JP2009164142A - Manufacturing method of catalyst for fuel cell containing noble metal particles carried on carbon substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst containing noble metal particles excellent in catalyst activity on a carbon base substrate by carrying fine noble metal particles on th carbon base substrate with good dispersivity and uniformity. <P>SOLUTION: The manufacturing method of a catalyst for a fuel cell which contains noble metal particles carried on a carbon base substrate, the mean diameter of the noble metal particles being 3 nm or less, and contains elements existing on a surface of the carbon base substrate, where a ratio of number of atoms of oxygen to that of nitrogen is 10% or less and a ratio of number of atoms of oxygen to that of silicon is 40% or less, includes: a step in which carbon powder for the carbon substrate is dispersed in solvent and a carbon powder dispersed liquid is produced; and a step in which a noble metal solution is added to the carbon powder dispersed liquid and the noble metal particles are carried on the carbon base substrate. Furthermore, at least either the carbon powder dispersed liquid or the noble metal solution contains a polymer pigment dispersing agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method of making catalyze comprising a noble metal particles supported on a carbon substrate, the catalyst is intended to be used preferably in fuel cells and electrochemical processes like.

  In noble metal catalysts widely used in fuel cells, electrochemical processes, etc., the surface area of the reaction is increased by dispersing and supporting noble metal particles as catalytic active components on a substrate such as carbon, and the catalytic activity per unit weight of the noble metal. Has been increased. As described above, in the catalyst containing the noble metal particles on the substrate, the noble metal particles having a small diameter are supported by being highly dispersed on the substrate in order to reduce the amount of noble metal used and at the same time further increase the catalytic activity of the noble metal. Technology is required.

  In addition, in a gas diffusion electrode used for a fuel cell or the like, it is indispensable to form a three-phase interface by the catalyst, fuel, and electrolyte involved in the reaction and increase the area of these interfaces. In particular, since improvement in catalytic activity greatly contributes to improvement in fuel cell performance, it is necessary to produce noble metal fine particles having a small diameter.

  Conventionally, as a method for producing a noble metal particle-supporting carbon powder used for producing a gas diffusion electrode for a fuel cell, for example, in Patent Document 1, chloroplatinic acid, tetraammineplatinum (II) chloride, dinitrodiammineplatinum (II) A method is disclosed in which carbon powder is dispersed in an aqueous solution of a platinum compound such as platinum, and after stabilization, the platinum complex ions are reduced on the carbon powder using a reducing agent, so that the platinum particles adhere to the carbon powder. ing. However, this method requires the use of a special platinum compound or a reducing agent, which is problematic in terms of manufacturing cost and ease of manufacturing.

  In Patent Document 2, a colloid method using a dispersant is proposed in order to support platinum particles having a minute diameter on a carbon powder. However, since this method uses a protective colloid, the protective colloid tends to remain on the catalyst surface, and there is a problem that the platinum particles are difficult to exhibit good catalytic activity.

  Patent Document 3 discloses a method in which a functional group is formed on the surface of a carbon powder by oxidation treatment, ions existing in the functional group are ion-exchanged with a platinum complex cation, and thus platinum particles are supported on the carbon powder. Has been. However, this method has a problem that the condition adjustment such as the surface treatment of the carbon powder is severe.

Japanese Patent Publication No. 61-1869 JP-A-56-155645 JP-A-8-162133

  As described above, with the conventional techniques disclosed in Patent Documents 1-3, it has been difficult to reliably obtain a noble metal particle-supported carbon powder having excellent catalytic activity simply and at low cost.

  In view of the state of the prior art as described above, the present invention provides a catalyst containing fine noble metal particles uniformly supported on a carbon substrate with good dispersibility and having noble metal particles having excellent catalytic activity on the carbon substrate. With the goal.

This onset Ming comprises noble metal particles supported on a carbon substrate, the average diameter of the noble metal particles is at 3nm or less, the atomic ratio of nitrogen to oxygen Te elements smell on the surface of the carbon substrate is less than 10% And a method for producing a fuel cell catalyst in which the atomic ratio of silicon to oxygen is 40% or less, comprising: dispersing carbon powder for a carbon substrate in a solvent to prepare a carbon powder dispersion; and carbon powder dispersion A step of adding a noble metal solution to the liquid to allow the noble metal particles to be supported on the carbon substrate, and at least one of the carbon powder dispersion and the noble metal solution further includes a polymer pigment dispersant .

In this case, high-molecular pigment dispersing agent is preferably an amphipathic polymer. Furthermore, the amphiphilic polymer preferably contains a compound having an amino group and an ether group. The polymer pigment dispersant is preferably removed after the noble metal particles are supported on the carbon substrate.

  The carbon powder dispersion is preferably subjected to a crushing treatment. It is preferable that the solvent for dispersing the carbon powder is alcohol, and the absolute value of the zeta potential of the carbon powder dispersion is 30 mV or more. The carbon powder dispersion preferably has a pH greater than 7.

  The mixed liquid obtained by adding the noble metal solution to the carbon powder dispersion is preferably heated. And it is also preferable that the liquid mixture is cooled at high speed compared with air cooling after heating.

  According to the present invention, fine noble metal particles can be uniformly supported on a carbon substrate with good dispersibility, so that a catalyst having excellent catalytic activity can be obtained.

It is a graph which shows the relationship between a current density, a voltage, and an output density about MEA of Example 1 and Comparative Example 1. It is a graph which shows the time-dependent change of the voltage by constant current load about MEA of Example 1 and Comparative Example 1. It is a graph which shows the relationship between a current density, a voltage, and an output density about MEA of Example 1 and Comparative Example 2. It is a graph which shows the time-dependent change of the voltage by constant current load about MEA of Example 1 and Comparative Example 2. It is a graph which shows the relationship between a current density, a voltage, and an output density about MEA of Example 1 and Comparative Example 3. It is a graph which shows the time-dependent change of the voltage by constant current load about MEA of Example 1 and Comparative Example 3. It is a graph which shows the relationship between a current density, a voltage, and an output density about MEA of Example 1 and Comparative Example 4. It is a graph which shows the time-dependent change of the voltage by constant current load about MEA of Example 1 and Comparative Example 4. It is a graph which shows the relationship of a current density, a voltage, and an output density about MEA of Example 1, Example 2, and Example 3. FIG. It is a graph which shows the time-dependent change of the voltage by constant current load about MEA of Example 1, Example 2, and Example 3. FIG.

  The present invention relates to a catalyst comprising noble metal particles supported on a carbon substrate. In the present application, the noble metal means a platinum group element, gold (Au), or silver (Ag). Note that the platinum group elements include ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). The noble metal particles may be composed of only one kind of these noble metals, or may be composed of two or more kinds of mixtures or alloys.

  In the present invention, the noble metal particles supported on the carbon substrate can most typically be composed of platinum or a platinum-containing alloy. The catalyst containing noble metal particles on the carbon substrate according to the present invention can be used, for example, as a positive electrode catalyst or a negative electrode catalyst of a fuel cell. As a typical positive electrode catalyst, a catalyst containing platinum particles on a substrate can be exemplified, and as a typical negative electrode catalyst, a catalyst containing platinum ruthenium alloy particles on a substrate can be exemplified.

  In the catalyst containing noble metal particles on the carbon substrate according to the present invention, the average diameter of the noble metal particles is 3 nm or less. This is because when the average particle diameter exceeds 3 nm, the specific surface area of the noble metal particles is small and the catalytic ability is not sufficiently exhibited. On the other hand, the average particle diameter is preferably 1 nm or more from the viewpoint of easy production.

  Note that the average diameter of the noble metal particles can be obtained from the measurement result of the diffraction peak by an X-ray diffractometer and the Scherrer equation.

  In the elements present on the surface of the carbon substrate supporting the noble metal particles contained in the catalyst according to the present invention, the atomic ratio of nitrogen to oxygen is 10% or less, and the atomic ratio of silicon to oxygen is 40% or less. The On the surface of the carbon substrate, if there are many components other than carbon (C) up to the third column of the periodic table, the catalytic reaction and electronic conduction are hindered, so components other than carbon up to the third column of the periodic table Is preferably as small as possible. When the atomic ratio of nitrogen to oxygen exceeds 10% on the surface of the carbon substrate, the catalytic reaction and electrical conduction are hindered and sufficient catalytic activity cannot be obtained. Also, when the atomic ratio of silicon to oxygen exceeds 40% on the surface of the carbon substrate, the catalytic reaction and electrical conduction are similarly inhibited, and sufficient catalytic activity cannot be obtained.

  In addition, the atomic ratio of nitrogen to oxygen and the atomic ratio of silicon to oxygen on the surface of the carbon substrate can be evaluated by elemental analysis using, for example, a wavelength dispersion X-ray analyzer.

  Examples of the carbon substrate used in the catalyst according to the present invention include ketjen black (manufactured by ketjen black international), Vulcan XC72 and Vulcan XC72R (both manufactured by Cabot). Ketjen black can be preferably used because of its excellent performance and electrochemical characteristics.

  In the catalyst according to the present invention, the precious metal particles supported on the carbon substrate may be within a range of 30 to 50% by mass, for example. When the proportion of the noble metal particles is 30% by mass or more, good catalytic activity can be obtained, and when it is 50% by mass or less, aggregation of the noble metal particles can be prevented and an excessive increase in production cost can be prevented.

<Method for Producing Catalyst Containing Noble Metal Particles on Carbon Substrate>
According to the present invention, the average particle diameter of the noble metal particles on the carbon substrate is 3 nm or less, the atomic ratio of nitrogen to oxygen in the elements present on the surface of the carbon substrate is 10% or less, and the atomic ratio of silicon to oxygen In a method for producing a catalyst having a carbon content of 40% or less, a step of preparing a carbon powder dispersion by dispersing carbon powder for a carbon substrate in a solvent, and adding a noble metal solution to the carbon powder dispersion to convert the noble metal particles into carbon And supporting on a substrate.

(Preparation of carbon powder dispersion)
First, a carbon powder dispersion is prepared by dispersing carbon powder in a solvent. Examples of the solvent for dispersion include alcohols and glycols, but in terms of being able to be the same solvent as the solvent of the noble metal solution, good dispersibility of the carbon powder, easy removal of the solvent, etc. Alcohols are preferred.

  In the present invention, it is preferable that at least one of the carbon powder dispersion and the noble metal solution contains a polymer pigment dispersant. In this case, aggregation of the noble metal particles is suppressed, and the noble metal particles can be supported on the carbon substrate more uniformly and with good dispersibility. In particular, when a polymer pigment dispersant is contained in the carbon powder dispersion, it is preferable in terms of improving the dispersibility of carbon in the solvent. In the case where at least one of the carbon powder dispersion and the noble metal solution contains a polymer pigment dispersant, after the noble metal particles are supported on the carbon substrate, the polymer pigment dispersant is removed and the residue is removed. It is preferable to prevent this.

  As the polymer pigment dispersant, for example, a dispersant containing polypropylene oxide as a base resin can be used.

  As the polymer pigment dispersant, an amphiphilic polymer can be preferably used. As described above, when the carbon substrate surface contains a large amount of components other than carbon (C) up to the third column of the periodic table, the catalytic reaction and electronic conduction are hindered. It is preferable that the amount of components other than is as small as possible. In particular, elements such as sulfur (S) and silicon (Si) are likely to remain as components derived from starting materials and dispersants, and need to be removed by complicated means such as acid treatment and heat treatment. Amphiphilic polymers have a surface-active effect regardless of the ionic species and can be dissolved in alcohol and water. Therefore, when an amphiphilic polymer is used as the polymer pigment dispersant, it is easy to remove the dispersant, and it is possible to satisfactorily prevent the remaining of components that inhibit catalytic reaction and electrical conduction. This is preferable because the atomic ratio of nitrogen and silicon to can be reduced satisfactorily.

  The amphiphilic polymer used in the present invention preferably contains a compound having an amino group and an ether group. The amino group is easily adsorbed on the carbon surface and is also easily coordinated to the colloid formed by the noble metal in the noble metal solution. Therefore, the compound having an amino group can promote the dispersion of the carbon powder in the alcohol and suppress aggregation of the noble metal colloid. Furthermore, compounds having an ether group have amphiphilic properties and tend to dissolve in alcohol and water. Therefore, by using a compound having an amino group and an ether group, the noble metal particles can be more uniformly dispersed, and the polymer pigment dispersant can be easily removed and its residue can be prevented.

  Examples of the compound having an amino group and an ether group may include those having polypropylene oxide as a base resin and containing monodiethylaminoalkyl ether as a protective group. Specific examples of commercially available products include “Solspers 20000” manufactured by Avicia, “Ajisper PN411” manufactured by Ajinomoto Co., Inc., and the like.

  In the preparation of the carbon powder dispersion, it is preferable that the carbon powder is crushed. By performing the crushing treatment, the dispersion stability of the carbon powder with respect to the solvent can be improved and the uniformity of the dispersion can be improved, and the nucleation sites when reducing and precipitating the noble metal particles described later can be more uniformly dispersed. Can do. The crushing treatment can be performed using a crusher, a paint conditioner, an attritor, a bead mill, or the like.

  The carbon powder dispersion is preferably prepared so that the absolute value of the zeta potential is 30 mV or more. In the case of such a zeta potential, the dispersibility of the carbon powder in the solvent is good, and the nucleation sites for reducing and precipitating the noble metal particles can be more uniformly dispersed. As a result, the noble metal colloid can be uniformly dispersed on the surface of the carbon substrate, and the noble metal particles having a smaller diameter can be more uniformly supported on the carbon substrate with good dispersibility. This advantage is better obtained particularly when the dispersion solvent is alcohol and a carbon powder dispersion having an absolute value of zeta potential of 30 mV or more is used.

  A larger absolute value of the zeta potential of the carbon powder dispersion is preferable from the viewpoint of the dispersibility of the carbon powder. However, for example, if the absolute value is about 70 mV, the above advantages can be obtained sufficiently satisfactorily. In the present invention, the absolute value of the zeta potential of the carbon powder dispersion may be, for example, 80 mV or less.

  Most typically, the dispersion solvent is alcohol, the carbon powder content is about 0.5 g in a 100 mL solvent, and the carbon powder dispersion is prepared so that the absolute value of the zeta potential is 30 mV or more. It is preferred that

  The zeta potential can be evaluated by electrophoresis using, for example, a zeta potential measuring device.

(Supporting precious metal particles on a carbon substrate)
The noble metal particles are supported on the carbon substrate by adding the noble metal solution to the carbon powder dispersion prepared as described above. In the present invention, the noble metal solution means a solution or a colloid solution containing a noble metal element, and typically means a solution or a colloid solution containing a cation of the noble metal element, particularly a complex ion. As such a noble metal solution, for example, a noble metal salt or complex salt solution or a colloidal solution can be used. Examples of the noble metal salt include ruthenium chloride, ruthenium nitrosyl complex, ruthenium ammine complex and ruthenium carbonyl complex. Examples of the noble metal complex salt include chloroplatinic acid, platinum ammine complex and platinum carbonyl complex.

  In the present invention, the noble metal solution preferably contains a polymer pigment dispersant. In this case, aggregation of the noble metal particles can be prevented, and the noble metal particles can be more finely and uniformly supported on the carbon substrate. Examples of preferable polymer pigment dispersants include the same polymer pigment dispersants as described above in the preparation of the carbon powder dispersion. Amphiphilic polymers such as those described above are more preferable, and amphiphilic polymers including compounds having an amino group and an ether group as described above are particularly preferable.

  The noble metal solution is added to the carbon powder dispersion, boiled for about 1 hour, then cooled to room temperature, and subjected to suction filtration, drying, etc., so that the noble metal particles reduced and precipitated from the noble metal solution are supported on the carbon substrate. be able to. By such a method according to the present invention, a catalyst containing noble metal particles on a carbon substrate can be obtained.

  More specifically, when a solution in which chloroplatinic acid is dissolved in an alcohol such as propanol is used as a noble metal solution, a catalyst containing platinum particles on a carbon substrate can be obtained. This catalyst containing platinum particles is useful as a catalyst for a positive electrode of a fuel cell, for example.

  Further, the platinum particle-supported carbon powder thus obtained is dispersed in an alcohol such as propanol to prepare a dispersion solution, to which a ruthenium chloride alcohol solution is added and boiled for about 2 hours, after cooling to room temperature, suction filtration, A catalyst containing platinum ruthenium alloy particles on a carbon substrate can be obtained by performing a treatment such as drying and firing in a reducing atmosphere such as a nitrogen-balanced 10% hydrogen mixed gas. The catalyst containing the platinum ruthenium alloy particles is useful as a catalyst for a negative electrode of a fuel cell, for example.

<Evaluation method>
(Zeta potential)
The zeta potential of the carbon powder dispersion is measured by electrophoresis using a zeta potential measuring device (manufactured by Otsuka Electronics Co., Ltd.) with the dispersion medium being n-propanol and the dispersion concentration being 0.5 mass% (carbon equivalent). did.

(Average diameter of noble metal particles supported on carbon substrate)
A diffraction peak was measured by an X-ray diffractometer (manufactured by Rigaku Corporation), and an average particle size was calculated by the Scherrer equation. The maximum particle size was determined as the maximum value of the noble metal fine particles by extracting about 200 noble metal fine particles using a transmission electron microscope (manufactured by Hitachi High-Technologies Corporation).

(Atom ratio in elements existing on the surface of the carbon substrate)
The elemental analysis of the carbon substrate surface was performed using a wavelength dispersion type X-ray analyzer (manufactured by Shimadzu Corporation), and the atomic ratio of various elements present on the surface was evaluated.

(Power generation characteristics)
Each of the membrane electrolyte composite membranes (MEA: Membrane Electrode Assembly) prepared in Examples 1 to 3 and Comparative Examples 1 to 4 described later is set in a commercially available standard cell (manufactured by Electrochem), and 3 mol / L methanol is used for the negative electrode. An aqueous solution was supplied at 300 μL / min, air was supplied to the positive electrode at 500 mL / min, and a current-voltage curve at a cell temperature of 40 ° C. and a time-dependent voltage change for 5 hours with a 0.1 A / cm ² constant current load were obtained. Measured with an electronic load device.

<Example 1>
In 50 mL of 1-propyl alcohol as a dispersion solvent, 0.22 g of Ketjen black (manufactured by Ketjen Black International Co., Ltd.) having a primary particle size of 30 to 40 nm is dispersed as carbon powder, and Solsperse as a polymer pigment dispersant is further dispersed. 7 mL of 20000 (Avisia) was added to prepare a carbon powder dispersion. The carbon powder dispersion was stirred for 10 minutes at 24,000 rpm using a crusher. The carbon powder dispersion subjected to this stirring treatment had a zeta potential of +65 mV.

  Thereafter, 25 mL of a 1-propanol solution containing 0.38% by mass of chloroplatinic acid was added to the carbon powder dispersion and boiled for 1 hour. After cooling to room temperature, suction filtration and drying at 60 ° C. were performed to prepare a catalyst in which the amount of platinum particles supported on carbon powder as a carbon substrate was about 24% by mass. This catalyst was used as a catalyst for a positive electrode of a fuel cell.

  In Example 1, the average diameter of the platinum particles supported on the carbon powder was 2 nm according to the result of X-ray diffraction measurement.

  On the other hand, 10.0 mL of a propanol solution containing 0.34% by mass of ruthenium chloride was added to a propanol dispersion containing 40% by mass of the platinum particle-supported carbon powder produced by the above-described production method, and the mixture was boiled for 2 hours. After cooling to room temperature, suction filtration and drying at 60 ° C. were performed, followed by firing at 200 ° C. for 1 hour in a nitrogen-balanced 10% hydrogen mixed gas. Thus, a catalyst containing platinum ruthenium alloy particles supported on carbon powder as a carbon substrate was obtained. The platinum amount was 21% by mass and the ruthenium amount was about 11% by mass with respect to the total mass. This catalyst was used as a negative electrode catalyst for fuel cells.

  In Example 1, the average diameter of the platinum ruthenium alloy particles supported on the carbon powder was 2.5 nm according to the result of X-ray diffraction measurement.

  Further, as elements present on the carbon surface of the positive electrode catalyst according to Example 1, 97.0% C, 2.4% Pt, 0.05% N, and 0.55% O are present in the atomic ratio. The elements present on the carbon surface of the negative electrode catalyst include 91.56% C, 3.9% Pt, 3.8% Ru, 0.06% N, and 0.68% O in atomic ratio. Existed. And elements other than these were not detected on the carbon surface.

  That is, in Example 1, on the carbon surface of the positive electrode catalyst, the atomic ratio of nitrogen to oxygen is 0.05 / 0.55 × 100 = about 9.1%, and the atomic ratio of silicon to oxygen is 0%. Further, on the carbon surface of the negative electrode catalyst, the atomic ratio of nitrogen to oxygen was 0.06 / 0.68 × 100 = about 8.8%, and the atomic ratio of silicon to oxygen was 0%.

  The positive electrode catalyst containing platinum particles and the negative electrode catalyst containing platinum ruthenium alloy particles are each immersed in a dispersion containing 20% solid polymer electrolyte (Aldrich Nafion solution), and 2-propanol is added to suspend the catalyst. It was made into a turbid liquid and stirred for about 30 minutes with a planetary ball mill made of zirconia. Thus, a positive electrode catalyst paste was obtained from the positive electrode catalyst, and a negative electrode catalyst paste was obtained from the negative electrode catalyst.

  These positive electrode catalyst paste and negative electrode catalyst paste were each applied to carbon paper (manufactured by Toray Industries, Inc.) using a bar coater to form a positive electrode catalyst layer and a negative electrode catalyst layer.

  A solid polymer electrolyte membrane (Nafion manufactured by DuPont) was sandwiched between the respective catalyst-coated surfaces of the positive electrode catalyst layer and the negative electrode catalyst layer, and bonded by hot pressing to produce the MEA of Example 1.

<Example 2>
To the same carbon powder dispersion as in Example 1, 25 mL of 1-propanol solution containing 0.38% by mass of chloroplatinic acid was added and boiled for 1 hour. This was immersed in ice water for 30 minutes, and then suction filtered and dried at 60 ° C. to prepare a catalyst in which the amount of platinum particles supported on the carbon powder was about 30% by mass. The catalyst containing platinum particles was used as a catalyst for a positive electrode of a fuel cell.

  In Example 2, the average diameter of the platinum particles supported on the carbon powder was 2.2 nm according to the result of X-ray diffraction measurement.

  On the other hand, the catalyst used as the negative electrode catalyst of the fuel cell in Example 2 was the same catalyst as in Example 1.

  Further, as the elements present on the carbon surface of the positive electrode catalyst according to Example 2, 96.47% C, 2.8% Pt, 0.03% N, and 0.7% O are present in the atomic ratio. Was. And elements other than these were not detected on the carbon surface. That is, on the carbon surface of the positive electrode catalyst, the atomic ratio of nitrogen to oxygen was 0.03 / 0.70 × 100 = about 4.3%, and the atomic ratio of silicon to oxygen was 0%. .

  Using the positive electrode catalyst and the negative electrode catalyst according to Example 2, an MEA was produced in the same process as in Example 1.

<Example 3>
25 mL of a 1-propanol solution containing 0.38% by mass of chloroplatinic acid is added to the same carbon powder dispersion as in Example 1, and then an n-propanol solution containing NaOH at a concentration in the range of 0.1 to 1N is added. The pH was adjusted to 11 using and stirred for a whole day and night. This was boiled for 1 hour, cooled to room temperature, suction filtered and dried at 60 ° C. to prepare a catalyst having a platinum particle amount of about 27% by mass. This catalyst containing platinum particles was used as a catalyst for a positive electrode of a fuel cell.

  In Example 3, the average diameter of the platinum particles supported on the carbon powder was 2 nm according to the result of X-ray diffraction measurement.

  The elements present on the carbon surface of the positive electrode catalyst according to Example 3 are 95.8% C, 2.7% Pt, 0.03% N, 1.05% O, and 0 in terms of the atomic ratio. .38% Si. And elements other than these were not detected on the carbon surface. That is, on the carbon surface of the positive electrode catalyst, the atomic ratio of nitrogen to oxygen is 0.03 / 1.05 × 100 = about 2.9%, and the atomic ratio of silicon to oxygen is 0.38 / 1. 0.05 × 100 = 36%.

  On the other hand, the catalyst used as the negative electrode catalyst of the fuel cell in Example 3 was the same as that in Example 1.

  Using the positive electrode catalyst and negative electrode catalyst according to Example 3, an MEA was produced in the same process as in Example 1.

The graph of FIG. 9 shows the relationship between the current density (mA), voltage (V), and output density (mW / cm ² ) for the MEAs according to Examples 1, 2, and 3 as described above. Yes. In addition, the graph of FIG. 10 shows the change over time of the voltage due to the constant current load for the MEAs according to Example 1, Example 2, and Example 3. From these FIG. 9 and FIG. 10, it can be seen that the MEAs according to Example 1, Example 2, and Example 3 have substantially the same excellent output characteristics.

<Comparative Example 1>
Also in Comparative Example 1, a positive electrode catalyst and a negative electrode catalyst were prepared by a process similar to that in Example 1. However, the difference was that Solsperse 20000 as a polymer pigment dispersant was not used.

  In the carbon powder dispersion prepared in this Comparative Example 1, the zeta potential was −24 mV. In the positive electrode catalyst according to Comparative Example 1, the average diameter of the platinum particles was 4 nm, the maximum diameter was 7 nm, and the amount of platinum particles was 30% by mass.

  The elements present on the carbon surface of the positive electrode catalyst according to Comparative Example 1 are 95.0% C, 3.9% Pt, 0.08% N, and 1.0% O in atomic ratio, and these No other elements were detected. That is, on the carbon surface of the positive electrode catalyst, the atomic ratio of nitrogen to oxygen was 8.0%, and the atomic ratio of silicon to oxygen was 0%.

  In the catalyst for negative electrode according to Comparative Example 1, the average diameter of the platinum ruthenium alloy particles was 5.5 nm, the maximum diameter was 8 nm, the platinum content was 26 mass%, and the ruthenium content was 13 mass%.

  The elements present on the carbon surface of the negative electrode catalyst according to Comparative Example 1 were 92.2% C, 3.3% Pt, 3.5% Ru, 0.05% N, 0.95% in atomic ratio. O and no other elements were detected. That is, on the carbon surface of the negative electrode catalyst, the atomic ratio of nitrogen to oxygen was 5.3%, and the atomic ratio of silicon to oxygen was 0%.

  Using the positive electrode catalyst and the negative electrode catalyst according to Comparative Example 1, an MEA was produced in the same process as in Example 1.

FIG. 1 is a graph showing the relationship between current density (mA), voltage (V), and output density (mW / cm ² ) for MEAs according to Example 1 and Comparative Example 1. Further, FIG. 2 is a graph showing a change with time in voltage due to a constant current load for the MEAs according to Example 1 and Comparative Example 1.

  As can be seen from FIG. 1, the power generation efficiency is higher in Example 1 than in Comparative Example 1, and the catalytic reaction resistance is reduced. In FIG. 2, compared to Comparative Example 1, Example 1 shows a higher voltage even at a constant current load.

<Comparative example 2>
Also in Comparative Example 2, a positive electrode catalyst and a negative electrode catalyst were prepared by a process similar to that in Example 1. However, the difference was that stirring using a crusher was not performed.

  In the carbon powder dispersion prepared in Comparative Example 2, the zeta potential was −8 mV. And in the catalyst for positive electrodes by this comparative example 2, the average diameter of platinum particle was 3.5 nm, the maximum diameter was 5 nm, and the amount of platinum particles was 30 mass%.

  The elements present on the carbon surface of the positive electrode catalyst according to Comparative Example 2 are 96.0% C, 3.1% Pt, 0.07% N, and 0.83% O in atomic ratio, No other elements were detected. That is, on the carbon surface of the positive electrode catalyst, the atomic ratio of nitrogen to oxygen was 8.4%, and the atomic ratio of silicon to oxygen was 0%.

  In the catalyst for negative electrode according to Comparative Example 2, the average diameter of the platinum ruthenium alloy particles was 3.1 nm, the maximum diameter was 5.0 nm, the platinum amount was 26 mass%, and the ruthenium amount was 13 mass%.

  The elements present on the carbon surface of the negative electrode catalyst according to Comparative Example 2 are 91.5% C, 3.9% Pt, 3.8% Ru, 0.06% N, and 0. It was 7% O, and no other elements were detected. That is, on the carbon surface of the negative electrode catalyst, the atomic ratio of nitrogen to oxygen was 8.6%, and the atomic ratio of silicon to oxygen was 0%.

  Using the positive electrode catalyst and the negative electrode catalyst according to Comparative Example 2, an MEA was produced in the same process as in Example 1.

FIG. 3 is a graph showing the relationship between current density (mA), voltage (V), and output density (mW / cm ² ) for MEAs according to Example 1 and Comparative Example 2. FIG. 4 is a graph showing the change over time of the voltage due to the constant current load for the MEAs of Example 1 and Comparative Example 2.

  From FIG. 3, it can be seen that the power generation efficiency is higher in Example 1 than in Comparative Example 2, and the catalytic reaction resistance is reduced. Further, in FIG. 4, a higher voltage is obtained even in the constant current load in Example 1 than in Comparative Example 2.

<Comparative Example 3>
In Comparative Example 3, a positive electrode catalyst and a negative electrode catalyst were prepared by a process similar to that in Example 1. However, propanol containing 2.0% by mass of a silane coupling agent was used instead of Solsperse 20000 as the polymer pigment dispersant. It was different in using 50 mL of the solution.

  In the catalyst for the positive electrode according to Comparative Example 3, the average diameter of the platinum particles was 2.3 nm, the maximum diameter was 4.5 nm, and the amount of platinum particles was 30% by mass.

  The elements present on the carbon surface of the positive electrode catalyst according to Comparative Example 3 were 94.2% C, 2.9% Pt, 0.07% N, and 0.8% O, 2.0 in atomic ratio. % Si, and other elements were not detected. That is, on the carbon surface of the positive electrode catalyst, the atomic ratio of nitrogen to oxygen is 0.07 / 0.8 × 100 = about 8.8%, and the atomic ratio of silicon to oxygen is 2.0 / 0.00. 8 × 100 = 250%.

  In the negative electrode catalyst according to Comparative Example 3, the average diameter of the platinum ruthenium alloy particles is 3.1 nm, the maximum diameter is 6.0 nm, the platinum amount is 26% by mass, and the ruthenium amount is 13% by mass. there were.

  The elements present on the carbon surface of the negative electrode catalyst according to Comparative Example 3 were 90.1% C, 3.7% Pt, 3.6% Ru, 0.06% N, 0.7% in terms of atomic ratio. O and 1.8% Si, and other elements were not detected. That is, the atomic ratio of nitrogen to oxygen is 0.06 / 0.7 × 100 = about 8.6%, and the atomic ratio of silicon to oxygen is 1.8 / 0.7 × 100 = about 257%. there were.

  Using the positive electrode catalyst and the negative electrode catalyst according to Comparative Example 3, an MEA was produced in the same process as in Example 1.

5, the MEA according to the comparative example 3 and Example 1 current density (mA), is a graph showing the relationship between the voltage (V) and power density (mW / cm ^2). FIG. 6 is a graph showing a change with time in voltage due to a constant current load for the MEAs of Example 1 and Comparative Example 3.

  From FIG. 5, it can be seen that the power generation efficiency is higher in Example 1 than in Comparative Example 3, and the catalytic reaction resistance is reduced. This is because, in Comparative Example 3, silicon (Si) derived from the polymer pigment dispersant is present as a residue on the catalyst surface, and as a result of inhibiting the catalytic reaction, the catalytic reaction resistance is high and the power generation efficiency is low. It is thought that. Further, in FIG. 6, a higher voltage is obtained even in the constant current load in Example 1 than in Comparative Example 3.

<Comparative example 4>
In Comparative Example 4, a positive electrode catalyst was prepared by a process similar to that in Example 1. However, the difference was that a 1-propanol solution containing 0.61% by mass of dinitrodiammineplatinum (II) was used as the noble metal solution. It was.

  In the catalyst for the positive electrode according to Comparative Example 4, the average diameter of the platinum particles was 2.5 nm, the maximum diameter was 4.2 nm, and the amount of platinum particles was 30% by mass.

  The elements present on the carbon surface of the positive electrode catalyst according to Comparative Example 4 are 96.7% C, 2.7% Pt, 0.2% N, and 0.4% O in atomic ratios. No other elements were detected. That is, on the carbon surface of this positive electrode catalyst, the atomic ratio of nitrogen to oxygen was 0.2 / 0.4 × 100 = 50%, and the atomic ratio of silicon to oxygen was 0%.

  Further, a 1-propanol solution containing 0.40% by mass of ruthenium nitrosyl chloride was added as a noble metal solution to a propanol dispersion containing 40% by mass of the platinum particle-supporting carbon powder of Comparative Example 4 to carry platinum ruthenium alloy particles. Carbon powder was prepared as a negative electrode catalyst. In this negative electrode catalyst, the average diameter of the platinum ruthenium alloy particles was 3.2 nm, the maximum diameter was 5.8 nm, the platinum content was 26 mass%, and the ruthenium content was 13 mass%.

  The elements present on the carbon surface of the negative electrode catalyst according to Comparative Example 4 were 90.8% C, 3.4% Pt, 3.5% Ru, 0.8% N, and 1.5 in terms of atomic ratio. % O, and other elements were not detected. That is, on the carbon surface of this negative electrode catalyst, the atomic ratio of nitrogen to oxygen was 0.8 / 1.5 × 100 = about 53%, and the atomic ratio of silicon to oxygen was 0%.

  Using the positive electrode catalyst and the negative electrode catalyst according to Comparative Example 4, an MEA was produced in the same process as in Example 1.

FIG. 7 is a graph showing the relationship between current density (mA), voltage (V), and output density (mW / cm ² ) for MEAs according to Example 1 and Comparative Example 4. FIG. 8 is a graph showing a change with time in voltage due to a constant current load for the MEAs of Example 1 and Comparative Example 4.

  From FIG. 7, it can be seen that the power generation efficiency is higher in Example 1 than in Comparative Example 4, and the catalytic reaction resistance is reduced. The reason for this is that in Comparative Example 4, nitrogen (N) derived from ruthenium nitrosyl chloride exists as a residue on the surface of the noble metal particles, and as a result of inhibiting the catalytic reaction, the catalytic reaction resistance is high and the power generation efficiency is low. It is considered a thing. Further, in FIG. 8, a higher voltage is obtained even in the constant current load in Example 1 than in Comparative Example 4.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The catalyst containing noble metal particles on the carbon substrate obtained by the present invention has excellent catalytic activity, and can be preferably applied to uses such as fuel cells and electrochemical processes.

Claims (9)

Including a carbon substrate and noble metal particles supported on the carbon substrate,
The noble metal particles have an average diameter of 3 nm or less,
The atomic ratio of silicon atomic ratio of nitrogen to oxygen Te elements smell on the surface of the carbon substrate for 10% or less and oxygen is a method for producing a catalyst for a fuel cell is 40% or less,
Disperse the carbon powder for the carbon substrate in a solvent to prepare a carbon powder dispersion;
Adding a noble metal solution to the carbon powder dispersion and supporting the noble metal particles on the carbon substrate;
The carbon powder dispersion liquid and at least one manufacturing method of a fuel cell catalyst, characterized in that it further comprises a polymeric pigment dispersant of the noble metal solution. The process according to claim 1, wherein the polymer pigment dispersing agent is an amphiphilic polymer. The method according to claim 2 , wherein the amphiphilic polymer contains a compound having an amino group and an ether group. The process according to any one of claims 1 to 3 wherein the polymeric pigment dispersant, characterized in that it is removed after the said noble metal particles are supported on the carbon substrate. The method according to any one of claims 1 to 4, characterized in that crushing process on the carbon powder dispersion liquid is subjected. Wherein the solvent is an alcohol The method according to any one of claims 1 to 5 in which the absolute value of the zeta potential of the carbon powder dispersion liquid is equal to or is 30mV or more. The process according to any one of claims 1 to 6, characterized in that it has a pH greater than the carbon powder dispersion liquid 7. The manufacturing method according to any one of claims 1 to 7 , wherein a mixed solution obtained by adding the noble metal solution to the carbon powder dispersion is heated. The manufacturing method according to claim 8 , wherein the mixed liquid is cooled at a higher speed than the air cooling after the heating.

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