JP2009252412A - CATALYST FOR DMFC TYPE FUEL CELL FOR PORTABLE ELECTRIC APPLIANCE CONTAINING RuTe2, ELECTRODE MATERIAL FOR FUEL CELL USING THE CATALYST FOR FUEL CELL, AND FUEL CELL - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for a DMFC type fuel cell for a portable electric appliance suppressing CO poisoning originated in methanol, the catalyst efficiently generating electric power at low temperatures, practically using at low price, and low in toxicity in the DMFC type fuel cell using a methanol aqueous solution as fuel. <P>SOLUTION: The catalyst for the DMFC type fuel cell for the portable electric appliance contains RuTe<SB>2</SB>as an active component. Since the catalyst containing RuTe<SB>2</SB>does not cause drop in catalytic activity by methanol, the catalyst for the DMFC type fuel cell for the portable electric appliance capable of replacing a platinum catalyst decreasing catalytic performance by methanol, low in price, high in practical use, and low in toxicity is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a direct methanol fuel cell (DMFC) which is a kind of a solid polymer fuel cell, particularly a DMFC fuel cell catalyst used in portable electrical products, and the fuel cell catalyst. The present invention relates to an electrode for a DMFC type fuel cell for portable electrical products and a DMFC type fuel cell for portable electrical products.
The present invention also relates to a DMFC fuel cell stack for portable electrical products and a DMFC fuel cell system for portable electrical products using the DMFC fuel cell for portable electrical products.

  There are many types of fuel cells depending on the type of electrolyte, for example, alkaline aqueous solution type, 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. Since the density is high and the exhaust gas is clean, development is being promoted as a household cogeneration type fuel cell and an automobile fuel cell in order to further improve energy efficiency and solve environmental problems.

  On the other hand, when a polymer electrolyte fuel cell is used as a power source for portable equipment, hydrogen gas as fuel has a low volumetric energy density and a large fuel tank volume, and fuel gas and oxidant gas are supplied to the power generator. Therefore, an auxiliary device such as a humidifier or the like for stabilizing the battery performance is required, so that the power generator becomes large and is not suitable as a power source for portable equipment.

  Therefore, development of a DMFC type fuel cell, which is a type of PEFC in which methanol is directly supplied as fuel and 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.

At the anode of the DMFC fuel cell, methanol and water react to generate carbon dioxide, protons, and electrons (reaction (1)). At the cathode, oxygen, protons and electrons react to produce water (reaction (2)).
Anode: CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Cathode: 3 / 2O 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, as a catalyst for such a DMFC type fuel cell, a catalyst mainly composed of a noble metal such as platinum is used for both the cathode and the anode. However, although platinum at the anode catalyzes the reaction between methanol and water, the platinum surface is poisoned by CO derived from methanol, resulting in a problem that the performance of the battery is lowered because the reaction area is reduced. Platinum at the cathode is also poisoned by CO derived from methanol crossed over from the anode side, and the same problem occurs.

The general reaction mechanism of methanol, water and platinum is represented by the following chemical reaction formula (reactions (3) and (4)).
_{CH 3 OH + Pt → Pt-} CO + 4H + + 4e - (3)
Pt—CO + H ₂ O → Pt + CO ₂ + 2H ⁺ + 2e ⁻ (4)

  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, since Ni, Fe, Co, Sn, Ti, and Mo are easily dissolved, they are not suitable for mass production of power sources for mobile electronic devices or for practical use as large-capacity power sources for automobiles.

  In addition, platinum is expensive and has few resources, so it is a big wall for practical use.

  Therefore, in order to commercialize a DMFC type fuel cell, it is desired to develop an electrode catalyst made of an inexpensive element that is not poisoned by CO and does not contain platinum.

  Patent Document 1 discloses a tellurium-containing catalyst deposited on a carbon-based substrate and a non-deposited tellurium-containing pure catalyst as fuel cell catalysts, and the ratio of Te / Ru of the produced catalyst is disclosed. It is disclosed as an invention that when the value exceeds a predetermined value, the catalytic activity of the reaction (2) is remarkably improved.

However, in this invention, there is no description of activity inhibiting action on the reaction (2) by MeOH in the DMFC type fuel cell, and there is no description suggesting this.
In the present invention, in the DMFC type fuel cell, it is disclosed as an invention that the activity of the RuTe ₂ catalyst for the reaction (2) does not decrease even if MeOH is present in the reaction field. Therefore, the effects of the invention according to Patent Document 1 and the present invention are different, and both are different inventions.
In Patent Document 1, as a method for producing a deposited catalyst in which an active component is deposited on a carbon-based substrate and a pure catalyst in which no active component is deposited, a precursor for each of Ru and Te is hydrogenated. Although the treatment temperature (hydrogen reduction treatment temperature) at the time of reduction is disclosed, this is merely an example of a general temperature range necessary for producing RuTe ₂ , and Patent Document 1 discloses RuTe. no description suggesting the relationship between Rute ₂ catalytic activity by MeOH in characteristics and DMFC fuel cell in the _second X-ray diffraction peaks.

In Non-Patent Document 1, since the catalytic activity for the reaction (2) of the RuSe _x / C catalyst does not change even when MeOH (1 M) is added to the H ₂ SO ₄ aqueous solution (0.5 M), RuSe _x It has been reported that no catalyst poisoning by MeOH is observed in the case of the / C catalyst. The value of the non-patent x in the RuSe _x / C in the literature 1 does not disclose specifically, the RuSe _x / C is in fact the same as RuSe _x / C disclosed in Non-Patent Document 2 that It is described that it is.

Non-Patent Document 2 discloses that RuSe _0.31 / C (carbon supported Ru (25 wt%) Se (6 wt%)) as RuSe _x / C gave the highest activity as a DMFC fuel cell MEA (Membrane Electrode Assembly). is doing. Although some of the added Se element forms RuSe ₂ , SeO ₂ and SeO ₄ are produced in a larger amount than that, and the Se element modifies the Ru element particles to prevent oxidation of the Ru element. It is concluded that it contributes to catalytic activity.

Non-Patent Document 3 discloses RuSe _0.15 / C, RuSe _0.3 / C, RuSe _0.6 / C, and RuSe / C as DMFC type fuel cell catalysts. From these detailed studies, these Se-modified Ru / C catalysts are (i) the oxygen reduction reaction proceeds on the Ru site without Se. (Ii) The surface modification with Se prevents OH from being generated on the Ru site. (Iii) The dissociative adsorption of O ₂ for the formation of H ₂ O from O ₂ that stabilizes adjacent Ru atoms requires at least two adjacent Rus, and the surface coverage by Se is very high Then, it is disclosed that the two adjacent Ru sites are reduced and the generation of H ₂ O ₂ is increased.

Non-Patent Document 4 discloses a Ru _x Se _y catalyst, which has a Ru core at the center, and this core is covered with Ru oxide, selenide, selenite, and metal organic residues. It is disclosed that it has an egg shell structure.

Summarizing the disclosure information of Non-Patent Documents 1 to 4, it is interpreted that in the Se-modified Ru / C catalyst, Ru in the central portion is an active species, and Se has modified the surface, giving some effect. . Therefore, there is no disclosure about a catalyst having RuSe ₂ up to the central portion, and there is no disclosure or suggestion about RuTe ₂ having tellurium as a chalcogenide element (oxygen, sulfur, selenium, tellurium). It has not been.

By the way, when the DMFC type fuel cell is used for portable electric products such as mobile phones, personal computers, and PDAs (Personal Digital Assistants) that are used in contact with the human body, the low toxicity of the catalyst is extremely important for industrialization. As a factor, selenium and its compounds are classified as “Class I Designated Chemical Substances” in the Law Enforcement Ordinance (regulation No. 138 of 2000) concerning the grasp of the release of specified chemical substances into the environment and the promotion of management improvements. ”And is highly toxic.
In contrast, tellurium and its compounds are “second-class designated chemical substances” and are safer elements than selenium. Therefore, tellurium element is a much more advantageous element than selenium element as a catalyst material for DMFC type fuel cells for portable electrical products used by touching human bodies such as mobile phones, personal computers and PDAs.
WO2006 / 137302 Electrochimica Acta 53 (2007) 1037-1041 ECS Trans. 3 (1) (2006) 1261-1270 J. Phys. Chem. C, 111 (3) (2007) 1273-1283 J. Phys. Chem. C, 111 (1) (2007) 477-487

  The present invention, in a DMFC type fuel cell using methanol aqueous solution as fuel, suppresses methanol-derived CO poisoning, can generate power efficiently at low temperature, and has low toxicity that can be practically used at low cost. It is an object of the present invention to provide a DMFC fuel cell catalyst for a portable electrical product, an electrode material for a DMFC fuel cell, a DMFC fuel cell, a DMFC fuel cell stack, and a DMFC fuel cell system.

As a result of intensive studies in view of the above circumstances, the present inventors have found that RuTe ₂ , preferably the diffraction angle 2θ (± 0.3 °) by X-ray diffraction (Cu-K _α- ray) is 27 ° or more and 29 ° or less. When RuTe ₂ having a specific half-value width of the maximum diffraction peak in the region of DMFC is used as a DMFC fuel cell catalyst for portable electronic products, particularly as a cathode electrode catalyst, the reaction (2) It was found that the activity against sucrose did not decrease. Therefore, the DMFC type fuel cell catalyst for portable electrical products of the present invention can be an inexpensive, practical and low-toxicity fuel cell catalyst that can be replaced with a platinum catalyst whose catalytic performance is lowered by methanol.

  The present invention has been completed based on such knowledge, and the gist thereof is as follows.

[1] A catalyst for a DMFC type fuel cell for portable electrical products, which contains RuTe ₂ as an active component.

[2] In [1], the RuTe ₂ is a half of the maximum diffraction peak in the region where the diffraction angle 2θ (± 0.3 °) by X-ray diffraction method (Cu-K _α- ray) is 27 ° to 29 °. A DMFC type fuel cell catalyst for portable electrical products characterized by a value range of 3.0 ° or less.

[3] A DMFC-type fuel cell catalyst for portable electrical products, wherein the active component in [1] or [2] is attached to a carbon-based substrate.

[4] A DMFC fuel cell catalyst for portable electrical products according to any one of [1] to [3], wherein the catalyst is a cathode electrode catalyst for a DMFC fuel cell for portable electrical products.

[5] A DMFC for a portable electrical product having an ion exchange membrane and a layer of a DMFC type fuel cell catalyst for a portable electrical product according to any one of [1] to [4] formed on the ion exchange membrane. Type fuel cell electrode material.

[6] The electrode gas diffusion layer and / or the methanol aqueous solution current collector, and the portable device according to any one of [1] to [4] formed on the electrode gas diffusion layer and / or the methanol aqueous solution current collector An electrode material for a DMFC fuel cell for a portable electrical product, comprising a layer of a DMFC fuel cell catalyst for the electrical product.

[7] A DMFC for a portable electrical product comprising a transfer film and a layer of a DMFC type fuel cell catalyst for a portable electrical product according to any one of [1] to [4] formed on the transfer film. Type fuel cell electrode material.

[8] A DMFC fuel cell for portable electrical products using the DMFC fuel cell catalyst for portable electrical products according to any one of [1] to [4].

[9] A DMFC type fuel cell stack for portable electrical products using the DMFC type fuel cell for portable electrical products according to [8].

[10] A DMFC fuel cell system for portable electrical products using the DMFC fuel cell stack for portable electrical products according to [9].

  According to the present invention, an inexpensive and practical DMFC type fuel cell for portable electrical products that exhibits good cathode catalytic activity even in the presence of methanol, which can be substituted for a noble metal catalyst such as platinum, which is expensive and has a resource problem. Catalyst, DMFC type fuel cell electrode material for portable electrical products using this fuel cell catalyst, DMFC type fuel cell for portable electrical products, DMFC type fuel cell stack for portable electrical products, and DMFC type for portable electrical products A fuel cell system is provided.

  Since the catalyst of the present invention has low toxicity, the present invention promotes the expansion and practical application of DMFC-type fuel cells to portable electrical products used by touching the human body such as power sources for mobile electronic devices. .

  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 fuel cell catalyst for portable electrical products]
The DMFC fuel cell catalyst for portable electrical products of the present invention contains RuTe ₂ as an active component.
The DMFC type fuel cell catalyst for portable electrical products of the present invention may contain only RuTe ₂ as an active component, or may contain other active components made of other transition metals.
Further, the DMFC fuel cell catalyst for portable electrical products of the present invention may be composed only of an active component, or may be obtained by adhering an active component to a substrate.
The DMFC fuel cell catalyst for portable electrical products of the present invention is particularly suitably used as a cathode electrode catalyst.

  In the following, a DMFC type fuel cell catalyst that is not coated with an active component and is substantially composed only of the active component is referred to as an “essential catalyst”. The deposited catalyst for a DMFC type fuel cell may be referred to as an “adhered catalyst”.

<Active ingredient>
Although the DMFC fuel cell catalyst for portable electrical products of the present invention contains RuTe ₂ as an active component, it may contain other components in addition to this RuTe ₂ as long as the effects of the present invention are not impaired. In this case, other components include ruthenium (Ru) and / or tellurium (Te).

When the DMFC fuel cell catalyst for portable electrical products of the present invention further contains Ru as an active component, the content is preferably 5 times the Ru element in RuTe ₂ contained in the catalyst in terms of Ru element. It is less than 1 mol, more preferably less than 3 times, most preferably less than 1 time.
Further, when the DMFC fuel cell catalyst for portable electrical products of the present invention further contains Te as an active component, the content thereof is preferably in terms of Te element with respect to the Ru element of RuTe ₂ contained in the catalyst. It is 10 times mol or less, More preferably, it is 5 times mol or less, Most preferably, it is 2 times mol or less.
If these abundance ratios exceed this range, the activity tends to be low.

In addition, when the DMFC fuel cell catalyst for portable electrical products of the present invention contains Ru and Te in addition to RuTe ₂ as active components, these contents are contained in the RuTe ₂ contained in the catalyst in terms of total elements. The amount is 5 times or less, more preferably 3 times or less, and most preferably 1 time or less of the Ru element.

  The abundance ratio of each element in the catalyst can be quantified by inductively coupled plasma emission spectrometry after the catalyst is weighed and then decomposed by melting with an alkali, added with an acid, and constant volume.

Incidentally, tellurium constituting the active ingredient may be a Te elements constituting the RuTe _2, TeO _2, TeO oxides such as _{3, H 2 TeO 3, H} 6 TeO 6 such oxo acids, TeCl _2, TeBr inorganic compounds such as chlorides, such as _2, and may be in the form of organic compounds such as tellurophenes. In addition, ruthenium can take a form of bonding with an organic compound in addition to an inorganic compound such as a metal element, an oxide, or a chloride. For example, ruthenium may be a Ru element constituting RuTe ₂ , an oxide such as RuO and RuO ₂ , a chloride such as RuCl ₃ .xH ₂ O, and an inorganic such as Ru (NO) (NO ₃ ) _3. It may be in the form of binding to a compound, an organic compound such as ruthenium acetylacetonate Ru (acac) ₃ and Ru ₃ (CO) ₁₂ .

  Further, the tellurium component and ruthenium component constituting the active component may be present without having a bond, or may be present with a bond. In the case where these elements have a bond and the elements are directly bonded to each other, the active component may be a so-called alloy.

  The presence form of the element constituting the active component in the DMFC fuel cell catalyst for portable electrical products of the present invention can be confirmed by X-ray diffraction (XRD). That is, for example, it can be confirmed by irradiating an active ingredient deposited on a substrate described later with X-rays (Cu-Kα rays) and observing the diffraction spectrum thereof.

  Examples of the measurement apparatus and measurement conditions include the following, but the analysis method by X-ray diffraction of the DMFC fuel cell catalyst for portable electrical products of the present invention is limited to the following measurement apparatus and measurement conditions. Is not to be done.

(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 90.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 3.0 ° / min
DS, SS, RS: 1 °, 1 °, 0.20mm

Specifically, RuTe ₂ has 21.808 °, 27.920 °, 31.287 °, 32.716 °, 43.369 ° as 2θ (± 0.3 °) peaks of X-ray diffraction. Those giving characteristic peaks such as 45.203 °, 48.322 °, 51.509 °, 53.981 °, 56.910 °, 68.565 °, 21.767 °, 26.189 °, 27 877 °, 31.249 °, 32.658 °, 33.847 °, 36.719 °, 39.822 °, 43.308 °, 44.377 °, 45.177 °, 45.801 °, 48 Those giving characteristic peaks such as 244 °, 50.117 °, 50.661 °, 51.426 °, 27.857 °, 31.271 °, 34.344 °, 39.873 °, 47. 123 °, 49.353 °, 51.532 °, 53.614 °, Characteristic peaks such as 7.636 °, 65.236 °, 67.032 °, 68.881 °, 72.414 °, 77.547 °, 80.922 °, 82.608 °, 85.948 °, etc. What you give.

<Half width of maximum diffraction peak by RuTe ₂ X-ray diffraction method>
The RuTe ₂ constituting the active component of the DMFC type fuel cell catalyst for portable electrical products of the present invention has a diffraction angle 2θ (± 0.3 °) of 27 ° by the above-mentioned X-ray diffraction method (Cu-K _α- ray). The half-width of the maximum diffraction peak in the region of 29 ° or less (hereinafter sometimes referred to simply as “half-width of the maximum diffraction peak”) is usually 3.0 ° or less, preferably 2.0 ° or less. Preferably it is 1.8 degrees or less. RuTe ₂ exhibiting such specific physical properties exhibits excellent applied voltage durability. When the half-value width of the maximum diffraction peak is larger than the above upper limit, the applied voltage durability is low.
Note that the lower limit of the half-width of the maximum diffraction peak of RuTe ₂ is usually 0.15 °.

There is no particular limitation on the method for obtaining RuTe ₂ exhibiting such a half-width of the maximum diffraction peak. However, in the process for producing a RuTe ₂ pure catalyst or RuTe ₂ adhering catalyst described later, a Ru element-containing compound and a Te element-containing compound are used. Is heated at 350 ° C. or higher under a reducing gas flow.

In the present invention, RuTe ₂ satisfies the half-width value of the maximum diffraction peak regardless of whether or not it is attached to a substrate described later.

<Pure catalyst shape>
There is no particular limitation on the shape of the pure catalyst made of the active component not deposited on the substrate, but it is most generally particulate. The average particle size of the particulate pure catalyst is usually 100 μm or less, preferably 1000 nm or less, more preferably 500 nm or less, especially 300 nm or less, usually 0.5 nm or more, preferably 1.0 nm or more, more preferably 2.0 nm. That's it. If the particle size of the pure catalyst is less than this range, it becomes unstable and easily deactivates, and if it exceeds this range, it becomes difficult to obtain high activity.

  In addition, the average particle diameter of the pure catalyst is measured by unifying the direction of measuring the length of the particle diameter with a scanning electron microscope (SEM) or transmission electron microscope (TEM) and measuring the particle length in that direction. This is shown as an average value.

<Substrate>
The DMFC type fuel cell catalyst for portable electrical products of the present invention may be a pure catalyst composed of only the above-mentioned active component, but the active component is contained in a substrate for holding and electrically conducting the active component. It is also possible to attach and use. In view of obtaining high conductivity, it is preferable to use the above-mentioned active component by applying it to a substrate.

  Although there is no restriction | limiting in particular as a base | substrate used by this invention, Use of a carbon-type base | substrate is suitable at the point from which high electroconductivity is acquired.

  Various carbon-based substrates can be used and are not particularly limited. Examples thereof include carbon black, ketjen black, carbon nanotube, carbon nanohorn, carbon nanocluster, fullerene, pyrolytic carbon, and activated carbon. The carbon-based substrate may be a vapor-grown carbon fiber (Vapor Growth Carbon Fiber: hereinafter sometimes abbreviated as “VGCF”) by a vapor-phase method. It has moderate elasticity and is suitable.

Among these carbon-based substrates, carbon black is industrially advantageous in terms of conductivity, availability, and cost. Examples of carbon black include channel black, furnace black, thermal black, acetylene black, oil furnace black, and gas furnace black.
These carbon-based substrates can be used singly or in combination of two or more.

The specific surface area of the substrate is not particularly limited, but is usually 5 m ² / g or more, preferably 100 m ² / g or more, more preferably 150 m ² / g or more, and usually 5000 m ² / g or less, preferably 2000 m ² / g. The following is preferable. If the specific surface area is too small, the effective area for depositing the active ingredient is reduced, and the reaction field is reduced, so that sufficient catalytic activity cannot be obtained. When the specific surface area is excessively large, the pore diameter of the substrate may be small, and even if the active component is deposited in the small pores, sufficient catalytic activity cannot be obtained. The specific surface area of the substrate is measured by the BET method.

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

<Adhesion of active ingredient to substrate>
In the present invention, the state in which the active component is applied to the substrate refers to a state in which the active component and the substrate are in contact with each other so as to obtain electrical conductivity. Therefore, the active ingredient can be applied to the substrate by simply mixing the active component and the substrate. However, as described later, after mixing the active compound supply compound and the substrate, the mixture is calcined and coated. It is preferable to wear. Alternatively, the substrate and the active component may be mixed and then fired. In the following, the state in which the active component is mixed with the active ingredient supply compound or the active ingredient and then fired to deposit the active ingredient is referred to as “supporting”.

  The shape of the active ingredient applied to the substrate is not particularly limited, but the most common is a particulate form. The average active particle size of the particulate active ingredient is usually 100 μm or less, preferably 1000 nm or less, more preferably 500 nm or less, especially 300 nm or less, usually 0.5 nm or more, preferably 1.0 nm or more, more preferably 2 It is desirable that it is 0.0 nm or more. If the particle size of the active ingredient is below this range, it becomes unstable and easily deactivated, and if it exceeds this range, it becomes difficult to obtain high activity.

  The average particle size of the active ingredient deposited on the substrate is determined by unifying the direction in which the particle length is measured with a scanning electron microscope (SEM) or transmission electron microscope (TEM). The particle length is measured and indicated as an average value.

  In order to deposit such a small average particle size active ingredient on a substrate, the production method may be devised as described later. Among these, it is preferable to control the state of crystal growth by lowering the firing temperature after mixing the substrate and the active component and shortening the firing time.

The deposition ratio of the active ingredient to the substrate is not particularly limited, but the weight ratio of Ru / (Ru + substrate) is usually 10 ⁻⁵ or more, preferably 0.001 or more, more preferably 0.
. It is preferably 01 or more, particularly 0.05 or more, and usually 0.95 or less, preferably 0.4 or less, and especially 0.3 or less. If the deposition ratio of the active ingredient is below this lower limit, the desired activity cannot be obtained, and if it exceeds the upper limit, the activity improvement effect due to deposition is less likely to occur.

<Other catalyst components>
In the present invention, a transition metal may be further deposited on the substrate as long as the effects of the present invention are not impaired.

This transition metal (hereinafter sometimes referred to as “other catalyst component”) is an element belonging to the fourth to sixth periods of groups IIIA to VIIA, VIII, and IB of the periodic table, and titanium ( Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), yttrium (Y), zirconium (Zr), niobium ( Nb), molybdenum (Mo), lanthanum (La), europium (Eu), gold (Au), cerium (Ce), tantalum (Ta), tungsten (W), rhenium (Re), praseodymium (Pr), neodymium ( Nd) is exemplified, and it is preferable that the value of the standard electrode potential E ° (25 ° C.) in an aqueous solution, which is represented by the following electrochemical equilibrium formula: oxidant + ne ⁻ = reduced, is positive. This is because elution due to oxidation is unlikely to occur as a natural property of metals, and there is little deterioration of the catalyst due to it. Specific examples of such materials include gold and silver.

  However, in order to make the catalyst more industrially advantageous, it is better to reduce the number of expensive catalyst components as much as possible.

  Of course, platinum (Pt) can be used in combination as a transition metal. However, since platinum is expensive, it is inexpensive and practical to add a small amount while considering the desired catalytic activity. It is desirable to provide a DMFC fuel cell catalyst. When platinum is added, specifically, the weight ratio of the total platinum component / active ingredient is usually 0.001 or more, preferably 0.01 or more, more preferably 0.05 or more, and usually 0.4 or less, preferably Is preferably 0.3 or less, and more preferably 0.2 or less.

  In addition, the following shows the electrochemical equilibrium formula of main transition metals and the standard electrode potential E ° (25 ° C.).

  These transition metals as other catalyst components may be used alone or in combination of two or more.

When the active component containing RuTe ₂ and another catalyst component are used in combination, examples of the combined form of the other catalyst component include the following.
i) RuTe ₂ is mixed with the substrate along with other active and catalytic components.
ii) RuTe ₂ is supported on the substrate together with other active components and catalyst components.
iii) Other active components and catalyst components are mixed with RuTe ₂ and then mixed with the substrate.
iv) Other active components and catalyst components are supported on RuTe ₂ and then mixed with the substrate.
v) After supporting RuTe ₂ on the substrate, other active components and catalyst components are supported on the substrate.
vi) RuTe ₂ is supported on the substrate after supporting other active components and catalyst components on the substrate.

When the DMFC fuel cell catalyst for portable electrical products of the present invention contains a transition metal as another catalyst component, the total ratio of transition metals in the DMFC fuel cell catalyst for portable electrical products of the present invention / RuTe ₂ weight ratio. Is usually 0.001 or more, preferably 0.01 or more, especially 0.05 or more, and usually 0.5 or less, preferably 0.4 or less, and particularly preferably 0.3 or less. If this weight ratio is less than this range, it is difficult to obtain the desired activity, and if it exceeds this range, it is difficult to improve the activity.

  The transition metal contained in the DMFC type fuel cell catalyst for portable electrical products of the present invention is preferably in the form of powder. The average particle size of the powder is usually 1000 nm or less, preferably 500 nm or less, and more preferably 300 nm or less, and usually 0.5 nm or more. When the average particle size is less than this range, the catalyst becomes unstable and easily deactivates, and when it exceeds this range, it is difficult to obtain high activity.

  The average particle diameter of the transition metal powder in the catalyst is determined by unifying the direction of measuring the length of the particles with a scanning electron microscope (SEM) or transmission electron microscope (TEM). The length is measured and shown as an average value.

  In the DMFC fuel cell catalyst for portable electrical products of the present invention, a metal component other than the transition metal element may be contained in an amount of several weight percent or less based on the weight of the active component.

A catalyst containing RuTe ₂ as an active component and a transition metal, particularly a catalyst in which RuTe ₂ and a transition metal are supported on a substrate has high catalytic activity. This is presumably because the transition metal functions as a promoter for RuTe ₂ and the activity is improved.

<Manufacture of pure catalyst>
There is no particular limitation on the method for synthesizing the pure catalyst of the first aspect composed only of the active component not deposited on the substrate, and any known method can be used.

  For example, an element supply compound as an active ingredient, that is, a precursor of the active ingredient is dissolved or dispersed in a solvent such as water in a predetermined molar ratio, and after filtration or evaporation of the solvent, the precursor is added as necessary. It is prepared by applying an activation step (for example, reduction treatment).

  The precursor of each element is not particularly limited as long as it can be thermally decomposed.

Tellurium precursors include tellurium powder (Te), halides such as TeCl ₂ , TeBr ₂ and TeCl ₄ , oxides such as TeO ₂ and TeO ₃ , and oxo acids such as H ₂ TeO ₃ and H ₆ TeO _6. Inorganic salts such as These Te precursors may be used alone or in combination of two or more.

On the other hand, examples of the ruthenium precursor include ruthenium halides, oxides, inorganic salts, organic acid salts, and the like, as well as compounds that bind to organic compounds. Specific examples of these ruthenium compounds include halides such as RuCl ₃ .xH ₂ O, RuBr ₃ , Ru (SO ₄ ) ₂ , Ru (NO) (NO ₃ ) ₃ , K ₂ RuO ₄ .H ₂ O. Inorganic salts such as Ru ₂ (OCH ₃ CO) ₄ and organic compounds such as ruthenium acetylacetonate (Ru (acac) ₃ ). These Ru precursors may be used alone or in combination of two or more.

In order to produce the RuTe ₂ pure catalyst of the present invention, for example, a Ru precursor such as RuCl ₃ or Ru (acac) ₃ and a Te precursor such as H ₆ TeO ₆ are mixed in a desired molar ratio (RuCl ₃ , Ru (acac). ) The molar ratio of H ₆ TeO ₆ to ₃ etc. is usually 0.2 or more, preferably 1 or more, usually 10 or less, preferably 4 or less) and dissolved in water 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, if necessary, a predetermined temperature (usually 60 ° C or more, preferably 100 ° C or more, usually 300 ° C or less, preferably 200 ° 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), heated or refluxed, and then the precipitate was removed by an evaporator. To. This is air-dried at room temperature, and then in an inert gas atmosphere such as nitrogen or argon for a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), a predetermined temperature (usually 100 The drying treatment is carried out at a temperature of not less than 200 ° C, preferably not less than 200 ° C, usually not more than 1000 ° C, preferably not more than 800 ° C. Next, a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), a predetermined temperature (usually 100 ° C. or more, preferably 200 ° C. or more, more preferably 300 ° C. or more) In general, it may be 1000 ° C. or lower, preferably 800 ° C. or lower, under a reducing gas flow, preferably in an air stream containing hydrogen (inert gas such as nitrogen or Ar may be mixed, and the hydrogen concentration in the inert gas is Is not particularly limited, but is heated at 1% or more, preferably 10% or more, 100% or less, or 80% or less. This makes it possible to obtain pure catalyst consisting of active component containing Rute ₂ according to the present invention.

  Thereafter, the pure catalyst is further subjected to a predetermined time (usually several tens of minutes or more) 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). Passivation treatment may be performed to form a passive film by treatment at a predetermined temperature (usually around room temperature), preferably 30 minutes or more, usually 10 hours or less, particularly 5 hours or less.

<Manufacture of a deposited catalyst>
The deposition catalyst of the second embodiment is produced by depositing an active component on a substrate. Here, the active component may be applied to the substrate by, for example, a loading method in which the active component or a precursor of the active component is mixed and baked with the substrate, a mixing method in which the active component and the substrate are simply mixed, and other impregnations. It can carry out by well-known methods, such as a method, a precipitation method, an adsorption method.

  For example, the deposited catalyst is prepared by dissolving or dispersing a precursor of each element in a solvent such as an aqueous solution in a desired molar ratio, and impregnating the substrate with the solution or immersing the substrate in the solution, followed by filtration. Alternatively, it is prepared by depositing the precursor on the substrate by distilling off the solvent and, if necessary, activating the precursor of the active ingredient (for example, reduction treatment).

In addition, the compound similar to the compound used for manufacture of a pure catalyst can be used for the precursor of an active ingredient. Among these, as the ruthenium precursor, RuCl ₃ .xH ₂ O, Ru (acac) ₃ , Ru (NO) (NO ₃ ) ₃ are preferable, and Ru (NO) (NO ₃ ) ₃ is particularly preferable. As the tellurium precursor, H ₆ TeO ₆ is preferable.

Next, an example of a method for producing a deposited catalyst containing RuTe ₂ of the present invention will be described.
RuCl ₃ or Ru _{(acac) 3} and _H 6 TeO ₆ blending ratio corresponding to the molar ratio of the desired _(RuCl 3, Ru _(acac) molar ratio of _H 6 TeO ₆ for like ₃ is generally 0.2 or more, Preferably, it is dissolved in water at 1 or more, usually 10 or less, preferably 4 or less, and a predetermined amount of a substrate such as carbon black is mixed therewith, and a predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50). Or less, preferably 30 hours or less). In this case, ultrasonic treatment may be performed. Next, if necessary, a predetermined temperature (usually 60 ° C or higher, preferably 100 ° C or higher, usually 300 ° C or lower, preferably 200 ° C or lower) for a predetermined time (usually 10 minutes or longer, preferably 30 minutes or longer, usually 50 ° C). Heating or refluxing for a period of time or less, preferably 30 hours or less). Thereafter, a precipitate is obtained by filtration or an evaporator. This is air dried at room temperature. Then, under an inert gas atmosphere such as nitrogen or argon, the predetermined time (usually 10 minutes or more, preferably 30 minutes or more, usually 50 hours or less, preferably 30 hours or less), the predetermined temperature (usually 100 ° C. or more, preferably Is 200 ° C. or higher, usually 1000 ° C. or lower, preferably 800 ° C. or lower) and then dried for a predetermined time (usually 10 minutes or longer, preferably 30 minutes or longer, usually 50 hours or shorter, preferably 30 hours or shorter). At a temperature (usually 100 ° C. or higher, preferably 200 ° C. or higher, more preferably 350 ° C. or higher, usually 1000 ° C. or lower, preferably 950 ° C. or lower) under a reducing gas flow, preferably under an air stream containing hydrogen (such as nitrogen or Ar) The inert gas may be mixed, and the hydrogen concentration in the inert gas is not particularly limited, but is 1% or more, preferably 10% or more, 100% or less, or It is heated at 0% or less). As a result, an adherent catalyst in which an active component containing RuTe ₂ is supported on a substrate is obtained.
In particular, by setting the calcination temperature in the hydrogen-containing gas stream to 350 ° C. or higher, a RuTe _2- deposited catalyst having a half-value width of the maximum diffraction peak of 3.0 ° or less, preferably 2.0 ° or less is obtained. be able to.

  Thereafter, 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) with respect to the deposited catalyst, a predetermined time (usually several tens of minutes or more, preferably Can be carried out at a predetermined temperature (usually around room temperature) for 30 minutes or more, usually 10 hours or less, especially 5 hours or less), and a passivation treatment for forming a passive film can be performed.

  Further, these active ingredients can be prepared in advance by the above-mentioned known methods, mixed with a base, and kneaded in a mortar or the like to adhere the active ingredient to the base. This mixing may be dry or wet, but is preferably wet mixed using a medium such as water and then dried at about 100 to 200 ° C.

  Among the above-described catalyst production methods, a support method in which a carbon base and a component selected from an active component and a precursor of the active component are mixed and then calcined is preferable. By this calcination, the activity of the obtained catalyst can be improved. The reason why the activity can be improved by firing in this way is not necessarily clear, but since the active component is deposited on the carbon-based substrate, the sintering of the active component is suppressed during firing, and the activity is reduced. Is estimated to be due to the improvement.

  When the above-mentioned transition metal is applied to the substrate together with the active component, the transition metal may be applied simultaneously in the active component application step, and the transition metal is applied before or after the active component application step. May be. Here, the “active component deposition step” includes the treatment process for depositing the active component, that is, the entire process from the addition of the active component precursor to the provision of the active component.

  As transition metal precursors for depositing transition metals on the substrate, oxides, inorganic acid salts such as nitrates, sulfates and carbonates, organic acid salts such as acetates, halides, hydrides, Examples include carbonyl compounds, amine compounds, olefin coordination compounds, phosphine coordination compounds, and phosphite coordination compounds. These may be used alone or in combination of two or more.

In order to deposit the transition metal together with the active component on the substrate, for example, a transition metal compound such as chloride is dissolved in the catalyst in which the active component containing RuTe ₂ synthesized by the method described above is supported on the substrate. The solution is added 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 distilled off with an evaporator. In this case, ultrasonic treatment may be performed. Next, under an air stream containing hydrogen (inert gas such as nitrogen or Ar may be mixed, the hydrogen concentration in the inert gas is not particularly limited, but is 1% or more, preferably 10% or more, 100 % Or less, or 80% or less) at a predetermined temperature (usually 100 ° C. or higher, preferably 150 ° C. or higher, usually 800 ° C. or lower, preferably 500 ° C. or lower) for a predetermined time (usually 10 minutes or longer, preferably 30 minutes or longer). Usually 50 hours or less, preferably 30 hours or less). As a result, an adherent catalyst in which both the active component containing RuTe ₂ and the transition metal are supported on the substrate is obtained.

  Thereafter, the adsorbed catalyst is further subjected to a predetermined time (usually several tens of minutes or more, preferably 30) in an inert gas atmosphere having a low oxygen concentration (for example, an oxygen concentration of about 5 wt% or less, especially about 2 wt% or less). It is also possible to carry out a passivation treatment for forming a passive film by treating at a predetermined temperature (usually around room temperature) at a time of not less than minutes and usually not more than 10 hours, especially not more than 5 hours.

  As described above, the transition metal may be used as it is by mixing it with the substrate to which the active component is applied, or may be used by mixing the active component with the substrate to which the transition metal is applied.

[Electrode materials for DMFC fuel cells for portable electrical products, DMFC fuel cells, DMFC fuel cell stacks, DMFC fuel cell systems]
The DMFC fuel cell electrode material for portable electrical products and the DMFC fuel cell for portable electrical products of the present invention preferably contain the above-described DMFC fuel cell catalyst for portable electrical products of the present invention as a cathode electrode catalyst. It is characterized by that. The DMFC fuel cell electrode material for portable electrical products and the DMFC fuel cell for portable electrical products of the present invention contain only one type of DMFC fuel cell catalyst for portable electrical products of the present invention. It may be sufficient and two or more types may be included. Further, the catalyst may be used in combination with a catalyst other than the DMFC type fuel cell catalyst for portable electrical products of the present invention. In such a case, a conventionally known catalyst mainly composed of a noble metal such as platinum is used. Can do.
The DMFC fuel cell stack for portable electrical products of the present invention is characterized by using such a DMFC fuel cell for portable electrical products of the present invention.
The DMFC type fuel cell system for portable electrical products according to the present invention uses the DMFC type fuel cell stack for portable electrical products according to the present invention.

  The DMFC type fuel cell according to the present invention supplies a methanol aqueous solution as a fuel to the anode and air as an oxidant to the cathode, and the potential difference between the anode and the cathode generated by the above reactions (1) and (2). It is a power generation device that takes out voltage and supplies it to a load, and is composed of an anode electrode, a cathode electrode, and an electrolyte sandwiched therebetween.

  In the case of a DMFC type fuel cell, a catalyst layer is formed on both surfaces of an ion exchange membrane as an electrolyte, a methanol aqueous solution current collector (anode) is outside one catalyst layer, and a cathode gas diffusion layer is outside the other catalyst layer. Thus, an electrolyte membrane / electrode assembly is used in which a methanol aqueous solution current collector and a cathode gas diffusion layer are integrally formed via an electrolyte membrane having catalyst layers formed on both sides. In the electrolyte membrane / electrode assembly, a partition plate is arranged on the methanol aqueous solution current collector and cathode gas diffusion layer side, and a unit cell composed of the partition plate, the electrolyte membrane / electrode assembly, and the partition plate is desired depending on the application. A DMFC type fuel cell stack is formed by stacking a plurality of layers until the voltage reaches Usually, a unit cell is stacked from several cells to several tens of cells to form a DMFC type fuel cell stack.

  As the catalyst for forming the catalyst layer of the electrolyte membrane / electrode assembly, the above-described catalyst for a DMFC fuel cell for portable electrical products according to the present invention is preferably used as a cathode electrode catalyst.

  An ion exchange membrane as an electrolyte may have a cation exchange ability, but since it is practically desired to withstand an oxidation-reduction atmosphere at about −20 ° C. to 70 ° C., a perfluoroalkylsulfonic acid resin is used. Used exclusively. 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.).

The ion exchange membrane preferably has a thickness of about 10 μm or more and several hundreds of μm or less, but it is desirable to make the thickness thinner in order to reduce the electric resistance. When the thickness is reduced, methanol crossover to the cathode increases, but the RuTe ₂ catalyst made of a specific precursor, or the catalyst for DMFC type fuel cell for portable electrical products of the present invention made of a catalyst containing RuTe ₂ and tungsten oxide. When used in the above, there is almost no decrease in catalytic activity due to the methanol crossed over in this way, and good battery characteristics can be obtained.
Taking Nafion as an example of an ion exchange membrane, Nafion 115 having a thickness of about 120 μm is often used. However, an electrolyte membrane having a thickness of 30 to 50 μm including a reinforcing material has begun to be developed. It can be used similarly.

  The cathode gas diffusion layer supplies air and also has a function as a current collector for taking out the generated voltage. Accordingly, the cathode gas diffusion layer is preferably made of a material that is an excellent electronic conductor and allows air to flow and withstand the working atmosphere. As a material constituting the cathode gas diffusion layer, a carbon porous material 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. Similarly, the material of the methanol aqueous solution current collector is selected from materials through which the methanol aqueous solution circulates and can withstand the use atmosphere. The carbon porous body is used.

  Although there is no restriction | limiting in particular as a method of producing the electrolyte membrane / electrode assembly of the DMFC type fuel cell for portable electrical products of this invention, For example, the following methods are mentioned.

  Next, an example of a method for forming the cathode side catalyst layer and the anode side catalyst layer on the ion exchange membrane will be described. First, the DMFC type fuel cell catalyst for portable electrical products of the present invention described above is placed in a suitable container, and a Nafion solution (concentration 5 wt%, manufactured by Aldrich) in which DuPont's Nafion (registered trademark) is dissolved, and alcohol The catalyst slurry is prepared by dispersing in a medium such as water. At this time, it is more preferable to apply ultrasonic vibration in order to promote the dispersion well. The concentration of the DMFC fuel cell catalyst for portable electrical products of the present invention in this catalyst slurry is preferably about 1 to 50 g / L in order to obtain the desired dispersibility. Of course, a binder such as polytetrafluoroethylene (PTFE) may be added to the slurry in the range of about 3 to 30% by weight for the purpose of imparting water repellency or preventing the catalyst layer from peeling off. In addition, when the contents are to be agglomerated and made into a paste, the alcohol has 2 to 5 carbon atoms such as ethanol or isopropyl alcohol, preferably a lower alcohol having about 2 to 4 carbon atoms, or 2 to 5 carbon atoms such as ethylene glycol, preferably A polyhydric alcohol having about 2 to 4 carbon atoms can be added and aggregated in a ratio of 0.25 to 1.0 with respect to water.

  The catalyst slurry thus obtained is deposited on an ion exchange membrane, a cathode gas diffusion electrode material or a methanol aqueous solution current collector, or a transfer film, and then dried to form a cathode side catalyst layer and an anode side catalyst layer. To do.

Specifically, the cathode side catalyst layer and the anode side catalyst layer are respectively formed on the ion exchange membrane, the cathode gas diffusion electrode material, or the methanol aqueous solution current collector by any one of the following methods a) to d). The
a) A catalyst slurry is sprayed on the ion exchange membrane to be used and dried.
b) A catalyst slurry is sprayed onto a cathode gas diffusion electrode material such as carbon paper or a methanol aqueous solution current collector and dried.
c) A 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 desired such as Nafion. The catalyst layer is transferred by appropriately pressing on the ion exchange membrane.
d) As in c), after the catalyst slurry is spread on the FEP film, the slurry is covered with a gas diffusion electrode material such as carbon paper or a methanol aqueous solution current collector and dried.

In any of the cathode side catalyst layer and the anode side catalyst layer, the catalyst adhesion amount is usually 0.01 mg / cm ² or more, preferably 0.1 mg / cm ² or more, usually 50 mg / cm as the Ru adhesion amount (weight per unit area). It is cm ² or less, preferably 20 mg / cm ² or less, and most preferably about 10 mg / cm ² or less. If the amount of the active component attached is less than this range, sufficient catalytic activity cannot be obtained, and if it is more than this range, it is difficult to form an electrolyte membrane / electrode assembly.

  The catalyst layer may be formed on the ion exchange membrane and then laminated with the methanol aqueous solution current collector material or the cathode gas diffusion layer material. The catalyst layer is formed on the methanol aqueous solution current collector material or the cathode gas diffusion layer material. Then, it may be laminated with an ion exchange membrane. The laminated body is preliminarily pressure-molded and then pressure-heat-molded with a press to obtain an electrolyte membrane / electrode assembly. In this joined body, the above-mentioned cathode-side catalyst layer is formed on one surface of the ion exchange membrane, the anode-side catalyst layer is formed on the opposite surface of the ion-exchange membrane, and the outer sides of both catalyst layers. In addition, a methanol aqueous solution current collector constituting an anode and a cathode gas diffusion layer constituting a cathode are laminated.

  In addition, when press-molding a laminated body preliminarily, it is preferable to set temperature and pressure lower than the conditions of the main molding and to set the time short as long as the collapse of the catalyst layer is prevented. This is because the catalyst particles, the cathode gas diffusion layer, or the porous body for the methanol aqueous solution current collector does not cause compression failure.

  The DMFC fuel cell system for portable electrical products of the present invention includes a DMFC type fuel cell stack for portable electrical products that obtains an electromotive force through an electrochemical reaction, a compressor that supplies compressed air as an oxygen-containing gas, and methanol as a fuel. An aqueous solution container is provided. The aqueous methanol solution is sent to the anode electrode of the DMFC type fuel cell 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 fuel cell stack for portable electrical products may be collected and returned to the methanol aqueous solution container. The methanol aqueous solution may be collected using a gas-liquid separator when 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.

  In the following examples and comparative examples, XRD analysis of the prepared catalysts was performed under the following 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 90.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Scanning speed: 3.0 ° / min
DS, SS, RS: 1 °, 1 °, 0.20mm

  In the following Examples and Comparative Examples, the activity evaluation of the prepared catalysts was performed by the following method.

[Evaluation of catalytic activity]
When the potential of the electrode is scanned in the direction from about 800 mV (RuTe ₂ ) or 1050 mV (Pt) to a low potential (50 mV) with respect to the standard hydrogen electrode, 4H ⁺ + O ₂ + 4e ⁻ → 2H ₂ between the working electrode and the Pt counter electrode. O
It can be seen that the oxygen reduction current due to. After the electrode potential reached 50 mV, it was turned back, and the catalytic activity was evaluated by the value of current flowing when scanning in the direction of high potential (800 mV).
Measurement conditions are as follows.
Electrolytic solution: The following three types of aqueous solutions were used.
0.5MH ₂ SO ₄ aqueous solution
1M MeOH + 0.5M H ₂ SO ₄ aqueous solution
10 M MeOH + 0.5 MH ₂ SO ₄ aqueous solution Atmosphere: 1 atmosphere oxygen atmosphere Scan speed: 5 mV / sec Scan range: RuTe ₂ = 50 to 800 mV
Pt = 50 to 1050 mV
Working electrode: rotating disk, glassy carbon disk 4φ
Counter electrode: Pt mesh electrode Comparative electrode: Standard hydrogen electrode (SHE)
Rotation speed: 1600rpm

[Example 1]
Using ruthenium chloride (water-containing ruthenium content 42 wt%, manufactured by NE Chemcat) 0.476 g and telluric acid (manufactured by Mitsuwa Chemical Co., Ltd.) 0.909 g so that the charged molar ratio of Ru and Te is 1: 2. Was dissolved in 50 ml of water. The carbon black (VULCAN XC-72) 0.8g was put so that it might become Ru / (Ru + carbon black) = 20 weight% in it, and it ultrasonicated at room temperature for 1 hour. Then, the solvent was distilled off with an evaporator, and the obtained residue was dried at 300 ° C. for 3 hours under an argon stream. Thereafter, the mixture was cooled to room temperature and heated from room temperature to 300 ° C. for 20 minutes and from 300 ° C. to 350 ° C. over 3 hours under a flow of hydrogen of 3 L / hr. Then, after hold | maintaining at 350 degreeC for 2 hours, it cooled to room temperature. Finally, it was left to passivate in a nitrogen atmosphere containing 1% oxygen for 2 hours to obtain a RuTe ₂ coated catalyst.

The obtained RuTe ₂ deposited catalyst was confirmed to contain RuTe ₂ by XRD analysis. The values of 2θ gave peaks at 27.850 °, 28.155 °, 31.447 °, 32.449 °, 39.763 °, 43.700 °, 48.254 ° and 57.108 °. The full width at half maximum of the 27.850 ° peak was 1.98 °.

<Creation of cathode electrode>
20 mg of the resulting RuTe _2- coated catalyst was suspended in 20 mL of water, sufficiently stirred with an ultrasonic washer, and then the amount of Ru deposited with a microsyringe (calculated assuming that Ru and Te elements were not volatilized. The same is applied to the glassy carbon electrode, which is the working electrode, so as to be 15 μg / cm ^2, and then a 5% Nafion (registered trademark) solution (alcohol solution, manufactured by Aldrich Chemical Co.) is added at a weight of 100. 10 μL of a liquid diluted twice with water was dropped and dried by standing to obtain a cathode electrode.

With respect to this cathode electrode, the oxygen reduction activity in a 0.5 M H ₂ SO ₄ aqueous solution, or a 1 M MeOH + 0.5 MH ₂ SO ₄ aqueous solution, or a 10 M MeOH + 0.5 MH ₂ SO ₄ aqueous solution was compared with the standard hydrogen electrode (SHE), respectively. And measured in the range of 50 to 800 mV. Table 2 shows the oxygen reduction activity at 0.7V, 0.6V, and 0.5V.

[Comparative Example 1]
<Creation of cathode electrode>
A cathode electrode was prepared in the same manner as in Example 1 using a commercially available platinum catalyst E-TEK (EC-20-PTC (Electro Chem, Inc.) Pt 20 wt% supported carbon black (Vulcan XC-72R)).
About this cathode electrode, the oxygen reduction activity in said 3 types of aqueous solution was measured in the range of 50-1050 mV with respect to a standard hydrogen electrode (SHE). Table 2 shows the oxygen reduction activity at 0.7V, 0.6V, and 0.5V.

As is clear from Table 2, the RuTe ₂ catalyst of Example 1 had almost the same cathode catalyst activity at 0.7V, 0.6V, and 0.5V within the range of MeOH up to 10M.
On the other hand, the activity of the Pt (E-TEK) catalyst of Comparative Example 1 was reduced due to the presence of MeOH, and at 0.7 V, the activity was reduced to 13% with no addition of 1M MeOH. In addition, it is thought that it was due to the oxidation reaction of MeOH that the current value flowed 19% in the reverse direction with 10M MeOH. Furthermore, at 0.6 V, 1M MeOH was 71% without addition, and 10M MeOH was 49%. At 0.5 V, the activity was lower than that of the RuTe ₂ catalyst in all cases.

  According to the present invention, a small and inexpensive DMFC-type fuel cell catalyst is provided that has almost no problem of reduction in output due to CO poisoning even when MeOH enters the cathode electrode due to crossover. Of commercial DMFC fuel cells will be promoted.

Claims (10)

A catalyst for DMFC type fuel cell for portable electrical products, characterized by containing RuTe ₂ as an active ingredient. In claim 1, the RuTe ₂ has a half-value width of a maximum diffraction peak in a region where a diffraction angle 2θ (± 0.3 °) by an X-ray diffraction method (Cu-K _α- ray) is 27 ° to 29 °, A DMFC type fuel cell catalyst for portable electrical products, characterized in that it is 3.0 ° or less.   3. The DMFC type fuel cell catalyst for portable electrical products according to claim 1, wherein the active component is coated on a carbon-based substrate.   4. The DMFC fuel cell catalyst for portable electrical products according to claim 1, wherein the catalyst is a cathode electrode catalyst for a DMFC fuel cell for portable electrical products.   A DMFC type fuel cell for portable electrical products, comprising: an ion exchange membrane; and a layer of a DMFC type fuel cell catalyst for portable electrical products according to any one of claims 1 to 4 formed on the ion exchange membrane. Electrode material.   5. The portable gas appliance according to claim 1, wherein the electrode gas diffusion layer and / or the methanol aqueous solution current collector are formed on the electrode gas diffusion layer and / or the methanol aqueous solution current collector. An electrode material for a DMFC fuel cell for a portable electrical product, comprising a catalyst layer for the DMFC fuel cell.   A DMFC type fuel cell for portable electrical products, comprising: a transfer film; and a layer of a DMFC type fuel cell catalyst for portable electrical products according to any one of claims 1 to 4 formed on the transfer film. Electrode material.   A DMFC type fuel cell for portable electrical products using the DMFC type fuel cell catalyst for portable electrical products according to any one of claims 1 to 4.   A DMFC type fuel cell stack for a portable electrical product using the DMFC type fuel cell for a portable electrical product according to claim 8.   A DMFC type fuel cell system for portable electrical products using the DMFC type fuel cell stack for portable electrical products according to claim 9.