KR102390091B1 - Development of efficient electrocatalyst using multicomponent base metal alloys - Google Patents

Abstract

The present invention provides a method for manufacturing a water electrolysis catalyst electrode made of a non-noble metal multi-component alloy, a water electrolysis catalyst electrode manufactured by the method, and a water electrolysis device including the same. The water electrolysis catalyst electrode prepared by the method of the present invention can be used as a catalyst material in the electrochemical water cracking process to produce oxygen and hydrogen.

Description

{Development of efficient electrocatalyst using multicomponent base metal alloys}

The present invention relates to a method for manufacturing a water electrolysis catalyst electrode made of a non-noble metal multi-component alloy, a water electrolysis catalyst electrode using the same, and a water electrolysis device including the same.

Recently, as the amount of hydrogen used in fuel cells is increasing, hydrogen production using renewable energy is receiving a lot of attention. In particular, various water electrolysis systems using surplus electricity from solar power generation or wind power generation facilities are being developed.

Water electrolysis is a method of producing hydrogen and oxygen by using electrons generated during the redox reaction of water. The unit cell structure of water electrolysis has a structure in which an anode and a cathode are coated on both sides of a solid polymer electrolyte membrane composed of a polymer material, which is called a membrane electrode assembly. do. Water is supplied from the anode and reacts on the catalyst electrode to generate oxygen, hydrogen ions and electrons. At the cathode, hydrogen ions passing through the solid polymer membrane combine with electrons to generate pure hydrogen. Accordingly, research on the material of the electrode for the water electrolysis catalyst is being actively conducted.

When a water electrolysis catalyst electrode is made using a metal alloy, the characteristics of the water electrolysis reaction are determined by the synergistic effect between the alloys, the change in mixing entropy, the crystal phase of the surface, and the orientation of the exposed surface. The prior art of making a water electrolysis catalyst electrode mainly utilizes a solution process such as an electrodeposition method and a hydrothermal synthesis method. However, there was a limitation in that it was difficult to accurately create an alloy of a desired composition when using a solution process.

Meanwhile, an alloy referred to as a high-entropy alloy is being developed as a new alloy system. A high-entropy alloy is a multi-element alloy of five or more elements. Even though the multi-component main elements are mixed, intermetallic compounds are not formed due to high constituent entropy, and face-centered cubic (FCC) or body-centered cubic lattice ( It means a new concept alloy composed of Body Centered Cubic (BCC).

In general, alloys are divided into high-entropy alloys, medium-entropy alloys (MEAs), and low-entropy alloys (LEAs) according to the compositional entropy (ΔSconf) according to the composition of the alloying elements, and the It is classified according to the conditions of the following formula.

[Equation 1] ΔS(LEAs) ≤ 1.0 R

[Equation 2] 1.0 R ≤ ΔS(MEAs) ≤ 1.5 R

[Equation 3] 1.6·R ≤ ΔS(HEAs)

(R: Gas constant)

In the past, the development of high-entropy alloys with the same atomic composition was actively developed, but recently, the types of high-entropy alloys with the same atomic composition showing excellent properties are quite limited, and it has been confirmed that high constitutional entropy is not a necessary condition for exhibiting excellent properties. there is. Accordingly, interest in various medium-entropy alloys is increasing.

Republic of Korea Patent No. 1950236

An object of the present invention is to provide a non-noble metal multi-component alloy having a medium entropy, an alloy that has optimal water electrolysis properties through anodization and a switched voltammetry method, and a water electrolysis catalyst electrode comprising the same will be.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

As a technical means for achieving the above technical problem, the first aspect of the present invention is to prepare a non-noble metal multi-component alloy containing cobalt, nickel, chromium and iron (S1);

After immersing the non-noble metal multi-component alloy in an electrolyte solution, applying a voltage to form a hydroxide film (S2); and

It provides a method for manufacturing a water electrolysis catalyst electrode made of a non-noble metal multi-component alloy, comprising the step (S3) of applying a cyclic voltage to the alloy on which the hydroxide film is formed.

According to one embodiment of the present application, the voltage of the step S2 is characterized in that the voltage of 50 V to 200 V.

According to another embodiment of the present invention, the cycle voltage of step S3 is characterized in that a voltage of 1.0 V to 2.0 V is periodically applied compared to the hydrogen exchange potential.

According to another embodiment of the present invention, the cyclic voltage of step S3 is characterized in that it is repeatedly applied 50 to 200 times in a cycle of 600 sec/cycle to 1800 sec/cycle.

A second aspect of the present invention provides a water electrolysis catalyst electrode made of a non-noble metal multi-component alloy, manufactured by the above method.

According to one embodiment of the present invention, the alloy is characterized in that it contains 50 to 70 atomic% of iron, 10 to 20 atomic% of cobalt, 10 to 20 atomic% of nickel, and 5 to 20 atomic% of chromium.

A third aspect of the present invention provides a water electrolysis device including the water electrolysis catalyst electrode.

According to the present invention, unlike the conventional synthesis method using a solution process, a multi-component metal alloy can be precisely cast to have a target level of mixed entropy by using the arc-melting method, and the metal alloy produced through this can be used with a high-efficiency faucet. It can be usefully used as a catalyst electrode. A metal alloy made using this has a characteristic charge transfer and diffusion rate due to entropy characteristics and lattice distortion effect due to atomic arrangement. Using this, an intermediate entropy alloy (MEA) having an optimized composition and entropy is made, and if the anodization method and the cyclic voltammetry method are continuously applied to this, a water electrolysis catalyst electrode with maximized oxygen generation characteristics can be made. Since the conventional method for synthesizing a catalyst electrode is a method of depositing or electrodepositing a new material on a substrate, there may be a problem in adhesion between the substrate and the catalyst and access at the atomic arrangement level is not possible. It has excellent stability because it is a method that can be used and a theoretical approach to the properties of the alloy is possible.

1 is a diagram showing an atomic arrangement schematic diagram of a conventional metal alloy (left) and an intermediate entropy alloy of the present invention.
2 is a view showing the results of confirming the oxygen generation characteristics according to the size of the mixed entropy and metal alloys of various compositions.
3 is a view showing the results of confirming the change in oxygen generation characteristics after applying the anodization method and the cyclic voltammetry method in the manufacturing method of the present invention.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, the terms include or have is intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features, number, step , it should be understood that it does not preclude in advance the possibility of the presence or addition of an operation, component, part, or combination thereof.

The need and interest in new and renewable energy is increasing worldwide, and hydrogen energy is particularly attracting attention, but there is a problem in that hydrogen production efficiency is not sufficient for commercialization. Accordingly, the present inventors have tried to develop a high-performance water electrolysis electrode material, and as a result, the water electrolysis electrode is connected to a solar cell and shows an efficiency of 18% or more when driven as a PV-EC system that does not require external energy, thereby completing the present invention did

Accordingly, the present invention comprises the steps of preparing a non-noble metal multi-component alloy containing cobalt, nickel, chromium and iron (S1);

After immersing the non-noble metal multi-component alloy in an electrolyte solution, applying a voltage to form a hydroxide film (S2); and

It provides a method for manufacturing a water electrolysis catalyst electrode made of a non-noble metal multi-component alloy, comprising the step (S3) of applying a cyclic voltage to the alloy on which the hydroxide film is formed.

The present invention utilizes a non-noble metal multi-component alloy as a material for a water electrolysis catalyst electrode. The non-noble metal multi-component alloy of the present invention is characterized in that it has neutral entropy. The alloy having a medium entropy means an alloy having an intermediate level of mixing entropy with a mixing entropy of 1.0R or more and 1.5R or less. As shown in FIG. 1, as compared with the atomic arrangement of the conventional metal alloy (left), it can be seen that the alloy of the present invention has a lattice distortion shape. Metal alloys have characteristic charge transfer and diffusion rates due to lattice distortion effects.

The non-precious metal multi-component alloy is manufactured using an arc-melting technique. Using the arc-melting technique, a multi-metal alloy can be precisely cast to have a desired level of mixing entropy. More specifically, after mixing the alloy materials, the step of melting; After loading the molten mixture into the arc melting chamber, filling the chamber in a vacuum state with an inert gas; After homogenization for 4 to 8 hours at 800 ~ 1400 ℃ in the chamber, performing a water quenching process at room temperature (15 ~ 35 ℃); compressing the alloy to a thickness of 0.5 to 10 mm by cold rolling after water cooling; Homogenizing the inside of the alloy through a re-homogenization process at 600 ~ 1200 ℃ 1 ~ 30 minutes; And performing a water cooling process at room temperature; may be prepared through, but is not limited thereto if the arc-melting technique is used.

In order to form a water electrolysis catalyst part on the surface of the non-noble metal multi-component alloy cast using the arc-melting technique as described above, a hydroxide film is formed in step S2. The hydroxide film is formed using an anodization technique. The anodic oxidation technique includes immersing the alloy in an electrolyte, connecting the alloy to an anode, and then applying a voltage to form a hydroxide film. The hydroxide film functions as a water electrolysis catalyst part, and unlike a conventional catalyst electrode manufactured by depositing or electrodepositing a new material on a substrate, the catalyst is formed directly on the substrate, and it can have excellent stability. . The voltage of step S2 may be applied in a range of 50 V to 200 V.

When the hydroxide film is formed, a cyclic voltammetry is applied in step S3 to increase the surface area of the hydroxide film. The cyclic voltammetry is to periodically apply a voltage, and may be to repeatedly apply a voltage of 1.0 V to 2.0 V at a cycle of 600 sec/cycle to 1800 sec/cycle 50 to 200 times.

Accordingly, the present invention can provide a water electrolysis catalyst electrode made of a non-noble metal multi-component alloy prepared by the above method.

The alloy may include 50 to 70 atomic% of iron, 10 to 20 atomic% of cobalt, 10 to 20 atomic% of nickel, and 5 to 20 atomic% of chromium. The alloy may further include unavoidable impurities, and the cobalt and nickel may be included in substantially the same ratio. Preferably, as an alloy having an excellent oxygen evolution reaction, an alloy containing 55 to 65 atomic % of iron, 10 to 20 atomic % of cobalt, 10 to 20 atomic % of nickel, and 5 to 15 atomic % of chromium may be used, more preferably Preferably, an alloy containing 58 to 62 atomic% of iron, 12 to 17 atomic% of cobalt, 12 to 17 atomic% of nickel, and 7 to 12 atomic% of chromium may be used.

In an embodiment of the present invention, alloys of various compositions were manufactured through an arc melting method. As a result, it was confirmed that the metal alloy having the above-described atomic ratio has oxygen evolution reaction characteristics. Accordingly, a hydroxide film was formed using an anodic oxidation technique to form a water electrolytic catalyst part on the alloy, and the surface area of the hydroxide film was improved through cyclic voltammetry. As a result, excellent oxygen generation properties were confirmed in the alloy prepared by the production method of the present invention, and it was confirmed that the alloy of the present invention can be usefully used as a water electrolysis catalyst electrode.

Hereinafter, preferred embodiments of the present invention will be described so that those of ordinary skill in the art can easily implement them with reference to the accompanying drawings. In addition, in the description of the present invention, if it is determined that a detailed description of a related known function or a known configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, some features presented in the drawings are enlarged, reduced, or simplified for ease of description, and the drawings and components thereof are not necessarily drawn to scale. However, those skilled in the art will readily understand these details.

Example 1. Preparation of alloy for high-efficiency water electrolysis catalyst electrode

Fe-based quaternary metal alloy (Fe _57.5 (CoNi) _32.5 Cr ₁₀ , Fe ₆₀ (CoNi) ₃₀ Cr ₁₀ , Fe _62.5 (CoNi) ) _27.5 Cr ₁₀ ) and CoCrFeMnNi and CoCrNi as controls were prepared by arc melting, respectively. First, the metal alloy of the above configuration was mixed and melted, and the molten alloy was charged into the arc melting chamber in a vacuum state. An inert gas was filled in the chamber, and after homogenization at 1100° C. for 6 hours, a water quenching process was performed at room temperature. After that, the thickness of the alloy was compressed to 1.5 mm by cold rolling, and the inside of the alloy was homogenized through a re-homogenization process at 800 °C for 10 minutes. Thereafter, an alloy was prepared by performing a water cooling process at room temperature.

Mixing entropy values of the metal alloys were calculated through thermodynamic calculation as shown in Table 1 below.

metal composition ΔS Fe _57.5 (CoNi) _32.5 Cr ₁₀ 1.139R Fe ₆₀ (CoNi) ₃₀ Cr ₁₀ 1.106R Fe _62.5 (CoNi) _27.5 Cr ₁₀ 1.07R CoCrFeMnNi 1.609R CoCrNi 1.098R

In order to evaluate the oxygen evolution reaction characteristics of the prepared metal alloy, water electrolysis characteristics were evaluated and shown in FIG. 2 . At this time, it was confirmed that the overvoltage at the point of the current density of 10mA ^-2 was 358-467 mV for the oxygen evolution reaction, respectively, and the characteristic was maintained constant even after repeated measurements. Through this, it was confirmed that the Fe ₆₀ (CoNi) ₃₀ Cr ₁₀ alloy had the best oxygen generation characteristics.

Example 2. Formation of a hydroxide film

In order to form a hydroxide film, which is a representative water electrolysis catalyst, on the surface of the Fe ₆₀ (CoNi) ₃₀ Cr ₁₀ alloy and at the same time increase the surface area, an anodization technique was used to primarily increase the oxygen generation characteristics of the alloy. In order to maximize the characteristics of the cyclic voltammetry was applied.

For anodization, Fe ₆₀ (CoNi) ₃₀ Cr ₁₀ alloy was put in an electrolytic cell and a voltage was applied to form a hydroxide film. Using ethylene glycol as an electrolyte, 3 wt% of ammonium fluoride and 3 vol% of purified water were added to prepare an anodizing solution. Using a platinum electrode as a counter electrode, the alloy was put into an electrolyzer, and a voltage of 200 V was applied for 30 sec.

After forming the hydroxide film, the surface area was improved by cyclic voltammetry. In the cyclic voltammetry, platinum was used as a counter electrode, 3M Ag/Agcl was used as a reference electrode, and 1N NaOH was used as an electrolyte. After that, the hydrogen reduction potential range of 1 V to 2 V was repeated 100 times at 1200 sec/cycle.

At this time, the alloy in which neither anodization nor cyclic voltammetry is applied (Bare), an alloy in which only anodization is applied (Anodized), and an alloy to which both anodization and cyclic voltammetry are applied (CV activated) The current density was measured and shown in FIG. 3 .

As a result, it was confirmed that the overvoltage at the point where the current density of the oxygenation reaction was 10mA ^-2 decreased from the existing 358 mV to 290 mV after the anodization method and 184 mV after the cyclic voltammetry method.

The present invention was carried out with the support of the "Heterojunction nanostructured photoelectrode material development for solar water splitting" project with the financial resources of Korea Hydro & Nuclear Power Co., Ltd. (0543-20190019).

As a specific part of the present invention has been described in detail above, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. will be. Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims (7)

Preparing a non-noble metal multi-component alloy containing cobalt, nickel, chromium and iron (S1);
After immersing the non-noble metal multi-component alloy in an electrolyte solution, applying a voltage to form a hydroxide film (S2); and
A method for manufacturing an electrolytic catalyst electrode comprising a non-noble metal multi-component alloy, comprising the step (S3) of applying a cyclic voltage to the alloy on which the hydroxide film is formed.
According to claim 1,
The voltage of step S2 is a voltage of 50 V to 200 V, a method for manufacturing a water electrolysis catalyst electrode comprising a non-noble metal multi-component alloy.
According to claim 1,
The cyclic voltage of step S3 is that a voltage of 1.0 V to 2.0 V is applied periodically.
According to claim 1,
The cyclic voltage of step S3 is to be repeatedly applied 50 to 200 times with a cycle of 600 sec/cycle to 1800 sec/cycle, a method for manufacturing a water electrolysis catalyst electrode comprising a non-noble metal multi-component alloy.
A water electrolysis catalyst electrode comprising a non-noble metal multi-component alloy prepared by the method of claim 1,
The non-noble metal multi-component alloy has an entropy of 1.0R or more and 1.5R or less, and has a lattice distortion shape, a water electrolysis catalyst electrode comprising a non-noble metal multi-component alloy.
6. The method of claim 5,
The alloy is 50 to 70 atomic% of iron, 10 to 20 atomic% of cobalt, 10 to 20 atomic% of nickel, and 5 to 20 atomic% of chromium, the water electrolysis catalyst electrode comprising a non-noble metal multi-component alloy.
A water electrolysis device comprising the water electrolysis catalyst electrode of claim 5 .

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