Metal chalcogenide comprising nanowire and branch-shaped nanostructure, method for manufacturing same, and electrochemical device comprising same

Abstract

Disclosed are a metal chalcogenide nanostructure comprising a nanowire and a branch shape, a method for manufacturing same, and an electrochemical device comprising same. The method for manufacturing a metal chalcogenide nanostructure comprising a nanowire and a branch shape may comprise: a first step of growing a WO2.9 nanowire on a substrate by vapor deposition of a WO3 precursor; a branch growth step of selectively growing a MoO3-x branch on the WO2.9 nanowire by vapor deposition of a MoO3 precursor; and a second step of substituting at least a portion of the oxygen in the nanowire and the branch with chalcogen by exposing the nanowire and the branch to a chalcogen environment.

Description

Metal chalcogenides including nanowires and branched nanostructures, methods for preparing the same, and electrochemical devices including the same

[0001] The present invention relates to a metal chalcogenide including nanowires and branched nanostructures, a method for producing the same, and an electrochemical device including the same.

[0002] Electrolysis of water is known as a method for efficiently producing hydrogen, a promising next-generation energy resource, without emitting carbon dioxide (CO2). Precious metals such as platinum (Pt), iridium (Ir), ruthenium (Ru), and palladium (Pd) are used as catalysts to lower the overpotential of the hydrogen evolution reaction (HER) through electrochemical water splitting. However, the high price and scarcity of precious metal catalysts limit their use on an industrial scale. Consequently, the development of cost-effective yet effective alternative catalysts has emerged as a critical research challenge, and Group VI transition metal dichalcogenides (TMDs) are attracting particular attention as such alternative catalysts. These TMDs have the characteristics of large surface area, Gibbs free energy for hydrogen adsorption close to zero, and low cost. However, most TMDs are stable in the semiconducting 2H phase with low conductivity and inactive basal plane, resulting in limited hydrogen evolution reaction catalytic performance. To improve this, phase transition from the semiconducting 2H phase to the metallic 1T phase has been attempted, but the phase-transferred TMDs are thermodynamically unstable. On the other hand, one of the TMDs, WTe2, has a semimetallic T phase with distorted orthorhombic coordination due to the strong intermetallic bonding of tungsten atoms. dIt is known as a type-II Weyl semimetal with a unique surface Fermi arc and thermodynamic stability. Weyl semimetals are expected to perform well as electrochemical catalysts due to their high charge carrier mobility and robust topological surface states.

[0003] Direct synthesis of WTe2 nanostructures on conductive substrates is challenging due to the low reactivity of tungsten (W) and tellurium (Te) and the low decomposition temperature of WTe2 at approximately 700°C. Due to these limitations, research on WTe2 catalysts has primarily focused on exfoliated flakes, which are difficult to mass-produce. Furthermore, exfoliated flakes have uncontrolled morphologies, and the morphology of the catalyst significantly influences the number of active sites and charge transfer, which significantly impacts its performance in electrochemical reactions. Catalysts with one-dimensional structures, such as nanowires, nanotubes, and nanorods, offer structural advantages, such as shortened charge transfer pathways between the active sites, which are abundantly exposed to the electrolyte, and the conductive substrate. Furthermore, the edges of WTe2 catalysts are known to exhibit higher catalytic activity than the basal planes. Therefore, WTe2 with a one-dimensional structure with maximized edge coverage is expected to exhibit superior electrochemical catalytic performance. In addition, compared to existing nanostructured electrochemical catalysts, the advantages of nanowire electrochemical catalysts, such as increased surface area and active sites and improved catalytic activity, can be further maximized in branched nanostructures in which nanowires are connected.

[0004] The development of nanowire- and branched-structure metal chalcogenide structures represents a significant advance in nanoscience and materials science. These structures are expected to enhance the efficiency of materials in various electrochemical applications, such as energy storage, electrochemical sensors, photocatalysis, and photodegradation, including electrochemical catalysis. Therefore, the efficient synthesis and optimization of these nanostructures is crucial for both academic and industrial applications.

[0005] The challenge of the present invention is to overcome existing limitations and develop a nanostructure that is more effective in electrochemical reactions. Specifically, the present invention utilizes high-performance catalytic materials, such as WTe2, to provide nanostructures that are cost-effective and exhibit high catalytic activity compared to existing noble metal catalysts. To this end, the present invention proposes novel heterogeneous nanostructures, such as nanowires and branched nanostructures formed by combining nanowires. These structures provide more active sites and surface area, improving the electrochemical properties of the catalyst, leading to enhanced performance in electrochemical applications such as the hydrogen evolution reaction. This innovative approach opens up new possibilities in nanostructure design and synthesis methodology and may contribute to improved performance in energy storage and conversion devices.

[0006] In one aspect, the present invention provides a WO3 precursor formed on a substrate by vapor deposition. 2.9 A method for manufacturing a nanowire and a branched metal chalcogenide nanostructure is provided, comprising: a first step of growing a nanowire; and a second step of exposing the nanowire to a chalcogen environment to replace at least a portion of the oxygen of the nanowire with a chalcogen.

[0007] In one aspect, the present invention provides a WO3 precursor formed on a substrate by vapor deposition. 2.9The first step of growing nanowires is to form WO by vapor deposition of MoO3 precursor. 2.9 MoO on nanowires 3-x A method for manufacturing a nanowire and branch-shaped metal chalcogenide nanostructure is provided, comprising: a branch growth step for growing a branch; and a second step for exposing the nanowire and branch to a chalcogen environment to replace at least some of the oxygen of the nanowire and branch with a chalcogen.

[0008] In one embodiment, the first step can be performed through a chemical vapor deposition (CVD) method.

[0009] In one embodiment, the chemical vapor deposition of the first step can be performed with a gas containing Ar and H2.

[0010] In one embodiment, the chemical vapor deposition of the first step can be performed at about 1000 to 1200°C.

[0011] In one embodiment, the chemical vapor deposition of the first step may be performed at about 0.5 to 1 Torr.

[0012] In one embodiment, the chemical vapor deposition of the first step can be performed by increasing the temperature at about 10 to 50° C. per minute.

[0013] In one embodiment, the WO3 precursor and the substrate may be spaced apart from each other by about 8 to 15 cm in the first step.

[0014] In one embodiment, the branch growth step can be performed through a chemical vapor deposition (CVD) method.

[0015] In one embodiment, the chemical vapor deposition of the branch growth step can be performed with a gas containing Ar and H2.

[0016] In one embodiment, the chemical vapor deposition of the branch growth step can be performed at about 500 to 700°C.

[0017] In one embodiment, the chemical vapor deposition of the branch growth step can be performed at about 0.5 to 1 Torr.

[0018] In one embodiment, the chemical vapor deposition of the branch growth step can be performed by increasing the temperature at about 30 to 50° C. per minute.

[0019] In one embodiment, the branch growth step may be performed with the MoO3 precursor and the substrate spaced apart from each other by about 8 to 15 cm.

[0020] In one embodiment, the chalcogen may include one or more elements selected from the group consisting of tellurium (Te), sulfur (S), and selenium (Se).

[0021] In one embodiment, the substrate may include carbon cloth (CC).

[0022] In one embodiment, the substrate may be a carbon cloth on which a gold (Au) catalyst is formed.

[0023] In another aspect, the present invention provides a nanowire and branched metal chalcogenide nanostructure manufactured by the method for manufacturing the nanowire and branched metal chalcogenide nanostructure.

[0024] In one embodiment, the nanowire and branched metal chalcogenide nanostructure may include WTe2 nanowires formed on a substrate.

[0025] In one embodiment, the nanowire and branched metal chalcogenide nanostructures are formed on a WO substrate. 3-x Nanowire; and MoO formed on the nanowire 3-x may include branches;

[0026] In one embodiment, the nanowire and branch-shaped metal chalcogenide nanostructure may include a WTe2 nanowire formed on a substrate; and a MoTe2 branch formed on the nanowire.

[0027] In one embodiment, the nanowire and branch-shaped metal chalcogenide nanostructure may include a WS2 nanowire formed on a substrate; and a MoS2 branch formed on the nanowire.

[0028] In one embodiment, the nanowire and branch-shaped metal chalcogenide nanostructure may include a WSe2 nanowire formed on a substrate; and a MoSe2 branch formed on the nanowire.

[0029] In another aspect, the present invention provides an electrochemical device comprising the metal chalcogenide structure as an electrode.

[0030] The effects of the present invention can contribute to improving catalytic efficiency in various electrochemical applications. In particular, the increased active sites and surface area, as well as the improved electrical properties, achieved through heterogeneous nanostructures can lead to high performance in processes such as the hydrogen evolution reaction. This structure not only enhances electrochemical stability but also enhances catalyst durability, offering the potential for implementing a long-term, sustainable catalyst system. Furthermore, the nanostructure of the present invention can be mass-produced cost-effectively and, through its environmentally friendly approach, can contribute to the sustainable development of energy-related industries. Thus, the present invention can significantly impact the energy and environmental fields by improving the performance and economic feasibility of electrochemical catalysts.

[0031] Figure 1. (a) Schematic diagram of the two-step process for growing WTe2NWs on CC. (b) Au-deposited CC, WO 2.9 Photographs of NWs / CC and WTe2NWs / CC.

[0032] Fig. 2. WO 2.9 SEM images of NWs and WTe2NWs. (a, b) WO 2.9 Low-magnification SEM image of NWs. (c) High-magnification SEM image of the white dotted square area in (b). (d, e) Low-magnification SEM images of WTe2NWs. (f) High-magnification SEM image of the white dotted square area in (e).

[0033] Fig. 3. (a) WO 2.9 NWs, core-shell WO 2.9 -XRD patterns and (a) Raman spectra of WTe2NWs and WTe2NWs. XPS scans of (c) W 4f and (d) Te 3d for the synthesized nanowires.

[0034] Fig. 4. (a, b) WO 2.9 NWs, (c, d) core-shell WO 2.9 -TEM and STEM images and EDS elemental maps for (e, f) WTe2NWs and (e, f) WTe2NWs.

[0035] Figure 5. WTe2NWs and core-shell WO synthesized with various tellurization times. 2.9 Electrochemical performance of WTe2NWs. (a) LSV polarization curve, (b) corresponding Tafel plot, (c) Nyquist plot, and (d) electric double-layer capacitor of the catalyst. (e) Durability test of WTe2NWs at a current density of -20 mA / cm2 for 12 h. (f) LSV polarization curve of WTe2NWs after 12 h of HER. The inset is an SEM image of WTe2NWs after 12 h of HER.

[0036] Figure 6. (a) SEM images of CC and (b) Au-deposited CC.

[0037] Fig. 7. WO 2.9 NWs, WO3, core-shell WO 2.9 -WTe2NWs (tellurization time: 1 hour), XPS survey spectra of WTe2NWs.

[0038] Figure 8. Core-shell WO 2.9 STEM image and EDS map of -WTe2NW (tellurization time: 30 min). (a) WO 2.9 STEM images of -WTe2NW. (b, c, d) WO 2.9 -EDS map images of WTe2 (b) Te, (c) O, (d) W elements.

[0039] Fig. 9. (a) WO 2.9 (b) LSV curves of NWs and WTe2NWs (tellurization time: 6 h). (c) Tafel plot of the sample obtained from the LSV curves.

[0040] Figure 10. SEM images and EDS analysis of WTe2NWs (tellurization time: 6 h). (a, b, c, d, e) SEM images of the samples. (f) EDS analysis in line scan mode obtained along the line indicated in (b). (g, h) EDS point analyses of the areas marked 1 and 2 in (d), respectively.

[0041] Figure 11. WTe2NWs / CC and core-shell WO obtained at various scan rates (10-110 mV / s). 2.9 -CV curve of WTe2NWs / CC.

[0042] Fig. 12. SEM image of WTe2NWs / CC after 12 h HER.

[0043] Figure 13. (a) Branched MoO synthesized on carbon cloth 3-x -WO 3-x and growth process of MoX2-WX2 (X=Te, S, Se) heterogeneous nanostructures. (b) Schematic diagram of the sequential experimental setup for fabricating branched nanostructures.

[0044] Figure 14. (a, b, c) Branched MoO synthesized at growth times ranging from 10 to 60 minutes. 3-x -WO 3-x SEM images of the nanostructured array. (d, e, f) Branched MoO grown on carbon cloth for 1 h.3-x -WO 3-x Low-magnification SEM images of nanostructures. SEM images of branched (g) MoTe2-WTe2, (h) MoS2-WS2, and (i) MoSe2-WSe2 nanostructures.

[0045] Figure 15. Branched MoO synthesized with growth times of (a) 20 min and (b) 60 min. 3-x -WO 3-x TEM image of the nanostructure. Branched MoO grown for 1 hour. 3-x -WO 3-x (c) High-magnification and (d) low-magnification TEM images of the nanostructure. (e) Branched MoO 3-x -WO 3-x TEM image and EDS map image of nanostructure.

[0046] Fig. 16. WO 3-x and MoO 3-x Nanowires and branched MoO 3-x -WO 3-x , Raman graphs of MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 nanostructures.

[0047] Fig. 17. MoO with branches 3-x -WO 3-x Electrochemical performances of MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 nanostructures and WTe2 nanowires. (a) LSV polarization curves and (b) Tafel curves of branched nanostructures and nanowires.

[0048] Fig. 18. MoO with branches 3-x -WO 3-x Transmission scanning electron microscopy (TEM) images and energy dispersive spectroscopy (EDS) mapping results performed to confirm the cross-section of the heterogeneous nanostructure.

[0049] Figure 19. (a, b) MoO synthesized over a growth time of 60 minutes. 3-x -WO 3-xCross-sectional STEM images of (c) low magnification and (d) high magnification TEM images of MoS2-WS2. (e) low magnification and (f) high magnification TEM images of MoSe2-WSe2. (g) low magnification and (h) high magnification TEM images of MoTe2-WTe2.

[0050] Fig. 20. (a) WO 3-x , MoO 3-x , MoO 3-x -WO 3-x , MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 XRD patterns of synthesized WO 3-x Wow MoO 3-x -WO 3-x XPS scans of (b) W 4f, (c) Mo 3d, (d) O 1s. XPS scans of (e) Mo 3d, (f) S 2p, (g) Se 3d, (h) Te 3d of the synthesized branched nanostructures.

[0051] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention may be modified in various ways and may take various forms. Therefore, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals are used to indicate similar components. In the attached drawings, the dimensions of structures are shown larger than actual size to ensure clarity of the present invention.

[0052] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof. In the context of this specification, the term "about" or the like can mean about ± 1%, about ± 2%, about ± 3%, about ± 4%, about ± 5%, about ± 6%, about ± 7%, about ± 8%, about ± 9%, or about ± 10% of a numerical value described in the specification.

[0053] Additionally, the description of one aspect of the present invention may be applied identically or similarly to the same or similar configurations or terms in the description of other aspects.

[0054] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0055] A method for manufacturing a nanowire and branched metal chalcogenide nanostructure according to an embodiment of the present invention comprises vapor deposition of a WO3 precursor onto a substrate. 2.9 The first step of growing nanowires is to form WO by vapor deposition of MoO3 precursor. 2.9 MoO on nanowires 3-xIt may include a branch growth step for growing a branch; and a second step for exposing the nanowire and branch to a chalcogen environment to replace at least some of the oxygen of the nanowire and branch with chalcogen.

[0056] In the context of this specification, branch may have the same or similar meaning as "branch".

[0057] The role of the above first step is WO as a infrastructure 2.9 The goal is to effectively form nanowires. In this step, a WO3 precursor is directly deposited on the substrate using a vapor deposition method, thereby forming a high-density nanowire array. This can provide a solid foundation for growing additional catalyst materials in the subsequent step. In the branch growth step, a MoO3 precursor is vapor-deposited to form WO 2.9 MoO in nanowires 3-x Branches can be formed. This process significantly increases the surface area of ​​the nanostructure and provides various active sites that enhance catalytic activity. Finally, in the second step, the nanowires and branches are exposed to a chalcogen environment, replacing surface oxygen with chalcogen elements, thereby optimizing the chemical and physical properties of the nanostructure.

[0058] As long as the above-described process is performed, the vapor deposition method in the first step is not particularly limited. In one embodiment, the first step may be performed via chemical vapor deposition (CVD). This CVD method may be an important process for ensuring uniform growth of nanowires and high adhesion to the substrate. The CVD process may be performed by converting a precursor into a gaseous state within a reactor and depositing the desired material on the substrate at high temperatures. Nanowires produced through this method can have high purity and uniform structural characteristics, which can lay an important foundation for branch growth in subsequent processes. Furthermore, the CVD process can provide the flexibility to precisely control the length, thickness, and arrangement of the nanowires by controlling the reaction conditions.

[0059] In one embodiment, the chemical vapor deposition of the first step can be performed using a gas containing Ar and H2. The use of Ar and H2 gases in this process can play an important role in increasing the stability and efficiency of the chemical vapor deposition process. Ar gas can provide an inert environment within the reactor, thereby preventing unwanted chemical reactions and helping to grow high-purity nanowires. On the other hand, H2 gas can promote the reduction reaction of the WO3 precursor, thereby forming WO 2.9 This can facilitate the formation of nanowires. This combination of gases can help control the growth rate and structure of nanowires, which can directly impact the quality and consistency of the nanowires.

[0060] In one embodiment, the chemical vapor deposition of the first step may be performed at about 1000 to 1200° C. This temperature range allows the WO3 precursor to be suitably reduced to WO 2.9This can aid in the formation of nanowires. These high-temperature conditions can play a crucial role in the effective conversion of precursors to a gaseous state and the uniform growth of nanowires on the substrate. The high-temperature environment can enhance the crystallinity and structural consistency of nanowires, which can positively impact the physical and chemical properties of the final product. Furthermore, this temperature range can increase the reaction rate, making it suitable for mass production, providing an economical and efficient method for the fabrication of nanostructures on an industrial scale.

[0061] In one embodiment, the chemical vapor deposition of the first step may be performed by increasing the temperature at a rate of about 10 to 50°C per minute. This heating rate can serve as an important variable in the chemical vapor deposition process and can determine the growth rate and quality of the nanowires. If the heating rate is too fast, the precursor may react incompletely, which may increase structural defects in the nanowires, and if the heating rate is too slow, it may result in inefficient process time. Therefore, a heating rate of about 10 to 50°C per minute can promote uniform and high-density nanowire growth during the chemical vapor deposition process and ensure that these nanowires are effectively formed on the substrate. This controlled heating process provides optimal nanowire growth conditions, which can maximize the functionality and applicability of the nanostructure.

[0062] In one embodiment, the WO3 precursor and the substrate may be spaced apart from each other by about 8 to 15 cm in the first step. This separation distance can significantly affect the growth rate and morphology of nanowires during the chemical vapor deposition process. A separation distance of about 8 to 15 cm can optimize the gas flow and heat distribution that occur between the substrate and the precursor, thereby promoting uniform nanowire growth. This distance can ensure smooth conversion of the precursor to a gaseous state and its transfer to the substrate, which can be important for ensuring uniform thickness and length of the nanowires. A distance that is too close can result in uneven deposition and excessive thermal effects, and a distance that is too far can hinder efficient gas transfer and sufficient reaction. Therefore, an appropriate separation distance of 8 to 15 cm in the first step can effectively manage the growth conditions of the nanowires, and consequently contribute to the synthesis of high-quality nanowires.

[0063] In one embodiment, the branch growth step may be performed by a chemical vapor deposition (CVD) method. The use of the CVD method in the branch growth step is MoO 3-x It can help to effectively grow branches of MoO. CVD is a technique that provides high reactivity and controllable growth, which allows for detailed nanostructure adjustment, which can ultimately contribute to enhancing the functionality and applicability of nanostructures. By precisely controlling the reaction conditions, gas flow rate, and temperature during the CVD process, MoO 3-x The growth rate, size, and morphology of branches can be controlled, and this control can impart customized properties to various nanostructures for various applications. Furthermore, the CVD method is suitable for industrial-scale production, providing an economical and efficient approach for mass production.

[0064] In one embodiment, the chemical vapor deposition of the branch growth step may be performed with a gas containing Ar and H2. Using a gas containing Ar and H2 in the branch growth step may be performed in the form of MoO 3-x This can help optimize the growth environment for branches. Ar gas maintains a stable environment within the reaction chamber, which can promote the uniform growth of nanostructures. The combination of these gases can play a crucial role in stably controlling the growth of nanostructures during the CVD process and forming uniformly distributed nanostructures on the substrate. The resulting nanostructures can have improved physical and chemical properties, which can enhance their performance in various applications.

[0065] In one embodiment, the chemical vapor deposition of the branch growth step can be performed at about 500 to 700° C. The chemical vapor deposition process of the branch growth step is performed at a temperature range of about 500 to 700° C. MoO 3-x This temperature range can help promote branch growth. This temperature range provides ideal conditions for efficient vaporization of the MoO3 precursor and growth of nanostructures. Furthermore, this temperature range can provide sufficient reactivity while maintaining the chemical stability of the material, which is advantageous for minimizing defects in the nanostructures and forming a uniform structure. Nanostructures synthesized under these conditions can exhibit excellent physical and chemical properties, which can enhance their applicability in various fields of nanotechnology, as well as electrochemical applications. Therefore, using a temperature range of 500 to 700°C during the branch growth stage can be a crucial factor for the high-quality and efficient production of nanostructures.

[0066] In one embodiment, the chemical vapor deposition of the branch growth step may be performed by increasing the temperature at a rate of about 30 to 50°C per minute. In one embodiment, the process of increasing the temperature at a rate of about 30 to 50°C per minute in the chemical vapor deposition of the branch growth step may be helpful in controlling the growth rate and quality of the nanostructure. This rate of temperature increase allows for uniform management of the chemical changes of the material in the process of reaching the reaction temperature, which may contribute to minimizing defects that may occur during the growth of the nanostructure. Furthermore, slowly and uniformly increasing the temperature allows for more efficient distribution of the energy required during the growth of the nanostructure, which may be advantageous in achieving more precise structural control and high-quality nanostructures. This controlled temperature increase rate optimizes the growth of the nanostructure, and the resulting nanostructure can more accurately exhibit the expected physical and chemical properties. Therefore, applying a temperature increase rate of 30 to 50°C per minute in the branch growth step may play a significant role in effectively achieving the desired properties during the nanostructure fabrication process.

[0067] In one embodiment, the MoO3 precursor and the substrate may be spaced apart from each other by about 8 to 15 cm in the branch growth step. In one embodiment, spaced apart from the MoO3 precursor and the substrate by about 8 to 15 cm in the branch growth step may help optimize the flow of gaseous compounds and diffusion within the reaction space. This separation distance may facilitate uniform diffusion and growth of the material by providing a sufficient reaction area necessary for vaporization of the MoO3 precursor and growth of the nanostructure. Controlling the separation distance may be an important factor in achieving uniform growth and high quality of the nanostructure, which may positively affect the overall performance and applicability of the nanostructure. In addition, by appropriately controlling the separation distance, sensitive control of the reaction temperature and chemical environment is possible, which may be useful in controlling the properties of the nanostructure in a desired direction. Therefore, setting the distance between the MoO3 precursor and the substrate to 8 to 15 cm during the branch growth stage can contribute to increasing efficiency and accuracy in the growth process of nanostructures.

[0068] In one embodiment, the chalcogen may include one or more elements selected from the group consisting of Te, S, and Se. This selection may contribute to diversifying the chemical properties and applicability of the nanostructure. For example, using one or more of Te, S, and Se provides a way to control the electrochemical properties, surface chemistry, and catalytic activity of the nanostructure. Each chalcogen element may impart unique properties to the nanostructure, which may be important for optimizing the nanostructure for specific applications. Furthermore, combinations of various chalcogen elements may form mixed oxides or composite materials, which may be useful for enhancing the functionality of the nanostructure.

[0069] In the context of this specification, the term "chalcogen" refers to chemical elements belonging to Group 16 of the periodic table. These elements include oxygen, sulfur (S), selenium (Se), tellurium (Te), and polonium, of which sulfur, selenium, and tellurium are particularly useful for fabricating nanostructures. Each chalcogen element can influence the physical and chemical properties of the nanostructure, thereby optimizing the performance of the nanostructure for specific applications. The selection of these chalcogen elements can be crucial for controlling the conductivity, catalytic activity, chemical resistance, and other related properties of the nanostructure, which can enable the effective utilization of nanostructures in various advanced applications such as energy conversion, sensor technology, and catalysis.

[0070] In one embodiment, the substrate may comprise carbon cloth. In the context of this specification, "carbon cloth" refers to a flexible, highly conductive carbon-based fiber material. Due to its structure and physical properties, carbon cloth can be utilized as an ideal substrate for the growth and synthesis of nanostructures. This is particularly important in electrochemical applications requiring conductivity. The flexibility of carbon cloth allows for the fabrication of nanostructures in various shapes and sizes, thereby optimizing the surface area of ​​the nanostructures and providing more active sites. Furthermore, carbon cloth is chemically stable, heat-resistant, and durable enough to withstand a wide range of chemical treatments and mechanical stresses. These properties make carbon cloth suitable for various conditions of nanostructure synthesis, enabling a wide range of applications. For example, carbon cloth can play an important role in various fields such as electrochemical energy storage devices, sensors, and catalysts.

[0071] In one embodiment, the substrate may be formed with a gold (Au) catalyst on a carbon cloth. This can facilitate the growth and synthesis of nanostructures by applying gold particles to the surface of the substrate. The gold catalyst plays a central role in the nanostructure synthesis process, and can be particularly important in processes such as chemical vapor deposition. This catalyst can help control the growth rate and directionality of the nanostructure, thereby enabling more precise control of the desired shape and size of the nanostructure. The use of a gold catalyst can play a particularly important role in the synthesis of complex structures, such as nanowires and branched metal chalcogenide nanostructures. This can enhance the multifunctionality and efficiency of the nanostructure, which can contribute to improving the performance of the nanostructure in various applications. For example, nanostructures using a gold catalyst can exhibit high activity and reactivity in catalysts, sensors, electronic devices, and the like.

[0072] Meanwhile, a heterogeneous nanostructure according to an embodiment of the present invention can be manufactured by the method for manufacturing nanowires and branched metal chalcogenide nanostructures according to an embodiment of the present invention described above. In one embodiment, the heterogeneous nanostructure can include a substrate, nanowires formed on the substrate, and branched structures formed on the nanowires. This configuration offers the possibility of improving the overall performance of the nanostructure by integrating various materials and functions. The addition of branched nanostructures can diversify the chemical and physical properties of the nanostructure and provide customized functions required in specific applications. For example, the branched structure can increase the surface area of ​​the nanostructure and improve catalytic activity, electron transport, sensor detection ability, etc. In addition, the heterogeneous nanostructure can obtain additional structural stability through interaction with the substrate, which can contribute to long-term use and higher durability.

[0073] In one embodiment, the nanowire and branched metal chalcogenide nanostructures are formed on a WO substrate. 3-x Nanowire; and MoO formed on the nanowire 3-x Branches; may include. In one embodiment, the nanowire and branch-shaped metal chalcogenide nanostructure may include: WTe2 nanowires formed on a substrate; and MoTe2 branches formed on the nanowires. In one embodiment, the nanowire and branch-shaped metal chalcogenide nanostructure may include: WS2 nanowires formed on a substrate; and MoS2 branches formed on the nanowires. In one embodiment, the nanowire and branch-shaped metal chalcogenide nanostructure may include: WSe2 nanowires formed on a substrate; and MoSe2 branches formed on the nanowires.

[0074] The materials, structures and forming methods of the substrate, nanowires and branched nanostructures may be the same as or similar to the description of the method for manufacturing nanowires and branched metal chalcogenide nanostructures according to the embodiments of the present invention described above.

[0075] Meanwhile, an electrochemical device according to an embodiment of the present invention may include the metal chalcogenide structure as an electrode. In such an electrochemical device, the metal chalcogenide structure plays a crucial role as an electrode. This structure contributes to improving the efficiency of the electrode in electrochemical reactions. In particular, the physical and chemical properties of the metal chalcogenide structure enhance the reactivity and conductivity of the electrode, which is important for optimizing the performance of the overall electrochemical system. Furthermore, the unique morphological characteristics of this structure increase the surface area of ​​the electrode, maximizing interaction with the electrolyte, which can improve charge transfer efficiency and enhance the catalytic activity of the electrode.

[0076] Examples of electrochemical devices described herein include, but are not limited to, hydrogen generation reactors, fuel cells, electrolysis devices, electrochemical sensors, and electrochemical energy storage devices. These devices utilize metal chalcogenide structures to optimize electrode performance and increase overall system efficiency. In hydrogen generation reactors, the metal chalcogenide structures provide high catalytic activity and conductivity, enabling efficient hydrogen production. In fuel cells, these structures improve the reactivity of the electrodes, thereby enhancing the electrochemical conversion efficiency of fuel. In electrolysis devices, the effective interaction with the electrolyte can increase the energy efficiency of the electrolysis process. In electrochemical sensors, the sensitive reactivity of the metal chalcogenide structures improves detection efficiency. Finally, in electrochemical energy storage devices, these structures can increase the overall energy storage efficiency by enabling high-density energy storage and rapid charge / discharge cycles.

[0077] Hereinafter, embodiments of the present invention will be described. However, the embodiments described below are merely some embodiments of the present invention, and the scope of the present invention is not limited to the embodiments described below.

[0078] <WTe2나노와이어의 합성>

[0079] result

[0080] The present inventors directly synthesized vertically aligned WTe2 nanowires on a carbon cloth (CC) substrate through a two-step growth process (see Fig. 1a). In the first step, WO was synthesized through a vapor-liquid-solid (VLS) synthesis method using a Au catalyst. 2.9 Nanowire array (WO 2.9 NW array) on a CC substrate (WO 2.9 / CC) was grown directly. Subsequently, the synthesized WO 2.9NWs / CC were annealed in a Te atmosphere to fabricate WTe2 nanowires aligned vertically on the substrate. Figure 1b shows the Au-deposited CC and WO 2.9 Showing the pictures of NWs / CC, WTe2NWs / CC, WO 2.9 The uniform color distribution on the substrate (blue) and WTe2 (black) shows that each nanowire is grown evenly on the centimeter-sized substrate.

[0081] The present inventors have grown WO on a carbon cloth (CC) substrate. 2.9 Scanning electron microscopy (SEM) measurements were performed to confirm the morphology of the WTe2 nanowires (see Fig. 2). As can be seen in Figs. 2a to 2c, WO 2.9 Nanowires were grown three-dimensionally and uniformly in a vertical direction on the CC surface with a uniform length of approximately 10 micrometers or more. WO was synthesized directly on the substrate. 2.9 Nanowires have high stability and WO through tellurization process 2.9 Even after the transition from WO to WTe2, the dense nanowire structure is maintained. Figures 2d to 2f show WTe2 nanowires uniformly grown in the vertical direction on the substrate. The synthesized WO 2.9 For morphological comparison of NWs and WTe2NWs, Fig. 6 provides SEM images of untreated CC and Au-deposited CC.

[0082] The present inventors have discovered WO through a tellurization process. 2.9 The characteristics of the nanowires converted from WTe2 were confirmed using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) (see Fig. 3). Fig. 3a shows the synthesized WO 2.9 , core-shell WO 2.9 - Shows XRD patterns of WTe2 and WTe2 nanowires. WO 2.9 The XRD pattern of the nanowire is monoclinic WO 2.9It shows the crystal structure, and the diffraction peaks observed at 23.5°, 24.4°, 34.1°, and 48.1° correspond to the (010), (106), (116), and (020) planes, respectively. Meanwhile, WO 2.9 Core-shell WO obtained by tellurization of nanowires for 1 or 2 hours 2.9 -XRD pattern of WTe2 nanowires is WO 2.9 and WTe2. Additionally, the peaks at 12.5, 29.2, 32.0, 38.4, 40.6, and 52.5° correspond to the (100), (021), (103), (024), and (122) planes of tetragonal WTe2, and the peak at 27.6° corresponds to the (101) plane of Te. As the tellurization time increases, the peak of WTe2 shifts to WO 2.9 It can be observed that the intensity increases compared to the peak of WO. This is because in the early stage of the tellurization reaction, WO 2.9 is partially converted to WTe2, indicating that Te conversion progresses more as the reaction time increases. On the other hand, WO 2.9 In the XRD pattern of the nanowires obtained by tellurization for 4 hours, only diffraction peaks corresponding to WTe2 and Te are observed, which are WO 2.9 This suggests that the nanowires have been completely converted into WTe2 nanowires.

[0083] The present inventors used a 532 nm laser to WO 2.9 The Raman spectrum of the nanowire was measured, and the results showed that the peaks at 269 and 325 cm-1 correspond to the bending vibration of the WOW bond and at 711 and 807 cm-1 correspond to the stretching vibration of the WOW bond. -1 (see Fig. 3b). WO 2.9 Core-shell WO obtained by tellurization of nanowires for 1 hour 2.9 -Raman spectrum of WTe2 nanowires WO 2.9It showed both characteristic peaks of WTe2 and core-shell WO. 2.9 -160 and 207 cm of WTe2 -1 Peak is A1 of WTe2 7 and A1 9 It corresponds to the mode. Meanwhile, WO 2.9 The Raman spectrum of WTe2 nanowires obtained by tellurization for 4 hours showed only the A1 of WTe2. 7 Mode and A1 9 Only the mode was shown.

[0084] The present inventors synthesized WO 2.9 , core-shell WO 2.9 - X-ray photoelectron spectroscopy (XPS) was performed to analyze the surface chemical states of WTe2 and WTe2 nanowires (NWs) (see Figs. 3c and 3d). The XPS survey measurement results of the nanowires synthesized on the CC substrate can be confirmed in Fig. 7. WO 2.9 has W, O, C elements, and WTe2 has W, O, C, Te elements. WO 2.9 The W 4f spectrum of W 6+ 38.1 eV (W 4f) corresponding to the state 5 / 2 ) and 35.8 eV(W 4f 7 / 2 ) Peak and W 5+ 36.5 eV (W 4f) corresponding to the state 5 / 2 ) and 34.5 eV(W 4f 7 / 2 ) represents the peak. W 5+ The peaks represent oxygen vacancies in WO3. Core-shell WO 2.9 -The W peak of WTe2 and WTe2 shifts to lower binding energy 4+ 34.1 eV (W 4f) corresponding to the state 5 / 2 ) and 32.0 eV(W 4f 7 / 2 ) is shown. Also, core-shell WO 2.9 -Te 3d spectra of WTe2 and WTe2 are at 583.3 eV (Te 3d 3 / 2 ) and 572.9 eV (Te 3d5 / 2 ) exhibited a strong peak at 587.4 eV and 577.0 eV corresponding to Te-O, and small peaks at 587.4 eV and 577.0 eV corresponding to Te-O were also detected. These XPS measurement results indicate that core-shell WO 2.9 -Indicates that the W and Te elements in WTe2 and WTe2 have the same chemical state.

[0085] In order to understand the structural change due to Te conversion of nanowires at the atomic level, the inventors of the present invention used WO 2.9 , core-shell WO 2.9 High-resolution transmission electron microscopy (HRTEM) imaging and energy dispersive spectroscopy (EDS) mapping analysis were performed on WTe2 and WTe2 nanowires (NWs) (see Fig. 4). WO 2.9 The 0.38 nm lattice spacing corresponds to the (010) plane of the monoclinic cell, which can be confirmed in Fig. 4a. WO 2.9 Core-shell WO synthesized by tellurization for 30 minutes 2.9 -HRTEM image of WTe2NW is WO 2.9 It shows a core-shell structure consisting of a core and a WTe2 shell (Fig. 4c and 4d). The WO of this core 2.9 is originally WO 2.9 It has the same (010) plane as NW, and the WTe2 of the shell has a 0.34 nm lattice spacing corresponding to the (100) plane of the orthorhombic cell. Core-shell WO 2.9 -In the EDS map of WTe2NW, the W element is evenly distributed on the surface, while the O element is concentrated in the core (see Fig. 4d and Fig. 8). Core-shell WO 2.9 -WTe2 structure is consistent with the XRD and XPS spectra results of Figures 3a, 3c and 3d. WO 2.9 WTe2NW obtained by tellurization for 4 hours is a core-shell WO 2.9 -WTe2 has a (100) plane that matches the shell of WTe2, and the Te element is evenly distributed (Fig. 4e and Fig. 4f). WO2.9 NWs have a diameter of about 50 nm and are core-shell WO fabricated by a tellurization process. 2.9 -WTe2 and WTe2NWs maintain similar diameters (Fig. 4b, Fig. 4d, and Fig. 4f).

[0086] The inventor is WO 2.9 Core-shell WO synthesized by tellurization of nanowires (NWs) for 30 min, 1 h, 2 h, and 4 h 2.9 The catalytic activities of WTe2NWs / CC and WTe2NWs / CC were evaluated (see Fig. 5). The measurements were performed in a three-electrode cell using a 0.5 M H2SO4 electrolyte. The nanowire catalyst grown on CC was used as the working electrode, the platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. CC substrates are widely used in electrochemical applications due to their excellent conductivity, good physical strength, and high flexibility. Fig. 5a shows the WTe2NWs / CC and core-shell WO obtained using linear scanning voltammetry (LSV). 2.9 -The polarization curves of WTe2NWs / CC are shown. All curves were corrected for the voltage drop due to the solution resistivity (iR drop) measured before the reaction. The Tafel plots in Fig. 5b and Fig. 9b were obtained by transforming the LSV curves (η = b log j + a). For the comparison of electrochemical performance, Pt / CC was fabricated by depositing 15-20 nm thick platinum on the CC by sputtering. WO 2.9 The catalytic performance enhancement was confirmed by the decrease in overpotential and Tafel slope of the synthesized catalyst due to the Te conversion of NWs. The overpotential of the catalyst obtained at a current density of 10 mA / cm² was higher than that of the core-shell WO 2.9 -The Tafel slope of WTe2NWs / CC (tellurization time: 30 min) decreases from 0.48 V [vs reversible hydrogen electrode (RHE)] to 0.36 V for WTe2NWs / CC. The Tafel slope of WTe2NWs is 49 mV / dec, which is higher than that of core-shell WO 2.9-The Tafel slope of WTe2 decreases from 91 mV / dec (tellurization time: 30 min) to 58 mV / dec (tellurization time: 2 h) with Te conversion (Fig. 5b). WO 2.9 NW has a Tafel slope of 123 mV / dec (Fig. 9). On the other hand, WO 2.9 WTe2NWs obtained by tellurization for 6 h exhibited a Tafel slope of 66 mv / dec and showed reduced catalytic activity compared to WTe2 synthesized by a 4-h reaction (Fig. 9). The decreased performance of the catalyst synthesized by the long tellurization process is presumed to be due to the excessive supply of Te particles. Figure 10 shows the SEM image and EDS results of WTe2NWs obtained by tellurization for 6 h. Through Te annealing, WO 2.9 After conversion to WTe2, additionally provided Te particles appear to have attached to the wire, reducing the performance of the WTe2NWs catalyst.

[0087] The present inventors have synthesized WTe2NW and core-shell WO in a hydrogen evolution reaction. 2.9 - Electrochemical impedance spectroscopy (EIS) was performed to understand the charge transfer process of the WTe2NW catalyst (see Fig. 5c). WTe2NW and core-shell WO 2.9 -The Nyquist plot of WTe2NW shows a semicircular shape, and the charge transfer resistance (R) increases with increasing Te conversion. ct ) is significantly reduced. These results indicate that the semiconductor WO 2.9 It is considered to be due to the transformation from NW to semimetal WTe2NW, with the lowest R of 72 Ω. ctWTe2 with exhibits improved catalytic activity due to the fast charge transfer rate. The performance of the catalyst is influenced by the intrinsic activity and the number of active sites, the latter of which is generally evaluated through the electrochemically active surface area (ECSA). To obtain the ECSA of the catalyst, the electrochemical double-layer capacitance (C ), which is directly proportional to the ECSA, is calculated. dl ) was measured. C dl Cyclic voltammetry (CV) graphs were obtained by varying the scan rate from 10 to 110 mV / s in the non-Faradaic potential range (see Fig. 11). As can be seen in Fig. 5d, C according to Te transition dl The value increases gradually. Core-shell WO 2.9 The ECSA of WTe2NWs, which is about 4 times larger than that of WTe2NWs (tellurization time: 30 min), increases the catalytic activity by exposing more active sites. The high-performance electrocatalytic activity of WTe2 is due to its smaller R ct This is considered to be due to efficient charge transfer and abundant active sites.

[0088] The present inventors confirmed that WTe2NWs / CC exhibited excellent operational stability in a continuous 12-hour hydrogen evolution reaction at a fixed potential of 0.38 V (see Fig. 5e). In the experiment, WTe2NWs / CC continuously performed a hydrogen evolution reaction (HER) between -0.45 V and 0.2 V (vs. RHE), maintaining a current density of approximately 20 mA / cm². The linear scanning voltammetry (LSV) curve and Tafel slope of the WTe2 / CC subjected to a long-term hydrogen evolution reaction did not show a significant decrease compared to the initial WTe2 / CC (see Fig. 5f). Fig. 5f and Fig. 12 show that the three-dimensionally vertically aligned WTe2NWs were maintained in the CC even after 12 hours of reaction. The WTe2 catalyst synthesized on the substrate has high physical stability and maintains high stability even in a continuous hydrogen evolution reaction. The rough surface of the wire that appeared after HER is considered to be due to the dissolution of Te in the acidic medium (WTe2→WTe 2-x + xTe).

[0089] conclusion

[0090] The present invention relates to a method for efficiently synthesizing vertically aligned metal WTe2 nanowires (NWs) on a conductive carbon cloth (CC) substrate. WO is synthesized through a tellurization process. 2.9 NWs are WTe2NWs and core-shell WO 2.9 -Selective conversion into WTe2NWs was demonstrated. The WTe2NWs synthesized by the present invention exhibit a low Tafel slope of 49 mV / dec, indicating excellent performance and high durability in the hydrogen evolution reaction. These findings provide a strategy for fabricating Weyl semimetallic transition metal dichalcogenide (TMD) nanowires applicable to various electrochemical reactions, including water electrolysis. This study is expected to be particularly useful for electrolysis processes for hydrogen generation.

[0091] Experimental method

[0092] Synthesis of WO2.9 NWs

[0093] The present inventors have synthesized WO on a carbon cloth (CC) substrate through a vapor-liquid-solid (VLS) method using Au as a catalyst. 2.9 Nanowires (NWs) were directly synthesized. For this purpose, Au was deposited on a CC substrate with a thickness of approximately 15-20 nm using a sputtering method. During the experiment, an alumina boat containing WO3 powder (0.3 g, Sigma-Aldrich, purity 99.5%) was placed in the center of a quartz tube with a diameter of 1 inch. The CC substrate was installed at a distance of approximately 12 cm from the WO3 powder. After the inside of the quartz tube was evacuated to less than 6 mTorr, argon (Ar) and hydrogen (H2) gases were injected at flow rates of 100 sccm (standard cubic centimeter per minute) and 1 sccm, respectively. WO 2.9 During the growth of NWs, the pressure inside the tube was maintained at approximately 1–0.5 Torr. The WO3 powder was heated to 1100 °C at a rate of approximately 27 °C / min and maintained at this temperature for 60 min. After the reaction was completed, the furnace lid was opened and the furnace was cooled to room temperature.

[0094] Synthesis of core-shell WO2.9-WTe2 NWs and WTe2 NWs

[0095] The present inventors synthesized WO 2.9 Core-shell WO was prepared by annealing nanowires (NWs) in a tellurium (Te) atmosphere. 2.9 -WTe2NWs and WTe2NWs were selectively fabricated. For this purpose, alumina boats containing tellurium slugs (0.3 g, Sigma-Aldrich, 99.999% purity) and WO were placed in a 1-inch diameter quartz tube. 2.9NWs / CCs were placed upstream and downstream, respectively. After evacuating the quartz tube to less than 5 mTorr, argon (Ar) gas was flowed at a rate of 400 sccm through a mass flow controller to raise the pressure to atmospheric pressure. Subsequently, argon and hydrogen (H2) gases were injected at a rate of 20 sccm each. WO 2.9 The NWs / CC were heated to 460 °C at a rate of approximately 29 °C / min, and the tellurium slugs were heated to 50 °C within 5 min and then to 550 °C at a rate of approximately 33 °C / min. Core-shell WO 2.9 -WTe2NWs were synthesized by maintaining the target temperature for 30 minutes, 1 hour, and 2 hours, and WTe2NWs were synthesized by maintaining the target temperature for 4 hours. Ten minutes after the completion of the reaction, the furnace lid was opened and the furnace was quickly cooled to room temperature.

[0096] characteristic

[0097] The inventors obtained the morphology of the samples by operating them at 5 kV in a JEOL JSM-6700F. X-ray diffraction (XRD) measurements were performed on a Rigaku Ultima III instrument using a Cu Kα radiation point source (λ = 1.5406 Å). Raman spectroscopy measurements were performed using a 532 nm laser focused through a 100X objective lens. X-ray photoelectron spectroscopy (XPS) measurements were performed on a Nexsa (Thermo Fisher Scientific) instrument equipped with an Al Kα radiation source. The XPS spectrum was calibrated to the peak located at 284.8 eV of carbon 1s. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) images and energy dispersive spectroscopy (EDS) maps were acquired on a JEOL JEM-2100F.

[0098] Electrochemical measurements

[0099] All electrochemical measurements were performed in a typical three-electrode cell using an SP-300 workstation at room temperature. A platinum wire and an Ag / AgCl electrode were used as the counter and reference electrodes, respectively. WTe2 nanowires (NWs) / CC, core-shell WO grown on a conductive carbon cloth (CC) substrate 2.9 -WTe2NWs / CC, and WO 2.9 / CC was used as a working electrode. Polarization curves were obtained by sweeping the range from 0 to -0.5 V (vs. RHE) at a scan rate of 5 mV / s in 0.5 M sulfuric acid (H2SO4) solution. All potentials were converted to the reversible hydrogen electrode (RHE) according to the following equation: E RHE = E Ag / AgCl + 0.059 Х pH + E o Ag / AgCl (E o Ag / AgCl = 0.1976 at 25 °C). Electrochemical impedance spectroscopy (EIS) was measured in the frequency range from 100 kHz to 0.01 Hz. The electric double layer capacitor (C) of the synthesized catalyst dl ) were measured at various scan rates from 10 to 110 mV / s. To examine the stability of the catalyst, WTe2 was measured in a 0.5 M H2SO4 solution in the range of 0 to -0.4 V vs. RHE at a scan rate of 5 mV / s for 12 h.

[0100] <Synthesis of metal chalcogenides containing branched nanostructures>

[0101] Figure 13. (a) Branched MoO synthesized on carbon cloth 3-x -WO 3-x and growth process of MoX2-WX2 (X=Te, S, Se) heterogeneous nanostructures. (b) Schematic diagram of the sequential experimental setup for fabricating branched nanostructures.

[0102] Figure 13 shows a three-dimensional vertically aligned branched transition metal oxide MoO on a carbon fiber substrate. 3-x -WO 3-x We present the growth process for synthesizing heterostructures and transition metal dichalcogenide (TMD) MoX2-WX2 (X=Te, S, Se) heterostructures. First, a carbon cloth sprayed with a gold (Au) catalyst was used as a substrate to form vertically aligned WO 2.9 Nanowire arrays were grown. Au-deposited substrates were obtained by sputtering to a thickness of approximately 10–20 nm on the substrate or by spraying gold nanoparticles on carbon cloth that had undergone plasma treatment. An alumina boat containing WO3 powder was placed in the center of a 1-inch quartz tube, and the substrate was positioned approximately 12 cm away from the WO3 powder. The inside of the quartz tube was evacuated to less than 6 mTorr, and then Ar and H2 gases were flowed at approximately 100 sccm and 1 sccm, respectively. WO 2.9 During the synthesis of nanowires, the inside of the quartz tube was maintained at a low pressure of approximately 1 to 0.5 Torr. The WO3 powder was heated to 1100 °C at a rate of 27 °C / min and maintained at this temperature for 60 minutes. When the reaction was completed, the lid of the furnace was opened and cooled to room temperature. Through this reduction process of WO3, WO 2.9 Nanowires were synthesized directly on the substrate.

[0103] Next, the synthesized WO 2.9 Branched MoO using carbon cloth synthesized with nanowires as a substrate 3-x -WO 3-x Nanostructures were fabricated. An alumina boat containing MoO3 powder was placed in the center of a 1-inch quartz tube, and the substrate was positioned approximately 10 to 12 cm away from the MoO3 powder. The inside of the quartz tube was evacuated to less than 6 mTorr, and then Ar and H2 gases were flowed at approximately 100 sccm and 1 sccm, respectively. WO 3-x MoO in3-x During the branching process, the inside of the quartz tube was maintained at a low pressure of approximately 1 to 0.5 Torr. The MoO3 powder was heated to 590 °C at a rate of 38 °C / min and maintained at this temperature for 10 to 60 minutes. Upon completion of the reaction, the lid of the furnace was opened and cooled to room temperature. Through this process, MoO3 was reduced to form MoO with three-dimensional vertically aligned branches. 3-x -WO 3-x Nanostructures were synthesized directly on the substrate.

[0104] As a final step, the branched MoO 3-x -WO 3-x Branched MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 heterostructures were fabricated by annealing the heterostructures in a chalcogenide environment. For the branched MoTe2-WTe2, an alumina boat containing Te slug (0.3 g) and MoO were placed in a 1-inch diameter quartz tube. 3-x -WO 3-x were placed upstream and downstream, respectively. After the quartz tube was evacuated to approximately 5 mTorr or less, Ar gas was flowed at a rate of 500 sccm through a mass flow controller until the pressure in the tube reached atmospheric pressure. Then, Ar and H2 gases were each flowed at 20 sccm. MoO with branches 3-x -WO 3-x was heated to 360 °C at a rate of about 22.7 °C / min and maintained for 4 hours and 5 minutes. The Te slug was heated to 50 °C within 5 minutes, then heated to 550 °C at a rate of about 35.3 °C / min and maintained for 4 hours. After 10 minutes of completion of the reaction, the lid of the furnace was opened and cooled to room temperature. For MoS2-WS2, an alumina boat containing S pieces (0.3 g) and MoO were placed in a 1-inch diameter quartz tube. 3-x -WO 3-xwere placed upstream and downstream, respectively. After the quartz tube was evacuated to approximately 5 mTorr or less, Ar gas was flowed at 100 sccm through a mass flow controller until the pressure in the tube reached atmospheric pressure. Then, Ar and H2 gases were each flowed at 10 sccm. MoO with branches 3-x -WO 3-x was heated to 400 °C at a rate of about 25.3 °C / min and maintained for 4 hours. S pieces were heated to 200 °C at a rate of about 12 °C / min and maintained for 4 hours. After 10 minutes of reaction completion, the lid of the furnace was opened and cooled to room temperature. For MoSe2-WSe2, an alumina boat containing Se slugs (0.3 g) and MoO were placed in a 1-inch diameter quartz tube. 3-x -WO 3-x were placed upstream and downstream, respectively. After the quartz tube was evacuated to approximately 5 mTorr or less, Ar gas was flowed at a rate of 500 sccm through a mass flow controller until the pressure in the tube reached atmospheric pressure. Then, Ar and H2 gases were flowed at 20 sccm and 7 sccm, respectively. MoO with branches 3-x -WO 3-x was heated to 400 °C at a rate of approximately 25.3 °C / min and maintained at this temperature for 4 hours. Se slugs were heated to 350 °C at a rate of approximately 22 °C / min and maintained at this temperature for 4 hours. Ten minutes after the completion of the reaction, the lid of the furnace was opened and the temperature was cooled to room temperature.

[0105] Figure 14. (a to c) Branched MoO synthesized at growth times ranging from 10 to 60 minutes. 3-X -WO 3-x SEM images of the nanostructured array. (d–f) Branched MoO grown on carbon cloth for 1 h. 3-X -WO 3-xLow-magnification SEM images of nanostructures. SEM images of branched (g) MoTe2-WTe2, (h) MoS2-WS2, and (i) MoSe2-WSe2 nanostructures.

[0106] Synthetic branched MoO 3-x -WO 3-x And scanning electron microscopy (SEM) measurements were performed to confirm the morphology of MoX2-WX2 (X=Te, S, Se) nanostructures (Fig. 14). MoO synthesized at various branch growth times in Figs. 14a to 14c 3-x -WO 3-x SEM image of WO 3-x MoO growing around 3-x It shows the synthesis process of eggplant. As time increases, the MoO becomes shorter. 3-x It was confirmed that the branches gradually grew to several hundred nanometers in length. Figures 14d to 14f show branched MoO grown for 1 hour. 3-x -WO 3-x Low-magnification SEM images of the nanostructures are shown. Branched MoO 3-x -WO 3-x The nanostructured array is a branched MoO grown uniformly and densely in the vertical direction on a three-dimensionally woven carbon cloth substrate. 3-x -WO 3-x Nanostructure arrays are shown. Figures 14g to 14i show SEM images of branched MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 nanostructures. MoO2, which is directly synthesized on a substrate and has high stability. 3-x -WO 3-x The nanostructure acts as a template, maintaining the branched structure shape as well as the high density and vertical orientation even after conversion to a transition metal heterostructure.

[0107] Figure 15. Branched MoO synthesized with growth times of (a) 20 min and (b) 60 min. 3-x -WO 3-xTEM image of the nanostructure. Branched MoO grown for 1 hour. 3-x -WO 3-x (c) High-magnification and (d) low-magnification TEM images of the nanostructure. (e) Branched MoO 3-x -WO 3-x TEM image and EDS map image of nanostructure.

[0108] To examine the morphology of branched nanostructures in detail, the inventors synthesized branched MoO 3-X -WO 3-x Transmission electron microscopy (TEM) measurements and energy dispersive spectroscopy (EDS) analysis were performed on the nanostructure (Fig. 15). Branched MoO grown for 20 min 3-X -WO 3-x In nanostructures, MoO 3-X MoO synthesized in a long growth time of 60 min, while the branch has a short length of 5 nm. 3-x The high-magnification and low-magnification TEM images of Figs. 15a to 15d confirmed that the MoO particles had a long length of more than 100 nm. MoO according to growth time 3-x The length growth of the branches is consistent with the SEM image results of Figs. 14a to 14c. Also, branched MoO 3-x -WO 3-x EDS measurements of the heterogeneous nanostructures were performed, and the core of the nanostructure was composed of tungsten oxide, while the branched portions were composed of molybdenum oxide, resulting in branched MoO 3-x -WO 3-x It was confirmed that it was a nanostructure (Fig. 15e).

[0109] Fig. 16. WO 3-x and MoO 3-x Nanowires and branched MoO 3-x -WO 3-x , Raman graphs of MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 nanostructures.

[0110] Raman measurements were performed to confirm the characteristics of the synthesized nanowires and branched nanostructures (Fig. 16). WO measured with a 532 nm laser 2.9 The Raman spectrum of is characterized by peaks at 270 and 326 cm corresponding to the bending vibration of the WOW bond. -1 712 and 808 cm corresponding to the stretching vibration of the WOW bond -1 , showing MoO3 3-x The Raman spectrum of is around 820 and 996 cm -1 It has characteristic Raman peaks corresponding to O-Mo-O and Mo=O stretching vibrations. Branched MoO 3-x -WO 3-x Nanostructures are MoO present on the surface 3-x The Raman peak corresponding to the branch appears strongly. The branched MoTe2-WTe2 nanostructure is B of 1T' MoTe2. g A1 of mode and WTe2 7 161 cm corresponding to the mode -1 It has a Raman peak of MoS2-WS2. MoS2-WS2 has an E of WS2. 1 2g 352 cm corresponding to mode -1 Weak Raman peak of MoS2 and E 1 2g Mode (380 cm -1 ) and A 1g Mode (404 cm -1 ) together, and MoSe2-WSe2 is A of MoSe2 1g 151 cm corresponding to the mode -1 It shows.

[0111] Fig. 17. MoO with branches 3-x -WO 3-x Electrochemical performances of MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 nanostructures and WTe2 nanowires. (a) LSV polarization curves and (b) Tafel curves of branched nanostructures and nanowires.

[0112] Branched MoO synthesized on a conductive carbon cloth substrate 3-x -WO 3-x , MoTe2-WTe2, MoS2-WS2, and MoSe2-WSe2 nanostructures and WTe2 nanowires were evaluated for their catalytic activities (Fig. 17). Electrochemical measurements were performed in a conventional three-electrode cell using a 0.5 M H2SO4 electrolyte. Nanostructured catalysts synthesized on carbon cloth and platinum wires, Ag / AgCl, were used as working, counter, and reference electrodes. Carbon cloth has high electrical conductivity and high physical strength, making it widely used as a support in electrochemical fields. The polarization of the catalysts obtained using linear scanning voltammetry (LSV) was calibrated through the resistance drop (iR drop). The Tafel plot in Fig. 17b was obtained through the LSV curve (η = b log j + a, where η is the overpotential, j is the current density, b is the Tafel slope, and a is the Tafel constant). 10 mA / cm 2 The overpotential of branched MoTe2-WTe2 nanostructured catalyst obtained at a current density of 3-x -WO 3-x The nanostructured catalyst exhibited a Tafel slope of 0.32 V [reversible hydrogen electrode (RHE)], which was lower than that of WTe2 at 0.36 V (Fig. 17a). In addition, the 3D vertically aligned branched MoTe2-WTe2 nanostructure array showed a very low Tafel slope of 40 mV / dec (Fig. 17b). This is much lower than that of branched MoO containing WTe2 nanowires with a Tafel slope of 49 mV / dec. 3-x -WO 3-x , MoS2-WS2 and MoSe2-WSe2 nanostructures are superior catalysts. The branched MoTe2-WTe2 nanostructure exhibits low overpotential and Tafel slope, making it an excellent HER catalyst compared to previously reported transition metal dichalcogenide-based catalysts.

[0113] Fig. 18. MoO with branches 3-x -WO 3-xTransmission scanning electron microscopy (TEM) images and energy dispersive spectroscopy (EDS) mapping results measured to confirm the cross-section of the heterogeneous nanostructure.

[0114] To confirm the structure of branched heterogeneous nanostructures, branched MoO 3-x -WO 3-x Cross-sectional transmission scanning electron microscopy (TEM) measurements and energy dispersive spectroscopy (EDS) mapping analysis were performed (Fig. 18). The nanostructure consists of a core of about 50 nm thick pillars made of W and O elements and branches made of Mo and O elements with a length of more than a micrometer. Through this, the synthesized nanostructure was WO 3-x Center and MoO 3-x MoO composed of branches 3-x -WO 3-x It was confirmed that a heterogeneous nanotree structure was formed.

[0115] Figure 19. (a, b) MoO synthesized over a growth time of 60 minutes. 3-x -WO 3-x Cross-sectional STEM images of (c) low magnification and (d) high magnification TEM images of MoS2-WS2. (e) low magnification and (f) high magnification TEM images of MoSe2-WSe2. (g) low magnification and (h) high magnification TEM images of MoTe2-WTe2.

[0116] Figure 19 is WO 3-x , MoO 3-x -WO 3-x , TEM and scanning transmission electron microscopy (STEM) images of MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 are shown in Fig. 19a and Fig. 19b. MoO 3-x -WO 3-x The cross-sectional TEM image of WO is shown in Fig. 19b. 3-x WO is indicated by a dotted line in the TEM image 3-xThe dark areas represent oxygen vacancies. Figures 19c, 19d, 19e, 19f, 19g, and 19h show low-magnification and high-magnification TEM images of MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2. MoS2 and MoSe2, which correspond to the branches of MoS2-WS2 and MoSe2-WSe2, have lattice spacings of 0.65 nm and 0.66 nm, respectively, which correspond to the (010) plane in the hexagonal structure of the two materials (Figures 19d and 19f). Single-crystal branch MoO 3-x is converted into polycrystalline branched MoS2 and WS2 through the sulfurization or selenization process. On the other hand, MoO 3-x The MoTe2 obtained through the tellurization process has lattice constants of a = 0.631 nm and b = 0.33 nm and high crystallinity (Figs. 19g and 19h).

[0117] Fig. 20. (a) WO 3-x , MoO 3-x , MoO 3-x -WO 3-x , MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 XRD patterns of synthesized WO 3-x Wow MoO 3-x -WO 3-x XPS scans of (b) W 4f, (c) Mo 3d, and (d) O 1s of the synthesized branched MoO 3-x -WO 3-x , XPS scans of (e) Mo 3d, (f) S 2p, (g) Se 3d, (h) Te 3d of MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 nanostructures.

[0118] XRD and XPS measurements were performed to confirm the characteristics of the synthesized nanostructure (Fig. 20). Fig. 20a shows the synthesized WO 3-x , MoO3-x , MoO 3-x -WO 3-x , MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 show XRD patterns. WO 2.9 XRD pattern of nanowires is monoclinic WO 2.9 It shows the crystal structure (JCPDS card no. 05-0386), and the diffraction peaks located at 23.5°, 24.4°, 34.1°, and 48.1° correspond to the (010), (106), (116), and (020) planes, respectively. The strong intensity at 23.4° corresponds to WO 2.9 It shows high crystallinity and anisotropic growth along the (010) direction. Branched MoO 3-x -WO 3-x In the XRD pattern of the nanostructure, WO 2.9Along with the diffraction peaks corresponding to the (021) and (040) planes of orthorhombic MoO3, the diffraction peaks appear at 25.9° and 27.4°, respectively (JCPDS card no. 05-0508). In the branched MoS2-WS2 nanostructures, the peaks appearing at 14°, 33.4°, and 43.5° correspond to the (002), (101), and (006) planes of 2H WS2 (JCPDS card no. 08-0237) and 2H MoS2 (JCPDS card no. 37-1492). Similarly, the peaks appearing at 13.4°, 31.5°, 37.6°, 47.3°, and 55.9° in the XRD pattern of the MoSe2-WSe2 nanostructure with a branched structure correspond to the (002), (100), (103), (105), and (110) planes of 2H WSe2 (JCPDS card no. 06-0080) and 2H MoSe2 (JCPDS card no. 15-0029). The peaks appearing at 12.6°, 29.25°, 32.2°, 38.5°, and 52.6° in the MoTe2-WTe2 nanostructures with branched structures correspond to the (100), (021), (103), and (122) planes of orthorhombic WTe2 (JCPDS card no. 24-1352) and 1T' MoTe2 (JCPDS card no. 71-2157).

[0119] Synthetic WO 3-x , MoO 3-x- WO 3-x XPS measurements were performed to analyze the chemical composition and bonding of the surfaces of MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 (Figs. 20b, 20c, 20d, 20e, 20f, 20g, and 20h). As a result of measuring the branched nanostructures through surface-sensitive XPS analysis, the Mo element located at the branched part of the surface was clearly confirmed, but the W element located at the center of the nanostructure was hardly confirmed. WO in Fig. 20b 2.9 The high-magnification W 4f spectrum of W6+ 38.1 eV (W 4f) corresponding to 5 / 2 ) and 35.8 eV (W 4f 7 / 2 ) and W 5+ 36.5 eV (W 4f) corresponding to 5 / 2 ) and 34.5 eV (W 4f 7 / 2 ) is shown. MoO of Fig. 20c 3-x -WO 3-x The Mo 3d spectrum is Mo 6+ 236.08 eV (Mo 3d 3 / 2 ) and 232.93 eV (Mo 3d 5 / 2 ) and Mo 5+ 234.68 eV (Mo 3d 3 / 2 ) and 231.63 eV (Mo 3d 5 / 2 ) represents WO 3-x W of 5+ Peak and MoO 3-x -WO 3-x Mo of 5+ The peaks represent oxygen vacancies of WO3 and MoO3, respectively. WO 3-x Wow MoO 3-x -WO 3-x The O 1s state of MoO shows a strong peak at the same position of 530.8 eV, along with weak peaks at 532.8 eV and 532.23 eV attributed to oxygen vacancies, respectively (Fig. 20d). 3-x -WO 3-x Compared to the Mo 4f peak of the nanostructures, the Mo 4f peak of the MoS2-WS2, MoSe2-WSe2, and MoTe2-WTe2 nanostructures shifts to lower binding energy, and Mo 4+ 232.83 eV (Mo 4f 5 / 2 ) and 229.68 eV (Mo 4f 7 / 2 ), 232.33 eV (Mo 4f 5 / 2 ) and 229.18 eV (Mo 4f 7 / 2 ), and 231.48 eV (Mo 4f 5 / 2 ) and 228.33 eV (Mo 4f7 / 2 ) appears. In the S 2p spectrum of MoS2-WS2, two strong peaks corresponding to the bonding between Mo or W and S are observed at 163.98 eV (S 2p 1 / 2 ) and 162.73 eV (S 2p 3 / 2 ) appears. In the Se 2p spectrum of MoSe2-WSe2, two slightly broad peaks are observed at 55.68 eV (Se 3d 3 / 2 ) and 54.78 eV (Se 3d 5 / 2 ) appears. In the Te 3d spectrum of MoTe2-WTe2, two strong peaks corresponding to the bonding between Mo or W and Te are observed at 583.28 eV (Te 3d 3 / 2 ) and 572.88 eV (Te 3d 5 / 2 ) appears. In addition, two small peaks corresponding to Te-O located at 587.13 eV and 576.68 eV were also identified.

[0120] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. WO formed on the substrate 3-x Nanowire; and MoO formed on the nanowire 3-x Branch; or WX2 nanowire formed on a substrate; and MoX2 branch formed on the nanowire; Nanowires, or metal chalcogenide structures comprising nanowires and branches: Here, X is tellurium (Te), sulfur (S), or selenium (Se).

2. WO on the substrate by vapor deposition of WO3 precursor 2.9 The first step of growing nanowires; and A second step of exposing the nanowire to a chalcogen environment to replace at least some of the oxygen of the nanowire with a chalcogen; A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

3. In paragraph 2, The above first step is performed through chemical vapor deposition (CVD) method. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

4. In paragraph 2, The chemical vapor deposition in the first step is performed with a gas containing Ar and H2. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

5. In paragraph 2, The chemical vapor deposition of the first step is performed at 1000 to 1200°C and 0.5 to 1 Torr. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

6. In paragraph 5, The chemical vapor deposition of the first step is performed by raising the temperature at 10 to 50°C per minute. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

7. In paragraph 2, WO by vapor deposition of MoO3 precursor 2.9 MoO on nanowires 3-x Further including a branch growth stage that grows a branch; The second step is to expose the nanowire and branch to a chalcogen environment to replace at least some of the oxygen of the nanowire and branch with chalcogen. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

8. In paragraph 7, The above branch growth step is performed through chemical vapor deposition (CVD) method. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

9. In paragraph 8, The chemical vapor deposition of the above branch growth step is performed with a gas containing Ar and H2. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

10. In paragraph 8, The chemical vapor deposition of the above branch growth step is performed at 500 to 700°C and 0.5 to 1 Torr. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

11. In paragraph 10, The chemical vapor deposition of the above branch growth step is performed by increasing the temperature at 30 to 50°C per minute. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

12. In paragraph 2, The above chalcogen comprises one or more elements selected from the group consisting of Te, S and Se. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

13. In paragraph 2, The above substrate comprises carbon cloth, A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

14. In paragraph 13, The above substrate is formed with a gold (Au) catalyst on a carbon cloth. A method for manufacturing a nanowire or a metal chalcogenide structure comprising a nanowire and a branch.

15. Manufactured by a method for manufacturing a nanowire according to Article 7, or a metal chalcogenide structure including a nanowire and a branch, WO formed on the substrate 3-x Nanowire; and MoO formed on the nanowire 3-x Branch; or WX2 nanowire formed on a substrate; and MoX2 branch formed on the nanowire; Nanowires, or metal chalcogenide structures comprising nanowires and branches: Here, X is tellurium (Te), sulfur (S), or selenium (Se).

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