JP6590405B2 - 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 platinum 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. Carbon monoxide is strongly adsorbed on platinum, and the catalytic function is greatly reduced.

  As a fuel electrode of such a low-temperature fuel cell, a fuel electrode catalyst using a combination of a transition metal or an alloy thereof and a specific organometallic complex has been reported (for example, Patent Document 1). However, few catalysts have been reported that are effective in actively oxidizing and removing carbon monoxide, and all the reported catalysts have a high reaction overvoltage.

  As a catalyst for oxidizing and removing such carbon monoxide and a catalyst used in the carbon monoxide removing apparatus, for example, rhodium porphyrin or a derivative thereof is known (for example, Patent Document 2). These rhodium porphyrins or derivatives thereof are catalysts having a low reaction overvoltage, but porphyrin ligands are expensive, and rhodium porphyrin complexes are easily eluted with respect to polar solvents. Since commonly used electrolytes are water-based, this elution is usually not a problem, but there is a possibility of elution into the electrolyte on a very long time scale. Moreover, since it melt | dissolves with respect to the electrolyte solution containing an organic solvent, it is inferior to long-term stability with respect to such electrolyte solution.

  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). However, this gas sensor has a high cost because a large amount of a noble metal catalyst such as platinum is used as an ionization electrode, and the detection voltage is inferior due to a large overvoltage when oxidizing carbon monoxide.

JP 2002-329500 A Japanese Patent Application Laid-Open No. 2006-261086 Japanese Patent Publication No. 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 be used in an anode electrode of a fuel cell, a carbon monoxide sensor, an electrochemical carbon monoxide removal device, and the like. It is an object to provide a novel catalyst which is suitable for an electrochemical oxidation reaction of carbon monoxide and excellent in long-term stability.

The present inventor has intensively studied to achieve the above-described object. As a result, the rhodium phthalocyanine complex has the reaction formula:
CO + H ₂ O → CO ₂ + 2H ⁺ + 2e ⁻
It has been found that it has catalytic ability for the electrochemical carbon monoxide oxidation reaction represented by In addition, the rhodium phthalocyanine complex was found to have a low reaction overvoltage, a high catalytic activity for removing carbon monoxide, and an excellent long-term stability because it hardly elutes into a polar solvent containing water. The present invention has been completed based on these findings. That is, the present invention includes the following configurations.

  Item 1. Catalyst for electrochemical oxidation of carbon monoxide containing rhodium phthalocyanine complex as an active ingredient.

  Item 2. The rhodium phthalocyanine complex has the general formula (1):

[Wherein, R ^{1 to} R ¹⁶ are the same or different and each represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryl group, or a substituted group. And an optionally substituted acyl group, an optionally substituted alkenyl group, or an amino group. X represents a halogen atom. A dotted line shows a coordination bond. ]
Item 2. The catalyst for electrochemical oxidation of carbon monoxide according to Item 1, which is a rhodium phthalocyanine complex represented by the formula:

Item 3. Item 3. The catalyst for electrochemical oxidation of carbon monoxide according to item 1 or 2, wherein in the general formula (1), R ^{1 to} R ¹⁶ are all hydrogen atoms.

  Item 4. Item 4. The catalyst for electrochemical oxidation of carbon monoxide according to any one of Items 1 to 3, wherein the rhodium phthalocyanine complex is supported on a conductive carrier.

  Item 5. Item 5. The catalyst for electrochemical oxidation of carbon monoxide according to Item 4, wherein the conductive support is carbon black.

  Item 6. Item 6. 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 5 and an anode catalyst material.

  Item 7. A solid polymer fuel cell using carbon monoxide as a fuel, comprising the anode electrode according to Item 6 as a constituent element.

  Item 8. Item 6. A carbon monoxide sensor comprising the catalyst for electrochemical oxidation of carbon monoxide according to any one of items 1 to 5 as a catalyst component for oxidation of carbon monoxide in a carbon monoxide detector.

  Item 9. Any one of Items 1 to 5 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 electrolytic solution, a working electrode, a counter electrode, and a power supply device An apparatus for removing carbon monoxide from an anode gas, comprising the catalyst for electrochemical oxidation of carbon monoxide according to claim 1.

  According to the catalyst for electrochemical oxidation of carbon monoxide of the present invention, since a rhodium phthalocyanine complex is used, carbon monoxide can be efficiently oxidized at a low overvoltage.

  Further, when the conductive support is carbon black, the rhodium phthalocyanine complex 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 expensive. It can be a catalyst for the electrochemical oxidation of active carbon monoxide.

  Furthermore, since rhodium phthalocyanine complex is hardly eluted with respect to a polar solvent containing water, it is excellent in long-term stability.

It is the schematic of the carbon monoxide oxidation removal apparatus for polymer electrolyte fuel cells. 2 is a linear sweep voltammogram of the rhodium phthalocyanine complex-supported carbon catalyst (Example 1) obtained in Example 1. FIG. A reference baseline is also shown. 2 is a potential-time curve when the rhodium phthalocyanine-supported carbon catalyst obtained in Example 1 is subjected to constant potential amperometry at 0.45 V, 0.55 V, or 0.65 V. FIG. 2 is a graph showing the results of an elution test of the rhodium phthalocyanine-carrying carbon catalyst obtained in Example 1 and the rhodium porphyrin-carrying carbon catalyst obtained in Comparative Example 1. FIG.

  The catalyst for electrochemical oxidation of carbon monoxide of the present invention contains a rhodium phthalocyanine complex as an active ingredient.

The rhodium phthalocyanine complex 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, it is possible to efficiently oxidize carbon monoxide with low overvoltage by electrochemically oxidizing carbon monoxide in the presence of the rhodium phthalocyanine complex. In addition, since the rhodium phthalocyanine complex hardly elutes with respect to a polar solvent containing water, it is excellent in long-term stability.

  Such rhodium phthalocyanine complexes have the general formula (1):

[Wherein, R ^{1 to} R ¹⁶ are the same or different and each represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryl group, or a substituted group. And an optionally substituted acyl group, an optionally substituted alkenyl group, or an amino group. X represents a halogen atom. A dotted line shows a coordination bond. ]
The complex represented by these is preferable.

In the general formula (1), examples of the halogen atom represented by R ^{1 to} R ¹⁶ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In the general formula (1), examples of the alkyl group represented by R ^{1 to} R ¹⁶ include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert -Lower alkyl groups such as butyl group, n-pentyl group and n-hexyl group (particularly linear or branched alkyl groups having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms). In addition, the alkyl group includes, for example, 1 to 6 substituents (particularly 1 to 3) such as the halogen atom, an alkoxy group described later, an aryl group described later, an acyl group described later, an alkenyl group described later, an amino group, and the like. ).

In the general formula (1), examples of the alkoxy group represented by R ^{1 to} R ¹⁶ include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, and lower alkoxy groups such as tert-butoxy group (particularly linear or branched alkoxy groups having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms). In addition, the alkoxy group includes, for example, 1 to 6 substituents (particularly 1 to 3) such as the halogen atom, the alkoxy group, an aryl group described later, an acyl group described later, an alkenyl group described later, and an amino group. Can also have.

In the general formula (1), examples of the aryl group represented by R ^{1 to} R ¹⁶ include a phenyl group, a naphthyl group, an anthranyl group, a phenanthryl group, a biphenyl group, and a pyridyl group. In addition, the aryl group includes, for example, 1 to 6 substituents such as the halogen atom, the alkyl group, the alkoxy group, the aryl group, an acyl group described below, an alkenyl group described below, and an amino group (particularly 1 to 3).

In the general formula (1), examples of the acyl group represented by R ^{1 to} R ¹⁶ include an acyl group having 2 to 20 carbon atoms such as an acetyl group and a propionyl group. In addition, this acyl group includes, for example, 1 to 6 substituents (particularly 1 to 3) such as the halogen atom, the alkyl group, the alkoxy group, the aryl group, the acyl group, an alkenyl group, and an amino group described below. Can also be included.

In the general formula (1), examples of the alkenyl group represented by R ^{1 to} R ¹⁶ include a vinyl group, allyl group, 2-butenyl group, 3-butenyl group, 1-methylallyl group, 2-pentenyl group, 2- C2-C20 linear or branched alkenyl groups, such as a hexenyl group, are mentioned. The alkenyl group includes, for example, 1 to 6 substituents (particularly 1 to 3) such as the halogen atom, the alkyl group, the alkoxy group, the aryl group, the acyl group, the alkenyl group, and the amino group. ).

In general formula (1), as R ^{1 to} R ¹⁶ , carbon atoms can be oxidized at a lower overvoltage, and from the viewpoint of better long-term stability, all are preferably hydrogen atoms.

  In the general formula (1), examples of the halogen atom represented by X include a chlorine atom, a bromine atom, and an iodine atom.

  In a polymer electrolyte fuel cell, a carbon monoxide sensor, a carbon monoxide removing device, and the like, when carbon monoxide is electrochemically removed by oxidation, a reaction is usually performed in an electrolytic solution. For this reason, in order to improve the long-term stability of the performance of the polymer electrolyte fuel cell, the carbon monoxide sensor, the carbon monoxide removal device, etc., it is preferable that the catalyst as the active ingredient does not elute with respect to the electrolyte solution. . Specifically, it is preferable that the catalyst does not dissolve in a polar solvent containing protons. In the present invention, the rhodium phthalocyanine complex hardly elutes with respect to a mixed solvent of water and a polar solvent (alcohol such as methanol) before, during and after the electrochemical oxidation of carbon monoxide. . Thus, since the solubility with respect to a solvent is very low, the long-term stability of performance, such as a polymer electrolyte fuel cell, a carbon monoxide sensor, a carbon monoxide removal apparatus, can be improved more.

  Examples of rhodium phthalocyanine complexes that satisfy the above conditions include:

Etc.

  The rhodium phthalocyanine complex represented by the general formula (1) can be obtained by reacting a rhodium salt with o-cyanobenzamide. Specifically, for example, it can be synthesized according to the method described in I. M. Keen, B. W. Malerbi, J. Inorg. Nucl. Chem. 27 (1965) 1311. That is, the target rhodium phthalocyanine complex can be obtained by heating the rhodium salt and o-cyanobenzamide and then performing Soxhlet extraction.

The rhodium salt is not particularly limited. From the viewpoint of yield, rhodium tetracarbonyl dichloride (Rh ₂ Cl ₂ (CO) ₄ ), rhodium chloride (RhCl ₃ ), hexarhodium hexadecacarbonyl (Rh ₆ (CO) ₁₆ ) and the like are preferable, and rhodium chloride (RhCl ₃ ) is more preferable.

  The amount of rhodium salt, complex, etc. used is not particularly limited, and from the viewpoint of yield and the like, for example, 0.01 to 3.0 moles of rhodium atoms are preferable with respect to 1 mole of o-cyanobenzamide, and 0.1 to 0.3 Mole is more preferred.

  From the viewpoint of yield and the like, the heating temperature is preferably, for example, 200 to 300 ° C, and more preferably 250 to 300 ° C.

  The heating time may be a time during which the reaction proceeds sufficiently, and is not particularly limited. For example, 1 hour to 6 hours is preferable, and 3 hours to 5 hours is more preferable.

  The rhodium phthalocyanine complex represented by the general formula (1) has the general formula (2):

[Wherein, R ^{1 to} R ¹⁶ are the same as defined above. ]
It can also be obtained by forming a chelate with a phthalocyanine compound represented by

  That is, the intended rhodium phthalocyanine complex can be obtained by reacting the phthalocyanine compound represented by the general formula (2) with a rhodium salt, complex or the like in an organic solvent. Specifically, the phthalocyanine compound represented by the general formula (2) and a rhodium salt, complex, or the like are dissolved or dispersed in an organic solvent, and then subjected to a heat treatment, and a purification treatment is performed as necessary. Thus, the intended rhodium phthalocyanine complex can be obtained.

The rhodium salt or complex is not particularly limited. From the viewpoint of yield, rhodium tetracarbonyl dichloride (Rh ₂ Cl ₂ (CO) ₄ ), rhodium chloride (RhCl ₃ ), hexarhodium hexadecacarbonyl (Rh ₆ ( CO) ₁₆ ) and the like are preferable, and rhodium tetracarbonyl dichloride (Rh ₂ Cl ₂ (CO) ₄ ) is more preferable.

  The amount of rhodium salt, complex, etc. used is not particularly limited, and from the viewpoint of yield and the like, for example, 1.0 to 2.0 mol is preferable in terms of the number of rhodium atoms with respect to 1 mol of the phthalocyanine compound, and 1.0 to 1.5 mol is preferable. More preferred.

  The organic solvent to be used is not particularly limited as long as both the phthalocyanine compound and the rhodium salt, complex and the like are dissolved, but toluene, xylene and the like are preferable from the viewpoint of yield and the like. Of these, toluene is particularly desirable.

  Although there will be no restriction | limiting in particular if heating temperature is lower than the boiling point of an organic solvent, From viewpoints, such as a yield, 30-150 degreeC is preferable, for example, and 80-120 degreeC is more preferable.

  The heating time may be a time during which the reaction proceeds sufficiently, and is not particularly limited. For example, 10 minutes to 24 hours is preferable, and 30 minutes to 5 hours is more preferable.

  The rhodium phthalocyanine complex represented by the general formula (1) of the present invention can be favorably dispersed by supporting the rhodium phthalocyanine complex on a conductive carrier, and the complex can be effectively utilized. In addition, it is considered that the electron transfer between the complex and the electrode can be rapidly performed by supporting the conductive carrier. Therefore, the overvoltage of the electrochemical oxidation reaction of carbon monoxide can be made smaller, and the catalytic activity of the electrochemical oxidation reaction of carbon monoxide can be made higher. This seems to be because the rhodium phthalocyanine complex is strongly adsorbed and supported on the carrier by the interaction with the conductive carrier.

  As the conductive carrier, for example, various carriers conventionally used for a catalyst carrier for a polymer electrolyte fuel cell, a carbon monoxide sensor, an electrochemical carbon monoxide removing device and the like can be used. Specific examples of such a conductive carrier include carbonaceous materials such as carbon black (Ketjen black, furnace black, acetylene black, etc.), activated carbon, and graphite. Among these, carbon black (especially ketjen black) has a large interaction with the rhodium phthalocyanine complex represented by the above general formula (1), and has a strong function of dispersing and supporting the rhodium phthalocyanine complex. Since it is excellent and has a large specific surface area, it is a particularly preferable substance as a conductive carrier.

There are no particular limitations on the shape or the like of the conductive carrier, and for example, the average primary particle size is preferably 10 to 1000 nm, more preferably 10 to 50 nm. When carbon black is used as the conductive carrier, for example, the specific surface area by the BET method is preferably 50 to 1600 m ² / g, more preferably 100 to 1200 m ² / g. As specific examples of such carbon black, for example, ketjen black, Vulcan XC-72R (manufactured by Cabot) and the like can be used.

  As a method for supporting the rhodium phthalocyanine complex on the conductive carrier, for example, a known method such as a dissolution drying method or a gas phase method can be employed.

  For example, in the dissolution drying method, a rhodium phthalocyanine complex is dissolved in an organic solvent, a conductive carrier is added to this solution, and the mixture is stirred as necessary to adsorb the rhodium phthalocyanine complex to the conductive carrier. The organic solvent may be dried as necessary. In addition, even when a large amount of rhodium phthalocyanine complex is contained in the organic solvent, the rhodium phthalocyanine complex that is not adsorbed on the conductive carrier is filtered by adsorbing the rhodium phthalocyanine complex on the conductive carrier until equilibrium is reached. Can be removed, leaving only the rhodium phthalocyanine complex interacting with the conductive support on the surface of the conductive support.

  In this method, any organic solvent can be used without particular limitation as long as it can dissolve the rhodium phthalocyanine complex. For example, toluene, dichloromethane, chloroform 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, the rhodium phthalocyanine complex, 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 catalyst having only high rhodium phthalocyanine complex and excellent in long-term stability.

  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 heating vapor deposition method can be adopted.

  The amount of the rhodium phthalocyanine complex supported on the conductive support is not particularly limited. For example, it is preferable to support 0.001 to 0.8 g, particularly 0.003 to 0.6 g of the rhodium phthalocyanine complex with respect to 1 g of the conductive support. .

  The method for supporting the rhodium phthalocyanine complex on the conductive carrier is not limited to the above method. For example, after the phthalocyanine compound represented by the general formula (2) is supported on the conductive carrier, A chelate can also be formed by the phthalocyanine compound and a rhodium atom. As a method of supporting the phthalocyanine compound on the conductive carrier, the above-described solution drying method, gas phase method, or the like can be employed. Specifically, the phthalocyanine compound can be supported on the conductive carrier according to the method described above except that a phthalocyanine compound is used instead of the rhodium phthalocyanine complex. Thereafter, a chelate can be formed by the phthalocyanine compound supported on the conductive carrier and the rhodium atom in accordance with the above-described method.

  The catalyst for electrochemical oxidation of carbon monoxide of the present invention comprising a rhodium phthalocyanine complex represented by the general formula (1) as an active ingredient is capable of electrochemically oxidizing oxygen monoxide with high selectivity. Since it is difficult to be poisoned by carbon oxide and it is difficult to elute into the electrolyte solution and has excellent long-term stability, it can be used for various applications requiring such characteristics.

  For example, in a polymer electrolyte fuel cell using hydrogen gas containing carbon monoxide obtained by reforming natural gas, methanol, gasoline, etc. as a fuel, carbon monoxide is selected by using it in combination with an anode catalyst material. Thus, it is possible to obtain an anode electrode that is excellent in carbon monoxide poisoning resistance, is not easily eluted in the electrolyte solution, and has excellent long-term stability.

  As the anode catalyst material in the anode electrode in this case, for example, a known catalyst such as platinum can be used. The ratio of the catalyst for electrochemical oxidation of carbon monoxide and the anode catalyst material of the present invention is not particularly limited. For example, the ratio is appropriately determined from the range of 1 to 500 parts by mass with respect to the former 100 parts by mass. Can do. The catalyst for electrochemical oxidation of carbon monoxide and the anode catalyst material can be used by being supported on separate conductive carriers, or can be supported on the same conductive carrier. In the case of supporting the same conductive carrier, for example, a method of supporting a rhodium phthalocyanine complex by the above-mentioned various methods on a conductive carrier supporting a catalyst material such as platinum, and a rhodium phthalocyanine complex. For example, a method of supporting a catalyst material such as platinum on the conductive carrier thus applied can be applied.

  The structure of the anode electrode and the structure of the polymer electrolyte fuel cell using this anode electrode are not particularly limited, and can be the same as that of a known fuel cell.

  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, similar to the sensor in the gas detection device described in Patent Document 3, an ionization electrode for oxidizing carbon monoxide by an electrode reaction to generate protons, a proton conductor, and protons from the proton conductors. A proton conductor gas sensor having a reference electrode for receiving and reacting with oxygen in the atmosphere to discharge as water can be obtained. In the gas sensor having such a structure, by using the catalyst of the present invention as the catalyst for oxidizing carbon monoxide in the ionization electrode, it is possible to detect carbon monoxide with higher sensitivity and in the long term.

  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 this case, before supplying the anode gas to the fuel cell, the carbon monoxide contained in the anode gas is oxidized and removed as a catalyst for carbon monoxide oxidation in a carbon monoxide oxidation removal apparatus for electrolysis. Oxygen can be oxidized electrochemically with good selectivity, and it is difficult to be poisoned by carbon monoxide, and it is difficult to elute into the electrolyte solution, so that a carbon monoxide oxidation removal device with excellent long-term stability can be obtained. . Such a carbon monoxide oxidation removal apparatus 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 0.1 to 1.0 M sulfuric acid solution or the like 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 is used as a base material, and the catalyst of the present invention can 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. Furthermore, in order to set the working electrode at a predetermined potential, a reference electrode can usually be 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 without oxidizing the fuel gas at a low overvoltage and stably for a long period of time. Anode gas can be purified. 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.

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

Production Example 1: Synthesis of rhodium phthalocyanine

  Rhodium phthalocyanine was synthesized according to the reference (J. M. Keen, B. W. Malerbi, J. Inorg. Nucl. Chem. 27 (1965) 1311.). Its synthesis was confirmed by elemental analysis and mass spectrometry.

Example 1: Preparation of rhodium phthalocyanine-supported carbon catalyst The rhodium phthalocyanine obtained in Production Example 1 was dissolved in dimethylformamide to 0.86 mM, and 18.6 mL of dimethylformamide was added to 1.4 mL of this solution. 30 mg of (specific surface area 250 m ² / g, trade name: Vulcan XC 72R, manufactured by Cabot) was added. After sealing the container, dispersibility was improved by placing it in an ultrasonic cleaner for 1 minute. The rhodium phthalocyanine solution in which the carbon black was suspended was stirred with a magnetic stirrer for 30 minutes, and then dimethylformamide was removed with a rotary evaporator. Thereafter, the remaining carbon black was recovered to obtain a rhodium phthalocyanine-supported carbon catalyst.

Evaluation of electrochemical carbon monoxide oxidation activity of rhodium phthalocyanine-supported carbon catalyst After suspending 5 mg of rhodium phthalocyanine-supported carbon catalyst obtained in the above method in 0.5 mL of a mixed solvent (water: ethanol = 1: 1) 5 μL of 5% Nafion solution (Aldrich) was added. The suspension was placed in an ultrasonic cleaner for 5 minutes to be well dispersed, and then 2 μL was placed on a rotating disk electrode (surface area 0.0707 cm ² ) and dried to obtain a rhodium phthalocyanine-supported carbon-modified electrode.

The carbon monoxide oxidation activity of the catalyst was evaluated using a potentiostat (ALS model 711B) manufactured by BAS. The rotational speed was controlled using a rotational speed control device (BAS RDE-1) manufactured by BAS Co., Ltd. A rhodium phthalocyanine-supported carbon modified electrode was used as a working electrode, a platinum electrode as a counter electrode, and a silver-silver chloride electrode (Ag | AgCl | KCl (sat.)) As a reference electrode. As the electrolyte, 0.1 MH ₂ SO ₄ was used. The measurement was performed at 25 ° C.

  First, argon gas was blown into the electrolytic cell for 10 minutes, and then a cyclic voltammogram was measured. This voltammogram is shown as “baseline” in FIG. Next, after carbon monoxide gas was blown into the electrolytic cell for 7 minutes, a linear sweep voltammogram (LSV) was measured while rotating the rhodium phthalocyanine-supported carbon-modified electrode at 6400 rpm. This LSV is shown as “Example 1” in FIG. An increase in oxidation current is observed compared to the baseline, indicating that CO is electrochemically oxidized by the catalytic action of the rhodium phthalocyanine complex.

Determination of carbon monoxide with rhodium phthalocyanine-supported carbon catalyst Real-time determination of carbon monoxide was performed by the potentiostatic amperometry method. The rhodium phthalocyanine-supported carbon-modified electrode obtained by the above method was used as a working electrode, a platinum electrode as a counter electrode, and a silver-silver chloride electrode (Ag | AgCl | KCl (sat.)) As a reference electrode. As the electrolyte, 0.1 MH ₂ SO ₄ was used. The measurement was performed at 25 ° C.

  First, argon gas was blown into the electrolytic cell for 10 minutes, and then cyclic voltammograms were measured in the range of −0.3 V to 0.6 V. Thereafter, constant potential amperometry was performed under the condition that the electrode was rotated at 3600 rpm while maintaining a constant potential (0.45 V). FIG. 3 shows a potential-time curve after holding the potential for 100 seconds until the transient current is stabilized. In FIG. 3, the gas was switched from argon to hydrogen gas after 200 seconds. A slight hydrogen oxidation current was observed. When the gas was switched from hydrogen gas to hydrogen gas containing 2% CO after 800 seconds, the current further increased. From this result, it was found that CO in hydrogen gas can be selectively quantified.

  Next, an experiment in which the amperometric potential was changed to 0.55 V or 0.65 V was performed in the same manner. The result is shown in FIG. From the comparison of the current value when the gas is hydrogen and the current value when the gas is hydrogen containing CO, it was found that 0.55 V, which is excellent in sensitivity of CO and selectivity for hydrogen, is suitable at the tested potential.

Comparative Example 1: Preparation of rhodium porphine-supported carbon catalyst Rhodium porphine was dissolved in dichloromethane to a concentration of 0.31 mM, and then 17 mL of dichloromethane was added to 2.9 mL of this solution, followed by carbon black (specific surface area 250 m ² / g (Trade name: Vulcan XC 72R, manufactured by Cabot) was added in an amount of 30 mg. After sealing the container, dispersibility was improved by placing it in an ultrasonic cleaner for 1 minute. The rhodium porphine solution in which the carbon black was suspended was stirred with a magnetic stirrer for 30 minutes, and then dichloromethane was removed with a rotary evaporator. Thereafter, the remaining carbon black was recovered to obtain a rhodium porphine-supported carbon catalyst.

Whether or not the active ingredient (rhodium phthalocyanine) from the rhodium phthalocyanine-carrying carbon catalyst or rhodium porphyrin-carrying carbon catalyst is eluted in the electrolytic solution was verified by the following method. The rhodium phthalocyanine-carrying carbon of Example 1 (active ingredient loading mol 0.04 mmol / g, 5 mg) was suspended in a mixed solvent of water and methanol (volume ratio 1: 1, 10 mL). Treated with an ultrasonic disperser for 1 minute. The suspension was allowed to stand for 20 minutes and then filtered, and the ultraviolet-visible spectrum of the filtrate was measured. The results are shown as Example 1 in FIG. No absorption derived from rhodium phthalocyanine was observed in the filtrate, and rhodium phthalocyanine was not eluted into the polar solvent under these conditions.

  On the other hand, as a comparative example, the elution of the active ingredient (rhodium porphine) from the rhodium porphine-carrying carbon of Comparative Example 1 was similarly examined. In the same manner, rhodium porphine-supported carbon (active ingredient supported amount: 0.03 mmol / g, 5 mg) was suspended in a mixed solvent of water and methanol (volume ratio 1: 1, 10 mL) and an elution test was performed. The ultraviolet-visible spectrum of the filtrate is shown as Comparative Example 1 in FIG. In this case, absorption derived from rhodium porphine was clearly observed. The amount of rhodium porphine eluted from this absorption spectrum was 22.3 nmol. Since the amount of rhodium porphine in 5 mg of the catalyst was 0.15 mmol, it was revealed that 15% of the supported amount was eluted. Although rhodium porphine has a smaller amount of active ingredient supported than rhodium phthalocyanine, such elution was observed.

  From the above results, the rhodium phthalocyanine-supported carbon catalyst used in the present invention can remarkably reduce the solubility in polar solvents containing protons compared to the conventionally used rhodium porphyrin-supported carbon catalyst. It can be understood that it is difficult to elute in the electrolyte solution before, during and after the carbon oxidation reaction, and is excellent in long-term stability.

Claims (8)

A catalyst for electrochemical oxidation of carbon monoxide containing a rhodium phthalocyanine complex as an active ingredient ,
The rhodium phthalocyanine complex has the general formula (1):

[Wherein, R ^{1 to} R ¹⁶ are the same or different and each represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryl group, or a substituted group. And an optionally substituted acyl group, an optionally substituted alkenyl group, or an amino group. X represents a halogen atom. A dotted line shows a coordination bond. ]
A catalyst for electrochemical oxidation of carbon monoxide, which is a rhodium phthalocyanine complex represented by the formula: The catalyst for electrochemical oxidation of carbon monoxide according to claim 1, wherein in the general formula (1), R ^{1 to} R ¹⁶ are all hydrogen atoms. The catalyst for electrochemical oxidation of carbon monoxide according to claim 1 or 2 , wherein the rhodium phthalocyanine complex is supported on a conductive carrier. The catalyst for electrochemical oxidation of carbon monoxide according to claim 3 , wherein the conductive support is carbon black. 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 4 , and an anode catalyst material. A polymer electrolyte fuel cell using carbon monoxide as a fuel, comprising the anode electrode according to claim 5 as a constituent element. A carbon monoxide sensor comprising the carbon monoxide electrochemical oxidation catalyst according to any one of claims 1 to 4 as a catalyst component for carbon monoxide oxidation in a carbon monoxide detector. Electrolyte, a working electrode, including a counter electrode and a power supply, the carbon monoxide oxidizing apparatus for removing solid polymer fuel anode gas for a battery, as a catalyst for the oxidation of carbon monoxide at the working electrode, as claimed in claim 1-4 The carbon monoxide oxidation removal apparatus in anode gas containing the catalyst for electrochemical oxidation of the carbon monoxide as described in any one of Claims.

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