JP5190965B2 - Catalyst for electrochemical oxidation of carbon monoxide - Google Patents

Description

  The present invention relates to a catalyst for electrochemical oxidation of carbon monoxide.

  The polymer electrolyte fuel cell is easy to handle due to its low operating temperature, and has excellent startability and operational operability, such as fast start-up time. Furthermore, it has a high current density and can be reduced in size and weight. For this reason, it is attracting attention as a small-capacity power source and a mobile power source. In a polymer electrolyte fuel cell, a Pt catalyst is mainly used as an anode catalyst. However, when hydrogen obtained by reforming natural gas, methanol, gasoline or the like is used as a fuel, it is generated by reforming. There is a problem that carbon monoxide is strongly adsorbed on Pt and greatly reduces the catalytic function.

  As a fuel electrode of such a low temperature fuel cell that is susceptible to catalyst poisoning by carbon monoxide, it is used for a fuel electrode having carbon monoxide resistance that uses a combination of a transition metal or its alloy and a specific organometallic complex. A catalyst or the like has been reported (for example, Patent Document 1). However, an effective catalyst for actively oxidizing and removing carbon monoxide has not been reported.

  On the other hand, it is known that Pt-based catalysts such as PtRu catalysts exhibit high activity in the oxidation of carbon monoxide, but it is still difficult to withstand high concentrations of carbon monoxide.

  Patent Document 2 reports a rhodium porphyrin complex in which meso-position is substituted with a phenyl group and a para-position of the phenyl group is substituted with a specific substituent as a catalyst capable of oxidizing and removing carbon monoxide. Yes. However, in Patent Document 2, only introduction of a substituent at the para-position of the benzene ring has been studied, and introduction of a substituent at the meta-position is not considered.

  On the other hand, as a gas sensor that electrically detects carbon monoxide, an ionization electrode and a reference electrode are connected to a proton conductor, and a proton current generated by an oxidation reaction of carbon monoxide at the ionization electrode is detected to detect a gas monoxide concentration. There is known a sensor having a structure for measuring (Patent Document 3).

  This gas sensor is disadvantageous in that the cost is high because a large amount of a noble metal catalyst such as Pt is used as the ionization electrode, and the detection sensitivity is inferior because the overvoltage of carbon monoxide oxidation is high.

JP 2002-329500 A JP 2008-36539 A JP-A-5-39509

  The present invention has been made in view of the current state of the prior art as described above, and its main purpose is to perform electrochemical oxidation of carbon monoxide suitable for use in a gas monoxide sensor, a fuel cell anode, and the like. It is to provide a novel catalyst effective for the reaction.

The present inventor has intensively studied to achieve the above-described object. As a result, in the rhodium porphyrin complex, a rhodium porphyrin complex in which the meso position is substituted with a phenyl group and the meta position of the phenyl group is substituted with a specific substituent has the reaction formula:
CO + H ₂ O → CO ₂ + 2H ⁺ + 2e ⁻
It was found to have a catalytic ability for the electrochemical carbon monoxide oxidation reaction indicated by Moreover, the rhodium porphyrin complex is considered to have high stability because the meso position is chemically protected.

  Furthermore, it has been found that when the rhodium porphyrin complex is supported on a conductive carrier (especially carbon black) together with a Pt catalyst (particularly PtRu catalyst), the carbon monoxide poisoning resistance of the Pt catalyst can be improved. That is, the present inventors have found that the rhodium porphyrin complex is suitable for improving carbon monoxide poisoning resistance in combination with a Pt-based catalyst.

  The present invention has been completed based on these findings.

  That is, the present invention provides the following catalyst for electrochemical oxidation of carbon monoxide and its use.

  Item 1. Chemical formula (1):

[Wherein, eight R _{1 s} are the same or different and are each a hydrogen atom or a substituent having a molecular weight of 15 to 100 (provided that at least one is a substituent having a molecular weight of 15 to 100); 4 R ₂ and 8 R ₃ are the same or different and are each a hydrogen atom, a halogen, an amino group, an alkyl group having 1 to 5 carbon atoms, —COOM ³ (M ³ is a hydrogen atom, 1 carbon atom). 5 is an alkyl group or an alkali _{metal), - (CH 2) n} -COOM 4 (M 4 represents a hydrogen atom, an alkyl group or an alkali metal C1-5, n represents 1 to 5), or —SO ₃ M ⁵ (M ⁵ is a hydrogen atom or an alkali metal)]
A catalyst for electrochemical oxidation of carbon monoxide containing rhodium porphyrin represented by

Item 2.4 The catalyst for electrochemical oxidation of carbon monoxide according to any one of Items 1, wherein 2.4 R ₂ and 8 R ₃ are both hydrogen atoms.

Item 3. The substituent in R ₁ is —COOM ¹ (M ¹ is a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or an alkali metal) or —OM ² (M ² is a hydrogen atom, an alkyl having 1 to 2 carbon atoms). Item 3. The catalyst for electrochemical oxidation of carbon monoxide according to Item 1 or 2, which is a group represented by

Item 4. Item 4. The catalyst for electrochemical oxidation of carbon monoxide according to any one of Items 1 to ₃ , wherein the substituent is —COOH or —OCH ₃ .

  Item 5. Item 5. The catalyst for electrochemical oxidation of carbon monoxide according to any one of Items 1 to 4, wherein the rhodium porphyrin represented by the chemical formula (1) is supported on a conductive carrier.

  Item 6. Item 6. The catalyst for electrochemical oxidation of carbon monoxide according to Item 5, wherein the conductive support is carbon black.

  Item 7. Item 7. Electrochemical oxidation of carbon monoxide according to any one of Items 1 to 6, wherein the rhodium porphyrin represented by the chemical formula (1) and platinum or platinum alloy particles are supported on a conductive carrier. Catalyst.

  Item 8. Item 8. The catalyst for electrochemical oxidation of carbon monoxide according to Item 7, wherein the platinum or platinum alloy particles are platinum ruthenium alloy particles.

  Item 9. Item 7. An anode for a polymer electrolyte fuel cell, comprising the catalyst for electrochemical oxidation of carbon monoxide according to any one of Items 1 to 6 and an anode catalyst material.

  Item 10. Item 10. A carbon monoxide sensor comprising the carbon monoxide electrochemical oxidation catalyst according to any one of Items 1 to 8 as a carbon monoxide oxidation catalyst component in a carbon monoxide detector.

  Item 11. Any one of Items 1 to 8 as a catalyst for oxidizing carbon monoxide in a working electrode in a carbon monoxide oxidation removing apparatus in an anode gas for a polymer electrolyte fuel cell, including an electrolyte, a working electrode, a counter electrode, and a power supply An apparatus for removing oxidization of carbon monoxide in an anode gas comprising the catalyst for electrochemical oxidation of carbon monoxide.

  Item 12. Item 9. An anode electrode for a polymer electrolyte fuel cell using carbon monoxide as a fuel, comprising the catalyst for electrochemical oxidation of carbon monoxide according to any one of Items 1 to 8 as an anode catalyst material.

  Item 13. Item 13. A polymer electrolyte fuel cell using carbon monoxide as a fuel, comprising the anode electrode according to Item 12 as a constituent element.

  The catalyst for electrochemical oxidation of carbon monoxide of the present invention has the chemical formula (1):

[Wherein, eight R _{1 s} are the same or different and are each a hydrogen atom or a substituent having a molecular weight of 15 to 100 (provided that at least one is a substituent having a molecular weight of 15 to 100); 4 R ₂ and 8 R ₃ are the same or different and are each a hydrogen atom, a halogen, an amino group, an alkyl group having 1 to 5 carbon atoms, —COOM ³ (M ³ is a hydrogen atom, 1 carbon atom). 5 is an alkyl group or an alkali _{metal), - (CH 2) n} -COOM 4 (M 4 represents a hydrogen atom, an alkyl group or an alkali metal C1-5, n represents 1 to 5), or —SO ₃ M ⁵ (M ⁵ is a hydrogen atom or an alkali metal)]
The rhodium porphyrin represented by these is an active ingredient.

The rhodium porphyrin represented by the chemical formula (1) has the reaction formula:
CO + H ₂ O → CO ₂ + 2H ⁺ + 2e ⁻
It has an excellent activity for the electrochemical oxidation reaction of carbon monoxide represented by Therefore, by electrochemically oxidizing carbon monoxide in the presence of the rhodium porphyrin, it becomes possible to efficiently oxidize carbon monoxide with a low overvoltage.

  Furthermore, the rhodium porphyrin represented by the chemical formula (1) has high stability against oxidation reaction and the like because the meso position is chemically protected.

In the above chemical formula (1), the eight R _{1 s} are the same or different and are each a hydrogen atom or a substituent having a molecular weight of 15 to 100 (however, at least one is a substituent having a molecular weight of 15 to 100). ).

When all of the eight R ₁ are hydrogen atoms, that is, when no substituent is bonded to any meta position of the four benzene rings, Pt catalyst is used to support Pt. The system catalyst is covered with the rhodium porphyrin complex. As a result, the active site of the hydrogen oxidation reaction of the Pt-based catalyst is covered and the hydrogen oxidation activity is lowered. In addition, there is a possibility that the carbon monoxide is more easily poisoned.

On the other hand, when at least one of R ₁ is a substituent, when the rhodium porphyrin complex coats the Pt-based catalyst due to its steric hindrance, the distance from the Pt-based catalyst is wide. Is difficult to be coated and the hydrogen oxidation activity is difficult to decrease. On the other hand, since the rhodium porphyrin complex can oxidize and remove carbon monoxide, it is possible to improve the carbon monoxide poisoning resistance of the platinum catalyst.

From such a viewpoint, among the eight R ₁ , the number of substituents is particularly preferably 2 to 8.

  Note that even if a substituent is bonded to the para-position of the benzene ring, the distance from the Pt-based catalyst cannot be increased. Therefore, it is necessary to bond the substituent to the meta-position of the benzene ring.

Examples of the substituent group to be bonded to at least one of the eight _{R 1,} molecular weight 15 to 100, and preferably from 15 to 60. When the molecular weight of the substituent is less than 15, the Pt catalyst is covered with the rhodium porphyrin complex when it is supported on the carrier together with the Pt catalyst.

Examples of the substituent satisfying the above conditions include -COOM ¹ (M ¹ is a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or an alkali metal (particularly K and Na)) or -OM ² ( M ² is a hydrogen atom or a C 1-2 alkyl group). Specifically, —COOH, —COOCH ₃ , —OH, —OCH _{3 and the} like can be mentioned. Among these, —COOH is preferable from the viewpoint of catalytic activity for the oxidation of carbon monoxide and carbon monoxide poisoning improvement, and —OCH ₃ is preferable from the viewpoint of cost.

In the above chemical formula (1), 4 R ₂ and 8 R ₃ are not particularly limited and may be any one. For example, a hydrogen atom, a halogen, an amino group, 1 carbon atom ˜5 alkyl group, —COOM ³ (M ³ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkali metal (particularly K or Na)), — (CH ₂ ) _n —COOM ⁴ (M ⁴ is hydrogen atom, a C1-5 alkyl group or an alkali metal (especially K or Na), n is ^{_{1~5), - SO 3 M 5}} (M 5 represents a hydrogen atom or an alkali metal (especially K or Na) in a), - OM 6 ^{(M 2} represents a hydrogen atom, there may be mentioned such as an alkyl group having 1 to 5 carbon atoms), from the viewpoint of low cost, it is preferred that all hydrogen atoms.

  Examples of rhodium porphyrins that satisfy the above conditions include:

Etc.

  The rhodium porphyrin represented by the chemical formula (1) has the chemical formula (2):

(In the formula, 8 R ₁ , 4 R ₂ and 8 R ₃ are the same as in the chemical formula (1)).
It can obtain by forming a chelate with the porphyrin compound represented by these, and a rhodium atom.

Specifically, it can be synthesized, for example, by the method described in Inorganica Chimica Acta 25 (1977) 215-218. That is, after the porphyrin compound represented by the chemical formula (2) is sufficiently dissolved in a solvent such as toluene, a rhodium salt, a complex or the like is added thereto. Then, the target rhodium porphyrin can be obtained by heating to reflux and purifying the reaction mixture by a conventional method.

  As the rhodium salt or complex, tetracarbonyldi-μ-chlorodirhodium or the like is desirable.

  The solvent to be used is not particularly limited as long as both the porphyrin compound and the rhodium salt are dissolved, but toluene, ethanol and the like are preferable. The heating reflux temperature is not particularly limited as long as it is lower than the boiling point of the solvent, but is preferably about 80 to 100 ° C. when toluene is used.

  The rhodium porphyrin represented by the chemical formula (1) used in the present invention stabilizes rhodium porphyrin by supporting intermolecular reactions such as dimerization reaction and disproportionation reaction by supporting it on a conductive carrier. be able to. As a result, the rhodium porphyrin represented by the chemical formula (1) can have high catalytic activity for the electrochemical oxidation reaction of carbon monoxide. This is presumably because the rhodium porphyrin is strongly adsorbed and supported on the carrier by the interaction with the conductive carrier.

  The conductive carrier is not particularly limited, and for example, various carriers conventionally used as catalyst carriers for polymer electrolyte fuel cells can be used. Specific examples of such a carrier include carbonaceous materials such as carbon black, activated carbon, and graphite. Among these, carbon black has a strong interaction with the rhodium porphyrin represented by the chemical formula (1) and has a strong function of stabilizing rhodium porphyrin, and further has excellent conductivity and a large specific surface area. It is a particularly preferable substance as a conductive carrier.

The shape and the like of the conductive carrier are not particularly limited. For example, those having an average particle diameter of about 0.1 to 100 μm, preferably about 1 to 10 μm can be used. When carbon black is used, for example, the specific surface area by the BET method is preferably in the range of about 50 to 1600 m ² / g, and more preferably in the range of about 100 to 1200 m ² / g. . As a specific example of such carbon black, for example, a commercially available product under the trade name Vulcan XC-72R (Cabot) can be used.

  As a method for supporting the conductive carrier, for example, a known method such as a dissolution drying method or a gas phase method can be applied.

  For example, in the dissolution drying method, rhodium porphyrin is dissolved in an organic solvent, and a conductive carrier is added to this solution. For example, the rhodium porphyrin is adsorbed on the carrier by stirring for several hours, and then the organic solvent is dried. Just do it. In addition, when rhodium porphyrin is contained in a large amount in an organic solvent, rhodium porphyrin is adsorbed on a conductive support until equilibrium is reached, and then filtered to remove rhodium porphyrin not adsorbed on the conductive support. Thus, only the rhodium porphyrin interacting with the carrier can be left on the surface of the carrier.

  In this method, the organic solvent can be used without particular limitation as long as it can dissolve rhodium porphyrin. For example, lower alcohols such as ethanol, halogen solvents such as dichloromethane, and the like can be suitably used.

  If the dispersion obtained by filtration is further washed with an organic solvent until the washing liquid becomes transparent, rhodium porphyrin, which has a weak interaction with the conductive carrier, can be washed away and firmly adsorbed on the conductive carrier. It is possible to obtain a highly active catalyst containing only the rhodium porphyrin.

  In the case of carrying by a vapor phase method, for example, a known method such as a plasma vapor deposition method, a CVD method, or a heat vapor deposition method can be adopted.

  The amount of rhodium porphyrin supported on the conductive carrier is not particularly limited. For example, about 20 to 80 μmol of rhodium porphyrin may be supported on 1 g of the conductive carrier, and about 20 to 30 μmol is supported. Is preferred.

  The rhodium porphyrin represented by the chemical formula (1) may be supported on a conductive carrier together with platinum or platinum alloy particles. Thus, when rhodium porphyrin represented by the chemical formula (1) is supported on a conductive support together with platinum or platinum alloy particles, the carbon monoxide poisoning resistance of the Pt-based catalyst can be improved. Compared with the case where rhodium porphyrin described in Kaikai 2008-36539 is carried on a conductive carrier together with platinum or platinum alloy particles, the carbon monoxide poisoning resistance can be improved.

  The size of the platinum or platinum alloy particles is not limited, but is preferably about 1 to 10 nm. In particular, in the case of plain platinum particles, about 1 to 5 nm is desirable, and in the case of platinum alloy particles, about 1 to 7 nm is desirable. The weight of platinum or platinum alloy particles in the entire catalyst of the present invention is preferably 5 to 75%, more preferably 10 to 60%.

When platinum alloy particles are used as platinum or platinum alloy particles, ruthenium is desirable as the metal alloyed with platinum. When alloying platinum and ruthenium, the ratio of ruthenium to platinum is desirably 0.5 to 3 in terms of molar ratio, and particularly 1 to 1.5.
It is desirable that

  When the rhodium porphyrin represented by the chemical formula (1) and the platinum or platinum alloy particles are supported on the conductive carrier, the rhodium porphyrin represented by the chemical formula (1) alone is supported on the conductive carrier. It can be supported by the same method. However, since an alcohol solvent may react with platinum and ignite, a halogen solvent such as dichloromethane or chloroform, acetone or the like is desirable.

  In this case, the rhodium porphyrin represented by the chemical formula (1) may be supported on the conductive support and then the platinum or platinum alloy particles may be supported, or the platinum or platinum alloy particles may be supported on the conductive support. The rhodium porphyrin represented by the chemical formula (1) may be supported after being supported. In the latter case, rhodium porphyrin represented by the chemical formula (1) may be supported on commercially available platinum-supported carbon or platinum alloy-supported carbon.

  The ratio of rhodium porphyrin represented by the chemical formula (1) to platinum or platinum alloy particles is preferably 5 to 50 μmol, particularly preferably 10 to 40 μmol, per 1 g of platinum or platinum alloy particles.

  In addition, the carbon monoxide electrochemical oxidation catalyst of the present invention can be used, for example, as a sensor for detecting carbon monoxide using an electrode reaction. In this case, a sensor including the catalyst of the present invention as a carbon monoxide oxidation catalyst is used, and detection methods include a method of detecting a current generated by an oxidation reaction of carbon monoxide, a method of detecting a potential difference, and a proton. A detection method or the like can be employed. For example, like the sensor in the gas detector described in Japanese Patent Publication No. 5-39509, an ionization electrode for oxidizing carbon monoxide by an electrode reaction to generate protons, a proton conductor, and a proton conductor A proton conductor gas sensor having a reference electrode for receiving protons from the gas, reacting with oxygen in the atmosphere and discharging it as water can be obtained. In the gas sensor having such a structure, the catalyst of the present invention can be used as a catalyst for oxidizing carbon monoxide in the ionization electrode.

  In addition, the catalyst for electrochemical oxidation of carbon monoxide of the present invention is, for example, a solid polymer fuel cell using a reformed gas obtained by reforming natural gas, methanol, gasoline or the like as an anode gas. In the above, before supplying the anode gas to the fuel cell, the carbon monoxide contained in the anode gas can be used as a catalyst for oxidizing carbon monoxide in a carbon monoxide oxidation removing apparatus for oxidizing and removing carbon monoxide by electrolysis. Such a carbon monoxide oxidation removal device has, for example, an electrolytic solution, a working electrode, a counter electrode, and a power supply device as basic components.

  A schematic diagram of the carbon monoxide removal apparatus is shown in FIG. The carbon monoxide oxidation removal apparatus can basically have the same structure as that of various ordinary electrolysis apparatuses. As the electrolytic solution, for example, a sulfuric acid solution of about 0.1 to 1M can be used. The catalyst of the present invention is used as a catalyst for oxidizing carbon monoxide at the working electrode. In the working electrode, a conductive material such as a carbon electrode may be used as a base material, and the catalyst of the present invention may be fixed to the base material with a conductive binder. There is no particular limitation on the counter electrode, and various electrodes used in a normal electrolysis apparatus can be used. For example, a carbon electrode can be used. As the power supply device, for example, a constant voltage power supply (potentiostat) or the like can be used. Further, in order to set the working electrode at a predetermined potential, a reference electrode is usually installed in the electrolyte solution. As the reference electrode, various electrodes used in a normal electrolysis apparatus can be used. For example, a silver / silver chloride electrode can be used.

In the carbon monoxide oxidation removing apparatus, for example, an anode gas is bubbled into the electrolyte solution by a method such as bubbling, and a positive voltage is applied to the working electrode with respect to the reference electrode using a constant voltage power source (potentiostat) during the ventilation. By applying, carbon monoxide contained in the anode gas can be electrochemically oxidized with high selectivity. At this time, by using the catalyst of the present invention as a working electrode catalyst, carbon monoxide can be electrochemically oxidized at a low overvoltage without oxidizing the fuel gas, and the anode gas can be purified. Become. By supplying the exhaust gas from the carbon monoxide oxidation removal apparatus to the polymer electrolyte fuel cell, it is possible to supply high purity hydrogen gas to the fuel cell.

  Furthermore, the catalyst for electrochemical oxidation of carbon monoxide of the present invention can be used as an anode catalyst for a polymer electrolyte fuel cell using carbon monoxide as a fuel. Normally, it is known that carbon monoxide is contained in the fuel gas even a little, but it is known that it causes catalyst poisoning. It can be used as fuel.

  When the catalyst of the present invention is used as an anode catalyst, except for using the catalyst of the present invention as an anode catalyst material, the structure of the anode electrode and the structure of the polymer electrolyte fuel cell using this anode electrode are particularly There is no limitation, and it may be similar to a known fuel cell. That is, the polymer electrolyte membrane, the electrode catalyst, the membrane-electrode assembly, the cell structure and the like may be the same as those of a known solid polymer fuel cell.

  For example, conventionally known various metals and metal alloys can be used as the cathode catalyst metal. Specific examples include various metal catalysts including platinum, palladium, iridium, rhodium, ruthenium, platinum-ruthenium, or a supported catalyst in which these catalyst fine particles are dispersed on a carrier such as carbon.

  Polymer electrolyte membranes include perfluorocarbon, styrene-divinylbenzene copolymer, polybenzimidazole and other ion exchange resin membranes, inorganic polymer ion exchange membranes, organic-inorganic composite polymer ion exchange membranes, etc. Can be used.

  The joined body of the solid polymer electrolyte membrane and the electrode catalyst can be produced by a known method. For example, a method in which a catalyst ink prepared by mixing a catalyst powder and an electrolyte solution is thinned and then hot-pressed on the electrolyte membrane, or a method of directly applying and drying on the polymer membrane is applied.

  A fuel battery cell can be produced by sandwiching both surfaces of the obtained membrane-electrode assembly between current collectors such as carbon paper and carbon cloth and incorporating them into the cell.

  In the fuel cell using the catalyst of the present invention as an anode catalyst, carbon monoxide may be supplied to the anode as a fuel, and air or oxygen may be supplied or naturally diffused on the cathode side.

  The operating temperature of the fuel cell of the present invention varies depending on the electrolyte membrane to be used, but is usually about 0 to 100 ° C, preferably about 10 to 80 ° C.

  According to the catalyst for electrochemical oxidation of carbon monoxide of the present invention, carbon monoxide can be efficiently oxidized at a low overvoltage. Furthermore, the catalyst of the present invention has high stability against oxidation reactions and the like.

  In addition, when the rhodium porphyrin used in the present invention is supported on a conductive carrier, the rhodium porphyrin can be stabilized by suppressing intermolecular reaction, and the electrochemical oxidation reaction of carbon monoxide. And high catalytic activity.

  When the conductive support is carbon black, the rhodium porphyrin can be dispersed and supported in a state close to atomic units, so that the amount of catalyst metal used can be greatly reduced, and it is inexpensive and highly active. The catalyst can be used for electrochemical oxidation of carbon oxide.

  Furthermore, when the rhodium porphyrin complex is supported on a conductive carrier (especially carbon black) together with a Pt catalyst (especially a PtRu catalyst), the carbon monoxide poisoning resistance of the Pt catalyst can be improved.

It is the schematic of a carbon monoxide oxidation removal apparatus. 4 is an absorbance curve of an ultraviolet / visible spectrum of tetrakis (3,5-dimethoxy) phenylporphyrin (curve A) and rhodium tetrakis (3,5-dimethoxy) phenylporphyrin (curve B) in Production Example 1. FIG. 4 is an absorbance curve of an ultraviolet / visible spectrum of tetrakis (3-carboxy) phenylporphyrin (curve A) and rhodium tetrakis (3-carboxy) phenylporphyrin (curve B) in Production Example 2. FIG. It is an absorption curve of the ultraviolet and visible spectrum of tetrakis (3-carboxymethyl) phenylporphyrin (curve A) and rhodium tetrakis (3-carboxymethyl) phenylporphyrin (curve B) in Production Example 3. It is an absorption curve of the ultraviolet and visible spectrum of tetrakis (3,5-dihydroxy) phenylporphyrin (curve A) and rhodium tetrakis (3,5-dihydroxy) phenylporphyrin (curve B) in Production Example 4. Cyclic voltammogram under curve of argon saturation (curve A) and linear sweep voltammogram under curve of carbon monoxide (curve B) of the rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-supported carbon catalyst obtained in Example 1 It is. FIG. 2 is a cyclic voltammogram (curve A) under an argon saturation condition and a linear sweep voltammogram (curve B) under a carbon monoxide saturation condition of the rhodium tetrakis (3-carboxy) phenylporphyrin-supported carbon catalyst obtained in Example 2. FIG. . Cyclic voltammogram (curve A) under argon saturation conditions and linear sweep voltammogram (curve B) under carbon monoxide saturation conditions of the rhodium tetrakis (3-carboxymethyl) phenylporphyrin-supported carbon catalyst obtained in Example 3 is there. Cyclic voltammogram (curve A) of the rhodium tetrakis (3,5-dihydroxy) phenylporphyrin supported carbon catalyst obtained in Example 4 under argon saturation conditions (curve A) and linear sweep voltammogram of carbon monoxide saturation conditions (curve B) It is. FIG. 6 shows the results of voltammetry of platinum-ruthenium-supported carbon obtained in Example 5 (curve A) and the results of voltammetry of rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-platinum ruthenium-supported carbon (curve B). It is the result (curve B) of the voltammetry of platinum ruthenium carrying | support carbon obtained in Example 6 (curve A) and the voltammetry of rhodium tetrakis (3-carboxy) phenylporphyrin-platinum ruthenium carrying carbon. It is the result (curve B) of the voltammetry of platinum ruthenium carrying | support carbon obtained in Example 7 (curve A) and the voltammetry of rhodium tetrakis (3-carboxymethyl) phenylporphyrin-platinum ruthenium carrying carbon. FIG. 9 shows the results of voltammetry of platinum-ruthenium-supported carbon obtained in Example 8 (curve A) and the results of voltammetry of rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-platinum ruthenium-supported carbon (curve B). It is the result (curve A) of the voltammetry of platinum ruthenium carrying | supporting carbon obtained in the comparative example 1 (curve A) and the voltammetry result of rhodium tetrakis (4-methoxy) phenylporphyrin-platinum ruthenium carrying carbon.

  Hereinafter, the present invention will be described in more detail with reference to production examples and examples.

Production Example 1
Synthesis of rhodium tetrakis (3,5-dimethoxy) phenylporphyrin

42.9 mg of a commercially available tetrakis (3,5-dimethoxy) phenylporphyrin represented by the following formula was weighed and suspended in 150 mL of ethanol. 10.9 mg of [Rh ₂ Cl ₂ (CO) ₄ ] was added to this suspension and heated to reflux. Concentrate the solution after reflux with a rotary evaporator, dissolve in ethanol, measure the ultraviolet and visible spectrum (UV-vis spectrum),

The synthesis of was confirmed.

  FIG. 2 shows an absorbance curve of an ultraviolet / visible spectrum (UV-vis spectrum). In FIG. 2, curve A corresponds to tetrakis (3,5-dimethoxy) phenylporphyrin used as a raw material, and curve B is a spectral curve corresponding to the target rhodium tetrakis (3,5-dimethoxy) phenylporphyrin. .

Production Example 2
Synthesis of rhodium tetrakis (3-carboxy) phenylporphyrin

10.3 mg of tetrakis (3-carboxy) phenylporphyrin represented by the following formula was weighed and suspended in 33 mL of ethanol. To this suspension, 3.0 mg of [Rh ₂ Cl ₂ (CO) ₄ ] was added and heated to reflux. Concentrate the solution after reflux with a rotary evaporator, dissolve in ethanol, measure the ultraviolet and visible spectrum (UV-vis spectrum),

The synthesis of was confirmed.

  FIG. 3 shows an absorbance curve of an ultraviolet / visible spectrum (UV-vis spectrum). In FIG. 3, curve A corresponds to tetrakis (3-carboxy) phenylporphyrin used as a raw material, and curve B is a spectroscopic curve corresponding to the target rhodium tetrakis (3-carboxy) phenylporphyrin.

Production Example 3
Synthesis of rhodium tetrakis (3-carboxymethyl) phenylporphyrin

10.3 mg of tetrakis (3-carboxymethyl) phenylporphyrin represented by formula (1) was weighed and suspended in 33 mL of toluene. To this suspension, 2.8 mg of [Rh ₂ Cl ₂ (CO) ₄ ] was added and heated to reflux. The solution after refluxing is concentrated with a rotary evaporator, dissolved in toluene, and an ultraviolet / visible spectrum (UV-vis spectrum) is measured.

The synthesis of was confirmed.

  FIG. 4 shows an absorbance curve of an ultraviolet / visible spectrum (UV-vis spectrum). In FIG. 4, curve A corresponds to tetrakis (3-carboxymethyl) phenylporphyrin used as a raw material, and curve B is a spectral curve corresponding to rhodium tetrakis (3-carboxymethyl) phenylporphyrin, which is the target product.

Production Example 4
Synthesis of rhodium tetrakis (3,5-dihydroxy) phenylporphyrin

50.0 mg of tetrakis (3,5-dihydroxy) phenylporphyrin represented by the following formula was weighed and suspended in 170 mL of ethanol. 14.2 mg of [Rh ₂ Cl ₂ (CO) ₄ ] was added to this suspension and heated to reflux. Concentrate the solution after reflux with a rotary evaporator, dissolve in ethanol, measure the ultraviolet and visible spectrum (UV-vis spectrum),

The synthesis of was confirmed.

  FIG. 5 shows an absorbance curve of an ultraviolet / visible spectrum (UV-vis spectrum). In FIG. 5, curve A corresponds to tetrakis (3,5-dihydroxy) phenylporphyrin used as a raw material, and curve B is a spectral curve corresponding to rhodium tetrakis (3,5-dihydroxy) phenylporphyrin, which is the target product. .

Example 1
Preparation of rhodium tetrakis (3,5-dimethoxy) phenylporphyrin- supported carbon catalyst Rhodium tetrakis (3,5-dimethoxy) phenylporphyrin synthesized in Production Example 1 was dissolved in 11 mL of dichloromethane so as to have a concentration of 0.7 mM. 30 mg of carbon black (manufactured by Cabot, Vulcan XC 72R) was added to this solution and dispersed with an ultrasonic disperser, followed by stirring for 2 hours and 30 minutes. After stirring, the solution was removed by filtration to recover the powder. This powder was used as a rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-supported carbon catalyst.

Rhodium tetrakis (3,5-dimethoxy) phenylporphyrin supported carbon catalyst
Evaluation of electrochemical carbon monoxide oxidation activity 5 mg of the prepared rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-supported carbon catalyst powder was weighed into a water: ethanol mixed solvent (water 0.25 mL: ethanol 0.25 mL). Suspend and add 5 μL of 5% Nafion solution from Aldrich. 2 μL of this suspension was dropped onto a glassy carbon electrode (surface area: 0.0707 cm ² ) manufactured by BAS and dried.

The electrochemical carbon monoxide oxidation activity of the rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-supported carbon catalyst was measured using the modified electrode as a working electrode, the silver-silver chloride electrode as a reference electrode, and the platinum electrode as a counter electrode. A three-electrode system was used. As the electrolytic solution, 0.1 M H ₂ SO ₄ was used.

  FIG. 6 shows that the cyclic voltammogram of the rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-supported carbon catalyst in the absence of carbon monoxide (argon saturation condition) is a curve A, and carbon monoxide gas is 7 in the electrolytic cell. A linear sweep voltammogram measured while rotating the electrode at 6400 rpm after blowing for a minute is shown as curve B. In curve B in which carbon monoxide gas was blown, an increase in oxidation current was observed from around 0 V, indicating that carbon monoxide was electrochemically oxidized by the catalytic action of the rhodium porphyrin complex.

Example 2
Evaluation of electrochemical carbon monoxide oxidation activity of rhodium tetrakis (3-carboxy) phenylporphyrin-supported carbon catalyst In the same manner as in Example 1, a rhodium tetrakis (3-carboxy) phenylporphyrin-supported carbon catalyst was prepared and its electrochemical properties were measured. Carbon monoxide oxidation activity was evaluated. The results are shown in FIG. In FIG. 7, a cyclic voltammogram of a rhodium tetrakis (3-carboxy) phenylporphyrin-supported carbon catalyst in a condition where there is no carbon monoxide (argon saturation condition) is taken as curve A, and carbon monoxide gas is blown into the electrolytic cell for 7 minutes. Thereafter, a linear sweep voltammogram measured while rotating the electrode at 6400 rpm is shown as a curve B. In curve B in which carbon monoxide gas was blown, an increase in oxidation current was observed from around 0 V, indicating that carbon monoxide was electrochemically oxidized by the catalytic action of the rhodium porphyrin complex.

Example 3
Evaluation of electrochemical carbon monoxide oxidation activity of rhodium tetrakis (3-carboxymethyl) phenylporphyrin-supported carbon catalyst In the same manner as in Example 1, a rhodium tetrakis (3-carboxymethyl) phenylporphyrin-supported carbon catalyst was prepared. Chemical carbon monoxide oxidation activity was evaluated. The results are shown in FIG. In FIG. 8, the cyclic voltammogram of the rhodium tetrakis (3-carboxymethyl) phenylporphyrin-supported carbon catalyst in the absence of carbon monoxide (argon saturation condition) is taken as curve A, and carbon monoxide gas is placed in the electrolytic cell for 7 minutes. A linear sweep voltammogram measured while rotating the electrode at 6400 rpm after blowing is shown as curve B. In curve B in which carbon monoxide gas was blown, an increase in oxidation current was observed from around −0.1 V, indicating that carbon monoxide was electrochemically oxidized by the catalytic action of the rhodium porphyrin complex.

Example 4
Evaluation of electrochemical carbon monoxide oxidation activity of rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-supported carbon catalyst As in Example 1, a rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-supported carbon catalyst was prepared. Its electrochemical carbon monoxide oxidation activity was evaluated. The results are shown in FIG. In FIG. 9, the cyclic voltammogram of the rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-supported carbon catalyst in the absence of carbon monoxide (argon saturation condition) is taken as curve A, and carbon monoxide gas is introduced into the electrolytic cell. A linear sweep voltammogram measured while rotating the electrode at 6400 rpm after blowing for a minute is shown as curve B. In curve B in which carbon monoxide gas was blown, an increase in oxidation current was observed from around −0.1 V, indicating that carbon monoxide was electrochemically oxidized by the catalytic action of the rhodium porphyrin complex.

Example 5
Preparation of rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-platinum ruthenium-supported carbon catalyst The rhodium tetrakis (3,5-dimethoxy) phenylporphyrin synthesized in Production Example 1 was dissolved in 30 mL of dichloromethane to a concentration of 0.3 mM. It was. 100 mg of commercially available platinum ruthenium-supported carbon (platinum / ruthenium supported amount 54%, molar ratio (platinum: ruthenium) = 1: 1.5) manufactured by Tanaka Kikinzoku Co., Ltd. was suspended in this solution. The powder was dispersed with an ultrasonic disperser for 5 minutes, stirred for 3 hours, filtered to remove the solution, and the powder was recovered. This powder was used as a rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-platinum ruthenium supported carbon catalyst.

Evaluation of carbon monoxide toxicity resistance of rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-platinum ruthenium supported carbon catalyst 2.0 mg of the prepared rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-platinum ruthenium supported carbon catalyst And suspended in a mixed solvent consisting of 5.7 mL of water and 3.8 mL of ethanol. 3.6 μL of this suspension was dropped onto a glassy carbon electrode (surface area: 0.0707 cm ² ) manufactured by BAS and dried. On top of this, 1.6 μL of a solution obtained by diluting a Nafion 5% solution manufactured by Aldrich to 1/100 was dropped and dried.

  The modified electrode thus prepared was used as a working electrode, the reversible hydrogen electrode was used as a reference electrode, the platinum electrode was used as a counter electrode, and the electrochemical oxidation activity of hydrogen containing 2% carbon monoxide was evaluated using a three-electrode system.

  First, under the condition that the electrochemical measurement cell is kept at 60 ° C., the working electrode voltage is kept at 0.05 V, the working electrode is rotated at 3600 rpm, and the ampero is contained in a hydrogen atmosphere containing 2% carbon monoxide. Measurement was performed. After confirming that the catalyst was poisoned by carbon monoxide and the current value was 10 μA or less, voltammetry was performed. The electrolyte used was 0.1M perchloric acid.

  FIG. 10 shows the result. With a platinum-ruthenium catalyst (curve A) that does not carry a rhodium porphyrin complex, a clear hydrogen oxidation current was not observed unless a voltage of 0.4 V or higher was applied. On the other hand, in the case of a rhodium tetrakis (3,5-dimethoxy) phenylporphyrin-platinum ruthenium-supported carbon catalyst, a hydrogen oxidation current starts to flow simply by applying a voltage of 0.2 V, It was found that hydrogen oxidation current was observed at low overvoltage even under high concentration conditions. This indicates that the platinum ruthenium catalyst is hardly poisoned by carbon monoxide by supporting the rhodium tetrakis (3,5-dimethoxy) phenylporphyrin complex.

Example 6
Evaluation of resistance to carbon monoxide poisoning of rhodium tetrakis (3-carboxy) phenylporphyrin-platinum ruthenium supported carbon catalyst In the same manner as in Example 5, a rhodium tetrakis (3-carboxy) phenylporphyrin-platinum ruthenium supported carbon catalyst was prepared. Its carbon monoxide toxicity was evaluated. The results are shown in FIG. With a platinum-ruthenium catalyst (curve A) that does not carry a rhodium porphyrin complex, a clear hydrogen oxidation current was not observed unless a voltage of 0.4 V or higher was applied. On the other hand, in the case of a rhodium tetrakis (3-carboxy) phenylporphyrin-platinum ruthenium-supported carbon catalyst, a hydrogen oxidation current starts to flow just by applying a voltage of 0.2 V, and the catalyst poisoning species carbon monoxide has a high concentration. It was found that hydrogen oxidation current was observed at low overvoltage even under the existing conditions. This shows that the platinum ruthenium catalyst is hardly poisoned by carbon monoxide by supporting the rhodium tetrakis (3-carboxy) phenylporphyrin complex.

Example 7
Evaluation of carbon monoxide poisoning resistance of rhodium tetrakis (3-carboxymethyl) phenylporphyrin-platinum ruthenium supported carbon catalyst In the same manner as in Example 5, a rhodium tetrakis (3-carboxymethyl) phenylporphyrin-platinum ruthenium supported carbon catalyst was prepared. The carbon monoxide toxicity was evaluated. The results are shown in FIG. With a platinum-ruthenium catalyst (curve A) that does not carry a rhodium porphyrin complex, a clear hydrogen oxidation current was not observed unless a voltage of 0.4 V or higher was applied. On the other hand, in the case of a rhodium tetrakis (3-carboxy) phenylporphyrin-platinum ruthenium-supported carbon catalyst, a hydrogen oxidation current starts to flow just by applying a voltage of 0.2 V, and the catalyst poisoning species carbon monoxide has a high concentration. It was found that hydrogen oxidation current was observed at low overvoltage even under the existing conditions. This shows that the platinum ruthenium catalyst is hardly poisoned by carbon monoxide by supporting the rhodium tetrakis (3-carboxy) phenylporphyrin complex.

Example 8
Evaluation of carbon monoxide poisoning resistance of rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-platinum ruthenium supported carbon catalyst As in Example 5, rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-platinum ruthenium supported carbon catalyst Were prepared and their carbon monoxide poisoning resistance was evaluated. The results are shown in FIG. With a platinum-ruthenium catalyst (curve A) that does not carry a rhodium porphyrin complex, a clear hydrogen oxidation current was not observed unless a voltage of 0.4 V or higher was applied. On the other hand, in the case of a rhodium tetrakis (3,5-dihydroxy) phenylporphyrin-platinum ruthenium-supported carbon catalyst, a hydrogen oxidation current starts to flow just by applying a voltage of 0.2 V, and the carbon monoxide of the catalyst poisoning species It was found that hydrogen oxidation current was observed at low overvoltage even under high concentration conditions. This shows that the platinum ruthenium catalyst is hardly poisoned by carbon monoxide by supporting the rhodium tetrakis (3,5-dihydroxy) phenylporphyrin complex.

Comparative Example 1
Evaluation of resistance to carbon monoxide poisoning of rhodium tetrakis (4-methoxy) phenylporphyrin-platinum ruthenium supported carbon catalyst In the same manner as in Example 5, a rhodium tetrakis (4-methoxy) phenylporphyrin-platinum ruthenium supported carbon catalyst was prepared. Its carbon monoxide toxicity was evaluated. The results are shown in FIG. With a platinum-ruthenium catalyst (curve A) that does not carry a rhodium porphyrin complex, a clear hydrogen oxidation current was not observed unless a voltage of 0.4 V or higher was applied. In the case of rhodium tetrakis (4-methoxy) phenylporphyrin-platinum ruthenium-supported carbon catalyst, a hydrogen oxidation current was not observed unless a voltage of 0.4 V or higher was applied.
From this, even when the rhodium tetrakis (4-methoxy) phenylporphyrin complex was supported, the carbon monoxide poisoning resistance of the platinum ruthenium catalyst was hardly improved. It was found that the complex in which the meta position is substituted is stronger in improving the carbon monoxide poisoning resistance of the platinum ruthenium catalyst than that in which the para position is substituted with a methoxy group.

Claims (13)

Chemical formula (1):

[Wherein, eight R _{1 s} are the same or different and are each a hydrogen atom or a substituent having a molecular weight of 15 to 100 (provided that at least one is a substituent having a molecular weight of 15 to 100); 4 R ₂ and 8 R ₃ are the same or different and are each a hydrogen atom, a halogen, an amino group, an alkyl group having 1 to 5 carbon atoms, —COOM ³ (M ³ is a hydrogen atom, 1 carbon atom). 5 is an alkyl group or an alkali _{metal), - (CH 2) n} -COOM 4 (M 4 represents a hydrogen atom, an alkyl group or an alkali metal C1-5, n represents 1 to 5), or —SO ₃ M ⁵ (M ⁵ is a hydrogen atom or an alkali metal)]
A catalyst for electrochemical oxidation of carbon monoxide containing rhodium porphyrin represented by The catalyst for electrochemical oxidation of carbon monoxide according to any one of claims 1 to 4, wherein each of four R ₂ and eight R ₃ is a hydrogen atom. The substituent in R ₁ is —COOM ¹ (M ¹ is a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or an alkali metal) or —OM ² (M ² is a hydrogen atom, an alkyl having 1 to 2 carbon atoms). The catalyst for electrochemical oxidation of carbon monoxide according to claim 1 or 2, wherein the catalyst is a group represented by: The catalyst for electrochemical oxidation of carbon monoxide according to any one of claims 1 to ₃ , wherein the substituent is -COOH or -OCH3. The catalyst for electrochemical oxidation of carbon monoxide according to any one of claims 1 to 4, wherein the rhodium porphyrin represented by the chemical formula (1) is supported on a conductive carrier. The catalyst for electrochemical oxidation of carbon monoxide according to claim 5, wherein the conductive support is carbon black. The electrochemical of carbon monoxide according to any one of claims 1 to 6, wherein the rhodium porphyrin represented by the chemical formula (1) and particles of platinum or a platinum alloy are supported on a conductive carrier. Oxidation catalyst. The catalyst for electrochemical oxidation of carbon monoxide according to claim 7, wherein the platinum or platinum alloy particles are platinum ruthenium alloy particles. An anode for a polymer electrolyte fuel cell, comprising the catalyst for electrochemical oxidation of carbon monoxide according to any one of claims 1 to 6, and an anode catalyst material. A carbon monoxide sensor comprising the carbon monoxide electrochemical oxidation catalyst according to claim 1 as a catalyst component for carbon monoxide oxidation in a carbon monoxide detector. In the carbon monoxide oxidation removal apparatus in the anode gas for a polymer electrolyte fuel cell including an electrolytic solution, a working electrode, a counter electrode, and a power supply device, the carbon monoxide oxidation catalyst in the working electrode is used as a catalyst for oxidizing carbon monoxide. The carbon monoxide oxidation removal apparatus in anode gas containing the catalyst for the electrochemical oxidation of the carbon monoxide in any one. An anode electrode for a polymer electrolyte fuel cell using carbon monoxide as a fuel, comprising the catalyst for electrochemical oxidation of carbon monoxide according to any one of claims 1 to 8 as an anode catalyst material. A polymer electrolyte fuel cell using carbon monoxide as a fuel, comprising the anode electrode according to claim 12 as a constituent element.

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