Method for preparing platinum nanocatalyst through dry process, and platinum nanocatalyst prepared using same

Abstract

The present invention relates to a method for preparing a platinum nanocatalyst through a dry process, and a platinum nanocatalyst prepared using same, and, specifically, to a method for preparing a platinum nanocatalyst, and a platinum nanocatalyst prepared using same, the method comprising the steps of: (step 1) mixing a platinum precursor and a support material in a solid state so as to prepare a mixture; and (step 2) heat-treating the mixture under a vacuum or inert atmosphere so as to prepare platinum nanoparticles (platinum nanocatalyst) having a carbon shell. According to the present invention, since the platinum nanoparticles of the present invention have a carbon shell appropriately formed the platinum nanoparticles, the prepared platinum nanoparticles are stably distributed, and thus can prevent aggregation and enable excellent electrochemical activity to be exhibited in an oxygen reduction reaction (ORR). In addition, platinum nanoparticles can be simply prepared in an eco-friendly manner with high productivity by using the method of the present invention, which uses a dry process.

Description

Method for manufacturing platinum nanocatalysts through a dry process and platinum nanocatalysts produced thereby

[0001] The present invention relates to a platinum nanocatalyst used in fuel cells, oxygen reduction reactions (ORR), and other catalytic applications, and a method for manufacturing the same.

[0002] Proton exchange membrane fuel cells (PEMFCs) efficiently generate electricity from hydrogen fuel. PEMFC vehicles, such as the NEXO or Mirai, are already on the market. Furthermore, these fuel cell vehicles can be used as mobile power supplies without pollutant emissions. Autonomous vehicles, which have high power demands, will make fuel cell vehicles more suitable than purely battery-powered vehicles.

[0003] However, PEMFCs still require large quantities of platinum catalysts to accelerate the slow oxygen reduction (ORR) reaction. While platinum catalysts are capable of performing electrochemical reactions quickly and efficiently, withstanding demanding acidic conditions, and possessing heat resistance, platinum is a rare and expensive precious metal. Consequently, as the PEMFC vehicle market grows, the high price and limited supply of platinum can become serious obstacles hindering market expansion. Therefore, there is an urgent need to develop catalysts with higher activity and durability while minimizing the use of platinum.

[0004] Conventionally, wet processes have been primarily used to manufacture catalysts for fuel cells. This method necessarily involves mixing and dispersing platinum precursors, carbon supports, etc., in a specific solvent, followed by filtering and drying the manufactured catalyst. However, this wet process has the following problems:

[0005] 1. The process is complex as it includes mixing and dispersion in a solvent, filtering, and drying steps.

[0006] 2. Mass production is difficult.

[0007] 3. The manufacturing process incurs high costs.

[0008] To solve these problems, it is necessary to develop a simpler catalyst manufacturing method suitable for mass production.

[0009] In this regard, Korean Patent No. 10-1484188 (Registration Date: January 13, 2015) describes a method for manufacturing a platinum catalyst, a platinum catalyst for an oxygen reduction reaction manufactured thereby, and a proton exchange membrane fuel cell containing the same. Specifically, the said patent describes a method for manufacturing a platinum catalyst comprising the steps of: dispersing a carbon support in an aqueous solution of urea to prepare a carbon support dispersion; injecting a platinum salt into the carbon support dispersion to form a platinum hydroxide complex and allowing the platinum hydroxide complex to be supported on the carbon support; and irradiating the platinum hydroxide complex with gamma rays to reduce platinum cations in the platinum hydroxide complex and form platinum clusters, a platinum catalyst for an oxygen reduction reaction manufactured thereby, and a proton exchange membrane fuel cell containing the same.

[0010] However, conventional technology has not taught or implied a method for producing platinum nanoparticles (platinum nanocatalysts) by mixing and heat-treating a platinum precursor and carbon in a dry process. Therefore, there remains a need for a simple and efficient manufacturing method that can replace the existing complex wet process.

[0011] The prior art related to this is as follows.

[0012] Korean Patent Registration No. 2724367 relates to a core-shell catalyst with improved durability and a method for manufacturing the same, comprising the steps of: irradiating a solution containing a reducing solvent, a precious metal precursor, a transition metal precursor, and a carbon support with ultrasound, thereby forming a cavity due to the irradiation of ultrasound and forming transition metal precursor core and precious metal precursor shell particles due to a vapor pressure difference; and nitriding the transition metal precursor core and precious metal precursor shell particles under a gaseous nitrogen source at a temperature of 450 to 550°C and a pressure of 60 to 100 bar, wherein the transition metal may be any one selected from the group consisting of Y, La, Ce, Zn, and Mn.

[0013] Korean Patent Publication No. 2023-0169749 relates to a method for controlling the shape of palladium for an electrode catalyst through concentration control, comprising: a first step of preparing a solution by dispersing a palladium precursor in a solvent; a second step of purging an inert gas into the solution prepared through the first step; a third step of inducing reduction of the palladium precursor in the solution by purging carbon monoxide (CO) gas into the solution obtained through the second step; a fourth step of adding and dispersing a carbon support into the solution obtained through the third step; and a fifth step of manufacturing a nanosheet by filtering and drying the dispersed solution obtained through the fourth step.

[0014] Korean Patent Publication No. 2023-0161557 relates to a palladium-transition metal core-based core-shell electrode catalyst and a method for manufacturing the same, comprising: a first step of preparing a slurry by irradiating a dispersion solution containing a solvent, a platinum precursor, a palladium precursor, a carbon support, and a transition metal precursor with ultrasound; a second step of preparing a solid by filtering the slurry prepared through the first step, followed by washing and drying; and a third step of preparing a core-shell electrode catalyst by heat-treating the solid prepared through the second step in a specific gas atmosphere.

[0015] Korean Patent Registration No. 2496278 relates to a method for controlling the size of core-shell nanoparticles, comprising the steps of: preparing a slurry by irradiating a dispersion containing a reducing solvent, a carbon support, a transition metal precursor, and a precious metal precursor with ultrasound; preparing a solid by filtering the prepared slurry, washing, and drying it; and preparing nanoparticles by heat-treating the dried solid under an N2 atmosphere at a pressure of 1 to 80 bar, a temperature of 450 to 600 ℃, and for 30 minutes to 10 hours, thereby controlling the size of core-shell nanoparticles to have excellent stability (durability) while simultaneously having a small average particle size and excellent dispersion and uniformity, without performing a complex post-treatment process to remove the protective layer used in conventional heat treatment.

[0016] Korean Patent Publication No. 2023-0130846 relates to a method for manufacturing core-shell particles using a divalent platinum precursor and carbon monoxide, comprising: a first step of adding a palladium (Pd) precursor to a solution in which carbon particles are dispersed by ultrasound; a second step of adjusting the pH of the solution from the first step to 10 to 12; a third step of purging the solution from the second step with nitrogen and purging with carbon monoxide to produce a solution containing Pd / C particles adsorbed with carbon monoxide; a fourth step of purging the solution from the third step with nitrogen and adding a divalent platinum precursor; and a fifth step of washing and drying the catalyst particles produced by the fourth step to produce particles in which core-shell particles are formed on carbon.

[0017] Korean Patent Registration No. 2398409 relates to a method for manufacturing core-shell particles using carbon monoxide, comprising the steps of adsorbing carbon monoxide onto a transition metal for the core and reacting the carbon monoxide adsorbed on the surface of the transition metal for the core with a metal precursor for the shell and a solvent to form a core-shell structured particle in which a reduced metal shell layer is formed on the transition metal core. This method enables particle manufacturing through a simple and rapid one-pot reaction, thereby reducing process costs, facilitating scale-up, and allowing for the modification of various types of core and shell metals and the formation of multilayer shell structures.

[0018] Korean Patent Publication No. 2022-0033545 relates to an apparatus and method for manufacturing core-shell particles utilizing carbon monoxide linked to laser ablation. The method comprises the steps of adsorbing carbon monoxide onto a transition metal for the core and reacting the carbon monoxide adsorbed on the surface of the transition metal for the core with a metal precursor for the shell and a solvent to form a core-shell structured particle in which a reduced metal shell layer is formed on the transition metal core. This enables particle manufacturing through a simple and rapid one-pot reaction, thereby reducing process costs, facilitating scale-up, and allowing for the modification of various types of core and shell metals and the formation of multilayer shell structures.

[0019] The objective of the present invention is to solve the problems of the prior art by resolving the issues of non-uniform distribution and aggregation of platinum nanoparticles, and to provide a method for producing a platinum nanocatalyst that is stable, has improved electrochemical activity, is simple and inexpensive, and the platinum nanocatalyst produced thereby.

[0020] Meanwhile, the technical problems to be solved by the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0021] To achieve the above objective,

[0022] One aspect of the present invention provides a method for manufacturing a platinum nanocatalyst through a dry process.

[0023] Specifically, the method for manufacturing the platinum nanocatalyst of the present invention

[0024] A step of preparing a mixture by mixing a platinum precursor and a support material in their solid state (Step 1); and

[0025] The method is characterized by including the step (step 2) of heat-treating the above mixture under vacuum or an inert atmosphere to produce platinum nanoparticles (platinum nanocatalysts) having a carbon shell.

[0026] A preferred embodiment of one aspect of the present invention is characterized in that step 1 involves mixing a platinum precursor and a support material and ball-milling the mixture to produce a mixture.

[0027] A preferred embodiment of one aspect of the present invention is characterized in that, in step 1, the platinum precursor is platinum acetate (Pt(acac)2).

[0028] A preferred embodiment of one aspect of the present invention is characterized in that, in step 2, the inert atmosphere is a nitrogen (N2) atmosphere and the heat treatment is performed at 200 to 800°C.

[0029] A preferred embodiment of one aspect of the present invention is characterized in that, in step 2, the heat treatment temperature is one or more temperatures selected from the group consisting of 200 to 300°C, 300 to 400°C, 400 to 500°C, 500 to 600°C, 600 to 700°C, and 700 to 800°C.

[0030] A preferred embodiment of one aspect of the present invention is characterized in that the heat treatment in step 2 is performed at 400°C.

[0031] A preferred embodiment of one aspect of the present invention is characterized in that the platinum nanoparticles have a size of 1 nm to 6 nm.

[0032] A preferred embodiment of one aspect of the present invention is characterized in that the platinum nanoparticles have a size of 2 nm to 4 nm, and the platinum is partially exposed in the platinum nanoparticles having a carbon shell.

[0033] Another aspect of the present invention provides a platinum nanocatalyst produced by the method of the present invention.

[0034] Another embodiment of another aspect of the present invention is characterized in that the platinum nanoparticles have a size of 1 nm to 6 nm.

[0035] Another embodiment of another aspect of the present invention is characterized in that the platinum nanocatalyst has a size of 2 nm to 4 nm, and the platinum is partially exposed in the platinum nanocatalyst having the carbon shell.

[0036] In addition, another aspect of the present invention is

[0037] It includes a carbon shell confirmed through TGA analysis results,

[0038] (i) Platinum nanoparticles are supported on a support, and

[0039] (ii) The carbon shell includes an amorphous state, and

[0040] (iii) The carbon shell content is 2.60 to 3.40 weight% based on 100 weight% of the platinum nanocatalyst composition, and

[0041] (iv) Provides a platinum nanocatalyst composition characterized in that the burning point of the carbon shell is between 150 and 200°C.

[0042] A preferred embodiment of another aspect of the present invention is characterized in that the platinum nanoparticles have a particle size of 1 to 6 nm, preferably 2 to 4 nm.

[0043] A preferred embodiment of another aspect of the present invention is characterized in that the carbon shell starts in an amorphous state and has a structure that becomes dense and stabilized as the heat treatment temperature increases.

[0044] A preferred embodiment of another aspect of the present invention is characterized in that the platinum nanoparticles are physically protected by a carbon shell during the heat treatment process, thereby preventing aggregation.

[0045] A preferred embodiment of another aspect of the present invention is characterized in that the carbon shell acts as a protective film that improves the electrochemical stability and durability of the catalyst.

[0046] A preferred embodiment of another aspect of the present invention is characterized in that the catalyst composition is used in a fuel cell, an oxygen reduction reaction (ORR), or other electrochemical reaction.

[0047] In addition, another aspect of the present invention is based on ECSA (Electrochemical Surface Area) analysis,

[0048] (i) Platinum nanoparticles are supported on a support, and

[0049] (ii) The exposed ratio of platinum nanoparticles is calculated as the ratio of the measured to the theoretical value of the electrochemical active area (ECSA), and

[0050] (iii) Provides a platinum nanocatalyst composition characterized by the above ratio being 0.563 or higher.

[0051] A preferred embodiment of another aspect of the present invention is characterized in that the platinum nanoparticles are physically protected by a carbon shell during the heat treatment process, thereby preventing aggregation.

[0052] A preferred embodiment of another aspect of the present invention is characterized in that the platinum nanoparticles have a particle size of 1 to 6 nm, preferably 2 to 4 nm.

[0053] A preferred embodiment of another aspect of the present invention is characterized in that the catalyst composition is prepared at a heat treatment temperature in the range of 200 to 500°C.

[0054] A preferred embodiment of another aspect of the present invention is characterized in that the catalyst composition is used in a fuel cell, an oxygen reduction reaction (ORR), or other electrochemical reaction.

[0055]

[0056] According to the present invention, the platinum nanoparticles of the present invention have a carbon shell appropriately formed on them, so that the manufactured platinum nanoparticles are stably distributed to prevent aggregation and can exhibit excellent electrochemical activity in the oxygen reduction reaction (ORR). In addition, by using the method of the present invention through a dry process, platinum nanoparticles can be manufactured simply, environmentally friendly, and with high productivity.

[0057] FIG. 1a is a schematic diagram of a method for manufacturing a platinum nanocatalyst (Pt@C / C) of the present invention, FIG. 1b to 1e are low-magnification TEM images of Pt@C / C_20, Pt@C / C_40, Pt@C / C_60, and Pt@C / C_80, respectively, FIG. 1f to 1i are high-magnification TEM images of Pt@C / C_20, Pt@C / C_40, Pt@C / C_60, and Pt@C / C_80, respectively, and FIG. 1j shows a histogram of the particle size distribution of Pt nanoparticles in a Pt@C / C sample.

[0058] Figure 2 is a TEM image of the platinum nanocatalyst of the present invention prepared in vacuum, N2, and H2 / N2 atmospheres from left to right.

[0059] Figure 3 is a graph showing the temperature profile of the heat treatment process in the method of the present invention.

[0060] Figure 4a is a real-time TEM temperature profile, and Figures 4b to 4e are real-time TEM images of the platinum nanocatalyst (Pt@C / C_20 sample) of the present invention.

[0061] Figure 5 is an XRD and TGA graph of the platinum nanocatalyst of the present invention according to the heat treatment temperature.

[0062] Figure 6 is a TEM image of the platinum nanocatalyst of the present invention according to the heat treatment temperature, the top image is a low-magnification image, and the bottom image is a high-magnification image.

[0063] FIG. 7 is a graph showing the thermal analysis results of ball-milled mixtures (BM-Pt(acac)2 (Comparative Example) and BM-Pt(acac)2 / C sample (Example) ((a) TGA analysis, (b) DSC analysis, (c) TPR analysis)).

[0064] Figure 8 shows the XPS analysis results of samples Pt / C, Pt@C / C_20, Pt@C / C_40, Pt@C / C_60, and Pt@C / C_80.

[0065] Figure 9 is experimental data showing that even when Pt@C / C_40 catalyst is synthesized in a large batch (2 g / batch), the catalyst can be prepared under the same conditions as the existing ones.

[0066] [Correction pursuant to Rule 91 12.03.2026] Figures 10a to 10l are experimental data showing that the catalyst can be produced under the same conditions as the existing ones even when synthesized in a large batch (2 g / batch).

[0067] Figure 11 provides a figure illustrating that the catalytic performance varies depending on the electrochemical data and the shape of the carbon shell according to the heat treatment temperature conditions.

[0068] Figure 12 shows electrochemical data according to heat treatment temperature conditions.

[0069] Figure 13 is a TEM image of the Pt@C / C_20 and Pt@C / C_40 samples, which is experimental data explaining the reason for high durability through the presence of a carbon shell even after durability evaluation.

[0070] Figure 14a is a graph showing the results of Thermogravimetric Analysis (TGA) of Pt@C / C samples according to heat treatment temperature, showing the weight loss of the samples with temperature change, and confirming the thermal stability and decomposition characteristics of the carbon shell.

[0071] Figure 14b is a table comparing the burning point (°C) and carbon shell content (wt%) of Pt@C / C samples according to heat treatment conditions.

[0072] Figure 15a is a table comparing the particle size (nm), theoretical and measured values ​​(m² / g) of the electrochemical active area (ECSA) of the Pt@C / C sample, and the ratio of measured to theoretical values.

[0073] Figure 15b is a graph showing the ratio of the measured to the theoretical value of the electrochemical active area (ECSA) of the Pt@C / C sample according to the heat treatment temperature (°C), showing the results of distinguishing between the usable area (ratio ≥ 0.55) and the unusable area (ratio < 0.55) based on whether the catalyst can be utilized.

[0074] Figure 16a is a step-by-step diagram illustrating the process for calculating the electrochemical active area (ECSA) of a platinum nanocatalyst, showing how to derive the theoretical ECSA through particle radius, surface area, volume, mass, and the total number of platinum surface atoms.

[0075] Figure 16b is a step-by-step diagram illustrating an example of calculating the electrochemical active area (ECSA) of a platinum nanocatalyst with a particle size of 2.59 nm, showing the process of deriving a final ECSA value of 108 m² / g through the calculation of radius, surface area, volume, and mass.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a skilled expert in the art to which this invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0077] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0078] The present invention will be described in detail below.

[0079] One aspect of the present invention provides a method for manufacturing a platinum nanocatalyst through a dry process.

[0080] Specifically, the method for manufacturing the platinum nanocatalyst of the present invention

[0081] A step of preparing a mixture by mixing a platinum precursor and a support material in their solid state (Step 1); and

[0082] The method includes the step (step 2) of heat-treating the above mixture under vacuum or an inert atmosphere to produce platinum nanoparticles (platinum nanocatalysts) having a carbon shell.

[0083] FIG. 1a is a schematic diagram illustrating the manufacturing method of the present invention, which will be explained in detail step by step below.

[0084] Step 1 involves preparing a mixture by mixing the platinum precursor and the support material in their solid state.

[0085] The platinum precursor serves as a source for platinum nanocatalysts, and in the present invention, Pt(acac)2, Pt(CH3)4, Pt(C6H5)4, Pt(CO)4, bis(dibenzylideneacetone) platinum (O), tetrakis(triphenylphosphine) platinum (O), MeCpPtMe3, Pt(acac)2, (H2NCH2CH2NH2)PtCl2, [C6H 10 [NH2]PtCl2, PtCl2, H2Pt(OH)6 can be used, and preferably Pt(acac)2 can be used.

[0086] The support material serves as a support for the platinum nanocatalyst, stably supporting the platinum nanoparticles, providing an active surface area for the catalyst during the reaction process, and facilitating electron transfer. The support materials used in this invention include carbon, oxides, nitrides, carbides, sulfides, etc., and depending on their respective characteristics and roles, they can significantly improve the performance and stability of the platinum nanocatalyst.

[0087] First, carbon-based supports possess high electrical conductivity, a large surface area, and excellent chemical stability, making them widely used as supports for platinum nanocatalysts. Representative examples of carbon-based supports include activated carbon, carbon black, mesoporous carbon, graphene, carbon nanotubes, and carbon fibers. Carbon helps to uniformly disperse platinum nanoparticles, effectively transfers electrons during catalytic reactions, and contributes to maintaining reaction stability.

[0088] Oxide-based supports possess high chemical stability and the ability to enhance catalytic activity in specific reaction environments. Examples of oxide supports that can be utilized include titanium oxide, cerium oxide, aluminum oxide, silicon oxide, and zirconium oxide. Oxide supports enhance the catalytic activity of platinum particles in oxygen reduction reactions (ORR) and other catalytic reactions, and help maintain stability even in high-temperature environments.

[0089] Nitride supports possess strong thermal and mechanical stability and excellent conductivity, maintaining stable performance even in high-temperature environments. Examples of nitride-based supports include titanium nitride, boron nitride, gallium nitride, aluminum nitride, silicon nitride, zirconium nitride, chromium nitride, and tantalum nitride. Nitride supports enhance the electrical properties of platinum particles and facilitate the uniform distribution of catalyst particles. In particular, the high conductivity of nitrides contributes to improving reaction rates by promoting electron transfer in catalytic reactions.

[0090] Examples of carbide supports are silicon carbide, tungsten carbide, titanium carbide, zirconium carbide, chromium carbide, tartalum carbide, molybdenum carbide, and boron carbide.

[0091] Examples of sulfide supports are molybdenum sulfide, tungsten sulfide, zinc sulfide, cobalt sulfide, nickel sulfide, iron sulfide, and copper sulfide.

[0092] The selection of the support material directly influences the final performance and stability of the catalyst. Carbon-based supports are widely used in fuel cells and oxygen reduction reactions (ORR) and are the most widely utilized due to their excellent conductivity and high surface area. Oxide-based supports improve catalyst stability and selectivity in specific environments and prevent the aggregation of platinum particles. Nitride-based supports exhibit excellent high-temperature stability and maximize catalytic performance through high conductivity and reaction characteristics. Through the combination and application of these support materials, the present invention is designed to maximize the performance and applicability of platinum nanocatalysts by utilizing various materials, rather than being limited to a specific support.

[0093] Any mixing device that can be conventionally used in the field may be used, and the present invention is not specifically limited thereto.

[0094] Subsequently, the mixture can be placed in a ball mill device and ball-milled to produce a mixture of small particles. In addition, a mixture of small particles can be produced using simple mixing methods such as hand mixing, in addition to ball milling.

[0095] The ball milling time can be appropriately adjusted by a person skilled in the art, and as an example, it can be performed for about 1 to 3 hours.

[0096] Step 2 involves heat-treating the mixture under vacuum or an inert atmosphere to produce platinum nanoparticles (platinum nanocatalysts) having a carbon shell.

[0097] The mixture prepared in Step 1 above is placed in a container and transferred to a heat treatment device.

[0098] Heat treatment can be performed under a vacuum or an inert atmosphere, preferably under an N2 atmosphere (see FIG. 2). As can be seen in FIG. 2, in a vacuum or inert gas atmosphere, carbon shells formed around the particles, forming small and uniform platinum nanoparticles of the 3 nm level, and in an H2 / N2 (5 mol% H2) gas atmosphere, large and non-uniform platinum nanoparticles of 20 to 50 nm or more can be confirmed.

[0099] Heat treatment can be performed at a temperature of 200 to 800°C (see FIG. 3) or at a temperature of 200 to 500°C, preferably at one or more temperatures selected from the group consisting of 200 to 300°C, 300 to 400°C, 400 to 500°C, 500 to 600°C, 600 to 700°C, and 700 to 800°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, and 800°C, more preferably at 400 to 500°C, and most preferably at 400°C. If the temperature is outside the above range, problems may arise in which the physical properties and electrochemical activity of the platinum nanocatalyst decrease due to heat treatment.

[0100] The heat treatment time can be appropriately adjusted according to the temperature, and preferably set to about 2 hours.

[0101] The platinum nanoparticles prepared in step 2 above are used as platinum nanocatalysts, and have a particle size of 1 nm to 6 nm, preferably 2 nm to 4 nm. They are uniformly distributed, which can solve the problem of aggregation (see FIG. 2).

[0102] The manufactured platinum nanoparticles have a carbon shell formed on their surface, and preferably, the carbon shell is formed on a part of the surface so that the platinum is partially exposed.

[0103] Specifically, as can be seen in FIG. 6,

[0104] At 200℃, an amorphous carbon shell covers the surface of the platinum nanoparticles well, and

[0105] At 300℃, part of the carbon shell decomposes and the platinum surface begins to be exposed, and

[0106] At 400℃, the platinum surface begins to be exposed further, and

[0107] The carbon shell remaining around the particle begins to cover the entire particle surface again starting at 500℃, and

[0108] As conditions exceed 600℃, the degree of crystallization of the carbon shell begins to increase,

[0109] At 800℃, one to two layers of graphene-shaped carbon shells are formed.

[0110] In addition, another aspect of the present invention provides a platinum nanocatalyst produced by the method of the present invention.

[0111] The platinum nanocatalyst of the present invention has a size of 1 to 6 nm, preferably 2 nm to 4 nm, and exhibits a uniform distribution, which can solve the aggregation problem.

[0112] In addition, the platinum nanocatalyst of the present invention has a carbon shell formed on its surface, and preferably, the carbon shell is formed on a portion of the surface so that the platinum is partially exposed. In particular, the platinum nanocatalyst with partially exposed platinum exhibits optimal electrochemical performance, and thus can be applied and used as a catalyst in fuel cells or oxygen reduction reactions.

[0113] In addition, another aspect of the present invention is a platinum nanocatalyst composition, wherein

[0114] It includes a carbon shell confirmed through TGA analysis results,

[0115] (i) Platinum nanoparticles are supported on a support, and

[0116] (ii) The carbon shell includes an amorphous state, and

[0117] (iii) The carbon shell content is 2.60 to 3.40 weight% based on 100 weight% of the platinum nanocatalyst composition, and

[0118] (iv) Provides a platinum nanocatalyst composition characterized in that the burning point of the carbon shell is between 150 and 200°C.

[0119] In the present invention, it is preferable that the platinum nanoparticles have a particle size of 1 to 6 nm, preferably 2 to 4 nm.

[0120] In addition, the carbon shell contains an amorphous state, which starts in an amorphous state and becomes denser and stabilized as the heat treatment temperature increases.

[0121] During this heat treatment process, platinum nanoparticles are physically protected by the carbon shell, preventing aggregation, and the carbon shell acts as a protective layer that enhances the electrochemical stability and durability of the catalyst.

[0122] The platinum nanocatalyst composition of the present invention can be used in fuel cells, oxygen reduction reactions (ORR), or other electrochemical reactions due to the features described above and the features described in the following examples.

[0123] In addition, another aspect of the present invention is based on ECSA (Electrochemical Surface Area) analysis,

[0124] (i) Platinum nanoparticles are supported on a support, and

[0125] (ii) The exposed ratio of platinum nanoparticles is calculated as the ratio of the measured to the theoretical value of the electrochemical active area (ECSA), and

[0126] (iii) Provides a platinum nanocatalyst composition characterized by the above ratio being 0.563 or higher.

[0127] In the present invention, it is preferable that the platinum nanoparticles have a particle size of 1 to 6 nm, preferably 2 to 4 nm.

[0128] The platinum nanocatalyst composition of the present invention is characterized by being prepared by a heat treatment temperature in the range of 200 to 500°C, and during this heat treatment process, platinum nanoparticles are physically protected by a carbon shell, so that aggregation can be prevented.

[0129] The platinum nanocatalyst composition of the present invention can be used in fuel cells, oxygen reduction reactions (ORR), or other electrochemical reactions due to the features described above and the features described in the following examples.

[0130] The details of the process of the present invention will be explained below through examples and experimental examples. These are representative examples related to the present invention, and it should be noted that the scope of application of the present invention cannot be limited solely by these examples.

[0131] <Example 1> Preparation of the platinum nanocatalyst of the present invention

[0132] Step 1: Prepare the mixture

[0133] 21.646 g of Pt(acac) was added to a mixing container along with 1.200 g of carbon powder (VXC-72), mixed using a stirrer, and ball-milled for 1 hour using a ball mill device (Planetary Micro Mill (FRITSCH, PULVERISETTE 7)) to prepare a mixture.

[0134] Step 2: Heat Treatment

[0135] Platinum nanoparticles (platinum nanocatalysts) were prepared by performing the above mixture under an N2 atmosphere at 200°C, 300°C, 400°C, 500°C, 600°C, or 800°C for 1 to 2 hours.

[0136] <Experimental Example 1> Characterization of the platinum nanocatalyst of the present invention

[0137] (1) Analysis of the size and distribution of platinum nanocatalysts and the characteristics of carbon shells

[0138] The size and distribution of the platinum nanocatalyst prepared in Example 1, and the characteristics of the carbon shell were confirmed through TEM (Transmission Electron Microscopy) (JEOL-F200), XRD (X-Ray Diffraction) (Rigaku DMAX-2500), and TGA (Thermogravimetric Analysis) (Scinco TGA-N 1000) analysis.

[0139] Results of XRD (crystal size) and TEM (particle size) analysis of the platinum nanocatalyst of the present invention Sample crystallite size (nm) Particle size (nm) Lattice distance (nm) Pt content (wg%) TGAPt / C 3.09 3.75 0.39 440.0Pt@C / C_20 2.33 2.59 0.39 632.0Pt@C / C_30 2.64 2.79 0.39 535.7Pt@C / C_40 2.64 2.79 0.39 535.9Pt@C / C_50 2.67 2.89 0.39 335.6Pt@C / C_60 3.36 3.29 0.39 334.6Pt@C / C_80 3.66 3.73 0.39 334.4

[0140] The XRD (crystal size) and TEM (particle size) analysis results of the platinum nanocatalyst of the present invention consist of key items measured to evaluate the physical properties of the catalyst. Crystalline size is a value calculated by determining the average size of platinum crystal particles using X-ray diffraction (XRD), providing information on crystal growth according to heat treatment conditions. Particle size is measured using a transmission electron microscope (TEM), allowing for visual confirmation of the actual size and distribution of platinum nanoparticles. Additionally, lattice distance is the distance between the lattices of platinum nanoparticles, which varies depending on the heat treatment temperature and atmosphere, affecting the crystal structure of platinum. Pt content is a value measured through thermogravimetric analysis (TGA) and plays an important role in verifying whether platinum was maintained at a constant level during the catalyst manufacturing process.

[0141] Looking at each sample, the reference sample Pt / C has a crystallite size of 3.09 nm and a particle size of 3.75 nm, with a stable lattice distance of 0.394 nm. The Pt content was found to be 40.0%, which accurately reflects the characteristics of existing commercial catalysts. Pt@C / C_20 is a sample heat-treated at 200°C; the crystallite size and particle size remained small at 2.33 nm and 2.59 nm, respectively, while the lattice distance increased slightly to 0.396 nm. The Pt content was 32.0%, which is lower than the reference sample but exhibits a uniform distribution. Pt@C / C_30 is a sample heat-treated at 300°C; the crystallite size and particle size increased to 2.64 nm and 2.79 nm, respectively, while the lattice distance remained stable and the Pt content increased to 35.7%. Pt@C / C_40 is a sample heat-treated at 400°C, exhibiting optimal uniformity with crystallite and particle sizes of 2.64 nm and 2.79 nm, respectively. The Pt content is also maintained at 35.9%, suggesting that the catalytic performance is expected to be the most desirable. Pt@C / C_50, heat-treated at 500°C, showed a slight increase in crystallite and particle sizes to 2.67 nm and 2.89 nm, respectively; however, the lattice distance remains stable, and the Pt content is maintained at 35.6%, still exhibiting desirable characteristics.

[0142] On the other hand, for Pt@C / C_60 heat-treated at 600℃, the crystallite size and particle size increased significantly to 3.36 nm and 3.29 nm, respectively, while the Pt content decreased to 34.6%. This indicates that aggregation occurred due to high-temperature heat treatment and shows undesirable results. The Pt@C / C_80 sample heat-treated at 800℃ showed inferior results, with the crystallite size and particle size further increasing to 3.66 nm and 3.73 nm, respectively, and the aggregation phenomenon becoming prominent, while the Pt content also decreased to 34.4%.

[0143] Analysis results showed that samples heat-treated at 200 to 500°C (Pt@C / C_20, Pt@C / C_30, Pt@C / C_40, Pt@C / C_50) exhibited desirable catalytic properties, with small and uniform crystal and particle sizes, and stable lattice distance and Pt content. In particular, the Pt@C / C_40 sample heat-treated at 400°C demonstrated the most optimal conditions. Conversely, high-temperature heat treatment above 600°C resulted in undesirable outcomes, such as increased particle size and non-uniform distribution due to the aggregation of platinum nanoparticles. These results clearly demonstrate that the size and uniformity of platinum nanoparticles have a significant impact on the electrochemical activity and stability of the catalyst.

[0144] (2) Electrochemical analysis of the platinum nanocatalyst of the present invention

[0145] The electrochemical properties of the platinum nanocatalyst prepared in Example 1 were evaluated through ECSA (Electrochemical Surface Area), MA (Mass Activity), and SA (Specific Activity) analysis.

[0146] The results were evaluated using a 3-electrode system (BioLogic, VSP-3e) equipped with a rotating disk electrode (RDE). Cycle voltamogram (CV) measurements were performed in a 0.1 M HClO4 solution saturated with N2 at a scan rate of 20 mV / s in the range of 0.03 V to 1.1 V (vs. RHE). The ECSA of each sample was calculated based on the proton adsorption current peak area (1 molar hydrogen adsorption current: 210 μC / cm²) from the CV curve. Oxygen reduction reaction (ORR) performance was evaluated by measuring linear sweep voltamograms (LSV) at a rotation speed of 1600 rpm in a 0.1 M HClO4 solution saturated with O2 at a scan rate of 10 mV / s in the range of 0.05 V to 1.1 V (vs. RHE). MA and SA were calculated by dividing the current density value obtained at 0.9 V from the obtained LSV curve by the platinum content and platinum surface area used in the electrode.

[0147] Sample ECSA(m 2 g -1 Pt )SA@0.9V(uA cm -2 Pt )MA@0.9V(A mg -1 Pt )E 1 / 2 (mV) Initial 30k Cycle Change Rate (%) Initial 30k Cycle Change Rate (%) Initial 30k Cycle Change Rate (%) Initial 30k Cycle Change Rate (%) Pt / C 5 4.0 3 3.6 3 7.8 0.4 19 0.3 96 5.5 0.2 26 0.1 33 4 1.2 88 88 6 32.8 Pt@C / C_20 6 4.4 5 1.8 19.6 0.5 26 0.5 14 2.3 0.3 38 0.2 66 21.3 89 78 90 0.8 Pt@C / C_40 5 6.5 45.9 18.8 0.5 23 0.5 21 0.4 0.2980.23919.88968900.7Pt@C / C_5056.354.63.040.2360.324-37.20.1330.177-33.186 3877-1.57Pt@C / C_6025.1--0.162--0.041--825--Pt@C / C_8027.6--0.044--0.012--786--

[0148] The results of evaluating the electrochemical properties of the platinum nanocatalyst of the present invention consist of key indicators representing the performance and durability of the catalyst. First, the electrochemical surface area (ECSA) represents the active surface area on the platinum catalyst surface where electrochemical reactions can occur, and a higher ECSA value indicates superior catalytic performance. The initial ECSA of the Pt / C reference sample was 54.0 m². 2 g -1 Pt Ro, 33.6 m after 30,000 cycles 2 g -1 Pt It decreased to , showing a rate of change of 37.8%. In comparison, Pt@C / C_20 had an initial ECSA of 64.4 m 2 g -1 Pt It was highest at , and 51.8 m even after 30k cycles. 2 g -1 Pt It was maintained at, and the rate of change was stable at 19.6%. For Pt@C / C_40, the initial ECSA was 56.5 m 2 g -1 Pt Low, 45.9 m after 30k cycles 2 g -1 Pt It decreased to , showing a rate of change of 18.8%, and for Pt@C / C_50, the initial ECSA was 56.3 m 2 g -1 Pt Low, 54.6 m even after 30k cycles 2 g -1 Pt It was maintained at , exhibiting excellent durability with the lowest rate of change at 3.04%. On the other hand, the initial ECSA of Pt@C / C_60 and Pt@C / C_80 was 25.1 m, respectively. 2 g -1 Pt Wow, 27.6 m 2 g -1 Pt It is low, showing that the high heat treatment temperature caused a degradation in the performance of the catalyst.

[0149] Specific activity (SA) represents the current density generated per catalytic active region. For Pt@C / C_20, the initial SA was 0.526 μA cm⁻¹. -2 Pt It was highest at , and 0.514 uA cm after 30k cycles. -2 Pt It decreased to , and the rate of change was very stable at 2.3%. For Pt@C / C_40, the initial SA was 0.523 uA cm -2 Pt Low, 0.521 uA cm after 30k cycles -2 Pt It remained almost unchanged, showing the best change rate of 0.4%. For Pt@C / C_50, the initial SA was 0.236 uA cm -2 Pt It was low, but after 30k cycles it was 0.324 uA cm -2 Pt It increased and showed a rate of change of -37.2%. The initial SA for Pt@C / C_60 and Pt@C / C_80 was 0.162 uA cm⁻¹, respectively. -2 Pt and 0.044 uA cm -2 Pt It can be seen that the low heat treatment temperature caused a decrease in the activity of the catalyst.

[0150] Mass activity (MA) is an indicator representing the efficiency of a catalyst per unit mass, and Pt@C / C_20 has an initial MA of 0.338 A mg -1 Pt 0.266 A mg after 30k cycles -1 Pt It decreased to , exhibiting stable characteristics with a rate of change of 21.3%. Pt@C / C_40 had an initial MA of 0.298 A mg -1 Pt 0.239 A mg after 30k cycles -1 Pt It decreased, and the rate of change was stable at 19.8%. On the other hand, the initial MA of Pt@C / C_60 and Pt@C / C_80 was 0.041 A mg, respectively. -1 Ptand 0.012 A mg -1 Pt It can be confirmed that the catalyst performance is significantly degraded under high temperature conditions because it is very low.

[0151] Finally, the half-potential of the oxygen reduction reaction (E 1 / 2 ) is a key indicator for evaluating the reactivity of a catalyst. Pt@C / C_20 and Pt@C / C_40 are based on the initial E 1 / 2 were excellent at 897 mV and 896 mV, respectively, and remained at 890 mV even after 30k cycles, showing stable rates of change of 0.8% and 0.7%. On the other hand, Pt@C / C_60 and Pt@C / C_80 had initial E 1 / 2 The values ​​are low at 825 mV and 786 mV, respectively, indicating inferior performance as a catalyst.

[0152] In conclusion, platinum nanocatalysts heat-treated at temperatures ranging from 200 to 500°C demonstrated excellent performance; in particular, performance was superior under these conditions, with the catalyst prepared at 400°C exhibiting the best characteristics. This is because, under the 200 to 500°C conditions, carbon shells were properly formed around the platinum nanocatalysts, preventing the aggregation of catalyst particles. Furthermore, the carbon shells effectively protected the catalyst while partially exposing the platinum surface, thereby maintaining high catalytic activity. Conversely, at temperatures above 600°C, carbon shells formed excessively densely, surrounding the platinum nanoparticles, which resulted in reduced catalytic activity. For this reason, catalysts prepared at temperatures above 600°C failed to achieve the desired level of performance, so a separate durability test was omitted. These results suggest that temperatures between 200°C and 500°C are suitable for the heat treatment of platinum nanocatalysts, and specifically demonstrate that the 400°C condition provides optimal performance.

[0153] (3) TGA analysis results of the platinum nanocatalyst of the present invention

[0154] The results of evaluating the carbon shell content and carbon shell burn point of platinum nanocatalysts through TGA analysis provide important information for understanding the thermal and structural properties of the catalyst. TGA was used to analyze the stability and changes in carbon shell content during the heat treatment process by measuring the weight loss of the samples with respect to temperature changes. Through this experiment, it was possible to confirm how the heat treatment temperature affects the characteristics of the carbon shell in platinum nanocatalysts.

[0155] The burning point of the carbon shell is an important indicator for evaluating thermal stability in catalyst structures. According to TGA analysis results, Pt@C / C_20, Pt@C / C_30, and Pt@C / C_40 all exhibited a burning point of 150°C. This indicates relatively low thermal stability, suggesting that the carbon shells of these samples were formed in an amorphous state. In contrast, Pt@C / C_50 and Pt@C / C_60 exhibited burning points of 200°C, respectively, indicating a transformation into a structure with higher thermal stability. Pt@C / C_80 showed the highest burning point at 215°C, demonstrating the formation of a very dense and stabilized carbon shell. These results demonstrate that the structure of the carbon shell gradually becomes denser and more stabilized as the heat treatment temperature increases.

[0156] The carbon shell content showed a decreasing trend with increasing heat treatment temperature. Pt@C / C_20 exhibited the highest carbon shell content at 3.40 wt%, indicating that amorphous carbon shells were formed at lower heat treatment temperatures. Pt@C / C_30 and Pt@C / C_40 maintained high content at 3.12 wt% and 3.31 wt%, respectively, and amorphous carbon shells were formed within this temperature range. However, as the heat treatment temperature increased, the carbon shell content of Pt@C / C_50 decreased to 2.60 wt%, while Pt@C / C_60 showed 2.31 wt% and Pt@C / C_80 showed the lowest values ​​at 1.85 wt%. This appears to be the result of some carbon shells being lost due to thermal decomposition or oxidation at high temperatures.

[0157] Overall, as the heat treatment temperature increased, the carbon shell formed a thermally stabilized structure, but the content tended to decrease. At low heat treatment temperatures (150°C to 200°C), amorphous carbon shells were formed in high amounts, which made it highly likely that the catalyst would maintain a high active area. On the other hand, at high heat treatment temperatures (200°C or higher), the carbon shells had a dense and stable structure, but the reduced content may result in a decrease in the catalyst's active area.

[0158] The Pt@C / C_40 sample (150℃) was presented as the optimal condition. This sample showed stable thermal characteristics with a high carbon shell content of 3.31 wt%, demonstrating excellent potential in terms of catalytic performance and durability. Pt@C / C_80 (215℃) exhibits excellent thermal stability with a high burning point and low carbon shell content, but there is a possibility that the catalytic active area may decrease. Therefore, considering the carbon shell content and thermal stability, the catalyst heat-treated in the range of 150℃ to 200℃ (Pt@C / C_40 or Pt@C / C_50) is judged to be a suitable condition for catalytic application.

[0159] (4) Evaluation of the exposure ratio of platinum nanoparticles and catalyst utilization through ECSA analysis results of the platinum nanocatalyst of the present invention

[0160] The utility of the platinum nanocatalyst was evaluated by analyzing the particle size, theoretical and measured values ​​of the electrochemical surface area (ECSA), and the ratio of measured to theoretical values. This analysis specifically explains the influence of heat treatment temperature on the characteristics and potential utility of the catalyst.

[0161] The exposed ratio of platinum nanoparticles is defined as the ratio of the theoretical to the measured electrochemical active surface area (ECSA). This definition is reasonable in that the theoretical ECSA represents the ideal surface area calculated based on particle size, while the measured value represents the active surface area obtained through actual experiments. The theoretical ECSA is calculated by assuming the maximum surface area under ideal conditions where platinum nanoparticles can participate in the reaction while exposed without a carbon shell. In contrast, the measured value reflects the results of heat treatment conditions, carbon shell coverage, and particle aggregation in real-world environments. Therefore, the ratio of the theoretical to the measured value serves as an indicator to quantitatively evaluate the extent to which platinum nanoparticles can participate in the reaction—that is, the exposed ratio.

[0162] The ratio of the ECSA theoretical value to the measured value holds significant meaning regarding the utilization and efficiency of the catalyst. A high ratio indicates that the surface of the platinum nanoparticles is well exposed, maximizing the active surface area and effectively participating in the catalytic reaction. Conversely, a low ratio suggests that the surface of the platinum nanoparticles is excessively covered by carbon shells or that the reactive surface area has decreased due to particle aggregation. For example, the Pt@C / C_20 sample (0.596), with a high ratio, indicates an optimized state of platinum nanoparticle surface exposure, while the Pt@C / C_60 sample (0.295), with a low ratio, reflects a state where the exposed surface area is significantly limited due to heat treatment conditions.

[0163] The particle size of the platinum nanocatalysts showed a tendency to increase with the heat treatment temperature. The Pt@C / C_20 sample had the smallest particle size at 2.59 nm, while the Pt@C / C_80 sample showed the largest size at 3.73 nm. This reflects the general trend of particle size increasing as the heat treatment temperature increases. The theoretical ECSA value was highest at 108.0 m² / g for Pt@C / C_20 and lowest at 75.0 m² / g for Pt@C / C_80. The actually measured ECSA value recorded a maximum of 64.4 m² / g for Pt@C / C_20 and was lowest at 25.1 m² / g for Pt@C / C_60.

[0164] Catalyst utilization was evaluated as the ratio of the ECSA measured value to the theoretical value. Pt@C / C_20 showed the highest utilization at 0.596, while Pt@C / C_60 showed the lowest at 0.295. In particular, samples heat-treated at temperatures between 200 and 500°C (Pt@C / C_20 to Pt@C / C_50) showed high catalyst utilization, but the Pt@C / C_40 sample prepared at 400°C exhibited the highest utilization. Samples heat-treated between 200 and 400°C (Pt@C / C_20 to Pt@C / C_40) maintained a similar level of high utilization, while utilization decreased sharply at temperatures above 600°C. This trend was also confirmed in the graph analysis, demonstrating that a heat-treated temperature of 400°C is the most suitable condition for catalyst utilization. Next, it can be seen that a range of 200 to 400°C is suitable, followed by 200 to 500°C. On the other hand, at 600°C or higher, the usability dropped significantly, and the use of the catalyst was limited.

[0165] In conclusion, the Pt@C / C_40 sample prepared at a heat treatment temperature of 400°C showed the highest catalyst utilization and was evaluated as the optimal condition. Samples at 200 to 400°C (Pt@C / C_20 ~ Pt@C / C_40) were evaluated as the second most suitable condition, and samples at 200 to 500°C (Pt@C / C_20 ~ Pt@C / C_50) were evaluated as the next most suitable condition. On the other hand, Pt@C / C_60 (600°C) and Pt@C / C_80 (800°C) showed low catalyst utilization, resulting in significantly degraded performance. Therefore, considering the particle size, active area, and utilization of the catalyst comprehensively, it can be seen that a heat treatment temperature of 400°C provides optimal catalyst performance and durability, followed by 200 to 400°C, and then 200 to 500°C.

[0166] The calculation process for the theoretical ECSA (Electrochemical Surface Area) value illustrates the derivation of the theoretical value based on the particle size and physical properties of platinum nanocatalysts. The calculation process begins by converting the particle size (X nm) measured via TEM into a radius (r). For example, a particle size of 2.59 nm is converted to a radius of 1.295 nm. Subsequently, the surface area formula for a sphere, A = 4πr 2 Calculate the surface area of ​​the particle using. In the example with a particle size of 2.59 nm, it is 21.08 nm 2 The surface area of ​​was derived.

[0167] Next, the formula for the volume of a sphere is V = 4 / 3πr 3 The volume of the particle is calculated through this, and a 2.59 nm particle is approximately 9.08 nm 3 It has a volume. Subsequently, the mass of the particle is calculated by multiplying by the density of platinum (21.45 g / cm³). In the example, it is approximately 1.948 × 10⁻⁶. 19 A mass of g was derived. Using this, the ECSA value is derived by calculating the mass relative to the surface area of ​​the unit particle, and the particle in question is 1.08 × 10⁻⁶ 6 It was calculated as cm² / g.

[0168] Finally, by converting the units, the final ECSA is derived to be 108 m² / g. This calculation is performed by systematically considering the size, surface area, volume, and density of the platinum nanoparticles. In the example with a particle size of 2.59 nm, the theoretical ECSA was calculated to be approximately 108 m² / g. While these results are based on the size and surface area of ​​the platinum nanoparticles, the actual value may vary depending on external factors such as heat treatment conditions, carbon shell covering, and particle aggregation.

[0169] In conclusion, this calculation yields the theoretical active area based on the physical properties of platinum nanoparticles, which is useful for evaluating the influence of heat treatment conditions and carbon shells.

[0170] (5) Preparation of platinum nanocatalysts utilizing the advantages of a dry process

[0171] The present invention provides a method for preparing a catalyst by mixing a platinum precursor and a carbon support using only a dry process without using a solvent. However, the reason for using a wet process in conventional technology is that there is a high possibility of non-uniform dispersion between particles in the case of a dry process. When a platinum precursor and a support are mixed without a solvent, platinum nanoparticles may be concentrated in specific areas, leading to aggregation, which can result in a reduction in the surface area of ​​the catalyst and a decrease in electrochemical activity. Furthermore, during the heat treatment process, unevenly distributed platinum nanoparticles may aggregate, potentially increasing the particle size of the nanoparticles, which can lead to a reduction in the active surface area and a decrease in durability of the catalyst.

[0172] However, experiments confirmed that the catalyst prepared by the method of the present invention did not exhibit these problems. First, TEM analysis confirmed that the platinum nanoparticles prepared by the method of the present invention were uniformly distributed on the carbon support; in particular, for the catalyst heat-treated at 400°C, platinum particles were formed small and uniformly at a level of 2 to 4 nm. Furthermore, ECSA and electrochemical performance evaluations showed that the catalyst of the present invention exhibited performance equivalent to or superior to that of the catalyst prepared by the wet process. For example, the Pt@C / C_20 sample had an initial ECSA of 64.4 m² g -1 Pt It was measured as such, and the rate of performance degradation remained low even after 30k cycles. In addition, excellent electrochemical activity was confirmed in MA and SA measurements, which was analyzed to be due to the uniform distribution of platinum nanoparticles and the protective effect of the carbon shell. XRD and TGA analysis results also confirmed that the platinum nanoparticles maintained a particle size range of 1 to 6 nm and did not aggregate, and confirmed that the carbon shell effectively encapsulated the platinum particles, preventing particle growth and aggregation during heat treatment.

[0173] The reason why platinum nanoparticles in the present invention can be uniformly distributed, prevent aggregation, and exhibit excellent catalytic performance without degradation without using a solvent can be inferred as follows. First, the carbon shell formed during the heat treatment process plays an important role. The carbon shell physically encases the platinum nanoparticles and acts as a protective barrier to prevent aggregation between particles. In particular, under heat treatment conditions (e.g., an inert gas atmosphere at 400°C), the carbon shell is uniformly formed, allowing the platinum nanoparticles to maintain a constant size and uniform distribution. This suggests the possibility that the problems of non-uniform distribution and aggregation that may occur when mixing without a solvent are naturally resolved during the heat treatment process.

[0174] In addition, physical and chemical interactions between the platinum precursor and the carbon support can also be considered a major factor. The platinum precursor (Pt(acac)2) used in the present invention can decompose during heat treatment and strongly bond with the carbon support; this interaction enables the uniform formation and stable distribution of platinum nanoparticles during the heat treatment process. Heat treatment conditions also play an important role in inducing the formation of uniform platinum nanoparticles. In the present invention, heat treatment was performed at 200 to 500°C in a vacuum or inert gas (N₂) atmosphere. In particular, under the 400°C condition, an optimal balance was achieved in which the active surface area and stability of the catalyst were simultaneously improved by forming a carbon shell while partially exposing the platinum surface.

[0175] The physical properties of the carbon support itself are also considered a contributing factor. The carbon support possesses a specific surface area and porous structure, providing an environment where platinum nanoparticles can be evenly loaded onto the support surface. Furthermore, the porosity of the support provides space for the platinum nanoparticles to form, which can inhibit excessive particle growth.

[0176] As such, the reason why the expected problems did not occur in the present invention even without a solvent appears to be due to the formation of a carbon shell during the heat treatment process and the interaction between the platinum precursor and the carbon support. In particular, it is highly likely that the optimized heat treatment conditions played a key role in preventing the growth and aggregation of platinum nanoparticles and inducing their uniform distribution. Through these results, it has been proven that the dry process of the present invention can produce uniform and stable platinum nanocatalysts without a solvent.

[0177] The platinum nanoparticles of the present invention have carbon shells appropriately formed on them, which allows the manufactured platinum nanoparticles to be stably distributed to prevent aggregation and exhibit excellent electrochemical activity in the oxygen reduction reaction (ORR). Furthermore, since platinum nanoparticles can be manufactured simply, environmentally friendly, and with high productivity using the method of the present invention through a dry process, they have industrial applicability.

Claims

1. A step of preparing a mixture by mixing a platinum precursor and a support material in their solid state (Step 1); and A method comprising the step (step 2) of heat-treating the above mixture under vacuum or an inert atmosphere to produce platinum nanoparticles (platinum nanocatalysts) having a carbon shell, Method for manufacturing platinum nanocatalysts.

2. A method according to claim 1, characterized in that step 1 involves mixing a platinum precursor and a support material and ball-milling the mixture to produce a mixture.

3. A method according to claim 1, characterized in that, in step 1, the platinum precursor is platinum acetate (Pt(acac)2) and the support material is carbon, oxide, nitride, carbide, or sulfide.

4. A method according to claim 1, characterized in that in step 2, the inert atmosphere is a nitrogen (N2) atmosphere and the heat treatment is performed at 200 to 800°C.

5. A method according to claim 4, characterized in that, in step 2, the heat treatment temperature is one or more temperatures selected from the group consisting of 200 to 300℃, 300 to 400℃, 400 to 500℃, 500 to 600℃, 600 to 700℃, and 700 to 800℃.

6. A method according to claim 4, characterized in that the heat treatment in step 2 is performed at 200 to 500℃.

7. The method according to claim 1, characterized in that the platinum nanoparticles have a size of 1 nm to 6 nm.

8. The method according to claim 1, characterized in that the platinum nanoparticles have a size of 2 nm to 4 nm, and the platinum is partially exposed in the platinum nanoparticles having a carbon shell.

9. Platinum nanocatalyst prepared by the method of claim 1.

10. A platinum nanocatalyst according to claim 9, characterized in that the platinum nanoparticles have a size of 1 nm to 6 nm.

11. A platinum nanocatalyst according to claim 10, wherein the platinum nanocatalyst has a size of 2 nm to 4 nm and is characterized in that the platinum is partially exposed in the platinum nanocatalyst having the carbon shell.

12. Includes a carbon shell confirmed through TGA analysis results, (i) Platinum nanoparticles are supported on a support, and (ii) The carbon shell includes an amorphous state, and (iii) The carbon shell content is 2.60 to 3.40 weight% based on 100 weight% of the platinum nanocatalyst composition, and (iv) A platinum nanocatalyst composition characterized in that the burning point of the carbon shell is between 150 and 200°C.

13. A platinum nanocatalyst composition according to claim 12, characterized in that the platinum nanoparticles have a particle size of 1 to 6 nm, preferably 2 to 4 nm.

14. A platinum nanocatalyst composition according to claim 12 or 13, characterized in that the carbon shell starts in an amorphous state and has a structure that becomes dense and stabilized as the heat treatment temperature increases.

15. A platinum nanocatalyst composition according to claim 12, characterized in that the platinum nanoparticles are physically protected by a carbon shell during the heat treatment process to prevent aggregation.

16. A platinum nanocatalyst composition according to claim 12, characterized in that the carbon shell acts as a protective film that improves the electrochemical stability and durability of the catalyst.

17. A platinum nanocatalyst composition according to claim 12, characterized in that the catalyst composition is used in a fuel cell, an oxygen reduction reaction (ORR), or other electrochemical reaction.

18. Based on ECSA (Electrochemical Surface Area) analysis, (i) Platinum nanoparticles are supported on a support, and (ii) The exposed ratio of platinum nanoparticles is calculated as the ratio of the measured to the theoretical value of the electrochemical active area (ECSA), and (iii) A platinum nanocatalyst composition characterized by the above ratio being 0.563 or higher.

19. A platinum nanocatalyst composition according to claim 18, characterized in that the platinum nanoparticles are physically protected by a carbon shell during the heat treatment process to prevent aggregation.

20. A platinum nanocatalyst composition according to claim 18 or 19, characterized in that the platinum nanoparticles have a particle size of 1 to 6 nm, preferably 2 to 4 nm.

21. A platinum nanocatalyst composition according to claim 18, characterized in that the catalyst composition is prepared at a heat treatment temperature in the range of 200 to 500°C.

22. A platinum nanocatalyst composition according to claim 18, characterized in that the catalyst composition is used in a fuel cell, an oxygen reduction reaction (ORR), or other electrochemical reaction.

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