catalyst

Abstract

Provided is a catalyst that exhibits a high initial activity and durability in oxygen reduction reactions and oxygen generation reactions. The catalyst contains a carbon carrier and a transition metal-containing catalyst supported on the carbon carrier. In the Raman spectrum, the catalyst exhibits a D1 band in the vicinity of a Raman shift of 1350 cm-1 and a G band in the vicinity of a Raman shift of 1590 cm-1. In the XPS spectrum, the catalyst exhibits a specific boron atom peak at a binding energy of 192.0 ± 0.3 eV, as yielded by peak separation of the B 1s spectrum. The catalyst has the following properties: (p1) a D1-FWHM by Raman spectroscopy of not more than 112 cm-1, and a specific B / C% by XPS of at least 0.7%; (p2) a D1-FWHM of at least 52 cm-1 and not more than 112 cm-1, and a specific B / C% of at least 0.1%; (p3) an ID1 / IG ratio in Raman spectroscopy of at least 1.06, and a specific B / C% of at least 0.7%; or (p4) an ID1 / IG ratio of at least 1.06 and not more than 1.99, and a specific B / C% of at least 0.1%.

Description

catalyst

[0001] The present invention relates to a catalyst comprising a carbon support and a transition metal-containing catalyst supported on the carbon support.

[0002] Patent Document 1 describes a conductive additive for an oxygen generating electrode containing carbon nanofibers having a platelet structure of a carbon hexagonal mesh plane. Non-Patent Document 1 describes a catalyst containing cobalt, boron atoms, nitrogen atoms, and carbon nanotubes, which is active in the oxygen generating reaction and the hydrogen generating reaction.

[0003] International Publication No. 2019-039538

[0004] Advanced Functional Materials, 2018, Volume 28, Issue 26, 1801136

[0005] Meanwhile, the inventors of the present invention have been developing electrode catalysts for metal-air secondary batteries that have high initial activity and durability not only in the oxygen reduction reaction (ORR) associated with discharge but also in the oxygen evolution reaction (OER) associated with charge.

[0006] The present invention has been made in view of the above problems, and one of its objects is to provide a catalyst having high initial activity and durability in the oxygen reduction reaction and the oxygen evolution reaction.

[0007] [1] A catalyst according to one embodiment of the present invention for solving the above problem is a catalyst comprising a carbon support and a transition metal-containing catalyst supported on the carbon support, wherein the catalyst has a Raman shift of 1350 cm in a Raman spectrum obtained by Raman spectroscopy. －１ D1 band with a peak top near 1590 cm －１and a G band having a peak top in the vicinity thereof, and a specific boron atomic peak having a peak top within a binding energy range of 192.0±0.3 eV obtained by peak separation of a B1s spectrum derived from the 1s orbital of a boron atom in a photoelectron spectrum obtained by X-ray photoelectron spectroscopy, and the specific boron atomic peak having a peak top within a binding energy range of 192.0±0.3 eV, and the specific boron atomic peak has the following characteristics (p1), (p2), (p3), or (p4): (p1) a D1-FWHM, which is the full width at half maximum of the D1 band obtained by the Raman spectroscopy, of 112 cm －１ and a specific B / C % which is the ratio of the concentration of specific boron atoms exhibiting the specific boron atom peak to the concentration of carbon atoms obtained by the X-ray photoelectron spectroscopy is 0.7% or more; (p2) the D1-FWHM is 52 cm －１ Above, 112cm －１ and the specific B / C % is 0.1% or more; (p3) I, which is the ratio of the peak top intensity of the D1 band to the peak top intensity of the G band obtained by the Raman spectroscopy Ｄ１ / I Ｇ The ratio is 1.06 or more, and the specific B / C% is 0.7% or more; (p4) The I Ｄ１ / I Ｇ The present invention provides a catalyst having high initial activity and durability for the oxygen reduction reaction and the oxygen evolution reaction, wherein the specific B / C % is 0.1% or more and the specific B / C % is 1.06 or more and 1.99 or less.

[0008] [2] The catalyst of [1] may have the characteristic (p1). [3] The catalyst of [1] or [2] may have the characteristic (p2). [4] Any of the catalysts of [1] to [3] may have the characteristic (p3). [5] Any of the catalysts of [1] to [4] may have the characteristic (p4).

[0009] [6] The catalyst according to any one of [1] to [5] may have a crystallite size Lc of 2.50 nm or less, which is obtained from the (002) diffraction line of carbon in an X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα radiation.

[0010] [7] The catalyst according to any one of [1] to [6] has a Raman shift of 1500 cm in a Raman spectrum obtained by Raman spectroscopy. －１ and the ratio of the peak top intensity of the D4 band to the peak top intensity of the G band is I Ｄ４ / I Ｇ The ratio may be 0.05 or greater.

[0011] [8] The catalyst according to any one of [1] to [7] has a Raman shift of 1500 cm in a Raman spectrum obtained by Raman spectroscopy. －１ The D4 band exhibits a peak top in the vicinity of 250 cm －１ It may be the following.

[0012] [9] The catalyst according to any one of [1] to [8] may have a ratio of nitrogen atom content to carbon atom content obtained by elemental analysis of 0.1% or more.

[10] The catalyst according to any one of [1] to [9] may have a ratio of nitrogen atom concentration to carbon atom concentration obtained by X-ray photoelectron spectroscopy of 0.1% or more.

[0013]

[11] The catalyst of any one of [1] to

[10] may exhibit a specific nitrogen atom peak having a peak top within a binding energy range of 399.5±0.3 eV, obtained by peak separation of an N1s spectrum derived from the 1s orbital of a nitrogen atom, in a photoelectron spectrum obtained by X-ray photoelectron spectroscopy, and may have a specific N / C % of 0.1% or more, which is the ratio of the concentration of specific nitrogen atoms exhibiting the specific nitrogen atom peak to the concentration of carbon atoms obtained by X-ray photoelectron spectroscopy.

[0014]

[12] The catalyst according to any one of [1] to

[11] has a pore diameter of 2 nm or more and 50 nm or less, as measured by a nitrogen adsorption method, and the volume of the pores is 1.00 cm ３

[13] The catalyst according to any one of [1] to

[12] may have a pore volume of 1.00 cm3 or less, the pore diameter of which is less than 2 nm as determined by a nitrogen adsorption method. ３

[14] The catalyst according to any one of [1] to

[13] may have a BET specific surface area of ​​1.0 m2 or less as determined by a nitrogen adsorption method. ２ / g or more.

[0015]

[15] The catalyst according to any one of [1] to

[14] may have a ratio of boron atom concentration to carbon atom concentration measured by X-ray photoelectron spectroscopy of 0.1% or more.

[16] The catalyst according to any one of [1] to

[15] may have a catalyst particle median diameter of 5.00 μm or less.

[17] The catalyst according to any one of [1] to

[16] may have a metal content of 1.0 wt% or more measured by inductively coupled plasma mass spectrometry.

[0016] According to the present invention, a catalyst having high initial activity and durability for the oxygen reduction reaction and the oxygen evolution reaction is provided.

[0017] FIG. 1 is an explanatory diagram showing a Raman spectrum obtained by Raman spectroscopy of the catalyst of Example 6 in an example according to the present embodiment. FIG. 2 is an explanatory diagram showing an N1s spectrum after baseline correction obtained by X-ray photoelectron spectroscopy of the catalyst of Example 6 in an example according to the present embodiment. FIG. 3 is an explanatory diagram showing the results of peak separation of the N1s spectrum obtained by X-ray photoelectron spectroscopy of the catalyst of Example 6 in an example according to the present embodiment. FIG. 4 is an explanatory diagram showing a B1s spectrum after baseline correction obtained by X-ray photoelectron spectroscopy of the catalyst of Example 6 in an example according to the present embodiment. FIG. 5 is an explanatory diagram showing the results of peak separation of the B1s spectrum obtained by X-ray photoelectron spectroscopy of the catalyst of Example 6 in an example according to the present embodiment. FIG. 6 is an explanatory diagram showing the results of peak separation of the X-ray diffraction pattern obtained by powder X-ray diffraction of the catalyst of Example 6 in an example according to the present embodiment. FIG. 7 is an explanatory diagram showing an oxygen reduction voltammogram obtained for the catalyst of Example 6 in an example according to the present embodiment. FIG. 8 is an explanatory diagram showing an oxygen evolution voltammogram obtained for the catalyst of Example 6 in an example according to the present embodiment. FIG. 9 is an explanatory diagram showing a carbon support and a transition metal-containing catalyst precursor used in the production of a catalyst in an example according to the present embodiment, and the results of evaluating the performance of the catalyst. FIG. 10 is an explanatory diagram showing the results of evaluating the characteristics of a catalyst in an example according to the present embodiment.

[0018] A catalyst according to one embodiment of the present invention (hereinafter referred to as "the catalyst") will be described below. However, the present invention is not limited to the examples shown in this embodiment.

[0019] The catalyst includes a carbon support and a transition metal-containing catalyst supported on the carbon support. The carbon support is mainly composed of carbon. The carbon content of the carbon support is not particularly limited as long as the effects of the present invention are obtained, but may be, for example, 70 wt % or more, preferably 75 wt % or more, more preferably 80 wt % or more, and particularly preferably 85 wt % or more.

[0020] The carbon content of the carbon support may be 100% by weight or less, 95% by weight or less, or 90% by weight or less. The carbon content of the carbon support may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values. The carbon content of the carbon support is obtained by elemental analysis (specifically, a combustion method).

[0021] The carbon support is a porous carbon material. That is, the carbon support contains pores for supporting the transition metal-containing catalyst. Therefore, the catalyst includes the transition metal-containing catalyst supported within the pores of the carbon support (more specifically, on the inner surfaces of the pores).

[0022] The carbon support is preferably a carbonized material obtained by carbonizing a raw material containing an organic substance (specifically, an organic compound or a composition containing an organic compound).

[0023] The transition metal-containing catalyst supported on the carbon support of the present catalyst contains a transition metal and exhibits catalytic activity. The transition metal is a metal belonging to Groups 3 to 12 of the periodic table of elements. The transition metal is preferably a transition metal that is not a noble metal (i.e., ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold). In this case, the present catalyst may not contain a noble metal. Furthermore, it is particularly preferable that the transition metal is a metal belonging to the fourth period of Groups 3 to 12 of the periodic table of elements.

[0024] Specifically, examples of the transition metal contained in the transition metal-containing catalyst of the present catalyst include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), 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 (e.g., gadolinium (Gd), lanthanum (La), cerium (Ce), and the like. The element may be one or more elements selected from the group consisting of Cr (Ce)) and actinides, preferably one or more elements selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, more preferably one or more elements selected from the group consisting of Mn, Fe, Co, Ni, and Zn, even more preferably one or more elements selected from the group consisting of Mn, Fe, Co, and Ni, and particularly preferably one or more elements selected from the group consisting of Fe, Co, and Ni.

[0025] More specifically, the transition metal-containing catalyst of the present catalyst preferably contains pure Co (unalloyed Co) and / or a Co alloy. The Co alloy is an alloy of Co and a metal other than Co. The metal that forms an alloy with Co is preferably a transition metal, more preferably a transition metal that is not a noble metal, and particularly preferably a transition metal belonging to the fourth period of Groups 3 to 12 of the periodic table.

[0026] Specifically, the Co alloy preferably contains Co and one or more elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Mo, tin (Sn), La, and Ce, more preferably contains Co and one or more elements selected from the group consisting of Mn, Fe, Ni, and Zn, further preferably contains Co and one or more elements selected from the group consisting of Mn, Fe, and Ni, and particularly preferably contains Co and one or more elements selected from the group consisting of Fe and Ni.

[0027] More specifically, the Co alloy is preferably at least one selected from the group consisting of an alloy containing Co and Ni, an alloy containing Co and Fe, and an alloy containing Co and Mn, and particularly preferably at least one selected from the group consisting of an alloy containing Co and Ni, and an alloy containing Co and Fe. Note that the Co alloy containing Co and Ni may further contain Fe. Also, the Co alloy containing Co and Fe may further contain Ni.

[0028] The metal content of the catalyst is not particularly limited as long as the effects of the present invention are obtained, but for example, the metal content measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) may be 1.0 wt% or more. In this case, the metal content of the catalyst is preferably 1.5 wt% or more, more preferably 2.0 wt% or more, even more preferably 2.5 wt% or more, even more preferably 3.0 wt% or more, even more preferably 3.5 wt% or more, even more preferably 4.0 wt% or more, even more preferably 4.5 wt% or more, even more preferably 5.0 wt% or more, even more preferably 6.0 wt% or more, even more preferably 7.0 wt% or more, even more preferably 8.0 wt% or more, even more preferably 8.5 wt% or more, even more preferably 9.0 wt% or more, and particularly preferably 9.5 wt% or more.

[0029] The metal content of the catalyst may be 40.0 wt% or less, 30.0 wt% or less, 20.0 wt% or less, 15.0 wt% or less, 14.0 wt% or less, 13.0 wt% or less, 12.0 wt% or less, 11.0 wt% or less, 10.5 wt% or less, or 10.0 wt% or less. The metal content of the catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0030] The catalyst exhibits a Raman shift of 1350 cm in the Raman spectrum obtained by Raman spectroscopy. －１(specifically, for example, 1340 cm －１ Above, 1360cm －１ The D1 band having a peak top within the range of 1000 to 15000 s (below).

[0031] This catalyst has a D1 band full width at half maximum (hereinafter referred to as "D1-FWHM") of 112 cm －１ In this case, the D1-FWHM of the present catalyst may be 110 cm or less. －１ Preferably, it is 105 cm or less. －１ More preferably, it is 100 cm or less. －１ More preferably, it is 95 cm or less. －１ More preferably, it is 90 cm or less. －１ More preferably, it is 85 cm or less. －１ More preferably, it is 80 cm or less. －１ More preferably, it is 75 cm or less. －１ More preferably, it is 70 cm or less. －１ More preferably, it is 65 cm or less. －１ More preferably, it is 60 cm or less. －１ It is particularly preferred that:

[0032] In addition, the D1-FWHM of this catalyst is 40 cm －１ It may be more than 45 cm －１ It is preferable that the length is 50 cm or more. －１ More preferably, it is 52 cm or more. －１ More preferably, it is 55 cm or more. －１ More preferably, it is equal to or greater than this.

[0033] The D1-FWHM of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values. That is, the D1-FWHM of the present catalyst is, for example, 52 cm －１ Above, 112cm －１ In this case, the upper limit of D1-FWHM of the present catalyst is 112 cm －１Any of the upper limits mentioned above may be substituted, and / or the lower limit of D1-FWHM of the present catalyst is 52 cm －１ Any of the larger lower limits mentioned above may be substituted.

[0034] The D1 band is a component derived from a disordered lattice structure, such as an edge or defect, in the graphene layer contained in the catalyst (specifically, a disordered lattice structure, such as an edge or defect, in the graphene layer contained in the carbon support, and / or a disordered lattice structure, such as an edge or defect, in the graphene layer contained in the transition metal-containing catalyst supported on the carbon support). The D1-FWHM indicates the homogeneity of the disordered lattice structure, such as an edge or defect, that exhibits the D1 band (hereinafter simply referred to as the "D1 lattice structure"). In this regard, as the homogeneity of the D1 lattice structure of the entire catalyst increases, the D1-FWHM of the catalyst decreases, and the stability of the catalyst structure increases. Therefore, a catalyst structure that exhibits a D1-FWHM equal to or less than the above-mentioned upper limit contributes to the durability of the catalyst.

[0035] However, a D1-FWHM that is too small may reflect that the proportion of the D1 lattice structure derived from the carbon support is too large relative to the D1 lattice structure of the entire catalyst, which may impair durability.In contrast, a catalyst structure that exhibits a moderate D1-FWHM indicates that the D1 lattice structure of the entire catalyst is highly homogeneous and that the proportion of the D1 lattice structure derived from the carbon support is not too large, which contributes to further improving the durability of the catalyst.

[0036] The catalyst exhibits a Raman shift of 1500 cm in the Raman spectrum obtained by Raman spectroscopy. －１ (specifically, for example, 1490 cm －１ Above, 1510cm －１ It may also be used to refer to a D4 band having a peak top within the range (below).

[0037] The catalyst has a D4 band full width at half maximum (hereinafter referred to as "D4-FWHM") of 250 cm －１ In this case, the D4-FWHM of the present catalyst may be 240 cm or less. －１Preferably, it is less than 230 cm －１ More preferably, it is equal to or less than 220 cm －１ More preferably, it is equal to or less than 210 cm －１ More preferably, it is 200 cm or less. －１ More preferably, it is 195 cm or less. －１ More preferably, it is 190 cm or less. －１ More preferably, it is 185 cm or less. －１ More preferably, it is 180 cm or less. －１ More preferably, it is 175 cm or less. －１ More preferably, it is 170 cm or less. －１ More preferably, it is 165 cm or less. －１ More preferably, it is 160 cm or less. －１ More preferably, it is 155 cm or less. －１ It is particularly preferred that:

[0038] In addition, the D4-FWHM of this catalyst is 80 cm －１ It may be more than 90 cm －１ It is preferable that the length is 100 cm or more. －１ More preferably, it is 110 cm or more. －１ More preferably, it is 120 cm or more. －１ More preferably, it is 130 cm or more. －１ More preferably, it is 140 cm or more. －１ More preferably, it is 145 cm or more. －１ More preferably, it is 150 cm or more. －１ The D4-FWHM of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0039] The D4 band is the carbon sp ３ Structure (specifically, carbon sp contained in the carbon support) ３ The carbon sp structure and / or the carbon sp contained in the transition metal-containing catalyst supported on the carbon support ３The D4-FWHM is a component derived from the carbon sp ３ This shows the homogeneity of the structure. ３ As the structure becomes more homogeneous, the D4-FWHM of the catalyst becomes smaller and the catalytic activity increases. Therefore, a catalyst structure exhibiting a D4-FWHM equal to or less than the upper limit mentioned above contributes to the initial activity of the catalyst.

[0040] However, a too small D4-FWHM may result in a large carbon sp ３ Carbon sp derived from carbon support for structure ３ In contrast, a catalyst structure showing a moderate D4-FWHM is characterized by a carbon sp structure of the entire catalyst. ３ Highly homogeneous structure and carbon sp derived from the carbon support ３ This indicates that the proportion of the structure is not too large, which contributes to further improving the durability of the catalyst.

[0041] The catalyst exhibits a Raman shift of 1590 cm in the Raman spectrum obtained by Raman spectroscopy. －１ (specifically, for example, 1580 cm －１ Above, 1600cm －１ The graph shows a G band having a peak top within the range of 1000 s.p.m.

[0042] The catalyst is characterized by the ratio of the peak top intensity of the D1 band to the peak top intensity of the G band obtained by Raman spectroscopy (hereinafter referred to as "I Ｄ１ / I Ｇ In this case, the I of the present catalyst may be 1.06 or more. Ｄ１ / I ＧThe ratio is preferably 1.08 or greater, more preferably 1.10 or greater, more preferably 1.12 or greater, even more preferably 1.15 or greater, even more preferably 1.20 or greater, even more preferably 1.25 or greater, even more preferably 1.30 or greater, even more preferably 1.35 or greater, even more preferably 1.40 or greater, even more preferably 1.45 or greater, even more preferably 1.50 or greater, even more preferably 1.55 or greater, and particularly preferably 1.60 or greater.

[0043] In addition, I of this catalyst Ｄ１ / I Ｇ The ratio may be 1.99 or less, preferably 1.95 or less, more preferably 1.90 or less, even more preferably 1.85 or less, even more preferably 1.80 or less, even more preferably 1.75 or less, even more preferably 1.70 or less, and particularly preferably 1.65 or less.

[0044] Catalyst I Ｄ１ / I Ｇ The ratio may be specified by any combination of the above-mentioned lower limit value and the above-mentioned upper limit value. Ｄ１ / I Ｇ The ratio may be, for example, 1.06 or more and 1.99 or less. In this case, the I Ｄ１ / I Ｇ The upper limit of the ratio may be replaced by any of the upper limits mentioned above that are less than 1.99, and / or the I Ｄ１ / I Ｇ The lower limit of the ratio may be replaced by any of the lower limits mentioned above that are greater than 1.06.

[0045] As described above, the D1 band is a component derived from the crystalline D1 lattice structure contained in the catalyst. The G band is a component derived from the crystal lattice at the center of the network plane of the graphene layer contained in the catalyst. Ｄ１ / I ＧThe ratio indicates the amount of the crystalline D1 lattice structure. In this regard, the higher the crystallinity of the entire catalyst and the more the crystalline D1 lattice structure, the higher the I Ｄ１ / I Ｇ The ratio increases, and the stability of the catalyst structure increases. Ｄ１ / I Ｇ The catalyst structure exhibiting this ratio contributes to improving the durability of the catalyst.

[0046] However, it is too large Ｄ１ / I Ｇ The ratio may reflect that the ratio of the crystalline D1 lattice structure derived from the carbon support to the crystalline D1 lattice structure of the entire catalyst is too large, and in this case, durability may be impaired. Ｄ１ / I Ｇ The catalyst structure showing this ratio indicates that the crystalline D1 lattice structure is abundant, and the proportion of the crystalline D1 lattice structure derived from the carbon support is not too large, which contributes to further improving the durability of the present catalyst.

[0047] The catalyst is characterized by the ratio of the peak top intensity of the D4 band to the peak top intensity of the G band obtained by Raman spectroscopy (hereinafter referred to as "I Ｄ４ / I Ｇ The ratio (hereinafter referred to as "ratio") may be 0.05 or more. In this case, the I Ｄ４ / I Ｇ The ratio is preferably 0.08 or greater, more preferably 0.10 or greater, even more preferably 0.15 or greater, even more preferably 0.20 or greater, even more preferably 0.25 or greater, and particularly preferably 0.30 or greater.

[0048] In addition, I of this catalyst Ｄ４ / I Ｇ The ratio may be 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less. Ｄ４ / I Ｇ The ratio may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0049] The D4 band is the carbon sp ３ The G band is a component derived from the crystal lattice at the center of the network plane of the graphene layer contained in the catalyst. Ｄ４ / I Ｇ The ratio is carbon sp ３ In this regard, the carbon sp ３ As the number of structures increases, the I Ｄ４ / I Ｇ The ratio increases, and the catalytic activity increases. Ｄ４ / I Ｇ The catalyst structure exhibiting this ratio contributes to further improving the initial activity of the catalyst.

[0050] The catalyst exhibits a Raman shift of 1620 cm in the Raman spectrum obtained by Raman spectroscopy. －１ (specifically, for example, 1610 cm －１ Above, 1630cm －１ D2 band having a peak top within the range of 1200 cm －１ (specifically, for example, 1190 cm －１ Above, 1210cm －１ The D3 band may further exhibit a peak top within the range of 0.01 to 0.15 (below).

[0051] The present catalyst contains boron atoms, and therefore exhibits a B1s spectrum derived from the 1s orbital of the boron atoms in a photoelectron spectrum obtained by X-ray photoelectron spectroscopy (XPS).

[0052] In the photoelectron spectrum obtained by XPS, the catalyst exhibits a boron atomic peak (hereinafter referred to as a "specific boron atomic peak") having a peak top within a binding energy range of 192.0±0.3 eV, which is obtained by peak separation of the B1s spectrum.

[0053] Specifically, in a photoelectron spectrum obtained by, for example, XPS, the catalyst exhibits a B1s spectrum derived from the 1s orbital of a boron atom, which is separated into the following boron atomic peaks (b1) to (b4): (b1) a first boron atomic peak having a peak top within a binding energy range of 189.5±0.3 eV; (b2) a second boron atomic peak having a peak top within a binding energy range of 190.6±0.3 eV; (b3) a third boron atomic peak having a peak top within a binding energy range of 192.0±0.3 eV; and (b4) a fourth boron atomic peak having a peak top within a binding energy range of 193.0±0.3 eV.

[0054] That is, in this case, in the photoelectron spectrum obtained by XPS of the present catalyst, the B1s spectrum can be separated into the four boron atom peaks (b1) to (b4) by the peak separation described in the Examples below. In other words, in the photoelectron spectrum obtained by XPS of the present catalyst, the B1s spectrum appears as a spectrum formed by the overlapping of the four boron atom peaks.

[0055] The specific boron atomic peak is identified as the third boron atomic peak (b3). Here, the specific boron atomic peak is a peak having a chemical structure including a boron atom and three nitrogen atoms bonded to the boron atom, with at least one of the three nitrogen atoms being bonded to a carbon atom (hereinafter referred to as "BN ３ and / or a chemical structure containing a boron atom contained in the boron atom and three nitrogen atoms bonded to the boron atom, and at least one of the three nitrogen atoms is bonded to another nitrogen atom different from the three nitrogen atoms (hereinafter referred to as "BN C structure"). ３ It is believed that this is derived from the boron atom contained in the hydroxyl group (hereinafter referred to as the "N structure").

[0056] Specifically, for example, the chemical structure shown in the following chemical formula (CI) is BN ３ This is an example of a C structure, in which one of the three nitrogen atoms bonded to the boron atom is bonded to a carbon atom.

[0057] The chemical structure shown in the following chemical formula (C-II) is BN ３ C structure and BN ３ This is an example of a chemical structure that is also an N structure, in which one of the three nitrogen atoms bonded to the boron atom is bonded to a carbon atom and also to another nitrogen atom different from the three nitrogen atoms.

[0058] The chemical structure shown in the following chemical formula (C-III) is BN ３ C structure and BN ３ This is another example of a chemical structure that is also an N structure, in which one of the three nitrogen atoms bonded to a boron atom is bonded to a carbon atom, and the other of the three nitrogen atoms is bonded to another nitrogen atom that is different from the three nitrogen atoms.

[0059] The specific boron atomic peak may be a boron atomic peak derived from one or more chemical structures selected from the group consisting of the chemical structure represented by the chemical formula (CI), the chemical structure represented by the chemical formula (C-II), and the chemical structure represented by the chemical formula (C-III). However, the chemical structure derived from the specific boron atomic peak may be BN ３ C structure and / or BN ３ As long as it has an N structure, it is not limited to those represented by the above chemical formulas (CI), (C-II) and (C-III).

[0060] The first boron atom peak (b1) is a peak of BC ３ Structure and / or BN ２ The (b2) second boron atom peak is thought to be derived from a boron atom contained in the hexagonal-BN structure, and the (b4) fourth boron atom peak is thought to be derived from a boron atom bonded to an oxygen atom.

[0061] The catalyst may have a ratio (atomic %) of the concentration (atomic %) of boron atoms (hereinafter referred to as "specific boron atoms") exhibiting a specific boron atomic peak to the concentration (atomic %) of carbon atoms obtained by XPS (hereinafter referred to as "specific B / C %) of 0.1% or more. In this case, the specific B / C % of the catalyst is preferably 0.3% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, even more preferably 1.3% or more, even more preferably 1.5% or more, even more preferably 2.0% or more, even more preferably 2.5% or more, even more preferably 3.0% or more, even more preferably 3.5% or more, even more preferably 4.0% or more, even more preferably 4.5% or more, even more preferably 5.0% or more, even more preferably 5.5% or more, even more preferably 6.0% or more, and particularly preferably 6.5% or more.

[0062] The specific B / C % of the present catalyst may be 20.0% or less, 18.0% or less, 15.0% or less, 12.0% or less, 10.0% or less, 9.5% or less, 9.0% or less, 8.5% or less, 8.0% or less, 7.5% or less, or 7.0% or less. The specific B / C % of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0063] The specific B / C % corresponds to a ratio calculated by dividing the concentration (atomic %) of specific boron atoms obtained by XPS by the concentration (atomic %) of carbon atoms and multiplying the result by 100.

[0064] Specifically, the specific B / C % is calculated, for example, by the following formula: [specific B / C %] = [B / C %] × [B3 / B ｔｏｔａｌHere, B / C% is the ratio of the boron atom concentration (total concentration of boron atoms including specific boron atoms) (atomic %) to the carbon atom concentration (atomic %) obtained by XPS, and is calculated by dividing the boron atom concentration (atomic %) by the carbon atom concentration (atomic %) and multiplying the result by 100. ｔｏｔａｌ The ratio (-) is the ratio of the content of the third boron atom (b3) (specific boron atom) to the total content of the boron atoms (b1) to (b4) obtained by XPS, and is calculated by dividing the peak area of ​​the third boron atom (specific boron atom) by the total peak area of ​​the boron atoms (b1) to (b4).

[0065] The specific B / C % of the catalyst by XPS indicates the ratio of the concentration of specific boron atoms to the concentration of carbon atoms near the surface of the entire catalyst. ３ C structure and / or BN ３ The specific B / C% is a boron atom that constitutes the N structure. Therefore, as the number of active sites associated with the specific boron atoms near the surface of the entire catalyst increases, the specific B / C% increases, and the catalytic activity improves. Therefore, a catalyst structure that exhibits a specific B / C% equal to or greater than the above-mentioned lower limit contributes to the initial activity of the catalyst.

[0066] The catalyst may have a B / C% (hereinafter referred to as "total B / C%), which is the ratio of the boron atom concentration (atomic %) to the carbon atom concentration (atomic %) obtained by XPS, of 0.1% or more. In this case, the total B / C% of the catalyst is preferably 0.5% or more, more preferably 1.0% or more, even more preferably 1.5% or more, even more preferably 2.0% or more, even more preferably 2.5% or more, even more preferably 3.0% or more, even more preferably 3.5% or more, even more preferably 4.0% or more, even more preferably 5.0% or more, even more preferably 6.0% or more, even more preferably 7.0% or more, even more preferably 8.0% or more, even more preferably 9.0% or more, even more preferably 10.0% or more, even more preferably 11.0% or more, and particularly preferably 12.0% or more.

[0067] The total B / C % of the catalyst may be 40.0% or less, 35.0% or less, 30.0% or less, 25.0% or less, 20.0% or less, 18.0% or less, 16.0% or less, or 15.0% or less. The total B / C % of the catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0068] In the present catalyst, the ratio (atomic %) of the concentration (atomic %) of boron atoms exhibiting the (b1) first boron atomic peak (hereinafter referred to as "first boron atoms") to the concentration (atomic %) of carbon atoms obtained by XPS (hereinafter referred to as "B1 / C %) may be 0.0% or more, preferably 0.1% or more, and particularly preferably 0.2% or more.

[0069] Furthermore, the B1 / C% of the present catalyst may be 2.0% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.8% or less, 0.6% or less, or 0.5% or less. The B1 / C% of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0070] In the present catalyst, the ratio (atomic %) of the concentration (atomic %) of boron atoms exhibiting the (b2) second boron atomic peak (hereinafter referred to as "second boron atoms") to the concentration (atomic %) of carbon atoms obtained by XPS (hereinafter referred to as "B2 / C %) may be 0.1% or more, preferably 0.2% or more, more preferably 0.3% or more, even more preferably 0.4% or more, and particularly preferably 0.5% or more.

[0071] Furthermore, the B2 / C% of the present catalyst may be 8.0% or less, 6.0% or less, 5.0% or less, 4.0% or less, 3.0% or less, 2.0% or less, 1.5% or less, 1.0% or less, or 0.8% or less. The B2 / C% of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0072] The catalyst may contain a nitrogen atom, and in this case, the catalyst exhibits an N1s spectrum derived from the 1s orbital of the nitrogen atom in a photoelectron spectrum obtained by XPS.

[0073] Furthermore, the catalyst preferably exhibits a nitrogen atom peak (hereinafter referred to as a "specific nitrogen atom peak") having a peak top within a binding energy range of 399.5±0.3 eV, which is obtained by peak separation of the N1s spectrum in a photoelectron spectrum obtained by XPS.

[0074] Specifically, in a photoelectron spectrum obtained by, for example, XPS, the catalyst exhibits an N1s spectrum derived from the 1s orbital of a nitrogen atom, separated into the following nitrogen atomic peaks (n1) to (n6): (n1) a first nitrogen atomic peak having a peak top within a binding energy range of 398.6±0.2 eV; (n2) a second nitrogen atomic peak having a peak top within a binding energy range of 399.5±0.3 eV; (n3) a third nitrogen atomic peak having a peak top within a binding energy range of 400.5±0.2 eV; (n4) a fourth nitrogen atomic peak having a peak top within a binding energy range of 401.3±0.3 eV; (n5) a fifth nitrogen atomic peak having a peak top within a binding energy range of 403.5±0.4 eV; and (n6) a sixth nitrogen atomic peak having a peak top within a binding energy range of 404.0±0.5 eV.

[0075] That is, in this case, in the photoelectron spectrum obtained by XPS of the present catalyst, the N1s spectrum can be separated into the six nitrogen atom peaks (n1) to (n6) by the peak separation described in the Examples below. In other words, in the photoelectron spectrum obtained by XPS of the present catalyst, the N1s spectrum appears as a spectrum formed by the six nitrogen atom peaks overlapping each other.

[0076] The specific nitrogen atom peak is identified as the second nitrogen atom peak (n2). Here, the specific nitrogen atom peak is believed to be derived from a nitrogen atom bonded to a metal atom. The first nitrogen atom peak (n1) is believed to be derived from a nitrogen atom contained in a pyridine functional group, the third nitrogen atom peak (n3) is believed to be derived from a nitrogen atom contained in a pyrrole functional group, the fourth nitrogen atom peak (n4) is believed to be derived from a nitrogen atom present in a carbon network plane, the fifth nitrogen atom peak (n5) is believed to be derived from a nitrogen atom contained in an N-O bond, and the sixth nitrogen atom peak (n6) is believed to be a satellite peak derived from an outer shell orbital of a nitrogen atom present in a carbon network plane.

[0077] The catalyst may have a ratio (atomic %) of the concentration (atomic %) of nitrogen atoms exhibiting a specific nitrogen atom peak (hereinafter referred to as "specific nitrogen atoms") to the concentration (atomic %) of carbon atoms obtained by XPS (hereinafter referred to as "specific N / C %") of 0.1% or more. In this case, the specific N / C % of the catalyst is preferably 0.2% or more, more preferably 0.3% or more, even more preferably 0.4% or more, still more preferably 0.5% or more, still more preferably 0.6% or more, still more preferably 0.7% or more, still more preferably 0.8% or more, still more preferably 0.9% or more, still more preferably 1.0% or more, still more preferably 1.1% or more, and particularly preferably 1.2% or more.

[0078] The specific N / C % of the present catalyst may be 20.0% or less, 15.0% or less, 10.0% or less, 8.0% or less, 6.0% or less, 4.0% or less, 3.5% or less, 3.0% or less, 2.5% or less, or 2.0% or less. The specific N / C % of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0079] The specific N / C % corresponds to a ratio calculated by dividing the concentration (atomic %) of specific nitrogen atoms obtained by XPS by the concentration (atomic %) of carbon atoms, and multiplying the result by 100.

[0080] Specifically, the specific N / C % is calculated, for example, by the following formula: [specific N / C %] = [N / C %] × [N2 / N ｔｏｔａｌ Here, N / C% is the ratio of the nitrogen atom concentration (total concentration of nitrogen atoms including specific nitrogen atoms) (atomic %) to the carbon atom concentration (atomic %) obtained by XPS, and is calculated by dividing the nitrogen atom concentration (atomic %) by the carbon atom concentration (atomic %) and multiplying the result by 100. ｔｏｔａｌThe ratio (-) is the ratio of the content of the second nitrogen atom (specific nitrogen atom) of (n2) to the total content of the nitrogen atoms of (n1) to (n6) obtained by XPS, and is calculated by dividing the peak area of ​​the second nitrogen atom (specific nitrogen atom) by the total peak area of ​​the nitrogen atoms of (n1) to (n6).

[0081] The specific N / C% of a catalyst measured by XPS indicates the ratio of the concentration of specific nitrogen atoms to the concentration of carbon atoms near the surface of the entire catalyst. The specific nitrogen atoms are nitrogen atoms bonded to metal atoms, and contribute to the catalytic activation of the metal atoms by donating electrons from the specific nitrogen atoms to the metal atoms. Therefore, a catalyst structure showing a specific N / C% equal to or greater than the above-mentioned lower limit contributes to further improving the initial activity of the catalyst.

[0082] The catalyst may have an N / C% (hereinafter referred to as "total N / C%), which is the ratio of the nitrogen atom concentration (atomic %) to the carbon atom concentration (atomic %) obtained by XPS, of 0.1% or more. In this case, the total N / C% of the catalyst is preferably 0.2% or more, more preferably 0.4% or more, even more preferably 0.6% or more, even more preferably 0.8% or more, even more preferably 1.0% or more, even more preferably 1.2% or more, even more preferably 1.4% or more, even more preferably 1.5% or more, even more preferably 2.0% or more, even more preferably 2.5% or more, even more preferably 3.0% or more, and particularly preferably 3.5% or more.

[0083] The total N / C % of the catalyst may be 30.0% or less, 25.0% or less, 20.0% or less, 15.0% or less, 13.0% or less, 10.0% or less, 8.0% or less, 6.0% or less, 5.0% or less, or 4.5% or less. The total N / C % of the catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0084] In the present catalyst, the ratio (atomic %) of the concentration (atomic %) of nitrogen atoms exhibiting the (n1) first nitrogen atom peak (hereinafter referred to as "first nitrogen atoms") to the concentration (atomic %) of carbon atoms obtained by XPS (hereinafter referred to as "N1 / C %) may be 0.1% or more, preferably 0.4% or more, more preferably 0.8% or more, even more preferably 1.0% or more, still more preferably 1.2% or more, and particularly preferably 1.5% or more.

[0085] Furthermore, the B1 / C% of the present catalyst may be 15.0% or less, 12.0% or less, 10.0% or less, 7.0% or less, 5.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less. The N1 / C% of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0086] The catalyst preferably has both one or more of the properties specified by the Raman spectroscopy and one or more of the properties specified by the XPS. That is, the catalyst preferably has the following properties (p1), (p2), (p3), or (p4): (p1) D1-FWHM is 112 cm －１ and the specific B / C% is 0.7% or more; (p2) D1-FWHM is 52 cm －１ Above, 112cm －１ and the specific B / C% is 0.1% or more; (p3) I Ｄ１ / I Ｇ The ratio is 1.06 or more, and the specific B / C% is 0.7% or more; (p4) I Ｄ１ / I Ｇ The ratio is 1.06 or more and 1.99 or less, and the specific B / C % is 0.1% or more.

[0087] That is, the present catalyst has, for example, the above-mentioned characteristic (p1). In this case, the upper limit of D1-FWHM of the present catalyst is 112 cm －１The lower limit of the specific B / C % of the catalyst may be replaced by any of the above-mentioned lower limit values ​​that is smaller than 0.7%, and / or the upper limit of D1-FWHM may be combined with any of the above-mentioned lower limit values.

[0088] Furthermore, the present catalyst has, for example, the above-mentioned characteristic (p2). In this case, the upper limit of D1-FWHM of the present catalyst is 112 cm －１ Any of the upper limits mentioned above may be substituted, and / or the lower limit of D1-FWHM may be 52 cm. －１ The specific B / C % lower limit of the present catalyst may be replaced by any of the above-mentioned lower limits that are greater than 0.1%, and / or the specific B / C % lower limit may be combined with any of the above-mentioned upper limits.

[0089] In addition, the present catalyst has, for example, the above-mentioned characteristic (p3). In this case, I of the present catalyst Ｄ１ / I Ｇ The lower limit of the ratio may be replaced by any of the lower limits mentioned above that are greater than 1.06, and / or Ｄ１ / I Ｇ The lower limit of the ratio may be combined with any of the upper limits described above. Also, the lower limit of the specific B / C % of the present catalyst may be replaced with any of the lower limits described above that are greater than 0.7%, and / or the lower limit of the specific B / C % may be combined with any of the upper limits described above.

[0090] In addition, the present catalyst has, for example, the above-mentioned characteristic (p4). In this case, I of the present catalyst Ｄ１ / I Ｇ The lower limit of the ratio may be replaced by any of the lower limits mentioned above that are greater than 1.06, and / or Ｄ１ / I ＧThe upper limit of the ratio may be replaced by any of the above-mentioned upper limits that are less than 1.99. Also, the lower limit of the specific B / C % of the catalyst may be replaced by any of the above-mentioned lower limits that are greater than 0.1%, and / or the lower limit of the specific B / C % may be combined with any of the above-mentioned upper limits.

[0091] The catalyst may also have the above-mentioned characteristic (p1) or (p2) and the above-mentioned characteristic (p3) or (p4). That is, the catalyst may have, for example, the above-mentioned characteristics (p1) and (p3), the above-mentioned characteristics (p1) and (p4), the above-mentioned characteristics (p2) and (p3), or the above-mentioned characteristics (p2) and (p4).

[0092] The catalyst may have a ratio of the nitrogen atom content (wt%) to the carbon atom content (wt%) obtained by elemental analysis (hereinafter referred to as "EA-N / C %") of 0.5% or more. In this case, the EA-N / C % of the catalyst is preferably 0.8% or more, more preferably 1.0% or more, even more preferably 1.2% or more, even more preferably 1.7% or more, even more preferably 2.0% or more, even more preferably 2.5% or more, even more preferably 3.0% or more, even more preferably 3.5% or more, even more preferably 4.0% or more, even more preferably 4.5% or more, even more preferably 5.0% or more, even more preferably 5.5% or more, even more preferably 6.0% or more, and particularly preferably 6.5% or more.

[0093] Furthermore, the EA-N / C % of the present catalyst may be 30.0% or less, 25.0% or less, 20.0% or less, 15.0% or less, 10.0% or less, or 8.0% or less. The EA-N / C % of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0094] The EA-N / C% is calculated by dividing the nitrogen atom content (wt%) obtained by elemental analysis of the catalyst by the carbon atom content (wt%) obtained by elemental analysis of the catalyst, and multiplying the obtained value by 100.

[0095] The catalyst may have a carbon atom content of 15.0% by weight or more as determined by elemental analysis. In this case, the carbon atom content of the catalyst as determined by elemental analysis is preferably 25.0% by weight or more, more preferably 31.0% by weight or more, even more preferably 35.0% by weight or more, and particularly preferably 37.0% by weight or more.

[0096] Furthermore, the carbon atom content of the present catalyst as determined by elemental analysis may be 99.0 wt% or less, 95.0 wt% or less, 93.0 wt% or less, 90.0 wt% or less, 88.0 wt% or less, 87.0 wt% or less, 86.0 wt% or less, or 85.0 wt% or less. The carbon atom content as determined by elemental analysis of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0097] The catalyst may have a crystallite size Lc of 2.50 nm or less, obtained from the (002) diffraction line of carbon in an X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα radiation. In this case, the Lc of the catalyst is preferably 2.20 nm or less, more preferably 2.00 nm or less, even more preferably 1.90 nm or less, even more preferably 1.80 nm or less, even more preferably 1.70 nm or less, even more preferably 1.65 nm or less, even more preferably 1.60 nm or less, even more preferably 1.55 nm or less, and particularly preferably 1.50 nm or less.

[0098] Furthermore, the Lc of the present catalyst may be 0.50 nm or more, preferably 0.80 nm or more, more preferably 0.90 nm or more, even more preferably 1.00 nm or more, even more preferably 1.10 nm or more, even more preferably 1.20 nm or more, and particularly preferably 1.25 nm or more. The Lc of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0099] As will be described in detail in the Examples below, the crystallite size Lc (nm) is determined by peak separation of diffraction lines at a diffraction angle 2θ of around 26° (specifically, for example, 2θ is in the range of 18° or more and 35° or less) in an X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα radiation, and the crystallite size Lc (nm) is determined by peak separation of diffraction lines at a diffraction angle 2θ of around 26° (specifically, for example, 2θ is in the range of 18° or more and 35° or less). ｂｒｏａｄ The Bragg angle and full width at half maximum of the crystal are used to calculate the Lc by the following Scherrer formula: Lc=Kλ / (β cos θ), where K is the Scherrer constant (0.94), λ is the wavelength of CuKα radiation (0.15418 nm), and β is the wavelength of f ｂｒｏａｄ is the full width at half maximum (radian) of f ｂｒｏａｄ is the Bragg angle (radian).

[0100] The crystallite size Lc indicates the size of the crystalline carbon network plane in the stacking direction of the carbon structure contained in the catalyst, and essentially reflects the number of stacked crystalline carbon network planes. A carbon structure having the crystallite size Lc equal to or less than the upper limit described above contributes to further improving the initial activity of the catalyst.

[0101] This catalyst has a volume of pores (hereinafter referred to as "mesopores") having a pore diameter of 2 nm or more and 50 nm or less, as determined by a nitrogen adsorption method, of 1.00 cm ３ In this case, the mesopore volume of the present catalyst may be 0.90 cm ３ / g or less, and ３ / g or less, and more preferably 0.70 cm ３ / g or less, and more preferably 0.60 cm ３ / g or less, and more preferably 0.50 cm ３ / g or less, and more preferably 0.40 cm ３ / g or less, and more preferably 0.30 cm ３ / g or less, and more preferably 0.20 cm ３ / g or less, and more preferably 0.15 cm ３ / g or less, and more preferably 0.14 cm ３ / g or less, and more preferably 0.13 cm ３ / g or less, and more preferably 0.10 cm ３ / g or less, and more preferably 0.09 cm ３ / g or less, and more preferably 0.08 cm ３ / g or less, and more preferably 0.07 cm ３ It is particularly preferable that the SiO2 content is 1 / g or less.

[0102] The mesopore volume of this catalyst is 0.01 cm ３ / g or more, and ３ / g or more, and ３ / g or more, and ３ / g or more, and ３ The mesopore volume of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0103] The transition metal-containing catalyst is preferably supported in small pores of the carbon support. In this regard, the more effectively the transition metal-containing catalyst is supported in the mesopores of the carbon support, the smaller the mesopore volume of the catalyst containing the carbon support and the transition metal-containing catalyst. Therefore, a mesopore volume equal to or less than the above-mentioned upper limit contributes to further improving the initial activity of the catalyst.

[0104] This catalyst has a volume of 0.090 cm3 of pores with a pore diameter of less than 2 nm (hereinafter referred to as "micropores") obtained by a nitrogen adsorption method. ３ In this case, the micropore volume of the catalyst may be 0.070 cm３ / g or less, and ３ / g or less, and more preferably 0.030 cm ３ / g or less, and more preferably 0.020 cm ３ / g or less, and more preferably 0.015 cm ３ / g or less, and more preferably 0.012 cm ３ / g or less, and more preferably 0.010 cm ３ / g or less, and more preferably 0.008 cm ３ / g or less, and more preferably 0.006 cm ３ / g or less, and more preferably 0.005 cm ３ It is particularly preferable that the SiO2 content is 1 / g or less.

[0105] The micropore volume of this catalyst is 0.001 cm ３ / g or more, and ３ / g or more, and ３ The micropore volume of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0106] The transition metal-containing catalyst is preferably supported in the pores of the carbon support having a small pore diameter. In this regard, the more effectively the transition metal-containing catalyst is supported in the micropores of the carbon support, the smaller the micropore volume of the catalyst including the carbon support and the transition metal-containing catalyst. Therefore, a micropore volume equal to or less than the upper limit described above contributes to further improving the initial activity of the catalyst.

[0107] This catalyst has a BET specific surface area of ​​550.0 m2 as determined by the nitrogen adsorption method. ２ In this case, the BET specific surface area of ​​the catalyst may be 400.0 m ２ / g or less, and ２ / g or less, and more preferably 150.0m ２ / g or less, and more preferably 100.0m ２ It is particularly preferable that the SiO2 content is 1 / g or less.

[0108] The BET specific surface area of ​​this catalyst is 1.0 m ２ / g or more, and ２ / g or more, and ２ / g or more, and 10.0m ２ / g or more, and more preferably 12.0m ２ The BET specific surface area of ​​the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0109] The BET specific surface area of ​​the catalyst is reduced by supporting the transition metal-containing catalyst in the pores of the carbon support. Therefore, the more effectively the transition metal-containing catalyst is supported in the pores of the carbon support, the smaller the BET specific surface area of ​​the catalyst including the carbon support and the transition metal-containing catalyst. Therefore, a BET specific surface area of ​​not more than the above-mentioned upper limit contributes to further improving the initial activity of the catalyst.

[0110] However, a BET specific surface area that is too small may reflect that the transition metal-containing catalyst is not stably supported on the carbon support and that there is little transition metal-containing catalyst contributing to the chemical reaction, which may result in a loss of durability.In contrast, a BET specific surface area of ​​an appropriate size indicates that the transition metal-containing catalyst is effectively and stably supported in the pores of the carbon support, which contributes to further improving the durability of the catalyst.

[0111] The catalyst may have a median diameter of catalyst particles (i.e., the median diameter of catalyst particles including a carbon support and a transition metal-containing catalyst supported on the carbon support) of 5.00 μm or less. In this case, the median diameter of the catalyst particles is preferably 4.00 μm or less, more preferably 3.00 μm or less, even more preferably 2.00 μm or less, even more preferably 1.50 μm or less, even more preferably 1.20 μm or less, even more preferably 1.00 μm or less, even more preferably 0.90 μm or less, even more preferably 0.80 μm or less, even more preferably 0.70 μm or less, even more preferably 0.60 μm or less, and particularly preferably 0.55 μm or less.

[0112] The median diameter of the present catalyst may be 0.10 μm or more, preferably 0.20 μm or more, preferably 0.30 μm or more, preferably 0.40 μm or more, and particularly preferably 0.45 μm or more. The median diameter of the present catalyst may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values. The median diameter is the particle diameter at which the cumulative relative particle amount in the particle size distribution is 50%.

[0113] The catalyst of the present invention does not need to contain the conductive additive used in the above-mentioned prior art. Therefore, the catalyst of the present invention may not contain carbon nanofibers. Furthermore, the catalyst of the present invention may not contain carbon nanotubes.

[0114] The present catalyst has high initial activity and durability in the oxygen reduction reaction and the oxygen evolution reaction. That is, when used as an electrode catalyst in a metal-air secondary battery, the present catalyst has high initial activity and durability in the oxygen reduction reaction (ORR) and also high initial activity and durability in the oxygen evolution reaction (OER).

[0115] Therefore, the present catalyst is preferably used as a catalyst for the oxygen reduction reaction and the oxygen evolution reaction (a bifunctional catalyst for the oxygen reduction reaction and the oxygen evolution reaction). More specifically, the present catalyst is preferably used, for example, as an electrode catalyst for a metal-air secondary battery, and is particularly preferably used as a catalyst for the air electrode (positive electrode) of a metal-air secondary battery.

[0116] Here, a metal-air secondary battery is a battery that has a metal anode and an air cathode and can be used repeatedly by charging. The metal-air secondary battery to which the present catalyst is applied is preferably, for example, a zinc-air secondary battery, a lithium-air secondary battery, or a sodium-air secondary battery, and particularly preferably a zinc-air secondary battery.

[0117] The metal-air secondary battery to which the present catalyst is applied is preferably an aqueous metal-air secondary battery, which is a metal-air secondary battery that uses an aqueous solution as the electrolyte.

[0118] The present catalyst is preferably produced by heating a mixture of a carbon support and a precursor of a transition metal-containing catalyst. That is, the method for producing the present catalyst preferably includes mixing the carbon support and the transition metal-containing catalyst precursor to prepare a mixture containing the carbon support and the transition metal-containing catalyst precursor, and heating the mixture to obtain the present catalyst containing the carbon support and the transition metal-containing catalyst supported on the carbon support.

[0119] The transition metal-containing catalyst precursor is not particularly limited as long as it is a compound or composition that supplies a transition metal that functions as a metal catalyst supported on a carbon support, but preferably contains, for example, a transition metal source and a boron source. In addition, the transition metal-containing catalyst precursor preferably further contains a nitrogen source and / or a carbon source.

[0120] The transition metal source is the transition metal supported on the carbon support of the present catalyst and / or a compound thereof. The transition metal may be any of the transition metals contained in the transition metal-containing catalyst of the present catalyst. The transition metal compound is preferably a transition metal chloride.

[0121] The boron source is a compound containing a boron atom in its molecule or a composition containing the boron-containing compound. Specifically, the boron source may be, for example, one or more selected from the group consisting of boric acid, boron nitride, boron carbide, sodium borohydride, lithium borohydride, boron phosphate, dimethylamine borane, trimethylamine borane, boron triiodide, boron tribromide, methylboronic acid, sodium tetraborate, and potassium tetrafluoroborate.

[0122] The nitrogen source is a compound containing a nitrogen atom in its molecule or a composition containing the nitrogen-containing compound, and is preferably an organic substance containing a nitrogen atom. The organic substance containing a nitrogen atom is an organic compound containing a nitrogen atom in its molecule or a composition containing the organic compound.

[0123] The carbon source is preferably an organic substance. The organic substance is an organic compound or a composition containing the organic compound. Alternatively, a compound or composition that is both a nitrogen source and a carbon source may be used.

[0124] Specifically, examples of the nitrogen source and / or carbon source include polyacrylonitrile, polyacrylonitrile-polyacrylic acid copolymer, polyacrylonitrile-polymethyl acrylate copolymer, polyacrylonitrile-polymethacrylic acid copolymer, polyacrylonitrile-polymethacrylic acid-polymethallylsulfonic acid copolymer, polyacrylonitrile-polymethyl methacrylate copolymer, melamine, melamine resin, nitrogen-containing chelate resin (for example, one or more selected from the group consisting of polyamine type, iminodiacetic acid type, aminophosphoric acid type, and aminomethylphosphonic acid type), polyamideimide resin, pyrrole, polypyrrole, polyvinylpyrrole, 3-methylpolypyrrole, acrylonitrile, oxazoline, methyl methacrylate ... The polymerizable monomer may contain one or more compounds selected from the group consisting of phenyl, thiazole, pyrazole, vinylpyridine, polyvinylpyridine, pyridazine, pyrimidine, piperazine, morpholine, imidazole, 1-methylimidazole, 2-methylimidazole, quinoxaline, aniline, polyaniline, succinic acid dihydrazide, adipic acid dihydrazide, polyaminobismaleimide, polyimide, benzimidazole, polybenzimidazole, polyamide, chitin, chitosan, pitch, silk, wool, polyamino acid, nucleic acid, DNA, RNA, hydrazine, hydrazide, urea, salen, polycarbazole, polybismaleimide, triazine, polyurethane, polyamidoamine, and polycarbodiimide.

[0125] The transition metal-containing catalyst precursor is prepared, for example, by mixing the above-mentioned transition metal source and boron source (and, as necessary, a nitrogen source and / or a carbon source). The composition of the transition metal-containing catalyst precursor is not particularly limited as long as the effects of the present invention can be obtained. For example, when the transition metal-containing catalyst precursor contains a transition metal source, a boron source, and a nitrogen source, the transition metal-containing catalyst precursor preferably contains, relative to 100 parts by weight of the transition metal-containing catalyst precursor, 20.0 parts by weight to 40.0 parts by weight of the transition metal source, 20.0 parts by weight to 40.0 parts by weight of the boron source, and 30.0 parts by weight to 50.0 parts by weight of the nitrogen source.

[0126] The temperature to which the mixture of the carbon support and the transition metal-containing catalyst precursor is heated is not particularly limited as long as the effects of the present invention can be obtained. For example, the temperature is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 650°C or higher, and particularly preferably 700°C or higher.

[0127] The temperature at which the mixture of the carbon support and the transition metal-containing catalyst precursor is heated is, for example, preferably 1100° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, and particularly preferably 900° C. or lower. The temperature at which the mixture of the carbon support and the transition metal-containing catalyst precursor is heated may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values.

[0128] When the transition metal-containing catalyst precursor contains a carbon source, the temperature to which the mixture of the carbon support and the transition metal-containing catalyst precursor is heated is preferably a temperature at which the carbon source is carbonized. In this case, the catalyst is obtained by carbonizing the mixture of the carbon support and the transition metal-containing catalyst precursor.

[0129] As described above, the carbon support used in producing the present catalyst is preferably a carbonized material. That is, in this case, the carbon support is a carbonized material produced by carbonizing a raw material containing organic matter. The content of the organic matter in the raw material for carbonization may be, for example, 5% by weight or more and 90% by weight or less, and preferably 10% by weight or more and 80% by weight or less.

[0130] The organic material contained in the raw material of the carbon carrier is not particularly limited as long as it can be carbonized. The organic compound contained in the organic material may be a polymer (e.g., a thermosetting resin and / or a thermoplastic resin) and / or an organic compound with a smaller molecular weight. The raw material preferably contains a nitrogen atom, and particularly preferably contains an organic material containing a nitrogen atom.

[0131] Specifically, examples of the organic substance include polyacrylonitrile, polyacrylonitrile-polyacrylic acid copolymer, polyacrylonitrile-polymethyl acrylate copolymer, polyacrylonitrile-polymethacrylic acid copolymer, polyacrylonitrile-polymethacrylic acid-polymethallylsulfonic acid copolymer, polyacrylonitrile-polymethyl methacrylate copolymer, phenol resin, polyfurfuryl alcohol, furan, furan resin, phenol formaldehyde resin, melamine, melamine resin, epoxy resin, nitrogen-containing chelate resin (for example, one or more selected from the group consisting of polyamine type, iminodiacetic acid type, aminophosphoric acid type, and aminomethylphosphonic acid type), polyamideimide resin, pyrrole, polypyrrole, polyvinylpyrrole, 3-methylpolypyrrole, acrylonitrile, polyvinylidene chloride, thiophene, oxazole, thiazole, pyrazole, vinylpyridine, polyvinylpyridine, pyridine, The polymerizable monomer may be one or more selected from the group consisting of dazine, pyrimidine, piperazine, pyran, morpholine, imidazole, 1-methylimidazole, 2-methylimidazole, quinoxaline, aniline, polyaniline, succinic acid dihydrazide, adipic acid dihydrazide, polysulfone, polyaminobismaleimide, polyimide, polyvinyl alcohol, polyvinyl butyral, benzimidazole, polybenzimidazole, polyamide, polyester, polylactic acid, polyether, polyether ether ketone, cellulose, carboxymethyl cellulose, lignin, chitin, chitosan, pitch, silk, wool, polyamino acid, nucleic acid, DNA, RNA, hydrazine, hydrazide, urea, salen, polycarbazole, polybismaleimide, triazine, polyacrylic acid, polyacrylic acid ester, polymethacrylic acid ester, polymethacrylic acid, polyurethane, polyamidoamine, and polycarbodiimide.

[0132] The carbon support preferably contains nitrogen atoms. Specifically, the carbon support is preferably a carbonized material containing nitrogen atoms (e.g., doped nitrogen atoms) in its carbon structure. The carbonized material containing nitrogen atoms is preferably obtained by carbonizing a raw material containing nitrogen atoms and / or by nitrogen doping.

[0133] The carbon support may contain a metal derived from the raw material for carbonization (hereinafter referred to as "raw material metal"). The raw material metal is preferably a transition metal (a metal belonging to Groups 3 to 12 of the periodic table), more preferably a transition metal that is not a noble metal, and particularly preferably a metal belonging to the fourth period of Groups 3 to 12 of the periodic table.

[0134] Specifically, the raw material metal may be, for example, one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, lanthanides (e.g., gadolinium (Gd)), and actinides, preferably one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, more preferably one or more selected from the group consisting of Fe, Co, Ni, Cu, and Zn, even more preferably one or more selected from the group consisting of Fe, Co, Ni, and Zn, and particularly preferably one or more selected from the group consisting of Co, Ni, and Zn.

[0135] When a carbon support, which is a carbonized material, contains a raw material metal, the raw material metal is contained inside the skeleton that constitutes the pores of the carbon support. In other words, when the carbon support is a carbonized material produced by carbonizing a raw material that contains an organic substance and a metal (raw material metal), the carbon support is contained not only on the inner surfaces of the pores but also inside the skeleton that constitutes the pores.

[0136] Here, the carbon support 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 metals derived from the raw materials contained in the carbonized material. Specifically, the metal removal treatment is preferably, for example, a washing treatment with an acid and / or an electrolytic treatment.

[0137] Even when the carbon support is a carbonized material that has been subjected to a metal removal treatment after carbonization, the raw material metal remains inside the skeleton that forms the pores of the carbon support. The raw material metal contained inside the skeleton that forms the pores of the carbon support can be detected, for example, by subjecting the skeleton to a surface etching treatment and analyzing the cross section exposed by the etching treatment. That is, in this case, when one particle of the carbon support is subjected to an etching treatment, the raw material metal is detected on the cross section of the particle exposed by the etching treatment. The raw material metal contained in the carbon support can be detected, for example, by inductively coupled plasma atomic emission spectroscopy of the carbon support.

[0138] On the other hand, the transition metal contained in the transition metal-containing catalyst of the present catalyst is mainly supported on the inner surfaces of the pores of the carbon support. That is, when the present catalyst is produced by heating a mixture of a carbon support containing a raw material metal, which is a transition metal, inside the framework that forms the pores and a transition metal-containing catalyst precursor that contains a transition metal for the transition metal-containing catalyst, the present catalyst contains a first transition metal contained in the transition metal-containing catalyst supported on the inner surfaces of the pores of the carbon support and a second transition metal (raw material metal) contained inside the framework that forms the pores of the carbon support.

[0139] In this case, the type of the first transition metal may be the same as the type of the second transition metal, but it is preferable that they are different. That is, the present catalyst preferably contains a first transition metal contained in a transition metal-containing catalyst supported on the inner surface of the pores of the carbon support, and a second transition metal of a different type from the first transition metal contained inside the framework that constitutes the pores of the carbon support.

[0140] Carbonization in the production of a carbon support, which is a carbonized material, is carried out by heating the raw material at a temperature at which the organic matter contained in the raw material is carbonized. The carbonization temperature is not particularly limited as long as it is a temperature at which the raw material is carbonized, and is, for example, preferably 1200°C or higher, more preferably 1300°C or higher, even more preferably 1400°C or higher, and particularly preferably 1500°C or higher.

[0141] The carbonization temperature may 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 may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values. The rate of temperature rise up to the carbonization temperature is not particularly limited, and may be, for example, 0.5°C / min or higher and 300°C / min or lower. Carbonization is preferably carried out in an inert atmosphere such as a nitrogen atmosphere.

[0142] Carbonization may be carried out under normal pressure (atmospheric pressure), but is preferably carried out under pressure (under pressure higher than atmospheric pressure). When carbonization is carried out under pressure, the pressure of the atmosphere in which the carbonization is carried out may be, for example, 0.05 MPa or more in gauge pressure, preferably 0.15 MPa or more in gauge pressure, more preferably 0.20 MPa or more, even more preferably 0.40 MPa or more, and particularly preferably 0.50 MPa or more. The upper limit of the pressure of the atmosphere in which the carbonization is carried out is not particularly limited, but the pressure may be, for example, 10 MPa or less in gauge pressure.

[0143] The carbon support is preferably a carbonized material that has been subjected to graphitization treatment after carbonization, i.e., the carbon support is preferably a carbonized material obtained by, for example, carbonizing a raw material containing an organic substance and then further graphitizing the carbonized material.

[0144] The graphitization treatment is carried out by heating the carbonized material at a temperature at which graphitization proceeds. The heating temperature at which the carbonized material is heated in the graphitization treatment is not particularly limited as long as it is a temperature at which graphitization proceeds in the carbonized material, but is preferably a temperature higher than the carbonization temperature for obtaining the carbonized material.

[0145] Specifically, the heating temperature in the graphitization treatment may be, for example, 1300°C or higher, preferably 1400°C or higher, more preferably 1500°C or higher, even more preferably 1600°C or higher, still more preferably 1700°C or higher, still more preferably 1750°C or higher, and particularly preferably 1800°C or higher.

[0146] The heating temperature in the graphitization treatment may be, for example, 3000°C or lower, preferably 2500°C or lower, more preferably 2400°C or lower, even more preferably 2300°C or lower, and particularly preferably 2200°C or lower. The heating temperature in the graphitization treatment may be specified by any combination of any of the above-mentioned lower limit values ​​and any of the above-mentioned upper limit values. The rate of temperature rise up to the heating temperature in the graphitization treatment is not particularly limited, and may be, for example, 0.5°C / min or higher and 300°C / min or lower. The graphitization treatment is preferably performed in an inert atmosphere such as a nitrogen atmosphere.

[0147] The carbon support is preferably a carbon material that exhibits catalytic activity. That is, in this case, the carbon support is a carbon catalyst that exhibits catalytic activity by itself. The carbon support that is a carbon catalyst is preferably a carbonized material obtained by carbonizing a raw material containing an organic substance and a metal, as described above.

[0148] The catalytic activity exhibited by the carbon support is preferably, for example, reduction activity and / or oxidation activity, more preferably oxygen reduction activity and / or oxygen evolution activity, and particularly preferably at least oxygen reduction activity.

[0149] Next, a specific example according to this embodiment will be described.

[0150] [Carbon Carrier] <Carbon Carrier A> 1.0 g of polyacrylonitrile, 1.0 g of 2-methylimidazole, and 6.0 g of zinc chloride (ZnCl ２ ) was mixed with 30.0 g of dimethylformamide. The solvent was removed from the resulting mixture by drying. The dried mixture was heated in an air atmosphere to 250°C to make it infusible.

[0151] The infusibilized mixture was heated at 1500°C under a gauge pressure of 0.90 MPa in a nitrogen atmosphere to perform carbonization. Dilute hydrochloric acid was added to the carbonized material obtained by carbonization and the mixture was stirred. Thereafter, the suspension containing the carbonized material was filtered using a filter membrane, and the carbonized material was washed with distilled water until the filtrate became neutral. In this way, metal removal treatment by acid washing was performed.

[0152] The carbonized material after the metal removal treatment was pulverized using a fine pulverizer until the median particle size was 0.4 μm or less. The pulverized carbonized material was vacuum dried to remove moisture. The carbonized material was then subjected to a heat treatment at 300°C in a nitrogen atmosphere. The carbonized material thus obtained was further graphitized by heating it at 2000°C in a nitrogen atmosphere under normal pressure. The particulate carbonized material thus obtained was used as carbon support A.

[0153] <Carbon carrier B> 2.0 g of polyacrylonitrile, 2.0 g of 2-methylimidazole, and 8.6 g of zinc chloride (ZnCl ２ ) and 0.04 g of iron(III) chloride hexahydrate (FeCl ３ ・6H ２ 0) was mixed with 30.0 g of dimethylformamide. The solvent was removed from the resulting mixture by drying. The dried mixture was heated in the air to 250°C to make it infusible.

[0154] The infusibilized mixture was heated at 1,300°C under a gauge pressure of 0.90 MPa in a nitrogen atmosphere to perform carbonization. Dilute hydrochloric acid was added to the carbonized material obtained by carbonization and the mixture was stirred. Thereafter, the suspension containing the carbonized material was filtered using a filter membrane, and the carbonized material was washed with distilled water until the filtrate became neutral. In this way, a metal removal treatment by acid washing was performed.

[0155] The carbonized material after the metal removal treatment was pulverized using a fine pulverizer until the median particle size was 1 μm or less. Furthermore, the pulverized carbonized material was heated at 900°C for 1 hour under normal pressure in an atmosphere where 100% ammonia gas was flowing at 0.15 L / min. The ammonia gas was then replaced with nitrogen gas, and the carbonized material was heated at 500°C for 10 minutes under normal pressure in a nitrogen atmosphere. The carbonized material was then allowed to cool naturally in the nitrogen atmosphere. The particulate carbonized material thus obtained was used as carbon support B.

[0156] <Carbon Carrier K> Commercially available Ketjenblack (KB EC600J, manufactured by Lion Specialty Chemicals Co., Ltd.) was used as the carbon carrier K.

[0157] <Carbon Carrier KG> Carbon carrier K was graphitized by heating it at 2000° C. under atmospheric pressure in a nitrogen atmosphere, and the resulting carbon material was used as carbon carrier KG.

[0158] <Carbon Carrier SG> Commercially available artificial graphite (AGB, manufactured by Ito Graphite) was used as the carbon carrier SG.

[0159] [Preparation of Catalyst] In Examples 1 to 9, a catalyst comprising the carbon support A and a transition metal-containing catalyst precursor containing a boron source, a nitrogen source, and a transition metal source was heated to prepare a catalyst comprising the carbon support A and a transition metal-containing catalyst supported on the carbon support A.

[0160] <Examples 1 to 4> Specifically, in Example 2, 0.148 g of boric acid (corresponding to 2.4 mmol of boron atoms), 0.197 g of 2-methylimidazole (corresponding to 2.4 mmol of nitrogen atoms), and cobalt chloride (CoCl ２ ・6H ２ 0.145 g (corresponding to 0.6 mmol of Co atoms) of Co was added, and the mixture was stirred using a magnetic stirrer.

[0161] Next, 0.5 g of carbon carrier A was added to the stirred solution, and the solution was stirred using a magnetic stirrer. The container containing the stirred solution was immersed in an ultrasonic water bath, and the solution was subjected to ultrasonic treatment for 2 minutes. The ultrasonically treated solution was then first held under reduced pressure of -0.10 (minus 0.10) MPa for 1 hour, and then held under increased pressure of 0.15 MPa for another 1 hour. The solution was then stirred using a magnetic stirrer for 16 hours.

[0162] The stirred solution was dried at 60°C under a reduced pressure of -0.10 MPa gauge pressure to obtain a solid product, which was then heated at 800°C for 30 minutes in a nitrogen atmosphere under normal pressure to obtain a particulate catalyst according to Example 2.

[0163] In Example 1, a particulate catalyst was obtained in the same manner as in Example 2 above, except that the amounts of boric acid, 2-methylimidazole, and cobalt chloride used were each reduced to half.

[0164] In Example 3, a particulate catalyst was obtained in the same manner as in Example 2, except that the amounts of boric acid, 2-methylimidazole, and cobalt chloride used were each increased four times.

[0165] In Example 4, a particulate catalyst was obtained in the same manner as in Example 2, except that the amounts of boric acid, 2-methylimidazole, and cobalt chloride used were each increased six times.

[0166] <Examples 5 to 7> In Example 5, 0.145 g of cobalt chloride was replaced with 0.097 g of cobalt chloride (equivalent to 0.4 mmol of Co atoms), nickel chloride (NiCl ２ ) 0.021 g (equivalent to 0.16 mmol of Ni atoms), and iron chloride (FeCl ３ ・6H ２ A particulate catalyst was obtained in the same manner as in Example 2 above, except that 0.0107 g (corresponding to 0.04 mmol of Fe atoms) of ZnO was used.

[0167] In Example 6, a particulate catalyst was obtained in the same manner as in Example 5, except that the amounts of cobalt chloride, nickel chloride, and iron chloride used were each increased four times.

[0168] In Example 7, a particulate catalyst was obtained in the same manner as in Example 5, except that the amounts of cobalt chloride, nickel chloride, and iron chloride used were each increased six times.

[0169] Examples 8 and 9 In Example 8, a particulate catalyst was obtained in the same manner as in Example 2 above, except that 0.165 g of iron chloride (corresponding to 0.6 mmol of Fe atoms) was used instead of cobalt chloride.

[0170] In Example 9, manganese chloride (MnCl) was used instead of cobalt chloride. ２ A particulate catalyst was obtained in the same manner as in Example 2 above, except that 0.118 g (corresponding to 0.6 mmol of Mn atom) of Mn was used.

[0171] <Examples C1 to C4> In Examples C1, C2, C3, and C4, particulate catalysts were obtained in the same manner as in Example 2 above, except that, as the carbon support, carbon support K, carbon support KG, carbon support SG, and carbon support B were used instead of carbon support A.

[0172] Example C5 In Example C5, a particulate catalyst was obtained in the same manner as in Example 2 above, except that boric acid and 2-methylimidazole were not used.

[0173] Example C6 In Example C6, a particulate catalyst was obtained in the same manner as in Example 2 above, except that boric acid was not used.

[0174] Example C7 In Example C7, a particulate catalyst was obtained in the same manner as in Example 2 above, except that 2-methylimidazole was not used.

[0175] Example C8 In Example C8, a particulate catalyst was obtained in the same manner as in Example 2 above, except that the carbon support A was not used.

[0176] [Raman spectroscopy] The catalyst was analyzed by Raman spectroscopy. The Raman spectrum was measured using a HORIBA laser microscopic Raman spectrometer (LabRam, HORIBA Jobin Yvon). The laser used for the measurement had an excitation wavelength of 532 nm, an output of 50 mW, and was measured through a neutral density filter D3 under the conditions of 90 seconds of exposure x 2 accumulations to obtain a Raman spectrum.

[0177] The obtained Raman spectra were subjected to baseline correction. －１ ) is 900 cm －１ Scattering intensity around 2000 cm －１ A straight line connecting the scattering intensities in the vicinity was determined as the baseline, and baseline correction was performed by subtracting the baseline from the intensity at each Raman shift of the scattering spectrum.

[0178] On the other hand, the Raman shift is 1590 cm －１ Around (specifically, 1580 cm －１ Above, 1600cm －１ The band with a peak top within the range of 1350 cm to 1350 cm is the G band, and the Raman shift is －１ Around (specifically, 1340 cm －１ Above, 1360cm －１ The band with a peak top within the range of 1620 cm －１ Around (specifically, 1610 cm －１Above, 1630cm －１ The band with a peak top within the range of 1200 cm to 1200 cm is the D2 band, and the Raman shift is 1200 cm －１ Around (specifically, 1190 cm －１ Above, 1210cm －１ The band having a peak top within the range of 1500 cm to 1500 cm is the D3 band, and the band having a Raman shift of 1500 cm is the D3 band. －１ Around (specifically, 1490 cm －１ Above, 1510cm －１ The bands having a peak top within the range below were defined as D4 bands.

[0179] Then, in the baseline-corrected Raman spectrum, fitting was performed using a Gaussian function to approximate the peak waveforms of the G band, D2 band, and D4 band, and a Lorentzian function to approximate the peak waveforms of the D1 band and D3 band. The fitting was performed so that the sum of the absolute values ​​of the residuals was minimized. The residual is the value obtained by subtracting the intensity of the approximate waveforms of all bands from the scattering intensity of the Raman spectrum at each Raman shift.

[0180] Here, the details of fitting are explained. For the i band, the Raman shift x (cm －１ ) is the spectral intensity at f ｉ If (x), the Gaussian function is expressed by the following formula (I), and the Lorentz function is expressed by the following formula (II).

[0181] In the above formulas (I) and (II), i represents the type of band, G, D1, D2, D3, or D4; ｉ indicates the peak top intensity of the i band, and σ ｉ denotes the scale parameter of the half width at half maximum of the i band.

[0182] For fitting, the solver function of commercially available software Microsoft Excel (trademark) was used. That is, first, in Microsoft Excel (trademark) installed on a computer, the scattering intensity I of the peak top of the i band (G band, D1 band, D2 band, D3 band, or D4 band) was entered as a variable cell. ｉ , the scale parameter σ of the half width at half maximum of the i band ｉ , and the Raman shift x of the i band ｉ Then, for the approximate curve of each i band, the variable cell I ｉ , σ ｉ , and x ｉ Numerical values ​​relating to the approximation curve were entered in each of the above.

[0183] Furthermore, constraints corresponding to the following formulas (III) to (IX) were set in Microsoft Excel (trademark).

[0184] Furthermore, in Microsoft Excel (trademark), the "Make unconstrained variables non-negative" option was checked, and the initial values ​​of all variable cells were set to zero. Then, in the "Select solution method" section, "Evolutionary" was selected, and the "Solve" button was pressed three times. After that, in the "Select solution method" section, "GRG nonlinear" was selected, and the "Solve" button was pressed once. The results thus obtained were used as parameters.

[0185] Specifically, for example, the peak top intensity of the i band, I ｉ Therefore, the intensity of the peak top of the D1 band, I Ｄ１ is the G-band peak top intensity I Ｇ By dividing by , the ratio of the intensity of the D1 band to the intensity of the G band, I Ｄ１ / I Ｇ Similarly, the peak top intensity I of the D4 band was calculated. Ｄ４is the G-band peak top intensity I Ｇ Dividing by , the ratio of the intensity of the D4 band to the intensity of the G band, I Ｄ４ / I Ｇ The ratio was calculated.

[0186] In addition, the scale parameter σ of the half width at half maximum of the i band obtained by the above operation ｉ was substituted into the following formula (X) to calculate D1-FWHM and D4-FWHM, which are the full widths at half maximum of the D1 band and D4 band, respectively.

[0187] As a result of performing the above-described peak separation of the Raman spectrum, in all examples, I ｉ and σ ｉ The values ​​of were within the ranges of the above formulas (III) to (IX) and were not the upper or lower limit values ​​of the formulas. That is, in all examples, the G band, D1 band, D2 band, D3 band, and D4 band contained in the Raman spectrum were identified.

[0188] Here, Figure 1 shows the Raman spectrum obtained by Raman spectroscopy of the catalyst of Example 6. As shown in Figure 1, as a result of performing the above-mentioned peak separation, the G band, D1 band, D2 band, D3 band, and D4 band were identified in the Raman spectrum of the catalyst of Example 6. In Figure 1, "after baseline correction" indicates the Raman spectrum after the above-mentioned baseline correction.

[0189] [X-ray photoelectron spectroscopy (XPS)] Using an X-ray photoelectron spectrometer (AXIS NOVA, manufactured by KRATOS) and data analysis software (Vision Processing), photoelectron spectra from the core levels of carbon atoms, oxygen atoms, nitrogen atoms, Co atoms, Ni atoms, Fe atoms, Mn atoms, and boron atoms on the surface of the catalyst were measured. AlKα radiation (10 mA, 15 kV, pass energy 40 eV) was used as the X-ray source. The relative sensitivity factor (RSF value) specific to the instrument was used for calculations.

[0190] <Total N / C Ratio and Total B / C Ratio> The atomic concentrations (atomic %) of carbon atoms, nitrogen atoms, and boron atoms on the catalyst surface were determined from the peak areas and detection sensitivity coefficients in the photoelectron spectrum obtained by XPS wide scan analysis of the catalyst. Specifically, for each of carbon atoms, nitrogen atoms, and boron atoms, the peak area / detection sensitivity coefficient ratio was calculated by dividing the peak area by the detection sensitivity coefficient of that element. Next, the peak area / detection sensitivity coefficient ratio of carbon atoms, the peak area / detection sensitivity coefficient ratio of nitrogen atoms, and the peak area / detection sensitivity coefficient ratio of boron atoms were each divided by the sum of the peak area / detection sensitivity coefficient ratio of carbon atoms, the peak area / detection sensitivity coefficient ratio of nitrogen atoms, and the peak area / detection sensitivity coefficient ratio of boron atoms, and the resulting value was multiplied by 100 to calculate the carbon atom concentration (atomic %), nitrogen atom concentration (atomic %), and boron atom concentration (atomic %), respectively.

[0191] The total N / C% of the catalyst was calculated by dividing the nitrogen atomic concentration (atomic %) by the carbon atom concentration (atomic %) and multiplying the result by 100. The total B / C% of the catalyst was calculated by dividing the boron atomic concentration (atomic %) by the carbon atom concentration (atomic %) and multiplying the result by 100.

[0192] <Peak separation of N1s spectrum> In the photoelectron spectrum obtained by XPS narrow scan analysis of the catalyst, the N1s spectrum derived from the nitrogen atom 1s orbital was separated into six components: (n1) a first nitrogen atomic peak having a peak top within a binding energy range of 398.6±0.2 eV, (n2) a second nitrogen atomic peak having a peak top within a binding energy range of 399.5±0.3 eV, (n3) a third nitrogen atomic peak having a peak top within a binding energy range of 400.5±0.2 eV, (n4) a fourth nitrogen atomic peak having a peak top within a binding energy range of 401.3±0.3 eV, (n5) a fifth nitrogen atomic peak having a peak top within a binding energy range of 403.5±0.4 eV, and (n6) a sixth nitrogen atomic peak having a peak top within a binding energy range of 404.0±0.5 eV.

[0193] Here, (n1) the first nitrogen atom peak is considered to be derived from the nitrogen atom (first nitrogen atom) contained in the pyridine functional group, (n2) the second nitrogen atom peak is considered to be derived from the nitrogen atom (second nitrogen atom) bonded to a metal atom, (n3) the third nitrogen atom peak is considered to be derived from the nitrogen atom (third nitrogen atom) contained in the pyrrole functional group, (n4) the fourth nitrogen atom peak is considered to be derived from the nitrogen atom (fourth nitrogen atom) present in the carbon net plane, (n5) the fifth nitrogen atom peak is considered to be derived from the nitrogen atom (fifth nitrogen atom) contained in an N—O bond, and (n6) the sixth nitrogen atom peak is considered to be a satellite peak derived from the outer shell orbital of the nitrogen atom (sixth nitrogen atom) present in the carbon net plane.

[0194] The peak separation of the N1s spectrum derived from the nitrogen 1s orbital was performed as follows: First, baseline correction was performed on the obtained photoelectron spectrum by the Shirley method. The Shirley method was performed with reference to the literature (Kazuhiro Yoshihara, J. Vac. Soc. Jpn., Vol. 56, No. 6, 2013).

[0195] As an example of baseline correction, Fig. 2A shows the N1s spectrum obtained for the catalyst of Example 6. As shown in Fig. 2A, the N1s spectrum after baseline correction ("After baseline correction" in the figure), shown by the dashed line, was obtained from the N1s spectrum before baseline correction ("N1s spectrum" in the figure), shown by the solid line, and the baseline ("Baseline" in the figure), shown by the dotted line.

[0196] Next, in the baseline-corrected N1s photoelectron spectrum, with reference to a literature (Isao Kojima et al., Analytical Chemistry, Vol. 35, No. 10, 1986, pp. T96-T100), the six components were identified by the asymmetric Voigt function F(x) obtained by converting the Voigt function f(x) expressed by the following formula (XI) using the following formula (XII) to introduce an asymmetric term. That is, (x - x ０ Each of the six peak components was identified by the asymmetric Voigt function F(x) obtained by substituting ∑ ...

[0197] In the above formula, I represents the peak height, x represents the binding energy (eV), and x ０ represents the position of the peak top, Γ represents a parameter representing the width of the peak, M represents the mixing ratio of the Gauss-Lorentz function, and α represents the coefficient of the asymmetric term, where M is a value within the range of 0≦M≦1, and α is a value within the range of -2≦α≦2, and all of these parameters are determined according to the shape of the obtained photoelectron spectrum.

[0198] That is, in the separation of the N1s photoelectron spectrum after baseline correction, it is assumed that each of the multiple nitrogen atom peaks obtained by the separation is expressed by the above-mentioned asymmetric Voigt function F(x), and the height I, width parameter Γ, and peak top position x of each of the multiple nitrogen atom peaks are determined so that the sum of squares of the differences (residuals) between the scattering intensity of the N1s spectrum after baseline correction at each binding energy of the photoelectron spectrum and the sum of the values ​​of the asymmetric Voigt function F(x) of each of the multiple nitrogen atom peaks is minimized. ０ This was done by optimizing the following.

[0199] As an example of peak separation, FIG. 2B shows the baseline-corrected N1s spectrum obtained for the catalyst of Example 6 ("Baseline-corrected" in the figure) and six separated peaks obtained by peak separation of the N1s spectrum ("First nitrogen peak," "Second nitrogen peak," "Third nitrogen peak," "Fourth nitrogen peak," "Fifth nitrogen peak," and "Sixth nitrogen peak" in the figure).

[0200] As shown in FIG. 2B , by the above-mentioned peak separation, the N1s spectrum in the photoelectron spectrum was separated into (n1) the first nitrogen atom peak, (n2) the second nitrogen atom peak (specific nitrogen atom peak), (n3) the third nitrogen atom peak, (n4) the fourth nitrogen atom peak, (n5) the fifth nitrogen atom peak, and (n6) the sixth nitrogen atom peak.

[0201] Based on the photoelectron spectrum and peak separation results obtained as described above, the content of nitrogen atoms was evaluated as follows: First, the total area of ​​the first nitrogen atom peak N1, the area of ​​the second nitrogen atom peak N2, the area of ​​the third nitrogen atom peak N3, the area of ​​the fourth nitrogen atom peak N4, the area of ​​the fifth nitrogen atom peak N5, and the area of ​​the sixth nitrogen atom peak N6 was calculated as the total area of ​​the nitrogen atom peaks N ｔｏｔａｌ (N ｔｏｔａｌ = N1 + N2 + N3 + N4 + N5 + N6).

[0202] Next, the area N2 of the second nitrogen atom peak (specific nitrogen atom peak) (n2) considered to be derived from the second nitrogen atom (specific nitrogen atom) bonded to the metal atom was calculated by dividing the area N2 by the total area N of the six nitrogen atom peaks. ｔｏｔａｌ The value obtained by dividing by 1 / N is the ratio of the content of the second nitrogen atom (specific nitrogen atom) to the total content of the six types of nitrogen atoms, "N2 / N ｔｏｔａｌ The ratio was calculated as follows:

[0203] The total N / C % (%) is then multiplied by the content ratio of the second nitrogen atom (N2 / N ｔｏｔａｌ The specific N / C % was obtained by multiplying the specific N / C % by the atomic concentration (atomic %) of the second nitrogen atom (specific nitrogen atom) to the atomic concentration (atomic %) of carbon atom.

[0204] Similarly, the area N1 of the first nitrogen atom peak (n1) was used to obtain N1 / C%, which is the ratio of the atomic concentration (atomic %) of the first nitrogen atom to the atomic concentration (atomic %) of carbon atom.

[0205] <Peak separation of B1s spectrum> In the photoelectron spectrum obtained by XPS narrow scan analysis of the catalyst, the B1s spectrum derived from the 1s orbital of boron atoms was separated into four components: (b1) a first boron atomic peak having a peak top within a binding energy range of 189.5±0.3 eV, (b2) a second boron atomic peak having a peak top within a binding energy range of 190.6±0.3 eV, (b3) a third boron atomic peak having a peak top within a binding energy range of 192.0±0.3 eV, and (b4) a fourth boron atomic peak having a peak top within a binding energy range of 193.0±0.3 eV.

[0206] Here, (b1) the first boron atom peak is BC ３ Structure and / or BN ２ (b2) the second boron atom peak is thought to be derived from a boron atom contained in the hexagonal-BN structure; and (b3) the third boron atom peak (specific boron atom peak) is thought to be derived from a boron atom contained in the BN structure. ３ C structure and / or BN ３ The fourth boron atom peak is thought to be derived from a boron atom (specific boron atom) contained in the N structure (b4), and the fourth boron atom peak is thought to be derived from a boron atom bonded to an oxygen atom.

[0207] The peak separation of the B1s spectrum originating from the 1s orbital of the boron atom was carried out as follows. First, the obtained photoelectron spectrum was subjected to baseline correction by the Shirley method. The Shirley method was performed with reference to the literature (Kazuhiro Yoshihara, J. Vac. Soc. Jpn., Vol. 56, No. 6, 2013).

[0208] As an example of baseline correction, Fig. 3A shows the B1s spectrum obtained for the catalyst of Example 6. As shown in Fig. 3A, the B1s spectrum after baseline correction ("After baseline correction" in the figure), shown by the dashed line, was obtained from the B1s spectrum before baseline correction ("B1s spectrum" in the figure), shown by the solid line, and the baseline ("Baseline" in the figure), shown by the dotted line.

[0209] Next, in the baseline-corrected B1s photoelectron spectrum, with reference to a literature (Isao Kojima et al., Analytical Chemistry, Vol. 35, No. 10, 1986, pp. T96-T100), the four components were identified by the asymmetric Voigt function F(x) obtained by converting the Voigt function f(x) expressed by the above formula (XI) using the formula (XII) to introduce an asymmetric term. That is, (x - x ０ Each of the four peak components was identified by the asymmetric Voigt function F(x) obtained by substituting ∑ ...

[0210] That is, in the separation of the B1s photoelectron spectrum after baseline correction, it is assumed that each of the multiple boron atomic peaks obtained by the separation is expressed by the above-mentioned asymmetric Voigt function F(x), and the height I, width parameter Γ, and peak top position x of each of the multiple boron atomic peaks are determined so that the sum of squares of the differences (residuals) between the scattering intensity of the B1s spectrum after baseline correction at each binding energy of the photoelectron spectrum and the sum of the values ​​of the asymmetric Voigt function F(x) of each of the multiple boron atomic peaks is minimized. ０ This was done by optimizing the following.

[0211] As an example of peak separation, FIG. 3B shows the baseline-corrected B1s spectrum obtained for the catalyst of Example 6 ("Baseline-corrected" in the figure) and four separated peaks obtained by peak separation of the B1s spectrum ("First boron peak," "Second boron peak," "Third boron peak," and "Fourth boron peak" in the figure).

[0212] As shown in FIG. 3B , by the above-mentioned peak separation, the B1s peak was separated into (b1) a first boron atomic peak, (b2) a second boron atomic peak, (b3) a third boron atomic peak (specific boron atomic peak), and (b4) a fourth boron atomic peak in the photoelectron spectrum.

[0213] Based on the photoelectron spectrum and peak separation results obtained as described above, the content of boron atoms was evaluated as follows: First, the total area B1 of the first boron atomic peak, the area B2 of the second boron atomic peak, the area B3 of the third boron atomic peak, and the area B4 of the fourth boron atomic peak was calculated as the total area B ｔｏｔａｌ (B ｔｏｔａｌ = B1 + B2 + B3 + B4). ｔｏｔａｌ corresponds to the total content of the four types of boron atoms contained in the B1s spectrum.

[0214] Next, the area B3 of the third boron atom peak (specific boron atom peak) (b3) considered to be derived from the third boron atom (specific boron atom) is calculated by dividing the area B3 by the total area B of the four boron atom peaks. ｔｏｔａｌ The value obtained by dividing by 1 / B is the ratio of the content of the third boron atom (specific boron atom) to the total content of the four types of boron atoms, "B3 / B ｔｏｔａｌ The ratio was calculated as follows:

[0215] The total B / C % (%) is then multiplied by the content ratio of the third boron atom (B3 / B ｔｏｔａｌ By multiplying the specific B / C % by the atomic concentration (atomic %) of the third boron atom (specific boron atom) to the atomic concentration (atomic %) of carbon atom, a specific B / C % was obtained.

[0216] Similarly, using the area B1 of the (b1) first boron atomic peak and the area B2 of the (b2) second boron atomic peak, B1 / C% and B2 / C% were obtained, respectively, as the ratios of the atomic concentration (atomic %) of the first boron atom and the atomic concentration (atomic %) of the second boron atom to the atomic concentration (atomic %) of carbon atom.

[0217] [Elemental analysis by combustion method] Elemental analysis of the catalyst was performed by combustion method. That is, using an organic trace elemental analyzer (2400II, PerkinElmer Co., Ltd.), the nitrogen atom content, carbon atom content, and hydrogen atom content of the catalyst were measured by combustion method. Specifically, helium was used as a carrier gas, and 2 mg of catalyst was analyzed under the conditions of a combustion tube temperature of 980°C and a reduction tube temperature of 640°C.

[0218] The nitrogen atom content (wt%), carbon atom content (wt%), and hydrogen atom content (wt%) of the catalyst were calculated by dividing the weight of the nitrogen atoms, carbon atoms, and hydrogen atoms contained in the catalyst by the weight of the catalyst, respectively, and multiplying the result by 100. Furthermore, the N / C % by elemental analysis (EA-N / C %) was calculated by multiplying the value obtained by dividing the nitrogen atom content (wt%) by the carbon atom content (wt%) by 100.

[0219] [Powder X-ray Diffraction] The catalyst was subjected to powder X-ray diffraction (XRD) measurement. That is, from the diffraction pattern obtained by the XRD measurement of the catalyst, the (002) diffraction line of carbon was analyzed to determine the crystallite size Lc (nm) of the carbon structure of the catalyst.

[0220] First, in the analysis of the carbon (002) diffraction line, correction was made based on the "Method for measuring lattice constants and crystallite sizes of carbon materials" prepared by the 117th Committee of the Japan Society for the Promotion of Science. Details of this correction are described in the reference (Carbon, No. 221, pp. 52-60 (2006)).

[0221] Specifically, in the "Method for Measuring the Lattice Constant and Crystallite Size of Carbon Materials," the measured intensity at each measurement angle was corrected by dividing it by the correction factor FCT at each measurement angle, which was calculated in advance using the following formula: Correction factor FCT = L P A Fc ２ .

[0222] In the above correction factor formula, L is expressed as follows: L=1 / (sin ２ θ·cos θ), P is expressed by the following formula: P=(1+cos ２ 2θ cos ２ 2θ') / (1+cos ２ 2θ'), A is expressed by the following formula: A = [1 - sin2θ / 2μ'br][1 - exp(-2μ't / sinθ)] + (2t cosθ / br) exp(-2μ't / sinθ). In these formulas, θ is the angle of the goniometer, θ' is the diffraction angle of the monochromator crystal when a counter monochromator is used, and is 0° when a counter monochromator is not used. μ' is the apparent linear absorption coefficient of the sample (0.4219 mm －１ ), t is the sample depth in the sample holder, and br is the X-ray beam width at the sample surface given by the following equation: br = R sin β, where β is the divergence slit width (2 / 3°) and R is the goniometer radius (285 mm).

[0223] In the above correction factor formula, Fc is the atomic scattering factor, which is given by the following formula: Fc = (2.26069 exp(-0.226907 s２ )+1.56165・exp(-0.00656665・s ２ )+1.05075・exp(-0.0975618・s ２ )+0.839259・exp(-0.555949・s ２ ) + 0.286977). In this formula, λ is the wavelength of the X-ray, and s is given by: s = (sin θ) / λ.

[0224] Then, in the obtained XRD pattern, diffraction peaks (i.e., the (002) diffraction line of carbon) at a diffraction angle 2θ of around 26° (specifically, for example, within a range of 2θ of 18° or more and 35° or less) were separated. Peak separation was performed by approximating overlapping diffraction peaks by superimposing Gaussian fundamental waveforms. Fitting was performed on the background-corrected XRD pattern by optimizing the peak intensity, full width at half maximum, and peak position of the Gaussian function that constitutes each component as parameters. Background correction was performed by subtracting the straight line connecting the diffraction line at a diffraction angle (2θ) of around 10 to 20° and the diffraction line at a diffraction angle (2θ) of around 30 to 40° from each diffraction intensity, using this background as the background.

[0225] Then, the diffraction peaks having a peak top at a diffraction angle 2θ of around 26° in the XRD pattern are designated as five diffraction peaks f ｂｒｏａｄ , f ｍｉｄｄｌｅ , f ｎａｒｒｏｗ , f ｍｅｔａｌ－１ and f ｍｅｔａｌ－２ The diffraction peaks were separated into two or more types.

[0226] Here, the diffraction peak f ｂｒｏａｄ is defined as a diffraction peak whose diffraction angle (2θ) is 24.0°±4.0° and whose full width at half maximum is 10°±7.0°. ｍｉｄｄｌｅ is defined as a diffraction peak whose diffraction angle (2θ) is 26.0°±1.0° and whose full width at half maximum is 2.0°±0.9°. ｎａｒｒｏｗ is defined as a diffraction peak whose diffraction angle (2θ) is 26.0°±0.6° and whose full width at half maximum is 0.5°±0.5°. ｍｅｔａｌ－１is defined as a diffraction peak whose diffraction angle (2θ) is 27.7°±0.4° and whose full width at half maximum is 0.7°±0.5°. ｍｅｔａｌ－２ is defined as the diffraction peak whose diffraction angle (2θ) is 29.6°±0.7° and whose full width at half maximum is 1.1°±1.0°.

[0227] In the peak separation, one or more of the five diffraction peaks may not appear. ｍｅｔａｌ－１ and f ｍｅｔａｌ－２ Regarding the diffraction peaks f, only one or none of them appeared. ｍｉｄｄｌｅ and f ｎａｒｒｏｗ For each of the above, two or more diffraction peaks with different diffraction angles (2θ) and full widths at half maximum may appear simultaneously.

[0228] More specifically, peak separation was performed by the following procedure: In the XRD pattern using CuKα radiation after the background correction, a diffraction peak having a peak top at a diffraction angle 2θ of around 26° was approximated by superimposing a Gaussian fundamental waveform, and the peak intensity, full width at half maximum, and peak position were optimized. Of the five diffraction peaks contained in the diffraction peak, two or more diffraction peaks were each subjected to curve fitting, thereby performing peak separation.

[0229] The curve fitting was performed so that the sum of squared residuals was minimized. Here, the squared residual refers to the square of the residual at each measured diffraction angle, and the sum of squared residuals is the sum of these squared residuals. The residual is the sum of the intensity of the diffraction peak having a peak top at a diffraction angle 2θ of around 26° in the XRD pattern using the corrected CuKα ray and the intensity sum of the diffraction peak obtained by separation (for example, the sum of the intensities of four diffraction peaks obtained by peak separation (for example, f ｂｒｏａｄ And, f ｍｉｄｄｌｅ And, f ｎａｒｒｏｗ and 、 f ｍｅｔａｌ－1 or f ｍｅｔａｌ－２ When four diffraction peaks (f, f, and f) are obtained, the difference between the intensities of the four diffraction peaks is the sum of the intensities of the four diffraction peaks. ｂｒｏａｄ , fｍｉｄｄｌｅ , f ｎａｒｒｏｗ , f ｍｅｔａｌ－2 and f ｍｅｔａｌ－2 Among these, two or more diffraction peaks (specifically, two, three or four diffraction peaks) were obtained.

[0230] 4 shows the results of peak separation of the diffraction peaks at a diffraction angle 2θ of about 26° in the XRD pattern obtained for the catalyst of Example 6. As shown in FIG. 4, the peak separation revealed three diffraction peaks f ｂｒｏａｄ , f ｎａｒｒｏｗ and a peak f due to transition metals ｍｅｔａｌ－1 was obtained.

[0231] Then, the diffraction peak f obtained by the above-mentioned peak separation ｂｒｏａｄ The crystallite size Lc (nm) was calculated by analyzing the diffraction peak f obtained by the peak separation. ｂｒｏａｄ The Bragg angle and full width at half maximum of the crystal were calculated by substituting the Bragg angle and full width at half maximum of the crystal into the following Scherrer equation: Lc = Kλ / (β cos θ), where K is the Scherrer constant (0.94), λ is the wavelength of CuKα radiation (0.15418 nm), and β is the wavelength of f ｂｒｏａｄ is the full width at half maximum (radian) of f ｂｒｏａｄ is the Bragg angle (radian).

[0232] [Nitrogen Adsorption Method] The pore volume and specific surface area of ​​the catalyst were measured by nitrogen adsorption using a specific surface area / pore distribution measuring device (ASAP 2020, manufactured by Micromeritics) and the attached analysis software (ASAP 2020, manufactured by Micromeritics).

[0233] That is, first, 0.1 g of the catalyst was heated at 100°C for 6.7 × 10 －２ The catalyst was then held at 77 K for 3 hours at 1000 K for 30 minutes to remove moisture adsorbed on the catalyst. ２ The nitrogen adsorption isotherm at 77 K was obtained by measuring the change in the amount of nitrogen adsorbed to the catalyst with the change in nitrogen gas pressure at a temperature of 77 K. From the nitrogen adsorption isotherm at a temperature of 77 K, the mesopore volume (cm３ / g) and micropore volume (cm ３ / g).

[0234] [Inductively Coupled Plasma Atomic Emission Spectroscopy] The metal content of the catalyst was measured by ICP-AES. Specifically, 25 mg of catalyst was first heated and held at 800°C for 3 hours in an air atmosphere to remove non-metallic components from the catalyst. The catalyst was then immersed in 5 mL of aqua regia to dissolve the metals contained in the catalyst. Distilled water was then added to dilute the catalyst to a total weight of 25 g, yielding a metal solution. The metal concentration of the resulting metal solution was then measured using a sequential plasma emission spectrometer (ICP-8100, manufactured by Shimadzu Corporation).

[0235] The metal concentration (mg / g) of the metal solution was multiplied by the weight of the metal solution (25 g) to obtain a value, which was then divided by the weight of the catalyst (25 mg). The value obtained was then multiplied by 100 to calculate the metal content (wt%) of the catalyst.

[0236] [Median diameter] The median diameter of catalyst particles was measured. First, a catalyst dispersion was prepared. That is, 10 mg of catalyst, 1 drop (approximately 0.05 mL) of surfactant (neutral detergent), and 40 mL of distilled water were placed in a glass container. Then, using a homogenizer (Nihon Seiki Seisakusho Co., Ltd., Model: US-150T Tip Φ12), the output adjuster was set to 8 and a dispersion treatment was carried out for 20 minutes to obtain a catalyst dispersion.

[0237] Next, using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, SALD-7100H), the catalyst dispersion was dropped into a cell so as to obtain an appropriate scattered light intensity, and particle size distribution data was obtained, with the horizontal axis representing particle size (μm) and the vertical axis representing cumulative relative particle amount (%). In the particle size distribution data, the particle size at which the cumulative relative particle amount was 50% was obtained as the median diameter (μm) of the catalyst.

[0238] [Evaluation of Initial Activity and Durability] The initial activity and durability of the catalyst were evaluated by a rotating ring-disk electrode method 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.).

[0239] <Rotating Ring-Disk Electrode Apparatus> First, a three-electrode rotating ring-disk electrode apparatus was prepared, having a working electrode containing a catalyst. Specifically, a slurry was prepared by mixing 5 mg of catalyst, 50 μL of 5% Nafion® (Sigma-Aldrich Nafion perfluorinated ion exchange resin, 5% solution (product number: 510211)), 400 μL of water, and 100 μL of isopropyl alcohol. Next, this slurry was subjected to ultrasonic treatment for 10 minutes, followed by homogenization for 2 minutes. The resulting slurry was then mixed with a catalyst coating amount of 0.2 mg / cm. ２ The catalyst was applied to a working electrode (RRDE-3A ring-disk electrode, platinum ring-gold disk electrode, disk diameter 4 mm, manufactured by BAS Inc.) so that the above-mentioned solution was obtained, and then dried to prepare a working electrode on which the catalyst was supported.

[0240] A gold electrode (23 cm Au counter electrode, manufactured by BAS Co., Ltd.) was used as the counter electrode, and an Hg / HgO electrode (alkaline reference electrode, manufactured by Interchem Co., Ltd.) was used as the reference electrode. Thus, a rotating ring-disk electrode device was obtained, which had a working electrode containing a catalyst, a gold electrode as the counter electrode, and an Hg / HgO electrode as the reference electrode. A 6 M KOH aqueous solution was used as the electrolyte.

[0241] <Initial Activity in Oxygen Reduction Reaction> Using the rotating ring-disk electrode apparatus, the initial activity of the catalyst in the oxygen reduction reaction (ORR) (initial ORR activity) was evaluated. That is, cyclic voltammetry (CV) was performed using a three-electrode rotating ring-disk electrode apparatus having a working electrode containing the catalyst, followed by linear sweep voltammetry (N ２ -LSV) and linear sweep voltammetry under oxygen atmosphere (O ２Initial activity was measured by performing a 100% RT-LSV (anticoagulation test).

[0242] In the CV measurement, nitrogen bubbling was first performed for 10 minutes, and then CV measurement was performed according to the following protocol. That is, a potential sweep was performed 10 times (0.082 V → -0.418 V) at a sweep rate of 0.05 V / sec in the potential range of -0.418 V to 0.082 V (vs. Hg / HgO) to remove oxygen from the electrolyte. The initial potential of the sweep was the open circuit potential (OCP), and the sweep started in the negative direction.

[0243] Next, N ２ The electrode was rotated at a rotation speed of 1600 rpm, and the potential was swept at a sweep rate of 0.02 V / sec in the potential range of −0.417 V to 0.282 V (vs. Hg / HgO), and the current density was recorded as a function of potential (N ２ -LSV function). The sweep was performed with a starting potential of 0.282 V (vs. Hg / HgO) and an ending potential of -0.417 V (vs. Hg / HgO).

[0244] After that, O ２ First, oxygen bubbling was performed for 10 minutes to saturate the electrolyte with oxygen. Then, the electrode was rotated at a speed of 1600 rpm, and the potential was swept at a sweep rate of 0.02 V / sec in the potential range of -0.417 V to 0.282 V (vs. Hg / HgO). The current density was recorded as a function of potential (O ２ -LSV function). The sweep was performed with a starting potential of 0.282 V (vs. Hg / HgO) and an ending potential of -0.417 V (vs. Hg / HgO). ２ -LSV function to N ２ The -LSV function was subtracted to obtain the oxygen reduction voltammogram. Figure 5A shows the oxygen reduction voltammogram obtained for the catalyst of Example 6.

[0245] Thereafter, from the oxygen reduction voltammogram obtained as described above, an index showing the initial ORR activity of the catalyst was calculated as −0.1 mA / cm ２ E is the potential when current flows at a current density of ＯＲＲ１(mV vs. Hg / HgO) was recorded. ＯＲＲ１ The larger the value, the more excellent the catalytic activity of the catalyst in the oxygen reduction reaction.

[0246] <Initial Activity in Oxygen Evolution Reaction> Using the rotating ring-disk electrode apparatus, the initial activity of the catalyst in the oxygen evolution reaction (OER) (initial OER activity) was evaluated. That is, cyclic voltammetry (CV) was performed using a three-electrode rotating ring-disk electrode apparatus having a working electrode containing the catalyst, followed by linear sweep voltammetry (N ２ Initial activity was measured by performing a 100% RT-LSV (anticoagulation test).

[0247] In the CV measurement, nitrogen bubbling was first performed for 10 minutes, and then CV measurement was performed according to the following protocol. That is, a potential sweep was performed 10 times (0.082 V → -0.418 V) at a sweep rate of 0.05 V / sec in the potential range of -0.418 V to 0.082 V (vs. Hg / HgO) to remove oxygen from the electrolyte. The initial potential of the sweep was the open circuit potential (OCP), and the sweep started in the negative direction.

[0248] Next, N ２ The electrode was rotated at a rotation speed of 1600 rpm, and the potential was swept at a sweep rate of 0.02 V / sec in the potential range of 0.2 V to 1.182 V (vs. Hg / HgO). The current density was recorded as a function of the potential (N ２ -LSV function), an oxygen evolution voltammogram was obtained. The sweep was performed with a starting potential of 0.2 V (vs. Hg / HgO) and an ending potential of 1.182 V (vs. Hg / HgO). Figure 5B shows the oxygen evolution voltammogram obtained for the catalyst of Example 6.

[0249] Thereafter, from the oxygen evolution voltammogram obtained as described above, a value of 10 mA / cm was determined as an index showing the initial OER activity of the catalyst. ２ E is the potential when current flows at a current density of ＯＥＲ１ (mV vs. Hg / HgO) was recorded. ＯＥＲ１The smaller the value, the better the catalytic activity of the catalyst in the oxygen evolution reaction.

[0250] <Durability> Using the rotating ring-disk electrode device, a load potential was applied to the working electrode, and the change in activity before and after the application was measured to evaluate the durability of the catalyst. That is, chronoamperometry (CA) was performed using a three-electrode rotating ring-disk electrode device having a working electrode containing the catalyst.

[0251] First, using the same procedure as in the above-mentioned <Initial activity in oxygen reduction reaction>, an index showing the initial ORR activity of the catalyst was calculated using a value of −0.1 mA / cm ２ E is the potential when current flows at a current density of ＯＲＲ２ (mV vs. Hg / HgO) was recorded.

[0252] Nitrogen bubbling was then performed for 10 minutes, followed by CA measurement. The electrode was rotated at 1600 rpm, and the potential was changed from 0 V (vs. Hg / HgO) to 0.6 V (vs. Hg / HgO) in one step (0 V → 0.6 V). After reaching 0.6 V, the potential was maintained for 20 minutes.

[0253] Next, in the same manner as in the above-mentioned <Initial activity in oxygen reduction reaction> and <Initial activity in oxygen evolution reaction>, the initial ORR activity and the initial OER activity of the catalyst were measured using a current of −0.1 mA / cm , respectively. ２ E is the potential when current flows at a current density of ＯＲＲ３ (mV vs. Hg / HgO) and 10 mA / cm ２ E is the potential when current flows at a current density of ＯＥＲ２ (mV vs. Hg / HgO) was recorded.

[0254] As an index showing the durability of the catalyst in ORR, E ＯＲＲ３ and E ＯＲＲ２ Absolute value of the difference between |E ＯＲＲ３ -E ＯＲＲ２ | (mV) was calculated. ＯＲＲ３ -E ＯＲＲ２ The smaller the value of |, the more durable the catalyst is in terms of catalytic activity in ORR.

[0255] In addition, E is used as an index showing the durability of the catalyst in terms of catalytic activity in the OER. ＯＥＲ２ and E ＯＥＲ１ Absolute value of the difference between |E ＯＥＲ２ -E ＯＥＲ１ | (mV) was calculated. ＯＥＲ２ -E ＯＥＲ１ The smaller the value of |, the higher the durability of the catalyst in terms of catalytic activity in the OER.

[0256] [Results] Figure 6A shows the carbon support and transition metal-containing catalyst precursor used in the production of each catalyst example, along with the evaluation results of the catalytic performance. Figure 6B shows the results of evaluating the properties of each catalyst example. Regarding the durability shown in Figure 6A, the catalyst of Example C5 had extremely low ORR initial activity, so it was determined that there was little point in evaluating its durability, and therefore a durability measurement test was not performed. Furthermore, regarding Lc shown in Figure 6B, for the catalyst of Example C3, the diffraction peak f ｂｒｏａｄ Since it was not possible to obtain Lc, it was not possible to calculate Lc.

[0257] 6A , the catalysts of Examples C1 to C8 were insufficient in initial activity (initial ORR activity and / or initial OER activity) and / or durability (ORR durability and / or OER durability). In contrast, the catalysts of Examples 1 to 9 were excellent in initial ORR activity and ORR durability, and also excellent in initial OER activity and OER durability.

[0258] Specifically, among Examples 1 to 9, the catalysts of Examples 2 to 7 were excellent in terms of initial ORR activity, with the catalysts of Examples 3 to 7 being particularly excellent. Among Examples 1 to 9, the catalysts of Examples 2 to 7 were excellent in terms of initial OER activity, with the catalysts of Examples 5 to 7 being particularly excellent.

[0259] Furthermore, the catalysts of Examples 1 to 9 were superior in ORR durability, and the catalysts of Examples 1 to 7 and 9 were superior in ORR durability, and the catalysts of Examples 2 to 4 and 6 to 9 were particularly superior.

[0260] As shown in FIG. 6B, the D1-FWHM of the catalysts of Examples C1, C3, C4, and C8 was 113 cm －１ In contrast, the D1-FWHM of the catalysts of Examples 1 to 9 was 108 cm －１ The D1-FWHM of the catalysts of Examples 1 to 3 and 5 to 9 was 84 cm －１ The D1-FWHM of the catalysts of Examples C2, C5 and C7 was 51 cm or less. －１ In contrast, the D1-FWHM of the catalysts of Examples 1 to 9 was 56 cm －１ The D4-FWHM of the catalysts of Examples 1 to 9 was 227 cm －１ It was as follows.

[0261] Catalysts I of Examples C1 to C4 and C8 Ｄ１ / I Ｇ In contrast, the I ratio of the catalysts of Examples 1 to 9 was 1.05 or less. Ｄ１ / I Ｇ The ratio is 1.11 or more, and the I of the catalysts of Examples 1 to 3 and Examples 5 to 9 Ｄ１ / I Ｇ The ratio was 1.29 or more. Ｄ１ / I Ｇ In contrast, the I ratio of the catalysts of Examples 1 to 9 was 2.00 or more. Ｄ１ / I Ｇ The ratio is 1.81 or less, and the I of the catalysts of Examples 2 to 7 Ｄ１ / I Ｇ The ratio was 1.63 or less. Ｄ４ / I Ｇ The ratio is 0.10 or more, and the I of the catalysts of Examples 2 to 7 Ｄ４ / I Ｇ The ratio was greater than 0.16.

[0262] The specific B / C% of the catalysts of Examples C5 and C6 was 0.0%, and the specific B / C% of the catalysts of Examples C2 and C7 was 0.6%. In contrast, the specific B / C% of the catalysts of Examples 1 to 9 was 0.8% or more, the specific B / C% of the catalysts of Examples 2 to 7 was 1.1% or more, and the specific B / C% of the catalysts of Examples 3, 4, 6 and 7 was 5.6% or more. The total B / C% of the catalysts of Examples 1 to 9 was 1.4% or more.

[0263] The specific N / C% of the catalysts of Examples 1 to 9 was 0.1% or more, the specific N / C% of the catalysts of Examples 2 to 7 was 0.5% or more, and the specific N / C% of the catalysts of Examples 3, 4, 6, and 7 was 1.3% or more. The total N / C% of the catalysts of Examples 1 to 9 was 0.3% or more, and the total N / C% of the catalysts of Examples 2 to 7 was 1.3% or more.

[0264] The N / C % (EA-N / C %) by elemental analysis of the catalysts of Examples 1 to 9 was 1.3% or more, and the EA-N / C % was 2.9% or more for the catalysts of Examples 2 to 7. The crystallite size Lc of the catalysts of Examples 1 to 9 was 1.58 nm or less.

[0265] The micropore volume of the catalysts of Examples 1 to 9 was 0.071 cm ３ / g or less, and the micropore volume of the catalysts of Examples 2 to 7 was 0.011 cm ３ The mesopore volumes of the catalysts of Examples 1 to 9 were 0.16 cm ３ / g or less.

[0266] The BET specific surface area of ​​the catalysts of Examples 1 to 9 is 357.4 cm ２ / g or less, and the BET specific surface area of ​​the catalysts of Examples 2 to 7 was 87.5 cm ２ The median diameter of the catalyst particles of the catalysts of Examples 1 to 9 was 0.87 μm or less. The metal content of the catalysts of Examples 1 to 9 was 2.2 wt % or more.

Claims

1. A catalyst comprising a carbon support and a transition metal-containing catalyst supported on the carbon support, wherein a Raman spectrum obtained by Raman spectroscopy shows a Raman shift of 1350 cm －１ D1 band with a peak top near 1590 cm －１ and a G band having a peak top in the vicinity of 192.0±0.3 eV in a photoelectron spectrum obtained by X-ray photoelectron spectroscopy, which is obtained by peak separation of a B1s spectrum derived from the 1s orbital of a boron atom, and which exhibits the following characteristics (p1), (p2), (p3), or (p4): (p1) a D1-FWHM, which is the full width at half maximum of the D1 band obtained by the Raman spectroscopy, is 112 cm －１ (p2) the D1-FWHM is 52 cm or less, and a specific B / C % which is the ratio of the concentration of specific boron atoms exhibiting the specific boron atom peak to the concentration of carbon atoms obtained by the X-ray photoelectron spectroscopy is 0.7% or more; －１ Above, 112cm －１ (p3) I, which is the ratio of the peak top intensity of the D1 band to the peak top intensity of the G band obtained by the Raman spectroscopy, Ｄ１ / I Ｇ The ratio is 1.06 or more, and the specific B / C% is 0.7% or more; (p4) The I Ｄ１ / I Ｇ The ratio is 1.06 or more and 1.99 or less, and the specific B / C% is 0.1% or more.

2. The catalyst according to claim 1, having the property (p1).

3. The catalyst according to claim 1, having the property (p2).

4. The catalyst according to claim 1, having the property (p3).

5. The catalyst according to claim 1, having the property (p4).

6. The catalyst according to any one of claims 1 to 5, wherein the crystallite size Lc obtained from the (002) diffraction line of carbon in an X-ray diffraction pattern obtained by powder X-ray diffraction using CuKα rays is 2.50 nm or less.

7. In the Raman spectrum obtained by Raman spectroscopy, the Raman shift is 1500 cm －１ and a ratio of the intensity of the peak top of the D4 band to the intensity of the peak top of the G band, I Ｄ４ / I Ｇ 6. The catalyst according to claim 1, wherein the ratio is 0.05 or more.

8. In the Raman spectrum obtained by Raman spectroscopy, the Raman shift is 1500 cm －１ The D4 band has a peak top in the vicinity of 250 cm －１ 6. The catalyst according to claim 1, wherein:

9. The catalyst according to any one of claims 1 to 5, wherein the ratio of the nitrogen atom content to the carbon atom content obtained by elemental analysis is 0.1% or more.

10. The catalyst according to any one of claims 1 to 5, wherein the ratio of the nitrogen atom concentration to the carbon atom concentration obtained by X-ray photoelectron spectroscopy is 0.1% or more.

11. The catalyst according to any one of claims 1 to 5, which exhibits a specific nitrogen atom peak having a peak top within a binding energy range of 399.5±0.3 eV, obtained by peak separation of the N1s spectrum derived from the 1s orbital of a nitrogen atom, in a photoelectron spectrum obtained by X-ray photoelectron spectroscopy, and a specific N / C % which is the ratio of the concentration of specific nitrogen atoms exhibiting the specific nitrogen atom peak to the concentration of carbon atoms obtained by X-ray photoelectron spectroscopy, is 0.1% or more.

12. The volume of pores with a pore diameter of 2 nm or more and 50 nm or less obtained by nitrogen adsorption is 1.00 cm ３ The catalyst according to claim 1 , wherein the SiO 2 content is 1 / g or less.

13. The volume of pores with a pore diameter of less than 2 nm obtained by nitrogen adsorption is 1.00 cm ３ The catalyst according to claim 1 , wherein the SiO 2 content is 1 / g or less.

14. The BET specific surface area obtained by the nitrogen adsorption method is 1.0 m ２ The catalyst according to claim 1 , wherein the SiO 2 content is 1 / g or more.

15. The catalyst according to any one of claims 1 to 5, wherein the ratio of the concentration of boron atoms to the concentration of carbon atoms obtained by X-ray photoelectron spectroscopy is 0.1% or more.

16. The catalyst according to any one of claims 1 to 5, wherein the catalyst particles have a median diameter of 5.00 μm or less.

17. The catalyst according to any one of claims 1 to 5, having a metal content of 1.0% by weight or more as measured by inductively coupled plasma mass spectrometry.

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