Fuel cell electrocatalyst and method of making same

Abstract

A fuel cell electrocatalyst comprising a platinum-based catalyst having a three-layer core-shell structure comprising a core and a shell layer, the core and the shell layer each independently comprising platinum, and an intermediate layer located between the core and the shell layer comprising a platinum-transition metal alloy, and a method of preparing the same are presented. The fuel cell electrocatalyst is prepared by preparing colloidal platinum particles in a solution phase and alloying a transition metal on the surface of the catalyst, thereby having a three-layer core-shell structure. Therefore, the electrocatalyst exhibits excellent dispersibility and durability.

Description

Technical Field

[0001] This disclosure relates to alloy electrocatalysts for fuel cells and methods for their preparation. In particular, this disclosure relates to fuel cell electrocatalysts and methods for their preparation, wherein the fuel cell electrocatalysts are platinum-based core-shell alloy catalysts supported on carbon and exhibit high activity and high durability.

[0002] The following describes two South Korean national projects supported by the South Korean government that are related to this invention.

[0003] Project unique number :1415186363

[0004] Project serial number :20020437

[0005] government departments Ministry of Trade, Industry and Energy (MOTIE)

[0006] Project Management Specialized Organization Korea Planning & Evaluation of Industrial Technology (KEIT)

[0007] Research Business Name Nanotechnology Integration and Innovative Product Technology Development

[0008] Project Name Development of Fuel Cell Module Technology for Hydrogen Electric Vehicle Based on Production of Platinum Alloy Nanocatalyst with Platinum Loading of 0.2 g / kW or Less in membrane electrode assembly (MEA)

[0009] Supervisory bodies THE CARBON STUDIO INC.

[0010] Research period January 1, 2023 to December 31, 2025

[0011] Project unique number :1415185115

[0012] Project serial number :20022451

[0013] government departments :MOTIE

[0014] Project Management Specialized Organization KEIT

[0015] Research Business Name Materials and Component Technology Development - Packaging

[0016] Project Name Development of production technology for electrolyte membranes and catalysts for PEM water electrolysis

[0017] Supervisory bodies CHEMTROS CO.,LTD.

[0018] Research period January 1, 2023 to December 31, 2025 Background Technology

[0019] Based on the type of electrolyte and fuel used, fuel cells can be classified into polymer electrolyte membrane fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and other fuel cells.

[0020] PEMFCs use hydrogen as fuel at low temperatures (typically below 100°C) and generate electricity through an electrochemical reaction between hydrogen and oxygen in the air. Such fuel cells produce water (H2O) as a byproduct during the electrochemical reaction process and can therefore be considered an environmentally friendly energy source.

[0021] A fuel cell consists of an anode where fuel is oxidized, a cathode where oxygen is reduced, and an electrolyte.

[0022] Hydrogen gas, used as fuel, is oxidized at the anode to produce hydrogen ions (H+) and electrons. The electrons generated at the anode generate energy via an external conductor, and the hydrogen ions move through the electrolyte to the cathode. At the cathode, oxygen (O2) supplied from the air reacts with the hydrogen ions transferred from the anode to the electrolyte to produce water (H2O).

[0023] Meanwhile, platinum (Pt)-based electrocatalysts (which are generally stable and highly active for the oxygen reduction reaction (ORR)) are mainly used as components of the anode and cathode to enhance ORR activity.

[0024] Platinum is an expensive precious metal. Therefore, to make fuel cell systems commercially available, it is necessary to develop technologies to reduce the platinum loading used in the electrodes. Furthermore, it is crucial to employ techniques to reduce the platinum loading by enhancing the inherent chemical activity of platinum through alloying with transition metals in platinum particles.

[0025] Compared to platinum, such alloy catalysts actually exhibit improved activity. However, during the synthesis process, the particle growth rate in the alloy catalyst varies due to the difference between the reduction rates of platinum and the transition metals, resulting in reduced dispersion of the alloy catalyst on the carbon support compared to the dispersion of platinum catalysts on the carbon support. As a result, improving initial performance is considered highly unlikely, and there is also the inherent problem that leaching of the transition metals caused by voltage variations during fuel cell system operation can lead to rapid performance degradation.

[0026] Extensive research has been conducted to improve inherent catalytic activity and address the problem of transition metal leaching. However, the development of existing alloy catalysts focuses more on structural modification rather than simple alloying.

[0027] U.S. Patent Application Publication No. US2023 / 0395818 A1 discloses a core-shell catalyst having a core composed of a PtCo alloy catalyst or a CoMn alloy catalyst and a shell composed of Pt, wherein the structural difference between the core and the shell is quantitatively determined by lattice parameter measurements, and the catalyst exhibits superior activity compared to platinum catalysts (Pt).

[0028] Furthermore, U.S. Patent Application Publication No. US2012 / 0316054 A1 discloses a supportless noble metal catalyst having a core composed of Ag, Ni, or an alloy thereof, while the outer shell is based on Pt. This catalyst is expected to exhibit high activity at a particle size of 20 nm.

[0029] Patents disclosed in related technologies involve alloy catalysts with a bilayered core-shell structure in which only platinum exists on the catalyst surface. Because the core is composed of a platinum alloy catalyst, such catalysts with a bilayered core-shell structure tend to exhibit poor dispersion on carbon and large particle size, leading to problems with inhibited catalytic activity. As a result, there are limitations in terms of the performance and durability levels required for commercialization. Summary of the Invention

[0030] To address the aforementioned issues, this disclosure aims to provide an ORR catalyst for fuel cells, and to improve catalytic activity and durability through partial alloying rather than alloying the entire fuel cell catalyst.

[0031] However, the technical problems to be solved by this disclosure are not limited thereto, and include other aspects that will be clearly understood by those skilled in the art to which this disclosure pertains based on the following description.

[0032] One embodiment of this disclosure provides a fuel cell electrocatalyst comprising a platinum-based catalyst, wherein the platinum-based catalyst has a three-layer core-shell structure comprising a core and a shell, each of the core and shell independently comprising platinum, and an intermediate layer between the core and shell comprising a platinum-transition metal alloy.

[0033] The transition metal can be one, two or more of the following: Fe, Co, Ni, Ti, V, Mn, Cu, Zr, Mo and W.

[0034] The core may contain platinum in an amount ranging from 90% to 95% by weight relative to the total amount of platinum contained in the entire fuel cell electrocatalyst; the intermediate layer may contain platinum in an amount ranging from 5% to 9% by weight relative to the total amount of platinum contained in the entire fuel cell electrocatalyst; and the shell layer may contain platinum in an amount ranging from 0.5% to 1% by weight relative to the total amount of platinum contained in the entire fuel cell electrocatalyst.

[0035] The transition metals may be included in amounts ranging from 33% to 100% by weight relative to the total amount of platinum contained in the electrocatalyst.

[0036] Platinum-based catalysts can be supported on crystalline carbon.

[0037] Platinum-based catalysts can be loaded in amounts ranging from 20% to 90% wt% relative to the amount of crystalline carbon.

[0038] Another embodiment of this disclosure provides a method for preparing a fuel cell electrocatalyst comprising a platinum-based catalyst, the method comprising the steps of: dispersing crystalline carbon in a polyol solvent to prepare a first dispersion; heating a platinum precursor dissolved in the polyol solvent to prepare colloidal platinum particles; preparing a mixed solution of the first dispersion and the colloidal platinum particles; adding a transition metal precursor to the mixed solution and heating the resulting product to prepare a catalyst having a bilayer core-shell structure including a core and a shell; and subjecting the catalyst having the bilayer core-shell structure to a washing, filtering, and post-treatment process to prepare a catalyst having a trilayer core-shell structure including a core and a shell.

[0039] The dual core-shell structure can have a core containing platinum and a shell containing a platinum-nonmetallic alloy.

[0040] In the method, the three-layer core-shell structure may have the form in which the core and shell each independently contain platinum, while the intermediate layer between the core and shell contains a platinum-transition metal alloy.

[0041] In the method, the core may contain platinum in an amount ranging from 90% to 95% by weight relative to the amount of platinum contained in the entire fuel cell electrocatalyst; the intermediate layer may contain platinum in an amount ranging from 5% to 9% by weight relative to the amount of platinum contained in the entire fuel cell electrocatalyst; and the shell layer may contain platinum in an amount ranging from 0.5% to 1% by weight relative to the amount of platinum contained in the entire fuel cell electrocatalyst.

[0042] In the method, the transition metal can be one, two or more of the following: Fe, Co, Ni, Ti, V, Mn, Cu, Zr, Mo and W.

[0043] Post-processing may include freeze-drying under vacuum.

[0044] In the method, the transition metal may be included in an amount ranging from 33% to 100% by weight relative to the total amount of platinum contained in the electrocatalyst.

[0045] In the step of preparing colloidal platinum particles, heating can be carried out at a temperature in the range of 90°C to 130°C.

[0046] In the step of preparing a catalyst with a double core-shell structure, heating can be carried out at a temperature in the range of 200°C to 250°C.

[0047] Before washing, the catalyst with a double core-shell structure can be subjected to at least one of heat treatment and acid treatment.

[0048] Heat treatment can be carried out in a vacuum, hydrogen, nitrogen, or argon atmosphere at temperatures ranging from 300°C to 900°C.

[0049] Acid treatment can be carried out in 0.5M to 1M nitric acid at temperatures ranging from 60°C to 100°C.

[0050] According to this disclosure, the fuel cell electrocatalyst has a three-layer core-shell structure in which the core and shell contain platinum, and the intermediate layer between the core and shell contains a platinum-nonmetallic alloy, thus achieving both catalyst dispersibility and durability.

[0051] According to this disclosure, a method for preparing fuel cell electrocatalysts can obtain a three-layered catalyst exhibiting excellent dispersibility and durability by preparing colloidal platinum particles in a solution phase and alloying a transition metal on the catalyst surface. Attached Figure Description

[0052] Figure 1 A diagram illustrating the three-layer core-shell structure of a fuel cell electrocatalyst according to the present disclosure;

[0053] Figure 2 A flowchart illustrating a method for preparing a fuel cell electrocatalyst according to this disclosure;

[0054] Figure 3 Transmission electron microscopy (TEM) images of the catalysts in colloidal form according to Examples 1 to 3 are shown;

[0055] Figure 4 TEM images of the catalysts according to Examples 1 to 3 and Comparative Examples 1 and 2 are shown;

[0056] Figure 5 The TEM-energy-dispersive X-ray (EDX) image of the catalyst according to Example 2 is shown.

[0057] Figure 6 The X-ray diffraction (XRD) results of the catalysts according to Examples 1 to 3 and Comparative Examples 1 and 2 are shown.

[0058] Figure 7A and Figure 7B ORR and catalytic durability results are shown to demonstrate the electrochemical performance of the catalysts according to Examples 1 to 3 and Comparative Examples 1 and 2; and

[0059] Figure 8A and Figure 8BThe cell voltage performance and catalytic durability results of the catalysts according to Examples 1 to 3 and Comparative Examples 1 and 2 are shown. Detailed Implementation

[0060] The embodiments of this disclosure will be described in detail below, enabling those skilled in the art to readily implement this disclosure. However, this disclosure may be presented in many different forms and is not limited to the embodiments set forth herein.

[0061] As used herein, the term "platinum particle" may refer to one or both of primary platinum particles and secondary platinum particles in the form of a particle structure formed by the aggregation of a plurality of primary platinum particles.

[0062] In the following, a fuel cell electrocatalyst according to one embodiment of the present disclosure will be described.

[0063] One embodiment of this disclosure provides a fuel cell electrocatalyst comprising a platinum-based catalyst, wherein the platinum-based catalyst has a three-layer core-shell structure comprising a core and a shell, each of the core and shell independently comprising platinum, and an intermediate layer between the core and shell comprising a platinum-transition metal alloy.

[0064] The fuel cell electrocatalyst according to this disclosure has a three-layer core-shell structure.

[0065] In this context, the three-layer core-shell structure refers to a three-dimensional structure consisting of three layers: 1) the innermost core of the catalyst, 2) the outermost (i.e., peripheral) shell of the catalyst, and 3) the intermediate layer between the core and the shell.

[0066] In the following text, reference will be made to Figure 1 Describe it.

[0067] Reference Figure 1 The core and shell of the fuel cell electrocatalyst contain platinum.

[0068] The core may contain platinum in an amount ranging from 90% to 95% by weight, relative to the amount of platinum contained in the entire fuel cell electrocatalyst.

[0069] The intermediate layer between the core and the shell comprises a platinum-transition metal alloy. The transition metal may be, for example, one, two or more of Fe, Co, Ni, Ti, V, Mn, Cu, Zr, Mo and W, but is not limited thereto.

[0070] The intermediate layer may contain platinum in an amount ranging from 5% to 9% by weight relative to the total amount of platinum contained in the fuel cell electrocatalyst, but is not limited thereto.

[0071] In the intermediate layer, platinum and transition metals do not need to be fully alloyed and can exist in part as a composite that is simply physically bonded rather than alloyed.

[0072] The shell (which is not only the outermost layer of the intermediate layer, but also the outermost layer of the electrocatalyst) contains platinum, and its amount may be in the range of 0.5% to 1% by weight relative to the total amount of platinum contained in the fuel cell electrocatalyst, but is not limited thereto.

[0073] The fuel cell electrocatalyst according to this disclosure comprises a three-layer platinum-based catalyst, and the amount of expensive platinum-based catalyst can be reduced by alloying with transition metals, while the increase in platinum surface roughness caused by the dissolution of transition metals is prevented by treating the shell with platinum. In other words, both catalytic activity and durability can be achieved simultaneously when using the platinum-based catalyst according to this disclosure.

[0074] In an electrocatalyst according to one embodiment, the transition metal may be included in an amount ranging from 33% to 100% by weight relative to the total amount of platinum contained in the electrocatalyst, but is not limited thereto. When the amount of transition metal is very small and does not fall within the above range, controlling the size, form, dispersion, etc., of platinum via the transition metal can be challenging. When the amount of the transition metal precursor is excessive, some of the transition metal particles reduced in the final step may be present in the outermost layer of the electrocatalyst, which is undesirable.

[0075] Platinum-based catalysts can be supported on crystalline carbon.

[0076] There are no restrictions on crystalline carbon, as long as it is a porous carbon material on which metal particles can be loaded.

[0077] In fuel cell electrocatalysts, platinum particles can be loaded in amounts ranging from 20% to 90% by weight, more particularly from 30% to 80% by weight, based on the total weight of the electrocatalyst. The electrocatalyst according to this disclosure can support a large number of platinum metal particles. Furthermore, as can be determined by the following experimental examples, almost no aggregation is observed because of the small median particle size of platinum, the small standard deviation of the particle size, and the uniform dispersion of the platinum-based catalyst on the crystalline carbon used as a support. Ultimately, the electrocatalyst can exhibit excellent electrochemical properties.

[0078] Another embodiment of this disclosure provides a method for preparing a fuel cell electrocatalyst comprising a platinum-based catalyst.

[0079] In the following text, reference will be made to Figure 2 A method for preparing a fuel cell electrocatalyst according to the present disclosure is described.

[0080] Reference Figure 2 The method for preparing a fuel cell electrocatalyst comprising a platinum-based catalyst according to this disclosure includes the following steps: a) dispersing crystalline carbon in a polyol solvent to prepare a first dispersion; b) heating a platinum precursor dissolved in a separate polyol solvent to prepare colloidal platinum particles; c) preparing a mixed solution of the first dispersion and the colloidal platinum particles; d) adding a transition metal precursor to the mixed solution and heating the resulting product to prepare a catalyst having a bilayer core-shell structure including a core and a shell; and e) subjecting the catalyst having the bilayer core-shell structure to a washing, filtering, and post-treatment process to prepare a catalyst having a trilayer core-shell structure including a core and a shell.

[0081] According to the method of this disclosure, colloidal platinum particles are formed in solution, a transition metal precursor is added to the surface of the platinum particles to form platinum-transition metal alloy particles on the surface of the platinum particles, and then the transition metal on the surface is leached to obtain a catalyst with a three-layer core-shell structure in which only platinum exists as the outermost particle.

[0082] According to this disclosure, since platinum forms alloys with transition metals, the amount of expensive platinum used can be reduced. Furthermore, by partially alloying rather than alloying the entire catalyst, the degradation of durability caused by the increased surface roughness of platinum during the dealloying process where the transition metal dissolves, and the reduction in catalytic activity caused by the increase in particle size due to high-temperature heat treatment during the alloying process, can be prevented.

[0083] In step a), crystalline carbon can be dispersed in a polyol solvent to prepare a first dispersion.

[0084] There are no restrictions on crystalline carbon, as long as it is a porous carbon material on which metal particles can be loaded.

[0085] Polyols act as both solvents and reducing agents, and can reduce metal precursors. There are no limitations on the type of polyol, but it can be, for example, selected from one or more of the following: ethylene glycol (EG), propylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, and glycerol. In particular, the polyol can be EG, which is inexpensive, readily oxidized to glycolaldehyde at high temperatures, and has strong reducing power.

[0086] In this disclosure, the first dispersion can be prepared by dispersing 1 part by weight of crystalline carbon in 100 to 1000 parts by weight of a polyol. Dispersion can be carried out using physical methods such as homogenizers or ultrasonic devices. When the amount of crystalline carbon is large and does not fall within the above range, or when the amount of polyol is small, the carbon particles acting as the carrier may form agglomerates and aggregates. Furthermore, when the amount of crystalline carbon is small or the amount of polyol is large, the processability of the reaction deteriorates, making it difficult to exhibit the intended effects of this disclosure. In particular, the first dispersion can be prepared by dispersing 1 part by weight of crystalline carbon in 200 to 400 parts by weight of a polyol.

[0087] In step b), the platinum precursor dissolved in a polyol solvent is heated to prepare colloidal platinum particles.

[0088] The types and amounts of transition metals have been described in the section on electrocatalysts according to this disclosure, and therefore redundant descriptions thereof will be omitted here.

[0089] In the step of preparing colloidal platinum particles, heating can be carried out at a temperature in the range of 90°C to 130°C, but is not limited to this.

[0090] In the preparation of colloidal platinum particles, the weight ratio of polyol solvent to platinum in the platinum precursor can be in the range of 1:488 to 1:732, but is not limited to this. When the weight ratio of polyol solvent to platinum is less than 1:488, the size of the colloidal platinum particles increases, leading to a decrease in activity. Furthermore, when the weight ratio of polyol solvent to platinum is greater than 1:732, the size of the colloidal platinum particles decreases, resulting in alloying of platinum in the core. As a result, it may be difficult to prepare particles with a three-layer core-shell structure.

[0091] In step c), the first dispersion obtained in step a) and the colloidal platinum particles obtained in step b) are mixed to prepare a mixed solution.

[0092] Subsequently, in step d), a transition metal precursor is added to the mixed solution obtained above, and the resulting product is then heated to prepare a catalyst with a bilayer core-shell structure (secondary core-shell catalyst).

[0093] In this case, according to the present disclosure, a bilayer core-shell structure having a core comprising platinum and an outer layer (i.e., shell) comprising a platinum-nonmetallic alloy corresponds to the state prior to obtaining a three-layer catalyst.

[0094] In the step of preparing a catalyst with a double core-shell structure, heating can be carried out at a temperature in the range of 200°C to 250°C, but is not limited thereto.

[0095] Then, in step e), the catalyst with a bilayer core-shell structure obtained above is subjected to washing, filtration and post-treatment processes to prepare a catalyst with a trilayer core-shell structure.

[0096] In this case, after washing and filtration, the catalyst with a double core-shell structure can be subjected to heat treatment and / or acid treatment. Heat treatment can be carried out for 4 to 8 hours at a temperature ranging from 300°C to 900°C in a vacuum, hydrogen, nitrogen, or argon atmosphere, but is not limited thereto. Acid treatment can be carried out for 2 to 6 hours in 0.5M to 1M nitric acid at a temperature ranging from 60°C to 100°C, but is not limited thereto.

[0097] In step e), a post-treatment process is performed after washing and filtration. This post-treatment process can be a freeze-drying process under vacuum. When such a post-treatment process is completed, a platinum-based catalyst with a three-layer core-shell structure according to this disclosure is obtained. Through the process in step e), the transition metals on the surface of the catalyst with a two-layer core-shell structure (secondary core-shell catalyst) are leached out, leaving only platinum on the catalyst surface.

[0098] The molar ratio of transition metals to platinum in catalysts with a double core-shell structure (secondary core-shell catalysts) can be in the range of 1:6 to 1:1, but is not limited thereto.

[0099] Furthermore, the three-layer structure is the same as described above, so its redundant description will be omitted here.

[0100] The present disclosure will be described in detail below through examples. However, the following examples are merely illustrative and the content of the disclosure is not limited thereto.

[0101] Preparation of electrocatalysts

[0102] Example 1

[0103] To prepare a platinum colloidal solution, 6.336 g of platinum precursor (10 wt% (MEA)2Pt(OH)6·xH2O, purchased from TMI Chem.Co.), 0.387 g of dispersant (50 wt% NaH2PO2·H2O in H2O) and 435.3 g of EG were added to a reflux glass reactor, and the reaction was carried out at 90 °C for 4 hours.

[0104] In this solution, 0.75g of carbon (420m) was added. 2 / g, with a particle size of 3.1nm) were mixed and ultrasonically / high-speed mixed for 30 minutes to prepare carbon dispersions and platinum colloidal particles.

[0105] Add 9.38 g of cobalt precursor (4 wt% CoCl2 in EG, purchased from Sigma-Aldrich) to the above dispersion and stir for about 60 minutes to prepare the alloy catalyst dispersion.

[0106] The resulting dispersion was placed in an autoclave reactor equipped with a stirrer, and the reactor temperature was then raised to approximately 250°C to carry out a reduction reaction. When the reaction was complete, the filtration and washing processes were repeated to obtain a slurry, which was then subjected to a drying process in a vacuum oven at 250°C for 4 hours to prepare the catalyst composition.

[0107] Upon completion of the drying process, the catalyst composition was subjected to a heat treatment process in a heat treatment furnace at 600°C in a hydrogen atmosphere for 6 hours, followed by an acid treatment process in 1M nitric acid at 90°C for 4 hours, for filtration and washing. After the obtained catalyst sample was placed in a freeze-drying apparatus and freeze-dried under vacuum, the final electrocatalyst (Pt@PtCo@Pt / C-1) was obtained.

[0108] Example 2

[0109] The electrocatalyst (Pt@PtCo@Pt / C-2) was prepared in the same manner as in Example 1, except that, unlike in Example 1, a platinum colloidal solution was prepared at a temperature of 110°C to change the size of the colloidal platinum particles.

[0110] Example 3

[0111] The electrocatalyst (Pt@PtCo@Pt / C-3) was prepared in the same manner as in Example 1, except that, unlike in Example 1, a platinum colloidal solution was prepared at a temperature of 130°C to change the size of the colloidal platinum particles.

[0112] Comparative Example 1

[0113] By using 0.75g of crystalline carbon (420m) 2 A crystalline carbon dispersion was prepared by mixing 435.3 g of EG (particle size 3.1 nm) with a carrier and dispersing the carrier using an ultrasonic / high-speed mixer for 30 minutes. Additionally, a dispersion was prepared by stirring 6.336 g of platinum precursor (4 wt% Pt(NH3)4Cl2·xH2O, purchased from TMI Chem.Co.) and 0.387 g of dispersant (10 wt% NaH2PO2·H2O in H2O) for approximately 30 minutes.

[0114] The above dispersions were mixed and then placed in a glass reactor equipped with a reflux device. The reactor temperature was then raised to approximately 165°C to carry out the reduction reaction. When the reaction was complete, the filtration and washing processes were repeated to obtain a slurry, which was then subjected to a drying process in a vacuum oven at 250°C for 4 hours to prepare the catalyst composition.

[0115] Upon completion of the drying process, the catalyst composition was subjected to a heat treatment process in a heat treatment furnace at 600°C in a hydrogen atmosphere for 6 hours, followed by an acid treatment process in 1M nitric acid at 90°C for 4 hours, for filtration and washing. After the obtained catalyst sample was placed in a freeze-drying apparatus and freeze-dried under vacuum, the final electrocatalyst (Pt / C) was obtained.

[0116] Comparative Example 2

[0117] By using 0.75g of crystalline carbon (420m) 2 A crystalline carbon dispersion was prepared by mixing 435.3 g of EG (particle size 3.1 nm) with a carrier and dispersing the carrier using an ultrasonic / high-speed mixer for 30 minutes. Additionally, a dispersion was prepared by stirring 6.336 g of platinum precursor (4 wt% Pt(NH3)4Cl2·xH2O, purchased from TMI Chem.Co.), 0.387 g of dispersant (10 wt% NaH2PO2·H2O in H2O), and 9.38 g of cobalt precursor (4 wt% CoCl2 in EG, purchased from Sigma-Aldrich) for approximately 30 minutes.

[0118] The dispersion was placed in an autoclave reactor equipped with a stirrer, and the reactor temperature was then raised to approximately 250°C to carry out the reduction reaction. Once the reaction was complete, the filtration and washing processes were repeated to obtain a slurry, which was then dried in a vacuum oven at 250°C for 4 hours to prepare the catalyst composition.

[0119] Upon completion of the drying process, the catalyst composition was subjected to a heat treatment process in a heat treatment furnace at 600°C in a hydrogen atmosphere for 6 hours, followed by an acid treatment process in 1M nitric acid at 90°C for 4 hours, for filtration and washing. After the obtained catalyst sample was placed in a freeze-drying apparatus and freeze-dried under vacuum, the final electrocatalyst (PtCo@Pt / C) was obtained.

[0120] Experimental Example 1: TEM image of colloidal platinum catalyst

[0121] The colloidal catalysts of Examples 1 to 3 were observed using TEM images. The results are shown in... Figure 3 middle.

[0122] according to Figure 3 It was determined that the colloidal platinum particles in Examples 1 to 3 were formed uniformly, and the particle size increased slightly with increasing reaction temperature.

[0123] As described above, when platinum-transition metal alloy particles are formed, it is expected that the uniform platinum particles in Examples 1 to 3 will have improved dispersion, even within the carbon support.

[0124] Experimental Example 2: TEM image of a three-layer core-shell platinum alloy catalyst

[0125] The catalysts of Examples 1 to 3 and Comparative Examples 1 and 2 were observed using TEM images. The results are shown in... Figure 4 middle.

[0126] according to Figure 4 It can be seen that the catalysts of Examples 1 to 3 exhibited excellent dispersion compared to the catalysts of Comparative Examples 1 and 2.

[0127] Experiment Example 3: TEM-EDX Image (Structure Determined)

[0128] The catalyst of Example 2 was observed using TEM-EDX images. The results are shown in... Figure 5 middle.

[0129] according to Figure 5 It was determined that the platinum layer existed in the outermost layer of the catalyst in Example 2.

[0130] Experimental Example 4: XRD and X-ray Fluorescence (XRF)

[0131] The XRD and XRF results of the catalysts of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in the figures. Figure 6 And in Table 1.

[0132] Reference Figure 6 It can be seen that, compared with the catalysts of Comparative Examples 1 and 2, the catalysts of Examples 1 to 3 exhibit a relatively wide 2θ value distribution (in the range of 39° to 41°). This means that the Pt and PtCo particles do not form a uniform phase, indicating that the Pt core and PtCo phase coexist.

[0133] [Table 1]

[0134]

[0135]

[0136] Referring to Table 1, it can be seen that the catalysts of Examples 1 to 3, which are prepared as platinum or existing PtCo, have smaller particle sizes. Based on this, the catalysts of Examples 1 to 3, which are prepared as three-layer core-shell structures, are expected to exhibit excellent electrochemical activity.

[0137] Experimental Example 5: Evaluation Results of Oxygen Reduction Reactivity and Durability

[0138] ORR results showing the electrochemical effects of the catalysts in Examples 1 to 3 and Comparative Examples 1 and 2 are presented in... Figure 7A and 7B And in Table 2.

[0139] [Table 2]

[0140]

[0141] Reference Figure 7A and 7B And Table 2 shows that the catalysts of Examples 1 to 3 had superior ORRs compared to the catalysts of Comparative Examples 1 and 2. Furthermore, during the durability evaluation conducted under conditions used to assess catalytic durability, at 0.6V to 1.0V and 10,000 cycles, Example 2 exhibited a lower performance degradation rate relative to its initial performance than Comparative Examples 1 and 2.

[0142] Experiment Example 6: Single Cell Performance

[0143] The cell voltage as a function of current density was measured to show the electrochemical effect of the catalysts in Examples 1 to 3 and Comparative Examples 1 and 2.

[0144] The results are shown in Figure 8A and 8B And in Table 3.

[0145] [Table 3]

[0146]

[0147] Reference Figure 8A and 8B Table 3 shows that, at the same current density, the catalyst of Example 2 exhibits superior voltage performance compared to the catalysts of Comparative Examples 1 and 2. Furthermore, even during the voltage evaluation following the testing of catalytic durability, the catalyst of Example 2 demonstrated excellent performance, thus confirming its superior durability compared to existing catalysts.

[0148] While preferred embodiments of this disclosure have been described in detail above, the scope of this disclosure is not limited thereto. That is, various modifications and alternatives made by those skilled in the art using the basic concepts of this disclosure as defined in the appended claims fall within the scope of this disclosure.

Claims

1. A fuel cell electrocatalyst comprising a platinum-based catalyst, The platinum-based catalyst described herein has a three-layered core-shell structure comprising a core and a shell. The core and the shell each independently contain platinum, and The intermediate layer located between the core and the shell contains a platinum-transition metal alloy.

2. The electrocatalyst according to claim 1, wherein the transition metal is selected from one, two or more of Fe, Co, Ni, Ti, V, Mn, Cu, Zr, Mo and W.

3. The electrocatalyst according to claim 1, wherein the core contains platinum in an amount ranging from 90% to 95% by weight relative to the amount of platinum contained in the entire electrocatalyst. The intermediate layer contains platinum in an amount ranging from 5% to 9% by weight, relative to the total amount of platinum contained in the electrocatalyst. The shell contains platinum in an amount ranging from 0.5% to 1% by weight, relative to the amount of platinum contained in the entire electrocatalyst.

4. The electrocatalyst according to claim 1, wherein the transition metal is included in an amount ranging from 33% to 100% by weight relative to the total amount of platinum contained in the electrocatalyst.

5. The electrocatalyst according to claim 1, wherein the platinum-based catalyst is supported on crystalline carbon.

6. The electrocatalyst according to claim 5, wherein the platinum-based catalyst is loaded in an amount ranging from 20% to 90% by weight relative to the amount of crystalline carbon.

7. A method for preparing a fuel cell electrocatalyst comprising a platinum-based catalyst, the method comprising: The crystalline carbon is dispersed in a polyol solvent to prepare a first dispersion; Platinum precursors dissolved in a polyol solvent are heated to prepare colloidal platinum particles; Prepare a mixed solution of the first dispersion and the colloidal platinum particles; A transition metal precursor was added to the mixed solution, and the resulting product was heated to prepare a catalyst having a bilayer core-shell structure including a core and a shell. as well as The catalyst having the said double core-shell structure is subjected to washing, filtration and post-treatment processes to prepare a catalyst having a triple core-shell structure including a core and a shell.

8. The method of claim 7, wherein the dual core-shell structure has the form in which the core comprises platinum and the shell comprises a platinum-nonmetallic alloy.

9. The method of claim 7, wherein the three-layer core-shell structure comprises wherein the core and the shell each independently contain platinum, and the intermediate layer between the core and the shell contains a platinum-transition metal alloy.

10. The method of claim 9, wherein the core comprises platinum in an amount ranging from 90% to 95% by weight relative to the amount of platinum contained in the entire electrocatalyst. The intermediate layer contains platinum in an amount ranging from 5% to 9% by weight, relative to the total amount of platinum contained in the electrocatalyst. The shell contains platinum in an amount ranging from 0.5% to 1% by weight, relative to the amount of platinum contained in the entire electrocatalyst.

11. The method of claim 7, wherein the transition metal is selected from one, two or more of Fe, Co, Ni, Ti, V, Mn, Cu, Zr, Mo and W.

12. The method of claim 7, wherein the post-processing includes a freeze-drying process under vacuum.

13. The method of claim 7, wherein the transition metal is included in an amount ranging from 33% to 100% by weight relative to the total amount of platinum contained in the electrocatalyst.

14. The method according to claim 7, wherein in the preparation of the colloidal platinum particles, the heating is carried out at a temperature in the range of 90°C to 130°C.

15. The method of claim 7, wherein in the preparation of the catalyst having the said double core-shell structure, the heating is carried out at a temperature in the range of 200°C to 250°C.

16. The method according to claim 7, wherein after the washing and the filtration, the catalyst having the double core-shell structure necessarily undergoes both heat treatment and acid treatment during the post-treatment process.

17. The method of claim 16, wherein the heat treatment is performed in a vacuum, hydrogen, nitrogen, or argon atmosphere at a temperature ranging from 300°C to 900°C.

18. The method of claim 16, wherein the acid treatment is carried out in 0.5M to 1M nitric acid at a temperature in the range of 60°C to 100°C.

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