KR101634077B1 - Pt-Au alloy catalyst having resistance to phosphoric acid poisoning, MEA and High temperature PEMFC including the same and method for preparing the same - Google Patents

Abstract

A phosphoric acid endotoxic toxic platinum and gold alloy catalyst, a membrane electrode assembly comprising the same, a high temperature polymer fuel cell, and a method of manufacturing the same. The platinum and gold alloy catalysts are resistant to poisoning with phosphoric acid and have a high catalytic activity against oxygen reduction reaction (ORR). Therefore, the use of a phosphoric acid-impregnated membrane in a high temperature polyelectrolyte membrane fuel cell . ≪ / RTI >

Description

FIELD OF THE INVENTION [0001] The present invention relates to a phosphorous-endotoxic toxic platinum and gold alloy catalyst, a membrane electrode assembly comprising the same, a high-temperature polymer fuel cell, and a method of preparing the same. same}

The present specification describes a phosphorous endotoxic platinum and gold alloy catalyst, a membrane electrode assembly comprising the same, a high temperature polymer fuel cell, and a manufacturing method thereof.

A polymer electrolyte membrane fuel cell (PEMFC) is a system that produces electricity through the flow of electrons generated through the hydrogen oxidation reaction of the anode and the oxygen reduction reaction of the anode.

The problems of the polymer electrolyte membrane fuel cell are the slow oxygen reduction reaction of the anode, the high cost of materials (Pt catalyst, separator, etc.), and the complexity of water management.

In contrast, a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) has a higher temperature (120 ° C ~ 80 ° C) than a general polymer electrolyte fuel cell, that is, a low temperature (60 ° C to 80 ° C) 180 < 0 > C).

Since such a high-temperature polyelectrolyte membrane fuel cell uses polybenzimidazole (PBI) impregnated with phosphoric acid (PA) as a membrane, a general low-temperature polyelectrolyte membrane fuel cell using a Nafion membrane impregnated with water It is possible to operate at high temperature (above 100 ℃) to improve fuel cell kinetic energy, and does not require complicated water management.

However, the biggest problem of the high temperature polyelectrolyte membrane fuel cell is phosphoric acid poisoning of the catalyst. Each of the electrode catalysts of the high temperature polyelectrolyte membrane fuel cell uses a platinum catalyst as in a general low temperature polyelectrolyte membrane fuel cell. However, due to the poisoning of phosphoric acid impregnated into the membrane by the phosphoric acid impregnated strongly in the membrane, the hydrogen oxidation and the oxygen reduction reaction site occurring at the electrode are blocked and the catalytic activity is drastically reduced.

In order to increase the activity of the conventional catalyst, it is necessary to study the catalytic activity depending on the crystal structure of the platinum catalyst or to use a catalyst of an alloy or a core-shell type by mixing platinum with another metal as a main catalyst And a method of improving the activity by changing the electronic structure is reported.

: K-S Lee et al. Electrochimica Acta 56, 8802 (2011) : J. Zhang et al. Science 315, 200 (2007)

In embodiments of the present invention, a phosphoric endotoxic platinum and gold alloy catalyst having high resistance to poisoning with phosphoric acid in a high temperature polyelectrolyte membrane fuel cell and high catalytic activity against an oxygen reduction reaction, A high temperature polymer fuel cell, and a manufacturing method thereof.

In an embodiment of the present invention, there is provided a platinum and gold alloy catalyst used in the presence of phosphoric acid and made of an alloy of platinum and gold, having oxygen reduction activity and phosphoric endotoxicity.

The composition of the gold in the alloy of platinum and gold is preferably 10% or more and 50% or less, particularly preferably 11% or more and 31% or less, and most preferably 31% or less.

The platinum and gold alloy catalysts are useful as electrode catalysts for high temperature polyelectrolyte membrane fuel cells.

In another embodiment of the present invention, there is also provided a membrane electrode assembly, wherein as the membrane electrode assembly, the electrode catalyst of the membrane electrode assembly includes the platinum and gold alloy catalysts, and the membrane of the membrane electrode assembly is a membrane impregnated with phosphoric acid.

The membrane electrode assembly is useful as a membrane electrode assembly of a high temperature polyelectrolyte membrane fuel cell.

Another embodiment of the present invention provides a high temperature polyelectrolyte membrane fuel cell comprising the membrane electrode assembly.

Another embodiment of the present invention provides a method for producing the platinum and gold alloy catalyst having oxygen reduction activity and phosphoric endotoxicity, comprising the step of alloying platinum with gold.

Here, examples of the alloying step may include a course putter alloying method, a colloidal alloying method, an impregnation alloying method, an electrolytic plating alloying method, and the like.

The phosphorus-endotoxic toxic platinum and gold alloy catalysts according to the embodiments of the present invention are resistant to phosphoric acid poisoning and have a high catalytic activity against the oxygen reduction reaction (ORR). Therefore, phosphoric acid poisoning due to use of phosphoric acid- The present invention can be particularly useful for a high temperature polymer electrolyte membrane fuel cell in which the problems of the present invention are present.

1 is a FE-SEM photograph showing the morphology of each catalyst of Comparative Examples and Examples of the present invention. Figure 1a shows platinum nanoparticles single catalyst (Pt Nps), Figure 1b is Pt ₈₉ Au ₁₁ (Example 1), Figure 1c Pt ₆₉ Au ₃₁ (Example 2), Fig. 1d is Pt ₆₃ Au ₃₇ (Example 3 1E shows Pt ₅₅ Au ₄₅ (Example 4), FIG. 1F shows Pt ₅₂ Au ₄₈ (Example 5), and FIG. 1G shows a case of Au nanoparticle single catalyst (Au Nps).
2A is a graph showing the oxygen reduction activity of a catalyst (Pt monocatalyst (Pt nanoparticles and PtAu alloy prepared by various compositions) prepared in the absence of phosphoric acid (0.1 M HClO ₄ ) in Experimental Example of the present invention LSV (Linear Sweep Voltammetry) (Scan rate: 5mV / s, RDE velocity: 1500rpm). The X axis represents the electrode potential (E / V vs. RHE) and the Y axis represents the current density [mAcm ^-2 (geo)], or activity.
Figure 2b is the oxygen in the experimental example of the present invention, if the phosphoric acid _{(0.1M HClO 4 + 0.1MH 3 PO} 4) a catalyst [Pt single catalyst (Pt nanoparticles) and the PtAu alloy produced in a variety of composition] Preparation of (Scan Rate: 5mV / s, RDE Velocity: 1500rpm) to investigate the reduction reaction activity. The X axis represents the electrode potential (E / V vs. RHE) and the Y axis represents the current density [mAcm ^-2 (geo)], or activity.
FIG. 2C is a graph illustrating the relationship between 0.8V vs. vs. FIG. FIG. 3 is a graph comparing the oxygen reduction activity of the prepared catalyst according to the geometrical surface area in RHE. FIG. The X-axis represents the respective catalyst composition and the Y-axis represents the current density [mAcm ^-2 (geo)], or activity.
FIG. 3 is a graph comparing Half wave potentials of the catalysts based on FIG. 2A and FIG. 2C. The X-axis is the respective catalyst composition and the Y-axis is the Half wave potential [V vs.. RHE].
FIG. 4A is a graph showing the relationship between 0.8V vs. the catalyst based on FIGS. 2A and 2C. FIG. RHE is a graph showing the comparison of mass activity. The X axis represents the respective catalyst composition and the Y axis represents the current density per unit milligram (mA / mg).
FIG. 4B is a graph showing the comparison of the oxygen reduction catalyst activity per the catalyst material price ($, 2013.07.09 Pt, Au rate) at 0.8V vs. RHE of the catalyst based on FIGS. 2A and 2C. The X axis represents the respective catalyst composition and the Y axis represents the current density per unit dollar (mA / $).
FIG. 5 is a graph of XRD results of Examples and Comparative Examples of the present invention. FIG. FIG. 5A shows the XRD peak of each catalyst, FIG. 5B shows each catalyst on the X-axis and 2θ (degrees) of the Pt (111) peak of each catalyst on the Y axis.

The present inventors have confirmed that phosphoric acid adsorption does not occur on the surface of gold (Au) irrespective of dislocations by using Raman spectroscopy. Based on this investigation, they have accomplished the present invention.

Embodiments of the present invention provide platinum and gold alloy catalysts which are used in the presence of phosphoric acid and are made of an alloy of platinum and gold and have oxygen reduction activity and phosphoric endotoxicity.

The composition of gold in the platinum and gold alloy is preferably 10% or more and 50% or less, more preferably 11% or more and 31% or less, and most preferably 31% or less.

The pH of the catalyst is preferably 7 or less.

The catalyst according to the embodiments of the present invention is distinguished from a core shell type (Non-Patent Document 1) in which platinum and gold are alloyed, for example, a gold core and a platinum surface is formed, Document 2).

The alloys of platinum and gold according to embodiments of the present invention may be entirely homogeneous homogeneous alloys.

The platinum and gold alloy catalysts are excellent in catalyst stability as well as high oxygen reduction activity and excellent phosphoric endotoxicity.

These platinum and gold alloy catalysts can be usefully used as electrode catalysts for high temperature polyelectrolyte membrane fuel cells in which phosphorus poisoning is a concern due to the use of phosphoric acid impregnated membranes.

For reference, for example, a platinum-gold core-shell type catalyst exhibits about half the catalytic activity of a platinum catalyst in which phosphoric acid is not poisoned, in terms of mass activity calculated by the platinum content alone As in the embodiments of the present invention, when the platinum-gold alloy catalyst is formed, the endotoxicity of phosphoric acid is remarkably improved and the catalytic activity is superior to that of the platinum single metal in the presence of phosphoric acid. For example, the platinum and gold alloy catalysts according to embodiments of the present invention may exhibit up to two-fold performance improvement over platinum catalysts in the presence of phosphoric acid. When the composition of gold in the platinum and gold alloy is 10% or more and 50% or less in atomic composition, the catalytic activity measured in the presence of phosphoric acid indicates the activity level or more of the platinum catalyst not poisoned with phosphorus, When the composition of gold in the gold alloy is 31% as the atomic composition, it is found that the catalytic activity measured in the presence of phosphoric acid is higher than that of the platinum catalyst in which phosphoric acid is not poisoned.

On the other hand, in another embodiment of the present invention, as the membrane electrode assembly, there is provided a membrane electrode assembly in which the electrode catalyst of the membrane electrode assembly includes the phosphoric acid platinum and gold alloy catalyst, and the membrane of the membrane electrode assembly is a membrane impregnated with phosphoric acid .

The membrane electrode assembly is useful as a membrane electrode assembly of a high-temperature polyelectrolyte membrane fuel cell in which a phosphoric acid-impregnated membrane is used. For example, the membrane electrode assembly may be a membrane electrode assembly in which a phosphate-impregnated polybenzimidazole electrolyte membrane and an electrode are combined.

Another embodiment of the present invention provides a high temperature polyelectrolyte membrane fuel cell comprising the membrane electrode assembly.

Another embodiment of the present invention provides a method for producing the platinum and gold alloy catalyst having oxygen reduction activity and phosphoric endotoxicity, comprising the step of alloying platinum with gold.

The alloying of the platinum and gold alloy catalysts may be carried out by known methods such as a course putter alloying method, a colloidal alloying method, an impregnation alloying method, an electrolytic plating alloying method, or the like. have.

For reference, platinum and gold alloy catalysts can be made into nanoparticles using the above-mentioned colloidal alloying method or impregnation alloying method.

Unlike the electrochemical deposition method, the course putter alloying method can control the electrode in various ways by adjusting the power of two or more sputter guns. That is, a coarse putter method is used in which a platinum target is mounted on a first sputter gun, gold is mounted on a second sputter gun, and then two guns are simultaneously operated. If the power of two or more sputter guns is adjusted, The content of the substance in the electrode is changed and the platinum and gold alloy electrodes exhibiting various compositions can be manufactured.

The colloidal alloying method is a method of chemically reducing by adding a stabilizer and a reducing agent in a solution containing a platinum precursor and a gold precursor. As precursors of platinum and gold, chlorides, nitrides, sulfides and the like can be used. As the stabilizer, oleylamine, oleic acid, polyvinylpyrrolidone and various kinds of surfactants can be used. As the reducing agent, NaBH ₄ , HCHO-based reducing agent and alcohol or ester-based material are generally used. The composition of the alloy can be controlled by adjusting the amount of the precursor, the kind and amount of the stabilizer and the reducing agent, the reaction time, and the temperature.

In the impregnation alloying method, the above-described gold precursor is put on a prepared carbon-supported platinum catalyst, dried at a temperature of about 100 ^° C for about 3 hours, and then subjected to grinding at a high temperature (200 to 500 ° C) Followed by heat treatment in a reducing atmosphere (hydrogen atmosphere). The composition of the alloy can be controlled by controlling the amount of platinum precursor and the temperature and time of the high temperature reduction.

The electrolytic plating alloying method is a method in which a certain potential or voltage is applied to an electrolytic solution containing the platinum and gold precursors to reduce and precipitate an alloy catalyst. The composition of the alloy catalyst can be controlled by adjusting the amount of each precursor and the reduction potential. The use of such an electrolytic plating method is preferable because it is easy to manufacture a large-capacity electrode and the manufacturing cost is reduced.

Hereinafter, the present invention will be described in more detail by way of Examples and Experiments, but the present invention is not limited to the following description.

Example  Manufacture of platinum and gold alloy catalysts

Electrodeposition was used to produce platinum and gold alloy catalysts.

The alloy catalyst compositions were Pt ₈₉ Au ₁₁ (Example 1), Pt ₆₉ Au ₃₁ (Example 2), Pt ₆₃ Au ₃₇ (Example 3), Pt ₅₅ Au ₄₅ (Example 4), Pt ₅₂ Au ₄₈ Example 5).

Electrodeposition was performed in a three electrode cell. The working electrode was a glassy carbon electrode (or glassy carbon film), the counter electrode was a Pt sheet, and the reference electrode was Ag / AgCl.

H ₂ PtCl ₆ · xH ₂ O (10 mM) was used as a precursor of platinum (Pt), and gold (III) chloride hydrate (HAuCl ₄ · xH ₂ O, 5, 6, 7mM) and sodium chloride (NaCl, 500mM) were used as the electrolyte. Argon purging for 40 minutes, deposition potential is -0.3 V vs. < RTI ID = 0.0 > Ag / AgCl, and electroplated for 20 minutes. Then, the plated electrode was cleaned with DI-water to remove the remaining electrolyte on the surface and dried with N ₂ gas.

Comparative Example  Catalyst preparation

In order to compare the prepared platinum and gold alloy with platinum, platinum nanoparticles (Pt Nps) were plated on glassy carbon through the above method (Comparative Example 1).

In addition, Au gold (Au Nps) was plated on glassy carbon (Comparative Example 2)

Example  And Comparative Example  Experimental evaluation of catalyst properties

All experiments were conducted at 298K.

The morphology and composition of the prepared platinum and gold alloys were measured by Field Emission Scanning Electrode Microscopy (FE-SEM) and Energy Dispersive Spectroscopy (EDS). The crystal structure change of the catalyst was measured by X-ray diffraction (XRD) at a rate of 5 ° / min.

1 is a FE-SEM photograph showing the morphology of each catalyst of Comparative Examples and Examples of the present invention.

Figure 1a shows platinum nanoparticles single catalyst (Pt Nps), Figure 1b is Pt ₈₉ Au ₁₁ (Example 1), Figure 1c Pt ₆₉ Au ₃₁ (Example 2), Fig. 1d is Pt ₆₃ Au ₃₇ (Example 3 1E shows Pt ₅₅ Au ₄₅ (Example 4), FIG. 1F shows Pt ₅₂ Au ₄₈ (Example 5), and FIG. 1G shows a case of Au nanoparticle single catalyst (Au Nps).

Meanwhile, FIG. 5 is a graph of XRD results of Examples and Comparative Examples of the present invention. FIG. 5A shows the XRD peak of each catalyst, FIG. 5B shows each catalyst on the X-axis and 2θ (degrees) of the Pt (111) peak of each catalyst on the Y axis.

As can be seen from the measurement results of Figures 1B-1F and 5, the platinum and gold alloy catalysts according to embodiments of the present invention are homogeneous alloy catalysts. In particular, as can be seen from the XRD of FIGS. 5A and 5B, it can be seen that as the amount of Au increases from Pt to PtAu, the Pt (111) peak approaches Au. Therefore, it can be seen that the PtAu prepared is not a heterogeneous mixture but a homogeneous alloy.

The electrochemical performance of the prepared catalysts was evaluated by lineer sweep voltammetry (LSV) and cyclic voltammetry (CV).

To investigate the oxygen reduction (ORR) performance, the measured LSVs were run on three electrode cells connected with potentiostat / galbanostat (Autolab, PGSTAT302F) and rotating-disk electrode (RDE). The working electrode was made of PtAu alloy / GC and PtNps / GC having various compositions as described above. The counter electrode was made of Pt sheet and the reference electrode was made of Ag / AgCl. Hydrogen Electrode (RHE) scale.

Perchloric acid (HClO ₄ ) and phosphoric acid (H ₃ PO ₄ ) were used as the electrolytes to measure the ORR activity depending on the presence or absence of phosphoric acid [HClO ₄ (0.1M), H _{3 PO 4 (0M, 0.1M)} ].

The experiment was carried out initially with 60 minutes of O ₂ followed by continued pursuit. The scan interval was 1.05V ~ 0.05V and the scan rate was 5mV / s. The rotation speed of the RDE was 1500 rpm and proceeded at 298K.

2A is a graph showing the oxygen reduction activity of a catalyst (Pt monocatalyst (Pt nanoparticles and PtAu alloy prepared by various compositions) prepared in the absence of phosphoric acid (0.1 M HClO ₄ ) in Experimental Example of the present invention LSV (Linear Sweep Voltammetry) (Scan rate: 5mV / s, RDE velocity: 1500rpm). The X axis represents the electrode potential (E / V vs. RHE) and the Y axis represents the current density [mAcm ^-2 (geo)], or activity.

Figure 2b is the oxygen in the experimental example of the present invention, if the phosphoric acid _{(0.1M HClO 4 + 0.1MH 3 PO} 4) a catalyst [Pt single catalyst (Pt nanoparticles) and the PtAu alloy produced in a variety of composition] Preparation of (Scan Rate: 5mV / s, RDE Velocity: 1500rpm) to investigate the reduction reaction activity. The X axis represents the electrode potential (E / V vs. RHE) and the Y axis represents the current density [mAcm ^-2 (geo)], or activity.

FIG. 2C is a graph illustrating the relationship between 0.8V vs. vs. FIG. FIG. 3 is a graph comparing the oxygen reduction activity of the prepared catalyst according to the geometrical surface area in RHE. FIG. The X-axis represents the respective catalyst composition and the Y-axis represents the current density [mAcm ^-2 (geo)], or activity.

Referring to FIG. 2C, when the platinum single catalyst is compared with the oxygen reduction activity according to the geometric electrode area, the activity is reduced to about half or more by poisoning in the presence of phosphoric acid.

0.8 V vs. Comparing the oxygen reduction activity according to the geometric electrode area in RHE, Pt ₆₉ Au ₃₁ showed the best activity and showed about twice as high activity as the Pt single catalyst of Comparative Example 1. However, thereafter, as the atomic composition of gold increased, the activity was lower than that of the platinum single catalyst of Comparative Example 1.

On the other hand, when phosphoric acid is present, 0.8 V vs. Comparing the oxygen reduction activity according to the geometric electrode area in RHE, Pt ₆₉ Au ₃₁ shows the highest activity, and even higher performance than the platinum single catalyst in the case of no phosphoric acid.

Pt ₆₃ Au ₃₇ From this point on, it can be seen that the performance is much higher than that of platinum in the presence of phosphoric acid, and the performance similar to that of platinum in the absence of phosphoric acid is realized.

FIG. 3 is a graph comparing Half wave potentials of the catalysts based on FIG. 2A and FIG. 2C. The X-axis is the respective catalyst composition and the Y-axis is the Half wave potential [V vs.. RHE].

In the absence of phosphoric acid, the half-wave potential of Pt ₆₉ Au ₃₁ is the most active, and thereafter, the activity of the catalyst decreases as the atomic composition of gold increases.

In the presence of phosphoric acid, the half-wave potential of Pt ₆₉ Au ₃₁ is the most active. After that, the activity of the catalyst decreases as the atomic composition of gold increases. However, The catalytic activity is superior.

FIG. 4A is a graph showing the relationship between 0.8V vs. the catalyst based on FIGS. 2A and 2C. FIG. RHE is a graph showing the comparison of mass activity. The X axis represents the respective catalyst composition and the Y axis represents the current density per unit milligram (mA / mg).

FIG. 4B is a graph showing the oxygen reduction reaction catalytic activity per catalyst (0.8, Pt / Au at 2013.07.09) at 0.8 V vs. RHE based on FIGS. 2A and 2C. The X axis represents the respective catalyst composition and the Y axis represents the current density per unit dollar (mA / $).

Referring to FIG. 4A, it is found that Pt ₆₉ Au ₃₁ is the most active catalyst per mg in the absence of phosphoric acid. Then, as the gold atom composition increases, the activity per mg decreases sharply and the mass activity becomes lower than that of the platinum single metal .

In the presence of phosphoric acid, Pt ₆₉ Au ₃₁ is the most active catalyst per mg, and then activity decreases per mg as the gold atom composition increases. However, in this case, the activity per mg is higher than that of the platinum single metal catalyst of Comparative Example 1 appear.

Meanwhile, referring to FIG. 4B, the oxygen reduction reaction catalyst activity per unit dollar based on the catalyst price of platinum and gold also showed a trend as shown in FIG. 4A.

From the above results, it can be seen that the platinum and gold alloy catalysts according to the embodiments of the present invention are highly resistant to poisoning with phosphoric acid and have a high catalytic activity for the oxygen reduction reaction (ORR). In particular, it was found that the catalytic activity was increased in the presence of phosphoric acid as compared with the platinum single metal catalyst. In particular, it was found that the activity increased markedly from 11% to 31%.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

As a high temperature polyelectrolyte membrane fuel cell,
A membrane electrode assembly having improved phosphoric endotoxicity,
Wherein the membrane electrode assembly having improved phosphoric endotoxicity includes a platinum and gold alloy catalyst, the membrane of the membrane electrode assembly is a membrane impregnated with phosphoric acid,
Wherein the platinum and gold alloy catalyst is used in the presence of phosphoric acid and has an oxygen reaction activity and a phosphorus endotoxicity, and the composition of gold in the alloy of platinum and gold is 31% in terms of atomic composition. battery.
delete delete delete delete delete delete delete As a method for improving the endotoxicity of phosphoric acid in a high temperature polyelectrolyte membrane fuel cell,
The electrode catalyst of the membrane electrode assembly is formed of an alloy of platinum and gold, the membrane electrode assembly is impregnated with phosphoric acid,
Wherein the composition of the gold in the platinum and gold alloy is 31% in terms of atomic composition. The method for improving the endotoxicity of phosphoric acid endothelium in a high temperature polyelectrolyte membrane fuel cell. delete

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