JP6159283B2 - Fuel cell electrode catalyst - Google Patents

Description

The present invention relates to an electrode catalyst for a fuel cell, and more specifically, it is preferably used as an anode catalyst for an electrode for a polymer electrolyte fuel cell, and can further improve CO resistance and catalyst durability, by adding a RuO ₂ nanosheet. The present invention relates to a fuel cell electrode catalyst.

  An anode catalyst of a polymer electrolyte fuel cell for home use is required to improve poisoning resistance to CO contained in fuel gas (Non-patent Document 1). Improvement in the performance of the reformer is effective in reducing the CO content in the fuel gas, but it has led to an increase in the cost of the fuel cell system and has become a barrier to full-scale spread. Under such circumstances, development of an anode catalyst having high CO resistance is expected for the purpose of full-scale popularization of household fuel cells.

A Pt ₂ Ru ₃ / C electrode catalyst having ruthenium-platinum alloy particles (Ru / Pt = 1.5 / 1 (molar ratio)) supported on a carbon black support has high CO resistance. Is commonly used in anode catalysts. In this Pt ₂ Ru ₃ / C electrode catalyst, the electronic state of Pt is changed by alloying Pt and Ru. Therefore, a dual function mechanism (a mechanism for oxidizing and removing CO strongly adsorbed to Pt) or a ligand effect ( It is known that the CO tolerance is increased by the effect of weakening the Pt-CO bond and facilitating CO oxidation.

However, since Ru of Pt ₂ Ru ₃ / C exists without being partly alloyed, it has been a problem that sufficient CO resistance cannot be extracted. Furthermore, Pt ₂ Ru ₃ / C is not sufficient performance because it has high CO tolerance but low CO-free hydrogen oxidation (HOR) activity. Further, the Pt / C electrode catalyst having platinum particles supported on a carbon black carrier has a hydrogen oxidation reaction activity (HOR activity) higher than Pt ₂ Ru ₃ / C because the catalyst surface is only Pt. There is also a drawback that the CO resistance is lower than ₂ Ru ₃ / C.

As described above, the fact that the CO-free HOR activity in Pt ₂ Ru ₃ / C is lower than that in Pt / C is considered to be due to enlargement of Pt ₂ Ru ₃ particles and a decrease in the amount of surface Pt. Therefore, there is a need for the synthesis of Pt _x Ru _y / C having a fine particle size and a Pt-rich surface, that is, a catalyst having high CO-free HOR activity and high CO resistance.

In response to such a demand, an example of synthesizing a Pt ₁ Ru ₁ / C electrode catalyst carrying ruthenium-platinum alloy particles (Ru / Pt = 1/1 (molar ratio)) on a carbon black support by a nanocapsule method is available. It has been reported. The CO-free HOR activity of Pt ₁ Ru ₁ / C was higher than Pt ₂ Ru ₃ / C obtained by the same synthesis method. This is reported because the surface of Pt ₁ Ru ₁ / C was Pt rich. It has also been reported that the CO tolerance is highest for Pt ₂ Ru ₃ / C, and next highest for Pt ₁ Ru ₁ / C. From these results, it can be said that CO-free HOR activity and CO tolerance are in a trade-off relationship between Pt ₂ Ru ₃ / C and Pt ₁ Ru ₁ / C, and need to be improved.

One of the means for increasing CO tolerance is improvement of Pt ₁ Ru ₁ / C. In order to increase the CO resistance of Pt ₁ Ru ₁ / C having a high CO-free HOR activity, it is said that addition of an oxide material is effective.

Combining MoO _x and _Pt 1 _Ru 1 / C, the _MoO x _-Pt 1 _Ru 1 / C obtained by a heat treatment of 300 ° C., CO tolerance and CO oxidation capacity is high as reported. In particular, as the amount of MoO _x added increased, the CO resistance and CO oxidation ability increased. It has been reported that as a result of complexing MoO _x and Pt ₁ Ru ₁ , CO adsorbed on Pt reacts with OH adsorbed on MoO _x , and CO is easily oxidized to increase CO tolerance. This has been confirmed by in-situ ATR-FTIR measurement. In addition, it has been reported that the change in the electronic state due to the alloying of Mo and Pt ₁ Ru ₁ is also a factor in improving the CO resistance. From these facts, it is known that the presence of a metal species that attracts OH species in the vicinity of Pt can enhance CO resistance and CO oxidation ability.

Further, it has been reported that a catalyst in which Pt ₁ Ru ₁ / C and SnO ₂ are combined improves CO-free HOR activity and CO resistance. It has also been reported that a catalyst in which Pt ₂ Ru ₃ / C and SnO ₂ are combined has higher CO resistance than Pt ₂ Ru ₃ / C. Moreover, even in composite catalyst with Pt / C and SnO _2, thereby improving the CO tolerance. It is known that the SnO ₂ particles are adjacent to the PtRu and Pt particles, so that CO oxidation is promoted by a dual function mechanism, and it has been reported that the CO resistance is increased due to this.

  However, the composite catalyst obtained by adding these metal oxides has reduced the electrochemically active surface area. If a catalyst that does not decrease the active surface area even if a metal oxide is added can be synthesized, it can be expected that the catalyst is high in both CO-free HOR activity and CO resistance.

As a catalyst with enhanced CO tolerance without reducing electrochemically active surface area be added metal oxides, _{RuO 2 -Pt RuO} 2 aggregates _Pt 1 Ru ₁ particle surface is in contact with part 1 _Ru 1 / C. It was found that the CO oxidation ability and the CO resistance are increased by the proximity of the RuO ₂ aggregate to the surface of the PtRu particles. If the surface area of the RuO ₂ aggregate can be increased, it can be expected that the CO oxidation ability can be further enhanced. Therefore, RuO ₂ having a large specific surface area is required.

In addition, it is known that Pt _x Ru _y / C is eluted in a durability test for starting and stopping of a fuel cell. As a result, the CO resistance of the electrode catalyst is significantly reduced. Therefore, the electrode catalyst is also required to have high durability against starting and stopping. It has been found that high durability of the catalyst can be realized by a composite catalyst with SiO ₂ , TiO _x , and RuO _x H _y .

S.M.M.Ehteshami and S.H.Chan, Electrochim.Acta, 93, 334 (2013). W. Sugimoto, H. Iwata, Y. Yasunaga, Y. Murakami, and Y. Takasu, Angew. Chem. Int. Ed., 42, 4092 (2003). W. Sugimoto, H. Iwata, Y. Murakami, and Y. Takasu, J. Electrochem. Soc., 151, A1181 (2004). T. Saida, W. Sugimoto, and Y. Takasu, Electrochim. Acta, 55, 857 (2010). W. Sugimoto, T. Saida, and Y. Takasu, Electrochem.commun., 8, 411 (2006). D. Takimoto, C. Chauvin, and W. Sugimoto, Electrochem.commun., 33, 123 (2013).

The problems that summarize the conventional research are that it is necessary to add an oxide material that does not reduce the active surface area, and that it is necessary to increase the surface area of the oxide material that is effective to enhance the CO oxidation ability. It can be said that there is. In addition to this, increasing the catalyst durability of Pt _x Ru _y / C is also an important issue.

In response to this problem, the present inventor has reported the synthesis of ruthenium oxide nanosheets obtained by peeling off layered ruthenium oxide (Non-patent Document 2). Since this ruthenium oxide nanosheet is a two-dimensional crystal having a thickness of about 1 nm and a spread of several μm in the lateral direction, it has a specific surface area of about 250 m ² g ⁻¹ (Non-patent Document 3). So far, it has been found that the composite catalyst of ruthenium oxide nanosheets and Pt / C has improved methanol oxidation reaction activity, CO oxidation ability, and catalyst durability (Non-patent Documents 4 and 5). In addition, it is reported that the CO oxidation ability is improved because the OH species adsorbed on the high specific surface area ruthenium oxide nanosheet oxidizes more CO adsorbed on Pt. Since the ruthenium oxide nanosheet at this time has a two-dimensional feature, it does not inhibit the diffusion of the reactive species. Therefore, the composite catalyst shows higher methanol oxidation reaction activity than Pt / C. Unlike the conventional composite catalyst, this composite catalyst does not require high-temperature heat treatment during synthesis, and thus does not reduce the Pt active surface area (Non-patent Document 6). In addition, since the surface area of the RuO ₂ nanosheet is large, it is likely to be adjacent to the CO-poisoned Pt, so that the CO oxidation ability can be expected to increase. Furthermore, since the synthesis method is merely mixing the RuO ₂ nanosheet colloid and the catalyst aqueous dispersion, the composition control is very simple.

  The present invention has been made to solve the conventional problems, and the object thereof is preferably used as an anode catalyst of a polymer electrolyte fuel cell electrode, and further improves CO resistance and catalyst durability. It is an object of the present invention to provide an electrode catalyst that can be used.

An electrode catalyst according to the present invention for solving the above-mentioned problems is a composite catalyst of an electrode catalyst in which platinum particles or ruthenium platinum particles are supported on carbon black, and a RuO ₂ nanosheet, and comprises Ru. The / Pt molar ratio is in the range of 0.1 to 1.5.

  The electrode catalyst according to the present invention can be configured such that the HOR activity retention rate is 72% or more and the catalyst deterioration rate is 13% or less.

  In the electrode catalyst according to the present invention, the electrode catalyst is preferably used for CO tolerance use and catalyst deterioration suppression use.

  The electrode catalyst according to the present invention is preferably used as an anode catalyst for an electrode for a polymer electrolyte fuel cell, and can further improve CO resistance and catalyst durability.

They are a chronoamperogram (A) assigned by the amount of Pt of each electrocatalyst under H ₂ saturation and a chronoamperogram (B) assigned by the amount of PtRu. They are a chronoamperogram (A) assigned by the amount of Pt of each electrocatalyst under H ₂ and 300 ppm CO / H ₂ saturation, and a chronoamperogram (B) assigned by the amount of PtRu. It is the chronoamperogram allocated | assigned by the amount of PtRu of each electrode catalyst before an endurance test (A) and after an endurance test (B).

  Hereinafter, although the electrode catalyst for fuel cells according to the present invention will be described in detail, the present invention is not limited to the following description as long as it is included in the technical scope.

The electrode catalyst according to the present invention is a composite catalyst of an electrode catalyst in which platinum particles or ruthenium platinum particles are supported on carbon black, and a RuO ₂ nanosheet. And the Ru / Pt molar ratio which comprises the composite catalyst exists in the range of 0.1 or more and 1.5 or less. By having such characteristics, it is possible to provide an electrode catalyst for a fuel cell that is preferably used as an anode catalyst for an electrode for a polymer electrolyte fuel cell and can further improve CO resistance and catalyst durability.

A RuO ₂ nanosheet (ruthenium oxide nanosheet; hereinafter referred to as “RuO ₂ ns”) is a scale-shaped compound having a thickness in the order of nm to sub-nm, and has a size in the order of several hundred nm to μm in length and width. This is a sheet-like crystalline ruthenic acid compound. This RuO ₂ ns can be easily laminated by electrophoresis or the like. In the present invention, it is used as an electrode catalyst having oxygen reducing ability, specifically an anode catalyst for a polymer electrolyte fuel cell, but it can also be used as a cathode catalyst, and further as a pseudo double layer capacitor. .

RuO ₂ ns is a layered ruthenium acid compound formed by stacking RuO ₂ ns, for example, a layered ruthenium oxide (hydrogen type: H _0.2 RuO _2.1 ) between layers of an alkylammonium ion, as will be described in Examples below. By providing the containing alkylammonium-layered ruthenic acid intercalation compound, it can be obtained by peeling.

In the present invention, RuO ₂ ns is used together with an electrode catalyst (Pt / C) having platinum particles supported on carbon black to form a composite catalyst, or RuO ₂ ns is an electrode catalyst having ruthenium platinum particles supported on carbon black. When used as a composite catalyst together with (Ru ₁ Pt ₁ / C), it is possible to further improve the resistance of the electrode catalyst comprising the composite catalyst and having an oxygen reduction ability, specifically, an electrode catalyst for a polymer electrolyte fuel cell. Can do. For Pt / C and Ru ₁ Pt ₁ / C, conventionally known ones described in, for example, Japanese Patent Application Laid-Open No. 2011-134477 can be applied.

  Excellent CO resistance and catalyst durability can be realized when the Ru / Pt molar ratio constituting the composite catalyst is in the range of 0.1 to 1.5.

  The electrode catalyst according to the present invention preferably has a HOR activity retention of 72% or more. The catalyst deterioration rate is preferably 13% or less. The electrode catalyst having such characteristics is preferably used for CO tolerance use and catalyst deterioration suppression use. The upper limit of the HOR activity retention rate is desirably large and is not particularly limited, but 87% can be exemplified as shown in the results of Examples described later.

The present invention will be specifically described with reference to experimental examples. In the following experiment, a composite catalyst of Pt ₁ Ru ₁ / C and RuO ₂ ns was prepared to be similar to the currently used Ru / Pt molar ratio of Pt ₂ Ru ₃ / C. The effect of addition of RuO ₂ ns on the electrocatalytic performance was examined. Moreover, in order to investigate what caused the improvement in CO tolerance, composite electrode catalysts of Pt / C and RuO ₂ ns prepared at various Ru / Pt molar ratios were used.

[Production of RuO ₂ ns]
First, layered ruthenium oxide for obtaining RuO ₂ ns was prepared. Layered ruthenium oxide is a complex oxide of ruthenium oxide and alkali metals (sodium, potassium, etc.). Among them, K _0.2 RuO _2.1 · nH ₂ O and Na _0.2 RuO ₂ · nH ₂ O utilize ion exchange capacity. By doing so, it is possible to delaminate the layer as a single unit, and thus RuO ₂ ns can be obtained.

Specifically, first, ruthenium oxide (RuO ₂ ) and potassium carbonate (K ₂ CO ₃ ) are weighed so as to have a molar ratio of 8: 5, and wet-mixed in acetone for 1 hour using an agate mortar. did. Thereafter, the mixed powder was pelletized using a tablet molding machine. The pellet was placed on an alumina boat and fired at 850 ° C. for 12 hours in a tubular furnace under an argon flow. After firing, the pellets were pulverized, washed with ion exchange distilled water, and the supernatant was removed. A layered ruthenium oxide (potassium type) was obtained by repeating this operation until the supernatant became neutral.

Next, 1M HCl is added to layered ruthenium oxide (potassium type), and acid treatment is performed in a water bath at 60 ° C. for 72 hours, so that K ⁺ ions contained in layered ruthenium oxide (potassium type) are converted into hydrogen ions (protons). ). Thereafter, the supernatant was removed by washing with ion-exchanged distilled water. This operation was repeated until the supernatant became neutral. After filtration, layered ruthenium oxide (hydrogen type: H _0.2 RuO _2.1 ) powder was obtained.

To the obtained layered ruthenium oxide (hydrogen type: H _0.2 RuO _2.1 ), 10% TBAOH aqueous solution as a release agent for obtaining RuO ₂ ns was added. The concentration of layered ruthenium oxide (hydrogen type: H _0.2 RuO _2.1 ) was TBA ⁺ / H ⁺ = 1.5 and the solid-liquid ratio = 4 g / L in terms of the ratio of TBAOH and proton. Then, layered ruthenium oxide (hydrogen type: H _0.2 RuO _2.1 ) was added to distilled water and shaken for 10 days. After the RuO ₂ ns peeled off by this method was centrifuged at 2000 rpm for 30 minutes, the supernatant liquid was collected, and a RuO ₂ ns aqueous dispersion diluted with ultrapure water to a concentration of 0.02 g / L ( Colloid).

[Experiment 1 / Preparation of RuO ₂ ns (x) -Pt / C]
In order to combine RuO ₂ ns with Pt / C (electrode catalyst having a platinum catalyst supported on a carbon black support), first, Pt / C was added to 15 mL of ultrapure water so as to be 10 mg / mL, followed by stirring for 30 minutes. And sonication for 30 minutes to disperse. In this solution, an appropriate amount of RuO ₂ ns water is used so that the ratio of platinum catalyst to Pt (Pt: Ru) is 1: 0.1, 1: 0.5, 1: 1.5. The dispersion was slowly added dropwise with stirring. The concentration of the RuO ₂ ns aqueous dispersion can be arbitrarily adjusted, but here it was 10 mg / mL.

Furthermore, in order to ensure a uniform reaction, stirring, ultrasonic treatment and ultrapure water washing are performed, and after removing excess TBAOH, the suspension is dried at 120 ° C. overnight, and then pulverized. obtain each _{RuO 2 ns (x) -Pt /} C. x is 0.1, 0.5, and 1.5, respectively.

[Experiment 2 / Preparation of RuO ₂ ns (x) -Pt ₁ Ru ₁ / C]
In order to combine RuO ₂ ns with Pt ₁ Ru ₁ / C (electrocatalyst carrying a ruthenium platinum catalyst on a carbon black support), first, Pt ₁ Ru ₁ / C was added to 15 mL of ultrapure water so as to be 10 mg / mL. In addition, the mixture was dispersed by stirring for 30 minutes and sonication for 30 minutes. To this solution, an appropriate amount of RuO ₂ ns aqueous dispersion was slowly added dropwise with stirring so that the ratio of the above ruthenium platinum catalyst to Pt (Pt: Ru) was 1: 1.5. The concentration of the RuO ₂ ns aqueous dispersion can be arbitrarily adjusted, but here it was 10 mg / mL.

Furthermore, in order to ensure a uniform reaction, after stirring, sonication, standing at 60 ° C., decantation (washing with water until neutrality) in order, drying at 120 ° C. for 12 hours, By grinding, each RuO ₂ ns (0.5) -Pt ₁ Ru ₁ / C was obtained.

[Experiment 3 / Preparation of catalyst dispersion and test electrode]
18.5 mg of the composite electrode catalyst obtained in Experiments 1 and 2 above was mixed with 25 mL of 2-propanol / ultra pure aqueous solution (75/25 volume ratio) to prepare a catalyst dispersion. In order to ensure good adhesion to the test electrode, 100 μL of a 5 mass% Nafion (registered trademark of DuPont) solution as a proton conductive binder was added. This catalyst dispersion was dispersed by sonication for 30 minutes.

Glassy carbon having a diameter of 6 mm, which was previously buffed with 0.05 μm alumina powder, was dried at 60 ° C. in a vacuum. A test dispersion for a polymer electrolyte fuel cell was prepared by applying a catalyst dispersion to such glassy carbon. The catalyst dispersion was applied so that the carbon content was 5.5 μg regardless of the content of RuO ₂ ns contained in the composite electrode catalyst provided on the test electrode.

[Experiment 4 / Electrochemical measurement]
The rotating disk electrode (RDE) measurement was performed on a standard three-electrode electrochemical cell. Carbon fiber (manufactured by Toho Tenax, HTA-3K, filament number: 3000) was used as the counter electrode, and a reversible hydrogen electrode (RHE) was used as the reference electrode. RDE measurements were performed in 0.1M HClO ₄ electrolyte.

[Evaluation of HOR activity]
In order to evaluate the HOR activity of each electrocatalyst, chronoamperometry of 20 mV (vs. RHE) was performed with 0.1 M HClO ₄ electrolyte solution (25 ° C.) under H ₂ saturation. FIG. 1A is a chronoamperogram (ω = 400 rpm) assigned by the amount of Pt of each electrode catalyst under H ₂ saturation, and FIG. 1B is a chronoamperogram assigned by the amount of PtRu (ω = 400 rpm). The HOR activity of RuO ₂ ns / C in FIG. 1 (A) was about 14A (g-RuO ₂ ) ⁻¹ . Tables 1 and 2 show the HOR activity under H ₂ saturation.

As shown in FIG. 1, the HOR activity of Pt ₁ Ru ₁ / C at 20 mV (vs. RHE) was equivalent to Pt ₂ Ru ₃ / C. Further, the difference in HOR activity between RuO ₂ ns (0.5) -Pt ₁ Ru ₁ / C and Pt ₁ Ru ₁ / C was about 10 A (g-Pt) ^−1, which was an error range.

The HOR activity at 20 mV (vs. RHE) of RuO ₂ ns (x) -Pt / C (x = 0.1, 0.5, 1.5) was the same even when RuO ₂ ns was added. From this, it was found that there was no inhibition of HOR activity by addition of RuO ₂ ns.

[Evaluation of CO tolerance]
The CO resistance in 20mV (vs.RHE) of each electrode catalyst was evaluated by comparing with _{H 2} saturated under a 300ppmCO / _{H 2} HOR activity 30 minutes after saturation pressure. Use H ₂ saturated with or 300ppmCO / _{H 2} saturated under 0.1MHClO ₄ electrolytic solution (25 ° C.), it was chronoamperometry held by 20mV (vs.RHE) 30 min. FIG. 2 (A) is a chronoamperogram (ω = 400 rpm) assigned by the amount of Pt of each electrode catalyst under saturation with H ₂ (A-1) and 300 ppm CO / H ₂ (A-2). B) is a chronoamperogram (ω = 400 rpm) assigned by the amount of PtRu of each electrode catalyst under saturation with H ₂ (B-1) and 300 ppm CO / H ₂ (B-2). Table 1 and Table 2 showed HOR activity and HOR activity retention of _{H 2} saturated with or 300ppmCO / _{H 2} saturated pressure.

The retention ratio of HOR activity of RuO ₂ ns (0.5) -Pt ₁ Ru ₁ / C under 300 ppm CO / H ₂ saturation was 78%. CO resistance increased by adding RuO ₂ ns to Pt ₁ Ru ₁ / C. _Moreover, CO tolerance of _{RuO 2 ns (0.5) -Pt 1} Ru 1 / C _was found to be similar to the Pt 2 _Ru 3 / C.

The HOR current of Pt / C decreased so as to draw a curve, and the HOR activity retention rate under 300 ppm CO / H ₂ saturation was 68%. The HOR current of RuO ₂ ns (x) -Pt / C (x = 0.1, 0.5, 1.5) decreased linearly. 300ppmCO / _{H 2} HOR activity retention rate in 300ppmCO / _{H 2} saturation of a _RuO 2 ns in the saturation under (x) -Pt / C (x = 0.1,0.5,1.5) is, Pt / It was higher than C.

CO resistance became high by adding RuO ₂ ns. The notable result is that the CO resistance of RuO ₂ ns (0.1) -Pt / C is higher than that of RuO ₂ ns (x) -Pt / C (x = 0.5, 1.5). When the Ru / Pt molar ratio was 0.5, the RuO ₂ ns overlapped and covered with each other, so it was predicted that the utilization rate of RuO ₂ ns decreased. It is expected that a Ru / Pt molar ratio of 0.1 is appropriate for increasing CO tolerance with a composite catalyst by adding RuO ₂ ns to Pt / C.

[Evaluation of catalyst durability]
The durability of CO resistance at 20 mV (vs. RHE) of each electrode catalyst was evaluated by comparing the HOR activity after 30 minutes under 300 ppm CO / H ₂ saturation before and after the durability test. In the durability test, a potential range of 0 V to 0.04 V (vs. RHE) was scanned at 100 mVs ⁻¹ and 1000 cycles were performed. Before and after the endurance test, chronoamperometry was performed using a 0.1 M HClO ₄ electrolyte solution (25 ° C.) under 300 ppm CO / H ₂ saturation and holding at 20 mV (vs. RHE) for 30 minutes. FIG. 3 shows the chronoamperograms (ω = 400 rpm) before (A) and after the durability test (B) assigned by the PtRu amount of each electrode catalyst. Table 3 shows the HOR activity and catalyst deterioration rate after 30 minutes under 300 ppm CO / H ₂ saturation before and after the durability test.

Pt ₂ Ru ₃ / C and Pt ₁ Ru ₁ / C deteriorated by about 20% in the durability test. It is expected that Ru was eluted in the durability test and the deterioration was remarkable. _Further, RuO 2 ns _(0.5) deterioration rate of -Pt 1 _Ru 1 / C at _13%, was greatly improved low durability of Pt 1 _Ru 1 / C. From this, it was found that addition of RuO ₂ ns can enhance both the CO resistance and the catalyst durability of the catalyst.

[result]
For the purpose of developing a catalyst having both higher CO tolerance and higher catalyst durability than standard performance Pt ₁ Ru ₁ / C and Pt ₂ Ru ₃ / C, as a result of evaluating and examining a composite catalyst to which RuO ₂ ns was added, _{RuO 2 ns-Pt 1 Ru 1} / C (Ru / Pt molar ratio = 1.5) _was high CO tolerance and catalyst durability than Pt 1 _Ru 1 / C and _Pt 2 _Ru 3 / C.

It was found that CO resistance was increased by adding RuO ₂ ns. It has been found that RuO ₂ ns itself has no CO oxidizing ability. In addition, it is known that the addition of RuO ₂ ns has no dual function mechanism or ligand effect. From these, considering that the increased CO resistant _RuO 2 ns addition, _RuO 2 ns is considered to be suppressed CO adsorption to Pt.

It was found that the catalyst durability was increased by adding RuO ₂ ns. Since RuO ₂ ns is negatively charged, it is expected that it acted as a reprecipitation site for Ru ions eluted during the durability test.

Claims (3)

An electrode catalyst supporting Le ruthenium platinum particles on carbon black, a composite catalyst of the RuO ₂ nanosheet,
An electrode catalyst for a fuel cell, wherein a Ru / Pt molar ratio constituting the composite catalyst is in a range of 0.1 to 1.5.   The electrode catalyst for a fuel cell according to claim 1, wherein the HOR activity retention rate is 72% or more and the catalyst deterioration rate is 13% or less. The electrode catalyst for fuel cells according to claim 1 or 2, which is used for CO tolerance use and catalyst deterioration suppression use.