KR20130060119A - Electrode catalyst for fuel cell, method for preparing the same, membrane electrode assembly and fuel cell including the same - Google Patents

Abstract

PURPOSE: An electrode catalyst for a fuel cell is provided to provide a battery with a long lifetime by having excellent oxidation activity and catalyst activity. CONSTITUTION: An electrode catalyst for fuel cells comprises an alloy particle including group 8 and group 9 metals. A manufacturing method of the electrode catalyst comprises a step of preparing a mixture including a group 8 metal precursor and group 9 metal precursor; and a step of reducing the group 8 metal precursor and group 9 metal precursor to obtain an electrode catalyst including the alloy particles of group 8 and group 9 metals. The group 8 metal includes one or more of Fe, Ru, and Os. The group 9 metal includes one or more of Co, Rh, and Ir.

Description

Technical Field [0001] The present invention relates to an electrode catalyst for a fuel cell, a method for producing the same, a membrane electrode assembly including the electrode catalyst and a fuel cell,

An electrode catalyst for a fuel cell, a method for producing the same, a membrane electrode assembly including the electrode catalyst, and a fuel cell including the membrane electrode assembly are disclosed.

A fuel cell is a power generation type cell that converts the chemical reaction energy of hydrogen and oxygen directly into electrical energy. Unlike a conventional battery, a fuel cell can produce electricity continuously as long as hydrogen and oxygen are supplied from the outside. Unlike conventional power generation systems, which can produce electricity at a loss of efficiency over a long period of time, the efficiency is twice as high as that of an internal combustion engine.

The fuel cell can be classified into a polymer electrolyte membrane fuel cell (PEMFC), a direct methanol fuel cell (DMFC), a phosphoric acid fuel cell (PAFC) (MCFC), and solid oxide (SOFC).

The polymer electrolyte fuel cell and the direct methanol fuel cell are generally composed of a membrane-electrode assembly (MEA) including an anode, a cathode, and a polymer electrolyte membrane disposed between the anode and the cathode. The anode electrode of the fuel cell is provided with a catalyst layer for promoting the oxidation of the fuel, and the cathode electrode is provided with a catalyst layer for promoting the reduction of the oxidant.

Catalysts containing platinum (Pt) as an active ingredient are generally used as constituent elements of anodes and cathodes. However, platinum catalysts are expensive noble metals, and in order to mass-produce commercially viable fuel cells, platinum The demand is still large and the cost of the system is required to be reduced.

Therefore, it is necessary to develop an electrode catalyst capable of reducing the amount of platinum and capable of providing excellent acid battery performance.

It is to provide an electrode catalyst for a fuel cell and a method for producing the same that can provide excellent catalyst activity and a long life battery.

A membrane electrode assembly including the electrode catalyst, and a fuel cell.

According to one aspect, there is provided an electrode catalyst for a fuel cell, including alloy particles comprising a Group 8 metal and a Group 9 metal.

The Group 8 metal may include one or more of iron (Fe), ruthenium (Ru), and osmium (Os).

The Group 9 metal may include one or more of cobalt (Co), rhodium (Rh), and iridium (Ir).

The content of the Group 8 metal may be 8 atomic% to 92 atomic% per 100 atomic% of the alloy particles.

The content of the Group 9 metal may be 8 atomic% to 90 atomic% per 100 atomic% of the alloy particles.

The alloy particles have a core-shell structure, the core includes the Group 8 metal and does not include the Group 9 metal, and the shell includes the Group 9 metal, or the Group 8 metal and the Group 9 metal. It may include.

The Group 8 metal may be ruthenium, and the Group 9 element may be iridium.

The alloy particles are made of ruthenium and iridium, the alloy particles have a core-shell structure, the core is made of the ruthenium, the shell is made of the iridium, or may be made of an alloy of ruthenium and iridium. have.

The fuel cell electrode catalyst may further include a carbon-based carrier, and the alloy particles may be supported on the carbon-based carrier.

According to another aspect, there is provided a method comprising: providing a mixture comprising a Group 8 metal precursor and a Group 9 metal precursor; And reducing the Group 8 metal precursors and the Group 9 metal precursors in the mixture to provide an electrode catalyst for a fuel cell including alloy particles including Group 8 metals and Group 9 metals. .

In the electrode catalyst manufacturing method, the mixture may further include a carbon-based carrier, the electrode catalyst may further include a carbon-based carrier, and the alloy particles may be supported on the carbon-based carrier.

According to another aspect, there is provided a cathode comprising: a cathode; An anode positioned opposite the cathode; And an electrolyte membrane positioned between the cathode and the anode, wherein at least one of the cathode and the anode includes the fuel cell electrode catalyst. Here, the electrode catalyst may be included in the anode.

According to another aspect, a fuel cell is provided, including the membrane electrode assembly. Here, the electrode catalyst may be included in the anode.

The electrode catalyst for the fuel cell has excellent hydrogen oxidation activity, and can be used to implement a fuel cell of low cost and high quality.

1 is a schematic cross-sectional view of an embodiment of the electrode catalyst.
2 is an exploded perspective view showing an embodiment of the fuel cell.
3 is a schematic cross-sectional view of a membrane-electrode assembly (MEA) constituting the fuel cell of FIG. 1.
Figure 4 shows the results of X-ray diffraction (XRD) analysis of the catalyst of Synthesis Example 3 and Comparative Synthesis Example 2.
FIG. 5 shows the results of X-ray diffraction (XRD) analysis of the catalysts of Comparative Synthesis Example 1, Synthesis Example 5, Synthesis Example 1, Synthesis Example 2, Synthesis Example 4, and Comparative Synthesis Example 2.
FIG. 6 shows Fourier transform graphs of EXAFS (Extended X-ray Absorption Fine Structure) spectra of Synthesis Examples 2 and 3 and Comparative Synthesis Examples 1 and 2. FIG.
FIG. 7 shows the results of evaluating the hydrogen oxidation (HOR) activity of half cells containing Synthesis Examples 1 to 4, Comparative Synthesis Examples 1 and 2, and PtRu / C catalysts.
8 is a current density-voltage graph of the unit cells of Example 1 and Comparative Examples 1 to 3. FIG.

The fuel cell electrode catalyst (hereinafter also referred to as "electrode catalyst") contains alloy particles containing a Group 8 metal and a Group 9 metal.

Since the atoms of Group 8 metals and atoms of Group 9 metals are present together in the unit lattice of the "alloy particles", the "alloy particles including Group 8 metals and Group 9 metals" are made of Group 8 metal particles and Group 9 metal particles. It is completely distinct from the mixture. The mixture of Group 8 metal particles and Group 9 metal particles has Group 8 metal atoms or Group 9 metal atoms in one unit lattice.

On the other hand, the "alloy particles" are amorphous particles, a plurality of "alloy particles" may be separated from each other and dispersed in a predetermined support (support), which is a layer consisting of the Group 8 metal and Group 9 metal Is distinct from. The "alloy particles including Group 8 metals and Group 9 metals" having an amorphous particle form are in contact with various gases and / or liquids that are subject to electrochemical reactions, as compared with layers made of Group 8 metals and Group 9 metals. Since the specific surface area which can be made is very large, it can be usefully applied as a catalyst, for example, an electrode catalyst for fuel cells. For example, the plurality of “alloy particles” may be supported and dispersed on a carbon-based carrier to be described later.

The Group 8 metal may include one or more of iron (Fe), ruthenium (Ru), and osmium (Os). For example, the Group 8 metal may be ruthenium, but is not limited thereto.

The Group 9 metal may include one or more of cobalt (Co), rhodium (Rh), and iridium (Ir). For example, the Group 9 metal may be iridium, but is not limited thereto.

The content of the Group 8 metal may be 8 atomic% to 92 atomic%, for example, 20 atomic% to 90 atomic% per 100 atomic% of the alloy particles. On the other hand, the content of the Group 9 metal may be 8 atomic% to 90 atomic%, for example, 10 atomic% to 80 atomic% per 100 atomic% of the alloy particles. When the content of the Group 8 metal and the Group 9 metal satisfy the above range, the electrode employing the electrode catalyst may have excellent hydrogen oxidation performance.

The alloy particles may have a core-shell structure, and the core-shell structure may refer to FIG. 1. 1 schematically shows a cross section of an alloy particle 50, wherein the alloy particle 50 includes a core 51 and a shell 53 covering at least a portion of the surface of the core 51. The shell 53 may be a continuous layer covering the entire surface of the core 51 or a discontinuous layer covering a part of the surface of the core 51.

The core 51 may include the Group 8 metal, but may not include the Group 9 metal. The shell 53 may include the Group 9 metal, or may include the Group 8 metal and the Group 9 metal.

The structure of the alloy particles 50 of FIG. 1 may be confirmed by an extended X-ray absorption fine structure (EXAFS) analysis as described below.

According to one embodiment, the Group 8 metal is ruthenium, the Group 9 element may be iridium, but is not limited thereto.

The alloy particles in the electrode catalyst may be made of an alloy of a Group 8 metal and the Group 9 metal. For example, the composition of the alloy particles may be represented by the following general formula 1, but is not limited thereto:

≪ General Formula 1 &

Ir _x Ru _y

In General formula 1, x and y are the real numbers of 1-10 independently from each other, and x / y represents the atomic ratio of Ir / Ru.

For example, in Formula 1, 1 ≦ x ≦ 8 and 1 ≦ y ≦ 9.7, but are not limited thereto.

As another example, in Formula 1, 1 ≦ x ≦ 4 and 1 ≦ y ≦ 9.5, but are not limited thereto.

As another example, 1 ≦ x ≦ 8 and 1 ≦ y ≦ 9 in Formula 1, but are not limited thereto.

As another example, 1 ≦ x ≦ 1.2 in Formula 1 and 1 ≦ y ≦ 9, but embodiments are not limited thereto.

As another example, 1 ≦ x ≦ 5 and 1 ≦ y ≦ 2 in Formula 1, but are not limited thereto.

According to one embodiment, the alloy particles 50 of FIG. 1 are made of ruthenium and iridium, the core 51 is made of ruthenium, and the shell 53 is made of iridium or an alloy of ruthenium and iridium. There may be.

The alloy particles may be nickel (Ni), palladium (Pd), platinum (Pt), cobalt (Co), iron (Fe), copper (Cu), tungsten (W), in addition to the Group 8 metals and Group 9 metals. , Vanadium (V), niobium (Nb), molybdenum (Mo), and hafnium (Hf) may be further included, and they may be present in an alloy with the Group 8 and Group 9 metals.

On the other hand, the electrode catalyst, in addition to the alloy particles as described above, nickel (Ni), palladium (Pd), platinum (Pt), cobalt (Co), iron (Fe), copper (Cu), tungsten (W), It may further comprise one or more of vanadium (V), niobium (Nb), molybdenum (Mo) and hafnium (Hf), which are present in the coating layer present on at least part of the surface of the alloy particles, or the alloy Various modifications are possible, such as being present in the form of particles that are physically mixed with the particles.

The average particle diameter of the alloy particles may be 0.5nm to 30nm. When the average particle diameter of the alloy particles satisfies the above range, the electrode including the electrode catalyst may have excellent hydrogen oxidation performance.

The electrode catalyst may further include a carbon-based carrier in addition to the alloy particles as described above. When the electrode catalyst further includes a carbon-based carrier, the alloy particles may be supported on the carbon-based carrier.

The carbon-based carrier may be selected from electrically conductive materials. For example, the carbonaceous carrier may include ketjen black, carbon black, graphite carbon, carbon nanotubes, carbon fibers, mesoporous carbon, graphene, and the like. Although it can be used, it is not limited to these, It is also possible to use these individually or in mixture of 2 or more.

When the electrode catalyst further comprises a carbon-based carrier, the content of the alloy particles is 10 parts by weight to 80 parts by weight, for example, 40 parts by weight to 60 parts by weight per 100 parts by weight of the electrode catalyst including the carbon-based support. Can be. When the ratio of the alloy particles and the carbon-based carrier satisfies the range as described above, it is possible to achieve a specific surface area and a high supporting amount of the excellent electrode catalyst particles.

Hereinafter, a method of manufacturing the electrode catalyst for a fuel cell will be described in detail.

First, a mixture comprising a Group 8 metal precursor and a Group 9 metal precursor is provided. When the alloy particles of the electrode catalyst include two or more different metals as Group 8 metals, two or more different Group 8 metal precursors may be used.

The Group 8 metal precursor is one of chlorides, nitrides, cyanides, sulfides, bromates, nitrates, acetates, sulfates, oxides, hydroxides and alkoxides containing the Group 8 metals as described above. It may contain the above compounds.

For example, when the Group 8 metal includes ruthenium, the ruthenium precursor is ruthenium nitride, ruthenium chloride, ruthenium sulfide, ruthenium acetate, ruthenium acetyl It may be one or more compounds of acetonate (ruthnium acetylacetonate), ruthenium cyanate, ruthenium isopropyl oxide, and ruthenium butoxide, but are not limited thereto.

The Group 9 metal precursor is one of chlorides, nitrides, cyanides, sulfides, bromates, nitrates, acetates, sulfates, oxides, hydroxides and alkoxides containing the Group 9 metals as described above. It may contain the above compounds.

For example, when the Group 9 metal includes iridium, the iridium precursor may be iridium nitride, iridium chloride, iridium sulfide, iridium acetate, iridium acetyl It may be one or more compounds of acetonate (iridium acetylacetonate), iridium cyanate, iridium isopropyl oxide and iridium butoxide, but is not limited thereto.

The mixture is nickel (Ni), palladium (Pd), platinum (Pt), cobalt (Co), iron (Fe), copper (Cu), in addition to the Group 8 metal precursor and Group 9 metal precursor as described above One or more precursors of stenium (W), vanadium (V), niobium (Nb), molybdenum (Mo), and hafnium (Hf) (eg, nickel (Ni), palladium (Pd), platinum (Pt)) Chlorides, nitrides of one or more of cobalt (Co), iron (Fe), copper (Cu), tungsten (W), vanadium (V), niobium (Nb), molybdenum (Mo), and hafnium (Hf) And one or more compounds of cyanide, sulfide, bromide, nitrate, acetate, sulfate, oxides and alkoxides).

The mixture may further include a carbon-based carrier in addition to the Group 8 metal precursor and the Group 9 metal precursor. When the mixture further includes a carbon-based carrier, an electrode catalyst including the carbon-based carrier and the alloy particles supported on the carbon-based carrier may be obtained.

In addition to the Group 8 metal precursor and the Group 9 metal precursor, the mixture may further include a solvent capable of dissolving them. Examples of the solvent include ethylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, diethylene glycol, 3-methyl-1,5-pentanediol, and 1,6- Glycol solvents such as hexanediol and trimethylol propane or alcohol solvents such as methanol, ethanol, isopropyl alcohol (IPA) and butanol or water (H ₂ O) may be used, but not limited thereto. Any known solvent that can be used can be used.

The mixture may include a chelating agent (eg, citric acid, ethylene diamine tetraacetic acid (EDTA), etc.), a pH adjusting agent (eg, aqueous NaOH solution, etc.) to simultaneously reduce the Group 8 metal precursor and the Group 9 metal precursor. ) May be further included.

Subsequently, the Group 8 metal precursor and the Group 9 metal precursor in the mixture are reduced to form an electrode catalyst including alloy particles containing a Group 8 metal and a Group 9 metal having hydrogen oxidation activity. Here, when the mixture includes a carbon-based carrier, it is possible to obtain an electrode catalyst in which the alloy particles are dispersed in the carbon-based carrier.

Reducing the precursor in the mixture may be performed by adding a reducing agent to the mixture. Alternatively, in the step of reducing the precursor in the mixture, the mixture is dried (eg, dried under reduced pressure) to obtain a complex of the carbon-based carrier and the precursor in which the precursor is supported on the carbon-based carrier, and then By heat treatment (eg, heat treatment in an electric furnace) under an inert or gas atmosphere (eg hydrogen atmosphere).

The reducing agent may be selected from materials capable of reducing the precursors included in the mixture. For example, the reducing agent may include hydrazine (NH ₂ NH ₂ ), sodium borohydride (NaBH ₄ ), and formic acid. Ascorbic acid may be used, but is not limited thereto. The reducing agent may be used in an amount of 1 to 3 moles based on a total of 1 mole of the Group 8 metal precursor and the Group 9 metal precursor. When the content of the reducing agent satisfies the range as described above, a satisfactory reduction reaction is induced. can do.

On the other hand, the heat treatment in an inert atmosphere of the composite of the carbon-based carrier and the precursor may be carried out at a temperature in the range of 100 ℃ to 500 ℃, for example, 150 ℃ to 450 ℃, but is not limited thereto.

A fuel cell membrane electrode assembly according to yet another aspect is a fuel cell membrane electrode assembly (MEA) comprising a cathode and an anode positioned to face each other, and an electrolyte membrane positioned between the cathode and the anode, wherein the cathode and the anode At least one includes the above-described electrode catalyst for fuel cell. For example, the electrode catalyst may be included in the anode of the membrane electrode assembly.

A fuel cell according to another aspect includes the membrane electrode assembly. Separation plates may be provided on both sides of the membrane electrode assembly. The membrane electrode assembly includes a cathode and an anode, and an electrolyte membrane positioned between the cathode and the anode, and at least one of the cathode and the anode includes the electrode catalyst described above. The electrode catalyst may be included in the anode of the fuel cell.

The fuel cell may be implemented as, for example, a polymer electrolyte fuel cell (PEMFC), a phosphoric acid fuel cell (PAFC), or a direct methanol fuel cell (DMFC).

FIG. 2 is an exploded perspective view showing one embodiment of the fuel cell, and FIG. 3 is a schematic cross-sectional view of a membrane-electrode assembly (MEA) constituting the fuel cell of FIG.

In the fuel cell 100 shown in FIG. 2, two unit cells 111 are sandwiched by a pair of holders 112 and 112, and the outline of the fuel cell 100 is illustrated. The unit cell 111 includes a membrane-electrode assembly 110 and bipolar plates 120 and 120 disposed on both sides of the membrane-electrode assembly 110 in the thickness direction. The bipolar plates 120 and 120 are made of a conductive metal, carbon, or the like, and are bonded to the membrane-electrode assembly 110 to function as a current collector and oxygen to the catalyst layer of the membrane-electrode assembly 110. And fuel.

2, the number of unit cells 111 is not limited to two but may be increased to several tens to several hundreds depending on characteristics required for the fuel cell. have.

As shown in FIG. 3, the membrane-electrode assembly 110 is disposed on both sides of the electrolyte membrane 200 and in the thickness direction of the electrolyte membrane 200, and an electrode catalyst according to one embodiment of the present invention A first gas diffusion layer 221 and 221 'laminated on the catalyst layers 210 and 210' and a second gas diffusion layer 220 and 220 'laminated on the first gas diffusion layers 221 and 221' respectively .

The catalyst layers 210 and 210 'function as a fuel electrode and an oxygen electrode, respectively. The catalyst layers 210 and 210' may include a catalyst and a binder, and may further include a material capable of increasing the electrochemical surface area of the catalyst.

The first gas diffusion layers 221, 221 ′ and the second gas diffusion layers 220, 220 ′ may be formed of, for example, carbon sheets, carbon paper, and the like, respectively, and oxygen and fuel supplied through the bipolar plates 120 and 120. Is diffused to the front surface of the catalyst layers 210 and 210 '.

The fuel cell 100 including the membrane-electrode assembly 110 operates at a temperature of 100 to 300 ° C., for example, hydrogen is supplied as fuel through the bipolar plate 120 to one catalyst layer side, and the other On the side of the catalyst layer, for example, oxygen or air is supplied as an oxidant through the bipolar plate 120. Hydrogen ions (H ⁺ ) are generated in the one catalyst layer by oxidizing hydrogen, and the hydrogen ions (H ⁺ ) conducts to the electrolyte membrane 200 to reach the other catalyst layer. In the other catalyst layer, hydrogen ions H ⁺ ) reacts with oxygen electrochemically to generate water (H ₂ O) and generates electrical energy. The hydrogen supplied as the fuel may be hydrogen generated by reforming the hydrocarbon or the alcohol, and the oxygen supplied as the oxidant may be supplied in the air.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the following Examples are only for the purpose of clear understanding of the present invention and the present invention is not limited to the following Examples.

Synthesis Example 1 Synthesis of IrRu / C Catalyst

To the mixture containing 0.785 g of iridium chloride, iridium (Ir) precursor, 0.443 g of ruthenium chloride (Ru) precursor, and distilled water, 0.5 g of Ketjen Black (KB), a carbon-based carrier, was added and stirred. The mixture obtained therefrom was distilled under reduced pressure at 50 ° C., and the resultant was heat-treated in a hydrogen atmosphere at a temperature of 300 ° C. to prepare an electrode catalyst for IrRu / C fuel cell by reducing the iridium precursor and the ruthenium precursor supported on the carbon-based carrier. .

Synthesis Example 2 IrRu ₄ Synthesis of A / C Catalyst

IrRu ₄ / C fuel cell electrode catalyst was prepared in the same manner as in Synthesis Example 1 except that the amount of iridium precursor was adjusted to 0.393 g and the amount of ruthenium precursor was adjusted to 0.885 g.

Synthesis Example 3 IrRu ₆ Synthesis of A / C Catalyst

An electrode catalyst for a fuel cell of IrRu ₆ / C was prepared in the same manner as in Synthesis Example 1 except that the amount of iridium precursor was adjusted to 0.293 g and the amount of ruthenium precursor was adjusted to 0.934 g.

Synthesis Example 4 IrRu ₉ Synthesis of A / C Catalyst

IrRu ₉ / C fuel cell electrode catalyst was manufactured in the same manner as in Synthesis Example 1, except that the amount of iridium precursor was adjusted to 0.213 g and the amount of ruthenium precursor was adjusted to 1.078 g.

Synthesis Example 5 Ir ₄ Synthesis of Ru / C Catalyst

An electrode catalyst for a fuel cell of Ir ₄ Ru / C was prepared in the same manner as in Synthesis Example 1 except that the amount of iridium precursor was adjusted to 1.077 g and the amount of ruthenium precursor was adjusted to 0.142 g.

Comparative Synthesis Example 1 Preparation of Ir / C Catalyst

Ir / C catalysts were prepared in the same manner as in Synthesis Example 1, except that the amount of the iridium precursor was adjusted to 1.219 g and the ruthenium precursor was not used.

Comparative Synthesis Example 2 Preparation of Ru / C Catalyst

A Ru / C catalyst was prepared in the same manner as in Synthesis Example 1, except that the amount of the ruthenium precursor was adjusted to 1.231 g without using an iridium precursor.

Catalyst composition Supported on a carbon-based carrier
Active particles Atomic ratio of iridium and ruthenium Synthesis Example 1  IrRu / C Alloy particles of iridium and ruthenium 1: 1 Synthesis Example 2 IrRu ₄ / C Alloy particles of iridium and ruthenium 1: 4 Synthesis Example 3 IrRu ₆ / C Alloy particles of iridium and ruthenium 1: 6 Synthesis Example 4 IrRu ₉ / C Alloy particles of iridium and ruthenium 1: 9 Synthesis Example 5 Ir ₄ Ru / C Alloy particles of iridium and ruthenium 4: 1 Comparative Synthesis Example 1 Ir / C Iridium particles - Comparative Synthesis Example 2 Ru / C Ruthenium particles -

Evaluation example  1: inductive coupling plasma ( ICP ) analysis

For the catalysts of Synthesis Examples 1 to 5 and Comparative Synthesis Examples 1 and 2, ICP analysis (ICP-AES, ICPS-8100, SHIMADZU / RF source 27.12 MHz / sample uptake rate 0.8 ml / min) was performed to obtain the results. Table 2 shows.

Catalyst composition

Metal content (% by weight)
Iridium ruthenium Synthesis Example 1  IrRu / C 13.1 29.8 Synthesis Example 2 IrRu ₄ / C 12.6 26.8 Synthesis Example 3 IrRu ₆ / C 9.1 28.4 Synthesis Example 4 IrRu ₉ / C 7.08 34.2 Synthesis Example 5 Ir ₄ Ru / C 35.5 4.5 Comparative Synthesis Example 1 Ir / C 39.2 - Comparative Synthesis Example 2 Ru / C - 40.5

From Table 2, it can be confirmed that both iridium and ruthenium are present in the catalysts of Synthesis Examples 1 to 5.

Evaluation Example 2: X-ray Diffraction (XRD) Analysis

X-ray diffraction (XRD) analysis (MP-XRD, Xpert PRO, Philips / Power 3kW) was carried out on the catalysts of Synthesis Examples 1, 2, 4 and 5 and Comparative Synthesis Examples 1 and 2, and the results are shown. Shown in 4 and 5, the lattice constants of each catalyst are summarized in Table 3 below:

Catalyst composition Catalyst particle crystal structure Diffraction angle
(2θ of Ir main peak)
(111) Diffraction angle
(2θ of Ru main peak)
(102) Synthesis Example 1 IrRu / C FCC ¹ 41.194 - Synthesis Example 2 IrRu ₄ / C HCP ² - 43.845 Synthesis Example 4 IrRu ₉ / C HCP - 43.977 Synthesis Example 5 Ir ₄ Ru / C FCC 40.734 Comparative Synthesis Example 1 Ir / C FCC 40.605 - Comparative Synthesis Example 2 Ru / C HCP - 44.037

1: Face Centered Cubic

2: Hexagonal Closed-Packed

According to Table 3 and FIGS. 4 and 5, each of the catalysts of Synthesis Examples 1, 2, 4 and 5 has a different crystal structure depending on the ratio of elements (metals) included in the catalysts of Synthesis Examples 1, 2, 4 and 5 It can be confirmed that it has an alloy particle having a crystal structure of the element having a high content ratio.

For reference, the actual composition of the IrRu / C catalyst of Synthesis Example 1 was confirmed by ICP analysis, and the actual composition of the IrRu / C catalyst of Synthesis Example 1 was Ir _1.2 Ru ₁ / C (see Table 2). The XRD pattern of the IrRu / C catalyst of 1 can confirm that the main peak of Ir is predominant.

Meanwhile, it can be seen that the main peak 2θ (41.194) of the catalyst of Synthesis Example 1 shifted to a value larger than the main peak 2θ (40.605) of the catalyst of Comparative Synthesis Example 1, thereby synthesizing It can be confirmed that the alloy particles of the catalyst of Example 1 are alloy particles of iridium and ruthenium. Further, the main peak 2θ (43.895) of the catalyst of Synthesis Example 2 and the main peak 2θ (43.977) of the catalyst of Synthesis Example 4 were higher than those of the catalyst of Comparative Synthesis Example 2 (44.037). It can be seen that the shift (shift) to a low value, thereby, it can be confirmed that the alloy particles of the catalyst of Synthesis Example 1 are alloy particles of iridium and ruthenium.

Evaluation Example 3: Extended X-ray Absorption Fine Sturcture (EXAFS) Analysis

For the catalysts of Synthesis Examples 2 to 5 and Comparative Synthesis Examples 1 and 2, EXAFS analysis was performed to evaluate the catalyst structure and the results are shown in FIG. 6 and Table 4. FIG.

The EXAFS experiment was performed by analyzing the results of Rigaku's R-XAS instrument at room temperature and atmospheric pressure using Artemis and Athena.

Absorbing edge
(Absorption edge) Synthesis Example No. Catalyst composition Observed coupling R (nm) N σ ² (pm ² ) Ir L _III absorption edge




Comparative Synthesis Example 1 Ir / C Ir-C
Ir-Ir 0.202
0.270 5.0
5.3 73
62 Synthesis Example 5 Ir ₄ Ru / C Ir-C
Ir-Ir
Ir-Ru 0.196
0.263
0.259 2.0
9.2
0.5 0
108
44 Synthesis Example 1 IrRu / C Ir-C
Ir-Ir
Ir-Ru 0.197
0.259
0.261 2.2
3.5
1.0 2
50
22 Synthesis Example 2 IrRu ₄ / C Ir-C
Ir-Ir
Ir-Ru 0.196
0.255
0.258 2.1
3.8
1.2 0
57
41 Synthesis Example 3 IrRu ₆ / C Ir-C
Ir-Ir
Ir-Ru 0.197
0.260
0.263 2.9
2.1
1.8 0
38
20 Synthesis Example 4 IrRu ₉ / C Ir-C
Ir-Ir
Ir-Ru 0.197
0.256
0.260 3.1
1.2
0.8 0
0
0 Ru K absorption edge


Comparative Synthesis Example 2 Ru / C Ru-ru 0.268 6.4 57 Synthesis Example 4 IrRu ₉ / C Ru-ru
Ru-ir 0.267
0.265 3.1
1.3 19
11 Synthesis Example 3 IrRu ₆ / C Ru-ru
Ru-ir 0.266
0.264 2.2
1.4 2
0 Synthesis Example 2 IrRu ₄ / C Ru-ru
Ru-ir 0.266
0.262 3.5
2.7 39
54

According to Table 4 and Figure 6, as a result of quantitative analysis of the local structure of the absorption stage of each metal, in the catalysts of Synthesis Examples 1 to 5, it is possible to confirm the bonding of Ir and Ru around the Ir atom, even around the Ru atom It can be seen that Ru and Ir exist at the same time. From this, it can be seen that an alloy of Ir and Ru is formed in the catalyst particles of Synthesis Examples 1 to 5.

On the other hand, when comparing the N value (atomic coordination number) of the Ru-Ir bond in the Ru K absorption edge of Table 4, as the Ir increases, the coordination of Ir around Ru increases (that is, Synthesis Example 4: 1.3 / Synthesis Example). 3: 1.4 / Synthesis Example 2: 2.7), and comparing the N value of the Ru-Ru bond in the Ru K absorption edge of Table 4, the coordination number between Ru does not increase significantly and is substantially maintained (ie , Synthesis Example 4: 3.1 / Synthesis Example 3: 2.2 / Synthesis Example 4: 3.5) can be confirmed. In addition, it can be seen that the N value of the Ir-C (O) coupling among the Ir L _III edge absorption edges of Table 4 has a certain level. This may be interpreted to be due to the presence of a relatively large amount of Ir on the outside of the catalyst particles of Synthesis Examples 1 to 5 to form a bond with carbon (C) or oxygen in the carrier. From this, it can be seen that the catalyst particles of Synthesis Examples 1 to 5 have a core-shell structure, Ru is present in the core, and Ir or an alloy of Ir and Ru is present in the shell.

Evaluation Example 4 Half Cell Performance Evaluation

A rotating disk electrode (RDE) was prepared as a working electrode. The RDE electrode is composed of PtRu / C catalysts of Synthesis Examples 1 to 4, Comparative Synthesis Examples 1 and 2, and TKK (the content of alloy particles of Pt and Ru supported on a carbon-based carrier is 53.4 wt% per 100 wt% of the catalyst, The atomic ratio of Ru is 1: 1.5), each of which is mixed with a Nafion perfluorinated ion-exchange resin (5 wt% solution in a mixture of lower aliphatic alcohols and water, Aldrich) and homogenized to prepare a catalyst slurry. It was produced by coating it on glassy carbon to form an electrode in the form of a thin film.

The electrochemical evaluation was performed using a three-electrode system, and the electrolyte solution was Pt foil and Ag / AgCl electrode as 0.1MH ₃ PO ₄ aqueous solution saturated with hydrogen, counter electrode and reference electrode, respectively. All electrochemical experiments were performed at room temperature. The measurement results are shown in FIG. 7.

According to Figure 7, it can be seen that the HOR performance of the half-cell each containing the catalysts of Synthesis Examples 1 to 4 is superior to the catalyst of Comparative Synthesis Example 1, the catalyst of Comparative Synthesis Example 2, the half containing the PtRu / C catalyst, respectively It can be confirmed that the battery is equivalent to or superior to the HOR performance.

Example 1

0.03 g of polyvinylidene fluoride (PVDF) per 1 g of the catalyst of Synthesis Example 2 (IrRu ₄ / C catalyst) and an appropriate amount of solvent n-methyl-2- were used to fabricate the anode electrode of the polymer electrolyte fuel cell (PEMFC). Pyrrolidone was mixed to prepare a slurry for forming an anode electrode. The anode slurry was coated with a bar coater on a carbon paper coated with a microporous layer, and then an anode was manufactured through a drying process of raising the temperature stepwise from room temperature to 150 ° C. . The loading of the catalyst in the anode was 1 mg _PdIr / cm ² .

As a cathode, a cathode was prepared in the same manner as the anode production method using a carbon supported PtCo catalyst (Tanaka noble metal, Pt: 45% by weight, Co: 5% by weight). The loading of the catalyst in the cathode was 1.5 mg _Pt / cm ² .

A fuel cell was prepared using polybenzimidazole (poly (2,5-benzimidazole)) doped with 85% phosphoric acid as an electrolyte membrane between the anode and the cathode.

Comparative Example 1

A fuel cell was manufactured in the same manner as in Example 1, except that the catalyst of Comparative Synthesis Example 1 (Ir / C catalyst) was used instead of the catalyst of Synthesis Example 2.

Comparative Example 2

A fuel cell was manufactured in the same manner as in Example 1, except that the catalyst of Comparative Synthesis Example 2 (Ru / C catalyst) was used instead of the catalyst of Synthesis Example 2.

Comparative Example 3

Instead of the catalyst of Synthesis Example 2, TKK's PtRu / C catalyst (the content of alloy particles of Pt and Ru supported on a carbon-based carrier is 53.4 wt% per 100 wt% of the catalyst, and the atomic ratio of Pt and Ru is 1: 1.5). A fuel cell was manufactured in the same manner as in Example 1, except that it was used.

Evaluation Example 5 Unit Battery Performance Evaluation

The battery performances of Example 1 and Comparative Examples 1 to 3 were evaluated at 150 ° C. using unhumidified air for the cathode and unhumidified hydrogen for the anode.

8, it can be seen that the open circuit voltage (OCV) of the battery of Example 1 is higher than that of the batteries of Comparative Examples 1 to 3. FIG. OCV is related to the oxygen reduction reaction onset potential of the catalyst, it can be seen that the performance of the battery of Example 1 is improved compared to the performance of the cells of Comparative Examples 1 and 2.

100 ... Fuel cell
110 ... Membrane-electrode assembly
112. holder
210, 210 '... Catalyst bed
220, 220 '... Second gas diffusion layer
221, 221 '... First gas diffusion layer
120... Bipolar plate

Claims (20)

An electrode catalyst for a fuel cell comprising alloy particles containing a Group 8 metal and a Group 9 metal. The method of claim 1,
An electrode catalyst for a fuel cell, wherein the Group 8 metal comprises at least one of iron (Fe), ruthenium (Ru), and osmium (Os). The method of claim 1,
An electrode catalyst for a fuel cell, wherein the Group 9 metal comprises one or more of cobalt (Co), rhodium (Rh), and iridium (Ir). The method of claim 1,
The content of the Group 8 metal is 8 atomic% to 92 atomic% per 100 atomic% of the alloy particles, the electrode catalyst for a fuel cell. The method of claim 1,
The content of the Group 8 metal is 20 atomic% to 90 atomic% per 100 atomic% of the alloy particles, the electrode catalyst for a fuel cell. The method of claim 1,
The content of the Group 9 metal is 8 atomic% to 90 atomic% per 100 atomic% of the alloy particles, the electrode catalyst for a fuel cell. The method of claim 1,
The alloy particles have a core-shell structure,
The core comprises the Group 8 metal and does not include the Group 9 metal,
Wherein said shell comprises said Group 9 metal or comprises said Group 8 metal and said Group 9 metal. The method of claim 7, wherein
An electrode catalyst for a fuel cell, wherein the shell comprises an alloy of the Group 8 metal and the Group 9 metal. The method of claim 1,
An electrode catalyst for a fuel cell, wherein the Group 8 metal is ruthenium and the Group 9 element is iridium. The method of claim 1,
The electrode catalyst for a fuel cell, wherein the alloy particles are made of an alloy of the Group 8 metal and the Group 9 metal. The method of claim 10,
The alloy particles are made of ruthenium and iridium,
The alloy particles have a core-shell structure,
The core consists of the ruthenium,
And the shell is composed of the iridium or an alloy of the ruthenium and iridium. The method of claim 1,
The alloy particles are nickel (Ni), palladium (Pd), platinum (Pt), cobalt (Co), iron (Fe), copper (Cu), tungsten (W), vanadium (V), niobium (Nb) Electrode catalyst for fuel cells, further comprising one or more of molybdenum (Mo) and hafnium (Hf). The method of claim 1,
An electrode catalyst for a fuel cell, further comprising a carbon-based carrier, wherein the alloy particles are supported on the carbon-based carrier. Providing a mixture comprising a Group 8 metal precursor and a Group 9 metal precursor; And
Reducing the Group 8 metal precursor and the Group 9 precursor in the mixture to provide an electrode catalyst for a fuel cell comprising alloy particles comprising a Group 8 metal and a Group 9 metal;
Method for producing an electrode catalyst for a fuel cell comprising a. 15. The method of claim 14,
The mixture further comprises a carbon-based carrier, the electrode catalyst further comprises a carbon-based carrier, the alloy particles are supported on the carbon-based carrier, the method for producing an electrode catalyst for a fuel cell. 15. The method of claim 14,
A method for producing an electrode catalyst for a fuel cell, wherein the mixture further comprises at least one of a glycol solvent and an alcohol solvent. Cathode;
An anode positioned opposite the cathode; And
And an electrolyte membrane disposed between the cathode and the anode,
A membrane electrode assembly for a fuel cell, wherein at least one of the cathode and the anode comprises the catalyst of any one of claims 1 to 13. 18. The method of claim 17,
The membrane electrode assembly for a fuel cell, wherein the catalyst is contained in the anode. A fuel cell comprising the membrane electrode assembly of claim 18. 20. The method of claim 19,
And the catalyst is contained in the anode.

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