KR102317733B1 - Catalyst compound, water electrolyser comprising thereof and synthetic method of catalyst compound - Google Patents

Abstract

According to one embodiment of the present invention, there is provided a catalyst compound represented by the following formula (1).
[Formula 1]
M-Ir _a Ru _b O _x
In Formula 1, M is at least one selected from alkali metals and alkaline earth metals, a and b are numbers between 0 and 1, and X is a number greater than 0.

Description

Catalyst compound, a water electrolyzer containing the catalyst compound, and a method for preparing a catalyst compound

The present invention relates to a catalyst for accelerating an oxygen evolution reaction and a method for preparing the catalyst.

Hydrogen and oxygen are widely used in many fields. Among the equipment for producing hydrogen and oxygen, the water electrolyzer has a great advantage of being environmentally friendly in that it can generate hydrogen and oxygen using electricity. Accordingly, many technologies are being researched and developed in relation to a water electrolyzer using electricity.

A water electrolyzer using electricity has the advantage of being eco-friendly, but has a big disadvantage that its efficiency may be relatively low. Accordingly, a relatively large amount of electricity is consumed in the process of producing hydrogen and oxygen, and when considering the resources required for electricity production, there is a problem that the eco-friendly advantage of the water electrolyzer may be lost.

Accordingly, the need for a highly efficient water electrolyzer capable of producing a lot of hydrogen and oxygen with relatively little electricity is increasing.

An object of the present invention is to provide a catalyst having high catalytic activity for oxygen evolution and excellent durability.

Another object of the present invention is to provide a manufacturing method capable of mass-producing a catalyst by simplifying the manufacturing process.

According to an embodiment of the present invention, a catalyst compound represented by the following Chemical Formula 1 is provided.

[Formula 1]

M-Ir _a Ru _b O _x

In Formula 1, M is at least one selected from alkali metals and alkaline earth metals, a and b are numbers between 0 and 1, and X is a number greater than 0.

According to an embodiment of the present invention, a catalyst compound comprising lithium (Li) is provided.

According to an embodiment of the present invention, a molar ratio of lithium (Li): iridium (Ir): ruthenium (Ru) in the catalyst compound is 3:5:2, there is provided a catalyst compound.

According to one embodiment of the present invention, the ratio of the mass of the mass of iridium contained in the catalyst compound to the metal M (mass of iridium/mass of metal M) is 40 to 50, there is provided a catalyst compound.

According to an embodiment of the present invention, a catalyst compound having amorphous properties is provided.

According to an embodiment of the present invention, the anode in which the oxygen evolution reaction occurs; a cathode provided spaced apart from the anode; and an electrolyte layer provided between the cathode and the anode, wherein a catalyst compound is provided on the anode, and the catalyst compound is represented by Formula 1 below.

[Formula 1]

M-Ir _a Ru _b O _x

In Formula 1, M is at least one selected from alkali metals and alkaline earth metals, a and b are numbers between 0 and 1, and X is a number greater than 0.

According to an embodiment of the present invention, the anode in which the oxygen evolution reaction occurs; a cathode provided spaced apart from the anode; and an electrolyte layer provided between the cathode and the anode, wherein a catalyst compound is provided on the anode, and the catalyst compound is provided in a water electrolyzer represented by Chemical Formula 1 below.

[Formula 1]

M-Ir _a Ru _b O _x

In Formula 1, M is at least one selected from alkali metals and alkaline earth metals, a and b are numbers between 0 and 1, and X is a number greater than 0.

According to an embodiment of the present invention, there is provided a water electrolyzer, wherein M in Formula 1 is lithium (Li), and the catalyst compound activates the oxygen evolution reaction.

According to an embodiment of the present invention, a molar ratio of lithium (Li): iridium (Ir): ruthenium (Ru) in the catalyst compound is 3:5:2, a water electrolyzer is provided.

According to an embodiment of the present invention, a first step of mixing the iridium precursor and the ruthenium precursor; a second step of adding an alkali metal hydroxide or alkaline earth metal hydroxide to the product of the first step; a third step of heating the second step product; and a fourth step of washing, filtering, and drying the third step product, wherein the fourth step product is a catalyst compound represented by the following formula (1).

[Formula 1]

M-Ir _a Ru _b O _x

In Formula 1, M is at least one selected from alkali metals and alkaline earth metals, a and b are numbers between 0 and 1, and X is a number greater than 0.

According to an embodiment of the present invention, a weight ratio of the iridium precursor and the ruthenium precursor in the first step is 1:1, a method for preparing a catalyst compound is provided.

According to an embodiment of the present invention, the ratio of the sum of the weights of the iridium precursor and the ruthenium precursor added in the first step to the weight of the alkali metal hydroxide or alkaline earth metal hydroxide added in the second step is 1:10 A method for preparing a phosphorus, catalyst compound is provided.

According to an embodiment of the present invention, in the second and third steps, the iridium precursor and the ruthenium precursor are reacted with the alkali metal hydroxide or alkaline earth metal hydroxide, and provided in the form of a hydroxide, a method for preparing a catalyst compound is provided .

According to an embodiment of the present invention, the alkali metal hydroxide or alkaline earth metal hydroxide includes lithium hydroxide (LiOH), a method for preparing a catalyst compound is provided.

According to one embodiment of the present invention, it is possible to provide a catalyst having high catalytic activity for oxygen evolution and excellent durability.

In addition, according to an embodiment of the present invention, it is possible to provide a manufacturing method capable of mass-producing a catalyst.

1 is a perspective view showing a water electrolyzer according to an embodiment of the present invention.
2 is a graph showing the discharge efficiency of an electrode including a catalyst compound according to Examples and Comparative Examples of the present invention.
3 is a graph showing the durability of catalyst compounds according to Examples and Comparative Examples of the present invention.
4 is an X-ray powder diffraction diagram of catalyst compounds according to Examples and Comparative Examples of the present invention.
5 is a flowchart illustrating a method for preparing a catalyst compound according to an embodiment of the present invention.

Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

According to an embodiment of the present invention, there is provided a catalyst compound that promotes an oxygen evolution reaction on the anode surface of a water electrolyzer. When the catalyst compound promotes the oxygen evolution reaction, the electrolysis efficiency of the water electrolyzer containing the catalyst compound can be greatly improved.

The catalyst compound may be represented by Formula 1 below. Specifically, the catalyst compound may be a ternary metal compound in which at least one metal selected from alkali metals and alkaline earth metals and iridium (Ir) and ruthenium (Ru) are combined.

[Formula 1]

M-Ir _a Ru _b O _x

In Formula 1, M is at least one selected from alkali metals and alkaline earth metals, a and b are numbers between 0 and 1, and X is a number greater than 0.

The catalyst compound may be provided on the surface of the anode of the water electrolyzer as described above to promote the following oxygen evolution reaction. The oxygen evolution reaction may include, for example, the following reaction.

Oxygen Evolution Reaction: 2H ₂ O -> 4H ⁺ + e ^- + O ₂

The catalyst compound may participate in the oxygen evolution reaction, thereby lowering the activation energy of the reaction. Accordingly, the electrolysis efficiency of the water electrolyzer may be improved.

The catalyst compound may include lithium (Li) according to an embodiment of the present invention. Specifically, the catalyst compound may be a compound having Formula 1-1 below.

[Formula 1-1]

Li-Ir _a Ru _b O _x

In Formula 1-1, a and b are numbers between 0 and 1, and X is a number greater than 0.

Accordingly, the catalyst compound may be a ternary metal compound in which at least one metal selected from alkali metals and alkaline earth metals and iridium (Ir) and ruthenium (Ru) are combined. The catalyst compound according to an embodiment of the present invention includes lithium (Li), iridium (Ir), and ruthenium (Ru), and thus has high activity for oxygen evolution and excellent durability. Specifically, in the case of a conventional catalyst containing ruthenium (Ru), although the activity for the oxygen evolution reaction is excellent, there is a problem that metal elution occurs in the electrolyte. Although the activity of the catalyst is relatively low, by using iridium (Ir) together with the catalyst, which can prevent the problem of metal elution, the problem of deterioration in durability of the conventional catalyst can be solved. In addition, lithium (Li) used together with ruthenium (Ru) and iridium (Ir) in the catalyst compound changes the iridium and ruthenium precursors to a hydroxide state during catalyst synthesis to increase the activity and durability of the catalyst.

Accordingly, the catalyst compound uses iridium (Ir) and lithium (Li) to solve the metal elution problem of the ruthenium (Ru) catalyst, while using lithium (Li) together to prevent degradation of the catalyst activity due to iridium (Ir). can

The catalyst compound may have a molar ratio of lithium (Li): iridium (Ir): ruthenium (Ru) of 3:5:2. In addition, the mass ratio of the mass of iridium contained in the catalyst compound to lithium (mass of iridium/mass of lithium) may be about 40 to about 50. When the catalyst compound has a composition within the above-mentioned range, the catalyst compound can exhibit excellent catalytic activity and durability.

In the above, the composition of the catalyst compound according to an embodiment of the present invention has been described. Hereinafter, the structure of the water electrolyzer including the catalyst compound according to an embodiment of the present invention and the function of the catalyst compound in the water electrolyzer will be looked at in more detail.

1 is a perspective view showing a water electrolyzer according to an embodiment of the present invention.

The water electrolyzer 1000 according to FIG. 1 is a device capable of performing electrolysis of water. The water electrolyzer 1000 according to an embodiment of the present invention includes the catalyst compound described above. Therefore, the description of the catalyst compound will be omitted below in order to avoid duplication of content.

The water electrolyzer 1000 includes an anode 10 , a cathode 20 , and a separator 30 .

The anode 10 is a place where the oxygen evolution reaction occurs, as discussed above. The oxygen evolution reaction occurring in the anode 10 may include the following reaction.

Oxygen evolution reaction: 2H ₂ O → 4H ⁺ + 4e ^- + O ₂

A catalyst compound is provided on the anode 10 in order to promote the above-described oxygen evolution reaction occurring in the anode 10 . The catalyst compound promotes the reaction by lowering the activation energy of the above-mentioned reaction. Accordingly, the efficiency of the water electrolyzer 1000 may be improved.

A cathode 20 is provided in the water electrolyzer 1000 in a spaced apart form from the anode 10 .

At the cathode 20 , a hydrogen evolution reaction may occur. The hydrogen evolution reaction may include the following reactions.

Hydrogen evolution: 4H ⁺ + 4e ^- → 2H ₂

A separator 30 is provided between the cathode 20 and the anode 10 .

The separation membrane 30 may prevent the hydrogen gas generated from the cathode 20 and the oxygen gas generated from the anode 10 from mixing.

According to an embodiment of the present invention, the catalyst compound provided on the anode 10 promotes/activates the oxygen evolution reaction occurring in the anode 10, and thus the water electrolyzer efficiency can be improved.

The external power source 40 applies power to the water electrolyzer 1000 . The external power source 40 is respectively connected to the anode 10 and the cathode 20 to apply a current. Oxygen generation reaction and hydrogen generation reaction may occur on the anode 10 and the cathode 20 by the external power source 40, respectively.

An electrolyte may be provided inside the water electrolyzer 1000 . The electrolyte may be provided in the form of immersing the anode 10 and the cathode 20 . The type of electrolyte may be varied. For example, the electrolyte may be water (H ₂ O) or an aqueous polymer solution.

In the above, the composition of the catalyst compound and the composition of the water electrolyzer including the catalyst compound according to an embodiment of the present invention have been described. However, the water electrolyzer disclosed above is only an exemplary form, and a person skilled in the art may use various types of water electrolyzer within the scope of utilizing the catalyst compound according to the present invention.

Hereinafter, the advantageous effects of the catalyst compound according to an embodiment of the present invention will be examined by comparing the test data of Examples and Comparative Examples.

2 is a graph showing the discharge efficiency of an electrode including a catalyst compound according to Examples and Comparative Examples of the present invention.

2 shows the discharge efficiency of the electrodes including the catalyst compounds of Example 1 and Comparative Examples 1, 2, and 3 as a graph of current density versus voltage.

Compositions of the catalyst compounds according to Example 1 and Comparative Examples 1 to 3 are shown in Table 1 below.

note catalyst composition Example 1 Li-Ir _0.5 Ru _0.5 O _x Example 2 Li-Ir _0.3 Ru _0.7 O _x Comparative Example 1 Commercial IrO2 (TKK-IrOx) Comparative Example 2 Li-IrOx Comparative Example 3 Li-RuOx

The catalyst compound of Example 1 was prepared by adding an iridium precursor and a ruthenium precursor in a ratio of 5:5, _{mixing with an excess of sodium nitrate (NaNO 3} ), and then adding an excess of lithium hydroxide again.

The catalyst compound of Example 2 was prepared in the same manner as the catalyst compound of Example 1, except that the iridium precursor and the ruthenium precursor were added in a ratio of 3:7.

As the catalyst compound of Comparative Example 1, a commercially available IrO ₂ catalyst was used (TKK Corporation). In addition, the catalyst compound of Comparative Example 2 was composed of lithium (Li) and iridium (Ir), and the catalyst compound of Comparative Example 3 was composed of lithium (Li) and ruthenium (Ru).

Examples 1, 2, and Comparative Examples 1 to 3, comprising an anode comprising the catalyst compound, and a half cell (Half Cell) having only the anode was evaluated for electrical properties.

After providing the catalyst compounds of Examples and Comparative Examples to the anode of the half cell, electrical properties were tested. Current density according to voltage of the half-cell including the catalyst compound according to Examples and Comparative Examples was evaluated.

As can be seen from FIG. 2 , it can be seen that the half-cells according to Examples 1 and 2 have higher current densities than the half-cells according to Comparative Examples 1 to 3. Therefore, it can be seen that the active effect of the catalyst compound according to the present invention on the oxygen evolution reaction is excellent.

3 is a graph showing the durability of catalyst compounds according to Examples and Comparative Examples of the present invention.

The data shown in FIG. 3 are shown together in Table 2. Examples 1 and 2 and Comparative Examples 1 to 3 shown in FIG. 3 and Table 2 are the same as the half cells of the Example and Comparative Example described in FIG. 2 above.

Voltage
(Measured at 10mA / cm ²⁾ durability
(voltage difference at 10mA/cm ^{2 after ADT)} Example 1 1.50V 16mV Example 2 1.49V 41mV Comparative Example 1 1.56V 16mV Comparative Example 2 1.53V 6mV Comparative Example 3 - -

As can be seen in FIG. 3 and Table 2, the half-cells according to Examples 1 and 2 had measured voltages of 1.50V and 1.49V, respectively, which was lower than that of the half-cells according to Comparative Example. This means that the catalyst compound according to the embodiment lowered the potential energy for the hydrolysis reaction. In addition, this means that the catalyst compound according to the embodiment promotes the oxygen evolution reaction occurring at the anode.

Next, durability of catalyst compounds according to Examples and Comparative Examples was evaluated. ^{For durability, measure the voltage at 10 mA/cm 2} immediately after the half-cell is manufactured, then measure the voltage after applying a current of 10 mA/cm ² to the half-cell for 2 hours, and then calculate the difference between the voltages measured at the two time points was evaluated by doing (ADT test).

As a result of the evaluation, it was confirmed that the voltage difference between the catalyst compound of Example 1 before and after the ADT test was relatively small. This shows that even after the ADT test, the catalyst functions substantially without degradation.

2 to 3 , it can be confirmed that the catalyst compound according to an embodiment of the present invention exhibits excellent catalytic activity and durability when the weight ratio of the iridium precursor and the ruthenium precursor is mixed at 1:1. . In this case, the prepared catalyst compound may have a molar ratio of lithium (Li): iridium (Ir): ruthenium (Ru) of 3:5:2. In addition, the mass ratio of the mass of iridium contained in the catalyst compound to lithium (mass of iridium/mass of lithium) may be about 40 to about 50. When the catalyst compound has a composition within the above-mentioned range, the catalyst compound can exhibit excellent catalytic activity and durability.

4 is an X-ray powder diffraction diagram of catalyst compounds according to Examples and Comparative Examples of the present invention.

As a result of examining FIG. 4 , it can be seen that the catalyst compound according to the embodiment of the present invention has higher amorphism than the catalyst compound according to the comparative example. Accordingly, it can be seen that the catalyst compound according to an embodiment of the present invention has the form of an amorphous ternary metal compound, which contributes to high catalytic activity and durability such as elution prevention.

In this case, the fact that the catalyst compound has amorphous properties means that the ternary metal atoms constituting the catalyst compound have an irregular arrangement in which they are not regularly arranged. In addition, the fact that the catalyst compound is amorphous does not mean that there is no region having a crystal structure in the catalyst compound. The catalyst compound includes both a crystalline region in which ternary metal atoms are regularly arranged and an amorphous region in which ternary metal atoms are not arranged regularly.

In the above, the composition of the catalyst compound according to an embodiment of the present invention and advantageous effects thereof have been examined. Hereinafter, a method for preparing a catalyst compound according to an embodiment of the present invention will be described in more detail.

5 is a flowchart illustrating a method for preparing a catalyst compound according to an embodiment of the present invention.

According to FIG. 5 , an iridium precursor and a ruthenium precursor are first mixed to prepare a catalyst compound (first step, S100 ). The iridium precursor and the ruthenium precursor may be mixed in a ratio of 1:1 or 3:7 by weight as described above. By mixing the iridium precursor and the ruthenium precursor within the above range, it is possible to prepare a catalyst compound having high catalytic activity and excellent durability. The contents of this are the same as described above. In addition, the iridium precursor and the ruthenium precursor may be mixed and stirred in the presence of water and sodium nitrate.

Next, an alkali metal hydroxide or alkaline earth metal hydroxide is added to the mixture generated in the first step (S100) (S200). At this time, the alkali metal hydroxide or alkaline earth metal hydroxide may be, for example, lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium hydroxide (NaOH). When lithium hydroxide is added, lithium hydroxide may be added in excess compared to the iridium precursor and the ruthenium precursor. For example, the addition amount of lithium hydroxide may be about 10 times the addition amount of the iridium precursor and the ruthenium precursor by weight. By adding an excessive amount of lithium hydroxide, the conversion of the iridium precursor and the ruthenium precursor to the hydroxide form by lithium hydroxide can be more active in the next step.

Next, the mixture generated in the second step (S200) is heated (S300). The heating process may be performed over several steps. In this case, the heating process may be performed two or more times at different process temperatures. For example, the product of the second stage may first be heated in a range from about 90 degrees Celsius to about 110 degrees Celsius. During the first heating process, moisture contained in the mixture may be removed. Next, after completing the first heating process, heat treatment may be performed. The heat treatment may be performed at about 400 degrees Celsius to about 500 degrees Celsius. In the heat treatment process, lithium, ruthenium, and iridium may react with each other. For example, an iridium precursor and a ruthenium precursor may be converted into a hydroxide form by lithium hydroxide.

Next, the compound produced in step 3 is washed, filtered, and dried (S400). Washing can be performed, for example, by placing the product in distilled water and stirring. Filtration and drying may be performed using a conventionally used method, and there is no particular restriction on the method.

As described above, the catalyst compound according to an embodiment of the present invention may be prepared through mixing and heating processes. In particular, the catalyst can be mass-produced in a relatively simple process by converting the iridium precursor and the ruthenium precursor into the hydroxide form using lithium hydroxide. In addition, since the iridium precursor and the ruthenium precursor converted to the hydroxide form have amorphous properties, catalyst activity and catalyst durability may be improved.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art or those having ordinary knowledge in the technical field will not depart from the spirit and technical scope of the present invention described in the claims to be described later. It will be understood that various modifications and variations of the present invention can be made without departing from the scope of the present invention.

Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

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Claims (13)

A catalyst compound represented by the following formula (1) and accelerating the oxygen evolution reaction:
[Formula 1]
M-Ir _a Ru _b O _x
In Formula 1, M includes lithium (Li), a and b are numbers between 0 and 1,
X is a number greater than 0
The lithium converts iridium and ruthenium precursors into a hydroxide state in the process of synthesizing the catalyst compound, so that the catalyst compound has an amorphous structure. delete According to claim 1,
The molar ratio of lithium (Li): iridium (Ir): ruthenium (Ru) in the catalyst compound is 3:5:2. According to claim 1,
The ratio of the mass of the mass of iridium contained in the catalyst compound to the metal M (mass of iridium/mass of metal M) is 40-50. delete an anode where oxygen evolution occurs;
a cathode provided spaced apart from the anode; and
An electrolyte layer provided between the cathode and the anode,
A catalyst compound is provided on the anode,
The catalyst compound is represented by the following Chemical Formula 1, and lithium changes the iridium and ruthenium precursors to a hydroxide state in the process of synthesizing the catalyst compound, and the catalyst compound has an amorphous structure.
[Formula 1]
M-Ir _a Ru _b O _x
In Formula 1, M includes lithium (Li), a and b are numbers between 0 and 1, and X is a number greater than 0. 7. The method of claim 6,
M in Formula 1 is lithium (Li),
The catalyst compound activates the oxygen evolution reaction, a water electrolyzer. 7. The method of claim 6,
The molar ratio of lithium (Li): iridium (Ir): ruthenium (Ru) in the catalyst compound is 3:5:2. A first step of mixing the iridium precursor and the ruthenium precursor;
a second step of adding lithium (Li) to the first step product;
a third step of heating the second step product; and
a fourth step of washing, filtering and drying the third step product;
The fourth step product is a catalyst compound represented by the following formula (1),
The lithium changes the iridium and ruthenium precursors to a hydroxide state in the process of synthesizing the catalyst compound so that the catalyst compound has an amorphous structure.
[Formula 1]
M-Ir _a Ru _b O _x
In Formula 1, M includes lithium (Li), a and b are numbers between 0 and 1, and X is a number greater than 0. 10. The method of claim 9,
In the first step, the weight ratio of the iridium precursor and the ruthenium precursor is 1:1. 10. The method of claim 9,
The ratio of the sum of the weights of the iridium precursor and the ruthenium precursor added in the first step to the weight of the lithium hydroxide added in the second step is 1:10. 10. The method of claim 9,
In the second and third steps, the iridium precursor and the ruthenium precursor are reacted with lithium hydroxide to provide a hydroxide form. 10. The method of claim 9,
A process for preparing a catalyst compound comprising lithium hydroxide (LiOH).

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