KR102554754B1 - Manufacturing method of hierarchically designed como marigold flower-like 3d nano-heterostructure as an efficient electrocatalyst for oxygen and hydrogen evolution reactions and layered double hydroxide manufactured by the same - Google Patents

Abstract

The present invention relates to a double-layered hydroxide, and more particularly, to a technology having high catalytic efficiency and stability by producing a three-dimensional hierarchical nanostructured cobalt-molybdenum double-layered hydroxide for efficient oxygen and hydrogen generation.
The three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide for efficient oxygen and hydrogen generation of the present invention has excellent OER and HER performance and reaction rate due to improved mass charge transfer, and can significantly improve electrocatalytic activity. It has various effects such as having long-term stability and showing a low overvoltage potential.

Description

Manufacturing method of cobalt-molybdenum double layer hydroxide with a three-dimensional hierarchical nanostructure for efficient oxygen and hydrogen generation and the double layer hydroxide prepared thereby HYDROGEN EVOLUTION REACTIONS AND LAYERED DOUBLE HYDROXIDE MANUFACTURED BY THE SAME}

The present invention relates to a double-layered hydroxide, and more particularly, to a technology having high catalytic efficiency and stability by producing a three-dimensional hierarchical nanostructured cobalt-molybdenum double-layered hydroxide for efficient oxygen and hydrogen generation.

The industrial growth of the hydrogen economy is one of the challenges that have attracted the attention of researchers seeking to develop renewable energy sources. There are various methods of generating hydrogen under direct sunlight in photocatalytic and photochemical water electrolysis technologies. Unfortunately, the low energy conversion in photocatalytic processes limits their efficiency in large-scale applications. In water splitting, electrochemical water splitting technology can overcome these problems. Water electrolysis in an alkaline solution is the most promising method for producing high-purity hydrogen (H ₂ ) and oxygen (O ₂ ) through hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Compared to HER, OER requires a higher overpotential to remove four electrons to convert oxygen from water. Therefore, choosing an appropriate electrocatalyst is important to promote the water electrolysis process with a low overpotential in the OER.

Water electrolysis catalysts mainly use noble metals such as platinum, ruthenium, and iridium, which are considered ideal electrocatalysts for OER and HER in alkaline solutions. However, high cost, low stability and precious metal depletion limit large-scale production. To overcome these drawbacks, HER and OER performances are evaluated using non-noble metal catalyst materials such as transition metal-based oxides, phosphates, selenides, sulfides, nitrides, borides, carbides, organometallic compounds, and hydroxides. Therefore, we developed layered double hydroxides (LDHs), which are terrestrially abundant, inexpensive, and environmentally benign for OER and HER due to their multiple valence states. In general, LDH materials are a type of ionic layered structure in which metal cations occupy the center of the edges sharing an octahedron, and the apex contains hydroxide ions that connect to form an infinite 2D sheet. This 2D-LDH material has a wide range of applications, such as dye removal, catalysis, fuel cells and CO2 capture. Collectively, LDH materials are non-surface and large, providing many active sites to facilitate the diffusion of the electrolyte and improve the electrocatalytic performance.

Ni, Fe, and Co-based LDH materials are three-dimensional transition metals with variable valence states, which have great advantages in improving OER and HER performance. Among other bimetal LDH materials, Co-based LDH is a highly active electrocatalyst due to the presence of unsaturated CoO6-x octahedra, which promotes more active sites in OER and HER processes. In addition, when Mo is incorporated with other metals, it has a high beneficial factor and opens up a wide range of applications. Specifically, the CoMo-LDH material has potential for dual functional water electrolysis. However, reducing the overvoltage of OER is still a difficult area.

To overcome this limitation, in this study, the OER overpotential was lowered by designing an electrocatalyst. developed a novel 3D structure of a hydrangea flower-like CoMo-LDH structure composed of nanosheets as an efficient bifunctional electrocatalyst.

Korean Registered Patent No. 10-2237529 (registration date: April 01, 2021) Korean Registered Patent No. 10-1733492 (Date of Registration: April 28, 2017) Korean Registered Patent No. 10-2188107 (registration date: December 01, 2020)

Therefore, in order to overcome these limitations in the present invention, an OER (Oxygen Evolution Reaction) overvoltage was lowered by designing an electrocatalyst and preparing a three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide for efficient oxygen and hydrogen generation. A novel 3D structure of hydrangea flower-like CoMo-LDH structure composed of nanosheets as an efficient bifunctional electrocatalyst was developed.

The method for producing a three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide for efficient oxygen and hydrogen generation of the present invention is (a) as a precursor, cobalt nitrate hydrate and sodium molybdate hydrate and hexamethylenetetramine (HMTA) ) preparing; (b) dissolving in distilled water; (c) as a hydrothermal synthesis step, heating for 5 to 7 hours at a temperature of 80 to 100 ° C. in an autoclave; (d) after cooling to room temperature, washing the precipitate produced in step (c) with distilled water and ethanol; and (e) drying at a temperature of 75 to 85 °C.

Preferably, in step (a), the cobalt nitrate hydrate is 5 to 45 mM Co(NO ₃ ) ₂ 6H ₂ O, and the sodium molybdate hydrate is 5 to 45 mM Na ₂ MoO ₄ .2H ₂ And, the hexamethylenetetramine may be at a concentration of 55 to 65 mM.

Preferably, in step (b), the distilled water may have a volume of 57 to 63 mL.

Preferably, in step (c), the autoclave is characterized in that it is a stainless steel autoclave lined with Teflon.

According to another aspect of the present invention, the three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide prepared using the method for preparing the three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide is Co ₁ Mo ₄ -LDH, Co It may be at least one selected from the group consisting of ₂ Mo ₃ -LDH, Co ₃ Mo ₂ -LDH, and Co ₄ Mo ₁ -LDH.

The three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide for efficient oxygen and hydrogen generation of the present invention has improved mass charge transfer phenomenon, has excellent OER, HER performance and reaction rate, and can significantly improve electrocatalytic activity It has effects such as having long-term stability, showing a low overvoltage potential, and the like.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention is the details described in such drawings should not be construed as limited to
1 is a flow chart of a cobalt-molybdenum double layer hydroxide manufacturing method according to the present invention.
2 is a schematic image of a cobalt-molybdenum bilayer hydroxide.
Figure 3 is a schematic diagram of the formation process of cobalt-molybdenum double layer hydroxide in the form of a flower.
4 is a field emission scanning electron microscope (FE-SEM) image of a cobalt-molybdenum double layer hydroxide.
5 is a TEM (transmission electron microscopy) image (FIG. 5 (a) to (c)) and a high-resolution transmission electron microscopy (HRTEM) image (FIG. 5 (d)) of cobalt-molybdenum double layer hydroxide.
6(a) is a TEM image, FIG. 6(b) is a scanning transmission electron microscope (STEM) image, and FIGS. 6(c) to 6(e) are Co ₃ Mo ₂ -LDH STEM mapping It shows a profile, and FIG. 6(f) shows an energy-dispersive X-ray spectroscopy (EDS) spectrum.
7 is a graph showing XRD patterns, (a) Co ₁ Mo ₄ , (b) Co ₂ Mo ₃ , (c) Co ₃ Mo ₂ and (d) Co ₄ Mo ₁ -LDHs.
8(a) is a graph showing nitrogen adsorption-desorption isotherms, and FIG. 8(b) is a graph of pore size distribution of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs. am.
9 shows XPS (X-ray Photoelectron Spectroscopy) spectra, Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs of (a) Co 2p, (b) Mo 3d, (c) It shows O 1s.
10(a) is a graph showing a potential-current curve using Linear Sweep Voltammetry (LSV).
10(b) is a graph of measuring overpotential at a current density of 10 mA cm ⁻² .
10(c) shows tafel plots of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs.
10(d) is a graph showing scan rates-current densities of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs.
10(e) shows a Nyquist plot of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs.
10(f) is chronopotentiometry measuring the temporal change of electrode potential of Co ₃ Mo ₂ -LDH at a current density of 10 mA cm ⁻² .
11(a) is a graph showing a potential-current curve using the linear scanning potential method.
11(b) is a graph of overvoltage measured at a current density of 10 mA cm ^-2 .
11(c) shows tafel plots of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs.
11(d) shows a Nyquist plot of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDHs.
11(e) is a graph showing LSV curves before and after 1000 cycles of cyclic voltammetry for Co ₃ Mo ₂ -LDH.
11(f) is chronopotentiometry measuring the temporal change of electrode potential of Co ₃ Mo ₂ at a current density of 10 mA cm ^-2 .

Hereinafter, the present invention will be described in detail with reference to the contents described in the accompanying drawings. However, the present invention is not limited or limited by exemplary embodiments.

Embodiments according to the concept of the present invention can apply various changes and can have various forms, so the embodiments are illustrated in the drawings and described in detail herein.

The objects and effects of the present invention can be naturally understood or more clearly understood by the following description, and the objects and effects of the present invention are not limited only by the following description. In addition, in describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings.

1 is an overall flow chart of a method for synthesizing a double-layer hydroxide catalyst according to the present invention. First, nickel cobalt, molybdenum nitrate and hexamethylenetetramine are prepared as precursors and dissolved in DI water. Thereafter, as a hydrothermal synthesis step, it is heated in an autoclave at 90° C. for 6 hours. Thereafter, after cooling at room temperature (21-25 ° C.), the formed precipitate was washed with DI water and ethanol, and dried at 80 ° C. to obtain CoMo-LDH.

2 is a schematic image of a cobalt-molybdenum bilayer hydroxide. According to FIG. 2, the cobalt-molybdenum double layer hydroxide can generate a large amount of hydrogen and oxygen.

Figure 3 is a schematic diagram of the formation process of cobalt-molybdenum double layer hydroxide in the form of a flower. According to FIG. 3, as a precursor, when nickel nitrate hydrate, sodium molybdate hydrate, and hexamethylenetetramine are mixed and subjected to hydrothermal synthesis, a 3D flower-shaped cobalt-molybdenum double layer hydroxide is formed in a 2D nanosheet structure. is synthesized The 3D flower-shaped cobalt-double-layered hydroxide is made of double layers, so water molecules or anions can be located between the layers.

Example 1. Preparation of 3D flower-shaped CoMo-LDH electrocatalyst

To prepare the 3D flower-shaped CoMo-LDH electrocatalyst, four ratios of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ were prepared by a hydrothermal method.

First, to prepare Co ₁ Mo ₄ , 10 mM Co(NO ₃ ) ₂ 6H ₂ O, 40 mM Na ₂ MoO ₄ 2H ₂ O, and 60 mM HTMA (hexamethylenetetramine) were dissolved in 60 mL distilled water. After that, it was put into an autoclave and subjected to hydrothermal synthesis at 90 °C for 6 hours. After that, it was washed 4 to 5 times with distilled water and ethanol, and dried overnight in an oven at 80 °C.

In the reaction process, HTMA is a dual-functional surfactant that forms an organometallic complex in water through hydrogen bonding by connecting metal atoms of Co and Mo.

The preparation of Co ₂ Mo ₃ was performed in the same manner as the preparation of Co ₁ Mo ₄ , except that 20 mM of Co(NO ₃ ) ₂ 6H ₂ O and 30 mM of Na ₂ MoO ₄ 2H ₂ O were used.

The preparation of Co ₃ Mo ₂ was performed in the same manner as the preparation of Co ₁ Mo ₄ , except that 30 mM of Co(NO ₃ ) ₂ 6H ₂ O and 20 mM of Na ₂ MoO ₄ 2H ₂ O were used.

The preparation of Co ₄ Mo ₁ was performed in the same manner as the preparation of Co ₁ Mo ₄ , except that 40 mM of Co(NO ₃ ) ₂ 6H ₂ O and 10 mM of Na ₂ MoO ₄ 2H ₂ O were used.

Finally, 2D-LDH nanosheets were formed to form a 3D flower-like structure. Specifically, in the hydrothermal synthesis process, that is, in the hydrolysis reaction, the cluster complex was linked with water molecules to form a 2D CoMo-LDH nanosheet layer. They form 1D chain-like units that form , which are further stacked in parallel to create 3D flower-like structures. Simultaneously, in this process, HMTA releases ammonia and formaldehyde and is then incorporated into the LDH layer as anionic species intercalated with CO ₃ ^2- ions by decomposition.

Experimental Example 1. Structural analysis of 3D flower-shaped CoMo-LDH

The 3D flower-shaped CoMo-LDH was observed through SEM (Scanning Electron Microscope) images. According to FIG. 4 , the SEM image can be confirmed, and it is composed of several ultra-thin 2D nanosheets and shows a 3D flower shape. In the low-magnification SEM image, the 2D nanosheets are densely connected to form a spherical structure, and CoMo-LDH of four ratios shows smooth and soft 2D ultrathin nanosheets. Through this, it can be seen that the nanosheet morphology is not affected by adjusting the ratio of Co and Mo.

In addition, high-magnification SEM images show that the nanosheets are interconnected through Y-shaped junctions to form a flower-like structure, and the formed structure is a proposed structure in which chain-like units of a 2D hierarchical structure are stacked to form a 3D flower-like structure. match the structure

In order to further analyze the structure of Co ₃ Mo ₂ -LDH, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) analysis were performed. According to FIG. 5, as in the SEM image of FIG. 4, numerous 2D nanosheets are gathered in the TEM image to show a 3D flower shape, and the high-magnification HRTEM image shows that the 2D ultrathin nanosheet has pores, which indicates electrocatalytic activity. It is an important structure of the 3D flower-like CoMo-LDH structure in enhancing the

Experimental Example 2. Confirmation of chemical composition of 3D flower-shaped CoMo-LDH

In order to confirm the chemical composition of the 3D flower-shaped CoMo-LDH, the chemical composition of Co ₃ Mo ₂ -LDH was confirmed using a scanning transmission electron microscope (STEM). Looking at (c) to (e) of FIG. 6, it can be seen that the uniform distribution of Co, Mo and O elements is shown, and is consistent with the EDS spectrum in (f) of FIG. In the spectrum, Cu element is a peak occurring on the TEM grid. The 2D ultrathin porous nanosheets of this type of 3D flower provide excellent surface accessibility for electron transport, thus significantly improving the OER and HER performance.

Experimental Example 3. Analysis of physical/chemical characteristics of 3D flower-shaped CoMo-LDH

The crystal structures of the four synthesized Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH samples were confirmed through XRD analysis. Referring to FIG. 7, all samples show that they have peaks on the (006), (012), and (110) planes corresponding to 25, 33.6°, and 59.5°, respectively. All CoMo-LDH peaks show low intensity, which means low crystallinity due to the low temperature during the synthesis process and the adsorption of anions between the bilayer hydroxides after synthesis.

In addition, all CoMo-LDHs show similar XRD patterns, which is consistent with the SEM image showing the same structure even after the Co/Mo ratio is changed.

Experimental Example 4. Comparative analysis of pore size of 3D flower-shaped CoMo-LDH

In order to compare the surface area and pore size distribution of four ratios of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH, BET (Brunauer-Emmett-Teller) isotherm and BJH (Barrett- Joyner_halenda) was analyzed through pore size distribution. According to FIG. 8 , Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH have BET surface areas of 73.39, 106.93, 130.40 and 103.89 m ² g ^-1 , respectively. The largest BET surface area of Co ₃ MO ₂ -LDH was observed. In addition, the pore distribution of each CoMo-LDH can be seen in FIG. 8(b), and this pore structure mainly appears due to the pores present in the 2D nanosheet. The improved charge transfer with these pores can significantly improve the OER and HER performance.

Experimental Example 5. XPS analysis of 3D flower-shaped CoMo-LDH

9 is a graph showing the results of XPS analysis to determine the surface element composition and valence state of four ratios of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH. 9 (a) shows the spectrum of Co 2p, (b) shows the spectrum of Mo 3d, and (c) shows the spectrum of O 1s. First, in the Co 2p spectrum, two major spin-orbit doublets (Co 2p _3/2 , Co2p _1/2 ) at 781 and 797 eV appear. In the Mo 3d spectrum, 233 and 236 eV are peaks of Mo 3d _5/2 and Mo 3d _3/2 , respectively, and are specific peaks of Mo ⁶⁺ . The small peak around 237 eV is a peak caused by partial oxidation of Mo ²⁺ on the catalyst surface. The O 1s spectrum shows splitting into two peaks. The main peak seen at 531.5 eV is characteristic of the surface hydroxy groups of the metal center (M-OH). The peak seen at 532.8 eV is the peak of water molecules. Through this, it was confirmed that it had the structure of a general LDH material.

Experimental Example 6. OER electrocatalyst performance evaluation of 3D flower-shaped CoMo-LDH

10 is a graph showing the results obtained by evaluating the electrocatalytic performance of four ratios of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH in a 1.0 M KOH electrolyte. Commercial RuO ₂ was also tested under the same conditions. All samples were coated on a GC (glassy carbon) electrode with a constant mass of 0.1 mg cm ^-2 and used as a working electrode.

In the LSV curve of FIG. 10(a), the voltages at which Co ₁ Mo ₄ Co ₂ Mo ₃ Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH and RuO ₂ can obtain a current of 10 mA cm ^-2 are 1.542, 1.516, 1.496, 1.531 and 1.63V (vs. RHE). In FIG. 10(b), Co ₃ Mo ₂ -LDH has an overvoltage of 266 mV for driving a current density of 10 mA cm ^-2 , which is Co ₁ Mo ₄ (312mV), Co ₂ Mo ₃ (286mV) and Co ₄ Mo ₁ ( 301mV) is lower than that of It is also significantly lower than RuO ₂ (400 mV).

During the entire OER process, Co in CoMo-LDH regenerates the active site at a faster rate. Therefore, all proportions of 3D flower-like CoMo-LDH show lower voltages than RuO ₂ , due to the high adsorption of -OH groups on the catalyst surface. In particular, Co ₃ Mo ₂ -LDH has a lower overvoltage of 266 mV at 10 mA cm ^-2 than CoMo-LDH with other ratios.

An important factor predicting catalytic activity in OER is the Tafel slope shown in Fig. 10(c). The Tafel slope represents the efficiency of the catalyst, and the lower the value, the higher the efficiency. Therefore, Co ₃ Mo ₂ -LDH is 49 mV dec ^-1 , Co ₁ Mo ₄ (120mVdec ^-1 ), Co ₂ Mo ₃ (64mVdec ^-1 ), Co ₄ Mo ₁ (117mVdec ^-1 ) and RuO ₂ (121mVdec ^{-1) 1} ) has higher catalytic efficiency.

10(d) is a graph showing current density values according to cyclic voltammetry (CV) scan rates, and shows an electrochemical surface area (ECSA). Here, Co ₃ Mo ₂ -LDH also has a high double-layer capacitance (Capacitance double-layer, C _dl ) of 151.8 μF cm ^-2 .

To see the resistance of the CoMo-LDH catalyst electrode, (a) EIS (Electrochemical Impedance Spectroscopy) was measured. Co ₃ Mo ₂ -LDH had the lowest electron transfer resistance (R _ct ) value. 10(f) is a graph comparing LSV before and after a CV cycle. In the inserted graph, a constant voltage value was obtained by flowing a current of 10 mA cm ^-2 for 12 hours, and it was proved that the stability of the electrode was high. In addition, it can be seen that the stability is excellent since there is almost no change in LSV after 1000 cycles of CV.

Experimental Example 7. Evaluation of HER electrocatalyst performance of 3D flower-shaped CoMo-LDH

HER performance was evaluated in 1.0 M KOH electrolyte as in OER. Four ratios of Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH and commercially available Pt/C catalysts were tested under the same conditions, and the graphs of the results are shown in FIG. 11 .

11(a) and (b), Pt/C shows a very low voltage of 62 mV (vs. RHE) for obtaining a current of -10 mA cm ^-2 compared to other CoMo-LDH. Among CoMo-LDH, Co ₃ Mo ₂ -LDH is 165 mV, which is lower than Co ₁ Mo ₄ (322mV), Co ₂ Mo ₃ (260mV) and Co ₄ Mo ₁ -LDH (304mV). In addition, Co ₃ Mo ₂ -LDH at a current of 100 mA cm ^-2 was measured as an overvoltage of 325 mV lower than that of Pt/C (455 mV).

11(c) is a Tafel graph, and the catalytic activity in HER can be predicted. Co ₃ Mo ₂ -LDH was 57 mV dec ^{-1 ,} higher than Pt/C (44 mV dec ^-1 ), but lower than other CoMo-LDHs. This proves that it has a higher catalytic efficiency than other ratios of CoMo-LDH.

11(d) is a graph showing the result of measuring the resistance of the catalyst through EIS. Among Co ₁ Mo ₄ , Co ₂ Mo ₃ , Co ₃ Mo ₂ and Co ₄ Mo ₁ -LDH, Co ₃ Mo ₂ -LDH had the smallest electron transfer resistance (R _ct ) value of about 10Ω.

11(e) is a graph comparing the LSV of the Co ₃ Mo ₂ -LDH catalyst before and after 1000 CV cycles, and it can be seen that they are almost the same before and after the cycle. This means that the catalyst stability is very high.

11(f) is a graph showing voltage when a constant current of -10 mA cm ^-2 is applied for 12 hours. This also showed a constant voltage value for 12 hours, indicating that the stability of the electrode catalyst was very high.

In the above, specific parts of the present invention have been described in detail, and for those skilled in the art, it is clear that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (6)

(a) preparing cobalt nitrate hydrate, sodium molybdate hydrate and hexamethylenetetramine (HMTA) as precursors;
(b) dissolving in distilled water;
(c) as a hydrothermal synthesis step, heating for 5 to 7 hours at a temperature of 80 to 100 ° C. in an autoclave;
(d) after cooling to room temperature, washing the precipitate produced in step (c) with distilled water and ethanol; and
(e) drying at a temperature of 75 to 85 ° C; includes,
In step (a), the cobalt nitrate hydrate is 30 mM Co(NO ₃ ) ₂ 6H ₂ O, the sodium molybdate hydrate is 20 mM Na ₂ MoO ₄ .2H ₂ O, and the hexamethylenetetra Min is at a concentration of 60 mM;
In the step (b), the distilled water is a method for producing a three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide, characterized in that the volume is 60 mL. delete delete According to claim 1,
In step (c), the autoclave is a teflon-lined stainless steel autoclave, characterized in that the three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide manufacturing method. A three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide prepared using the method of preparing the three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide according to any one of claims 1 and 4. According to claim 5,
The three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide is Co ₃ Mo ₂ -LDH, characterized in that the three-dimensional hierarchical nanostructured cobalt-molybdenum double layer hydroxide.

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