KR102659121B1 - Strong metal support interaction and hydrogen spillover-based catalysts for fuel cell, electrode for fuel cell comprising the same and membrane electrode assembly comprising the same - Google Patents

Abstract

One aspect of the present invention is an SMSI and hydrogen spillover-based catalyst for fuel cells that can improve durability by suppressing the carbon oxidation reaction of the anode electrode in an environment where hydrogen is insufficient at the anode electrode, an electrode for a fuel cell containing the same, and a catalyst containing the same. A membrane electrode assembly is provided. A mesoporous TiO ₂ support (hereinafter referred to as m-TiO ₂ ) according to an embodiment of the present invention; and a Pt catalyst atom supported on the m-TiO ₂ support, wherein the m-TiO ₂ support and the Pt catalyst atom are insulated by strong metal support interaction (SMSI) under a low hydrogen environment. A conduction path is realized on the m-TiO ₂ support through the first mechanism through which the properties are realized and hydrogen spillover in which hydrogen activated by the Pt catalyst atoms diffuses under a high hydrogen environment. It is characterized by utilizing a second mechanism.

Description

SMSI and hydrogen spillover-based catalyst for fuel cells, electrodes for fuel cells containing the same, and membrane electrode assemblies containing the same COMPRISING THE SAME}

The present invention relates to SMSI and hydrogen spillover-based catalysts for fuel cells, electrodes for fuel cells containing the same, and membrane electrode assemblies containing the same. More specifically, the present invention relates to the carbon electrode of the cathode electrode even in a start/stop environment where hydrogen is insufficient at the anode electrode. It relates to SMSI and hydrogen spillover-based catalysts for fuel cells that can improve durability by suppressing oxidation reaction (COR), electrodes for fuel cells containing the same, and membrane electrode assemblies containing the same.

A fuel cell is a device that generates power by converting chemical energy into electrical energy through oxidation of hydrogen, a fuel. Fuel cells can use hydrogen produced using renewable energy, produce water as a reaction product, and do not produce air pollutants or greenhouse gases, so they are attracting attention as an eco-friendly energy source. Depending on the type of electrolyte and fuel used, the fuel cell is a polymer electrolyte fuel cell (Proton Exchange Membrane Fuel Cell, PEMFC), direct methanol fuel cell (DMFC), phosphoric acid fuel cell (PAFC), and molten carbonate fuel cell. There are corrosion protection (MCFC) and solid oxide protection (SOFC).

Among these, polymer electrolyte fuel cells (PEMFC) have a relatively low operating temperature, high energy density, and excellent fast start-up and response characteristics, so technology research is being conducted to use them as an energy source for automobiles, various electronic devices, transportation, and power generation. is actively underway.

A fuel cell supplies hydrogen to the anode and oxygen to the cathode, where the catalyst at the anode oxidizes hydrogen to form protons, and the protons pass through the proton conductive membrane and undergo a reduction reaction with oxygen by the catalyst at the cathode. This produces electricity.

Figure 1 schematically shows the catalytic oxidation process that occurs at the cathode of a conventional fuel cell. Referring to FIG. 1, the fuel cell 1000 includes a cathode (10), an anode (20), and an electrolyte membrane (30) formed between the cathode (10) and the anode (20). Includes an electrode assembly (Membrane-Electrode Assembly, MEA) (100). The membrane electrode assembly 100 is a core component of a fuel cell vehicle and is an important core component that directly affects the output and durability of the fuel cell depending on its performance.

The anode and cathode of the membrane electrode assembly 100 include a catalyst, each including a Pt catalyst atom and a support supporting the Pt catalyst atom. Additionally, a gas diffusion layer (GDL) 40, 42 and a separator 50, 52 may be sequentially formed on both sides of the membrane electrode assembly 100, respectively.

Referring to FIG. 1, the hydrogen injected into the fuel cell anode (hydrogen electrode) is separated into hydrogen ions and electrons (H ₂ → 2H ⁺ + 2e ^- , E0 = 0.0V), and the fuel cell cathode (air electrode) Air is injected and oxygen ions and electrons are separated (1/2O ₂ + 2H ⁺ + 2e ^- → H ₂ O, E0=1.23V). Electricity is generated by the movement of separated electrons, and heat is generated as water (H ₂ O) is created when hydrogen and oxygen come into contact (total reaction = 1/2O ₂ + H ⁺ → H ₂ O, E0 = 1.23V) ). Meanwhile, catalysts are used to increase the reaction efficiency of fuel cells. The conventional fuel cell anode (hydrogen electrode) catalyst uses platinum (Pt), which has excellent oxygen reduction reaction characteristics, and the support for supporting the catalyst has a large specific surface area (more than 500 m ² /g) and excellent electrical conductivity. A carbon (C) support having (less than 25 S/cm) was used.

Specifically, in a polymer electrolyte fuel cell, a hydrogen oxidation reaction (HOR) occurs where hydrogen is oxidized to become protons and electrons at the anode (hydrogen electrode), and at the cathode (air electrode), these protons and electrons are converted to oxygen. It follows a mechanism that generates electricity by causing an oxygen reduction reaction (ORR) where oxygen is reduced.

However, automotive fuel cell stacks repeatedly experience start-up/shut-down (SU/SD). In these start-on/off (SU/SD) conditions, outside air leaks into the anode (hydrogen electrode), unlike the hydrogen environment conditions during normal operation. Due to this air, unnecessary oxygen reduction reaction (ORR) occurs locally at the anode (hydrogen electrode). In order to supply the protons and electrons necessary for the oxygen reduction reaction (ORR), the potential on the cathode (air electrode) side suddenly rises to 1.4 V or more, which causes carbon oxidation in which carbon is oxidized on the cathode (air electrode) side. The reaction (Carbon Oxidation Reaction, COR) is as follows: C + 2H ₂ O → CO ₂ + 4H ⁺ + 4e ^- As this happens, the cathode electrode corrodes.

To solve these problems, many methods have been reported from system and material design perspectives. First, looking at the systematic approach, a removal method using nitrogen gas was introduced to prevent the mixing of hydrogen and air, but it was not realistic in an actual operating environment.

When a fuel shortage occurs, oxygen has a concentration and pressure gradient due to the partial fuel distribution characteristics during operation and is mixed through the polymer membrane. Mixing of hydrogen and oxygen frequently occurs even when stopped, and hydrogen and oxygen are supplied. Even if this is stopped, residual gas may be generated in the separator channel, or atmospheric air may penetrate into the outlet of the fuel cell anode (hydrogen electrode), causing hydrogen and air to mix. Additionally, there is a method of suppressing the oxygen reduction reaction (ORR) by installing a gas control device outside the system to prevent oxygen inflow. However, there was a problem in that a new device had to be added, increasing the volume and manufacturing cost.

And, as an approach from a materials perspective, research was first conducted to find materials such as graphite, carbon nanotube, or metal oxide with strong corrosion resistance instead of the existing carbon support.

Although this method clearly had the effect of improving durability, it had the limitation of reducing performance due to the low surface area due to poor dispersion of platinum (Pt) particles and failing to provide any solution regarding the dissolution of platinum (Pt) particles.

Therefore, among material approaches, the method of newly designing catalysts is receiving the most attention. In the catalytic approach, a method was first proposed to protect the electrode by adding an oxygen evolution reaction (OER) active catalyst to the cathode (air electrode) and promoting OER, a competing reaction, instead of carbon corrosion. When Ru or Ir-based oxides, which are often used as oxygen evolution reaction (OER) active catalysts, are added to the cathode (air electrode) catalyst layer, reverse current decay (RCD) is induced through oxygen evolution reaction (OER), causing carbon oxidation reaction (COR). Electric charge supply is limited. Although effective, this approach also had the disadvantage of increasing the amount of precious metals loaded into the cathode (air electrode) catalyst layer, resulting in a negative economic impact.

One aspect of the present invention is an SMSI and hydrogen spillover-based catalyst for fuel cells that can improve durability by suppressing the carbon oxidation reaction (COR) of the cathode electrode even in a start/stop environment where hydrogen is insufficient at the anode electrode, and a fuel containing the same. Provided is a battery electrode and a membrane electrode assembly including the same.

One aspect of the present invention includes a TiO ₂ support and a Pt catalyst atom supported on the TiO ₂ support, wherein the TiO ₂ support and the Pt catalyst atom have strong catalyst-support interaction (SMSI) or It relates to SMSI and hydrogen spillover-based catalysts for fuel cells, characterized by using at least one of the hydrogen spillover mechanisms in which hydrogen activated by the Pt catalyst atoms diffuses.

In one embodiment, in a low hydrogen environment, insulator properties are realized by strong catalyst-support interaction (SMSI) of the TiO ₂ support and the Pt catalyst atoms. SMSI for fuel cells and hydrogen spillover- It concerns base catalysts.

In one embodiment, under a high hydrogen environment, a conduction path is implemented on the TiO ₂ support through hydrogen spillover in which hydrogen activated by the Pt catalyst atoms diffuses. SMSI for fuel cells and hydrogen spillover-based catalysts.

Another aspect of the present invention is a mesoporous TiO ₂ support (m-TiO ₂ ); and a Pt catalyst atom supported on the m-TiO ₂ support, wherein the m-TiO ₂ support and the Pt catalyst atom are insulated by strong metal support interaction (SMSI) under a low hydrogen environment. A conduction path is realized on the m-TiO ₂ support through the first mechanism through which the properties are realized and hydrogen spillover in which hydrogen activated by the Pt catalyst atoms diffuses under a high hydrogen environment. It relates to SMSI and hydrogen spillover-based catalysts for fuel cells, characterized by utilizing the second mechanism.

In one embodiment, the conduction path relates to SMSI and hydrogen spillover-based catalyst for fuel cells, wherein the conduction path is formed by the following reaction equation 1.

[Scheme 1]

Ti(IV)O ₂ +H ⁺ +e ^- →Ti(Ⅲ)OOH

In one embodiment, the low hydrogen environment relates to SMSI and hydrogen spillover-based catalysts for fuel cells, which are defined as engine start-up/shut-down (SU/SD) environments.

In one embodiment, it relates to an SMSI and hydrogen spillover-based catalyst for a fuel cell comprising 10 parts by weight of the Pt catalyst atoms based on 100 parts by weight of the m-TiO ₂ support.

In one embodiment, the present invention relates to SMSI and hydrogen spillover-based catalysts for fuel cells, wherein the average size of the Pt catalyst atoms is 2 to 10 mm.

Another aspect of the present invention relates to an electrode for a fuel cell, characterized in that it includes an SMSI for a fuel cell and a hydrogen spillover-based catalyst.

Another aspect of the present invention is an anode; cathode; and an electrolyte membrane formed between the anode and the cathode, wherein the anode includes the SMSI for fuel cells and a hydrogen spillover-based catalyst.

Another aspect of the present invention relates to a fuel cell comprising SMSI for a fuel cell and a hydrogen spillover-based catalyst.

Figure 1 schematically shows the catalytic oxidation process that occurs at the cathode of a conventional fuel cell.
FIG. 2A is a diagram illustrating the strong catalyst-support interaction (SMSI) mechanism in a low hydrogen environment of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention.
FIG. 2B is a diagram for explaining the hydrogen spillover mechanism of SMSI and hydrogen spillover-based catalyst for fuel cells in a high hydrogen environment according to an embodiment of the present invention.
Figure 3 is a diagram showing the results of H ₂ -TPR (H ₂ -temperature-programmed reduction) measurement to evaluate the oxidation-reduction ability of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention.
Figure 4 is a diagram showing the ECSA calculation results of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention under a low hydrogen environment.
Figure 5 is a graph showing an experiment verifying the performance durability effect of the polymer electrolyte membrane fuel cell manufactured in Examples and Comparative Examples according to the present invention under SU/SD conditions.

Hereinafter, embodiments will be clearly revealed through the accompanying drawings and descriptions of the embodiments. In the drawings, sizes are exaggerated, omitted, or schematically shown for convenience and clarity of explanation. Additionally, the size of each component does not entirely reflect the actual size. Additionally, the same reference numbers indicate the same elements throughout the description of the drawings. Hereinafter, embodiments will be described with reference to the attached drawings.

SMSI and hydrogen spillover-based catalysts for fuel cells

One aspect of the present invention relates to SMSI and hydrogen spillover-based catalysts for fuel cells.

In one embodiment, the SMSI and hydrogen spillover-based catalyst for fuel cells includes a mesoporous TiO ₂ support (hereinafter referred to as 'm-TiO ₂ ') and Pt catalyst atoms dispersed and adsorbed on the surface of the m-TiO ₂ support. , the first mechanism in which insulator properties are realized by strong catalyst-support interaction (SMSI) of the m-TiO ₂ support and Pt catalyst atoms under a low hydrogen environment, and the Pt catalyst atoms under a high hydrogen environment. It is characterized by utilizing a second mechanism in which a conduction path is implemented on the m-TiO ₂ support through hydrogen spillover, in which hydrogen activated by diffusion is diffused.

In one embodiment, the SMSI and hydrogen spillover-based catalyst for fuel cells includes a conduction path formed by Scheme 1 below.

[Scheme 1]

Ti(IV)O ₂ +H ⁺ +e ^- →Ti(Ⅲ)OOH

Through the conduction path in Scheme 1, electrical conductivity becomes excellent in a high hydrogen environment, so that a Pt catalyst reactor supported on an m-TiO ₂ support can provide a reaction site where the electrochemical reaction of the fuel cell occurs. do.

Furthermore, under low hydrogen environments such as engine startup (SU) and shutdown (SD), the SMSI (Strong Metal Support Interaction) effect, where the m-TiO ₂ support and Pt catalyst atoms interact strongly, is excellent. Since the catalytic insulator properties are realized, it plays a role in suppressing the electrochemical reaction of the fuel cell.

Figure 2a is a diagram for explaining the strong catalyst-support interaction (strong metal support interaction (SMSI)) mechanism in a low hydrogen environment of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention, and Figure 2b is This is a diagram to explain the hydrogen spillover mechanism in a high hydrogen environment of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention.

As shown in FIGS. 2A and 2B, the following two mechanisms are utilized to implement HOR-Selectivity, which is the hydrogen oxidation reaction of SMSI and hydrogen spillover-based catalyst (Pt/m-TiO ₂ ) for fuel cells.

1) Strong catalyst-support interaction (strong metal support interaction, SMSI)

2) Hydrogen Spillover

As shown in Figure 2a, the strong catalyst-support interaction (SMSI) between Pt and m-TiO ₂ in an Ar-purge atmosphere with low hydrogen concentration causes m-TiO ₂ to diffuse onto the Pt surface. Covers the active site of the catalyst.

As a result, as the active sites of the catalyst are blocked, the electrochemical active surface area (ECSA) decreases, and the entire surface of the catalyst is dominated by the low conductivity of m-TiO ₂ , thereby contributing to the electrochemical reaction of the fuel cell, e.g. It plays a role in suppressing oxygen reduction (ORR, Oxygen Reduction Reaction).

As shown in Figure 2b, conversely, under high hydrogen concentration, such as HOR conditions, which is a hydrogen oxidation reaction, Pt is exposed to the surface again in this reducing atmosphere.

Then, the surrounding hydrogen atoms are dissociated and adsorbed on the Pt surface in the form of protons, and then m-TiO ₂ is reduced to TiOOH by the high hydrogen concentration and the protons contained in the surrounding atmosphere.

Therefore, the insulating m-TiO ₂ layer changes into a conductive TiOOH layer according to Ti(IV)O ₂ +H ⁺ +e ^- →Ti(Ⅲ)OOH.

The OH species formed in this reaction gradually leak out to the surrounding surface of the catalyst due to additional OH species being generated.

As a result, protons move through the Grotthuss mechanism to continuously aid reduction, and a conduction path is created on the m-TiO ₂ support through hydrogen spillover where the entire catalyst surface has conductivity. Therefore, it is possible to provide a reaction site where the electrochemical reaction of the fuel cell, for example, Hydrogen Oxidation Reaction (HOR), occurs.

In one embodiment, the SMSI and hydrogen spillover-based catalyst for fuel cells may include 100 parts by weight of the m-TiO ₂ support and 10 to 20 parts by weight of Pt catalyst atoms.

When included in the above content range, the Pt catalyst atoms are stably supported on the TiO ₂ support, resulting in excellent high potential stability of the catalyst, and the amount of expensive Pt catalyst atoms used can be minimized, resulting in excellent economic efficiency.

For example, it may include 100 parts by weight of the m-TiO ₂ support and 10 parts by weight of Pt catalyst atoms.

Under the above conditions, the average size of the Pt catalyst atoms may be 2 to 10 nm.

The size may mean the maximum length of the Pt catalyst atom.

When included in the above content range, the Pt catalyst atoms are stably supported on the m-TiO ₂ support, and can exhibit insulator properties under a low hydrogen environment and excellent electrical conductivity under a high hydrogen environment.

The Pt catalyst synthesized on the surface of m-TiO ₂ , which is the SMSI and hydrogen spillover-based catalyst for fuel cells of the present invention, achieved initial performance equal to or higher than that of the membrane electrode assembly using the Pt catalyst synthesized on the surface of the existing carbon support. , which has the effect of improving durability in the fuel cell vehicle simulation system.

Electrodes containing SMSI and hydrogen spillover-based catalysts for fuel cells

Another aspect of the present invention relates to an electrode for a fuel cell including the SMSI for a fuel cell and a hydrogen spillover-based catalyst.

Membrane electrode assembly containing SMSI and hydrogen spillover-based catalyst for fuel cells

Another aspect of the present invention relates to a membrane electrode assembly including the SMSI for fuel cells and a hydrogen spillover-based catalyst.

In one embodiment, the membrane electrode assembly includes an anode; cathode; and an electrolyte membrane formed between the anode and the cathode, wherein the anode includes the SMSI for the fuel cell and a hydrogen spillover-based catalyst.

The electrolyte membrane is included for diffusion of reaction products and ions, and may include a conventional membrane. For example, the electrolyte membrane may be made of sulfonated hydrocarbon polymers, perfluorinated polymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyether ketone polymers, polyether-ether ketone polymers, and polyphenyl. It may contain one or more quinoxaline-based polymers. In one embodiment, the sulfonated hydrocarbon-based polymer is polyarylene ether sulfone (S-PES), sulfonated polybenzimidazole (S-PBI), sulfonated polyether ketone (S-PEEK), poly (para ) It may include one or more of phenylene (S-PP), sulfonated polyimide (S-PI), and sulfonated polysulfone (S-PS). In one embodiment, the perfluorinated polymer is Nafion (DuPont), Flemion (Asahi Glass), Asiplex (Asahi Chemical), Dow It may include one or more of Bion (Aquivion, Solvay).

Fuel cells containing SMSI and hydrogen spillover-based catalysts for fuel cells

Another object of the present invention relates to a fuel cell including the SMSI for fuel cells and a hydrogen spillover-based catalyst.

The fuel cell may include the membrane electrode assembly. In one embodiment, a gas diffusion layer and a separator plate may be sequentially formed on both sides of the cathode and anode of the membrane electrode assembly, respectively.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and should not be construed as limiting the present invention in any way. Any information not described here can be technically inferred by anyone skilled in the art, so description thereof will be omitted.

Examples and Comparative Examples

Example

SMSI and hydrogen spillover-based catalyst for fuel cells Pt/m-TiO ₂ manufacturing

The SMSI and hydrogen spillover-based catalyst for fuel cells of the present invention contains Pt catalyst atoms with an average size of 2 to 10 nm on an m-TiO ₂ support, and contains 10 weight of Pt catalyst atoms based on 100 parts by weight of the m-TiO ₂ support. The catalyst was prepared as follows.

First, 1.6 g of Pluronic F127, 2 mL of acetic acid, 3 mL of HCl, and 30 mL of THF were mixed and stirred vigorously.

Next, 3 mL of titanium butoxide (TBOT) was dropped into the solution, and then 0.2 mL of H ₂ O was added dropwise.

After vigorous stirring for 1 hour, the solution was dried at 50°C to obtain a gel-like sample.

4 g of the resulting sample was transferred to a 100 mL Teflon-lined autoclave and heated to 70°C in a box furnace (5°C/min for 24 hours).

The product was collected by centrifugation at 6,000 rpm, washed with water and ethanol, and dried in an oven at 85°C.

Finally, the resulting powder was annealed at 350°C in Ar atmosphere (1°C/min for 3 hours) and then calcined at 400°C in air atmosphere (1°C/min for 3 hours).

Then, Pt NPs were synthesized separately using the ethylene glycol method.

In summary, 0.5 g of H ₂ PtCl ₆ *6H ₂ O and 0.399 g of NaOH were dissolved in 50 mL of ethylene glycol solvent and stirred to obtain a homogeneous solution.

The solution was purged with Ar for 1 hour, then heated to 160°C and maintained in Ar atmosphere for 3 hours.

The obtained Pt NP solution was washed with 1M HCl and redispersed in acetone.

An appropriate amount of the resulting Pt NP solution was added to m-TiO ₂ dispersed in EtOH and dried at 50°C to obtain Pt/m-TiO ₂ powder.

Comparative example

Manufacture of commercial Pt/C catalyst for fuel cells

Ketjen Black (KB) and K ₂ [PtCl ₄ ] are added to water, and NaBH ₄ is added to induce a reduction reaction of Pt ²⁺ ions to generate platinum nanoparticles on C to produce SMSI and hydrogen spill for fuel cells. A conventional Pt/C catalyst was used as the over-based catalyst.

Experimental Example 1

H ₂ -TPR(H ₂ -Temperature-Programmed Reduction)

The results of H ₂ -TPR analysis conducted to investigate the reduction behavior of SMSI and hydrogen spillover-based catalyst (Pt/m-TiO ₂ ) for fuel cells and the interaction between Pt and m-TiO ₂ support are shown in Figure 3.

The degree of hydrogen consumption according to the temperature of the support C and m-TiO ₂ was observed and used as a baseline in interpreting the H ₂ -TPR results of Pt/C and Pt/m-TiO ₂ . H ₂ -TPR can reflect the effects of hydrogen reduction and hydrogen spillover during catalyst preparation.

Figure 3 is a diagram showing the results of H ₂ -TPR (H ₂ -temperature-programmed reduction) measurement to evaluate the oxidation-reduction ability of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention.

As shown in Figure 3, first, no signal peak appears in the C sample, which means that very little hydrogen is consumed for C reduction. In addition, in the case of the Pt/C catalyst, it can be confirmed that the hydrogen consumption level is 1 unit. The peak that appears in the 200°C region is the peak where Pt metal is reduced or the peak where Pt species interacts with the C support.

In contrast, if you look at the level of hydrogen consumption of Pt/m-TiO ₂ , you can see that it appears different from that of the Pt/C catalyst. In particular, in the case of the Pt/m-TiO ₂ catalyst, you can see that it shows two levels of hydrogen consumption.

The small peak that appears at 125°C is the peak of hydrogen consumption as Pt ^IV is reduced to Pt ^II or the reduction peak of Pt species due to weak interaction with the m-TiO ₂ support.

The large peak that appears in the 350°C region is the peak of reduction of Pt ^II to Pt ⁰ metal or the reduction peak of Pt species that strongly interacts with the support.

When comparing the sizes of the two peaks, it can be seen that the hydrogen consumption peak that appears in the high temperature region of 350℃ is much larger than the peak that appears in the low temperature region of 125℃. This is because most of the Pt species supported on m-TiO ₂ interact strongly with the m-TiO ₂ support.

In the case of the Pt/m-TiO ₂ catalyst, the reduction peak of Pt species appears in the high temperature range of 350°C, and it can be seen that the distribution area of the temperature of hydrogen consumption is widened.

The reason why the temperature range of the reduction peak of hydrogen widened and the maximum temperature difference of the reduction peak appeared at the same time means that m-TiO ₂ interacts more with Pt oxidation species compared to C. Hydrogen chemisorbed on Pt species easily spills over due to the enhancement effect of m-TiO compared to C.

Experimental Example 2

ECSA calculation results under low hydrogen environment start/stop (SU/SD)

For the catalysts of the above examples and comparative examples, the physical properties were measured as follows, and the results are shown in Figure 4 below. Figure 4 is a diagram showing the results of ECSA calculation under a low hydrogen environment (SU/SD) of SMSI and hydrogen spillover-based catalyst for fuel cells according to an embodiment of the present invention.

As shown in Figure 4, in the case of a commercial Pt/C catalyst, the Pt loading amount ([Pt]) of the electrode is 20 [μmcm ^-2 ], and the charge amount per unit area of hydrogen adsorbed on Pt, Q _UPD , is 3.17 [mCcm ^-2 ], the electrochemically active area (ECSA) of Pt was calculated to be 75.55 [m ² g ^-2 ], and the Pt loading of the electrode ([Pt]) was 60 [μmcm ^-2 ], per unit area of hydrogen adsorbed on Pt. From the charge Q _UPD value of 3.14 [mCcm ^-2 ], the electrochemical active area (ECSA) of Pt was calculated to be 24.93 [m ² g ^-2 ].

In contrast, in Pt/m-TiO ₂ catalyst Since the Pt loading amount of the electrode ([Pt]) is 60 [μmcm ^-2 ] and the charge per unit area of hydrogen adsorbed on Pt, Q _UPD , is 0.32 [mCcm ^-2 ], the electrochemical active area (ECSA) of Pt is 2.53[ m ² g ^-2 ] was calculated.

As a result, compared to the commercial Pt/C catalyst under a low hydrogen environment (SU/SD), the Pt/m-TiO ₂ catalyst significantly reduces the electrochemical active area (ECSA) of Pt and loses activity, resulting in unnecessary oxygen reduction reaction (ORR). ) can be suppressed.

Experimental Example 3

Experiment to verify performance durability effect under start/stop (SU/SD) conditions of polymer electrolyte membrane fuel cell

Membrane-electrode assembly (MEA) is a Nafion 1135 electrolyte membrane on one side (anode) directly coated with commercial Pt/C or manufactured SMSI and hydrogen spillover-based catalyst (Pt/m-TiO ₂ ) for fuel cells and on the other side. It was manufactured by coating the (cathode) with commercial Pt/C.

Catalyst ink is prepared by adding a certain amount of Pt/C catalyst or fuel cell SMSI and hydrogen spillover-based catalyst (Pt/m-TiO ₂ ) and Nafion to distilled water, dispersing them using an ultrasonic pulverizer for 90 seconds, and then hand-painting. It was directly coated on the electrolyte membrane.

Figure 5a is a diagram showing polarization curves of commercial Pt/C:Pt/C (anode:cathode) MEAs before and after SU/SD protocols, and Figure 5b is a diagram showing the Pt/m of an embodiment of the present invention before and after SU/SD protocols. This is a diagram showing the polarization curves of -TiO ₂ :Pt/C(anode:cathode) MEAs.

As shown in Figures 5a and 5b, in the case of commercial Pt/C:Pt/C (anode:cathode), compared to the initial stage when air flows to the anode electrode filled with hydrogen fuel in SU/SD, a hydrogen-poor environment. It was found that when the number of cycles reached 100, there was a rapid decline in performance.

On the other hand, in the case of Pt/m-TiO ₂ :Pt/C(anode:cathode) of the present invention, even if air flows to the anode electrode filled with hydrogen fuel in SU/SD, a hydrogen-poor environment, the number of cycles from the beginning is 100. It was found that equivalent performance was maintained up to .

Figure 5c is a diagram showing the results of direct measurement of the cell and electrode potential using DHE in a commercial Pt/C:Pt/C(anode:cathode), and Figure 5d is a diagram showing the results of direct measurement of the cell and electrode potential of the Pt/m-TiO ₂ :Pt/C(anode) of the present invention. :cathode) This is a diagram showing the results of direct measurement of cell and electrode potential using DHE.

As shown in Figures 5c and 5d, in the case of commercial Pt/C:Pt/C(anode:cathode), the potential of the cathode electrode when air flows to the anode electrode filled with hydrogen fuel in SU/SD, a hydrogen-poor environment. increases rapidly to 1.4V and then slowly decreases, while in the case of Pt/m-TiO ₂ :Pt/C(anode:cathode) of the present invention, air is supplied to the anode electrode filled with hydrogen fuel in SU/SD, a hydrogen-poor environment. Even if it flows, a sudden increase in the cathode electrode potential does not occur because insulator characteristics are realized by strong catalyst-support interaction (SMSI) between the m-TiO ₂ support and the Pt catalyst atoms.

Figure 5e is a cross-sectional SEM image of a membrane electrode assembly cathode before and after the SU/SD durability test in commercial Pt/C:Pt/C (anode:cathode), and Figure 5f is a cross-sectional SEM image of the Pt/m-TiO ₂ of the present invention: This is a diagram showing a cross-sectional SEM image of the membrane electrode assembly cathode before and after the SU/SD durability test in Pt/C (anode:cathode).

As shown in Figures 5e and 5f, in the case of commercial Pt/C:Pt/C(anode:cathode), the carbon support is oxidized in SU/SD, a hydrogen-poor environment, to an initial temperature of 9.88% by carbon oxidation reaction (COR). There was a problem in that the thickness of the catalyst layer and membrane electrode assembly decreased from μm to 5.36 μm, and the performance of the electrode decreased.

On the other hand, in the case of Pt/m-TiO ₂ :Pt/C(anode:cathode) of the present invention, the thickness of the cathode of the membrane electrode assembly is maintained without a significant decrease from the initial 9.19 μm to 8.71 μm of the thickness of the catalyst layer and membrane electrode assembly. It was found that this suppresses the carbon oxidation reaction (COR) of the cathode electrode even in a hydrogen-deficient environment at the anode electrode, improving durability compared to commercial Pt/C:Pt/C (anode:cathode).

The features, structures, effects, etc. described in the embodiments above are included in at least one embodiment of the present invention and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. illustrated in each embodiment can be combined or modified and implemented in other embodiments by a person with ordinary knowledge in the field to which the embodiments belong. Therefore, contents related to such combinations and modifications should be construed as being included in the scope of the present invention.

10: cathode 11: support
12: active material 20: anode
30: electrolyte membrane 1000: fuel cell

Claims (11)

delete delete delete Noncarbon and mesoporous TiO ₂ support (hereinafter, m-TiO ₂ ); and
Including a Pt catalyst atom supported on the m-TiO ₂ support,
A first mechanism in which insulator properties are realized by strong catalyst-support interaction (SMSI) of the m-TiO ₂ support and the Pt catalyst atoms under a low hydrogen environment;
Utilizing a second mechanism in which a conduction path is implemented on the m-TiO ₂ support through hydrogen spillover, in which hydrogen activated by the Pt catalyst atoms diffuses under a high hydrogen environment,
The low hydrogen environment is defined as the start-up/shut-down (SU/SD) environment of the engine, and the high hydrogen environment is defined as the normal operating environment of the engine,
SMSI and hydrogen spillover-based catalyst for fuel cells, comprising 10 parts by weight of Pt catalyst atoms based on 100 parts by weight of the m-TiO ₂ support. According to paragraph 4,
SMSI and hydrogen spillover-based catalyst for fuel cells, wherein the conduction path is formed by the following reaction formula 1.
[Scheme 1]
Ti(IV)O ₂ +H ⁺ +e ^- →Ti(Ⅲ)OOH delete delete According to paragraph 4,
SMSI and hydrogen spillover-based catalyst for fuel cells, characterized in that the average size of the Pt catalyst atoms is 2 to 10 mm. An electrode for a fuel cell comprising the SMSI for a fuel cell according to any one of claims 4, 5, and 8 and a hydrogen spillover-based catalyst. anode; cathode; and an electrolyte membrane formed between the anode and the cathode,
The anode is a membrane electrode assembly comprising the SMSI for fuel cells and the hydrogen spillover-based catalyst of any one of claims 4, 5, and 8. A fuel cell comprising the SMSI for fuel cells of any one of claims 4, 5, and 8 and a hydrogen spillover-based catalyst.