JP2009283165A - Activating method of catalyst for solid polymer fuel cell, and activated catalyst for solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve cell performance by activating a catalyst for a fuel cell. <P>SOLUTION: This activating method of the catalyst for the solid polymer fuel cell is to apply a potential to the catalyst for the solid polymer fuel cell using a prescribed potential application pattern. The potential application pattern includes (1) a potential dropping process to drop a potential to a lower limit reduction potential from an initial potential, (2) a lower limit reduction potential holding process to hold the reduction potential, and (3) a potential elevating process to elevate the potential from the lower limit reduction potential to the initial potential. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for activating a polymer electrolyte fuel cell catalyst and an activated polymer electrolyte fuel cell catalyst.

  In general, a gas diffusible electrode used in a polymer electrolyte fuel cell includes a catalyst layer containing catalyst-supported carbon coated with a polymer electrolyte, supplies a reaction gas to the catalyst layer, and collects electrons. Gas diffusion layer. In the catalyst layer, there is a void portion composed of fine pores formed between secondary particles or tertiary particles of carbon as a constituent material, and the void portion functions as a reaction gas diffusion channel. Yes. And as said catalyst, noble metal catalysts, such as platinum and a platinum alloy which are stable in a polymer electrolyte, are usually used.

  As described above, as a cathode and an anode catalyst of an electrode catalyst of a polymer electrolyte fuel cell, a catalyst in which a noble metal such as platinum or a platinum alloy is supported on carbon black has been used. Platinum-supported carbon black is obtained by adding sodium hydrogen sulfite to a chloroplatinic acid aqueous solution, then reacting with hydrogen peroxide solution, supporting the resulting platinum colloid on carbon black, washing, and heat-treating as necessary. It is common to prepare. The electrode of a polymer electrolyte fuel cell is prepared by dispersing platinum-supported carbon black in a polymer electrolyte solution, preparing an ink, applying the ink to a gas diffusion substrate such as carbon paper, and drying. . An electrolyte membrane-electrode assembly (MEA) is assembled by sandwiching a polymer electrolyte membrane between these two electrodes and performing hot pressing.

  Platinum is an expensive noble metal and it is desired to exhibit sufficient performance with a small amount of support. Therefore, studies have been made to increase the catalytic activity with a smaller amount. For example, Patent Document 1 below provides a fuel cell electrode catalyst that suppresses the growth of platinum particles during operation and has high durability performance. As an object, there is disclosed an electrocatalyst composed of a conductive carbon material, metal particles supported on the conductive carbon material that are less likely to be oxidized than platinum under acidic conditions, and platinum covering the outer surface of the metal particles. Specifically, examples of the metal particles include an alloy made of platinum and at least one metal selected from gold, chromium, iron, nickel, cobalt, titanium, vanadium, copper, and manganese.

On the other hand, it is known that when oxygen (O ₂ ) is electrolytically reduced, superoxide is generated by one-electron reduction, hydrogen peroxide is generated by two-electron reduction, and water is generated by four-electron reduction. In a fuel cell stack using platinum or a platinum-based catalyst as an electrode, if a voltage drop occurs for some reason, the 4-electron reducibility is reduced and the 2-electron reducibility is obtained. For this reason, hydrogen peroxide is generated, which causes deterioration of MEA.

  Recently, a low-cost fuel cell catalyst that does not require an expensive platinum catalyst has been developed by a reaction in which oxygen is reduced by four electrons to generate water. Non-Patent Document 1 below discloses that a catalyst having a chalcogen element is excellent in 4-electron reducibility and suggests application to a fuel cell.

  Similarly, Patent Document 2 below discloses an electrode catalyst made of at least one transition metal and a chalcogen as a platinum substitute catalyst, and an electrode catalyst made of Ru as the transition metal and S or Se as the chalcogen. Yes. Here, it is disclosed that the Ru: Se molar ratio is in the range of 0.5 to 2 and the stoichiometric number n of (Ru) nSe is 1.5 to 2.

  By the way, in the following Patent Document 3, a general aging method for a direct methanol fuel cell is disclosed. Specifically, an anode medium such as a methanol aqueous solution is supplied to the anode electrode of a fuel cell requiring aging such as a direct methanol fuel cell, and a cathode medium such as air is supplied to the cathode electrode, and the fuel cell is interposed between the two electrodes. The fuel cell is aged by forcibly energizing in the same direction as the energization during power generation.

Japanese Patent Laid-Open No. 2002-289208 JP-T-2001-502467 JP 2006-40869 A Electrochimica Acta, vol. 39, no. 11/12, pp. 1647-1653, 1994

  The conventional (A) noble metal catalyst, (B) noble metal-transition metal alloy catalyst, and (C) transition metal-chalcogenide catalyst, as described in Patent Documents 1 and 2 and Non-Patent Document 1, are all stored. In particular, there is a problem that power generation performance deteriorates during operation, and development of a method for activating these catalysts has been desired. The invention of Patent Document 3 relates to shortening of the initial running-in operation to cope with the low and unstable power generation characteristics immediately after cell assembly of the direct methanol fuel cell. This is the same direction as the energization and is not an activation method related to the fine structure of the catalyst layer.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to improve battery performance by bringing a fuel cell catalyst into an activated state.

  The present inventor has found that the performance deterioration of the conventional fuel cell catalyst is caused by oxidation of the metal on the catalyst surface to form an oxide, and a specific activation treatment for the fuel cell catalyst. As a result, it was found that the catalyst efficiency can be improved, and the present invention has been achieved.

  That is, the present invention is an invention of a method for activating a polymer electrolyte fuel cell catalyst that applies a potential to a polymer electrolyte fuel cell catalyst in a predetermined potential application pattern, wherein the potential application pattern is: (1) a potential drop step for lowering the potential from the initial potential to the lower limit reduction potential; (2) a reduction potential holding step for holding the lower limit reduction potential; and (3) a potential for raising the potential from the lower limit reduction potential to the initial potential. And an ascending step.

  By the method for activating a catalyst for a polymer electrolyte fuel cell of the present invention, the metal oxide on the catalyst surface is reduced, and the original high activity of the catalyst is obtained. The activation of the present invention is effective even before the fuel cell is operated or after the operation and before the next operation.

  In the activation of the present invention, a potential application pattern comprising (1) a potential drop step, (2) a reduction potential holding step, and (3) a potential rise step may be performed once. It is also effective to repeat a potential application pattern consisting of a step, (2) a reduction potential holding step, (3) a potential increase step, and (4) an interval.

  In the activation of the present invention, it is also effective to provide the potential application pattern with (3) an annealing step in which the potential increase rate is lowered in the latter half of the potential increase step.

  Various known catalysts can be used as the polymer electrolyte fuel cell catalyst to be activated in the present invention. Among these solid polymer fuel cell catalysts, (A) noble metal catalyst, (B) noble metal-transition metal alloy catalyst, and (C) transition metal-chalcogenide catalyst are preferably exemplified.

  Hereinafter, details of the case where (A) a noble metal catalyst, (B) a noble metal-transition metal alloy catalyst, and (C) a transition metal-chalcogenide catalyst are used will be described.

  When the polymer electrolyte fuel cell catalyst is a (C) transition metal-chalcogenide catalyst, it is preferable that the potential drop insertion speed in the (1) potential drop step is 0 to 50 mV / s. Even if the potential drop pulling speed exceeds 50 mV / s, the activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (C) a transition metal-chalcogenide catalyst, the lower limit reduction potential in the (1) potential lowering step is preferably 0 to 300 mV. When the lower limit reduction potential exceeds 300 mV, the catalyst is not dramatically activated.

  When the polymer electrolyte fuel cell catalyst is (C) a transition metal-chalcogenide catalyst, the retention time in the (2) reduction potential holding step is preferably 0 to 100 seconds. Even if the holding time exceeds 100 seconds, the activation of the catalyst does not occur dramatically.

  When the catalyst for a solid polymer fuel cell is (C) a transition metal-chalcogenide catalyst, it is preferable that the potential increase / subtraction speed in the (3) potential increase step is 100 mV / s or more. The activation of the catalyst does not occur drastically when the potential rise / pull speed is less than 100 mV / s.

  When the polymer electrolyte fuel cell catalyst is a (C) transition metal-chalcogenide catalyst, the interval of repeating the potential application pattern a plurality of times at intervals of (4) is preferably 0 to 50 seconds. Even if the interval exceeds 50 seconds, activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (A) a noble metal catalyst, the potential drop insertion speed in the (1) potential drop step is preferably 0 to 100 mV / s. Even if the potential drop pulling speed exceeds 100 mV / s, the catalyst is not dramatically activated.

  When the polymer electrolyte fuel cell catalyst is (A) a noble metal catalyst, the lower limit reduction potential in the (1) potential drop step is preferably 75 to 675 mV.

  When the polymer electrolyte fuel cell catalyst is (A) a noble metal catalyst, the retention time in the (2) lower limit reduction potential holding step is preferably 0 to 60 seconds. Even if the holding time exceeds 60 seconds, the activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (A) a noble metal catalyst, it is preferable that the potential increase insertion speed in the (3) potential increase step is 300 mV / s or more. When the potential rise / pull speed is less than 300 mV / s, the activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (A) a noble metal catalyst, it is preferable that the interval of repeating the potential application pattern a plurality of times at (4) intervals is 0 to 120 seconds. When the interval exceeds 120 seconds, the activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (A) a noble metal catalyst, it is preferable that the potential increase / subtraction speed in the (5) annealing step is 0 to 50 mV / s. When the potential rise / pull speed in the annealing process exceeds 50 mV / s, the catalyst is not dramatically activated.

  When the polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, it is preferable that the potential drop insertion speed in the (1) potential drop step is 0 to 50 mV / s. Even if the potential drop pulling speed exceeds 50 mV / s, the activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, (1) the lower limit reduction potential of the potential drop step is preferably 0 to 750 mV. When the lower limit reduction potential exceeds 750 mV, the catalyst is not dramatically activated.

  When the polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, the retention time in the (2) lower limit reduction potential holding step is preferably 0 to 16 seconds. Even if the holding time exceeds 16 seconds, the activation of the catalyst does not occur dramatically.

  When the polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, it is preferable that the potential increase / subtraction speed in the (3) potential increase step is 400 mV / s or more. When the potential rise / pull speed is less than 400 mV / s, the activation of the catalyst does not occur dramatically.

When the polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, it is preferable that the interval of repeating the potential application pattern at (4) intervals is 0 to 240 seconds. . Even if the interval exceeds 240 seconds, the activation of the catalyst does not occur dramatically.
The present invention also provides a polymer electrolyte fuel cell catalyst activated by the above-described method.

  In the polymer electrolyte fuel cell catalyst, the catalytic metal particle surface serves as a reaction point, but the surface is covered with a metal oxide under a noble potential, and the power generation performance is deteriorated. In the present invention, the power generation performance is improved by reducing the metal oxide on the surface of the catalyst metal particles to a metal by making the base potential by a specific operation.

  Examples of the catalyst metal supported on the support in the catalyst layer of the polymer electrolyte fuel cell of the present invention include (A) noble metal catalyst, (B) noble metal-transition metal alloy catalyst, and (C) transition metal-chalcogenide catalyst. Is possible.

  In the present invention, various known alloys are used in combination as the noble metal-transition metal alloy. Among them, the noble metal is platinum, and the transition metals are ruthenium (Ru), molybdenum (Mo), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), iron (Fe), nickel One or more selected from (Ni), titanium (Ti), tungsten (W), palladium (Pd), rhenium (Re), chromium (Cr), manganese (Mn), niobium (Nb), and tantalum (Ta) The combination of noble metal and transition metal alloy is preferably exemplified.

In the present invention, the basic composition of the transition metal-chalcogenide catalyst is one in which at least one transition metal element and at least one chalcogen element are supported on a conductive support. At least one transition metal element and at least one chalcogen element are represented by, for example, a general formula: M ₁ X in a binary catalyst using _one transition metal element (where M ₁ is a transition metal element) And X is a chalcogen element). In addition, a ternary catalyst using two kinds of transition metal elements is represented by a general formula: M ₁ M ₂ X (where M ₁ and M ₂ are transition metal elements, and X is a chalcogen element). . Furthermore, a multi-component catalyst using three or more transition metal elements may be used.

In the transition metal-chalcogenide catalyst of the present invention, the transition metal elements (M ₁ , M ₂ ...) Are ruthenium (Ru), molybdenum (Mo), osmium (Os), cobalt (Co), rhodium (Rh), It is at least one selected from iridium (Ir), iron (Fe), nickel (Ni), palladium (Pd), rhenium (Re), and the chalcogen element (X) is sulfur (S), selenium (Se) And at least one selected from tellurium (Te).

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
[Preparation of (A) noble metal catalyst, (B) noble metal-transition metal alloy catalyst, and (C) transition metal-chalcogenide catalyst]
(Preparation of Pt / C catalyst)
A platinum-supported carbon catalyst (Pt / C catalyst) was prepared by the following procedure.
1) Disperse 2.0 g of carbon (Ketjen Black) in 0.2 L of pure water to prepare a slurry.
2) While stirring the slurry, 33 g (1.6 g in terms of platinum) of 5 wt% hexahydroxo platinum nitric acid aqueous solution is dropped.
3) Stir the mixture.
4) 1 L of pure water is dropped into the obtained mixed solution, mixed and then filtered.
5) After filtration, the obtained cake is further washed with pure water.
6) After washing, disperse the obtained cake in 1 L of pure water.
7) A 0.01 N ammonia solution is added dropwise to the resulting mixture until the pH is 9.0.
8) Further, 140 mL of a 3 wt% aqueous sodium borohydride solution is added dropwise to the mixture.
9) Stir the above mixture sufficiently.
10) Filter the resulting mixture.
11) After filtration, the obtained cake is further washed with pure water.
12) After washing, the cake obtained is dried at 80 ° C. for 48 hours.
The obtained Pt / C catalyst had a Pt loading of 45 wt%.

(Preparation of PtCo / C catalyst)
A platinum-cobalt alloy-supported carbon catalyst (PtCo / C catalyst) was prepared by the following procedure.
1) Disperse 2.0 g of carbon (Ketjen Black) in 0.2 L of pure water to prepare a slurry.
2) While stirring the slurry, 33 g (1.6 g in terms of platinum) of 5 wt% hexahydroxo platinum nitric acid aqueous solution is dropped.
3) Stir the mixture.
4) 1 L of pure water is dropped into the obtained mixed solution, mixed and then filtered.
5) After filtration, the obtained cake is further washed with pure water.
6) After washing, disperse the obtained cake in 1 L of pure water.
7) 1.5 g of cobalt nitrate (containing 0.16 g of Co) is dissolved in 40 g of pure water.
8) The cobalt nitrate aqueous solution of 7) is dropped into the mixed solution of 6).
9) A 0.01 N ammonia solution is added dropwise to the resulting mixture until the pH is 9.0.
10) 1 L of pure water is dropped into the obtained mixed solution, mixed, and then filtered.
11) After filtration, the obtained cake is further washed with pure water.
12) After washing, the cake obtained is dried by heating at 100 ° C. for 24 hours in a vacuum atmosphere.
13) The dried powder is heat-treated at 700 ° C. for 2 hours in a hydrogen gas atmosphere.
14) Further, heat treatment is performed at 800 ° C. for 5 hours under an argon atmosphere.
The composition ratio of the obtained PtCo / C catalyst was Pt: Co = 5: 1, and the supported amount of PtCo was 45 wt%.

(Preparation of RuMoS / C catalyst)
A transition metal-chalcogenide-supported carbon catalyst (RuMoS / C catalyst) was prepared by the following procedure.
1) Xylene is degassed using an inert gas.
2) 1600 mg of ruthenium carbonyl, 250 mg of molybdenum carbonyl and 250 mg of sulfur powder are put into 1) xylene.
3) Stir the mixture.
4) After stirring, reflux is performed at 140 ° C. for 20 hours in an inert gas atmosphere.
5) Cool to room temperature.
6) Filter the resulting mixture.
7) Wash with acetone.
8) After natural drying, vacuum dry at 100 ° C. for 24 hours.
9) The obtained powder is heat-treated at 350 ° C. for 2 hours under vacuum.
The composition ratio of the obtained RuMoS / C catalyst was Ru: Mo: S = 5: 1: 5, and the amount of RuMoS supported was 60 wt%.

[Catalyst evaluation method]
Electrochemical evaluation was performed with a three-electrode rotating disk evaluation apparatus. FIG. 1 shows a standard pattern of catalyst activation according to the present invention.
1) The potential is controlled from the OCV state to the potential in the power generation state.
2) Hold for 10 seconds at the potential of the power generation state. The average value of the potential for 1 second in the latter half is defined as “initial performance value before control”.
3) Lower the potential to any potential (lower limit reduction potential) at any potential drop insertion speed.
4) After holding at the lower limit reduction potential for an arbitrary period of time, increase the potential to the power generation state at an arbitrary potential increase / subtraction speed.
5) Hold again for 10 seconds at the potential of the power generation state. The average value of the potential for 1 second in the latter half is defined as “performance value after control”.
6) Set to open circuit (OCV) state.
In the present invention, the oxygen reduction current value gain = “performance value after control” / “initial performance value before control”.

[Activation of transition metal-chalcogenide catalyst]
The RuMoS / C catalyst was activated in the pattern of FIG. The lower limit reduction potential was 100 mV.

  FIG. 2 shows the oxygen reduction current gain when the potential drop insertion speed is changed. From the results in FIG. 2, the potential drop insertion speed in the optimum potential drop process is 0 to 50 mV / s, and even if the potential drop draw speed exceeds 50 mV / s, the activation of the catalyst does not occur dramatically. I understand that.

  FIG. 3 shows the oxygen reduction current gain when the lower limit reduction potential in the potential drop step is changed. From the results of FIG. 3, it can be seen that the lower limit reduction potential of the optimum potential drop step is 0 to 300 mV, and that the catalyst is not dramatically activated when the lower limit reduction potential exceeds 300 mV. In addition, since a reverse reaction occurs at 0 mV or less and hydrogen is generated at the cathode electrode, it is not controlled to 0 mV or less.

  FIG. 4 shows the oxygen reduction current gain when the holding time in the reduction potential holding step is changed. From the results of FIG. 4, it can be seen that the optimum holding time of the reduction potential holding step is 0 to 100 seconds, and that the catalyst is not dramatically activated even if the holding time exceeds 100 seconds. Holding for a long time at the lower limit reduction potential deteriorates battery efficiency and durability, so the holding time is preferably the minimum time for obtaining the best oxygen reduction current gain.

  FIG. 5 shows the oxygen reduction current gain when the potential increase / subtraction speed in the potential increase step is changed. From the result of FIG. 5, it can be seen that the potential increase / subtraction speed in the optimum potential increase step is 100 mV / s or higher, and that the catalyst activation does not occur drastically when the potential increase / lower speed is less than 100 mV / s. . If the potential rise / pull speed is too high, the catalyst is oxidized by overshoot and the performance is lowered. For this reason, it is good to set it as the minimum electric potential rise insertion speed which can obtain the best oxygen reduction current gain.

  FIG. 6 shows the oxygen reduction current gain when the interval when the potential application pattern is repeated a plurality of times at intervals is changed. From the results of FIG. 6, it can be seen that the optimum interval is 0 to 50 seconds, and even if the interval exceeds 50 seconds, the activation of the catalyst does not occur dramatically.

[Activation of precious metal catalysts]
The Pt / C catalyst was activated in the pattern of FIG. The lower limit reduction potential was 600 mV.

  FIG. 7 shows the oxygen reduction current gain when the potential drop insertion speed is changed. From the result of FIG. 7, the potential drop insertion speed of the optimum potential drop process is 0 to 100 mV / s, and even if the potential drop insertion speed exceeds 100 mV / s, the activation of the catalyst does not occur dramatically. I understand that.

  FIG. 8 shows the oxygen reduction current gain when the lower limit reduction potential in the potential drop step is changed. From the results of FIG. 8, it can be seen that the lower limit reduction potential of the optimum potential drop step is 75 to 675 mV, and that the catalyst is not dramatically activated when the lower limit reduction potential exceeds 675 mV. In addition, since a reverse reaction occurs at 0 mV or less and hydrogen is generated at the cathode electrode, it is not controlled to 0 mV or less.

  FIG. 9 shows the oxygen reduction current gain when the holding time in the reduction potential holding step is changed. From the results of FIG. 9, it can be understood that the optimum holding time of the reduction potential holding step is 0 to 60 seconds, and that the catalyst is not dramatically activated even if the holding time exceeds 60 seconds. Holding for a long time at the lower limit reduction potential deteriorates battery efficiency and durability, so the holding time is preferably the minimum time for obtaining the best oxygen reduction current gain.

  FIG. 10 shows the oxygen reduction current gain when the potential rise insertion speed in the potential rise step is changed. From the result of FIG. 10, it can be seen that the potential increase / subtraction speed of the optimum potential increase process is 300 mV / s or higher, and that the catalyst activation does not occur drastically when the potential increase / subtraction speed is less than 300 mV / s. . If the potential rise / pull speed is too high, the catalyst is oxidized by overshoot and the performance is lowered. For this reason, it is good to set it as the minimum electric potential rise insertion speed which can obtain the best oxygen reduction current gain.

  FIG. 11 shows the oxygen reduction current gain when the interval is changed when the potential application pattern is repeated a plurality of times at intervals. From the results shown in FIG. 11, it can be seen that the optimum interval is 0 to 120 seconds, and even if the interval exceeds 120 seconds, the activation of the catalyst does not occur dramatically.

  FIG. 12 shows the oxygen reduction current when the potential increasing / decreasing speed of the annealing process is changed when the potential application pattern is provided with an annealing process in which the potential increasing speed is lowered in the latter half of the potential increasing process. Indicates gain. From the results of FIG. 12, the optimum potential increasing / lowering speed in the annealing process is 0 to 50 mV / s, and when the increasing potential in the annealing process exceeds 50 mV / s, the activation of the catalyst is dramatically increased. I know that doesn't happen.

[Activation of noble metal-transition metal alloy catalyst]
The PtCo / C catalyst was activated in the pattern of FIG. The lower limit reduction potential was 600 mV.

  FIG. 13 shows the oxygen reduction current gain when the potential drop insertion speed is changed. From the result of FIG. 13, the potential drop insertion speed in the optimum potential drop process is 0 to 50 mV / s, and even if the potential drop draw speed exceeds 50 mV / s, the activation of the catalyst does not occur dramatically. I understand that.

  FIG. 14 shows the oxygen reduction current gain when the lower limit reduction potential in the potential drop step is changed. From the results of FIG. 14, it can be seen that the lower limit reduction potential of the optimum potential drop step is 0 to 750 mV, and that the catalyst is not dramatically activated when the lower limit reduction potential exceeds 750 mV. In addition, since a reverse reaction occurs at 0 mV or less and hydrogen is generated at the cathode electrode, it is not controlled to 0 mV or less.

  FIG. 15 shows the oxygen reduction current gain when the holding time of the reduction potential holding step is changed. From the results of FIG. 15, it can be seen that the optimal holding time of the reduction potential holding step is 0 to 16 seconds, and that the catalyst is not dramatically activated even if the holding time exceeds 16 seconds. Holding for a long time at the lower limit reduction potential deteriorates battery efficiency and durability, so the holding time is preferably the minimum time for obtaining the best oxygen reduction current gain.

  FIG. 16 shows the oxygen reduction current gain when the potential increase / subtraction speed in the potential increase step is changed. From the results of FIG. 16, it can be seen that the potential increase / subtraction speed in the optimum potential increase step is 400 mV / s or higher, and that the catalyst activation does not occur drastically when the potential increase / subtraction speed is less than 400 mV / s. . If the potential rise / pull speed is too high, the catalyst is oxidized by overshoot and the performance is lowered. For this reason, it is good to set it as the minimum electric potential rise insertion speed which can obtain the best oxygen reduction current gain.

  FIG. 17 shows the oxygen reduction current gain when the interval when the potential application pattern is repeated a plurality of times at intervals is changed. From the results of FIG. 17, it can be seen that the optimum interval is 0 to 240 seconds, and that the activation of the catalyst does not occur dramatically even if the interval exceeds 240 seconds.

  The present invention activates various fuel cell catalysts. This contributes to the spread of fuel cells.

2 shows a standard pattern of catalyst activation of the present invention. The oxygen reduction current gain when the potential drop insertion speed is changed when the RuMoS / C catalyst is activated is shown. The oxygen reduction current gain when changing the lower limit reduction potential in the potential drop step when the RuMoS / C catalyst is activated is shown. The oxygen reduction current gain when changing the holding time of the reduction potential holding step when the RuMoS / C catalyst is activated is shown. The oxygen reduction current gain when changing the potential increase / subtraction speed in the potential increase step when the RuMoS / C catalyst is activated is shown. The oxygen reduction current gain is shown when the interval when the potential application pattern is repeated a plurality of times with an interval when the RuMoS / C catalyst is activated is changed. The oxygen reduction current gain when changing the potential drop insertion speed when the Pt / C catalyst is activated is shown. The oxygen reduction current gain when changing the lower limit reduction potential in the potential drop step when the Pt / C catalyst is activated is shown. The oxygen reduction current gain when changing the holding time of the reduction potential holding step when the Pt / C catalyst is activated is shown. The oxygen reduction current gain is shown when the potential rise insertion speed in the potential rise step is changed when activation is performed on the Pt / C catalyst. The oxygen reduction current gain when changing the interval when the potential application pattern is repeated a plurality of times with an interval when the Pt / C catalyst is activated is shown. When the Pt / C catalyst is activated, the potential increase insertion in the annealing step when the potential application pattern is provided with an annealing step in which the potential increase rate is reduced in the latter half of the potential increase step. An oxygen reduction current gain when the pulling speed is changed is shown. The oxygen reduction current gain when the potential drop pulling speed is changed when the PtCo / C catalyst is activated is shown. The oxygen reduction current gain when changing the lower limit reduction potential in the potential drop step when the PtCo / C catalyst is activated is shown. The oxygen reduction current gain when changing the holding time of the reduction potential holding step when the PtCo / C catalyst is activated is shown. The oxygen reduction current gain is shown when the potential increase insertion speed in the potential increase step is changed when the PtCo / C catalyst is activated. The oxygen reduction current gain when changing the interval when the potential application pattern is repeated a plurality of times with an interval when the PtCo / C catalyst is activated is shown.

Claims (21)

  A method for activating a polymer electrolyte fuel cell catalyst that applies a potential to a polymer electrolyte fuel cell catalyst in a predetermined potential application pattern, wherein the potential application pattern is (1) lower limit reduction from initial potential A potential drop step for dropping the potential to a potential; (2) a lower limit reduction potential holding step for holding the reduction potential; and (3) a potential increase step for raising the potential from the lower limit reduction potential to the initial potential. A method for activating a catalyst for a polymer electrolyte fuel cell.   2. The potential application pattern comprising (1) a potential drop step, (2) a lower limit reduction potential holding step, and (3) a potential rise step is repeated a plurality of times at (4) intervals. A method for activating a catalyst for a polymer electrolyte fuel cell as described in 1).   3. The polymer electrolyte fuel cell according to claim 1, wherein the potential application pattern is provided with (5) an annealing step in which the potential increase rate is lowered in the latter half of the potential increase step. Method for activating catalysts.   4. The polymer electrolyte fuel cell catalyst is selected from (A) a noble metal catalyst, (B) a noble metal-transition metal alloy catalyst, and (C) a transition metal-chalcogenide catalyst. A method for activating a catalyst for a solid polymer fuel cell according to any one of the above.   The catalyst for a solid polymer fuel cell is (C) a transition metal-chalcogenide catalyst, and (1) a potential drop insertion rate in the potential drop step is 0 to 50 mV / s. Item 5. A method for activating a polymer electrolyte fuel cell catalyst according to any one of Items 1 to 4.   The catalyst for a solid polymer fuel cell is (C) a transition metal-chalcogenide catalyst, and the lower limit reduction potential in the (1) potential drop step is 0 to 300 mV. A method for activating a catalyst for a solid polymer fuel cell according to any one of the above.   The catalyst for a solid polymer fuel cell is (C) a transition metal-chalcogenide catalyst, and the retention time of the (2) lower limit reduction potential holding step is 0 to 100 seconds. 7. A method for activating a polymer electrolyte fuel cell catalyst according to any one of items 1 to 6.   The catalyst for a solid polymer fuel cell is (C) a transition metal-chalcogenide catalyst, and (3) a potential increase insertion speed in the potential increase step is 100 mV / s or more. 8. A method for activating a polymer electrolyte fuel cell catalyst according to any one of 1 to 7.   The catalyst for a polymer electrolyte fuel cell is (C) a transition metal-chalcogenide catalyst, wherein (4) the interval of repeating the potential application pattern a plurality of times at intervals is 0 to 50 seconds. A method for activating a catalyst for a polymer electrolyte fuel cell according to any one of claims 1 to 8.   The catalyst for a solid polymer fuel cell is (A) a noble metal catalyst, and the potential drop insertion rate in the (1) potential drop step is 0 to 100 mV / s. 5. The method for activating a polymer electrolyte fuel cell catalyst according to any one of 4 above.   11. The polymer electrolyte fuel cell catalyst according to claim 1, wherein the catalyst for a solid polymer fuel cell is (A) a noble metal catalyst, and (1) a lower limit reduction potential in the potential drop step is 75 to 675 mV. A method for activating a catalyst for a solid polymer fuel cell according to any one of the above.   The catalyst for a solid polymer fuel cell is (A) a noble metal catalyst, and the holding time of the (2) lower limit reduction potential holding step is 0 to 60 seconds, A method for activating a catalyst for a polymer electrolyte fuel cell according to any one of 10 and 11.   5. The polymer electrolyte fuel cell catalyst according to claim 1, wherein (A) a noble metal catalyst, and (3) a potential increasing insertion rate in the potential increasing step is 300 mV / s or more. A method for activating a catalyst for a polymer electrolyte fuel cell according to any one of 10 to 12.   The catalyst for a polymer electrolyte fuel cell is (A) a noble metal catalyst, and (4) the interval of repeating the potential application pattern a plurality of times at intervals is 0 to 120 seconds. A method for activating a catalyst for a polymer electrolyte fuel cell according to any one of 1 to 4, 10 to 13.   The catalyst for a solid polymer fuel cell is (A) a noble metal catalyst, and (5) the potential increase / subtraction speed in the annealing step is 0 to 50 mV / s. 15. The method for activating a polymer electrolyte fuel cell catalyst according to any one of 14 above.   The polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, wherein (1) the potential drop insertion speed in the potential drop step is 0 to 50 mV / s. The method for activating the polymer electrolyte fuel cell catalyst according to any one of claims 1 to 4.   The catalyst for a solid polymer fuel cell is (B) a noble metal-transition metal alloy catalyst, wherein the lower limit reduction potential in the (1) potential drop step is 0 to 750 mV. 17. A method for activating a polymer electrolyte fuel cell catalyst according to any one of 4 and 16.   The solid polymer type fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, and the holding time of the (2) lower limit reduction potential holding step is 0 to 16 seconds. 18. A method for activating a polymer electrolyte fuel cell catalyst according to any one of 1 to 4, 16, and 17.   The catalyst for a polymer electrolyte fuel cell is (B) a noble metal-transition metal alloy catalyst, and (3) a potential increase insertion rate in the potential increase step is 400 mV / s or more. Item 19. A method for activating a catalyst for a polymer electrolyte fuel cell according to any one of Items 1 to 4 and 16 to 18.   The polymer electrolyte fuel cell catalyst is (B) a noble metal-transition metal alloy catalyst, and (4) the interval at which the potential application pattern is repeated a plurality of times at intervals is 0 to 240 seconds. The method for activating a polymer electrolyte fuel cell catalyst according to any one of claims 1 to 4 and 16 to 19.   A catalyst for a polymer electrolyte fuel cell activated by the method according to any one of claims 1 to 20.

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