KR102497272B1 - Alloy catalyst manufacturing method for reducing carbon dioxide - Google Patents

Abstract

The present invention relates to a method for preparing an alloy catalyst for reducing carbon dioxide, according to one aspect of the present invention, preparing a substrate; Forming a mainstream metal thin film on one surface of the substrate; Forming a heterogeneous metal layer on the surface of the mainstream metal thin film; immersing the substrate on which the main metal thin film and the dissimilar metal layer are formed in an aqueous solution, and applying an anode voltage to a surface of the dissimilar metal layer to form a metal oxide; And it may be provided with a method for preparing an alloy catalyst for reducing carbon dioxide, including the step of forming an alloy nanostructure by flowing a reduction current density through the metal oxide.

Description

Alloy catalyst manufacturing method for carbon dioxide reduction {ALLOY CATALYST MANUFACTURING METHOD FOR REDUCING CARBON DIOXIDE}

The present invention relates to a method for manufacturing an alloy catalyst for reducing carbon dioxide, and relates to a method for manufacturing an alloy catalyst for reducing carbon dioxide having high efficiency and stability.

Global warming, which increases the average temperature of the earth, causes various climate change phenomena, causes ecosystem changes, and ultimately poses a high threat to human survival. This global warming phenomenon is considered to be very closely related to changes in the concentration of carbon dioxide in the atmosphere. Therefore, research institutes in each country are conducting various studies in order to fundamentally lower the concentration of carbon dioxide in the atmosphere, which increases with the continuous increase in carbon dioxide emissions.

Recently, technologies for electrochemically converting carbon dioxide into useful chemical fuels have attracted a lot of attention, because the electrochemical conversion of carbon dioxide can reduce carbon emissions and economically produce chemical fuels with higher added value than carbon dioxide.

Electrochemical carbon dioxide conversion usually proceeds through a reduction reaction of carbon dioxide by applying electrical energy to an aqueous solution saturated with carbon dioxide. However, these techniques have several problems. First, the thermodynamic energy required to reduce physicochemically stable carbon dioxide is very large, and second, carbon dioxide has low solubility in an aqueous solution at room temperature and pressure.

When electric energy is applied to the aqueous solution, the reduction reaction of hydrogen ions (H ⁺ ) occurs before the carbon dioxide contained in the aqueous solution, and thus the efficiency of the reduction reaction of carbon dioxide is inevitably low.

Therefore, in order to solve the above problems, it is essential to develop a high-performance catalyst capable of effectively lowering the thermodynamic energy required for carbon dioxide reduction and selectively reducing carbon dioxide.

Gold (Au) and silver (Ag) are well-known carbon dioxide reduction catalysts.

In particular, gold is an excellent catalyst for reducing carbon dioxide to carbon monoxide. Carbon monoxide is an industrially very useful chemical fuel, and since it is a raw material of syngas, it has a much higher economic value than carbon dioxide.

However, when gold in general form, for example, gold foil or gold thin film having a relatively smooth and flat surface is used as a carbon dioxide reduction catalyst, the number of active sites participating in the reaction In addition to being limited, the hydrogen ion reduction reaction and the carbon dioxide reduction reaction occur competitively in aqueous solution. Therefore, in order to increase the efficiency of the carbon dioxide reduction reaction, relatively high energy must be input (eg, high overvoltage), resulting in poor economic efficiency.

In order to solve this problem, a technique for modifying the surface of gold has emerged, and there is a study on a gold nanostructure formation method that performs electrochemical surface modification.

Nanostructures formed through electrochemical surface modification exist in various forms such as nanopores and nanopillars, and these nanostructures can have more catalytically active sites due to a dramatic increase in surface area compared to flat plates. there is. In addition, the efficiency of the carbon dioxide reduction reaction can be increased at a relatively low overvoltage by creating an environment in which the carbon dioxide reduction reaction can occur, such that the hydrogen generation reaction is relatively suppressed by maintaining the local hydrogen ion concentration index (pH) high.

On the other hand, in order to develop a high-performance catalyst for economical carbon dioxide conversion, it is necessary to consider safety of the catalyst as not only the conversion efficiency is high, but also the conversion efficiency is maintained for a long time. As described above, when the nanostructure is used as a carbon dioxide reduction catalyst, although there is a high carbon dioxide conversion efficiency at a low applied voltage, it is difficult to continuously maintain high efficiency.

For example, in the case of a gold nanoporous catalyst formed to a thickness of about 200 nm on the surface of a gold thin film, when carbon dioxide is converted to carbon monoxide under the applied voltage condition of about -0.5V, the conversion efficiency is about 80%, but the holding time is about 5 There are problems that are as short as an hour.

Recently, in order to simultaneously improve the properties and stability of a catalyst, a technique using an alloy catalyst is used. The technology using an alloy catalyst is a surface diffusion of metal atoms composed of host atoms and major atoms during an (electro)chemical reaction of metal atoms composed of guest atoms and hetero atoms in the alloy. It acts as a diffusion barrier and maintains the fine structure of the catalyst similar to the initial state for a long time, so that the performance stability of the catalyst can be maintained for a relatively long time.

In the technology using an alloy catalyst, in the case of an alloy using gold as a main element and copper as a non-mainstream element, when the copper composition ratio is similar to or relatively high with gold, the catalytic properties of copper are mainly expressed, and the gold catalyst characteristics are weakened. Therefore, it is necessary to synthesize a carbon dioxide reduction catalyst with high efficiency and high stability so that the composition of non-mainstream metal elements is kept relatively low so that the existing catalytic properties can be improved by the presence of non-mainstream elements without weakening the catalytic properties of the main metal elements. there is

Conventionally, in order to prepare an alloy catalyst, a solution-based co-precipitation method or a method of preparing an alloy catalyst by changing the temperature and composition based on phase diagram information between dissimilar metals has been used.

However, as described above, when the alloy catalyst is prepared, first, the solution-based co-precipitation method can finely control the composition change of the alloy, but is limited to synthesizing nanoparticles, and residues such as precursors There is a problem that can remain on the surface of the alloy and weaken the catalytic properties.

In addition, secondly, in the case of manufacturing an alloy catalyst based on the phase equilibrium diagram between different metals, the alloy composition is determined according to specific temperature and composition conditions, and a solid solution is formed at a high temperature and then cooled to form an alloy. Therefore, it is difficult to prepare an alloy catalyst containing a small amount of non-mainstream atoms. Moreover, it is difficult to form an alloy having a three-dimensional nanostructure.

In addition, in common, there is a problem that the process itself is very complicated and takes a lot of time, thereby increasing the process cost and making it difficult to secure the process yield.

Republic of Korea Patent No. 10-1932195 (2018.12.18.)

Embodiments of the present invention have been invented against the above background, and it is possible to control the composition of non-mainstream metal elements in the alloy catalyst, and to provide an alloy catalyst manufacturing method for reducing carbon dioxide having high efficiency and stability.

According to one aspect of the present invention, preparing a substrate; Forming a mainstream metal thin film on one surface of the substrate; Forming a heterogeneous metal layer on the surface of the mainstream metal thin film; immersing the substrate on which the main metal thin film and the dissimilar metal layer are formed in an aqueous solution, and applying an anode voltage to a surface of the dissimilar metal layer to form a metal oxide; And it may be provided with a method for preparing an alloy catalyst for reducing carbon dioxide, including the step of forming an alloy nanostructure by flowing a reduction current density through the metal oxide.

Forming the mainstream metal thin film, forming an adhesive layer on one surface of the substrate, and forming the mainstream metal thin film on the adhesive layer, an alloy catalyst manufacturing method for carbon dioxide reduction may be provided.

The adhesive layer may be provided with an alloy catalyst manufacturing method for reducing carbon dioxide, including one or more metals of titanium (Ti), tantalum (Ta), and chromium (Cr).

The adhesive layer has a thickness of 1 nm to 10 nm, and the mainstream metal thin film has a thickness of 50 nm to 1000 nm, an alloy catalyst manufacturing method for carbon dioxide reduction may be provided.

The dissimilar metal layer formed by the step of forming the dissimilar metal layer is formed through one of an underpotential deposition (UPD) and an electrodeposition (electrodeposition) method, an alloy catalyst manufacturing method for reducing carbon dioxide can be provided. there is.

The substrate may be selected from among metals including at least one of iron (Fe), copper (Cu), zinc (Zn), and aluminum (Al), alloys including stainless steel, silicon (Si), and gallium arsenide (GaAs). Semiconductors containing one or more, polymer plastics containing one or more of silicon (Si), acrylate, vinyl, and carbonate, and compounds of indium and tin oxide, glass (Glass), and at least one selected from the group consisting of quartz (quartz), including, can be provided with an alloy catalyst manufacturing method for reducing carbon dioxide.

The mainstream metal thin film includes one metal selected from the group consisting of gold (Au), silver (Ag), palladium (Pd), zinc (Zn), etc., an alloy catalyst manufacturing method for carbon dioxide reduction can be provided there is.

The dissimilar metal includes at least one of silver (Ag), palladium (Pd), copper (Cu), tin (Sn), zinc (Zn) and iron (Fe), preparing an alloy catalyst for carbon dioxide reduction A method may be provided.

The heterogeneous metal layer may be provided with an alloy catalyst manufacturing method for carbon dioxide reduction formed in a continuous layer structure or a discontinuous island structure.

The thickness of the continuous layer may be 1Å to 10nm, an alloy catalyst manufacturing method for reducing carbon dioxide.

The thickness of the discontinuous mass may be provided with an alloy catalyst manufacturing method for reducing carbon dioxide, which is 50 nm to 400 nm.

In the step of forming the metal oxide, a method for preparing an alloy catalyst for reducing carbon dioxide may be provided by applying an anode voltage of 1.5 to 3V compared to a reversible hydrogen electrode (RHE) for 1 minute or more.

The reduction current density is -0.1 mA/cm 2 to -10.0 mA/cm 2 , a method for preparing an alloy catalyst for reducing carbon dioxide may be provided.

The forming of the metal oxide and the forming of the alloy nanostructure may be performed in the same aqueous solution, a method for preparing an alloy catalyst for reducing carbon dioxide.

The reduction current density may be provided with an alloy catalyst manufacturing method for reducing carbon dioxide, in which the electrode potential value applied to the metal oxide flows to the point where the value changes in a negative direction.

The composition of the dissimilar metal contained in the alloy nanostructure may be provided with an alloy catalyst manufacturing method for reducing carbon dioxide, which is 1 atomic% to 15 atomic%.

An embodiment of the present invention is to form a different metal by a method such as electrodeposition after depositing a mainstream metal thin film on a substrate and continuously perform an electrochemical oxidation and reduction reaction in an aqueous solution, thereby preparing an alloy catalyst. Therefore, the alloy catalyst can be prepared more easily than before.

In one embodiment of the present invention, the alloy catalyst can be formed into a three-dimensional nanostructure more easily and quickly than before, so that mass production possibility can be reviewed and productivity can be increased along with process convenience and cost reduction.

In one embodiment of the present invention, when the alloy catalyst is used as a catalyst for reducing carbon dioxide, the composition of the dissimilar metal in the alloy can be controlled to a small to small amount, so that the catalytic properties of the main metal in the alloy catalyst can not be weakened, In addition, it is possible to effectively suppress structural collapse due to the surface diffusion (movement) of mainstream metal atoms generated finely as the carbon dioxide reduction reaction proceeds, so that catalytic properties for carbon dioxide reduction can be maintained for a long time.

1 is a flowchart illustrating a method for preparing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention.
Figure 2 (a) is a schematic diagram showing a substrate on which an adhesive layer and a mainstream metal thin film are deposited on the substrate in the alloy catalyst manufacturing method for carbon dioxide reduction according to an embodiment of the present invention.
FIG. 2(b) is a photograph taken through a scanning electron microscope of the substrate shown in FIG. 2(a).
Figure 2 (c) is a schematic diagram showing a substrate on which a heterogeneous metal layer is formed in the method for manufacturing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention.
FIG. 2(d) is a photograph taken through a scanning electron microscope of the substrate shown in FIG. 2(c).
Figure 2 (e) is a schematic diagram showing a substrate on which a metal oxide is formed in the method for manufacturing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention.
FIG. 2(f) is a photograph taken through a scanning electron microscope of the substrate shown in FIG. 2(e).
Figure 2 (g) is a schematic diagram showing a substrate on which the alloy nanostructure is formed in the alloy catalyst manufacturing method for carbon dioxide reduction according to an embodiment of the present invention.
Figure 2 (h) is a photograph taken through a scanning electron microscope of the substrate shown in Figure 2 (g).
Figure 3 (a) is a photograph taken through an atomic force microscope of the upper surface of the substrate on which the gold thin film, which is the mainstream metal, is deposited in the method for manufacturing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention.
Figure 3 (b) shows a state in which copper, which is a heterogeneous metal, is electrodeposited on a mainstream metal substrate using an underpotential deposition method (UPD method) in the method for manufacturing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention. This is a picture taken through a force microscope.
3(c) shows a state in which copper, which is a heterogeneous metal, is electrodeposited on a mainstream metal substrate for 10 seconds through an electrodeposition method in an alloy catalyst manufacturing method for reducing carbon dioxide according to an embodiment of the present invention through a scanning electron microscope. this is a picture taken
3(d) shows a state in which copper, a heterogeneous metal, is electrodeposited on a mainstream metal substrate for 60 seconds through an electrodeposition method in an alloy catalyst manufacturing method for reducing carbon dioxide according to an embodiment of the present invention through a scanning electron microscope. this is a picture taken
3(b-1) to 3(d-1) show the electrochemically anodized state of the substrates shown in FIGS. 3(b) to 3(d) through a scanning electron microscope. this is a picture taken
3(b-2) to 3(d-2) show metal oxides formed by electrochemically anodizing the substrates shown in FIGS. 3(b) to 3(d), respectively, under a scanning electron microscope. This is a picture taken through
Figure 4 (a) is a photograph taken through a scanning transmission electron microscope of the copper and gold alloy nanostructure prepared in Example 1 of the alloy catalyst manufacturing method for carbon dioxide reduction according to an embodiment of the present invention.
FIG. 4(b) is an image obtained by mapping the captured picture of FIG. 4(a).
4(c) is a photograph of a state in which copper is electrodeposited on a mainstream metal substrate for 10 seconds in Example 2 of an alloy catalyst manufacturing method for reducing carbon dioxide according to an embodiment of the present invention through a scanning transmission electron microscope It is a picture.
(d) of FIG. 4 is an image obtained by mapping the photograph taken in (c) of FIG. 4 .
4(e) is a photograph of a state in which copper is electrodeposited on a mainstream metal substrate for 60 seconds in Example 2 of an alloy catalyst manufacturing method for reducing carbon dioxide according to an embodiment of the present invention through a scanning transmission electron microscope. It is a picture.
FIG. 4(f) is an image obtained by mapping the captured picture of FIG. 4(e).
Figure 5 (a) is a graph showing the results of measuring the binding energy position and strength of gold by X-ray photoelectron spectroscopy of the alloy catalyst prepared by the alloy catalyst manufacturing method for carbon dioxide reduction according to an embodiment of the present invention. .
Figure 5 (b) is a graph showing the results of measuring the binding energy position and strength of copper by X-ray photoelectron spectroscopy of the alloy catalyst prepared by the alloy catalyst manufacturing method for carbon dioxide reduction according to an embodiment of the present invention. .
FIG. 5(c) is an enlarged view of a part of FIG. 5(b).
Figure 6 is a graph showing the conversion selectivity of carbon dioxide to carbon monoxide according to the applied voltage in the alloy catalyst manufacturing method for carbon dioxide reduction according to an embodiment of the present invention.
7 is a graph showing changes in catalyst characteristics that can confirm catalyst stability over time when the applied voltage is fixed in the method for manufacturing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention.

Hereinafter, specific embodiments for implementing the present invention will be described in detail with reference to the drawings.

In addition, in the description of the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

In addition, when a component is referred to as 'connecting', 'supporting', 'connecting', 'supplying', 'transferring', or 'contacting' to another component, it is directly connected to, supported by, or connected to the other component. It may be supplied, delivered, or contacted, but it should be understood that other components may exist in the middle.

Terms used in this specification are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In addition, in this specification, expressions such as upper, lower, side, etc. are described based on the drawings, and it is made clear in advance that they may be expressed differently if the direction of the object is changed. For the same reason, some components in the accompanying drawings are exaggerated, omitted, or schematically illustrated, and the size of each component does not entirely reflect the actual size.

In addition, terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by these terms. These terms are only used to distinguish one component from another.

As used herein, the meaning of "comprising" specifies specific characteristics, regions, integers, steps, operations, elements, and/or components, and other specific characteristics, regions, integers, steps, operations, elements, elements, and/or groups. does not exclude the presence or addition of

Referring to Figures 1 to 7, a method for manufacturing an alloy catalyst for reducing carbon dioxide according to an embodiment of the present invention will be described.

As shown in FIG. 1, the method for manufacturing an alloy catalyst for reducing carbon dioxide according to the present embodiment includes preparing a substrate (S101), forming a mainstream metal thin film (S103), forming a heterogeneous metal layer (S105), and forming a metal oxide. A step (S107) and an alloy nanostructure forming step (S109) are included.

To prepare an alloy catalyst for reducing carbon dioxide, first, a substrate is prepared (S101).

The substrate is for fixing and supporting the metal thin film, and any substrate may be used. The substrate may include, for example, metals including at least one of iron (Fe), copper (Cu), zinc (Zn), and aluminum (Al), alloys including stainless steel, silicon (Si), and gallium arsenide (GaAs). Semiconductors containing at least one of silicon (Si), acrylate, vinyl, and carbonate, and polymer plastics containing at least one of silicon (Si), acrylate, and carbonate, and a compound of indium and tin oxide, At least one selected from the group consisting of glass and quartz may be included.

Specifically, the substrate may be a non-conductive or conductive substrate, and the substrate may be a conductive material such as iron, copper, aluminum, tin, zinc, silicon, gallium arsenide, indium tin oxide (ITO), and glass , quartz, polydimethylsiloxane (PDMS), polymethylmethacrylate (PMMA), polyvinylidenefluoride (PVDF), and non-conductive polymers such as polycarbonate (PV+C) may contain substances.

However, when the polymer material is used as a carbon dioxide reduction catalyst, organic matter such as carbon or carbon compounds in the aqueous solution may be leached out and the carbon dioxide reduction efficiency may be reduced, and thus may not be used.

In addition, in a substrate containing silicon or gallium arsenide, oxides may be naturally formed on the surface of the substrate, and thus bonding strength between the substrate and the adhesive layer may deteriorate when forming the adhesive layer on the substrate. Therefore, the substrate containing silicon or gallium arsenide is immersed in hydrofluoric acid or an aqueous solution diluted with hydrofluoric acid for a predetermined time (eg, one of 1 second to 90 seconds, 1 second to 60 seconds, and 1 second to 30 seconds), and distilled water. After washing with an inert gas (eg, helium (He), argon (Ar), nitrogen (N ₂ ), or carbon dioxide (CO ₂ )), it may be used by drying.

In addition, since the substrate including glass or quartz has a SiO _x structure, it can be dissolved in hydrofluoric acid or a solution in which hydrofluoric acid is diluted, so that an oxide removal process can be omitted.

The substrate may have a thickness of 100 μm to 1000 μm or 100 μm to 500 μm. Here, the shape of the substrate may have a circular or polygonal shape, and may have an area of at least 1 cm 2 or more. For example, the substrate may have a circular shape with a diameter of 2 inches, 3 inches, 4 inches, 6 inches, etc., a square or rectangle with a side length of at least 1 cm, etc., but is not limited thereto.

When the substrate is prepared, an adhesive layer and a mainstream metal thin film are formed on one surface of the substrate (S103).

The adhesive layer may include one or more metals of titanium (Ti), tantalum (Ta), and chromium (Cr). And the adhesive layer may have a thickness of 1 nm to 10 nm or 1 nm to 5 nm. In this embodiment, the adhesive layer can prevent the mainstream metal thin film from peeling off from the substrate.

The adhesive layer may be formed on the substrate in a vacuum atmosphere through one of chemical vapor deposition, thermal evaporation, E-beam evaporation, and RF or DC sputtering. there is.

When an adhesive layer is formed on the substrate, a mainstream metal thin film is formed on the adhesive layer.

The mainstream metal thin film includes one metal selected from the group consisting of gold (Au), silver (Ag), palladium (Pd), zinc (Zn), and the like. And the mainstream metal thin film may have a thickness of one of 50 nm to 1000 nm, 50 nm to 800 nm, 50 nm to 600 nm, 50 nm to 400 nm, and 50 nm to 200 nm.

Here, when the thickness of the mainstream metal thin film exceeds 400 nm, the time taken to form the thin film relatively greatly increases, and the amount of metal required to form the thin film increases, which is economically unfavorable. In addition, if the thickness of the mainstream metal thin film is less than 50 nm, problems such as peeling off during the carbon dioxide reduction reaction may occur because the thickness of the thin film is thin.

The mainstream metal thin film may have the same area as the substrate as it is formed on the entire surface of the substrate.

The mainstream metal thin film, like the adhesive layer, is applied to the plate on the adhesive layer by one of chemical vapor deposition, thermal evaporation, E-beam evaporation and sputtering deposition (RF or DC sputtering). It can be formed in a vacuum atmosphere through the method.

The adhesive layer and the mainstream metal thin film as required can be successively deposited on the substrate.

As described above, when the adhesive layer and the mainstream metal thin film are formed on the substrate, a different metal layer is mainly formed on the metal thin film (S105).

The dissimilar metal may include one or more of silver (Ag), palladium (Pd), copper (Cu), tin (Sn), zinc (Zn), and iron (Fe).

The dissimilar metal layer may be formed in a vacuum atmosphere through one of chemical vapor deposition, thermal evaporation, E-beam evaporation, and RF or DC sputtering. , Or, it may be formed through an electroplating method in an aqueous solution atmosphere through one of underpotential deposition (UPD) and electrodeposition (electrodeposition).

The dissimilar metal layer may have a thickness of several angstroms (Å) to several hundred nm.

Specifically, when a dissimilar metal layer is formed through the underpotential deposition method, the deposition proceeds at a potential (underpotential) lower than the equilibrium potential of the metal due to the characteristics of the underpotential deposition method, so the layer on which the dissimilar metal is deposited has an underpotential. It may be formed to a thickness of several angstroms (Å) to several nm in proportion to the applied time.

For example, when the dissimilar metal layer is formed in a continuous layer structure, it may have a thickness of 1 Å to 10 nm.

In addition, when the dissimilar metal layer is formed through electrodeposition, since precipitation proceeds at a potential higher than the equilibrium potential, the dissimilar metal layer may be formed to a thickness of several tens of nm to several hundreds of nm. Here, in the case of forming the dissimilar metal layer through the electrodeposition method, it may be formed as a discontinuous layer, such as randomly distributing a plurality of large and small islands.

For example, when the dissimilar metal layer is distributed in the form of a lump, it may be formed to a thickness of 50 nm to 400 nm.

This step may be performed continuously after the mainstream metal thin film is formed, if necessary.

As described above, when the dissimilar metal layer is formed, a metal oxide is formed on the surface of the formed dissimilar metal layer (S107).

The metal oxide may be formed by electrochemical anodization by applying a voltage to the surface of the dissimilar metal layer in a state where the substrate on which the main metal thin film and the dissimilar metal layer are formed is immersed in an aqueous solution. The metal oxide thus formed includes the main metal and trace to small amounts of dissimilar metals, and may specifically be an oxide or oxide hydrate system for two or more metals among gold, silver, copper, palladium, zinc, tin, bismuth, and indium.

In this step, when an anode voltage is applied to the dissimilar metal layer, the discontinuous or discontinuous dissimilar metal is dissolved and eluted into the aqueous solution as ions. Accordingly, in the process of reduction through the reduction current density in a later step, ions of different metals may be randomly distributed in small or small amounts within the alloy nanostructure.

Aqueous solutions may be acidic, neutral or basic aqueous solutions. For example, the aqueous solution may be an aqueous solution of sulfuric acid (H ₂ SO ₄ ), an aqueous solution of potassium hydrogen carbonate (KHCO ₃ ), an aqueous solution of sodium hydrogen carbonate (NaHCO ₃ ), an aqueous solution of potassium hydroxide (KOH), or an aqueous solution of sodium hydroxide (NaOH). The acidic aqueous solution may be one of pH 0.1 to pH 3, pH 0.1 to pH 2 and pH 0.1 to pH 1, the neutral to weakly basic aqueous solution may be pH 7 to pH 9, and the basic aqueous solution may be pH 12 or higher, or pH 13 or higher.

Voltage application, in preparation for a reversible hydrogen electrode (RHE), an anode voltage of one of 1.5V to 3.0V, 1.5V to 2.5V and 1.5 to 2.0V for 1 minute or more, 1 minute to 80 minutes, It may be applied for one of 1 minute to 60 minutes, 1 minute to 40 minutes, and 1 minute to 20 minutes.

Meanwhile, in this embodiment, after forming the metal oxide on the substrate, the surface of the metal oxide formed on the substrate may be washed with distilled water before forming the alloy nanostructure. This is to remove bubbles adhering to the surface of the anodized metal oxide.

In addition, after cleaning the surface of the metal oxide, it may be dried by spraying an inert gas such as helium (He), argon (Ar), nitrogen (N ₂ ), or carbon dioxide (CO ₂ ). For example, an inert gas may be sprayed on the surface of the metal oxide at room temperature for 5 to 20 seconds to dry it.

As described above, when the metal oxide is formed on the substrate, an alloy nanostructure having a carbon dioxide reducing property is formed (S109).

This step is a step of reducing a metal oxide composed of a main metal and a dissimilar metal in one of an acidic aqueous solution, a neutral aqueous solution and a basic aqueous solution. Here, the aqueous solution for reduction, when the aqueous solution used in step S107 is continuously used, ions of different metals eluted in the aqueous solution can be reduced simultaneously with metal oxides, so that more different metals are contained in the alloy nanostructure. can

In addition, in this step, a reduction current density of a certain size may be applied to the metal oxide formed on the substrate in order to form the alloy nanostructure. That is, an alloy nanostructure is formed through an electrochemical reduction treatment.

Here, the reduction current density may be one of -0.1 mA/cm 2 to -10.0 mA/cm 2 , -0.1 mA/cm 2 to -5.0 mA/cm 2 , and -0.5 mA/cm 2 to -2.0 mA/cm 2 .

The shape in which the alloy nanostructure is formed can be controlled according to the magnitude of the applied reduction current density. When the size of the reduction current density is relatively small, a pore-like alloy nanostructure can be formed, and when the size of the reduction current density is relatively large, a pillar-like alloy nanostructure is formed. It can be. In this way, a difference in mass transfer rates of reactants and products may occur depending on the shape of the alloy nanostructure, and a difference in alloy catalyst characteristics for carbon dioxide reduction may also occur.

The reduction current density can reduce the metal oxide by flowing it until the potential value of the working electrode of the mainstream metal thin film changes rapidly in a negative direction. Here, the timing at which the reduction current density is applied may vary depending on the magnitude of the reduction current density and the thickness of the metal oxide.

For example, a reduction current density of -10 mA/cm 2 is applied to the metal oxide layer formed to a thickness of 400 nm to 500 nm or 400 nm to 450 nm for about 10 seconds to 60 seconds or 10 seconds to 30 seconds to reduce the metal oxide. At this time, when a reduction current density of -0.5 mA/cm 2 is applied, the metal oxide may be reduced by flowing for 3 to 20 minutes or 3 to 10 minutes.

The alloy nanostructure produced through the above process may include 1 atomic % to 15 atomic % of the composition of copper, which is a different type of metal.

Referring to FIGS. 2 to 7 , Example 1 of a method for preparing an alloy catalyst for reducing carbon dioxide will be described.

substrate preparation

Prepare an n-type or p-type silicon wafer, immerse it for 20 seconds in an aqueous solution of hydrofluoric acid diluted to 10% by weight to remove a several nm thick silicon oxide (SiO _x ) layer naturally formed on the surface of the silicon wafer, After washing the surface with an excess of tertiary distilled water, it was dried with nitrogen gas. At this time, the size of the silicon wafer may be 4 inches to 6 inches, and a wafer having a large area such as 8 inches to 12 inches may also be used.

Formation of adhesive layer and mainstream metal thin film

Titanium (Ti) is deposited to a thickness of 5 nm on one side of a silicon wafer at a deposition rate of 1 Å/s using an electron beam evaporation method. Then, gold (Au) is continuously deposited at a rate of 5 Å/s to have a thickness of 200 nm, and as shown in FIG. 2(a), titanium and gold are sequentially formed on the silicon substrate.

In addition, it is possible to check the states of the gold, titanium, and silicon substrates through the photograph taken through the scanning electron microscope in (b) of FIG. 2, and it can be confirmed that the gold and titanium are deposited to a thickness of about 200 nm.

Formation of heterogeneous metal layer

Gold, titanium, and silicon substrates are prepared in a size of about 1 cm 2 so that the formation of the different metal layer is easy. What is thus produced is called a mainstream metal substrate.

And, with the mainstream metal substrate as the working electrode (WE) and the platinum wire as the counter electrode (CE), silver-silver chloride (Ag/ AgCl (NaCl, 3M) electrode constitutes a three-electrode system in which the Reference Electrode (RE) electrode is used.

The working electrode is immersed in a mixed solution composed of 0.05 molarity (50 mM) copper sulfate (CuSO ₄ ) aqueous solution and 0.05 molarity (50 mM) sulfuric acid (H ₂ SO ₄ ) aqueous solution, and the voltage of -0.1V compared to the reference electrode is about 60 By applying for a second time, copper (Cu), a different type of metal, is electrodeposited on the surface of the main metal substrate. Accordingly, copper, gold, titanium and silicon substrates can be manufactured as shown in FIGS. 2(c) and 2(d). What is manufactured in this way is called a dissimilar metal substrate.

The dissimilar metal layer of the dissimilar metal substrate thus prepared is randomly distributed in the form of islands on the surface of the mainstream metal substrate, and may have a thickness of several tens of nm to several hundreds of nm. Also, it can be seen from the photograph of (d) of FIG. 2 that copper in the form of a lump is electrodeposited on one surface of the mainstream metal substrate.

metal oxide formation

To manufacture the working electrode, an electrical contact surface is formed and fixed using Ag paste on one edge of the surface of the dissimilar metal substrate, and then adhesive tape is attached to the electrical contact surface and all edges of the dissimilar metal substrate to isolate the edge. Therefore, the dissimilar metal substrate can expose only the surface of the copper and gold thin films, and the adhesive tape has insulating properties and chemical resistance.

For the electrochemical anodic oxidation and reduction treatment, an aqueous solution of potassium hydrogen carbonate (KHCO ₃ ) having a hydrogen ion concentration index (pH) of 8.4 and a 0.2 molar concentration (0.2 M) was prepared in a volume of about 60 ml in a glass beaker. Here, a copper and gold thin film electrode is used as a working electrode, a platinum wire (Pt wire) is used as a counter electrode (CE), and silver-silver chloride (Ag/AgCl (NaCl, 3M)) electrode as a reference electrode (RE).

On the other hand, in order to uniformly maintain the ion composition in the aqueous solution during the electrochemical oxidation and reduction process, the aqueous solution is placed on a magnetic stirrer and rotated at a constant speed of 80 rpm.

And, for electrochemical anodic oxidation, a voltage of 1.8V (vs. Ag/AgCl) compared to the reference electrode is applied to the working electrode of the dissimilar metal substrate for 40 minutes. At this time, the applied voltage is 2.5V (vs. RHE) compared to the value (reversible hydrogen potential) converted by correcting the potential difference according to the hydrogen ion concentration index (pH) of the aqueous solution. This value can be calculated by adding the voltage applied to the working electrode, the potential difference correction value according to the reference electrode, and the potential difference correction value according to the hydrogen ion concentration index. That is, it may be 1.80 V + 0.209 V (for Ag/AgCl (NaCl, 3M)) + 0.059 X 8.4 (pH) = 2.50 V (vs. RHE).

As shown in FIG. 2(e) and FIG. 2(f), the copper and gold thin films formed on the substrate by electrochemical anodic oxidation are oxidized from the surface to form metal oxides having a nanoporous structure. It can be.

As shown in (f) of FIG. 2, looking at a photograph taken through a scanning electron microscope, the metal oxide has a thickness of 400 nm to 450 nm, the oxidation reaction does not proceed, and the thickness of the remaining gold thin film is about 90 nm to 100 nm. can confirm that In addition, it can be confirmed that nanopores of about 15 nm to 30 nm are distributed in the metal oxide.

As described above, the reason why the nanopores are formed in the metal oxide is that oxygen gas generated when water is electrochemically oxidized at the surface of the gold thin film or at the interface of the gold thin film that has not reacted with the gold oxide layer during the electrochemical oxidation reaction in the aqueous solution. It can be expected that pores are formed by the oxygen gas acting as a template while moving outward through the oxide layer during the process of forming the metal oxide.

After the electrochemical anodic oxidation treatment is completed, in order to remove air bubbles generated during the electrochemical oxidation reaction of copper and gold and attached to the surface of the working electrode, it is washed with tertiary distilled water and dried by spraying nitrogen gas.

reduction of metal oxides

A cathodic current density having a magnitude of -0.5 mA/cm2 is constantly applied to the working electrode on which the metal oxide is formed. At this time, the reduction current density flows until the electrode potential value of the working electrode rapidly changes in a negative direction to reduce the metal oxide formed on the substrate. As a result of the reduction, as shown in FIG. 2(g) and FIG. 2(h), pores in the form of a dilute alloy in which trace or small amounts of copper are evenly distributed in gold, which is the mainstream metal -like) copper/gold alloy nanostructures are formed.

As shown in (h) of FIG. 2, it can be confirmed that porous copper and gold alloy nanostructures are formed on the substrate by applying a reduction current density. Through this, the copper and gold alloy nanostructure has a height of about 200 nm, and considering the remaining gold thin film thickness (about 100 nm), the height of the copper and gold alloy nanostructure may have a height of about 300 nm. It can be seen that the thickness increased by about 1.5 times compared to the thickness of the initial mainstream metal thin film through electrochemical oxidation and reduction reactions.

Comparative Example 1: Preparation of Catalyst (Gold Thin Film) Showing Carbon Dioxide Reducing Characteristics

For comparison with the alloy catalyst prepared in Example 1, an adhesive layer and a main metal thin film were prepared in the same manner as in Example 1 without forming a dissimilar metal layer and without performing electrochemical oxidation and reduction steps.

Comparative Example 2: Preparation of high-efficiency carbon dioxide reduction catalyst (porous gold nanostructure)

For comparison with the alloy catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 1, a porous gold nanostructure without a heterogeneous metal layer was prepared in the same manner as in Example 1.

Example 2: Preparation of high-efficiency and high-stability carbon dioxide reduction catalyst by changing the time or method of forming a heterogeneous metal layer so that the composition of copper in the alloy is changed

In the dissimilar metal layer formation step, the same electrodeposition method as in Example 1 was used to form the dissimilar metal layer, but the formation time was kept short (10 seconds) to form the dissimilar metal layer, and the underpotential deposition method (UPD) was used to form the dissimilar metal layer. The formation time was maintained the same as in Example 1 (60 seconds) to prepare a copper and gold alloy nanostructure in which a heterogeneous metal layer was formed.

In (b) of FIG. 3, a dissimilar metal layer is formed for 60 seconds using the UPD method, and in (c) of FIG. 3, a dissimilar metal layer is formed for 10 seconds using the electrodeposition method. At this time, in the case of (b) of FIG. 3, since the electrodeposition is performed at the atomic level due to the nature of the UPD method, it is difficult to photograph due to the resolution limit of the scanning electron microscope, so it is photographed through Atomic Force Microscopy (AFM). it is a picture

The figure shown in (a) of FIG. 3 is the same surface of the gold thin film as in Comparative Example 1, and is a photograph taken through an atomic force microscope to visually confirm the difference in surface state compared to (b) of FIG. 3. And the drawing shown in (d) of FIG. 3 is a photograph taken through a scanning electron microscope formed in the same manner as in Example 1 for comparison with the alloy nanostructure formed through Example 2.

Comparing FIG. 3(b) with FIG. 3(d), it can be seen that significantly different results are obtained when electrodeposition is performed for the same time but different types of electrodeposition are used. In other words, the electrodeposition process for about 60 seconds at a potential below the equilibrium potential can form a copper atomic layer at the level of 2 nm, and the result of electrodeposition at a potential above the equilibrium potential for about 60 seconds is It can be confirmed that a dissimilar metal layer in which copper chunks of several hundred nm are discontinuously distributed is formed.

On the other hand, looking at (c) and (d) of FIG. 3, it can be seen that the same electrodeposition method is used, but the longer the electrodeposition time, the larger the size of the dissimilar metal formed, and the higher the density on the mainstream metal substrate. .

3(b-1) to 3(d-1) show the result of forming copper and gold oxide through electrochemical oxidation after copper, which is a different type of metal, is formed on the surface of gold, which is the main metal, through a scanning electron microscope. this is a picture taken 3(b-1) and 3(d-1) and FIG. 3(c-1) and FIG. 3(d-1) are compared, even though the dissimilar metal is formed immediately after , it can be seen that there is no significant difference in the appearance of electrochemical oxidation.

3(b-2) to 3(d-2) are photographs taken through a scanning electron microscope of the result of forming a copper and gold alloy nanostructure by reducing copper and gold oxides through electrochemical reduction. . Compared to (d-2) of FIG. 3 corresponding to Example 1, looking at (b-2) and (c-2) of FIG. 3, even if the same electrodeposition method is selected, the electrodeposition time is short (electrodeposition 10 seconds) or the underpotential deposition method (UPD 60 seconds) even with the same electrodeposition time, it can be confirmed that the shape of the alloy nanostructure is minutely changed when a small amount of different metal is electrodeposited at the atomic level to form a different type of metal. can

Specifically, as the amount of the initial dissimilar metal increases, the complexity of the alloy nanostructure formed after the electrochemical oxidation and reduction treatment or the gap between the structures may tend to narrow.

In addition, when forming the different metal layer, it can be confirmed that the content and composition of the different metal in the alloy nanostructure vary according to the electrodeposition method or time. This change can be confirmed through the photograph taken through the scanning transmission electron microscope of FIG. 4 and can be confirmed through the X-ray photoelectron spectroscopy result of FIG. 5 .

Compared to FIG. 4 (b) corresponding to Example 1, in the case of FIG. 4 (d) and FIG. 4 (f), it can be visually confirmed that the content appears qualitatively smaller.

The difference in copper composition can be confirmed through the results of X-ray photoelectron spectroscopy shown in FIG. 5 . The analysis results corresponding to Example 1, compared to the results of Example 2, Comparative Example 1 and Comparative Example 2, it can be confirmed that there is a large difference in the presence and absence of copper and the change in the binding energy of gold.

The presence and content of copper in the alloy nanostructure can be confirmed through the location and strength of binding energy to Cu ₂ P shown in (b) of FIG. 5 . In (b) of FIG. 5 , it can be seen that characteristic peaks of copper are confirmed only in Examples 1 and 2.

In addition, the intensity of the peak (the area within the peak in the graph) can be proportional to the distribution (content) of the element to be analyzed, which indicates that the alloy nanostructure formed in Example 1 contains the most copper. . In addition, it can be confirmed that among the samples formed through Example 2, copper in the alloy nanostructure formed through the underpotential deposition method (UPD method) is present the least. It can be seen that these results are in good agreement with the results obtained through scanning transmission electron microscopy mapping analysis in FIG. 4 .

On the other hand, it can be confirmed through (a) of FIG. 5 that copper and gold in the nanostructures formed in Examples 1 and 2 exist in the form of an alloy. Specifically, in the case of pure gold, its characteristic peaks exist at binding energies of 84.04 eV and 87.60 eV, but when other substances such as impurities are chemically bound, the corresponding characteristic peaks shift.

Looking at (a) of FIG. 5 through this, in the case of Comparative Examples 1 and 2 made of only pure gold, the characteristic peak is located at the theoretical value, but the alloy nanostructures corresponding to Examples 1 and 2 have characteristics It can be seen that the peak is shifted. That is, it can be seen that the central value of the peak shifts more greatly as the copper content increases.

Therefore, it can be seen from these results that forming a heterogeneous metal layer on the surface of the mainstream metal in Examples 1 and 2 and then performing electrochemical oxidation and reduction treatment is a method that can easily form an alloy nanostructure. In addition, it can be confirmed that the composition of the different metal in the alloy nanostructure is also controlled according to the degree (amount) of the formation of the different metal layer.

Experimental Example 1: Comparison of carbon dioxide reduction efficiency of alloy nanostructures containing trace to small amounts of copper

Experimental Example 1 is an experiment to confirm the conversion efficiency, which is a catalyst characteristic, for the carbon dioxide reduction catalyst including the alloy nanostructures formed in Examples 1, 2, Comparative Example 1, and Comparative Example 2.

To perform carbon dioxide reduction (reduction) electrochemically in an aqueous solution saturated with carbon dioxide, ultra-high purity (99.999%) carbon dioxide gas is purged in an aqueous solution of 0.2 mol (0.2M) potassium hydroxide (KHO ₃ ) for about 30 minutes ( After saturation by purging, the three-electrode system is configured as a closed system. At this time, the three-electrode system uses a carbon dioxide reduction catalyst as a working electrode, a graphite rod as a counter electrode, and silver-silver chloride (Ag / AgCl (Ag / AgCl ( NaCl, 3M)) electrode is used as a reference electrode.

The carbon dioxide reduction reaction proceeds until the amount of charge of about 0.5 Coulomb (C) per applied voltage is shed, and the carbon dioxide conversion product is measured and analyzed through Gas Chromatography (GC) equipment.

Meanwhile, a magnetic stirrer is constantly rotated at a speed of 400 rpm for effective mass transfer of reactants and products participating in the reaction while maintaining a uniform ionic composition in the aqueous solution during the carbon dioxide reduction (reduction) reaction.

And when carbon dioxide is converted to carbon monoxide using each catalyst of Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the conversion efficiency of each catalyst is compared through the amount of charge (C) used.

Accordingly, as shown in FIG. 6, it can be confirmed that the more nanostructures are formed, the higher the conversion selectivity is at a lower applied voltage. For example, compared to Comparative Example 1, Comparative Example 2 exhibits significantly higher conversion selectivity at the same applied voltage, and about 3 times or more conversion selectivity at a very low applied voltage (eg, -0.39V vs. RHE). indicate

On the other hand, in the low human contact area, in Examples 1 and 2, it can be confirmed that the carbon dioxide conversion efficiency is weakened as the composition of copper, which is a heterogeneous metal, is relatively increased. This is expected because the catalytic properties of gold, a mainstream metal, are changed by copper, a heterogeneous metal, so that copper prevents the catalytic properties of gold from being expressed. Therefore, it can be seen that the catalytic properties are improved due to the synergistic effect with gold when the amount of copper is small, but the catalytic properties are rather lowered when the copper content is increased. This can be clearly confirmed through comparison with the pure gold nanostructure prepared in Comparative Example 2.

Experimental Example 2: Comparison of stability of carbon dioxide reduction catalytic properties of copper and gold alloy nanostructures

Experimental Example 2 tests how long the carbon dioxide reduction catalytic properties of copper and gold alloy nanostructures last.

For evaluation of carbon dioxide reduction catalyst characteristics, the configuration is the same as in Experimental Example 1. However, in the evaluation method, the applied voltage is -0.49eV vs. It is kept constant by RHE, and the type and amount of carbon dioxide reduction products are measured by gas chromatography on an hourly basis.

At this time, after measuring and analyzing by gas chromatography, the aqueous solution is used in the same way, and ultra-high purity carbon dioxide is purged for about 5 minutes to re-saturate carbon dioxide as a reactant.

Referring to FIG. 7, when comparing the conversion selectivity change (stability) with time for the flat gold thin film prepared in Comparative Example 1 and the porous pure gold nanostructured catalyst prepared in Comparative Example 2, Comparative Example 2 It can be seen that the catalyst maintains its catalytic properties for a long time compared to the catalyst of Comparative Example 1.

It is expected that this difference is because the surface area of the nanostructure is rapidly larger than that of the flat plate structure, and thus there are many catalytically active sites.

In addition, comparing Comparative Example 2, Example 1 and Example 2, when a trace or small amount of a dissimilar metal is contained, a higher conversion selectivity to carbon monoxide is maintained for a long time compared to the case where it is not (Comparative Example 2). You can check what you can.

This is expected to be because copper in the alloy nanostructure acts as a barrier to suppress the surface diffusion of gold atoms during the electrochemical carbon dioxide reduction reaction process in aqueous solution.

On the other hand, Example 1 and Example 2 appear to have a difference in catalyst stability from each other. In Example 2, when the copper content is relatively small, the holding time becomes shorter as the copper content decreases. On the other hand, when the copper content is relatively high in Example 1, the holding time lasts relatively long. It is expected that this phenomenon is due to the presence of a different metal in a trade-off relationship in which the catalytic properties of gold, a mainstream metal, are expressed and the catalytic properties are maintained.

Although the embodiments of the present invention have been described as specific embodiments, this is merely an example, and the present invention is not limited thereto, and should be construed as having the widest scope according to the embodiments disclosed herein. A person skilled in the art may implement a pattern of a shape not indicated by combining/substituting the disclosed embodiments, but this also does not deviate from the scope of the present invention. In addition, those skilled in the art can easily change or modify the disclosed embodiments based on this specification, and it is clear that such changes or modifications also fall within the scope of the present invention.

Claims (16)

preparing a substrate;
Forming a mainstream metal thin film on one surface of the substrate;
Forming a heterogeneous metal layer on the surface of the mainstream metal thin film;
immersing the substrate on which the main metal thin film and the dissimilar metal layer are formed in an aqueous solution, and applying an anode voltage to a surface of the dissimilar metal layer to form a metal oxide; and
Forming an alloy nanostructure by flowing a reduction current density through the metal oxide,
The mainstream metal thin film includes one metal selected from the group consisting of gold (Au), silver (Ag), palladium (Pd), zinc (Zn), and the like,
The dissimilar metal includes one or more of silver (Ag), palladium (Pd), copper (Cu), tin (Sn), zinc (Zn), and iron (Fe).
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
Forming the mainstream metal thin film may include forming an adhesive layer on one surface of the substrate and forming the mainstream metal thin film on the adhesive layer;
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 2,
The adhesive layer contains one or more metals of titanium (Ti), tantalum (Ta), and chromium (Cr).
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 2,
The adhesive layer has a thickness of 1 nm to 10 nm,
The mainstream metal thin film has a thickness of 50 nm to 1000 nm,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
The dissimilar metal layer formed by the step of forming the dissimilar metal layer is formed through one of underpotential deposition (UPD) and electrodeposition (electrodeposition),
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
The substrate may be selected from among metals including at least one of iron (Fe), copper (Cu), zinc (Zn), and aluminum (Al), alloys including stainless steel, silicon (Si), and gallium arsenide (GaAs). Semiconductors containing one or more, polymer plastics containing one or more of silicon (Si), acrylate, vinyl, and carbonate, and compounds of indium and tin oxide, glass (glass), and containing at least one selected from the group consisting of quartz,
A method for preparing an alloy catalyst for reducing carbon dioxide. delete delete According to claim 1,
The dissimilar metal layer is formed in a continuous layer structure or a discontinuous island structure,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 9,
The thickness of the continuous layer is 1 Å to 10 nm,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 9,
The thickness of the discontinuous lump is 50 nm to 400 nm,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
In the forming of the metal oxide, an anode voltage of 1.5 to 3V compared to a reversible hydrogen electrode (RHE) is applied for 1 minute or more,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
The reduction current density is -0.1 mA / cm 2 to -10.0 mA / cm 2,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
Forming the metal oxide and forming the alloy nanostructure are made in the same aqueous solution,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
The reduction current density flows until the point where the value of the electrode potential applied to the metal oxide changes in a negative direction,
A method for preparing an alloy catalyst for reducing carbon dioxide. According to claim 1,
The composition of the dissimilar metal contained in the alloy nanostructure is 1 atomic% to 15 atomic%,
A method for preparing an alloy catalyst for reducing carbon dioxide.

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