KR102535864B1 - Manufacturing method of noble metal-free catalysts for water electrolysis - Google Patents

Abstract

The present invention relates to a method for preparing a non-noble metal catalyst for water electrolysis, which comprises preparing a mixture by mixing 0.01 to 0.1 parts by weight of carbon nanomaterials and 100 parts by weight of a polyol solvent, applying ultrasonic waves to the mixture, and It includes mixing and dispersing the nickel precursor and the pH regulator, irradiating the mixture with microwaves, and obtaining a catalyst from the mixture.

Description

Manufacturing method of non-precious metal catalyst for water electrolysis {MANUFACTURING METHOD OF NOBLE METAL-FREE CATALYSTS FOR WATER ELECTROLYSIS}

The present invention relates to a method for preparing a non-noble metal catalyst for water electrolysis, and more particularly, to a method for preparing a non-noble metal catalyst for water electrolysis having excellent electrochemical activity and durability in a water electrolysis reaction. It relates to a method for preparing a catalyst for water electrolysis.

Efforts to replace fossil fuels and find clean and sustainable energy sources have been challenges facing the world in recent decades, and with the recent problems of radiation and radiation waste from nuclear power generation and global warming caused by greenhouse gases, this has become a bigger problem. is emerging as an issue.

In this respect, the water electrolysis reaction using renewable energy has many advantages in that it produces hydrogen, which is a clean energy source, and can be used as a pollutant-free energy source or chemical raw material without self-discharge.

However, the oxygen evolution reaction (OER) of the water electrolysis reaction has a very slow reaction rate, so a lot of overvoltage must be supplied for normal operation of the water electrolysis system, causing a lot of energy loss. Ruthenium and iridium, which are used as catalysts, are precious metals and act as a factor in increasing the price of water electrolysis systems.

In addition, in the case of a hydrogen evolution reaction (HER) catalyst, platinum is widely used, but since platinum is a noble metal, it acts as a factor in increasing the price of a water electrolysis system. In addition, in general, catalysts using platinum in a hydrogen generation reaction have a problem in that the durability of the catalyst is deteriorated due to the carbon black as the platinum particles are supported on the carbon black.

Therefore, in order to solve the problems in the oxygen generation reaction and the hydrogen generation reaction in the above-described water electrolysis system, it is necessary to develop a non-noble metal based water electrolysis catalyst electrode having high electrochemical activity and excellent durability.

Republic of Korea Patent Registration No. 10-1733492, registered on April 28, 2017

An object of the present invention is to solve the above problems, and to solve the above-described reaction rate problems in the oxygen generation reaction and hydrogen generation reaction and the problems caused by the price and durability of the catalyst, electrochemical activity and durability in the water electrolysis reaction Its object is to provide a method for producing this excellent non-noble metal catalyst for water electrolysis.

The object of the present invention is not limited to the object mentioned above, and other objects not mentioned will be clearly understood from the description below.

In order to achieve the above object, a method for preparing a non-noble metal-based catalyst for water electrolysis according to an aspect of the present invention is to prepare a mixed solution by mixing 0.01 to 0.1 parts by weight of carbon nanomaterials and 100 parts by weight of a polyol solvent, and ultrasonic waves are applied to the prepared mixture. , mixing and dispersing the nickel precursor and the PH regulator in the mixed solution, irradiating the mixed solution with microwaves, and obtaining a catalyst from the mixed solution.

The method for preparing a non-noble metal-based catalyst for water electrolysis according to an embodiment of the present invention according to the above configuration can expect the following effects.

Since a catalyst for water electrolysis in which non-noble metal particles are supported on carbon nanomaterials can be prepared, a catalyst for water electrolysis having excellent electrochemical activity in a water electrolysis reaction can be prepared without using a precious metal-based material.

In addition, as the non-noble metal-based particles are supported on carbon nanomaterials instead of carbon black, a more durable catalyst for water electrolysis can be produced.

1 is a flow chart showing the sequence of a method for preparing a non-noble metal-based catalyst for water electrolysis according to an embodiment of the present invention.
2 is a view showing the results of analyzing carbon nanomaterials used in the preparation of catalysts according to Examples 1 and 2 by Raman spectroscopy according to Test Example 1.
3 is a view showing the results of measuring LSV curves in the hydrogen generation reaction using the catalysts according to Examples 1 to 4 and Comparative Example 1.
4 is a view showing the results of measuring LSV curves in the oxygen generation reaction using the catalysts according to Examples 1 to 4 and Comparative Examples 1 to 2.
5 is a view showing test results according to Test Example 3 of the catalyst according to Example 3;
6 is a view showing the results of analyzing the catalyst according to Example 1 with a transmission electron microscope before conducting 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3.
7 is a view showing the results of analyzing the catalyst according to Example 1 with a transmission electron microscope after performing 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3.
8 is a view showing the results of analyzing the catalyst according to Example 3 with a transmission electron microscope before performing the hydrogen generation reaction 1000 times by the cyclic potential method according to Test Example 3.
9 is a view showing the results of analyzing the catalyst according to Example 3 with a transmission electron microscope after performing 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3.
10 to 13 are diagrams showing the results of analyzing the catalyst according to Example 3 with a scanning transmission electron microscope before hydrogen generation reaction was performed 1000 times by the cyclic potential method according to Test Example 3.
14 is a view showing durability measurement results according to Test Example 5 of the catalyst according to Example 3;
15 is a view showing the results of analyzing the catalysts according to Examples 1 to 4 by thermogravimetry according to Test Example 6.
16 is a view showing the results of XPS analysis of catalysts according to Examples 1 and 3 according to Test Example 7;

Advantages and features of the present invention, and methods of achieving them, will become clear with reference to the detailed description of the following embodiments taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only the present embodiments make the disclosure of the present invention complete, and those skilled in the art in the art to which the present invention belongs It is provided to fully inform the person of the scope of the invention. Meanwhile, terms used in this specification are for describing embodiments, and are not intended to limit the present invention. In this specification, singular forms also include plural forms unless specifically stated otherwise in a phrase.

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

Referring to FIG. 1, the method for preparing a non-noble metal-based catalyst for water electrolysis of the present invention may include a mixture preparation step (S100), a precursor mixing step (S200), an irradiation step (S300), and a catalyst completion step (S400). there is.

First, a mixed solution is prepared by mixing carbon nanomaterials and a polyol solvent, and ultrasonic waves are applied to the prepared mixed solution (S100).

In the mixed solution manufacturing step (S100), the carbon nanomaterial mixed with the polyol solvent when preparing the mixed solution includes at least one selected from graphene oxide (GO) and reduced graphene oxide (rGO) it could be

In the mixed solution preparation step (S100), when a carbon nanomaterial mixed with a polyol solvent is used to include at least one selected from graphene oxide (GO) and reduced graphene oxide (rGO) during preparation of the mixed solution, an investigation step to be described below is used. In (S300), the nickel particles can be effectively supported on the carbon nanomaterial.

On the other hand, graphene oxide (GO) and reduced graphene oxide (rGO) are known to have relatively more defects on the surface than graphene, and in the mixed solution preparation step (S100), graphene is not By using graphene oxide (GO) and reduced graphene oxide (rGO) as carbon nanomaterials, at least one selected from graphene oxide (GO) and reduced graphene oxide (rGO) in the irradiation step (S300) to be described later. Nickel particles can be effectively supported on the defects of

Preferably, the carbon nanomaterial mixed with the polyol solvent during the preparation of the mixed solution in the mixed solution preparation step (S100) may be at least one selected from graphene oxide (GO) and reduced graphene oxide (rGO), and more preferably may be reduced graphene oxide (rGO).

On the other hand, in carbon materials including graphene, graphene oxide (GO), reduced graphene oxide (rGO) and carbon nanotubes, the peak around 1350 cm ^-1 of the Raman spectrum measured by Raman spectroscopy The ratio of the intensity (I _D ) and the peak intensity (I _G ) around 1580cm ^-1 is I _D /I _G It is known as a scale indicating the degree of defects in carbon materials.

In preparing the mixed solution (S100), I _D / I _G of the carbon nanomaterial mixed with the polyol solvent may be 0.94 to 1.75, preferably 1.22 to 1.71, and more preferably 1.55. there is.

When the I _D / I _G of the carbon nanomaterial mixed with the polyol solvent is less than 0.94 during the preparation of the mixed solution in the mixed solution preparation step (S100), the degree of defects of the carbon nanomaterial is low, and in the irradiation step (S300) to be described later, nickel is added to the carbon nanomaterial. Particles may not be effectively supported, and if I _D /I _G exceeds 1.75, the degree of defects of the carbon nanomaterial may be excessive, and thus the durability of the catalyst prepared by the manufacturing method according to the embodiment of the present invention may deteriorate.

In the mixed solution preparation step (S100), the polyol solvent may be at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol, preferably Preferably it may be diethylene glycol.

The mixture solution preparation step (S100) may be a step of preparing a mixture solution by mixing 0.01 to 0.1 parts by weight of a carbon nanomaterial with 100 parts by weight of a polyol solvent, and applying ultrasonic waves to the prepared mixture solution.

When the mixed solution is prepared in the mixed solution preparation step (S100), when the amount of carbon nanomaterials mixed with 100 parts by weight of the polyol solvent is less than 0.01 parts by weight, the amount of the catalyst produced by the manufacturing method according to the embodiment of the present invention is small. Productivity may decrease, and if the amount exceeds 0.1 parts by weight, the amount of carbon nanomaterials may be excessive compared to the polyol solvent, and the carbon nanomaterials may not be effectively dispersed in the polyol solvent.

Preferably, in the mixed solution preparation step (S100), the carbon nanomaterial mixed with 100 parts by weight of the polyol solvent may be 0.01 to 0.04 parts by weight, more preferably 0.014 to 0.021 parts by weight.

In the mixture solution preparation step (S100), ultrasonic waves may be applied to the mixture solution to uniformly disperse the carbon nanomaterials in the mixture solution.

In the mixed solution preparation step (S100), the power of ultrasonic waves applied when preparing the mixed solution may be 100 to 1200W, preferably 400 to 900W, and more preferably 600 to 800W.

If the output of ultrasonic waves applied to the mixed solution prepared in the mixed solution preparation step (S100) is less than 100 W, the output of ultrasonic waves is too weak, and the dispersion of carbon nanomaterials in the polyol solvent may not be effectively achieved. If it exceeds 1200 W, the output of ultrasonic waves is It is so strong that carbon nanomaterials can be damaged by the applied ultrasound.

In the mixed pressure solution preparation step (S100), the application time of ultrasonic waves may be 120 to 240 minutes, preferably 150 to 210 minutes.

If the time for which ultrasonic waves are applied to the mixed solution prepared in the mixed solution preparation step (S100) is less than 120 minutes, the carbon nanomaterials may not be sufficiently dispersed in the mixed solution, and if it exceeds 240 minutes, the dispersion of the carbon nanomaterials in the mixed solution may be difficult. If enough is done, further application of ultrasound may be meaningless.

The nickel precursor and the PH regulator are mixed and dispersed in the mixed solution obtained in the mixed solution preparation step (S100) (S200).

The nickel precursors mixed in the precursor mixing step (S200) include nickel (II) nitrate hexahydrate, nickel (II) chloride hexahydrate, and nickel (II) acetate tetrahydrate. ) and nickel (II) bromide hydrate, preferably nickel (II) chloride hexahydrate.

In the precursor mixing step (S200), the amount of the nickel precursor mixed in the mixed solution obtained in the mixed solution preparation step (S100) is 90 to 150 based on 100 parts by weight of the carbon nanomaterial mixed in the polyol solvent when preparing the mixed solution in the mixed solution preparation step (S100). It may be parts by weight, preferably 110 to 130 parts by weight.

If the amount of the nickel precursor mixed in the precursor mixing step (S200) is less than 90 parts by weight relative to 100 parts by weight of the carbon nanomaterial mixed in the polyol solvent when preparing the mixed solution in the mixed solution preparation step (S100), an irradiation step (S300) to be described later The activity of the catalyst prepared according to the embodiment of the present invention may be reduced because the amount of nickel particles supported on the carbon nanomaterial is small.

When the amount of the nickel precursor mixed in the precursor mixing step (S200) exceeds 150 parts by weight with respect to 100 parts by weight of the carbon nanomaterial mixed in the polyol solvent when preparing the mixed solution in the mixed solution preparation step (S100), an irradiation step (S300) to be described later Since the amount of nickel particles supported on the carbon nanomaterial is sufficient, it may be meaningless to further increase the amount of the nickel precursor.

Meanwhile, synthesis of nickel particles in the irradiation step (S300) to be described later may be performed as the nickel precursor mixed in the precursor mixing step (S200) is reduced.

In the precursor mixing step (S200), the PH regulator adjusts the PH of the mixed solution so that the nickel particles are synthesized and the nickel particles are supported on the carbon nanomaterial in the irradiation step (S300) so that the nickel precursor is smoothly reduced. It may be mixed with the mixed solution to do so.

In the precursor mixing step (S200), the pH adjusting agent mixed in the mixed solution may be an alkaline pH adjusting agent according to the prior art, and may be, for example, at least one selected from ammonia, urea, sodium hydroxide, and potassium hydroxide. It may be sodium hydroxide.

In the precursor mixing step (S200), the pH of the mixed solution adjusted according to the mixing of the PH regulator may be 9 to 11.

In the precursor mixing step (S200), dispersion of the mixed solution in which the nickel precursor and the PH regulator are mixed may be performed by applying ultrasonic waves to the mixed solution.

In the precursor mixing step (S200), after mixing the nickel precursor and the PH regulator in the mixed solution, ultrasonic waves having an output of 200 to 400W are applied to the mixed solution for 30 to 90 minutes to disperse the nickel precursor so that the nickel precursor is uniformly dispersed in the mixed solution. may be a step.

After mixing the nickel precursor and the PH regulator in the precursor mixing step (S200), if the ultrasonic power applied to the mixed solution is less than 200W, the ultrasonic output is too weak and the nickel precursor may not be effectively dispersed in the mixed solution, and if it exceeds 400W The output of the ultrasonic wave for dispersing the nickel precursor is sufficient, so further increase in output may not be meaningful.

After mixing the nickel precursor and the PH regulator in the precursor mixing step (S200), if the ultrasonic wave is applied to the mixed solution for less than 30 minutes, the nickel precursor may not be sufficiently dispersed in the mixed solution, and if it exceeds 90 minutes, the nickel precursor may not be sufficiently dispersed in the mixed solution. Since the nickel precursor is sufficiently dispersed, further application of ultrasonic waves may be meaningless.

Microwaves are irradiated to the mixed solution obtained in the precursor mixing step (S200) (S300).

The irradiation step (S300) is a step of irradiating microwaves to the mixed solution obtained in the precursor mixing step (S200) so that nickel particles are synthesized from the nickel precursor in the mixed solution and the nickel particles are chemically supported on the carbon nanomaterial. can be

In the irradiation step (S300), as the mixed solution is irradiated with microwaves, the mixed solution can be uniformly heated, and as the mixed solution is uniformly heated, nickel particles can be synthesized while nickel ions are reduced in the mixed solution, and the synthesized nickel particles may be supported on the carbon nanomaterial.

In the irradiation step (S300), the frequency of the microwave irradiated to the liquid mixture may be 1 to 5 GHz.

If the frequency of the microwave irradiated to the mixed solution in the irradiation step (S300) is less than 1 GHz, the mixture may not be sufficiently heated, so that the nickel particles may not be synthesized and supported smoothly. Safety problems may occur due to heating.

Preferably, in the irradiation step (S300), the frequency of the microwave irradiated to the liquid mixture may be 2 to 3 GHz.

In the irradiation step (S300), the output of the microwave irradiated to the mixture may be 400 to 1000W.

If the output of the microwave irradiated to the mixture in the irradiation step (S300) is less than 400W, the mixture may not be sufficiently heated, so that the nickel particles may not be smoothly synthesized and supported. If it exceeds 1000W, the mixture is overheated. Safety problems may arise as a result.

Preferably, in the irradiation step (S300), the power of the microwave irradiated to the mixture may be 600 to 800W.

In the irradiation step (S300), the irradiation time of the microwave irradiated to the mixture may be 80 to 160 seconds.

In the irradiation step (S300), if the microwave irradiation time is less than 80 seconds, the mixture may not be sufficiently heated, so that nickel particles may not be sufficiently synthesized and supported. If the microwave irradiation time exceeds 160 seconds, the mixture is heated sufficiently Synthesis and support of the nickel particles have already been sufficiently performed, and further heating may be meaningless.

A catalyst is obtained from the mixture obtained in the irradiation step (S300) (S400).

The catalyst completion step (S400) may include a separation step (S410) and a washing step (S420).

The separation step (S410) may be a step of phase-separating the mixed solution obtained in the irradiation step (S300) into a supernatant and a precipitate by centrifuging.

In the separation step (S410), the rotational speed of centrifugation of the mixed solution may be 7000 to 9000 RPM, and the centrifugation time may be 30 to 60 minutes.

Preferably, the separation step (S410) may be a step of centrifuging the mixed solution obtained in the irradiation step (S300) for 50 minutes at 8000 RPM to separate the mixed solution into a supernatant and a precipitate so that the mixed solution can be phase-separated sufficiently.

The washing step (S420) may be a step of obtaining a catalyst by removing the supernatant of the mixed liquid phase separated in the separation step (S410) to obtain a precipitate as a catalyst, washing the obtained catalyst with a washing solvent and then drying the washed catalyst. there is.

When washing the catalyst obtained in the washing step (S420), a solvent generally used for washing the obtained product may be used as a washing solvent, and for example, a solvent containing at least one selected from distilled water, acetone, and ethanol may be used. .

Drying of the washed catalyst in the washing step (S420) may be performed at 40 to 80 ° C. in a vacuum condition, and the drying time may be 6 to 24 hours.

The method for preparing a non-noble metal-based catalyst for water electrolysis according to an embodiment of the present invention may further include a heat treatment step (S500).

The heat treatment step (S500) may be a step of heat-treating the catalyst obtained in the catalyst completion step (S400).

On the other hand, the nickel particles synthesized and supported on the carbon support in the irradiation step (S300) may include a part corresponding to nickel oxide and a part corresponding to metallic nickel, and a part corresponding to nickel oxide If the fraction occupied by the part is high, the electrochemical activity of the catalyst prepared according to the embodiment of the present invention may be reduced.

The heat treatment step (S500) may be a step of heat-treating the catalyst obtained in the catalyst completion step (S400) to increase the purity of the nickel particles supported on the surface of the catalyst obtained in the catalyst completion step (S400).

More specifically, the heat treatment step (S500) reduces the portion corresponding to nickel oxide contained in the nickel particles supported on the surface of the catalyst obtained in the catalyst completion step (S400) to increase the fraction occupied by the portion corresponding to metallic nickel. In order to improve the electrochemical activity of the catalyst prepared according to an embodiment of the invention, the catalyst obtained in the catalyst completion step (S400) may be heat-treated.

in other words. The heat treatment step (S500) may be a step of heat-treating the catalyst obtained in the catalyst completion step (S400) to improve the electrochemical activity of the catalyst prepared according to the embodiment of the present invention in the electrochemical reaction.

The heat treatment step (S500) may be a step of heat-treating the catalyst obtained in the catalyst completion step (S400) for 120 to 240 minutes under atmospheric conditions of a mixed gas containing hydrogen and argon and a temperature of 350 to 450 ° C.

If the heat treatment temperature is less than 350 ° C in the heat treatment step (S500), the heat treatment temperature of the catalyst obtained in the catalyst completion step (S400) may not be performed smoothly because the heat treatment temperature is low, and if it exceeds 450 ° C, the heat treatment temperature is already sufficient and further An increase in the heat treatment temperature may not be meaningful, and when the heat treatment temperature is excessively high, nickel particles aggregate with each other, resulting in a decrease in the reaction surface area in the water electrolysis reaction, thereby lowering the electrochemical activity of the catalyst prepared according to the embodiment of the present invention. It can be.

If the heat treatment time is less than 120 minutes in the heat treatment step (S500), the heat treatment time of the catalyst obtained in the catalyst completion step (S400) may not be smoothly performed due to the short heat treatment time, and if it exceeds 240 minutes, the heat treatment time is already sufficient and further An increase in the heat treatment time may not be meaningful, and if the heat treatment time is excessively long, the nickel particles aggregate with each other, resulting in a decrease in the reaction surface area in the water electrolysis reaction, thereby reducing the electrochemical activity of the catalyst prepared according to the embodiment of the present invention. It can be.

In more detail, in the heat treatment step (S500), the catalyst obtained in the catalyst completion step (S400) is introduced into a tube of a tube furnace, and then the atmospheric conditions and temperature conditions of the tube furnace are vacuum conditions and a temperature of 350 to 450 ° C. Under the condition, the catalyst obtained in the catalyst completion step (S400) may be heat-treated while introducing argon gas and hydrogen gas into the tube at an input rate of 80 to 120 ml per minute and 60 to 120 ml per minute, respectively.

Preferably, in the heat treatment step (S500), the catalyst obtained in the catalyst completion step (S400) is introduced into a tube of a tube furnace, and then the atmospheric conditions and temperature conditions of the tube heating furnace are vacuum conditions and 400 ° C temperature conditions. And, it may be to heat-treat the catalyst obtained in the catalyst completion step (S400) while introducing argon gas and hydrogen gas into the tube at an input rate of 100 ml per minute and 80 ml per minute, respectively.

<Example 1>

First, 10 mg of carbon nanomaterials and 56 g of polyol solvent were put into and mixed in a 50 ml vial to prepare a mixed solution, and ultrasonic waves having a power of 700 W were applied to the mixed solution for 180 minutes. At this time, reduced graphene oxide (rGO) was used as the carbon nanomaterial, and diethylene glycol was used as the polyol solvent.

12 mg of nickel (II) chloride hexahydrate, a nickel precursor, was mixed with the mixed solution obtained after application of ultrasonic waves, and 1 ml of 0.5M sodium hydroxide was mixed as a pH adjusting agent to adjust the pH of the mixed solution. Ultrasonic waves having an intensity of 300 W were applied to the pH-adjusted mixed solution for 60 minutes.

Next, microwaves having a frequency of 2.45 GHz and an output of 700 W were applied to the mixture for 120 seconds.

Thereafter, the mixture was cooled to room temperature, and the cooled mixture was centrifuged at 8000 RPM for 50 minutes to separate the supernatant and the precipitate.

The supernatant of the phase-separated mixed solution was removed, and the precipitate was washed with acetone to obtain a catalyst. The obtained catalyst was dried at 60° C. for 12 hours in a vacuum condition using a vacuum oven to complete the catalyst.

<Example 2>

A catalyst was prepared in the same manner as in Example 1, except that graphene oxide (GO) was used instead of reduced graphene oxide (rGO) as a carbon nanomaterial.

<Example 3>

After introducing the catalyst obtained in Example 1 into a tube of a tube furnace, air inside the tube of the tube furnace was removed to create a vacuum inside the tube. Thereafter, argon gas and hydrogen gas were injected into the tube at an input rate of 100 ml per minute and 80 ml per minute, respectively, to create an atmospheric condition for a mixed gas containing argon gas and hydrogen gas, and then the obtained in Example 1 at a temperature of 400 ° C. The catalyst was heat treated for 180 min.

<Example 4>

After introducing the catalyst obtained in Example 2 into a tube of a tube furnace, air inside the tube of the tube furnace was removed to form a vacuum inside the tube. Thereafter, argon gas and hydrogen gas were injected into the tube at an input rate of 100 ml per minute and 80 ml per minute, respectively, to create an atmospheric condition for a mixed gas containing argon gas and hydrogen gas inside the tube, and then the obtained in Example 2 at a temperature of 400 ° C. The catalyst was heat treated for 180 min.

<Comparative Example 1>

A catalyst (product name: Platinum, nominally 20% on carbon black; supplied by Alfa Aesar) in which platinum particles are supported on carbon black was purchased and prepared.

<Comparative Example 2>

A catalyst in which iridium particles are supported on carbon black (product name: 20% iridium on vulcan; manufactured by PK Catalyst; supplied by Fuel Cell Store) was purchased and prepared.

<Test Example 1>

In Test Example 1, carbon nanomaterials used in the preparation of catalysts according to Examples 1 and 2 were analyzed using Raman spectroscopy.

The analysis results are shown in FIG. 2 .

2 is a view showing the results of analyzing the carbon nanomaterials used in the preparation of the catalysts according to Examples 1 and 2 by Raman spectroscopy according to Test Example 1, and the carbon nanomaterials used in the preparation of the catalysts in Example 1 A Raman spectrum 101 according to and a Raman spectrum 103 according to the carbon nanomaterial used in preparing the catalyst in Example 2 are shown.

Referring to FIG. 2, it can be confirmed that the I _D /I _G of the carbon nanomaterial (rGO) according to Example 1 is 1.55 and the I _D /I _G of the carbon nanomaterial (GO) according to Example 2 is 0.94. This is a result confirming that the degree of defects of the carbon nanomaterial (rGO) used in the preparation of the catalyst according to Example 1 is higher than that of the carbon nanomaterial (GO) used in the preparation of the catalyst according to Example 2.

<Test Example 2>

In Test Example 2, a working electrode was prepared to compare the performance of the catalysts according to Examples 1 to 4 and Comparative Examples 1 to 2 in the hydrogen evolution reaction and the oxygen evolution reaction, which are water electrolysis reactions, and linear sweep voltammetry , LSV), the onset potentials in the hydrogen evolution reaction and oxygen evolution reaction were measured for each working electrode.

1. Experiment method

1) Manufacture of the working electrode

4 mg of the catalyst according to Example 1, 1 ml of ethanol, and 80 μl of a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (trade name: Nafion) were mixed and homogenized for 30 minutes using an ultrasonic disperser to prepare ink did 15 μl of the prepared ink was applied to glassy carbon and then dried at room temperature for 10 minutes to prepare a working electrode.

Using the catalysts according to Examples 2 to 4 and Comparative Example 1 and Comparative Example 2, working electrodes corresponding to Example 2, Comparative Example 1 and Comparative Example 2, respectively, were prepared using the above method.

2) Electrochemical reaction

A 1M KOH solution in which nitrogen gas was injected for 60 seconds as an electrolyte, a working electrode prepared in 1) as a working electrode, a platinum counter electrode and a mercury-mercury oxide electrode (Hg/HgO Electrode) as counter and reference electrodes, respectively. ) was used to measure the LSV curves for each of the oxygen evolution reaction and the hydrogen evolution reaction.

However, when measuring the LSV curve for the oxygen evolution reaction, the LSV curve was measured for the working electrodes made of the catalysts according to Examples 1 to 4 and Comparative Examples 1 to 2, and when measuring the LSV curve for the hydrogen evolution reaction LSV curve measurements were performed on working electrodes prepared with the catalysts according to Examples 1 to 4 and Comparative Example 1.

The data obtained from the oxygen evolution reaction and the hydrogen evolution reaction were converted into data for the standard hydrogen electrode.

3) Experimental results

FIG. 3 shows LSV curves measured in the hydrogen generation reaction, LSV curve 201 corresponding to Example 1, LSV curve 203 corresponding to Example 2, and LSV curve 205 corresponding to Example 3 ), an LSV curve 207 corresponding to Example 4, and an LSV curve 209 corresponding to Comparative Example 1 are shown.

4 shows the results measured in the oxygen generation reaction as LSV curves, LSV curve 301 corresponding to Example 1, LSV curve 303 corresponding to Example 2, and LSV curve corresponding to Example 3 305, an LSV curve 307 corresponding to Example 4, an LSV curve 309 corresponding to Comparative Example 1, and a curve 311 corresponding to Comparative Example 2 are shown.

3 and 4, the overvoltage at the cathode current density of 10 mA/cm ² in the hydrogen evolution reaction is η ₁ , and the current density in the oxygen evolution reaction exceeds 1.23V at 10 mA/cm ^{2 .} The overvoltage was expressed as η ₂ and summarized in Table 1.

η ₁ (mV) η ₂ (mV) Example 1 353 369 Example 2 453 625 Example 3 201 398 Example 4 274 465 Comparative Example 1 21 450 Comparative Example 2 - 332

On the other hand, it is known that the catalyst exhibits excellent performance as the overvoltage is low at the cathode current density and the current density of 10 mA/cm ² in the hydrogen generation reaction and the oxygen generation reaction, respectively.

First, looking at the hydrogen generation reaction, it can be seen that overvoltages of 353, 453, and 21 mV were observed at a cathode current density of 10 mA/cm ² in Examples 1, 2, and Comparative Example 1. This is a result confirming that the catalysts according to Comparative Example 1, Example 1 and Example 2 exhibit excellent electrochemical activity in the hydrogen generation reaction in that order.

Looking at the oxygen generation reaction, the oxygen generation reaction using the catalysts according to Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the overvoltages exceeding 1.23V at a current density of 10 mA/cm ² were 369 and 625, respectively. , 450 and 332 mV, respectively. This is a result showing that the catalysts according to Comparative Example 2, Example 1, Comparative Example 1, and Example 2 showed excellent electrochemical activity in the oxygen generation reaction in that order.

In the hydrogen generation reaction, it can be confirmed that the performance of the catalyst according to Comparative Example 1 is the most excellent, and in the oxygen generation reaction, it can be confirmed that the catalyst according to Example 1 has better performance than Comparative Example 1.

However, it is known that the oxygen generation reaction in the water electrolysis reaction is a rate determining step (rds).

That is, in the case of the catalyst according to Comparative Example 1, compared to the catalysts according to Examples 1 and 2, the electrochemical activity is excellent in the hydrogen generation reaction, but the performance of the catalyst according to Example 1 is superior to that of Example 2 in the oxygen generation reaction. Considering that it is superior to the catalyst according to Comparative Example 1 and that the oxygen generation reaction in the water electrolysis reaction is the reaction rate determining step, the catalyst according to Example 1 is superior to the catalysts according to Example 2 and Comparative Example 1 in the water electrolysis reaction. It can be seen that it exhibits excellent electrochemical activity.

On the other hand, it can be seen that the electrochemical activity of the catalyst according to Example 1 is slightly lower than that of the catalyst according to Comparative Example 2 in the oxygen generation reaction, but referring to FIG. 4, when the catalyst according to Comparative Example 2 is used in the oxygen generation reaction It can be seen that the difference between the overvoltage when using the catalyst according to Example 1 and that of Example 1 is not very large.

That is, considering that the catalyst according to Example 1 has excellent electrochemical activity in the water electrolysis reaction compared to the catalyst according to Comparative Example 1 and the overvoltage difference between the catalyst according to Comparative Example 2 and the oxygen generation reaction is not large , If the catalyst according to Example 1 is used when constructing a water electrolysis system later, the catalyst according to Example 1 can be applied to both the reduction and oxidation electrodes without the need to apply different noble metal catalysts to the reduction and oxidation electrodes. It is judged that there is an effect that can more conveniently configure the water electrolysis system.

In addition, looking at Example 3 in which the catalyst according to Example 1 and the catalyst according to Example 1 were heat-treated, it can be seen that the electrochemical activity is somewhat improved in the hydrogen generation reaction.

In addition, looking at Example 4 in which the catalyst according to Example 2 and the catalyst according to Example 2 were subjected to heat treatment, it can be confirmed that the electrochemical activity is improved in the hydrogen generation reaction and the oxygen generation reaction.

<Test Example 3>

In Test Example 3, the durability of the catalyst was tested.

In more detail, a working electrode prepared by the method of 1) of Test Example 2 using the catalyst according to Example 3 as a working electrode, a platinum counter electrode and a mercury-mercury oxide electrode as a counter electrode and a reference electrode, respectively ( Hg / HgO Electrode) was used to measure LSV curves before and after hydrogen generation reaction was performed 1000 times by cyclic voltammetry (CV).

5 is a graph showing the test results according to Test Example 3 for the catalyst according to Example 3, and more specifically, the curve 601 according to Example 3 before performing the hydrogen generation reaction 1000 times and the hydrogen generation reaction 1000 It shows the curve 603 according to Example 3 after performing it twice.

Referring to FIG. 5, it can be seen that the catalyst according to Example 3 showed a meaningless change in the LSV curve before and after performing 1000 hydrogen generation reactions, which indicates that the catalyst according to Example 3 This result confirms that the durability is excellent in the water electrolysis reaction.

<Test Example 4>

In Test Example 4, the catalysts according to Examples 1 and 3 were analyzed by transmission electron microscopy (TEM).

In more detail, the catalysts according to Examples 1 and 3 before and after carrying out the hydrogen generation reaction 1000 times by the cyclic potential method according to Test Example 3 were analyzed with a transmission electron microscope.

In addition, in Test Example 4, the catalyst according to Example 3 was analyzed by Fast Fourier transform (FFT) using a high-resolution transmission electron microscope before hydrogen generation reaction was performed 1000 times by the cyclic potential method according to Test Example 3. did

The analysis results according to Test Example 4 are shown in FIGS. 6 to 11.

6 is the result of analyzing the catalyst according to Example 1 with a transmission electron microscope before performing 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3, and FIG. 7 is the hydrogen generation reaction by the cyclic potential method according to Test Example 3 This is the result of analyzing the catalyst according to Example 1 with a transmission electron microscope after performing the reaction 1000 times.

8 is a result of analyzing the catalyst according to Example 3 with a transmission electron microscope before performing 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3, and FIG. This is the result of analyzing the catalyst according to Example 3 with a transmission electron microscope after performing the reaction 1000 times.

Referring to FIG. 6, in the catalyst according to Example 1, it can be seen that the nickel particles are uniformly supported on the carbon support as a whole.

6 and 7, it can be seen that there is almost no change in the surface and structure of the catalyst according to Example 1 before and after performing 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3. This result confirms that the durability of the catalyst according to Example 1 is excellent.

8 and 9, it can be seen that there is almost no change in the surface and structure of the catalyst according to Example 3 before and after performing 1000 hydrogen generation reactions by the cyclic potential method according to Test Example 3. This result confirms that the durability of the catalyst according to Example 3 is excellent.

10 to 13 are the results of analyzing the catalyst according to Example 3 with a scanning transmission electron microscope before performing the hydrogen generation reaction 1000 times by the cyclic potential method according to Test Example 3.

In more detail, FIGS. 10 and 11 are images measured by a scanning transmission electron microscope before performing 1000 hydrogen generation reactions on the catalyst according to Example 3 by the cyclic potential method according to Test Example 3, and FIGS. 12 and 13 is an image obtained by performing Fast Fourier Transform (FFT) on area 1 and area 2 of the rectangle shown in FIG. 11, respectively.

10 to 13, it can be confirmed that the catalyst according to Example 3 has both a portion corresponding to metallic nickel and a portion corresponding to nickel oxide. This is a result confirming that, during heat treatment of the catalyst prepared according to the embodiment of the present invention, a portion corresponding to nickel oxide is reduced to form a portion corresponding to metallic nickel.

<Test Example 5>

In Test Example 5, the durability of the catalyst according to Example 3 was measured using chronoamperometry (CA).

More specifically, a working electrode prepared by the method of 1) using the catalyst according to Example 3 as a working electrode, a platinum counter electrode and a mercury-mercury oxide electrode (Hg/HgO) as a counter electrode and a reference electrode, respectively. Electrode) was used to measure the current generated when a reduction voltage of -0.3V compared to the reference potential was applied for a predetermined time in the hydrogen generation reaction.

The measurement results are shown in FIG. 14 .

14 is a view showing durability measurement results according to Test Example 5 of the catalyst according to Example 3;

Referring to FIG. 14, it can be seen that the current generated when a reduction voltage of -0.3V compared to the reference potential is applied for 12 hours in the hydrogen generation reaction for all catalysts according to Example 3 is almost constant. This is a result confirming that the durability of the catalyst according to Example 3 is excellent.

<Test Example 6>

In Test Example 6, the catalysts according to Examples 1 to 4 were analyzed by thermogravimetric analysis (TGA) to quantitatively measure the amount of nickel particles supported on the catalysts according to Examples 1 to 4.

15 shows the analysis results.

15 is a view showing the results of analyzing catalysts according to Examples 1 to 4 by thermogravimetric method according to Test Example 6, TGA curve 701 according to Example 1 and TGA curve 703 according to Example 2 , TGA curve 705 according to Example 3 and TGA curve 707 according to Example 4 are shown.

Referring to FIG. 15, it can be seen that in the catalyst according to Example 1, the amount of nickel particles supported on the carbon support was 10.92 wt% with respect to the total weight of the catalyst, and in the catalyst according to Example 2, nickel particles were supported on the carbon support. It can be seen that the amount of the catalyst is 10.48wt% based on the total weight of the catalyst.

In addition, in the case of the catalysts according to Examples 3 and 4, it can be confirmed that the amount of nickel particles supported on the carbon support was 13.9 and 16.3 wt%, respectively, based on the total weight of the catalyst, which is consistent with Example 1 and Example 2. It is understood that this is due to the fact that the fraction occupied by the part corresponding to metallic nickel relatively increases as the fraction occupied by carbon and oxygen atoms decreases during heat treatment of the catalyst according to the present invention.

<Test Example 7>

Test Example 7 is an experiment in which the catalysts according to Examples 1 and 3 were analyzed by X-ray photoelectron spectroscopy.

The analysis results are shown in FIG. 16 .

16 is a diagram showing the results of XPS analysis of the catalysts according to Examples 1 and 3 according to Test Example 7, and the graph for 'NiO/rGO' is a graph of the catalyst according to Example 1, and 'A-NiO The graph for /rGO' shows the graph of the catalyst according to Example 3.

Referring to FIG. 16, in the graph of the catalyst according to Example 1, the 'Ni 2p _3/2 ' peak corresponding to metallic nickel is not observed, whereas in the graph of the catalyst according to Example 3, the peak corresponding to metallic nickel is not observed. It can be confirmed that the peak for 'Ni 2p _3/2 ', which is the peak, is observed.

This is found to be due to the fact that the portion corresponding to nickel oxide is too large in the catalyst according to Example 1 than the portion corresponding to metallic nickel among the nickel particles supported on the carbon support. As the corresponding portion is reduced and the fraction occupied by the portion corresponding to metallic nickel increases, a peak corresponding to metallic nickel, 'Ni 2p _3/2 ', is observed.

Those skilled in the art to which the present invention pertains will understand that the present invention can be embodied in other specific forms without changing its technical spirit or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. The scope of the present invention is indicated by the claims to be described later rather than the detailed description above, and all changes or modifications derived from the scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention.

S100: mixed solution preparation step,
S200: precursor mixing step,
S300: investigation step,
S400: catalyst completion step,
S410: separation step, S420: washing step,
S500: heat treatment step.

Claims (4)

A mixed solution was prepared by mixing 0.01 to 0.1 parts by weight of reduced graphene oxide having an I _D /I _G of 1.22 to 1.71 and 100 parts by weight of a polyol solvent, and ultrasonic waves having an output of 100 to 1200 W were applied to the mixture for 120 to 240 minutes. applying while;
Mixing a nickel precursor and a PH regulator in the mixture and dispersing by applying ultrasonic waves having a power of 200 to 400 W for 30 to 90 minutes;
irradiating the mixture with microwaves having a frequency of 1 to 5 GHz and an output of 400 to 1000 W for 80 to 160 seconds;
obtaining a catalyst from the mixture; and
After the catalyst is introduced into the tube of the tube heating furnace, the atmospheric conditions and temperature conditions of the tube heating furnace are vacuum and 350 to 450 ° C, respectively, and argon gas and hydrogen gas are injected at 80 to 120 ml and 60 to 120 ml per minute, respectively. Injecting at a rate and heat-treating the catalyst for 120 to 240 minutes under atmospheric conditions of a mixed gas containing hydrogen and argon and a temperature condition of 350 to 450 ° C.;
Method for preparing a phosphorus non-noble metal catalyst for water electrolysis. delete delete delete

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