KR20200048442A - The method of generating oxygen vacancies in nickel-iron oxide catalyst for oxygen evolution reaction and the nickel-iron oxide catalyst manufactured thereby - Google Patents

Abstract

The present invention provides a method for inducing oxygen vacancies in a nickel-iron oxide catalyst for generating oxygen, in which the nickel-iron oxide catalyst with high activity as an electrochemical catalyst is synthesized by using a hydrothermal synthesis method and oxygen vacancies are generated in a nickel-iron oxide structure by partial reduction performed under a mixed gas atmosphere, in which hydrogen and argon are mixed at a predetermined ratio, to increase activity of an oxygen generation reaction and a nickel-iron oxide catalyst thereby. According to the present invention, the oxygen vacancies can be generated at low temperature and the synthesized nickel-iron oxide having an oxygen vacancy defect has increased hydroxyl absorptivity on a catalyst surface more than that of an existing nickel-iron oxide, thereby increasing the electrochemical activity and being usefully used as an oxygen reduction catalyst. According to the present invention, the method comprises a precursor solution preparation step, an alkaline precursor solution preparation step, a hydrothermal synthesis step, a washing and drying step, and an oxygen vacancy generation step.

Description

The method of generating oxygen vacancies in nickel-iron oxide catalyst for oxygen evolution reaction and the nickel-iron oxide catalyst manufactured thereby}

The present invention relates to a method for inducing oxygen deficiency in a nickel-iron oxide structure for oxygen generation, and more specifically, performing a partial reduction reaction of a nickel-iron oxide structure to generate oxygen deficiency inside or on the surface of the nickel-iron oxide. Thus it relates to a method for producing a catalyst having a high oxygen generating activity and a nickel-iron oxide catalyst thereby.

In recent years, the exhaustion of fossil fuels and environmental pollution are serious, and many researches in energy-related fields have been conducted to solve them. Among them, a metal-air cell, a fuel cell, and a water electrolyzer have attracted attention as a future energy device because of various advantages. The commonality of such energy devices is that they contain a series of processes to reduce or generate oxygen molecules, and since the process of generating these reductions is a sluggish reaction requiring high voltage, an efficient catalyst is required.

On the other hand, hydrogen energy is most noticed in that it uses water, which is the most abundant material on the earth, as a raw material, is a clean energy source that does not generate contaminants when burning hydrogen, and furthermore functions as an energy storage medium. Hydrogen can be a clean fuel by itself, as described above, and is required in many chemical reactions and processes.

Also, in recent years, hydrogen energy is needed as a clean fuel. Hydrogen energy is an energy source that is spotlighted as the next generation energy because it has no mining limits and local ubiquity and is environmentally friendly. Among them, the hydrogen station method, which directly generates and supplies hydrogen by electrolysis of water, provides the advantage of producing high-purity hydrogen without environmental damage.

The electrolysis reaction of water can be divided into a hydrogen evolution reaction (HER) reaction occurring at the cathode and an oxygen evolution reaction (OER) occurring at the anode.

-Reduction electrode _{(cathode): 4H 2 O +} 4e - → 2H 2 + 4OH -

- oxidation electrode ^{(anode): 4OH - → O} 2 + 2H 2 O + 4e -

The step of determining the most important rate for hydrogen generation during the entire electrolysis reaction is an oxygen evolution reaction at the anode. This is because the oxygen generation reaction (OER) requires much energy to break the O-H bond and form the O-O bond, which is much slower than that of the cathode. For this reason, there is a problem in that a high additional voltage (overvoltage) and energy must be injected in generating oxygen.

Ruthenium (Ru), which is the most widely known electrode material for oxygen production, has a problem of being eluted due to its high price and vulnerable to an acidic atmosphere, and research to replace it with a low-cost transition metal oxide catalyst has been actively conducted. In general, metal oxides based on transition metals have various oxidation values and are very advantageous for redox reactions, so they are used as catalyst materials for energy conversion reactions.

Among the transition metals, spinel-type oxides composed of two metals exhibit high activity in the electrochemical reaction, and the initiation potential through various synthesis methods and doping to synthesize them, and formation of a complex with a carbon material Attempting to develop a positive electrode catalyst having a higher activity by lowering and increasing the current density is underway.

Korean Registered Patent No. 10-1774154 (Announcement date: 2017.09.13) discloses a method for producing an oxygen generating or oxygen reducing catalyst containing a spinel crystalline material and a perovskite crystalline material having oxygen deficiency, Korean Patent Publication No. 10-2018-0012468 (published date: 2018.02.06.) Discloses a technique for producing a catalyst for an oxygen generating reaction comprising a metal oxide nanostructure doped with a transition metal cation.

However, although various kinds of methods for preparing an electrochemical catalyst have been tried in the prior art including the above-mentioned prior art, there is still a need to develop a more improved catalyst for oxygen generation.

Korean Registered Patent No. 10-1774154 (Announcement date: 2017.09.13.) Korean Patent Publication No. 10-2018-0012468 (published date: 2018.02.06.)

The main object of the present invention is to solve the above-mentioned problems, and a partial reduction reaction is performed under a mixed gas atmosphere containing a certain proportion of hydrogen gas in the nickel-iron oxide to deficient oxygen atoms inside or on the surface of the nickel-iron oxide. It is to provide a method for producing a catalyst having the activity of enhanced oxygen generation reaction by generating and a catalyst thereby.

In order to achieve the above technical problem, an embodiment of the present invention, (a) preparing a precursor aqueous solution by dissolving a nickel precursor and an iron precursor in distilled water; (B) adding a basic solution to the precursor solution to adjust the pH to prepare a basic precursor aqueous solution; (c) hydrothermal synthesis of the basic precursor aqueous solution; (d) washing and drying the result synthesized by the hydrothermal synthesis method; (e) performing a partial reduction reaction under a mixed gas atmosphere of a hydrogen (H ₂ ) gas and an inert gas to generate oxygen deficiency in the nickel-iron oxide; and the (e) step is 8 to 15 vol. It provides a method for producing a catalyst for oxygen generation, characterized in that to perform a partial reduction reaction in a temperature range of 80 ~ 150 ℃ under a mixed gas atmosphere containing a hydrogen (H ₂ ) gas.

In a preferred embodiment of the present invention, the nickel precursor in the step (a) is nickel (II) nitrate hexahydrate (Nickel Nitrate Hexahydrate), nickel (II) chloride hexahydrate (Nickel Chloride Hexahydrate), nickel (II) acetate It may be one or more selected from the group consisting of tetraelate tate (Nickel Acetate Tetrahydrate) and nickel (II) bromide hydrate (Nickel Bromide Hydrate).

In a preferred embodiment of the present invention, the iron precursor in the step (a) is iron (III) nitrate nonahydrate (Iron Nitrate Nonahydrate), iron (III) chloride hexahydrate (Iron Chloride Hexahydrate), iron (II) acetate Tetrahydrate (Iron Acetate Tetrahydrate) and iron (II) bromide hydrate (Iron bromide Hydrate) may be one or more selected from the group consisting of.

In a preferred embodiment of the present invention, the basic substance in the basic solution in step (b) is potassium hydroxide (KOH), sodium hydroxide (NaOH), calcium hydroxide (Ca (OH) ₂ ), barium hydroxide (Ba (OH) ₂ ) and ammonium hydroxide (NH ₄ OH).

In a preferred embodiment of the present invention, the pH range in step (b) may be 12-14.

In a preferred embodiment of the present invention, the hydrothermal synthesis temperature in step (c) may be 100 ~ 250 ℃.

In a preferred embodiment of the present invention, the inert gas in step (e) may be argon gas.

In addition, in another embodiment of the present invention, the present invention is prepared by any one of the above methods, and provides a catalyst for generating oxygen containing nickel-iron oxide having an oxygen deficiency on the surface.

In addition, in another embodiment of the present invention, the present invention provides an electrochemical water decomposition apparatus including the oxygen generating catalyst.

When the partial reduction reaction is carried out according to the partial reduction reaction conditions of the present invention, the partial reduction reaction easily proceeds even at a low temperature, and the nickel-iron oxide catalyst generated through the partial reduction reaction has high electrical conductivity and a lower starting potential. It exhibits high current density and shows high activity as a catalyst for oxygen generation reaction.

FIG. 1 is a photograph of a nickel-iron oxide having a spinel structure prepared by Example 1 and Comparative Examples 1 to 4 according to the present invention observed by an X-ray diffraction pattern (XRD).
Figure 2 is a photograph of the nickel-iron oxide of the spinel structure prepared by Example 1 and Comparative Examples 1 to 4 according to the present invention observed by X-ray diffraction pattern (XRD) enlarged at a specific angle.
FIG. 3 is a photograph showing the results of a photoelectric analyzer (XPS) of nickel-iron oxide having a spinel structure prepared by Examples 1 and 4 according to the present invention.
Figure 4 is a graph showing the results of the linear scanning voltage method of the nickel-iron oxide of the spinel structure prepared by Example 1 and Comparative Examples 1 to 4 according to the present invention.
Figure 5 is a graph showing the current density plot results according to the scanning speed of the nickel-iron oxide of the spinel structure prepared by Example 1 and Comparative Examples 1 to 4 according to the present invention.
6 is a graph showing the results of the linear scanning voltage method of the nickel-iron oxide of the spinel structure prepared by Example 1 and Comparative Examples 6 to 7 according to the present invention.

Hereinafter, with reference to the accompanying drawings to describe in detail a preferred embodiment of a method for preparing a catalyst for an oxygen evolution reaction according to the present invention so that those skilled in the art to which the present invention pertains can easily carry out the present invention. do.

In the detailed description of the principles of the preferred embodiment of the present invention, when it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted.

In addition, the configuration shown in the embodiments and drawings described in this specification is only one of the most preferred embodiments of the present invention, and does not represent all of the technical spirit of the present invention. It should be understood that there may be equivalents and variations.

The present invention is a method for producing a catalyst for an oxygen generating reaction that exhibits better electrical activity with a lower overvoltage and a higher limiting current density than a conventional nickel-iron oxide through partial reduction reaction under a mixed gas atmosphere containing hydrogen gas and inert gas. Specifically, (a) preparing a precursor aqueous solution by dissolving a nickel precursor and an iron precursor in distilled water; (B) adding a basic solution to the precursor solution to adjust the pH to prepare a basic precursor aqueous solution; (c) hydrothermal synthesis of the basic precursor aqueous solution; (d) washing and drying the result synthesized by the hydrothermal synthesis method; (e) performing a partial reduction reaction under a mixed gas atmosphere of a hydrogen (H ₂ ) gas and an inert gas to generate oxygen deficiency in the nickel-iron oxide; and the (e) step is 8 to 15 vol. It provides a method for producing a catalyst for oxygen generation, characterized in that to perform a partial reduction reaction in a temperature range of 80 ~ 150 ℃ under a mixed gas atmosphere containing a hydrogen (H ₂ ) gas.

Hereinafter, a method of manufacturing a nickel-iron oxide having oxygen deficiency according to the present invention will be described in detail for each step.

To explain the step (a), first, the nickel precursor and the iron precursor are dissolved in distilled water in an appropriate ratio, for example, in a ratio of 1: 2 to prepare a precursor aqueous solution.

Examples of the nickel compound as the nickel precursor include nickel (II) nitrate hexahydrate, nickel (II) chloride hexahydrate, nickel (II) acetate tetrahydrate, and nickel (II) ) Bromide hydrate (Nickel Bromide Hydrate) is preferably at least one selected from the group consisting of, nickel (II) chloride hexahydrate (Nickel Chloride Hexahydrate) is more preferred, but the scope of the present invention is not limited thereto .

Examples of the iron precursors are iron compounds (Iron Nitrate Nonahydrate), iron (III) chloride hexahydrate (Iron Chloride Hexahydrate), iron (II) acetate tetrahydrate (Iron Acetate Tetrahydrate) and iron (II) ) It is preferable that at least one selected from the group consisting of bromide hydrate (Iron bromide Hydrate), it is more preferable to use iron (III) chloride hexahydrate (Iron Chloride Hexahydrate), but the scope of the present invention is not limited thereto .

Subsequently, the step (b) is a step of preparing a basic precursor aqueous solution by adjusting the pH of the precursor aqueous solution by adding a basic solution to the precursor aqueous solution prepared in the step (a).

To describe the steps (a) and (b) in more detail, first, a nickel precursor and an iron precursor are dissolved in distilled water to prepare a precursor aqueous solution. Then, a basic aqueous solution in which a basic substance is dissolved in distilled water is added to the precursor aqueous solution to adjust the pH of the precursor aqueous solution. At this time, the pH should be adjusted until the color of the reactant formed by precipitation becomes blue. Thereafter, the solution in which the blue reactant is precipitated is dispersed well by stirring for 2 hours or more so that it can be well dispersed and synthesized. At this time, the pH range is preferably 12 ~ 14.

In the step (b), the basic substance in the basic solution is not particularly limited, and may be selected from organic and inorganic basic substances. The basic substance is one or more mixtures selected from potassium hydroxide (KOH), sodium hydroxide (NaOH), calcium hydroxide (Ca (OH) ₂ ), barium hydroxide (Ba (OH) ₂ ) and ammonium hydroxide (NH ₄ OH). It can be used, but is not limited by these. These basic substances are added to the precursor solution in an aqueous solution to adjust the pH of the precursor solution.

In addition, step (c) is a step of hydrothermal synthesis of the basic precursor aqueous solution prepared in step (b), specifically, put the basic precursor aqueous solution in an autoclave (100 to 250 ° C), preferably 150 The reaction is carried out at ~ 250 ° C for 4 to 24 hours, preferably 8 to 16 hours. This temperature and time control prevents agglomeration of particles and evenly disperses them to induce synthesis. After the reaction time is over, the autoclave is removed from the oven and allowed to cool in the natural state.

Subsequently, the step (d) is a process of washing and drying the product synthesized in the step (c). The result of the hydrothermal synthesis in step (c) is a process for removing these impurities because impurities such as sodium and chlorine are mixed. Specifically, centrifugation is performed about 5 times at 8000 rpm using distilled water. After centrifugation, the precipitated product is dried at 60 ° C. for preferably 12 to 24 hours, more preferably 20 to 24 hours to obtain a nickel-iron oxide in which impurities are removed.

In addition, step (e) is a step of generating oxygen deficiency through a partial reduction reaction in order to increase the activity of the nickel-iron oxide obtained in step (d) to an electrochemical catalyst.

Specifically, first, an inert gas is flowed into the tube furnace for 20 to 40 minutes to saturate the inside of the furnace with an inert gas, so that other addition reactions do not occur. After that, the temperature is raised to the target temperature to be changed, and the temperature is raised at a rate of 5 to 20 ° C / min. When the temperature rises to the target temperature, hydrogen (H ₂ ) gas is mixed with an inert gas to a certain volume ratio and flowed to perform a partial reduction reaction to generate oxygen deficiency inside or on the surface of the nickel-iron oxide structure. .

In addition, in the step (e), the hydrogen (H ₂ ) gas in the mixed gas is preferably added at 8 to 15 vol% relative to the total mixed gas. When the hydrogen (H ₂ ) gas exceeds 15 vol% with respect to the total mixed gas, the amount of oxygen deficiency is excessively formed, and the electrochemical activity may decrease due to amorphous formation and collapse of the lattice, and hydrogen (H ₂₎ ) When the gas is added in an amount of less than 8 vol% relative to the total mixed gas, a lot of energy is required to introduce oxygen deficiency inside or on the nickel-iron oxide.

In addition, the partial reduction temperature in the step (e) is preferably in the range of 80 ~ 150 ℃ in terms of effectively generating oxygen deficiency on the interior or surface of the nickel-iron oxide structure.

When the partial reduction temperature is less than 80 ° C., there is insufficient energy to break the bond between the metal atom and the oxygen atom in the nickel-iron oxide, resulting in insufficient generation of oxygen deficiency inside or on the surface of the nickel-iron oxide, and the partial reduction temperature. If the temperature exceeds 150 ° C, there is a possibility that the phases of some or all of the nickel-iron oxides, which have oxygen deficiency through partial reduction, change to nickel metal and lose the electrochemical activity of the nickel-iron oxide structure.

In the step (e), the temperature and gas atmosphere inside the tube furnace during the partial reduction reaction are always kept constant, and the partial reduction reaction is preferably performed for 2 to 10 hours.

In addition, the present invention is prepared by any one of the above methods, and provides a catalyst for oxygen generation reaction including nickel-iron oxide in which oxygen deficiency is present on the surface.

In addition, the present invention provides an electrochemical water decomposition device comprising the catalyst for the oxygen generation reaction.

The present invention as described above is specifically described based on the following examples, and the present invention is not limited by the following examples.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

Example 1

Step (a): 0.3 ml of NiCl _{2 and} 0.6 g of FeCl ₃ are added to a beaker in 60 ml distilled water, and a precursor solution is prepared by stirring for about 30 minutes.

Step (b): preparing a 1 M sodium hydroxide solution, mixing 15 ml of 1 M sodium hydroxide with the precursor solution prepared in step (a), followed by stirring to prepare a basic precursor solution.

Step (c): The basic precursor solution prepared in step (b) is placed in an autoclave and reacted by heating at 200 ° C. for 12 hours.

Step (d): After filtering the resultant produced in step (c), a powder is obtained through a washing process using a centrifuge.

Step (e): Put the washing material obtained in the step (d) into a tube furnace (tube furnace) by performing a partial reduction reaction at a temperature of 100 ℃ for about 5 hours to give a nickel-iron oxide of spinel structure having oxygen defects It was prepared. At this time, the rate of temperature increase to the target temperature was 10 ° C / min, and the mixing ratio of hydrogen gas and argon gas during the partial reduction reaction was maintained at 1: 9.

Comparative Example 1

It is the same as in Example 1, except that the partial reduction reaction was performed at a temperature of 200 ° C. in step (e) of Example 1.

Comparative Example 2

It is the same as in Example 1, except that the partial reduction reaction was performed at 300 ° C. in step (e) of Example 1.

Comparative Example 3

It is the same as in Example 1, except that the partial reduction reaction was performed at a temperature of 50 ° C. in step (e) of Example 1.

Comparative Example 4

It is the same as in Example 1, except that the partial reduction reaction in Step (e) of Example 1 was not performed.

Comparative Example 5

It is the same as in Example 1 except that in step (e) of Example 1, a partial reduction reaction is performed under an air atmosphere instead of a mixed gas atmosphere of hydrogen and argon gas.

Comparative Example 6

It is the same as in Example 1, except that the volume ratio of hydrogen and argon gas in Step (e) of Example 1 was injected at 5:95.

Comparative Example 7

It is the same as in Example 1, except that in the step (e) of Example 1, the volume ratio of hydrogen and argon gas is injected at 2: 8.

In addition, Table 1 below shows the partial reduction conditions in Comparative Examples 1 to 3, Comparative Examples 5 to 7, and Example 1.

Partial reduction conditions Hydrogen: argon ratio Temperature (℃) Example 1 10: 90 100 Comparative Example 1 10: 90 200 Comparative Example 2 10: 90 300 Comparative Example 3 10: 90 50 Comparative Example 5 Air atmosphere 100 Comparative Example 6 5: 95 100 Comparative Example 7 20: 80 100

Experimental Example 1. X-ray diffraction analysis of spinel structure oxide

In order to find out the characteristics of the spinel structure oxides prepared by Example 1 and Comparative Examples 1 to 4, X-ray diffraction analysis (Rigaku, Mini flex) was used to analyze the results, and the results are shown in FIGS. 1 and 2.

Figure 1 shows the X-ray diffraction pattern (XRD) of the spinel structure oxide prepared in Example 1 and Comparative Examples 1 to 4 above. According to FIG. 1, it can be confirmed that in both Example 1 and Comparative Examples 1 to 4, spinel structure oxide peaks appeared. This means that the prepared spinel structure oxide maintains the spinel structure without changing the crystal structure even after additional heat treatment in a hydrogen atmosphere.

FIG. 2 shows an X-ray diffraction pattern (XRD) by enlarging portions of 32 to 39 degrees from the results of FIG. 1 of the spinel structure oxides prepared in Example 1 and Comparative Examples 1 to 4. According to FIG. 2, it can be confirmed that the peaks of the spinel structure oxide prepared in Example 1 were moved. This indicates that the spinel structure contracted due to structural defects.

Experimental Example 2. Analysis of oxidation state of spinel structure oxide

In order to examine the oxidation state of the spinel structure oxides prepared by Example 1 and Comparative Examples 1 to 4, it was analyzed using a photoelectron spectroscopy (X-ray photoelectron spectroscopy, SPECS, EA200). The results are shown in FIG. 3.

Figure 3 shows the spectrum of the oxygen of the spinel structure oxide prepared by Example 1 and Comparative Examples 1 to 4, respectively. According to Figure 3, the oxygen peak (peak) is divided into a total of four bonds, starting from the low section of the oxygen element and the metal element bond (O _M ), the bonding of the hydroxyl group inside the oxygen element (O _OH ), oxygen deficiency ( O _V ), divided into peaks due to chemical bonding (O _C ) with moisture in the air. At this time, in Example 1 according to the present invention, it can be seen that oxygen deficiency occurred through partial reduction as the area ratio of the peak due to oxygen deficiency (O _V ) increased. Table 2 shows the measured values.

O _M O _OH O _V O _C Example 1 37.9 36.7 17.1 8.3 Comparative Example 1 51.1 25.4 16.5 7 Comparative Example 2 45.8 31.8 16.2 6.2 Comparative Example 3 57.8 27.4 8.9 5.9 Comparative Example 4 59.9 27.8 8.3 4 Comparative Example 5 45.5 28.5 16.1 9.9 Comparative Example 6 35.5 33.7 16.6 14.2 Comparative Example 7 52.6 22.1 20.5 4.8

As shown in Table 2, when comparing the area ratio of peaks due to oxygen deficiency (O _V ) in the oxygen peaks of Example 1 and Comparative Examples 6 and 7, the higher the proportion of hydrogen, the greater the amount of oxygen deficiency. Can be confirmed.

Compared to Example 1 and Comparative Examples 1 to 3, Comparative Example 3 in which the partial reduction reaction temperature is 50 ° C does not generate much oxygen deficiency, is the maximum at 100 ° C, and the reaction temperature is 200 ° C or 300 ° C. If you increase, you can see that the amount of oxygen deficiency decreases.

Experimental Example 3. Electrochemical activity analysis of spinel structure oxide

The following experiments were conducted to compare and analyze the performance of the spinel structure oxides prepared in Example 1 and Comparative Examples 1 to 7 as an electrode catalyst for oxygen generation reaction.

5 mV / s in 1 mol of KOH electrolytic solution using a potentiometer (Potentiostat, Princeton Applied Research, VSP) to determine the electrochemical properties of the spinel structure oxides prepared by Example 1 and Comparative Examples 1 to 7 The linear voltage current method was analyzed at the scanning speed of. The results are shown in FIG. 4. The high measured current density means that the electrochemical reaction is active, and therefore, the activity of the oxygen generating reaction is high.

As shown in FIG. 4, the spinel structure oxide of Example 1 of the present invention exhibits the highest current density per unit area, and thus, when used as an electrode catalyst material for oxygen generation reaction, has a higher oxygen defect compared to spinel structure oxide. It was found that it has electrochemical activity.

비교예 6 > 비교예 2 > 비교예 3

비교예 4 의 순으로 나타나고 있어, 산소 결핍의 정도의 순인 비교예 7 > 실시예 1 > 비교예 6

비교예 1 > 비교예 2

비교예 5 > 비교예 3 > 비교예 4와 대비하여 보면, 대체적으로 산소 결핍의 정도가 클수록 한계전류밀도 역시 증가되기는 하나, 완전히 일치하지는 않음을 알 수 있다.The order of the limiting current density is as shown in Figure 4 Example 1> Comparative Example 1> Comparative Example 5 * Comparative Example 7

Comparative Example 6> Comparative Example 2> Comparative Example 3

It is shown in the order of Comparative Example 4, which is pure order of the degree of oxygen deficiency Comparative Example 7> Example 1> Comparative Example 6

Comparative Example 1> Comparative Example 2

Compared to Comparative Example 5> Comparative Example 3> Comparative Example 4, it can be seen that, as the degree of oxygen deficiency is large, the limiting current density is also increased, but not completely.

In the case of Comparative Example 2, the oxygen deficiency was greater than that of Comparative Example 5, but the limiting current density was inferior. In particular, in Comparative Example 7, the limiting current density was not higher than that of Comparative Example 1 even though it had the largest oxygen deficiency value.

From this, it can be seen that other factors in addition to the factor of oxygen deficiency affect the limiting current density.

Experimental Example 4. Evaluation of electrochemical area through cyclic voltammetry

The following experiment was conducted to compare and analyze the performance of the spinel structure oxides prepared by Examples 1 and 4 as Comparative Electrodes for Oxygen Generation Reaction.

To determine the electrochemical properties of the spinel structure oxides prepared by Example 1 and Comparative Examples 1 to 4, 10, 20, in 1 mol of KOH electrolyte solution using a potentiostat (Potentiostat, Princeton Applied Research, VSP) Graphs were obtained through cyclic voltammetry at scan rates of 30, 40, 50, 60, 70, 80, 90 and 100 mV / s and then plotted for current density at 0.95 V at each scan rate. The results are shown in FIG. 5.

Referring to FIG. 5, it was confirmed that the spinel structure oxide of Example 1 of the present invention had the highest bilayer capacitance in a linear plot. The high capacitance of Example 1 indicates high electrochemical surface area and high surface roughness. When the electrochemical surface area is high, it indicates that it is an easy catalyst for the electrochemical reaction, and thus the value of Example 1 shows the highest double layer capacitance, which is consistent with the result of the limiting current density.

Since the specific parts of the present invention have been described in detail above, it will be apparent to those skilled in the art that this specific technique is only a preferred embodiment, and the scope of the present invention is not limited thereby. will be. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (8)

In the production method of the oxygen generating catalyst,
(a) dissolving a nickel precursor and an iron precursor in distilled water to prepare a precursor aqueous solution;
(B) adding a basic solution to the precursor solution to adjust the pH to prepare a basic precursor aqueous solution;
(c) hydrothermal synthesis of the basic precursor aqueous solution;
(d) washing and drying the result synthesized by the hydrothermal synthesis method;
(e) performing a partial reduction reaction under a mixed gas atmosphere of a small number (H2) gas and an inert gas to generate oxygen deficiency in the nickel-iron oxide;
The step (e) is a method for producing a catalyst for oxygen generation, characterized in that performing a partial reduction reaction in a temperature range of 80 to 150 ° C under a mixed gas atmosphere containing 8 to 15 vol% of hydrogen (H ₂ ) gas.
According to claim 1,
In the step (a), the nickel precursors are nickel (II) nitrate hexahydrate, nickel (II) chloride hexahydrate, nickel (II) acetate tetrahydrate, and nickel. (II) Method for producing a catalyst for oxygen generation, characterized in that at least one selected from the group consisting of bromide hydrate (Nickel Bromide Hydrate). According to claim 1,
In the step (a), the iron precursors are iron (III) iron nitrate nonahydrate, iron (III) chloride hexahydrate, iron (II) acetate tetrahydrate and iron acetate (II) Method for producing a catalyst for oxygen generation, characterized in that at least one selected from the group consisting of bromide hydrate (Iron bromide Hydrate). According to claim 1,
In the step (b), the basic substance in the basic solution is potassium hydroxide (KOH), sodium hydroxide (NaOH), calcium hydroxide (Ca (OH) ₂ ), barium hydroxide (Ba (OH) ₂ ) and ammonium hydroxide (NH ₄ OH ) One or more mixtures selected from the method for producing an oxygen generating catalyst. According to claim 1,
In the step (b), the pH range is 12 to 14, characterized in that the production method of the catalyst for oxygen generation. According to claim 1,
In the step (c), the hydrothermal synthesis temperature is 100 ~ 250 ℃ method for producing a catalyst for oxygen generation, characterized in that. According to claim 1,
In the step (e), the inert gas is a method for preparing a catalyst for oxygen reduction reaction, characterized in that it is an argon gas. A catalyst for oxygen production, which is prepared by any one of claims 1 to 6, and includes nickel-iron oxide in which oxygen deficiency is present.

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