JP5002761B2 - Oxoporphyrin-based electrode catalyst material - Google Patents

Description

  The present invention relates to an electrode catalyst material comprising an oxoporphyrin-based compound.

In recent years, the reduction of global environmental impact has become more and more important, but there are no signs that greenhouse gas emissions, especially CO ₂ emissions, will decrease. In particular, the emission ratio of CO ₂ caused by the vehicle is very large, and a fuel cell vehicle is considered to be a promising breakthrough measure for this reduction.

  However, there are many problems that must be overcome to achieve the commercial spread of fuel cell vehicles. One of them is cost reduction of the fuel cell main body. In particular, platinum (Pt), which has been conventionally used as an electrode catalyst for fuel cells, has become a major factor in increasing the cost of fuel cells. Regarding the reduction of platinum usage and the development of catalysts that do not use platinum at all, industry and academia Regardless of whether or not the research is being conducted energetically.

The outline of the power generation mechanism of the fuel cell is shown below. First, hydrogen gas is supplied from the fuel electrode of the fuel cell, and hydrogen molecules are decomposed into hydrogen ions and electrons by the action of the catalyst. Thereafter, hydrogen ions pass through the electrolyte membrane and reach the air electrode, and the hydrogen ions react with O ₂ molecules supplied to the air electrode by the action of the catalyst at the air electrode. In this series of reactions, electric power is supplied when electrons reach the air electrode through the load from the fuel electrode.

As described above, oxygen is reduced at the air electrode. When oxygen is reduced by four electrons, water is generated (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O). Hydrogen oxide is generated (O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O ₂ ). Hydrogen peroxide produced by the two-electron reduction of oxygen degrades the fuel cell electrolyte membrane and shortens the operating life of the fuel cell. Therefore, when designing an electrode catalyst for an air electrode, mainly or completely four electrons are used. The electrode catalyst is required to perform reduction.

For example, Non-Patent Documents 1 to 4 describe that a porphyrin binuclear complex or a porphyrin multinuclear complex of cobalt or iron generates oxygen by four-electron reduction of oxygen molecules. However, the production of these binuclear complexes and polynuclear complexes has the disadvantage that many processes are required. In addition, mononuclear complexes such as cobalt porphyrin have the above problem because oxygen molecules are reduced by two electrons instead of by four electrons to generate hydrogen peroxide.
B. Steiger, F.M. C. Anson, Inorg. Chem. 33, 5767 (1994) M.M. Yuasa, B .; Steiger, F.M. C. Anson, J.A. Porphyrins Phthalocyanines, 1,180 (1997) C. J. et al. Chang, ZH Loh, C Shi, F .; C. Anson, D.A. G. Nocera, J. et al. Am. Chem. Soc. 126, 10013 (2004) S. Fukuzumi, K. et al. Okamoto, C.I. P. Gros, R Guilard, J. et al. Am. Chem. Soc. 126, 10441 (2004)

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrode catalyst material for a fuel cell which does not use platinum and can be substituted for platinum, and which can reduce oxygen molecules by four electrons. It is to provide a catalyst material.

  As a result of intensive studies to solve the above problems, the present inventor has found that the problems can be solved by using an oxoporphyrin complex of a specific metal (hereinafter also referred to as oxo metalloporphyrin) as an electrode catalyst. Completed. That is, the present invention is as follows.

  The present invention relates to the following general formula (I):

[Wherein, each R is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a phenyl group optionally having a substituent, and M is a molybdenum atom (Mo) or a tungsten atom. (W). ]
A fuel cell electrode catalyst material comprising an oxoporphyrin-based complex represented by the formula:

  The electrode catalyst material of the present invention can be suitably used as an electrode catalyst for an air electrode in a polymer electrolyte fuel cell.

  Each R in the general formula (I) is preferably a hydrogen atom (H).

  ADVANTAGE OF THE INVENTION According to this invention, the novel electrode catalyst material which can substitute for a platinum catalyst is provided, The cost of a fuel cell can be reduced significantly by using the electrode catalyst material which concerns on this invention for a fuel cell.

  The electrode catalyst material of the present invention has the following general formula (I):

It consists of an oxoporphyrin-type complex represented by these.
Each R in the general formula (I) is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an optionally substituted phenyl group, and M is a molybdenum atom (Mo ) Or tungsten atom (W). Among these, oxometalloporphyrin MO (por) in which all R are hydrogen atoms (H) is preferable. Here, por means a porphyrin ring in which all of R is a hydrogen atom (H). Further, the metal atom M may be either a molybdenum atom (Mo) or a tungsten atom (W), but considering 4-electron reduction (ease of 4-electron reduction), the metal atom M is a molybdenum atom (Mo). preferable. When the metal atom M is, for example, titanium (Ti), vanadium (V), or chromium (Cr), oxygen molecules do not react with the oxoporphyrin complex, so that the electrode catalyst for the air electrode in the solid polymer fuel cell Difficult to use as.

  Specific examples of the substituent R include aliphatic alkyl groups such as methyl group, ethyl group, n-propyl group, iso-propyl group, and n-butyl group; phenyl group, o-, m-, p-tolyl group. And a substituted or unsubstituted aromatic group such as mesityl group (2,4,6-trimethylphenyl group), but is not limited thereto. Examples of the porphyrin ring having such a substituent include 5,10,15,20-tetra-p-tolylporphyrin (tp), 2,3,7,8,12,13,17,18-octaethylporphyrin. (Oep), 5,10,15,20-tetraphenylporphyrin (tpp), 5,10,15,20-tetramesityl porphyrin (tmp), and the like.

  The oxoporphyrin-based complex (oxometalloporphyrin) according to the present invention can be produced by a conventionally known method. For example, MoO (ttp) in which the porphyrin ring is 5,10,15,20-tetra-p-tolylporphyrin (tp) and the metal atom is Mo is described in T.W. Diego, B.B. Cheverier, R.A. Weiss, Inorg. Chem. 18, 1193 (1979). Other oxoporphyrin-based complexes such as MoO (por), MoO (tpp), MoO (tmp), and WO (por) can also be produced by the same method.

When the oxoporphyrin-based complex (oxometalloporphyrin) according to the present invention is used as a catalyst material for a fuel cell air electrode, the air electrode catalyst layer can be produced by a conventionally known method. Typically, it is formed by supporting the oxometal porphyrin of the present invention on a conductive carrier by a usual method. For example, a slurry, paste, or suspension containing the oxometalloporphyrin of the present invention is prepared, and a conductive carrier is immersed in the slurry, or the slurry or paste is applied to the carrier and dried. An air electrode catalyst layer can be formed. Solvents for slurry, paste, or suspension include halogenated hydrocarbon solvents such as chloroform and tetrachloroethane, acetonitrile, tetrahydrofuran, monocyclic aromatic hydrocarbon solvents (for example, benzene, toluene), C _1-6 lower Alcohol (for example, propanol, butanol) and the like can be mentioned.

  The conductive carrier is not particularly limited, and for example, a carbon material such as carbon black, graphite, carbon fiber, carbon nanotube, or carbon nanofiber can be used. The conductive carrier is preferably in the form of a powder because it has a large surface area per unit weight.

  The oxoporphyrin-based complex (oxometalloporphyrin) according to the present invention can be suitably used as an electrode catalyst for a fuel cell. In particular, since it has oxygen reducing ability and can reduce oxygen by four electrons, it can be suitably used as an electrode catalyst for an air electrode in a polymer electrolyte fuel cell.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
(Evaluation of oxygen reduction performance using first-principles calculation based on density functional theory)
For the two oxometalloporphyrins, MoO (po) and WoO (po), the interaction with the O ₂ molecule was investigated using first-principles calculations based on density functional theory. In addition, these results were compared with TiO (por), VO (por) and CrO (por).

(1) Calculation method First-principles calculation based on density functional theory was performed using the Vienna ab initio simulation package (VASP) (G. Kresse and J. Hafner, Phys. Rev. B47, 558 (1993); G Kresse and J. Hafner, Phys. Rev. B49, 14251 (1994); G. Kresse and J. Furthmuller, Comput. Mater. Sci. 6, 15 (1996), G. Kresse and J. Furthmuller, Phys. B54, 11169 (1996)). The potential of each electron was Vanderbilt's ultrasoft pseudopotential (D. Vanderbilt, Phys. Rev. B41, 7892 (1990) and G. Kresse and J. Hafner, J. Phys. Condens. Matter 6, 8245 ( 1994)).

  In addition, regarding the pseudopotentials of the metal atoms Mo, W, Cr, Ti, and V, the p orbital was considered in addition to the d orbital of the valence electron orbital. The cut-off energy of the plane wave base was 400 eV. For exchange / correlation gain energy, Perdew-Burke-Ernzerhof (PBE) was used in the generalized gradient approximation (GGA) (JP Perdew, K. Burke, M. Erzerhof: Phys. Rev. Lett. 77, 3865 (1996) and JP Perdew, K. Burke, M. Ernzerhof: Phys. Rev. Lett. 78, 1396 (1997)).

  A structure optimization calculation for all energies was performed for all atoms of the porphyrin complex in the supercell, and the technique was calculated using the conjugate gradient method (CG) (MP Teter, MC Payne). , DC Allan: Phys. Rev. B40, 12255 (1989) and DM ylander, L. Kleinman, S. Lee: Phys. Rev. B42, 1394 (1990)). The size of the supercell used is 20Å × 20Å × 20Å, and the oxometalloporphyrin adsorbed with oxometalloporphyrin and oxygen molecules is the oxometalloporphyrin of the adjacent supercell (or oxometalloporphyrin with oxygen molecules adsorbed). I chose something big enough that it wouldn't affect me. In addition, in order to correct the total energy in an isolated molecule in a vacuum, dipole and quadrupole corrections were performed on the total energy (G. Makov, MC Payne, Phys. Rev. B51, 4014 (1995). )).

(2) Calculation results and evaluation thereof FIG. 1 is a schematic diagram showing the structure of an oxometalloporphyrin based on the above calculation results. MoO (po), WoO (po), TiO (po), VO (po) and The structure of the oxo metalloporphyrin is optimized for CrO (por) when the total energy is minimized. FIG. 1A shows the oxometalloporphyrin seen from directly above, and FIG. 1B shows it seen from the side. Here, M represents a metal atom (Mo, W, Ti, V or Cr atom) constituting the oxo metal porphyrin, and is located in the center of the porphyrin ring. N1, N2, N3 and N4 represent nitrogen atoms constituting the porphyrin ring, and O1 represents an oxygen atom coordinated to the metal atom M. The smallest sphere located on the outer periphery of the porphyrin ring represents a hydrogen atom, and the other white spheres represent a carbon atom.

In addition, Table 1 shows molecular structure parameters after the structure optimization of these oxometalloporphyrins. In Table 1, "∠O1-M-N1~N4" is an angle (°) formed between O1 and metal atom M and N1-N4, "M-N _p distance", N1, N2, N3, This is the average distance between a plane that can be created from three N atoms of N4 and the metal atom M.

TiO (por), Looking for VO (por) and CrO (por), as it travels the periodic table to the right, M-O1, M-N1~N4 and M-N _p is shorter. This tendency is due to the difference in the atomic radius of M. That is, the atomic radii of Ti, V, and Cr are 1.47 Å, 1.32 Å, and 1.25 そ れ ぞ れ, respectively, and the atomic radius decreases as the periodic table is moved to the right. Thereby, it is considered that the bond distance with the metal atom M is also shortened as it goes to the right in the periodic table.

  Next, looking at CrO (por), MoO (por) and WO (por), M-O1 and M-N1 to N4 in CrO (por) are compared with those of MoO (por) and WO (por). And short. Further, when MoO (po) and WO (po) are compared, it can be seen that there is almost no difference between M-O1 and M-N1 to N4. This trend is also because the Cr atomic radius (1.25１．２) is shorter than the Mo atomic radius 1.36 原子 and the W atomic radius 1.37Å, and there is little difference between the Mo atomic radius and the W atomic radius. I can understand.

2 and 3 are schematic diagrams showing the structure of a complex in which O ₂ molecules are adsorbed on an oxo metalloporphyrin based on the above calculation results. MoO (po), WoO (po), TiO (po), VO ( por) and CrO (por) show the structure of the structure-optimized oxometalloporphyrin when the total energy is minimized. Here, FIG. 2 shows an optimized structure in the case of “side-on coordination” in which both oxygen atoms in the O ₂ molecule are bonded to the metal atom M, and FIG. 3 shows one oxygen in the O ₂ molecule. This is an optimized structure in the case of “end-on coordination” in which an atom is bonded to a metal atom M. 2 (a) and 3 (a) are views of the oxo metal porphyrin adsorbed with oxygen molecules from directly above, and FIGS. 2 (b) and 3 (b) are views from the side. . The meanings of the spheres in these figures are the same as those in FIG. 2 and O3 in FIG. 2 and FIG. 3 represent oxygen atoms in the adsorbed oxygen molecules.

  Table 2 shows the adsorption energy (that is, the binding energy of oxygen molecules) when oxygen molecules are adsorbed to these oxometalloporphyrins for each of “side-on coordination” and “end-on coordination”. . In Table 2, “-” means that neither a stable structure nor a metastable structure was found, and the oxygen molecule was separated from the oxometalloporphyrin.

From the calculation results, the binding energies of MoO (por) (O ₂ ) and WO (por) (O ₂ ) are positive in side-on coordination, but negative in end-on coordination. Or, it is a lower positive value compared to the side-on coordination, and it was found that both oxometalloporphyrins take side-on coordination when O ₂ molecules are adsorbed. The binding energy of MoO in the side-on coordination (por) (O ₂₎ and WO (por) (O ₂₎ are each 0.611EV, a sufficiently high positive value and 1.400eV, O ₂ The molecular adsorption reaction is considered to proceed sufficiently. On the other hand, the binding energy of TiO (por) (O ₂ ), VO (por) (O ₂ ), and CrO (por) (O ₂ ) is either side-on or end-on, From the result that it is negative or unstable (the oxygen molecule moves away from the oxometalloporphyrin), it is considered that the adsorption reaction of the oxygen molecule on these oxometalloporphyrins hardly proceeds.

Further, from the magnitude of the binding energy, it can be seen that WO (po) (O ₂ ) is more stabilized by adsorption of O ₂ molecules than MoO (po) (O ₂ ).

Table 3 shows the molecular structure parameters in the side-on coordination of MoO (por) (O ₂ ) and WO (por) (O ₂ ) based on the above calculation results.

Looking at MoO (por) (O ₂ ), the Mo—N1 bond is an oxo ligand (ie, O1), and the Mo—N3 bond is an adsorption of a peroxo ligand (ie, O 2 and O 3). The configuration is such that it is hidden by oxygen molecules (see FIG. 2). Moreover, it turned out that these coupling | bondings are slightly longer than the coupling | bonding of Mo-N2 and Mo-N4. The bond distance between Mo-O2 and Mo-O3 is completely equal, and both bonds are longer than the Mo-O1 bond. Furthermore, since the O2-O3 bond distance is 1.42 km and the bond length is considerably longer than the bond length between oxygen atoms of the gas O ₂ molecule, the O2-O3 bond is considered to be cleaved. Further, compared with MoO (port), Mo atoms protrude above the N atom plane by about 0.40 cm due to attraction by O ₂ molecules.

Next, with respect to WO (por) (O ₂ ), the W—N1 bond is formed by an oxo ligand (that is, O1), and the W—N3 bond is formed similarly to MoO (por) (O ₂ ). The configuration is such that it is hidden by a peroxo ligand (ie, adsorbed oxygen molecules consisting of O 2 and O 3) (see FIG. 2). Moreover, it turned out that these coupling | bondings are slightly longer than the coupling | bonding of W-N2 and W-N4. The bond distance between W-O2 and W-O3 is completely equal, and both bonds are longer than the W-O1 bond. Furthermore, the O2-O3 bond distance is 1.45 km, and the O2-O3 bond is considered to be cleaved. Further, compared with WO (port), W atoms protrude above the N atom plane by about 0.44 cm due to attraction by O ₂ molecules. The O2-O3 bond distance of 1.42 に お け る in MoO (por) (O ₂ ) and the O2-O3 bond distance of 1.45 に お け る in WO (por) (O ₂ ) are TiO (por) (O ₂ ), VO (por ) (O ₂ ) and CrO (port) (O ₂ ), which are longer than the O ₂ -O 3 bond distances (1.33, 1.30, and 1.37 そ れ ぞ れ, respectively).

The calculation results of the above-mentioned molecular structure parameters concerning MoO (po) (O ₂ ) and WO (po) (O ₂ ) are almost the same as those of MoO (po). Similar to the result, it means that the calculation result of the molecular structure parameter of WO (por) (O ₂ ) is not different from that of MoO (por) (O ₂ ). This is also thought to be due to the similarity in atomic radius between W and Mo.

As described above, it was found from the first principle calculation that the molecular structure parameters of MoO (por) (O ₂ ) and WO (por) (O ₂ ) are very similar. It was also found that the adsorption energy when adsorbing oxygen molecules on porphyrin is different between MoO (po) and WO (po) (MoO (po): 0.611 eV, and WO (po): 1). 400 eV, both side-on coordination). Such a difference in adsorption energy is qualitatively determined by the difference in energy between the HOMO of MoO (port) and WO (port), that is, the d orbital of the metal atom M and the π ^* orbital of the O ₂ molecule. Can be explained.

FIG. 4 is a schematic diagram showing molecular orbital energy diagrams and valence electron density diagrams for MoO (po), MoO (po) (O ₂ ), and O ₂ molecules in order from the left. Energy is graduated from the vacuum position. In each molecule, the left molecular orbital is due to α-spin electrons, and the right molecular orbital is due to β-spin electrons. Each electron density is depicted by 0.003 isoelectronic density surface of the electron number / Å ^3.

Looking at the electron density, two HOMOs of MoO (por) are mainly made from d orbitals of Mo atoms, and the two HOMOs of MoO (por) (O ₂ ) are mainly adsorbed O _2. It can be seen that it is created from the π ^* orbital (antibonding orbital) of the molecule. Therefore, electrons transition from MoO (por) the O ₂ molecules by adsorption of the O ₂ molecules, transition electrons occupy a [pi ^* orbital of the O ₂ molecules, as a result, O2-O3 bond in O ₂ molecule It can be seen that weakens. Therefore, O2-O3 bond in O ₂ molecule is longer by adsorption. On the other hand, there is almost no electron transition from d orbitals of Mo atoms to O1 atoms that originally existed in MoO (po).

The α (β) -HOMO-1 of MoO (por) and MoO (por) (O ₂ ) are almost the same, and the α (β) -HOMO of MoO (por) and MoO (por) (O ₂ ) -2 is almost the same. Although very few electrons of O ₂ molecules can be confirmed in α (β) -HOMO-1 and α (β) -HOMO-2 of MoO (por) (O ₂ ), most electrons are in MoO (por). Staying around the porphyrin ring. It can be said that these results mean that during the adsorption of O ₂ molecules on MoO (port), transition is made to the π ^* orbit of the O ₂ molecule to which the d orbital electron of the Mo atom is adsorbed.

The energy difference between α-HOMO and β-HOMO of MoO (port) is about 0.365 eV, and the energy difference between α-HOMO and β-HOMO of MoO (port) (O ₂ ) is about 0. Since it was 099 eV, it was found that α-HOMO was stabilized by about 0.924 eV due to adsorption of O ₂ molecules, and β-HOMO was stabilized by about 1.190 eV.

FIG. 5 is a schematic diagram showing molecular orbital energy diagrams and valence electron density diagrams for WO (port), WO (port) (O ₂ ), and O ₂ molecules in order from the left. Energy is graduated from the vacuum position. In each molecule, the left molecular orbital is due to α-spin electrons, and the right molecular orbital is due to β-spin electrons. Each electron density is depicted by 0.003 isoelectronic density surface of the electron number / Å ^3.

Regarding the valence density, it was almost the same as when the metal atom was Mo. Therefore, it can be said that during the adsorption of the O ₂ molecule onto WO (port), the transition is made to the π ^* orbit of the O ₂ molecule adsorbed by the d-orbital electron of the W atom.

Looking at the energy of each orbit, there is almost no energy difference between α-HOMO and β-HOMO in WO (port), but the energy difference between α-HOMO and β-HOMO in WO (port) (O ₂ ) is It was found to be about 0.096 eV. Compared to the case of Mo, MoO (por) originally has α-HOMO that is more stable than WO (por), so that it cannot be as stable as WO (por) due to adsorption of O ₂ molecules. I understand. That is, due to adsorption of O ₂ molecules, WO (por) produces a more stable product than MoO (por).

In summary, the following is clarified by first-principles calculations based on density functional theory.
(A) MoO (por) and WO (por) according to the present invention react with O ₂ molecules, while TiO (por), VO (por) and CrO (por) do not react with O ₂ molecules.
(B) Adsorption of O ₂ molecules to MoO (po) and WO (po) extends the bond distance between O 2 atoms and O ₃ atoms in the O ₂ molecules.
(C) The adsorption energy (1.400 eV) with O ₂ molecules in WO (po) is about twice that of WO (po) (0.611 eV), and in W atoms and O ₂ molecules The bond between O atoms is stronger than that of Mo atoms. This can be explained by the energy difference between the HOMO of these oxometalloporphyrins and the π ^* orbitals of the adsorbed O ₂ molecules. That is, the energy levels of α-HOMO and β-HOMO are almost equal in WO (por), but the energy level of α-HOMO is lower than β-HOMO in MoO (por). Therefore, WO (port) is more stabilized than MoO (port) by adsorption of O ₂ molecules.

From the above calculation results, MoO according to the present invention (por) and WO (por) is, O ₂ molecules can react, extending the coupling between O atoms of reacted O ₂ in the molecule, i.e. weakening function, It is what has. As shown in Table 3 above, when MoO (po) and WO (po) according to the present invention are used, the O—O bonds of the adsorbed oxygen molecules extend to 1.42 and 1.45, respectively. When platinum is used as the catalyst for the air electrode of the fuel cell, it is known that when the O—O bond distance of the adsorbed oxygen molecule extends to about 1.4 to 1.5 km, it binds to hydrogen ions. MoO (port) and WO (port) having such a function can be suitably used as an electrode catalyst material for a fuel cell, particularly as an electrode catalyst material for an air electrode in a solid polymer fuel cell. In particular, since MoO (por) has lower adsorption energy with O ₂ molecules than WO (por), it is possible to generate water more advantageously by the subsequent reaction with hydrogen ions and electrons. Since it is considered, it can be suitably used as an electrocatalyst material capable of four-electron reduction.

  In addition, although the said calculation is a thing about the case where a porphyrin ring does not have a substituent (namely, por), as mentioned above, the electrode catalyst material of this invention is not limited to this, For example, porphyrin The ring is 5,10,15,20-tetra-p-tolylporphyrin (tp), 2,3,7,8,12,13,17,18-octaethylporphyrin (oep), 5,10,15,20 -Tetraphenylporphyrin (tpp), 5,10,15,20-tetramesitylporphyrin (tmp), etc. may be sufficient. Even if it is a porphyrin ring having a substituent such as these, since these substituents are located outside the porphyrin ring, there is no influence on the coordination form when oxygen molecules are adsorbed to the oxometalloporphyrin. Since it is considered, it is considered that the same calculation result can be obtained.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows the structure of the oxo metalloporphyrin based on the first principle calculation result by the density functional theory. It is a schematic diagram showing the structure of a complex in which an O ₂ molecule is adsorbed in a side-on coordination to an oxo metalloporphyrin based on the first-principles calculation result by density functional theory. It is a schematic diagram showing the structure of a complex in which an O ₂ molecule is adsorbed in an end-on coordination to an oxo metalloporphyrin based on the first-principles calculation result by density functional theory. MoO (por) from left to _{right, MoO (por) (O 2} ), is a schematic diagram showing the molecular orbital energy diagram and valence electron density for O ₂ molecules. WO (por) from left to _{right, WO (por) (O 2} ), is a schematic diagram showing the molecular orbital energy diagram and valence electron density for O ₂ molecules.

Claims (3)

The following general formula (I):

[Wherein, each R is independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a phenyl group optionally having a substituent, and M is a molybdenum atom (Mo) or a tungsten atom. (W). ]
A fuel cell electrode catalyst material comprising an oxoporphyrin-based complex represented by the formula:   The electrode catalyst material according to claim 1, which is used as an electrode catalyst for an air electrode in a polymer electrolyte fuel cell.   The electrocatalyst material according to claim 1 or 2, wherein each R in the general formula (I) is a hydrogen atom (H).

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