KR20240083831A - Catalyst electrodes for electrolytes and its manufacturing methods - Google Patents

Abstract

The present invention relates to metal foam; MXene formed on the metal foam; and a transition metal sulfide formed on the MXene. It relates to a catalyst electrode for an electrolyzer and a method for manufacturing the same. Using the catalyst electrode for an electrolyzer of the present invention, high purity hydrogen can be produced, and improved electrochemical catalyst activity can be exhibited in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and further, the present invention Catalytic electrodes for electrolyzers can help reduce material and process costs due to low catalyst loading, low operating temperature, and use of non-precious metal catalysts.

Description

Catalyst electrode for electrolyzer and method of manufacturing same {CATALYST ELECTRODES FOR ELECTROLYTES AND ITS MANUFACTURING METHODS}

The present invention relates to a catalyst electrode for an electrolyzer and a method of manufacturing the same. Specifically, it relates to a catalyst electrode that can be used in an electrolyzer that generates hydrogen through electrolysis of water and a method of manufacturing the same.

Since the Industrial Revolution, as energy demand has soared, the use of fossil fuels has been explosively increasing. Excessive consumption of fossil fuels releases harmful gases such as nitrogen oxides, sulfur dioxide, carbon dioxide, and carbon monoxide into the atmosphere, causing environmental pollution and respiratory diseases, and accelerating the problem of global warming due to carbon dioxide emissions. Therefore, the development of new and renewable energy such as solar energy, wind power, hydrogen energy, and fuel cells is necessary to replace fossil fuels. In particular, hydrogen energy has a higher energy density (~120 MJ/kg) than fossil fuels, is non-toxic, and is classified as an eco-friendly clean energy resource that does not produce pollutants in combustion reactions. Hydrogen is contained in water and hydrocarbons, which are the most abundant elements on Earth. Therefore, hydrogen energy can be continuously produced and processed on a large scale from various sources and can be used as a sustainable energy resource.

Hydrogen energy is produced by various methods, such as steam reforming of natural gas, pyrolysis of water, electrolysis of water, and photolysis processes and biomass. Most of the methods used to produce hydrogen are produced through steam reforming of natural gas, so CO and CO ₂ are accompanied as reaction by-products during the process, causing problems such as low reactivity and environmental pollution. There is. Therefore, water electrolysis technology, which electrolyzes water to generate hydrogen in an environmentally friendly way, has recently been attracting attention. In the electrolysis of water, a reduction reaction occurs at the anode and an oxidation reaction occurs at the cathode, and this oxidation-reduction reaction occurs in an electrolyzer for water electrolysis. The hydrogen produced at the anode of the electrolyzer is of very high purity, up to >99.999%, and offers the advantage of being produced in a pollution-free manner. Additionally, when the water electrolysis system is combined with other renewable energy power systems, it can provide stable energy.

Depending on the type of electrolyte, water electrolysis systems are divided into alkaline electrolysis, proton exchange membrane (PEM) water electrolysis, and anion exchange membrane (AEM) water electrolysis. Among them, the currently most commercialized water electrolysis technologies are alkaline water electrolysis and PEM water electrolysis.

First, in alkaline water electrolysis, nickel-based oxide and cobalt-based oxide are generally used as cathode and anode materials, respectively, and 30-40% KOH is often used as the liquid electrolyte. Alkaline water electrolysis exhibits a current density of about 400 mA/cm ² , a relatively low operating temperature of 70-90 °C, and a conversion efficiency of 60-80% at cell voltages in the range of 1.85-2.2 V. Alkaline water electrolysis has the advantage of not requiring a precious metal catalyst and operating at relatively low temperatures. However, there is a problem that the hydrogen production rate is low and the size of the design system for hydrogen production must be large. In addition, alkaline electrolyte in liquid state is prone to leakage, and electrolyte leakage increases resistance, reduces current density, and has various problems such as reduced efficiency of water electrolysis.

PEM water electrolysis is a water electrolysis system that uses a solid membrane such as Nafion as an electrolyte instead of a liquid electrolyte. A solid membrane occupies a smaller electrolyte volume than a liquid electrolyte, so it can reduce the size of the overall system and provide high current density. Additionally, in order to withstand strong corrosion in an acidic environment, noble metals such as IrO ₂ and Pt are mainly used as cathode and anode catalysts, respectively. PEM electrolysis has an operating temperature of 90°C, a current density of 2000 mA/cm ² at about 2.1 V, and the hydrogen and oxygen production reaction is faster than alkaline electrolysis. Additionally, one of the advantages of PEM electrolysis is that high pressures can be used at the anode, while the cathode can operate at standard atmospheric pressure. However, noble metals such as IrO2 and Pr used in PEM water electrolysis and Nafion used as a membrane are expensive, which is the biggest limitation to the commercialization of PEM water electrolysis.

AEM water electrolysis combines the advantages of alkaline water electrolysis and PEM water electrolysis. It is easy to operate at high pressure and differential pressure, can be operated at high current density, and can also miniaturize the device. However, unlike PEM water electrolysis, AEM water electrolysis operates in an alkaline environment, allowing the use of non-precious metal catalysts rather than platinum-based catalysts, which is advantageous in securing the economic feasibility of green hydrogen production through lower cost of materials. However, AEM water electrolysis is still in the research and development stage, and for commercialization, problems related to the low ion conductivity of the anion exchange membrane and the performance and reliability of the non-precious metal catalyst must be overcome.

The present invention was developed to solve the above problems, and aims to present a catalyst electrode for an electrolyzer for producing high purity hydrogen and a method for manufacturing the same.

As a means to achieve the above-described object, the present invention provides a metal foam; MXene formed on the metal foam; and transition metal sulfide formed on the MXene. It provides a catalyst electrode for an electrolyzer, including a.

Here _, the MXene may be any one _or more materials selected from _the group consisting _of M ₂

Here, M is a transition metal, and X may be C or N.

Here, the MXene is Ti ₂ C, (Ti _0.5 , Nb _0.5 ) ₂ C, V ₂ C, Nb ₂ C, Mo ₂ C, Mo ₂ N, (Ti _0.5 , Nb _0.5 ) ₂ C, Ti ₂ N, W _1.33 C, Nb _1.33 C, Mo _1.33 C, Mo _1.33 Y _0.67 C, Ti ₃ C ₂ , TiCN, Zr ₃ C ₂ , Hf ₃ C ₂ , Ti ₄ N ₃ , Nb ₄ C ₃ , Ta ₄ C ₃ , V ₄ C ₃ , (Mo, V) ₄ C ₃ , Mo ₄ VC ₄ , Mo ₂ TiC ₂ , Cr ₂ TiC ₂ , Mo ₂ ScC ₂ and Mo ₂ Ti ₂ C ₃ It may be any one or more materials selected from the group consisting of .

Here, the transition metal sulfide may be one or more materials selected from the group consisting of nickel iron sulfide (NiFeS), cobalt iron sulfide (CoFeS), and lithium iron sulfide (LiFeS).

Here, the metal foam may be any one or more selected from the group consisting of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam.

Here, the transition metal sulfide may have a loading amount of 1 to 3 mg/cm ² .

Here, the operating temperature of the catalyst electrode for the electrolyzer may be 40 to 60 °C.

Here, the catalyst electrode for the electrolyzer may be characterized in that it exhibits an overpotential of 320 mV or less at an electrode current density of 50 mA/cm ² or more during a water decomposition reaction.

In addition, the present invention, as a means to achieve the above-described object, includes forming MXene on metal foam; and forming a transition metal sulfide on the MXene.

Here, the step of forming the MXene may be performed according to one or more methods selected from the group consisting of chemical vapor deposition, thermal evaporation, electron beam evaporation, sputtering, atomic deposition, and electrophoretic deposition.

Here, the step of forming the transition metal sulfide includes: a transition metal precursor; and a sulfur-containing compound; the metal foam formed with the MXene may be placed in an aqueous solution and heated.

Here, the transition metal precursor may include one or more selected from the group consisting of nickel (Ni), cobalt (Co), lithium (Li), and iron (Fe).

Here, the sulfur-containing compounds include L-cysteine, N-formylmethionine, cystathionine, homocysteine, cysteine sulfinic acid, and cystine. It may be any one or more compounds selected from the group consisting of.

Here, the heating may be performed at 100 to 200 °C.

In addition, the present invention is a means for achieving the above-described object, including a cathode; An anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode are electrolytic comprising metal foam, MXene formed on the metal foam, and transition metal sulfide formed on the MXene. A membrane electrode assembly is provided, characterized in that it is a silent catalytic electrode.

Using the catalyst electrode for an electrolyzer of the present invention, high purity hydrogen can be produced.

In addition, improved electrochemical catalyst activity can occur in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) during water decomposition reaction using the catalyst electrode for electrolyzer of the present invention.

In addition, the catalyst electrode for an electrolyzer of the present invention can help reduce material and process costs due to the small catalyst loading amount, low operating temperature, and use of a non-precious metal catalyst.

1 is an SEM image of a catalyst electrode for an electrolyzer of the present invention.
Figure 2 is a TEM image and HRTEM image of the catalyst electrode for an electrolyzer of the present invention.
Figure 3 shows the atomic arrangement of the catalyst electrode for an electrolyzer of the present invention.
Figure 4 is a TEM-EDS image of the catalyst electrode for an electrolyzer of the present invention.
Figure 5 is a flowchart showing the manufacturing process of the catalyst electrode for an electrolyzer of the present invention.
Figure 6 is a schematic diagram showing the manufacturing process of the catalyst electrode for an electrolyzer of the present invention.
Figure 7 is a schematic diagram showing a specific manufacturing process of a catalyst electrode for an electrolyzer according to an embodiment of the present invention.
Figure 8 is a schematic diagram of a hydrogen generation electrolyzer manufactured according to an embodiment of the present invention.
Figure 9 is a graph showing HER evaluation of a catalyst electrode for an electrolyzer manufactured according to an embodiment of the present invention.
Figure 10 is a graph of OER evaluation of a catalyst electrode for an electrolyzer manufactured according to an embodiment of the present invention.
Figure 11 is a current-voltage curve graph of an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention.
Figure 12 is a graph showing the current density at 1.85V and 1.95V of the anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention.
Figure 13 is a graph evaluating the long-term stability of an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention.
Figure 14 shows the purity of hydrogen produced from an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings 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 changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Throughout the specification of the present application, when a part “includes” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

As used herein, the terms “about,” “substantially,” and the like are used to mean at or close to a numerical value when manufacturing and material tolerances inherent in the stated meaning are presented, and to aid understanding of the present application. It is used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute figures. Additionally, throughout the specification herein, “step of” or “step of” does not mean “step for.”

Since those skilled in the art of the present invention can make various applications through the gist of the present invention, the scope of the present invention is not limited to the following examples. The scope of rights of the present invention extends to parts for which it is obvious that a person skilled in the art of the present invention can easily substitute or change the contents using prior art based on the matters stated in the patent claims.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings where necessary.

<Catalyst electrode for electrolyzer>

As a means to achieve the above-described object, the present invention provides a metal foam; MXene formed on the metal foam; and transition metal sulfide formed on the MXene. It provides a catalyst electrode for an electrolyzer, including a.

The catalyst electrode of the present invention can be used, for example, in an anion exchange membrane (AEM) electrolyzer. The AEM electrolyzer consists of a membrane, an ionomer, a membrane electrode assembly (MEA), and a gas diffusion layer (GDL), and the membrane electrode assembly also includes a cathode, an anion exchange membrane (Membrane), and It consists of an anode. The catalyst electrode of the present invention can be used as a cathode and anode of the membrane electrode assembly. Specific details related to this will be explained in more detail in the <Membrane electrode assembly including catalyst electrode for electrolyzer> section below.

The metal foam is a completely open porous metal structure in which all pores are connected, and is characterized by various pore sizes, low specific weight, and high ease of processing. Here, the metal foam may be one or more selected from the group consisting of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam, but is not limited thereto.

The MXene is a ceramic material with a two-dimensional planar structure and is composed of an atomic-thick layer of carbon or nitrogen bonded to a transition metal. The MXene has metallic properties (conductivity) due to the transition metal and can be hydrophilic due to the hydroxyl group or oxygen present at the terminal. The MXene is made from a crystalline material called MAX, which means a hexagonal layered carbide or nitride with an empirical formula of M _n+1 AX _n . Here, M is a transition metal, A is a group 13 or 14 element, X is carbon or nitrogen, and n is an integer from 1 to 4. The MXene can be manufactured through selective etching of the MAX with hydrofluoric acid (selectively removing A).

Here _, the MXene may be one _or more materials selected from _the group consisting _of M ₂ More specific examples of the MXene include Ti ₂ C, (Ti _0.5 , Nb _0.5 ) ₂ C, V ₂ C, Nb ₂ C, Mo ₂ C, Mo ₂ N, (Ti _0.5 , Nb _0.5 ) ₂ C, Ti ₂ N, W _1.33 C, Nb _1.33 C, Mo _1.33 C, Mo _1.33 Y _0.67 C, Ti ₃ C ₂ , TiCN, Zr ₃ C ₂ , Hf ₃ C ₂ , Ti ₄ N ₃ , Nb ₄ C ₃ , Ta ₄ C ₃ , V ₄ C ₃ , (Mo, V) ₄ C ₃ , Mo ₄ VC ₄ , Mo ₂ TiC ₂ , Cr ₂ TiC ₂ , Mo ₂ ScC ₂ and Mo ₂ Ti ₂ C ₃ Any one selected from the group consisting of It may be any of the above materials, but is not limited thereto.

Here, the transition metal sulfide may be one or more materials selected from the group consisting of nickel iron sulfide (NiFeS), cobalt iron sulfide (CoFeS), and lithium iron sulfide (LiFeS), but is not limited thereto.

Here, the transition metal sulfide may have a loading amount of 1 to 3 mg/cm ² . If the loading amount of the transition metal sulfide is less than 1 mg/cm ² , the problem of reduced activity as a catalyst may occur, and if the loading amount exceeds 3 mg/cm ² , the pores of the metal foam in which the MXene is formed may be blocked. , penetration of the electrolyte becomes difficult, and it may also become difficult to secure a sufficient surface area to perform a water decomposition reaction. Therefore, in the present invention, the loading amount of the transition metal sulfide is preferably 1 to 3 mg/cm ² .

1 is an SEM image of a catalyst electrode for an electrolyzer of the present invention. The catalyst electrode for an electrolyzer in FIG. 1 includes, for example, nickel foam as a metal foam, Ti ₃ C ₂ as MXene, and NiFeS as a transition metal sulfide. More specifically, FIG. 1A shows a nickel foam (inset) and a catalyst electrode in which Ti ₃ C ₂ is formed on the nickel foam, and FIG. 1B shows a catalyst electrode in which NiFeS is formed on the Ti ₃ C ₂ . Referring to FIG. 1, it can be seen that the catalyst electrode for an electrolyzer of the present invention has a smooth surface as Ti ₃ C ₂ is formed on nickel foam, which has a rough surface. Furthermore, it can be confirmed that the NiFeS is formed through vertical growth on the Ti ₃ C ₂ .

Figure 2 is a TEM image and HRTEM image of the catalyst electrode for an electrolyzer of the present invention. More specifically, Figure 2a is a TEM image of the catalyst electrode for an electrolyzer of the present invention, Figure 2b is a HRTEM image of the catalyst electrode for an electrolyzer of the present invention, and Figure 2c is a fast Fourier transform (FFT) of the catalyst electrode for an electrolyzer of the present invention. ) The spacing of each crystal plane was confirmed through the pattern. Referring to FIG. 2, the catalyst electrode for an electrolyzer of the present invention aggregates as transition metal sulfide (NiFeS) grows through vertical growth on the MXene (Ti ₃ C ₂ ), forming flower-like structures. ) can be confirmed to be formed. In addition, lattice patterns with spacings of 0.236 and 0.144 nm on the (400) and (533) crystal planes of Ni ₂ FeS ₄ and lattice spacings of 0.250 nm on the (006) crystal plane of Ti ₃ C ₂ can be confirmed.

Figure 3 shows the atomic arrangement of the catalyst electrode for an electrolyzer of the present invention. More specifically, Figure 3a shows the overall atomic arrangement of the catalyst electrode for an electrolyzer of the present invention, Figure 3b shows the atomic arrangement of MXene (e.g., Ti ₃ C ₂ ), and Figure 3c shows the atomic arrangement of transition metal sulfide (e.g., Ni ₂ FeS ₄ ). represents the atomic arrangement of . Referring to Figure 3, S defects (S vacancy) in the catalyst electrode for an electrolyzer of the present invention can be confirmed. These S defects can increase the electron density of Ni and Fe and improve the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) dynamics in the catalyst electrode for electrolyzer of the present invention. .

Figure 4 is a TEM-EDS image of the catalyst electrode for an electrolyzer of the present invention. Referring to Figure 4, from the results of EDS element mapping of the catalyst electrode for an electrolyzer of the present invention, it can be confirmed that Ti, C, Ni, Fe, and S are present. This means that the catalyst electrode for an electrolyzer of the present invention has a hybrid structure including NiFeS and Ti ₃ C ₂ .

Here, the operating temperature of the catalyst electrode for the electrolyzer may be 40 to 60 °C. As described above, the catalyst electrode for an electrolyzer of the present invention has a low operating temperature, thereby reducing various unwanted side reactions and deterioration problems of materials (anode, cathode, exchange membrane, etc.) during water decomposition reaction, thereby improving the durability of the catalyst electrode. It can contribute to improvement.

Here, the catalyst electrode for the electrolyzer may be characterized in that it exhibits an overpotential of 320 mV or less at an electrode current density of 50 mA/cm ² or more during a water decomposition reaction. More specifically, the overpotential may be 180 mV or less at an electrode current density of 20 mA/cm ² and 320 mV or less at an electrode current density of 50 mA/cm ² . More specific details related to the above will be explained in more detail in {Examples and Evaluation} below.

<Method for manufacturing catalyst electrode for electrolyzer>

In addition, the present invention, as a means to achieve the above-described object, includes the steps of forming MXene in metal foam; and forming a transition metal sulfide on the metal foam on which the MXene is formed.

Figure 5 is a flowchart showing the manufacturing process of the catalyst electrode for an electrolyzer of the present invention. Referring to Figure 5, the method for manufacturing a catalyst electrode for an electrolyzer of the present invention includes forming MXene on metal foam; and forming a transition metal sulfide on the MXene.

The step of forming MXene on the metal foam may be performed, for example, by electrochemically depositing MXene powder on the metal foam. The electrochemical deposition method may be performed according to one or more methods selected from the group consisting of chemical vapor deposition, thermal evaporation, electron beam evaporation, sputtering, atomic deposition, and electrophoretic deposition, but is limited thereto. That is not the case. According to one embodiment of the present invention, the most preferred method may be electrophoretic deposition.

Here, the step of forming the transition metal sulfide includes: a transition metal precursor; and a sulfur-containing compound; the metal foam formed with the MXene may be placed in an aqueous solution containing and heated.

Here, the transition metal precursor may include one or more selected from the group consisting of nickel (Ni), cobalt (Co), lithium (Li), and iron (Fe). More specifically, the transition metal precursor includes nickel nitrate (Ni(NO ₃ ) ₂ ), nickel acetate (Ni(CH ₃ COO) ₂ ), nickel chloride (NiCl ₂ ), and cobalt nitrate hexahydrate (Co(NO ₃ ). ₂ ·6H ₂ O), cobalt acetate (Co(CH ₃ COO) ₂ ), cobalt chloride (CoCl ₂ ), lithium phosphate (LiPO ₄ ), lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium acetate. (CH ₃ COOLi), iron nitrate (Fe(NO ₃ ) ₃ ), iron hydroxide (Fe(OH) ₃ ), iron oxide (Fe ₂ O ₃ ), etc., but is not limited thereto.

Here, the sulfur-containing compounds include L-cysteine, N-formylmethionine, cystathionine, homocysteine, cysteine sulfinic acid, and cystine. It may be any one or more compounds selected from the group consisting of.

The transition metal sulfide may be formed on the MXene through, for example, a hydrothermal reaction. The hydrothermal reaction is a reaction involving water at a high temperature and pressure of about 100° C. and 1 atm or more. To carry out the hydrothermal reaction, a high-temperature and high-pressure vessel commonly called an autoclave is required. Under saturated vapor pressure, the density, viscosity, surface tension, and dielectric constant of water decrease continuously with increasing temperature. Additionally, the ionic product of water increases with increasing temperature and reaches its maximum value at approximately 270°C. In this way, water under high temperature and pressure has the property of dissolving organic substances and at the same time forms an appropriate reaction field for ionic reactions, making it easy for ions or molecules to diffuse and becoming a solvent that can achieve high reaction rates. The hydrothermal method described above is used for the synthesis of various ceramic powders.

Here, the heating may be performed at 100 to 200 °C. If the heating temperature is less than 100°C and more than 200°C, the introduction of transition metal precursors and sulfur-containing compounds into the MXene may be difficult.

Figure 6 is a schematic diagram showing the manufacturing process of the catalyst electrode for an electrolyzer of the present invention. More specifically, Figure 6a shows nickel foam (Ni Foam, NF) as a metal foam, Figure 6b shows Ti ₃ C ₂ formed as MXene on the NF, and Figure 6c shows the transition on the Ti ₃ C ₂ It indicates that NiFeS was formed as a metal sulfide. Referring to Figure 6, it can be seen that the catalyst electrode for an electrolyzer of the present invention is manufactured through the step of forming MXene on metal foam followed by the step of forming transition metal sulfide on the MXene.

<Membrane electrode assembly including catalyst electrode for electrolyzer>

In addition, the present invention is a means for achieving the above-described object, including a cathode; An anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include metal foam, MXene formed on the metal foam, and a transition metal sulfide formed on the MXene. A membrane electrode assembly is provided, characterized in that it is a silent catalytic electrode.

As described above, the membrane electrode assembly is a component of an AEM electrolyzer and includes a cathode, an anion exchange membrane, and anode, and may include a catalyst electrode for an electrolyzer of the present invention. Hydrogen evolution reaction (HER) occurs at the anode and oxygen evolution reaction (OER) occurs simultaneously at the cathode as a half-cell reaction. That is, water is reduced at the anode and reacts with electrons to form hydrogen and hydroxide ions, the generated hydroxide ions diffuse to the cathode through an anion exchange membrane, and electrons are transferred to the cathode through an external circuit. At the cathode, hydroxide ions lose electrons and recombine into water and oxygen, and electrons are released from the cathode surface to proceed with the reaction. The water decomposition process involved in the anode and cathode is as follows.

Anode: 4OH ^- → O ₂ + 2H ₂ O + 4e ^- E ⁰ = 0.401 V

Cathode: 4H ₂ O + 4e ^- → 2H ₂ + 4OH ^- E ⁰ = -0.828 V

Overall: 2H ₂ O → H ₂ + O ₂ E ⁰ = 1.23 V

The AEM electrolyzer including the membrane electrode assembly of the present invention includes a cathode and an anode, metal foam, MXene formed on the metal foam, and transition metal sulfide formed on the MXene. Improved durability can enable continuous operation for up to 750 hours. Specific details related to this will be described in detail in {Examples and Evaluation} below.

Hereinafter, what the present specification claims will be described in more detail with reference to the accompanying drawings and examples. However, the drawings, examples, etc. presented in this specification may be modified in various ways by those skilled in the art to have various forms, and the description in the present invention does not limit the present invention to the specific disclosed form. Rather, it should be viewed as including all equivalents or substitutes included in the spirit and technical scope of the present invention. In addition, the attached drawings are presented to help those skilled in the art understand the present invention more accurately, and may be shown exaggerated or reduced compared to reality.

{Examples and Evaluation}

<Example>

Example 1

1. Synthesis of maxine

1 g Ti ₃ AlC ₂ powder was dissolved in 100 mL HF solution and stirred for 48 hours. Afterwards, the mixed solution was washed with deionized (DI) water and neutralized.

2. Ti ₃ C ₂ MXene/NF fabrication

Several 3D-NF pieces with sizes (1 Х 1) and (5 Х 5) cm were cut from commercially available 3D-NF sheets. Some 3D-NF pieces were soaked in hydrochloric acid (1 M) and then sonicated in an ultrasonic bath for 15 min. After sonication was completed, the washed 3D-NF was rinsed with deionized water and ethanol and dried in an oven for 6 hours.

Next, 200 mg Ti ₃ C ₂ powder was dispersed in 100 mL of water through ultrasound for 30 minutes. Afterwards, 10 mL of 0.1 mol/dm ³ NaOH was used as a supporting electrolyte. Electrophoretic deposition was performed at 22°C in a standard two-electrode H-type cell. Ni foam was used as the anode, and Pt foil was used as the cathode. The deposition of Ti ₃ C ₂ was performed by applying a voltage of 2 V for 45 seconds. The distance between the two electrodes was 1 cm. During deposition, Ti ₃ C ₂ was coated on Ni foam and stabilized by CTAB solution.

3. Fabrication of NiFeS@Ti ₃ C ₂ MXene/NF

First, 0.1 mmol NiCl ₂ ×2H ₂ O, 0.07 mmol FeCl ₃ Х6H ₂ O, and L-cysteine (1 g) were mixed in 30 mL water and sonicated for 30 minutes until L-cysteine was completely dissolved. Then, the solution and the prepared Ti ₃ C ₂ MXene/NF sample were transferred to a 50 mL Teflon-line stainless steel autoclave, and the temperature was maintained at 160 °C for 4 hours. After cooling the sample to room temperature, the NiFeS@Ti ₃ C ₂ MXene/NF composite was washed with deionized water and ethanol. The final product was obtained after drying at 60°C for 12 hours.

Transition metal sulfide is formed according to the following reaction equation through the above hydrothermal process.

C ₆ H ₁₄ N ₂ O ₄ S ₂ = NH ₃ + CO ₂ + H ₂ S (1)

Ni + Fe + H ₂ S = Ni ₂ FeS ₄ (2)

The catalyst loading of NF was about 1.25 mg/cm ² . Before electrochemical experiments, the electrodes were coated with 5% Nafion® binder to prevent mechanical loss of the catalyst during electrolysis, resulting in a loading of 0.25 mg/cm ² .

Figure 7 is a schematic diagram showing a specific manufacturing process of a catalyst electrode for an electrolyzer according to an embodiment of the present invention. In other words, Figure 7 shows the manufacturing process of Example 1. According to Figure 7 and Example 1, the catalyst electrode for an electrolyzer of the present invention is 1) depositing MXene (Ti ₃ C ₂ ) on metal foam (NF) through electrophoretic deposition, and then 2) depositing the MXene. It can be confirmed that the metal foam is manufactured through high temperature treatment while immersed in an aqueous solution containing a transition metal precursor (Ni precursor and Fe precursor) and a sulfur-containing compound (L-cysteine).

Comparative Example 1 (NiFeS/NF)

A catalyst electrode for an electrolyzer was manufactured in the same manner as Example 1, except that Ti ₃ C ₂ was formed in NF (hereinafter referred to as “Comparative Example 1”).

Comparative Example 2 (Ti ₃ C ₂ /NF)

In Example 1, <2. After performing the Ti ₃ C ₂ MXene/NF preparation step, 5% Nafion® binder was coated to prepare a catalyst electrode for an electrolyzer (hereinafter referred to as “Comparative Example 2”).

Comparative Example 3 (NF)

Several 3D-NF pieces with sizes (1 Х 1) and (5 Х 5) cm were cut from commercially available 3D-NF sheets. Some 3D-NF pieces were soaked in hydrochloric acid (1 M) and then sonicated in an ultrasonic bath for 15 min. After sonication was completed, the washed 3D-NF was rinsed with deionized water and ethanol and dried in an oven for 6 hours.

Next, 5% Nafion® binder was coated on the NF to prepare a catalyst electrode for an electrolyzer (hereinafter referred to as “Comparative Example 3”).

Comparative Example 4 (Pt/C/NF)

Commercial Pt/C catalyst and 5% Nafion® were dispersed in ethanol. The catalyst dispersed in ethanol was applied to the NF layer (catalyst loading was about 0.3 mg/cm ² ) to prepare a catalyst electrode coated with a Pt/C catalyst (hereinafter referred to as “Comparative Example 4”).

Comparative Example 5 (RuO ₂ /NF)

Commercial RuO ₂ catalyst and 5% Nafion® were dispersed in ethanol. The catalyst dispersed in ethanol was applied to the NF layer (catalyst loading was about 0.3 mg/cm ² ) to prepare a catalyst electrode coated with RuO ₂ catalyst (hereinafter referred to as “Comparative Example 5”).

Manufacturing example

Example 1 was used as the cathode and anode, and a membrane electrode assembly (MEA) was manufactured by inserting an anion exchange membrane (Sustainment Gold-plated nickel was used as the current collector and end plate.

Figure 8 is a schematic diagram of an anion exchange membrane electrolyzer manufactured according to a manufacturing example of the present invention. Referring to Figure 8, the anion exchange membrane electrolyzer of the present invention includes an end plate and a current collector (100, 300), a flow field (110, 310), and a membrane electrode assembly (200), and the membrane electrode current collector It can be confirmed that it includes a cathode catalyst and gas diffusion layer 210, an anion exchange membrane 220, and an anode catalyst and gas diffusion layer 230.

The single anion-exchange membrane water electrozer (AEMWE) cell prepared in this way was operated at 50°C using 1 M KOH aqueous medium. Electrolyte performance was evaluated by obtaining a load curve at an applied potential of 1.5 to 2.0 V, and the stability of the catalyst was evaluated under alkaline water electrolysis conditions at a constant applied potential.

Comparative manufacturing example (RuO2/NF(+)∥Pt/C/NF(-))

An anion exchange membrane electrolyzer was manufactured in the same manner as the above Preparation Example, except that Comparative Example 5 was included as the cathode and Comparative Example 4 as the anode (hereinafter referred to as “Comparative Preparation Example”).

<Evaluation>

HER and OER evaluation

Figure 9 is a graph showing HER evaluation of a catalyst electrode for an electrolyzer manufactured according to an embodiment of the present invention. More specifically, Figure 9a is a polarization curve showing the HER evaluation of the catalyst electrode for an electrolyzer of the present invention, and Figure 9b shows the HER overpotential at current densities of 20 and 50 mA/cm ² of the catalyst electrode for an electrolyzer of the present invention. . Referring to FIG. 9, the HER overpotentials required to obtain a current density of 20 and 50 mA/cm ² for Example 1 and Comparative Examples 1 to 4 are 320 and 550 (Comparative Example 2), 250, and 350 (Comparative Example 2), respectively. Example 1), 180 and 320 (Example 1), and 150 and 310 (Comparative Example 4) mV. That is, it can be seen that the HER overpotential of Example 1 is somewhat higher or similar to that of Comparative Example 4, but is lower than that of Comparative Examples 1 and 2.

Figure 10 is a graph of OER evaluation of a catalyst electrode for an electrolyzer manufactured according to an embodiment of the present invention. More specifically, Figure 10a is a polarization curve for the OER of the catalyst electrode for an electrolyzer of the present invention, and Figure 10b is the OER at 20 and 50 mA/cm ² current densities of Example 1, Comparative Examples 1 to 3, and Comparative Example 5. Indicates the overpotential value. Referring to FIG. 10, the OER overpotentials required to obtain current densities of 20 and 50 mA/cm ² for Example 1, Comparative Examples 1 to 3, and Comparative Example 5 are 370, 470 (Comparative Example 3), and 360, respectively. and 450 (Comparative Example 2), 300 and 360 (Comparative Example 1), 290 and 330 (Example 1), and 280 and 355 (Comparative Example 5) mV. That is, the OER overpotential value for obtaining a current density of 20 mA/cm ² in Example 1 is lower than that of Comparative Examples 1 to 3, and the OER overpotential value for obtaining a current density of 50 mA/cm ² is the lowest. You can check that it has a value.

In other words, in summary, the catalyst electrode for electrolyzer of the present invention exhibits lower HER and OER overpotential values compared to Comparative Examples 1 to 3, and has slightly higher or similar overpotential values than the commercially available Pt/C catalyst electrode and RuO ₂ catalyst electrode. You can see that it represents . However, in the case of Pt and Ru, they are precious metals and rare metals and are very expensive, so by using the non-precious metal catalyst electrode of the present invention, they have an overpotential value similar to that of the catalyst electrode using noble metals and at the same time, material and process costs are reduced. reduction can be achieved.

Electrolyzer performance evaluation

Figure 11 is a current-voltage curve graph of an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention. More specifically, the electrolyzer performance was investigated by measuring the load curve in the electrolyte input voltage range of 1.5 to 2.0 V. Referring to FIG. 11, it can be seen that the current density obtained at 1.85 V, which is the standard operating voltage of the industrial alkaline electrolyte system, is 401 mA/cm ² with a cell efficiency of 67.65% for the manufacturing example, and 452 mA/cm ² for the comparative manufacturing example. You can.

Figure 12 is a graph showing the current density at operating voltages of 1.85V and 1.95V of an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention. Referring to FIG. 12, it can be seen that the current density of the manufacturing example is 401 mA/cm ² at an operating voltage of 1.85 V, and the current density of the comparative manufacturing example is 452 mA/cm ² , and at an operating voltage of 1.95 V, the current density of the manufacturing example is 605 mA/cm 2 cm ² , it can be seen that the comparative manufacturing example shows a current density of about 574 mA/cm ² . From a commercial perspective, it is difficult to evaluate that the anion exchange membrane electrolyzer containing the membrane electrode assembly of the present invention has significantly improved electrolyzer performance compared to a commercially available membrane electrode assembly, but has low catalyst loading, low operating temperature, and non-precious metal content. By including materials, a significant effect can be seen in that material and process costs can be reduced.

Figure 13 is a graph evaluating the long-term stability of an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention. That is, the durability of the catalyst electrode in the electrolyte system and the reproducibility of experimental measurements were evaluated. Referring to FIG. 13, in the comparative manufacturing example, it can be seen that the current density gradually decreases over time at a potential of 1.85 V. On the other hand, it can be seen that the production example maintains the current density for up to 25 hours at a potential of 1.85 V, showing very high durability. In more detail, the manufacturing example shows a rapid increase in current density for up to 16 hours at a potential of 1.85 V, and then the current density levels off, showing a negligible current loss of 0.4 mA/h. Considering the above results, it can be expected that the anion exchange membrane electrolyzer containing the membrane electrode assembly of the present invention can operate continuously for 750 hours with the minimum current density reduced to 100 mA/cm ² .

Figure 14 shows the purity of hydrogen produced from an anion exchange membrane electrolyzer manufactured according to an embodiment of the present invention. More specifically, hydrogen was generated in an anion exchange membrane electrolyzer manufactured according to the manufacturing example. Referring to FIG. 14, it can be seen that 2.8 mL/min of hydrogen with a purity of 99.997% is produced when a water decomposition reaction is performed using the catalyst electrode for an electrolyzer of the present invention. It can be confirmed that these values are very close to the commercially required purity of hydrogen.

Using the catalyst electrode for an electrolyzer of the present invention, high purity hydrogen can be produced.

In addition, improved electrochemical catalytic activity can occur in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) during water decomposition reaction using the catalyst electrode for electrolyzer of the present invention.

Additionally, the catalyst electrode for an electrolyzer of the present invention can help reduce operating costs due to a small catalyst loading amount and low operating temperature.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations will be possible to those skilled in the art without departing from the essential characteristics of the present invention.

Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but are for illustrative purposes, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of the present invention.

Claims (15)

Metal foam;
MXene formed on the metal foam; and
A catalyst electrode for an electrolyzer, including a transition metal sulfide formed on the MXene. According to claim 1,
The MXene is _a catalyst electrode for _an electrolytic cell _, wherein the MXene is one or more materials selected from _the group consisting of M ₂
(M is a transition metal, and X is C or N.) According to claim 1,
The MXene is Ti ₂ C, (Ti _0.5 , Nb _0.5 ) ₂ C, V ₂ C, Nb ₂ C, Mo ₂ C, Mo ₂ N, (Ti _0.5 , Nb _0.5 ) ₂ C, Ti ₂ N, W _1.33 C , Nb _1.33 C, Mo _1.33 C, Mo _1.33 Y _0.67 C, Ti ₃ C ₂ , TiCN, Zr ₃ C ₂ , Hf ₃ C ₂ , Ti ₄ N ₃ , Nb ₄ C ₃ , Ta ₄ C ₃ , V ₄ C ₃ , (Mo, V) ₄ C ₃ , Mo ₄ VC ₄ , Mo ₂ TiC ₂ , Cr ₂ TiC ₂ , Mo ₂ ScC ₂ and Mo ₂ Ti ₂ C ₃ , for electrolyzer, which is one or more materials selected from the group consisting of Catalytic electrode. According to claim 1,
The transition metal sulfide is a catalyst electrode for an electrolyzer, wherein the transition metal sulfide is one or more materials selected from the group consisting of nickel iron sulfide (NiFeS), cobalt iron sulfide (CoFeS), and lithium iron sulfide (LiFeS). According to claim 1,
The metal foam is at least one selected from the group consisting of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam. According to claim 1,
The transition metal sulfide is a catalyst electrode for an electrolyzer with a loading amount of 1 to 3 mg/cm ² . According to claim 1,
The catalyst electrode for an electrolyzer is characterized in that the operating temperature is 40 to 60 ° C. According to claim 1,
The catalyst electrode for an electrolyzer is characterized in that it exhibits an overpotential of 320 mV or less at an electrode current density of 50 mA/cm ² or more during a water decomposition reaction. Forming MXene on metal foam; and
A method of manufacturing a catalyst electrode for an electrolyzer, comprising: forming a transition metal sulfide on the MXene. According to clause 9,
The step of introducing MXene is performed according to one or more methods selected from the group consisting of chemical vapor deposition, thermal evaporation, electron beam evaporation, sputtering, atomic vapor deposition, and electrophoretic deposition. Manufacturing method. According to clause 9,
The step of forming the transition metal sulfide includes: a transition metal precursor; And a sulfur-containing compound; A method of manufacturing a catalyst electrode for an electrolytic cell, wherein the metal foam formed with the MXene is placed in an aqueous solution containing and heated. According to claim 11,
The transition metal precursor is a method of manufacturing a catalyst electrode for an electrolytic cell, wherein the transition metal precursor includes one or more selected from the group consisting of nickel (Ni), cobalt (Co), lithium (Li), and iron (Fe). According to claim 11,
The sulfur-containing compounds include L-cysteine, N-formylmethionine, cystathionine, homocysteine, cysteine sulfinic acid, and cystine. A method of manufacturing a catalyst electrode for an electrolytic cell, which is one or more compounds selected from the group consisting of. According to claim 11,
A method of manufacturing a catalyst electrode for an electrolyzer, wherein the heating is performed at 100 to 200 °C. cathode;
An anion exchange membrane formed on the cathode; and
It includes an anode formed on the anion exchange membrane,
The cathode and the anode are characterized in that they include metal foam, MXene formed on the metal foam, and transition metal sulfide formed on the MXene.

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