KR102609729B1 - Making Process of Nickel Catalysts with Porous Structure For Oxygen Evolution Reaction Using Tungsten Melt - Google Patents

Abstract

The present invention relates to a method for producing a porous Ni catalyst for OER using tungsten dissolution. More specifically, the present invention has the advantage of being able to produce a porous Ni catalyst for OER with high economic value by using nickel, a non-precious metal-based active catalyst, without using noble metal materials.
The present invention has the advantage of providing a method for manufacturing a porous Ni catalyst for OER using tungsten dissolution, which has a maximized surface area compared to existing noble metal-based catalysts, exhibits excellent activity in oxygen evolution reactions, and greatly contributes to reducing hydrogen production costs.

Description

Manufacturing method of porous Ni catalyst for OER using tungsten melting {Making Process of Nickel Catalysts with Porous Structure For Oxygen Evolution Reaction Using Tungsten Melt}

The present invention relates to a method for producing a porous Ni catalyst for OER using tungsten dissolution. More specifically, the present invention has economic value because it does not use precious metal materials, and at the same time has a maximized surface area compared to existing noble metal-based catalysts, showing excellent activity in oxygen evolution reactions and contributing greatly to reducing the unit cost of hydrogen production. It relates to a method for producing Ni catalyst.

Alkaline electrolysis is an essential water electrolysis technology for economical and efficient hydrogen production. Meanwhile, measures to improve catalyst activity and durability are needed to reduce the unit cost of hydrogen production, and to this end, there is an urgent need to develop catalysts used in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).

Among them, the OER catalyst is a four-electron reaction that reacts slowly and requires a large overvoltage, so research on noble metal-based catalysts to improve this is underway. In addition, research is underway on methods for adjusting catalyst components or increasing the active surface area.

However, these existing studies mainly concern noble metal-based catalysts, which have the disadvantage of being expensive and difficult to commercialize. Among them, Ir-based catalysts are not low in activity in an alkaline environment, but their activity is still insufficient.

In addition, to solve this problem, various non-precious metal-based multi-atom catalysts are being studied, but there are limitations in terms of activity, and multi-atom catalysts also have significant side effects because several atoms may cause unintended reactions.

Therefore, there is an urgent need to develop technology to meet the rapidly increasing needs for low-cost, highly active OER or HER catalysts. KR10-2020-0028275 and KR10-1396374 are examples, but there is still no solution to the above problems. The initiation is not found.

Accordingly, while continuing to make diligent efforts to improve the above problems, the present inventor mixed tungsten and nickel precursors with a solvent, dried and heat-treated them to form an alloy, and then dealloyed it with electrochemical melting to produce precious metal materials. This invention has been completed, which has economic value because it does not use , and has a maximized surface area compared to existing noble metal-based catalysts, showing excellent activity in the oxygen evolution reaction (OER) and greatly contributing to reducing the unit cost of hydrogen production.

Prior Patent 1: Korean Patent Publication No. 10-2020-0028275 Prior Patent 2: Korean Patent No. 10-1396374

The purpose of the present invention is to provide a manufacturing method for producing a porous Ni catalyst for OER using nickel, a non-precious metal active catalyst, without using precious metal materials and dissolving tungsten, which has economic value.

Another object of the present invention is to provide a method for manufacturing a porous Ni catalyst for OER using tungsten dissolution, which has a maximized surface area compared to existing noble metal-based catalysts, exhibits excellent activity in oxygen evolution reactions, and greatly contributes to reducing hydrogen production costs.

The above and other objects of the present invention can all be achieved by the present invention described below.

One aspect of the present invention relates to a porous Ni catalyst for OER using tungsten dissolution, which includes tungsten and nickel supported on the surface of the tungsten, and wherein the tungsten and nickel are contained in a molar ratio of 2.5:1 to 3.5:1.

Another aspect of the present invention includes mixing tungsten and nickel precursors with a solvent, drying and heat treating the mixture to form an alloy, and dealloying the alloy by electrochemical melting to dissolve tungsten. It relates to a method for producing a porous Ni catalyst for OER using tungsten dissolution, including the step of obtaining a porous Ni catalyst for OER.

In a specific example, tungsten and nickel may be included in a molar ratio of 2.5:1 to 3.5:1.

In a specific example, the heat treatment may be performed at 1000 to 1500° C. in a hydrogen atmosphere for 50 to 100 seconds.

In a specific example, the electrochemical dissolution may be performed in the range of 0.8V to 1.6V and 3700 to 4300Cycle.

The porous Ni catalyst for OER using tungsten dissolution produced by the present invention has the advantage of high economic value by using nickel, a non-precious metal active catalyst, without using noble metal materials.

The method for manufacturing a porous Ni catalyst for OER using tungsten dissolution according to the present invention has other advantages such as maximizing the surface area over existing noble metal-based catalysts, showing excellent activity in oxygen evolution reactions, and greatly contributing to reducing the unit cost of hydrogen production.

Figure 1 is a flowchart showing a method for producing a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.
Figure 2 is a cyclic voltammetric graph comparing the molar ratio relationship between the materials forming the porous Ni catalyst for OER using tungsten dissolution according to one embodiment of the present invention and the comparative example catalyst.
Figure 3 is a cyclic voltammetry graph showing the dealloyed catalytic activity of a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.
Figure 4 is an SEM image showing the porous surface area of a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.
Figure 5 is a cyclic voltammetric graph comparing the degree of activity according to surface area change between a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention and a conventional catalyst.

Hereinafter, embodiments of the present application will be described in more detail with reference to the attached drawings. However, the technology disclosed in this application is not limited to the embodiments described herein and may be embodied in other forms. However, the embodiments introduced here are provided to ensure that the disclosed content is thorough and complete and that the spirit of the present application can be sufficiently conveyed to those skilled in the art. In order to clearly express the components of each device in the drawing, the sizes of the components, such as width and thickness, are shown somewhat enlarged.

In addition, only part of the components are shown for convenience of explanation, but those skilled in the art will be able to easily understand the remaining components. When describing the drawing as a whole, it is described from the observer's point of view, and when an element is mentioned as being located above or below another element, this means that the element is located directly above or below another element, or that an additional element is interposed between those elements. It includes everything that can be done.

Additionally, a person skilled in the art will be able to implement the ideas of this application in various other forms without departing from the technical spirit of this application. In addition, like symbols in a plurality of drawings refer to substantially the same elements.

Additionally, unless the context clearly indicates otherwise, singular expressions should be understood to include plural expressions, and terms such as include or have refer to the described features, numbers, steps, operations, components, parts, or combinations thereof. It is intended to specify the existence of one thing, but should be understood as not excluding in advance the possibility of the existence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

Additionally, when performing a method or manufacturing method, each process forming the method may occur differently from the specified order unless a specific order is clearly stated in the context. That is, each process may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the opposite order.

Hereinafter, the present invention will be described in more detail.

Porous Ni catalyst for OER using tungsten dissolution

A porous Ni catalyst for OER using tungsten dissolution, which is one aspect of the present invention, includes tungsten and nickel supported on the surface of the tungsten, and the tungsten and nickel are included in a molar ratio of 2.5:1 to 3.5:1.

For example, tungsten powder may be used as the tungsten. Additionally, for example, tungsten oxide may be used. However, as long as it is intended to implement the purpose of the present invention, it can be used without limitation in type.

The nickel is a transition metal that acts as a non-noble metal-based active catalyst to achieve the purpose of the present invention. The nickel may be supported on the tungsten surface. For support, for example, deposition precipitation, coprecipitation, wet impregnation, sputtering, gas-phase grafting, liquid-phase grafting. A variety of known methods can be used without limitation, such as phase grafting or incipient-wetness impregnation.

The tungsten and nickel are included in a molar ratio of 2.5:1 to 3.5:1. Preferably, it is included in a molar ratio of 2.7:1 to 3.3:1. If it is less than the above range, it may cause an incomplete reaction of the supporting compound between nickel, the base, and tungsten, the porogen, and if it exceeds the above range, the porous structure due to the combination of the two materials may not be properly formed and destruction or cracking may occur. There is.

The porous Ni catalyst for OER using tungsten dissolution according to the present invention has the advantage of high economic value by using nickel, a non-precious metal-based active catalyst, without using precious metal materials, and also has a maximized surface area compared to existing noble metal-based catalysts, thereby increasing oxygen It shows excellent activity in the generation reaction and has excellent effects that greatly contribute to reducing the unit cost of hydrogen production.

Method for manufacturing porous Ni catalyst for OER using tungsten dissolution

Another aspect of the present invention, a method for producing a porous Ni catalyst for OER using tungsten dissolution, includes mixing tungsten and nickel precursors with a solvent (S100), drying and heat treating the mixture to form an alloy (S100). S200) and dealloying the alloy by electrochemical melting to obtain a porous Ni catalyst for OER using tungsten melting (S300).

Figure 1 is a flowchart showing a method for producing a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.

Referring to Figure 1, the method for producing a porous Ni catalyst for OER using tungsten dissolution according to the present invention includes a precursor and solvent mixing step (S100), an alloy forming step (S200), and a dealloyed step. do.

Precursor and solvent mixing

The precursor and solvent mixing step (S100) is performed for the purpose of mixing the tungsten and nickel precursors constituting the porous Ni catalyst for OER using tungsten dissolution to be implemented by the present invention with a solvent.

For example, tungsten powder may be used as the tungsten. Additionally, for example, tungsten oxide may be used. However, as long as it is intended to implement the purpose of the present invention, it can be used without limitation in type. In particular, a tungsten precursor can be used to produce a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.

The tungsten precursor may be a compound that contains tungsten atoms and supplies tungsten atoms through sintering. For example, the tungsten precursor may be a tungstate. The tungstate salt can smoothly supply tungsten atoms. The tungstate salt may include, for example, ammonium metatungstate (AMT), ammonium tungstate, sodium tungstate, tungsten chloride, or mixtures thereof. You can. However, as long as it can implement the purpose of the present invention, the type is not limited to this.

The nickel is a transition metal that acts as a non-noble metal-based active catalyst to achieve the purpose of the present invention. The nickel may be supported on the tungsten surface. For support, for example, deposition precipitation, coprecipitation, wet impregnation, sputtering, gas-phase grafting, liquid-phase grafting. A variety of known methods can be used without limitation, such as phase grafting or incipient-wetness impregnation.

The nickel precursor is, for example, NiCl2·xH2O, (CH3COO)2Ni·xH2O, nickel(II) acetylacetonate, nickel(II) carbonate hydroxide, nickel(II) hydroxide, Ni(NO3)2· It may include any one or more selected from the group consisting of xH2O, NiSO4·xH2O, NiI2, or NiF2. However, as long as it is intended to implement the purpose of the present invention, the type is not limited thereto.

The solvent may be a polar solvent, for example, water or an alcohol-based solvent. The alcohol-based solvent may include, for example, one or more selected from the group consisting of methanol, ethanol, propanol, butanol, and pentanol. Preferably the water may be deionized water. More preferably, it may be ultrapure water (De Water). However, as long as it can implement the purpose of the present invention, the type is not limited to this.

In a specific example, tungsten and nickel may be included in a molar ratio of 2.5:1 to 3.5:1. Preferably, it may be included in a molar ratio of 2.7:1 to 3.3:1. If it is less than the above range, it may cause an incomplete reaction of the supporting compound between nickel, the base, and tungsten, the porogen, and if it exceeds the above range, the porous structure due to the combination of the two materials may not be properly formed and destruction or cracking may occur. There is.

Alloy formation

The alloy forming step (S200) is performed for the purpose of forming an alloy by mixing the tungsten and nickel, followed by drying and heat treatment.

In a specific example, the heat treatment may be performed at 1000 to 1500° C. in a hydrogen atmosphere for 50 to 100 seconds. Preferably, the heat treatment may be performed at 1200 to 1300° C. in a hydrogen atmosphere for 70 to 80 seconds. If it is less than the above range, it may be difficult to support nickel, a non-precious metal active catalyst component, on the tungsten surface, so a composite may not be created. If it is more than the above range, the specific surface area of the formed composite may be reduced by sintering.

Dealloyed

The dealloying step (S300) is performed for the purpose of dealloying the above-described alloy by electrochemical melting to obtain a porous Ni catalyst for OER using tungsten melting.

In a specific example, the electrochemical dissolution may be performed in the range of 0.8V to 1.6V and 3700 to 4300Cycle. Preferably, it can be performed in the range of 1.0V to 1.4V and 3900 to 4100Cycle. The dealloying process range is the voltage range in which nickel (Ni) is not passivated according to cyclic voltammetry. When within the above range, HER (Hydrogen Evolution Reaction) is performed by applying a constant voltage of 0.5V at intervals of 200 cycles. It has the advantage of being able to induce reduction of the Alpha-Ni phase through reaction.

The porous Ni catalyst for OER using tungsten dissolution manufactured by the manufacturing method of the present invention has high economic value by using nickel, a non-precious metal-based active catalyst, without using precious metal materials. In particular, the surface area is maximized compared to existing noble metal-based catalysts. It shows excellent activity in the oxygen generation reaction and has excellent characteristics that greatly contribute to reducing the unit cost of hydrogen production.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and should not be construed as limiting the present invention in any way.

Any information not described here can be technically inferred by anyone skilled in the art, so description thereof will be omitted.

Tungsten and nickel precursors were dissolved in ultrapure water (DI water) at a molar ratio of 3:1 and then placed on the Ni disk using a drop cast method. Afterwards, it was dried at room temperature and then heat treated at 1100°C for 70 seconds in a hydrogen atmosphere to form an alloy.

After forming the alloy, an electrochemical dealloying process was carried out through about 4000 cycles with the electrode cycled at 0.8V to 1.6V to dissolve tungsten. Through the above process, a porous Ni catalyst for OER using tungsten dissolution according to the present invention was finally completed.

[Comparative Example 1]

In Comparative Example 1, a porous Ni catalyst for OER was completed in the same manner as Example 1, except that molybdenum was used instead of tungsten.

[Comparative Example 2]

In Comparative Example 2, a porous Ni catalyst for OER was completed in the same manner as Example 1, except that vanadium was used instead of tungsten.

[Experimental example]

The catalyst was evaluated by the following method.

The experiment was conducted by using the manufactured catalyst as a working electrode, and designing a three-electrode experiment using a reference electrode and a counter electrode. After configuring the Rotating Disk Electrode (RDE) experiment, the OER polarization curve was measured under room temperature and pressure conditions. Afterwards, the potential at that current density was measured to compare the overvoltage at 10 mA/cm2.

- Full experimental conditions

a. Working electrode

- Using the manufactured catalyst, the electrode was rotated at 1600 rpm with a Rotating Disk Electrode (RDE).

Reference electrode

- Ag/AgCl Counter electrode - Pt Wire

b. Electrolyte: 1M KOH (pH 14)

c. Temperature: Room temperature (25℃)

- OER activity evaluation experiment

a. The electrolyte was purged with argon for 30 minutes to adjust the argon atmosphere.

b. The working electrode was rotated at 1600 rpm to remove oxygen generated from the electrode due to OER.

c. Scan rate: 1mV/s

d. Scan range: 0.05 V (vs RHE) ~ 2.00 V (vs RHE)

An experiment was conducted to evaluate the catalyst properties as described above, and the results of the experiment are shown in Figures 2 to 5.

Figure 2 is a cyclic voltammetric graph comparing the molar ratio relationship between the materials forming the porous Ni catalyst for OER using tungsten dissolution according to one embodiment of the present invention and the comparative example catalyst.

Referring to FIG. 2, as in Example 1, when tungsten is selected as the soluble porogen and maintained at a 3:1 molar ratio with respect to nickel as the base, unlike molybdenum in Comparative Example 1 or vanadium in Comparative Example 2, in an alkaline environment, Tungsten has the property of being easily soluble, so the surface area of the catalyst can be maximized through tungsten dissolution. In addition, when the ratio of dissolved tungsten is low, the amount of tungsten dissolved after alloying decreases, making it difficult to create a porous surface. However, it can be seen that optimal results can be obtained when the molar ratio of tungsten and nickel is set to 3:1. .

Figure 3 is a cyclic voltammetry graph showing the dealloyed catalytic activity of a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.

Referring to Figure 3, the potential of the catalyst whose surface area was maximized through tungsten dissolution at 10 mA/cm2 is about 1.52 V, and compared to regular nickel which is 1.59 V, it can be seen that the overpotential difference is about 70 mV. Meanwhile, the potential of the theoretical OER reaction is 1.23V, and the reaction occurs at a potential of 1.59V for currently commercialized nickel electrodes, and the overvoltage is about 360mV. The porous Ni catalyst electrode for OER using tungsten melt according to the present invention had an overvoltage of about 290 mV, showing superior activity to commercially available electrodes. Since the overvoltage of the catalyst using noble metal is about 310 mV, it can be seen that the result of 290 mV according to the present invention is an excellent result that exceeds the activity of noble metal even without using noble metal.

Figure 4 is an SEM image showing the porous surface area of a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention.

Referring to Figure 4, it can be seen that the SEM image (A) on the left, where tungsten has not been dissolved, is a Ni pellet without any treatment and has a smooth surface. On the other hand, the SEM image (B) on the right shows that a porous surface area was created through tungsten melting, and it can be seen that the surface area was maximized through this.

Figure 5 is a cyclic voltammetric graph comparing the degree of activity according to surface area change between a porous Ni catalyst for OER using tungsten dissolution according to an embodiment of the present invention and a conventional catalyst.

Referring to Figure 5, the difference in activity can be seen between a commercially available nickel catalyst, a NiFe catalyst excellent in alkaline oxygen generation reaction, and a porous Ni catalyst for OER using tungsten dissolution of the present invention. In other words, when the surface area is maximized through tungsten dissolution in a commercialized nickel catalyst as in the present invention, excellent activity can be achieved with an overvoltage of about 200 mV. This shows the potential as a catalyst for actual commercialization, not just a model catalyst experiment. can confirm.

As discussed above, the porous Ni catalyst for OER using tungsten dissolution manufactured by the present invention through physical property evaluation experiments uses a porous porous catalyst with a maximized surface area compared to the conventional invention, and does not use precious metal materials. It has a high economic value, and in particular, it has a maximized surface area compared to existing noble metal-based catalysts, showing excellent activity in oxygen generation reactions, and has an excellent effect that greatly contributes to reducing the unit cost of hydrogen production.

Meanwhile, although the present invention has been described with limited embodiments and drawings, the present invention is not limited to the above embodiments, and various modifications and variations can be made by those skilled in the art from these descriptions. possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the claims and equivalents as well as the claims described later.

S100: Precursor and solvent mixing step
S200: Alloyed formation stage
S300: dealloyed stage

Claims (5)

delete Mixing tungsten and nickel precursors contained in a molar ratio of 2.5:1 to 3.5:1 with a solvent;
Forming an alloy by drying the mixture and heat treating it at 1000 to 1500° C. in a hydrogen atmosphere for 50 to 100 seconds; and
Obtaining a porous Ni catalyst for OER by dealloying the alloy by electrochemical melting in the range of 0.8V to 1.6V and 3700 to 4300Cycle; Method for producing a porous Ni catalyst for OER using tungsten dissolution comprising.
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