KR102203640B1 - Three-Dimensional Nanostructure Metal Catalyst for Carbon Dioxide Reduction and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a three-dimensional nano-structured metal catalyst for carbon dioxide reduction and a method for producing the same.
The three-dimensional nanostructured metal catalyst for carbon dioxide reduction of the present invention has a structure in which aligned metal nanowires are stacked, and can increase CO selectivity by adjusting a local pH high by the thickness of the stacked catalyst.
In addition, due to the small particle size of the metal nanowires, a high-order crystal plane having high CO selectivity is included in the catalytically active site to remarkably increase the CO selectivity and suppress the hydrogen generation reaction to increase the carbon dioxide reduction reaction rate.
The space between the metal nanowires forming the 3D nanostructured metal catalyst facilitates the movement of reactants and products within the catalyst layer, thereby increasing the carbon dioxide reduction reaction rate.
In addition, the catalyst having a three-dimensional nanostructure of the present invention can have high stability through control of the nanostructure and can be used as a catalyst electrode for carbon dioxide reduction.

Description

Three-Dimensional Nanostructure Metal Catalyst for Carbon Dioxide Reduction and Manufacturing Method thereof

The present invention relates to a three-dimensional nano-structured metal catalyst for carbon dioxide reduction and a method for producing the same.

After a global agreement on reducing greenhouse gas emissions, including CO ₂ from the last Paris Convention in 2016 adopted a commitment to reduce the CO ₂ concentration in the atmosphere is accelerating worldwide. Therefore, various methods of electrochemical CO ₂ reduction using a metal catalyst to convert CO ₂ as a chemical source or a fuel with a value (CO ₂ reduction reaction, CO ₂ RR) are receiving significant attention.

However, electrochemical CO ₂ RR in an aqueous environment generally faces some limitations, such as poor energy efficiency and selectivity of carbon products. In general, high overpotentials are required to initiate CO ₂ RR from chemically stable CO ₂ molecules to form intermediates, leading to low energy efficiency. Also, because of the similar redox potential between the hydrogen generation reaction and the CO ₂ RR, hydrogen is produced together as a product and decreases the selectivity of the CO ₂ reduction product.

Therefore, there are many studies to reduce the overpotential required for CO ₂ RR and increase the selectivity of carbon-based products in aqueous solutions. Various metals including Au, Ag, Sn, and Cu are used as catalysts to suppress the hydrogen generation reaction and CO ₂ Research to increase RR activity is being conducted.

Non-Patent Document 1. Hori, Y.; Wakebe, H.; Tsukamoto, T.; Koga, O. Electrochim. Acta 1994, 39 (11-12), 1833-1839. Non-Patent Document 2. Chen, Y.; Li, C. W.; Kanan, M. W., J. Am. Chem. Soc. 2012, 134 (49), 19969-72 Non-Patent Document 3. Feng, X.; Jiang, K.; Fan, S.; Kanan, M. W., J. Am. Chem. Soc. 2015, 137 (14), 4606-9.

An object of the present invention is to provide a method of manufacturing a 3D nanostructured metal catalyst for carbon dioxide reduction.

Another object of the present invention is to provide a three-dimensional nanostructured metal catalyst for carbon dioxide reduction.

One aspect of the present invention for achieving the above object is (A) a photolithography process to prepare a patterned master mold and forming a hydroxyl-terminated polymer layer on the upper surface of the master mold; (B) forming an acrylic resin layer on the upper surface of the master mold on which the hydroxyl-terminated polymer layer is formed; (C) forming a plurality of intaglios in the same pattern as the master mold on one surface of the acrylic resin layer by separating the acrylic resin layer from the master mold; (D) depositing a metal nanowire along a straight pillar positioned between a plurality of intaglios formed on the acrylic resin layer; (E) attaching the metal nanowires deposited on the acrylic resin layer to a substrate and then removing the acrylic resin to prepare aligned metal nanowires; (F) manufacturing a metal nanostructure by laminating the aligned metal nanowires on a metal foil several times; (G) forming the acrylic resin layer on the upper surface of the metal nanostructure and then removing the metal foil by treating an aqueous metal etchant solution for removing the metal foil; And (H) removing the acrylic resin layer of the metal nanostructure to obtain a metal nanocatalyst. It relates to a method for producing a 3D nanostructured metal catalyst for carbon dioxide reduction.

Another aspect of the present invention relates to a 3D nanostructured metal catalyst for carbon dioxide reduction prepared according to the above manufacturing method.

In another aspect of the present invention, a plurality of metal nanowires are aligned metal nanowires spaced in parallel with each other at a predetermined interval; It relates to a 3D nanostructured metal catalyst for carbon dioxide reduction in which 2 to 50 layers are stacked so that the aligned metal nanowires form a predetermined angle with other aligned metal nanowires adjacent to each other.

Another aspect of the present invention relates to an electrode for carbon dioxide reduction including the three-dimensional nanostructured metal catalyst for carbon dioxide reduction.

The three-dimensional nanostructured metal catalyst for carbon dioxide reduction of the present invention has a structure in which aligned metal nanowires are stacked, and can increase CO selectivity by adjusting a local pH high by the thickness of the stacked catalyst.

In addition, due to the small particle size of the metal nanowires, a high-order crystal plane having high CO selectivity is included in the catalytically active site to remarkably increase the CO selectivity and suppress the hydrogen generation reaction, thereby increasing the carbon dioxide reduction reaction rate.

The space between the metal nanowires forming the 3D nanostructured metal catalyst facilitates the movement of reactants and products within the catalyst layer, thereby increasing the carbon dioxide reduction reaction rate.

In addition, the catalyst having a three-dimensional nanostructure of the present invention can have high stability through control of the nanostructure and can be used as a catalyst electrode for carbon dioxide reduction.

1A is a schematic diagram showing a process of manufacturing aligned Au nanowires.
FIG. 1B is a transmission electron microscope (TEM) image of a pure Au thin film, and the inset at the upper right is an image showing a Selected Area Electron Diffraction (SAED) pattern.
1C is a TEM image of Au nanowires, and an inset at the upper right is an image showing a SAED pattern.
1D is an X-ray diffraction (XRD) pattern of Au nanowires and pure Au thin films.
Figure 1e shows by observing an IPF (Inverse Pole Figure) map through electron backscattering diffraction (EBSD) of Au nanowires and pure Au thin film.
2A is a schematic diagram showing a process of preparing a three-dimensional nanostructured Au catalyst from aligned Au nanowires.
2B is an image of a scanning electron microscope (SEM) according to Example 1 of the present invention.
2C is a top SEM image of Example 2 of the present invention.
2D is a top SEM image of Example 3 of the present invention.
2E is a cross-sectional SEM image of Example 1 of the present invention.
2F is a cross-sectional SEM image of Example 2 of the present invention.
2G is a cross-sectional SEM image of Example 3 of the present invention.
3 is a graph measuring CO selectivity of electrodes including catalysts prepared from Examples 1 to 3 and Comparative Examples.
Figure 4a is a graph showing the total current density (j _tot = j _CO + j _H2 ) of the electrode including the catalyst prepared from Examples 1 to 3 and Comparative Examples of the present invention.
Figure 4b is a graph showing the CO generation current density (j _CO ) of the electrode including the catalyst prepared from Examples 1 to 3 and Comparative Examples of the present invention.
4C is a graph showing the hydrogen generation current density (j _H2 ) of HER of an electrode including a catalyst prepared from Examples 1 to 3 and Comparative Examples of the present invention.
Figure 4d is a graph measuring the Tafel slope based on j _CO of Examples 1 to 3 and Comparative Examples of the present invention.
5 is a graph measuring the catalyst stability for CO ₂ reduction of Examples 1 to 3 and Comparative Examples of the present invention.
6A is an SEM image in which the catalyst prepared in Example 2 of the present invention is applied to an upper surface of a gas diffusion layer electrode.
6B is a graph showing the CO ₂ RR activity of the gas diffusion layer electrode into which the catalyst prepared in Example 2 of the present invention is introduced.
6C is a graph showing the partial current density behavior according to the applied potential of the gas diffusion layer electrode into which the catalyst prepared in Example 2 of the present invention is introduced.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

An aspect of the present invention is (A) forming a patterned master mold by processing a photolithography process, and forming a hydroxyl-terminated polymer layer on the upper surface of the master mold; (B) forming an acrylic resin layer on the upper surface of the master mold on which the hydroxyl-terminated polymer layer is formed; (C) forming a plurality of intaglios in the same pattern as the master mold on one surface of the acrylic resin layer by separating the acrylic resin layer from the master mold; (D) depositing a metal nanowire along a straight pillar positioned between a plurality of intaglios formed on the acrylic resin layer; (E) attaching the metal nanowires deposited on the acrylic resin layer to a substrate and then removing the acrylic resin to prepare aligned metal nanowires; (F) manufacturing a metal nanostructure by laminating the aligned metal nanowires on a metal foil several times; (G) forming the acrylic resin layer on the upper surface of the metal nanostructure and then removing the metal foil by treating an aqueous metal etchant solution for removing the metal foil; And (H) removing the acrylic resin layer of the metal nanostructure to obtain a metal nanocatalyst. It provides a method for producing a 3D nanostructured metal catalyst for carbon dioxide reduction.

First, in step (A), a master mold is manufactured through a photolithography process followed by a reactive ion etching process, and an upper surface of the master mold is spin-coated with a hydroxyl-terminated polymer.

The hydroxyl-terminated polymer is used in order to completely separate the acrylic resin from the pattern when the acrylic resin is separated from the substrate in step (C) after coating the acrylic resin by lowering the surface energy.

According to an embodiment of the present invention, the hydroxyl-terminated polymer may be a hydroxyl-terminated polydimethylsiloxane (PDMS) or a hydroxyl-terminated polystyrene (PS).

The hydroxyl-terminated polymer is preferably a hydroxyl-terminated PDMS brush, and may be contained in an organic solvent in an amount of 0.5 to 5% by weight, preferably 1 to 2% by weight. If it is less than the above range, the acrylic resin cannot be completely separated from the trench substrate, and if it exceeds the above range, the polymer that has not reacted with the trench substrate may not be completely removed.

According to another embodiment of the present invention, in the step (A), annealing the master mold coated with the hydroxyl-terminated polymer; may further include.

The annealing may be performed at 200° C. for 2 hours, and the unattached polymer may be washed with heptane after annealing.

The master mold is a substrate on which a pattern having a width of 20 to 200 nm is formed, and the pattern is preferably formed in one direction to control orientation.

Next, in step (B), an acrylic resin layer is formed on the upper surface of the master mold coated with the hydroxyl-terminated polymer.

According to another embodiment of the present invention, the acrylic resin may be at least one selected from the group consisting of polymethylmethacrylate (PMMA), methyl acrylate, ethyl acrylate, n-butyl acrylate and t-butyl acrylate, and the substrate It is preferable to use PMMA for complete replication of the array.

According to another embodiment of the present invention, the formation of the acrylic resin layer may be performed by coating a solution containing 1 to 10% by weight of the acrylic resin in a solvent consisting of acetone, toluene and heptane.

The acrylic resin is contained in 1 to 10% by weight, preferably 3 to 5% by weight of acetone, toluene, and heptane in a volume ratio of 3 to 5: 3 to 5: 1 to 4, respectively. If the content of the acrylic resin is less than the above range, it may be difficult to shape the shape as the shape of the master mold in step (C), and if it exceeds the above range, it may be difficult to remove the acrylic resin in step (E). .

Next, in step (C), the acrylic resin layer is separated from the master mold to form a plurality of intaglios in the same shape as the master mold on one surface of the acrylic resin layer.

According to another embodiment of the present invention, the separation in step (C) may be separating the acrylic resin layer from the master mold by attaching and pulling a polyimide tape to the acrylic resin layer.

After attaching the polyimide tape to the upper surface of the acrylic resin layer and pulling the tape away, the acrylic resin layer is transferred to and separated from the polyimide tape side. In the separated acrylic resin layer, an intaglio is formed in the same shape as the trench substrate.

Next, in the step (D), metal nanowires are deposited along a straight column located between a plurality of intaglios formed on the acrylic resin layer.

The surface on which the intaglio pattern is formed of the acrylic resin layer is positioned so as to be inclined by 80 to 90° with respect to the direction in which the metal is deposited, and then the metal is deposited along a straight column located between a plurality of intaglios using an e-beam evaporator. The metal deposited along the straight column is called a nanowire.

The deposition rate of the metal is 0.5 to 2.0 Å/s, and the preferred deposition rate may vary depending on the type of metal.

Since the metal nanowire has a deposition thickness that is thinner than that of manufacturing a general metal thin film, the size of the metal particles can be reduced by about a third, and the small particle size allows the catalytically active surface to contain a higher-order crystal plane. It can suppress hydrogen generation reaction and increase CO selectivity in carbon dioxide reduction reaction.

According to another embodiment of the present invention, the metal may be at least one selected from the group consisting of Au, Ag, Sn and Cu.

Next, in step (E), a metal nanowire having an aligned pattern is prepared by attaching the metal nanowire deposited on the acrylic resin layer to a substrate and then removing the acrylic resin layer.

According to another embodiment of the present invention, after attaching the metal nanowires deposited on the acrylic resin layer to the substrate in step (E), it further comprises the step of exposing the acrylic resin layer to an organic solvent vapor. I can.

Specifically, in order to weaken the adhesion between the polyimide tape and the acrylic resin, an organic solvent vapor maintained at 45 to 90° C. for 10 minutes or longer is applied to the metal nanowires deposited on the acrylic resin layer for 20 to 40 seconds. Immediately after steaming, when the metal nanowires deposited on the acrylic resin layer are attached to the substrate and the polyimide tape is removed, only the nano metal wires and the acrylic resin layer are transferred to the substrate. Thereafter, when the acrylic resin layer is removed, only metal nanowires having an aligned pattern can be obtained.

The substrate is not particularly limited as long as it is a substrate that is not easily separated from the metal nanowire, and the organic solvent used in manufacturing the metal nanowire is not particularly limited, but preferably, heptane, acetone, and toluene may be mentioned.

Next, in step (F), the aligned metal nanowires are stacked on a metal foil several times to prepare a metal nanostructure.

According to another embodiment of the present invention, the stacking may be stacked so that the aligned metal nanowires form an angle of 70 to 90° with the aligned metal nanowires stacked immediately before, and preferably 80 to 90° It can be stacked to achieve an angle of.

Maintaining the angle in the above range can secure a sufficient space between the metal nanowires, and the secured space is filled with an electrolyte to increase the utilization efficiency of the catalyst, as well as to facilitate the movement of reactants and products inside the catalyst layer. can do. In addition, the local pH of the electrode surface is increased by the secured space, so that hydrogen generation reactions can be suppressed and CO selectivity can be improved.

According to another embodiment of the present invention, the metal foil may be at least one selected from the group consisting of copper foil, brass foil, white copper foil and aluminum foil, and any metal that can be easily removed is not particularly limited.

After the 3D metal nanostructure is manufactured, O ₂ plasma treatment and Ar/O ₂ plasma treatment may be performed using reactive ion etching in order to remove polymers that have not been removed during the metal nanowire manufacturing process.

Next, in step (G), after forming an acrylic resin layer on the upper surface of the metal nanostructure, the metal foil is removed by providing only the metal foil to be immersed in the metal etchant aqueous solution to remove the metal foil.

The acrylic resin is for protecting the 3D metal nanostructure from the external environment when the metal foil is removed. The formation of the acrylic resin layer may be used under the same conditions as in step (B).

When the removal of the metal oil is completed, the 3D metal nanostructure coated with the acrylic resin is separated from the metal etchant aqueous solution. In this case, a substrate may be used to easily separate the 3D metal nanostructure coated with the acrylic resin.

The type of the substrate is not particularly stable as long as it is a substrate that is stable in an aqueous metal etchant solution, but preferably, at least one selected from the group consisting of RDE, a membrane, and a gas diffusion layer may be mentioned.

According to another embodiment of the present invention, the metal etchant may be at least one selected from the group consisting of ammonium persulfate, ferric chloride, and kubrick chloride.

The metal etchant is not particularly limited as long as it can remove the metal foil, and may be appropriately selected and used according to the metal foil used.

Next, in step (H), the acrylic resin layer of the separated metal nanostructure is removed to obtain a 3D nanostructured metal catalyst for carbon dioxide reduction.

In particular, although not explicitly described in the following Examples or Comparative Examples, etc., various types of hydroxyl-terminated polymers, acrylic resins, composition ratios of solvents containing acrylic resins, weight% of acrylic resins, metals, methods of separation, alignment With respect to the stacking angle of the metal wire, the type of metal foil and metal etchant, a three-dimensional nanostructured metal catalyst for carbon dioxide reduction was prepared, and the CO selectivity and stability in the carbon dioxide reduction reaction of the prepared catalyst were measured. Was confirmed through a scanning electron microscope.

As a result, unlike other conditions, when the following conditions are all satisfied, it is very suitable for the enlargement of the aligned metal nanowires, success in increasing the size of the catalyst and remarkably increasing the number of stacked catalysts using the same, and selecting CO in the carbon dioxide reduction reaction of the catalyst It was confirmed that the stability of the catalyst and the catalyst was maintained.

(I) The hydroxyl-terminated polymer is hydroxyl-terminated PDMS, (ii) the acrylic resin is PMMA, (iii) the acrylic resin layer is formed in a volume ratio of acetone, toluene and heptane in a volume ratio of 4:4:2 to 4.5:4.5: Coating a solution containing 3 to 5% by weight of the acrylic resin in a solvent consisting of 1, (iv) in step (C), the separation is performed by attaching a polyimide tape to the acrylic resin layer and then pulling it from the trench substrate. Separating the acrylic resin layer, (v) metal is Au, (vi) attaching the metal nanowires deposited on the acrylic resin layer in step (E) to the substrate, and then exposing the acrylic resin layer to organic solvent vapor Further comprising a step, (vii) the lamination is lamination such that the aligned metal nanowires form an angle of 80 to 90° with the aligned metal nanowires stacked immediately before, (viii) the metal foil is a copper foil, (ix ) Metal etchant is ammonium persulfate.

However, if any of the above conditions are not satisfied, problems such as formation of intaglios of the acrylic resin, the removal of the acrylic resin in the future, and the deposition of the metal nanowires are not performed smoothly in the process of increasing the size of the aligned metal nanowires. It was confirmed that there is a limitation in increasing the size of the catalyst and increasing the number of stacked metal nanowires in the process of manufacturing a catalyst using the same, as it was not possible to manufacture an enlarged metal nanowire. In addition, when all of the above conditions were not satisfied, it was confirmed that CO selectivity and catalyst stability were decreased in the carbon dioxide reduction reaction of the catalyst even if the catalyst was successfully enlarged and the number of stacked layers was increased.

The catalyst having a three-dimensional nanostructure prepared according to this method is a structure in which aligned metal nanowires are stacked and can increase CO selectivity in the carbon dioxide reduction reaction by adjusting the local pH of the electrode surface, and small particles of metal nanowires Due to its size, a high-dimensional crystal plane having high CO selectivity is included in the catalytically active site to remarkably increase the CO selectivity and suppress the hydrogen evolution reaction.

In addition, the space between the metal nanowires facilitates the movement of reactants and products within the catalyst layer, thereby increasing the carbon dioxide reduction reaction rate, and increasing the utilization efficiency of the catalyst, thereby having high efficiency in carbon dioxide reduction.

Another aspect of the present invention is a plurality of metal nanowires are aligned metal nanowires spaced in parallel with each other at a predetermined interval; It provides a 3D nanostructured metal catalyst for carbon dioxide reduction in which 2 to 50 layers are stacked so that the aligned metal nanowires form a predetermined angle with other aligned metal nanowires adjacent to each other.

According to one embodiment, the metal may be at least one selected from the group consisting of Au, Ag, Sn, and Cu.

According to another embodiment, the predetermined interval may be 10 to 5000 nm, the predetermined angle may be 70 to 90°, preferably 500 to 2000 nm and an angle of 80 to 90°, further Preferably, it may have a spacing of 1000 to 1500 nm and an angle of 85 to 90°.

As described in the above manufacturing method, the space inside the catalyst formed by the predetermined interval and the predetermined angle can increase the CO selectivity by adjusting the local pH, improve the catalyst utilization efficiency, and the reactants and It makes the product move smoothly. If the distance and angle are out of the above range, the effect of controlling the local pH inside the catalyst may be difficult to develop, and there may be difficulties in the movement of reactants and products, which is not preferable.

Another aspect of the present invention provides an electrode for carbon dioxide reduction including the 3D nanostructured metal catalyst.

Carbon paper as a gas diffusion layer may be used as the electrode.

Hereinafter, manufacturing examples and examples according to the present invention will be described in detail together with the accompanying drawings.

Example 1. Aligned Au nanowires (monolayer)

A master mold having a width of 200 ㎚ and a height of 1.2 µm was fabricated through a reactive ion etching process after the KrF photolithography process. A hydroxyl-terminated PDMS solution (1.5 wt%) purchased from Polymer Source Inc. was spin-coated on the upper surface of the master mold and annealed at 200° C. for 2 hours. Thereafter, the remaining PDMS polymer that did not adhere to the master mold was washed with heptane and removed. PMMA (4 wt%, volume ratio toluene: acetone: heptane = 4.5: 4.5: 1, Sigma-Aldrich Inc.) solution was spin-coated on the master mold. After attaching a polyimide tape (3M Inc.) having adhesive strength to the upper surface of the PMMA, the PMMA was removed from the master mold to prepare a PMMA model in which the same shape as the pattern of the master mold was duplicated in an inverted structure.

Au nanowires were deposited on the PMMA according to the pattern of the PMMA model through oblique deposition (deposition angle = 85°) using an e-beam evaporator. To weaken the adhesion between the polyimide tape and PMMA, after exposure to organic solvent vapor (volume ratio acetone: heptane = 1:1) at 55° C. for 20 to 30 seconds, Au nanowires deposited on PMMA were attached to the substrate. , The PMMA model was washed with toluene and removed to obtain aligned Au nanowires.

1A is a schematic diagram showing a process of manufacturing aligned Au nanowires.

Example 2. Au catalyst with 3D nanostructure (5 layers)

The ordered Au nanowires obtained in the manner of Example 1 were stacked five times to form an angle of 90° with the aligned Au nanowires stacked just before on a copper foil to prepare an Au nanostructure having a three-dimensional nanostructure. Thereafter, PMMA was spin-coated on the Au nanostructures to transfer the Au nanostructures to a device for electrochemical measurement, and then floated in a solution of ammonium persulfate (0.1 M) as a copper etchant to selectively remove only the copper foil part. Through O2 plasma treatment using ICP-RIE, the Au nanostructure coated with PMMA was separated on the carbon paper with reduced surface hydrophobicity, and the remaining etchant was sufficiently washed off with DI water. Finally, PMMA was removed with toluene to finally obtain an Au catalyst having a three-dimensional nanostructure.

2A is a schematic diagram showing a process of preparing a three-dimensional nanostructured Au catalyst from aligned Au nanowires.

Example 3. Au catalyst having 3D nanostructure (10 layers)

An Au catalyst having a three-dimensional nanostructure was obtained in the same manner as in Examples 1 and 2, except that the aligned Au nanowires were stacked 10 times.

Comparative example. Pure Au thin film (bare Au)

A bare Au thin film was prepared by E-beam evaporation at a standard angle of incidence on a Si substrate.

Test Example 1. TEM, XRD, EBSD, SEM analysis

Analysis method

The surface morphology was measured with a Field Emission Scanning Electron Microscope (FE-SEM: Hitachi S-4800, JEOL 7600F) operating at 15 kV. The exposed crystal plane was observed through electron inverse scattering diffraction (EBSD) using a Hikari detector in SEM (Quanta 3D FEG) under 20 kV acceleration voltage. Top surface TEM samples were prepared by mechanical polishing and analyzed by TEM (JEOL JEM-ARM200F microscope) operated at 200 kV. The particle size and crystal plane were analyzed using a multipurpose thin film X-ray diffractometer (RIGAKU).

TEM analysis

1B is a transmission electron microscope (TEM) image of a pure Au thin film of a comparative example, and the inset at the upper right is an image showing a selected area electron diffraction (SAED) pattern.

1C is a TEM image of an Example Au nanowire, and the inset at the upper right is an image showing a SAED pattern.

From the TEM image, it was confirmed that the Au particle size of the Comparative Example was 3 times or more of the Example. This is because the particle size increases as the deposition thickness increases, and the deposition thickness for manufacturing the Au thin film of the comparative example is 100 nm, and is thicker than the deposition thickness (~30 nm) for manufacturing the Au nanowires of the Example.

XRD analysis

1D is an X-ray diffraction (XRD) pattern of Au nanowires and pure Au thin films.

As can be seen in Fig. 1d, in the case of the comparative example, only two peaks corresponding to the Au (111) and (222) planes were observed, but in the case of the example, Au (111), (200), (220), (311) And various peaks such as the (222) plane were observed.

EBSD analysis

Figure 1e shows the observation of an IPF (Inverse Pole Figure) map through electron backscattering diffraction (EBSD) of the Au nanowire of the Example and the pure Au thin film of the Comparative Example.

From the EBSD results, it was confirmed that the exposed crystal plane of the comparative example was a (111) plane, as confirmed by XRD analysis, whereas in the case of the example, it was more than the Au (111) plane with a smaller particle size compared to the comparative example. It could be confirmed that the higher-order crystal plane was included.

SEM analysis

2B and 2E are top and cross-sectional scanning electron microscope (SEM) images of Example 1, and FIGS. 2C and 2F are top and cross-sectional SEM images of Example 2, and FIGS. 2D and 2G are of Example 3 Top and cross-section SEM images.

As shown in FIG. 2, it was confirmed that the Au nano-catalyst was made of only Au nanowires, and a space between the nanowires was secured. The catalyst of the present invention can be prepared with a catalyst having a desired thickness by controlling the number of layers.

Test Example 2. CO Selectivity Measurement

Electrochemical CO ₂ reduction experiments were conducted in a hermetic single compartment reactor under room temperature and atmospheric pressure conditions. In the case of an airtight single compartment reactor having a 40 ml headspace volume and 20 ml electrolyte, Ag/AgCl and graphite rods were used as the reference electrode and the counter electrode, respectively, and Examples 1 to 3 and Comparative Example Au electrodes were used as operating electrodes. did. As an electrolyte, a CO2 saturated 0.2 M KHCO ₃ solution of pH 6.8 was used.

The carbon dioxide reduction reaction (CO ₂ Reduction Reaction, CO ₂ RR) characteristics of each electrode were observed in the potential range of -0.29 to -0.89 V using the Au electrode including the catalyst of Examples 1 to 3 and Comparative Examples, and the result Is shown graphically in FIG. 3.

As shown in Figure 3, Examples 1 to 3 showed higher CO selectivity in all potential ranges compared to the comparative example. In particular, it was confirmed that the CO selectivity in the low overpotential region of -0.29 to -0.49 V increased significantly from 10% to 22% in the electrode of the comparative example, while from 5% to 95% in the example. In addition, it was confirmed that the CO selectivity increases as the number of Au nanowire stacks of the examples increases. For example, at -0.39 V, the CO selectivity of Examples 1, 2 and 3 are 41%, 43% and 61%, respectively. In the high overpotential region of -0.59 V to -0.89 V, the CO selectivity of the examples began to gradually decrease, and in the case of Example 3, the CO selectivity was reduced by 9% compared to the highest value, and that of Examples 1 and 2 All cases showed 27% reduced CO selectivity.

Test Example 3. Current density measurement

4A is a graph showing the total current density (j _tot = j _CO + j _H2 ) of Examples 1 to 3 and Comparative Examples. All examples showed higher total current density at all applied potentials compared to the comparative examples, which means that the activity of the unique catalyst was increased.

4B is a graph showing the CO generation current density (j _CO ) of CO ₂ RR, and FIG. 4C is a graph showing the hydrogen generation current density (j _H2 ) of HER. As shown in Fig. 4b, the electrode of the example exhibited a higher j _CO compared to the comparative example. On the other hand, as shown in Figure 4c, it can be confirmed that j _H2 was successfully suppressed in the high potential region of -0.59 V to -0.89 V, which is localized near the active region of the catalyst surface due to the characteristic three-dimensional structure. This is because the pH is increased to show high CO selectivity.

4D is a graph measuring Tafel slope based on j _CO of Examples 1 to 3 and Comparative Examples. The Tafel slopes of Examples 1, 2 and 3 were 91, 85 and 85 mV/dec, respectively, and the Tafel slope of the comparative example was 126 mV/dec. In the case of the example, the difference was shown from the theoretical value of 120 mV/dec. It was confirmed that the small Au particle size of the example and the exposed high-order crystal plane also showed high j _CO and CO selectivity in the low potential region.

Test Example 4. Evaluation of catalyst stability

To evaluate the catalyst stability against CO ₂ reduction, -0.89 V vs. CO selectivity with time was measured in the conditions of RHE and CO ₂ saturated 0.2 M KHCO ₃ aqueous solution. 5 is a graph measuring catalyst stability for CO ₂ reduction in Examples 1 to 3 and Comparative Examples. In the case of the comparative example, the CO ₂ RR activity is lost after 30 minutes, but in the case of the example, it can be seen that the CO ₂ RR activity is maintained until 90 minutes. In addition, in the case of the example, it was confirmed that the high CO ₂ RR activity was maintained even after a longer time elapsed as the number of stacks increased.

Test Example 5. Application to gas diffusion layer electrode

The catalyst of Example 2 was applied on a carbon paper gas diffusion layer electrode having a nanoporous layer. 6A is a SEM image of the catalyst prepared in Example 2 applied to the upper surface of the gas diffusion layer electrode. It can be seen that the catalyst prepared from the examples was successfully applied to the gas diffusion layer electrode, and it was confirmed that the shape of the catalyst was maintained even after CO2RR.

In addition, CO ₂ RR was measured in a gas flow reactor using the carbon paper into which the catalyst of Example 2 was introduced. 1 M KOH with a pH of 13.65 was used as an electrolyte, and CO ₂ was injected in the cathode region at 20 sccm. Product gas was collected in a Tedlar gas sampling bag. As the reference electrode and the counter electrode, Ag/AgCl and Pt foil were used. 6B is a graph showing the CO ₂ RR activity of the gas diffusion layer electrode into which the catalyst prepared in Example 2 was introduced. In the case of the catalyst of Example 2 introduced on carbon paper, it was confirmed that the CO selectivity was overall increased compared to FIG. 3.

6C is a graph showing the partial current density behavior according to the applied potential of the gas diffusion layer electrode into which the catalyst prepared in Example 2 was introduced. In terms of current density, it was confirmed that j _CO was -2.07 mA/cm 2 at -0.11 V, and gradually increased to about -23 mA/cm 2 due to active site saturation. This corresponds to a significantly higher value compared to a single reactor. On the other hand, it was confirmed that j _H2 was suppressed up to -0.39 V.

The above-described Examples and Comparative Examples are examples for explaining the present invention, and the present invention is not limited thereto. Since those of ordinary skill in the art to which the present invention pertains will be able to implement the present invention by various modifications therefrom, the technical protection scope of the present invention should be determined by the appended claims.

Claims (17)

(A) processing a photolithography process to prepare a patterned master mold, and forming a hydroxyl-terminated polymer layer on the upper surface of the master mold;
(B) forming an acrylic resin layer on the upper surface of the master mold on which the hydroxyl-terminated polymer layer is formed;
(C) forming a plurality of intaglios in the same pattern as the master mold on one surface of the acrylic resin layer by separating the acrylic resin layer from the master mold;
(D) depositing a metal nanowire along a straight pillar positioned between a plurality of intaglios formed on the acrylic resin layer;
(E) attaching the metal nanowires deposited on the acrylic resin layer to a substrate and then removing the acrylic resin to prepare aligned metal nanowires;
(F) manufacturing a metal nanostructure by laminating the aligned metal nanowires on a metal foil several times;
(G) forming the acrylic resin layer on the upper surface of the metal nanostructure and then removing the metal foil by treating an aqueous metal etchant solution for removing the metal foil; And
(H) comprising the step of removing the acrylic resin layer of the metal nano structure to obtain a metal nano catalyst,
The hydroxyl-terminated polymer is a hydroxyl-terminated PDMS,
The acrylic resin is PMMA,
The formation of the acrylic resin layer is performed by coating a solution containing 3 to 5% by weight of the acrylic resin in a solvent having a volume ratio of acetone, toluene and heptane of 4:4:2 to 4.5:4.5:1,
In the step (C), the separation is to separate the acrylic resin layer from the master mold by attaching and pulling a polyimide tape to the acrylic resin layer,
Each metal of the metal nanowire and the metal nanostructure is Au,
After attaching the metal nanowires deposited on the acrylic resin layer to the substrate in step (E), further comprising exposing the acrylic resin layer to an organic solvent vapor,
The stacking is stacked so that the aligned metal nanowires form an angle of 80 to 90° with the aligned metal nanowires stacked immediately before,
The metal foil is a copper foil,
The metal etchant is ammonium persulfate, a method of manufacturing a 3D nanostructured metal catalyst for carbon dioxide reduction. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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