KR20050089324A - Oxygen adsorbing cocatalyst containg catalyst for fuel cell, electrode for fuel cell using the same, and fuel cell containing the electrode - Google Patents

Abstract

In the present invention, a platinum-silver or platinum-gold main catalyst, as a cocatalyst which selectively stores and releases oxygen, has an oxygen conductivity, and is easy to oxidize carbon monoxide at low temperatures, rhodium, a ceria component, or ruthenium, Or by incorporating a composite of these materials, it is possible to prepare a catalyst having excellent oxygen oxidation characteristics as well as methanol oxidation characteristics and endothelial toxicity to carbon monoxide. In particular, even when air is used in the cathode, the oxygen adsorption characteristics of the platinum catalyst It is possible to increase the performance of the electrode catalyst for fuel cells.

Description

A catalyst for a fuel cell containing an oxygen adsorption promoter, an electrode for a fuel cell manufactured using the same, and a fuel cell including the electrode TECHNICAL FIELD OF FUEL CELL, ELECTRODE FOR FUEL CELL USING THE SAME, AND FUEL CELL CONTAINING THE ELECTRODE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for a fuel cell containing an oxygen adsorption promoter, a method for manufacturing the same, a fuel cell electrode manufactured using the same, a method for manufacturing the same, and a fuel cell including the electrode. By adsorbing and releasing, having oxygen conductivity, and containing cocatalyst which is easy to oxidize carbon monoxide at low temperature, it has not only oxygen reduction characteristics but also excellent oxidation resistance of methanol and endothelial toxicity to carbon monoxide. Even in this case, as the oxygen adsorption characteristics of the platinum catalyst are increased by selectively supplying oxygen in the air to the platinum catalyst, a catalyst for a fuel cell containing an oxygen adsorption promoter, which can improve the performance of the platinum catalyst electrode, a method of manufacturing the same And a fuel cell electrode manufactured using the same, a method of manufacturing the same, and a fuel cell including the electrode. .

In the present invention, the ceria component means each of ceria, doped ceria, or an oxide thereof, or two or more thereof.

Direct Methanol Fuel Cell (DMFC, hereinafter referred to as DMFC) is a low-temperature fuel cell that converts chemical energy into electrical energy by electrochemical reaction of a mixture of methanol and water as fuel and pure oxygen or air as oxidant. It is an energy conversion device that converts energy into fuel, and it is easy to store fuel by using liquid fuel, it is possible to miniaturize it, and it does not need a reforming device, and it has relatively high power density and energy conversion efficiency. Applications include military, military equipment, and space energy production equipment.

DMFC electrodes are generally applied on top of a hydrophobic coated porous carbon cloth or carbon paper to prevent flooding, by applying a mixture of carbon and water repellent materials for diffusion of gas and liquid reactants. It is prepared by forming a diffusion layer and thinly applying a mixture of a catalyst and a polymer electrolyte, that is, an ionomer thereon.

In this case, as the method for applying the catalyst, spray coating, filtration and deposition, screen printing, and the like are used.

After placing a commercial electrolyte membrane such as a hydrogen ion exchange membrane between the anode and the cathode prepared as described above, the membrane is hot-pressed under a certain pressure at or above the glass transition temperature of the electrolyte to form a membrane-electrolyte assembly ( Membrane Electrolyte of Assembly (hereinafter referred to as MEA).

In order to form a unit cell, it is completed by closely contacting the MEA with a methanol solution, an oxygen or air storage tank, and a current collector. Thus, the MEA, the current collector of electrons formed through an electrochemical reaction, and gas tightness are maintained. The gasket is fitted together.

As the DMFC oxide electrode, a platinum-ruthenium black (Pt-Ru black) or a platinum-ruthenium (Pt-Ru / C) catalyst supported on carbon, or a nanocomposite may be used, and a reduction electrode Generally, a platinum black (Pt black) or a carbon (Pt / C) catalyst supported on carbon may be used.

Methods for preparing such a catalyst include a precipitation method, a sol-gel method, a vacuum deposition method such as sputtering, a pyrolysis method, an impregnation method, a colloid method, and the like.

In the precipitation method, precipitation occurs in a supersaturated state and undergoes two processes of nucleation and growth. Nucleation occurs as the carrier acts as a 'seed', and metal ions are adsorbed to the resulting nucleus to grow. The growth rate is then expressed as a function of concentration, temperature, and pH. When the precipitation of the catalyst is completed, the precipitate is filtered and then washed with distilled water to remove remaining alkali ions or anions. The dried catalyst is in the form of a salt and must be calcined to form a stable oxide.

In the impregnation method, 'incipient wetness' is most commonly used, and the purpose of this method is to ensure that a metal salt solution corresponding to an appropriate loading amount is uniformly filled in the pores of the carrier. The carrier is used in a state where water in the pores is removed, and the catalyst solution is impregnated into the carrier by dropping the metal salt solution as little as desired so that the carrier can be completely wetted into the pores of the carrier. After the drying process, the drying speed has a great influence on the supported form of the metal salt in the pores. After drying, a stable metal oxide catalyst is formed through a calcination process.

Impregnation method <M. In Gotz and H. Wendt, Electrochimica Acta, 43, 3637 (1998), generally, metal salts (H ₂ PtCl ₆ , RuCl ₃ , Pt (NH ₃ ) ₂ (OH) ₂ , Ru ₃ CO ₁₂ , Pt (NH ₃ ) ₂ (NO) _2, etc.) solution is impregnated with a carrier, and then using a reducing agent in aqueous solution (N ₂ H ₄ , NaS ₂ O ₃ , NaS ₂ O ₅ , NaBH ₄ ) or reduced in a hydrogen atmosphere to the catalyst Manufacture. The average particle size of the produced catalyst metal is 3-5 nm or more, and the size distribution is quite large, but it is relatively easy to manufacture and simple.

The colloidal method can be largely divided into two types. One is a method devised by Watanabe (see Jouranl of Electroanalytical Chemistry, 229, 395 (1987)), and the other is Bonnemann <Angewandte Chemie International Edition Engl., 30, 1312 (1991)> It is a method devised by.

The colloidal method by Watanabe is a metal complex intermediate through a process of adding a reducing agent (Na ₂ CO ₃ , NaHSO _4, etc.) to a hydrated platinum chloride (H ₂ PtCl ₆ · xH ₂ O) and a second metal chloride aqueous solution. The resulting intermediate is hydrolyzed to form a metal oxide, followed by reduction with hydrogen gas. In the production of metal oxides, adverse reactions are likely to occur, so temperature and pH control are essential.

In the colloidal method by Bonneman, a catalyst is prepared on a non-aqueous solution, and a surfactant-stabilized catalyst is prepared using a synthesized tetrabutylammonium-based reducing agent, and then the catalyst is subjected to heat treatment. It is a method of removing the surface active agent surrounding. Thereby, a high carrying amount of metal can be uniformly dispersed in carbon at a nano size of about 2 nm. However, this method has a disadvantage in that the overall process is complicated and the manufacturing cost increases because of using organic solvents and compounds.

Depending on which of the above methods is applied, the size of metal particles, pore size distribution, particle morphology, structure of catalyst surface, degree of metal dispersion, etc. are mainly used. Impregnation and colloidal methods are generally known to be more effective than colloidal methods. In addition, recently, methods of modifying the colloidal method or using plasma or sputtering have been proposed.

The DMFC manufactured as described above can be miniaturized because methanol is used instead of hydrogen as a fuel, and it is easy to supply fuel. However, compared with the case of using hydrogen as a fuel, the battery life and energy density are low. Due to the low activity of the catalyst, a large amount of noble metal catalysts are required, resulting in an increase in cost, and the catalyst is poisoned by carbon monoxide generated during the reaction.

Therefore, in order to commercialize DMFC, it is urgent to improve the performance of the anode electrode catalyst and thereby reduce the cost, and for this purpose, it has high methanol decomposition performance at low temperature, endothelial toxicity to carbon monoxide generated during methanol decomposition, Improved catalysts have to be developed.

Therefore, conventionally, metals such as ruthenium, osmium, iridium, tungsten, nickel, iron, gold, and vanadium are added to the platinum catalyst to prevent catalyst poisoning caused by carbon monoxide, which is a product of the methanol oxidation reaction, and to oxidize methanol. Research has been conducted to increase the amount of, and it has been reported that the loading of platinum on ceria (CeO ₂ ) forms a platinum-oxygen-cerium bond, indicating high activity in methanol degradation <S. See Imamura, T. Higashihara, Y. Saito, H. Aritani, H. Kanai, Y. Mastsumura, N. Tsuda, Catalysis Today, 50, 369 (1999).

On the other hand, in the reduction electrode of the DMFC, the problem of performance reduction due to air use or performance reduction due to methanol (hereinafter referred to as methanol crossover) passing through the electrolyte membrane from the anode should also be solved.

In other words, the platinum catalyst supported on platinum or carbon, which is a fuel cell cathode catalyst, exhibits a performance reduction of about 50% or more when air is used, which means that the partial pressure of the reactant oxygen in the Nernst equation is reduced. This is because the potential of the electrode decreases, resulting in a decrease in the electrochemical reaction rate.

Crossover methanol causes a mixed potential, and due to oxidation in the cathode, strong adsorption of carbon monoxide with platinum results in reduced performance due to catalyst deactivation.

In the past, a method of adding a ceria-based material having excellent oxygen storage capability in the production of an electrode in order to improve the utilization rate in air application has been reported <Z. Xu, Z. Qi, A. Kaufman, Journal of Power Sources, 115, 40 (2003)>.

In particular, zirconia (ZrO ₂ ) was added to supplement ceria's oxygen storage capacity and thermal stability (see Anca Faur Ghenciu, Current Opinion in Solid State and Materials Science, 6, 389 (2002)).

Japanese Unexamined Patent Publication No. 10-55807 discloses the use of air by using vanadium oxide, cerium oxide, zirconium oxide, or a composite of two or more kinds of such materials as cocatalysts. A method of improving this is proposed.

In addition, conventionally, in order to solve the problems caused by the crossover of methanol, in Japanese Patent Laid-Open No. 11-7963 and Japanese Patent Laid-Open No. 11-7964, the crossover methanol is not oxidized, and only oxygen is selectively reduced. A method of using gold (Au) and silver (Ag) or a complex thereof as a catalyst for a cathode is proposed.

On the other hand, in the case of a polymer electrolyte fuel cell (hereinafter referred to as PEMFC), which is a low-temperature fuel cell using hydrogen as an anode, the overvoltage of hydrogen oxidation in the anode is almost negligible in a high current density region. However, the oxygen reduction reaction in the cathode has a high overvoltage and the overall reaction rate is limited by the cathode. Therefore, the slow reduction reaction of oxygen on the platinum catalyst determines the overall energy conversion efficiency, and in order to improve the efficiency of the PEMFC fuel cell, it is necessary to develop a catalyst that increases the oxygen reduction reaction activity.

Therefore, various studies are being conducted to increase the activity of oxygen reduction reaction of the cathode, by coordinating iron and cobalt with organic polymer materials such as metallophthalocyanine, metalloporphyrin, and macrocyclic complexes to decompose oxygen molecules. It has been reported how to make it easier <J. Jiang, A. Kucernak, Electrochimica Acta, 47, 167 (2002)>, when iron, cobalt and nickel are added to platinum to make alloys, the adsorbed oxygen is strongly adsorbed with the catalyst, weakening the bond of oxygen atoms, It is reported that the activity is increased for the oxygen reduction reaction <T. See Toda, H. Igarashi, H. Uchida, M. Watanabe, Journal of Electrochemical Society, 146, 3750 (1999).

In addition, US Patent No. 4316944 proposes a method of improving the rate of oxygen reduction by adding chromium to platinum to form an alloy, and US Patent 665635 proposes to increase the activity of the oxygen reduction reaction. A method of improving the oxygen reduction activity by preparing a three-way catalyst composed of 40 to 60 atom.% Platinum, 10 to 20 atom.% Rhodium and 20 to 50 atom.% Iron is proposed.

However, from the results of the above conventional studies, the activity of the oxygen reduction reaction and the characteristics of the methanol oxidation reaction are simultaneously increased, and the endothelial toxicity to carbon monoxide is also increased, thereby improving the performance of the fuel cell for low temperature. When air with a low partial pressure of oxygen is used at the pole, oxygen is selectively supplied to the platinum catalyst in the air, and at the same time, carbon monoxide generated by the crossover methanol is removed, thereby reducing the deactivation of the platinum catalyst and improving the battery performance. There was no catalyst technology that could be improved.

Therefore, the present invention has been made to solve the above problems and needs,

An object of the present invention is to improve the performance of the low-temperature fuel cell by increasing the activity of the oxygen reduction reaction and the characteristics of the methanol oxidation reaction, and increase the endothelial toxicity to carbon monoxide. When oxygen is used, an oxygen adsorption promoter, which can selectively supply oxygen to the platinum catalyst and remove carbon monoxide generated by the crossover methanol, can reduce the deactivation of the platinum catalyst and improve the performance of the cell. A catalyst for a fuel cell, a method for producing the same, a fuel cell electrode produced using the same, a method for producing the same, and a fuel cell including the electrode are provided.

The object of the present invention as described above is a platinum-silver catalyst, or carbon supported on carbon, which is a main catalyst in an electrode catalyst for a polymer electrolyte fuel cell or a direct methanol fuel cell (hereinafter referred to as a low temperature fuel cell) which is a low temperature fuel cell. A platinum-silver catalyst, or a platinum-gold catalyst, or a carbon-supported platinum-gold catalyst, comprising as a promoter a rhodium (Rh), a ceria (CeO ₂ ) component, and at least one ruthenium (Ru) It is achieved by a catalyst for low temperature fuel cells containing an oxygen adsorption promoter.

The above object of the present invention is also achieved by a low temperature fuel cell electrode containing an oxygen adsorption promoter, which comprises the catalyst.

The above object of the present invention is also achieved by a low temperature fuel cell containing an oxygen adsorption promoter, which comprises the electrode.

The object of the present invention as described above, in the production of catalysts for low temperature fuel cells, further impregnated with platinum black or carbon-supported platinum in a silver nitrate (AgNO ₃ ) or gold chloride (HAuCl ₄ ) solution and dried, followed by nitrogen Heat-treating in an atmosphere to prepare a platinum-silver or platinum-gold catalyst (S1-1); Or adding a platinum-containing water-soluble compound or a platinum-containing complex salt, a silver nitrate or gold chloride solution and a reducing agent to a carbon black aqueous solution, stirring, washing and drying, and heat-treating in a hydrogen atmosphere to prepare a platinum-silver or platinum-gold catalyst. (S2-1); and thereafter, the prepared platinum-silver or platinum-gold catalyst is impregnated into an impregnation solution containing ceria component, followed by drying and heat treatment in a nitrogen atmosphere (S1-2, S2-2). ); Or impregnating the prepared platinum-silver or platinum-gold catalyst in a rhodium-containing impregnation solution and drying, followed by heat treatment in a hydrogen atmosphere (S1-3, S2-3); Or an oxygen adsorption promoter comprising the steps of: impregnating the prepared platinum-silver or platinum-gold catalyst in a ruthenium-containing impregnation solution, drying, and heat-treating in a hydrogen atmosphere (S1-4, S2-4). It is achieved by a method for producing a catalyst for low temperature fuel cells containing.

In this case, in the case of the platinum-silver or platinum-gold catalyst containing only the prepared rhodium or ruthenium, the manufacturing method includes the steps of: impregnating the prepared catalyst in a cerium nitrate solution, drying, and then heat-treating it under nitrogen atmosphere. (S1-5, S2-5); It is preferable to further include.

An object of the present invention as described above, further, in the preparation of a catalyst for a low temperature fuel cell, the step of mixing, respectively, the chloroplatinic acid solution, silver nitrate solution or geum chloride solution, and rhodium trichloride solution (S3-1); Injecting the mixed solutions into a carbon black aqueous solution, injecting a sodium hydroxide solution and a formaldehyde solution into the mixture, and mixing them (S3-2); And drying the mixed solution, and then performing heat treatment in a nitrogen atmosphere (S3-3). A method of manufacturing a catalyst for a low temperature fuel cell containing an oxygen adsorption promoter is provided.

In addition, the manufacturing method, the impregnated in the cerium nitrate solution and dried, the heat treatment in a nitrogen atmosphere (S3-4); preferably further comprises a.

An object of the present invention as described above, further, impregnating and drying carbon black or carbon nanotubes in a chloroplatinic acid solution, followed by heat treatment in a hydrogen atmosphere (S4-1); Impregnating the heat treated material with a cerium nitrate solution and drying the same, followed by heat treatment in air (S4-2); Impregnating the heat-treated with one or more solutions selected from the group consisting of a silver nitrate solution or a gold chloride solution and a rhodium-containing impregnation solution, followed by drying and heat treatment in a hydrogen atmosphere (S4-3). It is achieved by a method for producing a catalyst for low temperature fuel cells containing an oxygen adsorption promoter.

An object of the present invention as described above, furthermore, applying a diffusion layer containing carbon, a water-repellent material and an organic solvent to a carbon cloth or carbon paper (S5-1); And applying a catalyst ink including a powder of a catalyst to be prepared, a hydrogen ion conductor ionomer, and an organic solvent to the diffusion layer (S5-2). It is achieved by an electrode manufacturing method.

An object of the present invention as described above, also, after applying a mixture of carbon black and polytetrafluoroethylene (PTFE) on the gas diffusion layer, it is impregnated in chloroplatinic acid solution and dried, and then it is impregnated in silver nitrate solution or geum chloride solution After drying, heat treatment in a hydrogen atmosphere (S6-1); After the heat treatment, the impregnated in the rhodium trichloride solution and dried, the step of heat treatment in a hydrogen atmosphere (S6-2); After the heat treatment, the impregnated in a cerium nitrate solution and dried, heat treatment in a nitrogen atmosphere (S6-3); And impregnating the heat-treated thing with the ionomer solution, which is a hydrogen ion conductor, and then drying (S6-4). The method for preparing a catalyst for a low temperature fuel cell containing an oxygen adsorption promoter, comprising: .

The object of the present invention as described above, further, the platinum-ruthenium catalyst supported on platinum-ruthenium black or carbon, impregnated in a cerium nitrate solution and dried, and then heat-treating in a hydrogen atmosphere (S7-1); comprising It is achieved by a method for producing a catalyst for low temperature fuel cells containing an oxygen adsorption promoter.

An object of the present invention as described above, further, impregnated with carbon black in a chloroplatinic acid solution, a silver nitrate solution or a gold chloride solution, and a chlororuthenium solution and dried, followed by heat treatment in a hydrogen atmosphere (S8-1); And impregnating a cerium nitrate solution with the heat treatment, followed by drying, followed by heat treatment in air (S8-2). Achievable by the method for preparing a catalyst for a low temperature fuel cell containing an oxygen adsorption promoter, characterized in that it comprises a. do.

An object of the present invention as described above, further, impregnating a platinum-ruthenium catalyst supported on platinum-ruthenium black or carbon with a silver nitrate solution or a gold chloride solution and drying, followed by heat treatment in a hydrogen atmosphere (S9-1); And a step of impregnating the heat treatment with the rhodium trichloride solution and the cerium nitrate solution in order and drying, followed by heat treatment in a hydrogen atmosphere (S9-2). Low temperature fuel containing an oxygen adsorption promoter, comprising: It is achieved by a method for producing a battery catalyst.

Hereinafter, a catalyst for a low temperature fuel cell containing an oxygen adsorption promoter according to the present invention, a method for manufacturing the same, an electrode for a low temperature fuel cell manufactured using the same, a method for manufacturing the same, and a low temperature fuel cell including the electrode will be described in detail. .

In the cathode catalyst, the present invention provides a platinum-silver or platinum-gold mother catalyst, which selectively stores and releases oxygen, has an oxygen conductivity, and facilitates oxidation reaction of carbon monoxide at low temperature. By containing ruthenium, or ceria, or a complex of these materials, especially when air having a low partial pressure of oxygen is used in the reduction electrode, it selectively supplies oxygen to the platinum catalyst in the air, and carbon monoxide generated by the crossover methanol Based on the technical idea that the deactivation of the platinum catalyst can be reduced and the performance of the battery can be improved by removing the catalyst, and the present invention further provides a catalyst for the oxidation electrode by applying the catalyst as described above. It is based on the technical idea that oxidative properties and endothelial toxicity to carbon monoxide are excellent.

First, a catalyst for a low temperature fuel cell containing an oxygen adsorption promoter according to the present invention and an electrode including the same will be described in detail.

The catalyst for low temperature fuel cells containing the oxygen adsorption promoter according to the present invention is a platinum-silver catalyst or a platinum-silver catalyst supported on carbon, or a platinum-gold catalyst or carbon, which is a main catalyst in an electrode catalyst for low temperature fuel cells. To the platinum-gold catalyst supported thereon as a co-catalyst containing rhodium, or containing ceria components, or containing ruthenium, or containing a complex of rhodium and ceria components, or ruthenium and ceria Contains a complex of ingredients.

The rhodium, or the ceria component, or the ruthenium, or the complex of the rhodium and ceria component, or the complex of the ruthenium and ceria component, is more apparent from the activity of the oxygen reduction reaction and the methanol oxidation reaction, as will be clearer from the following. Increasing the characteristics can improve the performance of low temperature fuel cells.

The electrode of a low temperature fuel cell containing an oxygen adsorption promoter according to the present invention, on the water-repellent porous carbon cloth or carbon paper, a diffusion layer is formed on the diffusion layer of gas and liquid reactants, and the promoter is contained thereon. A catalyst layer comprising a catalyst, an ionomer which is a polymer electrolyte, and an organic solvent is formed.

In addition, the low temperature fuel cell containing the oxygen adsorption promoter according to the present invention, in the case of the unit cell, an oxidation electrode or a reduction electrode prepared as described above, and a conventional electrolyte membrane interposed therebetween, for example, hydrogen A membrane-electrolyte assembly (MEA) formed by compressing an ion exchange membrane, and a methanol solution, a storage tank of oxygen or air, and a current collector, are equipped with a gasket for maintaining gas tightness.

Next, the manufacturing method of the catalyst for low temperature fuel cells containing an oxygen adsorption promoter according to this invention, and the manufacturing method of the electrode containing this catalyst are explained in full detail.

In the present invention, as a cocatalyst, a platinum-silver catalyst or a carbon-supported platinum-silver catalyst having a rhodium or ceria component or a ruthenium or a complex of rhodium and ceria components or a complex of ruthenium and ceria components as a main catalyst, A method for preparing a multistage electrode catalyst for inclusion in a platinum-gold catalyst or a platinum-gold catalyst supported on carbon is proposed.

To this end, as a method for producing a catalyst for a low temperature fuel cell, a ternary catalyst containing a ceria component, rhodium, or ruthenium is prepared for the main catalyst, a platinum-silver catalyst or a platinum-gold catalyst, as described below; Or a process for producing a four or five membered catalyst containing two or more of the ceria component, rhodium, or ruthenium.

Wherein each of the three-, four- or five-membered catalysts comprises 30-99 wt.% Platinum, 0.1-10 wt.% Silver or gold, 1-70 wt.% Ruthenium or rhodium, and 0.1-10 It is preferable to include the wt.% ceria component from the viewpoint of improving the performance of the battery.

First, the preparation of the catalyst according to the present invention will be described in detail.

First, the manufacturing method of a three way catalyst is as follows.

That is, a platinum-silver or platinum-gold catalyst is first prepared as a mother catalyst. For example, platinum black or carbon-supported platinum is impregnated in a silver nitrate or gold chloride solution, then dried and heat-treated in a nitrogen atmosphere. Powdered, to prepare a platinum-silver or platinum-gold catalyst (S1-1).

Alternatively, to prepare a platinum-silver or platinum-gold catalyst, a carbon powder such as carbon black is dispersed in distilled water, and then dispersed in the prepared carbon black solution, a platinum-containing water-soluble compound or a platinum-containing complex salt, silver nitrate or chloride It is possible to use a method of adding the acid solution and the reducing agent, stirring, washing, drying, heat treatment under a hydrogen atmosphere, and powdering (S2-1).

At this time, as the platinum-containing water-soluble compound or platinum-containing complex salt, chloroplatinic acid, ammonium chloroplatinate, hydroxydisulfite platinum (II) acid, bromoplatinic acid, platinum trichloride, platinum tetrachloride hydrate, platinum dichlorocarbonyl di One selected from the group consisting of chloride, dinitrodiaminoplatinum and sodium tetranitroplatinate can be used.

At this time, the carbon black is selected from the group consisting of Vulcan XC-72, Black Pearl 2000, Conductex 975, Denka Black, Acetylene Black, and Ketjen Black. One may be used, in addition to that, carbon nanotubes may be used.

As such, a platinum-silver or platinum-gold catalyst is prepared, and then the prepared platinum-silver or platinum-gold catalyst is used to selectively adsorb and release oxygen, have an oxygen conductivity, and oxidize carbon monoxide at low temperatures. A platinum-silver or platinum-gold catalyst containing a metal oxide such as rhodium, ruthenium or in particular a ceria component, which is easy to react, is prepared as follows.

That is, when preparing a three-way catalyst containing a ceria component, the platinum-silver or platinum-gold catalyst prepared as described above is repeatedly impregnated in a solution containing a ceria component several times, then dried, and nitrogen. To undergo a heat treatment in the atmosphere (S1-2, S2-2).

At this time, the ceria component, gerianium (Gd), zirconium (Zr), samarium (Sm), yttrium (Y), strontium (Sr), lanthanum (La), calcium (Ca), And at least one of these oxides is doped to 30% or less.

On the other hand, in the case of preparing a rhodium-containing three-way catalyst, the platinum-silver or platinum-gold catalyst prepared as described above is impregnated in the rhodium-containing impregnation solution, and then dried and heat-treated under hydrogen atmosphere (S1). -3, S2-3).

At this time, as the rhodium-containing impregnation solution, one selected from the group consisting of rhodium trichloride, hexaamine rhodium chloride, rhodium carbonyl chloride, rhodium trichloride hydrate, rhodium nitrate, sodium hexachlororhodate and sodium hexanitrolodate Rhodium-based solutions can be used.

In addition, the following method may be used for production of a ternary catalyst containing rhodium.

That is, for example, a chloroplatinic acid solution, a silver nitrate solution or a gold chloride solution, and a rhodium trichloride solution are prepared, respectively, and mixed (S3-1), and then injected into a carbon black aqueous solution, and thus sodium hydroxide solution and form The aldehyde solution is slowly injected and mixed (S3-2). After drying it, heat treatment is performed under nitrogen atmosphere to obtain a platinum-silver or platinum-gold catalyst containing rhodium (S3-3).

On the other hand, for the production of ternary catalysts containing rhodium, the following method may be used.

That is, the chloroplatinic acid solution is impregnated with carbon black or carbon nanotubes, dried and heat-treated under hydrogen atmosphere to prepare a powder (S4-1). Subsequently, the powder is impregnated with cerium nitrate, dried, and then heat-treated in air to prepare a ceria-supported catalyst powder (S4-2). The catalyst powder is impregnated with a silver nitrate or gold chloride solution and a rhodium-containing impregnation solution, dried and then heat-treated in a hydrogen atmosphere (S4-3).

At this time, as the rhodium-containing impregnation solution, one selected from the group consisting of rhodium trichloride, hexaamine rhodium chloride, rhodium carbonyl chloride, rhodium trichloride hydrate, rhodium nitrate, sodium hexachlororhodate and sodium hexanitrolodate The rhodium-based solution can be used as described above.

On the other hand, in the case of preparing a ruthenium-containing three-way catalyst, the platinum-silver or platinum-gold catalyst prepared as described above is impregnated in the ruthenium-containing impregnation solution, and then dried and heat-treated in a hydrogen atmosphere (S1). -4, S2-4).

Further, platinum-ruthenium black or carbon-supported platinum-ruthenium catalyst was impregnated in a cerium nitrate solution, dried (S7-1), and the dried material was heat-treated under a hydrogen atmosphere to form a platinum-ruthenium ternary source. A catalyst may also be prepared (S7-2).

Next, the manufacturing method of a four-way catalyst is as follows.

As described above, when a ternary catalyst of platinum-silver-rhodium or platinum-gold-rhodium containing rhodium is prepared, the catalyst thus prepared is impregnated with cerium nitrate, dried and then heat treated in a nitrogen atmosphere to provide platinum- Silver-rhodium-ceria or platinum-gold-rhodium-ceria quaternary catalysts can be prepared.

On the other hand, for the production of the four-way catalyst, the following method can also be used.

That is, the chloroplatinic acid solution is impregnated with carbon black or carbon nanotubes, dried and heat-treated under hydrogen atmosphere to prepare a powder (S4-1). Subsequently, the powder is impregnated with cerium nitrate, dried, and then heat-treated in air to prepare a ceria-supported catalyst powder (S4-2). The catalyst powder was impregnated in a silver nitrate solution or a gold chloride solution, and a rhodium-containing impregnation solution in that order, dried, and then heat-treated in a hydrogen atmosphere to obtain platinum-silver-rhodium-ceria or platinum-gold-rhodium-ceria. The original catalyst is prepared (S4-3).

At this time, as the rhodium-containing impregnation solution, one selected from the group consisting of rhodium trichloride, hexaamine rhodium chloride, rhodium carbonyl chloride, rhodium trichloride hydrate, rhodium nitrate, sodium hexachlororhodate and sodium hexanitrolodate The rhodium-based solution can be used as mentioned above.

On the other hand, as another manufacturing method of a four-way catalyst, the following method is applicable.

That is, a carbon black and polytetrafluoroethylene (PTFE) mixture is applied to the gas diffusion layer by screen printing, and then impregnated in the chloroplatinic acid solution and the silver nitrate solution or the chloroplatinic acid solution in this order, dried, and then 180 Heat treatment is performed in a hydrogen atmosphere of ˜300 ° C. (S6-1), the electrode is immersed in a rhodium trichloride solution, dried, and heat-treated in a hydrogen atmosphere at 350 ° C. to powder (S6-2). It was impregnated with a cerium nitrate solution, dried, and then heat treated under a nitrogen atmosphere (S6-3), impregnated with an ionomer solution, a hydrogen ion conductor, and then dried and supported on carbon black by platinum-silver-rhodium-ceria or platinum- An electrode consisting of a four-way catalyst of gold-rhodium-ceria is prepared (S6-4).

On the other hand, as described above, when a three-way catalyst of platinum-silver-ruthenium or platinum-gold-ruthenium containing ruthenium is prepared, the catalyst thus prepared is impregnated with cerium nitrate, and heat-treated in a nitrogen atmosphere after drying. Platinum-silver-ruthenium-ceria or platinum-gold-ruthenium-ceria quaternary catalysts can be prepared.

On the other hand, as another manufacturing method of a four-way catalyst, the following method is applicable.

That is, the chloroplatinic acid solution, the silver nitrate solution or the gold chloride solution, and the chlororuthenium solution are impregnated with carbon black, for example, Vulcan XC-72, dried, and then heat treated in a hydrogen atmosphere (S8-1), and the powder subjected to the heat treatment. Is impregnated with cerium nitrate, dried, and then heat-treated in air to prepare a platinum-silver or platinum-gold catalyst powder loaded with ruthenium and ceria (S8-2).

Next, the manufacturing method of a 5-membered catalyst is as follows.

A platinum-ruthenium catalyst supported on platinum-ruthenium black or carbon was impregnated in a silver nitrate solution or a gold chloride solution, dried, and then heat-treated in a hydrogen atmosphere (S9-1), followed by an anneal solution of rhodium trichloride and cerium nitrate Impregnated in order and dried and then heat treated in a hydrogen atmosphere (S9-2) to prepare a five-way catalyst of platinum-silver-ruthenium-rhodium-ceria or platinum-gold-ruthenium-rhodium-ceria.

Using the catalyst prepared as described above, a method for producing an electrode for a low temperature fuel cell is as follows.

That is, first, a gas diffusion layer containing carbon, a water repellent, and an organic solvent is applied to a carbon cloth or carbon paper (S5-1), and the powder of the catalyst prepared as described above, a hydrogen ion conductor ionomer, and an organic solvent are included. The catalyst ink is coated on the gas diffusion layer to prepare an electrode (S5-2).

According to the catalyst for a fuel cell containing such an oxygen adsorption promoter, a manufacturing method thereof, a fuel cell electrode manufactured using the same, a manufacturing method thereof, and a fuel cell including the electrode, carbon monoxide generated by the crossover methanol By eliminating this, the deactivation of the platinum catalyst can be reduced, and the oxygen reduction activity and the methanol oxidation activity can be improved, thereby improving the performance of the low temperature fuel cell. In particular, the electrode catalyst according to the invention which contains a rhodium, ruthenium, or ceria component in a platinum-silver or platinum-gold catalyst, or a complex of these materials, selectively adsorbs oxygen in air and supplies it to the platinum catalyst. Even when low partial pressure air is used for the cathode, improved battery performance can be obtained.

Hereinafter, the present invention will be described in more detail by explaining preferred embodiments of the present invention. However, the present invention is not limited to the following examples, and various forms of embodiments can be implemented within the scope of the appended claims, and the following examples are only common in the art while making the disclosure of the present invention complete. It is intended to facilitate the implementation of the invention to those with knowledge.

Example 1

This Example 1 relates to the production of a platinum catalyst supported on carbon black containing silver.

After dissolving 1 g of chloroplatinic acid (H ₂ PtCl ₆ ) in 200 ml of distilled water, 4 g of 60 wt.% NaHSO ₃ was injected and stirred for 1 hour. At this time, the yellow solution turned into a colorless transparent solution. After dilution with 500 ml of distilled water, a pH of 5 was adjusted by adding 0.6M aqueous sodium carbonate solution (0.7631 g of Na ₂ CO ₃ + 12 ml of distilled water). 30 ml of hydrogen peroxide was slowly injected into the solution at a rate of 1 ml / min, and the pH was maintained at 4 to 4.5 with 5 wt.% Sodium hydroxide solution (5 g of NaOH + 95 g of distilled water). Following was added a carbon (Vulcan XC-72R) and 0.8577g of 4 hours, reduced in a hydrogen bubbling (H ₂ bubbling), washed several times and then dried in vacuum with distilled water for one day. The platinum catalyst supported on carbon prepared as described above was impregnated and dried in an aqueous solution of silver nitrate, and then heat-treated at 300 ° C. for 2 hours in a nitrogen atmosphere.

Example 2

This Example 2 relates to the production of a platinum catalyst supported on carbon black containing ceria doped with zirconium.

Cerium nitrate (Ce (NO _{3) 3)} in an aqueous solution and a mixed solution of zirconium nitrate (Zr (NO _{3) 4)} solution, to the aqueous ammonia solution was added, it was maintained at pH 4 ~ 5. After stirring for 1 hour, washed, dried and calcined at 600 ° C. for 3 hours to prepare a zirconium-doped ceria. The solution prepared by dissolving ceria doped with zirconium in distilled water was impregnated by adding a carbon catalyst (40 wt.%, Pt / C, E-TEK) supported on carbon. Drying and impregnation for one day in an oven were repeated to support the desired amount. After drying sufficiently in an oven to remove the water, it was subjected to a heat treatment process. In order to prevent the loss of carbon as a carrier, heat treatment was performed at 300 ° C. for 2 hours in a nitrogen atmosphere. The catalyst thus prepared was expressed as follows [Formula 1], and the catalyst was expressed using Table 1 and FIGS. 1 to 4 using [Formula 1].

[Formula 1]

xPyCzA

Where P is platinum, C is ceria and A is zirconium as an additive, x is the weight percent of platinum in the platinum catalyst, y is the weight percent of ceria to platinum, and z is the weight percent of zirconium to ceria. .

Table 1 shows the specific surface area of the catalyst prepared according to Example 2.

₄₀ P ₀ C ₀ A ₄₀ P _0.5 C ₃₀ A ₄₀ P ₁ C ₃₀ A ₄₀ P _1.5 C ₃₀ A ₄₀ P ₃ C ₃₀ A Specific surface area (m ³ / g) 122 120 117 111 98

As can be seen from Table 1, it can be seen that the specific surface area decreases as ceria is added.

1 is a graph showing the pore size distribution of a platinum catalyst supported on carbon black containing ceria doped with zirconium prepared according to Example 2 of the present invention.

As can be seen in Figure 1, as the ceria is added, the pore volume corresponding to the micropores of the catalyst is also reduced.

FIG. 2 is a graph showing the results of X-ray diffraction analysis (XRD) of a platinum catalyst supported on carbon black containing zirconium-doped ceria prepared according to Example 2 of the present invention.

As can be seen in Figure 2, even if the ceria is added to the curve does not appear, from which it can be confirmed that the amorphous present.

The powder thus prepared was crushed finely, evenly dispersed in water and an organic solvent (isopropanol), and an appropriate amount of ionomer, a hydrogen ion conductor, was added thereto to prepare a catalyst ink. The catalyst ink thus prepared was applied onto the carbon-teflon layer by spray coating to prepare a reduction electrode. A polymer electrolyte membrane was placed between the prepared reduction electrode and the oxidation electrode and hot-pressed to prepare an electrolyte membrane-electrode assembly (MEA).

3 and 4 show performance curves of a unit cell using a platinum catalyst supported on a carbon black containing ceria doped with zirconium prepared according to Example 2 of the present invention, and FIG. (250 sccm) is used, and FIG. 4 is a case where air (250 sccm) is used for the reduction electrode.

As can be seen in Figure 4, even when using the air instead of oxygen in the cathode, compared to using only platinum or carbon supported on the conventional, about 30% of the performance increase was shown.

Example 3

Example 3 relates to the preparation of a platinum-silver catalyst supported on carbon black containing rhodium and ceria.

The platinum-silver catalyst powder of Example 1 was placed in distilled water and stirred and mixed for 1 hour in an ultrasonic stirrer. On the other hand, a 7.9 g rhodium trichloride solution and a 14.47 g cerium nitrate solution were prepared and slowly injected into the carbon black solution prepared by the method as described above. After the mixture was stirred for 1 hour, 2.5M sodium hydroxide solution and 37 wt.% Formaldehyde solution were sequentially injected slowly. It was stirred for 1 hour, washed several times with distilled water and then dried in an 80 ° C. vacuum oven. The dried catalyst was heat treated in a nitrogen atmosphere at 300 ° C.

After finely crushing the powder thus prepared, a reduction electrode and MEA were prepared in the same manner as in Example 2.

FIG. 5 shows the performance curves of unit cells using platinum-silver catalysts supported on rhodium and ceria-containing carbon black prepared according to Example 3 of the present invention, in which air (250sccm) was used for the cathode. to be.

As can be seen in Figure 5, compared to when using only the carbon commercial catalyst supported on carbon, the performance was increased about 2 times.

Example 4

This Example 4 relates to the production of a platinum-ruthenium catalyst supported on carbon black containing ceria.

After dissolving 1 g of chloroplatinic acid (H ₂ PtCl ₆ ) in 200 ml of distilled water, 4 g of 60 wt.% NaHSO ₃ was injected and stirred for 1 hour. At this time, the yellow solution turned into a colorless transparent solution. After dilution with 500 ml of distilled water, a pH of 5 was adjusted by adding 0.6M aqueous sodium carbonate solution (0.7631 g of Na ₂ CO ₃ + 12 ml of distilled water). 50 ml of hydrogen peroxide was slowly injected into the solution at a rate of 1 ml / min, and the pH was maintained at 4 to 4.5 with 5 wt.% Aqueous sodium hydroxide solution (5 g of NaOH + 95 g of distilled water). Then, an aqueous ruthenium chloride solution (RuCl ₃ 0.4692 g + 50 ml of distilled water) was added at a constant rate of 1 ml / min, and the pH was maintained at 4 to 4.5 using an aqueous sodium hydroxide solution. Then, put a carbon (Vulcan XC-72R) 0.8577g, washed in a hydrogen bubbling (H ₂ bubbling), several times with distilled water was reduced 4 hours, dried for a day in a vacuum. The platinum-ruthenium catalyst supported on the carbon black thus prepared was impregnated and dried in an aqueous solution of cerium nitrate, and then heat-treated for 2 hours under a nitrogen atmosphere of 300 ° C.

Example 5

Example 5 relates to the production of a platinum-ruthenium catalyst supported on carbon black containing rhodium and ceria.

The platinum-ruthenium catalyst powder of Example 4 was added to distilled water and stirred and mixed for 1 hour in an ultrasonic stirrer. On the other hand, a 7.9 g rhodium trichloride solution and a 14.47 g cerium nitrate solution were prepared and slowly injected into the carbon black solution prepared by the method as described above. After the mixture was stirred for 1 hour, 2.5M sodium hydroxide solution and 37 wt.% Formaldehyde solution were sequentially injected slowly. It was stirred for 1 hour, washed several times with distilled water and then dried in an 80 ° C. vacuum oven. The dried catalyst was heat treated in a nitrogen atmosphere at 300 ° C.

Example 6

This Example 6 relates to the production of a platinum-gold catalyst supported on carbon black containing ceria.

First, 1 g of chloroplatinic acid (H ₂ PtCl ₆ ) was dissolved in 200 ml of distilled water, and 4 g of 60 wt.% NaHSO ₃ was injected and stirred for 1 hour. At this time, the yellow solution turned into a colorless transparent solution. After dilution with 500 ml of distilled water, a pH of 5 was adjusted by adding 0.6M aqueous sodium carbonate solution (0.7631 g of Na ₂ CO ₃ + 12 ml of distilled water). 30 ml of hydrogen peroxide was slowly injected into the solution at a rate of 1 ml / min, and the pH was maintained at 4 to 4.5 with 5 wt.% Sodium hydroxide solution (5 g of NaOH + 95 g of distilled water). Following was added a carbon (Vulcan XC-72R) and 0.8577g of 4 hours, reduced in a hydrogen bubbling (H ₂ bubbling), washed several times and then dried in vacuum with distilled water for one day. The platinum catalyst supported on the carbon prepared as described above was sequentially impregnated and dried in an aqueous solution of chloric acid and an aqueous solution of cerium nitrate, and then heat-treated at 300 ° C. for 2 hours in a nitrogen atmosphere.

According to the catalyst for a fuel cell containing the oxygen adsorption promoter of the present invention, a method for producing the same, a fuel cell electrode manufactured using the same, a method for producing the same, and a fuel cell including the electrode, the main catalyst is platinum-silver or platinum- On the basis of a gold catalyst, it selectively adsorbs and releases oxygen, selectively contains rhodium, ruthenium or ceria components, or complexes thereof, having an oxygen conductivity and facilitating the oxidation reaction of carbon monoxide at low temperatures, selectively in air. By supplying oxygen to the platinum catalyst and removing the carbon monoxide generated by the crossovered methanol, the deactivation of the platinum catalyst is reduced, thereby improving the performance of the cell, and the methanol oxidation activity and the endothelial toxicity to carbon monoxide are Better effects are achieved than catalysts. In particular, according to the present invention, even when air having a low oxygen partial pressure is used in the cathode, an effect of obtaining improved battery performance is achieved.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will cover such modifications and variations as fall within the spirit of the invention.

1 is a graph showing the pore size distribution of a platinum catalyst supported on carbon black containing ceria doped with zirconium prepared according to Example 2 of the present invention;

2 is a graph showing the results of X-ray diffraction analysis (XRD) of a platinum catalyst supported on a carbon black containing ceria doped with zirconium prepared according to Example 2 of the present invention;

3 is a performance curve of a unit cell when oxygen is used in a reduction electrode using a platinum catalyst supported on a carbon black containing ceria doped with zirconium prepared according to Example 2 of the present invention;

4 is a performance curve of a unit cell when air is used in a reduction electrode using a platinum catalyst supported on a carbon black containing ceria doped with zirconium prepared according to Example 2 of the present invention;

FIG. 5 is a performance curve of a unit cell when air is used for the reduction electrode using a platinum catalyst supported on carbon black containing rhodium and ceria prepared according to Example 3 of the present invention.

Claims (5)

In the electrode catalyst for low temperature fuel cell, To the main catalyst, the platinum-silver catalyst or the platinum-silver catalyst supported on carbon, or the platinum-gold catalyst or platinum-gold catalyst supported on carbon, as a promoter, rhodium (Rh), ceria (CeO2) component, ruthenium A catalyst for low temperature fuel cells containing an oxygen adsorption promoter, characterized by containing at least one (Ru). The method of claim 1, wherein the ceria component, At least one of gadolonium (Gd), zirconium (Zr), samarium (Sm), yttrium (Y), strontium (Sr), lanthanum (La), calcium (Ca), and oxides thereof A catalyst for low temperature fuel cells containing an oxygen adsorption promoter, which is doped at 30% or less. The method of claim 1, wherein the catalyst, Oxygen adsorption comprising 30-99 wt.% Platinum, 0.1-10 wt.% Silver or gold, 1-70 wt.% Ruthenium or rhodium, and 0.1-10 wt.% Ceria Catalyst for low temperature fuel cell containing a promoter. A low temperature fuel cell electrode containing an oxygen adsorption promoter, comprising the catalyst according to any one of claims 1 to 3. A low temperature fuel cell containing an oxygen adsorption promoter, comprising the electrode according to claim 4.