阅读说明：本技术 析氧电极、制备所述电极的方法以及包括所述电极的制氧装置 (Oxygen evolution electrode, method for preparing said electrode and oxygen production plant comprising said electrode ) 是由 李允洙 李恩直 张志勋 李东一 崔宇浚 于 2020-11-03 设计创作，主要内容包括：本发明特别公开了一种析氧电极、制备所述电极的方法以及包括所述电极的制氧装置。析氧电极包括金属纳米团簇以及金属载体,所述金属纳米团簇包括内核和有机含硫醇配体,所述内核由金属原子形成,所述有机含硫醇配体键合至内核的表面,所述金属纳米团簇固定于所述金属载体。根据本发明的各个示例性实施方案,例如通过使用所述电极,可以使用非贵金属/非碳催化剂作为用于析氧(碱性水电解的半反应)的催化剂,可以显著改善析氧活性和高稳定性,可以通过提高催化剂在电极中的分散性来最小化催化剂使用量,并且可以通过增加电极的表面积和减小电解质电阻来提高析氧装置的效率。(The invention particularly discloses an oxygen evolution electrode, a method for preparing the electrode and an oxygen generation device comprising the electrode. The oxygen evolution electrode comprises a metal nanocluster and a metal carrier, wherein the metal nanocluster comprises a core and an organic thiol-containing ligand, the core is formed by metal atoms, the organic thiol-containing ligand is bonded to the surface of the core, and the metal nanocluster is fixed on the metal carrier. According to various exemplary embodiments of the present invention, for example, by using the electrode, a non-noble metal/non-carbon catalyst may be used as a catalyst for oxygen evolution (half reaction of alkaline water electrolysis), oxygen evolution activity and high stability may be significantly improved, catalyst usage may be minimized by improving dispersibility of the catalyst in the electrode, and efficiency of an oxygen evolution device may be improved by increasing surface area of the electrode and reducing electrolyte resistance.)

1. An oxygen evolution electrode comprising:

a metal nanocluster including i) a core including a metal atom and ii) an organic thiol-containing ligand bonded to a surface of the core; and

a metal carrier to which the metal nanoclusters are fixed.

2. The oxygen evolution electrode according to claim 1, wherein the metal nanoclusters are represented by the following chemical formula 1:

[ chemical formula 1]

Ni_n(SR)_2n

In the chemical formula 1, the first and second,

r is one or more selected from the group consisting of a substituted or unsubstituted C1 to C24 aliphatic hydrocarbon group and a substituted or unsubstituted C6 to C20 aromatic hydrocarbon group, and

n is an integer of 4 to 12.

3. The oxygen evolution electrode according to claim 2, wherein the metal nanoclusters comprise a material selected from Ni₄(SC₂H₄Ph)₈、Ni₅(SC₂H₄Ph)₁₀、Ni₆(SC₂H₄Ph)₁₂、Ni₄(SC₂H₅)₈、Ni₅(SC₂H₅)₁₀、Ni₆(SC₂H₅)₁₂、Ni₉(SPh)₁₈、Ni₁₁(SPh)₂₂、Ni₁₀(StBu)₁₀(etet)₁₀、Ni₁₂(StBu)₁₂(etet)₁₂And combinations thereof, and one or more of,

wherein Ph is phenyl, StBu is tert-butyl thiolate, and et is 2-ethylthioethanethiolate.

4. The oxygen evolving electrode according to claim 1, wherein the metal support comprises nickel foam.

5. The oxygen evolution electrode of claim 1 wherein the metal support is acid etched to remove oxides from its surface.

6. The oxygen evolution electrode according to claim 1 wherein the electrode comprises a compressed body wherein the metal support with immobilized metal nanoclusters is compressed to a thickness of 1.0mm or less.

7. A method of making an oxygen evolving electrode comprising:

preparing metal nanoclusters including a core formed of metal atoms and organic thiol-containing ligands bonded to a surface of the core;

fixing the metal nanoclusters on a metal support.

8. The method of claim 7 further comprising removing a surface oxide layer of the metal support by acid etching the metal support.

9. The method of claim 8, wherein the acid comprises sulfuric acid, nitric acid, or a mixture thereof.

10. The method of claim 8, wherein the acid concentration is 3M or higher and the acid etch treatment time is within 3 minutes.

11. The method according to claim 8, wherein the metal carrier after the acid etching treatment has hydrophobicity with a contact angle increased by 10% to 50% compared to that of the metal carrier before the acid etching treatment.

12. The method of claim 7, further comprising compressing the metal support having the metal nanoclusters immobilized thereon, wherein the compressed metal support has a thickness of 1.0mm or less.

13. An oxygen plant, comprising:

a working electrode comprising the electrode of claim 1;

a counter electrode; and

an aqueous electrolyte.

14. The oxygen plant of claim 13, further comprising:

a reference electrode is arranged on the substrate,

wherein the distance between the working electrode and the reference electrode is 2mm to 5 mm.

15. The oxygen plant as set forth in claim 13 wherein the aqueous electrolyte has a concentration of 1.0M to 3.0M.

16. The oxygen plant of claim 13, wherein the working electrode has an area of 0.03cm²To 0.5cm²。

Technical Field

The present invention relates to an oxygen evolving electrode, a method for preparing said electrode and an oxygen generating plant comprising said electrode. The electrode may include a non-noble metal/non-carbon catalyst as a catalyst for oxygen evolution (semi-reaction of alkaline water electrolysis). In this way, the oxygen evolution activity and high stability can be significantly improved, the amount of catalyst used can be minimized by improving the dispersibility of the catalyst in the electrode, and the efficiency of the oxygen generation plant can be improved by increasing the surface area of the electrode and reducing the electrolyte resistance.

Background

The development of new and renewable energy sources is accelerating to cope with fossil fuel depletion and climate change. Wherein, the electrolysis of alkaline water consisting of hydrogen production reaction and oxygen production reaction is the core technology of hydrogen economy, fuel cells and artificial photosynthesis.

Relatively well studied hydrogen production technologies are currently going to mature (commercialization) stages. On the other hand, the water electrolysis oxygen production technology has a rather complicated mechanism and requires much research thereon. In particular, since the overall efficiency of the alkaline water electrolysis apparatus depends on oxygen evolution (relatively slow and large overvoltage is required), development of related technologies is urgently required.

In the development of the related art, since the cost of the catalytic electrode in the alkaline water electrolysis apparatus accounts for about 49% of the total cost thereof, it has become very important to develop the catalytic electrode, for example, a platinum (Pt) -based catalyst having high activity in most energy-related electrochemical reactions (e.g., hydrogen production and oxygen reduction) has low oxygen production activity.

Among the oxygen evolution catalysts studied so far, rubidium (Ru) -based catalysts have been used as materials having the highest activity, but their stability under alkaline conditions is poor. A relatively stable and highly activated iridium (Ir) -based catalyst was used as a commercial oxygen evolution catalyst. However, the use of Ir-based catalysts may be limited due to price, inventory, and uniformity limitations. Therefore, a catalyst is needed instead of an Ir-based catalyst.

In addition, non-noble metal catalysts have low stability under acidic conditions, while their stability problems can be overcome under alkaline electrolysis conditions. However, for fast electron transfer of the catalyst, when a carbon electrode or a carbon-based conductive material is mainly used as an electrode material, corrosion occurs under oxygen evolution conditions, resulting in poor long-term stability.

Accordingly, there is a need to develop a non-carbon based/non-noble metal based catalyst electrode that can stably operate under alkaline water electrolysis conditions.

The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person skilled in the art.

Disclosure of Invention

In a preferred aspect, there is provided an oxygen evolution electrode which can use a non-noble metal/non-carbon catalyst as a catalyst for oxygen evolution (half reaction of alkaline water electrolysis), which can have excellent oxygen evolution activity and high stability, which can minimize the amount of catalyst used by improving the dispersibility of the catalyst in the electrode, and which can improve the efficiency of an oxygen generation plant by increasing the surface area of the electrode and reducing the electrolyte resistance.

In another preferred aspect, a method of making an oxygen evolution electrode and an oxygen plant including an oxygen evolution electrode are provided.

In one aspect, an oxygen evolution electrode is provided, which may comprise: a metal nanocluster including i) a core including a metal atom and ii) an organic thiol-containing ligand bonded to a surface of the core, and a metal support to which the metal nanocluster is fixed.

As used herein, the term "nanocluster" or "metal nanocluster" refers to a group of similar atoms (metal atoms) or compounds that are held at a distance from each other or in close proximity to each other such that a substance forms a particular structure having nanoscale dimensions (e.g., a diameter or the maximum distance of two end positions in the structure), such as, for example, about 0.1nm to 100nm, about 0.1nm to 50nm, about 0.1nm to 40nm, about 0.1nm to 30nm, about 0.1nm to 20nm, about 0.1nm to 10nm, about 0.1nm to 5nm, about 0.5nm to 2.0nm, or about 1.0nm to 2.0 nm. In certain embodiments, the metal nanoclusters may be formed of a metal ligand complex or coordination complex, which may include one or more transition metal atoms and a ligand or one or more complexing (chelating) agents. For the metal nanoclusters, preferred metal ions may include Au, Cu, Ni, Fe, Co, Ag, etc., and preferred ligands may include hydrocarbons (e.g., aliphatic or aromatic hydrocarbons) in sulfide or oxide form capable of donating unpaired electrons to the metal atoms.

The metal nanoclusters may be represented by chemical formula 1 as follows.

[ chemical formula 1]

Ni_n(SR)_2n

R is one or more selected from a substituted or unsubstituted C1 to C24 aliphatic hydrocarbon group and a substituted or unsubstituted C6 to C20 aromatic hydrocarbon group, and n is an integer of 4 to 12.

The metal nanoclusters may include a material selected from Ni₄(SC₂H₄Ph)₈、Ni₅(SC₂H₄Ph)₁₀、Ni₆(SC₂H₄Ph)₁₂、Ni₄(SC₂H₅)₈、Ni₅(SC₂H₅)₁₀、Ni₆(SC₂H₅)₁₂、Ni₉(SPh)₁₈、Ni₁₁(SPh)₂₂、Ni₁₀(StBu)₁₀(etet)₁₀And Ni₁₂(StBu)₁₂(etet)₁₂Wherein Ph is phenyl, StBu is tert-butyl mercaptide, and et is 2-ethylthioethanemercaptide.

The metal support may suitably comprise nickel foam.

The metal support may be acid etched to remove oxides from its surface.

The electrode may include a compressed body in which the metal carrier having the metal nanoclusters immobilized thereon is compressed to a thickness of about 1.0mm or less.

In one aspect, a method of making an oxygen evolution electrode is provided. The method may include: preparing metal nanoclusters including a core formed of metal atoms and organic thiol-containing ligands bonded to a surface of the core; and fixing the metal nanoclusters on a metal support.

The method may further include removing a surface oxide layer of the metal carrier by acid etching the metal carrier.

The acid may suitably comprise sulphuric acid, nitric acid or a mixture thereof.

The acid concentration may be about 3M or higher and the acid etch treatment time may be within about 3 minutes.

The metal carrier after the acid etching treatment may have hydrophobicity in which a contact angle thereof may be increased by about 10% to 50% compared to that of the metal carrier before the acid etching treatment.

The method of preparing the oxygen evolution electrode may further include compressing the metal support on which the metal nanoclusters are immobilized, and the compressed metal support has a thickness of about 1.0mm or less.

In one aspect, there is provided an oxygen plant comprising: a working electrode comprising an electrode as described herein, a counter electrode, and an aqueous electrolyte.

The oxygen generation plant can further include a reference electrode, wherein the distance between the working electrode and the reference electrode can be about 2mm to 5 mm.

The concentration of the aqueous electrolyte may be about 1.0M to 3.0M.

The area of the working electrode may be about 0.03cm²To 0.5cm²。

According to various exemplary embodiments of the present invention, a non-noble metal/non-carbon catalyst may be used in an electrode as a catalyst for oxygen evolution (half reaction of alkaline water electrolysis), oxygen evolution activity and high stability of the electrode may be improved, catalyst usage may be minimized by improving dispersibility of the catalyst in the electrode, and efficiency of an oxygen generation plant may be improved by increasing surface area of the electrode and reducing electrolyte resistance.

Drawings

FIG. 1 shows a chemical composition consisting of Ni₅(SC₂H₄Ph)₁₀Exemplary structures of exemplary metal nanoclusters are shown.

Fig. 2 shows a photograph of an exemplary nickel foam (left) and a Scanning Electron Microscope (SEM) photograph of the microstructure of an exemplary nickel foam (right).

Fig. 3 shows an exemplary method of making an exemplary oxygen evolution electrode.

Fig. 4 shows an exemplary oxygen plant according to an exemplary embodiment of the present invention.

FIG. 5 shows the separation of Ni used in preparation example 1₅(SC₂H₄Ph)₁₀A photograph of an exemplary PTLC result of (a).

FIG. 6 shows exemplary Ni prepared in preparation example 1₅(SC₂H₄Ph)₁₀The measurement result of electrospray ionization mass spectrometry.

Fig. 7 to 9 show graphs of XPS measurement results of exemplary surface-treated foamed nickel in preparation example 2.

Fig. 10 shows the results of measuring the contact angle of the exemplary surface-treated nickel foam in production example 2.

Fig. 11 shows a graph of the measurement results of the electrochemical surface area of the exemplary surface-treated nickel foam in production example 2.

Fig. 12 shows a graph of the results of measuring the oxygen generation activity of the exemplary oxygen evolution electrode in experimental example 3.

Fig. 13 and 14 are graphs showing the results of measuring the stability of the exemplary oxygen evolution electrode in experimental example 3 in generating oxygen by the loop current method and the constant voltage method.

Fig. 15 shows a graph of the results of measuring the oxygen generation activity of an exemplary oxygen evolution electrode compressed in experimental example 4.

Fig. 16 shows a graph of the results of measuring the oxygen generation activity of an exemplary oxygen evolution electrode when the distance between the working electrode and the reference electrode in experimental example 5 was minimized.

FIG. 17 shows measurement of the charge transfer impedance (R) of an exemplary oxygen evolution electrode when the distance between the working electrode and the reference electrode in Experimental example 5 was minimized_ct) And electrolyte resistance (R)_s) And (4) a graph of the results.

Fig. 18 shows a graph of the results of measuring the oxygen generation activity of the exemplary oxygen evolution electrode when the concentration of the electrolyte was increased in experimental example 5.

FIG. 19 shows the charge transfer resistance (R) of an exemplary oxygen evolution electrode measured when the concentration of the electrolyte was increased in Experimental example 5_ct) And electrolyte resistance (R)_s) And (4) a graph of the results.

Fig. 20 shows a graph of the results of measuring the oxygen generation activity of an exemplary oxygen evolution electrode when the area of the oxygen generation electrode was reduced in experimental example 5.

FIG. 21 shows measurement of the charge transfer resistance (R) of an exemplary oxygen evolution electrode when the area of the oxygen generation electrode was reduced in Experimental example 5_ct) And electrolyte resistance (R)_s) And (4) a graph of the results.

Description of the reference numerals

10: oxygen-generating device

11: container with a lid

12: aqueous electrolyte

Detailed Description

Advantages and features of the present application and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present application and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In this specification, unless explicitly described to the contrary, the word "comprise" and variations such as "comprises" or "comprising", will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

Furthermore, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Unless otherwise indicated, all numbers, values, and/or expressions referring to quantities of ingredients, reaction conditions, polymer compositions, and formulas used herein are to be understood as modified in all instances by the term "about" as these numbers are approximations in nature and reflect the various measurement uncertainties encountered in obtaining these values.

Further, unless specifically stated or otherwise apparent from the context, the term "about" as used herein is understood to be within the normal tolerance of the art, e.g., within 2 standard deviations of the mean. "about" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05% or 0.01% of the stated value. Unless otherwise apparent from the context, all numbers provided herein are modified by the term "about".

In this specification, when a range of a variable is described, it is to be understood that the variable includes all values that include the end points described within the range. For example, a range of "5 to 10" should be understood to include any subrange, e.g., 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., as well as individual values of 5, 6, 7, 8, 9, and 10, and should also be understood to include any value between the effective integers within the range, e.g., 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, etc. Further, for example, a range of "10% to 30%" should be interpreted as including sub-ranges, e.g., 10% to 15%, 12% to 18%, 20% to 30%, etc., as well as all integers including values from 10%, 11%, 12%, 13%, etc. up to 30%, and also as including any value between the significant integers within the range, e.g., 10.5%, 15.5%, 25.5%, etc.

Unless otherwise defined below, "substituted" means that a hydrogen in a compound is substituted with one or more substituents selected from C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C6 to C30 aryl, C7 to C30 alkylaryl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C30 heteroaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (-F, -Cl, -Br, or-I), hydroxyl (-OH), nitro (-NO), or-l)₂) Cyano (-CN), amino (-NRR 'wherein R and R' are independently of each other hydrogen or C1 to C6 alkyl), azido (-N)₃) Amidino (-C (═ NH)₂) Hydrazino (-NHNH)₂) Hydrazono (═ N (NH)₂) Aldehyde (-)), aldehyde (-O) H), carbamoyl (-C (O) NH)₂) Thiol (-SH), ester (-C (═ O) OR where R is C1 to C6 alkyl OR C6 to C12 aryl), carboxyl(-COOH) or a salt thereof (-C (═ O) OM where M is an organic cation or an inorganic cation), a sulfonic acid group (-SO)₃H) Or a salt thereof (-SO)₃M, wherein M is an organic cation or an inorganic cation) and a phosphate group (-PO)₃H₂) Or a salt thereof (-PO)₃MH or-PO₃M₂Wherein M is an organic cation or an inorganic cation).

The term "aliphatic hydrocarbon group" as used herein means a straight-chain or branched, saturated or unsaturated, chain alkyl group, for example, a C1-C30 alkyl group, a C1-C24 alkyl group or a C1-C20 alkyl group.

The term "aromatic hydrocarbon group" as used herein means a C6 to C30 aryl group (e.g., phenyl, naphthyl or anthracenyl) forming a ring structure.

The term "alicyclic hydrocarbon group" as used herein means a C3 to C30 cycloalkyl group, C3 to C30 cycloalkenyl group, or C3 to C30 cycloalkynyl group, and a carbon atom forms a cyclic structure or a ring structure.

The oxygen evolving electrode may comprise metal nanoclusters and a metal support, said metal nanoclusters being immobilized to said metal support.

The metal nanoclusters may include a large or small amount of metal atoms and may have a transition form between atoms and nanoparticles, so that the metal nanoclusters may have completely different electrical, magnetic, optical, and electrochemical properties from existing metal nanoparticles or semiconductor quantum dots. In addition, the metal nanoclusters may control the structure and composition of particles at an atomic level, and in particular, may have high uniformity at a molecular level and high stability at a metal level, and thus may be applied as an electrochemical catalyst having high reaction selectivity.

In particular, the metal nanoclusters may include i) a core including or formed of metal atoms and ii) an organic thiol-containing ligand bonded to a surface of the core. For example, the metal nanoclusters may include a core formed of metal atoms and organic thiol-containing (SR) ligands protecting the environment surrounding the core as an outer shell.

The metal nanoclusters may suitably comprise a non-noble metal/non-carbon catalyst and the metal atoms forming the inner core may suitably comprise a transition metal, e.g. nickel.

Suitable thiol-containing ligands may include one or more thiol moieties (e.g., -SH-or > S), and may also suitably include one or more saturated or unsaturated carbon atoms, e.g., a C1-20 group or a C1-12 group or a C1-6 group. Preferred thiol-containing ligands may comprise 1, 2 or 3 sulfur atoms, more preferably 1 or 2 sulfur atoms. Suitable thiol-containing ligands may be saturated or unsaturated, and may suitably include phenyl or other aryl groups. Suitable thiol-containing ligands may also be saturated and include, for example, 1 to 20 or 1 to 12 or 1 to 6 saturated carbons and 1, 2 or 3 sulfur atoms, more typically 1 or 2 sulfur atoms.

Particularly preferred organic thiol-containing ligands may include one or more selected from the group consisting of ethanethiol, phenethylthiol, benzenethiol, t-butyl thiol, and 2-ethylthioethanethiol (2-ethylthioethanethiol).

As an example, the metal nanoclusters may be represented by chemical formula 1 as follows.

[ chemical formula 1]

Ni_n(SR)_2n

In chemical formula 1, R may be one or more selected from a substituted or unsubstituted C1 to C24 aliphatic hydrocarbon group and a substituted or unsubstituted C6 to C20 aromatic hydrocarbon group, and n may be an integer of 4 to 12.

For example, the metal nanoclusters may include a material selected from Ni₄(SC₂H₄Ph)₈、Ni₅(SC₂H₄Ph)₁₀、Ni₆(SC₂H₄Ph)₁₂、Ni₄(SC₂H₅)₈、Ni₅(SC₂H₅)₁₀、Ni₆(SC₂H₅)₁₂、Ni₉(SPh)₁₈、Ni₁₁(SPh)₂₂、Ni₁₀(StBu)₁₀(etet)₁₀And Ni₁₂(StBu)₁₂(etet)₁₂Wherein Ph is phenyl, StBu is tert-butyl thiolate and etet is 2-ethylthioethanethiolate.

FIG. 1 shows a chemical composition consisting of Ni₅(SC₂H₄Ph)₁₀Schematic representation of the structure of the metal nanoclusters is shown.

As shown in fig. 1, the metal nanoclusters may include a core composed of five nickel atoms and an organic thiol-containing ligand derived from phenethyl mercaptan (PET), which protects the surrounding environment of the core like a shell, and the metal atoms and the organic thiol-containing ligand are bonded through a sulfur (S) atom of thiol. The organic thiol-containing ligand protective layer may provide a uniquely high stability of the metal nanoclusters.

The size of the metal nanoclusters may be about 0.5 to 2.0nm, for example, about 1.0 to 2.0 nm. When the size of the metal nanocluster is less than about 0.5nm, the uniformity thereof may be reduced and the metal nanocluster may be unstable, and when the size of the metal nanocluster is greater than about 2.0nm, the unique molecular properties of the metal nanocluster may be lost and the behavior thereof may be similar to that of the metal nanoparticles.

Meanwhile, a high-activity catalyst for efficiently evolving oxygen is important, but it is also important to select an electrode material having high stability and low resistance, and an electrode in which the catalyst is uniformly dispersed. Thus, the oxygen evolving electrode comprises a metal support to which the metal nanoclusters are fixed.

As a material of the metal support, aluminum (Al), nickel (Ni), iron (Fe), titanium (Ti), stainless steel, or the like may be suitably used, and the metal support may have a foil, plate, mesh (or net), or foam (or sponge) shape. For example, the metal support may be nickel foam.

In particular, the metal support may have a porous structure (e.g., foam), and in this case, the porosity of the metal support may be about 90% to 97%, for example about 95% to 96%.

Fig. 2 shows a photograph of the nickel foam (left) and a Scanning Electron Microscope (SEM) photograph of the microstructure of the nickel foam (right). As shown in fig. 2, the nickel foam is suitable as an electrode material for alkaline water electrolysis because it can have a large surface area and high stability in an oxidizing environment.

In addition, in order to improve the dispersibility of the metal nanoclusters, the surface oxide layer of the metal carrier may be removed by acid etching. For example, when the metal support is nickel foam, metal oxides (NiO, Ni) on the surface of the metal support can be removed₂O₃Etc.) and may include metals or metal sulfides (Ni, NiS, Ni), among others₂S₃Etc.).

Since the oxide layer on the surface of the metal support is removed by the acid etching treatment, the metal support after the acid etching treatment may have relative hydrophobicity as compared to the metal support before the acid etching treatment, thereby improving the dispersibility of the metal nanoparticles. For example, the contact angle of the nickel foam before the acid etching treatment may be about 40 to 70 degrees, the contact angle of the nickel foam after the acid etching treatment may be about 70 to 150 degrees, and the nickel foam after the acid etching treatment may have hydrophobicity in which the contact angle is increased by about 10 to 50% as compared to the nickel foam before the acid etching treatment.

The oxygen evolution electrode may comprise a compressed body in which the metal carrier with the metal nanoclusters immobilized thereon is compressed to a thickness of about 1.0mm or less, for example about 0.3mm to 1.0 mm. Further, the oxygen evolution electrode may correspond to an electrode in which a plurality of compacts are stacked, for example, 1 to 10 compacts may be stacked. Therefore, the surface area of the oxygen evolution electrode can be increased, and the oxygen generation activity can be further improved.

The method of manufacturing an oxygen evolution electrode according to an exemplary embodiment of the present invention includes preparing metal nanoclusters and immobilizing the metal nanoclusters on a metal support.

Fig. 3 shows a schematic of an exemplary method of making an exemplary oxygen evolution electrode. The method of preparing the oxygen evolution electrode will be described in detail below with reference to fig. 3.

First, a metal nanocluster including a core formed of metal atoms and an organic thiol-containing ligand bonded to the surface of the core may be prepared.

The metal nanoclusters may be prepared by: the organic thiol-containing ligand is added to the solution comprising the metal precursor, and then the reducing agent is introduced and reacted.

For example, when the metal is nickel and the organic thiol-containing ligand is phenethyl thiol, for example, Ni (NO) may be added₃)₂Or NiCl₂Is added to a solvent such as n-propanol or 2-propanol to prepare a solution including the metal precursor. Preferably, the concentration of the metal precursor may be 1mM or less.

The organothiol-containing ligand can be added dropwise to the solution comprising the metal precursor over a period of 2 minutes or more. After the dropwise addition of the organic thiol-containing ligand, a compound selected from triethylamine, NaBH₄CO and mixtures thereof.

After the addition of the reducing agent, the reduction is carried out for a period of 12 hours or more and 24 hours or less. Alternatively, the reduction may be performed for 24 hours or more. When the reduction time is too short or too long, the final yield of the metal nanoclusters may be reduced.

Ni may be mixed in the prepared mixed solution of the metal nanoclusters₄(SC₂H₄Ph)₈、Ni₅(SC₂H₄Ph)₁₀And Ni₆(SC₂H₄Ph)₁₂For the separation of these substances, Preparative Thin Layer Chromatography (PTLC) can be used.

After dissolving and purifying the final product in toluene, the metal nanoclusters may be obtained by adding ethanol to the solution to form crystals.

Then, an oxygen evolution electrode is prepared by fixing the prepared metal nanoclusters to a metal support.

As a method of immobilizing the metal nanoclusters on the metal support, a method of dissolving the prepared metal nanoclusters in a solution and then dropping the solution onto the metal support may be used. By this method, a monolayer of metal nanoclusters may be deposited on a metal support.

However, the present invention is not limited thereto, and any conventional method of supporting a catalyst on a carrier may be used. For example, the metal support may be immersed in a solution containing the metal nanoclusters, or various coating methods may be used.

In addition, in order to improve the dispersibility of the metal nanoclusters, a surface treatment step of removing a surface oxide layer of the metal carrier by acid etching may be further included.

In particular, in the acid etching, the metal oxide (NiO or Ni) on the surface of the metal support can be removed by etching the metal support using sulfuric acid, nitric acid or a mixture thereof₂O₃) It may comprise a metal or metal sulfide (Ni, NiS or Ni)₂S₃)。

The metal support after the acid etching treatment may have hydrophobicity, wherein the contact angle may be increased by about 10% to 50% as compared to the metal support before the acid etching treatment. In this case, the dispersibility of the hydrophobic metal nanoclusters on the metal support may be further improved. For example, the nickel foam prior to the acid etching process may have a contact angle of about 40 to 70 degrees, and the nickel foam after the acid etching process may have a contact angle of about 70 to 150 degrees.

In the acid etching, the concentration of the acid may be about 3M or more, for example, about 3M to 18M, and the treatment time may be within about 3 minutes, for example, 1 minute to 2 minutes. When the acid concentration is less than 3M, etching may be insufficient, and when the treatment time is more than about 3 minutes, the nickel foam may be dissolved.

Impurities remaining on the surface of the surface-treated metal carrier may be removed by using an ultrasonic disperser, for example, in a distilled water and ethanol solution, and the metal carrier from which the impurities are removed may be stored in a toluene solution from which oxygen is removed to minimize air contact.

Alternatively, the method of preparing the oxygen evolution electrode may further comprise compressing the metal support immobilized with the metal nanoclusters to a thickness of about 1.0mm or less, for example, about 0.3mm to 1.0mm, and may further comprise stacking a plurality of the compressed metal supports immobilized with the metal nanoclusters. Therefore, the surface area of the oxygen evolution electrode can be increased, and the oxygen generation activity can be further improved.

An oxygen plant according to an exemplary embodiment of the invention includes a working electrode, a counter electrode, and an aqueous electrolyte.

Fig. 4 shows a schematic diagram of an exemplary oxygen plant according to an exemplary embodiment of the present invention. The oxygen plant will be described in detail below with reference to fig. 4.

The oxygen production plant 10 comprises a container 11, an aqueous electrolyte 12 filled in the container 11, and a working electrode w.e., a counter electrode c.e., and optionally a reference electrode r.e., mounted in the container 11.

The aqueous electrolyte 12 can be a source of water for the decomposition of oxygen from water and includes water and OH^-、K⁺And the like. The concentration of the aqueous electrolyte may be about 0.1M to 6.0M, for example, about 1.0M to 3.0M. When the concentration of the aqueous electrolyte is less than about 0.1M, the resistance of the solution may be high, and when it is greater than about 6.0M, the catalyst may be unstable or the electrolyte may precipitate.

The working electrode w.e. comprises an oxygen evolving electrode according to an exemplary embodiment of the invention. Since the description of the oxygen evolution electrode is the same as before, the repeated description is omitted.

The counter electrode c.e. may comprise one selected from platinum, nickel, carbon and iron. For example, a platinum mesh may be used as the counter electrode c.e.

The reference electrode R.E. can include a material selected from Ag/AgCl, Saturated Calomel Electrode (SCE), Hg/HgO, and Hg/Hg₂SO₄One of (1) and (b). For example, Ag/AgCl (3M NaCl) may be used as reference electrode r.e.

The distance between the working electrode and the reference electrode can be about 2mm to 10mm, for example, about 2mm to 5 mm. In addition, when the distance between the working electrode and the reference electrode is less than about 2mm, the resistance may be caused by the generated oxygen bubbles, and when it is greater than about 10mm, the resistance of the entire reaction cell may increase.

In this case, the area of the working electrode may be about 0.03cm²To 6.25cm²E.g. about 0.03cm²To 0.5cm². When the area of the working electrode is less than about0.03cm²When the current generated may be too small, and when it is greater than about 6.25cm²In time, the reaction solution may be consumed rapidly.

According to various exemplary embodiments, non-noble metal-based or non-carbon-based metal nanoclusters may be used for oxygen evolution (half reaction of alkaline water electrolysis). By using the catalyst preparation method of the present invention, it is possible to prepare metal nanoclusters (having a size purity of 95% or more) having high efficiency and high stability, improve the dispersibility of the catalyst in the electrode, and minimize the amount of the catalyst (e.g., -4 μ g/cm)²) And the highest level of oxygen evolution activity worldwide (e.g., 1.3A/cm at 1.60V) can be achieved by increasing the efficiency of the oxygen plant by increasing the surface area of the electrodes and decreasing the electrolyte resistance²) And high stability (e.g., 400 hours or more).

Examples

(preparation example 1: preparation of Metal nanocluster)

200mg of Ni (NO)₃)₂(0.7mmol) was added to 12mL of n-propanol and stirred for 20 minutes to prepare a solution including the metal precursor.

1.4mmol of phenethylthiol as an organic thiol-containing ligand was added dropwise to the solution comprising the metal precursor over 2 minutes. After addition of the organic thiol-containing ligand and stirring for 15 minutes, triethylamine (3.6mmol) was added as a reducing agent and reduced for 24 hours.

As shown in fig. 5, a nickel nanocluster mixture solution ((Ni) prepared for separation)₄(SC₂H₄Ph)₈、Ni₅(SC₂H₄Ph)₁₀Or Ni₆(SC₂H₄Ph)₁₂) Preparative Thin Layer Chromatography (PTLC) was used. In dichloromethane: the developer was developed for 10 minutes at a ratio of hexane to hexane from 1:1 to 1:3 (v/v).

The final product (Ni)₅(SC₂H₄Ph)₁₀) Dissolved in toluene, and then ethanol was added in an amount corresponding to 3 times that of the solution, thereby forming crystals. In particular, after the nickel nanoclusters, toluene, and ethanol solution are completely mixed,the crystal formation was slowly performed at a low temperature of 4 degrees celsius or less for 12 hours. In order to obtain the nickel nanoclusters of high purity, three or more repeated crystallization processes are performed.

(Experimental example 1 measurement of Properties of Metal nanoclusters)

Confirmation of synthesized Ni by electrospray ionization Mass Spectrometry (ESI-MS)₅(SC₂H₄Ph)₁₀The results are shown in fig. 6.

Ni separation by PTLC, as shown in FIG. 6₅(SC₂H₄Ph)₁₀The size purity of (a) is 95% or more, demonstrating that a high-purity nickel nanocluster is synthesized.

Therefore, it is possible to mass-produce high-purity nickel nanoclusters by increasing the precursor and reaction solution.

(preparation example 2: preparation of oxygen evolving electrode)

To form stable Ni₅(SC₂H₄Ph)₁₀A nickel foam electrode is first prepared by removing the surface oxide layer of nickel foam by etching with sulfuric acid and nitric acid, respectively. Specifically, the concentration of sulfuric acid and nitric acid was 3M, and each treatment time was 3 minutes.

Impurities remaining on the surface of the surface-treated nickel foam were removed using an ultrasonic disperser in distilled water and an ethanol solution for 20 minutes each. The nickel foam, freed of impurities, is kept in a toluene solution freed of oxygen to minimize air contact.

Further, Ni synthesized in preparation example 1 was added₅(SC₂H₄Ph)₁₀Dissolved in a tetrahydrofuran solution, and then the solution was dropped onto the surface-treated nickel foam, thereby forming an electrode.

Highly dispersed Ni₅(SC₂H₄Ph)₁₀The catalytic activity can be achieved with a very small deposition amount (about 4 μ g).

(Experimental example 2: measurement of characteristics of surface-treated Metal Carrier)

The chemical properties of the surface-treated foamed nickel in preparation example 2 were determined by X-ray photoelectron spectroscopy (XPS), and the results are shown in fig. 7 to 9.

In FIGS. 7 to 9, "H₂SO₄Treated NF "means nickel foam surface treated with sulfuric acid," HNO₃Treated NF "refers to nickel foam surface treated with nitric acid and" bare NF "refers to nickel foam not surface treated with sulfuric or nitric acid.

As shown in fig. 7 to 9, in all of the nickel foams surface-treated with sulfuric acid or nitric acid, the surface oxide layer rapidly decreased. That is, NiO or Ni is formed on the surface of the foamed nickel₂O₃The oxide layer in the form of Ni, NiS and Ni is removed₂S₃In the form of (1).

In addition, the physical properties of the surface-treated nickel foam were determined by a contact angle measuring instrument, and the results are shown in fig. 10.

In FIG. 10, "H₂SO₄Treated NF "means nickel foam surface treated with sulfuric acid," HNO₃Treated NF "refers to nickel foam surface treated with nitric acid and" bare NF "refers to nickel foam not surface treated with sulfuric or nitric acid.

As shown in fig. 10, it was confirmed that the nickel foam before surface treatment had hydrophilicity (contact angle: 45.8 degrees), while all of the sulfuric acid-treated nickel foam (contact angle: 90.5 degrees) and the nitric acid-treated nickel foam (contact angle: 82.8 degrees) had relatively high hydrophobicity due to the reduction of the surface oxide layer.

The dispersion degree of the nickel nanoclusters in the electrode is significantly increased due to hydrophobic-hydrophobic interaction between the foamed nickel changed to be hydrophobic and the ligands of the nickel nanoclusters.

In addition, the electrochemical surface area of the surface-treated nickel foam was measured by the ferrocene cyclic amperometry (A)_ECSA) The results are shown in fig. 11.

As shown in FIG. 11, A of the nickel foam was determined_ECSAAnd geometric area (A)_geo) The ratio of (A) to (B) is 4.86.

(Experimental example 3: measurement of characteristics of oxygen evolution electrode)

By passingLoop current method and constant voltage method measurement of nickel (H) foam surface-treated by fixing nickel nanoclusters to sulfuric acid and nitric acid₂SO₄_NF，HNO₃NF) and nickel foam without surface treatment (untreated NF), the results of which are shown in fig. 12 to 14, respectively. The oxygen evolution activity was measured at 1.0M KOH (pH 14).

As shown in FIG. 12, in Ni₅(SC₂H₄Ph)₁₀In the case of nickel foam (nitric acid surface treatment), the initial voltage was 1.50V and 200mA cm^-2The realized voltage of (2) is 1.70V. In Ni₅(SC₂H₄Ph)₁₀In the case of nickel foam (sulfuric acid surface treatment), the initial voltage was 1.5V and 200mA cm^-2The realized voltage of (2) is 1.65V.

And the absence of Ni₅(SC₂H₄Ph)₁₀Compared with the nickel foam (bare NF), the oxygen evolution activity of the two electrodes is improved by about 5 times or more, and compared with Ni₅(SC₂H₄Ph)₁₀Oxygen evolution activity was increased by about 2-fold or more (based on current density at 1.70V) compared to the nickel foam electrode without surface treatment.

As shown in FIGS. 13 and 14, Ni was measured by the loop current method₅(SC₂H₄Ph)₁₀Nickel foam (sulfuric acid surface treatment) has high oxygen evolution stability of 500 or more cycles and when measured by a constant voltage method at 200 mA-cm^-2Or higher current density, Ni₅(SC₂H₄Ph)₁₀Nickel foam (sulfuric acid surface treatment) has high oxygen evolution stability of 400 hours or more.

In addition, as determination of Ni₅(SC₂H₄Ph)₁₀Results of stability of the/carbon electrode during oxygen evolution, in experiments with loop current method of 200 or more cycles, it was determined that corrosion occurred in the electrode, resulting in a rapid decrease in oxygen production activity.

(Experimental example 4 surface area of oxygen evolution electrode)

The oxygen evolution electrode having a thickness of 1.6mm prepared in preparation example 2 was compressed to a thickness of 1.0mm or less, the surface area thereof was increased to 1, 2, 3 and 4 times, respectively, and their oxygen generation activities were measured, respectively, and the results are shown in fig. 15.

As shown in FIG. 15, Ni having a surface area increased by 4 times by compression₅(SC₂H₄Ph)₁₀The nickel foam (sulfuric acid surface treatment) electrode realizes 200 mA-cm under the voltage of 1.57V^-2Oxygen generation activity of 280mA cm at a voltage of 1.60V^-2Oxygen generating activity of (1.63) and realized 400mA cm at a voltage of 1.63V^-2Oxygen generating activity of (1).

(Experimental example 5 optimization of oxygen generating apparatus)

An oxygen generation apparatus having the structure shown in fig. 4 was manufactured using the oxygen evolution electrode prepared in preparation example 2.

In this case, in order to minimize the resistance R of the aqueous electrolyte_sThe distance W between the working electrode and the reference electrode was minimized (2mm), and the distance C between the counter electrode and the reference electrode was set to 10 mm.

In this case, the oxygenerating activity of the oxygen evolution electrode, the charge transfer resistance R of the oxygen evolution electrode, is determined by Electrochemical Impedance Spectroscopy (EIS)_ctAnd electrolyte resistance R_sThe results are shown in fig. 16 and 17, respectively.

As shown in fig. 16 and 17, when R is_sWhen minimized, determine Ni₅(SC₂H₄Ph)₁₀Oxygen generation activity of nickel foam (sulfuric acid surface treatment) electrode (x4) was 1.50V initial voltage, 400 mA/cm at 1.60V^-2At this time, the electrolyte resistance R_sIs 0.25 omega.

To further reduce the electrolyte resistance R_sThe distance between the working electrode and the reference electrode was fixed at 2mm, and then the concentration of the electrolyte was increased from 1.0M to 5.0M. In this case, the charge transfer resistance R of the oxygen evolution electrode is still determined by EIS_ctAnd electrolyte resistance R_sAnd the results are shown in fig. 18 and fig. 19.

As shown in FIGS. 18 and 19, R is determined_sReduceTo 0.15. omega. Ni₅(SC₂H₄Ph)₁₀Nickel foam (sulfuric acid surface treatment) electrode (x4) having oxygen generation activity of 1.50V at 5.0M and 840 mA-cm at 1.60V^-2。

To minimize the corrected iR effect, the electrode area was varied from 0.5cm²Reduced to 0.03cm². In this case, the charge transfer resistance R of the oxygen evolution electrode is still determined by EIS_ctAnd electrolyte resistance R_sThe results are shown in fig. 20 and 21.

As shown in FIGS. 20 and 21, Ni is applied before iR correction₅(SC₂H₄Ph)₁₀Foamed nickel (sulfuric acid surface treatment) electrode (x4, 0.03 cm)²) The oxygen generation activity at 5.0M is an initial voltage of 1.48V and 1100mA cm at 1.60V^-2After iR correction, the voltage was 1.48V at 1.60V at 1300mA cm^-2. This is the world's highest level of oxygen production activity.

While the invention has been described in connection with the presently exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.