KR20210061958A - Method for manufacturing Metal-Organic Frameworks and Layered Double Hydroxide Composite Using Electrodeposition - Google Patents

Abstract

The present invention relates to a method for manufacturing a metal-organic framework catalyst and a layered double hydroxide composite using an electrodeposition method, in which a cobalt-phosphorus framework and a cobalt-iron layered double hydroxide derived from the metal-organic framework through a simple electrodeposition method are manufactured as a hierarchical structure so as to provide a water electrolytic electrode in which both hydrogen and oxygen evolution reactions occur well under basic conditions.

Description

Method for manufacturing Metal-Organic Frameworks and Layered Double Hydroxide Composite Using Electrodeposition}

The present invention relates to a method for producing a metal organic skeleton and a layered double hydroxide composite using an electro-deposition method.

As the hydrogen energy industry becomes active, electrochemical water electrolysis, which uses water to obtain hydrogen without releasing pollutants, is in the spotlight. Electrochemical water electrolysis is a reaction in which electric energy is applied to water to generate hydrogen and oxygen, respectively, and consists of an oxygen generating reaction and a hydrogen generating reaction, respectively. Since it is necessary to consume a minimum amount of energy while obtaining hydrogen, it is essential to develop a material having a minimum overvoltage at a target current. Precious metals such as ruthenium and iridium are known to exhibit high activity and stability as a catalyst for generating oxygen, and a platinum catalyst is the most representative catalyst for generating hydrogen. However, due to the high price of these catalysts, it is necessary to develop a catalyst having a performance comparable to that of these precious metals while being inexpensive for practical industrial applications.

Metal-Organic Frameworks are materials having a large surface area and pores by combining metal ion clusters and organic material ligands. Due to the manufacturing characteristics, gas adsorption and catalyst characteristics can be expressed as desired depending on the type and size of metal ions and ligands used. In addition, it is possible to prepare a catalyst that is stable even in strong acids and strong bases while removing organic substances through additional heat treatment and gas phase reaction to the resulting skeleton.

Layered double hydroxide is a material having a layered structure represented by the formula ^{[M 2+} _1-x M ³⁺ x(OH) ₂ ](A ^n- ) _x /n·H _{2 O.} Here, M means a metallic substance, and it means divalent and trivalent ions, respectively. A ^n- means an anion inserted into each layer. It is widely known that various catalytic properties can be expressed depending on the type and composition of metal ions used in this structure. In particular, materials made of transition metal complexes such as nickel, iron, and cobalt are being studied as catalysts for generating oxygen and hydrogen.

One of the important factors as a water electrolytic electrode is a large catalytic activity site. Even if a material with a large surface area is used, the reaction does not easily occur if there is no active site that can actually participate in the reaction. In addition, unlike hydrogen evolution, the mechanism of oxygen evolution is very complex and electron transfer is involved a lot. Therefore, it is essential to develop a material having an active and large surface area.

The metal organic framework is a material sufficiently satisfying the above-described large surface area. However, by itself, the structure is broken under the conditions of strong acid and strong base where the actual reaction takes place, and the water electrolysis efficiency is not high. In a recent study, an attempt was made to synthesize a material having a hierarchical structure by forming a complex of this metal-organic framework and a layered double hydroxide. However, most of the manufacturing methods are hydrothermal synthesis that requires high temperature and a long time. Instead of depositing directly on the electrode, it is not deposited directly on the electrode, but synthesizes a powdery material and mixes it with an adhesive to form a slurry. do. This process not only requires a long time, but also has a disadvantage in that the adhered material comes off as time passes, and as a result, it becomes vulnerable to long-time driving.

Therefore, in order to solve the above problems, it is necessary to develop a high-performance catalyst having a simple manufacturing process, can be deposited directly on an electrode, and has low interfacial resistance. The present invention is a water electrolytic electrode in which both hydrogen and oxygen generation reactions occur well under basic conditions by preparing a cobalt-phosphorus skeleton and a cobalt-iron layered double hydroxide in a hierarchical structure through a simple electro-deposition method. I want to provide.

In order to achieve the object of the present invention as described above, the present invention comprises the steps of forming a cobalt-phosphorus skeleton on a carbon substrate; And electro-depositing a cobalt-iron layered double hydroxide on the cobalt-phosphorus skeleton.

The composite may be prepared through an electro-deposition method.

In addition, the present invention provides a metal-organic framework-layered double hydroxide composite prepared by the above method.

In addition, it provides a water electrolytic electrode comprising the metal-organic framework-layered double hydroxide complex.

The formation of the metal-organic framework and the layered double hydroxide complex has been reported in recent papers, but most methods do not deposit directly on the substrate, but (1) obtain the metal-organic framework in the form of powder (2) the obtained powder through hydrothermal synthesis. Evaporation of layered double hydroxide (3) The obtained powder is deposited on a substrate through a binder. However, this process is inefficient for practical use. In the present invention, it is significant that the metal-organic framework and the layered double hydroxide composite were deposited directly (In-situ) on a substrate without a binder.

Specifically, in the present invention, a metal-phosphorus structure derived from a metal-organic framework and a layered double hydroxide composite are manufactured using an electrodeposition method.

In general, the formation of a layered double hydroxide complex with a material derived from a metal-organic framework is prepared by hydrothermal synthesis, but this process requires high temperature and high pressure conditions and a long reaction time. In the present invention, a metal-phosphorus structure derived from a metal organic framework and a layered double hydroxide composite structure are synthesized directly on a carbon substrate by using an electro-deposition method. It is expected that it can be synthesized in a similar manner to not only cobalt-phosphorus, but also cobalt-sulfur, nickel-sulfur, nickel-phosphorus, and the like.

The metal-organic framework-layered double hydroxide composite prepared by the present invention exhibits better catalytic performance than a single cobalt-phosphorus structure and a cobalt-iron layered double hydroxide, and the prepared composite is lower than that of a single cobalt-iron layered double hydroxide. It shows the interface resistance.

1 is a schematic diagram of a process for preparing a cobalt-phosphorus skeleton-layered double hydroxide derived from a cobalt-based metal organic skeleton.
2 is an FE-SEM photograph of a cobalt-phosphorus skeleton synthesized on a carbon substrate and a layered double hydroxide composite ((a) and (e) are cobalt-based metal organic skeletons, and (b) and (f) are metal organic skeletons. Cobalt-phosphorus skeleton substituted from the skeleton, (c), (g) are cobalt-iron layered double hydroxide, (d), (f) are cobalt-phosphorus skeleton and layered double hydroxide complex).
Figure 3 shows the FE-SEM picture and EDS-mapping of the cobalt-phosphorus skeleton ((a) is the FE-SEM picture of the cobalt-phosphorus skeleton, (b) is the cobalt atom distribution of the cobalt-phosphorus skeleton, ( c) is the distribution of nitrogen atoms in the cobalt-phosphorus skeleton, (d) is the distribution of phosphorus atoms in the cobalt-phosphorus skeleton).
Figure 4 shows the FE-SEM photograph and EDS-mapping of the cobalt-iron layered double hydroxide ((a) is the FE-SEM photograph of the cobalt-iron layered double hydroxide, (b) is the cobalt atom of the cobalt-iron layered double hydroxide Distribution, (c) is the distribution of iron atoms in the cobalt-iron layered double hydroxide, (d) is the distribution of oxygen atoms in the cobalt-iron layered double hydroxide).
5 shows the FE-SEM and EDS-mapping of the cobalt-phosphorus skeleton and the layered double hydroxide complex ((a) is an FE-SEM picture of the cobalt-phosphorus skeleton and the layered double hydroxide complex, and (b) is cobalt -Cobalt atom distribution in the phosphorus skeleton and the layered double hydroxide complex, (c) is the iron atom distribution in the cobalt-phosphorus skeleton and the layered double hydroxide complex, (d) is the oxygen atom of the cobalt-phosphorus skeleton and the layered double hydroxide complex Distribution, (e) is the distribution of nitrogen atoms in the cobalt-phosphorus skeleton and the layered double hydroxide complex, (f) is the distribution of phosphorus atoms in the cobalt-phosphorus skeleton and the layered double hydroxide complex).
6 shows the XPS spectrum of the electrode of the cobalt-phosphorus skeleton-layered double hydroxide composite ((a) is the XPS spectrum of the cobalt-phosphorus skeleton-layered double hydroxide composite electrode, and (b) is the cobalt-phosphorus skeleton- XPS spectrum of elemental cobalt of the layered double hydroxide composite electrode, (c) is the XPS spectrum of elemental iron of the cobalt-phosphorus skeleton-layered double hydroxide composite electrode, and (d) is the XPS spectrum of the cobalt-phosphorus skeleton-layered double hydroxide composite electrode. XPS spectrum of elemental phosphorus)
7 shows a Fourier transform infrared spectroscopy graph of a cobalt-based metal organic skeleton, a cobalt-phosphorus skeleton, a layered double hydroxide, a cobalt-phosphorus skeleton and a layered double hydroxide complex.
8 is an electrochemical analysis result of an electrochemical oxygen generation experiment of a cobalt-phosphorus skeleton prepared in the present invention, a layered double hydroxide, two cobalt-in skeletons and a layered double hydroxide composite electrode with different deposition times, and carbon fiber. ((A) is the linear scanning potential method, (b) is the Tafel slope, (c) is ^{the overvoltage required to reach the current density of 10 mA cm -2} , (d) is the impedance spectroscopy method, and (e) is the current density. Required overvoltage, (f) is a long-term stability test at ^{10 mA cm -2 condition).}
9 is an electrochemical analysis of the cobalt-phosphorus skeleton prepared in the present invention, a layered double hydroxide, two cobalt-phosphorus skeletons with different deposition times and a layered double hydroxide composite electrode, and an electrochemical hydrogen generation experiment of carbon fiber and 2 -The results of the electrode experiment are shown ((a) is the linear scanning potential method, (b) is the Tafel slope, (c) is ^{the overvoltage required to reach a current density of 10 mA cm -2} , (d) is the impedance spectroscopy method, and (e) is Linear scanning potential method of a two-electrode experiment, (f) is a long-term stability test under ^{10 mA cm -2 condition of a two-electrode experiment).}
FIG. 10 shows a graph of electrochemically active surface area analysis using cyclic voltammetry ((a) is a cyclic voltammetric current curve of a cobalt-phosphorus skeleton, (b) is a cyclic voltammetric current curve of a cobalt-iron layered double hydroxide, ( c) is the cyclic voltammetry curve of the cobalt-phosphorus skeleton and the layered double hydroxide complex, (d) is the cobalt-phosphorus skeleton, the cobalt-iron layered double hydroxide, and the electrochemical of the cobalt-phosphorus skeleton and the layered double hydroxide complex. Active surface area comparison graph).

Hereinafter, the present invention will be described in detail.

The present invention comprises the steps of forming a cobalt-phosphorus skeleton on a carbon substrate; And

It provides a method for producing a metal-organic framework-layered double hydroxide composite comprising; electro-depositing a cobalt-iron layered double hydroxide on the cobalt-phosphorus skeleton.

In the present invention, the metal-organic framework-layered double hydroxide composite may be deposited in-situ on a carbon substrate without using a binder.

A schematic diagram of the manufacturing method is shown in FIG. 1, and an FE-SEM photograph of a cobalt-phosphorus skeleton-layered double hydroxide is shown in FIG. 2.

The surface of the carbon substrate may be modified with hydroxy. In the present invention, the carbon substrate is supported in a piranha solution and then washed with distilled water to modify the surface with hydroxy, but is not limited thereto.

In the present invention, "Piranha solution" refers to a liquid in which concentrated sulfuric acid: hydrogen peroxide is mixed in a ratio of 2:1 to 7:1, and in the present invention, it is used in a ratio of 3:1.

In the present invention, the cobalt-phosphorus skeleton can be prepared by depositing and firing a cobalt zeolite imidazolate skeleton (CoZIF) on a carbon substrate to obtain cobalt oxide, and then replacing it with a cobalt-phosphorus skeleton.

In the cobalt zeolite imidazolate skeleton (CoZIF), the surface-modified carbon substrate is used as cobalt nitrate hydroxide (Co(NO ₃ ) ₂ ·6H ₂ O):2-methylimidazole 1:4 to 1:20, Preferably, it can be deposited by supporting the mixed solution in a molar ratio of 1:5 to 1:15, more preferably 1:7 to 1:9. For example, 80 mL of distilled water may be used based on a 2 cm x 5 cm substrate.

In the present invention, when the cobalt zeolite imidazolate skeleton (CoZIF) is deposited on a carbon substrate, it can be fired at a temperature of 300 to 450°C, preferably 300 to 370°C, more preferably 300 to 350°C. When firing at a temperature of less than 300℃ during firing, the precursor may not be decomposed, so that phosphorus compounds may not be formed. If fired at a temperature higher than 450℃, the zeolite imidazolate skeleton (ZIF) structure is greatly The catalytic performance may decrease due to shrinkage.

The firing may be performed for 0.1 to 2 hours, preferably 0.5 to 1.5 hours, more preferably 0.8 to 1.2 hours. If it is fired for less than 0.1, sufficient phosphorus compounds cannot be formed, and if it is fired for more than 2 hours, the zeolite imidazolate skeleton (ZIF) structure shrinks greatly due to the rapid reaction rate, and catalytic performance may deteriorate.

During this process, the skeleton of the zeolite imidazolate skeleton (ZIF) is maintained, while cobalt is oxidized to cobalt oxide.

In the present invention, when the cobalt oxide obtained above is substituted with a cobalt-phosphorus skeleton, it may be substituted by a gas phase reaction using a phosphorus compound.

The phosphorus compound may be sodium hypophosphite or red phosphorous, more preferably sodium hypophosphite, but is not limited thereto.

The gas phase reaction may be carried out under an argon atmosphere.

The gas phase reaction is heated by 2 degrees per minute, and may be carried out at a temperature of 200 to 400°C, preferably 250 to 350°C, and more preferably 280 to 330°C. The gas phase reaction may increase the temperature every 1 to 5 minutes, and if the temperature is rapidly increased, it may not be easy to control the temperature inside the furnace, and it may be difficult to accurately adjust the desired temperature to experiment. At a temperature of less than 200° C., the precursor for the ignition reaction may not be sufficiently vaporized and thus may not react with the electrode.

The gas phase reaction may be carried out for 0.1 to 2 hours, preferably 0.5 to 1.5 hours, more preferably 0.8 to 1.2 hours. In a reaction time of less than 0.1 hour, sufficient ignition may not be achieved.

In the present invention, the gas phase reaction is based on the carbon fiber substrate 2 cm x 5 cm, the flow rate of argon gas is 100 to 300 ccm, sodium hypophosphite may be used 0.1 to 0.4 g.

In the present invention, the electrodeposition may be performed by supporting a carbon substrate on which a cobalt-phosphorus skeleton is formed in an electrolyte, and using a reference electrode and a counter electrode.

The electrolyte is an aqueous solution containing 0.1 to 0.2 mol/L of a cobalt compound and an iron compound, respectively. A method for preparing a metal organic skeleton-layered double hydroxide composite.

The cobalt compound may be cobalt nitrate or cobalt chloride, preferably cobalt nitrate. The iron compound may be iron sulfate or iron chloride, preferably iron sulfate. Each of the cobalt compound and the iron compound may be 0.1 to 0.2, preferably 0.12 to 0.18, more preferably 0.14 to 0.16 mol/L, and the sum of the cobalt compound and the iron compound may be 0.3 mol/L. Divalent ions and trivalent ions must be mixed for smooth electrodeposition. If only one ion is present, the electro-deposition process does not proceed well, and may have lower electrical performance than a single compound of cobalt and iron.

The reference electrode is Ag/AgCl electrode, Calomel electrode, Hg/HgO electrode or Ag/Ag ₂ SO ₄ electrode, counter electrode is platinum electrode, more preferably reference electrode is Ag/AgCl electrode, counter electrode is platinum It may be an electrode, but is not limited thereto.

The electrodeposition may be performed at a voltage of -1 to -2V, preferably -0.9 to -1.5V, more preferably -0.8 to -1.2V. At voltages lower than -0.8V, only one metal can be deposited, and at voltages exceeding -2V, hydrogen gas formed around it due to too much current may interfere with the electric deposition.

Electrodeposition may be performed for 1 to 300 seconds, preferably 10 to 200 seconds, more preferably 15 to 100 seconds. At a deposition time of less than 1 second, the amount of deposition may be small and the catalytic active surface area may be insufficient, and a deposition time of more than 300 seconds may cause an increase in series resistance and inhibition of electrolyte penetration.

The composite according to the present invention can be prepared through the following steps.

1. Deposition of cobalt zeolite imidazolate frameworks (ZIF) after hydrophilic treatment of carbon substrates.

2. Cobalt zeolite imidazolate skeleton calcined.

3. Substitution of cobalt oxide with cobalt-phosphorus.

4. Cobalt-iron layered double hydroxide deposition.

It is possible to provide a metal-organic framework-layered double hydroxide composite prepared according to the manufacturing method of the present invention.

The metal-organic framework-layered double hydroxide composite prepared according to the production method of the present invention has an active surface area of ^{1 to 10 mF cm 2} , preferably 2 to 8 mF cm ² , more preferably 4 to 6 mF cm ^2. I can have it.

It is possible to provide an electrode including the metal organic skeleton-layered double hydroxide complex.

The electrode provided by the present invention can be used in photoelectrochemistry. Preferably, it may be used as a supercapacitor electrode, an oxygen reduction electrode, a photoelectrochemical water electrolysis, and more preferably a photoelectrochemical water electrolysis electrode, but is not limited thereto.

Hereinafter, preferred examples and experimental examples are presented to aid in understanding the present invention. However, the following Examples and Experimental Examples are provided for easier understanding of the present invention, and the contents of the present invention are not limited by the following Examples and Experimental Examples.

Example

<Production Example 1> Method for forming a composite of a metal-organic skeleton and a layered double hydroxide

Step 1: Hydrophilic treatment of carbon substrate and deposition of cobalt zeolite imidazolate frameworks (ZIF)

The carbon substrate was treated with a piranha solution and supported for 24 hours. Carbon substrate hydrophilic treatment in an aqueous electrolyte solution in which 0.582 g of cobalt nitrate hydroxide (Co(NO ₃ ) ₂ ·6H ₂ O) and 1.312 g of 2-methylimidazole (molar ratio 1:8) were dissolved in 80 mL of distilled water Cobalt on the substrate by carrying Zeolite Imidazolate Frameworks (ZIF) are deposited. At this time, the part to be in contact with the electrode is blocked using PTFE tape. After soaking for 4 hours, the substrate is taken out and washed several times with an excess of distilled water.

Step 2: Calcination of cobalt zeolite imidazolate skeleton

The cobalt-based metal-organic structure (ZIF) manufactured through step 1 is fired through heat treatment at 350° C. for 1 hour. At this time, the temperature increase rate was 2°C/min, and air in the atmosphere was used as the internal gas.

Step 3: Substitution of cobalt oxide with cobalt-phosphorus

The cobalt oxide that has passed through step 2 is put into a tubular furnace and replaced with a cobalt-phosphorus structure through a gas phase reaction of sodium hypophosphite. At this time, the heating rate is 2℃/min, and the internal gas flows argon at a flow rate of 200ccm. It is allowed to react at 300° C. for 1 hour, and hypophosphorous acid is placed above the tubular furnace.

Step 4: Cobalt-iron layered double hydroxide deposition

The cobalt-phosphorus structure that has passed through step 3 forms a composite through an electro-deposition method. An electrode was connected and supported in a 0.15 M aqueous solution of cobalt nitrate and iron sulfate, and electro-deposited at -1 V for 25 seconds using the structure of step 3 as a working electrode, Ag/AgCl as a reference electrode, and platinum electrode as a counter electrode. The prepared composite is washed several times in distilled water and then sufficiently dried in an oven.

A method of forming a composite of the metal-organic skeleton and the layered double hydroxide is schematically shown in FIG. 1.

In the present invention, an FE-SEM photograph of a cobalt-based metal organic skeleton deposited on a carbon fiber is shown in FIG. 2. The metal organic framework was grown in the shape of a leaf (Fig. 2(a), 2(e)), and it was confirmed that the structure was well maintained even when substituted with cobalt oxide, and cobalt-phosphorus structure (Fig. 2(b), 2 (f)). The layered double hydroxide prepared by the electro-deposition method was uniformly deposited in the form of a sheet on a carbon fiber substrate (Figs. 2(c) and 2(g)). The cobalt-phosphorus structure and the layered double hydroxide composite prepared in the present invention were thinly and uniformly deposited on the structure of the leaf-shaped metal organic framework.

EDS analysis was used to determine the element of the material deposited on the carbon fiber substrate, and is shown in FIG. 3. From the cobalt-phosphorus structure, it can be seen that cobalt (FIG. 3(b)), nitrogen (FIG. 3(c)), and phosphorus (FIG. 3(d)) are uniformly distributed throughout. 3(a) is an SEM image used for EDS analysis. Here, it was confirmed that nitrogen was contained in 2-methylimidazole, and remained after heat treatment at about 350°C.

The cobalt-iron layered double hydroxide was also analyzed through EDS and shown in FIG. 4. It was confirmed that cobalt (FIG. 4(b)), iron (FIG. 4(c)), and oxygen (FIG. 4(d)) were uniformly distributed at a voltage of about -1 V despite the different reduction potentials of cobalt and iron. I did. Fig. 4(a) is an SEM image used for this EDS analysis.

After depositing a cobalt-iron layered double hydroxide on the prepared cobalt-phosphorus structure, through EDS analysis, cobalt (Fig. 5(b)), iron (Fig. 5(c)), oxygen (Fig. 5(d)), It was confirmed that nitrogen (FIG. 5(e)) and phosphorus (FIG. 5(f)) were uniformly deposited. 5(a) is an SEM image used for this EDS analysis.

In the XPS experiment, data corrected according to the carbon 1s level was used, and a spectrum graph is shown in FIG. 6. The spectrum shows that the prepared cobalt-phosphorus structure-layered double hydroxide complex detected cobalt, iron, oxygen, nitrogen, carbon, and phosphorus, respectively (FIG. 6(a)). In cobalt, the ratio of trivalent ions to divalent ions was approximately 1.12 (Fig. 6(b)). In the case of iron ions, divalent and trivalent ions also appeared together, and the ratio of trivalent ions to divalent is about 0.69. Two characteristic 2p spectra of phosphorus, Pox and a doublet near 130 eV, indicate that phosphorus was well substituted through a gas phase reaction (Fig. 6(d)).

The results of the FT-IR experiment are shown in FIG. 7. The cobalt organometallic complex prepared through the FT-IR experiment showed a broad and strong pattern due to hydrogen bonding between nitrogen and hydrogen present in 2-methylimidazole, and a characteristic ring of methyl imidazole was confirmed. The layered double hydroxide exhibits a wide range of stretching bonds due to a hydroxyl group, and at the same time exhibits a characteristic due to a symmetric-asymmetric stretching bond of a carboxyl group. Even after the cobalt organometallic structure was substituted with phosphorus, a certain aspect was exhibited, and the cobalt-phosphorus structure and the layered double hydroxide composite showed all of their characteristic bonds.

Electrochemical analysis

Electrochemical properties of the electrode prepared according to Preparation Example 1 were confirmed.

First, an oxygen generation experiment was performed, and is shown in FIG. 8. In the oxygen evolution experiment, each electrode was tested by a linear scanning potential method in 1M potassium hydroxide solution. The electrode made as Preparation Example 1 showed a higher current density at a lower overvoltage than that of a pure layered double hydroxide and cobalt-phosphorus structure (FIG. 8(a)). The Tafel slope can be shown as the activity of the electrochemical reaction, and the cobalt-phosphorus structure and the layered double hydroxide composite exhibited excellent performance with the lowest Tafel slope (FIG. 8(b)). 270 mV was required as an overvoltage to reach the current density of 10 mA cm ^-2 (Fig. 8(c)), and the electron transfer resistance was the lowest through impedance spectroscopy, and the interface resistance was large compared to the pure layered double hydroxide. Decreased (Fig. 8(d)). Increasing the current density little by little, the required overvoltage showed a stable appearance in a stepped shape (FIG. 8(e)), and even if it was operated for a long time, there was no deterioration in performance (FIG. 8(f)).

It was confirmed that the electrode prepared according to Preparation Example 1 can also be used as a working electrode for a hydrogen generation experiment, and is shown in FIG. 9. The performance confirmed by the linear scanning potential method was excellent in cobalt-phosphorus double layered hydroxide (FIG. 9(a)). The degree of activity of the reaction observed through the Tafel slope was also excellent as a slope lower than that of other pure cobalt-phosphorus structures or cobalt-iron layered double hydroxides (FIG. 9(b)). The overvoltage to reach the current density of 10 mA cm ^-2 was 172 mV (Fig. 9(c)), and the electron transfer resistance observed through impedance spectroscopy also showed the lowest resistance, and similar to the oxygen generation experiment, the interface resistance was pure. It was reduced than that of the layered double hydroxide and there was no significant difference from the cobalt-phosphorus structure (Fig. 9(d)). The electrode prepared in the present invention is a two-electrode experiment, and hydrogen and oxygen can be generated by placing the same electrode on both sides. When tested by the linear scanning potential method using both of the cobalt-phosphorus structure and the layered double hydroxide, the ^{voltage for reaching the current density of 10 mA cm -2} was 1.66V (Fig. 9(e)). In addition, a long-term stability test was conducted under this condition, but no deterioration in performance was observed even when driving for 50 hours (Fig. 9(f)).

The electrode prepared in the present invention is a composite in which a layered double hydroxide is bonded to a metal organic skeleton having a large surface area. The layered double hydroxide also has a large surface area and a structure having pores that can easily remove air bubbles from water electrolysis, and the electrochemical surface area of the resulting composite was confirmed by using a cyclic current voltage method. The cobalt-phosphorus structure (Fig. 10(a)), the cobalt-iron layered double hydroxide (Fig. 10(b)), and the cobalt-phosphorus structure and the layered double hydroxide complex (Fig. 10(c)) are in the range of -0.025 V and 0.025 V. The cyclic current voltammetry is investigated at various potential scan rates, and the relative electrochemically active surface area can be calculated through the difference in current values according to the scan rates (FIG. 10(d)). Among them, the cobalt-phosphorus structure and the layered double hydroxide composite showed the largest active surface area of ^{5.60 mF cm 2.}

Claims (21)

Forming a cobalt-phosphorus skeleton on a carbon substrate; And
Electrodepositing a cobalt-iron layered double hydroxide on the cobalt-phosphorus skeleton; a method for producing a metal organic skeleton-layered double hydroxide composite comprising. The method of claim 1,
The carbon substrate is a metal organic framework whose surface is modified with hydroxy-a method for producing a layered double hydroxide composite. The method of claim 1,
The cobalt-phosphorus skeleton is a metal organic skeleton-layered double hydroxide composite obtained by depositing and firing a cobalt zeolite imidazolate skeleton (CoZIF) on a carbon substrate to obtain cobalt oxide, and then replacing it with a cobalt-phosphorus skeleton. Way. The method of claim 3,
The cobalt zeolite imidazolate skeleton is supported in a solution in which a carbon substrate _{is mixed with cobalt nitrate hydroxide (Co(NO 3} ) ₂ ·6H ₂ O):2-methylimidazole in a molar ratio of 1:4 to 1:20. The method of producing a metal-organic framework-layered double hydroxide composite by vapor deposition. The method of claim 3,
The sintering is carried out at a temperature of 300 to 450° C. A method for producing a metal-organic skeleton-layered double hydroxide composite. The method of claim 3,
The sintering is carried out for 0.1 to 2 hours. The method for producing a metal organic skeleton-layered double hydroxide composite. The method of claim 3,
A method for producing a metal organic skeleton-layered double hydroxide complex in which cobalt oxide is substituted with a cobalt-phosphorus skeleton through a gas phase reaction of a phosphorus compound. The method of claim 7,
The phosphorus compound is sodium hypophosphite or red phosphorous, which is a method for producing a metal organic skeleton-layered double hydroxide complex. The method of claim 7,
The gas phase reaction is carried out under an argon atmosphere, a metal organic framework-a method for producing a layered double hydroxide composite. The method of claim 7,
The gas phase reaction is carried out at a temperature of 200 to 400 ℃ metal organic framework-a method for producing a layered double hydroxide composite. The method of claim 7,
The gas phase reaction is carried out for 0.1 to 2 hours, the method for producing a metal-organic framework-layered double hydroxide composite. The method of claim 1,
Electrodeposition is carried out by supporting a carbon substrate on which a cobalt-phosphorus skeleton has been formed in an electrolyte, and using a reference electrode and a counter electrode to prepare a metal organic skeleton-layered double hydroxide composite. The method of claim 12,
The electrolyte is an aqueous solution containing 0.1 to 0.2 mol/L of a cobalt compound and an iron compound, respectively. A method for preparing a metal organic skeleton-layered double hydroxide composite. The method of claim 13,
The cobalt compound is cobalt nitrate or cobalt chloride. A method for preparing a metal organic skeleton-layered double hydroxide complex. The method of claim 13,
The iron compound is iron sulfate or iron chloride. A method for preparing a metal-organic framework-layered double hydroxide composite. The method of claim 12,
The reference electrode is an Ag/AgCl electrode, a Calomel electrode, an Hg/HgO electrode or an Ag/Ag ₂ SO ₄ electrode, and the counter electrode is a platinum electrode. The method of claim 12,
Electrodeposition is carried out at a voltage of -0.8 to -2V metal organic framework-a method for producing a layered double hydroxide composite. The method of claim 12,
Electrodeposition is carried out for 1 to 300 seconds metal organic framework-a method for producing a layered double hydroxide composite. A metal-organic skeleton prepared according to the manufacturing method of any one of claims 1 to 18-a layered double hydroxide composite. The method of claim 19,
With an active surface area of 1 to 10 mF cm ²
Metal organic framework-layered double hydroxide complex. An electrode comprising the metal-organic framework according to claim 19-layered double hydroxide complex.

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