JP2008210572A - Electrocatalyst and power generation system using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode catalyst that has superior activity in both of mass activity and specific activity. <P>SOLUTION: This is the electrode catalyst that is formed by a catalyst component which contains platinum of 70 atom% or more against catalyst component of 100 atom% is carried by a conductive carrier, and in this electrode catalyst, a peak current value (I<SB>190-230 mV</SB>) within a range of 190-230 mV in a hydrogen adsorption-desorption current of the hydrogen adsorption desorption wave form by a cyclic voltammetric method, and a peak current value at 250-270 mV, or an inflection point current value (I<SB>250-270 mV</SB>) satisfy a relationship of an expression. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrode catalyst, and more particularly to an electrode catalyst having high activity and excellent durability.

  In recent years, in response to social demands and trends against the background of energy and environmental problems, various fuel cells have been developed for application as power sources for electric vehicles and stationary power sources. As a structure of the fuel cell, for example, in a polymer electrolyte fuel cell, an electrolyte layer made of a film-like solid polymer membrane is used, and is generally also referred to as a membrane-electrode assembly (hereinafter referred to as “MEA”). ) Are stacked via a separator.

  In the MEA, the electrolyte layer is sandwiched between the cathode and the anode, and therefore, the electrode catalyst layer has a structure in which at least one surface is in contact with the electrolyte layer.

  Conventionally, an electrode catalyst in which a catalytic metal such as platinum or a platinum alloy is refined and supported on a conductive carrier having a large specific surface area such as carbon black in a highly dispersed manner has been used for both the cathode and the anode. Since such an electrode catalyst has a large electrode reaction area on the surface of the catalyst metal, the catalytic activity can be increased. In addition, the amount of expensive platinum used can be reduced.

  However, when carbon is used as the conductive carrier, there is a problem that when the electrode is in a noble potential environment (about 0.8 V or more), an electrochemical oxidation reaction of the carrier occurs and the corrosion reaction of the carrier proceeds. Such a corrosion reaction of the carrier is a reaction for generating carbon dioxide using water as an oxidizing agent, as shown in the following chemical formula.

  As a result, the carrier disappears, and the catalyst metal supported on the surface of the carrier is liberated and agglomerated. The liberation / aggregation of the catalyst metal decreases the electrode reaction area of the catalyst metal, resulting in a decrease in catalyst activity and a factor in reducing battery performance.

  On the other hand, when fuel shortage occurs at the anode, reactions such as electrolysis of water and oxidation of the carrier proceed in place of the fuel oxidation reaction in order to maintain a desired current density. Therefore, as in the case of the cathode, the support also corrodes and disappears in the anode, and the catalyst metal is liberated and agglomerated.

  Such a decrease in catalytic activity becomes a significant problem when platinum is used as a catalyst because platinum is very expensive.

In order to prevent a decrease in the catalytic activity and improve the life characteristics of the electrode catalyst (improve durability), a method of heat-treating the electrode catalyst at a high temperature in advance has been conventionally employed. For example, in Patent Document 1, the oxidation-reduction potential by cyclic voltammetry is 430 mV or more (vs. SCE) (about 680 mV or more when RHE (Reversible Hydrogen Electrode) is used as a reference electrode). Catalysts have been proposed. In order to obtain the catalyst, in Patent Document 1, platinum supported on a carbon support is heat-treated for 2.5 hours in a mixed atmosphere of 400 to 1100 ° C. and N ₂ : H ₂ = 1: 3.
JP 2005-327721 A

  However, even using the technique of Patent Document 1, a catalyst excellent in both mass activity (activity per mass) and specific activity (activity per real area) has not been obtained, and also in durability, It was not satisfactory.

  In general, the more heat-treated platinum-supported electrode catalyst having carbon as a support, the higher the crystallinity and the specific activity of platinum particles, but the higher the heat-treatment temperature of platinum particles supported on a carbon support. Particles aggregate and mass activity decreases. In other words, the mass activity and the specific activity are in a contradictory relationship. When the electrode catalyst is heat-treated, the specific activity cannot be maintained when focusing on the mass activity, and conversely, the mass activity cannot be maintained when focusing on the specific activity. There was a problem.

  Therefore, an object of the present invention is to provide an electrode catalyst excellent in both mass activity and specific activity.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, an electrode catalyst in which a catalyst component containing 70 atomic% or more of platinum is supported on a conductive support with respect to 100 atomic% of the catalyst component, and a hydrogen desorption current having a hydrogen adsorption / desorption waveform by a cyclic voltammetry method. The peak current value in the range of 190 to 230 mV (I _{190 to 230 mV} ) and the peak current value of 250 to 270 mV or the current value at the inflection point (I _{250 to 270 mV} )

The present inventors have found that an electrode catalyst characterized by satisfying the above relationship solves the above object.

  Since the electrode catalyst of the present invention is an electrode catalyst having high activity and excellent durability, when applied to a fuel cell, it can be widely applied to automobiles, households, electronic devices and the like.

A first aspect of the present invention is an electrode catalyst in which a catalyst component containing platinum is supported on a conductive carrier, and a peak current value in a range of 190 to 230 mV in a hydrogen desorption current of a hydrogen adsorption / desorption waveform of a cyclic voltammetry method. (I _{190 to 230 mV} ) and a current value at an inflection point (I _{250 to 270 mV} ) of _{250 to 270 mV} ,

It is an electrode catalyst characterized by satisfying this relationship.

  The platinum particles used as the catalyst component consist of a cubic single crystal, and the shape of this cubic crystal varies depending on the size of the crystallite, and only the (111) plane appears from the cubic shape where only the (100) plane appears. There are various shapes up to the octahedral shape, and it has been conventionally known that, as there are (111) planes, the stability is excellent, and the (100) planes are excellent in activity as disclosed in, for example, JP-A-2005-166409. ing. When each single crystal plane has a waveform by cyclic voltammetry (CV), the peak in the hydrogen desorption current of (100) plane is in the range of 250 to 270 mV (vs. RHE), and the hydrogen desorption of (111) plane. The peak in current is at 190-230 mV (vs. RHE) (J. Solla-Gullon et al., Journal of Electrochemical Chemistry 491 (2000), P69-77).

Based on these facts, the inventors focused on the peak current at 250 to 270 mV and the peak current at 190 to 230 mV in the hydrogen desorption current of CV. As a result, the peak current value (I _{190 in} the range of ₁₉₀ to 230 mV with respect to the peak current value of 250 to 270 _mV or the current value at the inflection point (I ₂₅₀ to 270 _mV ) in the hydrogen desorption current of the hydrogen adsorption / desorption waveform of the cyclic voltammetry method. _The present inventors have found that an Ip value _represented by a ratio of _{~ 230 mV} ), i.e., I _{250-270 mV} / I _{190-230 mV} , is one important measure of the abundance of exposed crystal faces of platinum particles. . Furthermore, the present inventors have found that by optimizing the Ip value, an electrode catalyst having an appropriate platinum particle size and hence excellent in both specific activity and mass activity can be obtained.

  FIG. 1 is an example of a hydrogen adsorption / desorption waveform obtained by CV. The upper side of the waveform is a hydrogen desorption waveform, and the lower side is a hydrogen adsorption waveform. Catalyst B (Ip value 0.92) and Catalyst C (Ip value 0.96) are products of the present invention, and Catalyst A is not a product of the present invention (Ip value 0.78). In the calculation of the Ip value, when the peak current appears in the range of 250 to 270 mV, the peak current value is obtained. When the peak current does not appear, the current value at the inflection point at 250 to 270 mV is obtained. It shall be used for calculation of Ip value. Since the current in the range of 250 to 270 mV expresses the (100) surface having high activity as described above, the form that appears as the peak current is preferable.

  In the first aspect of the present invention, the Ip value of the electrode catalyst is 0.9 to 1.1. When the Ip value is less than 0.9, the proportion of the (111) plane having a relatively low oxygen reduction reaction activity (ORR) is increased, and the activity of the electrode catalyst is lowered. On the other hand, when the Ip value exceeds 1.1, the (100) plane, which is a crystal plane having a high oxygen reduction reaction activity, is exposed to some extent, but the mass activity of the platinum is decreased because the platinum particle size is increased. On the other hand, if the Ip value is from 0.9 to 1.1, the platinum particle size is appropriate, and the catalyst becomes an electrode catalyst having not only mass activity but also high specific activity, and a catalyst having a very good balance. Furthermore, the durability of the electrode catalyst is also high. The Ip value is preferably 0.9 to 1.05, and more preferably 0.95 to 1.0, since the effects of the present invention are more remarkably exhibited.

  In addition, the hydrogen desorption waveform used for calculating the Ip value is obtained by CV described in the following examples.

  The electrode catalyst of the present invention includes a catalyst component composed of 70 atomic percent or more of platinum with respect to 100 atomic percent of the catalyst component, and a conductive carrier that supports the catalyst component.

  Any conductive carrier may be used as long as it has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electron conductivity, but the main component is carbon. Is preferred. Specifically, carbon black such as acetylene black, channel black, lamp black, oil furnace black, and thermal black; carbon nanotube; carbon nanofiber; carbon nanohorn; carbon fibril; activated carbon; coke; natural graphite; Carbon material. Carbon black may be subjected to graphitization. Among these, carbon black is preferable because it is suitable for mass production at low cost. “The main component is carbon” means that the main component contains carbon atoms, and is a concept that includes both carbon atoms and substantially carbon atoms. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. Note that “substantially consisting of carbon atoms” means that contamination of about 2 to 3 mass% or less of impurities can be allowed.

The BET specific surface area of the conductive support may be a specific surface area sufficient to support the catalyst component in a highly dispersed state, but is preferably 50 to 1500 m ² / g, more preferably 60 to 1300 m ² / g. It is preferable that the specific surface area of the conductive support is in such a range because the highly dispersed state can be maintained even when the particle size of the catalyst component is 10 nm or less and the supported amount is 30 wt% or more.

  The average particle diameter of the conductive carrier is not particularly limited, but the average particle diameter is preferably 10 to 100 nm, more preferably 20 to 50 nm, from the viewpoints of ease of loading, catalyst utilization, and the like. The “average particle diameter of the conductive carrier” is defined by the so-called primary particle diameter observed with a scanning electron microscope.

  The catalyst component in the present invention contains 70 atom% or more of platinum with respect to 100 atom% of the catalyst component from the viewpoint of catalyst activity, poisoning resistance to carbon monoxide and the like, and heat resistance. Preferably it is 80-100 atomic%, More preferably, it is 90-100 atomic%, More preferably, it is 100 atomic%. The content ratio of the catalyst component can be measured by ICP emission spectroscopic analysis, and specifically, a value measured using an inductively coupled plasma emission spectroscopic analyzer SPS-1700HVR type manufactured by SII Nanotechnology is adopted.

  As a catalyst component, components other than platinum include metals such as ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum. It is done.

  The shape of the catalyst component is not particularly limited, and the same shape as a known catalyst component can be used, but a particulate shape is preferable. The average particle diameter of the catalyst component is preferably 3 to 7 nm, more preferably 3 to 5 nm. If the particle diameter of the catalyst component is in such a range, both the specific activity and mass activity of the electrode catalyst are good, which is preferable. The “average particle diameter of the catalyst component particles” in the present invention employs an average crystallite diameter determined by a half-value width of a diffraction peak measured by an X-ray diffraction method (hereinafter referred to as XRD method). To do. Specifically, it is calculated | required by the method employ | adopted in the Example.

  The content of the catalyst component is preferably 10 to 60% by mass, more preferably 30 to 50% by mass with respect to 100% by mass of the electrode catalyst. When the supported amount of the catalyst component is within such a range, the balance between the degree of dispersion of the catalyst component on the conductive support and the catalyst performance can be appropriately controlled.

  Although the manufacturing method of the 1st electrode catalyst of this invention is not restrict | limited in particular, A suitable manufacturing method is described below.

First, a catalyst component having an average particle diameter of 1 to 5 nm, preferably 2 to 5 nm, more preferably 2.5 to 5 nm, has a BET specific surface area of 50 to 1500 m ² / g, preferably 60 to 1200 m ² / g. An electrode catalyst precursor supported on a conductive support is prepared. A commercial item may be used for such an electrode catalyst precursor, and it may be manufactured by a well-known method. Commercially available products include TEC10E50E (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.), SA50BK (manufactured by N.E. Chemcat), HiSPEC8000 (manufactured by Johnson Matthey), and the like. When producing an electrode catalyst precursor, it is not particularly limited, but known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle method, etc. It can be easily prepared by utilizing the method. Preferably, a liquid phase reduction loading method that can carry a catalyst component at a low cost and in a highly dispersed manner is used.

  Next, the electrode catalyst precursor is heat-treated. The heat treatment condition is not particularly limited as long as the Ip value is set to be 0.9 to 1.1, but specifically, it is as follows.

  The heat treatment temperature in the case of heat treatment is preferably 200 to 1000 ° C., more preferably 400 to 1000 ° C., further preferably 600 to 1000 ° C., and particularly preferably 600 to 800 because the particle size of the catalyst component falls within an appropriate range. ° C. Moreover, the heat processing time in heat processing becomes like this. Preferably it is 0.5-3 hours, More preferably, it is 1-3 hours, More preferably, it is 1 hour. When the heat treatment time is in such a range, the particle size is in an appropriate range, the activity is high, and the methanation reaction of the conductive support does not proceed so much.

Moreover, it is preferable to perform the atmosphere at the time of heat processing in the mixed atmosphere of nitrogen gas and hydrogen gas. Under a mixed atmosphere of nitrogen gas and hydrogen gas at the time of heat treatment, the flow rates of nitrogen gas and hydrogen gas are preferably 100% of the total mixed gas flow rate of 100%. In addition to hydrogen gas and nitrogen gas, an inert gas such as argon or helium may be included. Further, the flow rate of the hydrogen gas is preferably H ₂ / (N ₂ + H ₂ ) = 5 to 25 in terms of a flow rate ratio with respect to the total flow rate (N ₂ + H ₂ ) of the hydrogen gas and the nitrogen gas, More preferably, it is 20, and more preferably 10-20. In such a range, the particle size becomes an appropriate range, the activity becomes high, and the methanation reaction of the conductive support does not progress so much.

  As described above, the first electrode catalyst of the present invention can be obtained by appropriately setting the temperature, time, and atmosphere conditions in the heat treatment. Under appropriate heat treatment conditions, hydrogen is adsorbed on the Pt surface and the surface energy is lowered. Therefore, it is considered that a crystal surface having a high surface energy can be exposed while maintaining a small particle size.

  As described above, the electrode catalyst obtained by the production method of the present invention has excellent activity and durability, and greatly contributes to improving the durability of the battery when applied to a fuel cell. PEFC is mentioned as an application use of an electrode catalyst. In PEFC, the electrode catalyst is disposed in the catalyst layer. A general configuration of PEFC includes a configuration in which a separator, a gas diffusion layer, a cathode catalyst layer, a solid polymer electrolyte membrane, an anode catalyst layer, a gas diffusion layer, and a separator are arranged in this order. However, the basic configuration of the PEFC is not limited to the above, and the present invention can also be applied to PEFCs having other configurations.

  The electrode catalyst of the present invention is suitably used as both an anode and a cathode electrode catalyst. However, since the operating potential of the reduction reaction at the cathode is higher than the oxidation reaction of hydrogen at the anode, the electrode catalyst is likely to deteriorate. Accordingly, it is preferable that the electrode catalyst is used at least for the cathode.

  Furthermore, as application applications when applied to fuel cells, it can be widely applied to automobile fuel cells, household fuel cells, electronic device fuel cells and the like. The PEFC of the present invention is excellent in durability because the catalyst layer is hardly deteriorated. That is, the PEFC of the present invention has little voltage drop even when the PEFC is used for a long period of time. Therefore, it can be widely applied to automobile fuel cells, household fuel cells, electronic device fuel cells, and the like. Furthermore, a fuel cell including the electrode catalyst of the present invention is particularly useful in applications that require durability over a long period of time. Examples of such applications include those for automobiles. Since the power generation characteristics of the PEFC of the present invention can be maintained over a long period of time, it is possible to extend the life of a vehicle equipped with the PEFC of the present invention and improve the vehicle value.

A second aspect of the present invention is a method for evaluating the activity of an electrocatalyst in which a catalyst component containing 70 atomic percent or more of platinum is supported on a conductive support with respect to 100 atomic percent of the catalyst component, and is based on a cyclic voltammetry method. The ratio of the peak current value in the range of 190 to 230 mV (I _{190 to 230 mV} ) in the hydrogen desorption current of the hydrogen adsorption / desorption waveform to the peak current value of ₂₅₀ to 270 mV or the current value at the inflection point (I _{250 to 270 mV} ). This is an activity evaluation method for evaluating the activity of an electrode catalyst based on the activity. As described above, the Ip value is one important standard indicating the abundance ratio of the exposed crystal plane of the platinum particle, and the degree of activity of the catalyst can be predicted by the Ip value. For example, it can be predicted that if the Ip value is too small, there will be a problem in terms of specific activity, and if the Ip value is too large, it may be a problem in terms of mass activity. As an evaluation example, an example in which an electrode catalyst having Ip = 0.9 to 1.1, more preferably 0.95 to 1.0, is determined to have excellent activity as a catalyst.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to the following Example.

(Example 1)
As a catalyst component, an electrode catalyst (Tanaka Kikinzoku Kogyo Co., Ltd .: TEC10E50E, platinum loading amount 50 wt%) in which only platinum having an average particle diameter of 2.5 nm is supported on ketjen black having a BET specific surface area of 800 m ² / g is a tubular furnace. And purged with atmospheric gas (hydrogen gas and nitrogen gas) where H ₂ / (H ₂ + N ₂ ) = 10 for 30 minutes (flow rate; hydrogen gas: 10 mL / min, nitrogen gas: 90 mL / min). Thereafter, with the gas flowing, the temperature rise rate was increased to 800 ° C. at 10 ° C./min, held at 800 ° C. (heat treatment temperature) for 1 hour (heat treatment time), and then naturally cooled (rapidly cooled) to 100 ° C. When it became the following, the gas to flow was switched to air, and it cooled to room temperature, and produced the heat processing catalyst.

(Example 2)
A catalyst was prepared in the same procedure as in Example 1 except that the heat treatment temperature was changed to 600 ° C.

(Example 3)
A catalyst was prepared in the same procedure as in Example 1 except that the heat treatment temperature was changed to 1000 ° C.

Example 4
A catalyst was prepared in the same procedure as in Example 1 except that the atmosphere was changed to an atmosphere gas of H ₂ / (H ₂ + N ₂ ) = 5.

(Example 5)
A catalyst was prepared in the same procedure as in Example 1 except that the atmosphere was changed to an atmosphere gas of H ₂ / (H ₂ + N ₂ ) = 25.

(Example 6)
A catalyst was prepared in the same procedure as in Example 1 except that the heat treatment time was changed to 3 hours.

(Comparative Example 1)
A comparison was made of an electrode catalyst (Tanaka Kikinzoku Kogyo Co., Ltd .: TEC10E50E, platinum loading 50 wt%) in which only platinum having an average particle diameter of 2.5 nm was supported on a ketjen black having a BET specific surface area of 800 m ² / g as a catalyst component. The catalyst of Example 1 was obtained.

(Comparative Example 2)
A catalyst was prepared in the same procedure as in Example 1 except that the heat treatment temperature was changed to 200 ° C.

(Comparative Example 3)
A catalyst was prepared in the same procedure as in Example 1 except that the heat treatment temperature was changed to 400 ° C.

(Comparative Example 4)
A catalyst was prepared in the same procedure as in Example 1 except that the atmosphere was changed to 100% nitrogen gas.

(Comparative Example 5)
A catalyst was prepared in the same procedure as in Example 1 except that the atmosphere was changed to 100% hydrogen gas.

(Comparative Example 6)
A catalyst was prepared in the same procedure as in Example 1 except that the heat treatment time was changed to 6 hours.

  The said Examples 1-6 and Comparative Examples 1-6 were evaluated with the following evaluation methods.

(Evaluation Example 1: Method for measuring crystallite size of catalyst component)
The crystallite diameter of the catalyst component of each Example and Comparative Example was measured by the XRD method, and the crystallite diameter was calculated from the peak value near 39 ° using the Scherrer equation.

The measurement conditions for XRD are as follows:
Measuring instrument: X-ray diffractometer (MXP18VAHF type), manufactured by Mac Science Co., Ltd., radiation source: (CuKα), output setting: voltage 40 kV, current 300 mA, divergence slit 1.0 °, scattering slit 1.0 °, light receiving slit 0. 3 mm, scanning range 5 to 90 °.

(Evaluation Example 2: Catalyst Evaluation Method)
(1) Electrochemical measuring device system Using a rotating disk electrode device (HZ-301, manufactured by Hokuto Denko), apply a catalyst wire to a platinum wire for the counter electrode, a standard hydrogen electrode for the reference electrode, and a glassy carbon electrode for the working electrode. And 0.5 mol / L sulfuric acid aqueous solution (made by Wako Pure Chemical Industries Ltd.) was used for electrolyte solution. The electrochemical measurement was performed using a potentiostat (electrochemical measurement system HZ-5000 manufactured by Hokuto Denko).

(2) Preparation for electrochemical measurement The prepared catalyst Pt / C was weighed so that the amount of carbon was 20 mg and placed in a beaker. In this beaker, 18 mL of water, 6 mL of isopropanol, 0.2 mL of 5 wt% Nafion (registered trademark) solution (manufactured by Du Pont) were added, and ultrasonic stirring was performed for 30 minutes. 10 μL of this catalyst ink was applied to a 5 mmφ GC (glassy carbon) electrode using a micropipette and dried in an oven at 80 ° C. for 10 minutes.

(3) Electrochemical measurement (3-1) Cyclic voltammetry After setting the electrode and electrolyte on the rotating disk electrode device and purging the electrolyte with nitrogen for 30 minutes, cyclic voltammetry was performed at a potential scanning speed of 50 mV / s. The potential scanning range was 0 to 1200 mV (vs. RHE) at room temperature. The cyclic voltammogram (representing a graph measured by cyclic voltammetry) used for the determination employs the results of the 15th cycle measured under the above conditions. A total of 15 cycles were performed.

(3-2) Durability Evaluation One cycle of a pulse wave of 5 seconds in a potential range of 1.0 to 0.6 V (vs. RHE) was performed in an electrolytic solution purged with nitrogen for 2000 cycles. After performing a cycle test, measurement was performed under the same conditions as in the above cyclic voltammetry, an ECA value was calculated, and the catalyst of Example 3 was compared and evaluated with the catalyst of Comparative Example 1 as a reference. In addition, ECA value is a value which shows the electrochemical specific surface area per Pt mass, and the calculation method is as follows. First, in order to obtain the electrochemical surface area of Pt, the amount of hydrogen adsorbed charge (area obtained from the reduction side potential × current) occurring between the potential range of 50 mV to 400 mV from the cyclic voltammogram is calculated per unit platinum area. The Pt surface area is determined by dividing by the amount of charge adsorbed by hydrogen (210 μC / cm ² -Pt). The ECA value is obtained by dividing the obtained Pt surface area by the Pt mass in the catalyst.

(3-3) Oxygen reduction activity evaluation (specific activity)
After the cyclic voltammetry in (3-1) above, after purging the electrolyte with oxygen for 30 minutes, the working electrode is rotated at 1600 rpm and the potential is scanned from 200 mV to 1200 mV (vs. RHE) to measure the oxygen reduction current. did. The specific activities of Examples and Comparative Examples were calculated by dividing the oxygen reduction current value at 900 mV (vs. RHE) by the Pt surface area obtained in (3-2) above.

(3-4) Oxygen reduction activity evaluation (mass activity)
The mass activities of the examples and comparative examples were calculated by integrating the specific activity determined in (3-3) with the ECA value determined in (3-2).

  The results are shown in Table 1 below.

  From the above results, it was found that an electrode catalyst having an Ip value in the range of 0.9 to 1.1 is a catalyst having an excellent balance of both mass activity and specific activity. Furthermore, the electrode catalyst was excellent in durability.

It is an example of a cyclic voltammogram.

Claims (8)

An electrode catalyst in which a catalyst component containing 70 atomic percent or more of platinum with respect to 100 atomic percent of a catalyst component is supported on a conductive carrier,
Cyclic voltammetry peak current value in the range of 190～230MV in the hydrogen desorption current hydrogen adsorption and desorption wave by the _{(I 190~230mV),} the current value at the peak current value or the inflection point of _{250~270mV (I} 250~270mV )

An electrode catalyst characterized by satisfying the relationship:   The electrode catalyst according to claim 1, wherein the material constituting the conductive support is carbon. An electrode catalyst precursor in which a catalyst component having an average particle diameter of 1 to 5 nm is supported on a conductive carrier having a BET specific surface area of 50 to 1500 m ² / g, has a temperature of 200 to 1000 ° C. and an atmosphere at a gas flow rate ratio. _{H 2 / (H 2 + N} 2) = 5~25, time is heat treated under conditions 1 to 3 hours, the electrode catalyst according to claim 1 or 2.   The electrode catalyst according to any one of claims 1 to 3, wherein the average particle diameter of the catalyst component is 3 to 7 nm.   It is an object for fuel cells, The electrode catalyst of any one of Claims 1-4.   A power generation system, wherein the electrode catalyst according to claim 5 is used in any one of an automobile fuel cell, a household fuel cell, and an electronic device fuel cell. A method for evaluating the activity of an electrode catalyst in which a catalyst component containing 70 atomic percent or more of platinum is supported on a conductive support with respect to 100 atomic percent of a catalyst component, and hydrogen desorption of a hydrogen adsorption / desorption waveform by a cyclic voltammetry method The activity of the electrocatalyst is determined based on the ratio of the peak current value in the range of 190 to 230 mV (I _{190 to 230 mV} ) and the peak current value of 250 to 270 mV or the current value at the inflection point (I _{250 to 270 mV} ). Activity evaluation method to evaluate. An electrode catalyst precursor in which a catalyst component having an average particle diameter of 1 to 5 nm is supported on a conductive carrier having a BET specific surface area of 50 to 1500 m ² / g is produced at a temperature of 200 to 1000 ° C. and an atmosphere H ₂ / (H ₂ + N ₂ ) = 5 to 25 (gas flow rate ratio), a method for producing an electrode catalyst, wherein heat treatment is performed for 1 to 3 hours.

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