JP2009125693A - Catalyst body and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst body for a fuel cell which can greatly reduce a using amount of a noble metal material which is expensive and limited in terms of natural resources, has a high conductivity and a high catalytic activity, also hardly undergoes deterioration with time due to diffusion of a catalyst particle, etc. and is high in stability, and to provide its production method. <P>SOLUTION: The catalyst body has a carbon material containing boron as a base body, wherein a nitrogen atom is doped on the surface of the B containing carbon material and further a catalytic active metal particle is preferably supported on the surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a catalyst body for a polymer electrolyte fuel cell and a method for producing the same.

  Since noble metal catalysts such as platinum have excellent catalytic activity, they are used in various fields. For example, in fuel cells, electrochemical processes, and the like, those in which a noble metal that is a catalytically active component is dispersed and supported on a carrier such as carbon are widely used.

  In recent years, awareness of the suppression of the discharge of environmentally hazardous substances and the efficient use of energy has increased, and the development of using fuel cells as automobiles and household power sources has been actively promoted. Among them, a polymer electrolyte fuel cell, which is abbreviated as PEFC (Polymer Electrolyte Fuel Cell), is attracting attention because it can operate at a relatively low temperature. In this PEFC, a platinum catalyst is mainly studied as an electrode catalyst. However, the present platinum-supported catalyst body is insufficient in terms of durability in terms of application to an automobile in which a severe use environment is assumed. Further, platinum is expensive, and it is said that there is anxiety in terms of resource supply, and development of a more efficient method of using platinum and development of a catalyst material that is inexpensive and does not cause anxiety of supply are required.

As a method of efficiently using expensive platinum, for example, Patent Document 1 discloses that platinum particles having a small particle diameter are dispersed and supported on the surface of a carbon support to increase the reaction surface area and increase the catalytic activity per unit catalyst weight. Techniques have been disclosed for enhancing and thereby increasing the utilization efficiency of platinum.
In the method of this document, while platinum can be highly dispersed, the supported platinum is easily removed from the carbon support, and the problem is that platinum is supported more stably.

In addition, platinum-supported catalysts are known to undergo repeated dissolution and reprecipitation of platinum while the cell is in operation. Degradation suppression methods are actively studied. As a method for increasing the dissolution stability of a platinum catalyst, for example, Patent Document 2 discloses a method for increasing resistance to dissolution and precipitation by covering platinum particles with a conductive polymer.
According to this document, since platinum particles are coated with a conductive polymer, there is a problem that high activity cannot be expected due to obstacles in mass transfer of fuel and the like.

  Patent Document 3 discloses a fuel cell electrode based on carbon alloy fine particles in which a carbon material is doped with nitrogen atoms and / or boron atoms, and a method for producing the same. In this method, since nitrogen and boron are simultaneously doped, it is difficult to obtain a catalyst body having high conductivity, and as a result, it is difficult to obtain high catalytic activity. Further, the method described in this document has a limitation on the heating temperature for carbonization, and high conductivity cannot be expected.

Patent Document 4 and Non-Patent Document 1 have a hollow carbon shell-like nanocarbon structure with a diameter of several tens of nanometers obtained by adding a transition metal complex to a polymer that is a carbon raw material and carbonizing it. A fuel cell catalyst in which nitrogen and boron are contained in the edge surface of the carbon network surface of the carbon particles and a method for producing the same are disclosed.
It is described that the carbon material having such a special structure itself has oxygen reduction activity, so that it can be non-platinized and the amount of platinum used can be significantly reduced. However, it is estimated from Non-Patent Document 2 that the conductivity of the carbon material is reduced by simultaneously doping nitrogen and boron, and it is considered that further improvement in conductivity is necessary to obtain a practical catalyst.

  Non-Patent Document 3 discloses a catalyst body in which a carbon material is doped with nitrogen and metal ions are coordinated on its surface. However, when nitrogen is doped only, nitrogen components are removed due to environmental changes such as heating. There is a problem in the durability of the catalyst because it is easily separated. On the other hand, when only boron is doped, the boron component exposed on the surface is easily oxidized, and easily flows out by contact with water or the like, and it is difficult to form active sites.

  As described above, a catalyst body having both high catalytic activity, high conductivity, and high durability has not been found. As a method for enhancing the catalytic activity, a method is proposed in which the surface of the carbon support is modified with a functional group to form a structure in which platinum is easily dispersed when platinum or the like is deposited. However, in order to obtain high activity, not only a catalyst such as platinum is highly dispersed, but also high conductivity must be maintained.

  Further, while a method for increasing the catalytic activity is proposed, deterioration of the catalytic activity with time is also a serious problem. In a power generation test of a fuel cell, a phenomenon in which catalyst particles are enlarged while noble metal catalyst particles such as platinum are temporarily dissolved and re-deposited is repeated, and the catalyst performance gradually decreases. Further, it has been reported that the diffusion of the platinum catalyst into the electrolyte membrane due to this phenomenon, and how to form a stable catalyst has become a major issue. Thus, in order to spread the fuel cell technology, establishment of a method that achieves both high catalytic activity and high stability is strongly demanded.

Japanese Patent No. 2642888 JP 2007-175558 A JP 2004-362802 A JP 2007-207662 A Ozaki, “Carbon-based non-platinum cathode catalyst”, Industrial Materials, Nikkan Kogyo Shimbun, October 2006, Vol. 54, No. 10, p. 42-47 Masayuki Kawaguchi, “Preparation of Carbon Materials Containing Boron and Nitrogen, Nanostructures and Physical Properties”, Carbon, 2007, Vol. 227, No., p. 107-114 Frederic Jouen et al., "Oxygen Reduction Catalysts for Electricity Fuel Cells from the polarity of Iron Accompanied on Various Corp.". Phys. Chem. B, USA, 2003, vol. 107, no. 6, p. 1376-1386

  The present invention has been made in view of such a situation, and can reduce the amount of expensive and resource-limited noble metal material used as much as possible, obtain high catalytic activity, and diffuse catalyst particles. It is an object of the present invention to provide a highly stable catalyst body that is less likely to deteriorate with time.

  The present invention pays attention to what function the doping of hetero elements such as boron and nitrogen brings to the carbon material, and realizes high conductivity by introducing only boron into the base material portion that requires conductivity, By introducing nitrogen atoms so as to have many active sites in the surface layer, a catalyst body having high activity is formed, and furthermore, it is found that such a catalyst body has high durability and has high activity. A catalyst body with high durability was completed. Furthermore, a catalyst body having higher activity and higher durability has been constructed by supporting a catalytically active metal, metal complex or metal ion on the surface of the catalyst body.

  Therefore, the present invention is as follows.

The first invention is a catalyst body containing carbon, boron and nitrogen,
The base material is a carbon material containing boron,
The catalyst body is characterized in that the surface of the boron-containing carbon material is doped with nitrogen atoms.

  A second invention is the catalyst body according to the first invention, further comprising a catalyst metal supported thereon.

  A third invention is the catalyst body according to the first or second invention, wherein the boron-containing carbon material has a measured value of powder resistance of 1.0 Ω · cm or less.

  A fourth aspect of the present invention is the catalyst body according to any one of the first to third aspects, wherein the doping amount of the nitrogen atom is 0.5 to 30% by weight as measured by X-ray photoelectron spectroscopy. It is.

  A fifth invention is characterized in that the catalyst metal is at least one metal selected from the group consisting of platinum, gold, rhodium, ruthenium, cobalt, nickel, tin, iron, copper, palladium, and silver. The catalyst body according to any one of the second to fourth inventions.

  A sixth invention is an electrode for a fuel cell comprising the catalyst body according to any one of the first to fifth inventions.

  7th invention is a fuel cell comprised using the electrode as described in 6th invention.

The eighth invention is a step of pyrolyzing a hydrocarbon and a boron-containing compound at a temperature of 500 to 2000 ° C. in an inert gas atmosphere to prepare a boron-containing carbon powder,
Next, the boron-containing carbon powder and ammonia gas, oxygen, nitrogen, water vapor and / or nitrogen monoxide are allowed to act at 500 to 1000 ° C., and nitrogen atoms are doped on the surface of the boron-containing carbon powder. Obtaining a powder;
Is a method for producing a catalyst body characterized in that

The ninth invention comprises a step of thermally decomposing a hydrocarbon and a boron-containing compound at a temperature of 500 to 2000 ° C. in an inert gas atmosphere to prepare a boron-containing carbon powder,
Next, after coating the boron-containing carbon powder with a nitrogen-containing polymer, a step of obtaining a nitrogen-doped boron-containing carbon powder by firing at a temperature of 500 ° C. to 1300 ° C. under an inert gas,
Is a method for producing a catalyst body characterized in that

The tenth invention further includes a step of adding the catalyst-containing metal compound solution after dispersing the nitrogen-doped boron-containing carbon powder in the liquid, and adsorbing the catalyst metal ions on the surface of the nitrogen-doped boron-containing carbon powder,
A step of chemically reducing the catalytic metal ion and supporting the catalytic metal on the surface of the nitrogen-doped boron-containing carbon powder,
The method for producing a catalyst body according to the eighth or ninth invention, characterized in that

  Since the catalyst body of the present invention has high catalytic activity, excellent durability, and can reduce the amount of expensive noble metal such as platinum used, a catalyst body having low cost and excellent reliability can be obtained.

Hereinafter, the best mode for carrying out the present invention will be described.
A feature of the catalyst body of the present invention is that it has high conductivity by using a boron-containing carbon substrate obtained by a heating reaction (including thermal decomposition) in a gas phase and doping the surface with nitrogen in an atomic state. The boron-containing carbon substrate has a structure in which nitrogen atoms having high stability are contained.

The reason why only the boron is contained in the carbon substrate and nitrogen is not introduced is known to be that the carbon material containing boron is improved in conductivity, and if it contains boron, it is heated to a high temperature. This is because it has been experimentally found that the boron component is not easily desorbed.
On the other hand, in the case of containing only nitrogen, there is a drawback that the nitrogen component is easily desorbed when heated to a high temperature. Further, when nitrogen and boron were contained at the same time, semiconductor properties were exhibited, and the conductivity of the carbon substrate was lowered, so that high catalytic activity could not be obtained.

The carbon substrate used in the present invention will be described below.
A carbon substrate containing only boron is 1) a method of obtaining a target product by thermally diffusing into a carbon structure by mixing a boron source and a carbon source and heating to a temperature of 2000 ° C. or higher, and 2) containing boron 3) A method of obtaining a target product by heating and carbonizing at a temperature of 600 ° C. or higher in an inert atmosphere after forming a polymer to be polymerized, and 3) Pyrolysis while heating the raw material gas at a temperature of 600 ° C. or higher And / or by reaction.

  Here, since the method 1) requires a high heating temperature, special manufacturing equipment is required, and it cannot be said that it is an efficient method when considering industrial production. The method 2) is a method in which a raw material to be a polymer is first polymerized to obtain a precursor, followed by heat carbonization treatment in an inert atmosphere, and a complicated synthesis process is required. The method 3) can be said to be an ideal production method because it can be obtained by a simple method by thermal decomposition of the raw material gas and / or high temperature reaction.

  3) The method of synthesizing the boron-containing carbon by the thermal decomposition method is described by Masayuki Kawaguchi, “Preparation of carbon materials containing boron and nitrogen, nanostructure and physical properties”, Carbon, 2007, Vol. 227, No., p. 107-114. That is, it can be obtained by a method in which a boron source is present at the time of hydrocarbon pyrolysis reaction and / or combustion reaction. Examples of hydrocarbons include gaseous hydrocarbons such as methane, ethane, propane, butane, acetylene, natural gas, petroleum hydrocarbons that are liquid hydrocarbons, and paraffins that are solid hydrocarbons. it can. Examples of the boron source include boron chloride, boric acid, and organic boron. Preferably, the hydrocarbon includes acetylene, and the boron source includes an organic boron compound and boron chloride.

As a method for synthesizing boron-containing carbon used in the present invention, it is preferable to introduce a gaseous hydrocarbon and a heated and vaporized boron source into a reaction tube heated to a predetermined temperature in advance by an inert gas stream, and perform a pyrolysis reaction. By doing. The thermal decomposition reaction temperature is preferably 500 to 2000 ° C.
The boron source content relative to the hydrocarbon is preferably 0.3 to 10.0% by weight after calcination.

  In the boron-containing carbon substrate thus obtained, in the present invention, the boron-containing carbon powder has a powder resistance measurement value of 1.0 Ω · cm or less, preferably 0.001 to 1.0 Ω · cm. Use.

Next, a method for doping nitrogen on the surface of the carbon substrate will be described.
The method for doping nitrogen on the surface of the boron-containing carbon substrate obtained above is as follows: 4) A method of obtaining the target product by heat treatment in an inert atmosphere after coating the boron-containing carbon with a polymer containing nitrogen. There is a method of doping the surface with nitrogen by reacting with nitrogen, oxygen, ammonia, water vapor and / or nitrogen monoxide under heating in the gas phase.

  As the method of 4), a method of carbonizing in an inert atmosphere after adsorbing and / or polymerizing a nitrogen-containing resin on the surface of the boron-containing carbon substrate, a resin containing nitrogen on the surface of the boron-containing carbon substrate, and / or Or the method of carbonizing in an inert atmosphere after making a monomer adhere | attach with the other non-nitrogen containing resin component used as a binder, etc. are mentioned.

  Here, the inert atmosphere is an inert gas atmosphere such as nitrogen, argon, or helium, and is an atmosphere that prevents desorption of the carbon component and the nitrogen component. The carbonization treatment is performed by a heat treatment in a temperature range of 500 ° C. to 1300 ° C., more preferably in a temperature range of 600 ° C. to 1000 ° C. in an inert gas atmosphere. Here, carbonization is difficult to proceed efficiently at temperatures below 500 ° C., and as a result, high conductivity may not be obtained, and the catalytic activity may be lowered. At temperatures above 1300 ° C., stabilization is achieved by the presence of boron. This is because it is considered that even nitrogen that is present is desorbed. Further, when heating at a temperature of 600 ° C. or higher, carbonization tends to proceed, and heating at 1000 ° C. or lower is more advantageous in terms of energy and at the same time is less susceptible to heating method limitations.

  The nitrogen-containing resin is not particularly limited as long as it contains nitrogen, and examples thereof include melamine resin, aniline resin, pyrrole resin, benzoxazine resin, bismaleimide resin, and vinylpyrrolidone resin. As the nitrogen-containing monomer, melamine derivatives, urea, lignin, aniline derivatives, pyrrole derivatives, etc. may be used alone or in combination of two or more. Examples of the non-nitrogen-containing resin include phenol resin, polyvinyl alcohol, butyral resin, acrylic resin, celluloses, vinyl chloride resin, furan resin, butadiene rubber, and epoxy resin, and a curing agent may be used in combination. For example, in the case of a phenol-based resin, nitrogen-containing isocyanate, hexamethylenetetramine, or an amine-based curing accelerator may be used. When an epoxy resin is used, imidazole, acid anhydride, or the like may be added separately. When using a urethane-based resin, a tertiary amine, water, or the like may be added separately.

  As a method of 5), the boron-containing carbon substrate is heated at 500 ° C. to 1000 ° C. while flowing a gas such as nitrogen, oxygen, ammonia, water vapor and / or nitrogen monoxide in the gas phase, In this method, nitrogen is contained in the surface of the carbon substrate. Non-Patent Documents 1 and 3 disclose a method of doping nitrogen by heating a target carbon material at 550 ° C. to 800 ° C. under a flow of ammonia gas and oxygen as a method of introducing nitrogen into the surface of the carbon material. ing.

  The present invention is characterized by applying the known method and doping nitrogen at a heating temperature of 500 ° C. to 1000 ° C. using ammonia gas, oxygen, nitrogen, water vapor and / or nitrogen monoxide. These gases may flow continuously, intermittently, or alternately. The reason why the reaction temperature was set to 500 ° C. or higher was that doping could be performed from this temperature in the mixed gas, and the reason why the reaction temperature was set to 1000 ° C. or lower was that nitrogen could be doped by a method of alternately flowing the gas.

  The catalyst body thus obtained may be in the form of particles or fibers. In the case of particle diameter or fiber, those having a cross-sectional diameter of 10 nm to 100 μm can be suitably used. When a layer containing nitrogen is formed on the carbon substrate, the thickness of the layer needs to maintain high conductivity. It is better that the thickness is thinner, and most ideally, the surface is doped with an atomic level thickness. However, in actuality, considering the irregularities on the particle surface and coating via a polymer, the thickness is preferably 50 nm or less, and more ideally 20 nm or less.

The amount of boron contained in the catalyst body can be determined by a method in which boron oxide remaining by combustion is eluted into an aqueous hydrochloric acid solution and analyzed by ICP, and the preferable boron content is 0.3 wt% to 10 wt%. is there.
Nitrogen contained in the catalyst body may be measured by X-ray photoelectron spectroscopy (hereinafter referred to as XPS) as an analytical method, or by an organic element measuring device applying a thermal conductivity method. The analysis by can detect nitrogen contained in the particle surface, and the analysis by the organic element measuring device applying the thermal conductivity method can detect the amount of nitrogen contained in the whole. Therefore, 0.5 to 30% by weight is preferable in the nitrogen amount evaluation by XPS, and it is desirable that the detected amount be 10% or less in the evaluation by the organic element measuring device applying the thermal conductivity method.
The conductivity of the obtained powder can be evaluated by measuring the powder resistance with a powder resistance measuring apparatus (MCP-PD51 type manufactured by Dia Instruments).
The preferable measured value of the powder resistance of the catalyst body of the present invention is 1.0 Ω · cm or less, preferably 0.001 to 1.0 Ω · cm.

The catalyst body of the present invention preferably has a catalyst metal supported on the surface of the nitrogen-doped boron-containing carbon powder. The catalyst metal is preferably at least one metal element selected from the group consisting of platinum, gold, rhodium, ruthenium, cobalt, nickel, tin, iron, copper, palladium and silver.
As the method for supporting the metal, the nitrogen-doped boron-containing carbon powder is dispersed in a liquid, a catalyst-containing metal compound solution is added, and catalytic metal ions are adsorbed on the surface of the nitrogen-doped boron-containing carbon powder. There is a method in which metal ions are chemically reduced and a catalyst metal is supported on the surface of the nitrogen-doped boron-containing carbon powder.

Next, a method for producing an evaluation electrode using the catalyst body of the present invention will be described.
First, 1 ml of a 5 wt% perfluorosulfonic acid (registered trademark Nafion) solution was added to 30 mg of the obtained catalyst body to prepare a paste. This paste was applied onto a glassy carbon electrode and dried to obtain an evaluation electrode. The thus produced electrode was used as a working electrode, and a platinum electrode was used as a counter electrode to evaluate catalyst characteristics. The measurement was performed by Hokuto Denko's electrochemical measurement system HZ-3000. The working electrode and the platinum electrode were immersed in a 0.5 M aqueous sulfuric acid solution, and LSV measurement was performed in a scanning range of +1.0 V to −0.2 V (vs. Ag / AgCl electrode) under oxygen flow.

  As a durability test, a method of examining the change in catalyst performance by performing the above LSV measurement after maintaining at a potential of 1.0 V (vs. Ag / AgCl electrode) for several hundred hours is assumed. However, here, in order to perform the measurement efficiently, this was replaced by repeating a scanning cycle including a higher potential. That is, after repeating the scanning cycle 10 times in the range of −0.2 to +1.3 V in an argon gas atmosphere, the LSV measurement was performed to obtain the catalyst performance after the durability test.

  A solid polymer fuel cell is composed of an anode (fuel electrode) and a cathode (air electrode), which are arranged facing each other so that cells incorporated in a battery module sandwich a sheet-like solid polymer electrolyte. As this solid polymer electrolyte, a fluorine ion exchange resin membrane represented by a perfluorosulfonic acid resin membrane is mainly used. The catalyst powder is applied to the surface of the solid polymer film to form a layered electrode reaction layer. Furthermore, the anode and the cathode are configured to include a current collector that serves both as an electrode reaction layer support including the fuel cell electrode catalyst and a gas diffusion layer, and are brought into close contact with each other by hot pressing, whereby a MEA (membrane electrode assembly). Integrated as

The current collector supports the catalyst layer and supplies and discharges reaction gas (fuel gas and air). As the current collector material, a porous and highly conductive sheet such as carbon paper is used. When a reactive gas is supplied to each of the electrodes, a gas phase (reactive gas), a liquid phase (electrolyte), a solid phase (catalyst) are formed at the boundary between the catalyst layer and the solid polymer electrolyte membrane provided on both electrodes. A three-phase interface is formed, and a direct current is generated by an electrochemical reaction.
In the above electrochemical reaction,
Cathode side: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
Anode side: H ₂ → 2H ⁺ + 2e ⁻
The H ⁺ ions generated on the anode side move toward the cathode side through the solid polymer electrolyte membrane, and e ⁻ (electrons) move to the cathode side through an external load. On the other hand, on the cathode side, oxygen contained in the air reacts with H ⁺ ions and e ⁻ that have moved from the anode side to produce water. As a result, the polymer electrolyte fuel cell generates direct current from hydrogen and oxygen to generate water.

  In the present invention, carbon containing boron is used as a base material for the purpose of obtaining high conductivity, and a layer containing nitrogen atoms is formed on the surface of the carbon base for the purpose of imparting a catalytic active point. The target catalyst body was obtained. It was found that the obtained catalyst body not only has high catalytic activity, but also exhibits high stability. Here, although the reason why the stability of nitrogen introduced to the surface is high is not clearly understood, it is considered that the nitrogen exists as stable nitrogen that is difficult to desorb due to interaction with boron.

  This carbon material exhibited catalytic activity even in this state, but by supporting a metal, metal complex, metal ion, etc. (hereinafter referred to as catalyst component) on this surface, a catalyst with higher activity and excellent stability can be obtained. I was able to get it. This is presumably because the supported component was supported in a highly dispersed state by nitrogen contained on the surface, and at the same time, the catalyst component was supported and fixed on nitrogen stabilized by boron as described above.

  Hereinafter, specific embodiments of the catalyst body obtained in the present invention will be described in detail.

Example 1
Acetylene gas and heated and vaporized boron chloride were fed into a reaction tube (total length: 2 m, diameter: 0.1 m) in a region heated to 1200 ° C. in advance by a nitrogen stream, and boron-containing carbon powder was obtained by pyrolysis reaction of acetylene. . When the amount of boron contained in the obtained powder was measured, it was 1.3% by weight. The powder resistance of this powder was measured and found to be 0.083 Ω · cm. Using this powder, the reaction was performed in a region heated to 700 ° C. in a reaction tube under the flow of nitrogen, ammonia, oxygen, and water vapor. Here, nitrogen is a role of a medium and a nitrogen source for stably flowing gas, ammonia is a nitrogen source, and oxygen is necessary for activating the surface, but if the flow rate is large, the yield is extremely reduced. Therefore, the necessary minimum amount was introduced intermittently. Water vapor was intermittently introduced in the minimum amount necessary to control the reaction. The amount of boron contained in the obtained powder was measured and found to be 1.2% by weight. The amount of nitrogen contained in the powder was measured by a heat conduction method (organic element analyzer 2400IICHNS / O, manufactured by Perkin Elmer) and found to be 0.4% by weight. Further, the nitrogen content of this powder was measured by XPS and found to be 3.4% by weight. The powder resistance of this powder was measured and found to be 0.097 Ω · cm. The results of examining the catalytic activity using the powder obtained here are shown in FIG. The results of the durability test are shown in FIG.

Example 2
The boron-containing carbon powder obtained in the same manner as in Example 1 was dispersed in distilled water, methylolmelamine and a phthalocyanine compound were added thereto, and refluxed for 1 hour. After removing the water, a catalyst powder was obtained by further calcining at 750 ° C. for 1 hour in an argon atmosphere. When the amount of nitrogen contained in the obtained powder was measured by XPS, it was 2.8% by weight. The powder resistance of this powder was measured and found to be 0.127 Ω · cm. FIG. 6 shows the durability test result of this catalyst body.

Example 3
The powder obtained in Example 2 was dispersed in distilled water, an aqueous chloroplatinic acid solution was added so that the addition amount was 20% by weight as Pt, and about 2% of ethanol was added to the dispersion. A catalyst body was obtained by dropping a 05% aqueous sodium borohydride solution to precipitate Pt.

Example 4
Disperse the powder obtained in Example 1 in distilled water, add an aqueous solution of chloroplatinic acid so that the addition amount as Pt is 20% by weight, remove water, and then heat to 300 ° C. under hydrogen flow. Thus, a catalyst powder carrying platinum was obtained. The result of examining the catalytic activity of the obtained powder is shown in FIG. The durability test results are shown in FIG.

Example 5
Using the catalyst powder obtained here, a single cell electrode for a polymer electrolyte fuel cell was produced as follows. Each catalyst powder was dispersed in an organic solvent, and this dispersion was applied to a PTFE sheet to form a catalyst layer. The catalyst layers formed from these obtained catalyst powders were placed on both sides of the polymer electrolyte membrane, bonded by hot pressing, and diffusion layers were placed on both sides to form single cell electrodes. Humidified air that passed through a bubbler heated to 70 ° C. was supplied to this single cell electrode at 1 L / min, and humidified hydrogen that was passed through a bubbler heated to 85 ° C. was supplied to the electrode on the anode side at 0.5 L / min, Current-voltage characteristics were measured.
As a result, (the battery voltage 0.67V at a current density of 1.2A / cm ²⁾ catalyst of Example 4 the catalyst of Comparative Example 4 (battery voltage 0.59V at a current density of 1.2A / cm ²⁾ It was found that a higher voltage can be obtained in the high current density region than in FIG.

Comparative Example 1
Using a commercially available carbon powder (Vulcan XC-72 manufactured by Cabot Corporation), the reaction was carried out in a region heated to 700 ° C. in a reaction tube under the flow of nitrogen, ammonia, oxygen, and steam in the same manner as in Example 1. Here, nitrogen is a role of a medium and a nitrogen source for stably flowing gas, ammonia is a nitrogen source, and oxygen is necessary for activating the surface, but if the flow rate is large, the yield is extremely reduced. Therefore, the necessary minimum amount was introduced intermittently. The nitrogen content of this powder was measured by XPS and found to be 4.5%. The powder resistance of this powder was measured and found to be 0.160 Ωcm. The result of examining the catalytic activity of the obtained powder is shown in FIG. The results of the durability test are shown in FIG.

Comparative Example 2
Using a commercially available carbon powder (Vulcan XC-72 manufactured by Cabot Corporation), the reaction was performed in a region heated to 800 ° C. in a reaction tube under nitrogen, ammonia, oxygen, and steam flow. Here, nitrogen is a role of a medium and a nitrogen source for stably flowing gas, ammonia is a nitrogen source, and oxygen is necessary for activating the surface, but if the flow rate is large, the yield is extremely reduced. Therefore, the necessary minimum amount was introduced intermittently. Further, after this operation, nitrogen gas and heated and vaporized boron chloride were introduced into the reaction tube using argon as a carrier. At this time, since boron chloride easily reacts with oxygen and oxidizes, careful attention was paid to the replacement of the supply gas and the supply method. The resulting powder had a boron content of 0.3%. The nitrogen content of this powder was measured by XPS and found to be 4.3%. The powder resistance of this powder was measured and found to be 12 Ω · cm.

Comparative Example 3
Using commercially available carbon powder (Valkan XC-72 manufactured by Cabot Corporation), an aqueous solution of chloroplatinic acid is added so that the amount added as Pt is 20% by weight. After removing moisture, the mixture is heated to 300 ° C. under hydrogen flow. Thus, a catalyst powder carrying platinum was obtained. The result of examining the catalytic activity of the obtained powder is shown in FIG.

Comparative Example 4
Using the powder obtained in Comparative Example 1, an aqueous solution of chloroplatinic acid was added so that the addition amount as Pt was 20% by weight, and after removing moisture, the platinum was supported by heating to 300 ° C. under a hydrogen flow. A catalyst powder was obtained. The result of examining the catalytic activity of the obtained powder is shown in FIG. The durability test results are shown in FIG.

Comparative Example 5
Acetylene gas, heated and vaporized boron chloride and acrylonitrile were fed into a reaction tube (total length 2 m, diameter 0.1 m) in a region heated to 1200 ° C. in advance by a nitrogen stream, and boron and nitrogen were contained by the thermal decomposition reaction of acetylene. Carbon powder was obtained. The amount of boron contained in the obtained powder was measured and found to be 2.1% by weight. The amount of nitrogen contained in the powder was 1.3% by weight as measured by a heat conduction method (organic element analyzer 2400IICHNS / O, manufactured by Perkin Elmer). The powder resistance of this powder was measured and found to be 180 Ω · cm.

  As shown in FIG. 1, the electrode containing the catalyst body obtained in Example 1 has a large negative current due to the reduction reaction and a high starting potential of the reduction reaction as compared with that of Comparative Example 1, and thus has excellent catalytic activity. It was suggested to have Similarly, it is clear that the electrode containing the catalyst body obtained in Example 4 also has excellent catalytic activity when compared with the electrodes of Comparative Examples 3 and 4.

  Moreover, from the results of FIGS. 2 to 6, it is clear that the electrode containing the catalyst body of the present invention is a catalyst body that is extremely excellent in durability since the catalytic activity hardly changes before and after the durability test. It was.

FIG. 1 shows the oxygen reduction activity of each catalyst determined by LSV measurement. FIG. 2 compares the oxygen reduction activity before and after the durability test for the catalyst obtained in Example 1. FIG. 3 compares the oxygen reduction activity before and after the durability test for the catalyst obtained in Comparative Example 1. FIG. 4 compares the oxygen reduction activity before and after the durability test for the catalyst obtained in Example 4. FIG. 5 compares the oxygen reduction activity before and after the durability test for the catalyst obtained in Comparative Example 4. FIG. 6 compares the oxygen reduction activity before and after the durability test for the catalyst obtained in Example 2.

Claims (10)

In a catalyst body containing carbon, boron and nitrogen,
The base material is a carbon material containing boron,
A catalyst body, wherein a nitrogen atom is doped on a surface of the boron-containing carbon material.   The catalyst body according to claim 1, further comprising a catalyst metal supported thereon.   The catalyst body according to claim 1, wherein the boron-containing carbon material has a measured value of powder resistance of 1.0 Ω · cm or less.   The catalyst body according to any one of claims 1 to 3, wherein the doping amount of the nitrogen atom is 0.5 to 30 wt% as measured by X-ray photoelectron spectroscopy.   The catalyst metal is at least one metal selected from the group consisting of platinum, gold, rhodium, ruthenium, cobalt, nickel, tin, iron, copper, palladium, and silver. The catalyst body according to any one of the above.   A fuel cell electrode comprising the catalyst body according to any one of claims 1 to 5.   A fuel cell configured using the electrode according to claim 6. A step of thermally decomposing a hydrocarbon and a boron-containing compound at a temperature of 500 to 2000 ° C. in an inert gas atmosphere to prepare a boron-containing carbon powder;
Next, the boron-containing carbon powder and ammonia gas, oxygen, nitrogen, water vapor and / or nitrogen monoxide are allowed to act at 500 to 1000 ° C., and nitrogen atoms are doped on the surface of the boron-containing carbon powder. Obtaining a powder;
A process for producing a catalyst body comprising at least A step of thermally decomposing a hydrocarbon and a boron-containing compound at a temperature of 500 to 2000 ° C. in an inert gas atmosphere to prepare a boron-containing carbon powder;
Next, after coating the boron-containing carbon powder with a nitrogen-containing polymer, a step of obtaining a nitrogen-doped boron-containing carbon powder by firing at a temperature of 500 ° C. to 1300 ° C. under an inert gas,
A process for producing a catalyst body comprising at least Furthermore, after the nitrogen-doped boron-containing carbon powder is dispersed in the liquid, a step of adding a catalyst-containing metal compound solution and adsorbing catalyst metal ions on the surface of the nitrogen-doped boron-containing carbon powder,
A step of chemically reducing the catalytic metal ion and supporting the catalytic metal on the surface of the nitrogen-doped boron-containing carbon powder,
The process for producing a catalyst body according to claim 8 or 9, wherein

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