon structure has a disordered structure. Therefore, there may be a problem that almost no electron conduction path is formed in the carbon structure. In contrast, when the crystallite size La is equal to or greater than the lower limit value mentioned above, an electron conduction path is effectively formed in the carbon structure, and therefore the catalytic activity of the catalyst of the present invention is more effectively improved.

[0034] The average carbon network plane size L of the carbon catalyst is obtained by performing temperature-programmed desorption (TPD) analysis on the carbon catalyst that can be heated up to 1600 °C. That is to say, in the embodiments of the present invention, based on the results of quantitative determination of the desorbed gas during high-temperature TPD of the carbon catalyst using a temperature-programmed desorption analyzer (high-temperature TPD analyzer) that can be heated up to 1600 °C, the total amount of carbon edge planes of the carbon catalyst was calculated, and the average carbon network plane size L obtained from this total amount was calculated using the coronene model shown in Figure 1 . In the formula shown in Figure 1 , a0 represents the lattice constant of the graphite crystal in the a-axis direction, which is 0.2461 nm.

[0035] The average carbon network plane size L of the catalyst of the present invention is not particularly limited as long as the effects of the present invention are achieved. The average carbon network plane size L can be, for example, 5 nm or more, preferably 10 nm or more, more preferably 15 nm or more, still more preferably 20 nm or more, still more preferably 23 nm or more, still more preferably 25 nm or more, still more preferably 26 nm or more, still more preferably 27 nm or more, still more preferably 28 nm or more, and particularly preferably 29 nm or more.

[0036] The average carbon network plane size L of the catalyst of the present invention can be, for example, 5000 nm or less, 2000 nm or less, 1000 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 120 nm or less, 115 nm or less, or 113 nm or less. The average carbon network plane size L of the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above.

[0037] The average carbon network planar size L falling within the range mentioned above contributes to improving the catalytic activity of the catalyst of the present invention. That is to say, when the average carbon network planar size L is too small, the continuity of the carbon structure is too low. Therefore, there may be a problem that almost no conductive path of electrons is formed in the carbon structure. In contrast, when the average carbon network planar size L is equal to or greater than the lower limit value mentioned above, the continuity of the carbon structure is improved, and thus the catalytic activity of the catalyst of the present invention is effectively improved. On the other hand, when the average carbon network planar size L is too large, the hexagonal network planes included in the carbon structure are likely to stack. Therefore, the carbon structure has a structure with too large planarity. Therefore, there may be a problem that the non-active structures included in the carbon structure increase excessively. In contrast, when the average carbon network planar size L is equal to or less than the upper limit value mentioned above, the hexagonal network planes in the carbon structure do not stack excessively, and the non-active structures included in the carbon structure are effectively reduced. Therefore, the catalytic activity of the catalyst of the present invention is more effectively improved.

[0038] The BET specific surface area of the catalyst of the present invention is not particularly limited as long as the effects of the present invention are obtained. The BET specific surface area can be, for example, 100 m 2 / g or more, preferably 200 m 2 / g or more, more preferably 300 m 2 / g or more, still more preferably 400 m 2 / g or more, still more preferably 500 m 2 / g or more, still more preferably 600 m 2 / g or more, still more preferably 650 m 2 / g or more, particularly preferably 700 m 2 / g or more.

[0039] The BET specific surface area of the catalyst of the present invention can be, for example, 4000 m 2 / g or less, 3500 m 2 / g or less, 3000 m 2 / g or less, or 2500 m 2 / g or less. The BET specific surface area of the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above. The BET specific surface area is obtained by the nitrogen adsorption method.

[0040] The BET specific surface area falling within the range mentioned above contributes to improving the catalytic activity of the catalyst of the present invention. That is, when the BET specific surface area is too small, the carbon structures are closely stacked and the amount of exposed carbon atoms is small. Therefore, there may be a problem that it becomes difficult for the carbon structures to come into contact with the reactive material. In contrast, when the BET specific surface area is equal to or greater than the lower limit value mentioned above, the carbon structures effectively come into contact with the reactive material, and thus the catalytic activity of the catalyst of the present invention is effectively improved. On the other hand, when the BET specific surface area is too large, the carbon structures have a disordered structure. Therefore, there may be a problem that almost no conductive path for electrons is formed in the carbon structures. In contrast, when the BET specific surface area is equal to or less than the upper limit value mentioned above, a conductive path for electrons is effectively formed in the carbon structures. Therefore, the catalytic activity of the catalyst of the present invention is more effectively improved.

[0041] The micropore volume of the catalyst of the present invention is not particularly limited as long as the effects of the present invention are obtained. The micropore volume can be, for example, 0.05 cm 3 / g or more, preferably 0.07 cm 3 / g or more, more preferably 0.10 cm 3 / g or more, still more preferably 0.15 cm 3 / g or more, still more preferably 0.20 cm 3 / g or more, still more preferably 0.25 cm 3 / g or more, still more preferably 0.30 cm 3 / g or more, particularly preferably 0.35 cm 3 / g or more.

[0042] The micropore volume of the catalyst of the present invention can be, for example, 2.50 cm 3 / g or less, preferably 2.00 cm 3 / g or less, more preferably 1.50 cm 3 / g or less, still more preferably 1.40 cm 3 / g or less, still more preferably 1.30 cm 3 / g or less, still more preferably 1.20 cm 3 / g or less, still more preferably 1.15 cm 3 / g or less, still more preferably 1.10 cm 3 / g or less, still more preferably 1.05 cm 3 / g or less, still more preferably 1.00 cm 3 / g or less, particularly preferably 0.95 cm 3 / g is smaller. The micropore volume of the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above.

[0043] In an embodiment of the present invention, the micropores are pores each having a diameter of less than 2 nm, and the micropore volume is the total volume of the micropores included in the catalyst of the present invention. The micropore volume is obtained by the nitrogen adsorption method.

[0044] The micropore volume falling within the range mentioned above contributes to improving the catalytic activity of the catalyst of the present invention. That is, when the micropore volume is too small, the carbon structure is closely stacked, and the amount of exposed carbon atoms is small. Therefore, there may be a problem that it is difficult to contact between the carbon structure and the reactive material. In contrast, when the micropore volume is equal to or greater than the lower limit value mentioned above, the carbon structure effectively contacts the reactive material, and thus the catalytic activity of the catalyst of the present invention is effectively improved. On the other hand, when the micropore volume is too large, the carbon structure has a disordered structure. Therefore, there may be a problem that almost no conductive path of electrons is formed in the carbon structure. In contrast, when the micropore volume is equal to or less than the upper limit value mentioned above, a conductive path of electrons is effectively formed in the carbon structure. Therefore, the catalytic activity of the catalyst of the present invention is more effectively improved.

[0045] The mesopore volume of the catalyst of the present invention is not particularly limited as long as the effects of the present invention are obtained. The mesopore volume can be, for example, 0.001 cm 3 / g or more, preferably 0.005 cm 3 / g or more, and can be 0.01 cm 3 / g or more, preferably 0.05 cm 3 / g or more, particularly preferably 0.06 cm 3 / g or more.

[0046] The mesopore volume of the catalyst of the present invention can be, for example, 5.00 cm 3 / g or less, preferably 4.00 cm 3 / g or less, more preferably 3.00 cm 3 / g or less, still more preferably 2.00 cm 3 / g or less, still more preferably 1.70 cm 3 / g or less, still more preferably 1.60 cm 3 / g or less, still more preferably 1.50 cm 3 / g or less, still more preferably 1.45 cm 3 / g or less, particularly preferably 1.43 cm 3 / g or less. The mesopore volume of the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above.

[0047] In an embodiment of the present invention, mesopores are pores each having a diameter of 2 nm or more and 50 nm or less, and the mesopore volume is the total volume of the mesopores included in the catalyst of the present invention. The mesopore volume is obtained by the nitrogen adsorption method.

[0048] A mesopore volume falling within the range mentioned above contributes to improving the catalytic activity of the catalyst of the present invention. That is, when the mesopore volume is too small, the transport of substances having a size of about several tens of nanometers (for example, water and / or ion-exchange substances) in and out of the carbon structure is hindered. Therefore, there may be a problem that the catalytic reaction is inhibited. In contrast, when the mesopore volume is equal to or greater than the lower limit value mentioned above, the transport of substances to the carbon structure proceeds smoothly, and thus the catalytic activity is effectively improved. On the other hand, when the mesopore volume is too large, the volume of the carbon structure becomes too large, and there may be a problem that the catalytic activity is significantly reduced with respect to a carbon catalyst of a constant volume. In contrast, when the mesopore volume is equal to or less than the upper limit value mentioned above, the catalytic activity with respect to a constant volume is effectively maintained. Therefore, the catalytic activity of the catalyst of the present invention is more effectively improved.

[0049] The catalyst of the present invention preferably contains nitrogen atoms. That is, in this case, for example, the catalyst of the present invention contains nitrogen atoms doped into the carbon structure. Specifically, the ratio (hereinafter referred to as "N / C ratio") of the nitrogen atom concentration (atomic %) to the carbon atom concentration (atomic %) obtained by X-ray photoelectron spectroscopy (XPS) of the catalyst of the present invention can be, for example, 0.0005 or more, preferably 0.0007 or more, 0.0010 or more, preferably 0.0020 or more, more preferably 0.0030 or more, still more preferably 0.0040 or more, still more preferably 0.0050 or more, and particularly preferably 0.0055 or more.

[0050] The N / C ratio of the catalyst of the present invention can be, for example, 0.2000 or less, 0.1000 or less, 0.0500 or less, 0.0400 or less, 0.0300 or less, 0.0200 or less, or 0.0150 or less. The N / C ratio of the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above.

[0051] The N / C ratio falling within the range mentioned above contributes to improving the catalytic activity of the catalyst of the present invention. That is, when the N / C ratio is too small, the amount of nitrogen contained in the carbon structure is small, and the electron doping effect of nitrogen into carbon is small. Therefore, there may be a problem that the catalytic activity cannot be sufficiently improved. In contrast, when the N / C ratio is equal to or greater than the lower limit value mentioned above, the electron doping effect of nitrogen into carbon is obtained, and thus the catalytic activity of the catalyst of the present invention is effectively improved. At the same time, when the N / C ratio is too large, the carbon structure becomes disordered. Therefore, there may be a problem that almost no conductive path of electrons is formed in the carbon structure. In contrast, when the N / C ratio is equal to or less than the upper limit value mentioned above, a conductive path of electrons is effectively formed in the carbon structure. Therefore, the catalytic activity of the catalyst of the present invention is more effectively improved.

[0052] The catalyst of the present invention may contain a non-noble metal other than iron. Herein, a non-noble metal is a metal other than a noble metal. Noble metals are ruthenium (Ru), palladium (Pd), rhodium (Rh), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), or gold (Au).

[0053] The non-noble metal contained in the catalyst of the present invention is not particularly limited as long as the effects of the present invention are obtained. The non-noble metal may be, for example, a non-noble metal belonging to Groups II to XIV of the periodic table, preferably a non-noble metal belonging to the third to fifth periods of Groups II to XIV of the periodic table.

[0054] Specifically, the non-noble metal contained in the catalyst of the present invention is more preferably, for example, one or more selected from the following: magnesium (Mg); aluminum (Al); calcium (Ca); titanium (Ti); manganese (Mn); cobalt (Co); nickel (Ni); copper (Cu); zinc (Zn); yttrium (Y); zirconium (Zr); niobium (Nb); molybdenum (Mo); and tin (Sn), particularly preferably one or more selected from the following: Mg; Al; Ca; Cu; Zn; Y; Zr; Mo; and Sn.

[0055] The content of non-noble metals other than iron in the catalyst of the present invention (when the catalyst of the present invention contains a plurality of non-noble metals, this content is the total content of the plurality of non-noble metals) can be, for example, 50 ppm or more, 100 ppm or more, 1000 ppm or more, 10000 ppm or more, or 100000 ppm or more. The content of non-noble metals other than iron in the catalyst of the present invention can be, for example, 500000 ppm or less, 400000 ppm or less, 300000 ppm or less, or 200000 ppm or less. The content of non-noble metals other than iron in the catalyst of the present invention can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above. The content of non-noble metals is obtained by inductively coupled plasma (ICP) atomic emission spectrometry.

[0056] The non-noble metals other than iron contained in the catalyst of the present invention contribute to improving the catalytic activity of the catalyst of the present invention. That is, for example, when the catalyst of the present invention contains non-noble metals other than iron derived from the following raw materials for carbonization, a specific carbon structure having catalytic active sites can be effectively formed by carbonization in the presence of non-noble metals.

[0057] When the catalyst of the present invention contains non-noble metals derived from the following raw materials for carbonization, since the non-noble metals are contained in the raw materials for carbonization, the catalyst of the present invention contains non-noble metals. In this case, the catalyst of the present invention contains non-noble metals within the framework of the porous structure forming the catalyst. Even when the catalyst of the present invention is a carbonized material produced by carbonization followed by the following metal removal treatment, the non-noble metals derived from the raw materials for carbonization remain within the framework of the catalyst of the present invention. Among the non-noble metals contained in the catalyst of the present invention, the weight of the non-noble metals contained within the framework of the catalyst of the present invention can be greater than the weight of the non-noble metals contained on the surface of the framework of the catalyst of the present invention.

[0058] The non-noble metals within the framework of the catalyst of the present invention can be detected, for example, by subjecting the framework to a surface etching treatment and analyzing the cross-section exposed by the etching treatment. That is, in this case, when an etching treatment is performed on one particle of the catalyst of the present invention, non-noble metals are detected in the cross-section of the particle exposed by the etching treatment. The non-noble metals contained in the catalyst of the present invention can be detected, for example, by inductively coupled plasma (ICP) atomic emission spectrometry of the catalyst of the present invention.

[0059] The carbon material forming the catalyst of the present invention is preferably a carbonized material obtained by carbonizing a raw material containing the following organic substances. In this regard, when the catalyst of the present invention is a carbonized material obtained by carbonizing a raw material containing an organic substance and a non-noble metal other than iron, the carbon structure of the catalyst of the present invention contains the non-noble metal. However, it is conceivable that the catalytic activity of the catalyst of the present invention is mainly based on the active sites included in the carbon structure itself, rather than the non-noble metal. This is supported by the following fact. Even when a metal removal treatment is performed on the catalyst of the present invention containing a non-noble metal derived from the raw material for carbonization to reduce the content of the non-noble metal, the catalytic activity of the catalyst of the present invention after the metal removal treatment is not significantly reduced compared to before the metal removal treatment.

[0060] The catalyst of the present invention may not contain any noble metals. That is, as described above, the catalyst of the present invention itself exhibits catalytic activity without containing noble metals supported thereon, and thus the catalyst does not have to contain noble metals. However, the catalyst of the present invention can be used as a carbon support for supporting a metal catalyst (such as a noble metal).

[0061] When the catalyst of the present invention contains a non-noble metal other than iron, the content of metals other than Mg, Al, Ca, Ti, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, and Sn, or the content of metals other than Mg, Al, Ca, Cu, Zn, Y, Zr, Mo, and Sn in the catalyst of the present invention can be, for example, 3000 ppm or less, 2000 ppm or less, 1000 ppm or less, 500 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, or 50 ppm or less.

[0062] The method for preparing the catalyst of the present invention is not particularly limited as long as the method can provide the catalyst of the present invention having the characteristics mentioned above. For example, the method is preferably a method including carbonizing a raw material containing an organic substance. The organic substance contained in the raw material is not particularly limited as long as the organic substance can be carbonized. The organic compound contained in the organic substance can be a polymer (for example, a thermosetting resin and / or a thermoplastic resin), and / or can be an organic compound having a relatively small molecular weight.

[0063] Specific examples of the organic substance may include one or more selected from the following: polyacrylonitrile; polyacrylonitrile-polyacrylic acid copolymer; polyacrylonitrile-poly(methyl acrylate) copolymer; polyacrylonitrile-poly(methacrylic acid) copolymer; polyacrylonitrile-poly(methacrylic acid)-poly(methallyl sulfonic acid) copolymer; polyacrylonitrile-poly(methyl methacrylate) copolymer; phenolic resin; polyfurfuryl alcohol; furan; furan resin; phenol formaldehyde resin; melamine; melamine resin; epoxy resin; nitrogen-containing chelating resin (e.g., one or more selected from the following: polyamine type resin; iminodiacetic acid type resin; aminophosphoric acid type resin; and aminomethylphosphonic acid type resin); polyamideimide resin; pyrrole; polypyrrole; polyvinylpyrrole; 3-methylpolypyrrole; acrylonitrile; poly(vinylidene 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; carboxymethyl cellulose; lignin; chitin; chitosan; asphalt; silk; wool; polyamino acid; nucleic acid; DNA; RNA; hydrazine; hydrazide; urea; salen; polycarbazole; polybismaleimide; triazine; polyacrylic acid; polyacrylate; polymethacrylate; polymethacrylic acid; polyurethane; polyamide-based amine; polycarbodiimide; naphthalene; naphthalene analog; anthracene; anthracene analog; hydroxybenzene; hydroxybenzene analog; carbazole; quinoline; cyanuric acid; naphthoic acid; methylene blue; and phthalocyanine.

[0064] The organic substance is preferably a nitrogen-containing organic substance. For example, the nitrogen-containing organic substance contains a nitrogen-containing organic compound. The nitrogen-containing organic compound is not particularly limited as long as the organic compound contains a nitrogen atom in its molecule.

[0065] The catalyst of the present invention is preferably a carbonized material obtained by carbonizing a raw material containing an organic substance and a non-noble metal. In this case, the catalyst of the present invention may be a carbonized material that has been subjected to a metal removal treatment after carbonization. The metal removal treatment is a treatment for reducing the amount of non-noble metal derived from the raw material contained in the carbonized material. Specifically, for example, the metal removal treatment preferably involves pickling treatment and / or electrolysis treatment.

[0066] Carbonization is carried out by heating the raw material at a temperature at which the organic substance contained in the raw material is carbonized. The carbonization temperature is not particularly limited as long as the raw material is carbonized at this temperature. For example, the carbonization temperature is preferably 900 °C or higher, more preferably 1000 °C or higher, still more preferably 1100 °C or higher, and particularly preferably 1200 °C or higher.

[0067] The carbonization temperature can be, for example, 3000 °C or lower, preferably 2500 °C or lower, more preferably 2000 °C or lower, and particularly preferably 1900 °C or lower. The carbonization temperature can be specified by arbitrarily combining any one of the lower limit values mentioned above with any one of the upper limit values mentioned above. The heating rate to reach the carbonization temperature is not particularly limited and can be, for example, 0.5 °C / minute or greater and 300 °C / minute or smaller. The carbonization is preferably carried out in an inert atmosphere (such as a nitrogen atmosphere).

[0068] The catalyst of the present invention can be a carbon material obtained by further incorporating a non-noble metal to be supported on a carbonized material, which is obtained by carbonizing a raw material containing an organic substance and a non-noble metal. In this case, the catalyst of the present invention contains a first non-noble metal derived from the raw material used for carbonization and a second non-noble metal supported on the catalyst after carbonization. The first non-noble metal and the second non-noble metal can be the same non-noble metal or different non-noble metals.

[0069] The first non-noble metal and the second non-noble metal are not particularly limited as long as the effects of the present invention are obtained. For example, the non-noble metals can each independently be non-noble metals belonging to Groups II to XIV of the periodic table, and are preferably non-noble metals belonging to the third to fifth periods of Groups II to XIV of the periodic table.

[0070] Specifically, for example, the first non-noble metal and the second non-noble metal are each independently preferably one or more selected from the following: Mg; Al; Ca; Ti; Mn; Co; Ni; Cu; Zn; Y; Zr; Nb; Mo; and Sn, and particularly preferably one or more selected from the following: Mg; Al; Ca; Cu; Zn; Y; Zr; Mo; and Sn.

[0071] For example, preferably, the first non-noble metal is one or more selected from the following: Mg; Al; Ca; Ti; Mn; Co; Ni; Cu; Zn; and Sn, and the second non-noble metal is one or more selected from the following: Y; Zr; Nb; and Mo, and particularly preferably, the first non-noble metal is one or more selected from the following: Mg; Al; Ca; Cu; Zn; and Sn, and the second non-noble metal is one or more selected from the following: Y; Zr; and Mo.

[0072] When the catalyst of the present invention contains a specific type of first non-noble metal (e.g., one selected from the groups mentioned above) and a specific type of second non-noble metal different from the first non-noble metal (e.g., one selected from the groups mentioned above and different from the first non-noble metal), the weight of the first non-noble metal contained within the framework of the catalyst of the present invention can be greater than the weight of the first non-noble metal contained on the surface of the framework of the catalyst of the present invention, and the weight of the second non-noble metal contained on the surface of the framework of the catalyst of the present invention can be greater than the weight of the second non-noble metal contained within the framework of the catalyst of the present invention.

[0073] An electrode according to an embodiment of the present invention (hereinafter referred to as "the electrode of the present invention") includes the catalyst of the present invention. That is, the electrode of the present invention can include an electrode substrate and the catalyst of the present invention supported on the electrode substrate. The electrode of the present invention is preferably a battery electrode. Specifically, the electrode of the present invention is preferably an electrode for, for example, a fuel cell (e.g., a polymer electrolyte fuel cell or a microbial fuel cell), an air battery, a water electrolyzer (e.g., a polymer electrolyte water electrolyzer), a redox flow battery, or a halogen battery.

[0074] The electrode of the present invention can be a cathode or an anode, but is preferably a cathode. That is, the electrode of the present invention is a cathode or an anode of a fuel cell, an air battery, a water electrolyzer, a redox flow battery, or a halogen battery, and is preferably a cathode thereof.

[0075] A battery according to an embodiment of the present invention (hereinafter referred to as "the battery of the present invention") includes the electrode of the present invention. Specifically, the battery of the present invention is preferably a fuel cell (e.g., a polymer electrolyte fuel cell or a microbial fuel cell), an air battery, a redox flow battery, or a halogen battery including the electrode of the present invention. The battery of the present invention is preferably a membrane electrode assembly (MEA) including the electrode of the present invention.

[0076] The battery of the present invention is a battery including the electrode of the present invention as a cathode or an anode, preferably a battery including the electrode of the present invention as a cathode. That is, the battery of the present invention is a fuel cell, an air battery, a redox flow battery, or a halogen battery including the electrode of the present invention as a cathode or an anode, and is preferably a fuel cell, an air battery, a redox flow battery, or a halogen battery including the electrode of the present invention as a cathode.

[0077] Next, specific examples according to embodiments of the present invention will be described.

[0078] Embodiment

[0079] [Example 1]

[0080] Dissolve 0.5 g of polyvinylpyridine (PVP) in 200 mL of DMF, and further add 18.03 g of tin(II) chloride (SnCl2) thereto to prepare a homogeneous solution. The solution is vacuum dried at 80 °C for 1 day to provide a raw material for carbonization.

[0081] Load the obtained raw material into a quartz tube, heat it up to 1200 °C at a rate of 50 °C / min in a nitrogen atmosphere in a focusing furnace (image furnace), and hold it at 1200 °C for 1 hour to carry out carbonization.

[0082] Subsequently, place silicon nitride balls each having a diameter of 10 mm in a planetary ball mill (P-7, manufactured by Fritsch Japan Co., Ltd.), and crush the carbonized material obtained by carbonization with the planetary ball mill.

[0083] Add 100 mL of concentrated hydrochloric acid to the crushed carbonized material, and heat the mixture under reflux for 2 hours. Thereafter, filter the solution containing the carbonized material with a filter membrane, and wash the carbonized material with distilled water until the filtrate becomes neutral. Vacuum dry the collected carbonized material.

[0084] Load the carbonized material that has undergone the metal removal treatment as described above into a quartz tube, heat it in a nitrogen atmosphere in a focusing furnace, and hold it at 1200 °C for 30 minutes to carry out heat treatment. Thus, the carbon catalyst of Example 1 is obtained.

[0085] [Example 2]

[0086] Except for the following, the preparation of the raw material, the carbonization of the raw material, and the crushing of the obtained carbonized material are carried out in the same manner as in Example 1 above: use 0.5 g of cyanuric acid instead of PVP; and use 10.56 g of zinc(II) chloride (ZnCl2) instead of tin chloride.

[0087] Add 20 mL of concentrated hydrochloric acid to the crushed carbonized material, and stir the mixture for 30 minutes. Thereafter, allow the carbonized material to precipitate, and remove the solution. This treatment is repeated several times, then add distilled water to the precipitate, and stir the mixture. Filter the solution containing the carbonized material with a filter membrane, and wash the carbonized material with distilled water until the filtrate becomes neutral. Vacuum dry the collected carbonized material.

[0088] Load the carbonized material that has undergone the metal removal treatment as described above into a quartz tube, heat it in a nitrogen atmosphere in a focusing furnace, and hold it at 1200 °C for 30 minutes to carry out heat treatment. Thus, the carbon catalyst of Example 2 is obtained.

[0089] [Example 3]

[0090] Example 3's carbon catalyst was obtained in the same manner as Example 2 above, except as follows: 0.5 g of polyacrylonitrile (PAN) was used instead of cyanuric acid; and 25.34 g of copper(II) chloride (CuCl2) was used instead of zinc chloride.

[0091] [Example 4]

[0092] Example 4's carbon catalyst was obtained in the same manner as Example 2 above, except as follows: 0.5 g of polyvinylidene chloride (PVDC) was used instead of cyanuric acid; 34.67 g of copper(II) chloride (CuCl2) was used instead of zinc chloride; and 20 mL of concentrated nitric acid was used instead of concentrated hydrochloric acid.

[0093] [Example 5]

[0094] Example 5's carbon catalyst was obtained in the same manner as Example 3 above, except that 17.94 g of magnesium chloride (MgCl2·6H2O) was used instead of copper chloride.

[0095] [Example 6]

[0096] A carbon catalyst was obtained in the same manner as Example 1 above, except as follows: 0.5 g of PAN was used instead of PVP; and 10.56 g of zinc(II) chloride (ZnCl2) was used instead of tin chloride. The carbon catalyst was heated to 900 °C at a rate of 50 °C per minute in an ammonia atmosphere and held at 900 °C for 1 hour for nitrogen doping treatment.

[0097] 100 mg of the nitrogen-doped carbon catalyst was further immersed in 130 mL of an aqueous solution containing 1.3 mg of yttrium chloride (YCl3·6H2O). Thus, the carbon catalyst was impregnated with yttrium chloride.

[0098] After that, the aqueous solution containing the carbon catalyst and yttrium chloride was dried at 60 °C, heated to 1000 °C at a rate of 50 °C per minute in a hydrogen atmosphere, and held at 1000 °C for 0.5 hour for hydrogen reduction. Thus, the carbon catalyst of Example 6 was obtained.

[0099] [Example 7]

[0100] Example 7's carbon catalyst was obtained in the same manner as Example 6 above, except that 1.2 mg of molybdenum(V) chloride (MoCl5) was used instead of yttrium chloride.

[0101] [Example 8]

[0102] Example 8's carbon catalyst was obtained in the same manner as Example 6 above, except that 1.0 mg of zirconium(IV) chloride (ZrCl4) was used instead of yttrium chloride.

[0103] [Example 9]

[0104] Dissolve 0.5 g of linear phenolic resin in 80 g of acetone, and further add 11.20 g of copper(II) chloride (CuCl₂) thereto to prepare a homogeneous solution. Vacuum-dry the solution at 80 °C for 1 day to provide a raw material for carbonization.

[0105] Load the obtained raw material into a quartz tube, heat it up to 1200 °C at a rate of 50 °C / minute in a nitrogen atmosphere in a focusing furnace, and hold it at 1200 °C for 1 hour to carry out carbonization.

[0106] Subsequently, place silicon nitride balls each having a diameter of 10 mm in a planetary ball mill (P-7, manufactured by Fritsch Japan Co., Ltd.), and crush the carbonized material obtained by carbonization with the planetary ball mill.

[0107] Add 20 mL of concentrated nitric acid to the crushed carbonized material, and stir the mixture for 30 minutes. After that, allow the carbonized material to precipitate and remove the solution. This treatment is repeated several times, then add distilled water to the precipitate and stir the mixture. Filter the solution containing the carbonized material with a filter membrane, and wash the carbonized material with distilled water until the filtrate becomes neutral. Vacuum-dry the collected carbonized material.

[0108] Load the carbonized material that has undergone the metal removal treatment as described above into a quartz tube, heat it in a nitrogen atmosphere in a focusing furnace, and hold it at 1200 °C for 30 minutes to carry out heat treatment. Thus, the carbon catalyst of Example 9 was obtained.

[0109] [Example 10]

[0110] Dissolve 1.5 g of naphthoic acid in 80 g of acetone, and further add 23.23 g of aluminum(III) chloride (AlCl₃) and 23.75 g of zinc(II) chloride (ZnCl₂) thereto to prepare a homogeneous solution. Vacuum-dry the solution at 80 °C for 1 day to provide a raw material for carbonization. After that, obtain the carbon catalyst of Example 10 in the same manner as in Example 9 above, except that 20 mL of nitric acid-hydrofluoric acid (HNO₃:HF = 1 mol:1 mol) is used instead of concentrated nitric acid.

[0111] [Example C1]

[0112] Dissolve 0.5 g of linear phenolic resin in 80 g of acetone, and further add 1.08 g of copper phthalocyanine thereto, and ultrasonically stir the mixture for 30 minutes. Subsequently, evaporate the acetone serving as the solvent with a rotary evaporator. After that, vacuum-dry the residue at 70 °C overnight to provide a raw material for carbonization.

[0113] The obtained raw materials were heated to 800 °C at a rate of 10 °C per minute in a nitrogen atmosphere in a focusing furnace and held at 800 °C for 1 hour for carbonization.

[0114] After that, the carbonized material was pulverized and pickled in the same manner as in Example 2 above to provide the carbon catalyst of Example C1.

[0115] [Example C2]

[0116] The carbon catalyst of Example C2 was obtained in the same manner as in Example 2 above, except for the following: 0.5 g of carbazole was used instead of cyanuric acid; and in addition to 10.56 g of zinc chloride, 8.50 g of zinc chloride and 8.29 g of aluminum(III) chloride (AlCl3) were further added thereto.

[0117] [Powder X-ray diffraction]

[0118] Powder X-ray diffraction (XRD) measurements were performed on the carbon catalysts of the respective examples using an X-ray powder diffractometer (XRD-6100, manufactured by Rigaku Corporation). CuKα rays were used as the incident X-rays, the voltage and current applied to the X-ray tube were set to 40 kV and 15 mA, respectively, and the measurement angle range (2θ) was set in the range of 5° to 90°.

[0119] As described above, when the carbon catalyst has a structure in which carbon hexagonal network planes are connected and extended in the a-axis direction, in the microcrystals forming the curved carbon network plane contributing to its catalytic activity, a diffraction peak f appears in the X-ray diffraction pattern using CuKα rays. 10 , the diffraction peak f 10 is a diffraction line (10) of carbon having a peak top near a diffraction angle (2θ) of 43° (for example, in the range of 35° to 60°). Specifically, in the examples, the diffraction peak f 10 is defined as a diffraction peak having a diffraction angle (2θ) of 43.5° ± 1.0° and a full width at half maximum of 7.5° ± 6.5°.

[0120] Then, the diffraction peak f 10 was analyzed, and the crystallite size La was calculated. That is, the crystallite size La was calculated by substituting the Bragg angle and the full width at half maximum of the diffraction peak f 10 into the following Scherrer formula: La = Kλ / (βcosθ). In the Scherrer formula, K represents the Scherrer constant (0.94), λ represents the wavelength of CuKα rays (0.15418 nm), β represents the full width at half maximum (in radians), and θ represents the Bragg angle (in radians).

[0121] [Temperature-programmed desorption analysis]

[0122] The carbon catalysts of the respective examples were subjected to temperature-programmed desorption analysis using a temperature-programmed desorption analyzer (high-temperature TPD analyzer) capable of heating up to 1600°C. The high-temperature TPD analyzer is a device capable of heating a graphite crucible serving as a main body to be heated to a high temperature of 1600°C or higher by high-frequency electromagnetic induction heating. Details of the high-temperature TPD analyzer are described in the journal Carbon (Takafumi Ishi, Susumu Kashihara, Yasuto Hoshikawa, Jun-ichi Ozaki, Naokatsu Kannari, Kazuyuki Takai, Toshiaki Enoki, Takashi Kyotani, Carbon, Vol. 80, December 2014, pp. 135-145).

[0123] The carbon catalyst was placed in the high-temperature TPD analyzer and heated under a high vacuum of 5×10 -5 Pa or less, and the desorbed gas was measured using a quadrupole mass spectrometer (QMS).

[0124] Specifically, first, 1 mg of the carbon catalyst was filled into the graphite crucible and placed in a quartz reaction tube attached to the high-temperature TPD analyzer. Subsequently, the inside of the analyzer was evacuated to a pressure of 5×10 -5 Pa using a turbomolecular pump, and then heated from room temperature to 1600°C at a heating rate of 10°C / minute. During the heating, the desorbed gas was detected, and the correlation between the temperature (horizontal axis) and the detection intensity (vertical axis) was recorded. Then, the amount of the desorbed gas was determined. That is, the integral value (detection intensity area) of the desorbed gas detection intensity from room temperature at the start of the heat treatment to the temperature (1600°C) at the time of measurement was calculated.

[0125] Meanwhile, by using a predetermined amount of standard gas, a calibration curve showing the correlation between the desorption amount of gas and the detection intensity area was formed. When analyzing the desorbed gas from the sample with the QMS, the fragment intensity ratios of various gaseous species (H2, H2O, CO, CO2, N2, HCN, O2, CH4, C2H6, C3H6, and C3H8) were studied and used for the qualitative analysis of the desorbed gas to clearly distinguish gaseous species with the same mass included in the desorbed gas (species with a mass number of 28 can be CO, N2, C2H4, etc.). Then, based on the detection intensity area obtained by measurement, as well as the calibration curve and the fragment intensity ratio, the desorption amount (release amount) of gas from the carbon catalyst was determined. In addition, to verify the appropriateness of the formed calibration curve, Ketjen black EC600JD (Lion Specialty Chemicals Co., Ltd.) was used for measurement, and it was recognized that the amount of edge hydrogen fell within the range of 1000 [μmol / g] to 1500 [μmol / g].

[0126] In this paper, the actual size of the carbon network plane forming carbon can be evaluated according to the average carbon network plane size L determined by the amount of the edge plane of carbon. In the embodiments of the present invention, based on the results of the quantitative determination of the desorbed gas by high-temperature TPD of the carbon catalyst, the total amount of the carbon edge plane of the carbon catalyst was calculated, and the average carbon network plane size L determined by this total amount was calculated using the coronene model shown in Figure 1 . In the formula shown in Figure 1 , a0 represents the lattice constant of the graphite crystal in the a-axis direction, which is 0.2461 nm.

[0127] Furthermore, it is known that the phenolic hydroxyl group of the oxygen-containing compound decomposes in the form of carbon monoxide by heating, and the hydrogen atom derived from the hydroxyl group remains at the carbon edge. Therefore, the amount of hydrogen determined by high-temperature TPD may include the contribution of hydrogen derived from the phenolic hydroxyl group. Therefore, for the strict calculation of the total amount of the edge plane, it is necessary to consider the phenolic hydroxyl group. For example, both the ether (-O) and the phenolic hydroxyl group (-OH) are functional groups that desorb in the form of CO near 700 °C. After the phenolic hydroxyl group desorbs in the form of CO, H remains at the edge site. Therefore, the phenolic hydroxyl group desorbs in the form of CO and then desorbs in the form of H2 at a temperature of 1000 °C or higher. In addition, the phenolic hydroxyl group is different from the ether in that two gaseous species (CO and H2) desorb from one functional group. According to the CO desorption observed by TPD analysis, the ether and the phenolic hydroxyl group cannot be distinguished. Therefore, the CO desorption is divided into two cases: the case where CO is derived only from the ether; and the case where CO is derived only from the phenolic hydroxyl group. In each case, the amount of the carbon edge site and L are calculated.

[0128] In high-temperature TPD, it is assumed that CO desorbs from phenolic hydroxyl groups or ethers. The possible values of the total amount (N 边缘 ) of the edge plane of the carbon catalyst are calculated using the following two formulas. When all the desorbed CO originates from ethers, the amount of N 边缘 always has a maximum value. Therefore, N 边缘 (maximum) is calculated by the following formula: N 边缘 (maximum) [mol / g] = CO [mol / g] + CO2 [mol / g] + H2 [mol / g] × 2. When all the desorbed CO originates from phenolic hydroxyl groups, the amount of N 边缘 has a minimum value. Therefore, N 边缘 (minimum) is calculated by the following formula: N 边缘 (minimum) [mol / g] = CO2 [mol / g] + H2 [mol / g] × 2. In this formula, CO [mol / g], CO2 [mol / g], and H2 [mol / g] are the desorption gas amounts of carbon monoxide, carbon dioxide, and hydrogen determined by high-temperature TPD, respectively.

[0129] On the other hand, the average carbon network plane size L is determined by the following formula using the atomic weight of carbon atoms of 12 g / mol and the lattice constant of graphite crystals in the a-axis direction of 0.2461 nm: L [nm] = 2 × 1 / 12 × 0.2461 / N 边缘 [mol / g]. In this article, the maximum value "L (maximum)" and the minimum value "L (minimum)" of L are calculated using the following two formulas: "L (maximum)" [nm] = 2 × 1 / 12 × 0.2461 / N 边缘 (minimum) [mol / g]; and "L (minimum)" [nm] = 2 × 1 / 12 × 0.2461 / N 边缘 (maximum) [mol / g].

[0130] As described above, since CO originating from ethers and CO originating from phenolic hydroxyl groups cannot be distinguished, two values (maximum and minimum) of the average carbon network plane size L are calculated. "L (maximum)" corresponds to the case where only phenolic hydroxyl groups are present, and "L (minimum)" corresponds to the case where only ethers are present. However, it is difficult to consider that the actual material has only one of phenolic hydroxyl groups or ethers. Therefore, the average carbon network plane size L of the carbon catalyst is defined as the median "L (average)" of "L (maximum)" and "L (minimum)". "L (average)" is obtained by dividing the sum of "L (minimum)", which is the minimum value of the possible values of the average carbon network plane size L, and "L (maximum)", which is the maximum value of the possible values, by 2. "L (average)" is obtained as the average carbon network plane size L of the carbon catalyst.

[0131] [X-ray photoelectron spectroscopy (XPS)]

[0132] The photoelectron spectra of the inner shell energy levels of carbon atoms and nitrogen atoms on the surface of the carbon catalysts of each example were measured using an X-ray photoelectron spectroscopy apparatus (AXIS Nova, manufactured by Kratos Analytical Ltd.). AlKα rays (10 mA, 15 kV, pass energy: 40 eV) were used for the X-ray source. In the obtained photoelectron spectra, the binding energy was corrected so that the peak top of the C1s peak from the 1s orbital of carbon atoms was located at 284.5 eV.

[0133] By XPS wide scan analysis, the atomic concentrations (atomic %) of carbon atoms and nitrogen atoms on the surface of the carbon catalysts were determined based on the peak areas and detection sensitivity coefficients in the photoelectron spectra. In addition, the N / C ratio was calculated by dividing the nitrogen atom concentration (atomic %) by the carbon atom concentration (atomic %). In the calculation of the atomic concentration (atomic %), it was assumed that the carbon catalyst contained carbon atoms, nitrogen atoms, oxygen atoms, sulfur atoms, boron atoms, chlorine atoms, and metal atoms included in the raw materials for carbonization.

[0134] [Specific surface area and pore volume]

[0135] The specific surface area and pore volume of the carbon catalysts of each example were measured by the nitrogen adsorption method using a specific surface area - pore distribution measuring apparatus (BELSORP MAX, manufactured by MicrotracBEL Corp.).

[0136] That is, first, 0.01 g of the carbon catalyst was held at 200 °C and 6.7×10 -2 Pa for 2 hours to remove the water adsorbed on the carbon catalyst. Subsequently, the nitrogen adsorption isotherm at 77 K was obtained by the BET method. By measuring the change in the amount of nitrogen adsorbed on the carbon catalyst related to the change in nitrogen pressure at 77 K, the nitrogen adsorption isotherm at 77 K was obtained. In addition, the BET specific surface area (m 2 / g) of the carbon catalyst based on the nitrogen adsorption method was obtained from the nitrogen adsorption isotherm at 77 K. In addition, from the nitrogen adsorption isotherm at 77 K, the micropore volume (cm 3 / g) was obtained by the MP method, and the mesopore volume (cm 3 / g) was obtained by the DH method.

[0137] [Evaluation of catalytic activity]

[0138] The catalytic activity of each carbon catalyst was evaluated using a rotating ring-disk electrode apparatus (RRDE-3A Rotating Ring-disk Electrode Apparatus ver.1.2, manufactured by BAS Inc.) and a dual electrochemical analyzer (CHI700C, manufactured by ALS Co., Ltd.).

[0139] That is, first, a rotating ring-disk electrode apparatus of a three-electrode system was fabricated, and the three-electrode system included a working electrode containing each carbon catalyst. Specifically, 5 mg of the carbon catalyst, 50 μL of 5% NAFION (trademark) (manufactured by Sigma-Aldrich, NAFION perfluorinated ion-exchange resin, 5% solution (product number: 510211)), 400 μL of water, and 100 μL of isopropanol were mixed to prepare a slurry. Then, the slurry was ultrasonically treated for 10 minutes and then homogenizer-treated for 2 minutes. Then, the resulting slurry was applied to the working electrode (ring-disk electrode for RRDE-3A, platinum ring-gold disk electrode, disk diameter: 4 mm, manufactured by BAS Inc.) so that the content of the carbon catalyst per unit area of the electrode became 0.1 mg / cm 2 , and dried to produce a working electrode loaded with the carbon catalyst.

[0140] In addition, a platinum electrode (23 cm Pt counter electrode, manufactured by BAS Inc.) was used as the counter electrode, and a reversible hydrogen electrode (RHE) (storage type reversible hydrogen electrode, manufactured by EC Frontier Co., Ltd.) was used as the reference electrode. Thus, a rotating ring-disk electrode apparatus was obtained, which included a working electrode containing the carbon catalyst, a platinum electrode serving as the counter electrode, and a reversible hydrogen electrode (RHE) serving as the reference electrode. In addition, a 0.1 M aqueous perchloric acid solution was used as the electrolyte.

[0141] In addition, the catalytic activity of each carbon catalyst was measured using the rotating ring-disk electrode apparatus. That is, linear sweep voltammetry in a nitrogen atmosphere (N2-LSV) and linear sweep voltammetry in an oxygen atmosphere (O2-LSV) were performed using the rotating ring-disk electrode apparatus of the three-electrode system, and the three-electrode system included a working electrode containing each carbon catalyst.

[0142] In N2-LSV, first, nitrogen was bubbled for 10 minutes to remove oxygen in the electrolyte. After that, the electrode was rotated at a speed of 1600 rpm, and the current density when the potential was scanned at a scan rate of 20 mV / second was recorded as a function of the potential (N2-LSV).

[0143] Thereafter, in O2-LSV, oxygen was bubbled for 10 minutes and the electrolyte was saturated with oxygen. Thereafter, the electrode was rotated at 1600 rpm, and the current density during potential scanning at a scan rate of 20 mV / second was recorded as a function of potential (O2-LSV).

[0144] Then, by subtracting N2-LSV from O2-LSV, an oxygen reduction voltammogram was obtained. In the obtained oxygen reduction voltammogram, the plus and minus signs were placed before the numerical values so that the reduction current had a negative value and the oxidation current had a positive value.

[0145] Based on the oxygen reduction voltammogram thus obtained, the voltage (oxygen reduction onset potential EO2) (V, relative to NHE) at which a reduction current of -10 μA / cm 2 flowed was recorded as an index of the catalytic activity of each carbon catalyst itself.

[0146] [Results]

[0147] Figure 2 The evaluation results of the characteristics of the carbon catalysts of the examples are shown. As Figure 2 shown, the oxygen reduction onset potential EO2 (V, relative to NHE) of the carbon catalysts of Examples 1 to 10 was higher than that of the carbon catalysts of Examples C1 and C2. That is, the catalytic activity exhibited by each of the carbon catalysts of Examples 1 to 10 was higher than that of the carbon catalysts of Examples C1 and C2.

[0148] In particular, the oxygen reduction onset potential EO2 (V, relative to NHE) exhibited by each of the carbon catalysts of Examples 1 to 8 was higher than that of the carbon catalysts of Examples 9 and 10. That is, the catalytic activity exhibited by each of the carbon catalysts of Examples 1 to 8 was even higher than that of the carbon catalysts of Examples 9 and 10.

[0149] The L / La ratio (the ratio of the average carbon network plane size L to the crystallite size La) of the carbon catalysts of Examples 1 to 10 was greater than that of the carbon catalysts of Examples C1 and C2. The average carbon network plane size L of the carbon catalysts of Examples 1 to 10 was significantly greater than that of the carbon catalysts of Examples C1 and C2. On the other hand, among Examples 1 to 10, the crystallite size La of the carbon catalysts of Examples 9 and 10 was smaller than that of the carbon catalysts of Examples 1 to 8. The N / C ratio of the carbon catalysts of Examples 9 and 10 was zero. That is, the carbon catalysts of Examples 9 and 10 were those that did not contain nitrogen atoms.

[0150] The BET specific surface area (S BET) The BET specific surface area (S BET ) of the carbon catalyst of Example 9 is significantly smaller than that of the carbon catalysts of other examples. The micropore volume (V 微 ) of the carbon catalyst of Example 9 is larger than the micropore volume (V 微 ) of the carbon catalysts of other examples. On the other hand, the micropore volume (V 微 ) of the carbon catalyst of Example C1 is significantly smaller than the micropore volume (V 微 ) of the carbon catalysts of other examples.

Claims

1. A carbon catalyst, wherein the carbon catalyst has an L / La ratio of an average carbon network plane size L to a crystallite size La of 12 or greater, the average carbon network plane size L is obtained by temperature-programmed desorption analysis capable of heating up to 1600 °C, the crystallite size La is obtained from a diffraction peak near a diffraction angle (2θ) of 43° in an X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα radiation, and wherein the carbon catalyst has an iron content of 3000 ppm or less.

2. The carbon catalyst according to claim 1, wherein the carbon catalyst has a crystallite size La of 10.00 nm or less.

3. The carbon catalyst according to claim 1, wherein the carbon catalyst has an average carbon network plane size L of 5 nm or greater.

4. The carbon catalyst according to claim 1, wherein the carbon catalyst contains nitrogen atoms.

5. The carbon catalyst according to claim 1, wherein the carbon catalyst has a ratio of the nitrogen atom concentration to the carbon atom concentration obtained by X-ray photoelectron spectroscopy of 0.0005 or greater.

6. The carbon catalyst according to claim 1, wherein the carbon catalyst has a BET specific surface area of 100 m 2 / g or more.

7. The carbon catalyst according to claim 1, wherein the carbon catalyst has a micropore volume of 0.05 cm 3 / g or greater.

8. The carbon catalyst according to claim 1, wherein the carbon catalyst has a micropore volume of 2.50 cm 3 / g or less.

9. The carbon catalyst according to claim 1, wherein the carbon catalyst has a mesopore volume of 0.001 cm 3 / g or greater.

10. The carbon catalyst according to claim 1, wherein the carbon catalyst contains a non-noble metal other than iron.

11. An electrode, the electrode comprising the carbon catalyst according to any one of claims 1-10.

12. A battery, the battery comprising the electrode according to claim 11.

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