Two-dimensional platinum nanodendrite sheet and method for manufacturing the same

Abstract

A two-dimensional platinum (Pt) nanodendrite sheet is disclosed, comprising a plurality of platinum nanocrystalline domains interconnected to form a continuous and porous metallic structure. The nanodendrite sheet exhibits a highly branched morphology with an average thickness ranging from 1.0 nm to 10.0 nm. The sheet is further characterized by its large-scale structural integrity, having a largest planar area of 1.0 cm2 or greater. These nanocrystalline domains are distributed uniformly throughout the two-dimensional plane to provide a high surface-area-to-volume ratio, which is suitable for various electrochemical and catalytic applications requiring high-performance efficiency and structural stability.

Description

DETAILED DESCRIPTION OF THE INVENTIONTechnical Field

[0001] Embodiments of the present invention relate to a two-dimensional platinum nanodendrite sheet and a method for manufacturing the same, and more specifically, to a two-dimensional platinum nanodendrite sheet having a large planar area and a method for manufacturing the same.Background Art

[0002] Hydrogen energy is attracting worldwide attention as an eco-friendly new and renewable energy source because it has fewer problems with reserves and regional bias, is easy to store, and produces minimal pollution when used as an energy source. Alkaline water electrolysis combined with renewable energy is spotlighted as a simple technology for producing hydrogen for end-use and energy storage purposes, and the most important factor in improving the efficiency of alkaline water electrolysis is to secure high-activity water electrolysis catalyst manufacturing technology.

[0003] Platinum (Pt)-based catalysts are widely used as efficient catalysts for water electrolysis because the alkaline hydrogen evolution reaction (HER) proceeds through surface hybridization of metal-hydroxides. However, in the case of conventional Pt catalysts, the morphology and size of Pt particles are non-uniform on a nanometer (nm) scale, and the interface structure is not optimized, resulting in low Pt catalyst efficiency and unsuitability for stable long-term use.

[0004] In order to solve the above problems, research on two-dimensional (2D) platinum nanostructures is being actively conducted, but there are still difficulties in expanding the structure beyond several hundred nanometers (nm), and unavoidable agglomeration phenomena during subsequent deposition processes cause performance degradation and limit practical application on large surfaces of centimeter (cm) scale.SUMMARY OF INVENTIONTechnical Problem

[0005] An embodiment of the present invention is to provide a two-dimensional platinum (Pt) nanodendrite sheet having a centimeter (cm)-scale planar area and a method for manufacturing the same.Technical Solution

[0006] A two-dimensional platinum nanodendrite sheet according to an embodiment of the present invention may have an average thickness from 1.0 nm to 10.0 nm and a largest planar area of 1.0 cm2 or greater.

[0007] The two-dimensional platinum nanodendrite may be composed of platinum (Pt) nanocrystalline domains having an average diameter from 1 nm to 5 nm.

[0008] The two-dimensional platinum nanodendrite sheet may be formed by a plurality of platinum (Pt) nanocrystalline domains that are laterally and continuously connected to form a dendritic structure.

[0009] The nanodendrite sheet may include pores having an average diameter from 2 nm to 5 nm in the largest planar surface.

[0010] A method for manufacturing a two-dimensional platinum nanodendrite sheet according to another embodiment of the present invention comprises: forming an LDH-coated substrate by coating LDH nanosheets on an oxide-coated active substrate to obtain a flat LDH coating layer; and reacting the LDH-coated substrate with a platinum precursor solution and a reducing agent to obtain a substrate on which a two-dimensional platinum (Pt) nanodendrite sheet layer is formed.

[0011] The method may further comprise: after performing the step of reacting the LDH-coated substrate with the platinum precursor solution and the reducing agent to obtain the substrate on which the two-dimensional platinum (Pt) nanodendrite sheet layer is formed, obtaining a composite-layer substrate by forming an auxiliary layer on the two-dimensional platinum nanodendrite sheet layer; removing the active substrate from the composite-layer substrate to form a two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon; loading the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon onto a target substrate; and removing the auxiliary layer from the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon.

[0012] The step of loading the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon onto the target substrate may comprise transferring the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon onto a transfer substrate.

[0013] The step of removing the active substrate from the composite-layer substrate to form the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon may comprise etching the oxide film coated on the active substrate to separate the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon.

[0014] In the step of forming the LDH-coated substrate by spin-coating LDH nanosheets on the active substrate to obtain a flat LDH coating layer, the LDH coating layer may have a thickness from 1 nm to 10 nm.

[0015] In the step of forming the LDH-coated substrate by spin-coating LDH nanosheets on the active substrate to obtain a flat LDH coating layer, the LDH-coated substrate may have a root mean square surface roughness (Rq) of 3 nm or less.

[0016] In the step of reacting the LDH-coated substrate with the platinum (Pt) precursor solution and the reducing agent to obtain the substrate on which the two-dimensional platinum (Pt) nanodendrite sheet layer is formed, the reducing agent may comprise one or more selected from ascorbic acid (AA), hydroquinone, and hydrazine.

[0017] A hydrogen-evolution electrode of the present invention may comprise the two-dimensional platinum nanodendrite sheet according to another embodiment.Advantageous Effects

[0018] The two-dimensional platinum (Pt) nanodendrite sheet according to embodiments of the present invention is formed in a freestanding structure having a large planar area while being of a nanometer-scale thickness, thereby having effects of improving electrochemical catalytic activity and enhancing long-term stability.BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a schematic diagram illustrating a method for manufacturing a two-dimensional platinum (Pt) nanodendrite sheet according to an embodiment of the present invention.

[0020] FIG. 2 illustrates a structural conceptual diagram (i), AFM / SEM analysis results (ii) of surface morphology, and TEM analysis results (iii) in the manufacturing process of a two-dimensional platinum (Pt) nanodendrite sheet according to Example 1.

[0021] FIG. 3 illustrates a structural conceptual diagram (i), AFM / SEM analysis results (ii) of surface morphology, and TEM analysis results (iii) in the manufacturing process of a two-dimensional platinum (Pt) nanodendrite sheet according to Comparative Example 1.

[0022] FIG. 4 illustrates a structural conceptual diagram (i), AFM / SEM analysis results (ii) of surface morphology, and TEM analysis results (iii) in the manufacturing process of a two-dimensional platinum (Pt) nanodendrite sheet according to Comparative Example 2.

[0023] FIG. 5 illustrates step-by-step actual photographs in the process of manufacturing a two-dimensional platinum (Pt) nanodendrite sheet in Example 1.

[0024] FIGS. 6a, 6b, and 6c illustrate TEM, SAED, and AFM analysis results of structural characteristics of a two-dimensional platinum (Pt) nanodendrite sheet according to Example 1.

[0025] FIG. 7 illustrates HAADF-STEM analysis results for a platinum (Pt) nanodendrite sheet according to Example 1.

[0026] FIG. 8 illustrates XRD analysis results of a two-dimensional platinum (Pt) nanodendrite sheet obtained by using glass as a transfer substrate instead of PET in Example 1.

[0027] FIG. 9 illustrates FT-IR analysis results of a two-dimensional platinum (Pt) nanodendrite sheet obtained by using glass as a transfer substrate instead of PET in Example 1.

[0028] FIG. 10 is a polarization curve comparing and evaluating the electrochemical performance of hydrogen evolution reaction (HER).

[0029] FIG. 11 illustrates electrochemical stability and durability evaluation results of hydrogen evolution reaction (HER).

[0030] FIG. 12 illustrates performance quantitative analysis results of hydrogen evolution reaction (HER).DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

[0031] Terms such as “first,”“second,” and “third” are used herein to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. The meaning of “comprising” used in the specification specifies a specific characteristic, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0033] When a part is referred to as being “on” or “above” another part, it may be directly on or above the other part, or other parts may be accompanied therebetween. In contrast, when a part is referred to as being “directly on” another part, no other part is interposed therebetween.

[0034] Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are further interpreted as having meanings consistent with the related technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined.

[0035] In addition, unless otherwise specified, “%” means “weight %”.

[0036] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereto; rather, the present invention is defined only by the scope of the claims to be described later.

[0037] A two-dimensional platinum (Pt) nanodendrite sheet according to an embodiment of the present invention may have an average thickness from 1.0 nm to 10.0 nm and a largest planar area of 1.0 cm2 or greater.

[0038] The two-dimensional platinum (Pt) nanodendrite sheet may have an average thickness from 1.0 nm to 10.0 nm, and specifically 3 nm to 7 nm, 4 nm to 7 nm, or 5 nm to 7 nm.

[0039] When the thickness of the two-dimensional platinum (Pt) nanodendrite sheet satisfies the above range, it possesses high mechanical flexibility and surface continuity, and can be transferred onto various substrates to improve its utility as a catalyst. When the average thickness is less than the above range, mechanical instability increases, and when the average thickness exceeds the above range, the electrochemical active area decreases, which may cause a problem of performance degradation.

[0040] The largest planar area of the two-dimensional platinum (Pt) nanodendrite sheet may be 1.0 cm2 or greater, and specifically 1.0 cm2 to 100 cm2.

[0041] In the present invention, since the largest planar area of the two-dimensional platinum (Pt) nanodendrite sheet satisfies the above range, it is possible to realize a platinum catalyst layer for large-area electrode coating.

[0042] Conventional Pt nanosheets have had an area of several hundred nm to several mm2 or less due to agglomeration phenomena or growth area limitations during synthesis, which has acted as a factor hindering practical application as actual fuel cell electrodes or water electrolysis catalysts. In contrast, the present invention has an advantage in that a continuous Pt sheet without defects is grown and transferred over a large area in units of cm2 through a growth process based on a flat LDH interfacial template and a surface transfer technology to be described later, thereby providing a single catalyst layer that can be evenly coated even on a large-area substrate.

[0043] The two-dimensional platinum (Pt) nanodendrite sheet may include hexagonal planar-shaped two-dimensional platinum (Pt) units. The planar diameter of the hexagonal planar-shaped units may range from 150 nm to 350 nm, and specifically 200 nm to 300 nm.

[0044] In the present invention, the planar diameter of the hexagonal planar-shaped units may be calculated as an average value of the length of the longest major axis passing through the center of the hexagonal planar-shaped unit and the diameter passing through the center of the hexagonal planar-shaped unit and perpendicular to the major axis.

[0045] If the planar diameter of the units is less than the above numerical range, the connectivity between the units may be insufficient, causing the entire sheet to break, and if it exceeds the above numerical range, uniformity within the structure may decrease, resulting in a problem of degraded catalytic performance.

[0046] The hexagonal planar-shaped two-dimensional platinum (Pt) units are composed of platinum (Pt) nanocrystalline domains having an average diameter of 1 nm to 5 nm, and the nanocrystalline domains may be laterally connected to each other to form a dendritic structure. Since this structure continuously provides electron transfer paths between crystalline domains, the conductivity of the entire sheet is maintained excellently. At the same time, pores are naturally formed by the gaps between particles, serving as channels through which reactants and products can easily diffuse into the interior.

[0047] The average diameter of the platinum (Pt) nanocrystalline domains may be 2 nm to 4 nm, and they are gradually formed by the action of a reducing agent in the manufacturing process described later, and then connected in a branching manner according to the self-catalytic growth mechanism of the Pt metal itself. Accordingly, not only the connectivity between units but also the location and size of pore formation can be uniformly controlled, so that the structural integrity and electrochemical characteristics of the entire Pt sheet can be improved.

[0048] The nanodendrite sheet may include pores having an average diameter from 2 nm to 5 nm in the largest planar surface. The pores are naturally generated in the gaps between branches formed as the Pt nanocrystalline domains grow in a dendritic manner. In the process where Pt nanocrystalline domains with an average diameter of about 2 nm to 5 nm are laterally connected to each other, micropores may be generated therebetween because complete filling is not achieved.

[0049] Since the nanodendrite sheet includes the pores, there is an advantage in that, when the nanodendrite sheet is applied as a catalyst, ion diffusivity is improved and electron transfer paths are developed, thereby maximizing catalytic performance. If the average diameter of the pores is less than the above numerical range, reactant diffusion may be limited and accessibility to internal active sites may be reduced. If the average diameter of the pores exceeds the above numerical range, the mechanical stability of the nanodendrite sheet may be weakened, and structural discontinuity hindering electron flow may increase, resulting in a problem of degraded catalytic performance.

[0050] If the pore area ratio of the nanodendrite sheet is less than the above numerical range, the ECSA value of the catalyst decreases, and there is a problem that the efficiency as a catalyst sharply decreases, limiting performance compared to the amount of expensive Pt used. If the pore area ratio exceeds the above numerical range, the continuity of the sheet is broken due to excessive pores, and not only does the conductivity sharply decrease, but the possibility of physical damage during transfer also increases, resulting in a problem of degraded catalyst stability.

[0051] According to another embodiment of the present invention, a hydrogen-evolution electrode comprising the two-dimensional platinum nanodendrite sheet according to the present invention is provided. In the hydrogen-evolution electrode, the two-dimensional platinum nanodendrite sheet is applied as a catalyst, thereby improving ion diffusivity and developing electron transfer paths to maximize catalytic performance. Therefore, the hydrogen-evolution electrode comprising the two-dimensional platinum nanodendrite sheet can exhibit excellent hydrogen evolution reaction (HER) performance.

[0052] A method for manufacturing a two-dimensional platinum (Pt) nanodendrite sheet according to another embodiment of the present invention is provided.

[0053] FIG. 1 is a schematic diagram illustrating a method for manufacturing a two-dimensional platinum (Pt) nanodendrite sheet according to an embodiment of the present invention.

[0054] Hereinafter, a method for manufacturing a two-dimensional platinum (Pt) nanodendrite sheet according to an embodiment of the present invention will be described with reference to FIG. 1.

[0055] A method for manufacturing a two-dimensional platinum (Pt) nanodendrite sheet according to an embodiment of the present invention may comprise: forming an LDH-coated substrate by coating LDH nanosheets on an oxide-coated active substrate to obtain a flat LDH coating layer; reacting the LDH-coated substrate with a platinum (Pt) precursor solution and a reducing agent to obtain a substrate on which a two-dimensional platinum (Pt) nanodendrite sheet layer is formed; and separating the two-dimensional platinum (Pt) nanodendrite sheet layer from the active substrate to obtain a two-dimensional platinum (Pt) nanodendrite sheet.

[0056] First, a step of forming an LDH-coated substrate by coating LDH nanosheets on an oxide-coated active substrate to obtain a flat LDH coating layer is performed.

[0057] As the active substrate, for example, a Si wafer substrate may be used, and a SiOx oxide film having a thickness of about 450 nm to 550 nm may be coated on the surface thereof.

[0058] In the present invention, by using the oxide-coated active substrate, the alignment and interfacial adhesion of LDH plates can be improved, leading to the formation of a continuous coating layer with fewer defects.

[0059] The LDH (Layered Double Hydroxide) nanosheets have a single-crystalline slab structure composed of Ni and Co-based double hydroxides, and mainly exhibit a plate-like structure with a planar size of about 260±30 nm and a thickness of about 1 nm. The LDH nanosheets are prepared as a colloidal solution dispersed in ethanol or a mixed solvent (e.g., ethanol:water=9:1). The concentration of the LDH colloidal solution may be 1 mg / mL to 40 mg / mL, specifically 5 mg / mL to 30 mg / mL, 10 mg / mL to 30 mg / mL, or 15 mg / mL to 20 mg / mL. The high-concentration LDH colloidal solution is applied to the oxide film surface of the oxide-coated active substrate by a spin coating method. Spin coating is performed, for example, at a rotation speed of 4000 rpm to 7000 rpm, specifically 5000 rpm to 6500 rpm, for 30 seconds to 120 seconds, specifically 40 seconds to 100 seconds or 50 seconds to 70 seconds, thereby inducing LDH particles to be arranged in the form of a uniform and continuous monolayer or a nano-scale thick thin film over the entire surface of the substrate.

[0060] By spin-coating the high-concentration LDH colloidal solution as described above, the entire area can be uniformly coated without individual LDH plates being separated into island shapes.

[0061] In an embodiment of the present invention, the thickness of the LDH coating layer may be 1 nm to 10 nm. When the thickness of the LDH coating layer satisfies the above range, Pt2+ ions are selectively adsorbed on the surface, and the reduction reaction is induced to develop in the planar direction, so that Pt grows horizontally rather than vertically to form a large-area sheet.

[0062] If the thickness of the LDH coating layer is less than the above numerical range, it is difficult to form a continuous LDH coating layer, and as a result, there is a problem that it is difficult to manufacture a large-area two-dimensional platinum (Pt) nanodendrite sheet. If the thickness of the LDH coating layer exceeds the above numerical range, the horizontal growth directionality of Pt is collapsed, making it difficult to manufacture a flat and uniform large-area two-dimensional platinum (Pt) nanodendrite sheet.

[0063] Thereafter, the solvent is dried to form a flat and closely adhered LDH nanosheet coating layer (f-LDH layer) on the surface of the active substrate. As a result of AFM analysis, the LDH coating layer may have a root mean square roughness (Rq) of 3.0 nm or less, specifically 2.0 nm or less, or 1.15 nm or less.

[0064] This provides a foundation for defect-free horizontal expansion during subsequent platinum (Pt) growth. The flat LDH coating layer serves as a support on which a Pt precursor to be described later is selectively diffused and reduced, and provides conditions for Pt to grow along the LDH plates to form a two-dimensional sheet based on hexagonal units. In particular, as the height difference between LDHs is smaller and defects are fewer, Pt branches can grow smoothly connected to neighboring LDHs, which is advantageous for forming a cm2-sized continuous sheet.

[0065] Subsequently, a step of reacting the LDH-coated substrate with a platinum (Pt) precursor solution and a reducing agent to obtain a substrate on which a two-dimensional platinum (Pt) nanodendrite sheet layer is formed is performed.

[0066] According to an embodiment of the present invention, the LDH-coated substrate formed above is utilized as a reaction platform for growing a platinum (Pt) nanodendrite structure. Specifically, by contacting the LDH-coated substrate with a reaction mixture containing a platinum precursor solution and a reducing agent, a two-dimensional platinum (Pt) nanodendrite sheet layer is selectively grown on the surface of the LDH coating layer.

[0067] First, a platinum salt is used as the platinum precursor, and this is dissolved in deionized water at a concentration of 0.5 mM to 2.0 mM, specifically 1.0 mM to 1.5 mM, to prepare a platinum ion aqueous solution. The aqueous solution is introduced into a reaction vessel containing the LDH-coated substrate. At this time, the aqueous solution is introduced so that the LDH-coated substrate is sufficiently submerged, and it may be left at room temperature for 10 minutes or more.

[0068] In this process, platinum ions are selectively adsorbed through electrostatic or coordination bonding with hydroxyl groups (—OH), metal centers (MW), or edge sites on the LDH surface, and act as initial nucleation sites for subsequent reduction reactions.

[0069] Then, a reducing agent and an interfacial stabilizer are sequentially introduced to induce the growth of a two-dimensional dendritic structure of platinum (Pt).

[0070] By reacting the reaction mixture to which the reducing agent and interfacial stabilizer are added at a temperature of 40° C. or higher, specifically 40° C. to 90° C., 50° C. to 80° C., or 60° C. to 80° C., for 10 minutes or more, specifically 10 minutes to 60 minutes, platinum ions are selectively reduced on the LDH surface, Pt grains are laterally connected to grow into a dendritic structure, and a two-dimensional platinum nanodendrite sheet layer continuously expanded along the LDH interface can be formed.

[0071] The reducing agent may include one or more selected from L(+)-ascorbic acid, hydroquinone, and hydrazine. Specifically, an aqueous solution prepared at a concentration of 1 mM to 10 mM, 4 mM to 9 mM, or 6 mM to 8 mM using the reducing agent is added to the platinum precursor solution containing the substrate. The reducing agent is an eco-friendly reducing agent capable of reducing Pt2+ to Pt under mild conditions, and uniform and refined Pt growth is possible through a slowly progressing reduction reaction. The reaction mixture to which both the reducing agent and the Pt precursor are added is then placed in an oil bath set at 50° C. or higher, specifically 50° C. to 100° C. or 60° C. to 80° C., and subjected to a heating reaction while being maintained for 10 minutes or more, specifically 10 minutes to 60 minutes or 20 minutes to 40 minutes. Heating at the above temperature and time provides favorable thermodynamic conditions for promoting the reduction reaction of the reducing agent and allowing Pt grains to diffuse along the LDH surface and grow continuously.

[0072] As the reaction progresses, Pt ions are selectively reduced to Pt on the LDH surface, nucleation starts around the edge sites, and then grains are laterally connected to form a continuous nanobranch structure. These branches are intertwined and connected to eventually grow into a platinum nanodendrite sheet layer (den-2DPtwaf) having a two-dimensionally horizontally expanded structure.

[0073] After completion of the reaction, the substrate on which the two-dimensional platinum (Pt) nanodendrite sheet layer is formed is separately isolated, washed one or more times with deionized water and ethanol, and then dried, thereby removing reaction residues from the substrate surface and securing structural stability of the Pt sheet layer. Through the washing and drying, excellent quality of the finally manufactured two-dimensional platinum (Pt) nanodendrite sheet can be secured.

[0074] Subsequently, a step of separating the two-dimensional platinum (Pt) nanodendrite sheet layer from the active substrate to obtain a two-dimensional platinum (Pt) nanodendrite sheet is performed.

[0075] An embodiment of the present invention includes a step of separating the two-dimensional platinum (Pt) nanodendrite sheet layer from the active substrate to obtain a two-dimensional platinum (Pt) nanodendrite sheet.

[0076] In addition, after performing the step of reacting the LDH-coated substrate with the platinum precursor solution and the reducing agent to obtain the substrate on which the two-dimensional platinum (Pt) nanodendrite sheet layer is formed, the method may further comprise: forming a composite-layer substrate by forming an auxiliary layer on the two-dimensional platinum (Pt) nanodendrite sheet layer; removing the active substrate from the composite-layer substrate to form a two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon; loading the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon onto a target substrate; and removing the auxiliary layer from the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon.

[0077] The step of loading the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon onto the target substrate may be a step of transferring the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon onto a transfer substrate.

[0078] In the step of forming the composite-layer substrate by forming the auxiliary layer on the two-dimensional platinum (Pt) nanodendrite sheet layer, the auxiliary layer functions as a transfer support layer in a subsequent transfer step.

[0079] Specifically, the auxiliary layer may be uniformly formed by spin-coating an auxiliary layer solution containing one or more selected from PMMA (poly(methyl methacrylate)), polystyrene (PS), polycarbonate (PC), polypropylene carbonate (PPC), and polyvinyl alcohol (PVA). Here, spin coating is performed by rotating at a rotation speed of 2000 rpm or higher, specifically 3000 rpm to 5000 rpm, for 30 seconds or more, specifically 30 seconds to 120 seconds, to form a thin single thin film on the surface of the two-dimensional platinum (Pt) nanodendrite sheet layer, thereby manufacturing a composite-layer substrate.

[0080] Then, thermal drying is performed at a temperature of 100° C. or higher for about 30 minutes to evaporate the solvent and form a protective layer with enhanced adhesion to the two-dimensional platinum (Pt) nanodendrite sheet layer.

[0081] The auxiliary layer solution is used by dissolving one or more selected from PMMA (poly(methyl methacrylate)), polystyrene (PS), polycarbonate (PC), polypropylene carbonate (PPC), and polyvinyl alcohol (PVA) in an organic solvent such as chlorobenzene, chloroform, or toluene, and a solution prepared at a concentration of 50 mg / mL to 100 mg / mL is used.

[0082] By forming the auxiliary layer in the present invention, it is possible to separate the two-dimensional Pt sheet without structural collapse in a state where it cannot be maintained alone.

[0083] Subsequently, the step of removing the active substrate from the composite-layer substrate to form the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon may be to separate the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon by etching the oxide film coated on the active substrate by immersing the composite-layer substrate in an etching solution. Specifically, the oxide film and the LDH support layer coated on the active substrate are removed, and as a result, the two-dimensional platinum (Pt) nanodendrite sheet film in a state where the auxiliary layer is attached is separated.

[0084] In the present invention, the etching solution may be an acidic aqueous solution or a basic aqueous solution, and specifically, an HF aqueous solution at a concentration of 1 wt % or more, specifically an aqueous solution at a concentration of 1 wt % to 10 wt %, or a 0.1 M alkali hydroxide aqueous solution, or a 0.1 M to 5 M alkali hydroxide aqueous solution.

[0085] In the present invention, by using the etching solution, the LDH support layer and the active substrate can be separated without damaging the two-dimensional platinum (Pt) nanodendrite sheet.

[0086] The separated two-dimensional platinum (Pt) nanodendrite sheet film with the auxiliary layer attached thereto may be used in a subsequent process after removing impurities through one or more water washes.

[0087] The separated two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon is moved onto a desired transfer substrate, and finally, a transfer process for moving the Pt sheet to the target substrate is performed.

[0088] Examples of the transfer substrate include, but are not limited to, slide glass, FTO glass, carbon paper, Ti felt, Cu foil, ITO or FTO electrode, polyimide (PI), PET film, Si wafer, and the like.

[0089] A transfer film can be formed by placing the two-dimensional platinum (Pt) nanodendrite sheet film with the auxiliary layer attached thereto in a water bath and transferring it to a transfer substrate by a wet transfer method. Specifically, the Pt sheet can be attached to the substrate by pre-positioning the transfer substrate at the bottom of the water bath and slowly lifting the transfer substrate while the film is spread on the water surface. Alternatively, transfer is possible by spreading the film on the water surface and then immersing the transfer substrate from top to bottom to make contact.

[0090] In the present invention, the direction or method in which the transfer substrate and the film contact is not limited, and any method is applicable as long as the two-dimensional platinum (Pt) nanodendrite sheet layer effectively faces and is transferred to the transfer substrate.

[0091] The transfer film obtained through the transfer may increase adhesion between sheet layers through drying. Drying may be performed by natural drying or at a temperature of 40° C. to 60° C. for a predetermined time.

[0092] In addition, air bubbles or wrinkles can be removed by lightly pressing with a roller or a rubber blade.

[0093] Through the transfer process, there is an advantage in that a large area can be maintained without damage to the two-dimensional platinum (Pt) nanodendrite sheet.

[0094] Then, a step of removing the auxiliary layer of the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon is performed.

[0095] Specifically, it is performed by selectively dissolving the auxiliary layer by immersing the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon in a solution.

[0096] The solution may include one or more selected from deionized water or organic solvents soluble in PMMA, such as chloroform and NMP (N-methylpyrrolidone), in addition to acetone, and the treatment can be performed by heating to room temperature or a predetermined temperature.

[0097] By removing the auxiliary layer, a transfer substrate in which only the two-dimensional platinum (Pt) nanodendrite sheet remains is formed, which has an advantage in that the two-dimensional platinum (Pt) nanodendrite sheet can be manufactured without damage while maintaining a large area.

[0098] The transfer substrate in which only the two-dimensional platinum (Pt) nanodendrite sheet remains is washed one or more times with deionized water to remove residues, and a freestanding two-dimensional platinum (Pt) nanodendrite sheet is obtained on the transfer substrate.

[0099] Hereinafter, Examples and Comparative Examples of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereto; rather, the present invention is defined only by the scope of the claims to be described later.Example 1(1) Manufacture of LDH-Coated Substrate (f-LDH / Si)(Preparation of Active Substrate)

[0100] An active substrate having a thin SiOx oxide film formed on the surface of a Si wafer substrate (standard area: 1 cm×1 cm) was prepared. The active substrate was ultrasonically cleaned for 5 minutes each in the order of acetone, ethanol, and deionized water to completely clean the surface, and then dried.(Preparation of LDH Dispersion)

[0101] A 10.0 mL aqueous solution (concentration=0.32 M) containing a mixture of Ni(NO3)2·6H2O and Co(NO3)3·6H2O in a 3:1 molar ratio, 10.0 mL SDS (0.58 M), and 20.0 mL HMT (0.36 M) were mixed at room temperature. Then, the entire mixture was dissolved in 40 mL Milli-Q water (18 mΩ), transferred to a Teflon-lined stainless-steel autoclave, and heat-treated in an oven preheated to 110° C. for 24 hours. The precipitate generated after the reaction, i.e., (DS)NiCo-LDH, was collected by centrifugation, repeatedly washed with deionized water and ethanol, and then dried in air at a temperature of 60° C. to obtain (DS)NiCo-LDH powder. Subsequently, the obtained (DS)NiCo-LDH powder was mixed with formamide (1 mg / mL) to exfoliate the DS host layer, and the resulting suspension was heated at 40° C. for 24 hours without stirring. Then, the suspension was centrifuged at 2000 rpm, and the supernatant was repeatedly washed with ethanol and deionized water to finally maintain it in the form of monolayer NiCo-LDH dispersed in an aqueous solution. At this time, the thickness of the monolayer NiCo-LDH is about 1 nm, and the average planar size is 262±28 nm.(Formation of LDH Coating Layer)

[0102] The NiCo-LDH was redispersed in ethanol to prepare an SL-LDH ethanol suspension with a concentration of 20 mg / mL. 0.01 mL of the suspension was spin-coated on the SiOx / Si substrate prepared above at 6000 rpm for 60 seconds to form a flat LDH coating layer (f-LDH layer) on the SiOx oxide film surface of the SiOx / Si substrate. As the solvent evaporated naturally, SL-LDH was uniformly aligned, and a 1 nm coating layer covering the entire substrate was formed, and it was completely dried at room temperature to form an LDH coating layer.(2) Growth of Pt Nanodendrite Sheet (den-2DPtwaf)

[0103] The f-LDH / Si substrate (area: 1.0 cm2) manufactured above was introduced into a reaction vessel containing a Na2PtCl4·xH2O platinum precursor solution (1.25 mM, 2.0 mL), and immersed at room temperature for 30 minutes to adsorb platinum ions on the LDH surface. Thereafter, an ascorbic acid (6.7 mM, 1.0 mL) solution as a reducing agent and PVP (molecular weight about 55,000, 45 mg / mL, 1.0 mL) serving as an interfacial stabilizer were quickly added to form a reaction mixture.

[0104] The reaction mixture was maintained at a pH of about 3.5, and the reactor was placed in an oil bath at 70° C. and reacted for 30 minutes to allow Pt nanocrystals to grow continuously into a dendritic structure along the LDH surface. After completion of the reaction, the substrate from which the solution was separated and removed was washed with deionized water, washed again with ethanol, and then dried at room temperature. The sample thus prepared was named den-2DPtwaf / f-LDH / Si.(3) PMMA Formation and Substrate Removal

[0105] 0.03 mL of a solution in which PMMA (molecular weight about 996,000) was dissolved in chlorobenzene at a concentration of 80 mg / mL was spin-coated (4000 rpm, 60 seconds) on the surface of the den-2DPtwaf / f-LDH / Si substrate, and thermally dried at 120° C. for 30 minutes to manufacture a den-2DPtwaf / f-LDH / Si substrate having an auxiliary layer formed thereon.

[0106] The den-2DPtwaf / f-LDH / Si substrate having the auxiliary layer formed thereon was immersed in a 5% HF aqueous solution for 1 hour to remove both the sacrificial layer SiOx and the LDH layer. At this time, the Pt sheet protected by PMMA is maintained without damage and remains suspended on the water surface in the form of a PMMA / den-2DPtwaf film. After HF treatment, etching residues were removed by washing with deionized water to form a two-dimensional platinum (Pt) nanodendrite sheet film (PMMA / den-2DPtwaf) having an auxiliary layer formed thereon.(4) Transfer of Pt Sheet and Removal of Auxiliary Layer

[0107] A PET film, which is a substrate for transfer, was ultrasonically cleaned with acetone, ethanol, and deionized water and then dried to form a purified PET film.

[0108] The two-dimensional platinum (Pt) nanodendrite sheet film (PMMA / den-2DPtwaf) having the auxiliary layer formed thereon was suspended in water contained in a reactor, and the suspended PMMA / den-2DPtwaf was transferred by contacting it with the purified PET film using tweezers or a slide glass tool on the water surface, or by lifting the PET film from below the water surface.

[0109] At this time, the PET film was transferred in close face-to-face contact with the two-dimensional platinum (Pt) nanodendrite sheet surface of PMMA / den-2DPtwaf to form a transfer substrate. After transfer, adhesion was improved through natural drying or vacuum drying, and then the dried transfer substrate was immersed in acetone for 15 minutes to remove the PMMA protective layer. The substrate from which the PMMA protective layer was removed was naturally dried to manufacture a freestanding two-dimensional platinum nanodendrite sheet (den-2DPtwaf) PET film.Comparative Example 1

[0110] A freestanding two-dimensional platinum nanodendrite sheet (den-2DPtwaf) PET film was manufactured in the same manner as in Example 1, except that 0.04 mL of an SL-LDH ethanol suspension with a concentration of 50 mg / mL was drop-casted onto a SiOx / Si substrate and then naturally dried to form an LDH coating layer with a thickness of about 8 nm.Comparative Example 2

[0111] A freestanding two-dimensional platinum nanodendrite sheet (den-2DPtwaf) PET film was manufactured in the same manner as in Example 1, except that an FL-LDH (multilayer NiCo-LDH) ethanol suspension with a concentration of 40 mg / mL was spin-coated on a SiOx / Si substrate at 6000 rpm for 60 seconds to form an LDH coating layer having a thickness exceeding 40 nm.Comparative Example 3

[0112] A Pt nanoparticle dispersion (den-2DPtcol) generated by mixing a Pt precursor (H2PtCl6) and a reducing agent (AA, ascorbic acid) through a chemical reduction method in a colloidal phase was recovered and dried without a substrate to form a Pt nanofilm.

[0113] FIG. 2 illustrates a structural conceptual diagram (i), AFM / SEM analysis results (ii) of surface morphology, and TEM analysis results (iii) in the manufacturing process of a two-dimensional platinum (Pt) nanodendrite sheet according to Example 1.

[0114] Referring to (i) to (iii) of FIG. 2, in Example 1, an LDH coating layer having a thickness of about 1 nm was formed, and Pt crystalline domains having an average size of about 3 nm were continuously connected in the horizontal direction on the surface thereof to form a dendritic structure, resulting in the formation of a two-dimensional platinum (Pt) nanodendrite sheet in which Pt crystalline domains were connected without interruption.

[0115] The surface morphology of the Pt nanodendrite sheet of Example 1 was analyzed using an atomic force microscope (AFM), and the analysis was performed in a range of 25.0 μm2 in tapping mode using Bruker Dimension Icon equipment.

[0116] As a result, the sample of Example 1 exhibited a very flat structure with a root mean square roughness (Rq) of 1.15 nm (refer to (ii) of FIG. 2), which means that platinum crystalline domains were uniformly arranged on the monolayer LDH.

[0117] In addition, scanning electron microscopy (SEM) analysis was performed using a HITACHI S-4800 instrument, and it could be confirmed that the platinum crystalline domains were continuously connected in the horizontal direction within the entire sheet plane. These analysis results support that the two-dimensional Pt sheet of the present invention was implemented as a catalyst structure having a high electrochemical surface area (ECSA) and excellent electrical connectivity.

[0118] The two-dimensional platinum (Pt) nanodendrite sheet of Example 1 was analyzed using a transmission electron microscope (TEM) and a high-resolution TEM (HRTEM). The sample was analyzed under an acceleration voltage of 200 kV after placing the transferred sheet on a TEM grid and drying it. As a result, it could be confirmed that a dendritic network structure in which platinum nanocrystalline domains having an average diameter of about 3 nm were continuously connected in the horizontal direction was formed.

[0119] FIG. 3 illustrates a structural conceptual diagram (i), AFM / SEM analysis results (ii) of surface morphology, and TEM analysis results (iii) in the manufacturing process of a two-dimensional platinum (Pt) nanodendrite sheet according to Comparative Example 1.

[0120] Referring to (i) of FIG. 3, it can be confirmed that in Comparative Example 1, the Pt precursor was excessively grown on the LDH coating layer having a thickness of about 8 nm, so that the Pt crystalline domains were not horizontally connected but existed as disconnected 2D-Pt particles. As a result of AFM analysis, the surface roughness (Rq) was measured as 8.14 nm, which means that the surface is not flat and Pt particles are locally agglomerated and distributed. In addition, in the SEM and TEM analysis results, it was observed that Pt particles were not uniformly spread but existed in the form of clusters, and it was a discontinuous structure with low connectivity between particles. Such a structure means that electrical connectivity and active site diffusion effects as a catalyst are degraded, which is disadvantageous for catalytic performance and long-term stability.

[0121] FIG. 4 illustrates a structural conceptual diagram (i), AFM / SEM analysis results (ii) of surface morphology, and TEM analysis results (iii) in the manufacturing process of a two-dimensional platinum (Pt) nanodendrite sheet according to Comparative Example 2.

[0122] Referring to FIG. 4, it was confirmed that Pt crystalline domains grew randomly in the vertical direction to form a three-dimensional stereostructure (3D-Pt). As a result of AFM analysis, the surface roughness (Rq) is very rough and non-uniform at 45.3 nm, and in the SEM image, coating incompleteness was confirmed where Pt particles gathered and existed in the form of clusters in some areas, while the LDH substrate remained exposed in others. In TEM and HRTEM analysis, individual Pt crystalline domains (about 3 nm) were observed, but it can be seen that they did not form a dendritic connection structure and existed as inefficient aggregates.

[0123] FIG. 5 illustrates step-by-step actual photographs in the process of manufacturing a two-dimensional platinum (Pt) nanodendrite sheet in Example 1.

[0124] Referring to FIG. 5, after forming a PMMA auxiliary layer on the surface of the den-2DPtwaf / f-LDH / Si substrate, the SiOx sacrificial layer was etched and separated using an HF solution, and then [PMMA]-den-2DPt_waf was transferred to a PET substrate, and the PMMA was removed by acetone treatment to finally obtain a freestanding two-dimensional Pt sheet (den-2DPt(T)).

[0125] FIG. 6 illustrates TEM, SAED, and AFM analysis results of structural characteristics of a two-dimensional platinum (Pt) nanodendrite sheet according to Example 1.

[0126] FIG. 6a shows that through high-resolution TEM analysis, Pt nanocrystals with a size of about 3 nm form a dendritic network structure uniformly connected in the horizontal direction, and lattice fringes of the Pt(111) crystal plane are clearly observed within the crystalline domains, confirming a highly crystalline fcc structure.

[0127] In the SAED pattern of FIG. 6b, (111), (200), (220), and (311) diffraction rings are identified, indicating that the Pt sheet maintains a polycrystalline face-centered cubic crystal structure.

[0128] In the AFM analysis of FIG. 6c, the thickness of the sheet was measured to be about 5.9 nm, indicating that the Pt nanosheet of the present invention was implemented as a very thin and transparent freestanding film.

[0129] FIG. 7 illustrates HAADF-STEM analysis results for a platinum (Pt) nanodendrite sheet according to Example 1.

[0130] Specifically, FIG. 7 shows the results of HAADF-STEM analysis performed on a two-dimensional platinum (Pt) nanodendrite sheet sample transferred onto a TEM grid. Through the high-angle annular dark-field (HAADF) condition, the gaps and structural clarity between platinum (Pt) branches were visualized as a high-contrast image. The two-dimensional platinum (Pt) nanodendrite sheet sample is in a freestanding transferred state, and Pt nanocrystals form a dendritic branch structure in the horizontal direction, and it was confirmed that gaps of several nanometers exist uniformly between each Pt branch. The gaps play an important role in reactant accessibility (ECSA improvement) in electrochemical reactions and can contribute to spatial separation of Pt active sites and securing diffusion paths.

[0131] FIG. 8 illustrates XRD analysis results of a two-dimensional platinum (Pt) nanodendrite sheet obtained by using glass as a transfer substrate instead of PET in Example 1.

[0132] FIG. 8 shows the results of X-ray diffraction (XRD) analysis performed on the den-2DPt_waf(T) sample transferred onto a glass substrate. In the XRD spectrum, a clear diffraction peak corresponding to the Pt(111) crystal plane is observed around 39.7°, proving that the Pt nanodendrite sheet of the present invention contains highly crystalline Pt particles in a face-centered cubic (fcc) crystal structure.

[0133] FIG. 9 illustrates FT-IR analysis results of a two-dimensional platinum (Pt) nanodendrite sheet obtained by using glass as a transfer substrate instead of PET in Example 1.

[0134] FIG. 9 is a result of comparing FT-IR spectra before the PMMA auxiliary layer was removed (blue, [PMMA]-den-2DPt_waf) and after it was removed (red, den-2DPt_waf(T)) among den-2DPt_waf samples formed on a glass substrate. Referring to FIG. 9, in the sample where PMMA exists, C—H stretching (ν_CH), C═O stretching (ν_C═O), and C—O stretching (ν_C—O) vibration peaks are clearly observed around 2950, 1730, and 1140 cm−1. On the other hand, in the sample after PMMA removal, all these peaks disappeared or decreased significantly, confirming that the PMMA auxiliary layer was completely removed and a pure Pt sheet remained.Evaluation of Hydrogen Evolution Reaction Performance

[0135] The catalytic performance of the hydrogen evolution reaction was evaluated in a standard three-electrode electrochemical cell using an Autolab PGSTAT302N potentiometer. In this experiment, the catalyst was used as a working electrode in a state transferred onto a gas diffusion layer (GDE, 1.0 cm2) based on carbon paper, and an Ag / AgCl (saturated KCl) electrode and a graphite rod were used as a reference electrode and a counter electrode, respectively. The electrolyte was an Ar-saturated 0.5 M H2SO4 aqueous solution, all experiments were performed at room temperature, and the potential was normalized based on a reversible hydrogen electrode (RHE), and 95% iR correction was applied. All measurements were made in a three-electrode system using an Autolab PGSTAT302N potentiometer, and were recorded based on the LSV curve after 95% iR correction.

[0136] FIG. 10 is a polarization curve comparing and evaluating the electrochemical performance of hydrogen evolution reaction (HER).

[0137] In FIG. 10, for den-2DPt_waf and den-2DPt_col, the Pt loading amount is about 12 μg_Pt cm−2, and for Pt black and 20% Pt / C, the Pt loading amount is about 150 μg_Pt cm−2. In addition, for den-2DPt_col, an additional experiment was performed with a Pt loading amount of 150 μg_Pt cm−2. Here, Pt / C refers to a commercially available catalyst in which 2-3 nm Pt NCs (Nanocrystals) are supported on several to dozen nm carbon spheres, and Pt black refers to Pt NCs without carbon in the Pt / C.

[0138] Referring to FIG. 10, when the two-dimensional platinum (Pt) nanodendrite sheet (den-2DPt_waf) of Example 1 was applied, it exhibited a very low overpotential of about 7.8 mV at 20 mA cm−2, confirming superior HER performance even compared to commercial Pt / C. When the Pt nanofilm of Comparative Example 3 was applied, despite the same loading conditions as in Example 1, the electrochemical activity appeared to be low due to the randomly agglomerated structure of Pt particles. In addition, when the Pt nanofilm of Comparative Example 3 was applied at a high loading amount of 150 μg_Pt cm−2, despite the high loading conditions, it was confirmed that the catalyst efficiency was degraded due to particle agglomeration and an increase in surface inactive sites with a higher overpotential compared to Example 1. When a commercial catalyst (a-20% Pt / C (green)) was applied, the performance was lower than that of Example 1.

[0139] FIG. 11 illustrates electrochemical stability and durability evaluation results of hydrogen evolution reaction (HER).

[0140] Referring to FIG. 11, when the two-dimensional platinum (Pt) nanodendrite sheet (den-2DPt_waf) of Example 1 was applied, it was confirmed that it maintained a stable current density for 50 hours, had almost no current change, and exhibited excellent corrosion resistance and stability. On the other hand, when the Pt nanofilm according to Comparative Example 3 or a commercial catalyst (a-20% Pt / C (green)) and Pt black were applied, electrochemical stability and durability were significantly lower.

[0141] FIG. 12 illustrates performance quantitative analysis results of hydrogen evolution reaction (HER).

[0142] Referring to FIG. 12, in all of (i) overpotential, (ii) Tafel slope, (iii) mass activity, and (iv) platinum constant current density normalized values, when the two-dimensional platinum (Pt) nanodendrite sheet (den-2DPt_waf) of Example 1 was applied, performance was superior to other catalysts.

[0143] The present invention is not limited to the above embodiments but can be manufactured in various different forms, and those skilled in the art will be able to understand that it can be implemented in other specific forms without changing the technical idea or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A two-dimensional platinum (Pt) nanodendrite sheet having an average thickness from 1.0 nm to 10.0 nm and a largest planar area of 1.0 cm2 or greater.

2. The two-dimensional platinum nanodendrite sheet of claim 1, wherein the two-dimensional platinum nanodendrite comprises platinum (Pt) nanocrystalline domains having an average diameter from 1 nm to 5 nm.

3. The two-dimensional platinum nanodendrite sheet of claim 1, wherein the two-dimensional platinum nanodendrite sheet is formed by a plurality of platinum (Pt) nanocrystalline domains that are laterally and continuously connected to form a dendritic structure.

4. The two-dimensional platinum nanodendrite sheet of claim 1, wherein the nanodendrite sheet includes pores having an average diameter from 2 nm to 5 nm in the largest planar surface.

5. A method for manufacturing a two-dimensional platinum nanodendrite sheet, comprising:forming an LDH-coated substrate by coating LDH nanosheets on an oxide-coated active substrate to obtain a flat LDH coating layer; andreacting the LDH-coated substrate with a platinum precursor solution and a reducing agent to obtain a substrate on which a two-dimensional platinum (Pt) nanodendrite sheet layer is formed.

6. The method for manufacturing a two-dimensional platinum nanodendrite sheet of claim 5, further comprising:after obtaining the substrate having the two-dimensional platinum (Pt) nanodendrite sheet layer formed thereon by reacting the LDH-coated substrate with the platinum precursor solution and the reducing agent,forming an auxiliary layer on the two-dimensional platinum nanodendrite sheet layer to obtain a composite-layer substrate;removing the active substrate from the composite-layer substrate to form a two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon;loading the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon onto a target substrate; andremoving the auxiliary layer from the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon.

7. The method for manufacturing a two-dimensional platinum nanodendrite sheet of claim 6, wherein the step of loading the two-dimensional platinum nanodendrite sheet film having the auxiliary layer formed thereon onto the target substrate comprises transferring the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon onto a transfer substrate.

8. The method for manufacturing a two-dimensional platinum nanodendrite sheet of claim 5, wherein the step of removing the active substrate from the composite-layer substrate to form a two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon comprises etching the oxide film coated on the active substrate to separate the two-dimensional platinum (Pt) nanodendrite sheet film having the auxiliary layer formed thereon.

9. The method for manufacturing a two-dimensional platinum nanodendrite sheet of claim 5, wherein in the step of forming the LDH-coated substrate by spin-coating LDH nanosheets on the active substrate to obtain a flat LDH coating layer, the LDH coating layer has a thickness from 1 nm to 10 nm.

10. The method for manufacturing a two-dimensional platinum nanodendrite sheet of claim 5, wherein in the step of forming the LDH-coated substrate by spin-coating LDH nanosheets on the active substrate to obtain a flat LDH coating layer, the LDH-coated substrate has a root mean square surface roughness (Rq) of 3 nm or less.

11. The method for manufacturing a two-dimensional platinum nanodendrite sheet of claim 5, wherein in the step of reacting the LDH-coated substrate with the platinum (Pt) precursor solution and the reducing agent to obtain the substrate on which the two-dimensional platinum (Pt) nanodendrite sheet layer is formed, the reducing agent comprises one or more selected from ascorbic acid (AA), hydroquinone, and hydrazine.

12. A hydrogen-evolution electrode comprising the two-dimensional platinum nanodendrite sheet of claim 1.

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