KR20110139080A - Electrocatalyst layer for inhibiting carbon corrosion in polymer electrolyte membrane fuel cells, membrane-electrode assembly comprising the same and method of the same - Google Patents

Abstract

PURPOSE: An electrode catalyst layer for a fuel cell, a membrane-electrode assembly including thereof, and a producing method thereof are provided to prevent the carbon corrosion of cathode and anode catalyst layers by water. CONSTITUTION: An electrode catalyst layer for a fuel cell comprises a carbon-supported platinum catalyst, and a water electrolysis catalyst capable of decomposing water inserted to the catalyst layer when the voltage over 1.4V is applied. A carbon carrier for the carbon-supported platinum catalyst is selected from carbon nanotubes, carbon nanofibers, and carbon nanocage.

Description

Catalyst layer for fuel cell for inhibiting carbon corrosion, membrane-electrode assembly for fuel cell comprising the same and method for manufacturing the same {electrocatalyst layer for inhibiting carbon corrosion in polymer electrolyte membrane fuel cells, membrane-electrode assembly comprising the same and method of the same}

The present invention relates to an electrode catalyst layer for a fuel cell, and more particularly to an electrode catalyst layer for a fuel cell that can prevent carbon corrosion by water in the cathode and anode catalyst layer even when a high voltage is applied.

A fuel cell is a device that generates electricity by using hydrogen as fuel and oxygen in air. Membrane Electrode Assembly (MEA), which is a major component of fuel cells, is coated with an electrolyte membrane capable of transporting hydrogen cations and a catalyst layer capable of reacting hydrogen and oxygen on both sides of the electrolyte membrane. Platinum is mainly used for the catalyst used in the fuel cell catalyst layer, and in order to increase the activity of the catalyst, platinum is manufactured in nano size, and the carbon carrier is supported on a high dispersion high ratio.

In general, carbon black is used as the carrier. However, when carbon black is used as a support, durability of carbon corrosion may be degraded during abnormal operation caused by repeated starting and stopping of a fuel cell such as a fuel cell vehicle, thereby reducing the life of the fuel cell. .

In this case, a boundary layer of air and hydrogen is formed in the anode, and the voltage of the cathode rises to 1.4 V or more in part. At such a high voltage, carbon gasification reaction in which carbon used as a catalyst carrier reacts with water and becomes carbon dioxide is performed. Such carbon corrosion has recently been reported to have a great influence on the presence of water in the catalyst layer. (J. Power Sources, 193, 575)

In order to solve this problem, studies on fuel cell catalysts using CNT or CNF, which are crystalline carbon having high water repellency and good corrosion resistance, are being actively conducted. (J. Power Sources, 158, 154) In recent years, fuel cell catalysts that inhibit carbon and water reaction using carbon nanocage (CNC), which has not only crystallinity but also high water repellency, have been studied. However, even in the case of the catalyst using such crystalline carbon, the corrosion of carbon is suppressed up to 1.4V, but at higher voltages above 1.4V, the carbon is still corroded, and the water repellency of carbon does not completely inhibit the reaction of water and carbon. The effect is not complete.

In addition, there are studies to improve the corrosion resistance by Ti-based metal carriers, which have high corrosion resistance. However, when these carriers are used, the surface area of the carriers is small and it is difficult to increase the amount of platinum catalyst supported and the oxide film at high voltage. There is a problem in that fuel cell performance decreases due to an increase in resistance due to formation.

The first problem to be solved by the present invention is to provide a catalyst layer of a fuel cell membrane-electrode assembly, characterized in that it comprises a catalyst for suppressing the electrochemical corrosion of carbon used as a catalyst carrier of the membrane-electrode assembly for fuel cells will be.

A second problem to be solved by the present invention is to provide a fuel cell membrane electrode assembly including a catalyst layer of the fuel cell membrane electrode assembly.

A third object of the present invention is to provide a method for manufacturing a fuel cell membrane electrode assembly including the catalyst layer of the fuel cell membrane electrode assembly.

The present invention to achieve the first object,

In the catalyst layer of the conventional fuel cell membrane-electrode assembly, a fuel cell for a fuel cell, characterized in that a hydrolytic catalyst capable of decomposing water flowing into the catalyst layer is added when a voltage of 1.4 V or more is applied to the crystalline carbon supported platinum catalyst. A catalyst layer of a membrane-electrode assembly is provided.

According to a preferred embodiment of the present invention, the carbon carrier of the carbon supported platinum catalyst is selected from carbon nanotubes (CNT), carbon nanofibers (CNF) and carbon nano cages (CNC) having strong water repellency It can be either.

According to a preferred embodiment of the present invention, the hydroelectrolytic catalyst is iridium (Ir), ruthenium (Ru), their oxides (IrO _{x ,} RuO _x ), their alloys (IrRu) and their oxides (IrRuO _x ) It may be at least one selected from the group consisting of, and it is preferable that the electrolytic catalyst is iridium oxide, iridium, ruthenium oxide, iridium ruthenium oxide.

According to another preferred embodiment of the present invention, the electrolytic catalyst may be 0.1% to 20% by weight, more preferably 2% to 5% by weight relative to the carbon supported platinum catalyst.

According to another preferred embodiment of the present invention, the hydroelectrolytic catalyst may form a catalyst layer in the form of physical mixing with the platinum catalyst, supported on the platinum catalyst, or an alloy with the platinum catalyst.

When the hydroelectrolyte catalyst is mixed with the carbon supported platinum catalyst to form a catalyst layer, the amount of supported electrolytic catalyst may be 0.0008 mg / cm 2 to 0.16 mg / cm 2.

According to an embodiment of the present invention, when the amount of platinum used is 0.4 mg / cm 2 and the platinum loading rate in carbon is 50%, the amount of platinum catalyst supported on carbon may be 0.8 mg / cm 2.

Since the amount of the electrolytic catalyst may be 0.1 wt% to 20 wt% and more preferably 2 wt% to 5 wt% with respect to the carbon supported platinum catalyst, the amount of the electrolytic catalyst may be 0.0008 mg / cm 2 to 0.16 mg / cm 2 And more preferably 0.016 mg / cm 2 to 0.04 mg / cm 2.

According to another aspect of the present invention,

In the fuel cell membrane-electrode assembly formed between the electrolyte membrane and the electrolyte membrane, and including an anode electrode and a cathode electrode each comprising a catalyst layer and a gas diffusion layer,

Provided is a membrane-electrode assembly for a fuel cell, characterized in that the catalyst layer of the anode electrode or the cathode electrode comprises the high crystalline carbon supported platinum catalyst and the hydroelectrolyte catalyst.

In order to achieve the third object,

(1) dissolving an iridium precursor, ruthenium precursor or iridium ruthenium precursor in alcohol, adding sodium nitrate or sodium hydroxide, and mixing and drying the solution prepared to heat to prepare iridium oxide, ruthenium oxide and iridium ruthenium oxide, respectively. Or dissolving iridium precursor and tetradecyl trimethyl ammonium bromide (TTAB) in water at a molar ratio of 1: 100, stirring and reducing iridium with sodium borohydride to prepare iridium, (2) adding iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium prepared in step (1) to a carbon supported platinum catalyst and mixing alcohol to prepare a catalyst slurry, and (3) (2) In the step, the catalyst slurry is coated on the electrolyte membrane or the gas diffusion layer and dried to form a catalyst layer. A membrane for fuel cells comprising the steps - providing a method of manufacturing a membrane electrode assembly.

According to a preferred embodiment of the present invention, the solvent of step (1) and (2) is characterized in that it comprises one or more selected from the group consisting of ethanol, isopropanol, methanol, n-propanol and butanol More preferably, the solvent may be ethanol and isopropanol, and ethanol and isopropanol may be a solvent mixed in a volume ratio of 1: 2 to 2: 1.

According to another embodiment of the present invention, in the step (2), the iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium may be 0.1% to 20% by weight relative to the weight of the carbon supported platinum catalyst.

In addition, when preparing the catalyst slurry in the step (2) it may further comprise an ionomer binder to prepare a catalyst slurry. In one embodiment of the present invention, a catalyst slurry was prepared using a Nafion ionomer binder (Nafion sol.).

According to the method of manufacturing a fuel cell membrane-electrode assembly according to the present invention, in step (2), the iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium is physically mixed with the platinum catalyst, supported on the platinum catalyst or the platinum catalyst The catalyst layer can be formed in the form of an alloy.

According to another embodiment of the present invention, when the iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium is mixed with the carbon supported platinum catalyst to form a catalyst layer, the supported amount of iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium 0.0008 mg / cm 2 to 0.16 mg / cm 2.

According to an embodiment of the present invention, when the amount of platinum used is 0.4 mg / cm 2 and the platinum supporting ratio in carbon is 50%, the amount of platinum supported carbon catalyst may be 0.8 mg / cm 2.

Since the amount of the electrolytic catalyst may be 0.1 wt% to 20 wt% and more preferably 2 wt% to 5 wt% with respect to the carbon supported platinum catalyst, the amount of the electrolytic catalyst may be 0.0008 mg / cm 2 to 0.16 mg / cm 2 And more preferably 0.016 mg / cm 2 to 0.04 mg / cm 2.

According to the fuel cell including the membrane-electrode assembly for a fuel cell according to the present invention, the water in the catalyst layer is decomposed and removed by a hydroelectrolyte catalyst added to the carbon-supported platinum catalyst even when a high voltage of 1.4 V or higher is applied, thereby resulting from water in the catalyst layer. Corrosion of carbon can be suppressed and fuel cell durability is improved.

Further, according to the present invention, the current density is constant, the membrane resistance and the charge transfer resistance are low, the activation area of the platinum catalyst is constant, and the high voltage of 1.4 V or more, as compared with the membrane-electrode assembly to which the conventional electrolytic catalyst is not added. It is also possible to manufacture a membrane-electrode assembly for a fuel cell in which carbon corrosion is suppressed.

1 is a graph showing current density performance before and after corrosion for evaluation of corrosion resistance of a unit cell including a membrane-electrode assembly for fuel cell for inhibiting carbon corrosion according to the present invention.
Figure 1a is a graph showing the current density performance before and after corrosion when no electrolytic catalyst is added.
Figure 1b is a graph showing the current density performance before and after corrosion when 2wt% of iridium oxide is added.
Figure 1c is a graph showing the current density performance before and after corrosion when iridium oxide is added 5wt%.
Figure 1d is a graph showing the current density performance before and after corrosion when ruthenium oxide is added 2wt%.
FIG. 1E is a graph showing current density performance before and after corrosion when 2 wt% of iridium ruthenium oxide is added.
Figure 1f is a graph showing the current density performance before and after corrosion when iridium is added 2wt%.
FIG. 2 is a graph illustrating changes in impedance before and after corrosion for evaluation of corrosion resistance of a unit cell including a membrane-electrode assembly for fuel cell for inhibiting carbon corrosion according to the present invention.
Figure 2a is a graph showing the measurement of the impedance of the membrane resistance and charge transfer resistance before and after corrosion when no electrolytic catalyst is added.
Figure 2b is a graph showing the measurement of the impedance of the film resistance and charge transfer resistance before and after corrosion when iridium oxide 2wt% is added.
Figure 2c is a graph showing the measurement of the impedance of the film resistance and charge transfer resistance before and after corrosion when iridium oxide is added 5wt%.
Figure 2d is a graph showing the measurement of the impedance of the film resistance and charge transfer resistance before and after corrosion when ruthenium oxide is added 2wt%.
FIG. 2E is a graph illustrating impedance measurements of film resistance and charge transfer resistance before and after corrosion when 2 wt% of iridium ruthenium oxide is added.
Figure 2f is a graph showing the measurement of the impedance of the film resistance and charge transfer resistance before and after corrosion when iridium is added 2wt%.
3 is a graph showing changes in the surface area of platinum activity before and after corrosion for evaluation of corrosion resistance of a unit cell including a membrane-electrode assembly for fuel cell for inhibiting carbon corrosion according to the present invention.
Figure 3a is a graph (Cyclic Voltammgram) before and after corrosion when iridium oxide is not added.
Figure 3b is a graph (Cyclic Voltammgram) before and after corrosion when 2wt% of iridium oxide is added.
Figure 3c is a graph (Cyclic Voltammgram) before and after corrosion when 5 wt% of iridium oxide is added.
Figure 3d is a graph (Cyclic Voltammgram) before and after corrosion when ruthenium oxide is added 2wt%.
3E is a graph of CV (Cyclic Voltammgram) before and after corrosion when 2 wt% of iridium ruthenium oxide is added.
Figure 3f is a graph (Cyclic Voltammgram) before and after corrosion when 2wt% of iridium is added.
4 is a result of measuring the amount of CO ₂ generated before and after corrosion by using a mass spectrometry to evaluate the corrosion resistance of a unit cell including a membrane-electrode assembly for fuel cells for inhibiting carbon corrosion according to the present invention. Is a graph.
FIG. 5 illustrates that water is decomposed through an oxidation reaction while supplying a constant potential of 1.6 V _SHE to the cathode for 30 minutes to evaluate corrosion resistance of a unit cell including a membrane-electrode assembly for fuel cell according to the present invention. It is a graph showing the result of measuring the oxidation current generated.
Figure 6 is a graph showing the results of measuring the oxidation current while increasing the potential at a rate of 5mV / s from 1.24V _SHE to 1.84V _SHE for the comparison of the electrolytic performance of the iridium oxide catalyst and platinum catalyst according to the present invention.

Hereinafter, the present invention will be described in more detail.

In general, the fuel cell is not severely corroded because the voltage does not rise above 1V during normal operation.However, when the fuel cell is turned on or off, the voltage rises rapidly above 1V during the abnormal state of a few seconds to several seconds. Carbon corrosion is accelerated.

Below 1.4 V, corrosion can be suppressed by the crystalline carbon carrier used in a conventional fuel cell. However, above 1.4 V, the crystalline carbon carrier alone cannot completely inhibit carbon corrosion due to moisture in the catalyst layer.

Therefore, according to a preferred embodiment of the present invention, a carbon supported platinum catalyst having crystalline carbon as a support for the fuel cell catalyst layer, and a hydroelectrolyte catalyst capable of decomposing water in the catalyst layer when a voltage of 1.4 V or more is applied to the fuel cell catalyst layer It is characterized by including.

In addition, according to a preferred embodiment of the present invention, at a voltage of 1.4V or less, the crystalline carbon carrier serves to inhibit the corrosion of carbon, and when a voltage of 1.4V or more is applied, a hydroelectrolytic catalyst decomposes water and It is characterized in that it serves to suppress the corrosion of.

When the steady state is reached after a short abnormal state, the voltage drops below 1V and since the electrolytic catalyst no longer decomposes water, the concentration of water necessary for driving the fuel cell is increased again, thereby driving the fuel cell. In the fuel cell including the catalyst layer according to the present invention, carbon corrosion is suppressed and durability of the fuel cell is improved.

The steady state refers to a state in which only hydrogen is present without oxygen in the anode.

The electrolytic catalyst refers to a catalyst that serves to promote the reaction when generating oxygen by decomposing water through an electrochemical reaction.

The hydrocatalytic catalyst can decompose water by the electrochemical oxidation reaction with water introduced into the catalyst layer by the following reaction mechanism.

_{S + H 2 O S-OH} ad + H + + e - ( formula 1)

_{S-OH ad SO ad + H} + + e - ( Equation 2)

SO _ad + SO _ad 2S + O ₂ (Equation 3)

In the above formula, S represents a hydroelectrolyte catalyst, OH _ad represents a hydroxyl group adsorbed on the surface of the electrolytic catalyst, and O _ad represents an oxygen atom adsorbed on the surface of the electrolytic catalyst. The equilibrium potential of the above equation is 1.23V.

According to a preferred embodiment of the present invention, the carbon carrier of the carbon-supported platinum catalyst is itself carbon nanotubes (CNT), carbon nanofibers (CNF) having a strong water repellency that can prevent contact with water itself ), Carbon nanocage (CNC) and the like are preferable.

In addition, the electrolytic catalyst may be at least one selected from iridium (Ir), ruthenium (Ru), iridium oxide (IrO _x ), ruthenium oxide (RuO _x ), iridium ruthenium (IrRu), and iridium ruthenium oxide (IrRuO _x ). desirable.

According to a preferred embodiment of the present invention, the hydrophilic catalyst may be physically mixed with the platinum catalyst, supported on the platinum catalyst, or the catalyst layer may be formed in the form of the platinum catalyst and the alloy.

According to a preferred embodiment of the present invention, the weight of the electrolytic catalyst mixed in the carbon supported platinum catalyst may be 0.1% to 20% by weight relative to the weight of the platinum catalyst, more preferably 2% by weight of the electrolytic catalyst It may be ~ 5% by weight, and thus the amount of the electrolytic catalyst loaded may be 0.0008 mg / cm 2 ~ 0.16 mg / cm 2, more preferably 0.016 mg / cm 2 ~ 0.04 mg / cm 2.

According to a preferred embodiment of the present invention, there is provided a method for preparing an electrolytic catalyst, a catalyst slurry comprising adding an electrolytic catalyst to a carbon supported platinum catalyst and mixing an ionomer binder and a solvent; It may include the step of applying.

In the step of preparing the iridium oxide (IrO _x ), ruthenium oxide (RuO _x ), iridium ruthenium oxide (IrRuO _x ), each of the iridium precursor, ruthenium precursor, iridium ruthenium precursor is dissolved in a mixed solvent of ethanol and isopropanol, NaNO ₃ Alternatively, NaOH is added to form a complex (Iridium complex), and then synthesized by heat treatment at 300 to 900 for 30 minutes to 2 hours in an oxygen gas atmosphere selected from N ₂ + O ₂ , O ₂ , and Ar + O ₂ gases. can do. In the ethanol and isopropanol mixed solvent, the volume ratio of ethanol and isopropanol is preferably 1: 2 to 2: 1.

The step of preparing the iridium (Ir) is dissolved in water in a molar ratio of 1: 100 iridium and tetradecyltrimethyl ammonium bromide (TTAB) in a molar ratio, and stirred, and after heating, added NaBH ₄ reducing agent and reduced the iridium Post iridium can be prepared.

In the step of preparing the catalyst slurry is not limited to the method of forming the catalyst slurry, preferably, iridium oxide (IrO _x ), ruthenium oxide (RuO _x ), iridium ruthenium oxide (IrRuO _x ), iridium (Ir) platinum catalyst Can be added to form a catalyst slurry.

According to a preferred embodiment of the present invention, the weight of the electrolytic catalyst mixed in the carbon supported platinum catalyst may be 0.1% to 20% by weight relative to the weight of the platinum catalyst, more preferably 2% by weight of the electrolytic catalyst It may be ~ 5% by weight, and thus the amount of the electrolytic catalyst loaded may be 0.0008 mg / cm 2 ~ 0.16 mg / cm 2, more preferably 0.016 mg / cm 2 ~ 0.04 mg / cm 2.

According to a preferred embodiment of the present invention, the carbon supported platinum catalyst is a commercially available 50 wt% carbon supported platinum catalyst Pt / C (Tanaka corrosion resistance 50wt% Pt / C) using crystalline carbon supported on the cathode, and carbon black on the anode. 40 wt% carbon supported platinum catalyst Pt / C (Johnson Matthey 40 wt% Pt / C) using a carbon carrier was used, and 5 wt% Nafion ionomer (Nafion sol.) Was used as the ionomer binder.

In the applying of the catalyst slurry, the catalyst slurry prepared in the present invention was applied to the air surface of the Nafion membrane (N212 Nafion Membrane) to prepare a membrane-electrode assembly, whereby a fuel cell cathode catalyst according to the present invention will be described later. The corrosion resistance of was evaluated.

In the case of a fuel cell including a membrane-electrode assembly composed of a commercially available corrosion resistant catalyst without addition of a hydrolytic catalyst, the performance of 44.9% decreases at the application of a 1.6V voltage, thereby reducing the carbon corrosion resistance effect. The fuel cell to which the catalyst is added is excellent in corrosion resistance and the durability of the fuel cell is improved.

Hereinafter, the present invention will be described in more detail with reference to preferred examples. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

< Manufacturing example  1> iridium oxide ( IrOx Manufacturing

Iridium precursor into the _{(H 2 IrCl 6 xH 2 O} ) in ethanol (ethanol) and isopropanol (Isopropanol) mixed solvent were dissolved by stirring well, the mixture was stirred by adding a certain amount of sodium nitrate (NaNO _3). After heating to 60 ° C. to evaporate and dry both ethanol and isopropanol as solvents, the mixture was further dried for 30 minutes in an 80 ° C. oven. The dried powder was evenly placed on a boat and placed in an electric furnace, flowing a gas containing oxygen, and heated at 500 ° C. for 30 minutes. After washing the powder after the heat treatment several times in a third order, the washed powder was dried for 30 minutes in an 80 ℃ oven to prepare an iridium oxide.

< Manufacturing example  2> ruthenium oxide ( RuOx Manufacturing

Ruthenium precursor (RuCl ₃ xH ₂ O) was added to a mixed solvent of ethanol and isopropanol, and the mixture was sufficiently stirred to dissolve, followed by addition of a certain amount of sodium nitrate (NaNO ₃ ). After heating to 60 ° C. to evaporate and dry both ethanol and isopropanol as solvents, the mixture was further dried for 30 minutes in an 80 ° C. oven. The dried powder was evenly placed on a boat and placed in an electric furnace, flowing a gas containing oxygen, and heated at 500 ° C. for 30 minutes. The powder subjected to the heat treatment was washed several times with third order, and then the washed powder was dried in an oven at 80 ° C. for 30 minutes to prepare ruthenium oxide.

< Manufacturing example  3> Iridium Ruthenium Oxide ( IrRuOx Manufacturing

Iridium and ruthenium were dissolved in a mixed solvent of iridium precursor (H ₂ IrCl ₆ xH ₂ O) and ruthenium precursor (RuCl ₃ xH ₂ O) in a mixed solvent of ethanol and isopropanol at a molar ratio of 1: 1. A certain amount of sodium nitrate (NaNO ₃ ) was added and stirred. After heating to 60 ° C. to evaporate and dry both ethanol and isopropanol as solvents, the mixture was further dried for 30 minutes in an 80 ° C. oven. The dried powder was evenly placed on a boat and placed in an electric furnace, flowing a gas containing oxygen, and heated at 500 ° C. for 30 minutes. The powder after the heat treatment was washed several times with third order, and then the washed powder was dried in an oven at 80 ° C. for 30 minutes to prepare iridium ruthenium oxide.

< Manufacturing example  4> Preparation of Iridium

Iridium and tetradecyltrimethyl ammonium bromide (TTAB) were added in a 1: 100 molar ratio of iridium precursor (H ₂ IrCl ₆ x H ₂ O) and TTAB together with water to stir to dissolve TTAB. After heating to 50 ° C., NaBH ₄ was added thereto, and iridium was reduced. Closing the vial cap and punched a small hole, the hydrogen gas was blown out for about 10 minutes, the hole was blocked and sealed, and then heated at 50 ° C. for 6 to 7 hours, followed by centrifugation of the solution 2-3 times. Iridium in the shape of) was prepared.

< Example  1> Fabrication of fuel cell membrane-electrode assembly and unit cell including same

A commercially prepared 40 wt% carbon supported platinum catalyst Pt / C (Johnson Matthey 40 wt% Pt / C) was mixed with 5 wt% Nafion ionomer (Nafion sol.) And isopropanol and sonicated to prepare a catalyst slurry. The prepared catalyst slurry was applied to the anode surface of the Nafion membrane (N212 Nafion Membrane) in a loading amount of platinum 0.4mmg / cm 2 to prepare a cathode catalyst layer.

To commercial 50 wt% carbon supported platinum catalyst Pt / C (Tanaka corrosion resistance 50wt% Pt / C), iridium oxide (IrO _x ) prepared in Preparation Example 1 was added at 2 wt% based on Pt / C weight. , 5% by weight of Nafion ionomer (Nafion sol.) And isopropanol mixed with ultrasonic treatment to prepare a catalyst slurry. The prepared catalyst slurry was coated on a cathode surface of a Nafion membrane (N212 Nafion Membrane) with a supporting amount of platinum 0.4 mg / cm 2. As a result, platinum 0.4 mg / cm 2 and iridium oxide 0.016 mg / cm 2 were applied to the catalyst layer. In the electrode membrane assembly prepared as described above, a gas diffusion layer and a gasket were laminated to manufacture a unit battery cell, and the respective unit cells were fastened by applying a predetermined pressure to the unit battery cell, and the fastened unit battery cell was connected to a predetermined station.

< Example  2> Fabrication of fuel cell membrane-electrode assembly and unit cell including the same

The anode catalyst layer was prepared in the same manner as in <Example 1>.

To commercial 50 wt% carbon supported platinum catalyst Pt / C (Tanaka corrosion resistance 50wt% Pt / C), iridium oxide (IrO _x ) prepared in Preparation Example 1 was added at 5 wt% based on Pt / C weight. , 5% by weight of Nafion ionomer (Nafion sol.) And isopropanol mixed with ultrasonication to prepare a catalyst slurry. The prepared catalyst slurry was coated on a cathode surface of a Nafion membrane (N212 Nafion Membrane) with a supporting amount of platinum 0.4 mg / cm 2. As a result, platinum 0.4 mg / cm 2 and iridium oxide 0.04 mg / cm 2 were applied to the catalyst layer. In the electrode membrane assembly prepared as described above, a gas diffusion layer and a gasket were laminated to manufacture a unit battery cell, and the respective unit cells were fastened by applying a predetermined pressure to the unit battery cell, and the fastened unit battery cell was connected to a predetermined station.

< Example  3> Manufacture of membrane-electrode assembly for fuel cell and unit cell comprising same

The anode catalyst layer was prepared in the same manner as in <Example 1>.

To a commercial 50 wt% carbon supported platinum catalyst Pt / C (Tanaka corrosion resistance 50wt% Pt / C), ruthenium oxide (RuOx) prepared in Preparation Example 2 was added at 2 wt% based on Pt / C weight, A catalyst slurry was prepared by sonicating 5% by weight of Nafion ionomer (Nafion sol.) And isopropanol. The prepared catalyst slurry was coated on a cathode surface of a Nafion membrane (N212 Nafion Membrane) with a supporting amount of platinum 0.4 mg / cm 2. As a result, platinum 0.4 mg / cm 2 and ruthenium oxide 0.016 mg / cm 2 were applied to the catalyst layer. In the electrode membrane assembly prepared as described above, a gas diffusion layer and a gasket were laminated to manufacture a unit battery cell, and the respective unit cells were fastened by applying a predetermined pressure to the unit battery cell, and the fastened unit battery cell was connected to a predetermined station.

< Example  4> Fabrication of fuel cell membrane-electrode assembly and unit cell including same

The anode catalyst layer was prepared in the same manner as in <Example 1>.

To commercial 50 wt% carbon supported platinum catalyst Pt / C (Tanaka corrosion resistance 50wt% Pt / C), iridium ruthenium oxide (IrRuOx) prepared in Preparation Example 3 was added at 2 wt% based on Pt / C weight. , 5% by weight of Nafion ionomer (Nafion sol.) And isopropanol mixed with ultrasonication to prepare a catalyst slurry. The prepared catalyst slurry was coated on a cathode surface of a Nafion membrane (N212 Nafion Membrane) with a supporting amount of platinum 0.4 mg / cm 2. As a result, platinum 0.4 mg / cm 2 was applied to the catalyst layer and 0.016 mg / cm 2 of iridium ruthenium oxide. In the electrode membrane assembly prepared as described above, a gas diffusion layer and a gasket were laminated to manufacture a unit battery cell, and the respective unit cells were fastened by applying a predetermined pressure to the unit battery cell, and the fastened unit battery cell was connected to a predetermined station.

< Example  5> Manufacture of membrane-electrode assembly for fuel cell and unit cell comprising same

The anode catalyst layer was prepared in the same manner as in <Example 1>.

To commercial 50 wt% carbon supported platinum catalyst Pt / C (Tanaka corrosion resistance 50wt% Pt / C), iridium (Ir) prepared in Preparation Example 4 was added at 2 wt% based on Pt / C weight, and 5 A catalyst slurry was prepared by sonication of Nafion ionomer (Nafion sol.) And isopropanol by weight. The prepared catalyst slurry was coated on a cathode surface of a Nafion membrane (N212 Nafion Membrane) with a supporting amount of platinum 0.4 mg / cm 2. As a result, platinum 0.4 mg / cm 2 and iridium 0.016 mg / cm 2 were applied to the catalyst layer. In the electrode membrane assembly prepared as described above, a gas diffusion layer and a gasket were laminated to manufacture a unit battery cell, and the respective unit cells were fastened by applying a predetermined pressure to the unit battery cell, and the fastened unit battery cell was connected to a predetermined station.

< Comparative example  1>

The anode catalyst layer was prepared in the same manner as in <Examples 1 to 2>.

A catalyst slurry was prepared in the same manner as in <Examples 1 to 2>, except that the electrolytic catalyst was not added to the carbon supported platinum catalyst. The prepared catalyst slurry was applied to the cathode surface of the Nafion membrane (N212 Nafion Membrane). As a result, platinum 0.4 mg / cm 2 was applied to the catalyst layer. In the electrode membrane assembly prepared as described above, a gas diffusion layer and a gasket were laminated to manufacture a unit battery cell, and the respective unit cells were fastened by applying a predetermined pressure to the unit battery cell, and the fastened unit battery cell was connected to a predetermined station.

The structure of the cathode electrode catalyst layer according to <Examples 1 to 5> and <Comparative Example 1> is as shown in the following [Table 1].

division Platinum loading
(Mg / cm 2) Carbon loading
(Mg / cm 2) Used Hydrocatalyst Hydrolytic Catalyst Support
(Mg / cm 2) Pt / C weight
Hydrolysis Catalyst
% By weight Example 1 0.4 0.4 Iridium Oxide 0.016 2 Example 2 0.4 0.4 Iridium Oxide 0.04 5 Example 3 0.4 0.4 Ruthenium oxide 0.016 2 Example 4 0.4 0.4 Iridium Ruthenium Oxide 0.016 2 Example 5 0.4 0.4 Iridium 0.016 2 Comparative Example 1 0.4 0.4 - 0 0

Hereinafter, the present invention will be described in more detail with reference to corrosion resistance evaluation examples and drawings of a unit cell including a membrane-electrode assembly for fuel cells manufactured according to Examples and Comparative Examples.

< Evaluation example > Fuel Cell Air cathode  Catalytic Corrosion resistance  evaluation

Corrosion evaluation was performed on the unit battery cells of Examples 1 to 5 and Comparative Example 1 prepared according to the present invention, and the corrosion evaluation was performed by the following corrosion evaluation method.

In the cathode catalyst corrosion evaluation step, 20ccm of hydrogen was flowed into the anode and 30ccm of nitrogen was flowed into the cathode, and the temperature of the unit cell was maintained at 70 ° C and the humidification temperature was also 70 ° C. Thereafter, a constant voltage of 1.6 V _SHE was supplied to the cathode for 30 minutes to artificially corrode the cathode catalyst. Thus, the mass of carbon dioxide (CO ₂ ) generated during corrosion evaluation was measured using a mass spectrometry connected to the cathode outlet of the unit cell.

After completion of the above steps, the reduction rate of the unit cell, which is measured before and after corrosion, the reduction rate of effective active surface area (Spt) of platinum measured by the CV test, the increase rate of resistance measured through impedance, and the mass spectrometry were measured. The corrosion resistance of the catalyst was evaluated by comparing the amount of carbon dioxide (CO ₂ ) measured through. The smaller the surface area (Spt) reduction rate, the smaller the resistance increase rate measured through the impedance, and the smaller the amount of carbon dioxide (CO ₂ ) measured by mass spectrometry, the stronger the corrosion resistance catalyst.

[ Evaluation example  1] Reduction of current density performance of unit cell before and after corrosion

Figure 1 shows the unit cell performance before and after corrosion, the performance before corrosion is 1.73A / ㎠ in <Comparative Example 1>, 1.74A / ㎠ in <Example 1>, 1.69A in <Example 2> / Cm <2>, <Example 3> is 1.68A / cm <2>, <Example 4> is 1.75A / cm <2>, and <Example 5> is 1.74A / cm <2>, and there was no big difference in the performance before corrosion.

As described above, the cathode catalyst was corroded by supplying an artificial potential of 1.6 V _SHE to the cathode. As shown in FIG. 1A, the change in unit cell performance was 0.6 V in the case of the membrane-electrode assembly according to <Comparative Example 1>. As shown in FIG. 1B, the membrane-electrode assembly according to Example 1 of the present invention was 4.0%, the membrane-electrode assembly according to <Example 2> of FIG. 1C was 0.6%, The membrane-electrode assembly according to <Example 3> of FIG. 1D is 18.5%, the membrane-electrode assembly according to <Example 4> of FIG. 1E, and 32.6% of the membrane-electrode assembly according to <Example 5> of FIG. 1F. Shows a 1.7% reduction in performance.

The membrane-electrode assembly according to <Comparative Example 1> was evaluated to be susceptible to corrosion under artificial dislocation conditions of 1.6 V _SHE even though crystalline carbon was used as a carrier, and it was found that the crystalline carbon carrier alone has a limit on the inhibition of carbon corrosion. Can be.

The membrane-electrode assembly according to <Examples 1 to 5> of the present invention was evaluated to have increased corrosion resistance due to the removal of water in the catalyst layer due to the addition of the hydroelectrolyte catalyst. It can be seen that the corrosion resistance is very excellent compared to the conventional membrane-electrode assembly using crystalline carbon as a support without the addition of.

[ Evaluation example  2] before and after corrosion Membrane resistance  Change in charge transfer resistance

FIG. 2 is a graph showing measurement results of changes in membrane resistance and charge transfer resistance by measuring impedance before and after corrosion of a unit cell.

As shown in FIG. 2A, the membrane-electrode assembly according to Comparative Example 1 has a 1.4% increase in film resistance and a 97.9% increase in charge transfer resistance after corrosion, whereas as shown in FIG. > Is 1.4% in film resistance, 11.6% in charge transfer resistance is reduced, as shown in Figure 2c <Example 2> of the present invention is reduced in film resistance of 0%, 19.5% in charge transfer resistance, as shown in Figure 2d As shown in Example 3 of the present invention, the film resistance increased by 0.7% and the charge transfer resistance increased by 12.6%. As shown in FIG. The resistance increased by 44.4%, and as shown in FIG. 2F, it can be seen that in Example 5 of the present invention, the film resistance increased by 3.57% and the charge transfer resistance increased by 1.6%.

It can be seen that the membrane-electrode assembly to which the electrolytic catalyst according to the present invention is added has a small change in impedance before and after corrosion and is excellent in corrosion resistance.

[ Evaluation example  3] Changes in active surface area of platinum catalysts before and after corrosion

3 shows a CV graph before and after corrosion of <Comparative Example 1> and <Examples 1 to 5>.

As shown in FIG. 3A, the change in platinum active surface area before and after corrosion of the membrane-electrode assembly according to <Comparative Example 1> was reduced by 32.9% from 31.6 m 2 / g to 21.2 m 2 / g, as shown in FIG. 3b. The membrane-electrode assembly according to Example 1 was 13.9% from 36.7 m 2 / g to 31.6 m 2 / g, and the membrane-electrode assembly according to <Example 2> shown in FIG. 3C was 10.2 at 26.4 m 2 / g to 26.4 m 2 / g. %, The membrane-electrode assembly according to <Example 3> shown in FIG. 3D is 21.2% from 26.4 m 2 / g to 20.8 m 2 / g, and the membrane-electrode assembly according to <Example 4> shown in FIG. 3E is 31.5 m 2 / It can be seen that the membrane-electrode assembly according to <Example 5> shown in FIG. 3F at 23.6 m 2 / g in g, decreased 6.2% from 33.7 m 2 / g to 31.6 m 2 / g.

When the carbon is corroded, the platinum active surface area decreases due to the detachment and agglomeration of the platinum catalyst. In Examples 1 to 5, the corrosion of carbon was suppressed and the change of platinum active surface area was small even after the corrosion test. On the contrary, the membrane-electrode assembly according to Comparative Example 1 is very vulnerable to corrosion, and Examples 1 to 5 to which the electrolytic catalyst is added can be reconfirmed that the corrosion resistance is increased due to the removal of water in the catalyst layer. .

[ Evaluation example  4] The amount of carbon dioxide generated as a corrosion product before and after corrosion

4 is a result of directly measuring carbon dioxide, which is a corrosion product of carbon used as a support in the catalyst layer of the membrane-electrode assembly according to Comparative Example 1 and Examples 1 and 2, using a mass spectrometer.

As can be seen in Figure 4, in the membrane-electrode assembly without the addition of the electrolytic catalyst according to Comparative Example 1, the maximum amount of carbon dioxide generation was 1659 ppm, and the total amount was measured at 1018 μl. On the contrary, in the membrane-electrode assembly to which the 2 wt% electrolytic catalyst according to <Example 1> was added, carbon dioxide generation was measured at a maximum amount of 653 ppm and a total amount of 248 μl, and 5 wt% of the electrolytic electrolyte according to <Example 2>. In the membrane-electrode assembly to which the catalyst was added, a maximum amount of carbon dioxide generated was 186 ppm and a total amount of 34.84 μl was measured. Accordingly, it can be seen that Comparative Example 1 has a much higher amount of carbon dioxide than <Examples 1 to 2>.

According to the above results, it can be reconfirmed that the membrane-electrode assembly of <Examples 1 to 2> to which the electrolytic catalyst according to the present invention is added is increased in corrosion resistance due to water removal in the catalyst layer.

[ Evaluation example  5] Oxidation before and after corrosion Current value

5 is a result of measuring the current value generated while supplying a constant potential of 1.6V _SHE to the cathode for 30 minutes to evaluate the corrosion of the electrode catalyst layer of the present invention according to <Comparative Example 1> and <Examples 1 to 2> The higher the current value, the more active the oxidation reaction.

The membrane-electrode assembly without the electrolytic catalyst according to <Comparative Example 1> measured the least oxidation current, and the membrane-electrode assembly according to <Examples 1 to 2> of the present invention to which the electrolytic catalyst was added was Compared with <Comparative Example 1>, significantly higher oxidation current values were measured, indicating that the oxidation reaction was actively progressed.

The high oxidation current generated in the membrane-electrode assembly according to <Examples 1 and 2> is an oxidation current generated when water is decomposed through the addition of a hydroelectrolyte catalyst through an oxidation reaction, whereby the addition of the hydroelectrolyte catalyst is humidified. It can be seen that moisture in the catalyst layer supplied can be removed.

[ Evaluation example  6] Electrolytic Performance of Iridium Oxide Catalysts and Platinum Catalysts

FIG. 6 shows a comparison of the electrolytic performance of the iridium oxide used in the present invention with a platinum catalyst. The reaction electrode is rotated at a speed of 1200 rpm in a 0.5 M sulfuric acid solution in a nitrogen atmosphere, and 5 mV / s from 1.24 V to 1.84 V. This is the result of measuring the current value generated by increasing the potential at the speed of.

In the case of the platinum catalyst shows an activity for the electrolytic reaction from the potential of 1.6V or more, it can be seen that the electrolytic reaction hardly occurs at the 1.6V potential advanced for corrosion evaluation in the present invention. On the other hand, in the case of the iridium oxide catalyst showed an activity for the electrolytic reaction from the potential of 1.45V or more and showed a high activity at the potential of 1.6V proceeded for the corrosion evaluation in the present invention.

Through this, in the present invention, the membrane-electrode assembly to which the electrolytic catalyst according to <Comparative Example 1 is not added is not able to remove water in the catalyst layer because the platinum catalyst shows low activity for the electrolytic reaction. In the membrane-electrode assembly according to 2>, it can be seen that the added iridium oxide catalyst exhibits high activity in the electrolytic reaction, thereby removing water in the catalyst layer.

As can be seen from the results of <Evaluation Example>, the membrane-electrode assembly to which the electrolytic catalyst according to the present invention is added has a high oxidation current before and after corrosion, a small amount of carbon dioxide is generated, an active area of the platinum catalyst and a membrane The change in resistance, charge transfer resistance, and current density is small, so that the water flowing into the catalyst layer and the electrolytic catalyst decompose the water through oxidation reaction, thereby preventing the carbon carrier from contacting with the water, and thus the corrosion resistance effect of the carbon carrier is conventional. It is much superior to the membrane-electrode assembly.

The corrosion resistance evaluation results of the fuel cell cathode catalyst including the membrane-electrode assembly according to <Comparative Example 1> and <Examples 1 to 5> according to the present invention are shown in Table 2 below.

sample MEA@0.6V
(A / ㎠) Catalytic activity area
(㎡ / g _pt ) Membrane resistance Charge transfer resistance CO ₂ Occurrence
(total / peak)
(Μl / ppm) I'm after I'm after I'm after I'm after Comparative Example 1 1.73 0.954 31.6 21.2 0.0140 0.0142 0.0469 0.0928 1018/1659 -44.9% -32.9% + 1.4% + 97.9% Example 1 1.74 1.67 36.7 31.6 0.0146 0.0144 0.0424 0.0375 248.03 / 653 -4.0% -13.9% -1.4% -11.6% Example 2 1.69 1.68 29.4 26.4 0.0150 0.0150 0.0435 0.0364 34.84 / 186 -0.6% -10.2% 0% -19.5% Example 3 1.68 1.37 26.4 20.8 0.0142 0.0143 0.0414 0.0466 284/738 -18.5% -21.2% + 0.7% + 12.6% Example 4 1.75 1.18 31.5 23.6 0.0140 0.0145 0.0435 0.0628 418.4 / 783 -32.6% -25.1% + 3.57% + 44.4% Example 5 1.74 1.71 33.7 31.6 0.0140 0.0145 0.0431 0.0438 15.35 / 145.6 -1.7% -6.2% + 3.57% + 1.6%

In the above [Table 2], the membrane-electrode assembly using the hydroelectrolyte catalyst according to the present invention has a reduction of 5% or less in the performance of the unit cell expressed by the current density at a voltage of 1.6V or more, and the reduction of the active area of the platinum catalyst. It is 15% or less, it can be seen that the film resistance and charge transfer resistance is reduced, and the generation amount of carbon dioxide is significantly reduced, the membrane-electrode assembly using the electrolytic catalyst according to the present invention is excellent in corrosion resistance of carbon, The containing fuel cell is excellent in durability.

Claims (14)

In the catalyst layer of the fuel cell membrane-electrode assembly,
The catalyst layer is a catalyst layer of a fuel cell membrane-electrode assembly, characterized in that it comprises a carbon-supported platinum catalyst and a hydrolysis catalyst capable of decomposing water flowing into the catalyst layer when a voltage of 1.4 V or more is applied. The method of claim 1,
The carbon carrier of the carbon supported platinum catalyst is any one selected from carbon nanotubes, carbon nanofibers and carbon nanocages, and a catalyst layer of a membrane-electrode assembly for a fuel cell. The method of claim 1,
The electrolytic catalyst is a catalyst layer of a fuel cell membrane-electrode assembly, characterized in that it comprises at least one selected from the group consisting of iridium, ruthenium, iridium oxide, ruthenium oxide, iridium ruthenium alloy, iridium ruthenium oxide. The method of claim 1,
The electrolytic catalyst is a catalyst layer of a membrane-electrode assembly for a fuel cell, characterized in that 0.1% to 20% by weight relative to the carbon supported platinum catalyst. The method of claim 1,
The catalyst layer of the fuel cell membrane-electrode assembly, characterized in that the electrolytic catalyst is physically mixed with the platinum catalyst, supported on the platinum catalyst or to form a catalyst layer in the form of an alloy with the platinum catalyst. The method of claim 5, wherein
The catalyst layer of the fuel cell membrane-electrode assembly, wherein the amount of the electrolytic catalyst supported is 0.0008 mg / cm 2 to 0.16 mg / cm 2 when the hydroelectrolyte catalyst is mixed with the carbon supported platinum catalyst to form a catalyst layer. Electrolyte membrane; And an anode electrode and a cathode electrode formed between the electrolyte membrane and having a catalyst layer and a gas diffusion layer, respectively.
The anode or cathode electrode catalyst layer is a fuel cell membrane-electrode assembly, characterized in that the catalyst layer of the fuel cell membrane electrode assembly according to any one of claims 1 to 6. (1) dissolving an iridium precursor, ruthenium precursor or iridium ruthenium precursor in alcohol, adding sodium nitrate or sodium hydroxide, and mixing and drying the solution prepared to heat to prepare iridium oxide, ruthenium oxide and iridium ruthenium oxide, respectively. ;
Or dissolving an iridium precursor and tetradecyltrimethyl ammonium bromide (TTAB) in water at a molar ratio of 1: 100, stirring, and reducing iridium by sodium borohydride to prepare iridium;
(2) adding iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium prepared in step (1) to the carbon supported platinum catalyst and mixing alcohol to prepare a catalyst slurry; And
(3) forming a catalyst layer by coating and drying the catalyst slurry on the electrolyte membrane or the gas diffusion layer in the step (2); and a method of manufacturing a membrane-electrode assembly for a fuel cell, characterized in that it comprises a. The method of claim 8,
The alcohol of step (1) and (2) is a method for producing a membrane-electrode assembly for a fuel cell, characterized in that it comprises one or more selected from the group consisting of ethanol, isopropanol, methanol, n-propanol and butanol. . The method of claim 9,
The alcohol is made of ethanol and isopropanol, the method of producing a membrane-electrode assembly for a fuel cell, characterized in that the ethanol and isopropanol is mixed in a 1: 2 to 2: 1 volume ratio. The method of claim 8,
In the step (2), the iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium is 0.1 to 20% by weight based on the weight of the carbon supported platinum catalyst manufacturing method of the fuel cell membrane electrode assembly. The method of claim 8,
Method of producing a membrane-electrode assembly for a fuel cell, characterized in that further comprising an ionomer binder when the catalyst slurry is prepared in the step (2). The method of claim 8,
In the step (2), the iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium is physically mixed with the platinum catalyst, supported on the platinum catalyst or to form a catalyst layer in the form of the platinum catalyst and the alloy for a fuel cell, characterized in that Method for producing a membrane-electrode assembly. The method of claim 13,
When the iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium is mixed with the carbon supported platinum catalyst to form a catalyst layer, the supported amount of iridium oxide, ruthenium oxide, iridium ruthenium oxide or iridium is 0.0008 mg / cm 2 ~ 0.16 mg / cm 2 Method for producing a membrane-electrode assembly for a fuel cell, characterized in that.

Images