JP3576108B2 - Electrode, fuel cell using the same, and method of manufacturing electrode - Google Patents

Description

【表２】

以上の結果から、導電性粒子を加えることで、触媒粒子に導電性機能を持たない親水性のＳｉＯ_２を主成分とする触媒担体を使用した電極を用いた場合、実施例９乃至１４に示すように、電池性能が向上することが分かる。
【０１０８】
また、ＳｉＯ_２を主成分とする触媒担体のうち、ルイス酸を有する複合酸化物を使用したときに特に電池性能が向上していることが分かる。
【０１０９】
【発明の効果】
上述したように、本発明によれば、発電効率の高い電極、電極用組成物、それを用いた燃料電池をえることが可能になる。
【図面の簡単な説明】
【図１】本発明の燃料電池の基本構成を示す断面図。
【図２】本発明の電極の一例を示す概念図。
【図３】本発明の燃料電池の単セルを示す断面図。
【符号の説明】
１…集電体
２…燃料極
３…プロトン伝導性膜
４…酸化剤極
５…起電部
２０…電極
２１…触媒担体
２２…白金系金属粒子
２３…触媒粒子
２４…導電性粒子
２５…プロトン伝導性物質[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrode, a composition for an electrode, and a fuel cell using the same, and particularly to an electrode for transferring protons.ExtremeAnd a fuel cell using the same.
[0002]
[Prior art]
Fuel cells convert fuel chemical energy directly into electric energy by electrochemically oxidizing fuel such as hydrogen and methanol in the cell, and take out NOx by burning fuel like thermal power generation. Because there is no generation of SOx or SOx, it is attracting attention as a clean electric energy supply source.
[0003]
The electrode structure of a conventional fuel cell has, for example, a five-layer structure in which a cathode current collector / cathode / proton conductive membrane / anode / anode current collector are sequentially stacked.
[0004]
Electrodes such as anodes and cathodes are conventionally composed of a catalyst in which metal particles such as platinum or a platinum alloy are supported on the surface of a catalyst carrier such as carbon and a proton conductive material represented by, for example, a fluororesin having a sulfonic acid group. Compositions have been used. Carbon is used as the catalyst carrier because carbon is considered to be effective for extracting electrons generated on the surface of metal particles because carbon has conductivity.
[0005]
In order to uniformly disperse the catalyst and the proton conductive substance, it is usually necessary to mix the proton conductive substance with carbon fine particles in a state of being dissolved in an organic solvent. However, a catalyst in which metal particles such as platinum and an alloy thereof are supported on a carbon surface has a problem that it ignites when it comes into contact with an organic solvent (particularly alcohol) in an atmosphere containing oxygen.
[0006]
Therefore, when preparing the conventional electrode, first, the catalyst is dispersed in water to prevent the organic solvent from directly contacting the catalyst surface in the presence of air (oxygen), and then the organic solvent in which the proton conductive material is dissolved Then, after mixing to form a slurry, the organic solvent and water were volatilized to produce an electrode.
[0007]
However, when a fuel cell is assembled using the electrodes obtained in this manner, there is a problem that the cell characteristics vary, and in most cases, the fuel cell cannot efficiently generate power.
[0008]
[Problems to be solved by the invention]
As described above, when an electrode obtained by a conventional manufacturing method is used in a fuel cell, there is a problem that power cannot be efficiently generated.
[0009]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an electrode having a high power generation efficiency, a composition for an electrode, a fuel cell using the same, and a method for producing an electrode.
[0010]
[Means for Solving the Problems]
The electrode of the present invention is obtained by converting metal particles composed of platinum or an alloy thereof to SiO_TwoThe catalyst particles supported on the surface of the catalyst carrier having as a main component, the conductive particles, and the proton conductive materialWherein the catalyst support is SiO 2 _Two A composite oxide exhibiting Lewis acidity containing at least 50 wt% of a componentIt is characterized by.
[0012]
The method for manufacturing an electrode according to the present invention comprises the steps of:₂A catalyst particle dispersion step of preparing catalyst particle dispersion water by dispersing catalyst particles supported on the surface of a catalyst carrier containing as a main component, and containing an organic solvent in which a proton conductive substance is dissolved and the catalyst particle dispersion. A mixing step of preparing a mixed solution to be performed, the catalyst particle dispersion liquid, the organic solvent or a conductive particle dispersion step of dispersing conductive particles in the mixed liquid, and drying the mixed liquid, the water and the organic solvent And a drying step for removing
[0014]
The proton conductive substance may be dissolved in an organic solvent.
[0015]
The fuel cell of the present invention includes a fuel electrode to which a fuel containing a hydrogen element is supplied, an oxidant electrode to which oxygen is supplied, and a proton conductor layer sandwiched between the fuel electrode and the oxidant electrode. In the fuel cell provided, at least one of the fuel electrode and the oxidant electrode is made of a metal particle made of platinum or an alloy thereof formed of SiO._TwoContains catalyst particles supported on the surface of a catalyst carrier mainly composed of, conductive particles, and a proton conductive materialAnd the catalyst support is SiO 2 _Two A composite oxide exhibiting Lewis acidity containing 50% by weight or more of a component.It is characterized by the following.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the basic configuration of a fuel cell is shown in FIG.
[0017]
In FIG. 1, a current collector 1, a fuel electrode 2, a proton conductive membrane 3, an oxidant electrode 4, and a current collector 1 are sequentially stacked to form a fuel cell (electric generator) 5.
[0018]
When a mixed fuel composed of methanol and water is supplied to the fuel electrode 2 and air (oxygen) is supplied to the oxidant electrode 4, a catalytic reaction represented by chemical formulas (1) and (2) occurs at each electrode.
[0019]
Fuel electrode: CH₃OH + H₂O → CO₂+ 6H⁺+ 6e⁻  (1)
Oxidant electrode: 6H⁺+ (3/2) O₂+ 6e⁻  → 3H₂O (2)
As described above, the protons generated at the fuel electrode 2 move to the proton conductive membrane, the electrons move to one current collector 1, and the electrons supplied from the other current collector 1 and the proton conductivity move to the oxidant electrode 4. By reacting the proton supplied from the membrane 3 with oxygen, a current flows between the pair of current collectors 1.
[0020]
Therefore, each of the electrodes (the fuel electrode and the oxidizer electrode) has a catalyst particle that causes the reaction of the chemical formula (1) or the chemical formula (2), a conductive property between the catalyst particle and the current collector, and a catalyst particle. And proton conduction properties between the proton conductive membranes.
[0021]
In the present invention, by making the electrode structure as shown in FIG. 2, the above three characteristics can be efficiently exhibited.
[0022]
FIG. 2 is an enlarged view schematically showing the vicinity of the electrode of the present invention, which is composed of a catalyst carrier 21 and metal particles 22 of platinum or an alloy thereof exhibiting catalytic properties (hereinafter referred to as platinum-based metal particles). The electrode 20 is formed from the catalyst particles 23, the conductive particles 24, and the proton conductive material 25 to be formed.
[0023]
In the electrode 20, electrons move between the current collector 1 and the platinum-based metal particles 22 via the conductive particles 24, and protons are transferred through the platinum-based metal particles 22 and the proton-conductive film 4 via the proton-conductive substance 25. Move between. The electrode having such a configuration enables the catalyst particles 23 and the proton conductive substance to be uniformly dispersed, so that the above-described three characteristics including the proton conductivity can be efficiently exhibited.
[0024]
That is, an electrode composed of a catalyst particle and a proton conductive material, in which platinum-based metal particles are supported on the surface of a conventional carbon carrier (a catalyst carrier having a conductive function), has a high water-repellent carbon property in its manufacturing process. Even if the mixture is stirred together, the dispersion does not disperse uniformly and forms an aggregate, so that a proton conductive substance (a proton conductive substance dissolved in an organic solvent) cannot enter the aggregate. For this reason, the contact ratio between the catalyst particles (platinum-based metal particles) and the proton-conductive substance in the obtained electrode is reduced, and the protons generated by the platinum-based metal particles cannot be transferred to the proton-conductive membrane. Was.
[0025]
The present inventors disperse the conductive particles 24 in the electrode 20, as shown in FIG. 2, thereby enabling a hydrophilic material for the catalyst carrier 21. As a result, the platinum-based metal particles 22 It has been confirmed that the proton conduction efficiency with the conductive membrane 4 is increased, and that the power generation efficiency when used as a fuel cell is drastically improved, leading to the present invention.
[0026]
Hereinafter, the catalyst particles 23, the conductive particles 24, and the proton conductive substance 25 will be described in detail.
[0027]
<Catalyst particles 23>
The catalyst particles include platinum-based metal particles 22 and a catalyst carrier 21 that supports the platinum-based metal particles.
[0028]
The catalyst carrier according to the present invention does not need to have the conductive property as described above, and is a hydrophilic material such as SiO.₂Alone or SiO₂Can be used. SiO₂The particles whose main component is SiO₂And other components may be used.₂-M_xO_y(M is an arbitrary element), and is preferably a particle containing at least 50 mol% of a SiO 2 component.
[0029]
In particular, SiO exhibiting Lewis acidity₂-M_xO_yIt is preferable to use a composite oxide represented by the following formula, and for example, M is desirably at least one or more elements selected from elements in the second to sixth periods. More specific materials showing Lewis acidity include SiO 2₂-Al₂O₃, SiO₂-B₂O₃, SiO₂-WO₃, SiO₂-P₂O₅, SiO₂-MoO₃, SiO₂-RuO₂, SiO₂-Ir₂O₃, SiO₂-PtO₂, SiO₂-Rh₂O₃, SiO₂-PdO, SiO₂-ZrO₂, SiO₂-TiO₂, SiO₂-Hf₂O₃, SiO₂-Al₂O₃-P₂O₅, SiO₂-TiO₂-P₂O₅  , SiO₂-WO₃-P₂O₅, SiO2-MnO2, SiO2-SnO2, etc., but are not limited thereto.
[0030]
The average particle size of the catalyst carrier is preferably in the range of 10 nm to 1 μm. When the average particle diameter is smaller than 10 nm, the productivity and handleability of the catalyst carrier become difficult, and when the average particle diameter is larger than 1 μm, the contact ratio of platinum-based metal particles in contact with the conductive particles described below decreases. The specific surface area (measured by the BET method) of the catalyst carrier is 10 to 2500 m²/ G range is good, especially 50-600m²/ G is good. When the specific surface area is smaller than 10, the amount of the platinum-based metal particles that can be supported is reduced, and the²If it exceeds / g, its synthesis is difficult and there is a problem in productivity.
[0031]
The platinum-based fine particles (fine particles made of platinum or an alloy thereof) according to the present invention are fine particles made of a metal that activates the reaction of the chemical formula (1) or the chemical formula (2) described above.
[0032]
Examples of the metal alloyed with platinum in the platinum alloy include platinum group elements such as Ru, Rh, Ir, Os, and Pd, and transition metals in the fourth to sixth cycles. Pt-Ru, Pt-Ru-Ir, Pt-Ru-Ir-Os, Pt-Ir, Pt-Mo, Pt-Fe, Pt-Co, Pt-Ni, Pt-W, Pt-Sn, Pt-Ce or Examples include alloys such as Pt-Re, but are not particularly limited thereto. The ratio of platinum to the other elements in the platinum alloy varies depending on the combination thereof, but the ratio of the other elements is usually adjusted so as to be in a range that forms a solid solution in platinum.
[0033]
In particular, it is preferable to use fine particles made of Pt as the oxidant electrode and Pt-Ru alloy as the fuel electrode.
[0034]
The platinum-based metal particles composed of such a material usually have an average particle size of about 1 to 10 nm.
[0035]
Next, an example of a method for supporting platinum-based metal particles on the surface of the catalyst carrier will be described.
[0036]
First, the catalyst support is suspended in water, heated to about 40 ° C. to 100 ° C., and then a precursor of platinum-based metal particles is added.
[0037]
In the case of obtaining platinum fine particles as platinum-based metal particles, for example, chloroplatinic acid (H₂PtCl₆), Dinitrodiaminoplatinum, second platinum chloride, first platinum chloride, bisacetylacetonato platinum, dichlorodiammine platinum, dichlorotetramine platinum, second platinum sulfate and the like. Further, when obtaining a platinum alloy as platinum-based metal particles, the precursor of platinum fine particles further ruthenium chloride, iridium chloride, osmium chloride, rhodium chloride, ferric chloride, cobalt chloride, chromium chloride, gold chloride, silver nitrate, A precursor to which an alloy component such as rhodium nitrate, palladium chloride, nickel nitrate, iron sulfate, and copper chloride is added may be used.
[0038]
By dissolving such a precursor in the suspension, the suspension is made an acidic solution.
[0039]
An alkali is added to the acidified suspension, and the suspension is heated appropriately to neutralize the suspension. For example, Pt (OH)₄For example, a hydroxide of platinum or a metal constituting the platinum alloy is generated and supported on the surface of the catalyst carrier. The suspension is filtered and dried to obtain Pt (OH)₄Thus, a catalyst carrier carrying the above is obtained. If necessary, washing and filtration of the catalyst particles may be repeated to further remove impurity ions generated by the neutralization reaction.
[0040]
Pt (OH)₄Is placed in a reducing atmosphere, and Pt (OH)₄The catalyst particles having platinum-based metal particles supported on the surface of the catalyst carrier can be obtained by reducing such as to generate platinum-based metal particles.
[0041]
The reducing atmosphere may be a temperature range of 100 ° C. to 900 ° C., preferably 200 ° C. to 500 ° C. in a gas atmosphere containing a reducing gas such as hydrogen. If the reduction temperature is lower than 100 ° C., the crystallization of the platinum-based metal particles becomes insufficient, and when used for an electrode, the particle diameter tends to increase. If the reduction temperature is higher than 900 ° C., the diameter of the platinum light metal particles increases, and the catalytic activity decreases.
[0042]
It is desirable that the supported amount of the platinum-based metal particles in the catalyst particles is 20 wt% to 80 wt%. If it is less than 20 wt%, the battery performance will not be obtained, and if it is more than 80 wt%, it will not be able to be properly supported on the catalyst carrier.
[0043]
<Conductive particles 24>
The material constituting the conductive particles can be used without particular limitation as long as it is a conductive material. For example, carbon materials such as carbon particles, carbon fibers or carbon nanotubes, and metal particles can be used. In particular, a carbon material is preferable in terms of cost reduction, mass productivity, and weight reduction of the electrode. Further, particles in which the surface of an insulating material such as a resin is coated with a conductive material can also be used. However, since protons move in the electrode, the electrode is in an acidic state when the electrode is used. Therefore, it is desirable to use a material having high acid resistance, for example, a carbon material or a noble metal material as the conductive material.
[0044]
As the average particle size of the conductive particles, those having a diameter of 5 nm to 50 μm can be used, and those having a diameter of 100 nm to 10 μm are particularly preferable. If the particle size of the conductive particles is smaller than 100 nm, the conductive particles may not come into contact with each other, a conductive path may not be formed in the electrode, and if the particle size is larger than 10 μm, the conductive particles may be uniformly formed in the electrode. It becomes difficult to disperse. In addition, the shape of the conductive particles is not limited to a spherical shape, and a fiber shape such as the carbon fiber described above can be used.By using the fiber-shaped conductive particles, the ratio of the conductive particles can be reduced. It is also possible to form conductive paths in the electrodes.
[0045]
The ratio of the conductive particles to the catalyst particles is preferably in the range of 10 parts by weight to 1000 parts by weight, more preferably 50 parts by weight to 500 parts by weight, based on 100 parts by weight of the catalyst particles. When the ratio of the conductive particles is less than 10 parts by weight, a conductive path cannot be secured, and when the ratio is more than 1000 parts by weight, the ratio of the catalyst particles decreases, and the catalytic function decreases.
[0046]
<Proton conductive substance 25>
The proton conductive substance can be used without any particular limitation as long as it can transmit protons. Examples include, but are not limited to, fluorine resins having a sulfonic acid group, such as Nafion (manufactured by DuPont), Flemion (manufactured by Asahi Kasei Corporation), and Ashbreck (manufactured by Asahi Glass), and inorganic substances such as tungstic acid and phosphotungstic acid. is not.
[0047]
The ratio of the proton conductive substance in the electrode is 1 to 1000 parts by weight, particularly 10 to 200 parts by weight, per 100 parts by weight of the catalyst particles. When the amount is less than 1 part by weight, the proton conductivity of the electrode cannot be sufficiently obtained, and when the amount is more than 1000 parts by weight, the ratio of the catalyst particles is reduced to deteriorate the catalytic function, or the ratio of the conductive particles is reduced and the conductive path is reduced. May not be formed.
[0048]
The electrode composed of these materials is preferably a porous body having a porosity of about 0.1% to 85%. When the porosity is less than 0.1%, the contact area of the electrode with the fuel or oxygen supplied to the electrode becomes small, and the catalytic reaction of the above-mentioned chemical formula (1) or (2) can be performed efficiently. It may not be possible. If the porosity is more than 85%, the probability of contact between the conductive particles decreases, and there is a possibility that a conductive path in the electrode may not be formed.
[0049]
Next, a method for manufacturing an electrode will be described.
[0050]
In the preparation of the electrode of the present invention, after preparing an electrode composition containing the above-described catalyst particles, conductive particles, proton conductive material, water and an organic solvent, the water and the organic solvent are removed by volatilization or the like. It can be obtained by: The materials of the catalyst particles, the conductive particles, and the proton conductive substance, and the respective ratios may be the same as those described above.
[0051]
For the electrode composition, for example, a dispersion water in which conductive particles are dispersed in an organic solvent in which a proton conductive substance is dissolved, and a suspension in which catalyst particles are dispersed in water are prepared, and both are sufficiently stirred and mixed. It is obtained by doing.
[0052]
The proton conductive substance was dissolved in the organic solvent because the proton conductive substance generally has low solubility in water and high solubility in the organic solvent. It becomes possible to disperse uniformly in an object. The organic solvent to be used is not particularly limited as long as it can dissolve the proton conductive substance. For example, ethanol, 1-propanol, and the like can be used. It is also possible to use liquids.
[0053]
In addition, the catalyst particles are dispersed in water because the platinum-based metal particles may ignite when they come into contact with an organic solvent in an oxygen atmosphere (in air). This is for bringing the solvent into contact.
[0054]
The conductive particles do not necessarily need to be dispersed in an organic solvent, and may be dispersed in water with a catalyst, for example, or in a mixed solution in which an organic solvent in which proton conductive particles are dissolved and a suspension of catalyst particles are mixed. Conductive particles may be added and dispersed in the mixture. However, when a material having a low affinity for water, such as a carbon material, is used as the conductive particles, if the conductive particles are administered directly into water, they may not be uniformly dispersed. It is preferable to mix with a suspension of catalyst particles after dispersing in a solvent. However, in the case of a carbon material that has been subjected to a hydrophilic treatment by surface oxidation or the like, there is no major problem even if it is directly administered to water.
[0055]
In this manner, the electrode composition can be obtained. However, the electrode composition in which only a more volatile organic solvent component is vaporized may be subjected to a film formation process described later.
[0056]
Further, in order to improve the film forming property of the electrode composition described later, water is added so that the ratio of the solid components (conductive particles and catalyst particles) in the electrode composition is in the range of 2 to 60 wt%. It is preferable to adjust the amount of the organic solvent.
[0057]
In addition, dispersion of conductive particles in an organic solvent, dispersion of catalyst particles in water, or stirring of a mixed solution containing conductive particles and catalyst particles, such as ball mill, sand mill, bead mill, paint shaker or nanomizer What is necessary is just to perform using a known disperser.
[0058]
The electrode composition thus obtained can form an electrode layer by, for example, using a current collector or the like as a support and applying it on the support and then drying.
[0059]
As the current collector, a material having gas permeability or liquid permeability, such as carbon cloth or carbon paper, is used. In addition, if necessary, the surface of the current collector may be subjected to a water-repellent treatment to adjust the film thickness of the composition for an electrode on the surface of the current collector.
[0060]
Further, the electrode of the present invention is not limited to the manufacturing method described above. For example, after a porous body composed of a catalyst, conductive particles and a binder resin is formed, a proton conductive substance can be produced on the pore surfaces of the porous body by the method described below. This manufacturing method will be specifically described.
[0061]
A suspension in which the catalyst particles are dispersed in water, a dispersion in which the conductive particles and the pore-forming agent are dispersed in an organic solvent in which a thermoplastic binder resin is dissolved is prepared, and the obtained suspension and dispersion are dispersed. The mixture is mixed to form a mixture, and the mixture that is kneaded while heating the mixture is an integrated solid.
[0062]
The solid is formed into a desired shape, dried if necessary, and then immersed in a dissolving agent to dissolve the pore-forming agent, thereby making the mixture porous.
[0063]
After the porous mixture is washed, it is immersed in an inorganic liquid such as water, and an organic solvent in which a proton conductive substance is dissolved in the liquid is added. As a result, the proton conductive material penetrates into the pores of the mixture. Further, the electrode of the present invention is formed by volatilizing water, an organic solvent, and the like existing in the pores.
[0064]
According to this manufacturing method, since the electrode can be formed into a desired shape, it is easy to increase the thickness of the electrode, for example.
[0065]
Also in this manufacturing method, the materials and ratios of the catalyst particles, the conductive particles, and the proton conductive substance may be the same as those described above.
[0066]
The pore-forming agent may be a predetermined dissolving agent, for example, a solution that is dissolved in an acidic solution, an alkaline solution, or the like and does not dissolve in the above-described solid such as water or an organic solvent. , Ammonium carbonate, lithium fluoride, polyvinyl alcohol, polyethylene oxide, lintangenic acid or a salt thereof, phosphomolybdic acid and a salt thereof, ammonium chloride, and the like, but are not limited thereto.
[0067]
The composition ratio of the pore-forming agent in the solid is preferably in the range of 1 wt% to 50 wt%, more preferably in the range of 5 wt% to 30 wt%. If the content is less than 1 wt%, the proton conductive substance cannot be impregnated into the pores, or even if the impregnation is performed, the ratio of the proton conductive substance in the electrode decreases, and the proton conductivity decreases. If it exceeds 50% by weight, the ratio of pores increases, the mechanical strength of the electrode decreases, and the ratio of catalyst particles and conductive particles decreases, so that a sufficient catalytic function and conductive function cannot be obtained.
[0068]
The average particle size of the pore-forming agent is preferably about 0.01 μm to 100 μm. When the average particle diameter is smaller than 0.01 μm, the proton conductive material may not be able to be impregnated in the pores formed in the electrode. When the average particle diameter is larger than 100 μm, the specific surface area of the pores becomes small, so that the pore surface becomes small. The amount of the proton conductive substance adhering to the surface decreases.
[0069]
As the binder resin, for example, a thermoplastic resin such as polyolefin, polyester, fluororesin, polyketone, polyether, and polysulfone may be used.
[0070]
The amount of the binder resin may be in the range of 10 to 200 parts by weight based on 100 parts by weight of the total of the catalyst and the conductive substance. If the amount is less than 10 parts by weight, the moldability of the solidified material will be poor. If the amount exceeds 200 parts by weight, the binder resin will have electrical resistance and the conductive function of the electrode will be reduced.
[0071]
The fuel electrode (electromotive force) according to the present invention is obtained by pressing the fuel electrode formed on the current collector surface and the oxidizer electrode formed on the current collector surface via a proton conductive membrane. Part) is produced.
[0072]
As the proton conductive membrane, a sheet made of the same material as the proton conductive substance mentioned as the electrode material, that is, a fluororesin having a sulfonic acid group, tungstic acid or phosphotungstic acid may be used.
[0073]
Compression bonding at the time of manufacturing a fuel cell is performed, for example, at 100 ° C. to 180 ° C. and at 10 to 200 kg / cm.²Thermocompression bonding may be performed for about 1 minute to 30 minutes.
[0074]
Although the basic configuration of the fuel cell is shown in FIG. 1, the desired electromotive force is usually obtained by assembling a single cell sandwiched between the fuel cell separators shown in FIG. To achieve.
[0075]
FIG. 3 shows a sectional view of this single cell.
[0076]
The electromotive unit 5 is sandwiched between a pair of separators 31. The separators 31 are made of a conductive material and are connected to the fuel electrode 2 or the oxidizer electrode 4 via the respective current collectors 1. The separators 31 are electrically insulated by the proton conductive film 3. I have.
[0077]
A plurality of grooves 34 are formed on the surface of the separator 31 on the side of the current collector 1. By supplying fuel or oxidant to the grooves 34, fuel or oxidant is supplied to the fuel electrode 2 or the oxidant electrode 4. Supply the agent.
[0078]
By laminating the electromotive sections partitioned by the separators in this way, the electromotive sections can be connected in series, and the output of the fuel cell can be increased.
[0079]
【Example】
(Example 1)
Preparation of catalyst particles
SiO as catalyst carrier₂-Al₂O₃Powder (Aerosil, MOX80, average particle size 0.03 μm, specific surface area 80 m²/ G, Al₂O₃(Content 1%) and 20 g of this catalyst carrier was dispersed in 1000 ml of water using a honogenizer to prepare a suspension.
[0080]
The suspension was charged into a three-necked flask equipped with a mechanical stirrer, a reflux condenser, and a dropping funnel, and refluxed for 1 hour with stirring. 160 ml of Pt (42 mg / ml).
[0081]
After stirring for 20 minutes to uniformly dissolve the precursor of the platinum-based metal particles in the suspension, a precipitant is added to the suspension to convert the precursor of the platinum-based metal particles to Pt (OH).₄It has become. As a precipitant, a solution prepared by dissolving 21.0 g of sodium bicarbonate in 600 ml of water was gradually added dropwise over 60 minutes, and after the addition, the suspension was refluxed for 2 hours to complete the reaction. I let it.
[0082]
Pt (OH) obtained by filtering this suspension₄Was washed with pure water, then the catalyst carrier was transferred to a flask, refluxed with pure water for 2 hours, filtered, and the precipitate was thoroughly washed with pure water. The catalyst carrier thus washed was dried with a dryer at 100 ° C. The dried catalyst carrier is housed in a high-purity zirconia boat, placed in a cylindrical furnace, and 3% H₂/ N₂Pt (OH) by reducing at 200 ° C for 10 hours while flowing gas at a flow rate of 129 ml₄Is converted to platinum, so that SiO₂-Al₂O₃24.1 g of catalyst particles having platinum fine particles supported on the support surface were obtained.
[0083]
Preparation of composition for electrode
1 g of the catalyst particles obtained in a 50 ml plastic container, 2 g of pure water and zirconia balls (25 g of a 5 mm diameter and 50 g of a 10 mm diameter) were added and stirred to obtain a suspension in which the catalyst particles were dispersed in water. Was.
[0084]
Further, 4.5 g of an organic solvent (a mixed solution of 1-propanol, ethanol and water) in which a fluororesin having a sulfonic acid group as a proton conductive substance (Nafion manufactured by DuPont) was dissolved by 20%, and an organic solvent was further added. 10 g of 2-ethoxyethanol was added, and the organic solvent in which the proton conductive material was dissolved and the suspension were stirred and mixed to obtain a mixed solution.
[0085]
1 g of graphite (average particle diameter: 3 μm) as conductive particles was added to the obtained mixture, and the mixture was dispersed in a table-top ball mill for 6 hours to prepare a composition for an electrode.
[0086]
Fabrication of electrodes
As a support for the electrode, a water-repellent treated carbon paper (270 μm, manufactured by Toray Industries Inc.), which also serves as a current collector, is prepared, and the obtained electrode composition is coated on the support with a control coater (gap: 750 μm). After that, the electrode composition was air-dried to form an electrode (cathode 1) on the surface of the current collector. The thickness of the obtained electrode was 110 μm.
[0087]
(Comparative Example 1)
Carbon black (Printex L, manufactured by Degussa, having a specific surface area of 150 m)²/ G, average particle size 0.023 μm), except that 20 g of the catalyst particles were prepared in the same manner as in Example 1 except that platinum fine particles were supported on the surface of the carbon black carrier. However, when removing the catalyst after reduction, cool it with dry ice and₂To obtain catalyst particles.
[0088]
An electrode (cathode a) was formed on the surface of the current collector in the same manner as in Example 1, except that the catalyst particles were used and no conductive particles were added. The thickness of the obtained electrode was 100 μm.
[0089]
(Example 2)
SiO as catalyst carrier₂-Al₂O₃Powder (Aerosil, MOX170, specific surface area 170m²/ G, average particle size 0.015 μm, Al₂O₃Except that 10 g (content 1%) was used, the preparation of the catalyst particles and the preparation of the electrode (cathode 2) were performed in exactly the same manner as in Example 1. The thickness of the electrode formed on the current collector surface was 100 μm.
[0090]
(Example 3)
Catalyst particles were prepared in the same manner as in Example 1, except that 120 ml of chloroplatinic acid aqueous solution and 60 ml of ruthenium chloride aqueous solution (Ru: 43 mg / ml) were used as precursors of the platinum-based metal particles.₂-Al₂O₃Catalyst particles having Pt-Ru alloy fine particles supported on the support surface were produced.
[0091]
Further, except that the catalyst particles were used, and a water repellent carbon paper (thickness: 350 μm, manufactured by Toray Industries, Inc.) was used as a current collector, and the electrode composition was applied by a control coater (gap: 900 μm). An electrode (anode 1) was produced in the same manner as in Example 1.
[0092]
(Comparative Example 2)
Carbon black (Printex L, manufactured by Degussa, having a specific surface area of 150 m)²/ G, average particle size 0.023 μm), except that 20 g of catalyst particles were prepared in the same manner as in Example 3, except that platinum fine particles were supported on the surface of the carbon black carrier. However, when removing the catalyst after reduction, cool it with dry ice and₂To obtain catalyst particles.
[0093]
An electrode (anode a) was formed on the surface of the current collector in the same manner as in Example 3, except that the catalyst particles were used. The thickness of the obtained electrode was 140 μm.
[0094]
(Example 4)
Catalyst particles were prepared in the same manner as in Example 2, except that 80 ml of chloroplatinic acid aqueous solution and 40 ml of ruthenium chloride aqueous solution (Ru: 43 mg / ml) were used as the platinum-based metal particles.₂-Al₂O₃Catalyst particles having Pt-Ru alloy fine particles supported on the support surface were produced.
[0095]
An electrode (anode 2) was formed on the surface of the current collector in the same manner as in Example 3 except that the catalyst particles were used. The thickness of the obtained electrode was 150 μm.
[0096]
(Example 5)
As catalyst carrier, average particle size 0.050 μm, specific surface area 50 m²/ G SiO₂An electrode (cathode 3) was produced in the same manner as in Example 1, except that 20 g of particles (Aerosil 50 manufactured by Nippon Aerosil Co., Ltd.) was used. The thickness of the obtained electrode was 110 μm.
[0097]
(Example 6)
Average particle size 0.02 μm, specific surface area 170 m as catalyst carrier²/ G SiO₂An electrode (cathode 4) was produced in the same manner as in Example 2, except that 20 g of particles (AEROSIL 200 manufactured by Nippon Aerosil Co., Ltd.) was used. The thickness of the obtained electrode was 100 μm.
[0098]
(Example 7)
After 2 g of catalyst particles and 2 g of water obtained in the same manner as in Example 2 were mixed in an agate mortar, 2 g of graphite as conductive particles, 4 g of diethylene glycol, and 0.5 g of lithium carbonate as a pore-forming agent were added. And kneaded to mix uniformly.
[0099]
Further, 1.5 g (PTFE solid part 60 wt%) of a PTFE dispersion containing PTFE (polytetrafluoroethylene) as a thermoplastic resin was added and kneaded to obtain a solid body in which everything was integrated. This was rolled to form a sheet having a thickness of about 80 μm. This was placed in 6N sulfuric acid to dissolve the pore-forming agent, and then repeatedly washed with water several times. Thereafter, the excess liquid component was sucked off with a filter paper, and the sheet-like solid substance was put into water. Further, 20% of a fluororesin having a sulfonic acid group as a proton conductive substance (Dafon Nafion) was dissolved. An organic solvent (a mixture of 1-propanol, ethanol and water) was added, and the mixture was stirred and dried under reduced pressure to remove the organic solvent and water, thereby producing a sheet-like electrode (cathode 3).
[0100]
(Example 8)
Catalyst particles were produced in the same manner as in Example 4, and an electrode (anode 4) was produced in the same manner as in Example 7, except that the catalyst particles were used.
[0101]
Table 1 shows the catalyst carriers, platinum-based metal particles, and conductive particles used in Examples 1 to 8 and Comparative Examples 1 and 2.
[0102]
(Examples 9 to 13)
Using the two electrodes shown in Table 1 among the electrodes (and current collectors) produced in Examples 1 to 6, a single cell of a fuel cell as shown in FIG. 3 was assembled as follows. Was.
[0103]
As the proton conductive membrane, a fluorocarbon resin having a thickness of 200 μm and having a sulfonic acid group (manufactured by DuPont: Nafion 117) was used. The contact area between each electrode and the proton conductive membrane is 10 cm²Each electrode (and the current collector) was processed to 3.2 cm × 3.2 cm so that the proton conductive membrane was interposed between the electrodes, and the temperature was set at 125 ° C. for 10 minutes at 100 kg / cm.²To obtain a fuel cell.
[0104]
A 2 M methanol solution as a fuel was supplied to the anode electrode at a flow rate of 0.6 ml / min. And air was supplied to the cathode electrode at 60 ml / min. At 60 ° C. and 40 mA / cm²And the closed circuit voltage (OCV) of the fuel cell was measured. Was measured for fuel cell evaluation. Table 2 shows the results.
[0105]
(Comparative Example 3)
A fuel cell was fabricated and evaluated in the same manner as in Example 9, except that the electrodes obtained in Comparative Examples 1 and 2 were used. Table 2 shows the results.
[0106]
(Example 14)
The same current collectors as those used in Example 1 and the same proton conductive membrane as in Example 9 were prepared, and the electrode (cathode 4) obtained in Example 7 and the electrode obtained in Example 7 were obtained. The obtained electrode (anode 4) was processed to 3.2 cm × 3.2 cm.
[0107]
After laminating these in order of a current collector, a cathode, a proton conductive membrane, an anode, and a current collector, the laminate was placed at 125 ° C. for 30 minutes at 100 kg / cm.²A fuel cell was produced by thermocompression bonding at a pressure of, and the fuel cell was evaluated in the same manner as in Example 1. Table 2 shows the results.
[Table 1]

[Table 2]

From the above results, by adding the conductive particles, the catalyst particles have hydrophilic SiO 2 having no conductive function.₂As shown in Examples 9 to 14, it is found that the performance of the battery is improved when the electrode using the catalyst carrier mainly composed of is used.
[0108]
In addition, SiO₂It can be seen that among the catalyst carriers mainly containing, the use of a composite oxide having a Lewis acid particularly improves the battery performance.
[0109]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain an electrode having high power generation efficiency, an electrode composition, and a fuel cell using the same.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a basic configuration of a fuel cell according to the present invention.
FIG. 2 is a conceptual diagram showing an example of an electrode of the present invention.
FIG. 3 is a sectional view showing a single cell of the fuel cell of the present invention.
[Explanation of symbols]
1 ... current collector
2. Fuel electrode
3: Proton conductive membrane
4: Oxidizer electrode
5 ... electromotive part
20 ... electrode
21 ... catalyst carrier
22 ... Platinum-based metal particles
23 ... catalyst particles
24 ... conductive particles
25 ... Proton conductive material

Claims (3)

Catalyst particles carrying metal particles made of platinum or an alloy thereof on a catalyst carrier surface containing SiO ₂ as a main component, conductive particles, and a proton conductive material ,
An electrode, wherein the catalyst carrier is a Lewis acidic composite oxide containing 50 wt% or more of a SiO ₂ component . Metal particles made of platinum or an alloy thereof are made of SiO _Two A catalyst particle dispersion step of preparing catalyst particle dispersion water by dispersing the catalyst particles carried on the surface of the catalyst carrier containing as a main component a water,
  A mixing step of preparing a mixed solution containing an organic solvent in which the proton conductive substance is dissolved and the catalyst particle dispersion liquid,
  Conductive particle dispersion step of dispersing conductive particles in the catalyst particle dispersion, the organic solvent or the mixture,
  Drying the mixed solution to remove the water and the organic solvent. In a fuel cell including a fuel electrode to which a fuel containing a hydrogen element is supplied, an oxidant electrode to which oxygen is supplied, and a proton conductor layer sandwiched between the fuel electrode and the oxidant electrode,
  At least one of the fuel electrode and the oxidant electrode is formed by depositing metal particles made of platinum or an alloy thereof with SiO. _Two Containing catalyst particles supported on the surface of the catalyst carrier having as a main component, conductive particles, and a proton conductive material,
  The catalyst support is SiO 2 _Two A fuel cell characterized by being a Lewis acidic composite oxide containing 50% by weight or more of a component.

Images