JP2008021609A - Direct methanol fuel cell and catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DMFC (direct methanol fuel cell) catalyst which enhances the activity of an anode catalyst, suppresses CO poisoning, and enables effective power generation at low temperature and inexpensive practical application in a DMFC employing a methanol water solution for fuel, a DMFC electrode material and a DMFC fabricated thereby. <P>SOLUTION: This DMFC employs a catalyst containing a tungsten carbide obtained, by transforming a compound selected from a group comprising tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide and tungsten silicide. Preferably, this DMFC catalyst contains tungsten carbide and platinum and is conconstituted with these adhering to a carbonaceous base substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a direct methanol fuel cell (DMFC) which is a kind of a polymer electrolyte fuel cell using a catalyst containing a specific tungsten carbide.
The present invention also relates to a catalyst and electrode material used in the DMFC.

  There are many types of fuel cells depending on the type of electrolyte, for example, alkaline aqueous solution type, phosphoric acid aqueous solution type, molten carbonate type, solid oxide type and solid polymer type. Among them, a polymer electrolyte fuel cell (PEFC) that generates power by reducing hydrogen gas at the anode electrode and reducing oxygen at the cathode electrode using a perfluorocarbon sulfonic acid electrolyte is output. Due to its high density and clean exhaust gas, it is being developed as a power source for automobiles in order to further improve energy efficiency and solve environmental problems.

  However, PEFC has a low volumetric energy density of hydrogen gas as a fuel, the volume of the fuel tank becomes excessive, and a device for supplying fuel gas and oxidizing gas to a power generator and a battery performance are stabilized. Since an auxiliary device such as a humidifier is required, the power generation device becomes large, so that it is not suitable as a power source for portable equipment.

  Accordingly, development of a direct methanol fuel cell (DMFC), which is a type of PEFC in which methanol is directly supplied as a fuel and the methanol fuel is directly reformed inside the cell, is also under development. Since this fuel cell can be easily miniaturized, it is regarded as a promising power source for future mobile electronic devices and a light power source for automobiles.

In DMFC, methanol and water react at the anode electrode to generate carbon dioxide, protons, and electrons (reaction (1) below). On the other hand, at the cathode electrode, oxygen, protons and electrons react to produce water (reaction (2) below).
Anode electrode: CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Cathode electrode: 3/2 O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O (2)

  These reactions proceed with the help of a catalyst supported on the electrode. The theoretical voltage of this reaction is 1.18 V, but in an actual battery, the voltage is lower than this value for various reasons.

Conventionally, platinum is generally used as a catalyst for the anode of DMFC. The reaction mechanism of the catalytic action of the reaction between methanol and water at the anode electrode by the platinum catalyst is shown by the following chemical reaction (the following reactions (3) and (4)).
CH ₃ OH + Pt → Pt—CO + 4H ⁺ + 4e ⁻ (3)
Pt—CO + H ₂ O → Pt + CO ₂ + 2H ⁺ + 2e ⁻ (4)

  As a result of the reaction as described above, the platinum catalyst is poisoned over time by the methanol-derived CO generated during the reaction, resulting in a problem that the battery performance deteriorates because the reaction area decreases. .

  Conventionally, in order to prevent the platinum catalyst from being poisoned by CO, methods for improving the surface structure of platinum or adding different metals (Ru, Ni, Fe, Co, Sn, Ti, Mo, etc.) have been proposed. Yes. However, Ni, Fe, Co, Sn, Ti, and Mo are easy to dissolve, and since Ru is small in the amount of resources, mass production of power sources for mobile electronic devices, or practical application as large-capacity power sources for automobiles, etc. Is a problem.

Non-Patent Document 1 discloses that Pt is supported on tungsten carbide as an anode catalyst for methanol, whereby the activity is improved and the CO poisoning resistance is improved. This document discloses that tungsten carbide is mainly composed of W ₂ C and includes WC (hcp) and WC _1-x (fcc). Here, the effect of W ₂ C is mainly examined, but the effect of WC is not described, and further, the influence on the anode catalyst activity with respect to methanol by changing the preparation method of WC, and the resistance to CO poisoning There is no disclosure or suggestion about the effect on. Further, tungsten carbide in Non-Patent Document 1 is synthesized from resorcinol-formaldehyde polymer and ammonium metatungstate salt, and is selected from a compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide, and tungsten silicide. It is clearly different from the tungsten carbide according to the present invention to be synthesized.
Angew. Chem. Int. Ed. 2005, 44, 6557-6560

  The present invention relates to a DMFC that uses an aqueous methanol solution as a fuel. The DMFC can increase the activity of an anode catalyst, suppress CO poisoning, generate power efficiently at low temperatures, and can be practically used at low cost. An object is to provide a catalyst, an electrode material for DMFC, and DMFC.

As a result of intensive studies in view of the above situation, the present inventors have found that tungsten carbide particles obtained by conversion from a specific tungsten compound have a specific crystal form, and use this together with a noble metal catalyst such as platinum. Thus, it has been found that it becomes an inexpensive and highly practical electrode catalyst for DMFC using methanol aqueous solution as fuel.
The present invention has been completed on the basis of such knowledge, and the gist thereof is as follows.

[1] In a direct methanol fuel cell using a methanol aqueous solution as a fuel,
A direct methanol characterized by using a catalyst containing as a catalyst component tungsten carbide obtained by conversion from a compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide and tungsten silicide. Fuel cell.

[2] The direct methanol fuel cell according to [1], wherein the catalyst further contains platinum as a catalyst component.

[3] The direct methanol fuel cell according to [1] or [2], wherein the catalyst further contains an alloy of a Group VIII element of the periodic table and platinum as a catalyst component.

[4] A direct methanol fuel cell according to any one of [1] to [3], wherein the catalyst component is attached to a carbon-based substrate.

[5] In a catalyst used in a direct methanol fuel cell using a methanol aqueous solution as a fuel,
For direct methanol fuel cell, characterized by containing as a catalyst component tungsten carbide obtained by conversion from a compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide and tungsten silicide. catalyst.

[6] An electrode material for a direct methanol fuel cell, wherein a catalyst layer containing the catalyst for a direct methanol fuel cell according to [5] is formed on an ion exchange membrane.

[7] An electrode material for a direct methanol fuel cell comprising a catalyst layer containing the catalyst for a direct methanol fuel cell according to [5] on an anode fuel diffusion layer or a cathode gas diffusion layer .

[8] An electrode material for a direct methanol fuel cell, wherein a catalyst layer containing the catalyst for a direct methanol fuel cell according to [5] is formed on a transfer film.

  According to the present invention, the tungsten carbide particles obtained by conversion from a specific tungsten compound are used in combination with a catalyst for a noble metal DMFC such as platinum, thereby exhibiting a stable and good catalytic action, and an inexpensive and practical DMFC. The catalyst for DMFC, the electrode material for DMFC using this catalyst for DMFC, and DMFC are provided.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[DMFC catalyst]
The DMFC of the present invention was obtained by conversion from a compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide and tungsten silicide (hereinafter sometimes referred to as “precursor compound”). It is characterized by using a catalyst containing tungsten carbide.

  Details of the mechanism of action in which tungsten carbide produced via the above-mentioned specific precursor compound exhibits high catalytic activity when used in combination with a transition metal exhibiting activity in the oxidation reaction of the aqueous methanol solution (the reaction (1)). Is not clear, but is estimated as follows.

When a widely known PtRu alloy catalyst is used as an anode catalyst for DMFC, according to Non-Patent Documents 2 to 4, methanol is dissociatively adsorbed on the Pt site even in a low potential range of about 0.1 V with respect to a standard hydrogen electrode. Then, the dehydrogenation rate to CO proceeds rapidly (the following reaction (3)).
CH ₃ OH + Pt → Pt—CO + 4H ⁺ + 4e ⁻ (3)

Moreover, at the Ru site, the adsorbed water is discharged at about 0.4 V, and active species such as Ru-OH are generated (reactions (3A) and (3B) below), which are thought to oxidize CO at the adjacent Pt site. ing. The series of reactions (3), (3A), (3B), and (3C) proceed rapidly, so that the PtRu alloy is higher than the PtRu to the oxidation reaction of the aqueous methanol solution (the reaction (1)). It is considered to show catalytic activity.
H ₂ O + Ru → Ru—OH ₂ (3A)
Ru—OH ₂ → Ru—OH + H ⁺ + e ⁻ (3B)
Pt—CO + Ru—OH → Pt + Ru + CO ₂ + H ⁺ + e ⁻ (3C)

On the other hand, Non-Patent Document 5 reports that WC is weakly bound to CO, and that CO does not adsorb to WC at temperatures of about −3 ° C. or higher.
Therefore, when Pt is supported on WC and used as a negative electrode catalyst of DMFC, it is not considered from the knowledge of Non-Patent Document 5 that CO is adsorbed on WC, and WC acts like Ru of a PtRu alloy catalyst. It is estimated (the following reactions (5A) to (5C)).
_{H 2 O + WC → WC-} OH 2 (5A)
WC-OH ₂ → WC-OH + H ⁺ + e ⁻ (5B)
Pt—CO + WC—OH → Pt + WC + CO ₂ + H ⁺ + e ⁻ (5C)

The WC produced via the specific precursor compound described above is larger than the half-value width of WC produced directly from WO _{3 as} will be described later in the Examples section. A large half-value width indicates that the WC crystallites are small. Although WC and Pt do not form an alloy, the WC according to the present invention has a small crystallite, so that the action like Ru that forms an alloy with Pt is more easily achieved, and the above reactions (5A) to (5C) It is presumed that the catalyst proceeds more rapidly, and as a result, high catalytic activity is obtained.
M. Watanabe and S. Motoo, J. Electroanal. Chem., 60, 275 (1975). M. Watanabe and S. Motoo, Denki Kagaku, 41, 190 (1973). M. Watanabe and S. Motoo, J. Electroanal. Chem., 60, 267 (1975). Surface Science, 397 (1-3), 137-144 (1998)

<Tungsten carbide>
Tungsten carbide has a form in which a tungsten (W) atom and a carbon (C) atom exist as a compound having a bond. For example, WC, WC _1-x (0 <x <1), W ₂ C and the like.

The form of this tungsten carbide can be confirmed by X-ray diffraction (XRD). That is, it can be confirmed by giving a characteristic peak to tungsten carbide by irradiating tungsten carbide with X-rays (Cu- _Kα rays) and observing a diffraction spectrum.

  Examples of the measurement apparatus and measurement conditions include the following, but the XRD analysis technique for tungsten carbide in the present invention is not limited to the following measurement apparatus and measurement conditions.

(Powder XRD analysis)
Measuring device X-ray powder analysis device / PANallytical PW1700
Measurement conditions X-ray output (Cu-Kα): 40 kV, 30 mA
Scanning axis: θ / 2θ
Measurement range (2θ): 3.0 ° to 70.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 3.0 ° / min
DS, SS, RS: 1 °, 1 °, 0.20mm
Gonometer radius: 173mm

Specifically, WC is a peak of 2θ (± 0.3 °) of X-ray diffraction, such as 31.513 °, 35.639 °, 48.300 °, 64.016 °, 65.790 °, etc. A characteristic peak is given. WC _1-x is a characteristic peak of 36.977 °, 42.887 °, 62.027 °, 74.198 °, 78.227 °, etc. as a 2θ (± 0.3 °) peak of X-ray diffraction. It gives a peak. In addition, W ₂ C is a peak of 2θ (± 0.3 °) of X-ray diffraction such as 34.535 °, 38.066 °, 39.592 °, 52.332 °, 61.879 °, etc. Giving a positive peak.

  Although there is no restriction | limiting in particular as a shape of tungsten carbide, The most common is a particulate form. In the particulate tungsten carbide, the upper limit of the average particle diameter is usually 100 μm or less, preferably 1000 nm or less, more preferably 500 nm or less, especially 300 nm or less, and the lower limit is usually 0.5 nm or more, preferably 1.0 nm or more. Preferably it is 2.0 nm or more. If the particle size of tungsten carbide is less than this lower limit, it becomes unstable and tends to be deactivated, and if it exceeds the upper limit, it becomes difficult to obtain high activity.

  The average particle size of tungsten carbide is determined by unifying the direction in which the particle size is measured by measuring with a scanning electron microscope (SEM) or transmission electron microscope (TEM). Measured and averaged.

  In the measurement by scanning electron microscopy (SEM), the sample surface is visualized by scanning the surface of the sample with an electron beam and detecting secondary electrons generated. Using this technique, the particle size of tungsten carbide can be measured. Examples of the measuring apparatus and measuring method include the following, but the measuring method using the SEM of the tungsten carbide particle size in the present invention is not limited to the following measuring apparatus and measuring method. .

(Measurement by SEM)
Measurement device “S-4100” manufactured by Hitachi, Ltd. is used, and the acceleration voltage of the electron beam is controlled to 15 kV for observation.
Measuring method An appropriate amount of a powder sample is dispersed on a carbon-deposited Si wafer, and methanol is dropped to dry. Specifically, a photograph is observed from a dispersion state of 100 to 1000 times, and a particle diameter is examined from conventional photographs of 10,000 and 100,000 times or more.

  The tungsten carbide according to the present invention is synthesized by conversion from a specific tungsten compound, as will be described later in the section of the catalyst production method. Thereby, high activity as a catalyst for DMFC can be expressed.

<Substrate>
In the DMFC catalyst of the present invention, the substrate is not necessarily essential, but it is preferable that tungsten carbide is applied to the substrate in terms of maintaining the activity, and among them, the use of a carbon-based substrate is highly conductive. It is suitable at the point obtained.

  Various carbon-based substrates can be used, and are not particularly limited. For example, carbon black, carbon nanotube, carbon nanohorn, carbon nanocluster, fullerene, pyrolytic carbon, activated carbon, etc. Two or more kinds can be used in combination.

  Among these, carbon black is industrially advantageous in terms of conductivity, availability, and price. Specifically, carbon black includes channel black, furnace black, thermal black, and acetylene black. Oil furnace black, gas furnace black, and the like.

  The form of the substrate is not particularly limited, but the most commonly used is a powder form.

When the powder of the substrate, such as carbon powder, the specific surface area (BET) is usually several tens of ^m 2 / g or more, preferably 200 meters ² / g or more, more preferably 500 meters ² / g or more and usually 5000 m ² / g or less, preferably several thousand m ² / g or less (in the present invention, “number” such as “thousand” or “tens” refers to about “2 to 4”). If the specific surface area is too small, the effective area for depositing tungsten carbide is reduced, and the reaction field is reduced, so that sufficient catalytic activity cannot be obtained. An excessively large specific surface area is expensive, and the object of the present invention to provide an inexpensive DMFC catalyst is impaired by using tungsten carbide.

<Adhesion of tungsten carbide to the substrate>
In the present invention, the state in which tungsten carbide is deposited on the substrate refers to a state in which both are in contact with each other so as to obtain electrical conductivity between the tungsten carbide and the substrate. Therefore, tungsten carbide can be deposited on the substrate by simply mixing the tungsten carbide and the substrate, but this mixture may be fired. In the following, the state in which the substrate is mixed and then fired and deposited is referred to as “support”.

  As a deposition method, a known method such as a supporting method, a mixing method, an impregnation method, a precipitation method, an adsorption method or the like can be adopted, but the tungsten carbide precursor compound or raw material compound is mixed with the substrate and then tungsten carbide. In the case of performing a conversion reaction for producing, it is usually preferable to perform a baking treatment after producing tungsten carbide.

  The deposition ratio of tungsten carbide to the substrate is not limited, but the lower limit is usually 0.001 or more, preferably 0.01 or more, and the weight ratio of tungsten carbide / (tungsten carbide + substrate). It is 0.05 or more, and the upper limit is usually 0.95 or less, preferably 0.4 or less, and particularly preferably 0.3 or less. If the deposition ratio of tungsten carbide is below this lower limit, the desired activity cannot be obtained, and if it exceeds the upper limit, the effect of improving the activity due to deposition is less likely to occur.

<Other catalyst components>
In the present invention, a transition metal is preferably used in combination with the tungsten carbide according to the present invention as a catalyst component. Furthermore, a catalyst component selected from transition metal compounds other than tungsten carbide (hereinafter sometimes referred to as “other catalyst component”) may be used in combination. The transition metal compound other than tungsten carbide may be a tungsten compound other than tungsten carbide.

As a transition metal used in combination, platinum (Pt) is most preferable from the viewpoint of high activity expression. Further, an alloy of platinum and a group VIII element of the periodic table (hereinafter sometimes simply referred to as “group VIII element”) may be used in combination. Here, the group VIII element is one or more selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, and Ir. Specific alloys include PtRu, Pt ₅₄ Ru ₄₆ , Pt ₅₃ Ni _{47, and the} like. Among these, an alloy of Pt and Ru is preferable because of its high activity.

  Examples of transition metal compounds other than tungsten carbide include oxides, carbides, nitrides, borides, etc., with oxides and carbides being preferred.

Examples of tungsten compounds other than tungsten carbide include WO ₃ , WO ₂ , WN, W ₂ N, WB, W _1-y Mo _y C _1-z , Ni ₂ W ₄ C, Co ₃ W ₃ C, WP, WP _2. And tungsten compounds such as WO ₃ and WO ₂ are preferable, and WO ₃ is more preferable. In W _1-y Mo _y C _1-z , y is preferably in the range of 0 <y ≦ 0.5, and z is in the range of 0 ≦ z ≦ 0.3.

Any one of these platinum, an alloy of platinum and a Group VIII element (hereinafter referred to as “Pt alloy”), and other catalyst components may be used alone, or two or more thereof may be used in combination. . One type may be used for each, or two or more types may be used.
Hereinafter, among catalyst components according to the present invention such as Pt, Pt alloy, and other catalyst components, catalyst components other than tungsten carbide may be referred to as “other catalyst components and the like”.

  The other catalyst components and the like are preferably in the form of powder, and the average particle size in this case is usually 1000 nm or less as an upper limit, preferably 500 nm or less, especially 300 nm or less, and the lower limit is usually 0.5 nm or more. Is preferred. If the average particle size of other catalyst components is less than this lower limit, it becomes unstable and easily deactivated, and if it exceeds the upper limit, it becomes difficult to obtain high activity.

When such other catalyst components are used in combination as a cocatalyst, examples of the combined use include the following.
(1) Load other catalyst components on tungsten carbide and mix with substrate
(2) After mixing tungsten carbide and other catalyst components, mix with the substrate.

  When other catalyst components are used, the other catalyst components are the total of other catalyst components / weight ratio of tungsten carbide, and the lower limit is usually 0.001 or more, preferably 0.01 or more, especially 0.05. Thus, the upper limit is usually 2.0 or less, preferably 1.0 or less, and more preferably 0.8 or less. If the amount of the other catalyst component used is less than this lower limit, the desired activity due to the use of the other catalyst component cannot be obtained, and if it exceeds the upper limit, the activity improving effect is difficult to be obtained.

  In the DMFC catalyst of the present invention, even if a metal component other than the transition metal element is contained in an amount of several weight percent or less based on the weight of tungsten carbide, it is acceptable for the purpose and effect of the present invention.

<Manufacturing method>
(Manufacture of tungsten carbide)
The tungsten carbide according to the present invention is a precursor compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide, and tungsten silicide, that is, Pauling's electronegativity is 1.8 or more and 3.0 or less. It is obtained by converting from a tungsten compound other than tungsten carbide having at least one bond between the typical nonmetallic element and tungsten.

  Note that typical nonmetallic elements having a Pauling electronegativity of 1.8 or more and 3.0 or less include H (2.1), B (2.0), N (3.0), Si (1.8 ), P (2.1), S (2.5), Cl (3.0), As (2.0) Se (2.4) Br (2.8), Te (2.1), I (2.5), At (2.2) are mentioned (the electronegativity is in parentheses), and among these, it is selected from the group consisting of typical nonmetallic elements in the second and third periods of the periodic table. Since elements of B, N, Si, P, and S are preferable for reasons such as low toxicity, tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide, and silicide are used as precursor compounds in the present invention. A compound selected from the group consisting of tungsten is used.

[1] Precursor compound Specific examples of the precursor compound used in the present invention include tungsten boride such as WB, WB ₄ and W ₂ B ₅ , and nitriding such as WN, W ₂ N, WN ₂ and W ₃ N _4. Examples include tungsten, tungsten silicide such as WSi ₂ and W ₅ Si ₃ , tungsten sulfide such as WS ₂ and WS ₃ , tungsten phosphide such as WP and WP ₂ , among these, tungsten nitride, tungsten phosphide, Tungsten sulfide is preferred because it is industrially advantageous. These compounds have a form in which tungsten (W) atoms and boron (B), nitrogen (N), silicon (Si), phosphorus (P) or sulfur (S) atoms are directly bonded to each other, and X-ray It can be confirmed by diffraction (XRD).

[2] Raw Material Compound The tungsten compound for deriving the precursor compound used in the present invention (hereinafter sometimes referred to as “raw material compound”) is not particularly limited, but specifically, WO ₃ , WO ₂ , H _{2 WO 4, (NH 4)} 10 W 12 O 41 · 5H 2 other tungsten oxides O, _{etc., WF 6, WCl 4, WCl} 6 and WBr ₅ inorganic tungsten compound such as tungsten halides such as or (NH ₄ ) sulfur-containing tungsten compounds such as ₂ WS ₄ and the like. In addition, a tungsten complex is mentioned as an organic tungsten compound. Specifically, boron atom coordinated tungsten complexes such as ethylborylethylidene ligands, carbons such as carbonyl ligands, cyclopentadienyl ligands, alkyl group ligands, and olefinic ligands. Atom coordinated tungsten complex, nitrogen coordinated tungsten complex such as pyridine ligand, acetonitrile ligand, phosphorus atom coordinated tungsten complex coordinated with phosphine ligand, phosphite ligand, etc., diethylcarbamodithio And a sulfur atom coordinated tungsten complex coordinated with a lato ligand or the like. Further, it may be a complex having a plurality of these ligands or a complex having a plurality of types of ligands. Specifically, a tungsten complex in which a hydride ligand and an olefin ligand are coordinated, W (CO) ₃ (NCCH ₃ ) ₃ , W (CO) ₄ (bipyridyl) in which a carbon atom and a nitrogen atom are coordinated And tungsten complexes.

  Among these, compounds such as carbon atom-coordinated tungsten complex, nitrogen atom-coordinated tungsten complex, and phosphorus atom-coordinated tungsten complex are preferable because they are abundant and easy to handle and industrially advantageous.

  For the raw material compound, the upper limit of the average particle size is usually 100 μm or less, preferably 1000 nm or less, more preferably 500 nm or less, especially 300 nm or less, particularly 100 nm or less, and the lower limit is usually 0.5 nm or more, preferably 1.0 nm or more, More preferably, the thickness is 2.0 nm or more. When the particle size of the raw material compound is less than this lower limit, the tungsten carbide produced becomes unstable and easily deactivated, and when it exceeds the upper limit, it becomes difficult to obtain high activity.

[3] Conversion from raw material compound to precursor compound For the conversion reaction from the raw material compound to the precursor compound, any known method can be used. For example, the conversion reaction from the raw material compounds of tungsten nitride, tungsten sulfide, and tungsten phosphide, which are preferable precursor compounds, can be performed under the following conditions.

(1) Tungsten nitride The method for synthesizing tungsten nitride as the precursor compound is not particularly limited, and can be performed by any known method.

For example, in “Applied Catalysis A: General”, 183, 253 (1999), heating of WO ₃ was started at 270 ° C. under NH ₃ flow, the heating temperature was increased at a rate of 30 ° C. per hour, and the final temperature Although it is disclosed that W ₂ N can be produced by heating at 560 ° C., and that it can be stabilized by forming a passive film by flowing 1% O ₂ / He gas at room temperature. This method can also be adopted.

  In addition, the following method can also be employed.

The inorganic tungsten compound _{(NH 4) 10 W 12 O} 41 · 5H 2 O and tungsten oxide, an organic medium (e.g., alcohols such as ethanol, carbonyl such as acetone, ethers such as tetrahydrofuran, toluene, etc. Hydrocarbons, chlorides such as methylene chloride) or an aqueous medium (for example, water, etc.), and if necessary, add a desired amount of HCl for complete dissolution, or make a slurry, (Normally 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), and then the solvent is removed by distillation or the like. If necessary, a predetermined temperature (usually 10 minutes or more, usually at 100 ° C. or higher, preferably 200 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower) under a flow of an inert gas such as argon. (Preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) Drying by heating. Thereafter, under the flow of an inert gas containing NH ₃ (usually 10% or more, preferably 30% or more, 100% or less, or 90% or less NH ₃ concentration. High concentration reduces the firing time, but for safety reasons. The concentration may be lowered.) At a predetermined temperature (usually 300 ° C. or higher, preferably 400 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower) for a predetermined time (usually 10 minutes or longer, preferably 30 minutes or longer). (Typically 50 hours or less, preferably 30 hours or less) Tungsten nitride can be produced by heating. In this heating, a predetermined rate (usually 10 ° C./hr or more, preferably 20 ° C./hr or more) from a predetermined temperature (usually room temperature or higher, preferably 100 ° C. or higher, usually 600 ° C. or lower, preferably 400 ° C. or lower). As described above, heating is generally performed at a temperature of 600 ° C./hr or less, preferably 400 ° C./hr or less) to a predetermined temperature (usually 300 ° C. or more, preferably 400 ° C. or more, usually 1000 ° C. or less, preferably 800 ° C. or less). You can go. Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less.

Furthermore, tungsten nitride can be synthesized from an organic tungsten compound. Specifically, W (CO) ₃ (CH ₃ CN) ₃ is distributed under an inert gas containing NH ₃ (normally 10% or more, preferably 30% or more, 100% or less, or NH ₃ concentration of 90% or less). If the concentration is high, the firing time is shortened, but the concentration may be lowered for safety.) At a predetermined temperature (usually 200 ° C. or higher, preferably 300 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower). The tungsten nitride can be produced by heating for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less). In this heating, a predetermined rate (usually 10 ° C./hr or more, preferably 20 ° C./hr or more) from a predetermined temperature (usually room temperature or higher, preferably 100 ° C. or higher, usually 600 ° C. or lower, preferably 400 ° C. or lower). As described above, heating is generally performed at a temperature of 600 ° C./hr or less, preferably 400 ° C./hr or less) to a predetermined temperature (usually 300 ° C. or more, preferably 400 ° C. or more, usually 1000 ° C. or less, preferably 800 ° C. or less). You can go. Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less.

(2) Tungsten sulfide The shape of tungsten sulfide as a precursor compound is not particularly limited, and may be nanomaterials such as nanorods, nanotubes, nanotwists, nanoclusters, nanofibers, and sub-microcoils, in addition to those having no specific structure. . Moreover, there is no restriction | limiting in particular also about the synthesis method, It can carry out by well-known arbitrary methods. For example, “Journal of Materials Chemistry Vol. 12, p. 1450 (2002) states that W (CO) ₆ was sonicated in diphenylethane at 90 ° C. in an argon atmosphere in the presence of a slight excess of S. It is reported that WS ₂ nanorods are produced by heating at 800 ° C. in an argon atmosphere.

  In addition, the following method can also be employed.

W (CO) ₆ together with S in an organic medium (for example, alcohols such as ethanol, carbonyls such as acetone, ethers such as tetrahydrofuran, hydrocarbons such as toluene and xylene, chlorides such as methylene chloride) Dissolve or form a slurry, heat or reflux for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), and collect the precipitate by filtration or distillation of the solvent. If necessary, in order to further remove unreacted W (CO) ₆ , the precipitate is added to a predetermined amount of an organic solvent (for example, a nitrogen-containing organic solvent such as acetonitrile, alcohols such as ethanol, carbonyls such as acetone, tetrahydrofuran, etc. In ethers such as toluene, hydrocarbons such as toluene and xylene, chlorides such as methylene chloride) Predetermined time Te (usually 10 minutes or more, preferably 30 minutes or more, usually at most 50 hours, preferably 30 hours or less) performs heating or reflux, collecting the precipitate by hot filtration and the like. The obtained precipitate is passed through an inert gas such as argon at a predetermined temperature (usually 100 ° C or higher, preferably 200 ° C or higher, usually 1000 ° C or lower, preferably 800 ° C or lower) for a predetermined time (usually 10 minutes or longer). (Preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) Tungsten sulfide is obtained by drying by heating.

(3) Tungsten phosphide The method for synthesizing tungsten phosphide as a precursor compound is not particularly limited, and can be performed by any known method.

For example, “Studies in Surface Science and Catalysis” volume 143, page 247 (2002) includes (NH ₄ ) ₆ H ₂ W ₁₂ O ₄₀ · 18H ₂ O and (HN ₄ ) ₂ HPO ₄ , W and P Is dissolved in water so that the molar ratio thereof becomes 1: 1, and then water is distilled off, followed by heating under air circulation conditions, followed by heat reduction treatment under hydrogen circulation conditions to reduce WP. It is disclosed that it can be stabilized by forming a passive film by flowing 0.5% O ₂ / He gas at room temperature, but this method can also be adopted. .

  Specifically, a tungsten supply compound such as metatungstic acid and a phosphorus supply compound such as diammonium phosphate are mixed in an organic medium (for example, ethanol or the like) at a blending ratio corresponding to a desired molar ratio of tungsten phosphide. Alcohols, carbonyls such as acetone, ethers such as tetrahydrofuran, hydrocarbons such as toluene, chlorides such as methylene chloride) or aqueous media (for example, water, etc.), or dissolved or dispersed for a predetermined time (Normally 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) After standing, the solvent is removed by distillation or the like. Next, under a flow condition of oxygen atmosphere gas, at a predetermined temperature (usually 300 ° C. or more, preferably 400 ° C. or more, usually 1000 ° C. or less, preferably 800 ° C. or less) for a predetermined time (usually 10 minutes or more, preferably 30 minutes). As described above, heating is usually performed for 50 hours or less, preferably 30 hours or less, and then a predetermined temperature (usually 300 ° C. or higher, preferably 400 ° C. or higher, preferably 1000 ° C. or lower) under a reducing atmosphere (for example, under hydrogen gas flow). WP is preferably obtained by heating at 700 ° C. or less for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less). Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less.

  Among the conversion reaction from the raw material compound to the precursor compound, tungsten oxide or tungsten complex having a carbonyl ligand is used as the raw material compound, and tungsten nitride or tungsten sulfide obtained from this raw material compound is used as the precursor compound of tungsten carbide. It is preferable to use it as a raw material because the raw material is inexpensive and the reaction is easy.

[4] Conversion from precursor compound to tungsten carbide In the present invention, a compound selected from tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide, and tungsten silicide is used as a precursor compound, and this is used in the presence of a substrate or In the absence, it is preferable to convert hydrocarbons or further hydrogen into contact with them under predetermined heating conditions to convert them into tungsten carbide.

  In the case where tungsten carbide is obtained by bringing the precursor compound into contact with hydrocarbon or hydrocarbon and hydrogen in the presence of the substrate, the substrate may be used so as to have the above-mentioned suitable amount of tungsten carbide deposited on the substrate.

  The hydrocarbon is usually methane, ethane, propane, butane, ethylene, propylene, acetylene, preferably methane, ethane, ethylene or a mixed gas thereof, usually at 1 mL / min. Or more, preferably 5 mL / min. As described above, usually 500 mL / min. Hereinafter, preferably 400 mL / min. It is preferable to supply the following. If the hydrocarbon is less than the above lower limit, the carbonization reaction is difficult to proceed, and if it exceeds the upper limit, the amount of hydrocarbon gas not subjected to the reaction increases, which is not preferable for the reaction. By using hydrogen in combination, the effect of preventing the formation of a carbon layer on the surface of tungsten carbide can be obtained, but the use ratio is usually 5% or more, preferably the ratio of hydrocarbon in the mixed gas of hydrocarbon and hydrogen. It is preferable to supply 10% or more, usually 90% or less, preferably 30% or less. If the amount of hydrocarbon is less than the above lower limit, the carbonization reaction is difficult to proceed, and if it exceeds the above upper limit, an inactive carbon layer adheres to the tungsten carbide surface, which is not preferable for the reaction.

  The conversion reaction is usually performed at 500 ° C or higher, preferably 600 ° C or higher, usually 1200 ° C or lower, preferably 1000 ° C or lower. If the reaction temperature is lower than the lower limit, the carbonization reaction does not proceed easily. If the reaction temperature is higher than the upper limit, highly active tungsten carbide is difficult to obtain.

  While the reaction time varies depending on the reaction temperature, it is usually 10 minutes or longer, preferably 30 minutes or longer, usually 50 hours or shorter, preferably 30 hours or shorter. If this reaction time is shorter than the above lower limit, the reaction does not proceed completely, and if it is longer than the upper limit, highly active tungsten carbide is difficult to obtain.

  This heating is performed from a predetermined temperature (usually room temperature or higher, preferably 100 ° C. or higher, usually 600 ° C. or lower, preferably 400 ° C. or lower) to a predetermined speed (usually 10 ° C./hr or higher, preferably 20 ° C./hr or higher, usually The temperature may be raised to a predetermined temperature (usually 500 ° C. or more, preferably 600 ° C. or more, usually 1200 ° C. or less, preferably 1000 ° C. or less) at 600 ° C./hr or less, preferably 400 ° C./hr or less. After the formation of tungsten carbide, it is further performed for a predetermined time (usually several tens of minutes or more, preferably 30 minutes) in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of 5 wt% or less, especially 2 wt% or less). As described above, the passivation treatment for forming a passive film can be performed by treatment at a predetermined temperature (usually around room temperature) usually for 10 hours or less, particularly 5 hours or less.

  Hereinafter, a method for producing tungsten carbide from a precursor compound such as tungsten nitride in the absence of a substrate will be described more specifically, but the present invention is not limited to the following method.

(1) Conversion from tungsten nitride to tungsten carbide There is no particular limitation on the synthesis method for providing tungsten carbide used in the present invention from tungsten nitride, and any known method can be used. For example, in “Applied Catalysis A: General”, 183, page 253 (1999), W ₂ N was started to be heated at 25 ° C. under a flow of methane and hydrogen, and the heating temperature was increased at a rate of 60 ° C. per hour. It is disclosed that WC _1-x can be produced by heating at a final temperature of 750 ° C., and that it can be stabilized by forming a passive film by flowing 1% O ₂ / He gas at room temperature. However, this method can also be adopted.

  In addition, tungsten nitride is used in a predetermined hydrocarbon gas (usually methane, ethane, propane, butane, ethylene, propylene, acetylene, preferably methane, ethane, ethylene) or a mixed gas thereof and hydrogen gas (usually a mixed gas). The mixing ratio of the hydrocarbon gas is usually 5% or more, preferably 10% or more, usually 90% or less, preferably 30% or less), a predetermined temperature (usually 500 ° C or more, preferably 600 ° C or more, usually 1000 ° C). Tungsten carbide can be produced by heating for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, preferably 50 minutes or less, preferably 30 hours or less) preferably at 900 ° C. or less. In this heating, as described above, a predetermined rate (usually 10 ° C./hr or more, preferably 100 ° C. or more, preferably 600 ° C. or less, preferably 400 ° C. or less), from a predetermined temperature (usually 10 ° C./hr or more, preferably 20 ° C / hr or higher, usually 600 ° C / hr or lower, preferably 400 ° C / hr or lower) to a predetermined temperature (usually 500 ° C or higher, preferably 600 ° C or higher, usually 1000 ° C or lower, preferably 900 ° C or lower). You may heat with temperature. Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less.

(2) Conversion from tungsten sulfide to tungsten carbide There is no particular limitation on the synthesis method for providing tungsten carbide used in the present invention from tungsten sulfide, and any method can be used.

  Specifically, tungsten sulfide is converted into a predetermined hydrocarbon gas (usually methane, ethane, propane, butane, ethylene, propylene, acetylene, preferably methane, ethane, ethylene) or a mixed gas thereof and hydrogen gas (usually The mixing ratio of the hydrocarbon gas in the mixed gas is usually 5% or more, preferably 10% or more, usually 90% or less, preferably 30% or less), a predetermined temperature (usually 550 ° C. or more, preferably 650 ° C. or more, Tungsten carbide can be generated by heating for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) at 1100 ° C. or less, preferably 1000 ° C. or less. . In this heating, as described above, a predetermined rate (usually 10 ° C./hr or more, preferably 100 ° C. or more, preferably 600 ° C. or less, preferably 400 ° C. or less), from a predetermined temperature (usually 10 ° C./hr or more, preferably 20 ° C / hr or more, usually 600 ° C / hr or less, preferably 400 ° C / hr or less) to a predetermined temperature (usually 550 ° C or more, preferably 650 ° C or more, usually 1100 ° C or less, preferably 1000 ° C or less) You may heat with temperature. Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less.

(3) Conversion from tungsten phosphide to tungsten carbide There is no particular limitation on the synthesis method for providing tungsten carbide used in the present invention from tungsten phosphide, and any method can be used. Tungsten carbide can be obtained under the same reaction conditions as the conversion reaction to tungsten.

[5] Production of Tungsten Carbide / Substrate-Deposited Catalyst When producing the DMFC catalyst of the present invention in which tungsten carbide is deposited on a substrate, the timing for applying the substrate in the synthesis process of tungsten carbide is arbitrary. For example, the following method is mentioned.
(1) After the substrate is mixed with the raw material compound, the conversion reaction of the raw material compound to the precursor compound is performed, and then the conversion reaction of the precursor compound to tungsten carbide is further performed.
(2) After mixing the substrate with the precursor compound, the conversion reaction of the precursor compound to tungsten carbide is performed.
(3) After preparing the tungsten carbide, the substrate is mixed with the tungsten carbide, and further subjected to a firing treatment or the like as desired.

In the case of (1) above, for example, after dissolving the raw material compound in a solvent such as an aqueous solution, dissolved or dispersed in a solvent such as an aqueous solution together with the substrate, and after removing the solvent, if necessary, under an inert gas flow Then, drying is performed by heating at a desired temperature and time, and then W ₂ N supported on the substrate can be obtained by heating under a flow of NH ₃ . Furthermore, by heating at a desired temperature and time under a flow of hydrocarbon gas and hydrogen, a DMFC catalyst in which tungsten carbide disclosed in the present invention is deposited on a substrate is produced. Further, a passivation treatment may be performed in which a passivation film is formed by processing at a predetermined temperature and time (usually around room temperature) in an inert gas atmosphere having a desired low oxygen concentration.

_{Specifically, (NH 4)} a _{10 W 12 O 41 · 5H 2} O, organic medium (e.g., alcohols such as ethanol, carbonyl such as acetone, ethers such as tetrahydrofuran, hydrocarbons such as toluene, Chlorides such as methylene chloride) or in an aqueous medium (for example, water), and if necessary, add a desired amount of HCl for complete dissolution, or make a slurry, and add carbon black A predetermined amount of the substrate is mixed and allowed to stand for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), and then the solvent is removed by distillation or the like. If necessary, a predetermined temperature (usually 10 minutes or more, usually at 100 ° C. or higher, preferably 200 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower) under a flow of an inert gas such as argon. (Preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) Drying by heating. Thereafter, under the flow of an inert gas containing NH ₃ (usually 10% or more, preferably 30% or more, 100% or less, or 90% or less NH ₃ concentration. High concentration reduces the firing time, but for safety reasons. The concentration may be lowered.) At a predetermined temperature (usually 300 ° C. or higher, preferably 400 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower) for a predetermined time (usually 10 minutes or longer, preferably 30 minutes or longer). (Typically 50 hours or less, preferably 30 hours or less) By heating, tungsten nitride can be generated and supported on the substrate. In this heating, a predetermined rate (usually 10 ° C./hr or more, preferably 20 ° C./hr or more) from a predetermined temperature (usually room temperature or higher, preferably 100 ° C. or higher, usually 600 ° C. or lower, preferably 400 ° C. or lower). As described above, heating is generally performed at a temperature of 600 ° C./hr or less, preferably 400 ° C./hr or less) to a predetermined temperature (usually 300 ° C. or more, preferably 400 ° C. or more, usually 1000 ° C. or less, preferably 800 ° C. or less). You can go.

  Next, tungsten nitride is mixed with a predetermined hydrocarbon gas (usually methane, ethane, propane, butane, ethylene, propylene, acetylene, preferably methane, ethane, ethylene) or a mixed gas thereof and hydrogen gas (usually mixed). The mixing ratio of hydrocarbon gas in the gas is usually 5% or more, preferably 10% or more, usually 90% or less, preferably 30% or less), a predetermined temperature (usually 500 ° C. or more, preferably 600 ° C. or more, usually 1000). Tungsten carbide is deposited on the substrate by heating at a temperature of ℃ or less, preferably 900 ℃ or less for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less). The resulting DMFC catalyst is produced. In this heating, as described above, a predetermined rate (usually 10 ° C./hr or more, preferably 100 ° C. or more, preferably 600 ° C. or less, preferably 400 ° C. or less), from a predetermined temperature (usually 10 ° C./hr or more, preferably 20 ° C / hr or higher, usually 600 ° C / hr or lower, preferably 400 ° C / hr or lower) to a predetermined temperature (usually 500 ° C or higher, preferably 600 ° C or higher, usually 1000 ° C or lower, preferably 900 ° C or lower). You may heat with temperature. Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less.

In addition, WO ₃ and other tungsten compounds are physically mixed with a carrier such as carbon black in a predetermined amount, and when necessary, a predetermined temperature (usually 100 ° C. or higher, preferably 200 ° C. or higher, usually 1500 under oxygen-containing gas flow conditions). ° C. or less, preferably 1000 ° C. or less) a predetermined time (usually 10 minutes or more, not preferably 30 minutes or more, usually at most 50 hours, preferably 30 hours or less) was heated, as above, the NH ₃ By heating under active gas flow, tungsten nitride can be generated and supported on the substrate. This heating may be performed by raising the temperature. Next, in the same manner as described above, a DMFC catalyst in which tungsten carbide is deposited on a substrate is produced by heating at a predetermined temperature and for a predetermined time under a flow of hydrocarbon gas and hydrogen. This heating may be performed by raising the temperature. Further, a passivation treatment may be performed in which a passivation film is formed by processing at a predetermined temperature and time (usually around room temperature) in an inert gas atmosphere having a desired low oxygen concentration.

[6] Manufacture of a catalyst containing other catalyst components, etc. When the DMFC catalyst of the present invention containing other catalyst components, etc. is manufactured, other catalyst components, etc. or other catalyst components, etc. Although there is no particular limitation on the timing of applying the substance to be generated (hereinafter referred to as “other catalyst component etc. source”), the following method is usually employed.
(1) After mixing other catalyst components and the like with tungsten carbide, mixing with the substrate is performed.
(2) After mixing other sources of catalyst components and the like with tungsten carbide, a reduction treatment or a firing treatment is performed, followed by mixing with the substrate.
(3) After preparing the tungsten carbide deposited on the substrate, other catalyst components and the like are mixed.
(4) After preparing what tungsten carbide adhere | attached on the base | substrate, after mixing other sources, such as a catalyst component, a reduction process or a calcination process is given.

  Among these, the methods (1) and (2) are preferred because they are expected to have a large amount of other catalyst components and the like deposited on the catalyst surface.

  Other sources such as catalyst components include the above transition metal oxides, inorganic acid salts such as nitrates, sulfates and carbonates, organic acid salts such as acetates, halides, hydrides, and carbonyl compounds. , Amine compounds, olefin coordination compounds, phosphine coordination compounds or phosphite coordination compounds. Preferred are oxides, carbonates, organic acid salts, carbonyl compounds, and olefin coordination compounds that do not contain halogen elements or nitrogen elements.

  When the method (2) is performed, for example, a compound selected from tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide, and tungsten silicide is used as a precursor compound, and this is performed in the absence of a substrate. Add the hydrocarbon or tungsten carbide obtained by further contacting the hydrocarbon under the heating conditions of the above to a solution such as an aqueous solution in which a chloride of a transition metal as a source of other catalyst components is dissolved or dispersed. After removing the solvent, if necessary, it is dried by heating at a desired temperature and time under an inert gas flow, and then heated at a desired temperature and time under a hydrogen flow. Then, a catalyst is produced in which other sources such as catalyst components are deposited on tungsten carbide. Further, a passivation treatment may be performed in which a passivation film is formed by processing at a predetermined temperature and time (usually around room temperature) in an inert gas atmosphere having a desired low oxygen concentration. Next, the obtained tungsten carbide to which the other source of the catalyst component is deposited is mixed together with the base in a mortar.

More specifically, the WC catalyst synthesized by the above method is converted into an organic medium in which H ₂ PtCl ₄ is dissolved or in a slurry state (for example, alcohols such as ethanol, carbonyls such as acetone, tetrahydrofuran, etc. Ethers, hydrocarbons such as toluene, chlorides such as methylene chloride), or an aqueous medium (for example, water, etc.), and a predetermined amount mixed, for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, (Normally 50 hours or less, preferably 30 hours or less) After standing, the solvent is removed by distillation or the like. If necessary, a predetermined temperature (usually 10 minutes or more, usually at 100 ° C. or higher, preferably 200 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower) under a flow of an inert gas such as argon. (Preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less) Drying by heating. Next, under a hydrogen gas flow, at a predetermined temperature (usually 100 ° C. or more, preferably 200 ° C. or more, usually 1000 ° C. or less, preferably 900 ° C. or less) for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, (Normally 50 hours or less, preferably 30 hours or less) By heating, a DMFC catalyst in which Pt is deposited on tungsten carbide is produced. In this reduction process by hydrogen circulation, a predetermined rate (usually 10 ° C./hr or more, preferably 100 ° C. or more, preferably 600 ° C. or less, preferably 400 ° C. or less) from a predetermined temperature (usually room temperature or more, preferably 100 ° C. or more, preferably 400 ° C. or less, preferably 400 ° C. or less, 20 ° C / hr or higher, usually 600 ° C / hr or lower, preferably 400 ° C / hr or lower) to a predetermined temperature (usually 200 ° C or higher, preferably 300 ° C or higher, usually 1000 ° C or lower, preferably 900 ° C or lower). You may heat with temperature. Furthermore, in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5% by weight or less, especially about 2% by weight or less), a predetermined time (usually several minutes or more, preferably 30 minutes or more, usually 10 hours or less). In particular, a passivation treatment for forming a passivation film can be performed by treating at a predetermined temperature (usually around room temperature) for 5 hours or less. Next, the obtained tungsten carbide to which the other source of the catalyst component is deposited is mixed together with the base in a mortar.

[7] Surface treatment of catalyst The catalyst activity can be further improved by heating the catalyst of the present invention under a hydrogen flow to perform a reduction treatment. This is because the inactive carbon layer adhering to the catalyst surface is removed as CH ₄ or the like, and the active WC surface is exposed.

  Hydrogen to be circulated may be circulated only with hydrogen, or may be circulated together with an inert gas such as argon or nitrogen. The hydrogen to be circulated is usually 1 mL / min. Or more, preferably 5 mL / min. As described above, usually 500 mL / min. Hereinafter, preferably 400 mL / min. It is preferable to supply the following. If the amount of hydrogen to be circulated is less than the above lower limit, removal of the inactive carbon layer attached to the catalyst surface is difficult to proceed, and if it is higher than the above upper limit, the amount of hydrogen gas not subjected to the reaction increases, which is not preferable for the treatment. .

  The treatment temperature depends on the particle size of the catalyst and the nature of the attached carbon layer, but is usually 100 ° C. or higher, preferably 200 ° C. or higher, usually 1200 ° C. or lower, preferably 1000 ° C. or lower. When the treatment temperature is lower than the lower limit, removal of the inactive carbon layer attached to the catalyst surface is difficult to proceed, and when the treatment temperature is higher than the upper limit, desorption of carbon from the catalyst WC itself proceeds. Decreases.

  The treatment time varies depending on the treatment temperature, but is usually 5 minutes or more, preferably 10 minutes or more, usually 50 hours or less, preferably 30 hours or less. If this treatment time is shorter than the above lower limit, the reaction is difficult to proceed completely, and if it is longer than the upper limit, it becomes difficult to obtain a highly active catalyst.

Moreover, catalytic activity can also be improved by making the catalyst of this invention contact alkaline solutions, such as sodium hydroxide aqueous solution and ammonia water. This is due to a decrease in the inactive WO ₂ layer present on the catalyst surface.

  This alkali treatment is preferably carried out by charging the catalyst into an alkali solution and maintaining it under reflux conditions. The treatment time varies depending on the type of alkali used, but is usually 5 minutes or more, preferably 10 minutes. As described above, it is usually 50 hours or less, preferably 30 hours or less. If this treatment time is shorter than the above lower limit, the reaction is difficult to proceed completely, and if it is longer than the upper limit, it becomes difficult to obtain a highly active catalyst.

  Furthermore, by performing the reduction treatment in combination with the alkali treatment, the WC component advantageous for exhibiting high catalytic activity for the oxidation reaction (1) of the aqueous methanol solution described above can be more effectively exposed to the catalyst surface. Can do.

[DMFC electrode material and DMFC]
The electrode material for DMFC of the present invention has a catalyst layer containing the above-described catalyst for DMFC of the present invention. The catalyst layer containing the catalyst for DMFC of the present invention is placed on an ion exchange membrane, on an anode fuel diffusion layer, It is formed on a cathode gas diffusion layer or a transfer film.

  The DMFC of the present invention is a power generator that supplies an aqueous methanol solution as a fuel to the anode as described above, supplies an oxidant (usually air) to the cathode, extracts a potential difference between the anode and the cathode as a voltage, and supplies it to a load. It consists of an anode and a cathode and an electrolyte sandwiched between them, and an ion exchange membrane is used as the electrolyte. That is, an electrolyte membrane / electrode assembly is used in which a catalyst layer is formed on both surfaces of an ion exchange membrane as an electrolyte, and an anode fuel diffusion layer and a cathode gas diffusion layer are integrally formed on the outside of the catalyst layer. The electrolyte membrane / electrode assembly is provided with a partition plate on the diffusion layer side, and a plurality of unit cells including the partition plate, the electrolyte membrane / electrode assembly, and the partition plate are stacked until a desired voltage is obtained according to the application. To form a DMFC stack. Usually, several to hundreds of unit cells are stacked to form a DMFC stack.

  In the DMFC of the present invention, the aforementioned DMFC catalyst of the present invention is used as a catalyst for forming the catalyst layer of the electrolyte membrane / electrode assembly. The DMFC catalyst of the present invention can be used as an anode electrode catalyst or a cathode electrode catalyst.

  An ion exchange membrane as an electrolyte may have a cation exchange capacity, but it is practically desired to withstand an oxidation-reduction atmosphere at a temperature of about 80 to 100 ° C., which is the use temperature of DMFC. Sulfonic acid resins are exclusively used. Specific examples include perfluoroalkylsulfonic acid resin membranes such as Nafion (registered trademark manufactured by DuPont), Flemion (registered trademark manufactured by Asahi Glass Co., Ltd.), and Aciplex (registered trademark manufactured by Asahi Kasei Co., Ltd.).

  As the thickness of the ion exchange membrane, a thickness of about 10 μm or more and about several 100 μm or less is used, but it is desirable to make the thickness thinner in order to lower the electric resistance. Taking Nafion as an example, Nafion 115 having a thickness of about 120 μm is often used. However, an electrolyte having a thickness of 30 to 50 μm has begun to be developed, and these can be used in the same manner.

  As the constituent material of the diffusion layer, the anode has a methanol aqueous solution, the cathode supplies air, and also has a function as a current collector for taking out the generated voltage. A material is selected that allows both air and air to flow and withstands the working atmosphere. As a material constituting the anode fuel diffusion layer and the cathode gas diffusion layer, a carbon porous body such as carbon paper or carbon cloth having a thickness of usually about 100 to 500 μm, preferably about 100 to 200 μm is used.

  When the electrolyte membrane / electrode assembly is used for DMFC, a partition plate made of a material such as carbon, or in some cases, stainless steel or titanium is usually disposed behind the aqueous methanol solution and air so that the aqueous methanol solution and air are not mixed behind it. In general, the partition plate is formed with grooves for the purpose of uniform and stable supply of an aqueous methanol solution and air.

  The method for producing an electrolyte membrane / electrode assembly of DMFC by forming a catalyst layer using the DMFC catalyst of the present invention is not particularly limited, and examples thereof include the following methods.

  Although there is no restriction | limiting in particular about the method of producing a cathode side catalyst layer and an anode side catalyst layer, For example, it can produce as follows. First, the DMFC catalyst of the present invention formed by depositing tungsten carbide on a substrate is placed in a suitable container and dispersed in a medium such as alcohol or water to prepare a catalyst slurry. At this time, it is more preferable to apply ultrasonic vibration in order to promote the dispersion well. In order to obtain a desired dispersibility, the catalyst concentration for DMFC of the present invention in the catalyst slurry is preferably about 1 to 50 g / L. In addition, a binder such as polytetrafluoroethylene (PTFE) can be added to the slurry in the range of about 3 to 30% by weight for the purpose of imparting water repellency and preventing peeling of the catalyst layer. When the contents are agglomerated and made into a paste, alcohol having 2 to 5 carbon atoms, preferably about 2 to 4 carbon atoms such as ethanol and isopropyl alcohol, is used in a ratio of 0.25 to 1.0 with respect to water. In addition, it can be aggregated.

  The catalyst slurry thus obtained may be dried in layers to form the cathode side catalyst layer and the anode side catalyst layer of the electrolyte membrane / electrode assembly. As the method, for example, the catalyst layer may be an ion exchange membrane. Examples thereof include a method in which the anode fuel diffusion layer and the cathode gas diffusion layer are laminated after being formed thereon, and a method in which the catalyst layer is formed on the anode fuel diffusion layer and the cathode gas diffusion layer and then laminated with the ion exchange membrane.

Specifically, the cathode side catalyst layer and the anode side catalyst layer are respectively formed on the ion exchange membrane, the anode fuel diffusion layer, or the cathode gas diffusion layer by the following methods.
(1) The catalyst slurry is sprayed onto the ion exchange membrane to be used and dried.
(2) The catalyst slurry is sprayed onto a diffusion layer material such as carbon paper and dried.
(3) The catalyst slurry is sprayed onto a transfer film material such as a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) film (development treatment) and dried, and the surface opposite to the transfer film surface is made of Nafion, etc. The catalyst layer is transferred onto the desired ion exchange membrane by appropriately pressing.
(4) As in (3), after spreading the catalyst slurry on the FEP film, the slurry is covered with a diffusion layer material such as carbon paper and dried.

Both the cathode-side catalyst layer and / or the anode-side catalyst layer are typically 0.01 mg / cm ² or more, preferably 0.1 mg / cm ² or more, and usually 20 mg / cm ² or less, as tungsten carbide adhesion amount (weight per unit area). Preferably, it is formed so as to have an amount of about 5 mg / cm ² or less. If the tungsten carbide adhesion amount is less than the above lower limit, sufficient catalytic activity cannot be obtained, and if it exceeds the upper limit, it is difficult to form an electrolyte membrane / electrode assembly.

  After each forming step of the cathode side catalyst layer and the anode side catalyst layer, preliminary pressure molding is appropriately performed, and then the final electrolyte membrane / electrode assembly, that is, the surface on one side of the ion exchange membrane is described above. A cathode side catalyst layer is formed, an anode side catalyst layer is formed on the opposite side of the ion exchange membrane, and an anode fuel diffusion layer and a cathode gas diffusion layer constituting the anode and the cathode are respectively formed on the outside of both catalyst layers. An electrolyte membrane / electrode assembly is produced by press-heating (main molding) using a press so as to be laminated.

  In addition, as conditions for preliminary pressure molding, it is preferable to set the temperature and pressure lower and the time shorter than the conditions of the main molding to be performed later within the range in which the collapse of the catalyst layer can be prevented. This is because the catalyst particles and the porous body for each diffusion layer do not cause compressive fracture.

  The DMFC system using the DMFC of the present invention includes a DMFC stack that obtains an electromotive force by an electrochemical reaction, a compressor that supplies compressed air as an oxygen-containing gas, and a methanol aqueous solution container as a fuel. The aqueous methanol solution is sent to the anode electrode of the DMFC stack by a feed pump. The aqueous methanol solution may be supplied to the anode electrode after being heated and vaporized by an evaporator in advance. In addition, a methanol aqueous solution that has not been used for power generation in the DMFC stack may be collected and returned to the methanol aqueous solution container. The methanol aqueous solution may be collected using a gas-liquid separator as necessary.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited by a following example, unless the summary is exceeded.

  In the following examples and comparative examples, the performance (catalytic activity) of the produced anode electrode was measured by the following cyclic voltammetry (CV) measurement.

[CV measurement]
Cyclic voltammetry (CV) measurement was performed under the condition that methanol (CH ₃ OH) was not rate-controlled while bubbling nitrogen into the electrolytic solution using a stopper capable of keeping hermeticity in the electrolytic cell. The measurement conditions are as follows.
Electrolytic solution: 2.0 M CH ₃ OH, 1.0 M H ₂ SO ₄ aqueous solution Scanning speed: 10 mV / sec Scanning range: 100 to 800 mV
Counter electrode: Pt
Reference electrode: Standard hydrogen electrode (SHE)

If the potential of the electrode is made noble with respect to the standard hydrogen electrode, CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ between the working electrode and the Pt counter electrode.
It is recognized that the hydrogen oxidation current due to. When scanning in your direction, measure the current value that flows at 700 mV (SHE standard), and convert the measured current value to the current value per total weight (1 g) of Pt and WC contained in the catalyst. The catalytic activity was evaluated.

[Example 1]
<Synthesis of WC>
0.7 g of WCl ₄ manufactured by Kishida Chemical Co., Ltd. was put in a quartz baking tube and NH ₃ gas 30 ml / min. Then, the temperature was increased from 300 to 630 ° C. over 5 hours at a temperature increase rate of 66 ° C./hr, and further maintained at 630 ° C. for 0.5 hr for reduction and nitriding to obtain a W ₂ N black powder. 1.0 g of W ₂ N thus obtained was put in a quartz tube, and 70 ml / min. Of a mixed gas of CH ₄ / H ₂ (mixing ratio 2/8). Then, the mixture was reduced and carbonized at 777 ° C. for 7 hours to obtain an α-WC black powder. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed by XRD analysis to have an α-WC structure (the values of 2θ gave peaks at 31.551 °, 35.744 °, 48.200 °, and 64.639 °). . The half width of the 48.200 ° peak was 1.852 °.

<Synthesis of Pt-WC>
A catalyst solution prepared by dissolving 0.85 g of H ₂ PtCl ₄ manufactured by NE Chemcat in 10 ml of demineralized water was added to 0.2 g of WC obtained by the above synthesis method, and 1 ml and 5 ml of demineralized water were added and left overnight. Water was removed with an evaporator. The dried product was dried at 200 ° C. under an argon stream for 3 hours. After cooling to room temperature, it was switched from argon to hydrogen and reduced at 350 ° C. for 1.5 hr. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.598 °, 35.598 °, 39.758 ° (Pt), 46.352 ° (Pt). , 48.051 °, 64.798 °, 67.598 ° (Pt). The half width of the peak at 48.051 ° was 1.892 °.
The ratio of Pt to WC was 10% by weight of Pt and 90% by weight of WC based on the raw material charge.

<Creation of anode electrode>
10 mg of α-WC powder coated with Pt obtained by the above synthesis method and 90 mg of carbon black (VULCAN XC-72R (manufactured by Cabot, specific surface area (BET) 254 m ² / g)) are mixed in a mortar, and After 42.41 mg was mixed with 5 mL of ethanol and sufficiently stirred with an ultrasonic cleaner, the amount of tungsten carbide deposited (weight per unit, hereinafter referred to as “α-WC carrying amount”) was 0.03 mg with a microsyringe. The solution was dropped onto a glassy carbon electrode as a working electrode so as to be / cm ² and dried by being left standing. Next, a commercially available Nafion solution in which a Nafion membrane manufactured by DuPont was dissolved in a solvent was dropped, dried by standing, and then further dried under vacuum to obtain an anode electrode.
CV measurement was performed on this anode electrode, and the evaluation results of catalyst activity are shown in Table 1.
The average particle diameters of WC and Pt calculated from the half width of XRD are also shown.

[Example 2]
<Synthesis of WC>
1.0 g WO ₃ manufactured by Kishida Chemical Co., Ltd. was put in a quartz tube and NH ₃ gas 30 ml / min. Then, the temperature was increased from 300 to 630 ° C. over 7 hours at a temperature increase rate of 49 ° C./hr, and further maintained at 630 ° C. for 0.5 hr for reduction and nitriding to obtain a W ₂ N black powder. 1.0 g of W ₂ N thus obtained was put in a quartz tube, and 70 ml / min. Of a mixed gas of CH ₄ / H ₂ (mixing ratio 2/8). Was reduced and carbonized at 777 ° C. for 6 hours to obtain an α-WC black powder. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed by XRD analysis to have an α-WC structure (2θ values peaked at 31.649 °, 35.801 °, 48.251 °, and 65.598 °). . The half width of the 48.251 ° peak was 1.888 °.

<Synthesis of Pt-WC>
Instead of α-WC synthesized in Example 1, α-WC obtained by depositing Pt was obtained in the same manner as in Example 1 except that α-WC obtained by the above synthesis method was used.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.502 °, 35.750 °, 39.801 ° (Pt), 46.349 ° (Pt). 48.204 °, 65.251 ° and 67.511 ° (Pt). The half width of the 48.204 ° peak was 1.800 °.

<Creation of anode electrode>
In place of α-WC coated with Pt used in Example 1, α-WC coated with Pt obtained by the above synthesis method was used in the same manner as in Example 1 to the electrode. An anode electrode was prepared so that the amount of α-WC supported by the Pt was 0.03 mg / cm ² , evaluated in the same manner, and the results are shown in Table 1. The average particle diameters of WC and Pt calculated in the same manner are also shown.

[Example 3]
<Synthesis of WC>
When Aldrich W (CO) ₆ 4.22 g, Kishida S 0.832 g and xylene 80 ml were placed in a glass Kolbe and refluxed for 4 hours with stirring, black particles were precipitated. After completion of the reaction, the precipitate was collected by filtration. Further, in order to remove unreacted W (CO) ₆ , the precipitate was refluxed with 60 ml of CH ₃ CN for 2 hours, followed by hot filtration. The obtained precipitate was finally heat-treated at 350 ° C. for 3 hours under an argon stream to obtain WS ₂ . 0.5 g of WS ₂ obtained in this way was put in a quartz firing tube, and 70 ml / min. Of a mixed gas of CH ₄ / H ₂ (mixing ratio 2/8). The carbon was reduced and carbonized at 900 ° C. for 7 hours under an air current of α to obtain a black powder of α-WC. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed by XRD analysis to have an α-WC structure (2θ values were peaks at 31.500 °, 35.501 °, 48.200 °, 63.849 °). . The half width of the peak at 48.200 ° was 1.912 °.

<Synthesis of Pt-WC>
Instead of α-WC synthesized in Example 1, α-WC obtained by depositing Pt was obtained in the same manner as in Example 1 except that α-WC obtained by the above synthesis method was used.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.551 °, 35.452 °, 39.899 ° (Pt), 46.400 ° (Pt). 48.150 °, 63.703 °, and 67.555 ° (Pt)). The half width of the peak at 48.150 ° was 2.105 °.

<Creation of anode electrode>
In place of α-WC coated with Pt used in Example 1, α-WC coated with Pt obtained by the above synthesis method was used in the same manner as in Example 1 to the electrode. An anode electrode was prepared so that the amount of α-WC supported by the Pt was 0.03 mg / cm ² , evaluated in the same manner, and the results are shown in Table 1. The average particle diameters of WC and Pt calculated in the same manner are also shown.

[Example 4]
<Synthesis of WC>
1.0 g WO ₃ manufactured by Kishida Chemical Co., Ltd. was placed in a quartz firing tube, and argon 80 ml / min. H ₂ 20 ml / min. H ₂ S 20 ml / min. Then, the temperature was raised and treated at 850 ° C. for 2.0 hours. 0.3 g of WS ₂ obtained in this way was put in a quartz-made calcining tube, and a mixed gas of CH ₄ / H ₂ (mixing ratio 2/8) was 70 ml / min. Was reduced and carbonized at 850 ° C. for 15 hours to obtain an α-WC black powder. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ gave peaks at 31.351 °, 35.402 °, 48.252 °, 63.652 °). . The half width of the 48.252 ° peak was 1.970 °.

<Synthesis of Pt-WC>
Instead of α-WC synthesized in Example 1, α-WC obtained by depositing Pt was obtained in the same manner as in Example 1 except that α-WC obtained by the above synthesis method was used.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.447 °, 35.499 °, 39.803 ° (Pt), 46.306 ° (Pt). , 48.101 °, 63.601 °, 67.760 ° (Pt). The half width of the peak at 48.101 ° was 1.931 °.

<Creation of anode electrode>
In place of α-WC coated with Pt used in Example 1, α-WC coated with Pt obtained by the above synthesis method was used in the same manner as in Example 1 to the electrode. An anode electrode was prepared so that the amount of α-WC supported by the Pt was 0.03 mg / cm ² , evaluated in the same manner, and the results are shown in Table 1. The average particle diameters of WC and Pt calculated in the same manner are also shown.

[Example 5]
<Synthesis of WC>
0.6 g (nanopowder, catalog number 55,008-6) of WO ₃ manufactured by Aldrich was put in a quartz baking tube, and argon 80 ml / min. H ₂ S 20 ml / min. Then, the temperature was raised and baked at 820 ° C. for 2.0 hours. 0.3 g of WS ₂ obtained in this way was put in a quartz-made calcining tube, and a mixed gas of CH ₄ / H ₂ (mixing ratio 2/8) was 70 ml / min. Was reduced and carbonized at 840 ° C. for 15 hours to obtain an α-WC black powder. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed to have an α-WC structure by XRD analysis (the values of 2θ gave peaks at 31.449 °, 35.502 °, 48.250 ° and 63.851 °). . The half width of the peak at 48.250 ° was 1.773 °.

<Synthesis of Pt-WC>
Instead of α-WC synthesized in Example 1, α-WC obtained by depositing Pt was obtained in the same manner as in Example 1 except that α-WC obtained by the above synthesis method was used.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.793 °, 35.500 °, 39.797 ° (Pt), 46.354 ° (Pt) 48.150 °, 63.559 °, and 67.502 ° (Pt). The half width of the peak at 48.150 ° was 1.970 °.

<Creation of anode electrode>
In place of α-WC coated with Pt used in Example 1, α-WC coated with Pt obtained by the above synthesis method was used in the same manner as in Example 1 to the electrode. An anode electrode was prepared so that the amount of α-WC supported by the Pt was 0.03 mg / cm ² , evaluated in the same manner, and the results are shown in Table 1. The average particle diameters of WC and Pt calculated in the same manner are also shown.

[Example 6]
<Synthesis of WC>
(NH ₄ ) ₂ WS ₄ (manufactured by Aldrich) 0.7 g was put in a quartz baking tube, and 25 ml / min. In a glass reaction tube filled with thiophene. While the _{H 2} was bubbled, 600 ° C. with _{H 2} introduced into the quartz tube by entraining thiophene was 0.5hr reaction. The obtained WS ₂ was put into a quartz fired tube, and a CH ₄ / H ₂ (2/8) gas of 70 ml / min. In an air stream, reduction and carbonization were performed at 840 ° C. for 30 hours to obtain an α-WC black powder. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed by XRD analysis to have an α-WC structure (2θ values were peaks at 31.500 °, 35.501 °, 48.101 °, and 64.001 °). . The half width of the peak at 48.101 ° was 1.773 °.

<Synthesis of Pt-WC>
Instead of α-WC synthesized in Example 1, α-WC obtained by depositing Pt was obtained in the same manner as in Example 1 except that α-WC obtained by the above synthesis method was used.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.364 °, 35.599 °, 39.801 ° (Pt), 46.199 ° (Pt). 48.152 °, 64.046 ° and 67.557 ° (Pt). The half width of the 48.152 ° peak was 2.488 °.

<Creation of anode electrode>
In place of α-WC coated with Pt used in Example 1, α-WC coated with Pt obtained by the above synthesis method was used in the same manner as in Example 1 to the electrode. An anode electrode was prepared so that the amount of α-WC supported by the Pt was 0.03 mg / cm ² , evaluated in the same manner, and the results are shown in Table 1. The average particle diameters of WC and Pt calculated in the same manner are also shown.

[Comparative Example 1]
<Synthesis of WC>
1.2 g of WO ₃ manufactured by Kishida Chemical Co., Ltd. was put in a quartz tube and 70 ml / min. Of a mixed gas of CH ₄ / H ₂ (mixing ratio 2/8). Then, reduction and carbonization were performed at 877 ° C. for 6 hours to obtain an α-WC black powder. After cooling to room temperature, the inside of the firing tube was replaced with argon gas, and then the mixture was passivated with 2% O ₂ -98% N ₂ mixed gas for 1.5 hr and taken out into the air.

  This compound was confirmed to have an α-WC structure by XRD analysis (the values of 2θ peaked at 31.404 °, 35.652 °, 48.254 °, and 64.278 °). . The half width of the peak at 48.254 ° was 0.570 °.

<Synthesis of Pt-WC>
Α-WC coated with Pt was obtained in the same manner as in Example 1 except that α-WC synthesized in Comparative Example 1 was used instead of α-WC synthesized in Example 1.

  This compound was confirmed by XRD analysis to have an α-WC structure (values of 2θ were 31.401 °, 35.605 °, 39.800 ° (Pt), 40.342 °, 46. 253 ° (Pt), 48.254 °, 58.311 °, 64.350 ° and 67.690 ° (Pt). The half width of the 48.254 ° peak was 0.566 °.

<Creation of anode electrode>
In place of α-WC coated with Pt used in Example 1, α-WC coated with Pt obtained by the above synthesis method was used in the same manner as in Example 1 to the electrode. An anode electrode was prepared so that the amount of α-WC supported by the Pt was 0.03 mg / cm ² , evaluated in the same manner, and the results are shown in Table 1. The average particle diameters of WC and Pt calculated in the same manner are also shown.

As is clear from Table 1, among Examples, Examples 3 to 6 synthesized via Pt / WC and WS ₂ of Example 1 and Example 2 synthesized via W ₂ N were used. Compared with Pt / WC of Comparative Example 1 synthesized from WO ₃ , Pt / WC has a peak FWHM of 48.051 ° to 48.204 °, and the catalytic activity is clearly improved. Yes.

From Example _1~6, W 2 _N, a WC which has been synthesized via the specific precursor compounds such as WS ₂ by use with Pt, it can be seen that the higher the anode catalytic activity for methanol solution is obtained.

  According to the present invention, since a highly efficient direct methanol fuel cell using a highly active catalyst is provided, its practical use is promoted.

Claims (8)

In direct methanol fuel cell using methanol aqueous solution as fuel,
A direct methanol characterized by using a catalyst containing as a catalyst component tungsten carbide obtained by conversion from a compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide and tungsten silicide. Fuel cell.   2. The direct methanol fuel cell according to claim 1, wherein the catalyst further contains platinum as a catalyst component.   3. The direct methanol fuel cell according to claim 1, wherein the catalyst further contains an alloy of a group VIII element of the periodic table and platinum as a catalyst component.   4. The direct methanol fuel cell according to any one of claims 1 to 3, wherein the catalyst component is attached to a carbon-based substrate. In a catalyst used in a direct methanol fuel cell fueled with an aqueous methanol solution,
For direct methanol fuel cell, characterized by containing as a catalyst component tungsten carbide obtained by conversion from a compound selected from the group consisting of tungsten boride, tungsten nitride, tungsten sulfide, tungsten phosphide and tungsten silicide. catalyst.   An electrode material for a direct methanol fuel cell, comprising a catalyst layer containing the catalyst for a direct methanol fuel cell according to claim 5 formed on an ion exchange membrane.   An electrode material for a direct methanol fuel cell, comprising a catalyst layer containing the catalyst for a direct methanol fuel cell according to claim 5 formed on an anode fuel diffusion layer or a cathode gas diffusion layer.   An electrode material for a direct methanol fuel cell, comprising a catalyst layer containing the catalyst for a direct methanol fuel cell according to claim 5 formed on a transfer film.