KR101790291B1 - Precursor of catalyst for hydrogenation reaction of co2, method for manufacturing the same, catalyst for hydrogenation reaction of co2, and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a precursor of a catalyst for hydrogenation of carbon dioxide, a method for producing the precursor, a catalyst for hydrogenation of carbon dioxide, and a method for producing the same.
One embodiment of the present invention provides a precursor of a hydrogenation catalyst of carbon dioxide comprising CuFeO ₂ .

Description

TECHNICAL FIELD The present invention relates to a precursor of a catalyst for the hydrogenation of carbon dioxide, a method for producing the same, a catalyst for hydrogenation of carbon dioxide, and a method for producing the same. BACKGROUND ART SAME}

The present invention relates to a precursor of a catalyst for hydrogenation of carbon dioxide, a method for producing the precursor, a catalyst for hydrogenation of carbon dioxide, and a method for producing the same.

Recently, research has been actively conducted to convert carbon dioxide gas, one of the main causes of climate change, into chemical fuels or high value-added materials. Accordingly, the catalyst for the carbon dioxide hydrogenation reaction has been actively invested.

However, in the carbon dioxide hydrogenation reaction, a substance produced by a catalyst is limited to a hydrocarbon gas having a small molecular weight. More specifically, it is difficult to produce a hydrocarbon gas having a high molecular weight such as a liquid fuel suitable for transportation or an olefin having a higher value.

Accordingly, in one embodiment of the present invention, a catalyst capable of producing liquid hydrocarbons and olefins, such as olefins, from a carbon dioxide hydrogenation reaction, a precursor of a catalyst, and a method for producing the same will be described below.

One embodiment of the present invention provides a precursor of a catalyst for hydrogenation of carbon dioxide, a method for producing the precursor, a catalyst for hydrogenation of carbon dioxide, and a method for producing the same.

The precursor of the carbon dioxide hydrogenation catalyst, which is an embodiment of the present invention, may include CuFeO ₂ . The precursor may be in a three-way system.

In another aspect of the present invention, there is provided a process for preparing a precursor of a catalyst for hydrogenation of carbon dioxide, comprising the steps of: preparing an iron raw material and a copper raw material; Adding the iron and copper raw materials to a solvent to prepare a solution; Introducing a reducing agent into the solution; And hydrothermally synthesizing the solution to which the reducing agent is added to prepare a catalyst precursor.

The solution may be hydrothermally synthesized at a temperature in the range of 180 to 200 ° C by hydrothermally synthesizing the solution to which the reducing agent is added to produce a catalyst precursor.

The solution may be hydrothermally synthesized for 6 to 24 hours by hydrothermally synthesizing the solution to which the reducing agent is added to produce a catalyst precursor.

Preparing a ferrous raw material and a copper source material; in the iron raw material is _{Fe (NO 3) 3, FeCl} 3 Or a combination thereof. The copper raw material may be Cu (NO _{3) 2,} CuCl, or a combination thereof.

In the step of preparing the solution by adding the raw material to the solvent, the raw material may be added in an amount of 5 to 10 parts by weight based on 100 parts by weight of the solvent.

In the step of preparing the solution by introducing the raw material into the solvent, sodium hydroxide (NaOH) at a concentration of 0.05 to 0.1 mol may be further added.

More specifically, for 100 parts by weight of the solution, the sodium hydroxide may be added in an amount of 6 to 11 parts by weight.

Introducing a reducing agent into the solution; , The reducing agent may include propionaldehyde, ethylene glycol, or a combination thereof.

More specifically, with respect to 100 parts by weight of the solution, the reducing agent may be added in an amount of more than 0 and 3 parts by weight or less.

The catalyst for hydrogenation of carbon dioxide, which is another embodiment of the present invention, includes Cu and Fe, has a three-way system, and may have a specific surface area of 10 m ² / g or more.

The porosity of the catalyst may be from 0.12 to 0.17 cm ³ / g.

The weight ratio of Cu to Fe (Cu / Fe) of the catalyst may be 0.594 or more.

The distance of the Fe metal (110) lattice plane of the catalyst may be 0.2 nm or more.

Spherical Cu particles may be located on the surface of the catalyst.

FTY value of the catalyst may be at least _{^{2.0x10 -6 molco 2 g fe -1 s}} -1.

The O / P value of the catalyst may be at least 7.0.

The catalyst is used for the hydrogenation reaction of carbon dioxide, the product by the reaction includes hydrocarbon, and the hydrocarbon having C5 or more carbon atoms relative to 100 weight% of hydrocarbon in the product may be 60 weight% or more.

With respect to 100 wt% of the hydrocarbons in the product, the hydrocarbon having carbon number C may be 4 wt% or less.

In another aspect of the present invention, there is provided a method of preparing a catalyst for hydrogenation of carbon dioxide, comprising the steps of: preparing an iron raw material and a copper raw material; Introducing the raw material into a solvent to prepare a solution; Introducing a reducing agent into the solution; Hydrothermally synthesizing the solution to which the reducing agent is added to prepare a catalyst precursor; And reducing the prepared catalyst precursor; . ≪ / RTI >

In the reduction of the prepared catalyst precursor, the catalyst precursor may be reduced in the temperature range of 180 to 200 ° C. In addition, the catalyst precursor may be reduced for 1 to 2 hours. The catalyst precursor may be reduced under a hydrogen gas atmosphere, and the flow rate of the hydrogen gas may be 50 to 100 sccm.

By reducing the prepared catalyst precursor, the obtained catalyst contains Cu and Fe, has a three-way system, and can have a specific surface area of 10 m ² / g or more.

And hydrothermally synthesizing the solution to which the reducing agent is added to produce a catalyst precursor, the catalyst precursor may include CuFeO ₂ .

And hydrothermally synthesizing the solution to which the reducing agent has been added to produce a catalyst precursor, the catalyst precursor may be in a trihedral form.

According to one embodiment of the present invention, a catalyst can be easily produced at a low temperature by using a delafosite precursor. The prepared catalyst can also be used in a carbon dioxide hydrogenation reaction. In addition, the catalyst can excellently improve the production of hydrocarbons having a large molecular weight.

FIG. 1 shows the XRD analysis results of the delaposite precursor according to hydrothermal synthesis time.
2 shows an image of a delapo-site precursor observed with an SEM.
Figure 3 shows the XRD results of a catalyst prepared by reduction in one embodiment of the present invention.
Figure 4 shows an HR-TEM image of the catalyst prepared according to one embodiment of the present invention.
5 graphically illustrates the yield of Fe metal over time.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

One embodiment of the present invention may provide a precursor of a carbon dioxide hydrogenation catalyst comprising CuFeO ₂ . More specifically, the precursor may be a delapo site. In addition, the precursor may be in the form of a three-ring system. In addition, the precursor may comprise Cu ₂ O and Fe ₂ O ₃ impurities.

This is also disclosed in FIG. Herein, FIG. 1 shows XRD analysis results of the delaposite precursor according to hydrothermal synthesis time.

More specifically, as disclosed herein, in Figure 1, DE Four sites precursor addition CuFeO ₂ Cu ₂ O and Fe ₂ O ₃ You can see the peak value at that point. From this, it can be seen that the precursor is Cu ₂ O and Fe ₂ O ₃ It can be confirmed that it contains impurities.

In another aspect of the present invention, there is provided a process for preparing a precursor of a catalyst for hydrogenation of carbon dioxide, comprising the steps of: preparing an iron raw material and a copper raw material; Introducing the raw material into a solvent to prepare a solution; Introducing a reducing agent into the solution; And hydrothermally synthesizing the solution to which the reducing agent is added to prepare a catalyst precursor.

First, a step of preparing an iron raw material and a copper raw material may be carried out.

The iron source material may be Fe (NO ₃ ) ₃ , FeCl _3, or a combination thereof, but is not limited thereto.

The copper raw material may be Cu (NO ₃ ) ₂ , CuCl, or a combination thereof, but is not limited thereto.

Thereafter, the raw material may be added to a solvent to prepare a solution.

The raw material may be added in an amount of 5 to 10 parts by weight based on 100 parts by weight of the solvent. More specifically, 6 to 9 parts by weight, or 7 to 9 parts by weight may be added. More specifically, 8 to 9 parts by weight or 8.03 to 8.06 parts by weight may be added. The amount of the impurities can be reduced by injecting by the weight portion. At this time, the impurities may be Fe ₂ O ₃ , Cu ₂ O, or a combination thereof.

Further, 0.05 to 0.1 mol of sodium hydroxide (NaOH) may be further added to the solution.

With respect to 100 parts by weight of the solution, the sodium hydroxide may be further added in an amount of 6 to 11 parts by weight. More specifically, for 100 parts by weight of the solution, the sodium hydroxide may be further added in an amount of 8 to 11 parts by weight. More specifically, for 100 parts by weight of the solution, the sodium hydroxide may be further added in 9 to 11 parts by weight.

This is to control the basicity of the solution in the range of pH 11 to 13, and it can have a rhomboheral structure by controlling the basicity of the solution.

Thereafter, a reducing agent may be added to the solution.

More specifically, the reducing agent may include propionaldehyde, ethylene glycol, or a combination thereof. However, the present invention is not limited thereto.

The reducing agent may be added in an amount of more than 0 and 3 parts by weight based on 100 parts by weight of the solution. More specifically, for 100 parts by weight of the solution, the reducing agent may be added in an amount of 1 to 3 parts by weight. More specifically, with respect to 100 parts by weight of the solution, the reducing agent may be added in an amount of 2 to 3 parts by weight.

More specifically, the reason for introducing the reducing agent as described above is to derive the effect that copper ions are reduced one by one.

Finally, a step of hydrothermally synthesizing the solution into which the reducing agent is introduced to prepare a catalyst precursor may be performed.

At this time, the solution may be hydrothermally synthesized at a temperature range of 180 to 200 ° C.

In addition, the solution may be hydrothermally synthesized for 6 to 24 hours.

More specifically, the solution can be hydrothermally synthesized at the above temperature and time to synthesize delaposte at a low temperature.

The catalyst for hydrogenation of carbon dioxide, which is another embodiment of the present invention, can provide a catalyst for hydrogenation of carbon dioxide, which contains Cu and Fe, has a trihedral form, and has a specific surface area of 10 m ² / g or more. More specifically, the specific surface area of the catalyst may be 10 m ² / g or more. More specifically, it may be 10 to 15 m ² / g.

More specifically, the catalyst comprising Cu and Fe may be due to the delaforth precursor described above. Thus, the catalyst may also be in the form of a three-way system like the precursor described above.

In addition, since the above-mentioned precursor is in a reduced form, the catalyst may have more surface pores than the precursor described above.

The porosity of the catalyst may be 0.1 to 0.2 cm ³ / g. More specifically, the porosity of the catalyst may be 0.1 to 0.18 cm ³ / g. More specifically, it may be from 0.12 to 0.17 cm ³ / g.

More specifically, when the specific surface area and the porosity of the catalyst prepared by the reduction are within the above range, the reaction rate can be improved. Further, the liquid hydrocarbon can be easily desorbed.

This is as disclosed in Fig. 2 herein. 2 shows an image of a delapo-site precursor observed with an SEM. More specifically, in the above-described method for producing a catalyst precursor, the SEM images of the precursors corresponding to the hydrothermal synthesis time of 6 hours, 12 hours and 24 hours correspond to a, b and c, respectively, and the 12 hour hydrothermally synthesized precursor is reduced The SEM image of the prepared catalyst corresponds to d.

Thus, as shown in Figs. 2A, 2B, and 2C, it can be confirmed that the precursor of the catalyst is a three-way system, and small particles around the three-directional system can be confirmed as the above-mentioned impurities.

In addition, as shown in FIG. 2 (d), it can be confirmed that the catalyst prepared by reducing the catalyst precursor has many pores formed on the surface of the tridecahedron due to reduction.

The weight ratio of Cu to Fe (Cu / Fe) of the catalyst may be 0.59 or more. More specifically, the weight ratio of Cu to Fe (Cu / Fe) of the catalyst may be 0.594 or more. More specifically, the weight ratio of Cu to Fe (Cu / Fe) of the catalyst may be from 0.591 to 0.595. More specifically, it may be from 0.594 to 0.5941.

This is the same as that shown in Fig. 3 shows XRD results of a catalyst prepared by reduction in one embodiment of the present invention.

More specifically, as shown in FIG. 3, in the catalyst produced by reduction, the peak value of Cu and Fe metal can be confirmed. In addition, one embodiment of the present invention shows that the weight ratio of Cu to Fe is not less than 0.594, which is superior to the comparative example, and the complete reduction effect of iron can be expected.

Further, spherical Cu particles may be located on the surface of the catalyst. More specifically, some or all of the total Cu particles may be spherically located on the surface of the catalyst. The proportion of Cu particles present on the surface of the catalyst may be 50 to 80 wt% of 100 wt% of the total Cu particles. If Cu is present on the surface, Fe can be easily and completely reduced.

The distance of the Fe metal (110) lattice plane of the catalyst may be 0.2 nm or more. More specifically, the distance of the Fe metal (110) lattice plane of the catalyst may be between 0.2 nm and 0.21 nm. More specifically, it may be 0.2 to 0.201 nm.

This is as described in Fig. 4 herein. 4 shows an HR-TEM image of the catalyst prepared according to one embodiment of the present invention.

More specifically, when the distance of the Fe metal lattice plane is 0.2 nm or more, Fe can be completely reduced.

The FTY (Fe time yield) value of the catalyst may be 2.0 x ₁₀ ^-6 molco ₂ g _fe ^-1 s ^{-1 or} more. More specifically, it may be 2.6 x 10 ^-6 molco ₂ g _fe ^-1 s ^{-1 or} more.

The O / P (olefin-to-paraffin ratio) value of the catalyst may be at least 7.0. More specifically, it may be 7.6 or more.

More specifically, the FTY (Fe time yield) value of the catalyst means a change amount of carbon dioxide per unit iron, per unit time. Also, the O / P (olefin-to-paraffin) value of the catalyst means the ratio of paraffins to olefins. More specifically, when the FTY value and the O / P value are in the above range, the selectivity of liquid hydrocarbons may be increased.

This is as described in Fig. 5 herein. More specifically, Figure 5 graphically illustrates the yield of Fe metal over time. More specifically, it can be seen that the amount of change in the amount of carbon dioxide per unit iron, unit time, and the amount of change in carbon dioxide is larger in Example 2 of the present invention than in Comparative Example 1 and Comparative Example 2. Thus, it can be seen that the yield of Fe metal is high.

The catalyst may be used for the hydrogenation reaction of carbon dioxide, and the product by the reaction may include hydrocarbon.

More specifically, the hydrocarbon having C5 or more carbon atoms may be at least 60% by weight based on 100% by weight of the hydrocarbons in the product. More specifically, it may be 64.9% by weight or more. More specifically, it may be 66.3% by weight or more. The higher the conversion ratio is, the better, but it may theoretically be 100% by weight or 99% by weight or less.

Further, the hydrocarbon having the carbon number of C1 may be 4% by weight or less based on 100% by weight of the hydrocarbon in the product. More specifically, it may be 3.9% by weight or less. More specifically, it may be 2.4 wt% or less.

This is as described in Fig. 6 herein. 6 is a graphical representation of the selectivity (product) of the product according to the precursor. More specifically, when the catalyst of Example 2 according to an embodiment of the present invention is used, the selectivity of hydrocarbons having a large molecular weight can be high. Therefore, it is possible to convert carbon dioxide to high value-added liquid hydrocarbon materials such as gasoline and diesel.

Finally, a method for producing a carbon dioxide hydrogenation catalyst, which is another embodiment of the present invention, comprises the steps of: preparing an iron raw material and a copper raw material; Introducing the raw material into a solvent to prepare a solution; Introducing a reducing agent into the solution; Hydrothermally synthesizing the solution to which the reducing agent is added to prepare a catalyst precursor; And reducing the prepared catalyst precursor; . ≪ / RTI >

First, preparing the iron raw material and the copper raw material; Introducing the raw material into a solvent to prepare a solution; Introducing a reducing agent into the solution; And the step of hydrothermally synthesizing the solution to which the reducing agent has been added to produce a catalyst precursor are the same as the method and conditions for producing the precursor of the catalyst described above and will not be described in detail below.

Thereafter, the catalyst precursor may be further reduced.

The catalyst precursor may be reduced in the temperature range of 300 to 400 < 0 > C.

The catalyst precursor may be reduced for 1 to 2 hours.

More specifically, the catalyst precursor can be completely converted to Fe metal, which is the active point, by being reduced during the temperature range and the time.

Further, in the step of reducing the prepared catalyst precursor, the catalyst precursor may be reduced in a hydrogen gas atmosphere. At this time, the flow rate of the hydrogen gas may be 50 to 100 sccm. By limiting the flow rate of the hydrogen gas as described above, the delapositite can be completely reduced to Fe metal.

More specifically, a carbon dioxide hydrogenation catalyst can be obtained by reducing the prepared catalyst precursor.

The obtained catalyst contains Cu and Fe, has a three-way system, and may have a specific surface area of 10 m ² / g or more. More specifically, it may be at least 15 m ² / g.

Example  And Comparative Example

Catalyst preparation method

The _{Fe (NO 3) 3 · 9H} 2 O 2.02g and _{Cu (NO 3) 2 · 3H} 2 O 1.2g was prepared a solution dissolved in distilled water 40ml. Thereafter, 4 g of 0.1 mol of NaOH was added to the solution, followed by stirring for 30 minutes. In addition, 0.5 ml of propionaldehyde was added to the solution to prepare a mixture.

The mixture was transferred to a 100 ml Teflon-drawn stainless steel autoclave and hydrothermalized at 180 ° C for 6 to 24 hours. As a result, CuFeO ₂ -6, CuFeO ₂ -12, and CuFeO ₂ -24 catalysts synthesized by 6 hours, 12 hours, and 24 hours hydrothermal action were prepared.

In addition, a spinel structure nano powder (less than 100 nm), CuFe ₂ O ₄ The catalyst was purchased from Sigma-Aldrich and prepared as Comparative Example 1. In addition, pure Fe ₂ O ₃ was purchased from Kanto and prepared as Comparative Example 2. In addition, Cu ₂ O-Fe ₂ O ₃ Were mixed at a weight ratio of 1: 1, respectively.

Catalytic Hydrogenation of Carbon Dioxide

The catalytic hydrogenation of carbon dioxide was performed in a fixed bed of a stainless steel reactor with CO ₂ / H ₂ = 1: 3.

First, preliminary reduction was performed at 400 DEG C for 2 hours under a pure H ₂ gas atmosphere of 100 sccm. For the catalytic reaction, CO ₂ and H ₂ gases were fed into the reactor together with nitrogen gas. At this time, the reducing conditions were 300 DEG C, 10 bar, and the gas space velocity was 1800 mlg ^-1 h ^-1 .

The concentrations of CO ₂ , CO and N ₂ were measured by an on-line Agilent 7890A gas chromatograph with a thermal conductivity detector and a Carboxen 1000 packed column. C ₁ -C ₆ hydrocarbons were analyzed by gas chromatography (GC) such as a flame ionization detector and an Alumina Sulfate PLOT capillary column.

As a result, high molecular weight hydrocarbon products were collected in the cooling traps. In addition, the composition of hydrocarbons having large molecular weights was calculated as weight percent of carbon atoms, using simulated distillation (SIMDIS) analysis.

Experimental Example

catalyst Carbon dioxide conversion, % Carbon monoxide selectivity,% Hydrocarbon selectivity (except for carbon monoxide), % O / P C1 C2 C3 C4 C5 + Comparative Example 1 Fe ₂ O ₃ 14.3 33.2 60.2 22.5 11.3 3.7 2.3 0.03 Example 1 CuFeO ₂ -6 17.3 31.7 2.7 8.3 12.6 10.1 66.3 7.3 Example 2 CuFeO ₂ -12 18.1 31.9 3.9 10 14.5 11.3 60.3 7 Example 3 CuFeO ₂ -24 16.7 31.4 2.4 8.7 13.3 10.7 64.9 7.7 Comparative Example 2 CuFe ₂ O ₄ 13.3 28.4 38.3 19.7 20.1 10.5 11.4 0.02 Comparative Example 3 Cu ₂ O-Fe ₂ O ₃ 15.7 28.9 57.6 22.8 12.6 4.4 2.6 0.03

As shown in Table 1, it can be confirmed that Examples 1 to 3 of the present invention have an excellent carbon dioxide conversion rate as compared with Comparative Examples 1 to 3.

In addition, it can be seen that the selectivity of the number of carbon atoms having a large number of carbon atoms C5 or more is significantly different from that of the comparative example. In Examples 1 to 3 of the present invention, the ratio of olefin to paraffin is 7.0 or more.

Thus, as described above, the present inventors have found that carbon dioxide can be easily converted into a high value additive material such as diesel or gasoline due to the high selectivity of hydrocarbons having a large molecular weight.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (28)

delete delete delete delete delete delete delete delete delete delete Cu and Fe,
Three-
A catalyst having a specific surface area of 10 m ² / g or more,
The catalyst is used for the hydrogenation reaction of carbon dioxide,
The product of the reaction comprises hydrocarbon,
Wherein the hydrocarbon having C5 or more carbon atoms is at least 60% by weight based on 100% by weight of the hydrocarbons in the product.
12. The method of claim 11,
Wherein the hydrocarbons having a carbon number of C1 are not more than 4% by weight based on 100% by weight of hydrocarbons in the product.
Cu and Fe,
Three-
A hydrogenation reaction catalyst of carbon dioxide having a specific surface area of 10 m ² / g or more,
Wherein the catalyst has a porosity of 0.12 to 0.17 cm < ³ > / g.
delete 14. The method of claim 13,
Wherein the weight ratio of Cu to Fe (Cu / Fe) of the catalyst is 0.594 or more.
16. The method of claim 15,
Wherein the distance of the Fe metal (110) lattice plane of the catalyst is at least 0.2 nm.
17. The method of claim 16,
Wherein spherical Cu particles are placed on the surface of the catalyst.
18. The method of claim 17,
Wherein the amount of change (FTY) of carbon dioxide per unit iron and unit time of the catalyst is not less than 2.0 × ₁₀ ^-6 molco ₂ g _fe ^-1 s ^-1 .
19. The method of claim 18,
Wherein the olefin to paraffin ratio (O / P) of the catalyst is at least 7.0.
delete delete Preparing an iron raw material and a copper raw material;
Introducing the raw material into a solvent to prepare a solution;
Introducing a reducing agent into the solution;
Hydrothermally synthesizing the solution to which the reducing agent is added to prepare a catalyst precursor; And
Reducing the prepared catalyst precursor; Lt; / RTI >
Reducing the prepared catalyst precursor;
Wherein the catalyst precursor is reduced in a hydrogen gas atmosphere.
23. The method of claim 22,
Reducing the prepared catalyst precursor,
Wherein the catalyst precursor is reduced in the temperature range of 180 to 200 < 0 > C.
24. The method of claim 23,
Reducing the prepared catalyst precursor,
Wherein the catalyst precursor is reduced for 1 to 2 hours.
25. The method of claim 24,
Reducing the prepared catalyst precursor,
The catalyst precursor is reduced in a hydrogen gas atmosphere,
Wherein the flow rate of the hydrogen gas is 50 to 100 sccm.
26. The method of claim 25,
And reducing the prepared catalyst precursor,
The obtained catalyst contains Cu and Fe,
Three-
Wherein the specific surface area is 10 m ² / g or more.
23. The method of claim 22,
And hydrothermally synthesizing the solution to which the reducing agent is added to produce a catalyst precursor,
Wherein the catalyst precursor comprises CuFeO ₂ .
28. The method of claim 27,
And hydrothermally synthesizing the solution to which the reducing agent is added to produce a catalyst precursor,
Wherein the catalyst precursor is in the form of a three-ring system.

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