Metal catalyst composite including carbon support and manufacturing method thereof

Abstract

A method for manufacturing a metal catalyst composite according to an embodiment of the present invention comprises: a first step for adding an initiator to a mixture containing a monomer, a first crosslinking agent, and a surfactant to prepare polystyrene-based copolymer particles; a second step for hyper-crosslinking the polystyrene-based copolymer particles to prepare hyper-crosslinked polystyrene-based copolymer particles; a third step for carbonizing the hyper-crosslinked polystyrene-based copolymer particles to prepare carbonized polystyrene-based copolymer particles; and a fourth step for dispersing the carbonized polystyrene-based copolymer particles in a first solvent, adding a catalyst metal precursor, and then reducing same to manufacture a metal catalyst composite.

Description

Metal catalyst complex comprising carbon support and method for preparing the same

[0001] The present invention relates to a metal catalyst complex including a carbon support and a method for producing the same.

[0002]

[0003] A fuel cell is a type of power generation device that converts the chemical energy of fuel into electrical energy through an electrochemical reaction within a fuel cell stack rather than converting it into heat through combustion. It not only supplies electricity for industrial, household, and vehicle use, but can also be applied to supplying electricity to small electric / electronic products, especially portable devices. These fuel cells come in various types depending on the type of fuel and electrolyte used, and can be classified by fuel type into polymer electrolyte membrane fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and alkaline electrolyte fuel cells (AFC). Among these, polymer electrolyte membrane fuel cells have the advantages of low operating temperature, prevention of leakage problems due to the use of solid electrolytes, and fast operation. Compared to other types of fuel cells, they are high-power fuel cells with high current density, operate at temperatures below 100°C, have a simple structure, fast start-up and response characteristics, and have excellent durability. In addition to hydrogen, methanol or natural gas can be used as fuel.

[0004] Factors that must be improved for the commercialization of polymer electrolyte membrane fuel cells include improved performance, extended lifespan, and lower cost. The component that most significantly influences these factors is the membrane electrode assembly (MEA). The MEA is the unit cell structure of the fuel cell, and it consists of an electrolyte membrane made of a polymer material, with an anode and a cathode coated on both sides. This MEA is where the electrochemical reaction between hydrogen and oxygen occurs and is composed of the cathode, the anode, and the electrolyte membrane, i.e., the ion-conducting electrolyte membrane. At the anode, the fuel oxidizes to produce hydrogen ions and electrons. The hydrogen ions then migrate to the cathode through the electrolyte membrane. At the cathode, the hydrogen ions and electrons transferred through the oxygen and electrolyte membrane react to produce water. This reaction causes electrons to move to the external circuit.

[0005] The efficiency of these fuel cells is largely determined by the reaction rate of the electrodes (anode, cathode), and nano-sized catalysts can be used as electrode materials.

[0006] Conventional catalysts typically have polymer-based carbon particles forming the support, with an average particle diameter exceeding approximately 100 nm. These particles vary in size and variability across the particle, resulting in insufficient or inconsistent support of metal-based materials. Furthermore, catalysts containing the support may lack sufficient durability and struggle to maintain stable performance over long periods of time.

[0007]

[0008] One embodiment of the present invention is to provide a metal catalyst composite capable of improving the performance of a membrane-electrode assembly.

[0009] One embodiment of the present invention is to provide a metal catalyst composite that significantly reduces the amount of platinum (Pt) used while improving the performance of a membrane-electrode assembly.

[0010] One embodiment of the present invention provides a method for producing a metal catalyst composite having an average particle size of less than 50 nm.

[0011] One embodiment of the present invention provides a method for producing a metal catalyst composite having excellent performance, durability, and long-term stability.

[0012] One embodiment of the present invention provides a method for producing a metal catalyst composite capable of increasing the specific surface area of ​​a support of the metal catalyst composite.

[0013] One embodiment of the present invention is to provide a metal catalyst composite having an increased metal catalyst loading amount.

[0014] One embodiment of the present invention provides a method for producing a metal catalyst composite capable of mass-producing a metal catalyst composite of uniform size.

[0015] In addition to the above-mentioned tasks, embodiments according to the present invention can be used to achieve other tasks not specifically mentioned.

[0016]

[0017] A method for producing a metal catalyst composite according to one embodiment of the present invention comprises a first step of producing polystyrene-based copolymer particles by adding an initiator to a mixture including a monomer, a first crosslinking agent, and a surfactant, a second step of hyper-crosslinking the polystyrene-based copolymer particles to produce hyper-crosslinked polystyrene-based copolymer particles, a third step of carbonizing the hyper-crosslinked polystyrene-based copolymer particles to produce carbonized polystyrene-based copolymer particles, and a fourth step of dispersing the carbonized polystyrene-based copolymer particles in a first solvent, mixing in a precursor of a catalyst metal, and then reducing the mixture to produce a metal catalyst composite.

[0018] The metal catalyst composite may include carbonized polystyrene-based copolymer particles and a catalyst layer positioned on the carbonized polystyrene-based copolymer particles, and the catalyst layer may include a catalyst metal.

[0019] The catalytic metal may include one or more of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), or iron (Fe).

[0020] The catalytic metal may include one or more of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), or iron (Fe).

[0021] The fourth step may include a step of preparing a dispersion in which carbonized polystyrene-based copolymer particles are dispersed in a first solvent, a step of adjusting the pH of the dispersion and then raising the temperature, a step of adding a precursor solution containing a precursor of a catalyst metal to the dispersion and then stirring, and a step of preparing a metal catalyst complex by reducing the precursor of the catalyst metal.

[0022] The first solvent may comprise ethylene glycol.

[0023] The step of adjusting the pH of the dispersion and then raising the temperature may include a step of stirring the dispersion at 40 to 60°C, a step of adjusting the pH of the dispersion by adding NaOH, and a step of raising the temperature to 100 to 120°C.

[0024] The step of preparing a metal catalyst complex by reducing a precursor of a catalytic metal can be performed at a temperature range of 400 to 800°C for 10 minutes to 2 hours.

[0025] The average particle diameter of the metal catalyst complex may be less than 50 nm.

[0026] The first crosslinking agent may include a compound of the divinylbenzene series.

[0027] The surfactant may include one or more of sodium dodecyl sulfate, cetrimonium bromide, dodecyltrimethylammonium bromide, or polyvinyl alcohol.

[0028] The second step may be to disperse the polystyrene-based copolymer particles manufactured in the first step in a second solvent, add a crosslinking catalyst and a second crosslinking agent, stir, and then raise the temperature to manufacture hyper-crosslinked polystyrene-based copolymer particles.

[0029] The crosslinking catalyst may include one or more of FeCl3, FeCl3·6H2O, AlCl3, CoCl3, ZnCl3, or CrCl4.

[0030] The second cross-linking agent may include one or more of formaldehyde dimethyl acetal, trichloromethane, or carbon tetrachloride.

[0031] The second solvent may comprise dichloroethane.

[0032] A metal catalyst composite according to one embodiment of the present invention is manufactured by the method for manufacturing the metal catalyst composite.

[0033] A membrane-electrode assembly according to one embodiment of the present invention comprises a polymer electrolyte membrane, and an electrode positioned on one or the other surface of the polymer electrolyte membrane, the electrode comprising a metal catalyst complex manufactured by the method for manufacturing the metal catalyst complex.

[0034]

[0035] A metal catalyst composite manufactured by a method for manufacturing a metal catalyst composite according to one embodiment of the present invention can improve the performance of a membrane-electrode assembly, and at the same time, can significantly reduce the amount of platinum (Pt) used, can have excellent performance, durability, and long-term stability, can increase the specific surface area of ​​the support of the metal catalyst composite, and can increase the amount of metal catalyst supported.

[0036] In addition, the size of the metal catalyst complex and the support manufactured by the method for manufacturing the metal catalyst complex according to one embodiment of the present invention can be uniform, and the amount of metal catalyst supported per unit volume can be constant.

[0037] Additionally, the average particle size of the support of the metal catalyst complex may be less than 50 nm.

[0038] In addition, the method for manufacturing a metal catalyst composite according to one embodiment of the present invention can mass-produce a metal catalyst composite of uniform size.

[0039]

[0040] Figure 1 is a reference diagram showing the state when the starting material is stirred for a certain period of time in the method for manufacturing a metal catalyst complex according to Example 1.

[0041] Figure 2 shows the scanning electron microscope results for the PtCo / Carbon catalyst composite manufactured according to Example 1.

[0042] Figures 3a and 3b show the results of a full-cell test using a metal catalyst composite manufactured according to Example 1.

[0043] Figure 4 shows the results of a full-cell test using a metal catalyst composite manufactured according to Examples 2 and 3.

[0044] Figure 5 shows the results of a full-cell test using metal catalyst composites manufactured according to Comparative Examples 1 to 3.

[0045]

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily practice the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted to clearly explain the present invention, and the same reference numerals are used throughout the specification for identical or similar components. In addition, detailed descriptions of widely known and publicly known technologies are omitted.

[0047] In order to clearly represent various layers and regions in the drawings, the thicknesses are enlarged. When a layer, membrane, region, plate, etc. is said to be "over" another part, this includes not only the case where it is "directly over" that part, but also the case where there is another part in between. On the other hand, when a part is said to be "directly over" another part, it means that there is no other part in between. Conversely, when a layer, membrane, region, plate, etc. is said to be "under" another part, this includes not only the case where it is "directly under" that part, but also the case where there is another part in between. On the other hand, when a part is said to be "directly under" another part, it means that there is no other part in between.

[0048] Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0049]

[0050] The present invention relates to a method for manufacturing a metal catalyst composite capable of improving the performance, efficiency, durability, and long-term stability of a membrane electrode assembly (MEA). Here, the metal catalyst composite may be positioned on one or both sides of the electrolyte membrane of the membrane electrode assembly.

[0051] In addition, the specific surface area of ​​the support of the metal catalyst complex manufactured by the method for manufacturing the metal catalyst complex according to the present invention can be significantly wider than that of the prior art, the catalyst loading amount of the metal catalyst complex can be significantly greater than that of the prior art, and the catalyst loading amount per unit volume can be uniform.

[0052] In addition, the metal catalyst composite manufactured by the method for manufacturing a metal catalyst composite according to the present invention can improve the performance, durability, and long-term stability of the catalyst composite and the membrane-electrode assembly, while simultaneously reducing the amount of platinum used to about 1 / 4 of that of the prior art.

[0053] Furthermore, the average particle diameter (size) of the support manufactured by the method for manufacturing a metal catalyst composite according to the present invention and the average particle diameter of the metal catalyst composite can be uniform. The average particle diameter of the manufactured metal catalyst composite is less than 50 nm, which is a significantly smaller average particle diameter (size) than that of conventional technologies, and has a size very suitable for actual commercial membrane-electrode assemblies.

[0054] In addition, the method for manufacturing a metal catalyst complex according to the present invention is a method capable of mass-producing a support of uniform size (particle diameter, particle size) and a metal catalyst complex of uniform size, and has the characteristic of minimizing performance inhomogeneity that may occur during mass production, and thus can be very advantageous for commercialization.

[0055] A method for manufacturing a metal catalyst composite according to an embodiment includes a first step of manufacturing polystyrene-based copolymer particles, a second step of manufacturing hyper-crosslinked polystyrene-based copolymer particles, a third step of manufacturing carbonized polystyrene-based copolymer particles, and a fourth step of dispersing the carbonized polystyrene-based copolymer particles in a first solvent, mixing in a precursor of a catalyst metal, and then reducing the mixture to manufacture a metal catalyst composite.

[0056] First, a first step of manufacturing polystyrene-based copolymer particles is performed. The first step is a step of obtaining polystyrene-based copolymer particles by adding an initiator to a mixture containing a monomer, a first crosslinking agent, and a surfactant.

[0057] The monomer may include, for example, one or more compounds selected from the group consisting of styrene, 4-vinylbiphenyl, 2-vinyl pyridine, N-ethyl-2-vinylcarbazole, benzyl methacrylate, and benzyl acrylate.

[0058] The first crosslinking agent may include, for example, a compound of the divinylbenzene series.

[0059] The surfactant may include, for example, one or more of sodium dodecyl sulfate, cetrimonium bromide, dodecyltrimethylammonium bromide, or polyvinyl alcohol.

[0060] The initiator may include, for example, potassium persulfate (K2S2O8).

[0061] When a mixture containing such a monomer, a first cross-linking agent, and a surfactant is used as an initiating material (starting material), the monomer and the first cross-linking agent can be positioned within the region formed by the surfactant to cause a reaction (see Fig. 1), thereby significantly reducing the average particle diameter of the particles and making the uniformity of the average particle diameter (size) of the particles very excellent. In addition, due to these characteristics, the metal catalyst complex can be manufactured to have an average particle diameter of less than 50 nm, and for example, the metal catalyst complex can be manufactured to have an average particle diameter (D50) of 20 to 45 nm.

[0062] Typically, polyvinylpyrrolidone (PVP) is primarily used as a surfactant. However, when PVP is used as a surfactant in the starting material, the size of the resulting polystyrene-based copolymer particles can be relatively large, with an average particle diameter exceeding 100 nm. This can result in insufficient catalyst metal loading on the carbon support, which can deteriorate the performance of the metal catalyst composite and the membrane-electrode assembly, and can also deteriorate durability and long-term stability.

[0063] On the other hand, in the case of the embodiment, by utilizing the first cross-linking agent and the surfactant, the size of the obtained particles can be formed to a relatively remarkably small level, and thus the average particle diameter (size) of the metal catalyst composite can also be significantly reduced, and a uniform average particle diameter can be implemented, so that the amount of catalyst metal supported can be very large, and the performance of the metal catalyst composite and the performance of the membrane-electrode assembly can be improved, and durability and long-term stability can also be excellent. In addition, the content of platinum (Pt) as a catalyst metal can be significantly reduced, and thus the manufacturing cost can be greatly reduced.

[0064] The content of the surfactant may be about 5 to 20 wt% based on the total weight of the mixture including the monomer, the first cross-linking agent, and the surfactant. For example, when the surfactant is sodium dodecyl sulfate, the content may be about 10 to 15 wt% based on the total weight of the starting material (mixture) including the monomer, the first cross-linking agent, and the sodium dodecyl sulfate. Within this numerical range, the average particle diameter of the metal catalyst composite can be formed smaller, and the performance, durability, and long-term stability of the metal catalyst composite can be further improved.

[0065] Next, a second step is performed to manufacture hyper-crosslinked polystyrene copolymer particles by hyper-crosslinking polystyrene copolymer particles.

[0066] The second step is a step of dispersing the polystyrene-based copolymer particles obtained in the first step in a second solvent, adding a crosslinking catalyst and a second crosslinking agent, stirring, and then raising the temperature to produce the hyper-crosslinked polystyrene-based copolymer particles.

[0067] More specifically, the polystyrene-based copolymer particles obtained in the first step are dispersed in a second solvent, a cross-linking catalyst is added, and then a second cross-linking agent is added. Subsequently, the solution is stirred at about 40 to 60°C for about 1 to 3 hours, and then the temperature is increased to about 70 to 90°C and cross-linking is performed for about 20 to 30 hours. Next, the solution is washed with a washing solution to remove excess cross-linking catalyst, filtered, and dried to obtain hyper-cross-linked polystyrene-based copolymer particles.

[0068] Here, the second solvent may include dichloroethane.

[0069] The crosslinking catalyst may include, for example, one or more of FeCl3, FeCl3·6H2O, AlCl3, CoCl3, ZnCl3, or CrCl4.

[0070] The second cross-linking agent may include, for example, one or more of formaldehyde dimethyl acetal, trichloromethane, or carbon tetrachloride.

[0071] In the process steps and process conditions described above, when the second solvent, cross-linking catalyst and second cross-linking agent described above are used, the durability of the support and metal catalyst composite can be further improved, and the long-term stability can also be further improved.

[0072] Next, a third step is performed to carbonize a hyper-crosslinked polystyrene series copolymer to produce carbonized polystyrene series copolymer particles.

[0073] The carbonization process is carried out in a nitrogen flow at approximately 700 to 1100°C for approximately 1 to 3 hours. Within this range, efficient carbonization can be achieved, and carbonized polystyrene copolymer particles with excellent physical properties can be formed.

[0074] Here, carbonized polystyrene copolymer particles function as a carbon support for the metal catalyst composite. The average particle diameter (size) of the carbon support may be less than about 50 nm, for example, about 20 to 45 nm. In addition, the specific surface area of ​​the support manufactured by the manufacturing method according to the embodiment may be large, thereby increasing the catalyst metal loading amount. In addition, the uniformity of the average particle diameter of the support manufactured by the manufacturing method according to the embodiment may be excellent, thereby improving the performance and physical properties of the metal catalyst composite.

[0075] Next, a fourth step is performed to manufacture a metal catalyst complex by dispersing carbonized polystyrene series copolymer particles in a first solvent, mixing in a precursor of a catalyst metal, and then reducing the mixture.

[0076] The catalytic metal may be a single metal or an alloy. The catalytic metal may include, for example, one or more of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), or iron (Fe).

[0077] Alternatively, the catalytic metal may be, for example, an alloy including platinum (Pt) and one or more of palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), or iron (Fe). The catalytic metal may include platinum (Pt) or may include an alloy including platinum (Pt). For example, the catalytic metal may be a PtCo alloy, in which case a fuel cell including the same may exhibit an output performance of 450 mW / cm² or more while maintaining Pt at 5 wt% or less relative to the total weight of the catalytic metal.

[0078] The fourth step may include, for example, a step of preparing a dispersion in which carbonized polystyrene-based copolymer particles are dispersed in a first solvent, a step of increasing the pH (acidity) of the dispersion and then raising the temperature, a step of adding a precursor solution containing a precursor of a catalyst metal to the dispersion and then stirring, and a step of reducing the precursor of the catalyst metal to prepare a metal catalyst complex.

[0079] More specifically, step 4 is performed by first preparing a dispersion in which carbonized polystyrene-based copolymer particles are dispersed in a first solvent. Here, the first solvent may include ethylene glycol.

[0080] A precursor solution is prepared by mixing the catalyst metal precursor and ultrapure water separately from the dispersion.

[0081] Platinum (Pt) precursors include hexachloroplatinic acid (H2PtCl6·6H2O), tetraammineplatinum(II) chloride (Pt(NH3)4Cl2), potassium tetrachloroplatinate(II), K2PtCl4, and dinitrodiammineplatinum(II), Pt(NH3)2(NO2)2.

[0082] Palladium (Pd) precursors include palladium(II) chloride (PdCl2), palladium(II) acetate (Pd(CH3COO)2), and tetraamminepalladium(II) chloride (Pd(NH3)4Cl2·H2O).

[0083] Ruthenium (Ru) precursors include ruthenium (III) chloride (RuCl3·xH2O), ruthenium nitrosyl chloride (Ru(NO)Cl3), and ruthenium (III) nitrosyl nitrate (Ru(NO)(NO3)3).

[0084] Iridium (Ir) precursors include iridium (III) chloride (IrCl3·xH2O), hexachloroiridic acid (H2IrCl6), and iridium (III) acetylacetonate (Ir(acac)3).

[0085] Nickel (Ni) precursors include nickel (II) nitrate (Nickel (II) nitrate hexahydrate, Ni (NO 3 ) 2 6H 2 O), nickel (II) acetate (Nickel (II) acetate tetrahydrate, Ni (CH 3 COO) 2 4H 2 O), nickel (II) chloride hexahydrate (Ni Cl 2 6H 2 O), and nickel (II) acetylacetonate (Ni (acac) 2 ).

[0086] Cobalt (Co) precursors include cobalt (II) nitrate (Cobalt (II) nitrate hexahydrate, Co(NO3)2·6H2O), cobalt (II) acetate tetrahydrate (Co(CH3COO)2·4H2O), cobalt (II) chloride hexahydrate (CoCl2·6H2O), and cobalt (II) acetylacetonate (Co(acac)2).

[0087] Iron (Fe) precursors include iron (III) chloride hexahydrate (FeCl3·6H2O), iron (III) nitrate nonahydrate (Fe(NO3)3·9H2O), iron (II) sulfate heptahydrate (FeSO4·7H2O), and iron (III) acetylacetonate (Fe(acac)3).

[0088] The above examples are representative examples, and other suitable precursors that can be generally used in catalyst manufacturing may also be included.

[0089] Here, when the catalyst metal includes two or more metals, the precursor solution includes a precursor corresponding to each metal.

[0090] In addition, when the catalyst layer is to be composed of two or more layers, separate precursor solutions are prepared. For example, a precursor solution corresponding to the first catalyst layer (Fe) (e.g., FeCl3 or Fe(NO3)3 aqueous solution) and a precursor solution corresponding to the second catalyst layer (Pt) (e.g., H2PtCl6 or Pt(NH3)4Cl2 aqueous solution) are prepared.

[0091] Next, a step is performed in which the dispersion is mixed at about 40 to 60°C for about 3 to 7 minutes, NaOH is added to raise the pH to 10 to 15, and then the temperature is raised to about 100 to 120°C. Here, when the pH of the dispersion is raised by adding NaOH to the dispersion, mutual attraction between the carbonized polystyrene particles and the catalyst metal is induced in the subsequent process, which can increase the amount of catalyst metal loaded.

[0092] Afterwards, the precursor solution is added and stirred at about 140 to 180°C for about 1 to 5 hours, then washed and dried to obtain a powder.

[0093] Next, the obtained powder is reduced at about 400 to 800°C for about 10 minutes to 2 hours in a nitrogen flow to produce a metal catalyst composite. The reduction process can be performed in a hydrogen / nitrogen atmosphere. In this step, the catalytic metal can be formed in the form of a catalyst layer on a carbonized polystyrene-based copolymer particle (support).

[0094] The manufactured metal catalyst composite may include, for example, carbonized polystyrene-based copolymer particles and a catalyst layer positioned on the carbonized polystyrene-based copolymer particles, and the catalyst layer may include a catalyst metal.

[0095] In the case of conventional technology, a separate material was added to form a separate catalyst layer, but according to the manufacturing method according to the embodiment, a catalyst layer can be formed without a separate material, so the number of processes can be reduced and the manufacturing cost can be reduced.

[0096] In the case where a catalyst layer is to be formed of two or more layers (core-shell structure), each metal precursor solution is sequentially added and stirred to produce metal nanoparticles having a core-shell structure. For example, in order to form a metal including nickel (Ni), iron (Fe), palladium (Pd) or a combination thereof into a core structure, a precursor of the metal (e.g., Ni(NO3)2·6H2O, FeCl3·6H2O, PdCl2, etc.) is added, and then a reduction reaction is carried out while stirring at about 140 to 180°C for about 1 to 5 hours. Next, to form a shell structure including a precious metal such as platinum (Pt), ruthenium (Ru), or iridium (Ir), a precursor solution such as H2PtCl6·6H2O, RuCl3, or IrCl3 is added, and stirred under the same conditions (stirring at about 140 to 180°C for about 1 to 5 hours) so that the precious metal is uniformly deposited on the surface of the core metal particle.

[0097] Thereafter, the catalyst precursor having the core-shell structure produced is washed and dried to obtain a catalyst precursor powder. Subsequently, a step of mixing the obtained core-shell catalyst precursor with a carbon support is performed. At this time, the carbon support may be composed of, for example, carbonized polystyrene copolymer particles, and the catalyst precursor powder is added and stirred while dispersed in a solvent such as ethanol, isopropanol, or distilled water, so that the catalyst particles can be uniformly supported on the surface of the support. This mixture is filtered, washed, and dried to produce a carbon support composite having a catalyst supported thereon.

[0098] Next, the obtained complex is heat-treated at approximately 400 to 800°C for approximately 10 minutes to 2 hours in a nitrogen flow or hydrogen / nitrogen mixed atmosphere to produce a core-shell structured metal catalyst complex. This reduction process stabilizes the core-shell structure and modulates the electronic structure and lattice gap, thereby enhancing catalytic activity.

[0099] The manufactured metal catalyst complex may include, for example, carbonized polystyrene-based copolymer particles (carbon support) and core-shell structured metal nanoparticles supported on the surface of the support. In this case, the core-shell structured catalyst layer has a non-precious metal or transition metal such as Ni, Fe, Pd, etc. positioned at the center (core), and a precious metal such as Pt, Ru, Ir, etc. uniformly formed at the outside (shell), and can exhibit high catalytic activity for the oxygen reduction reaction (ORR).

[0100] Furthermore, unlike conventional techniques, the manufacturing method according to the present invention allows for the direct formation of a core-shell metal catalyst on the surface of a carbon support without the use of separate materials such as binders or adhesives, thereby simplifying the process and reducing manufacturing costs. This core-shell structure is highly effective in that it enables the realization of a highly active and durable catalyst while reducing the amount of platinum used.

[0101] Furthermore, in the case of the metal catalyst composite according to the embodiment, the catalyst layer is very firmly bonded to the carbon support, so that it is hardly separated even under conditions such as high temperatures and high pressures, and can be stably maintained for a long period of time. Therefore, the excellent performance of the metal catalyst composite can be maintained for a long period of time, and the durability and long-term stability of the metal catalyst composite can be significantly improved.

[0102] In addition, the metal catalyst complex according to the embodiment has a very large specific surface area, the amount of catalyst metal supported can be increased, the range of the amount of catalyst metal supported can be expanded to about 1 to 70%, and the amount of catalyst metal supported can be freely controlled.

[0103] In all cases where platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), and iron (Fe) are used alone or in an alloy as catalyst metals, the loading amount of the catalyst metal can be uniformly controlled in the range of about 1 to 70%, and dispersibility can be maintained without particle agglomeration even at high contents.

[0104] In addition, the metal catalyst composite according to the embodiment can exhibit excellent performance and durability while reducing the amount of platinum (Pt) used to 1 / 4 compared to a conventional metal catalyst composite.

[0105] The average particle diameter of the metal catalyst complex is less than about 50 nm, and may be, for example, about 20 to 45 nm.

[0106] A membrane-electrode assembly (MEA) according to one embodiment of the present invention includes a polymer electrolyte membrane and an electrode positioned on one or the other surface of the polymer electrolyte membrane, wherein the electrode may include a metal catalyst complex.

[0107] A metal catalyst composite according to one embodiment of the present invention is compatible with various electrolyte membranes, such as PFSA, Fumapem, and Aquivion, in addition to Nafion, and can exhibit high adhesion and electrochemical stability on the membrane surface.

[0108] The metal catalyst complex according to the embodiment can also be manufactured in the form of an ink that can be directly applied onto a film, and can be suitable for automation and continuous production due to its high integration with the MEA manufacturing process.

[0109] The membrane-electrode assembly according to the embodiment has superior efficiency, performance, durability and long-term stability compared to the prior art.

[0110] These metal catalyst composites and membrane-electrode assemblies have potential applications in a variety of technological fields. For example, the metal catalyst composites can be used as cathode catalysts in fuel cells, serving as oxygen reduction catalysts, and as a hydrogen oxidation catalyst (anode catalyst).

[0111] In addition, metal catalyst composites can be used in various applications, including water electrolysis (HER / OER), secondary battery cathode materials, CO2 reduction reaction catalysts, supercapacitor electrodes, and catalytic sensors, in addition to fuel cells.

[0112] Hereinafter, the present invention will be described with examples, comparative examples, and experimental examples. However, the present invention is not limited thereto.

[0113]

[0114] Example 1

[0115] The starting material was prepared by mixing styrene (7 g), divinylbenzene (1 g), and sodium dodecyl sulfate (1.1 g) with 68 mL of deionized water and stirring for about 30 minutes. Then, potassium persulfate (0.05 g / 2 mL of deionized water) was added dropwise to the starting material, and after bubbling with nitrogen (N2) for about 30 minutes, the starting material was emulsion polymerized by reacting at about 70 °C for about 18 hours in a nitrogen atmosphere. Excess surfactant was removed by repeated centrifugation, and dried under a vacuum for about 12 hours to obtain polystyrene-based copolymer particles.

[0116] The manufactured polystyrene copolymer particles (400 mg) were dispersed in dichloroethane. Then, FeCl3 (1 g) was added to the solution, and formaldehyde dimethyl acetal (1 ml) was slowly poured. The solution was stirred at about 50°C for about 2 hours, then the temperature was increased to 80°C and crosslinked for about 24 hours. To remove excess FeCl3, the solution was washed with a mixture containing 90 wt% ethanol and 10 wt% hydrochloric acid, filtered, and dried for about 12 hours.

[0117] The hyper-crosslinked resultant was carbonized at about 900°C for about 2 hours in a nitrogen flow at a ramping rate of 2°C / min to obtain carbonized polystyrene copolymer particles.

[0118] 500 mg of the carbonized product was dispersed in 20 mL of ethylene glycol. To deposit cobalt atoms (Co) and platinum atoms (Pt), Co(NO3)2·6H2O (675 mg) and H2PtCl6·6H2O (85 mg) were added to 2 mL of ultrapure water to prepare a PtCo precursor mixture. The ethylene glycol solution in which the carbonized particles were dispersed was mixed at about 50 °C for about 5 minutes, the pH was increased to 14 using 1 M NaOH, and the temperature was raised to about 110 °C. After adding the PtCo precursor mixture, the mixture was stirred at about 160 °C for about 3 hours. The mixture was then washed, and the product was dried under vacuum at 50 °C. Afterwards, the powder was reduced at about 500°C for 1 h under a H2 / N2 flow rate (10:190 sccm) in a hydrogen / nitrogen flow at a ramping rate of 2°C / min. Finally, the PtCo / Carbon particle catalyst (metal catalyst composite) was obtained as a black powder. The platinum content of the catalyst was controlled to 5 wt%.

[0119] Example 2

[0120] 500 mg of the carbonized polystyrene copolymer particles obtained in Example 1 were dispersed in 20 ml of ethanol. To deposit cobalt atoms (Co) and platinum atoms (Pt), Co(NO3)2·6H2O (675 mg) and H2PtCl6·6H2O (85 mg) were added to the above solution. The solution was continuously stirred at 80°C. After evaporation of ethanol, the product was dried under vacuum at 50°C. The powder was then reduced at about 500°C for 1 h in a hydrogen / nitrogen flow at a ramping rate of 2°C / min under a H2 / N2 flow rate (10:190 sccm). Finally, the PtCo / Carbon particle catalyst was obtained as a black powder. The platinum content of the catalyst was controlled to 5 wt%.

[0121] Example 3

[0122] Of the carbonized polystyrene copolymer particles obtained in Example 1, 500 mg was dispersed in 20 ml of ethanol. To deposit iron (Co) and platinum (Pt) atoms, FeCl3 (360 mg) and H2PtCl6·6H2O (85 mg) were added to the above solution. The solution was continuously stirred at approximately 80°C. After evaporating the ethanol, the product was dried at approximately 50°C in a vacuum atmosphere. Thereafter, the powder was reduced at approximately 500°C for 1 h in a hydrogen / nitrogen flow at a ramping rate of 2°C / min under a H2 / N2 flow rate (10:190 sccm). Finally, the PtFe / Carbon particle catalyst was obtained as a black powder. The platinum content of the catalyst was controlled to 5 wt%.

[0123] Example 4

[0124] Of the carbonized polystyrene copolymer particles obtained in Example 1, 500 mg was dispersed in 20 mL of ethylene glycol. To deposit iridium atoms (Ir) and platinum atoms (Pt), IrCl3·xH2O (120 mg) and H2PtCl6·6H2O (85 mg) were dissolved in 2 mL of ultrapure water to prepare a precursor mixture. The mixed precursor was adjusted so that the Pt:Ir molar ratio was 1:1.

[0125] This precursor mixture was added to an ethylene glycol solution containing a dispersed carbonized support, and the mixture was premixed at about 50°C for 5 minutes, after which the pH of the solution was adjusted to 14 using 1 M NaOH. The solution was then heated to 110°C, the precursor mixture was added, and the reaction was stirred at about 160°C for about 3 hours. After completion of the reaction, the product was washed with a large amount of ultrapure water and then dried under vacuum at 50°C.

[0126] The dried powder was reduced by heat treatment at 500°C for 1 hour in a hydrogen / nitrogen mixed gas atmosphere (H2 / N2 flow ratio: 10:190 sccm) while ramping at a temperature of 2°C / min. Finally, a PtIr / Carbon particle catalyst (metal catalyst composite) was obtained in the form of a black solid powder, and the platinum content of the catalyst was controlled to 5 wt%.

[0127] Example 5

[0128] Of the carbonized polystyrene copolymer particles obtained in Example 1, 500 mg was dispersed in 20 mL of a mixed solvent containing glycerol and ethanol in a volume ratio of 3:1. To deposit nickel atoms (Ni) and platinum atoms (Pt), Ni(NO3)2·6H2O (535 mg) and H2PtCl6·6H2O (85 mg) were dissolved in 2 mL of ultrapure water to prepare a precursor mixture. The mixed precursor was adjusted so that the Pt:Ni molar ratio was 1:1.5.

[0129] The mixed solvent solution containing dispersed carbon particles was premixed at approximately 50°C for 5 minutes, and the pH of the solution was adjusted to 13 using 1 M NaOH. The solution was then heated to 110°C, the precursor mixture was added, and the reaction was stirred at approximately 160°C for approximately 3 hours. After completion of the reaction, the product was thoroughly washed with ultrapure water and ethanol, and then dried under vacuum at 50°C.

[0130] The dried powder was reduced at 500°C for 1 hour in a hydrogen / nitrogen mixed gas atmosphere (H2 / N2 flow ratio: 10:190 sccm) while the temperature was increased at a ramping rate of 2°C / min. Finally, a PtNi / Carbon particle catalyst (metal catalyst composite) was obtained in the form of a black solid powder, and the platinum content of the catalyst was controlled to 5 wt%.

[0131]

[0132] Comparative Example 1

[0133] A PtCo / Carbon particle catalyst was prepared in the same manner as in Example 1, except that 0.2 g of sodium dodecyl sulfate was used in the starting material.

[0134] Comparative Example 2

[0135] A PtCo / Carbon particle catalyst was prepared in the same manner as in Example 1, except that styrene (1.66 g), divinylbenzene (0.24 g), and polyvinylpyrrolidone (PVP) (0.6 g) were used as starting materials.

[0136] Comparative Example 3

[0137] A PtCo / Carbon particle catalyst was prepared in the same manner as in Example 1, except that styrene (1.66 g), divinylbenzene (0.24 g), and polyvinylpyrrolidone (PVP) (0.15 g) were used as starting materials.

[0138] Comparative Example 4

[0139] A PtCo / Carbon particle catalyst was prepared in the same manner as in Example 1, except that the hyper-crosslinking process was omitted.

[0140]

[0141] Experimental Example 1 - Measurement of the average particle size of a metal catalyst composite

[0142] The average particle diameter (D50) of the metal catalyst complexes manufactured according to Examples 1 to 5 and Comparative Examples 1 to 4 was measured, and the results are shown in Table 1 and Fig. 2 below.

[0143] Sample Styrene (g) Divinylbenzene (g) Sodium dodecyl sulfate (g) PVP (g) Average particle size (D50) (nm) Example 17 11.1-34.5 ± 2.7 Example 27 11.1-35.1 ± 2.9 Example 37 11.1-34.3 ± 2.7 Example 47 11.1-32.7 ± 2.3 Example 57 11.1-36.0 ± 2.6 Comparative Example 17 10.2-162 ± 5.8 Comparative Example 21.66 0.24-0.68 8.5 ± 6.3 Comparative Example 31.66 0.24-0.15 176 ± 7.2 Comparative Example 47 11.1-220 ± 9.2

[0144]

[0145] Referring to Table 1 and FIG. 2, it can be seen that the average particle diameters of the metal catalyst complexes according to Comparative Examples 1 to 4 were all larger than 80 nm, and the average particle diameters of the metal catalyst complexes according to Examples 1 to 5 were significantly smaller than those of the Comparative Examples, and showed an average particle diameter of less than 40 nm.

[0146]

[0147] Experimental Example 2 - Full-cell Test

[0148] Full-cell tests were performed on MEA samples containing metal catalyst composites manufactured according to Examples 1 to 5 and Comparative Examples 1 to 4, and MEA samples containing commercial catalysts (Pt / Carbon). Here, the commercial catalyst used was Platinum on graphitized carbon (20% Pt on Vulcan XC72) purchased from Sigma-Aldrich.

[0149] Full-cell tests were performed using a PEMFC station (HTS-05, Horizon Fuel Cell). At the cathode electrode, the Pt loading was 0.05 mg for Examples 1 to 5 and Comparative Examples 1 to 4. Pt / cm 2 , 0.2 mg for commercial catalyst (Pt / Carbon) Pt / cm 2 The catalyst ink was directly sprayed onto the Nafion 211 membrane until it reached the active area of ​​the MEA of 5 cm 2 At the anode electrode, the Pt loading was 0.2 mg Pt / cm 2 Commercial Pt / Carbon (20 wt%) was used. The fuel cell temperature was maintained at 80°C, and H2 / Air flowed into the anode and cathode. The flow rate of H2 / Air was 200 sccm at atmospheric pressure.

[0150] The experimental results are shown in FIGS. 3a to 5 and Table 2 below. FIGS. 3a and 3b show the results of a full-cell test using a metal catalyst composite manufactured according to Example 1, FIG. 4 shows the results of a full-cell test using a metal catalyst composite manufactured according to Examples 2 to 5, and FIG. 5 shows the results of a full-cell test using a metal catalyst composite manufactured according to Comparative Examples 1 to 4.

[0151] Sample Power density (mW.cm -2)Example 1475.3Example 2473.3Example 3465.0Example 4482.8Example 5478.5Comparative Example 1388.9Comparative Example 2417.6Comparative Example 3321.7Comparative Example 4310.2Commercial Catalyst (Pt / Carbon) 460.5

[0152] Referring to FIGS. 3a, 3b, and Table 2, it can be confirmed that the metal catalyst composite according to Example 1 exhibits an IV curve that is equal to or higher than that of a commercial catalyst composite (Pt / C) having a platinum (Pt) content of 20 wt% in all current sections, even though the metal catalyst composite has a platinum (Pt) content of 5 wt% (see FIG. 3a). In addition, examining the power density graph according to current (see FIG. 3b), it can be seen that the IV curve is approximately 1200 mA / cm 2 In the high current range above, the metal catalyst composite according to Example 1 exhibited a higher current density (maximum current density 475.3 mW / cm) than the commercial catalyst composite. 2 ), indicating a commercial catalyst composite (460.5 mW / cm 2 ) can be confirmed to show superior performance.

[0153] Referring to FIG. 4 and Table 2, it can be confirmed that Examples 2 to 5 also exhibit a power density equivalent to that of Example 1. From this, it can be seen that excellent performance is maintained even when the transition metal included in the catalyst metal is changed from Co to Fe, and even though the platinum content of the metal catalyst composite according to Examples 2 to 5 is 5 wt%, which is a low platinum content, the maximum current density of the commercial catalyst composite is 460.5 mW / cm. 2 Each of them has a better performance (Example 2: 473.3 mW / cm 2 , Example 3: 465.0 mW / cm 2 , Example 4: 482.8 mW / cm 2 , Example 5: 478.5 mW / cm 2 ) can be confirmed.

[0154] Referring to FIG. 5 and Table 2, it can be confirmed that the metal catalyst composites manufactured according to Comparative Examples 1 to 3 exhibit significantly lower power densities compared to the examples. In addition, the metal catalyst composites manufactured according to Comparative Examples 1 to 4 exhibited power densities of about 800 to 1100 mA / cm. 2 It can be confirmed that the performance is significantly reduced in the above section. In the case of the metal catalyst composite according to Comparative Example 1, since the content of sodium dodecyl sulfate in the starting material is 0.2 g, which is lower than the content of sodium dodecyl sulfate in the examples, the size of the carbonized polystyrene particles increases and the power density value is confirmed to be lowered. In the case of Comparative Examples 2 and 3, it can be confirmed that the power density value is significantly lowered when PVP is used as a surfactant instead of sodium dodecyl sulfate. In the case of the metal catalyst composite according to Comparative Example 4, the same starting materials as in the examples were used, but the main difference is that the hyper-crosslinking process was omitted. Since the hyper-crosslinking process was omitted, the micropores and porous network structure between the polymer chains were not sufficiently formed, and the penetration and dispersion of the metal precursor were uneven. Accordingly, the aggregation and clustering of metal particles were aggravated in the finally generated metal catalyst complex, which led to a decrease in the active area of ​​the catalyst, resulting in a significant deterioration in the output characteristics in the high current density range.

[0155]

[0156] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. A first step of manufacturing polystyrene series copolymer particles by adding an initiator to a mixture containing a monomer, a first crosslinking agent, and a surfactant. A second step of manufacturing hyper-crosslinked polystyrene copolymer particles by hyper-crosslinking the above polystyrene copolymer particles, A third step of carbonizing the above hyper-crosslinked polystyrene series copolymer particles to produce carbonized polystyrene series copolymer particles, and A fourth step of manufacturing a metal catalyst complex by dispersing the above carbonized polystyrene series copolymer particles in a first solvent, mixing them with a precursor of a catalyst metal, and then reducing them. Including Method for preparing a metal catalyst complex.

2. In paragraph 1, The above metal catalyst complex comprises carbonized polystyrene series copolymer particles and a catalyst layer positioned on the carbonized polystyrene series copolymer particles, The above catalyst layer comprises the above catalyst metal. Method for preparing a metal catalyst complex.

3. In paragraph 1, A method for producing a metal catalyst complex, wherein the above catalyst metal comprises at least one metal selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), and iron (Fe).

4. In paragraph 3, A method for producing a metal catalyst complex, wherein the above catalyst metal is an alloy containing at least one metal selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), nickel (Ni), cobalt (Co), and iron (Fe).

5. In paragraph 1, The fourth step above is, A step of preparing a dispersion liquid by dispersing the above carbonized polystyrene series copolymer particles in a first solvent, A step of adjusting the pH of the above dispersion and then raising the temperature, A step of adding a precursor solution containing a precursor of the catalyst metal to the dispersion and then stirring, and A step of producing the metal catalyst complex by reducing the precursor of the above catalyst metal. A method for producing a metal catalyst complex comprising:

6. In paragraph 5, A method for producing a metal catalyst complex, wherein the first solvent comprises ethylene glycol.

7. In paragraph 5, The step of adjusting the pH of the above dispersion and then increasing the temperature is as follows: A step of stirring the above dispersion at 40 to 60°C, A step of adjusting the pH of the dispersion by adding NaOH, and Step of raising the temperature to 100 to 120 ℃ A method for producing a metal catalyst complex comprising:

8. In paragraph 5, A method for producing a metal catalyst complex, wherein the step of producing the metal catalyst complex by reducing the precursor of the catalyst metal is performed at a temperature range of 400 to 800°C for 10 minutes to 2 hours.

9. In paragraph 1, A method for producing a metal catalyst complex, wherein the average particle diameter of the metal catalyst complex is less than 50 nm.

10. In paragraph 1, A method for producing a metal catalyst complex, wherein the first cross-linking agent comprises a compound of the divinylbenzene series.

11. In paragraph 10, A method for producing a metal catalyst complex, wherein the surfactant comprises at least one of sodium dodecyl sulfate, cetrimonium bromide, dodecyltrimethylammonium bromide, or polyvinyl alcohol.

12. In paragraph 1, The second step above is, A method for producing a metal catalyst composite, comprising dispersing polystyrene-based copolymer particles manufactured in the first step in a second solvent, adding a crosslinking catalyst and a second crosslinking agent, stirring, and then raising the temperature to produce hyper-crosslinked polystyrene-based copolymer particles.

13. In paragraph 12, The above crosslinking catalyst is a method for producing a metal catalyst complex including one or more of FeCl3, FeCl3·6H2O, AlCl3, CoCl3, ZnCl3, or CrCl4.

14. In paragraph 13, A method for producing a metal catalyst complex, wherein the second cross-linking agent comprises at least one of formaldehyde dimethyl acetal, trichloromethane, or carbon tetrachloride.

15. In paragraph 14, A method for producing a metal catalyst complex, wherein the second solvent comprises dichloroethane.

16. A metal catalyst complex manufactured by the method for manufacturing a metal catalyst complex according to any one of claims 1 to 15.

17. Polymer electrolyte membrane, and An electrode positioned on one side or the other side of the polymer electrolyte membrane, and comprising a metal catalyst complex manufactured by the method for manufacturing a metal catalyst complex according to any one of claims 1 to 15. Including Membrane-electrode assembly.

Images